Xerographic Reproduction Machine

Abstract

A reproduction machine having a photoreceptor imaging medium in belt configuration which is exposed by a flash illumination system in timed relation to the feeding of sheets of copy paper prior to image transfer. The belt is arranged to be maintained flat during exposure and development with image transfer being effected along a curved presentation of the belt between the two flat sections of the belt.

Description

This invention relates to improvements in reproduction systems such as copiers or duplicators and, particularly, to improvements in automatic xerographic systems that is particularly adapted to high speed operation and is capable of having its sequence timing varied thereby permitting variable speeds of output.

Since the process of xerography was pioneered by Chester Carlson and originally disclosed in the Carlson U.S. Pat. No. 2,297,691, many improvements have been made in xerographic devices and techniques and new applications therefor. As the result, automatic machines of various arrangements and speeds for carrying out xerographic reproduction processes are in wide commercial use. The present invention constitutes a further improvement in automatic xerographic processing systems whereby the system may be more readily employed for relatively high speed production as well as being adapted to various speeds of production and may be fabricated into a relatively compact size.

As is well known in recent years, the steadily increasing size of various industries has required an enormous increase in the amount of paper work that must be accomplished, maintained, and made available for wide interplant circulation. In the present day commercial xerographic machine, which is adapted to produce copies of between 5 and 60 81/2 .times. 11 inch sheets of copy per minute, the photoreceptor device is in the form of a drum which rotates in timed unison relative to a plurality of processing stations. These devices employ a charging device, a stationary copy projection device, a developing mechanism, a sheet feeding mechanism, a transfer charging device, a sheet pick-off device, a paper transport mechanism and a fuser mechanism. In addition, there is provided a drum cleaning mechanism in order to remove excess or residual toner particles from the drum surface prior to the recharging of the drum preparatory to document exposure.

The limiting feature in these present day machines is the use of the xerographic drum which seriously limits the positioning and action of each of the processing devices and, in particular, the requirement of presenting a flowing image upon the xerographic drum as a document is being scanned. In commercial machines it has been proven that the preferred handling of documents during scanning thereof is provided by a fixed glass platen upon which a document to be scanned is placed in fixed relation. As the conventional xerographic drum is rotated, a scanning mechanism scans across the document and presents light images of the document in the form of a narrow band of light upon the drum surface as it rotates, thereby producing a flowing presentation of the light rays upon the drum surface.

The mechanism which accomplishes the scan of the fixed document generally involves a slidable carriage for supporting illumination lamps in addition to drive mechanisms, levers, pulleys, switches, etc. for accomplishing scanning of the document. As the demands for faster copying or duplicating has come about, these conventional machines gnerally have been modified in their respective drive systems and electrical circuits in order to accomplish a faster scan for the scanning mechanisms already in the machine. The result of these modifications is to propel the structures that go to make up the scanning mechanisms at very great speeds and, as will be apparent, will place great undue burdens upon the structural supports of the machine and the scanning mechanism.

Another inherent disadvantage of the drum type printing means for reproduction machines is the inability to effect a plurality of images or image areas on the periphery of the drum without requiring extremely large size drums with their attendant extra large drive systems and other size requirements for the other processing components for the machine. With the capability for utilizing a xerographic surface of relatively large area or length, it is possible to conduct processing operations simultaneously as the xerographic surface moves rather than permitting such action to occur in sequence as is generally the case. Such xerographic surface may have as many as five document exposures thereon in various stages of processing thereby permitting simultaneous processing steps wherein each step may be optimized to a greater extent than is usually found in practice on machines employing xerographic drums.

It is therefore the principal object of this invention to improve xerographic reproduction machines that are capable for general copying applications and for making high speed copies automatically and in variable time sequences.

Another object of this invention is to improve xerographic reproduction machines so that reproductions of a fixed document can be made quickly and automatically.

Another object of this invention is to improve xerographic machines of the photoreceptor belt type whereby the operations of the machine are effected independently of the positioning of the belt to permit more efficient use of the belt surface.

Another object of this invention is to improve xerographic machines in a manner such that the various operating cycles are effected in time relation to the movement of the photoreceptor.

The invention has among its objects a provision of a xerographic copier-duplicator machine in a compact self-contained form of a modular design defined by a minimum size and adapted to be dismantled for replacement of module components, repairs and cleaning in a minimum of time with minimum effort.

These and other objects of this invention are obtained by means of the provision of a selenium belt assembly which is adapted to move a selenium belt through various processing stations two of which present the belt in flat condition, a stationary-copy projection apparatus adapted to flash expose a document for exposing a selenium belt at one of its flat portions, a developer apparatus adapted to cascade developer material over a portion of the selenium belt when it is in another flat condition, a sheet feeding mechanism arranged to quickly present a sheet of paper at a transfer station which occupies a minimal of area of the belt, a transfer charging device arranged in conjunction with a paper transport mechanism for conveying a sheet of paper to a transfer station and to effect image transfer to the sheet, a sheet pick-off apparatus and a fuser mechanism arranged to receive individual sheets of paper for effecting fixing of toner images thereon. The sheet feeding mechanism, the paper transport, the transfer station and the fuser mechanism are arranged to provide a paper movement which generally assumes a straight and shortened path. These components are modular in design and are operatively positioned relative to the movable endless selenium belt, the movement of which is controlled to permit coordinated operation of the apparatus to reproduce a copy from the stationary document selectively and automatically.

For a better understanding of the invention as well as other objects and further features thereof, reference is had to the following detailed description of the invention to be read in conjunction with the accompanying drawings, wherein:

FIG. 1 is an exploded right-hand perspective view of the xerographic reproduction machine with the modular processing components separated to better illustrate the invention;

FIG. 2 is a schematic sectional view of the xerographic machine showing the various xerographic processing stations;

FIG. 3 is an isometric view of the illumination and optical system for the xerographic machine;

FIG. 4 is a sectional view of one side of the lamp assembly utilized for the illumination device;

FIG. 5 is a sectional view of one end of the lamp assembly;

FIG. 6 is a partial top view of a portion of the lamp assembly and document platen;

FIG. 7 is a perspective view of the photoconductive belt assembly utilized in the machine;

FIG. 8 is an elevational view of the belt assembly as seen from the rear of the machine;

FIG. 9 is an elevational view of the other side of the belt assembly as seen from the front of the machine;

FIG. 10 is an elevational view of the belt assembly with the belt mounted thereon partly in section to show various portions of the interior of the belt assembly;

FIG. 11 is a sectional view taken along line 11--11 in FIG. 10;

FIG. 12 is a partial view of the lower section as seen from the front of the developer assembly showing the selenium belt in a relaxed condition;

FIG. 13 is a perspective view of the developer apparatus as seen from the front of the machine away from association with the selenium belt utilized in the machine;

FIG. 14 is a front view of the developer mechanism as applied to a selenium belt;

FIG. 15 illustrates the other side of the developer housing of that side which faces the rear of the machine;

FIG. 16 is a rear elevational view partly broken away of the developer housing of that side that is remote from the selenium belt;

FIG. 17 is a cross-sectional view taken along line 17--17 in FIG. 16 and showing the vertical transport belt;

FIG. 18 is a cross section view of the developer housing taken along 18--18 in FIG. 16;

FIG. 19 is a cross-sectional view of the upper horizontal developing material transport device taken along line 19--19 in FIG. 14;

FIG. 20 is a cross-sectional view of the lower horizontal developer material transport taken along line 20--20 in FIG. 14;

FIG. 21 is a perspective view of the internal bucket conveyor belt for the toner materials;

FIG. 22 is a cross section taken along line 22--22 in FIG. 21;

FIG. 23 is an end view of the conveyor belt of FIG. 21;

FIG. 24 is a front view partly in section of the conveyor belt;

FIG. 25 is a plan view partly in section of the toner dispensing mechanism utilized with the developer assembly of FIG. 13;

FIG. 26 is an enlarged sectional view, partly broken away, of the toner dispenser, taken along the line 26--26 in FIG. 25;

FIG. 27 is an elevational view, with parts broken away, of the automatic toner sensor control device used in the developer housing;

FIG. 28 is a side view of the toner sensor with parts broken away;

FIG. 29 is a cross-sectional view taken along the line 29--29 in FIG. 27;

FIG. 30 is a fragmentary view of a detail in the toner sensor;

FIG. 31 is a schematic of the control circuit for the toner sensor of FIG. 27;

FIG. 32 is an elevational view of the timer mechanism for the toner sensor;

FIG. 33 is an end view of the timer mechanism shown in FIG. 32;

FIG. 34 is a timing chart indicating the operative sequence of the timer mechanism;

FIG. 35 is an isometric view of the paper handling and feeding component;

FIG. 36 is a side elevational view of the paper handling device as viewed from the rear of the machine;

FIG. 37 is a side elevational view of the paper handling device as viewed from the front of the machine;

FIG. 38 is a plane view of the paper handling device with parts broken away;

FIG. 39 is a sectional view taken along line 39--39 in FIG. 38;

FIG. 40 is a sectional view taken along the line 40--40 in FIG. 37;

FIG. 41 is a sectional view of the paper feeding mechanism taken along line 41--41 in FIG. 37;

FIG. 42 is a sectional view with parts broken away of the paper registration rollers utilized along with the paper feeding mechanism;

FIG. 43 is an end view of the double rotary solenoid utilized to effect sheet registration and feed out;

FIG. 44 is a fragmentary enlarged view of a rotary drive device taken along the line 44--44 in FIG. 43;

FIG. 45 illustrates another position of operation of the rotary device of FIG. 44;

FIG. 46 is a sectional view of a detail used with the registration rollers taken along line 46--46 in FIG. 42;

FIG. 47 is a sectional view of another detail taken along line 47--47 in FIG. 42;

FIG. 48 is a sectional view showing the registration fingers and taken along line 48--48 in FIG. 42;

FIG. 49 is a sectional view of the roller bearing support taken along line 49--49 in FIG. 42;

FIG. 50 is a sectional view of a double sheet sensing device used in conjunction with a paper handling mechanism;

FIG. 51 is a plane view of the device of FIG. 50;

FIG. 52 is an isometric of the horizontal sheet transport system utilized at a transfer station;

FIG. 53 is a sectional view of the sheet transport system shown in relation to other components of a reproduction machine;

FIG. 54 is a plane view of the sheet transport system;

FIG. 55 is a perspective view of the fuser assembly utilized in the machine;

FIG. 56 is an elevational view of the fuser assembly as seen from the front of the machine;

FIG. 57 is an end view of the fuser assembly as seen from the output side of the assembly;

FIG. 58 is a sectional view taken along line 57--57 in FIG. 56;

FIG. 59 is a sectional view taken along line 58--58 in FIG. 55;

FIG. 60 is a sectional view taken along line 59--59 in FIG. 55;

FIGS. 61 and 62 are the front view and end view, respectively, of the drive system for some of the processing components of the xerographic machine;

FIG. 63 is an elevational view, partly broken away in section of the brush cleaning assembly used in the xerographic machine;

FIG. 64 is a sectional view of the brush cleaner taken along the line 64--64 in FIG. 63;

FIG. 65 is a fragmentary view of a detail utilized in the brush cleaner;

FIG. 66 is a schematic electrical diagram of the fade out lamp control system view in the xerographic machine;

FIGS. 67 and 68 are schematic electrical diagrams of the xerographic apparatus and, when combined in end-to-end relationship, illustrate the complete wiring system; and

FIGS. 69 and 70 are timing charts which when joined illustrate the timing sequence of operation of some of the processing components.

Throughout this description, the front of the xerographic reproduction machine as viewed in FIGS. 1 and 2 is regarded as that portion which the operator faces while placing a document to be reproduced in the machine. The right and left end of the machine are regarded as being to the right and left of the operator as he faces the machine as he would in viewing FIG. 2.

For a general understanding of the xerographic processing arrangement in which the invention is incorporated, reference is had to FIGS. 1 and 2 in which the various system components are schematically illustrated. As in all xerographic systems based on the concept disclosed in the above-cited Carlson patent, a light image of a document to be reproduced is projected onto the sensitized surface of a xerographic plate to form an electrostatic latent image thereon. Thereafter, the latent image is developed with an oppositely charged developing material to form a xerographic powder image, corresponding to the latent image on the plate surface. The powder image is then electrostatically transferred to a support surface to which it may be fused by a fusing device whereby the powder image is caused permanently to adhere to the support surface.

In the machine disclosed herein, an original to be copied is placed upon a transparent support platen P fixedly arranged in an illumination assembly generally indicated by the reference numeral 10, arranged at the left end of the machine. While upon the platen, an illumination system, to be described herein, flashes light rays upon the original thereby producing image rays corresponding to the informational areas on the original. The image rays are projected by means of an optical system in the illumination device and for exposing the photosensitive surface of a xerographic plate in the form preferably of a flexible photoconductive belt arranged on a belt assembly generally indicated by the reference numeral 11. Any flexible photoconductive device may be utilized such as a selenium belt or the like for purposes of producing an electrostatic latent image.

The photoconductive belt assembly 11 is slidably mounted upon a support bracket secured to the frame of the machine and is adapted to drive a selenium belt 12 in the direction of the arrow as shown in FIG. 2 at a constant rate. During this movement of the belt, the reflected light image of an original on the platen is flashed upon the xerographic surface of the belt at such a speed, measured in microseconds, that the relative motion of the light rays comprising the light image and the belt surface is minimal. The belt surface that intercepts the light rays comprises a layer of photoconductive material such as selenium on a conductive backing that is sensitized prior to exposure by means of a charging corona generator device indicated at 13.

The flash exposure of the belt surface to the light image discharges the photoconductive layer in the areas struck by light, whereby there remains on the belt a latent electrostatic image in image configuration corresponding to the light image projected from the original on the supporting platen. As the belt surface continues its movement, the electrostatic image passes through a developing station B in which there is positioned a developer assembly generally indicated by the reference numeral 14 and where the belt is maintained in a flat condition. The developer assembly 14, as will be described in detail hereafter, comprises a vertical conveying mechanism which carries developing material to the upper part of the belt assembly 11 whereat the material is dispensed and directed to cascade down over the upperwardly moving inclined selenium belt 12 in order to provide development of the electrostatic image.

As the developing material is cascaded over the xerographic plate, toner particles in the development material are deposited on the belt surface to form powder images. As toner powder images are formed, additional toner particles are supplied to the developing material in proportion to the amount of toner deposited on the belt during xerographic processing. For this purpose, a toner dispenser generally indicated by reference numeral 15 is used to accurately meter toner to the developer material in the developer assembly 14.

The developed electrostatic image is transported by the belt to a transfer station C whereat a sheet of copy paper is moved at a speed approximately in synchronism with the moving belt in order to accomplish transfer of the developed image. There is provided at this station a sheet transport mechanism generally indicated at 16 adapted to transport sheets of paper from a paper handling mechanism generally indicated by the reference numeral 18 to the developed image on the belt at the station C. The paper handling mechanism includes a paper support tray for holding a stack of paper or the like, separating rollers adapted to feed the top sheet of the stack to feed rollers which direct the sheet material into contact with transporting devices in the sheet transport mechanism 16.

The transfer of the developed powder image from the selenium belt surface to sheet material is effected by means of a corona transfer device 19 that is located within the sheet transport mechanism to the point of contact between the sheet and selenium belt. The corotron 19 may include one or more corona discharge electrodes that are energized from a suitable high potential source and extend transversely across the selenium belt and are substantially enclosed within a shielding member.

In operation, the electrostatic field created by the corona discharge device 19 is effective to attract the toner particles comprising the xerographic powder image from the belt surface and cause them to adhere electrostatically to the surface of the sheet material. As the powder image is being transferred to the sheet material in a flowing manner, the sheet continues to adhere to the selenium belt however, as the portion of the sheet passes the transfer station C, the sheet is stripped from the conveyor belts by means of a stripping device generally indicated by the reference numeral 20. This device includes an AC corona discharge device adapted to produce a charge which neutralizes that which causes the sheet material to adhere to the selenium belt, and a manifold supplied with a plurality of small outlets which when induced with air pressure is effective to pull mechanically the paper off the belt in cooperation with the corona discharge device.

As a sheet of paper leaves the sheet transport, it is conveyed into a fuser assembly generally indicated by the reference numeral 21 wherein the developed and transferred xerographic powder image on the sheet material is permanently affixed thereto. After fusing, the finished copy is discharged from the apparatus at a suitable point for collection externally of the apparatus. To accomplish this there is provided a short horizontal conveyor 22 which conveys a sheet of material out of the fuser assembly 21 and into a catch tray 23 supported upon the machine frame.

The next and final station in the device is a belt cleaning station having positioned therein a corona precleaning device 24 similar to a corona charging device to impose an electrostatic charge on the selenium belt and residual powder adherent thereto to aid in effecting the removal of the powder, a belt cleaning assembly 25 including a rotating brush device adapted to remove any powder remaining on the xerographic belt after transfer and a source of light, in the form of lamp LMP-1, whereby the selenium belt 12 is flooded with light to cause dissipation of any residual electrical charge remaining on the xerographic drum.

Suitable drive means described hereinafter are arranged to drive the selenium belt 12 in conjunction with timed flash exposure of an original to be copied, to effect conveying and cascade of toner material, to separate and feed sheets of paper and to transport the same across the transfer station C and to convey the sheet of paper through the fuser assembly in timed sequence to produce copies of the original.

ILLUMINATION APPARATUS

The illumination assembly 10 is illustrated in detail in FIGS. 3-6 and is designed for irradiating the diffusely reflecting original D such that the image of the original produced by a lens has irradiance uniformity to a maximum of one per cent. This uniform image irradiance is obtained by the orthogonal placement of four linear light sources L.sub.1, L.sub.2, L.sub.3, L.sub.4, and is enhanced by the use of the associated reflectors R.sub.1, R.sub.2, R.sub.3 and R.sub.4. The arrangement is such as to compensate for the relative illumination functions of the lens, for example, the illumination falloff due to vignetting of the optical aperture for the system and to the cosine to the fourth power law.

Each of the four linear light sources, which may be in the form of a fluorescent lamp or other gaseous discharge tube, is provided with two spaced apart reflectors one of which is elliptical and/or other cylindrical. The radiometric equations for the elliptical and the cylindrical reflectors are utilized to project reflected light from a platen supporting an original onto an image plane where the irradiated image has near perfect irradiance.

As shown in FIGS. 4 and 5, the lamps L.sub.1, L.sub.2, L.sub.3 and L.sub.4 are arranged along the sides of a rectangle somewhat larger than the rectangle defined by the original D. The inner edges of the reflectors R.sub.1, R.sub.2, R.sub.3 and R.sub.4 being parallel to the respective lamps are also arranged as the sides of a rectangle having its inner edges spaced slightly outwardly from the edges which define the original. With this arrangement, the light rays which emanate from each of the lamps, are directed toward the original, to impinge thereon at various angles other than directly or at 90.degree.. This arrangement, then, eliminates direct perpendicular impingement of the light rays upon the document thereby preventing excessively high intensity illumination of the edges of the document if such were extended over the light sources.

With light sources being located beyond the corresponding edges of the original D and, without the use of additional devices for directing light rays from the sources, the light impinging upon the document from the light source lamps would result in the homogeneous illumination of the photoconductive surface, but with a somewhat diminished intensity since much of the light emanating from the lamps are directed away from the original. The orthogonal relationship of the lamps located outside the outer edges of originals will effect this homogeneous irradiance that is not possible with an arrangement wherein only two sides of an original are provided with a lamp.

In order to enhance the homogeneous illumination wherein there will be a minimum amount of variation in the image irradiance from an original and, to increase the amount of light that can be directed toward the original D, the illumination system 10 is provided with specifically shaped bireflective surfaces for each of the linear lamps. These reflective surfaces are designed to direct light to specific portions of the original being illuminated and are so arranged that the impinging rays of one lamp and its corresponding bireflective pair of surfaces overlap with the impinging rays of the opposing lamp and its corresponding bireflective pair of surfaces. These reflected rays coupled with the rays from each of the lamps upon the original and result in a more uniform, homogeneous illumination of the photoconductive surface.

Each of the reflectors, and for simplicity the reflector R.sub.1 will be the only one described in detail, comprises two reflecting surfaces. The reflector R.sub.1 includes a first reflector surface R.sub.a having a flat spacer portion 26 between two segments of this surface and, is in the form of a right circular cylinder or, an ellipse of unit eccentricity having the axis of the surface of revolution or line foci coincident with the axis of the linear lamp L.sub.1. The reflector surfaces R.sub.a, one for each of the reflectors in the illumination system 10, define the inner limits of the four assembled reflectors. When assembled, the surfaces define an opening through which the light rays emanating from an illuminated original are directed therethrough to a projection lens for the document illumination system.

Joined along the outer edge of the reflector surface R.sub.a is a second reflector surface R.sub.b in the form of an arc of an ellipse with one of its foci, illustrated at point F, along the line A.sub.1 A.sub.2 which represents a light ray trace to the adjacent edge of the original D. One of the line foci for the surface R.sub.a commences at the point F and extends for the full length of the surface. This line foci is parallel to the edge of the original D that has point A.sub.2 thereat. The other focus point for the ellipsoid surface R.sub.b and therefore, its other line foci, coincides with the point on L.sub.1, the lamp center line. The light ray A.sub.1 A.sub.2 is produced by the reflection of a light ray from the lamp L.sub.1 directed to the point A.sub.1. Another light ray from the lamp L.sub.1 is shown being reflected by the reflector surface R.sub.b at a point B.sub.1 and is reflected to the opposite edge of the original D to a point B.sub.2. The light rays A.sub.1 A.sub.2 and B.sub.1 B.sub.2 intersect at the focus F, in fact, it is this positioning of the focus that results in the positioning of the intersecting lines. Similar light rays from the lamp L.sub.1 falling between the points A.sub.1 and B.sub.1 on the surface R.sub.b will be reflected toward the original at points between the points A.sub.2 and B.sub.2.

Similarly, each of the reflecting surfaces R.sub.b on the reflectors R.sub.2, R.sub.3 and R.sub.4, the corresponding light ray lines A.sub.1 A.sub.2 and B.sub.1 B.sub.2 will be limiting light rays, that is, those light rays between which light rays will be reflected onto a document.

With the axis of the linear light source L.sub.1 being the center of revolution for the cylindrical reflecting surface R.sub.a, light rays emanating from the light source and impinging upon this reflecting surface will be directed to the original along different lines. Light impinging at the point C.sub.1 on the surface R.sub.a for instance will be directed to the point A.sub.2 on the original. Another light ray from the lamp L.sub.1 impinging upon a point E.sub.1 will be directed upon the point B.sub.2, the other side of the document. Any other light ray impinging upon the reflecting surface R.sub.a between the points C.sub.1 and E.sub.1 will be reflected upon the original between the points A.sub.2 and B.sub.2.

The segment of the surface R.sub.a closest to the inner edge of the illumination assembly reflects light rays impinging thereon upon the ellipsoid surface R.sub.b rather than reflecting directly toward the document. For example, a light ray impinging upon the point G.sub.1 will be directed to the point B.sub.1 and redirected to the point B.sub.2 upon the document. Similarly, light impinging upon point H.sub.1 will be directed to the point A.sub.1 whereupon this light ray will be reflected to the point A.sub.2.

From the foregoing it will be apparent that the reflecting surfaces R.sub.a and R.sub.b serve to reflect the light rays emanating from the lamp L.sub.1 upon the original D between both extreme edges thereof in overlapping fashion. This means the light reflected from the surface R.sub.a will be directed upon the document starting from the line coincident with the adjacent edge of the original, that is, the line extending along the edge of the original starting at point A.sub.2, and sweeping across the document to the other edge thereof terminating in a line having its beginning at point B.sub.2. Light reflected from the ellipsoid reflector R.sub.b is directed upon the document between these identical lines, that is, between lines beginning at A.sub.2 and B.sub.2, respectively. The light rays reflected from the surface of the segment of the surface R.sub.a nearest the adjacent edge of the original is reflected back upon the ellipsoid reflector R.sub.b and reinforces the light already directed upon this surface from the lamp L.sub.1 directly, and from the outer segment of the surface R.sub.a.

Similarly, as viewed in FIG. 5, the reflector R.sub.3 serves to reflect light from the lamp L.sub.3 upon the original D. The light rays so reflected overlap those reflected from the reflecting surfaces of the reflector R.sub.1. In similar fashion, light is directed from the reflectors R.sub.2 and R.sub.4 by reflection from the lamps L.sub.2 and L.sub.4, respectively, upon the original in overlapping ray-trace arrangement.

The effect then, of the use of four orthogonally arranged lamps arranged beyond the edges of an original being illuminated, and especially with the provision of the specifically designed reflecting surfaces for each of the reflectors and the relative positions thereof, an original is illuminated in such a manner that the object irradiance is cos.sup..sup.-4 or otherwise circularly symmetrical for the center point of the surface of the original. It will be apparent from this arrangement of reflecting surfaces that the illumination apparatus 10 makes effective use of a large part of the light flux emitted from the light sources except for those areas wherein reflection losses are behind the lamps themselves.

It will be appreciated that the arrangement of the lamps provides cos.sup..sup.-4 illumination. By incorporating the illustrated elliptical reflector R.sub.b with each of the lamps, the resultant illumination profile for an object being illuminated is changed to be symmetrical. The use of the right circular cylindrical surfaces R.sub.a adds efficiency to the system.

Each of the lamps L.sub.1, L.sub.2, L.sub.3 and L.sub.4 is connected to an electrical circuit for energizing these lamps. For the particular reproduction machine illustrated in FIG. 2, the particular electrical circuit for energizing the lamps is in the form of a flashing circuit which will energize the lamps for short periods of time, such as, for example, 100 microseconds. In this particular use, this short period of time will be suitable for flash exposing the original D upon a photoreceptor surface such, for example, as the selenium belt 12, to be described hereinafter.

The image forming light rays emanating from the original D during illumination thereof are directed to a projection lens system generally indicated by the reference numeral 30. For simplicity, light rays from each of the four corners of the original will be described and illustrated as an indication of the ray traces for the illuminated original. The light rays from the four corners of the original, illustrated at A.sub.2, B.sub.2, K.sub.2 and M.sub.2 in FIG. 3, are directed through the projection lens 30 onto a first plane mirror 36 supported by brackets 37 within a mirror housing 38 secured to a suitable frame 39. The mirror is inclined at approximately 45.degree. from the horizon for the vertically oriented optical axis 0 of the projection lens. Light rays reflected from the mirror 36 are directed upon a second plane mirror 40 supported by clamps 41 to inside portions of the housing 38 and is arranged with its plane at 45.degree. to the optical axis of the projection lens 30. The mirror 40 is also rotated 45.degree. relative to the plane of the mirror 36 in order to direct image rays therefrom along an optical axis normal to the optical axis 0 for the lens 30. The light rays reflected from the mirror 40 are directed upon the photoconductor surface of the selenium belt 12 arranged so that the exposure section thereof is flat and, positioned vertically and normal to the impinging leg of the optical axis 0 for the image rays emanating from the mirror 40.

Each of the brackets 37, 41 are adapted to adjustably support their respective mirrors 36, 40 in order to insure that the image rays emanating from the document D will be directed centrally upon the selenium belt 12 at the exposure station A. With the use of a projection lens and two plane mirrors, the image formed upon the surface of the belt 12 will be upright and wrong reading and will expose the previously charged belt 12 for producing an electrostatic latent image thereon.

The illumination assembly 10, by virtue of the illumination housing 31 and the mirror housing 38 both of which are light tight and preferably coated with black paint or the like internally, will prevent image light rays from being distorted and affected by any external lighting. The assembly 10 is adapted to present light image representation of an original upon the selenium belt 12 sequentially in timed relation to the movement of the belt which in the particular xerographic reproduction apparatus to be described hereinafter, continuously moves during the xerographic processing stations. The light image of the original being reproduced, in being reflected by the mirror 40 is directed out of the mirror housing 38 through a suitable rectangular opening on the side of the housing adjacent the selenium belt 12. The housing 38 then serves as a light shield for the selenium belt in order to prevent extraneous light from impinging upon a belt during use of the apparatus.

PHOTOCONDUCTIVE BELT ASSEMBLY

(FIGS. 7-13)

The selenium belt comprises the photoconductive layer selenium which is the light receiving surface and imaging medium for the apparatus, on a conductive backing. The belt is journaled for continuous movement upon three rollers 45, 46 and 47 located with parallel axes at approximately the apex of a triangle. During exposure of the belt 12, the portion thereof being exposed is that part of the belt run between the upper roller 45 and the lower roller 46. As shown in FIG. 7, the photoconductive belt assembly 11 is illustrated with the selenium belt removed in order to illustrate the assembly mechanisms located adjacent the belt.

The upper and lower pulleys 45 and 47 are journaled in two side plates 48 and 49, each having the general configuration of a triangle. The upper apex of the side plate 48 is formed with an opening for containing and supporting a bearing 50 which rotatably supports one end of the shaft 51 for the roller 45. At the other end, the shaft 51 is journaled in a bearing 52 supported at the upper apex for the side plate 49 in the same manner; however, the shaft extends beyond the side plate and through an opening 53 formed concentrically with the shaft in a main support plate 54 for the reproduction apparatus. A shaft extension 55 is formed on this end of the shaft and extends through the opening 53.

The purpose for the extension 55 of the shaft 51 is to support a drive mechanism for rotating the roller 45 when the belt assembly 11 is in operating position, that is, when the side plate 49 is positioned against the main frame plate 54, and still permit the easy removal of the belt assembly 11 from the machine frame. To this end, the main frame plate 54 is provided with a quick disconnect mechanism for releasably receiving the extension 55 and to become drivingly engaged with the extension when the assembly 11 is in operating position. As shown in FIG. 10, the opening 53 in the frame plate 54 is covered on one side, the side removed from the roller 45, by a support ring 56 suitably secured by bolts to the remote side of the plate 54. The ring 56 is formed with an opening 57 concentric with the opening 53 and the shaft 51 when in operating position. Within the opening 57 is retained a bearing 58 having an inner race 60 secured by a lock ring 61 to a drive member 62 rotatably retained by the bearing 58 upon the plate 54. The drive member 62 is formed with a concentrically positioned recess 63 into which is inserted the extreme end of the extension 55. This end of the extension has a snug fit within the opening 63 and serves to precisely locate the axis of the shaft 51 relative to the support frame plate 54 thereby insuring accurate driving of the selenium belt 12.

The driving connection between the shaft 51 and the drive member 62 is in the form of a one way clutch 64 drivingly connected between the extension 55 and the member 62. The clutch 64 is adapted to become engaged when the assembly 11 is in operating position in order to permit rotation of the roller 45 by rotation of the drive member 62. When the belt assembly 11 is slightly removed or pulled away from the frame plate 54, the clutch 64 and the extension 55 are pulled out of the recess 63 in the drive member 62 in order to disengage the connection therebetween.

The outer extremity of the drive member 62 is adapted to support a drive gear 65 which meshes with a smaller gear 66 secured to a pulley 67 drivingly connected by way of a timing belt 68 to a drive system to be described hereinafter.

The side plates 48 and 49 are maintained in parallel planes and rigidly supported in spaced relation for supporting the rollers 45, 46 and 47 and all of the other structures that comprise the belt assembly 11 by an internal T-member to be described below. The side plates 48, 49 also support a flat front plate 69 and a rear flat plate 70 by suitable means such as screws 71. Each of the plates 69 and 70 are formed with a plurality of apertures 72 which extend through the respective plates. As will be described in detail hereinafter, the plates 69 and 70 serve as vacuum hold down plates for supporting the selenium belt 12 flat against the plates during movement thereof on the assembly 11. The apertures 72 are in communication with a plenum chamber which, in turn, is connected by suitable ducts to a vacuum chamber for drawing air inwardly through the apertures 72 and thereby hold by vacuum the adjacent runs of the belt 12.

The lower roller 47 is similarly mounted upon the side plates 48, 49 as is the left-hand end of the shaft 51 for the roller 45. The shaft 73 for the roller 47 may be suitably supported in ball bearings similar to bearing 50 supported in the side plates 48, 49.

As previously stated, the selenium belt assembly 11 is slidably supported on the machine frame plate 54. To this end, the frame plate 54 has extending horizontally and perpendicular thereto a support arm 75 having a cross section shaped as the letter T.

Secured to the upper cross bar of the support arm 75 is the lower race 76 of a slide suspension arm which also includes an upper race 77 secured to the upper leg of a T shaped channel member 78 secured between and supporting the side plates 48, 49 of the belt assembly 11. The channel member 78 is approximately positioned within the center space of the belt assembly and also has secured on one side thereof a race 80 of another slide suspension arm which has its other race 81 secured to the adjacent lower section of the support arm 75. Upon viewing FIG. 11 it will be apparent that a belt assembly 11 is adapted to be moved toward and away from the frame plate 54 and to be supported thereon for sliding movement by the support arm 75, the sliding characteristic being supplied by the slide suspension arms comprising the races 76, 77 and 80, 81. When mounted on the arm 75 in cantilever fashion, all of the mounting means for the belt assembly are positioned within the confines of the assembly as defined by the axes of the rollers 45, 46, 47. This arrangement allows access to and clearance for the belt for permitting removal or installation of the same without endangering its structure.

The T-members 75 and 78 together with the slide suspension arms connected therebetween and the shaft extension 55 and the drive member 62, allows the belt assembly 11 to be removed and positioned for support upon the fixed support plate 54 without disrupting or requiring a drive connection and, to insure safe positioning of the belt and the assembly. Guide slots 79 formed in the plate 54 receive locating pins secured to the plate 49 for precisely locating the assembly 11 once it has been moved into operating position.

Each of the side plates 48, 49 is formed with axially aligned openings 82 in order to accommodate the support arm 75 during mounting or removal of the assembly 11. These openings, only one of which is shown, also serve to permit the extension therethrough of a locking mechanism for releasably holding the assembly 11 upon the plate 54 when the assembly has been moved thereto.

This locking mechanism includes a pair of blocks 83, 84 secured within the chamber defined by the plates 48, 49 and one to each of these plates. A shaft 85 is slidably received in the blocks 83, 84 and extends through the opening 82 formed in the plate 48 a short distance to accommodate a handle 86 at that end thereof. The other end of the shaft 85 extends through the other opening 82 formed in the side plate 49 and extends beyond an opening formed in the frame plate 54 in line with the opening 82. This end of the shaft 85 terminates in a bent portion 87 (see FIG. 8) which is adapted to be moved to assume different radial directions upon rotation of the shaft 85 by the handle 86. The bent portion 87 is adapted to be received in a depression 88 formed in a circular lock member 89 secured upon the outer surface of the frame plate 54.

Normally, the shaft 85 is urged outwardly or to the right as viewed in FIG. 10 by a spring 90 held in compression between the handle 86 and one side of the block 83. When the assembly 11 is removed from the frame plate 54, the spring 90 will cause the bent portion 87 to abut against the block 84. In order to lock the assembly 11 against the plate 54 and assuming that the assembly 11 is properly oriented upon the plate, the handle is pushed toward the adjacent side plate 48 in order to drive the bent portion 87 through the opening 82 in the plate 49 and the adjacent opening in the frame plate 54. Rotation of the handle while so depressed will rotate the bent portion 87 in position to be in alignment with the depression 88 formed in the lock member 89. Upon release of the handle 86, the spring 90 will force the shaft 85 outwardly thereby causing the bent portion 87 to assume a locked position within the sides of the depression 88. In this manner, the assembly 11 remains rigidly locked in proper position and alignment upon the frame plate 54.

As previously stated, the apertures 72 formed in the vacuum plates 69 and 70 are in communication with plenum chambers which, in turn, are connected to a vacuum manifold which is suitably connected to an evacuation system, such as a blower and the like, in order to produce a slight vacuum within the plenum chambers. As shown in FIG. 11 the front or exposure side of the belt assembly 11 is connected by means of end strips 92 to a rear base plate 93 mounted parallel to but spaced slightly from the front vacuum plate 69. The flat chamber formed between the plates 69 and 93 and the end strips 92 define a vacuum plenum having an outlet slot 94 (see FIG. 8) which is arranged, when the assembly 11 is in locked position upon the plates 54, to be in communication with an opening formed in the plate 54. The edges of the slot 94 are gasketed so that when in abutment with the adjacent surface of the frame plate 54 and in alignment with a slot opening formed therein of a size and shape as the opening 94, there will be a minimal amount of leakage of air through these abutting surfaces.

The opening 94 may be suitably connected to a hose or manifold to a suitable blower which would in operation evacuate air from the plenum chamber and cause the flow of air inwardly through the openings 72. This vacuum condition will cause the selenium belt 12 to be drawn against the plate 69 during movement of the belt during processing by the machine. Since the plate 69 lies in alignment with the exposure station for the selenium belt, it is imperative that the selenium belt, as it moves across the station, be as flat as possible so that light ray impinging upon the selenium belt at this area will be in focus at all points.

Similarly, the rear vacuum plate 70 combines with a parallel spaced base plate 96 and end strips 97 to form a second plenum chamber which is also connected to a suitable opening in the base plate 54 and connected to a blower or vacuum producing apparatus. The rear vacuum plate 70 and its related plenum structure is adapted to hold the selenium belt in a flat plane on this side of the belt assembly, which side is adjacent, as will be described hereinafter, to a development apparatus which requires that the selenium belt be or remain in a flat condition.

As previously stated, the selenium belt rollers 45 and 47 are mounted for rotation upon the side plates 48, 49, being held against any other movement relative to the side plates by suitable mounting bearings. In order to permit the mounting and dismounting of a selenium belt 12 upon the belt assembly 11, the assembly is provided with an arrangement for moving the third roller 46 inwardly in order to form a slack in the belt 12 for permitting its removal by sliding axially of the rollers. As part of this arrangement, the roller 46 is rigidly secured upon a shaft 100, the ends of which are each mounted within a self-aligning bearing element 101 adapted to be secured to each support arm 102, 103.

Each of the support arms 102, 103 is arranged for longitudinal movement for one operative function therefor and, for limited rocking or slight pivotal movement for another operative function. To this end, each of the support arms comprises a first slide member 104 to which the bearing element 101 is secured for supporting the roller 46 upon the belt assembly and a second slide member 105 slidably mounted relative to the first member. In order to accomplish sliding movement of one slide member relative to the other, the member 104 is formed with an elongated depression 106 running along the longitudinal axis thereof and, within the depression, the slide member 105 conforms and is held against removal therefrom by suitable lock strips 107 mounted in parallel to the adjacent edges of the member 104 in overlapping relationship relative to adjacent edges of the member 105. When mounted together, the members resemble a slide rule device which may be elongated by extending the members.

The support arms 102, 103 are supported by pivot pins 108, each securing one of the arms to the lower portion of the side plates 48, 49. Each pin 108 is rotatably fastened to the slide member 105 and is slidably related to the first member 104. This arrangement has the affect of preventing axial movement of the second slide member 105 while allowing sliding movement of the first member 104 relative to the second member.

Manually operated control means are provided for producing simultaneous sliding movement of each first member relative to the respective second member in order to move the roller 46 inwardly relative to the belt assembly to permit the removal or installation of the selenium belt 12. The end of the first member 104 remote from the end thereof which supports the roller shaft 100 is provided with a cam follower 109. As shown in FIG. 12, the follower extends in a direction normal to the longitudinal axis of the support arm 102 and has a lateral extending cam surface 110 adapted to cooperate with a cam 111 formed as a semi-circular disc and being mounted eccentrically relative to the semi-circular cam surface 112 thereon. Each of the cams 111 is secured for rotation upon a shaft 113 which in turn, is mounted for rotation on the side plates 48, 49 of the belt assembly. In being secured to the shaft 113, the cam surface 112 for each of the cam plates 111 will be moved in unison when the shaft is rotated and, upon rotation, will simultaneously engage the camming surface 110 of each of the cam followers 109.

Rotation is imparted to the shaft 113 by way of a manually actuable handle 114 secured to one end of the shaft extending through the side plate 48. As shown in full lines in FIG. 9, the handle 114 is positioned such that the cam plates 110, as shown in FIG. 11, is against the shortest camming position for the cam surfaces 110, in fact, there is a slight spacing between the surface 110 and the follower 109, thereby allowing the slide member 104 to be extended outwardly to its maximum, belt supporting and tensioning limit. When the handle 114 is moved to the dotted position in FIG. 9, which corresponds to its full line position in FIG. 12, the cam plates 111, being moved thereby, will contact the surface 110 and drive the support member 104 along its longitudinal axis at its high points to the position of the cam follower 109 as shown in full lines in FIG. 12. With each slide member 104 being thereby moved, the roller 46 is moved inwardly to the position shown in FIG. 12. In this position of the roller, an operator may remove the selenium belt 12, which will be in a loose condition, from the selenium belt assembly 11.

Normally the support slide member 104 is held in its outermost maximum belt tensioning limit by means of a pair of relatively stiff springs 115 each having one end secured to a post 116 secured to the member 104 and their other ends secured to a post 117 secured to the support member 105. The post 117 extends through a slot 118 formed in the support member 104 being arranged to permit extension of the post 117 therethrough and movement of support member 104 relative to the post 117. Normally the springs 115 are held extended between the post 116, 117 thereby normally maintaining the slide members 104, 105 toward their extended position.

This arrangement places a spring bias upon the supporting shaft 100 for the roller 46 toward its fully extended position during operation of the belt assembly. The springs 115 therefore also serve to place appreciable tension upon the selenium belt 12 during movement thereof on the belt assembly. In the event that the photoconductive belt is to be removed and replaced by another belt, the operator manipulates the handle 114 from the position shown in dotted lines to the position shown in full lines in FIG. 12 thereby actuating the support member 104 inwardly against the bias provided by the springs 115. This movement is accomplished rather smoothly with the shaft 100 being moved from its outermost operative position to its most inwardmost position that is parallel to the operative position.

Each of the support arms 102, 103 is adapted to be rotated about its respective pivit pin 108 and in opposite directions in order to rock the shaft 100 in a plane normal to the plane defined by axes of the support arms. This rocking movement is provided in order to permit tracking of the selenium belt during its continuous movement around its three support rollers. This tracking capability is provided in order to maintain the belt in a precise predetermined position for all xerographic stations surrounding the belt assembly 11 when in operation. The tracking is accomplished by mechanisms which are adapted to slightly pivot each of the arms 102, 103 in opposite directions about their respective pivot pins 108, as previously stated.

As shown in FIG. 12, the end of each slide member 105 remote from the end adjacent the shaft 100 is formed as a yoke element 120 that is in alignment with the longitudinal axis of the slide member. This end of each support arm is also formed with a slot 121 having its longitudinal axis normal to thelongitudinal axis of the member 105. Each slot is adapted to accommodate a screw 122 having its threaded portion secured into the inner surface of the plates 48, 49 of the belt assembly 11. Portions of the screws 122 that are cooperable with the sides of the slots 121 are free of threads and serve to maintain the arms 102, 103 against the side plates for the selenium belt assembly. The inner edges of the yoke element 120 are formed with camming surfaces 123 and 124 held in abutment against a cam shaft 128 which extends through the belt assembly 11 and is mounted in suitable bearings 130 secured to the side plates 48, 49.

As shown in FIGS. 10 and 11, the shaft 128 has its on-axis end portions 131 mounted in the bearings 130 and portions 132 eccentric relative to the main portion of the shaft. Each eccentric portion 132 is adapted to engage one or the other of the camming surfaces 123, 124. Upon rotation of the shaft 128 in either direction, each eccentric portion is adapted to drive the corresponding yoke member 120 laterally in opposite directions in order to pivot the corresponding support arm 102, 103 about their respective pivots in opposite rotational directions thereby effecting opposite movements to each end of the shaft 100.

In order to provide movement of both ends of the shaft 100 in opposite directions thereby effecting a greater available movement to the roller 46 the eccentricity of the cam portions 132 are in opposite directions. Upon rotation of the shaft 128, the axis of the main portion thereof will remain fixed and will move the cams 132 in the same direction to effect corresponding pressures upon one of the camming surfaces 123, 124 in opposite directions, that is, the camming surface 123 for one of the support arms 102, 103 will be moved in one direction, and the camming surface 124 of the other arm will be moved in the opposite direction. The effect of this opposite directional movement of the support arms 102, 103 will produce rocking movement of the shaft 100 and consequently the roller 46. The spherical bearings upon which the shaft 100 is mounted will permit this slight relative rocking movement of each end of the shaft relative to its fixed mounting arrangement in the form of the members 104.

As shown in FIG. 11 the axes of the shaft 100, the pins 108 and the shaft 128 for the support arm 102 are in alignment and, for both arms 102, 103 these axes lie in a common plane. This plane is in coincidence with the bisector of the angle formed between the planes of the belt runs on either side of the roller or, in other words between the plane defined by the axes of the shafts 100 and 73 and the plane defined by the axes of the shaft 100 and the shaft 51. With the support arms 102, 103 being equally pivotable in opposite direction the roller 46, during tracking operation, will rock about an axis lying on the bisector plane and positioned intermediate the ends of the roller. For tracking then, such skew action of the roller will effect an angular relationship of the roller relative to the direction movement of the belt thereby causing the same to steer or follow the roller surface and be displaced laterally in order to return the belt back to a centered position rather than exerting pressure on the belt adjacent one edge portion thereof. In this manner pressure is applied equally to all portions of the belt affected during tracking action thereby minimizing the tendency of the tracking arrangement to adversely affect belt structure by exerting undue pressures of the belt structure adjacent one edge of the portion between the midline of the belt and one edge. With the axis of pivoting of the roller 46 lying on the bisecting plane for the planes of the selenium belt runs, the deflection of the ends of the roller occurs in opposite direction to provide maximum belt correction with minimum roller skewing. Preferably the roller 46 is covered with a rubber coating which will prevent slippage of the belt as it steers during tracking. During rocking of the shaft 100, both edges of the belt are affected equally and, as skewing increases during tracking action, any tendency of the belt to lessen in circumference will cause movement of the roller 46 inwardly against the tension of the springs 115 which serve as shock absorbers for tracking action.

In the event that the selenium belt 12 is removed and a new one applied to the belt assembly which has a slightly larger or smaller circumference, the springs 115 will always maintain the same pressure of the roller 46 upon the belt thereby insuring the same tension upon a belt regardless of its circumferential size. The arrangement also eliminates any two-directional forces being applied to the belt which could have a destructive effect upon the relatively thin film of the photoconductive material on the belt. In addition, with the axis of the roller 46, lying on the bisecting plane of the angle between the adjacent belt runs during rocking movement of the roller 46, there is a minimum of deflection, caused by skewing of the belt, along the exposure belt run between the rollers 45, 46 thereby minimizing the effect of belt skewing upon the imaging abilities on this run during an exposure of an original.

Drive means are provided in the belt assembly 11 in order to impart controlled instantaneous rotation of the shaft 128 in either direction depending upon the slipping of the belt axially relative to the shafts of the rollers 45, 46, 47 in either direction. The shaft 128 has its end portion 131 extending through the side plate 49 and terminating in a gear 133 secured thereto. The gear 133 is in mesh with a second gear 134 secured to a shaft 135 for a reversible motor M-11 and gear reduction arrangement 136. Energization of the motor M-11 will impart rotation to the gears 133,134 for rotating the shaft 128 in either direction depending which direction the belt 12 slips relative to supporting rollers.

Energization of the motor is accomplished by means of a sensing device comprising a potentiometer POT (not shown) having a sensing finger positioned adjacent an edge of the belt 12. In the event the belt strays the potentiometer and its associated circuitry will produce a signal to cause energization of the motor M-11 and rotation thereof in a direction to cause the roller 46 to rock into a position to force the belt back toward the direction opposite the slipping direction.

DEVELOPER ASSEMBLY

In order to effect development of the electrostatic latent image on the selenium belt 12, the development system for the xerographic reproduction machine, shown in FIG. 2, includes a developer assembly 14 (see FIGS. 13-27) which coacts with the selenium belt 12 at the development zone B along the rear vacuum plate 72 of the belt assembly 11. At this development zone, the charged exposed surface of the belt 12 is developed to form a powdered toner image of the original that was previously illuminated.

For this purpose, the developer assembly 14 is mounted adjacent to the belt assembly 11 to establish the development zone B. Mounted within the developer assembly 14 is a screw conveyor arrangement utilized in conjunction with an internal bucket conveyor belt for continuously circulating developer material previously supplied to the upper end of the developer assembly and from where the developer material is cascaded over the now inclined upperly moving selenium belt 12 in order to accomplish development of the latent image thereon. As the developer material cascades over the flat run of the belt 12, toner particles of the developing material adhere electrostatically to the previously formed electrostatic latent image areas on the belt, the remaining developer material falling off the lower portion of the belt assembly adjacent the roller 47 or the peripheral surface thereof to be deflected by suitable baffle plates into the bottom sump of the developer assembly 14. Toner particles consumed during the developing operation to form the visible powder toned image is replenished by the toner dispenser 15 mounted external to the developer assembly.

Specifically, the developing assembly 14 includes an elongated, vertically inclined, boxlike developer housing 200 having a top wall 201, a bottom wall 202 in the form of a toner pick-off baffle, side walls 203 and 204, a front wall 205, and a rear wall 206. As shown in FIGS. 13 and 18, the side walls 203 and 204 are shaped with a vertically inclined straight edge portion and a lower curved portion in conformity with the shape the selenium belt 12 assumes during the development function of the machine, as defined by the vacuum plate 70 and the adjacent portions of the belt roller 47 to permit the developer housing to be positioned closely adjacent to the belt. Secured to the inside faces of the side walls 203 and 204 are side baffle plates 207 which support upon and hold against the respective side plates a packing material in the form of strips 208 which extend slightly toward and against the selenium belt when the developer housing 200 is in operating position in order to prevent excessive dust and air currents from circulating within the developer zone adjacent the belt during a developing function. In effect, the packing strips 208 conform to the shape of the belt 12 and may be depressed slightly as the case of a sealing element in order to form a powder tight seal between the developer housing 200 and the photoconductor belt 12.

In order to be disposed for high quality reproduction, the developing assembly is capable of accomplishing line copy development and solid area development. This is made available by use of a development electrode 210 mounted upon the housing 200 as the front wall 205. The development electrode 210 is positioned so as to assume a spaced relationship relative to the adjacent run of the selenium belt or that run when the belt is held against the rear vacuum plate 70. The development electrode is shaped as a thin wall rectangular plate and includes a thinner walled narrow extension plate 211 which serves as an entrance chute for developer material and which is mounted on but electrically insulated from the top edge of the main electrode plate 210.

Means are provided for mounting the development electrode such that the electrode may be individually adjusted at each of the corners thereof in order to insure exact spacing of the electrode relative to the selenium belt at all points thereon. Since all four of these devices are exactly the same, only one of them will be described in detail. In FIG. 18, the electrode 210 is shown as being formed with a recess 212 for rigidly supporting a bearing block 213 into which is positioned a spherical knob 214 having a screw shank 215 secured thereto and being threadedly received in a supporting block 216. The support blocks 216 used in supporting the electrode 210 may be suitably secured to the side plates 203, 204 of the developer housing and are suitably insulated relative thereto. A lock plate 217 is secured to the inner surface of the electrode 210 in a position to overlie the recess 214 and, is formed with an opening through which the threaded shank 215 projects.

This arrangement secures the knob 214 and shank 215 to the development electrode but allows a limited rotary or universal pivoting movement of the shank 215. The shank portion 215 is adapted to receive a nut 218 which bears against the surface of the support block 216 thereby serving as a means for axially moving the shank 215 for positioning this particular corner of the development electrode 210 relative to the fixed support block 216. The electrode adjustment device is provided on each four corners of the development electrode 210 thereby providing individual adjustment means for the electrode.

During the developing function, development material comprising very small diameter carrier beads having smaller toner particles electrostatically adhering thereto, is introduced in the space between the development electrode 210 and the adjacent run of the selenium belt 12. As will be described more fully hereinafter, the development material is introduced along a thin slot formed between the belt 12 and the adjacent longitudinal edge of a plate 220 secured in the upper region of the developer housing 200. The development material then is cascaded downwardly and enters the space between the tapered portion 221 at the upper edge of the electrode entrance chute 211 which, as observed in FIG. 18, is spaced at a slightly greater distance from the belt 12 than is the lower main portion of the electrode. The development material then falls freely between the electrode portions and the selenium belt during which time and distance the toner particles are pulled away from the carrier beads by action of the electrostatic charged image on the belt 12.

In order to enhance high quality development of the electrostatic latent image, it is desirable that the electric lines of force be drawn from the image itself with equal effect. Since development of latent image depends upon field strength and time within the developing zone, and field strength is a function of area charge or charge density, the areas of the latent image possess varying charge densities depending upon and related to the light pattern produced during the illumination stage of the reproduction cycle. In order to develop areas in proportion to their charge densities, it is necessary to create an external field strength pattern corresponding to the charge pattern on the plate surface. This field pair is created by the use of the development electrode 210 being properly spaced uniformly relative to the adjacent run of the selenium belt and the amount of electrical potential applied to the electrode. This spacing results in equal representation of field strength over areas of the electrostatic latent image having equal charges and proportionately different representations over proportionately different charged areas of the image. Since development time is the same over all areas on the selenium belt and inasmuch as field strength extended outwardly from this surface is proportional to the charge pattern, then the developed image is a true representation of the existing charge pattern.

Preferably, the development electrode 210 is spaced as close as possible taking in consideration that the spacing between electrode and the selenium belt 12 influences the electrostatic field strength and must be such that the cascading development material has sufficient spacing to be free to fall in cascading motion therebetween. This spacing is also arranged as a factor of the strength of the charge pattern in the latent image itself. For relatively high charges, a greater spacing may be possible.

The free-flowing cascading movement of the development material is relatively fast since the fall is at a relatively small angle relative to the vertical. This developer material movement results in a reduction in pressure in the development zone that encompasses the entire area of the development electrode. This reduction in pressure has a tendency to draw the selenium belt closer to the development electrode. However, in view of the provision of the vacuum producing device and the vacuum plate 70 immediately behind the selenium belt, the latter is held against the vacuum plate in order to maintain uniform spacing at all times for the belt as it travels in continuous motion around the belt assembly. As will be described hereinafter, the selenium belt is charged with a potential of approximately 800 volts and when areas are discharged thereon after the exposure function, the background areas which become discharged may possess a residual charge of anywhere from 0 to 50 volts. Generally the full charge remains on the image areas, that is, 800 volts or slightly less.

The development electrode 210 causes the lines of force from the charged areas to be directed in general parallel relationship toward the electrode and in perpendicular relationship to the image surface. This results in uniform inherence of the developer toner powder over the image area and produces a uniformly dark or concentrated image with lines that are not diffused as distinguished from powder developing devices in which there is no development electrode and in which the lines of force from the edges or outer portions of the high charged image areas are consequently directed in curved paths to the adjacent discharged or background areas resulting in the lines of force being dissipated from the image area and producing black or dark effects around the edges and light or white effects at the central portions of the normally solid areas.

A potential is applied to the development electrode 210 and another potential to the entrance chute 211 by a circuit to be described hereinafter in order to maintain a bias on the electrode elements of approximately 80 to 100 volts with the polarity the same as that of the charged image areas and which is at a greater voltage but of the same polarity as the charge on the background areas. In this manner, the residual charge on the background areas are neutralized and the electrode 210 prevents toner particles from adhering to the background areas. In effect, the resultant transferred image upon support material such as a sheet of paper will be relatively free of background toner particles thereby enhancing the contrast and improving the quality of the resultant reproduced copies.

Denuded carrier particles and other toner particles which were not employed in developing the latent image and which have passed into the lower spacing between the plate 210 and the belt 12 are deflected upon the pick-off baffle 202 which is electrically biased and carries the particles back into a conveyor system for the development material. These particles are conveyed to a chute 223 extending across the entire width of the housing 200 and being suitably mounted on the side plates 203, 204 thereof. The toner particles and denuded carrier particles are directed by the chute 223 into a developer material return system comprising a first conveyor screw arrangement for conveying development material that has been cascaded over the surface of the belt 12, an internal bucket vertical conveying belt for conveying this material vertically to a position above the entrance chute 211 for the development electrode 210 and, a second conveyor screw for conveying the development material horizontally from the internal bucket conveyor belt to position developer in a sump which is in communication with the upper reaches of the spacing between the development electrode and the belt 12 preparatory to continuous recascading of the material across the selenium belt 12. The chute 223 directs developer material through an elongated slot 224 formed in a lower conveyor tube 225 secured to the side plates 203, 204 and extending out of the housing 200. The tube 225 houses a screw conveyor 226 which is continuously rotated during operation of the developer assembly and which functions to convey developer material horizontally out of the developer housing 200 and into a vertical return system.

Developer material is conveyed out of the developer housing 200 and into a developer return housing 227 mounted in spaced relation and parallel to the side plate 203 for the housing 200. The developer return housing has an elongated configuration, the axis of which is in alignment approximately with the planar format of the developer housing, that is, slightly inclined relative to the vertical. The screw conveyor 226 is mounted on a shaft 228 that has one end mounted for rotation in bearing 230 secured to an end wall 204 of the developer housing and the other end rotatably mounted in a bearing 231 secured in a hub 232 which, in turn, is secured to the inner surface of the conveyor tube 225 at that end thereof positioned within the return housing 227. As will be described hereinafter, a drive mechanism for the screw conveyor 226 is provided for this function and other driving functions relative to the developer return system.

Developer material being conveyed by the screw 226 is carried within the housing 227 and to an opening 234 formed in the lower portion of the tube 225 within the housing 227. The opening 234 permits the egress of the developer material from the tube and directs the material into any one of a plurality of internal buckets 235 formed as part of an internal bucket conveyor belt 236 which encircles the tube 225 at this point.

The conveyor belt 236 is constructed so that its internally directed buckets 235 are slightly longer in length than the egress opening 234 to insure a minimum of loss of developer material. The construction of the belt 236 is shown in greater detail in FIGS. 21-24 and, as illustrated, it will be appreciated that the belt is constructed as a unitary element that may be fabricated as an integral unit by a suitable molding process. The belt 236 is relatively wide and is constructed as an endless conveyor utilizing a plurality of internal buckets 235 each of which has a length approximately two-thirds the width of the belt. Formed internally along each of the outer edges of the belt for the entire circumference thereof are evenly spaced teeth 237 which are arranged for use as timing belts 238 for driving the conveyor belt 236 during conveying of the developer material.

Each of the internal buckets is defined by a circular wall 240, one on each side of the belt between the buckets and the adjacent timing belt. During construction of the belt 236, it is preferable that the timing belts 238, the circular walls 240, and the buckets 235 are fabricated as a unitary structure. The portion of the circular walls 240 located at the end of each bucket is formed with a fanfold construction comprising small triangular shaped panel walls 241, 242 for each end of a bucket 235. The panel sections are adapted to be flexed relative to each other along flexure lines 243 formed in the circular wall and, each of the panels 241 is adapted to flex inwardly along a line 244 formed at each end of a bucket. This flexure occurs for both of the circular walls 240 when the conveyor belt 236 is driven around the tube 225 for the screw conveyor 226. As shown in FIG. 17, as the buckets 235 are driven around the tube, the entrance slots for the buckets become more narrow since they are assuming a smaller circumference than the outer portions of the buckets adjacent the outer-most portions of the belt. In order to prevent compaction of the material contained in each of the buckets as the entrance slots therefor become smaller, the amount of developer material allowed to enter a bucket is held to approximately two-thirds of its total volume. During movement of the belt around the tube 225, the panels 241 and 242 will deflect slightly inwardly without causing compaction of the material therein in order to prevent the lateral lengthening of the buckets with the consequent bending of the material comprising the walls 240 against supporting pulleys therefor.

As the developing material is directed into the buckets 235, the belt 236 continuously moves in the direction shown by the arrow in FIG. 17 to bring the development material to a higher point above that in which cascade upon the selenium belt 12 will occur. Upon reaching its uppermost point, each of the buckets are drawn around a conveyor tube 245 extending through the return housing 227 through a slot 246 formed in the upper portion of the tube. As the buckets 235 are moved upwardly and around the tube 245 and when the opening slots of the buckets are in register with the opening 246, the development material is adapted to be poured from each of the buckets and into the interior of the tube 245.

The tube 245 is similar to the tube 225 and serves to contain a conveyor screw 247 which serves to convey developing material horizontally from the developer return housing 227 and into the developer housing 200 preparatory to movement of the developer material into cascading position. The screw 247 is mounted for rotation upon a shaft 248 supported in a bearing 249 mounted in the end plate 204 and a bearing 251 secured in a hub 252 mounted on the internal surface of the end of the tube 245. The shafts 228 and 248 for the screw conveyors 226 and 247, respectively, are parallel to each other and preferably, have their axes in a plane parallel to the plane of the selenium belt 12. During operation of the developer assembly, the lower conveyor screw 226 and the upper conveyor screw 247 are driven in unison in opposite directions and, are adapted to convey each in its own direction as indicated by the arrow, approximately the same quantity of development material in order to prevent the advancement of movement of development material of one of the screw conveyors over the other.

In order to effect vertical continuous movement of the developer material from the sump of the developing housing and into a higher position by means of the conveyor belt 236, there is provided a pair of pulleys 253, 254 arranged around conveyor screw 226 for the lower end of belt 236 and, a second pair of pulleys 255, 256 arranged around the conveyor screw 247 for the upper end of the conveyor belt. The lower pulleys 253, 254 are arranged co-axially in spaced relation by a cylindrical cage element 257. The spacing of the lower pulleys 253, 254 are slightly greater than the length of the buckets 235 and are formed as of timing pulleys engageable with the timing belts 238 formed on each edge of the conveyor belt 236. Similarly, the timing pulleys 255 and 256 are held apart in spaced relation upon a cage element 258 and engage the timing belt 238. Each of the cage elements 257 and 258 are formed as rods 259 (see FIG. 17) radially extending from the axis of a shaft 228 and evenly spaced therefrom to provide fairly large openings therebetween. The rods 259 are preferably made integral with the spaced pulleys which they separate in parallel relationship. Similarly, the upper cage element 258 is formed as a semi-cylindrical thin walled element which may be made integral with the adjacent sides of the pulleys 255, 256.

In order to impart movement to the belt 236 for producing conveying action, the lower outside pulley 254 is formed with an annular hub 260 which extends through a suitable opening in the side plate of the housing 227. A driven pulley 261 is fastened by screws to the hub 260 and is connected by a timing belt 262 to a smaller pulley 263 secured to a shaft 264 mounted by brackets 265 on the developer housing 200. The shaft 264, in turn, is connected to a drive system to be described in detail hereinafter.

The driven pulley 261 and the lower pulleys 253, 254 are supported for rotation upon the tube 225 by a pair of bearings 266 one of which is positioned between the pulley 253 and the tube and, the other, positioned between the driven pulley 261 and the outer end of the tube 225. In order to prevent the leakage of developer material out of the housing 227, the opening through which the hub 260 projects outwardly is surrounded by a sealing device 267 held onto the outside wall of the housing 227 by a cover plate 268. At the other side of the housing 227 an O-ring 269 is suitably locked in position encircling the tube 225 and against metallic lock rings which hold the tube 225 in position relative to that side of the housing 227.

The upper conveyor belt pulleys 255 and 256 are mounted for rotation upon the tube 245 by a pair of bearings 270 mounted between the external surfaces of the tube 245 and the pulleys. This arrangement permits unobstructed free rotation of the pulleys 255 and 256 relative to the tube 245 and the conveyor screw 247. A threaded thimble 271 serves to lock to the outer bearing to the tube 245 and to compress a suitable sealing device 272 between the tube 245 and the side of the housing 227 in order to prevent leakage of developer material through the opening in the side wall occasioned by the protrusion of the tube.

It will be apparent that rotation of the driven pulley 261 will produce rotation of the lower conveyor pulleys 253, 254 to cause movement of the conveyor belt 236. In operation of the development return system, both of the pulley arrangements 253, 254 and 255, 256 are driven in unison in order to convey development material out of the tube 225 after the material has been cascaded across the selenium belt 12 and to convey the material vertically to a higher point to the interior of the upper tube 245. The material is poured from each of the buckets 235 in the belt 236 and through the opening 246 into the interior of the tube 245 whereupon the development material is conveyed horizontally to be spread across the entire length of a longitudinal slot 273 formed in a lower region of the tube 245 that extends into the developer housing 200.

Rotation of the conveyor screws 226 and 246 is imparted by means of a lower sprocket 274 connected to the outer end of the lower shaft 220 and an upper sprocket 275 of equal diameter, connected to the outer end of the screw shaft 248. A chain 276 is arranged around the sprockets 274, 275 for causing the same rotative movement of the screws. A drive pulley 277 is also secured to the lower conveyor shaft 228 and is connected by a timing belt 278 to a drive system to be described hereinafter.

From the foregoing description of the developer material return system, it will be appreciated that the system is adapted to retrieve previously cascaded development material and to convey the same horizontally, that is, perpendicular in direction to the free fall cascading motion of the development material, thence to convey the material vertically in a line perpendicular to the previous stage of horizontal and conveyance, to bring the development material to a higher level preparatory to the cascading action. After the development material is brought to a higher plane, it is once again conveyed horizontally and positioned to assume a continuous relatively long, flat sheet or shower of fallen developer material which disposed for cascading action over the selenium belt 12.

As the development material is poured out of the slot 273 (see FIG. 18) the material is directed into an elongated hopper 280 mounted upon the upper plate 220 in the upper region of the developer housing 200. The hopper 280 extends across the entire width of the housing 200 and is defined by an inclined top wall 281, a curved bottom wall 282 and a deflection plate 283 for directing the flow of most of the developer material from slot 273 and into the long narrow passageway 284 defined by the walls 281, 282. Some of the developer material as it leaves the deflection plate 283, is carried upon the other side of the curved plate 282 remote from the passageway 284 in order to permit some of the development material to fall by gravity through an opening 285 formed in the support plate 220 for purposes to be described hereinafter.

The development material leaving the passageway 284 continues its downward movement and flows between one edge of the plate 220 and a control plate 286 which is relatively narrow and extends across the entire width of the housing 200. The plate 286 is in the same plane as the out surface of the development electrode 205 and is formed with a lower tapered edge 287 that cooperates with the tapered edge portion 221 of the electrode entrance chute 211. Developer material in passing between the edge of the plate 220 and the opposite side of the plate 286 slides down the tapered portion 287 and into the region between it and the tapered edge 221 and then between the chute 211 and the selenium belt in position to begin the cascade development function. The developer material falls in the form of a thin, wide sheet of falling particulate material to be influenced by the electrical charge on the belt 12 and the field charge between the belt and the electrode 210. The plate 286 may be raised or lowered in order to vary the spacing between the tapered edge 287 and the cooperating adjacent tapered edge 221 to control the amount of developer material that is permitted to fall between itself and the chute.

Positioning of the control plate 286 is provided by a movable plate 290 positioned across the width of the development housing 200 and approximately in the same plane as the control plate 286 which is connected along one edge thereof. The upper edge and ends of the plate 290 are provided with tongues 291 carrying pins 292 insertable in slots 293 formed in plates 294 secured to and positioned inwardly of the plates 202, 203. At the lower tapered edge 287 of the control gate 286, there is formed at each end thereof a strap 295 having its free end formed with a suitable opening through which screw 296 extends and is fastened and received in a slot 297 for permitting the smooth control movement of the gate 286 along its plane. The screw 296 is arranged to position the tapered edge 287 closer or further away from the adjacent tapered edge of the chute 211 in order to control the amount of development material flowing therebetween. The cam screw 296 also carries a locking nut in order to lock the gate 286 in a desirable adjusted position.

The flow of developer material through the passageway 284 is under control of a gate member 298 mounted for movement toward and away from the plate 220 for controlling the amount of developer material that may reach the space between the opposing tapered edges 221 and 287. Planar movement of the gate 298 is accomplished by means of cam screw 299 made cooperable with the edges of a slot and which not only supports the gate 298 but also serves to place the lower edge thereof in abutment against the top surface of the plate 220 or to provide sufficient spacing therebetween in order to permit full egress of developer material from the hopper 280.

TONER DISPENSER

As the developing mixture is cascaded over the xerographic belt 12, toner particles are pulled away from the carrier beads and deposited on the belt to form powder images, while the partially denuded carrier beads and excess toner pass off the belt and into the developer housing 200 by way of the pick-off baffle 202 as previously described. As toner powder images are formed especially for solid area development additional toner particles must be supplied to the developing mixture in proportion to the amount of toner deposited on the selenium belt. To supply additional toner particles to the developing mixture, the toner dispensing system 15 is utilized to accurately meter toner to the developing mixture within the lower portion of the developer housing 200.

Referring now to FIGS. 16, 18, 25 and 26, toner dispenser 15 comprises a hopper or toner container 300 into which is contained a relatively large supply of toner particles that may be poured into the container from an external source through a suitable cover 301.

The container 300 is formed as a truncated bin having a lower discharge nozzle section 302 through which toner is fed into the lower conveyor tube 225. Control of the flow of toner in accordance with the density characteristic of developed images is in the form of a toner plate 303 and a metering gate 304, the latter being mounted for reciprocatory movement across the lower opening of the nozzle 302.

The metering gate 304 is mounted in a carriage 305 which is mounted for reciprocatory movement in order to move the metering gate 304 relative to the toner plate 303 and thereby produce controlled flow of toner from the container 300 into the lower conveyor tube 225.

The container 300 rests upon a frame structure 306 which has a slightly enlarged, generally rectangular shape similar to that of the nozzle section 302. Actually the nozzle section 302 fits into the interior of the frame structure which comprises longitudinally extending side frame elements 307, 308 and end elements 309. The lower edges of the side elements 309 are formed with circular edges 310 adapted to rest upon adjacent circular end edges of the opening 224 as formed in lower conveyor tube 225 and may be arranged to prevent the leakage of toner material between the edge 310 and the tube during flowing of the toner particles.

The end elements 309 are also formed with deep recesses which terminate in a flat plane surface 311 having a width slightly larger than the width of the toner plate 303 and which accommodate the ends of this plate. Each end of the plate 303 is provided with adjusting set screws 312 which are suitably rotated to position the corresponding end of the plate 303 relative to the surface 311. A lock screw 313 is slidably received through a suitable opening in each end of the plate 303 and adapted to be threadedly received in a tapered opening formed in the lower section of each of the end elements 309. The set screw 313 is formed with a shoulder engageable with the top surface of the plate 303 and when turned down serves to lock the plate upon the surface 311, being spaced therefrom by the set screws 312. The set screws 312 serve as adjusting devices for the plates 303 in relation to the relatively fixed metering plate 304 in order to maintain the spacing between these plates at a predetermined distance which may be set in accordance with the toner material and the diameter of the individual particles thereof.

As previously stated, the carriage 305 is mounted for reciprocatory motion relative to the nozzle section 302 for imparting corresponding motion to the metering gate 304. In order to accomplish this reciprocatory motion the frame structure 306 is provided with a pair of guide rods 314 mounted with their axes in parallel, in spaced relation on either side of the nozzle section 302 and slightly above the position of the gate. The rods 314 are suitably retained within apertures formed on both of the end elements 309. As shown in FIG. 25, the carriage 305 includes end slide elements 315 which are connected at the ends of a longitudinally extending frame 316 to which the metering gate 304 is attached. The frame 316 is also provided with a rear upstanding slide element 317 through which the rear guide rod 314 extends. The rods 314 support the carriage 305 by means of the two end elements 315 and the rear element 317 in a sliding relationship in order to permit reciprocatory motion by the carriage.

In order to impart motion to the carriage 305, a front frame section of the frame 316 is provided with a vertically extending slot 318 formed in a central portion between the end elements 315. The slot 318 is adapted to slidably receive a drive pin 320 secured off center relative to a rotatable drive element 321 which in turn is secured to the drive shaft 322 extending from a gear reduction box 323 which derives its power from a motor M-10. Upon energization of the motor M-10, the gear box 323 imparts motive force to the drive element 321 for producing circular orbital movement of the drive pin 320. Since the drive pin 320 is confined within the vertical slot 318, as the pin orbits, the carriage 305 will reciprocate in a horizontal plane a total distance equal to the diameter of the orbital movement of the pin 320. Energization of the motor M-10 for this purpose is under control of a toner sensor control to be described hereinafter.

The toner container 300 is also provided with a periodically energized solenoid on each side thereof. As shown in FIGS. 16 and 18 a pair of solenoids SOL-5 are mounted on each side of the container 300 and are contained in suitable housings 326. Each solenoid is provided with a weight 327 attached to the armature for the solenoid and a spring 328 held in compression between the weight and the solenoid coil for normally biasing the weight outwardly to the outer extent of movement for the armature. Upon energization of the solenoids, the respective armature is drawn inwardly to force its associated weight toward the solenoid coil against the bias of the spring 328. Upon release of energization of the solenoid the weight will be driven under action of the spring to its extreme outer position. As will be described hereinafter, a control circuit is provided for energizing the solenoids SOL-5 periodically in order to impart quick motion to the weights 327 to produce a slight hammering upon the toner container 300 thereby preventing impaction of the toner particles and constantly maintaining the downward movement of toner for eventual egress through the nozzle section 302. Normally in the operation of the toner dispenser, with a supply of toner particles placed within the container 300, the metering plate 304 and the toner plate 303 form a control gate for holding back the toner particles from entering the conveyor tube 225 through the conforming opening 224a. Upon reciprocation of the gate 304 by the rotation of the drive element 321, a metered quantity of toner particles will be permitted to pass through the double row of large openings 330 formed in the gate 304 and to fall upon the stationary plate 303. With toner particles being built up upon the plate 303, a metered quantity of toner will steadily cascade over the two longitudinal edges of the plate from where the toner will fall into the tube 225. Since the width of the toner plate 303 is greater than the internal width of the nozzle section 302, the latter prevents the toner particles from falling directly through the openings 330 and into the tube 225 without first falling upon the plate 303 to be metered thereby. The toner then actually follows a tortuous path as shown in FIG. 18 by the reference numeral T indicating a typical path of toner fall.

Since the toner dispenser 15 dispenses a uniform quantity of toner for a given stroke length of the metering gate 304, it is apparent that the quantity of toner delivered by the toner dispenser may be varied by the number of strokes of such movement per unit of time. Accurate control of the dispensing rate for the toner dispenser can be accomplished by controlling the time in which the motor M-10 is energized and the rate of reciprocation of the gate 304, the latter activity being determined by the gear reduction ratio for the gear box 323. Assuming that the gear box is adapted to rotate the drive shaft 322 at approximately 50 r.p.m., it will be seen that the metering gate 304 will experience relatively few reciprocatory cycles for any particular time during which the motor M-10 is energized. It will be apparent with the foregoing arrangement then that more accurate control is available with the use of a relatively slow reciprocatory movement of the metering plate 304 since only the motor energization period which can be relatively broad in view of this slow movement, need be varied to control toner dispensing.

TONER CONCENTRATION CONTROL

In order to control the dispensing of toner from the toner dispenser 15, there is shown in FIG. 27-34 the details of an automatic toner control system which ultimately controls the time of energization for the dispenser motor M-10 at start up and during continuous operation of the machine.

Basically, the automatic toner dispensing system comprises a toner sensor 340 mounted within the developer housing 200 by any suitable means which electrically grounds the sensor, a flat funnel bin 341 which conveys some of the developer material passing through the slot 285 in the plate 220 into the sensor 340. As shown in FIG. 27 developer material entering the bin 341, slides downwardly to the left along the inclined plane 342 of the bin on its way to a bypass conduit 343. The plane 342 supports an upstanding deflector plate 344 in the path of the downwardly moving material. The conduit 343 is arranged to conduct the flow of the developer material that does not enter the sensor 340 back into the lower conveyor tube 225 for continued circulation of the material.

The toner sensor 340 is generally square in shape having a relatively narrow depth, and resembling a flat box-shaped housing. It is arranged such that diagonal corners are aligned with the vertical in order to permit the flow of toner into the upper corner and to permit egress from the sensor from the diagonally placed lower corner. Within the sensor housing, there is positioned at the upper corner of the housing, a triangular shaped baffle element 345 which has the apex of a corner thereof facing upwardly into the path of the free-falling developer material which flows through a conduit 346 connected between the upper corner of the housing and an opening 347 formed in the bin 341. The angled element 345 serves to split the downwardly flowing developer material into two separate paths of approximately equal flowing widths. The developer material flowing along the left path, as viewed in FIG. 27 slides along one leg 348 of the angled element 345 and along an extension in the form of an adjustable control gate 349 of the leg until the development material has its flow obstructed by a guide baffle plate 350 positioned 90.degree. relative to the path of movement of the development material and the plane of the gate 349. The lower end of the control gate 349 is spaced from the guide plate 350 a narrow distance to permit a controlled amount of the developer material to change its direction of flow 90.degree., or toward the lower right corner as viewed in FIG. 32. Excess developer material, or that material which does not pass between the edge of the gate 349 and the plate 350 flows around the outer end thereof and to an outlet tube to be described. The developer material now slides in this direction along the guide plate 350 and onto a conductive glass plate 351 secured thereon and across which the developer material flows. A sensing photocell P-1 is secured to the sensor housing immediately below the plate 351 for a purpose to be described hereinafter.

Similarly, the element 345 has a second leg which is adapted to convey development material along another path of movement upon entering the sensor 340. This leg 352 is also provided with a projecting extension in the form of a control gate 353 which directs development material downwardly and to the right and against a second guide plate 354 positioned 90.degree. to the flow of the development material in this trunk and relative to the gate 353. As was the case with the guide plate 350, a second conductive glass plate 355 is insulatingly attached to the plate 354 across which development material is directed as the material is permitted to flow through the lower edge of the gate 355 and the adjacent surface of the plate 354 in a controlled quantity manner. A lamp LMP-1 is mounted immediately below the plate 355 and arranged so that when energized, some of the lights rays therefrom will be transmitted through both NESA plates and impinge upon the photocell P-1.

The development material which has passed across the plates 351 and 355 and which pass as an overflow across the ends of the guide plates 350 and 354 are brought together again at the lower corner of the sensor housing 340 and into an outlet tube 356 which is in communication with this lower corner. The lower end of the pipe 356 is in communication with opening 224 formed in the lower conveyor tube 225.

Each of the sensing plates 351 and 355 has a thin transparent layer of a conductive oxide, preferably formed of "NESA" glass, a trademark of the Pittsburgh Glass Company, which is generally a tin oxide coated glass that is transparent to white light. Since both plates are mirror images of each other, details of only one of the plates will be described. A pattern 357 is formed on the plate 351 as shown in FIG. 30 and is of L-shape, being produced by scribing through the oxide layer in order to electrically separate the pattern 357 from the remaining portion 358. Each of the conductive portions 357, 358 are connected to a circuit to be described hereinafter.

In order to accumulate toner in an amount fairly indicative of the total amount of toner in the developing system, the pattern 357 on both plates 351 and 355 have applied thereto an electrical potential of a polarity and amount to attract and retain toner particles for some predetermined unit of time. During this time, the light transmission through the accumulated toner on both patterns 357 will be determined in terms of toner concentration for the developer material. When the predetermined unit of time has terminated and after the toner accumulation is sensed, the polarity on the patterns of the sensing plates is reversed in order to permit the patterns to repel toner particles thereby effecting the cleaning of the patterns by means of the developer material allowed to continue flowing across the patterns brushing toner therefrom.

As shown in FIG. 31, the conductive portions of each of the plates 351, 355 are connected in parallel and to a timer mechanism generally indicated by the reference numeral 360, shown in detail in FIGS. 34 and 35. The timer mechanism 360 is in the form of a continuously rotating bank of cams which periodically make and break switches connected to the toner sensor circuit. The timer comprises a motor M-6 connected to a gear reduction drive mechanism 362 which has its output shaft connected to a shaft 363 rotatably mounted on a frame 364 for the timer mechanism. The shaft 363 has mounted thereon for rotation therewith a first cam 365 for controlling the electrical supply to the timer drive motor M-6 during shutdown of the xerographic machine, a second cam 366 which controls the time during which the accumulated toner on each of the plates 351 and 355 is sampled and, a third cam 367 which controls the polarity upon the plates 351, 355. The cam 365 assures that a positive polarity is applied to the patterns 357 whenever the sensor is "cycled out" for a purpose to be described hereinafter.

The first cam 365 is formed with a control lobe 368 which is arranged to actuate an actuator 370 for a switch 371 which is connected to a suitable source of electrical power supply to the timer motor M-6. This motor is energized whenever a main switch in the electrical circuit for the machine is closed and the drive for the horizontal conveyor screws 226 and 247 is activated. During the shutdown of the machine when it is still processing a last copy and when the drive to the conveyor screws 226, 247 has terminated, the switch 371 will maintain the motor M-6 energized for a complete sensing cycle which, as will be further described, lasts about 6 seconds. The developer material used in this last cycle is furnished from the conduit 346 which serves as a sump for this purpose. Closing of the switch 371 assures shutdown of the motor M-6 only when the regions 357 have a positive polarity or that polarity opposite that of the toner particles utilized.

Before proceeding further in the description of the timer circuit a brief description of the sensing and nonsensing mode of operation for the toner sensor 340 will be described in relation to the timer 360 and the electrical power thereto.

The circuit for the toner sensor and the components thereto are arranged and programmed so that sensing of toner concentration occurs periodically and asymmetrically, that is, for a short, predetermined time interval, or, after a relatively long predetermined time period. For purposes of illustration of these time periods and controls, the sensor control circuit is adapted to "sample" or sense the toner concentration accumulated upon the patterns 357 for a period of one-tenth of a second, which period occurs after the patterns are in the "attract" mode for about four-tenths of a second prior to sampling. During the "attract" mode which encompasses the "sampling" period, the patterns 357 are of positive polarity or that polarity opposite the polarity on the toner particles. After approximately one-tenth of a second for the "sampling" period, the electrical power for this sensing function will be terminated until the next cycle. The cycle of placing the sensor in the "attract" condition, sampling, and cleaning the sensor occurs every 6 seconds when the xerographic machine is in the continuous print mode of operation. In the illustrated example with the "attract" mode lasting approximately five-tenths of a second and the "clean" cycle 51/2 seconds, the toner density sensing is asymmetrical in its cycling.

As shown in FIG. 34 there is illustrated a series of time graphs for a 6 second cycle of toner concentration sampling and control. During this 6 seconds, the output shaft 363 for rotating each of the cams 365, 366 and 367 makes one complete revolution. As previously stated, the switch 371 is actuated by the cam lobe 368 on the cam 365 and comes into service only for the last 6 second sensing cycle during processing of the last copy of a particular production run. The circular length of the lobe 368 is such as to maintain closing of the circuit to the timer motor M-6 for nearly the entire 6 second period and as shown in FIG. 34 the switch 371 is actuated to a closed position until approximately 5.85 seconds has transpired or when the cam reaches the line 372 on the curve A. During use of the machine before the last copy is being processed, the switch 371 is bypassed. It is, in effect, an auxiliary AC path to assure shutdown in the "attract" mode. At the end of the 6 second period the switch 371 is again actuated to a closed condition commencing the next cycle of the sensor control.

As shown by the time curve B, just prior to reaching the line 372, the cam 367 which actuates a normally closed switch 373 to an open position and a normally open switch 374 to a closed position causes these switches to be actuated such that the normally open switch 373 closes to cause the patterns 357 to be supplied with positive potential from the power supply 375, thereby holding the patterns in the "attract" mode. This "attract" mode will remain until the termination of the 6 second cycling period. This is illustrated in the timing curve B by the line 376. Simultaneous with this actuation of the switch 373 is the actuation of the normally closed switch 374 which when open prevents the flow of negative potential to the areas 358 of each of the sensor plates 351, 355. This occurrence is illustrated in time curve C by the line 377.

After the plates 351, 355 have been placed in the "attract" mode for approximately four-tenths of a second, the cam 366 actuates a switch 378 which controls activation of a control circuit in a threshold detector 369 for conditioning the photocell P-1 to vary its resistance in accordance with the intensity of the light rays from the continually energized lamp LMP-1. This "sample" period remains for approximately one-tenth of a second, starting from the sampling "ON" time when the photocell P-1 is energized, illustrated by the line 380 in time curve D. As shown in FIG. 33, the control end of the lobe 368 for the cam 365 is spaced angularly from the control end of the lobe 381 for the cam 366 and also spaced from the control end of the lobe 382 for the cam 367. The angular relationship between the lobes 382 and 381 is such as to permit the elapsed time between the beginning of the "attract" mode and the instant that the photocell P-1 is energized. The angular distance between the lobes 382 and 368 is such that the patterns 357 are energized to a positive potential before the motor M-6 is de-energized in the processing of a last copy.

For illustrative purposes, the polarity indicated in FIG. 30 and 31 in relation to the sensing plates 351, 355 are those polarities of the supply voltage when the plates are in the "attract" mode. For this convention then, it was assumed that the charge upon toner particles is negative and, therefore, would be attracted to the control patterns 357 for each of the sensing plates. It is also assumed that the other conductive areas 358 are being supplied with negative DC potential. This electrical configuration is merely illustrative and has been chosen for descriptive purposes because of the particular charge chosen for the toner particles which, as previously stated, is negative. The positioning then of the actuator arms for the switches 373 and 374 is such that toner particles will be attracted to the patterns 357 and repelled from the patterns 358.

As previously stated, in order to exhibit high sensitivity and rapid response time, the electrical circuit shown in FIG. 31 is adapted for periodic sensing action, for every 6 second period during which the reproduction machine is in continuous operation. During the "attract" mode, the toner will accumulate upon the patterns 357 and, in an amount indicative of the amount of toner in the developer material. When the timer 360 has effected switching of the switches 373, 374 the polarity of the patterns 357 and the portions 358 are reversed where upon the patterns 357 assumed a negative polarity and the portions 358 a positive potential. In this manner, the control patterns 357 will repel the toner cascading down the inclined plates 351 and 355 during this portion of the control cycle. When the polarity is thus reversed, the patterns 357 are cleaned by the cascading developer material and thereby is preconditioned during this "clean" cycle for another "attract" cycle.

In order to determine the extend of toner concentration that has accumulated on both control patterns 357, the toner sensor 340 is provided with the photocell lamp combination P-1 and LMP-1. As previously stated, the photocell is positioned adjacent the lower surface of the plate 351 so that toner particles cascading through the toner sensor and accumulating upon both regions 357 will intercept light rays from the lamp LMP-1 positioned behind the lower surface of the other plate 355. The photocell P-1 in effect will "see" light rays which traverses the cascading developer stream flowing upon both plates 351, 355 and, the accumulated toner particles on each of the patterns 357.

Electrically the photocell P-1 is connected to the threshold detector 379 in form of a Schmitt trigger which is adapted to produce a pulse when the resistance in the photocell attains a predetermined value indicative of the intensity of the light rays that reach the photocell from the lamp LMP-1 during the "sample" cycle. The detector 379 derives its power from a power supply 386 which also supplies the lamp LMP-1 with its electrical energy.

The pulse generated from the Schmitt trigger 379 is fed to a machine logic circuit 387 which, when combined with other necessary signals from the reproduction machine, is fed to a timer relay 388 by way of an amplifier 390 and then to the toner dispenser motor M-10 connected in series with the relay contact for the relay 388. The timer relay 388 is arranged to remain "ON" for any adjustable predetermined timed period for each pulse thereto from the threshold detector 379. For each pulse fed to the timer relay, the motor M-10 will remain energized until the timer period, which may be in the range from 1-10 seconds, has terminated whereupon the motor M.varies.10 will become de-energized for that pulse. As previously stated during energization of the motor M-10 the metering gate 304 is cyclically moved by means of the carriage 305.

During normal operation of the automatic toner dispensing apparatus, the light source LMP-1 is continuously energized for presenting light for both plates 351 and 355 arranged optically in series. The light rays which traverse both of these plates impinges upon the photocell P-1 which is compared with predetermined values in the Schmitt Trigger 379. In the event that the predetermined value is not exceeded during the sampling step wherein the photocell is energized, the excess is utilized to produce a pulse which is fed to the logic 387 as an indication that the toner concentration in the development material is below a desired level.

As the density of the toner that cascades over the sensing plates 351, 355 increases, the signal on the photocell P-1 will be in balance with the predetermined value in the Schmitt trigger 379 thereby terminating periodic energization of the motor M-10.

It will be appreciated that with the presence of both sensing plates 351 and 355, the sensitivity of the sensing circuit is relatively high since there is a much wider range of variation that light rays may experience in reaching the photocell P-1. This also results in the control of a relatively wide density range that the xerographic reproductions may attain, or in other words, the density that the toner concentration maintains can be closely regulated. With this narrow range of variations and with the continuous short sampling time per unit of time, the xerographic machine is capable of experiencing a relatively narrow, high quality contrast control since the slightest unbalance will demand toner and produce replenishment thereof.

The toner dispenser 15 functions to sift toner material into the development material in the conveyor tube 225 in order to insure maximum mixture of the fresh toner with the material already in the development process. The metering gate 304 and the toner plate 303, upon which toner particles fall, are of sufficient length as to span a relatively long length of the conveyor 226. The continual motion of the screw conveyor 226 brings the newly mixed development material into position to be carried upwardly by the vertical conveyor belt 236.

SHEET FEED MECHANISM

The sheet feeding mechanism 18 illustrated in FIGS. 35-41 is positioned for the seriatim feeding of cut sheet transfer material into contact with the xerographic belt 12 so that developed powder images on the surface of the belt may be transferred to the transfer material. The mechanism includes a tray for holding a supply of cut sheet transfer material, separator rollers and devices for separating a single sheet of transfer material from the top of the stack of transfer material on the tray, feed rollers for feeding a single sheet into the transport system 16 in order to bring the sheet into impression contact with the belt 12 and means for coordinating the operation of the separator rollers and feed rollers to thereby feed a single sheet of transfer material into contact with the belt 12 at proper registration of the powder image on the belt onto the transfer material. A paper tray level control device is also provided for raising the tray as sheets of paper are fed from the top of the paper supply.

Referring now specifically to the drawings, the apparatus for feeding sheets of transfer material to the transport system 16 in timed relation to the appearance of a developed image on the belt 12 includes a paper tray 400 slidably positionable from the side of the machine between frame plates 401, 402 and arranged to hold a stack S of various widths of sheet material such as paper.

The paper tray 400 includes a paper stack supporting base comprising two sections: a stationary base section 403, and a movable base plate 404, both plates being coplanar and including flat relatively wide fingers 405 (see FIG. 38) which intermesh when both plates are joined to support a stack of paper. The fingers 405 support the stack when the rearwardly extending movable base plate 404 is pulled rearwardly to the position shown in dotted lines in FIG. 39 and indicated by the numeral 406. The base plate may be placed in this position when loading the paper tray with long (legal size) paper which requires the machine to run in a long pitch mode.

The stationary plate 403 is held against movement within its plane by means of box-like structure 407 having one edge 408 welded to an intermediate plate 409 which in turn is spot welded to the bottom surface of the stationary plate 403. The sides of the intermediate plate 409, which extends in a plane parallel to and below the combined plane for the plate 403, 404 are formed into downwardly projecting tapered side panels 411 which are held against forward or rearward movement by a slide mechanism to be described hereinafter. The intermediate plate 409 is formed with a slot 412 arranged centrally between the side panels 411 and extending for nearly the entire length of the plate 409. Through this slot extends a pair of screws 413 secured to the bottom surface of the central finger 405 of the movable base plate 404. These screws serve to support a ribbon 414 positioned parallel to and below the plate 404 and is formed with a depending portion 415 which is adapted to engage an actuator 416 of a switch SW when the movable plate 404 is pulled rearwardly. The switch SW may be connected as an interlock circuit to effect change in machine pitch resulting from the use of longer sheets of transfer material. In loading the paper tray with longer sheets, the plate 404 is extended not only to accommodate longer sheets but also to condition the machine for the long pitch mode.

Each of the side panels 411 is adapted to be driven vertically in order to cause raising and lowering of the paper tray during paper feed operation. To this end, the base plate 401 has secured thereto a channel member 420 having its open side extending inwardly and arranged in a vertical position. Similarly the base plate 402 is provided with a channel member 421 secured thereon to face the channel 420. The channel member 420 is adapted to receive a pair of guide rollers 422 mounted in space relation upon a vertically extending plate 423 secured in a vertical arrangement upon one of the side panels 411. In like manner, the channel 421 serves to guide vertically a pair of vertically spaced rollers 424 mounted upon a plate 425 secured to the other side panel 411. With this arrangement, the paper tray is free to move vertically and is held against horizontal movement by the confinement of the side panels 411 to the fixed channels 420, 421.

In order to produce control and automatic movement of the paper tray vertically, the forward edges of each of the plates 423, 425 is provided with a gear rack 426, 427 respectively. A train of three vertically aligned gears are adapted to drive each of the gear racks in order to impart vertical motion of the paper tray. As shown in FIG. 39, the gear rack 427 is in direct mesh with an upper gear wheel 428 mounted for rotation upon a stud shaft 430 secured to the frame plate 402. Mounted below the gear 428 upon a stud shaft 431 is an intermediate gear 432. Below the intermediate gear 432 is a third lower gear 433 secured to a drive shaft 434 having one end secured to the frame plate 402 and its other end mounted for rotation on the frame plate 401.

This completes the three gear train for the side of the paper feeder frame which supports the gear rack 427. On the other side of the paper frame is a second gear train comprising gears 435, 436 and 437 arranged on stud shafts 438, 439 respectively for the gears 435 and 436 and the drive shaft 434 to which the lower-most gear 437 is secured. It will be apparent that the shaft 430 and 438 are in actual alignment as are the shafts 431 and 439. It will also be apparent that upon rotation of the lower-most gears, 433 and 437, motion will be imparted to each of the respective upper gears which in turn produce corresponding movement of the respective gear racks 426, 427.

In order to produce rotation of the lower-most gears, the outer extremity of the drive shaft 434 on that side of the sheet feed mechanism having the base plate 401, has secured thereto a drive gear 440 which is in mesh with a worm gear 441 formed on a shaft 442 mounted for rotation between flanges of a bracket 443 which also supports a paper elevation motor M-2 having its shaft connected to the shaft 442 for imparting rotation thereto. Preferably the motor M-2 is adapted to produce low r.p.m. rotation which when coupled with the worm gear 441 and drive gear 440 impart relatively slow motion to the paper tray.

Centering of the stack S of paper relative to the optical centerline of the copier/duplicator machine in order to insure proper registration and feeding of individual sheets of paper from the top of the stack is accomplished by a pair of vertically extending guide members 445, 446 arranged at the forward corners of the stack when in position for separation operation. The guide member 445 is supported in an upright position by means of a horizontally extending guidepin 447 suitably secured to the frame plate 401 and extending through a boss 448 formed in the guide member 445. Similarly the member 446 is supported in a vertical position by a guide pin 450 secured to the frame plate 402 and slidably received in a boss 451 formed in the upright. The guide members 445 and 446 are also formed at the lower ends with bosses 452 and 453 respectively which extend inwardly toward one another and in axial alignment. As shown in FIG. 40, the drive shaft 434 is positioned within the bosses 452, 453 for supporting the guide members 445, 446 and to permit movement of these guide members toward and away from each other.

As shown in FIGS. 39 and 41 the guide member 445 is formed with a guide edge 454 that extends vertically along the length of the guide member and adapted to engage the leading edge of the stack of paper at one corner thereof. Engaging the side edges of the stack S along the same corner is a guiding surface 455 also formed along the length of the member 454. The guide member 446 is similarly formed with a front guide edge 456 and a side guide edge 457 for guiding the leading and side edges of the stack of paper at that corner. The side edges 455 and 457 are adapted to be moved toward and away from each other and relative to the center line of the paper tray 400 in order to center the stack S relative to the optical axis of the xerographic machine as the axis will manifest itself during the image transfer step.

In order to drive the side edges 455, 457 toward and away from each other, the paper feeder 18 is provided with a manually operable centering drive system comprising a pair of links 460, 461 each having an end connected to one of the bosses 452, 453 and the other end connected to a block 462 mounted for rotation upon a shaft 463. The points of connection of the links 460, 461 with the block 462 are offset relative to the axis of rotation for the block in order to cause movement of the bosses 452, 453 upon rotation of the block 462 in either direction. Rotation of the shaft 463 is accomplished by a knob 464 secured at the outer end of the shaft 463 at the rear of the paper handling mechanism 18. A lock knob 465 secured to the extremity of the shaft 463 serves to move the knob 464 axially relative to the shaft and against a non-rotatable block 466 mounted on a spacer block 469 and held axially thereto by a suitable shoulder 467 formed on the shaft. Rotation of the knob 465 will lock the knob 464 against rotation in order to prevent inadvertent driving movement being imparted to the guide members 445, 446. It will be apparent that upon rotation of the knob 464, the block 462 will be rotated for driving the links 460, 461 in either direction in order to impart corresponding movement of the bosses 452, 453 respectively. During a paper loading operation, the knob 464 is rotated to space the members 445, 446 apart to accommodate various widths of transfer material on the tray 400 and to permit the easy loading of additional sheets upon the tray. After the tray has been supplied with sheets the knob 464 is rotated to drive the guide members toward each other in unison thereby aligning the stack relative to the optical center line of the xerographic machine in proper position for paper feeding.

The driving action produced by the knob 464 and the shaft 463 in order to separate the members 445, 446 is against the bias of a spring 468 held in tension by being connected at its ends to each of the guide members and normally biasing them toward one another. Preferably, the spring is of such a strength that with the knob 464 left unsecured the guide members will be normally forced inwardly against the adjacent side edges of the stack of papers thereby enhancing good side-to-edge alignment.

The coacting side guide edges 455, 457 coacting with guide follower elements 470 secured on the outwardly extending ends of a pair of rods 471, 472 held in axial alignment and being slidably mounted within blocks 473, 474 respectively, secured below and in spaced relation to the stationary plate 403 of the paper tray support the corners of the stack of transfer material. A rod 475 is slidably retained in the opposing ends of the rods 471, 472 and has a spring 476 encircling it in order to maintain the rods 471, 472 outwardly to force the follower elements 470 against the guide members 445, 446. The guide elements 470 fill the corner gaps and support paper of all widths.

Generally, the upper ends of the guide edges 454, 456 are held at a point slightly below the top sheet of the stack S. As individual sheets of paper are fed from the stack, each is adapted to slide or to be driven over the top ends of the members. Means are provided for separating only the top sheet from the stack during a paper feed operation. In order to insure separation of the topmost sheet only from the stack, there is provided at opposite corners of the stack, separating devices which apply a light restraining force on the forward corners of the topmost sheet and the leading edge of the paper stack. Each of the separating devices comprise a vertically movable plunger 476, 477 freely movable in a vertical passageway 478 formed in each of the forward portions of the guide members 445, 446. Each of the plungers has a snubber 480, 481 secured thereto at a plane slightly above the upper ends of the plungers and to be movable therewith.

The weight of each of the plungers 476, 477 is imposed on the upper forward corners of the paper stack. Normally the weight on each corner is such that the plungers will follow the level of the stack downwardly as the stack level is lowered by continuous feeding of paper. Their weights also provide a restraining force which will assist in the feeding of a single sheet of paper when the stack is acted upon by separator rollers to be described hereinafter. It is preferred that the limits of downward movement for the plungers 474, 476 are short in order to limit the downward movement of the corresponding snubbers. This is to limit the lowering of the snubbers when the level of the stack is lowered prior to a tray loading procedure and to guarantee that the snubbers are atop the corners of a freshly loaded stock without manual manipulation thereof. As it is raised assuming proper centering by the guide members 445, 446 the adjacent corners of the stack will engage the snubbers and carry them upwardly until the top of the stack is at its proper predetermined position for feeding of the top sheet.

To feed sheets of paper one at a time from the stack S and into the narrow slot formed between two closely spaced guide chutes 482, 483 arranged just forward of the top few sheets of the stack S, there is provided a paper separating means comprising a first pair of intermittently driven rollers 485 mounted for rotation adjacent the side edges of the stack and a second pair of driven rollers 486 mounted inwardly of the rollers 485. All of the rollers are engageable with the top of the paper stack. Each of the outboard rollers 485 is mounted for rotation on and by a driven shaft 487 associated with each of the rollers by means of a one way clutch 488 which permits each roller 485 to rotate freely in that direction that the topmost sheet moves when it is pulled out from the stack at a greater rate than the roller is capable of moving the sheet.

The inboard rollers 486 are mounted for rotation upon a drive sleeve 490 which is drivingly connected to each roller by means of a one way roller clutch 491 similar to the clutch 488. The shafts 487 are mounted each within an end of the drive sleeve 490 which also contains within its interior a coil spring 492 which serves to force the two shafts 487 outwardly for positioning the outboard rollers 485 to a predetermined position relative to the edge of the stack. This outward movement is limited by suitable buttons 493 which engage the edge guides 455, 457. As the guide members 445 and 446 are moved outwardly the shafts 487 will follow the same in order to insure that the rollers 485 maintain their set relation to the edges of the stack regardless of stack width.

Rotation is imparted to each of the shafts 487 by a pin 494 connected between each shaft and the end of the drive sleeve 490. The sleeve shaft 490 at each end is formed with a slot into which each pin is adapted to be inserted for connecting the shaft and for permitting limited axial movement of each outer roller 485.

Driving rotation is imparted to the drive sleeve 490 by way of a timing pulley 495 secured axially of and at the center of the sleeve and held between the flanges of a channel support arm 496 which supports the sleeve 490 and the rollers 485, 486. The channel arm 496 is formed in two parts: a forward part 497 the end of which supports the sleeve 490 as previously stated and a supporting section 498 which conforms with the shape and direction of the portion 497. These sections are connected in end-to-end relation by means of an opposing slot 500 formed in the portion 498 and co-acting tongue 501 on the section 497 loosely insertable in the slot 500 to permit disconnection of the parts 497, 498. The loose connection between the slot 500 and tongue 501 also permit limited rotation of the portion 497 about its longitudinal axis in order to allow all four rollers to contact the material surface regardless of stack deformation due to humidity.

The portions 497, 498 are detachably held one to another by means of an adjusting screw 502 positioned within the channel shape of the arm 496 and which is threadedly received at one end in a tapped portion 503 formed in the section 498 and at its other end that it received in a boss 504 formed in the portion 497. A suitable retaining ring is employed relative to the boss 504 for permitting rotary action of the screw 502 but preventing axial motion relative to the boss. The screw 502 serves as adjsutment means between the portions 497 and 498 to control tension on the timing belt utilized to rotate the rollers 485, 486.

The support arm 496 is secured between the frame plates 401, 402 by means of a sleeve 505 which is mounted at one end through a knurled thimble 506 which is rotatably adjustable and supported upon a support sleeve 507 secured by suitable screws to the frame plate 401. Normally the arm 496 is under the influence of gravity in a direction to maintain the two pairs of rollers 485, 486 into engagement with the topmost sheets of the paper stack. However, additional force must be added in order to increase the force of the rollers upon the stack. This is accomplished by means of a torsion spring 508 having one end secured to the thimble 506 and its other end connected to a retaining plate 509 through which the sleeve 505 extends and is secured. The spring 508 may be adjusted in tension between its two supporting structures in such a manner as to impart rotation to the support sleeve 505 in addition to that rotation produced by gravity for more reliable feeding of heavier weight transfer material. When the stack is removed, the retaining plate 509 also serves to limit the downward movement or rotation of the arm 496 and prevent the undue stress on the structural parts. The retaining plate 509 also serves to actuate the "up" elevator switch SW-3 and the "down" elevator switch SW-4 in a manner to be described hereinafter.

Held within the support sleeve 505 and extending across almost the distance between the plates 401, 402 is a drive sleeve 510 mounted for rotation at one end by a bearing 511 having its outer race secured to the inner recess of the support sleeve 507 and, a clutch mechanism 512 supported by suitable screws upon the frame plate 402. Axially rotatable within the drive sleeve 510 is a drive shaft 513 supported at one end in a bearing 514 mounted within the support sleeve 507 and, at the other end extending beyond the frame plate 402 and terminating in a drive pulley 515 associated with a drive system to be described hereinafter. The clutch is adapted, when energized, to operatively connect the drive shaft 513 with the driven sleeve 510 in order to produce rotation of a timing pulley 516 positioned between the flanges of the arm 496 and which is associated with a timing belt 517 also wrapped around the timing pulley 495 in order to impart rotation thereto. During operation when the clutch 512 is energized rotative motion is imparted to the pulley 516 which correspondingly imparts rotation to the timing pulley 495 for rotating the inboard paper feed rollers 486 and consequently the outboard rollers 485.

In operation, as the topmost sheet is frictionally advanced by the rollers 485, 486, the leading edge corners of the sheet engage the snubbers 480, 481 which are formed so as to present a continuation of the vertical front guide edges 454, 456 and hence a vertical barrier to the passage of sheets, but one limited to the outer extremes of the leading edge of the forward moving topmost sheet. As the rollers 485, 486 apply a forward force to the topmost sheet, the two forward corners of the sheet thus restricted by the snubbers, create a lag in the forward movement of the corners as the sheet is continually advanced. This lag will produce slight inward sliding movement of the corners of the sheet of paper with consequent buckling of the sheet. This buckling action of the topmost sheet insures its separation from the underlying sheets in the stack.

During feeding of the topmost sheet into the space between the guide baffles 482, 483, both pairs of feed rollers 485, 486 are positively driven to affect this movement. As the sheet advances, its leading edge moves into the gate of the slightly separated registration rollers 520, 521 which eventually engage the sheet and pulls the same their remaining distance in order to clear the stack S. This second movement of the sheet is slightly faster than the initial driving action produced by the feed rollers 485, 486 and thereby results in the feed rollers rotated individually and freely in view of the individual one-way clutches associated with each of the rollers. Actually at this point, when the registration rollers 502, 521 take over control of the feeding of the sheet, energization of the clutch 512 is terminated thereby stopping the positive drive action by the drive sleeve 490. In the event the topmost sheet becomes slightly askew as it is advanced across the remaining portion of the paper stack, perpetuation of this unwanted skew condition is prevented in view of the fact that the feed rollers 485 and 486 will stop individually and sequentially as the topmost sheet trailing edge is pulled from under them. Without individual one-way clutches, the next sheet in the stack will skew as each successive roller drops off the trailing edge of the previous sheet being skewed. Since these rollers would be secured to a common shaft, none can stop turning until all have cleared the trailing edge. Rollers still on a skewed top sheet will continue to drive those rollers that have cleared the trailing edge, thereby urging that portion of the next sheet forward, perpetuating the skew.

The paper tray 400 is limited in its downward movement by means of a limit switch SW-7 mounted upon the frame plate 401 and electrically connected to the paper elevation motor M-2 through a logic circuit for de-energizing M-2 upon activation of the switch when the tray reaches a predetermined low position. This is accomplished by means of a projection 522 secured to the plate 425 and which actuates the switch SW-7 at the predetermined low point. Another switch SW-8 mounted on the frame plate 401 controls the upper limit of travel of the paper tray 400 by means of a projection 523 mounted on the plate 425. In the event the tray 400 attains a predetermined high point, the switch SW-8 is actuated through the logic circuit in order to terminate energization of the paper elevation motor M-2. The relationship between the switches SW-3, SW-4, SW-7 and SW-8 in conjunction with manually operable switches for the motor M-2 will be described in description of the electrical circuit.

SHEET REGISTRATION MECHANISM

In the sheet registration mechanism illustrated in FIGS. 39, 42-29 the registration rollers 520, 521 are adapted to cooperate with a pair of registering fingers interposed in the path of movement of a sheet being fed by the separator rollers 485, 486 in order to align the leading edge of each sheet to a precise position before the sheet is permitted to continue on to the paper transport mechanism 16 whereat the developed electrostatic image on the belt 12 will be transferred. As shown in in FIG. 43, the upper registration roll 520 comprises a central metallic core 525 having a plurality of soft rubber layers 526 therearound adapted to engage frictionally a sheet of paper. The roller 520 is mounted at one end on a stub shaft 527 (see FIG. 47) supported in a bearing housing 528 held by a clamp 530 to the shaft and, at its other end on a stub shaft 531 supported in a bearing housing 532 held thereto by a clamp 533.

At the left end of the registration roller 520 as viewed in FIG. 42 a sprocket 534 is secured to the stub shaft 531. The bearing housings 528 and 532 are eccentric in nature so as to provide adjustment to the pinch between the upper register roller 520 and the lower roller 521. The ends of the registration roller 520 is also supported by levers 535, 536 (see FIG. 36) pivotally mounted at their ends by fixed stub shafts 537 secured on the frame plates 401, 402, respectively, in axial alignment. The stub shaft 537 that is fixed to the plate 402 also has secured thereto a sprocket 538 which is arranged in driving connection with the sprocket 534 by a drive chain 540 for driving the registration rollers to be described hereinafter. A suitable idler sprocket 541 is also mounted on the lever 536 and operatively associated with the chain 540 to permit tightening of the chain 540 or removal thereof from the operating sprockets.

The top edge of the frame plate 401 is formed with a generally vertically extending slot 542 into which the stub shaft 527 for the upper roller 520 is adapted to be placed when this roller is in operating position. Similarly, the shaft 531 at the other end of the roller is adapted to be positioned within the open ended slot 543 formed in the upper edge of the frame plate 402. The provision of the slots permits the pivoting movement of the driven roller 520 out away from the lower idler roller 521 and of the path of movement of the paper and, in fact, away from the cooperating structure therefor to permit maintenance and paper jam clearing.

Located immediately below the top registration roller 520 and parallel therewith, the lower roller 521 comprises a plurality of free-wheeling, short rollers 544 all of which are rotatably mounted with ball bearings upon a common sleeve 545 which is rotatably mounted on a shaft 546 by means of a roller bearing 547 provided at each end thereof. The shaft 546 is mounted at one end to the frame plate 401 by suitable bearings and at the other end by a bearing 548 secured in a solenoid mount 549. At this end, the shaft 546 terminates in a straight slot 550 into which projects a tongue 551 formed on the end of a movable actuator 553 for a double-acting rotary solenoid 554 the details of which will be described hereinafter. The solenoid 554 comprises an "up" solenoid SOL-1 and a "down" solenoid SOL-2 and is adapted to impart non-axial rotary motion to the drive shaft 546 in either direction for approximately 45.degree. upon energization of each of the solenoid coils associated with the solenoids SOL-1 and SOL-2.

Mounted upon the sleeve 545 between any two of the free wheeling rollers 544 are registration fingers 555 which are secured by suitable set screws upon the sleeve 545 to be moved therewith or held stationary when the sleeve is held against rotation.

As shown in FIG. 48, the periphery of the roller 520 is slightly spaced from the periphery of the rollers 544. This spacing is greater than the thickness of a sheet of paper and permits the sheet to enter within the nip between the rollers and, against the fingers 555 and to maintain this position until a feed cycle is activated. At this time in the cycle, paper is still being driven by the feed rollers 485, 486. This action is opposed by the fingers 555 in the paper path causing the paper to buckle momentarily, squaring the front edge. With the forward edge of a sheet of paper against the fingers 555, the upper roller 520 is continuously driven but being spaced slightly from the top surface of the sheet of paper it is incapable of driving the sheet beyond the fingers 555. In order to permit the proper alignment of the forward edge of the sheet of paper against the registration fingers 555 and then to accomplish forward feeding movement to the sheet by means of the rollers 521, 520, the registration system is provided with a control mechanism which controls the movement of the upper roller 520 downwardly into engagement with the sheet of paper located therebelow in order to drive the same at the same time as the retracting movement of the fingers 555 in order to eliminate the impeding action by these fingers against the forward edge of the sheet.

This control mechanism includes a first link member 556 arranged to encircle both shafts 531, 546 for the rollers 520, 521 respectively adjacent the frame plate 402, and, a second link member 557 arranged to encircle both shafts for the upper and lower registration rollers adjacent the frame plate 401. These link members more or less hold the two rollers in superimposed close relationship. Movement of the upper registration roller 520 toward the lower roller a slight increment is accomplished during energization of the solenoid SOL-2. Upon this energization, the actuator 553 is rotated an angular distance of 45.degree. which action imparts similar rotation to the drive shaft 546. As shown in FIG. 50, a crank 558 secured to the shaft 546 of the lower roller 521 and having a cam pin 559 arranged for movement in a cooperating arcuate internal cam 560 formed in the lower end of the link 556 is adapted to force the shaft 531 toward the shaft 546. As previously stated, the levers 535 and 536 permit limited movement of the upper roller 520 toward and away from the lower roller 521. As the crank 558 is rotated clockwise as viewed in FIG. 49 the cam pin 559, as it moves from the right hand end of the cam 560 to approximately the center point thereof, will drive the link member 556 slightly downwardly carrying therewith the roller 520 toward the roller 521.

In order to maintain the fixed position of the shaft 546 for the lower roller, the link 556 is formed with a vertical extending slot 561 through which the shaft 546 extends. This provides a lost motion connection between the link 556 and the shaft 546 during the slight upper and lower movement of this link. Continuing movement of the cam pin 559 from the approximate center point of the cam 560 to the left hand end of the cam, a total angular distance equal to 45.degree. produced by the continued rotation of the solenoid SOL-2 armature 553, the distance between the axes of the shafts 531 and 546 remains the same. This movement of the cam pin 559 can be considered dwell time for the operation of the motion producing mechanism to effect engagement of the rollers 520, 521 in order to permit the remaining rotation of the shaft 546 to perform another function, that of rotating the registration fingers 555 out of engagement with the leading edge of a sheet of paper positioned in the paper guides 482, 483.

The mechanism to control movement of the fingers 555 is illustrated in two sequences of operation in FIGS. 46 and 47 and is effected by actuation of the link member 557. The link member 557 is identical with the link member 556 and is formed with a vertical straight slot 562 through which the shaft 546 extends for lost motion when the link member 557 is moved and , an internal cam 563 through which a control cam pin 564 projects. The curvature and angular relationship and distance of the cam 563 relative to the axis of the shaft 546 is the same as the cam 560. Consequently during rotation of the shaft 546 in a clockwise direction, as viewed in FIG. 49, the positioning and movement of the pin 564 is the same as the pin 559.

Secured to the shaft 546 adjacent the link member 557 is a sector gear 565 to which the cam pin 564 is attached. Meshing with the gear 565 is a second sector gear 566 mounted for rotation on a pivot pin 567 secured to the frame plate 401. The pivot pin 567 also supports for rotation thereon a cam member 568 secured to the sector gear 466 and made adjustable therewith by means of a set screw 569 threadedly received in the member 568 and engageable with the sector 566 to permit angular adjustment of one with the other. It will be apparent upon rotation of the shaft 546, the sector 565 will be rotated and the cam pin 564 will be moved in the cam 563 thereby driving the link member 557 downwardly. This motion of the link member 557 is simultaneous and equal to the motion of the downward link 556 in order to impart the smooth uniform motion of the roller 520 downwardly.

As shown in FIG. 47 the cam member 568 is formed with an angled internal cam which is formed so as to have a first cam portion 570 with a center of curvature approximately coincident with the axis of the pivot pin 567 and a second cam portion 571 which merges with one end of the angled cam but extends radially toward the pivot pin axis. The angled cam is adapted to control movement of a rotatable actuating element 572 rotatably mounted on the shaft 546 adjacent the sector gear 565 and secured to one end of the sleeve 545. This is accomplished by means of a control pin 573 secured to one end of the actuating element 572 and retained within the cam portions 570, 571 to be movable therein. Upon rotation of the member 568 from the position shown in FIG. 47 wherein the pin 573 is in the arcuate cam portion 570 of the angled cam, no rotation is imparted to the actuating member 572 that is, the register fingers 555 will not be rotated. This result occurs because the control pin 573 merely slides in an arcuate cam as the cam member 568 pivots about its axis. This initial rotation of the member 568 is produced by the initial energization of the solenoid armature SOL-2 which action also produces the short movement of a control pin 559 for the first portion of its movement in the cam 560 as previously described. The resultant action merely keeps the upper roller 520 against the lower roller 521 and the register fingers in dwell.

When the pin 573 reaches the end of the cam 570 at the apex of the cam angle, continued rotation of the link member will actuate the pin 573 in the same direction therewith to produce clockwise rotation of the actuating element 572 as viewed in FIG. 47 in order to produce slight rotation of the sleeve 545 along its axis. Since the fingers 555 are secured to the sleeve 545 this last motion of the rotation of the link members 557 causes movement of the fingers away from the leading edge of the sheet of paper between the rollers 520, 521. This rotation of the fingers will be clockwise as viewed in FIG. 48. The set screw 569 is utilized to orientate the member 568 relative to the sector gear 566 in order to insure proper rotation of the actuating member 572 at a time when the rollers 520, 521 are in engagement. When this occurs the upper roller 520 engages the short rollers 544 of the lower roller to impart rotation thereto for driving this sheet therebetween at the same time that the fingers 555 are moving in the same direction as the leading edge of the sheet but in additional downwardly motion in order to become clear of this edge.

From the foregoing the paper sheet feeding mechanism 18 is adapted to feed continuously individual sheets of paper to the sheet registration device in the form of the rollers 520, 521 and the fingers 555 located in the path of movement of the paper. The sheet registration device arrests and aligns each individual sheet of material and then in timed relation to the movement of the xerographic belt 12 advances the sheet material into contact with the belt in registration with a previously formed xerographic powder image on the belt.

As previously stated the double-acting rotary solenoid 554 comprises a pair of pan-cake solenoids SOL-1 and SOL-2 and, is arranged to produce rotation of the shaft 546 in either direction without the usual incidental movement in the axial direction. In accomplishing this function, the "up" solenoid SOL-1 has its armature 574 in the form of a flat disc and arranged to be rotated in one direction when the solenoid is energized and, the "down" solenoid SOL-2 has its armature 575 also in the form of a flat disc arranged to be rotated in the opposite direction when this solenoid is energized.

The disc armatures are arranged in parallel planes and have their axes in alignment. Each is formed with an axial opening through which a rotary element 576 extends and is secured to the armatures to be movable therewith as a unit. The element 576 slidably receives the actuator 553 and is provided with internal teeth that mesh with the splined exterior surface of the actuator to which is connected the tongue 551 and groove 550 as a driving connection to the shaft 546 for the lower registration roller 521. As each of the armatures 574 and 575 is moved by its respective energized solenoid coil, it moves the element axially along the actuator and moves the other armature away therewith.

Upon energization of either of the coils for the solenoids, the respective armature will be driven in rotational movement. This rotary motion is produced by the cooperative action of a plurality of balls 577 rotatably held within a pair of coacting inclined depressions 578 formed one on the outer surfaces of each armature and the other cover plates 579 which may surround the solenoids as a casing therefor. The depressions 578 are disposed so that their longitudinal axes and therefore, the inclined surfaces are circular having a radius of curvature on the axes for the armatures. Each of the cover plates 579 and armature associated therewith are held one parallel to the other and close enough so that the balls are retained within the inclined depressions in the armatures and their co-acting inclined depression 578 in the cover plates.

In operation, when the solenoid SOL-2 is energized and the other SOL-1 de-energized, the armature 575 is attracted to the coil for SOL-2. This causes the element 576 to slide to the right, as viewed in FIG. 42 without producing axial movement of the actuator 553. Movement of the element 576 causes the other armature 574 to be driven toward the adjacent cover plate 579, this is, from the position shown in FIG. 44 to that shown in FIG. 45. The normal magnetic action of the coil for the solenoid SOL-2 would want to force the armature to the right as viewed in FIG. 10. Since the balls 577 prevent axial motion directly, the magnetic force will cause the balls to move along the inclined planes of the depressions 578 on the plate 579. Because of the locking action between the balls and the leading edges of the inclined planes of the depressions formed in the armature 574, the same will be caused to rotate. The armature 574 will rotate in an amount determined by the length of the depressions 578 and the distance the armature is allowed to move axially. For purposes of actuating the upper registration roller 520 into a paper feeding position and to reposition the fingers 555, the amount of angular rotation desirable is approximately 45.degree..

In the event the "up" solenoid SOL-1 is energized, the armature 575 will be rotated in the opposite manner as the armature 574. Regardless of which of the solenoids are energized, both armatures with the elements 576, secured therebetween will move as a unit and will slide relative to the actuator 553. However, the actuator will be rotated, the direction being determined by which of the solenoids being energized. With the "up" solenoid SOL-1 energized, the roller 520 will be held in its uppermost position and the fingers 555 in a sheet engaging condition.

DOUBLE SHEET SENSING MECHANISM

To sense the delivery of multiple sheets of paper to the transport 16 wherein the developed xerographic image is transferred to a sheet of paper, there is provided a double sheet sensing mechanism illustrated in FIGS. 50 and 51 which is adapted to signal the presence of two or more sheets and, if desirable, to interpose a reject finger into the path of movement of the sheets in order to deflect the sheet into a suitable paper tray and prevent the possibility of two or more sheets entering the transfer station for the xerographic machine. The multiple sheet sensing mechanism is generally indicated by the reference numeral 580 and illustrated in detail in FIGS. 51 and 52.

The sensing mechanism 580 includes a depending bifurcated base 581 secured to a support bar 582 mounted at its ends upon the base plates 401, 402 of the paper feeder mechanism 18. Pivotally mounted at the lower end of the bifurcated frame 581 by means of a pivot pin 583 extending through both legs of the frame is a movable frame member comprising two identically shaped and parallel arranged plate elements 584, 585. The plates 584, 585 are in the form of a bell crank with the pivot pin 583 extending through the apex thereof and one of its legs being adapted to support a pivot pin 586 for pivotally supporting a sensor shoe 587 thereon.

The other leg for each of the plates 584, 585 are joined together by means of a block 588 having a bearing surface arranged in cooperative relationship with an adjusting cam 589 mounted for camming rotation upon the support bar 582. A spring plunger 590 is threadedly received in the bar 582 and is made engageable with the rear surface of the block 588 in order to provide positive pressure against the cam 589 when the latter has been turned to affect proper setting of the sensor shoe 587. Proper setting of the cam 589 can be made by a suitable knob 591 secured to one end of the cam 589 and held rigid by a locking screw 592 engageable with a portion of the cam screw.

The sensor shoe is preferably formed with an outer layer arranged so as to be in the path of movement of one or more sheets of paper being fed by the paper handling device 18 and forced into the paper chutes 482, 483. The shoe is adjusted to be one and one-half paper thickness in proximity of a roller 593 mounted for rotation on a suitable pivot by means of a cross bar 594 also secured at its end to the base plates 401, 402 of the paper handling mechanism 18. The roller 593 is in frictional engagement with an idler roller 595 which in turn is in frictional engagement with the lower registration roller 521 from where motion is imparted thereto. As shown in FIG. 50 the lower registration roller 521 rotates in a counterclockwise direction which by means of the idler roller 595 will impart counterclockwise rotation to the roller 593, which direction is the same as the movement of a sheet of paper passing between the cooperating surfaces of the roller 593 and the shoe 587. Normally the shoe 587 is biased in a counterclockwise direction about its pivot 586 by a torsion spring 596 held in tension between an anchor pin 597 secured to the plate 585 and the shoe 587 against which the other end of the spring is engaged.

In order to control the progress of sheet movement between the shoe 587 and the roller 593 for each of sheet paper being fed into the xerographic transfer station, the shoe has secured thereto and movable therewith an actuator arm 598 which is arranged to engage a leaf spring actuator 599 during rotating movement of the sensor shoe 587 in order to actuate a normally closed switch SW-6 to an open position. In FIG. 50 the solid lines for the elements 598 and 599 illustrate the positions of these parts when a sheet is not being fed to the transfer station.

During normal operation, a single sheet of paper being forwarded to the transfer station by the registration rollers 520, 521 will be directed by the paper chutes 582, 583 between the sensing shoe 587 and the roller 593. With the sensing shoe and the roller being spaced slightly greater than the thickness of the sheet of paper, as the sheet is conveyed, the frictional pad on the sensing shoe will ride over the top surface of the sheet. This is achieved by the position of the cam 589 which may be adjusted so that the shoe 587 is spaced from the roller 593 one and one-half times the thickness of the sheets being used. In the event that two or more superposed sheets are driven between the chute 587 and the roller 593, the additional thickness of the sheets will cause rotation of the shoe 587 to produce actuation of the switch SW-6. This actuation may be utilized in a reject mechanism which may include a solenoid for causing reject fingers to be interposed in the path of movement of the sheet for deflecting the same into a suitable tray and out of the transporting system for the sheets of paper.

After a single sheet of paper has been transported through the double sheet sensing device by the rollers 520, 521 the sheet is directed by these rollers into the horizontal transport mechanism 16 for presenting the sheet to the transfer station C whereat the developed electrostatic image on the selenium belt 12 will be transferred to the under surface of the sheet as the same is moved in unison while in the transport in order to transfer the image to the sheet.

TRANSPORT MECHANISM

The transport 16, as shown in FIGS. 52, 53 and 54 comprises a relative flat fine structure formed by two transversely extending fine elements 600, 601 to which are attached side elements 602, 603 arranged in spaced apart relationship. The input side of the transport 16, or that side into which the sheet of paper is introduced is provided with an upper roller 604 mounted on shaft 605 rotatably retained by suitable bearings upon openings formed in the adjacent ends of the side plates 602, 603. Actually the shaft 604 comprises a plurality of resilient rollers 606 mounted on the shaft 605 for rotation therewith and which are adapted to project downwardly slightly from an upper flat grid-like guide member 607 which guides a sheet of paper thereunder. The guide member 607 cooperates with a lower grid-like member 608 mounted on a transversely extending support member 610 so that the planes of the guide members are parallel and closely spaced to permit a sheet of paper to be moved therebetween and therealong. A lower roller 611 also mounted on the support member 610 projects through the grid-like structure 608 and cooperates to assist in the movement of a sheet of paper through the transport 16 at this point.

At the output end of the transport 1y, the ends of the side elements 602, 603 are formed with suitable apertures for supporting bearings through which a drive shaft 612 is rotatably mounted. The drive shaft has secured thereto at one end outboard of the side element 602 a sprocket 613. Similarly, the shaft 605 terminates in a sprocket 614 positioned on the outboard side of the element 603. A chain 615 encircles both sprockets 613, 614 and an idler sprocket 616 rotatably mounted on a stub shaft 617 adjustably mounted in a slot 618 formed in the side element 602 to permit the adjustment of the sprocket 616 and the tension on the chain 615.

Also mounted in the transport 16 on the side elements 602, 603 is the transfer corotron 19 which is arranged as part of an integral channel member 620 which contains a detack corotron 621 located slightly downstream from the transfer corotron 19. The corotrons 19, 621 are connected by conductors 622 to a suitable source of electrical power for energizing the corotrons in order to accomplish their respective functions.

The frame structure for the transport comprising the frame elements 600, 601 and side elements 602, 603 is pivotally mounted by suitable bearings upon the shaft 612 in order to permit rotative movement of the transport out of the paper path and the clearing of paper jams in the event such occurs or, to perform any other maintenance at this station. The shaft 612 terminates at one end in a socket 623 secured by an aligned adjusting rod 624 to the machine frame plate 54a. The other end of the shaft is formed with a groove adapted to receive a tongue formed on an adjusting rod 625 adjustably mounted in retaining thimble 626 mounted upon the main frame plate 54. The socket 623 and the rod 625 are such as to hold the transport frame by cantilever action in the position shown in FIG. 40 in full lines but to permit pivotal movement to the position shown in dotted lines. This arrangement permits rotation of the frame 600, 601, 602, 603 about the axis of the shaft 612. The frame may be retained in its uppermost pivoted position by a spring latch 627 secured to a support brace 628 also mounted between the frame plates 54, 54a. As shown in FIG. 53 by the dotted line, the transport 16 may be pivoted and held away from the selenium belt 12 and the other structure included in the movement of the sheet of paper such as the roll 611 and the guide element 608.

As shown in FIG. 53 a sheet of paper W is shown in position that it would occupy during the transfer of an electrostatic image while being moved by the transport 16. While moving past the transfer station C, the latent image on the selenium belt 12 comes in contact with the under surface of the sheet W and, in cooperation with the transfer corotron 19, the image is transferred to the under surface. Immediately after the transfer of portions of a developed latent image, the sheet of paper has applied thereto an AC bias by the detack corotron 621 in order to overcome the electrostatic forces which normally hold the sheet W upon the belt 12. This detack charging neutralizes the charge on the leading edge and the other portions of the sheet of the belt 12 and, cooperates with an air puffer having nozzles 630 to continue stripout of the paper mechanically as it is moved from the surface of the belt 12. The charge upon the upper surface of the sheet W by virtue of the AC detack corotron 621 has a residual charge which permits the sheet to adhere to a guide plate 631. The guide plate 631 comprises a plurality of flat strips of metal against which the sheet W slightly adheres as it moves into the fuser assembly 21. The strips 631 are suitably mounted upon a channel 632 secured to a top frame plate 633 for the xerographic machine. A slow moving electric fan 634 mounted across the plates 54, 54a and arranged to convey air upwardly provides a slight negative pressure upon the upper surface of the sheet of paper W which tends to lift the sheet against the upper guide member 607 during travel of a sheet through the transport system.

It will be noted that the sheet W, after transfer of the developed electrostatic image thereon, is conveyed upsidedown or in such a manner that the transferred powdered image is on the under surface of the sheet. Any movement of the sheet of paper from this point on such as the sliding movement relative to the guide plate 631 will be upon structure that is positioned above the sheet and in contact with its upper surface in order to prevent smudging or smearing or any contact whatsoever with the yet unfused powder image. As is known in the art, the developing material used to form the powder images are specifically designed to permit the images to be fixed to sheets of paper by heat fusing, that is, the individual toner particles or resin softened and coalesce when heated so that they become sticky and readily adhere to the paper. With the shafts 605 and 612 being operationally connected by the chain 615, these shafts move in unison in the same direction for rotating the rollers 606 and 611 and transmitting sheets of paper. Adjacent the sprocket 613, a pulley 635 is secured to the end of the shaft 612 and is connected by the timing belt 68 to a drive system, to be described later, for the transport system.

FUSER APPARATUS

As shown in FIGS. 55-61 the fuser apparatus 21 is of the oven type and includes a main housing 650 formed with an upper section housing 651 in communication with the interior of a lower section housing 652 and, an electric motor M-5 for maintaining circulation of the heated air within the fuser housing 650. The walls of the sections 651 and 652 are preferably made from thick heat insulating material for minimizing heat losses through the walls.

Direct fusing of a particulate toner image on the lower surface of a sheet of paper W is achieved by forwarding the sheet bearing the power image to be fused through a slot 653 formed in the wall of the upper housing 651 by means of the guide plates 631 on the transport 16. As shown in FIG. 53, the plates 631 extend to the slot 653 and the sheet W is adapted to bridge across the fuser end of the strips 631 until the leading edge of the sheet is picked up by the conveyor system for the fuser 21. The fusing occurs while the sheet W is transported through the upper fusing housing 651 by virtue of the convection and radiation and, to a limited extent, some conduction of heat during the paper travel.

The conveying system for the fuser apparatus comprises a relatively wide, single, endless belt 655 having a width greater than the width of a sheet of paper being conveyed thereby. The belt is formed with many small apertures and is arranged to be driven around two rollers 656, 657 mounted transverse to the paper travel. The roller 656 is arranged at the input section of the fuser or adjacent the entrance slot 653 in order to present to the belt 655 the leading edge of a sheet of paper entering the fuser housing.

The roller 656 is supported on a shaft 658 supported by bearings mounted on each end of a U-shaped support device 659 secured to the outer walls of the housing 651. The other support roller 657 for the conveyor belt 655 is supported for rotation upon a shaft 660 mounted at one end in a bearing secured to one end of a U-shaped support device 661 and, at the other end to a drive system to be described hereinafter.

As the sheet of paper bearing a transferred powder image enters the housing 651 it comes in contact with the moving belt 655 in an inverted condition. This is accomplished by means of a vacuum plenum 662 arranged between the two runs of the belt and adapted to provide a reduced pressure upon the lower run of the belt for lightly maintaining the sheet against the lower run to be carried thereby. The apertures formed in the belt 655 insure that there is a gradual flow of air from the space below the lower run of the belt toward the space between the runs of the belt.

As the sheet of paper enters the housing 651 and becomes positioned to be conveyed by the belt 655, successively moving portions of the inverted toner image are immediately influenced by a steady flow of hot air which is of sufficient temperature as to cause the toner particles to become tacky in this preheat condition. This preheat condition continues for most of the belt travel and is provided by a heating and conveying apparatus to be described below.

In the lower heating chamber 652 there is formed an inner chamber 663 into which is positioned a rotatable impeller 664 supported and driven by a drive shaft 665 arranged axially thereof and connected to a motor M-5 adapted to imparting rotation to the impeller 664. Within the impeller 664 and arranged generally along the axis thereof and the shaft 665 is a heater coil 666 comprising relatively large diameter heat conducting material connected to a terminal 667 which in turn is connected to a suitable source of electrical power to be energized thereby.

The impeller 664 is provided with vanes arranged in a pattern such that upon rotation of the impeller, air will flow axially in toward the center space of the impeller vanes from the space below the impeller and then radially outwardly from the general direction of the axis of the impeller toward and through the impeller vanes. During energization of the motor M-5, air then is conveyed from within the internal space of the impeller where the air is continually heated by the coil 666 and then driven outwardly into the lower heating chamber 663. This air is conveyed out of the chamber 663 through an opening 668 formed in a separation wall 670 separating the chamber 663 within the housing 651 from a layer chamber 671 within the housing 651.

As the hot air under pressure leaves the chamber 663 and enters the chamber 671, it becomes slightly reduced since the chamber 671 is larger. This is effective to aid in directing heated air to the toner image on the sheet W that is under low pressure but of high volume and of sufficient temperature to preheat the toner particles in the image to the tacky condition referred to above. This flow of air also maintains the sheet of paper against the lower run of the belt 655. In this stage of heating of the toner image, the same is affected by convection type heating.

The second heating stage that the powder image on the sheet experiences is in the form of radiated heat produced by a pair of parallel arranged linear infrared heat lamps 672 arranged transverse to the paper travel, slightly below the lower run of the belt 655 and in a position just before the belt moves out of conveying relationship with a sheet in traveling around the roller 657. The lamps 672 are arranged in side by side relationship and each is arranged at the focal point of concave reflectors 673. The adjoining edges of the reflectors are secured together and are supported by a strip of metal 674 secured at its lower edge upon the separation wall 670. The heat lamps 672 are preferably of the quartz infrared type which are capable of producing relatively high heat quickly. The reflectors 673 are formed with a plurality of small openings 675 which provide communication between the interior chambers for the reflectors and the space surrounding the outer confines of the reflectors, this later space being connected by a narrow transversely extending passageway 677 formed in the lower wall 678 of the housing 651. Some of the air produced by rotation of the impeller 664 is conveyed by the passageway 677 and the openings 675 into the interior of the reflector 673 under a slight pressure in order to enhance the heating effect produced by the lamps 672. In addition, the heat produced by the lamps 672 is added to the heat produced by the coil 666 before being applied to the tackified image on the sheet W.

Throughout the time during which the sheet W is within the chamber 671 of the upper heating house 651 and during the operation of the heating means produced by the heating coil 666 and the impeller 664 and the heat produced by radiation from the lamp 672, the sheet is continually heated to some extent by conduction on the upper surface thereof. This heating by conduction is produced by a quartz infrared lamp 680 mounted at the apex of focus line for a reflector 681 having a configuration similar to that of the reflectors 673 arranged to concentrate heat rays upon the belt 665 as the same commences its return run preparatory to the picking up of another sheet of paper. The lamp 680 and the reflector 681 are suitably mounted by a bracket 682 to the sides of the housing 651 in a position to heat the belt 655 while the same is being run on the roller 657. This heating of the belt has two functions, one to present a heated conveying means which will be in intimate contact with a sheet of paper entering the fuser at a relatively cool temperature or, at least relative to the heat within the fuser interior. This eliminates the prospect of the belt 655 becoming a heat sink for the heat being absorbed by the sheet as it enters and becomes attached to the belt. The other function of the heating means produced by the lamp 680 is to provide heat by way of conduction to the powder image on the sheet of paper.

With the toner image now completely fused by the combined action of the convection air produced by the coil 666 and the impeller 664 and the irradiated heat produced by the lamps 672 and with the aid of the heat produced by conduction on the belt 655 by the lamp 680, the sheet is now conveyed through a rear opening slot 683 formed in the rear wall of the housing 651. In leaving the fuser assembly 21, the sheet of paper is conducted by a short running conveyor system 22 to a suitable output tray 23.

During continuous operation of the fuser apparatus 21, the motor M-5 remains continuously energized in order to continuously impart rotation to the impeller 664. Continuous movement of the belt 655 is maintained by a drive system connected to the shaft 660. The drive system includes a timing pulley 684 connected by a belt 685 to a timing pulley 686 connected to the shaft 612 on the horizontal transport 16. Air is continuously circulated throughout the entire outer housing 650 by virtue of the rotation of the impeller 664. The air that is directed through the opening 668 is expanded as it enters the chamber 667 and impinges upon the powder image on the sheet of paper W. The air is then directed upwardly through and around the conveyor belt 665 and rollers 656, 657 and conveyed back to the space below the impeller 664 and into the interior space thereof by means of a duct 687 (see FIG. 59) which is in communication with the upper regions of the interior of the housing 655 and with a chamber 688 formed in the lower section of the lower housing 652 below the lower end of the impeller as indicated by the flow arrows. This movement of air creates the previously described vacuum conditions in the plenum chamber 662 and the vacuum, in conjunction with the upward flow of air from the chamber 663, maintains each sheet of paper entering the fuser assembly against the conveyor belt 655 to permit movement thereby.

Also, by maintaining a closed loop air flow pattern, that is, a re-heat recirculating system, high heating efficiency is achieved since there is relatively little heat loss and this may be made up by a substantially reduced heat input. In order to minimize the time in bringing the temperature within the fuser assembly to a predetermined optimum valve, the entry slit 653 for the housing 650 through which sheets of paper are conveyed by the transport 16 and the exit slit 683 are provided with gates 695, 696 respectively which are adapted to close their respective slots during the warm-up period for the reproduction machine. A solenoid SOL-3 is connected to each gate for actuating the same upon the reception of control signals as will be described hereinafter.

MAIN DRIVE SYSTEM

The combined operation of the sheets feed mechanism 18, the sheet transport mechanism 16, the fuser assembly 21 the selenium belt assembly 11 and the developer assembly 14 consisting of the vertical transport arrangement and the horizontal conveying arrangement is provided by a drive system illustrated in FIGS. 61 and 62 and under control of an electric circuit to be described hereinafter to insure proper component coordination in time sequence during machine operation. In FIG. 61 and 62, the motor M-4 is provided with a gear reduction device 700 having an output shaft 701 and two pulleys mounted thereon for rotation during energization of the motor M-4.

The first pulley on the shaft 701 and designated by the numeral 702 is connected by a timing belt 703 to the pulley 515 on the shaft 513 for the sheet separating apparatus in the paper handling apparatus 18. The belt 703 is also directed around the pulley 539 for imparting a driving rotation to the upper registration roller 520. As shown in FIG. 61, the belt 703 is directed around an idler pulley 704 and 705 in order to provide a means for adjusting the tension on this belt and also for producing proper direction of movement for the pulleys 515 and 539. The other pulley 706 in the pair of pulleys on the shaft 701 is connected by the timing belt 68 for imparting drive to the pulley 67 for eventually effecting drive to the selenium belt assembly 11 and to the pulley 635 mounted on the shaft 612 for the transport 16.

Another motor, M-7 in the main drive system, has a drive pulley 707 connected by a timing belt 708 to a pulley 710 secured to one end of the shaft 264 which serves to drive the developer return mechanism comprising the internal bucket conveyor belt 236 within the return housing 227. Another pulley 711 is also driven by the motor M-7 and is connected by the timing belt 278 to the pulley 277 secured on the shaft 228 which drives the two screw conveyors 226 and 247.

From the foregoing description of the main drive system for the sheet feed mechanism 18, the transport 16, the fuser assembly 21, the selenium assembly 11 and the developer system 14, it will be appreciated that upon energization of the motors M-3, M-4, and M-7 these components will commence and remain in operation in timed sequence.

BELT CLEANING MECHANISM

The belt cleaning assembly 25 shown in FIGS. 63-65 comprises the rotatable brush 720 of such construction as to apply extremely light pressure to the photoconductive surface of the selenium belt 12 and to dislodge any powder particles that may adhere thereto. The brush is preferably formed of synthetic fur secured to a rigid cylinder 721 and is supported at its left end by a truncated cone shaped plug 722 formed with serrations thereon to grip the internal surface of the cylinder for rotation therewith. The plug 722 is fixed by a pin 723 to a shaft 724 of a motor M-9 mounted in a frame 725, bearings 726 being positioned within the frame and surrounding the shaft 724 for rotatably supporting the shaft. At its opposite end the cylinder 721 is supported by a second truncated cone shaped plug 727 provided with serrations thereon similar to the plug 722 that is rotatably and movably mounted by a bearing 728 to a stub shaft 730 fastened at a casing cover 731 secured by nuts to a housing 732 which serves to contain the brush 720. A coil spring 733 encircles the shaft 730 between the internal surface of the cover 731 and the adjacent end of the bearings 728 in order to permit limited axial movement of the plug 727 for permitting easy removal of the brush 720 and maintain constant pressure on the drive arbor for the brush despite variations in brush length.

For containing toner powder particles removed from the belt 12 by the belt cleaning device, the housing 732 encompasses approximately the entire brush area and as shown in FIG. 64 when applied to the belt 12 the opened end of the housing is nearly rendered closed by the adjacent surface of the belt. In order to insure as close as possible an air tight relationship between the selenium belt 12 and the interior of the brush housing 732 the upper edge portion of the housing is provided with an adjustable seal plate 734 which may be moved circumferentially relative to the housing wall in order to permit close positioning of the leading edge of the seal plate to the selenium belt during movement thereof. Similarly the lower wall section of the housing 732 is provided with an adjustable seal plate 735 which has a leading that may be moved toward and away relative to the belt 12 in order to minimize the spacing therebetween.

At the other end remote from the side thereof which faces the selenium belt, the housing 732 is formed with an exhaust opening 736 in the form of an elongated slot having its axis parallel to the axis of the brush cylinder 721. An adapter 737 is fastened to the housing 732 by suitable screws 738 and is formed with an opening conforming to the opening 736. The adapter serves to connect an exhaust duct 740 to the housing. The exhaust duct 740 may be connected to a suitable high volume, low pressure vacuum system in order to continuously exhaust toner particles accumu1ating within the housing 732 during brush cleaning operation.

In order to aid in the removal of toner particles from the bristles of the brush 720 during rotation thereof, the belt cleaning assembly is provided with a flicker device including a flicker rod or bar 741 mounted between the exhaust slot 736 and the brush and extends throughout the length of the housing 732 parallel to the axis of the cylinder 721. Actually the flicker device comprises the rod 741 and a flicker plate 742 in the form of a curved sheet metal plate extending the entire length of the housing 732 in the path or in alignment between the axis of the cylinder 721 and the exhaust opening 736. The flicker bar 741 is spaced slightly from the interior edge of the plate 742 and serves as the leading edge thereof interposed in the path of movement of the bristles for the brush 720 in order to cause flickering thereof.

The rod 721 is held between a thin ribbon 743 formed from the material of the plate 742 at each end thereof as shown in FIG. 65 and a flat spring element 744 secured by rivets 745 to the ribbon material 743 at each end thereof. The spring 744 is formed with an angled or curved portion 746 spaced from the ribbon 743 and between which the end of the rod 741 may be placed under spring bias provided by the element 744. The structure 743, 744 and 746 are provided at each end of the flicker plate 742 in order to releasably hold the flicker rod 741. These structures also permit rotation of the rod 741 which occurs by the continuous engagement of the moving bristles on the brush 720 during rotation thereof.

During cleaning operation using synthetic fur brushes 720 to clean a photoconductive surface such as a xerographic plate 12 there has been found severe filming of toner particles of the surface after short use thereof. The cause of this filming has been traced to some degree to the impaction of toner particles onto the brush bristle tips which occurs where the bristles strike the conventional stationary flicker bar. It has been found that the filming occurs since the toner build up on the fixed flicking bar leading edge where it contacts the bristles and becomes "tar-like" after several cycles with the tar-like toner being transferred to the bristle tips and in turn to the photoconductive surface being cleaned. The rotation of the flicker rod 741 minimizes toner buildup because of the continuously changing surface area exposed to the bristles at any one instant of time and the cooler temperature provided by a moving area such as afforded by a rotating rod.

For optimum cleaning situations, the bar 741 is coated with material having triboelectric properties matched with the brush bristles and the polarity of the preclean corotron 24. Like charges on the flicker bar with those produced by the preclean corotron and with the opposite charge on the brush bristles, as induced by the bar, will give optimum cleaning of residual toner particles having charges opposite to that of the bristles.

During operation of the belt assembly 25 the rotating bristles of the brush 720 continuously wipe off the residual toner particles resting upon the belt 12 as it moves from the transfer station of the machine to the charging station thereof. The residual toner particles are pulled off the surface of the belt and brought into contact with the flicker rod 741 thereby becoming disengaged from the brush bristles and allowed to be sucked through the exhaust adapter 737 and into the exhaust duct 740. A filter mechanism may be attached to the remote end of the duct 741 in order to receive the air entrained toner particles for separating the same and permit reclaiming of the toner particles. The vacuum system utilized with the duct 740 produces a flow of air through the brush cleaning housing 732 drawing air through the narrow slits between the seal plates 734 and 735 and the adjacent surface of the belt 12.

SELECTIVE DEVELOPMENT CONTROL

The xerographic machine previously described is adapted to copy originals and produce multiple copies thereof at a relatively high rate of speed. With provision for solid area coverage and a developing system which is adapted to supply toner particles to an electrostatic latent image in relatively high quantity, it is desirable that means be provided for controlling development either directly or indirectly in order to effect development only during those times in which a latent image is actually being processed. To this end there is provided with a selective development control arrangement, see FIGS. 2 and 66, which will selectively dissipate the charges upon the selenium belt during those period in which an original, has not been exposed which result in the formation of narrow strips between electrostatic images moving upon the belt, the initial movement of the belt before the machine is conditioned to trigger the first exposure and during the production of the last copy immediately after the trailing edge thereof is being moved into the development zone of the machine.

Since the electrical inertia and hysteresis effects limit the "Off-On" response time for corotron energization, the charging corotron 13 for the xerographic machine remains "On" during the complete printing cycle operation for the machine. With the charging corotron continuously placing a solid charge upon the selenium belt, the development control circuit is arranged to dissipate the charge in those areas of the moving belt where exposure has not been provided in order to prevent development of these areas and consequently minimize the loss of toner particles occasion by developing a solidly charged area of the belt.

The control circuit includes a discharge fluorescent lamp LMP-5 which is mounted in a suitable housing 750 secured to the base of the machine and arranged so that the lamp extends transversely across the path of movement of the selenium belt 12 after the same traverses the exposure station A.

The end coils for the lamp LMP-5 are connected respectively, to a secondary coil TS-2, TS-3 of a transformer TR. The primary TP for the transformer TR is connected to a suitable source of 120 volt 60 cycle electrical power. The transformer TR also includes a third secondary coil TS-1 which is adapted to step up the voltage and is connected to a full wave rectifier having positive and negative output terminals 751, 752, respectively. Preferably the output of the rectifier is approximately 300 volts DC and each of the secondaries TS-2, TS-3 capable of producing 6.3 volts.

With the two secondary windings being connected to the lamp coils as previously stated, the energization of the transformer primary TP will cause energization of the coils within the lamp tending to cause illumination thereof. However, with the center tap of the transformer secondary TS-2 being connected to the positive terminal 751 for the rectifier, the amount of energization provided for the lamp is sufficient to maintain the temperature of the gas therein at a sufficient temperature just below the threshold necessary to cause illumination thereof. As will be described hereinafter during description of the operation and electrical circuit for the xerographic machine this condition of the lamp LMP-5 is maintained during standby condition of the machine and in those periods when the lamp is not in illumination condition. The lamp circuit however is arranged such that with a proper input signal thereto additional energizing current is supplied to the two lamp coils in order to trigger the lamp to full illumination condition.

By maintaining the standby energization thereof just slightly below that voltage necessary to produce full illumination and allowing an extremely short duration pulse to trigger the lamp circuit to cause full illumination thereof, the pulse may be extremely short duration and the response time for the lamp to arrive at its full lumen output will become likewise extremely short. These time periods, that is, the duration of the input triggering signal and the response time in which the lamp achieves full illumination from a darkened or non-illumination condition and then reverts back again to a non-illumination condition can be measured in micro seconds.

In order to accomplish this short duration illumination response time, the transformer secondary TS1-3 has its center tap connected to the collector of a first transistor TR-1 which is normally maintained in a quiescent state. The emitter for this transistor is connected to the start shield 753 for the lamp LMP-5 and has its other end connected to the negative terminal 752 of the rectifier. Conduction of the transistor TR-1 will provide a small DC voltage to the start shield 753 in order to accomplish an additional triggering voltage to the lamp LMP-5 to effect the additional voltage bringing this lamp to full illumination condition.

In order to control conduction of the transistor TR-1 the base thereof is connected to the emitter of a second transistor TR-2 having its collector connected to a source of DC current on the order 24 volts. The bases for the transistors are connected respectively by diodes D-1, D-2 to the connection between the emitter for the transistor TR-1 and the shield 753 in order to provide leakage compensation for the circuit. The transistor TR-2 is normally held in a non-conducting state, however it is triggered into conduction by means of a pulse signal from the logic circuits indicated by the reference letter L for the xerographic machine to which the development control circuit is applied. The signal is connected to the base of the transistor TR-2 by way of a Zener diode Z and a variable resistor VR connected in series between the base of the transistor and the logic circuit. The pulse signal from the logic circuit is adapted to drive the transistor TR-2 thereby rendering the transistor TR-1 conductive for the DC power supply which supply is instantaneously connected to the shield 753 to provide the additional voltage for the lamp LMP-5 to produce full illumination thereof.

The machine logic L is arranged so that a pulse signal is generated for illuminating the lamp LMP-5 a short predetermined period of time after de-energization of the exposure lamps in the illumination system 10 for the xerographic machine. These occasions occur between each exposure on the selenium belt 12 which, in the event multiple copies of a single document are being made, is in the short interval that normally results in the spacing between the sheets being copied. The logic circuit L is also adapted to provide a continuous signal for the lamp LMP-5 during a time that the machine is turned "on" when belt charging and development operation occur and just prior to the first illumination cycle of the system 10. Another time in which a continuous control signal is generated is after the short predetermined period of time after the last flash of illumination produced in the system 10 when belt charging and developer operation continues just prior to the time the machine goes into its shutdown mode. This short predetermined period of time referred to is determined by the time required for the belt 12 to travel in order that an electrostatic image thereon is clear of the influence of the lamp LMP-5.

During those times that the discharge lamp LMP-5 is illuminated, the uniform charge placed upon the selenium belt 12 by the charge corotron 13 is erased since the light exposure by the lamp LMP-5 will cause conduction of the photoconductor on the selenium belt. Upon each of these occurrences, the area of the belt affected by the lamp LMP-5 will not carry a charge and therefore will not be developed as these portions of the belt traverse the development station B. With this arrangement it will be apparent only those portions of the selenium belt which actually carry electrostatic latent images of information to be copied or reproduced will be treated at the development station B. At all other times especially during the start up of the machine and the terminating processing station will not result in the full development of uniform charged areas which do not carry information to be reproduced. In this manner there is little loss of toner or developer material during a development process that is not necessary for machine use. With the provision of the control circuit the charging corotron 13 may be maintained in continuous energizing condition and the discharge lamp control will, in effect, provide that necessary "On-Off" requirement for determining whether the selenium belt will have or not have charged images thereon.

MACHINE OPERATION AND ELECTRICAL CIRCUIT

A clearer understanding of the operation of the xerographic machine and of the electrical circuit controlling the various components can best be obtained by reference to the schematic wiring diagrams of FIGS. 67 and 68 and the timing sequence chart of FIGS. 69 and 70.

Assuming that the power lines W-1, W-2 are connected to a suitable source of electrical power and with the neutral line N connected as shown in FIG. 67 and DC power supply PS-1 will be connected to a source of electrical power to provide multiple outputs of different voltages of direct current. The first operation on starting the machine is for the operator to press the "Start" button or "on" switch SW-1. The "On" switch SW-1, when closed, is connected in series with a relay contact 2CR-1 and a main relay 1CR which has an electrical connection with the neutral line N. In order to affect machine operation, the normally open contact 2CR-1 must be actuated to a closed condition in order to provide energization of the main relay 1CR. The contact 2CR-1 is actuated to a closed condition when the relay 2CR is energized and this is accomplished when the machine is initially connected to the source of electrical power.

The machine logic L also connected to the source of electrical power is in warm up condition or that condition which permits full operation of the logic system. Upon this occurrence a signal will be generated by the logic L for energizing the relay 2CR, the signal from the logic L functioning in the sam way as a circuit interlock switching arrangement.

With the contact 2CR-1 closed to affect machine operation, the operator pushes the "On" button for causing energization of the main control relay 1CR. This latches in the main relay which closes its own holding contact 1CR-2 by way of the closed "Off" switch SW-2. Energization of the main relay 1CR causes closing of the main relay contacts, 1CR-1, and 1CR-2 for providing electrical power to the electrical machine components of the machine.

Closing of the main contact 1CR-2 in the main line W-2 closes the circuit to the main vacuum motor M-1 which may be connected to a vacuum exhaust system for providing vacuum for the plenum chambers provided in the belt assembly 10 for holding the selenium belt 12 against the face plates 66, 67 and, a duct system for connection to the brush cleaning duct 740. In addition to the motor M-1, upon closing of the contact 1CR-2, the motor M-8 is also energized for providing a negative pressure immediately above the paper transport frame comprising the frame elements 600, 601, 602 and 603 for times when a sheet of paper is transported from the registration rollers to the fuser assembly.

In the timing charts of FIGS. 69, 70 it will be seen that during the warm up phase of the machine operation, that is, the time between closing of the "On" switch SW-1 and just prior to the machine going on into "Standby" mode, the main vacuum motor M-1 is energized and remains so for the entire machine operation. In addition to this closing of the "On" switch the switch 1CR-1 in the line W-1 also closes the circuit to the fuser heaters 672, 680 which provides electrical power thereto of approximately 2,500-3,000 watts for the quick warming up of these heaters, the fuser main drive motor M-3 for the sheet conveyor device within the fuser assembly 21 and, the motor M-5 for producing a vacuum in the fuser vacuum platen 662 and for conveying warm air toward the toner image upon a sheet of paper thereby preheating the same.

Closing of the contact 1CR-1 also provides electrical power to the paper elevation motor M-2 which is under control of the "up" switch SW-3 and the "down" switch SW-4. In the event that the paper tray 400 is in a position wherein the last few sheets of paper remain the switch SW-8 will be actuated to a closed position by the uppermost position of the tray thereby energizing the motor M-2 for initiating the shutdown of the machine by a relay circuit under control of relay 3CR and placing the machine in Standby condition and driving the tray to a lowermost position permitting the operator to add more sheets of paper thereto. In addition to the motors M-2 and M-3, energization of the main relay 1CR causes closing of the normally open switch 1CR-3 for providing electrical power to the solenoids SOL-3 which, when energized, actuate the normally open fuser flaps 695, 696 to their closed positions thereby permitting a quicker warm up of the fuser. Lastly, the initial closing of the "On" switch SW-1 provides for the energization of the solenoids SOL-5 through a timer circuit and the fuser control circuit FC which controls energization of the fuser heater lamps 672 and 680. The circuit FC also provides power for the control circuit to the thermostats THS-1 which controls the temperature of the fuser conveyor belt 655 and the thermostat THS-2 which controls the air temperature within the fuser housing chamber. The timer circuit for the solenoids SOL-5 is arranged to provide energization periodically for the solenoids thereby maintaining steady movement of toner through the hopper 300. During initial start-up of the machine, when the contact 1CR-1 is closed this energization is provided to insure adequate supply of toner and movement thereof in the event the previous non-use of the machine caused some settling of toner.

As shown in FIG. 69 in the timing chart for the operating cycles of the xerographic machine, closing the "On" switch SW-1 initially provides electrical power for the fuser main drive motor M-3, the fuser vacuum motor M-5, the fuser flap solenoids SOL-3, the fuser heaters 672, 680 and the main vacuum producing motor M-1. Except for the fuser drive motor M-3, these components remain energized during the Standby mode of the machine and remain so until the Print operation is initiated. As the machine assumes "Standby," the electrical power to the fuser heaters 672 and 680 is reduced to approximately 500 watts where they remain until the machine is placed in operation and, the fuser drive motor M-3 becomes inoperative. When the temperature within the fuser housing attains a predetermined temperature sensed by the thermostat THS-2, the power to the fuser heaters is reduced to 500 watts. The machine is now in condition to be operated for copying or duplicating purposes.

In order to commence further operation, the operator, after placing an original to be copied upon the platen P, will depress the "Print" button to close switch SW-5 which in affect electrically causes the grounding of the logic circuits L. Closing of the "Print" switch effectively causes the energization of the shutdown relay 3CR which closes a first contact 3CR-1 in the power line W-1 and the switch 3CR-2 in the power line W-2. Closing of these two switches supplies electrical power to the remaining components of the electrical circuit for the xerographic machine in the order to produce copies of the document. In FIG. 69, the timing chart is arranged so that the "Print" button actuation initiates the timing cycle for machine operation and all component energization at this point until shutdown of the machine occurs.

The timing cycle of operation is arranged in accordance with timing increments of 1 second for each increment and wherein each second is further sub-divided into four equal increments. As for those components which are energized at the depression of the "Print" switch, they will be described and discussed hereinafter in accordance with the order of listing shown in FIGS. 69 and 70.

With the closing of the switches 3CR-1 and 3CR-2 by actuation of the "Print" button, electrical power is supplied to the main drive motor M-4 which supplies power to the paper feeder 18, the transport system 16 and the selenium belt assembly 11. This electrical supply remains continuous during the complete operation of the machine thereby assuring continuous operation of the components that are actuated. In addition, the development electrode 210 and the entrance chute extension 211 are energized as is the development control lamp circuit. Also energized when the "Print" button is actuated are the DC and AC corotrons PS-2, PS-3, respectively. With the AC power being supplied to PS-3, the detack corotron 621, the preclean corotron 24 and the pre-transfer corotron 755 are supplied with electrical power for energizing the same for the entire operation of the machine. With the DC power supply PS-2 energized, electrical power is supplied to the charge corotron 13 and the transfer corotron 19.

The DC power supply PS-2 also supplied DC power having various voltages to the development electrode 210, the entrance chute 211 and the pick-off baffle 202. This then completes the circuit to those components enumerated above and illustrated in the timing charts in FIGS. 69 and 70 at the instant that the "Print" switch is closed. It will be noted that at "standby" condition, the fuser heater lamps 672, 680 are supplied with approximately 500 watts of electrical power which places the heater lamps into prefusing condition which of itself is not sufficient to provide enough heat for complete fusing or fixing of a toner image upon a sheet of paper. This supply of power to the fuser lamps will maintain the lamps in readiness for instant energization by a larger supply of electrical power when needed, which time occurs after a predetermined time period after the "Print" switch has been closed. When in fusing condition, the electrical power to the fuser heaters 672, 680 is approximately 2,000 watts.

While not illustrated, the logic circuits L are provided with suitable timing circuits which when conditioned for operation, are adapted to provide signal pulses to the various control devices for each xerographic processing component. As shown in the diagrams of FIGS. 67 and 68 the dashed line from the logic circuits L indicate the path of control pulses which serve to energize or de-energize or otherwise influence the components connected thereto.

After a period of 1 second has transpired after the actuation of the "Print" switch, the flash power supply for the illumination lamps L-1, L-2, L-3, L-4 becomes energized in order to condition the lamps for an instant supply of full power. With the flash power supply PS-4 energized, the lamps are supplied with a voltage which will cause illumination thereof when an appropriate trigger signal is applied.

After an additional second has transpired, or 2 seconds after the "Print" button has been actuated, the developer drive motor M-7 is pulsed by the logic circuit L for energizing the same. This causes the vertical conveying of developer material from the lower conveyor screw 226 onto the vertical conveyor belt 236 and the rotation of the upper conveyor screw 247 for initiating the circulation of developer material within the developer assembly 14 just prior to the developing stage of machine operation. At about 3 seconds after "Print" switch actuation, the fuser heaters 672, 680 are energized with additional electrical power to bring them up to 2,000 watts.

This condition of each of the above described operations occurring after the closing of the "Print" switch and those which were energized during the "Standby" mode of machine condition remain energized until the passage of slightly over 3 seconds from the time the "Print" button was actuated which time period is sufficient to bring all of the affected components to their full operating condition. The next phase of operation occurs after the referred-to 3 second period when the machine logic circuits L, after it has since sensed the condition of all the affected components, will produce a signal for the lamp trigger circuit PS-5 which will instantly supply that extra electrical power necessary for each of the illumination lamps for bringing the same to full illumination ability for a timed period measurable in microseconds. The pulse signal then from the logic circuit L to the flash power supply will also be directed to the lamp trigger circuit PS-5 which will provide full illumination for the illumination lamps and cause exposure of the selenium belt 12 thereby.

In exposing the selenium belt, an electrostatic latent image of the original is produced in a manner well known in a xerographic art and, with the selenium drive in operation, the area of the selenium belt exposed will move downwardly toward the lower roller 46 and toward the development control lamp LMP-5. As shown in the timing chart of FIG. 69, this control lamp is de-energized approximately a quarter of a second after exposure thus allowing time for the selenium belt to move the latent image out of the influence of the discharge lamp or, at the time the trailing edge of the electrostatic latent image area is opposite the influence of the lamp.

Approximately three-fourths of a second later or, after 4 seconds after the "Print" switch has been actuated, the toner control system will come into play and, as previously described, the 6 second toner control operation will commence. This has the affect of energizing the toner timer motor M-6 for conditioning the toner control system to sense the toner density in the developing system every 6 seconds in order to control operation if necessary of the toner dispenser motor M-10.

As the electrostatic latent image makes the turn at the lower conveyor roller 47, it approaches the development zone determined by the development electrode 210, 211. During movement through the development zone, the cascading developer material flowing downwardly between the development electrode and the selenium belt moving upwardly, the electrostatic latent image becomes developed. In this process step, toner particles are pulled away from the developer material carrier beads and applied to the latent image thereby producing a developed image of the original.

Approximately 2 seconds after exposure, the paper feed clutch coil 512 is energized upon reception thereof by a signal from the logic circuit L. This action operatively connects the rotating drive shaft 513 with the drive belt 516 in order to produce rotation of the separating rollers 485, 486. After a sheet of paper has been fed to the registration rollers 520, 521 and leading thereof is in register with the register fingers 555, the paper feed clutch 512 is de-energized for the copying cycle affecting the particular sheet of paper thus fed out from the paper feed mechanism.

Immediately after the paper feed clutch 512 is de-energized, the "up" register solenoid SOL-1 is energized in order to insure that the register fingers are in the up position to engage the leading edge of the sheet of paper arriving thereat and that the upper registration roller 520 is out of contact with the lower registration roller 521. Immediately after this actuation, the "down" register solenoid SOL-2 is energized in order to move the register fingers out of impeding engagement with the leading edge of the sheet of paper now between the registration rollers and to affect downward movement of the upper registration roller 520 for imparting feeding movement to the sheet of paper. At a time between the energization of the solenoid SOL-1 and the solenoid SOL-2, the signal from the logic circuit L will cause the de-energization of the developer drive motor M-7 since at this time there is no need to maintain the movement of the developing material into the development zone of the machine.

With the sheet of paper being driven by the upper and lower registration rollers, it is now within the influence of the transport system 16 as the paper moves to the image transfer station C. As shown in the timing chart 73, this action, which comprises the time in which the sheet of paper is being transported by the system 16 occurs for a period of approximately 1 second in duration.

As the sheet of paper is being so transported, the developed electrostatic image on the selenium belt 12 is transferred to the under-surface of the horizontally moving sheet of paper when the sheet is tangent to the belt while moving around the upper roller 45. Immediately after transfer of successive segments of the developed image occur, the sheet of paper is stripped away from the selenium belt as it is moved in curvature around the roller 45. Immediately after the segments are transferred, the puffer solenoid SOL-4 is energized by virtue of a signal from the logic circuit L for causing a low pressure high volume, flow of air from the nozzle 630 for starting the separation of the leading edge of the sheet of paper from the belt thereby permitting further separation of the detack corotron 621. This corotron places an electrostatic charge upon the upper surface of the sheet of paper for affecting the attraction of the sheet to the upper plates 631 and away from the selenium belt.

For the next second or more, the development electrode 210, 211 remains energized, in the event only one copy is being made, in order to insure complete development of the electrostatic image the last phases of which may be developed as the earlier stages or leading edge thereof is transferred. Just prior to the de-energization of the development electrode at approximately a second and a half after the transfer of the electrostatic images commences, the DC power supply PS-2 will be de-energized in order to terminate energization of the charge corotron 13, the transfer corotron 19 and the pre-transfer corotron 755.

As the latent image continues to be transferred to the trailing portions of the sheet of paper, the leading edge of the sheet will be directed into the fuser assembly 21 in order to insure fixation of the developed transferred image thereon. As shown in the timing chart FIGS. 69 and 70 just prior to the exposure of the original, the fuser heater lamps 672, 680 are energized with additional electrical power in order to bring the lamps to approximately 2,000 watts thereby effecting a temperature which is optimum for the complete fusing of powder images at the speed in which the sheet is transported through the fuser assembly. This high heat of the fuser lamps continues until some time after transfer of the developed image upon a sheet of paper whereupon a further signal from the logic circuit L will return the fuser lamps to its "Standby" heating condition of producing approximately 500 watts.

The timing charts in FIGS. 69 and 70 illustrate the energization and timing of energization for some of the components of the xerographic machine for the production of one copy of an original. The entire process beginning from the actuation of the "Print" switch takes approximately 10 seconds after which the logic circuit L will control the machine components and revert the same into "Standby" condition. This is accomplished by a circuit in the logic system coupled to the shutdown relay 3CR for de-energizing the same when the last copy being made has accomplished into its processing steps. As previously described, at "Standby," the only machine mechanisms that remain energized are the main vacuum motor M-1, the fuser vacuum motor M-5, the fuser heater control FC and the fuser flap solenoids SOL-3 to maintain closing of these fuser flaps. At this point the xerographic machine is in condition for the initiation of the print cycle to produce another copy of the same original or a new copy of another original.

In the event that multiple copies of an original are to be produced, some of the electrical components previously described will cycle automatically periodically in accordance with the timing arrangement provided in the logic circuit L. In the multiple copy mode, the shutdown relay will remain energized permitting all necessary components to function. Assuming that the xerographic machine as described is capable of producing one copy per second it will be apparent that exposure will occur every second and that paper feed registration transfer puffer operation and development lamp control will cycle, as previously described, once every second. To illustrate this in the timing chart of FIG. 70 additional exposure events are illustrated by the reference letter X once every second after the initial exposure. After the second exposure approximately 2 seconds later or 1 second after the energization of the feed clutch 512, the same will be actuated to affect separation of a second sheet of paper from the paper stack S. Similarly the "up" solenoid SOL-1 will be energized again 1 second after its first energization in order to insure proper registration of the leading edge of the second sheet of paper prior to its entering the transfer station.

It will be apparent that operation of the "down" solenoid SOL-2, the commencement of the paper separation and transfer movement, the commencement of the developed image transfer operation, and the operation of the puffer solenoid SOL-4 will occur repeatedly with 1 second intervals. In this manner then, multiple copies of an original will be produced until the machine is shutdown by the energization of the shutdown relay 3CR either automatically after the preset number of copies have been made or the machine is shutdown by the operator say by closing the "Off" switch SW-2. During multiple copy operation, the development control discharge lamp LMP-5 will be energized to discharge the portion of the drum moving past the lamp during those times that a latent image is not traveling past this lamp. These times occur for the spaces between copies and at the time that the trailing edge of the last copy has moved past the lamp and before the belt drive is terminated which occurs at shutdown condition of the machine. As shown in the timing chart of FIG. 70, the discharge lamp is energized during a single copy operation at a time when no latent image is present upon the selenium belt and, for illustration is designated by the reference letter Y.

As shown by the hatch marks, the discharge lamp will remain energized during single copy operation until the machine assumes a shutdown mode in order to completely discharge the charged areas of the belt. During multiple copy operation however, the discharge lamp will be energized only for short periods of time, those times between the trailing edge of one latent image and the leading edge of a succeeding latent image. These short periods of time would occur once a second in the event that the machine is producing one copy a second. In FIG. 70 the short periods of times are indicated by the reference letter N. After the last copy of a multiple series of copies have been made, the lamp will remain on until the selenium belt drive terminates and the DC corotron supply is de-energized.

During automatic operation when multiple copies are being produced, the paper tray 400 in the paper handling mechanism 18 continues to rise as paper sheets are fed off the stack. Upward movement on the top of the paper stack during this normal continuous paper feed operation is accomplished by the action of the switches SW-3, SW-4 which control the paper level to within a few sheet thicknesses. At its upper limit, the control arm 496 will be rocked about the axis of the shaft 513 by the upward movement of the separation rollers 485, 486 and this will cause opening of the normally closed switch SW-4 for de-energizing the motor M-2. As the paper level drops below a predetermined level, the arm 496 is rocked in the other direction to cause closing of the normally open switch SW-3 to energize the motor M-2 and effect raising of the paper tray and, consequently the paper level. In effect, the switches SW-3, SW-4 provide the differential, measured in a few thicknesses of paper sheets that determine the lower and upper limits, respectively, of the paper stack level.

When the supply paper has been depleted, a "low" paper level condition as far as the circuit for the switches SW-3, SW-4 is concerned, the tendency would be to maintain energization of the elevator motor. This prospect would cause damage to the structure of the paper handling mechanism. In order to avoid this prospect, the switch SW-8 is arranged to override the "low" level condition, to cause reverse energization of the motor M-2 regardless of the apparent closed circuit arrangement that would produce tray up movement effected by the closed "up" switch SW-4 when the paper level is low and, to produce de-energization of the shutdown relay 3CR for placing the machine in "Standby" condition. This reverse energization of the motor M-2 will cause the paper tray to revert to its lowermost position and in condition to accept more paper.

As shown in FIG. 67 the circuit for the switches SW-3, SW-4 also includes a manually operable switch SW-9 which may be mounted on the console for the machine. This switch is arranged to cause energization of the motor M-2 to produce up movement of the paper tray in the event the operator desires to accomplish this movement at the console or the switches SW-3, SW-4 have been disassociated from the paper control arm 496. This control of the motor can also be overridden by the switch SW-8 in the event the operator fails to release the manual switch with no paper in the paper tray. Again, upon activation of the switch SW-8, the tray is immediately lowered and the machine reverts to shutdown condition. If there is paper in the paper tray, the switch SW-4 will produce de-energization of the motor M-2 and the tray will be in paper feed position.

Similarly, there is provided another manually operated switch SW-10 for controlling the elevator motor for causing the same to drive the paper tray to its lowermost point. Actuating this switch energizes the elevator motor to lower the tray until the same reaches its lowermost position whereupon the lower limit switch SW-7 will be actuated to open the circuit to the motor. Actuation of the switch SW-7 occurs the, to override either the manual switch SW-10 or the normal mode of automatic operation which occurs when the upper limit switch SW-8 is activated, as previously described.

Throughout operation of the machine whether in the single copy mode or the multiple copy mode, the tracking of the selenium belt is under the control of the reversible motor M-11. A suitable belt edge sensing finger for a potentiometer POT and its associated circuitry BT may be arranged to control the energization of the motor and its direction of rotation.

While there is in this application specifically described one form which the invention may assume in practice, it will be understood that this form of the same is shown for purposes of illustration, and that the invention may be modified and embodied in various other forms without departing from the scope of the appended claims.

Claims

What is claimed is:

1. In an electrostatic machine for reproducing copies of originals onto sheets of copy paper having a photoconductive plate in the form of a flexible belt, means for producing a uniform charge thereon, means for supporting and moving the belt at a predetermined rate and in a path having at least one section wherein the belt travels in a flat condition to define the exposure station therefor, an illumination device for illuminating an original in full frame when the device is in its operative condition and projecting the illuminated full frame area onto the belt at the exposure station to produce an electrostatic latent image of an original thereon, energizing means for activating the illumination device to its operative condition for a short period of time to effect flash exposure of the original in full frame while the belt moves, the time of each flash exposure being sufficiently short so as not to cause a blurred latent image, means for developing the latent image with toner particles, a paper supply, paper feed means for feeding individually sheets of paper from the paper supply and into contact with the belt at the transfer station therefor preparatory to the transfer of developed images thereon, the improvement including control means operatively connected to the energizing means and the paper feed means for actuating the latter in a predetermined timed relationship to activation of said illumination device by the energizing means for effecting the feed of sheets of paper in timed relation to the production of corresponding latent images on the belt.

2. The machine of claim 1 including a registration mechanism interposed between the paper supply and the transfer station and including a member movable into the paper feed path to momentarily arrest and register the leading edge of a sheet of paper prior to the movement thereof to the transfer station, said control means being associated with the registration mechanism for actuating the member to release a sheet for movement in timed relation to activation of said illumination device.

3. In an electrostatic machine for reproducing copies of originals onto copy paper having a photoconductive plate in the form of an endless flexible belt, means for producing a charge thereon, means for supporting and moving the belt at a predetermined rate and in a continuous path having at least one section wherein the belt travels in a flat condition and which defines the exposure station for the machine, an illumination device for illuminating an original in full frame when the device is in its operative condition and projecting the illuminated full frame area onto the belt at the exposure station to produce an electrostatic latent image of an original thereon, means for developing the latent image with toner particles, an image transfer station, and paper feed means for moving individual sheets of paper into contact with the belt at the transfer station therefor in order to accomplish the transfer of developed images to sheets of paper, the improvement including

energizing means for activating the illumination device to its operative condition for a short period of time to effect flash exposure of the original in full frame while the belt is in continuous movement, the time of the flash exposure being sufficiently short so as not to cause a blurred latent image, control means operatively connected to said energizing means and said paper feed means for effecting equally timed successive activations of the illumination device for producing multiple exposures of an original and for activating the paper feed means in the same timed relationship to each activation of the illumination device.

4. In an electrostatic machine for reproducing copies of originals onto copy paper having a photoconductive plate in the form of an endless flexible belt, means for producing a charge thereon, means for supporting and moving the belt at a predetermined rate and in a continuous path, an exposure station for the machine, an illumination device for illuminating an original in full frame when the device is in its operative condition and projecting the illuminated full frame area onto the belt at the exposure station to produce an electrostatic latent image of each original thereon, means for developing the latent image with toner particles, an image transfer station, a paper supply, and paper transport means for moving individual sheets of paper from the paper supply into contact with the belt at the transfer station therefor in order to accomplish the transfer of developed images thereon, and toner fixing means arranged for receiving the sheets after the transfer of developed images, the improvement wherein

the transport means, the transfer station and the toner fixing means are arranged in a position so that paper movement occurs in substantially the same plane thereby effecting the movement of each sheet in substantially a straight path from the paper supply to the fixing means.

5. In an electrostatic machine for reproducing copies of originals onto copy paper having a photoconductive plate in the form of an endless flexible belt, means for producing a charge thereon, means for supporting and moving the belt at a predetermined rate and in a continuous path having at least one section wherein the belt travels in a flat condition and which defines the exposure station for the machine, an illumination device for illuminating an original in full frame when the device is in its operative condition and projecting the illuminated full frame area onto the belt at the exposure station to produce an electrostatic latent image of an original thereon, means for developing the latent image with toner particles, an image transfer station, and paper feed means for moving individual sheets of paper into contact with the belt at the transfer station therefor in order to accomplish the transfer of developed images to sheets of paper, the improvement including

energizing means for activating the illumination device to its operative condition for a short period of time to effect flash exposure of the original in full frame while the belt is in continuous movement, the time of the flash exposure being sufficiently short so as not to cause a blurred latent image, control means operatively connected to said energizing means for effecting successive activations of the illumination device for producing multiple exposures of an original, said control means being operatively connected to the paper feed means for activating the paper feed means in timed relationship to activation of the illumination device while said activation of the illumination device is being effected.