Cleaning Apparatus

Abstract

An elastomeric blade is herein disclosed for removing a dry particulate material from a surface to which the particulate material is electrostatically bonded. An edge of the blade is supported in pressure contact against the surface in a cutting tool fashion and relative motion between the blade and the surface produced wherein the edge of the blade moves between the particulate material and the surface to cut or chisel the material from the surface.

Description

This invention relates to apparatus for removing a finely divided particulate material from a support surface and, in particular, to a xerographic cleaning apparatus.

More specifically, this invention relates to apparatus for use in automatic xerographic reproducing apparatus for removing a residual toner material from an image retaining member after a developed image is transferred from the member to a final support material. In the art of xerography, a xerographic plate, which is generally formed of a photoconductive surface placed upon a conductive backing, is charged uniformly and the surface of the plate exposed to a light image of an original to be reproduced. The photoconductive coating is caused to become conductive under the influence of the light image so as to selectively dissipate the electrostatic charge found thereon thus producing an electrostatic latent image. The latent image is made visible by developing the image with any one of a variety of finely divided pigmented resins which have been specifically developed for this purpose. In the xerographic process, the pigmented resin material, or toner, is electrostatically attracted to the latent image on the photoconductive surface in proportion to the amount of charge found thereon. Areas of small charge concentration become areas of low toner density while areas of greater charge concentration become proportionally more dense. The fully developed image is generally transferred from the plate surface to a final support material, as for example, paper, and the image affixed thereto to form a permanent record of the original.

A preponderance of the toner material is generally transferred from the photoconductive surface to the final support material during the transfer operation. However, it has been found that the forces holding some of toner particles to the plate surface are stronger than the transfer forces involved and, therefore, some of the particulates remains behind on the photoconductive surface after image transfer. This residual toner, if not removed from the xerographic plate, will have a deleterious affect on subsequent imaging and developing processes.

In automatic xerographic machines, a wide variety of devices are employed to clean residual toner from the image retaining member. These devices include brushes or webs which wipe the surface of the plate in a manner so as to affect transfer of the residual toner from the surface to the wiping member. After prolonged usage, however, the cleaning member becomes contaminated with toner and must be replaced in the automatic machine. The cleaning member and the residual toner thereon are both generally discarded. In high-speed machines, this practice has proven not only to be wasteful but also expensive.

Another prevalent form of xerographic cleaning known and disclosed in the art is wiper blade cleaning in which a wiper blade of rubber-like material is dragged or wiped across the plate surface to effect separation of the residual toner from the plate. However, it has been found that the separated toner rapidly builds up or collects between the wiper blade and plate surface and is, therefore, extremely difficult to remove from the vicinity of the plate. Elaborate electrostatic and/or pneumatic means are generally utilized to effect toner removal.

It is, therefore, an object of this invention to improve xerographic cleaning apparatus.

A further object of this invention is to improve apparatus for simply and efficiently removing dry powder from a support surface.

Yet another object of this invention is to improve xerographic cleaning apparatus wherein residual toner material can be readily collected and reused in the xerographic process.

These and other objects of the present invention are attained by means of an elastomeric cleaning blade, means to support an edge of the blade in pressure contact with a residual image bearing surface, and means to produce relative motion between the blade and the surface wherein the edge of the blade moves between the toner material and the surface forcing the residual toner to be separated from the surface and directed behind the blade.

For a better understanding of the present 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 connection with the accompanying drawings, wherein:

FIG. 1 illustrates schematically an automatic xerographic reproducing apparatus employing the cleaning device of the present invention;

FIG. 2 is a side elevation in partial section showing the drum cleaning station and associated elements of the toner reclaiming system shown in FIG. 1;

FIG. 3 is a partial top view of the cleaning apparatus and toner reclaiming system shown in FIG. 2 constructed in accordance with the present invention;

FIG. 4 is a partial sectional view showing the toner reclaiming bead chain position in relation to the toner dispensing apparatus of the automatic xerographic machine shown in FIG. 1;

FIG. 5 is an enlarged partial side elevation showing the cleaning blade of the present invention supported in pressure contact with the photoconductive surface of the automatic xerographic machine;

FIG. 6 is an enlarged perspective view of the bead chain and tubular conduit illustrating the metering means associated therewith to distribute recovered toner material evenly throughout the developer housing.

As shown, the automatic xerographic reproducing apparatus comprises a xerographic plate including a photoconductive layer of a light receiving surface on a conductive backing and formed in the shape of a drum, generally designated 10, which is journaled in the frame of the machine by means of shaft 11. The xerographic plate is rotated in the direction indicated in FIG. 1 to cause the drum surface to pass sequentially through a plurality of xerographic processing stations.

For the purpose of the present disclosure the several xerographic processing stations in the path of movement of the drum surface may be described functionally as follows:

A charging station A, in which a uniform electrostatic charge is deposited on the photoconductive layer of the xerographic drum;

an exposure station B wherein a light or radiation pattern of an original document to be reproduced is projected onto the drum surface to dissipate the charge found thereon in the exposed areas to form a latent electrostatic image;

a development station C, at which a xerographic developing material having toner particles possessing an electrostatic charge opposite to the charge found on the drum surface in the latent image areas are cascaded over the moving drum surface whereby the toner particles adhere to the electrostatic latent image to make visible the image in the configuration of the original document to be reproduced;

a transfer station D, in which the xerographic powder image is electrostatically transferred from the drum surface to a final support material; and,

a drum cleaning and toner collecting station E, wherein the drum surface is first treated with corona and then treated with a doctor blade to remove residual toner particles remaining thereon after image transfer and wherein the removed toner is collected from reuse in the xerographic process and in which the drum surface is exposed to an incandescent panel to effect substantially complete discharge of any residual electrostatic charge remaining thereon.

The charging station is preferably located at the bottom of the drum in the position indicated by reference character A in FIG. 1. The charging arrangement consists of a corona charging device 13 which includes a corona discharge array of one or more corona discharge electrodes that extend transversely across the drum surface and are energized from a high potential source. The corona discharge electrode is substantially enclosed within a shielding member and is adapted to generate a charge confined within this specific area.

Next subsequent thereto in the path of travel of the xerographic drum is an exposure station B wherein a flowing light image of a stationary original is placed on the moving drum surface. Basically, the optical scanning and projecting assembly comprises a stationary transparent copy board 14 adapted to support the original to be copied: an illuminating means LMP-1 to illuminate uniformly the original supported on the copy board; a folded optical system including an object mirror 16 a movable lens system 17, and an image mirror 18 arranged in light projecting relationship with the moving drum surface to project successive, illuminated incremental areas on the original document onto the drum surface to form a flowing light image thereon. The lens element is positioned beneath the copy board and is arranged to move through a path of travel transverse to the plane of the copy board whereby the subject image of the original is scanned in timed relation to the movement of the light receiving surface on the xerographic drum.

Positioned adjacent to the exposure station is a fade out panel arranged to discharge or expose the drum surface in the areas between copies to a level below that required for xerographic development so that these charged but non-imaged areas will not be developed as the drum moves through the subsequent developing station.

Next adjacent to the exposure station is a developing station C in which is positioned developing apparatus 20 including a housing 28 having a lower sump portion therein capable of supporting a quantity of two component developer material. A bucket type conveyor 27, having any suitable drive means, is employed to carry the developer material from the lower sum area to the upper part of the developer housing where it is deposited in hopper 29. The developer material moves downwardly into contact with the upwardly moving photoconductive drum surface. Toner particles are deposited in the image areas on the drum surface in relation to the charge pattern found thereon to form a developed xerographic image. The unused developer material passes from the development zone back into the lower portion of the developer housing. Fresh xerographic toner material is supplied to the developer mix in proportion to the amount of toner deposited on the drum surface by means of dispensing apparatus positioned in the lower portion of toner dispensing bottle 21, as well as by means of the toner reclaiming apparatus of the present invention which will be explained in greater detail below.

Positioned next and adjacent to the developing station is the image transfer station D. Individual sheets of final support material are fed seriatim into sheet registering and forwarding apparatus 22 from either upper feed tray 35 or lower feed tray 34. The properly registered sheets are then forwarded into moving contact with the moving drum surface and the developed image electrostatically transferred from the drum to the final support material by means of transfer corotron 24. In operation, the electrostatic field created by the corona discharge device electrostatically tacks the transfer material to the drum surface whereby the transfer material moves synchronously with the drum while in contact therewith.

A mechanical stripper finger 25 is pivotally mounted in close proximity to the drum surface immediately adjacent to the transfer corotron. The finger is arranged to move into contact with the drum surface prior to the arrival of the leading edge of the support material. The arcuate shaped stripper finger moves between the drum surface and the leading edge of the final support material to mechanically break the electrostatic bond holding the material to the drum surface. Because of the positioning and the shape of the finger, the leading edge portion of the sheet of final support material is directed upwardly into contact with stationary vacuum transport 26. The trailing edge of the support material which at this time is still electrostatically tacked to the drum surface, continues to drive the support material forward so that it moves along the bottom surface of the vacuum transport towards fuser assembly 30.

The image bearing support material moving along the stationary vacuum transport moves into the nip between upper fuser roll 31 and lower fuser roll 32 of fuser assembly 30. The two rolls coact to deliver pressure driving force to the sheet of support material positioned therebetween. A radiant heat source of heat energy 33 extends transverse to the lower roll surface and transfers heat energy to the roll. The roll is specifically coated so that the heat energy transferred thereto is stored on the outer surface of the roll. As the roll rotates in the direction indicated, the heat energy stored there is brought into rubbing contact with the image bearing support material passing through the nip between the two rolls where image fixing is accomplished by delivering a combination of heat and pressure energy to the image bearing support material.

After leaving the fuser assembly, the fixed copy is transported through a circular paper path into a movable guide and drive roll assembly 36. The movable guides can be prepositioned to either feed the paper delivered from the fuser into upper feed tray 35 or into discharge catch tray 37. The apparatus can be programmed by means of the machine control logic system to precondition the paper handling equipment to accept simplex copies in upper feed tray 35. The simplex copy is then once again reprocessed through the xerographic transfer station to form a duplex image and then discharged from the machine as described above.

The next and final station in the automatic xerographic reproducing apparatus is a drum cleaning and toner recovery station E at which cleaning apparatus constructed in accordance with the present invention removes substantially all residual toner particles remaining on the xerographic drum surface after image transfer and recovers the residual toner as removed for reuse in the automatic reproducing apparatus in a manner to be described below.

A rectangular shaped flexible blade is utilized in the preferred embodiment of the present invention to remove residual toner from the moving drum surface. The blade is securely mounted in a suitable blade holder 51 formed by a dependent wall of the cleaning housing 40. The blade, in a working condition, normally rests transversely in pressure contact across the entire drum surface as illustrated in FIG. 5. The cutting edge of the blade, that is, the edge of the blade formed by the upper face surface, or top surface 47 and the front side surface 48, is positioned slightly below the horizontal center line of the drum and the cutting edge held in a manner to readily cut or chisel toner material from the drum surface much in the same manner as the lathe cutting tool removes material from a work piece. In fact, it has been found that the forces experienced by this type of cleaning blade are quite similar to those encountered by a lathe tool and the blade, therefore, is best shaped and supported in a tool-like fashion. The upper surface 47 of the blade is provided with a slight back rake so that the upper surface 47 and side surface 48 meet at an acute angle to produce a relatively sharp cutting edge. The blade is also supported in the present apparatus so that an end relief angle is provided between the side 48 of the blade and a line (t) tangent to the plate surface passing through the point of cutting edge contact. The relief angle will, of course, vary as the blade material varies in order to place the blade in an optimum cutting position while still supporting the blade against impact and frictional forces generated as the drum surface moves past the cutting edge. Experiments have shown that the blade cutting angles can be varied for different blade materials to effectively eliminate blade chatter and other undesirable effects associated with blade movement and the like.

Any suitable non-metallic flexible cleaning blade material exhibiting high resiliency and high tensile strength may be employed in the cleaning apparatus of the present invention. Typical non-metallic flexible materials include: polysiloxane rubber, polyurethane rubber, polytetrafluoroethylene resin, polytrifluorochloroethylene resin, styrenebutadiene rubber, nitrile rubber, nitro-silicone rubber, flexible polyurethane foam, polyethylene resin, and blends, mixtures and copolymers thereof. The blade should be, however, sufficiently soft enough to minimize abrasion to the support surface and, in particular, abrasion to a selenium type imaging type surface. The blade material should preferably have a Shore hardness of between 55 and 70 durometers, a tensile modulus of between 200 and 300 psi at 100 percent elongation, and have a resiliency giving a 35 percent rebound when tested by ASTM standard test D-1564. Tests have shown that a relatively wide latitude in the thickness of the blade can be tolerated with no noticeable change in the quality of the cleaning produced.

The entire cleaning housing 40 is mounted upon a pivot arm 58 which is, in turn, pivotally supported upon shaft 59 securely affixed to the machine frame. To facilitate the removal of the drum from the machine, the entire housing 40 is capable of being swung downwardly about shaft 59 moving the blade out of interference with the drum surface. As can be seen, open side channel 53 (FIG. 2) pivots downwardly to form a trough capable of containing any loose toner particles which may be within the housing at the time of drum removal. When the assembly is moved upwardly into the operative position shown in FIG. 2, a spring biased latch 86 is locked into supporting engagement with a latch pin assembly 87 and the latch locked in place by means of locking mechanism 88. With the assembly in operative position, the cutting edge of the flexible blade is supported in pressure contact with the drum surface as illustrated in FIG. 5.

Preferably, the blade is constructed of a polyurethane material having the physical properties herein disclosed and being supported in a cantilever fashion within housing 40 with the blade extending a length (L) beyond the support holder 51. When the housing is latched in the up or operative position, the cutting edge of the blade is placed in pressure contact against the drum surface causing the blade to be deflected a distance (d). Because of its resiliency, the blade will exert a pressure upon the surface 10 and adjust itself to any irregularities found in the drum surface thereby maintaining edge contact across the drum surface. It has been found that a deflection which is equal to the unsupported length raised to the third power (L.sup.3) will give optimum cleaning with a minimum amount of blade chatter for blade lengths between 0.35 and 0.50 inch. Furthermore, employing a back rake angle, angle (a) in FIG. 5, of about 95.degree. and a edge relief angle (b) of approximately 25.degree. reduces blade chatter to a minimum while at the same time, supporting the blade in a position to provide excellent cutting action.

To further reduce the tendency of the blade to walk or chatter during the toner cleaning operation, the housing support shaft 59 is best located upon the tangent line (t) wherein impact and frictional forces generated by the moving drum are absorbed by the support shaft.

It should be clear that by positioning the doctor blade slightly below the horizontal center line of the drum surface and providing the blade with a slight back rake, the removed residual toner material will be forced to fall to the backside of the blade, that is, to the side away from the photoconductive drum surface. As illustrated in FIGS. 2 and 3, the removed toner falls into an open side channel 53 adjacent to, and running longitudinally along the drum surface. A screw type conveyor 55 mounted upon shaft 54 is journaled for rotation in end plate 56 and cover plate 62. The conveyor is supported in the open side channel in substantially parallel relation to the doctor blade and is arranged to convey the toner particles removed from the drum surface towards toner recovery drive housing 61.

The open side channel 53 is closed at one end by means of end plate 56 while the opposite end of the channel is securely mounted in drive housing 61. The channel communicates with a reservoir or collecting area, generally referred to as 57, within the housing. A top portion of shaft 54 as seen in FIG. 3, extends through end plate 56 and has rigidly affixed thereto driving gear 85. Although not shown, driving gear 85 is driven from the machine main drive system to rotate the conveyor in a direction whereby the screw transports toner material laterally behind the blade into reservoir area 57 wherein the residual toner is collected.

A bead chain drive sprocket 63 is rotatably mounted on shaft 82 which is journaled for rotation in drive housing 61. The drive sprocket is driven directly from the main machine drive through screw conveyor shaft 54. Driven gear 84, mounted on the bottom end of shaft 54, as shown in FIG. 3, turns intermediate gear 83 which, in turn, drives sprocket drive gear 81 in the desired direction. Passing over the rim of the drive sprocket 63 is endless bead chain 64. The drive sprocket is arranged to engage and guide the bead and link members of the chain to move the chain in the direction indicated.

In the present invention, the residual toner which is collected in reservoir area 57 of the drive housing 61 is transported back to the developer housing by means of a conveyor system made up of supply and return tubing 66, 67; developer housing connector 70; and toner metering and return loop 71. The various parts making up the conveyor system are mated together so that a continuous substantially closed circuit conduit 68 having a uniform inside diameter runs from reservoir area 57 across the width of the developer housing and returns once again to said reservoir. As illustrated in FIGS. 2 and 3, the endless bead chain passes over drive sprocket 63 and is arranged to move through conduit 68 along a circular path of travel extending from the reservoir area through the developer housing and back. The inside diameter of conduit 60 is slightly larger than the diameter of the chain beads so that the beads will move freely through the conduit but yet be capable of pushing particulate toner material therethrough.

In operation, the endless chain moves downwardly through the collected toner material in reservoir area 57. The chain beads mechanically force the particulate toner material downwardly into supply tubing 66. The tubing is secured in operative relation with the drive housing by pressing the tubing firmly into the receiving adapter positioned in the bottom of the drive housing plate 65. Although not necessary in the present invention, the tubing can be locked in place by means of set screws or the like. The opposite end of tubing 66 is similarly connected in developer housing connector 70. Supply tubing 66 and the return tubing 67 are preferably constructed of a flexible plastic material which, as shown in FIG. 1, is conveniently routed from the toner cleaning and collecting apparatus 40 to the developer housing 20 through the machine so as to avoid the stationary machine components. Clearly, the above arrangement gives the present apparatus an extremely wide flexibility of usage in that the toner cleaning and collecting area can be positioned at any remote position in the machine and still be able to operatively communicate with the developer system.

New toner is dispensed in the present apparatus by means of a roll dispenser 77 positioned in the bottom portion of toner dispensing bottle 75. The bottle is seated between rails 73, 74 (FIG. 4) extending laterally across the dispensing opening provided in the developer housing. The bottle is adapted to dispense toner at a predetermined rate directly into the developer housing as dispensing roll 77 is rotated in the direction indicated. Developer housing connector 70 is secured to the developer housing by affixing embossed sections 72 thereon to rails 73, 74 as for example, by screws. The bead chain, which has transported toner material through supply tubing 66, is guided through approximately a 90.degree. turn as the chain passes through connector 70 so that the chain leaves the connector along a path of travel substantially parallel to rail 73. Loop 71, which is also fabricated of a relatively rigid plastic material, is supported in the connector 70 so that the loop is suspended just below the toner dispenser bottle in substantially parallel relation to the support rails. The bead chain entering the dispensing area of the developer housing first passes through a portion of tubing having a series of step-like cut-outs 90 formed in one side wall of the U-shaped tubing. As illustrated in FIG. 5, the elevation of each cut-out is lowered incrementally as the tubing extends across the developer housing, As the chain moves toner through this area, the toner is dispensed through the cut-outs so that the toner is distributed equally across the width of the housing. The bead chain continues around the loop and once again makes a 90.degree. turn through connector 70 and returns once again to drive housing 61 through return tube 67.

Although not shown, seals are provided between the top of the open side channel 53 and the rotating drum surface to prevent residual toner material from escaping from the toner cleaning and collecting apparatus 40. As can be seen, because a close system is thus provided, little or no free toner material is permitted to escape to the surrounding machine areas. The toner cleaning and recovery system as herein disclosed is not only extremely clean to operate but also protects the surrounding machine components from being contaminated by loose or free toner particles.

While this invention has been described with reference to the structure disclosed herein, it is not confined to the details set forth, and this application is intended to cover such modifications or changes as may come within the scope of the following claims.

Claims

I claim:

1. In combination,

an elongated blade constructed of a resilient elastomeric material, said blade having a top surface and one side surface meeting at an acute angle to from an extended cutting edge at one end of said blade, the acute angle facing at a first direction,

an image retaining member having a surface capable of electrostatically supporting dry toner powder particles thereon,

means positioned adjacent said member to securely mount the opposite end of said blade therein and being arranged to position the cutting edge of the blade in pressure contact with the member to support the cutting edge of said blade in intimate contact against said member, and

means to move said member in a path of movement whereby the surface thereof travels in a direction generally opposite said first mentioned direction to remove the dry toner powder particles from said member.

2. In combination,

an elongated blade constructed of a resilient elastomeric material, said blade having a top surface and at least one other side surface meeting at an acute angle to from an extended cutting edge at one end of said blade, the acute angle facing in a first direction,

an image retaining member formed in a closed loop configuration having a surface capable of electrostatically supporting dry toner particles thereon,

means positioned adjacent said member to securely mount the opposite end of said blade therein and being arranged to position the cutting edge of the blade in pressure contact with the member, and

means to move the surface of said member in a path of movement in a direction generally opposite said first mentioned direction whereby the dry toner powder particles on said member are caused to move over the top surface of said blade.

3. The combination as set forth in claim 2 wherein said mounting means is pivotable about a line which lies substantially in a plane tangent to the line on said member where said member is contacted by said blade.

4. In combination,

an image retaining member in an endless configuration and having a surface capable of electrostatically supporting dry toner powder particles thereon,

an elongated generally rectangular shaped blade constructed of a resilient, elastomeric material, said blade having a top surface and one side surface meeting at an acute angle to from an extended cutting edge at the upper end of said blade,

mounting means positioned adjacent said member to securely mount the lower end of the blade therein and being arranged to position the cutting edge of the blade in pressure contact with the member wherein the blade is deflected over the unsupported length thereof,

means to produce relative motion between the blade and the member to pass the cutting edge of the blade between the surface of the member and toner particles supported thereon to separate the toner particles from the member and force the toner particles downwardly from the top of the acute angle along said top surface.

5. The combination as set forth in claim 4 wherein said blade is constructed of a polyurethane elastomer having a high tensile strength.

6. The combination as set forth in claim 4 wherein said image retaining member is a horizontal supported xerographic drum.

7. The combination as set forth in claim 6 wherein the cutting edge of said blade is supported transversely across the drum surface in contact with a downwardly moving portion of the drum below the horizontal center line thereof.