Electrophotographic Duplicator

Abstract

An electrophotographic copying machine utilizes an endless belt having a conductive film and carrying a photosensitive surface thereon. The photosensitive surface comprises a thin evaporated film of a non-crystalloid selenium formed on at least a portion of the film and an organic semiconductor film deposited on the evaporated film. The endless belt also includes means for indicating exposure frames and the endless belt is positioned so that the photosensitive surface receives the image by a detector mechanism which senses the exposure frames. The apparatus also includes a movable frame which is detachably mounted to the copying machine for tensioning, aligning, and maintaining the belt flat.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a practical copying machine serviceable to produce a copy of books or the like, and more particularly, to an electrophotographic copying machine of the type in which an electrostatic latent image is formed on a photosensitive plate in response to a mirror image of an original picture image by applying the Carlson image producing process. Subsequently, thereafter a dielectric coated paper contacts the photosensitive plate and the electrostatic latent image is transferred onto the dielectric coated paper by means of the so-called electrostatic transfer method.

The practical copying machine in the prior art has been represented by a xerography type copying machine and an electrofax type copying machine. The former has been used because a plurality of copied sheets can be rapidly obtained thereby and these copies consist of uncoated papers of light weight, and therefore are easy to handle. However has the disadvantage that good clarity of a picture can not be expected from these copies since the exposure of a picture image is carried out by means of an original picture projecting optical system which moves relative to the angular velocity of and concurrently with a photosensitive substance on the surface of a drum. Further, due to the physical processes such as the cascade development, the transfer, and the cleaning operation carried out directly on the photosensitive substance, the quality of the picture is degraded on account of the photosensitive substance which is accordingly damaged and degenerated. Moreover; the outstandingly large size of the copying machine itself cannot be avoided in relation to the image making process which must be accomplished therein.

The latter type machine has been used because the copying machine itself is of a small size owing to the simplified image making process, and the copying speed of the first copy sheet is fast, as well as the quality of the obtained copy is superior to that of the former machine. However, it has the great disadvantage in that due to the quality of the photosensitive zinc oxide paper of the obtained copy, the treatment of the obtained copy is not so feasible as the instance of an uncoated paper.

As described above, even though these practical copying machines in the prior art have been widely used by making use of their respective advantages, neither of them is completely satisfactory due to the aforementioned disadvantage.

The known TESI method is an image producing method by which an electrostatic latent image formed on a photosensitive body is transferred onto a different dielectric coated paper and is then developed, but there are a variety of modes involved therein. For example, a dielectric coated paper contacts a photosensitive substance having an electrostatic latent image formed thereon, and both bases of the dielectric coated paper and the photosensitive substance are grounded. Then the dielectric coated paper is separated therefrom, and the electrostatic latent image being accordingly transferred onto the dielectric coated paper. According to this method, no physical process to be affected on the photosensitive substance is required in order to transfer the electrostatic latent image on the photosensitive substance, and a copy consisting of a desirable dielectric coated paper can be effected therefrom.

While, at present, no practical copying machine in which the aforementioned method was embodied has been developed. This fact depends on the conventional photosensitive substance according to which the intensity of a copy is too low to obtain clear copies, in a case of the repeated use of an identical photosensitive plate, on account of the pre-exposure effect, and which is never appropriate to practical use from the view point of the required high speed in the copying operation.

SUMMARY OF THE INVENTION

The inventors of the present invention have disclosed a photosensitive plate of which the structure and the photosensitive mechanism are quite different from those of a photosensitive substance or a photosensitive sheet for use in a practical copying machine in the prior art, and which has great mechanical strength and flexibility, and is capable of being charged to a high potential of 1,000V or higher. Also the photosensitive plate also is highly sensitive to such a degree that the exposure of a picture image can be carried out solely with several lux-sec and with the pre-exposure effect reduced to an outstandingly small value. Additionally it is further capable of forming an electrostatic latent image of high contrast and high resolving power. The inventors have also disclosed a transfer sheet onto which an electrostatic latent image formed on the photosensitive plate can be efficiently transferred by means of the most simplified TESI method as described above.

It is an object of the present invention to provide a practical electrophotographic copying machine of the electrostatic latent image transfer type which uses the aforesaid photosensitive plate and transfer sheet.

It is another object of the present invention to provide an electrophotographic copying machine of the electrostatic latent image transfer type, in which an electrostatic latent image consisting of a mirror image of a picture image is formed on a photosensitive plate disposed on an endless belt, and the electrostatic latent image is transferred onto a transfer sheet.

It is still another object of the present invention to provide an electronic photograph copying machine which is endowed with high sensitivity and high resolving power so that the electrostatic latent image therein can be easily transferred.

The other objects and advantages of the present invention will become apparent through the description of an embodiment thereof as set forth below.

The present invention is characterized by the following features which are required to attain the various objects of the present invention as described above.

One feature of the present invention resides in that an original sheet exposure station is mounted to the top of a copying machine, and an exposure optical system which projects the overall mirror image of a picture image is disposed under the rest exposure station. An endless belt conveying device which includes such structure as a belt zigzag preventer, a belt tensioner and a belt flattener at the projecting location. Also a photosensitive plate is adhered to the endless belt so as to provide an original picture projection part. The result is the capability of a picture image copy having outstandingly high quality as compared with that of the drum type sequential exposure process of the prior art.

Another feature of this invention resides in that the photosensitive plate disposed on the endless belt is the same size as an original picture to be projected thereon, and either one sheet or plural sheets thereof are arranged thereon so that the photosensitive plate is effectively made use of.

Still another feature of this invention resides in that arranged around the endless belt conveying device are a corona discharge device, an electrostatic image transfer conductive roller and a photosensitive plate location detecting device, and the photosensitive plate is set up in such a manner that it is usually kept stationary at the location of the linear plane portion of the endless belt, and is conveyed during a copying operation. Then it is stopped at the initial location just when the final copying operation is completed, the mechanical degeneration of the photosensitive plate being accordingly prevented.

Further another feature of this invention resides in that a control circuit is provided in order to programmably control the drive and stop actions for the endless belt conveying device, as well as all operations such as the ON-OFF action for the corona discharge device, the ON-OFF action for the illuminating light source of the original sheet exposure station, and the ON-OFF action for the transfer sheet supplying device. Thereby any useless conveyance of the photosensitive plate and any wasteful consumption of power are obviated, in addition, a speedy copying operation is accordingly made possible.

Another specific feature of this invention resides in that the endless belt conveying device is removably mounted to the machine body, and a belt zigzag preventing roller of the endless belt device is pressed against a belt tensioner device so as to enable the endless belt to be easily replaced.

Still another specific feature of this invention resides in that a thin evaporated aluminum film is provided on the endless belt as an electrode. Also arranged thereon is a flexible photosensitive plate composed of successive laminations of a thin evaporated film of a non-crystalloid selenium, either an organic semiconductor paint film or a thin evaporated film of a non-crystalloid selenium, a thin evaporated film of a Se-Te alloy, and an organic semiconductor paint film. The transfer sheet is such that a thin film of a high dielectric substance is coated on a paper base which has been given a conductive treatment. Copies thereby obtained are better and clearer than those obtainable by means of a practical copying machine in the prior art, in addition, a speedy copying operation being accordingly made possible.

BRIEF DESCRIPTION OF THE DRAWING

FIGS. 1A - 1C are illustrative views showing respectively the structure of a photosensitive plate and a transfer sheet which are adoptable to a copying machine in accordance with the present invention.

FIG. 2 is a perspective view showing the outside appearance of a copying machine in accordance with the present invention.

FIG. 3 is a sectional elevation view showing an essential part of the copying machine.

FIG. 4 is a perspective view showing an endless belt of the copying machine, wherein a part of the endless belt is cut away.

FIG. 5 is a perspective view showing an essential part of the endless belt.

FIG. 6 is a sectional elevation view showing the photosensitive plate location detecting device of the copying machine, and

FIG. 7 is an illustrative electric diagram of control circuitry for the copying machine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A photosensitive plate P for use in the present invention is, as shown by FIG. 1A, composed of a flexible film base a consisting of a polyester film with a thickness of 75.mu., a thin aluminium film b evaporated on base a to serve as an electrode, a very thin non-crystalloid selenium evaporated film c laminated on aluminium film b, and an organic semiconductor paint film d coated on selenium film c. The semiconductor paint consisting of a polyvinyl carbazole (PVK), a diphenyl trichloride (flexibility agent) and a monochlorobenzene (solvent). The PVK film d of the uppermost layer holds electric charges, and the thin selenium film c is for absorbing light rays and generating electric charge carriers. The thin aluminium film b forms a high rectifying barrier at the boundary interface with the selenium film c and completely checks positive holes from pouring into the thin selenium layer c. When the surface of the photosensitive plate is negatively charged and exposed to light rays, the positive holes generated in the thin selenium film c migrate to the PVK film d, and are shifted towards the surface thereof. The electric charge at the surface is neutralized so as to form an electrostatic latent image thereon. The above construction is a particular photosensitive plate which has been improved intensity and contrast characteristics of the picture image.

Next, if the photosensitive plate is modified, as shown by FIG. 1B, in such a manner that a thin evaporated film e of a Se-Te alloy is interposed as an intermediate film between the PVK film d and the thin selenium film c, the sensitivity of the photosensitive plate P is greatly increased because the thin selenium film c will no more longer absorb light rays and merely checks positive holes against their migration thereinto by forming a high rectifying barrier at the boundary interface with the aluminium evaporated film b. It is possible to mix tellurium in a weight ratio ranging from 10 percent up to 60 percent into the selenium so as to make up the Se-Te alloy film e.

Moreover, since photosensitive plates P are respectively so constructed that the selenium film c and the Se-Te alloy film e are so thin- each thickness is less than 1.mu. -the PVK film d is made of a macromolecular substance, and the aluminum film b and the selenium evaporated film c are solidly adhered to each other in such a way that the aluminium film is first exposed to the glow discharge and forcibly oxidized by ion-bombardment. Selenium is evaporated thereon in a vacuum so as to obtain a strong cohesion therebetween, and when the photosensitive plate is shaped, for example, into an endless belt, even if it is stretched between two rollers of 30 m .phi. and continuously rotated at the high speed of 1 m/sec for a period of 1,000 hours, the aluminium film does not separate from the selenium film, and accordingly it can be reliably put to practical use as a belt-like photosensitive plate.

The photosensitive plate P is charged and an electrostatic image is formed thereon by an exposure of a picture image. Subsequently a transfer sheet T, as shown by FIG. 1C is contacted therewith which is composed of a paper g of a thickness from 25 .mu. to 150 .mu.. The combined plate and transfer are given a conductive treatment, and a dielectric resin film h coated on the paper g by painting to a dry thickness from 2 .mu. up to 10 .mu.. The resin may comprise any resin of high dielectric strength such as, for instance, polyethylene, wax, alkyd resin, cellulose acetate, epoxide, and vinyl chloride acetate copolymer. The attached transfer sheet T is then pressed from its rear side by means of a roller which has been grounded and thereafter it is developed in a liquid. The result is a copy which is better than that obtainable by a practical copying machine in the prior art, particularly, if the photosensitive plate of the construction shown in FIG. 1B is used. It was confirmed that when it was charged to a potential higher than --1,000V, and exposed to a picture image of several lux-sec, then obtained on the transfer sheet T was a very clear visible image with no background contaminated and having high contrast and high resolving power (more than 50 lines/mm).

FIG. 2 and FIG. 3 are schematic views showing the overall construction of the copying machine in accordance with the present invention, wherein, on the top of a housing 1 of the copying machine, a glass plate 2 for use as a photographing station is fixed. Arranged under both sides of the photographing glass plate 2 are light sources 5 affixed with reflection shades 4 which illuminate the photographing surface of an original picture 3 which is positioned on the glass plate 2. Light sources 5 being, for example, an iodine lamp or a xenon lamp with a form approximate to a tubular light source. The light rays incident upon the surface of the original picture 3 are introduced to a mirror image projecting optical system which comprises a first planar mirror 6 for reflecting the light, a set of projection lenses 7, and a second planar mirror 8. The optical system is arranged underneath the glass plate 2 as shown in FIG. 3. Projection lenses 7 comprising either one lens or plural lenses, or else a zoom lens, and being arranged in such a way that the enlargement, the equality and the reduction of an image size is thereby made possible as desired. But such an arrangement is not shown in the drawing, as it is a well known means. A photosensitive plate P on which a mirror image of the original picture 3 being focused by means of the projecting optical system is mounted onto an endless belt 10 which is conveyed by an endless belt conveying system 9, and only one plate P is shown in the drawing, but it may be modified to a number of plates.

The detailed construction of the endless belt conveying device 9 will be hereinbelow described with reference to FIG. 4. Both side plates 11 and 12 composing the main body of the endless belt conveying device 9 are solidly built up by means of both side plate connecting members 13 and 14, and a plate 15 is disposed so as to occupy the area corresponding to the projected location between the top levels of both side plates 11 and 12 in order to keep endless belt 10 flat. Moreover rollers 16 and 17 are rotatably mounted to both side plates 11 and 12 on the fore and aft sides of the flatness keeper plate 15 in order to keep the endless belt 10 in a plane. Members 15 through 17 constituting a belt flatness keeping device.

Furthermore, on a bearing holding member 18 rigidly fixed to the side plate connecting member 13, two bearings 20 and 21 which hold a shaft 19 are mounted, and fixed on one end of the shaft 19 is the main part of a metal fitting 24 of which side flanges 23 rotatably support a roller 22 for preventing any possible zigzag of the endless belt 10. Formed on the side flanges 23 are protrusions 23' which prevent the belt 10 from projecting axially outwards of the roller 22 due to any zigzag tendency. Assuming now that the belt 10 is dislocated towards the side plate 12, the side edge 10' of the belt 10 comes into contact with the protrusion 23', thereby the metal fitting 24 is clockwise rotated about the shaft 19 so as to raise up that side with respect to the shaft 19. The lateral tensional mode of the belt 10 is accordingly varied, tbe belt 10 is therefore shifted towards the side plate 11 so that it is automatically returned to its initial situation, as well as the metal fitting is also returned concurrently to its initial status.

Also provided is a belt tensioning device which comprises a collar 25 disposed between bearings 20 and 21 of the shaft 19 and fixed to the shaft 19 by means of a stop screw. A compression spring 26 is interposed between the collar 25 and the bearing 21,and which tensions the belt 10 by biasing the metal fitting 24 together with the roller 22 at all times in the axially left direction of the shaft 19 on account of the compression spring 26.

The belt zigzag preventing roller, flatness keeper rollers 16 and 17, and a belt driving roller 27 which is rotatably fitted to both side plates 11 and 12 and drives the endless belt 10, are all covered by the endless belt 10.

An grounded conductive roller 28 is rotatably mounted on the main body of the copying machine so as to abut the belt drive roller 27 as shown in FIG. 3, and an electrostatic transfer station is composed of these two rollers 27 and 28.

As shown in FIG. 4, a gear 29 which is fixed on one end axle of the roller 27 is arranged so as to mesh, at the time when the endless belt conveying device is placed into its operating location, with a gear 31 which is driven by a sprocket wheel 30 which is rotatable only when it is engaged by an electromagnetic clutch CL so as to be interlocked with the chain transmission from a motor Mm which is continuously running as a driving source provided in the main body of the copying machine.

In the case where the endless belt 10 is composed of a flexible dielectric substance, such as polyester film, namely, in the case where the flexible film base a in the photosensitive plate P of the construction shown by FIGS. 1A and 1B, the photosensitive plate P is composed of a conductive layer 32, as shown in FIG. 5, such as an evaporated aluminum layer, a carbon powder containing resin layer, a CuI layer etc., which is made up around the periphery of both side edges of the endless belt. Roller 33 is rotatably fitted to a spindle rigidly fixed to the main body of the copying machine, grounded and arranged so as to be always kept in contact with the conductive layer 32. Aluminum electrode b of the photosensitive plate P shown in FIGS. 1A and 1B is also grounded.

Whereas, in the case where the endless belt 10 itself is a conductive belt, such as a stainless belt, a Ti belt etc., it is sufficient to use a roller 27 which has been made conductive and is grounded.

Arranged around the endless belt conveying device 9 and installed to the main body of the copying machine are, with the exception of the conductive transfer roller 28, the devices that are included shown in FIG. 3 in which are a corona discharge device 34 and two photosensitive plate tip detecting devices 36 and 37 for detecting a photosensitive plate tip detection mark 35 which has been inscribed on the endless belt 10 as shown in FIG. 5.

The photosensitive plate location detecting devices 36 and 37 are respectively as shown in FIG. 6. A dark chamber 38 is separated into two compartments, an illuminating lamp L is disposed in one compartment thereof, and a photoelectric element CdS is disposed in the other compartment. The compartments being respectively provided with a small hole 38' through the bottom thereof, whereby a photosensitive plate tip detection mark 35 which has been inscribed on a highly reflective member such as an evaporated aluminium layer is detected by the photoelectric element CdS by virtue of the lamp L of which the light beam is reflected on the mark 35, and becomes incident upon the photoelectric element CdS so that the arrival of the photosensitive plate P thereat can be determined. However, the top detection for the photosensitive plate P may be carried out in accordance with any other known means such as, for instance, to provide the belt 10 with a small hole by which a micro switch is actuated, or else to provide a cam which can be interlocked with the belt 10.

The photosensitive plate P on the endless belt 10 is operated in such a manner that it is usually kept stationary at the location detected by the detecting device 36 as shown in FIG. 3. But during a copying operation it is conveyed until it arrives at the projecting location where its movement is terminated on account of its being detected by the other detecting device 37. Upon completion of the exposure, it is again conveyed until it arrives at the initial location where its movement is stopped owing to the detecting device 36 which detects it again.

At a location above both rollers 27 and 28 composing the electrostatic image transfer station, stacked on a rack 39 are a plurality of transfer sheets T each of which is to be made up into a final copy, and which are sent out one by one sequentially by means of a feeding roller 40 driven by a motor M.sub.T. It is understood that each sheet is transmitted in accordance with a predetermined control determined by the movement of the belt 10. It is controlled so that both tips of the photosensitive plate P on the belt 10 and the transfer sheet T are simultaneously conveyed into the clearance between both rollers 27 and 28.

Arranged beneath the transfer station are a pair of transmitting rollers 44 and 45 for introducing the transfer sheet T into the clearance between a developing belt 42 and an electrode 43 which are both disposed in a liquid type developing apparatus 41. The developing apparatus being constructed in such a manner that a liquid type developer is circulated by means of a pump 47 driven by a pump motor M.sub.p (not shown in FIG. 3) so that the developer sucked from a developer reservoir 46 is supplied to the developing apparatus 41 through a supply pipe 48. Any excess of the developer is returned to the reservoir 46 via a return pipe 49, and excessive developer contained in transfer sheet T being squeezed by means of a pair of squeezing rollers 50 and 51 arranged appropriately in the developing apparatus 41. A conveyor belt 54 is disposed for conveying the transfer sheet from the developing apparatus 41 to a copy receiving tray 53 which is fixed to the side plate 52 of the copying machine. Also disposed above the conveyor belt 54 is a dry fixing device 57 consisting of a heater 55 and an air fan 56 driven by a fan motor M.sub.F not shown in the drawing. The heater 55 is not necessarily required in the case where a self fixing agent is contained in the developer. In addition, transmitting rollers 44 and 45, developing belt 42, squeezing rollers 50 and 51, and conveyor belt 54 are all interconnected with the motor M.sub.M, which is the driving source of the endless belt 10, by the transmitting means of the sprocket wheel and the chain.

The copying machine of the present invention being constructed as described above, the electric circuit thereof is connected as shown in FIG. 7. A main switch S.sub.M, a starting switch S.sub.W and an exposure light quantity regulating dial D are mounted at their respective locations where they are easily handled from the outside of the copying machine as shown in FIG. 2.

The operation of the copying machine in accordance with the present invention will now be described. The main switch S.sub.M is first switched to "ON". The motor M.sub.M, the pump motor M.sub.P and the fan motor M.sub.F are thereby driven, and the heater 55 is simultaneously activated. The transmitting rollers 44 and 45, the developing belt 42, the squeezing rollers 50 and 51, and the conveyor belt 54 are concurrently driven, but the endless belt 10 is not driven owing to the clutch having been disengaged. The liquid type developer is continuously circulated by the pump motor M.sub.P which is running.

After an original picture 3 is placed on the glass plate of the photographing exposure station 2, if the starting switch S.sub.W is pressed in order to start a copying operation, thereby the first control circuit A.sub.1 is actuated so that the clutch CL is operated so as to have the driving force of the motor M.sub.M transmitted to the driving roller 27. The endless belt 10 is accordingly rotated to have the photosensitive plate P conveyed, and a high voltage transformer HV shown in FIG. 7 is simultaneously activated so as to render a corona discharge device 34 shown in FIG. 3 operable. Consequently, the photosensitive plate P is in sequence charged so as to be made photosensitive as it is conveyed under the corona discharge device 34. At the time when the photosensitive plate P arrives at the projecting location, more particularly, at the moment when the top detection mark 35 is aligned with the photosensitive plate tip detecting device 37, the tip detection circuit B.sub.1 is actuated so as to render the second control circuit A.sub.2 operable. On account of the activation of this control circuit A.sub.2, the high voltage transformer HV is cut off so as to have the operation of the corona discharge device 34 terminated. Concurrently the current to the clutch CL is also shut off so that the rotation of the endless belt 10 is terminated, the photosensitive plate P being thereby stopped at the projecting location.

Simultaneously, the light source 5 is actuated so as to illuminate the original 3, thereby a mirror image of the original image is projected on the photosensitive plate P via the planar mirror 6, the projection lens 7 and the planar mirror 8, and an electrostatic image being accordingly formed thereon.

Additionally, the control of the second control circuit A.sub.2 is carried out by means of the exposure light quantity adjusting dial D via an exposure light quantity adjustment circuit C.

Upon completion of the operation due to the second control circuit A.sub.2, the third control circuit A.sub.3 is actuated so that the light source 5 is extinguished, and the current to the clutch CL is in turn restored so as to have the endless belt 10 again rotated. Simultaneously, the motor M.sub.T is also started so that another transfer sheet is taken out from the stack by means of the feeding roller 40.

The photosensitive plate P and the transfer sheet T are together caught between both rollers 27 and 28 so as to contact closely with each other. The electrostatic image on the photosensitive plate P is transferred to the transfer sheet T. The photosensitive plate P is conveyed after the completion of the transfer, and at the moment when the tip detection mark 35 thereof is sensed by the detecting device 36, the tip detection circuit B.sub.2 is actuated so as to terminate the operation of the third control circuit A.sub.3.

Consequently, the clutch CL is disengaged so as to terminate the rotation of the endless belt 10, and the photosensitive plate P being thereby stopped at the initial location thereof.

Whereas, the transfer sheet T having the electrostatic image transferred thereon is immediately conveyed by means of the transmitting rollers 44 and 45 to the liquid type development apparatus 41. The electrostatic image is developed with a toner while the transfer sheet T is being conveyed by the development belt 42 towards the squeezing rollers 50 and 51 which squeeze off the excessive developer contained in the transfer sheet T, which is thereafter conveyed on the revolving conveyor belt 54 and dried thereon until it is sent out to be stacked in the receiving tray 53.

In addition, the control circuits aforementioned are respectively composed of by making use of various known means such as, for example, a timer, a cam and a microswitch, a means being sequentially operated by virtue of a relay and a microswitch, and the like.

The descriptions shown hereinbefore are all concerned solely with the operation in the case where only one photosensitive plate P is disposed on the endless belt 10 and only one copy is produced therefrom. However, any predetermined number of copies can be continuously made up when plural copies are demanded, if a known counter which is not shown in the drawing is provided, and the first control circuit A.sub.1 is made operative at each time when the detection mark 35 is detected by the detecting device 36 until the final transfer sheet is signaled by the counter, and the endless belt 10 is continuously rotated until the predetermined number of copies are made.

Furthermore, if another photosensitive plate is additionally mounted on the planar portion of the endless belt 10, so that plural photosensitive plates are arranged thereon, the copying speed for the plural sheets is thereby made faster. Moreover, in the case where the photosensitive plate P is flexible, wherein disposed on the endless belt 10 is a thin evaporated aluminium film, and sequentially laminated thereon are a thin evaporated non-crystalloid selenium film, a thin film layer consisting of either an organic semiconductor paint or an evaporated non-crystalloid selenium, a thin evaporated Se-Te allow film, and an organic semiconductor paint film, the photosensitive plate P is not always required to stop at the original picture projecting location because of its outstandingly high sensitivity. The formation of an electrostatic image can be successfully carried out by means of a mere instantaneous projection thereof with a flash bulb such as a xenon lamp or the like. Moreover, if the second control circuit A.sub.2 is not endowed with the function to cut off the current flowing to the clutch CL, the continuous copying operation can be accomplished at an increased high speed.

Furthermore, in the copying machine according to the present invention, the endless belt conveying device 9 can be easily taken out of the copying machine by disengaging its gear 29 from the gear 31. The endless belt 10 is also capable of being taken out by inwardly pushing the zigzag preventing roller 22 against the bias of the compression spring 26. Accordingly, the replacement of the photosensitive plate P can be easily accomplished.

Since the copying machine according to the present invention is as described above, a picture image of an outstandingly high quality can be produced, as compared with that in accordance with a conventional copying machine, for example, a transfer type copying machine such as a sequential exposure system provided on a drum with a photosensitive substance. Any change of the magnification such as the reduction or the enlargement thereof can be very simply put in practice, also on account of no drum being required therein. There exists only a small dead space so that there is provided a transfer type copying machine of a compact conformation size which could not be heretofore realized. Further, there are obtained copies that are light and easy to handle, since they are comprised of dielectric coated sheets of high quality owing to the super fine grains particular to the liquid type development. Additionally, because the photosensitive plate P is disposed on the flat portion of the endless belt 10, and it is located at the flat portion at all times when the belt is stationary, the photosensitive plate is not impaired by any mechanical permanent strain so that it can be effectively put to use. Moreover, the copying machine is capable of rapidly producing a plurality of copies by means of the program control, and each of the copies obtained by said copying machine provided on the endless belt thereof with a flexible photosensitive plate composed of a thin evaporated aluminum film, and thin film layers which are further laminated in sequence thereon, and which comprise an evaporated non-crystalloid selenium film, a film of either an organic semiconductor paint or an evaporated non-crystalloid selenium, an evaporated Se-Te alloy film, and an organic semiconductor paint film, is better and clearer than the same obtained by any conventional practical copying machine as well as it becomes possible to make a multitude of copies at a higher speed than ever before. In addition, the photosensitive plate can be replaced merely by replacing the endless belt only, and the replacement can be very simply and easily carried out. As described hereinabove, the present invention is outstandingly effective in that it is capable of providing an ideally practical copying machine which is endowed with the advantages of the individual copying machines in the prior art, and from which the disadvantages thereof have been eliminated.

Claims

1. An electrophotographic copying machine, comprising:

an exposure station for supporting an original document to be exposed;

an optical system for projecting a mirror image of said original document;

means for conveying a photosensitive surface to receive the projected image, and including an endless belt having a conductive film thereon and supporting said photosensitive surface, said photosensitive surface comprising a thin evaporated film of non-crystalloid selenium formed on at least a portion of said conductive film, and an organic semiconductor film deposited on said evaporated film;

means for driving said endless belt;

a movable frame for tensioning and aligning said endless belt;

said endless belt including means for indicating exposure frames;

means for detecting said exposure frames;

means responsive to said detecting means for controlling said driving means to position said photosensitive surface to receive said image;

means for supplying transfer sheets;

means for contacting individual ones of said transfer sheets with said photosensitive surface; and

2. An electrophotographic copying machine as in claim 1 wherein said thin

3. An electrophotographic copying machine, comprising:

an exposure station for supporting an original document to be exposed;

an optical system for projecting a mirror image of said original document;

means for conveying a photosensitive surface to receive the projected image and including an endless belt supporting said photosensitive surface;

means for driving said endless belt;

frame means for maintaining the longitudinal alignment of said endless belt while being driven including a movable frame supported on a shaft extending along the longitudinal axis of said endless belt, said movable frame including a pair of said frames between which an idling roller is rotatably mounted and over which said endless belt travels, said side frames each having a protrusion extending outwardly of said idling roller so that should said endless belt shift toward either of said side frames, the edges of said belt will come into contact with one of said protrusions thereby causing said movable frame to rotate about said shaft to realign said belt;

said endless belt including means for indicating exposure frames;

means for detecting said exposure frames;

means responsive to said detecting means for controlling said driving means to position said photosensitive surface to receive said image;

means for supplying transfer sheets;

means for contacting individual ones of said transfer sheets with said photosensitive surface; and

4. An electrophotographic copying machine, comprising:

an exposure station for supporting an original document to be exposed;

an optical system for projecting a mirror image of said original document;

means for conveying a photosensitive surface to receive the projected image and including an endless belt supporting said photosensitive surface;

a movable frame for tensioning and aligning said endless belt;

means for driving said endless belt and including a clutch;

said endless belt including means for indicating exposure frames;

means for detecting said exposure frames;

means for supplying transfer sheets;

means for contacting individual ones of said transfer sheets with said photosensitive surface;

means for developing and fixing the image on said transfer sheets; and

means responsive to said detecting means for controlling said clutch to position said photosensitive surface to receive said image and including a circuit for controlling said means for driving and said means for

5. An electrophotographic copying machine, comprising:

an exposure station for supporting an original document to be exposed;

an optical system for projecting a mirror image of said original document;

means for conveying a photosensitive surface to receive the projected image, and including an endless belt having a conductive film thereon and supporting said photosensitive surface, said photosensitive surface comprising a thin evaporated film of non-crystalloid selenium formed on at least a portion of said conductive film, and an organic semiconductor film deposited on said evaporated film;

means for driving said endless belt;

a movable frame for tensioning and aligning said endless belt;

said endless belt including means for indicating exposure frames;

means for detecting said exposure frames;

means responsive to said detecting means for controlling said driving means to position said photosensitive surface to receive said image;

means for supplying transfer sheets, said transfer sheets each comprise a conductive base member and a thin dielectric film coated on said conductive base member;

means for contacting individual ones of said transfer sheets with said photosensitive surface and including a conductive roller engaging said conductive base member; and

6. An electrophotographic copying machine, comprising:

an exposure station for supporting an original document to be exposed;

an optical system for projecting a mirror image of said original document and including a flash device for illuminating said original document;

means for conveying a photosensitive surface to receive the projected image, and including an endless belt having a conductive film thereon and supporting said photosensitive surface, said photosensitive surface comprising a thin evaporated film of non-crystalloid selenium formed on at least a portion of said conductive film, and an organic semiconductor film deposited on said evaporated film;

means for driving said endless belt;

a movable frame for tensioning and aligning said endless belt;

said endless belt including means for indicating exposure frames;

means for detecting said exposure frames;

means responsive to said detecting means for actuating said flash device;

means for supplying transfer sheets;

means for contacting individual ones of said transfer sheets with said photosensitive surface; and

7. An electrophotographic copying machine as in claim 6 wherein said movable frame is detachably mounted to the copying machine and includes a driving roller for moving said endless belt, a movable frame supporting said driving roller and supported on a shaft extending along the longitudinal axis of said endless belt, and means for extending said

8. An electrophotographic copying machine as in claim 7 wherein said movable frame further includes means for engaging each side of said endless belt to rotate said movable frame about said shaft to re-align

9. An electrophotographic copying machine as in claim 6 wherein said means for driving includes a clutch and said means responsive to said detecting means controls said clutch and includes a circuit for controlling said

10. An electrophotographic copying machine as in claim 6 wherein said thin

11. An electrophotographic copying machine as in claim 6 wherein said transfer sheets each comprise a conductive base member and a thin dielectric film coated on said conductive base member and said means for contacting includes a conductive roller engaging said conductive base member.