CA1097722A

CA1097722A - Electrophotographic copying apparatus

Info

Publication number: CA1097722A
Application number: CA251,101A
Authority: CA
Inventors: Yasuhiko Doi; Shunji Yamamoto; Osamu Okada; Takashi Hikosaka; Masamichi Hayashi
Original assignee: Minolta Co Ltd
Current assignee: Minolta Co Ltd
Priority date: 1975-04-30
Filing date: 1976-04-27
Publication date: 1981-03-17
Also published as: GB1538751A; FR2309907A1; DE2618983A1; FR2309907B1; JPS51128538A

Abstract

ABSTRACT OF THE DISCLOSURE

An electrophotographic copying apparatus of the electrostatic latent image transfer type has a reciprocat-ingly movable platform on which an original to be copied is placed. A rotatable photoreceptor drum is disposed below the platform and has a photosensitive surface onto which an image of the original is projected. A corona charging device is disposed around the drum for applying charges uniformly onto the drum. An image of the original is projected through an exposure slit so as to form an electrostatic latent image on the photosensitive surface.
The thus formed latent image is transferred onto a copying paper sheet. The copying paper sheet is separated from the drum, and residual charges are erased from the drum.
The image transfer mechanism is shifted between a first position in which it is out of contact with the drum and a second position in which it is in contact with the drum.
The image transfer mechanism is shifted from its first to its second position upon detection of the arrival of a copying paper sheet at a predetermined location. The platform is normally locked against movement, but is released to allow movement upon such detection.

Description

1~"77Z2 - The present invention relates to a copying apparatus and, more particularly to a transfer type electrophotographic copying apparatus with a movable platform to place an original to be copied thereon.
Conventionally, in the copying apparatus of the above described type, there is usually employed a copying system known as the Carlson system, in which an electrostatic latent image formed on an electrophoto-sensitive photoreceptor in the configuration of a drum or an endless belt is subsequently visualized by apply-ing thereto a developing material in the form of powder or liquid for the transfer of the visualized image onto a copy paper sheet, or another system wherein the latent image formed on the photoreceptor is directly transferred onto a copy paper sheet without visualization, with the latent image transferred onto the copy paper sheet sub-sequently developed for obtaining the copy of the original.
- In the copying apparatus of the above described type, however, despite the long felt needs for compact size and simple handling, there has been none which com-pletely satisfies such needs.
In other words, in the conventional visualized image transfer type copying apparatus as described above, it is necessary to dispose various processing devices, such as a corona charger, an exposure device, a develop-ing device, a transfer device, a copy paper sheet separating device, charge erasing devices and a clean-ing device etc., around the photoreceptor, which arrangement inevitably results in a large si7e of the photoreceptor itself and complicated construction of 1~977ZZ

the copying apparatus as a whole with consequent trouble-some maintenance, while in the latter type which develops the latent image transferred on the copy paper sheet, no copying apparatus sufficiently fit for practical use has been developed as yet, though this latter type of copying apparatus can eliminate the disadvantages in-herent in the former type since the developing device needs not be located around the photoreceptor.
Furthermore, in the latter type of copying apparatus wherein the latent image formed on the photo-receptor is directly transferred onto the copy paper sheet, the copy sheet is fed in synchronization with the movememnt of the latent image on the photoreceptor drum, while the same copy paper is pressed, at the transfer station, against the photoreceptor surface by an elect-rically conductive roller or a grounded roller so as to induce charge having the same polarity as that of the latent image on an insulating layer of the copy paper sheet for transferring the latent image onto the copy paper sheet, in which case, if the copy paper sheet is directly fed between the photoreceptor surface of the photoreceptor drum and the grounded roller, a phenomenon similar to that in rapid generation of a strong electric field between the leading edge of the latent image formed portion on the photoreceptor drum surface and the grounded roller is observed, such a phenomenon giving rise to white spots or absence of black tone in the developed image due to undesirable electrical discharge between the photo-receptor drum surface and the reverse side of the copy paper sheet in a position, i~mediately before the copy ~0977ZZ

paper sheet contacts the latent image formed portion on the photoreceptor surface, where the gap between the photoreceptor drum surface and the copy paper sheet is larger than the gap whereat the transfer is normally S carried out. To eliminate the disadvantages as described above, there is conventionally proposed a method wherein the copy paper sheet is caused to contact the photorecep-tor drum surface before the former is pressed against the latter by the grounded roller, in which method the copy paper sheet initially pressed against the photo-receptor drum surface by an electrically insulating roller is subsequently fed between the neighboring grounded roller and the photoreceptor surface. The above described conventional arrangement is effective for preventing generation of the white spots or absence of black tone in the developed image, since the surface of the insulating roller insulated from the copying ap-paratus housing is in an electrically isolated condition, with the surface potential of the former being varied according to the potential of the latent image formed portion when the latent image formed portion on the photo-receptor drum approaches the insulating rol~er as the photoreceptor drum rotates. In other words, in the above described conventional arrangement, transfer of the high potential part of the latent image formed portion is nearly completed at the portion of the insulating roller without generating the strong electric field between the copy paper sheet and the photoreceptor drum surface or the electrical discharge therebet~een , in which case, however, there must be a certain distance between the 10~772Z

insulating roller and the grounded roller, since if the distance between the two rollers is excessively small with respect to the copy paper sheet, the portion of the copy paper sheet whose reverse surface has electrical S conductivity to a certain extent and which contacts the insulating roller is electrically connnected to the grounded roller, thus giving rise to the absence of black tone in the developed image. However, separating the two rollers to a suitable extent from each other requires 1~ means for positively keeping the copy paper sheet in con-tact with the photoreceptor drum surface between the same rollers, because static charge on the photoreceptor drum surface after exposure is rather weak for positively hold-ing the copy paper sheet on the photoreceptor drum surface, and especially when a photoreceptor drum of a small diameter is employed, it is extremely difficult to hold the copy paper sheet on the drum surface by the electrostatic at-tracting force alone.
In order to overcome disadvantages as described above, there are proposed transfer devices wherein a plural-ity of narrow belts of insulating nature such as rubber are directed around the insulating roller and the grounded roller or wherein guide member is provided between the two rollers for preventing the copy paper sheet from coming off the photoreceptor surface, the former device of which, how-ever, still has such a trend that the state under which the copy paper sheet contacts the photoreceptor surface tends to differ from one portion to another, thus result-ing in fogging or blur at the trailing edge of the developed image on the copy paper sheet, while in the latter device, 10"77Z2 the guide member itself has no positive effect for holding the copy paper sheet on the photoreceptor drum surface, tending to cause jamming of the copy paper sheet.
Accordingly, an essential object of the present invention is to provide an electrophotographic copying apparatus which is equipped with an improved transfer device in addition to compact size and light weight of the copying apparatus.
~ o this erld the invention consists of an electrophoto-graphic copying apparatus of the electrostatic latentimage transfer type, said apparatus comprising: a reciprocatingly movable platform on which an original to be copied is placed; a rotatable photoreceptor drum disposed below said platform and having a photosensitive surface onto which an image of the original is projected;
means disposed around said drum and including a corona charging means for applying charges uniformly onto said drum, an exposure slit means through which an image of the original is projected so as to form an electrostatic latent image on said photosensitive surface, an image transfer means for transferring the thus formed latent image onto a copying paper sheet, a separating means for separating said copying paper sheet from said drum, and an erasing means for erasing residual charges from said drum;
a paper feeding means for feeding a copying paper sheet along a path to said image transfer means; a developing means for developing the copying paper sheet; a fixing means for fixing the thus developed image;

~6~"772Z
means for detecting the arrival of a copying paper sheet at a predetermined location along said path;
shifting means for shifting said image transfer means between a first position in which said image transfer means is out of contact with said drum and a second position in which said image transfer means is in contact with said drum; control means, actuatable by said detection means, for operating said shifting means for shifting said image transfer means from said first to second positions thereof; and locking means ~-normally preventing said platform from movement, and actuatable by said detecting means to release said platform and allow movement thereof.
According to the preferred forms of copying apparatus of the present invention, various devices, such as devices for corona charging, exposure, trans-fer, and charge erasing etc., are made compact in size, each of which devices is efficiently disposed around the photoreceptor drum with minimum spaces necessary therebetween, thus making it possible to adopt the photoreceptor drum of a small diameter. At least part of the surface of the photoreceptor drum is adapted to form the latent image more than one time during one copying operation, and a slit exposure type optical system with a movable platform for placing an original thereon, in which the light path from the original to be copied to the photoreceptor surface on the drum is arranged to cross one time at a predeter-mined position, is employed for use with the small sized photoreceptor drum so that the distance between lQ~7722 the platform and the photoreceptor drum is minimized and consequently the size of the copying apparatus can be reduced to a size approximately equal to a small type of a so called Electrofax type copying apparatus.
Additionally, the preferred form of copying apparatus of the present invention is characterized in the inclusion of an improved transfer device wherein, instead of the insulating roller convent-ionally employed for the transfer, a guide platemember of electrically insulating nature if provided in a position immediately before the conductive grounded roller for causing the plate member to perform same functions as in the insulating roller so that the copy paper sheet is efficiently guided toward the grounded roller with substantial elimin-ation of the disadvantages inherent in the conven-tional transfer devices.
These and other features of embodiments of the present invention will become apparent from the following description taken in conjunction with such embodiments with reference to the accompanying drawings, in which;

Fig. 1 is a schematic diagram showing a sec-tional side view of a copying apparatus according to one embodiment of the present invention;
Fig. 2 is a similar view to Fig. 2, but parti-cularly shows driving systems thereof;
Fig. 3 is a timing chart showing the sequence of operation for the copying apparatus of the invention;
Figs.4(a) to 4(c) are schematic diagrams show-ing, each on an enlarged scale, a transfer device and associated mechanisms therewith employed in the copying apparatus of Fig. l;
Fig. 4(d) is an exploded view showing various parts and components associated therewith of the transfer device of Figs. 4(a) to 4(d) arranged in the order of their assembly;
Figs. 5(a) to 5(d) are similar views to Fig. 4(a), but particularly show sequence of operations thereof;
Fig. 6 is a similar view to Fig. 1, but parti-cularly shows a ~.odification thereof, and Fig. 7 is a schematic diagram showing, on an enlarged scale, a sectional side view of a modification of the fixing device and an associated device employed in t~e apparatus of Fig. 6.
Before the description of the present invention proceeds, it is to be noted that like parts are designated by like numerals throughout the several views of the ac-companying drawings.
Referring to Fig. 1, the transfer type electro-photographic copying apparatus cf the present invention 3~ with a movable platform to ~lace an criginal to be copied lQ~77Z2 thereon generally comprises a drum 1 having a photo-receptor surface or photoconductive layer 3 on the outer periphery thereof and rotatably mounted on a shaft journal-ed'in the frame of the apparatus housing ~ to rotate in the 5`~ direction indicated by an arrow to cause the photoreceptor' surface 3 sequentially pass various processing stations disposed therearound, such as a charging station with a corona charger 28, a slit exposure station associated with a slit exposure device E, a transfer station having a transfer device T and a residual charge erasing station provided with a charge eraser ex. The apparatus also broadly comprises horizontally movable platform 11 provid-ed above the drum 1 and reciprocatingly supported at the upper portion of the housing G, a copy paper feeding device including a plurality of rollers and a copy paper roll 16 rotatably enclosed in a casing 18, a developing device D of wet type disposed at the left lower portion of the drum 1, and a drying and fixing device F for copy paper sheets p disposed subsequent to the developing device D.
The movable platform 11 on which is placed the original to be copied further includes a frame 10 which has a transparent support platen 12 set therein, for e~ample of glass, a platen cover 13 pivotally secured on - the frame 10 so as to cover the platen 12 wi'th the original to be copied therebetween, a pair of guide rails 14 for reciprocating the platform 11 and a rack 15 for trans-mitting a driving force from a driving means.
The image rays from the original placed on the platform 11 are directed onto the photoreceptor 3 on the drum 1 through the slit exposure device E fixedly provided 10~7722 between the platform 11 abd the photoreceptor drum 1.
The slit exposure device E enclosed, for shielding unnecessary light, in an optical frame 19 suitably fixed to the apparatus housing G includes a light source 20, for example, a halogen lamp or fluore-scent lamp having a reflecting shade 21 for illuminating the original to be copied, a slit optical system L com-prising a first mirror 22 fixedly provided below the platform 11 and inclined at approximately 45 with respect to the lower surface of platform 11 for directing the light rays from the original ro a second mirror 23 through a lens 23a enclosed in a lens tube 23b, and a third mirror 24 fixedly provided immediately below the platfo;m 11 and suit-ably inclined so as to direct the light rays reflected by the mirror 23 through the lens 23a to a fourth mirror 25 secured in the optical frame 19 adjacent to the drum 1, which mirror 25 in turn directs the light images from the original onto the photoreceptor surface 3 through a slit adjusting vane 26 and a plate 27 for eliminating uneven exposure disposed adjacent to the image forming portion on the photoreceptor 3.
It should be noted here that, in the above - optical system L, the light path between the first mirror 22 and the second mirror 23 through the lens 23a is adapted to intersect the light path between the third mirror 24 and the fourth mirror 25 so that the space required for the optical system i.e., mainly the distance between the plat-form 11 and the photoreceptor drum 1, is reduced to a large extent.
The photoreceptor drum 1 has a small diameter, lQ97722 for example, in the range of approximately 50 to lOOmm.
Although the conventional photoreceptor drum had a minimum limit of approximately 120mm in diameter, the present inventors confirmed that a photoreceptor drum having a small diameter in the range of S0 to lOOmm had an efficient copying performance without any optical distortion of the fGrmed images, after repeated experi-ments and trial productions, also taking into considera-tion the relation of the photoreceptor drum to other processing devices mentioned later, which findings con-tribute much to the reduction of the size of the copying apparatus.
As described above, since the photoreceptor drum 1 of small diameter is employed in the present in-vention for reduction of the size of the copying apparatus, the drum 1 is arranged to make at least more than one rotation even in copying an ordinary size of copy paper, for example, A4 size (210 x 297mm), while various improve-ments have been made on the light path for projecting the image rays onto the photoreceptor surface 3, and the transportation passage for the copy paper, following the above described miniaturization of the photoreceptor drum 1.
In the electrophorographic copying apparatus of the above described type, it has been the most im-portant problem how the potential of the electrostatic latent image formed on the photoreceptor drum 1 should be effectively utilized for visualization of the latent image. In order to solve such a problem, it is of course necessary to improve transfer efficiency at the transfer 1~977ZZ

device T referred to above, but it is simultaneously required to bring the latent image formed on the photo-receptor surface 3 through corona charging and exposure of the same surface 3 to image rays into contact with the copy paper P in as short a period of time as possible for efficient transfer. For meeting such requirements, the electrophotographic copying apparatus of the embodi-mnet of Fig. 1, is so arranged that the image rays of the original finally reflected by the fourth mirror 25 are projected onto the photoreceptor surface 3 from the same side as that from which the copy paper p advances toward the photoreceptor drum 1 for bringing the exposure station as close to the passage of the copy paper as possible. In Fig. 1, the path of the finally reflected image rays is shown to be approximately parallel to the passage of the copy paper p, although it is possible to make the angle between the two in the region approximately 0 to 60, by which arrangement, the processing elements such as the corona charger 28, slit exposure device E, transfer device T, charger eraser ex and the like can be disposed in optimum positions despite the small diameter of the photoreceptor drum 1, with the limited space fully utilized, thus contri-buting much to compact size of the copying apparatus as well as effective utilization of the potential of the electrostatic latent image.
Furthermore, in the electrophotcgraphic copying apparatus of the above described type, when the latent image transferred onto the copy paper p is to be developed, it is generally necessary to allow the copy paper pbear-ing the transferred latent image thereon to pass through 10~77Z2 the developing device D for as long a period of time as possible for perfect adhesion of tone particles thereonto, since surface potential of such copy paper is not sufficiently high ( in the range from 100 to l50V). For such purposes, the developing device should preferably be long, extending in the direction of the passage of copy paper p, but it is rather difficult to secure sufficient length thereof, when reduction of the apparatus size is taken into account. In order to cope with such problems, in the copying appratus of the inven-tion of Fig. 1, the feeding path of the copy paper p is formed into an approximately V-shape with the develop-ing device D disposed at an apex of the V-shaped path, which arrangement, in cooperation with the formation of lS feeding roller 42 in the developing device D as electrode rollers mentioned later, has made it possible to develop the electrostatic latent image transferred on the copy paper p with sufficient definition and clarity. Further-more, the arrangement that the passage of the copy paper p is directed slantwise toward the left upper portion of the developing device D as shown in Fig. 1 is particularly effective for preventing jamming of the copy paper p or turbu-lence of copied image due to contact of the copy paper P
with various guide members or the like.
Still referring to Fig. 1, the corona charger 28 is fixedly mounted, above the photoreceptor drum 1, adjacent to the photoreceptor layer 3 on the drum 1 for uniformly charging the layer 3. The image rays from the original to be copied are projected onto the layer 3 through the slit exposure device E which seo,uentially scans the original 10"772Z

placed on the platform 11, moving in a scanning direction indicated by an arrow a with a resultant electrostatic latent image corresponding to the image of the original formed on the photoreceptor layer 3.
The roll 16 of the copy paper p is rotatably supported in the casing 18 releasably attached to the rear side wall of the apparatus housing G. The casing 18 ~ade, for example, of transparent plastic material com-prises an upper casing 18a and an lower casing 18b con-10- nected together by hinges 18c so that the upper casing 18a can be raised or lowered about the hinges 18c. It should be noted here that the material for the casing 18 need not necessarily be totally transparent, but may be partially transparent when observed from a proper angle, or semi-transparent, or may be simply provided with a suitableopening for confirmation. The paper web drawn out from the roll 16 is fed to the transfer device T through first rollers 60, a cutting device k having a stationary blade 61 and rotary blade 62 for cutting the paper web to a required size, a loop forming roller 63 for cutting the paper web in a state of tension and another pair of second rollers 65 for feeding the cut copy paper sheet p into the transfer device T.
Moreover, since the roll 16 of the copy paper enclosed in the casing 18 is wound with its photosensitive surface outward, the resultant curling of the copy paper p to a certain extent is effective for ma~lng it very easy to separate the copy paper sheet from the photoreceptor surface 3 of the drum 1 after the transfer of the latent image , as will be described later.

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The above described loop forming roller 63 is disposed in the approximately linear transportation passage between the first rollers 60 and the second rol-lers 65 in such a relation as to block the advance o~
S the copy paper p, and is adapted to be movable appro-ximately vertically in the directions shown by arrows, which roller 63 is normally located in the position shown in Fig. 1 for the formation of the loop through passing of the copy paper p over the upper portion thereof.
For cutting the web of copy paper into a copy paper sheet of desired size, the rotations of the first rollers 60 and loop forming rollers 63 are stopped with the roller 65 rotating, by the signal from a paper cut switch (not shown) acuated as the platform ll advances in the direction shown by an arrow a, and simultaneously a solenoid for ~he cutting device k (not shown~ actuated to turn the rotatory blade 62 so as to cut the web of paper between the rotatory blade 62 and the stationary blade 61.
During the above cutting process, the second rollers 65 keep rotating, whereby the copy paper web being fed through the second rollers 65 is gradually stretched for depressing the loop roller 63 at which time the copy paper web at the cutting device ~ seemingly in a stationary state enables the web to be smoothly cut.
Between the first and second ro.lers 60 and 65, there is provided a copy paper detecting actuator d which has a base portion dl extending along the path of copy paper, a first detecting projection d2 extending upwardly at approximately right angles from the ce~.tral portion of the base portion dl bet~een the cuttir.g device k aA.d the rollers 65, and a second detecting projection d4 also extending upwardly from one base edge portion of said base portion dl between the rollers 65 and the trans-fer device T, while the other edge of the base portion d is pivotally supported, as at d3, by a frame (not shown) of the apparatus housing for pivotal movement of the detect-ing actuator d. Upon depressing of the first detecting projection d2 by the leading edge of the copy paper web, the detecting actuator d is turned clockwise about the pivotal point d3 for turning on a leading edge detection switch (not shown). During the passage of the copy p~per therethrough, the detecting actuator d remains depressed until the trailing edge of the copy paper cut to the pre-determined length by the cutting device k has passed through the second detecting projection d4, when the actuator d pivotes counterclockwise about the pivotal point d3 to return to the original position for turning the leading edge detection switch off.
When the leading edge detection switch ~not shown) is turned on in a manner as described above, the platform 11 is caused to start moving, with the light source 20 turned on, thus the light image of the original to be copied is projected onto the photoconductive photoreceptor surface 3 of the photoreceptor drum 1 which is preli~inarily charged by the corona charger 28, through the optical system L
including the mirrors 22, 23, 24 and 25 fcr forming the electrostatic latent image of the original on the photo-receptor surface 3. The copy paper p is fed in synchro-nization with the movement of the latent i~age formed Gn the photorecepto. drum 1 and is pressed, at the transfer 10"77ZZ

device T mentioned later, against the photoreceptor surface 3 by an electrically conductive grounded roller 30 so as to induce charge having the same polarity as that of the latent image on an insulating layer of the copy paper for transferring the latent image onto the copy paper. Subsequently, the web of copy paper is cut to a predetermined length by the cutter k having the blades 61 and 62 with the feeding rollers 60 stopped. The copy paper sheet p thus cut passes through the transfer device T
an~ is separated from the photoreceptor surface 3 by the separating claw 226 to be further fed into the wet type developing device D whereat the transferred latent image on the copy paper sheet is developed into a visible toner powder image, and thereafter is dried at a fixing device F
by heating means for completing the copying operations.
Referring now to Figs. 4(a) to 5(d), general construction and effect of the transfer device T are briefly described hereinbelow prior to detailed descrip-tion thereof taken up later.
In Figs. 4(a) and 4(b), the transfer ~e~ice T
of the invention mainly includes a flexible guide plate 211 in the form of a sheet of electrically insulating nature and an electrically conductive roller 30, both incorpo-rated as one unit in a frame member 210. The surface of the electrically insulating guide plate 211 is also formed with an insulating material, such as polyester fibers or the like filled on said surface, the tips of which fibers are adapted to contact the photoreceptor surface or photoconductive layer 3 under pressure for keeping the copy Faper p in close contact with the same surface 3 1~77Z2 to prevent abnormal electrical discharge from the photo-receptor surface 3 to the copy paper sheet p during the time period from approach of the copy paper p toward the photoreceptor surface 3 to the close contact thereof S therebetween. On the other hand, the electrically con-ductive roller 30 is composed of an electrically insulat-ing material such as rubber, polyrethane or the like which is applied or impregnated with electrically con-ductive adhesive having elasticity for imparting electrical conductivity thereto. The roller 30 which contacts the reverse surface of the copy paper p and the electrode at the backing of the photoreceptor layer 3 are electrically connected with each other to be grounded for efficient electro-~static transfer. Incidentally, the surface potential of the electrostatic latent image formed on the photoreceptor surface 3 of the drum 1 is in the region from 800V to 1600V.
Since atmospheric discharge in the ordinary condition can be caused to take place in the presence of potential dif-ference approximately more than 600V in the case where the width of gap between the latent image and the copy paper sheet p is in the range from several tens to 100 microns, if the copy paper sheet p is passed between the conductive roller 30 and the photoreceptor surface at the gap width set as above, with the roller 30 and the back electrode of the photoreceptor layer 3 being short-circuited for grounding, the electrostatic latent image corresponding to the latent image on the photoreceptor layer 3 is formed on the copy paper sheet p.
It should be noted here, however, that instead of short-circuitin~ the roller 30 and the back electrode 10"7722 of the photoconductive layer 3 for grounding in the manner as described above, bias voltage may be applied to the conductive roller 30, with the potential of the powér source being so adjusted as to match image re-producibility of the latent image to be transferred,with conditions due to characteristics of the exposure, development, photoconductive layer, copy paper and the like.
The transfer device T including the flexible guide plate 211 and the electrically conductive roller 30 as described above is adapted to cause the copy paper sheet p to evenly contact the photoreceptor surface 3 through said guide plate 211 for starting transfer, with the transfer being further expedited by the conductive roller 30. Since the guide plate 211 itself is made of electrically insulating material, any abnormal electrical discharge is advantageously prevented during approaching of the same plate 211 toward the electrostatic latent image formed on the photoreceptor surface 3 for effecting transfer in the range restricted by high resistance value of the plate 211, with the transfer being subsequently completed through action of the electrically conductive roller 30. The arrangement that the guide plate 211 extends to a position close to the conductive roller 30 is particularly effective for preventing blur or de-gradation at the trailing edge of the developed image, since the trailing edge of the copy paper sheet p which has passed the guide plate 211 is continuously kept in contact with the photoreceptor surface 3.
The copy paper sheet p bearing the latent 1~77ZZ

image thus formed thereon is separated, against the electrostatic attraction by the photoreceptor drum l, from the surface of said drum l, being advantageously assisted by its own resilience. I~ preparation for a case where the separation is not sufficient due to employment of a particularly thin copy paper having small resilience as compared with one ordinarily used, separating claws 226 of low friction coefficient such as Teflon* which are arranged in a row at suitable in-tervals are employed for synchronous rotation with the transfer device T as described in more detail hereinbelow.
Still referring to Figs. 4(a) to 5(d), the transfer device T comprises, a transfer frame f which includes a pair of spaced frame plates fa of triangular configura-tion and the frame member 210 of U-shaped cross section suitably secured at end portions thereof, to the frame plates fa in a direction parallel to the axis of the drum 1. Each of the frame plates fa is pivotally supported, at one edge portion fb thereof, by a pin or shaft fp secured to a frame (not shown) of the apparatus housing G for pivotal movement toward and away from the photoreceptor p surfaces 3 of the drum l, while the pivotal movement thereof toward the surface 3 being limited by a stop pin 247 fixedly disposed at the lower left-hand portion of the drum 1, on each of which frame plates fa, there are mounted a bearing 208 suitably earthed and adapted to be slidably movable in a corresponding notch formed in the frame plate fa for upward and downward move-* Trade Mark lQ~772Z

ments, and a grounded roller or an electrically con-ductive transfer roller 30 rotatably supported by and electrically connected to the bearing 208 through a shaft 30a of the roller 30, while the bearing 208 is in turn supported by a substantially V-shaped wire spring 209 which is suitably secured to the plate fa, so that the bearing 208 together with the roller 30 are urged upward to the photoreceptor sur-face 3 as seen in Fig. 4(a). One upper edge portion 210a of the frame member 210 adjacent to the rollers 65 extends leftwardly at approximately right angles to the side of the member 210 with the upper surface of the edge portion 210a being in parallel with the upper edges of the plates fa, while the other edge lS 210b of the member 210 extends rightwardly, toward the rollers 67 as in Fig. 4(a). On the surface of the edge 210a of the frame member 210, the flexible guide plate 211 which is operated by mechanisms mentioned later is secured, with the front free edge of the plate 211 extending close to the roller 30 into such a position that, while the roller 30 is pressed against the photoreceptor surface 3 of the drum 1, the copy paper contacting the photoreceptor surface 3 is fed between the roller 30 and the photo^
receptor surface 3. Furthermore, in order to pre-vent damage to the photoreceptor surface 3, the brush bristles 211a composed of fibers of elec-trically insulating nature are secured on the sur-face of the guide plate 211. At the upper right-hand portion of the roller 30 adjacent to the - Zl -1~"772Z

photoreceptor surface 3 of the drum 1, the separating claw 226 is pivotally supported by a shaft 226a, on a frame (not shown) of the apparatus housing G.
Referring particularly to Figs. 4(b) to S 4(d), the mechanisms for operating the transfer frame f and the separating claw 226 in association with the copying operation is described hereinbelow. The mechanisms intend to press the guide plate 211 and the grounded roller 30 against the photoreceptor surface 3 only when the copy paper passes therebetween and also to cause the separating claw 226 to function in synchronization with the movement of the leading edge of the copy paper, since the photoreceptor surface 3 tends to be damaged or the same surface 3 and the grounded roller 30 are worn out rapidly if the plate 211, the roller 30 and the claw 226 are always kept in contact with the photoreceptor surface 3. On one end of the shaft fp for the transfer frame f, a lift-ing lever Q is rotatably mounted at one end portion thereof, while a transfer frame operating lever 246 is fixedly mounted on the shaft fp for simultaneous rotation therewith, so that rotation of the lever Q
is transmitted to the lever 246 through a torsion spring 216 suitably disposed therebetween. A cam member 217 of circular configuration disposed adjacent to the lifting lever Q is adapted to rotate integrally with a.gear member 219 and is in frictional engage-ment with a rotational axis 218 thereof. Pins 220, 221 and 222 spacedly disposed to one another and ex-tending upwardly at right angles from the surface lQ~7722 of the cam member 217 are adapted to engage the other end of the lever ~ and turn the same lever Q clock-wise as the cam member 217 rotates in the direction of an arrow in Fig. 4(c). The cam member 217 has a cut or stepped portion 217a at an outer periphery thereof, at which portion 217a the teeth of the gear member 219 are exposed out of the cam member 217.
A U-shaped lever 223 is pivotally supported at the central portion thereof, by a pin 224 on a frame (not shown) of the apparatus housing G, while a V-shaped wire spring 225 (Fig.4(c)) is disposed between a pin 225a suitably secured to the housing G and a pin 223a fixed to the lever 223 for urging the lever 223 counter-clockwise. The upper end of the U-shaped lever 223 is adapted to contact an elastic member 227 secured to the lower end of a stop lever 229 for the platform 11.
The lever 229 disposed in a direction normal to the surface of the platform 11 has a laterally projecting portion 229c to which a solenoid SOL is connected, and pins 233 and 234 fixed to the same lever 229, while elongated openings 229a and 229b are formed in the lever 229 along the verti~al axis thereof, in which openings 229a and 229b, stop pins 235 and 236 secured to the apparatus housing G are slidably received, with the lever 229 being normally urged upward by springs 231 and 232 disposed between the pins 235, 233 and 236, 234 respectively, so that when the stop lever 229 is pulled downward upon actuation of the solenoid SOL, the elastic member 227 at the lower end of the lever 3Q 229 depresses the upper edge of the U-shaped lever 223 against 10~772Z

the urging force of the spring 225 for rotating the lever 223 clockwise so that the lower edge of the lever 223 is released from the gear 219. At the lower surface edge of the plateform ll, there is provided a separating claw S operating cam 237, which is formed in such a shape as to contact a separating claw operating roller 238 rotatably disposed at the upper-most portion of a lever 239 mentioned below. The lever 239 disposed at the right-hand portion in Figs. 4(c) and 4(d) in a direction parallel to the axis of the lever 229 is formed with elongated openings 239a and 239b along the vertical axis thereof, in which openings 239a and 239b, stop pins 240 and 241 suitably secured to the ap-paratus housing G and slidably received for supporting the lever 239, while the lever 239 is urged upward through a spring 242 suitably stretched between the pin 240 and a projection 239c of the lever 239. The lower portion of the lever 239 has a laterally projecting catch portion 239c, which normally engages a separating claw operating lever 243 disposed adjacent to the lifting lever Q and pivotally sup-ported by one end of the separating claw shaft 226a as at 214 for limiting rotation of the lever 243 normally urged clockwise by an adjustable weight or balancer 243a (Fig. 4(d)) which is fixed to the other end of the claw shaft 226a.
Upon lowering of the lever 239 and consequently of the projecting portion 239c, the lever 243 released from the catch portion 239c of the lever 239 turns clockwise about the pivotal point 214 and contacts a pin Qa fixed on the lifting lever Q so as to be limited for further rotation.
~y this arrangement, the functions of the above mechanisms are described hereinbelow in association with 1(~'377~2 the copying operations.
Upon depression of a print button (Fig. 1), the shaft 218 for the cam member 217 and the gear 219 starts rotating with rotation of a main motor M (Fig. 2), the copy paper feed rollers 60 (Fi.g 1) and the photo-receptor drum 1, and with consequent feeding of the copy paper, in which case, various elements of the above described mechanisms are in positions shown in real lines in Fig. 4(c), while the lower end of the U-shaped lever 223 is in the stepped portion 217a of the cam member 217 and engaged with the gear 21g without any relative movements therebetween, with the transfer frame f together with the guide plate 211 and the grounded roiler 30 thereof being spaced away from the photoreceptor surface 3 of the drum 1.
When the leading edge of the web of the copy paper strikes against the copy paper detection portion d2 of the actua-tor d disposed along the path of the copy paper, a lead-ing edge detection switch (not shown) is turned on, which switch in turn actuates the solenoid SOL so as to pull the platform stop lever 229 downward and simultaneously the platform 11 starts moving rightward in Fig. 4(c). Re-ferring particularly to F~gs. 5(a) to 5(c), in the above case, the elastic member 227 provided at the lower end of the stop lever 229 depresses the upper end of the U-shaped lever 223 for rotating the same clockwise, with the lower edge of the lever Z23 which is located in the stepped portion 217a being disengaged from the gear 21~.
for being released therefrom, by which action, the cam member 217 which is in frictional engagement with the shaft 218 starts rotating and the pin 220 secured on 10"77Z2 the member 217 initially contacts the lifting lever Q
for rotating the same lever Q clockwise, with the trans-fer frame shaft operating lever 246 being consequently turned clockwise through the torsion spring 216 as shown S in Fig. 5 (a). Consequently, the transfer frame f is pivoted integrally with the rotation of the transfer frame shaft fp until it stops by engaging the stop pin 247 as is shown in Fig. 5(b), in which case, any mechanical error in the amount of rotation of the frame f is adapted to be absorbed by the torsion spring 216. Meanwhile, the cam member 217 continues to rotate, and when the stepped portion 217a of the member 217 has reached a position where the member 217 has made approximately a half turn, the upper end of the lever 223 depressed by the elastic member 227 of the lever 229 again falls into the stepped portion 217a so as to be engaged with the exposed portion of the gear 219, with relative movement therebetween be-ing restricted as shown in Fig. 5(c), in which state, the transfer frame f is continuously held in the same position, with the guide plate 211 and the grounded roller 30 press-ed against the photoreceptor surface 3 of the drum 1, since the pin 221 of the member 217 is kept in contact with the - lifting lever Q as shown in Fig. 5(c).
In the above state, the copy paper is fed bet-ween the roller 30 and the photoreceptor surface 3 through the guide plate 211, and at the front portion of the guide plate 211, contacts the surface 3 bearing the latent image of the original placed on the platform 11, while the platform 11 is moving in synchronization with the rotation of the drum 1. The copy paper is further pressed 10"7~22 - against the surface 3 by the roller 30 for transferring the latent image on the surface 3 onto the copy paper.
Following the movement of the platform 11, the separating claw operating cam 237 contacts the roller 238 of the lever 239 for depressing the latter lever 239 and consequently the projecting portion 239c thereof, which permits the separating claw operating lever 243 which is limited for rotation by the portion 239c to rotate clock-wise by the weight of the balancer 243a (Fig. 4(d)) for simultaneous rotation with the separating claw rotating shaft 226a. Consequently, the tip of the claw 226 con-tacts the photoreceptor surface 3 as shown in Fig. 5(c) for separating the leading edge of the copy paper from the latter, in which state, the lever 243 restricted in its rotation by the contact with the stop pin Qa of the lifting lever ~ is released from the stop pin Qa which is in a position as isshown in chain lines in Figs. 4(b) and 4(c). It is to be noted that the claw 226 contacts the photoreceptor surface 3 only during contact of the projecting portion of the separating claw operating cam 237 with the roller 238 of the lever 239.
When the trailing edge of the copy paper sheet passes the second detecting projection d4 of the copy paper detecting actuator d (Fig. 1), the actuator d re-turns to its original position, with the leading edge detect-ing switch and the solenoid SOL turned off, while the plat-form stop lever 229 is raised by the urging force of the springs 231 and 232 with consequent releasing of the U-shaped lever 223 from the elastic member 227. The lever 223 thus released from the depression by the stop lever 229 1(~1"772Z

turns counterclockwise and is disengaged from the step-ped portion 217a of the cam member 217 so as to permit the cam member 217 and the gear 219 to rotate again.
Although transfer at the trailing edge of the copy paper sheet has not been completed upon rotation of the cam member 217 and the gear 219, the transfer frame f remains stataionary until the pin 222 of the cam member 217 is disengaged from the lifting lever Q, and after the trail-ing edge of the copy paper has passed the grounded roller 30, the pin 222 leaves the lifting lever Q, with the transfer frame f returned to its original position and with the guide plate 211 and the grounded roller 30' dis-engaged from the photoreceptor surface 3. ThereafteT, the end of the U-shaped lever 223 contacting the periphery of the cam member 217 by the urging force of the spring 225 falls into the stepped portion 217a of the cam 217 for stopping rotation of the cam member 217 and the gear 219, which state is maintained until subsequent signal through the leading edge of the copy paper sheet is received.
In the returning movement of the platform 11, the separating claw operating cam 237 again contacts the roller 238 of the lever 239 for depressing the lever 239, in which case, however, the separating claw 226 does not contact the photoreceptor surface 3, since the rotation of the separating claw operating lever 243 is limited by the contact thereof with the stop pin Qa of the lever Q
which is lowered in the above state as shown in the real line in Fig. 4(c).
As is seens from the foregoing description, in the transfer device T of Figs. 4(a) to 5(d~, there is - ~8 -la~77zz employed the guide plate 211 at least whose upper surface is of electrically insulating nature and which causes the copy paper to contact the photoreceptor surface , as the same plate 211 guides the copy paper between the photo-receptor surface 3 and the conductive grounded roller 30,by which arrangement, the copy paper is posivitely press-ed against the photoreceptor surface 3 of the drum 1 by the guide plate 211, before the copy paper sheet being transported is held between the grounded roller 30 and the photoreceptor surface 3 without any possibility of the copy paper sheet being separated from the photorecep-tor surface 3 between the guide plate 211 and the roller 30, thus fogging or blur of the image at the transfer station or absence of black tone in the transferred image due to electrical discharge being advantageously eliminated. Furthermore, the brush bristles 211a secured on the upper surface of the guide plate 211 are also very effective for cleaning the photoreceptor surface 3 as the former contacts the latter surface 3, which fact contributes much to the prevention of the deterioration of the photoreceptor surface and eliminates disadvanges inherent in the conventional devices that the photo-receptor surface subjected to harmful gases such as ozone generated by the corona charger or the like tends to be readily deteriorated.

- to be continued -lQ"7722 Referring back to Fig. 1, after the transfer and separation of the copy paper sheet as described above, the electrostatice charge remaining on the photoreceptor surface 3 is removed by a static eliminating device, for example, by the erasing lamp 133 provided adjacent to the separating pieces 226.
The copy paper sheet separated from the photo-receptor surface 3 is transported into the developing de-vice D through the static eliminating rollers 67, in which case the surface potential of the electrostatic latent image formed by the transfer on the copy paper sheet is comparatively low normally in the range from 60 to 150 volts, though the potential may dif~er depending on the conditions such as characteristics of the copy paper sheets and the photoreceptor 1, charging potential on the photoreceptor, and the presence of bias voltages during transfer etc., so that a liquid developing means using electrode rollers are advantageously employed in the above case.
Still referring to Fig. 1, the developing device D of the invention mainly comprises a first developing frame 49 in which there are provided four rotatable lower electrode rollers 42 of metallic material, three guide plates 44 for guiding the copy paper sheet, two cleaning brushes 43 rotatably provided in contact with the elec-trode rollers 42, a pair of squeezing rollers 46 for remov-ing developing liquid from the copy paper sheet after de-veloping, and a guide plate 45 disposed between the last electrode roller 42 and the squeezing rollers 46, and a second developing frame 50 provided on the first developing frame 49, in which frame 50 four upper electrode rollers 41 of metallic material movable upward or downward are rotatably provided at positions corresponding to and in contact with the lower electrode rollers 42 of the first frame 49 with a receiving plate 51 for a developing solu-tion supply tank Db fixedly provided at the upper portion of the frame 50.
The above described first and second developing frames 49 and S0 are releasably received in a developing tank Db formed integrally with a bas~ plate of the appara-tus houding G, and when the second frame 50 is mounted on the first frame 49, the upper electrode rollers 41 are adapted to engage the lower electrode rollers 42 under pressure due to the weight of the former.
The lower electrode rollers 42 are adapted to be driven by the driving force transmitted from the driv-ing motor M (Fig. 2) with the upper rollers 41 rotating following the rotation of the lower rollers 42, and the copy paper sheet p is transported while being held between the rollers 41 and 42~ Each of the above upper electrode rollers 41 is electrically shortcircuited through the first and second developing frames 49 and 50.
Generally, the relation of the field strength in the vicinity of the electrostatic latent image to the distance between electrodes, for exampie, the distance between a latent image formed surface of a copy paper sheet and an electrode roller or a facing electrode such as an electrode p]ate is such that the ficld strength increases to a large extent as the dista-Jlce between electrodes de-creases, while it greatly decreases as the distance betwcen 3] -10~77ZZ

electrodes increases. Accordingly, in a developing means employing electrode rollers, the developing position is limited to be located in the neighborhood of the develop-ing rollers. In the developing device D of the present invention having a construction as described above, opti-mum developing efficiency due to the large increase of the field strength is achieved with sufficient density of the developed images by the adoption of a plurality of electrode rollers. The cleaning brushes 43 which are adapted to rotate in contact with the electrode rollers 42 are effec-tive not only for preventing soiling at the reverse side of the copy paper sheet by removing developing toner adhering to the surfaces of the rollers 42, but for pre-venting the lowering of developing efficiency due to precipitation by uniform stirring of the developing solu-tion, since the brushes 43 are rotating in the developing solution, stirring the latter.
The developing solution supply tank Da releasably received in the receiving plate 51 fixedly mounted on the second developing frame 50 is provided with an opening h for supplying the developing solution at the lower portion thereof, which opening h has a stopper plug t which is normally urged to the inner edge of the opening h by a spring (not shown) to close the opening h with the lower end of the plug t projecting from the opening h.
Accordingly, when the tank Da is placed in posi-tion on the receiving plate 51, the projecting end of the plug t and consequent]y the spring (not shown), is pressed back with the projecting end of the plug t contacting a part of the developing tank Db, and consequentl~- developing solution flows from the supply tank Da into the developing tank Db. When the level of the developing solution reaches the opening h, air is prevented from entering the tank Da and flow of the developing solution from the tank Da stopped, and with the supplying of the same finished.
In the mean time, the copy paper sheet developed in the developing solution while passing between the elec-trode rollers 41 and 42 is transported through the guide plates 44 and 45 to the squeezing rollers 46 disposed im-mediately above the level of developing solution for remov-ing unnecessary developing solution from the copy paper sheet, and subsequently fed into the drying and fixing de-vice F. Immeidately before entering the drying and fixing device F, the copy paper sheet is again passed through rollers 48 of liquid absorbing material for further remov-ing unnecessary developing solution.
It should be noted here that the developing de-vice D of wet developing type described as employed in the apparatus of Fig. 1 may be replaced by a developing device D' of dry developing type which is described later with reference to Fig. 6.
Still referring to Fig. 1, the drying and fixing device F comprises a hollow cylinder R which is made of good heat transfer material, for example, of aluminum with either the inner periphery or both the inner and outer peripheries thereof treated with black anodized aluminum for better heat transfer. The cylinder R is supported for rotation in the direction of an arrow by two rollers rl and r2 rotatably provided below the cylinder R. A heater H of suitable type is enclosed in the cylinder R. Flat ~Q"~72Z

belt V comprising a sheet material having permeability to air is suspended, so as to be in close contact with the upper surface of the cylinder R, by three rollers ra, rb and rc rotatably provided along the upper periphery of the cylinder R so that the belt V contacting the upper sur-face of the cylinder R is driven following the rotation of the cylinder R at the same peripheral speed.
It is needless to say that the belt V may be separately driven by a suitable independent driving means connected to one of the rollers ra, rb and rc.
The cylinder R should preferably be of air tight construction (not shown) so that the air inside the cylinder R is not affected by the external air for maintaining the cylinder R at an optimum temperature for fixing the copy paper sheet with a temperature detector (not shown) of a thermistor or thermocouple incorporated therein the belt V is employed as a means for bringing the copy paper sheet p into close contact with the upper periphery of the cylin-der R, and the wet copy paper sheet p subjected to develop-ment is adapted to pass between the cylinder R and thebelt V along the surface of the cylinder R at the same peripheral speed as that of the latter.
A guide pawl 111 for guiding the wet copy paper p from the absorbing rollers 48 is provided adjacent to the surface of the cylinder R in a position between the roller ra for the belt V and the cylinder R close to the inlet for the copy paper sheet p.
Similarly, a separating pawl 110 for separating the copy paper sheet p transported between the belt V and the cylinder R, and directing the same toward the discharg-lQ"77Z2 -ing rollers 58 is pivotally provided in contact with the surface of the cylinder R in a position between the roller rc for the belt V and the cylinder R and adjacent to the rollers 58 for discharging the fixed copy paper sheet out of the apparatus G.
The guide pawl 111 and the separating pawl 110 should preferably be made of material free from adhesion - of toner, for example, fluoroplastics.
By this arrangement, the wet copy paper sheet p, the electrostatic latent image on which is visualized by the developing device D, is squeezed by the squeezing rollers 46 equipped with the cleaner 47 and fed between the belt V and the cylinder R after having passed through the absorbing rollers 48 for further absorbing the develop-ing solution remaining in the copy paper sheet. The copy paper sheet thus fed onto the cylinder R is heated ~at temperatures approximately 80 to 100C) by the cylinder R as it passed between the belt V and the cylinder R for drying and fixing, and subsequently delivered out of the apparatus G through the discharge rollers 58.
The copying apparatus G of the invention is further provided with a prevention device W for preventing disorder or disturbance of the transferred image resulting from the gradual deterioration of the photoreceptor sur-face 3 due to accumulation of harmful gases such as ozone,nitrogen oxides and the like which are generated following the corona discharge by the corona charger 28. The device W generally includes an air duct 300 disposed between the photoreceptor surface 3 and a fan 303, another air duct 305 provided between a fan 304 which is disposed adjacent to 10"77Z2 the fan 303 and a louver 307 attached to a discharge open-ing 308 of the apparatus housing G for preventing mixing of the exhaust air with the suction air and a panel heater 309 of self-equilibrium type disposed below the photorecep-tor drum 1. The duct 300 is divided into a suction duct 300a and an injection duct 300b by a partition plate 301 provided therein, with one end portion of the suction duct 300a adapted to enclose the corona charger 28 therein, while the other end portion 302 of the duct 300 surrounded by arcuate upper and lower walls of the duct 300 defines a space in which the fan 303 is rotatably housed and forms a suction passage 302a and an injection passage 302b bet-ween the upper and lower walls of the same duct 300, while separator members Yl and Y2 for air flow are each disposed bet~een the fan 303 and a corresponding edge of the parti-tion plate 301 and between the fan 303 and the fan 304.
The air duct 305 is also divided into an exhaust duct 305a and a suction duct 305b by a partition plate 306, with the fan 304 rotatably disposed adjacent to one end portion of the exhaust duct 305a remote from the discharge opening 308. The panel heater 309 is adapted to be energized upon insertion of a plug of the copying apparatus ~not shown3 in the power source receptacle (not shown) for constantly maintaining the temperatures on the photoreceptor surface 3 in the range from 40 to 50C, so that during suspension of copying operations, the reduction of charge holding capacity of the photoreceptor surface 3 due to absorption of moisture is prevented.
P,y this arrangement, upon turning on the main switch M.S. for copying operation, tne fans 303 and 304 - ~6 -10~77;~2 start rotating, and the outside air is sucked in through the duct 305b and injected toward the underside of the corona charger 28 through the injection duct 300b, while the air in the duct 300a is discharged out of the appara-tus G through the duct 305a together with the air heatedby the light source 20 by the action of the fan 303 backed up by the fan 304. Accordingly, the air injected through the duct 300b fully passes through the interior of the corona charger 38 by the suction of the duct 300a and by the presence of an air flow shield member 301a fixed to the charger 28 without being drawn toward other portions in the vicinity of the exposure surface 3, thus any harmful gases, such as ozone, nitrogen oxides and the like existing within the corona charge 28 and thereabout being efficient-ly discharged out of the apparatus G through the opening308 and the louver 307.
It should be noted that the fan 303 described as employed in the above device W may be replaced by two fans each exclusively used for air flow suction and injection, and that the direction of air flow may reversed, i.e., from the side of the corona charger 2~ toward the photo-receptor 3.
Referring now to Fig. 2, driving systems of the copying apparatus of the invention are described herein-below.
~ An endless first driving chain 500 is directed, to be moved in a direction of an arrow, over a motor sprocket 5~1 fi~edly mounted on a driving shaft of a main motor ~, a scanning sprocket 503 secured to the same shaft as a scanning clutch 502 for advancing the platform l-l in the direction shown by the arrow a, a returning sprocket 505 secured to the same shaft as a return clutch 504 for re-turning the platform 11 in the direction of the arrow e, a drum sprocket 506 fixed to the same shaft as a drum gear 505' for driving the photoreceptor drum 1, a roller sprocket 507 for driving the second roller 65, a sprocket 508 for driving the feeding roller 67 disposed immediately after the transfer device T, a sprocket 509 for driving the squeezing roller 46, a sprocket 510 for driving the absorb-ing roller 48 disposed between the developing device D andthe drying and fixing device F, and also a tension sprocket 511, while the scanning clutch 502 and the returning clutch 504 are adapted to selectively drive clockwise and counter-clockwise the pinion 513 disposed immediately below the platform ll and engaged with a rack 15 which is secured to the lower surface of the platform 11 through an idle gear 512 for reciprocating movement of the platform 11. On the other hand, an endless second driving belt 515 is passed to be driven in the direction of an arrow around a driving sprocket 514 secured to the same shaft as the motor sprocket 501, a sprocket 516 for driving the squeezing roller 46, a sprocket 517 for driving discharging rollers 58, a sprock-et 51~ for driving the roller ra of the belt V for the dry-ing and fixing device F, and a tension sprocket 519. It is to be noted here that the cylinder R for the drying and - fixing device F is also rotated by a gear ~not shown) secured to the same shaft as the sprocket 518. A third driving chain 520 for driving the first feeding rollers 60 is directed around a paper feeding sprocket 522 which is secured on the same shaft as a paper feeding clutch 521 ~0"77ZZ

connected to the paper feeding solenoid (not shown), a tension sprocket 523 and a sprocket 524 fixed to the same shaft as the sprocket 507 for driving the second paper feeding roller 65. It is to be noted here that the elec-trode rollers 41 and 42 for the developing device D areconnected to a pulley 526 secured to the same shaft as the squeezing sprocket 516 through a timing belt 525.
Referring now to Fig. 3, by the foregoing ar-rangement, when the main switch M.S. (Fig. 1) is turned on, the driving motor M (Fig. 2), driving motors (not shown) for the fans 303 and 304, the fixing heater H, and the erasing lamp ex are energized, with all the driving systems except for the first feeding roller 60 being driven. Subsequently, when a printing switch P.SW (Fig. 1) is pushed to be "on", the illuminating light 20 is lit, with simultaneous energization of the paper feeding sole-noid, and the first feeding roller 60 starts rotation through actuation of the paper feeding clutch 521 for feed-ing the copy paper p from the paper roll 16. When the leading edge of the copy paper web p strikes against the first detecting projection d2 of the copy paper detecting actuator d tFig. 1) to turn on the leading edge detection switch, the scanning clutch 503 is actuated with simulta-neous energization of the platform locking solenoid (not shown), thus the platform 11 starting scanning, in which time, the transfer device T and the copy paper separating claws 226 start operation. During the scanning operation of the platform 11, a paper cut switch Sl~8 (Fig. l) is turned on, with the paper feeding solenoid turned off, and with the cutter solenoid turned on to cut the copy 1~)977Z2 paper web into a required size. When the trailing edge of the copy paper sheet p thus cut passes the second detect-ing projection d4 for copy paper trailing edge detection, the switch is turned off to de-energize the solenoid of the scanning clutch 502, with simultaneous actuation of the returning clutch 505 for returning movement of the platform 11. It is to be noted that a repeat switch R.SW
(Fig. 1) is adapted to be actuated in copying for two copies and more, the turning on of the repeat switch R.5W
causing the subsequent copy paper feeding to be started.
Referring now to Fig. 6, there is shown a second embodiment of the copying apparatus of dry developing pro-cess type according to the present invention. As compared with the copying apparatus of Fig. 1, major differences in construction of the apparatus G' of Fig. 6 are in that the developing device D of wet type and the drying and fixing device F described as employed in the embodiment of Fig. 1 are replaced by a developing device D' of dry type and a modified drying and fixing device F' mentioned below, so that constructions and functions of other parts which are generally indicated by similar numerals to those of Fig. 1 are abbreviated for brevity. In this embodiment of Fig. 6 also, the copy paper feeding means is arranged along a substantially V-shaped path with the developing means D' disposed at about an apex of the V-shaped path in the similar manner to that in the apparatus of Fig. 1.
In the modification of Fig. 6, the dry type developing device D' comprises a cylinder D'c which is fixedly provided above a pair of copy paper transportation rollers D'r rotatably supported on a base Ds which is ~0~7722 secured to the bottom of the apparatus G', a plurality of magnets D'm rotatably disposed in sai~ cylinder D'c and a funnel shaped tank D'a for dispensing toner powder fixed-ly mounted above the drum D'c.
The plurality of magnets D'm enclosed in the cylinder D'c are adapted to rotate in the direction of an arrow, while an opening h' is formed at the lower portion of the tank D'a for uniformly supplying toner powder onto the surface of the cylinder D'c. The toner powder thus supplied is formed into magnetic brush bristles f on the surface of said cylinder D'c by the action of the magnets D'm.
The copy paper sheet p fed onto the rollers D'r is further t~ansported to the developing position immedi-ately below the cylinder D'c as the rollers D'r rotate, in which developing position the copy paper sheet p bear-ing an electrostatic latent image formed thereon is slight-ly rubbed by the brush bristles f with the latent image visualized by the adhesion of the toner powder to the charged portion thereof, and further fed into the subse-quent processing station, such as a drying and fixing de-vice F'. The toner particles remaining on the cylinder D'c after passing the developing position are carried back to a position in the vicinity of the opening h' of the tank D'a as the magnets D'm rotate and are replenished - with fresh toner from the tank D'a so as to again form brush bristles f with uniform toner concentration.
Still referring to Fig. 6, the copy paper sheet bearing a visible toner powder image thereon developed by the developing device D' is further fed into a drying and ~0~77ZZ
fixing device F' through a copy paper transportation belt 400 movably supported by a driving roller 400a, and rollers 400b and 400c. The belt 400 has an electrically high resistant layer, for example, of Teflon* thereon and is adapted to be uniformly charged by a corona charger 401a integrally formed with a corona charger 401b and disposed below and adjacent to the belt 400 to charge the same belt 400 for electrostatically attracting thereto the copy paper to be transported. Adjacent to the roller 400a for the belt 400, there is rotatably provided a cylinder ;;
or a drum 402 for carrying the copy paper fed from the belt 400 through electrostatic attraction and heating the same from its reverse side. The drum 402 is composed of heat conductive material such as an aluminum cylinder formed, on the outer periphery thereof, with a heat resist-ing high resistant layer such as Teflon*, and is adapted to be uniformly charged with the corona charger 401b.
Within the drum 402, there is disposed a quartz infrared lamp 402a, while the drum 402 is caused to rotate in the direction of an arrow in synchronization of the movement of the belt 400 through a driving source (not shown). It should be noted that the flat belt surface S between the rollers 400a and 400b is disposed in the tangential direction to the drum 402 for preventing any inconveniences which may occur when the copy paper is separated from the surface of the belt 400 and passed onto the surface of the drum 402. It is preferable that the both sides of the drum 402 be closed by suitable heat shielding material (not shown) with inner periphery of the same drum 402 treated for good heat absorption so that warming-up time * Trade Mark ~0~77ZZ

for the fixing device F' can be reduced. It is to be noted that the infrared lamp 402a described as employed in the device F' of Fig. 6 may be replaced by a heating member having a flat surface and disposed along the inner face of the drum 402, and that the position of the lamp 402a is not limited to be within the drum 402, but the same lamp 402a may be disposed outside of the drum 402 so far as the lamp 402a does not directly heat the copy paper through heat radiation, in which latter case, however, the drum 402 is preferably of heat insulating nature. A pres-sing roller 403 rotatably provided at the right upper por-tion of the drum 402 contacts the outer periphery of the drum 402 for synchronous rotation with the latter drum 402, and is composed of material such as silicon rubber having no adhesion to toner particles and simultaneously having heat insulating properties. Below the roller 403 in a position adjacent to the surface of the drum 402, there is pivotally disposed a separating claw 404 of metal-lic material for separating the copy paper from the surface of the drum 402 and for subsequently guiding the separated copy paper toward a pair of discharge rollers 405 disposed adjacent to a discharge opening 406 of the apparatus hous-ing G'. A thermistor disposed adjacent to the lower por-tion of the surface of the drum 402 is substantially in

2~ sliding contact with the latter so as to control function of the lamp 402a for constantly maintaining the surface temperature of the drum 402 at a predetermined level.
Furthermore, a cleaning pad 402b made of material such as felt is disposed on the frame below the drum 402 in contact with the surface of said drum for cleaning toner - ~3 -7'722 particles adhering thereto from the reverse face of the copy paper. The upper portion F'a of the device F'is composed of heat insulating material for improving thermal efficiency of the fixing device F'. In the above described fixing device F', a separate heating source which is ener-gized only during warming-up time may be provided for the roller 403 in order to increase speed for temperature rise at initial stage of copying operation and thus to reduce the warming-up time. For ensuring separation of the copy paper from the surface of the drum 402, the separating claw 404 should preferably be of a type in which part of the front edge portion thereof is received in narrow grooves (not shown) formed around the outer periphery of the drum 402.
It should be noted here that the above described fixing device F' of the invention may be used as a drying and fixing device for copy paper developed through a wet developing process, in which case, the roller 403 described as employed in the embodiment ofjFig. 6 may be replaced by a roller having brush bristles (not shown) secured on the outer periphery thereof.
By this arrangement, the copy paper sheet bear-ing an unfixed toner powder image on the surface thereof is electrostatically attracted and carried by the belt 400, and is separated by its own resilience from the belt 400 at the portion of the roller 400a so as to be subsequently attracted onto the surface of the drum 402 electrostatical-ly. The copy paper sheet thus attracted onto the surface of the drum 402 is subjected to heat conduction from the reverse surface thereof until the same is held between the lOg77Z2 roller 403 and the drum 402, and is heated to such an ex-tent that the toner powder image thereon is partly fixed so as to withstand any slight mechanical contact thereof with other parts. Between the roller 403 and the drum 402, the toner powder image is completely fixed on the copy paper sheet through heat conduction from the roller 402, with the surface of the fixed toner powder image being smoothed by the pressure therebetween. The fixed copy paper sheet is subsequently separated from the surface of the drum 402 by the claw 404 and discharged out of the apparatus G' through the rollers 405.
As is clear from the foregoing description, ac-cording to the fixing device F' of the invention, the copy paper sheet bearing the toner powder image formed thereon lS is electrostatically attracted onto the drum 402 provided with the heating source 402a, and is initially, heated to such an extent that the toner powder image is partly fixed merely through heat conduction from the reverse surface of the copy paper sheet, while the same sheet is being transported as the drum 402 rotates. The copy paper sheet is then passed between the drum 402 and the roller 403 of heat insulating nature which contacts the drum 402 under low pressure and rotates following the rotation of the drum 402 for perfectly fixing the toner powder image on the copy paper sheet, by which arrangement, possibility of ignition of the copy paper sheet due to excessive heating is eliminated, since radiation heat of the heating source is not directly applied to the surface of the copy paper sheet, while pre-vention o-f offset of the toner powder image and improvement in the durability of the roller 403 are advantageously lQ~7722 achieved, because the toner powder image is adapted to be fixed on the copy paper sheet under slight pressure after the same has been semi-fixed. Furthermore, by the above arrangement, fixing of a copy paper sheet having a special-S ly treated surface thereon may be effected without rumplingor wrinkle of the copy paper sheet. Additionally, the simple construction of the fixing device F' which requires only a single heating source or control means therefor con-tributes much to the reduction of space when incorporated in the copying apparatus.
Referring now to Fig. 7, there is shown a modifi-cation of the fixing device F' of Fig. 6. In this modifi-cation, the fixing device F" for use in a copying appa-ratus of dry developing process type is intended to fix the toner lS powder image only through pressure without utilizing any heat. The fixing device F" generally includes a pair of pressing rollers 501 and 502 of metallic material each heat-treated for the increase of hardness and rotatably supported on frames 503 and 504 by corresponding shafts 501a and 502a, with the upper frame 503 being adapted, at one end thereof, to pivot about a pin 503a fixed on a frame of the appara-tus housing, while the lower frame 504 is suitably fixed and remains stationary. A bolt 505 passes through a notch or an opening formed at the other end of the frame 503 with the lower end of the bolt 505 being threaded into an internally threaded opening formed a~ the othcr end of the frame 504 and secured thereto hy a nut. The uppe-r threaded end of the bolt 505 engages a nut 505a and a torsion spring 506 is coaxially disposed in the portion of the bolt 505 between a ~Yashe-r 505b disposed belo~ the nut SOSa and upper lQ"7722 wall of a housing Mol for a driving motor Mo which is adapted to engage the upper surface of the notched end of the frame 501 when the spring 506 is compressed. The spring 506 is for pressure adjustment between the rollers 501 and 502, and if there is tendency to unsatisfactory fixing, the nut 505a is further turned and threaded into the bolt 505 to compress the spring 506 for rotating the upper frame 503 clockwise in Fig. 19 about the pivotal connection 503a and consequently for further pressing the roller 501 dis-posed on the frame 503 against the roller 502 to adjust the pressure therebetween. A pulley 507 fixedly mounted on a driving shaft (not shown) of the motor ~o is connected to another pulley 508 secured to the shaft 502a of the roller 502 through a chain 509 for driving the roller 502, with the upper roller 501 being rotated following the rota-tion of the lower roller 502.
By this arrangement, the copy paper developed by the developing device D' and bearing the toner powder image thereon is transported on a belt 510 disposed between the developing device D' and the rollers 501 and 502, and movably supported by a plurality of rollers and is subse-quently fed between the rollers 501 and 502, thus the toner powder image being fixed on the copy paper sheet by the pressure acting between the rollers 501 and 502.
In the fixing device F" of Fig. 7 3 since no 'neat-ing elements are employed for fi~ing, not only the danger for ignition of the copy paper sheet is complctely elimi-nated, but also power consumption is .educed to an appre-ciable extent, and simple constructi,on of t~.e devi,ce F"
contributes to compact size and reduction of manufacturing 10~7722 cost of the copying apparatus.
As is clear from the foregoing description, ac-cording to the copying apparatus G' of the embodiment of Fig. 6, very efficient copying operations are carried out through the adoption of the fixing device F' of simple construction.
Although the present invention has been fully described by way of example with reference to the attached drawings, it is to be noted that various changes and modifi-cations are apparent to those skilled in the art. There-fore, unless otherwise such changes and modlfications de-part from the scope of the present invention, they should be construed as included therein.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An electrophotographic copying apparatus of the electrostatic latent image transfer type, said apparatus comprising:
a reciprocatingly movable platform on which an original to be copied is placed;
a rotatable photoreceptor drum disposed below said platform and having a photosensitive surface onto which an image of the original is projected;
means disposed around said drum and including a corona charging means for applying charges uniformly onto said drum, an exposure slit means through which an image of the original is projected so as to form an electrostatic latent image on said photosensitive surface, an image trans-fer means for transferring the thus formed latent image onto a copying paper sheet, a separating means for separating said copying paper sheet from said drum, and an erasing means for erasing residual charges from said drum;
a paper feeding means for feeding a copying paper sheet along a path to said image transfer means;
a developing means for developing the copying paper sheet;
a fixing means for fixing the thus developed image;
means for detecting the arrival of a copying paper sheet at a predetermined location along said path;
shifting means for shifting said image trans-fer means between a first position in which said image trans-fer means is out of contact with said drum and a second position in which said image transfer means is in contact with said drum;
control means, actuatable by said detection means, for operating said shifting means for shifting said image transfer means from said first to second positions thereof; and locking means normally preventing said platform from movement, and actuatable by said detecting means to release said platform and allow movement thereof.

2. An electrophotographic copying apparatus as claimed in claim 1, further comprising cam means on said platform, a shifting member engaging said cam means and movable thereby, and said shifting member operably connected to said separating means to move the same between a first position out of contact with said drum and a second position in contact with said drum upon movement of said shifting member by said cam means.

3. An electrophotographic copying apparatus of the electrostatic latent image transfer type, said apparatus comprising:
a reciprocatingly movable platform on which an original to be copied is placed;
a rotatable photoreceptor drum disposed below said platform and having a photosensitive surface onto which an image of the original is projected;
means disposed around said drum and including a corona charging means for applying charges uniformly onto said drum, an exposure slit means through which an image of the original is projected so as to form an electrostatic latent image on said photosensitive surface, an image trans-fer means including at least an electrically conductive roller for transferring the thus formed latent image onto a copying paper sheet, a separating means including claw member for separating said copy paper sheet from said drum, and an erasing means for erasing residual charges from said drum;
a paper feeding means for feeding a copying paper sheet along a path to said image transfer means;
a developing means for developing the trans-ferred image;
a fixing means for fixing the thus developed image;
means for detecting leading and trailing edges of the copying paper at predetermined locations along said path;
first control means for shifting said image transfer means between a first position out of contact with said drum and a second position in contact with said drum, said first control means including a shifting lever, a platform locking lever for locking said platform from moving, and a cam member rotatable by said shifting lever for shift-ing said image transfer means;
second control means for shifting said separating means between a first position out of contact with said drum and a second position in contact with said drum, said second control means including a shifting member operatively connected to said separating means and actuatable by a cam means on said platform during the movement thereof to shift said separating means;
said shifting lever and locking lever of said first control means being actuated upon detection of the leading edge of said copying paper sheet by said detecting means to release said locking lever and to rotate said cam member to thereby move said platform and shift said image transfer means; and said shifting member of said second control means being actuated as said platform moves by said cam means to shift said separating means to said second position thereof into contact with said drum.