US3923391A - Electrostatic photographic copying apparatus - Google Patents

Abstract

An electrostatic photographic copying apparatus comprising a frame member having a transparent plate on which to place an original to be copied, a rotatable photosensitive drum having an electrostatic photographic material on its periphery, an optical system for projecting an image of the original onto the surface of the photographic material, an image-forming zone disposed exteriorly of, and alongside, the periphery of said photosensitive drum for forming on said sensitive material an electrostatic latent image corresponding to the image of the original or a developed image corresponding to the latent image, a transfer zone for transferring said image to a transfer paper, and a transfer paper forwarding system for feeding the transfer paper on which the image has been transferred to a discharge end through a desired treating zone.

Description

United States Patent Washio et al. 1 1 Dec. 2, 1975 [54] ELECTROSTATIC PHOTOGRAPHIC 3,635,554 1/1972 Hodges 355/8 COPYING APPARATUS 3,689,146 9/1972 Ito et al. 3,784,297 1/1974 [to et a1 355/3 R [75] Inventors: TakaJi Washio, Toyonaka; Koichi Sasakl; (Tatsuo Alzawa both of Primary ExaminerRobert P. Greiner Osaka of Japan Attorney, Agent, or FirmSherman & Shalloway [73] Assignee: Mita Industrial Company, Ltd.,

Osaka, Japan [57] ABSTRACT [22] Filed: Sept. 21, 1973 An electrostatic photographic copying apparatus comprising a frame member having a transparent plate on [21] Appl' 399516 which to place an original to be copied, a rotatable photosensitive drum having an electrostatic photo- [30] Foreign Application Priorit D t graphic material on its periphery, an optical system for Sept. 24 1972 Japan 47-95460 Projecting image of the Original Onto the surface of the photographic material, an image-forming zone dis- 52 US. Cl ass/3 R; 355/8' 355/14 Posed exteriorly and alongside the Periphery f [51 1 Int. Cl. G03C /00 Said photo'sensitive drum for forming on said sensitive .[58] Field of Search H 355, R, 8, 1 1, 14, 50, material an electrostatic latent image corresponding to 355/51 66 the image of the original or a developed image corresponding to the latent image, a transfer zone for trans- [56] References Cited ferring said image to a transfer paper, and a transfer paper forwarding system for feeding the transfer paper UNITED STATES PATENTS on which the image has been transferred to a disgrztlvesnkwl. 355/3 R charge end through a desired treating Zone. u us e a 3,399,610 9/1968 Eichorn 355/8 8 Claims, 16 Drawing Figures a ill? 9 5 424 48 48 48" I5 o '1 & 7 "45A 3? I2- 23 38 44' '3' i n 274 45B 29\3O .i' fit 7 I/ 23 4 26kg 3O 4 Q b 5 43 b 3 14,

35f) 1 3| 35 n I b 5| 24 5 35f 35c 35 US. Patant Dec. 2, 1975 Sheet 2 of 11 U.S. Patent Dec.2,1975 Sheet40f1l 3,923,391

2, 1975 Sheet 5 of 11 3,923,391

US. Patent Dec.

US. Patent Dec. 2, 1975 Sheet60fll 3,923,391

US. Patent Dec. 2, 1975 Sheet 8 of 11 3,923,391

Sheet 10 of 11 US. Patent Dec. 2, 1975 US. Patent D60 2, 1975 Sheet 11 of 11 3,923,391

m m T5 3 F E ma ELECTROSTATIC PHOTOGRAPI'IIC COPYING APPARATUS SUMMARY OF THE INVENTION This invention relates to an improvement in electrostatic photographic copying apparatus, and specifically to an improvement in an electrostatic photographic copying apparatus of the type equipped with a rotatable photosensitive drum.

The conventional electrostatic photographic copying apparatus of this type generally requires a synchronization control mechanism having a complicated structure in order to expose an image of an original a photosensitive drum synchronously with the rotation of the photosensitive drum, and in order to a transfer paper synchronously with the rotation of the photosensitive drum. Furthermore, it is necessary to provide an electrical charging mechanism or an exposing section for an optical system, etc. along the circumference of the photosensitive drum. These provisions tend to increase the size of the apparatus.

It is an object of this invention to provide an electrostatic photographic copying apparatus in which the exposure of images can be effected synchronously with rotation of a sensitive drum by means of a device having a relatively simple structure.

Another object of this invention is to provide an electrostatic photographic copying apparatus in which the photosensitive drum and a transfer paper can be moved in exact synchronization with each other by a device having a relatively simple structure.

Still another object of this invention is to provide an electrostatic photographic copying apparatus which includes a cut length adjusting device having a relatively simple structure whereby a continuous web of transfer paper can be cut exactly according to the required copying length of the original.

A further object of this invention is to provide an electrostatic photographic copying apparatus which is relatively compact.

According to this invention there is provided an electrostatic photographic copying apparatus comprising a frame member having a transparent plate on which an original to be copied is placed, a rotatable photosensitive drum having electrostatic photographic material on its periphery, an optical system for projecting an image of the original onto the surface of the photographic material, an image-forming zone disposed exteriorly of, and alongside, the periphery of said photosensitive drum for forming on said sensitive material an electrostatic latent image corresponding to the image of the original or a developed image'corresponding to the latent image, a transfer zone for transferring said image to a transfer paper, and a transfer paper forwarding system for feeding the transfer paper on which the image has been transferred to a discharge end through a desired treating zone.

This invention can be applied to any electro-static photographic copying machine of the type in which a photosensitive drum is provided in a machine housing and transfer paper is brought into contact with the photosensitive drum to thereby transfer the image from the photosensitive drum to the transfer paper. For instance, this invention can be applied to either a copying machine of the so called original-moving, slit-exposure type in which an original to be copied is supported on a transparent plate mounted movably in the machine housing and an optical system is fixed in the housing, or the so called optical system-moving type in which an original is supported on a transparent plate fixed in the machine housing, while the optical system is moved to effect the slit exposure. In addition, this invention can be applied to a copying machine of the so called static image-transferring type in which an electrostatic image is formed on the surface of a photosensitive layer of a photosensitive drum, transferred to transfer paper and then visualized, or to a copying machine of the so called toner image-transferring type in which an electrostatic image formed on the surface of a photosensitive drum is developed with a toner and the toner image is transferred to transfer paper and, if required, fixed.

This invention can also be applied to a copying machine of the type in which transfer paper is fed in a separate sheets or from a web-like form as withdrawn from a paper roll. For instance, this invention can be applied to a copying machine of the type in which a container or cartridge of transfer paper sheets is provided on one end wall of the machine housing and transfer paper sheets are automatically fed from such container or cartridge, or to a copying machine of the type in which transfer paper sheets are manually fed into a passage for transportation of transfer paper sheets.

Accordingly, this invention will be described hereinafter mainly with reference to embodiments in which this invention is applied to a copying machine of the original-moving, toner image-transferring type, but it must be noted that the application is not limited to such application.

This invention will now be illustrated in more detail by reference to embodiments shown in accompanying drawings.

FIG. 1 is an arrangement diagram illustrating the outline of the copying machine of this invention.

FIG. 2 is a sectional side view in which the optical system and static image-forming zone of the copying machine of FIG. 1 are illustratively enlarged.

FIG. 3 is an enlarged sectional side view illustrating an embodiment of the developing apparatus usable in the copying machine of this invention.

FIGS. 4 and 5 are diagrams illustrating the arrangement and function of the magnet mechanism used in the developing apparatus of FIG. 3.

FIG. 6 is a side view illustrating the arrangement of the developing counter pole used in combination with the developing apparatus of FIG. 3.

FIG. 7 is a perspective view illustrating a toner supply cartridge used in the developing apparatus of FIG. 3.

FIG. 8-A is a simplified side view of the transfer apparatus used in the copying machine of this invention.

FIG. 8-B is an enlarged sectional side view of the fixation zone of the copying machine of this invention.

FIG. 9 is a diagram illustrating the principle of the copying machine of this invention.

FIG. 10 is an arrangement view of various control mechanisms used in the copying machine of this invention.

FIG. ll-A is an arrangement view showing the driving system of the copying machine of this invention.

FIG. 11-3 is a sectional view showing the system for driving the moving frame.

FIG. ll-C is a perspective view illustrating the restraint mechanism for the moving frame.

FIG. l2-A and l2-B are wiring diagrams of the electric circuit of the copying machine of this invention.

ENTIRE STRUCTURE In FIG. 1 illustrating an outline of the entire arrangeexposure mechanism '11 and the entire surface exposure mechanism 12 maybe omitted. Furthermore,

ment in the electrostatic photographic copying masupported by a moving frame 3 capable of moving reciprocatingly in the horizontal direction and an original-pressing flexible plate 4 is attached to the moving frame 3 so that it can cover the transparent plate 2. In the interior of the housing 1, a photosensitive drum 6 having on the surface thereof a electrostatic photosensitive layer is rotatably mounted. This photosensitive layer 5 may be any of a monolayer photosensitive plate formed by applying an inorganic photoconductor such as selenium, zinc oxide, cadmium sulfide, or cadmium selenide or an organic photoconductor such as polyvinyl carbazole, optionally together with a binder, on a substrate such as a metal plate or a paper rendered electrically conductive, a multilayer photosensitive plate formed by laminating a plurality of photoconductor layers or a sandwich-type multilayer photosensitive plate forming by inserting a photoconductor layer between an insulator layer and a conductor layer.

An image-forming zone 7 and a transfer zone 8 are grouped along the peripheral surface of the photosensitive drum 6. In the embodiment shown in FIG. 1 where a sandwich-type multilayer photosensitive plate forming by inserting a photoconductive layer between an insulating layer and a conductor layer is employed and the toner image transfer is effected, the image-forming zone 7 comprises a static latent image-forming area including a preliminary electrification mechanism 9 for erasing the charge remaining on the surface of the photosensitive layer, a primary electrification mechanism 10 for charging the surface of the photosensitive layer with a specific polarity, a secondary electrification and simultaneous exposure mechanism 11 for effecting the secondary electrification while an image is being exposed on the primarily electrified photosensitive layer and an exposure mechanism 12 for exposing to light the entire surface of the secondarily electrified and imagelight-exposed photosensitive layer, and a developing area including a development'mechanism 13 for developing the electro-static latent image with a toner powder. Each of the foregoing electrification mechanisms includes a corona wire on which a high voltage is applied, and the photosensitive layer is electrified by the corona discharge from this corona wire. The secondary electrification and simultaneous exposure mechanism 1 1 comprises an optical passage 14 connecting the photoconductive layer 5 optically with an opening for exposing the photosensitive layer to light and a corona wire 15 in said optical passage 14, on which a high voltage is applied. The voltage to be applied on the 15 of the secondary electrification and simultaneous exposure mechanism 11 may be a direct current voltage of a polarity reverse to the polarity of the primary electrification, an alternating current voltage or an asymmetric alternating current voltage.

The toner powder development mechanism 13 may be of any desired type such as for example, a magnetic brush type, a cascade type or a powder cloud type.

When the photoconductive layer 5 is composed of a monolayer photosensitive plate, the charging element 15 of the secondary electrification and simultaneous where the electro-static image on the photosensitive layer 5 is directly transferred to transfer paper (in the case of electro-static image transfer), the development mechanism 13 need not be provided along the periphery of the photosensitive drum 6.

An optical system indicated as a whole by reference numeral 16 is provided to project an image of the original a supported on the transparent plate 2, onto the photosensitive layer 5 in the above-mentioned imageforming zone. This optical system 16 comprises an opening 17 mounted in the upper portion of the housing 1 to expose the original to light, a light source 18 for illuminating the original a to be copied, a photosensitive layer-light-exposing opening 19 provided in the vicinity of the photosensitive layer 5 of the photosensitive drum in the image-forming zone 7, and a group of reflex mirrors 20, 21 and a mirror lens 22 provided to connect optically the original-light-exposing opening 17 with the photosensitive layer-light-exposing opening 19 and to form a reverse image of the original a to be copied on the photosensitive layer 5.

Along the periphery of the photosensitive drum 6, the transfer zone 8 is disposed in succession to the image-forming zone 7. In the housing 1 a passage for transfer paper b (indicated as a whole by reference numeral 23) is provided so that said passage is circum-. scribed with the photosensitive drum 6 in the transfer zone 8. At the upstream end of this transfer paper passage 23, a transfer paper feed mechanism is mounted. For instance, in the embodiment illustrated in FIG. 1, a roll stand 25 supported rockably on the machine housing by means of a fulcrum 24 is mounted on the upstream end of the transfer paper passage 23, and a shaft 28 of a reel 27 is removably and rotatably mounted on a fitting recess 26 formed on the upper end of this roll stand 25.

Downstream of the reel 27, there are provided both a guide roller 29 and a pair of driven feed rollers 30, 30 provided with a roll paper feeding clutch C2 in order to introduce transfer paper from a transfer paper roll b wound on the shaft of the reel 27. A pair of transfer papertransporting rollers 31, 31 which are normally driven are disposed between the feed rollers 30, 30 and the transfer zone 8, and a transfer papercutting mechanism 32 is mounted between the feed roller 30, 30 and the transfer paper-transporting rollers 31, 31'.

This transfer paper-cutting mechanism 32 includes a stationary blade member 33 and a rotary blade member 34. The rotary blade member 34 is rotated by excitation of a cutter solenoid and cuts transfer paper b passing through the stationary blade member 33 and rotary blade member 34. Accordingly, the position (Pl) shown in FIG. 9 and 10 for actuation of the transfer paper-cutting mechanism is the position of the upper edge of the stationary blade member 33. In the non-actuated state, the blade of the rotary blade member 34 is positioned on the upper side of the transfer paper passage between the feed rollers 30, 30' and the transporting rollers 31, 31' so that it does not intersect the transfer paper passage. In this invention, as will be detailed hereinafter, the position of the leading edge of transfer paper atthe beginning of feeding and the position for stoppage and standing-by of the leading edge of rolllike transfer paper cut are set at the position (Pl) for actuation of the transfer paper-cutting mechanism. In

order to attain this feature, upper and lower guide plates 35a and 35'a'are disposed between the cutting mechanism 32 and feed rollers 30, 30, and another upper and lower guide plates 35b and 35b, between the cutting mechanism 32 and transporting rollers 31, 31, so that lower guide plates 35a and 35b are positioned in an almost straight line with the upper edge of the stationary blade member 33 and the upper guide plates 35a and 35b are positioned in an almost straight line with the lower edge of the rotary blade member 34 in the non-actuated state. The foregoing structures make it possible to conduct the transportation and stoppage of transfer paper smoothly without occurrence of paper jamming or other troubles. Further downstream of the normally driven, transporting rollers 31, 31, there are provided upper and lower guide plates 35c and 350' to introduce transfer paper b into the transfer zone 8.

In the embodiment of the copying machine in FIG. 1, a paper feed mechanism for feeding a sheet-like transfer paper b is provided independently of the paper feed mechanism for feeding a roll-like transfer paper. More specifically, a paper-feeding table 51 is provided openably or removably at the end of the machine housing 1 at the upstream end of the transfer papertransporting passage 23 to feed a sheet-like transfer paper b", and at the tip of this paper-feeding table, there are mounted a paper sheet feeding opening 52 and upper and lower guide plates 35d and 35'd connected to this opening 52. A pair of paper sheet feed driven rollers 53, 53 provided with a sheet paper feed clutch C3 (shown in FIG. 11-A) are mounted downstream of the upper and lower guide plates 35d, 35d. Between said sheet paper feed rollers 53, 53 and the abovementioned transfer paper-transporting rollers 31, 31', upper and lower guide plates 35e and 35'e, a pair of sheet-transporting rollers 54, 54 and upper and lower guide plates 35f and 35]. are mounted to transport sheet-like transfer paper b" to said rollers 31, 31 In the copying machine illustrated in FIG. 1, the above-mentioned transfer paper-transporting passage 23 is circumscribed with the photosensitive drum 6 in the transfer zone 8 and forms almost one plane extending from sheet-transporting means 53, 53' to the abovementioned fixation zone 46. This passage 23 for feeding roll-like transfer paper b joins a passage 23' for feeding sheet-like transfer paper b" in the position of transporting rollers 31, 31' disposed upstream of the transfer zone 8, and transfer paper is then forwarded through the common transfer paper-transporting passage 23, extending in a straight line. When the passage for transporting a sheet-like transfer paper is thus disposed in a straight line in the machine housing and is circumscribed with the photosensitive drum 6 in the transfer zone 8, even if a very thin or soft paper, cloth, film or foil is used as the sheet-like transfer paper b, paper jamming can be greatly reduced and the copying operation can be accomplished very assuredly.

Further, if paper jamming is caused to occur in the transfer paper-transporting passage of the copying machine, removal of the jammed paper can be facilitated by disposing openably or dismountably each of members positioned in the transporting passage except for some pairs of transporting rollers. For instance, the roll-like transfer paper-cutting mechanism 32 and guide plates 35a, 35a, 35b, 35b positioned between the roll-feeding rollers 30, 30 and transporting rollers 31, 31, and guide plates 35f, 35] positioned between the transporting rollers 54, 54 and transporting rollers 31, 31 are integrally attached to a supporting frame 55 mounted detachably on the frame of the machine housing 1. Thus, the jamming of paper can easily be inspected by dismounting the foregoing members together with the supporting frame 55. Similarly, guide plates 35e, 35e positioned beteween the sheet-like transfer paper-transporting rollers 53, 53' and the transporting rollers 54, 54' are integrally attached to a supporting frame 56 mounted dismountably on the frame of the machine housing 1, so that these plates can be dismounted from the machine housing together with the supporting frame 56. The foregoing structure makes it possible to check jamming of transfer paper in the transfer paper-transporting passage with ease.

In the transfer zone 8, a transfer mechanism 36 is disposed to bring transfer paper b into contact with the photosensitive layer 5 of the photosensitive drum 6 and thereby transfer the image onto the transfer paper. This transfer mechanism 36 is constructed of a transfer roller alone or in combination with a corona discharge mechanism. For instance, when the image to be transferred is an electrostatic image, it may be transferred onto transfer paper merely by contacting it with the electrostatic image-carrying photosensitive drum by means of a roller. Of course, in this case, the transfer of the electrostatic image can be accomplished effectively by forming an electric field between the transfer roller and the substrate of the photosensitive drum or by effecting the corona discharge from the back face of transfer paper. When the image to be transferred is a toner image, it may be transferred onto transfer paper by contacting it with the toner image-carrying photosensitive drum by means of the transfer roller or by static force and forming an electric field between the transfer roller and the substrate of the photosensitive drum or effecting the corona discharge from the back face of the transfer paper.

The transfer papentransporting passage indicated as a whole by reference numeral 23 extends downstream of the transfer zone 8. On the discharge side the transfer zone of, and adjacent to the photosensitive drum 6 there is provided a peeling mechanism 37 which removes transfer paper b from the photosensitive layer 5 of the photosensitive drum 6 and directs it toward the said transporting passage. This peeling mechanism 37 is provided with a peeling projection 38 disposed so that its leading edge brought into contact with the photosensitive layer of said photosensitive drum. Said peeling projection 38 peels off the leading edge of the transfer paper b from the photosensitive layer surface and guides the transfer paper b to the transfer papertransporting passage. A fan 40 provided with a projection nozzle 39 directed toward the peeling projection 38 is disposed to assist peeling of the transfer paper b from the photosensitive layer surface and introduction of transfer paper b into the transfer paper-transporting passage and to accomplish these operations stably and assuredly.

In position spaced from the peeling mechanism 37 along the direction of rotation of the rotary drum 6, there may be provided a cleaning mechanism 41 to clean the photosensitive layer of the photosensitive drum 6 by removing the toner from the surface thereof.

' This cleaning mechanism 41 comprises a roller 42 provided with a rubber or brush surface which is rotated while in contact with the photosensitive layer of the drum 6. In the case of electro-static image transfer, of course, this cleaning mechanism may be omitted.

The transfer paper-transporting passage 23 extending to the downstream of the transfer zone 8 is provided with pair of driven rollers or one or more endless belts and it transports transfer paper through a subsequent treating zone. The treating zone may be an imagefixing zone, when a toner image is transferred and may include development and fixing zones when a static image is transferred. In the embodiment shown in FIG. 1, an endless belt 45 supported and driven by a driving pulley 43 and driven pulleys 44, 44 is mounted to define the lower side of the transfer paper-transporting passage 23 on the upper side of the transfer papertransporting passage 23, a fixation mechanism 46 is disposed to fix the toner image on transfer paper b. This fixation mechanism 46 includes an infrared lamp or electric heater 47 and the fixation of the toner image is accomplished by meltbonding it to transfer paper with heat from the heater. In order to prevent transfer paper from making direct contact with the fixation mechanism, another guiding belt 49 may be mounted on the upper side of the transfer paper-transporting passage 23. The guiding belt 49 is driven and supported by a driving pulley 48 and driven pulleys 48', 48", 48". It is also possible to position pulleys 44' and 48' supporting belts 45 and 49 near the discharge end 203 of the passage 23 in a manner such that the pulleys 44 and 48' contact each other through the belts, whereby transfer paper on which the image has been formed can be discharged assuredly from the fixing zone. In addition, on the lower side of the transfer papertransporting passage 23, a suction mechanism 50 may be provided to suck transfer paper through the endless belt 45, whereby transfer paper will adhere closely and fixedly to the endless belt 45. In this case, the guiding belt 49 may be omitted. Instead of a combination of the infrared lamp or electric heater with transfer papertransporting belts, a known combination (not shown) of an iron roller and a pressing roller may be used as the fixation mechanism 46 without disadvantages.

As is shown in FIG. 1, it is preferred that the photosensitive drum 6 be located so that the uppermost part of its circumferential surface is in proximity to, and faces, the upper surface plate 201 of the machine frame 1. This is because by opening the upper surface plate 201, the inspection, repair, etc., of the photosensitive drum 6 can be very easily performed.

The transfer paper transporting passage 23 can be oriented substantially horizontally in the lengthwise direction of the machine or it may be oriented in a plane inclined with respect to the lengthwise direction of the machine. However, as is shown in FIG. 1, it is preferred that the transfer section 8 be located in a position which is at an angle exceeding 180C. in the direction of rotation of the photosensitive drum from the uppermost part of the photosensitive drum. Furthermore the transfer paper transporting passage 23 form an upwardly inclined plane ranging from the positions of transfer roller 33, 33 upstream of the transfer zone 8 to the discharge end 201 through the transfer zone 8. This is because in the case of a copying machine provided with a photosensitive drum, such numerous treating zones as preliminary electrification zone 9, primary electrification zone 10, secondary electrification and simultaneous exposure zone 11, exposure zone 12 and development zone 13 should be disposed alongside the peripheral surface of the photosensitive drum 6 from the transfer zone 8 in the direction opposite to the direction of rotation of the transfer drum 6, and only peeling zone 37 and cleaning zone 41 should be disposed along the periphery of the photosensitive drum 6 from the transfer zone 8 in the direction of rotation of the drum 6. As mentioned above, the transfer papertransporting passage 23 is provided to contact the photosensitive drum 6 in an upwardly inclined state. Consequently a broad treating space can be obtained on the upstream side, that is the left side in FIG. 1, of the photosensitive drum 6. In addition to the above-mentioned various treating zones, the optical system and various paper feed mechanisms are provided above the feed side of the transfer zone 8, only when the transfer paper-transporting passage is provided in the upwardly inclined state, it is possible to secure a space sufficient to house these mechanisms therein. Thus, in the embodiment of the copying machine of the invention illustrated in FIG. I, either the height or the length of the machine can be greatly shortened as compared with conventional copying machines of this type. Furthermore, since the transfer paper-transporting passage 23 is provided in the state upwardly inclined with respect to the direction of advance of transfer paper, a space sufficient for opening the endless belt 45 downwardly can be provided below the fixing zone and hence, removal of jammed paper can be accomplished with ease.

The foregoing embodiment of the copying machine of this invention has the following particular structure.

Optical System As shown in an enlarged sectional side view of FIG. 2, the optical system of the copying machine comprises a light source 18 for light exposure, an opening 17 for exposing the original to light, two reflex mirrors 20 and 21, a mirror lens 22 and an opening 19 for exposing the photosensitive layer 5 to light, these members being disposed on partition walls 61, 62 and 63 or disposed so as to constitute at least part of these partition walls. The opening 17 for exposing the original to light is disposed in the upper portion of the machine housing 1 so that when a moving frame 3 is positioned at a point of initiation of light exposure, it can be optically connected to the standard end point of initiation of light exposure (position P6 detailed hereinafter) which is formed on a transparent plate 2 mounted on the moving frame 3. This opening 17 may be shielded by a transparent plate or it may not be shielded by a transparent plate. The light source 18 for light exposure is disposed on one 61 of partition walls 61, 62 inserting the opening 17 therebetween, in the vicinity of said opening for exposing the original to light. Alternatively, the light source 18 may be disposed on both the partition walls 61 and 62. The opening 19 for exposing the photosensitive layer to light is disposed in the partition wall 62 positioned on the side of the photosensitive drum, and the first reflex mirror 20 is mounted on the partition wall 63 of the optical system while the second reflex mirror 21 and mirror lens 22 are disposed on the partition wall 61 positioned on the opposite side. The first reflex mirror 20 connects the opening 17 for exposure of the original optically with the in-mirror lens 22 and simultaneously connects the mirror lens 22 optically with the second reflex mirror 21. This second reflex mirror 21 is disposed in such a position that it connects the first reflex mirror 20 optically with the opening 19 for exposing the photosensitive layer to light. In order to attain the foregoing positional relationship to the optical system, it is preferred that the optical axis x of the mirror lens 22 be inclined from the horizontal plane by a small angle (generally to 20) in the clockwise direction, and the first and second reflex mirrors 20 and 21 be deviated by an angle of 0 (generally +5 to +20) and 0 (generally 0 to in a clockwise direction from the position at an angle of 45 to the horizontal plane in a counterclockwise direction.

In the optical system 16 of this embodiment, light projected from the light source 18 and reflected from an original a to be copied is reflected by the first reflex mirror 20 and propagated to the mirror lens 22. The light is then reflected from the surface of the mirror lens 22, and is reflected again on the first and second reflex mirrors 20 and 21 and propagated to the photosensitive surface 5 through the opening 19 for exposing the photosensitive layer to light. Thus an image of the original is formed on the photosensitive surface 5. As is seen from the foregoing explanation, in this optical system, by arranging the first and second reflex mirrors and the in-mirror lens in an optical chamber so that a specific positional relationship as mentioned above can be attained among these optical members, it is made possible to utilize the first-reflex mirror in a duplicate manner for reflection and propagation of the light. As a result, a 4-fold optical passage for the reverse image can be formed by a minimum unit combination of two reflex mirrors and one mirror lens, and since the optical passage is of such 4-fold structure, the space for the optical system can be greatly reduced. Further, since the number of members constituting the optical system is very small, the angle determination in these members can be accomplished very easily. Preferably, the mirror lens 22 is mounted adjustably on the partition wall 61 to permit easy adjustment of the focal point of the optical system. By this contrivance, the focal point can be adjusted as desired by adjusting the mirror lens 22 even when the height of the transparent plate 2 for supporting an original to be copied or the position of the photosensitive layer on the surface of the photosensitive drum is varied.

In the embodiment illustrated in FIG. 2, the optical system 16 forms one chamber 64 substantially isolated from a static image-forming zone 7 and a developing zone 7 which are disposed along the passage for movement of the photosensitive layer 5. More specifically, each member of the optical system 16 is disposed inside the partition walls 61, 62, 63 or mounted on such partition wall so that it will act as a part of the partition wall. The opening 19 for light-exposing the photosensitive layer is covered with a transparent plate 65 such as a transparent glass plate and is supported on partition side walls 62, 63 through a sealing packing 66. Accordingly, in the area of the opening 19 of the optical system 16, an optical connection is attained to the area of the photosensitive layer 5 to be exposed while the air current is interrupted. Alternatively, air may be positively passed into the electrostatic image-forming zone 7' by providing an exhaust port of an exhaust gas duct 67 of a fan 40' on a side wall 1 of the machine housing confronting the electrostatic image-forming zone 7.

In an electrostatic photographic copying machine of the type wherein the development is effected using a toner powder, the developing zone is generally disposed just below the zone for forming an electrostatic image by electrification and light exposure. Therefore, operational troubles are brought about by scattering of the toner powder caused with rotation of the developing drum. When the side wall of the developing chamber is closely contacted with the photosensitive layer, the electrostatic image formed on the surface of the photosensitive layer is disturbed by friction. In order to prevent occurrence of this undesired phenomenon, a certain clearance should be formed between the side wall of the developing chamber and the surface of the photosensitive layer. However, if such clearance is formed, a fine powder of the toner is scattered from this clearance and adheres to the electrification and light exposure mechanisms of the electro-static imageforming zone, thereby contaminating these mechanisms. In the electrification zone, contamination is a special problem and is readily brought about by adsorption of the toner powder toner by the influence of static electricity generated by corona discharge. Thus, the image is disturbed in the optical system by scattering of the toner powder and a normal discharge of the electrification mechanism is inhibited by the scattered toner powder.

In the embodiment illustrated in FIG. 2, the optical system 16 including lens, mirrors and the like is so constructed as to form one chamber and the area of the opening 19 for exposing the photosensitive layer to light is kept in the air-tight state by the transparent plate 65. Therefore, intrusion of the toner powder into the optical system can be effectively prevented. Furthermore since air is positively blown into the static image-forming zone 7' including the electrification and light exposure mechanisms and the pressure can be maintained in this zone 7' at a level higher than in the developing zone 7", scattering and intrusion of the toner powder into the electrostatic image-forming zone can be prevented effectively. Thus, in the embodiment of the copying machine illustrated in FIG. 2, the need to frequency clean the electro-static image-forming zone can be greatly reduced and clear copy sheets can be obtained stably even if the copying machine is operated for a long period of time.

Developing Device The developing device used in the copying apparatus of this invention has such a structure as illustrated in FIGS. 3 to 7. In FIG. 3, the developing device shown generally at 13 includes a developing vessel 68 containing a developer, a stirring member 69 for stirring the developer, and a magnetic brush member 70 provided within the developer vessel 68. The developer may be composed of a toner powder and a magnetic carrier, or of a toner having magnetic properties. When the developer is composed of the toner powder and magnetic carrier, the toner powder is rubbed and electrically charged as a result of being stirred by the stirring member 69.

As is illustrated in FIG. 4, this magnetic brush member 70 includes a development sleeve 71 which is hollow and composed of a non-magnetic substance and a magnet means 72 disposed in the stationary state in said development sleeve 71. The magnet means 72 comprises a plurality of magnets 73 and 74 and a magnetism-intercepting member 75, which are provided to satisfy the following positional and arrangement requirements. The magnet forms a magnetic field sufficient to attract a developer to the sleeve surface and to retain the developer there in a zone ranging in therotating direction of the sleeve from the position P of pumping up the developer to the developing position P and the magnetism-intercepting member is disposed so that it weakens the magnetic field in at least a part of a zone ranging in the rotating direction of the sleeve from the developing position P,,, to the position P of pumping up the developer. Preferably, the magnetic field formed by the magnet has a flux (f,, for example, about 1000 gauss) suitable for taking up the developer C at the pumping position P under the sleeve 71, a flux (f about 700 gauss) substantially normal to the circumferential surface of the sleeve at the developing position P and a concentrated flux 02,) along the circumferential surface of the sleeve ranging from the developer-pumping position P to the developing position For example, in the embodiment illustrated in FIG. 4, a first magnet (i.e., a magnet brush-forming magnet 73) is disposed so that one end 76 of one pole N (or S) is directed to the developing position P,,. In the embodiment shown in FIG. 4, the magnetic brush-forming magnet 73 is composed of a plurality of rectangular magnet pieces bonded to one another, but of course, the magnet 73 may be composed of a single magnet piece. I

On the side of the other end 77 of the magnetic brush-forming magnet73, a secondary magnet (i.e., a developer-pumping magnet 74) is disposed so that its pole S (or N) is directed to the developer-pumping position P,,. In this case, it is indispensable that the polarity of the acting pole of the magnetic brush-forming magnet 73 is contrary to the polarity of the acting pole of the developer-pumping magnet 74. Needless to say, this developer-pumping magnet 74 may be formed integrally with the brush-forming magnet 73. It is preferred that these magnet brush-forming magnet 73 and developer-pumping magnet 74 are so arranged that their exciting directions are substantially perpendicular to each other.

The magnetism-shielding member 75 composed of a non-magnetized magnetic material (for example, nonmagnetic iron) is provided, as shown, so that it weakens a magnetic field formed between the other pole S (or N) of the magnetic brush-forming magnet 73 and the developer-pumping magnet 74 in the rotating direction of the sleeve.

By adopting the above-mentioned arrangement of the magnets 73 and 74 and the magnetism-shielding member 75, the magnetic flux density can be heightened especially at the developing zone Pd to which the end 76 of the pole N of the magnetic brush-forming brush 73 is directed and at the developer-pumping position P, to which the pole S of the developer-pumping magnet 74 is directed. Furthermore, at the area of the developing position Pd, a magnetic flux substantially vertical to the circumference of the sleeve is formed, and moreover, a flux of a relatively high density, i.e., a concentrated flux, is formed between the pole N of the magnet 73 and the pole S of the magnet 74, namely between the developer-pumping position P, and the developing position P along the circumference of the sleeve. Since the polarity of the other pole S of the magnetic brush-forming magnet 73 is the same as the polarity of the acting pole S of the developer-pumping magnet 74 and since the pole S of the magnet 73 and the space of portions of the magnet 74 other than the acting pole S are covered and filled with the magnetism-shielding member 75, the magnetic flux passes the interior of the magnetism-shielding member 75 between the pole S of the magnetic 73 and the magnet 74, namely between the carrier-peeling position Pf located on the opposite side of the developing position Pd and the developer-pumping position P Hence, the magnetic flux density is extremely low on the circumference of the sleeve in such area.

In conducting the developing operation, the magnet mechanism 72 is arranged fixedly in the state shown in FIG. 4, and when the sleeve 71 is rotated in the counterclockwise direction, the developer c is applied to the peripheral face of the sleeve at the developer-pumping position, whereby pumping of the developer is accomplished. The developer c is transported to the developing zone Pd while being carried on the circumference of the sleeve. At the developing zone Pd, a magnetic brush of a high density uniformly extending vertically from the peripheral face of the sleeve is formed, and a close contact of this magnetic brush with the electrostatic image carried on the photosensitive layer 5 can be ensured. Thus, the electro-static image on the photosensitive layer is developed with the charge toner retained by the magnetic carrier. The developer which has completed the developing operation is rotated in the counterclockwise direction from the developing position Pd while being carried on the circumference of the sleeve and is transported to the carrier-peeling position Pf located on the opposite side of the developing position Pd. At this carrier-peeling position Pf, the the magnetic flux density on the peripheral face of the sleeve is drastically lowered and the developer 0' transported while being retained on the circumferential face of the sleeve is peeled off therefrom by the gravity and centrifugal force and is allowed to fall down on the bottom of a developer vessel 68. At the point of falling of the developer c, there is provided a stirring mechanism 69 which rotates in the direction opposite to the direction of rotation of the sleeve, namely in the clockwise direction. This stirring mechanism 69 is mounted to stir the developer c having a lowered concentration of the toner powder with a freshly supplied toner powder and to feed a fresh supply of the developer to the developer-pumping position after adjustment of the toner concentration. In the development apparatus of this embodiment having the foregoing structure, it is possible to form a clear toner image stably even after the operation has continued for a long time.

The surface of the developing sleeve 71 may be smooth or, in order to retain the developer thereon assuredly and easily, the surface can have a roulette, for example, a roulette with a parallel pattern.

Furthermore, the magnetism-shielding member 75 or a combination of the magnetism-shielding member 75 with a member 78 composed of non-magnetic substance (for example, aluminum) may be disposed as the magnet-supporting member on the side wall of the developer vessel so that the angle of the magnet mechanism can be adjusted. In addition, the magnetic carrierpeeling position Pf can be made closer to the developing position Pd, if, as illustrated in FIG. 4, the magnetism-shielding member 75 is disposed to cover the opposite side pole S of the magnetic brush-forming magnet 73 and the side portion of the pole S positioned on the side where the developer-pumping magnet 74 is provided, and if at the same time as illustrated in FIG. 5, the magnetism-shielding member 75 is disposed to cover the side portion of the pole S positioned on the side opposite to the side where the developer-pumping magnet 74 is provided.

In the developing apparatus shown in FIGS. 3 to 5, a brush length-adjusting mechanism 79 is disposed in the vicinity of the magnetic brush-supporting surface of the magnetic brush mechanism 70, i.e., the surface of the developing sleeve 71, between the developerpumping position P, of the magnetic brush mechanism and the developing position Pd where the magnetic brush is brought into contact with the electro-static image-carrying surface 5. This brush length-adjusting mechanism 79 comprises a sharp edged blade 80 and a slide member 82 mounted movably along the bottom face of the developer vessel 68 on a supporting seat 81 provided on the bottom face of the vessel 68.

This slide member 82 includes slots 83 extending in a direction normal to the axis of the magnetic brush mechanism 70. Screws 84 are fitted to the supporting seat 81 through said slots 83, allowing the brush lengthadjusting mechanism 79 to be adjusted. In addition to these adjustment members, any other known mechanisms can be optionally used to adjust the position of the blade edge 80 of the brush length-adjusting mechanism.

The adjustment of the position of this brush lengthadjusting mechanism 79 is performed in the following manner by the above-mentioned adjustment mechanism.

a. The distance a between the blade edge 80 of the brush length-adjusting mechanism 79 and the magnetic brush-supporting surface (the surface of the sleeve 71) is made shorter than the distance d between the magnetic brush-supporting surface and the bottom face of the developer vessel at the develeper-pumping position P,,.

b. The distance d between the electro-static imagecarrying surface 5 and the magnetic brushsupporting surface at the developing position P, is made a little shorter than the distance d between the blade edge 80 of the brush length-adjusting mechanism and the magnetic brush-supporting surface.

The distance d;, between the electro-static imagecarrying surface 5 and the magnetic brush-supporting surface is varied considerably depending on the kind of the electro-static image-carrying surface. For instance, a good image is obtained when in the case of a zinc oxide photosensitive layer the distance d;, is about 4 mm and in the case of a cadmium sulfide photosensitive layer the distance d is about 2 mm. The distance d; can be easily adjusted as desired, for example, by mounting the entire developing device or the magnetic brush member movably with respect to the sensitive drum. The distance d between the magnetic brush-supporting surface and the bottom face of the developer vessel is made longer than the distance d so that at the developer-pumping position Pp the pumping of the developer can be readily accomplished and a fresh developer can be sufficiently supplied at said pumping position P The distance d, between the blade edge 80 of the brush length-adjusting mechanism and the magnetic brushsupporting surface is made a little longer than said distance d More specifically, the distance d is so set that the value of (d, d is generally 0 to 2 mm, especially about 0.5 mm.

When the distance d between the tip point of the bush-length-adjusting mechanism and the magnetic brush-supporting surface is adjusted in the foregoing manner, the developer 0 pumped at the developerpumping position P, and transported therefrom is brought into a slidable contact with the blade edge 80 of the brush length-adjusting mechanism and the excessive portion of the developer is removed. Accordingly, a magnetic toner provides magnetic brush of uniform density and a uniform length at the developing zone Pd. An appropriate amount of a developing toner is always stably and uniformly transported to the developing zone Pd. (The amount of the developing toner transported is not so excessive as will cause excessive application of the toner on the electrostatic imagesupporting face and is not so scarce as will cause insufficient application of the toner on the electro-static image-supporting surface. Furthermore, by adjusting the above distance d within a specific range in relation to the clearance d at the developing zone Pd, a light, sure and uniform contact can be attained between the magnetic brush and the electro-static image-carrying face at the developing position Pd, whereby the electrostatic image can be developed faithfully.

In the magnetic brush mechanism 70, it is preferred that a substantially parallel magnetic brush is formed at the above-mentioned developing zone Pd. In this case, the toner powder can be tightly and uniformly contacted with the electro-static image-carrying surface 5 according to the magnetic brush. In order to attain this feature, as is illustrated in FIG. 6, a developing counter pole 84 may be disposed in the substantially stationary state in the vicinity of the inner face of the portion of the photosensitive drum 6 confronting the magnetic brush mechanism 70.

In order to dispose the developing counter pole 84 in the substantially stationary state in the vicinity of the inner face of the photosensitive drum 6, the developing counter pole 84 is attached to one end of an arm 85, both ends of which are directed downwardly, and a balancing weight 86 is attached to the other end of this arm 85. The central portion of the arm 85 is engaged with or fitted to the rotary shaft 87 of the photosensitive drum 6, so that the arm is freely hanging down from the shaft 87. Thus, even when the photosensitive drum 6 supported on the ends of the shaft is rotated, off the weight 86 the developing counter pole 84 can be always located to align the magnetic mechanism 70 with the developing position Pd. When the photosensitive drum is supported in the open side manner on one frame of the machine housing, the developing counter pole 84 is fixed to the other frame of the machine housing. This enables the developing counter pole 84 to always confront the magnetic brush mechanism at the developing position. When the developing counter pole 84 is disposed in the vicinity of the inner face of the photosensitive drum in the foregoing manner to confront the magnetic brush mechanism at the developing position, the caring of the magnetic brush can be always kept parallel in the vertical direction and maintained in good conditions, and at the same time, the effective area can be enlarged at the developing zone Pd. Alternatively, the substrate of the photosensitive drum may be composed of a magnetic substance, but since the magnetic flux extends in a broad region, the magnetic carrier is adsorbed on the surface of the photosensitive drum 6 and it is transported to the transfer zone and other treatment zones in the state absorbed on the drum surface, which results frequently in bad influences on the image. It is also possible to wind a thin magnetic substance on the inner face of the photosensitive drum, but when this is done, the magnetic resistance is too great and the intended effects cannot be obtained. In the foregoing embodiment of this invention, by disposing the developing counter pole 84 to meet the abovementioned positional requirements, it is possible to reduce the magnetic resistance and to attain the desired effects.

The supply of the developing toner will now be described by referring to FIG. 3 again.

In the upper portion of the developer vessel 68 forming one chamber, an inlet 90 (see FIG. 6) is provided to insert a cylindrical cartridge 89 for supply of a toner into the side wall 88 of the developer vessel, and a supporting member 91 is provided on a toner supply chamber 93 to support rotatably the cartridge 89 inserted from the inlet 90. This toner supply chamber 93 is separated through partition walls 94 and an opening 92 is provided on the lower partition wall.

The toner supply cartridge 89 comprises, for instance, as illustrated in FIG. 7, a cylinder 97, both ends 95, 95' of which are closed and which is provided with an opening 96 scalable and openable along the substantially entire length of the cylinder. A toner power is contained in the cylinder. The opening 96 of the cylinder 97 includes outlets of such configuration and dimension that when the sealing of the opening is released and the opening faces downwardly, the toner powder 0 contained in the cylinder is discharged uniformly along substantially the entire length of the cylinder. At such outlet, there may be positioned, for instance, slit-like openings formed along the entire length of the cylinder and a number of holes distributed along the entire length of the cylinder. At least part of at least one of the side walls 95, 95 of the cylinder is made of a transparent or semi-transparent material so that the toner contained in the cylinder can be observed from the outside. On this portion 95 or 95 of the cylinder a mark 98 is provided indicating the position of the opening 96. The mark may be an arrow, letter, figure, projection or convexity. The opening 96 of the cartridge 89 may be sealed by adhesive tape 99 or the like, or outside edges of the opening 96 may be integrally formed with the cylinder through a cuttable perforated line or the like.

In supplying a toner into the toner supply chamber 93, the opening 96 of the cartridge 89 initially faces upwardly, and in this orientation the opening 96 is unsealed. Then, while maintaining the cartridge in this state, it is inserted into the interior of the toner supply chamber 93 through the inlet 90 provided on the side wall 88 of the developer vessel. The cartridge 89 is then rotated 180, whereby the opening 96 of the cartridge faces downwardly and a necessary amount of the toner is supplied into the toner supply chamber 93.

When the toner supply cartridge 89 as shown in FIG. 7 is employed, the supply of the toner into the developing apparatus 13 can be accomplished very easily without contaminating hands of a machine operator or scattering fine toner powder. Further, provision of the mark 98 indicating the position of the opening 96 on the side edge portion 95 or 95' of the cylinder makes it possible to conduct unsealing of the opening 96 easily without mistake, and insertion of the cartridge into the toner supply chamber 93 and supply of the toner by turning the cartridge to the prescribed position can be performed very easily with certainty. Moreover, it is easy to confirm whether the cartridge is located correctly at the toner supply position. Moreover, since the side edge portion or 95 of the toner supply cartridge 89 is composed of a transparent or semitransparent material, the amount of the toner contained in the cartridge can be easily confirmed from the outside and hence, the supply of the toner can be accomplished promptly without delay. In order to facilitate insertion and turning of the cartridge 89, it is generally preferred that the cylinder of the toner supply cartridge and the inlet 90 have a circular form, but when the inlet 90 is constructed of an individual member rotatable on the side wall of the developer vessel, they may take any other optional form.

In order to prevent the toner from scattering into the outside and ensure the support of the cartridge while preventing shaking of the cartridge, it is preferred that a packing member 100 of planted hairs or sponge be provided along the periphery of the inlet 90.

In the embodiment shown in FIG. 3, at the position of the opening 92 provided in the lower portion of the toner supply chamber 93, there is rotatably mounted a toner supply roller 102 having grooves 101 on the surface thereof. On the lower end portion of the partition wall 94, ends of elastic members 103 are fixed. The elastic members 103 are composed of a flexible material such as a Mylar film. The free ends of the elastic members 103 are allowed to make contact with the peripheral surface of the toner supply roller 102.

When the toner supply roller 102 is stopped, the toner supply chamber 93 and a developing chamber 104 are in an enclosed state. When the toner supply roller 102 is rotated in the clockwise direction, the toner contained in spaces of the grooves 101 is fed into the developing room 104. The afore-mentioned agitation mechanism 69 is disposed below the toner supply roller 102, and it frictionally charges the freshly supplied toner while mixing it with the magnetic carrier. The resulting developer composition is then fed to the developer-pumping position of the magnetic brush mechanism 70 by means of the agitation mechanism 69.

In the foregoing manner, in the toner supply mechanism illustrated in FIG. 3, an appropriate amount of a toner powder is freshly supplied by rotating manually or automatically the toner supply roller 102 after obtaining a prescribed number of copies. An advantage to this toner-supplying operation is that it can be accomplished without taking the development mechanism 13 from the machine housing.

Transfer Mechanism As is illustrated in FIG. 8A, the transfer mechanism 36 used in this embodiment comprises a transfer roller 107 including a roller base 105 composed of an electrically conductive rubber or other electric conductive material such as a metal and an insulating thin layer 106 which is coated on the roller base 105, and an electric source 109. The transfer roller 107 is disposed to press transfer paper 12 against the surface layer 5 of the photosensitive drum 6, and the electric source 109 is provided to apply a voltage between the electrically

Claims (8)

1. An electrostatic photographic copying apparatus comprising: a frame defining a housing with a top surface having a transparent plate on which an original to be copied is placed, a rotatable photosensitive drum for rotation in one direction as the apparatus copies having an electrostatic photographic material on the periphery thereof, an image-forming zone disposed adjacent to the periphery of said photosensitive drum for forming on said photosensitive material an electrostatic latent image corresponding to the image of the original and a developed image corresponding to the latent image, a transfer zone for transferring said image to a transfer paper, and a transfer paper forwarding system for feeding the transfer paper on which the image has been transferred to said transfer zone and through a desired treating zone to a discharge end; wherein said photosensitive drum is disposed within the housing with the top of the periphery thereof approaching and confronting an inner surface of the top plate of the housing adjacent a location on the inner surface; wherein said transfer zone is positioned at an angle exceeding 180* in the direction of rotation of the photosensitive drum from the location on the inner surface of the top plate; wherein said transfer paper forwarding system forwards a transfer paper in a substantially linear, upwardly inclined passage extending from an inlet end through the transfer zone to the discharge end; wherein said inlet end is preceded by a nip roller adjacent thereto; wherein said image forming zone includes at least one charging member for electrically charging said photographic material, an optical system for projecting an image of the original onto the surface of the photographic material and a developing device for developing the electrostatic latent image formed on said photographic material which are all housed within a first area defined on at least three sides of the top surface of said housing, the circumferential surface of the photosensitive drum extending from the top thereof to the transfer zone in the direction of rotation of the photosensitive drum and the transfer paper forwarding system; and wherein a transfer paper removing member and a photosensitive drum cleaning member are housed within a second area defined on at least three sides by the top surface of the housing, the circumferential surface of the photosensitive drum which extends from thE top of the photosensitive drum to the transfer zone in a direction opposite to the direction of rotation of the photosensitive drum and by the transfer paper forwarding system.

2. The apparatus of claim 1, wherein said transfer paper forwarding system includes means for feeding a continuous web of transfer paper to said nip roller, a cutting device for cutting the continuous web, an insertion opening for a separated sheet-like transfer paper, means for feeding the sheet-like transfer paper inserted from said insertion opening to said nip roller and means for bringing the web of transfer paper and sheet-like transfer paper into contact with the surface of the photographic material.

3. The apparatus of claim 2, wherein said means for feeding the sheet-like transfer paper feeds the paper into an extension of the substantially linear, upwardly inclined passage from said insertion opening to said nip roller, wherein said passage and said extension combine to make a single, continuous linear passage, whereby the sheet-like transfer paper is forwarded substantially linearly from said insertion opening to said discharge end.

4. The apparatus of claim 3, wherein said transfer paper forwarding system includes a synchronizing transfer roller provided downstream of the insertion opening, a sheet-like transfer paper detecting switch provided adjacent to the nip position of the synchronizing transfer roller, a drive system for rotating said photosensitive drum at substantially the same speed as the transfer speed of the sheet-like transfer paper, a switch means which emits a signal upon detecting arrival of a forward edge of an area of the photosensitive drum on which an image is formed, said switch means being spaced from a position of contact between the photosensitive drum and the sheet-like transfer paper by a distance equal to the distance between said contact position and the sheet-like transfer paper detecting switch in a direction opposite to the direction of rotation of the drum, means for stopping rotation of said synchronizing transfer roller when the leading edge of the sheet-like transfer paper has touched the detecting switch and for resuming rotation thereof in response to the signal from said switch means, whereby the leading edge of the sheet-like transfer paper reaches the transfer zone in synchronization with the forward edge of the area on the photosensitive drum on which an image is formed.

5. The apparatus of claim 1, wherein the transfer paper is dispensed from a roll in a continuous web, wherein said roll is contained in a space adjacent said first area to place said first area between said drum and said roll.

6. The apparatus of claim 5, wherein means are provided for feeding separate sheets of the transfer paper and wherein said means includes a downwardly directed linear extension of said upwardly inclined passage positioned upstream of said nip roller, said extension extending below said space in which said roll is contained.

7. The apparatus of claim 1, wherein a substantially empty space is provided in said housing below said upwardly inclined passage, said space extending downstream of said transfer zone to said discharge end to facilitate access to said transfer passage.

8. The apparatus of claim 7, wherein said discharge end is positioned in a plane above the bottom of said drum.

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