IMAGE FORMING MACHINE

Abstract: An image forming machine provided with an image bearing member (28) having a photosensitive material on its surface, a developing device (34) for developing a latent electrostatic image formed on the surface of the photosensitive material, a cleaning device (36) for removing toner remaining on the surface of the photosensitive material, and toner feed means for feeding the toner recovered in the cleaning device (36) to the developing device (34). According to one aspect, the machine is constructed such that the color of toner used in the developing device (34) can be easily determined. According to a second aspect, the image bearing member (28), the developing device (34) and the cleaning device (36) are mounted on a detachable unit frame (22), and the unit frame (22) is adapted to be mounted and detached by means of a simple structure. According to a third aspect, the machine is cnstructed such that the toner recovered in the cleaning device (36) is mixed in a predetermined amount with fresh toner and then fed to a developing chamber in the developing device (34). According to a fourth aspect, the machine is constructed such that fresh toner is sealed in a toner recovery chamber in the cleaning device (36) during machine production. According to a fifth aspect, the machine is constructed such that a toner cartridge is loaded into the toner recovery chamber of the cleaning device.

Description: This invention relates to improvements in an image forming machine. As is well known to those skilled in the art, image forming machines such as electrostatic copying machines or electrostatic printing machines of the type adapted to form a latent electrostatic image on an electrostatographic material and then develop the latent electrostatic image to a toner image have gained widespread commercial acceptance. There is an electrostatic copying machine as one example of such an image forming machine which can perform not only ordinary copying using black toner but also monocolor copying using colored toner such as red or blue toner. Such a conventional electrostatic copying machine cannot easily recognize the color of the toner in use, and it is judged from the image obtained by performing a copying operation. Hence, the copying operation is frequently performed wastefully. There is also a type of electrostatic copying machine which is provided with a process unit to be detachably mounted on a supporting structure in a main copying system of the machine. In such a conventional electrostatic copying machine, a gripping member exclusively used for mounting and detaching the process unit on and from the supporting structure is provided on a unit frame. Hence, this type of electrostatic copying machine has the defect that the provision of the gripping member makes the structure of the process unit complex. From prior art document JP-A-61-114 277 an image forming device is known, in which the residual developer of the visual image on a cleaned photosensitive body which is deposited in a cleaner box is carried a toner storage box through the rotation of a conveying auger. It is then conveyed to the side of the photosensitive body by a spiral auger which is driven. The toner storage box serves as a grip of the unit. It is the object of this invention to provide an image forming machine which permits easy recognition of the color of toner in use. This object is solved in accordance with the features of the independent claims, dependent claims are directed on preferred embodiments of the present invention. In the following, single embodiments according to the present invention are described with reference to the Figures, wherein Figure 1 is a front elevation of a first embodiment of an electrostatic copying machine as one example of the image forming machine constructed in accordance with this invention; Figure 2 is a sectional view showing the electrostatic copying machine of Figure 1 in a simplified form; Figure 3 is a front elevation showing the state in which an upper supporting frame in the electrostatic copying machine of Figure 1 is held at an open position and a front cover member in it is held in an open state; Figure 4 is a sectional view showing the state of Figure 3 in a simplified form; Figure 5 is a perspective view showing a process unit in the electrostatic copying machine of Figure 1; Figure 6 is a sectional view showing a rotating drum, a developing device and a cleaning device mounted on a unit frame in the process unit of Figure 5; Figure 7 is a partial perspective view showing on an enlarged scale part of a hollow guide member in the process unit shown in Figure 5; Figure 8 is a perspective view showing toner feed means and elements related thereto in the process unit shown in Figure 5; The invention will be described in detail with reference to the accompanying drawings. The following description is directed specifically to the electrostatic copying machine as one example of the image forming machine, but is also applicable to other types of the image forming machine such as an electrostatic printer. With reference to Figures 1 to 8, a first embodiment of the electrostatic copying machine as one example of the image forming machine of the invention will be described. With reference to Figures 1 to 4, mainly to Figure 2, the illustrated electrostatic copying machine has a nearly parallelepipedal housing shown generally at 2. The housing 2 in the illustrated embodiment is defined by a supporting structure comprised of a lower supporting frame 4 and an upper supporting frame 6. The lower part of the right end portion of the upper supporting frame 6 is pivotably linked to the lower supporting frame 4 via a shaft 8. The upper supporting frame 6 can pivot between a closed position shown in Figures 1 and 2 and an open position shown in Figures 3 and 4. At the front surface of the housing 2, a front cover 10 is mounted on the upper supporting frame 6 for free pivoting between a closed position (the position shown in Figure 1) and an open position (the position shown in Figure 3) around its lower end portion as a center. Document placing means 11 capable of reciprocation in the left-right direction is mounted on the upper surface of the housing 2, i.e. the upper surface of the upper supporting frame 6. The document placing means 11 includes a transparent plate 12 on which to place a document to be copied, and a document cover 14 which can be opened or closed and covers the transparent plate 12 and a document to be placed on it. A process unit shown generally at 16 is detachably mounted on the upper supporting frame 6 and positioned nearly centrally in the housing 2. A pair of supporting rails 18 and 20 spaced from each other in the left-right direction and extending in a direction perpendicular to the sheet surface are fixed to the upper supporting frame 6. On the other hand, the process unit 16 has a unit frame 22, and portions 24 and 26 to be supported extending in a direction perpendicular to the sheet surface are formed on the left and right side portions of the unit frame 22. The process unit 16 is mounted on and detached from the upper supporting frame 6 by bringing the portions 24 and 26 of the unit frame 22 into engagement with the supporting rails 18 and 20 and sliding the unit frame 22 in a direction perpendicular to the sheet surface. A rotating drum 28 constituting an image bearing member is rotatably mounted on the nearly central part of the unit frame 22. A suitable electrostatographic material is disposed on the peripheral surface of the rotating drum 28. Furthermore, around the rotating drum 28 to be rotated in the direction shown by an arrow 30, a charging corona discharge device 32, a developing device shown generally at 34, and a cleaning device shown generally at 36 in this sequence as viewed in the rotating direction of the rotating drum 28 are mounted on the unit frame 22. The developing device 34 and the cleaning device 36 will be more specifically described hereinafter. An illuminating lamp 46, a reflecting plate 48 and an optical system 50, positioned above the process unit 16, are also mounted on the upper supporting frame 6. The optical system 50 is comprised of many elongate optical units (for example, rod-like lenses sold under the tradename "Selfoc Microlens" by Nippon Sheet Glass Co., Ltd.) extending in the vertical direction. The light from the illuminating lamp 46 illuminates the document placed on the transparent plate 12 as shown by a one-dot chain line. The reflected light from the document passes through the optical system 50 and an exposure opening 54 formed in the upper wall 52 of the unit frame 22 and is projected onto the peripheral surface of the rotating drum 28 in an exposure zone 56. Part of the light from the illuminating lamp 46, as shown by a one-dot chain line, is projected onto the rotating drum 28 in a charge eliminating zone 62 via an opening 58 formed in the under surface of the reflecting plate 48 and an opening 60 formed in the upper wall 52 of the unit frame 22 for passing charge eliminating light. Nearly centrally of the lower supporting frame 4 are disposed a transfer corona discharge device 66 facing the peripheral surface of the rotating drum 28 in a transfer zone 64 and a peeling charge-eliminating device 68 located adjacent to, and downstream of, the transfer corona discharge device 66. Furthermore, in the right end portion of the lower supporting frame 4, copying paper feed means shown generally at 72 is disposed, and a copying paper receiving tray 74 is provided in the left end portion of the lower supporting frame 4. A copying paper conveying system shown generally at 76 is disposed between the paper feeding means 72 and the paper receiving tray 74 for conveying paper through the transfer zone 64. The paper feed means 72 comprises a paper receiving stand 78 and a paper delivery roller 80 disposed above the downstream end portion of the paper stand 78. The paper delivery roller 80 is adapted to be selectively elevated or lowered and simultaneously rotated in the direction shown by an arrow 82. The paper feed means 72 further includes a paper feed roller 86 disposed downstream of the paper stand 78 and adapted to be rotated in the direction shown by an arrow 84, and paper separating means 88 disposed below it. The paper separating means 88 has a supporting member 92 pivotably mounted by a pin 90 and a separating member 94 made, for example, of a high friction material such as synthetic rubber and disposed on the upper surface of the supporting member 92. The supporting member 92 is elastically biased clockwise by suitable spring means (not shown). Thus, the separating member 94 is elastically pressed against the paper feed roller 86. In the paper feed means 72 described above, a layer of copying paper sheets of a suitable size is manually inserted and placed on the paper stand 78. Every time the paper delivery roller 80 is lowered and rotated in the direction of arrow 82, one uppermost sheet is delivered and further advanced by the feed roller. The separating member 94 serves to prevent sheets other than the uppermost sheet from being advanced by the paper feed roller 86 when two or more sheets are delivered at a time by the delivery roller 80, and thus to ensure that the copying sheets are fed one by one by the paper conveying system 76. The paper conveyor system 76 comprises a guide plate pair 96, a conveying roll pair 100 to be rotated in the direction shown by an arrow 98, guide plates 102 and 104, a conveyor belt mechanism 108 to be rotated in the direction shown by an arrow 106, a heat fixing roller pair 112 to be rotated in the direction of an arrow 110, a guide plate pair 114 and a discharge roller pair 118 to be rotated in the direction shown by an arrow 116. Suitable heating means 122 is disposed in an upper heating roller 120 in the heat fixing roller pair 112. A separating member 124 is annexed to the upper heating roller 120 to prevent wrapping of the paper. In the electrostatic copying machine described above, while the rotating drum 28 is rotated in the direction of arrow 30, the charging corona discharge device 32 substantially uniformly charges the photosensitive material on the rotating drum 28 to a specified polarity. Then, in the exposure zone 56, the image of the document on the transparent plate 12 is scanned and exposed onto the photosensitive material whereby a latent electrostatic image corresponding to the image of the document is formed on the photosensitive material. During scanning and exposure, the document placing means 11 is moved rightward for scanning and exposure from a start-of-scan position shown by a two-dot chain line 11A to an end-of-scan position shown by a two-dot chain line 11B. Thereafter, the latent electrostatic image on the photosensitive material is developed to a toner image by the developing device 34. Copying paper fed from the paper feed means 72 by the paper conveying system 76 is brought into intimate contact with the peripheral surface of the rotating drum 28 in the transfer zone 64, and by the action of the transfer corona discharge device 66, the toner image on the photosensitive material is transferred to the copying paper. Subsequently, the copying paper is separated from the rotating drum 28 by the action of the charge eliminating device 68. The separated copying paper is conveyed through the heat fixing roller pair 112, and during this time, the toner image on the paper is heat-fixed, and the paper is discharged onto the paper receiving tray 74. In the meantime, the rotating drum 28 continues to rotate, and the toner remaining on the photosensitive material after the transfer is removed from it by the action of the cleaning device 36. Then, charge-eliminating light is irradiated onto the photosensitive material in the charge eliminating device 62 to erase the residual charge on the photosensitive material. With reference mainly to Figures 5 and 6 taken in conjunction with Figure 2, the unit frame 22 of the illustrated process unit 16 has a front wall 126 (Figure 5) and rear Ball 128 (Figure 2) disposed in spaced-apart relationship in the front-rear direction (the direction perpendicular to the sheet surface in Figures 2 and 6, and the direction from right bottom to left top in Figure 5), and the rotating drum 28, the developing device 34 and the cleaning device 36 are mounted between the front wall 126 and the rear wall 128. A bottom wall 130, a left side wall 132 and a right side wall 134 together with the upper wall 52 mentioned hereinabove are provided between the front wall 126 and the rear wall 128. A transfer opening is formed in the bottom wall 130 to permit copying paper conveyed by the action of the paper conveying system 76 to make contact with the peripheral surface of the rotating drum 28 in the transfer zone 64, and the lower end portion of the right side wall 134 serves as the portion 26 to be supported. The rotating drum 28 is mounted rotatably between the front wall 126 and the rear wall 128. The rotating drum 28 is designed to be drivingly connected to a driving source (not shown; constituting a driving source of the electrostatic copying machine) disposed in the lower supporting frame 4 when the process unit 16 is mounted detachably on the upper supporting frame 6 and the upper supporting frame 6 is brought to the closed position, and there by to rotate in the direction of arrow 30. The illustrated developing device 34 has walls 138, 140, 142, 144, 146, 148, 150, 152 and 154 fixed between the front wall 126 and the rear wall 128 of the unit frame 22, and includes three chambers defined by these walls, i.e. a developing chamber 156, a developer holding chamber 158 and a toner holding chamber 160. A toner cartridge 162 is detachably loaded into the toner holding chamber 160. Fresh toner (not shown) is held in the toner cartridge 162, and by loading the toner cartridge 162, the fresh toner can be supplied. A discharge opening 164 of the toner cartridge 162 is sealed by a suitable sealing member (not shown). The toner cartridge 162 is loaded as shown in Figures 2 and 6 by inserting the toner cartridge 162 into the toner holding chamber 160 while peeling the sealing member. As a result, the discharge opening 164 is opened and the fresh toner in the cartridge 162 is supplied through the discharge opening 164. The illustrated embodiment is in such a condition that fresh toner can be supplied. When toner supply is not necessary (for example, if the machine is of such a type that when all the toner held in the toner holding chamber 160 is used up, the entire process unit 16 is replaced by a new one), fresh toner may be directly supplied to the toner holding chamber 160 defined by the walls 140, 142 and 144. A toner discharge opening 166 is formed at the bottom of the toner holding chamber 160, and a slender cylindrical toner feed roller 168 is disposed in the toner discharge opening 166. The toner feed roller 168 is rotated in the direction shown by an arrow 170 thereby to cause the toner in the toner holding chamber 160 to be fed into the developing chamber 156 through the toner discharge opening 166. The developing chamber 156 is opened at its left side facing the rotating drum 28. Applicator means 172, developer agitating means 174 and a guide plate 176 are disposed in the developing chamber 156. The applicator means 172 may be comprised of a cylindrical sleeve 180 to be rotated in the direction shown by an arrow 178 and a stationary permanent magnet 182 disposed within the sleeve 180 and having a plurality of circumferentially spaced magnetic poles. The agitating means 174 has a plurality of helical vanes 186 to be rotated in the direction shown by an arrow 184 and serves to agitate the developer within the developing chamber 156 and feed it to the applicator means 172. Brush cutting means 188 projecting toward the sleeve 180 of the applicator means 172 is formed in the wall 154 defining the upper wall of the left side of the developing chamber 156. The brush cutting means 188 acts on the developer moving while being magnetically held to the surface of the sleeve 180, and removes the excess of the developer. A toner concentration detector 190 positioned above the brush cutting means 188 is provided in the wall 154. The detector 190 which may be of a known type has a detecting surface exposed to the inside of the developing chamber 156 and detects the toner concentration of the developer removed from the applicator means 172 by the action of the brush cutting means 188. The developer holding chamber 158 is disposed on the developing chamber 156. A starting developer (a fresh developer consisting of carrier and toner in a particular mixing ratio) is held in the developer holding chamber 158. When a two-component developer is used, a mixture composed of carrier and toner is held in the developing chamber 156. When a one-component developer is used, toner is held in it, and the developer holding chamber 158 may be omitted. In starting to use the developing device 34, the starting developer held in the developer holding chamber 158 is supplied to the developing chamber 156. Then, the toner cartridge 162 is loaded in position into the toner holding chamber 160 by inserting it while removing the sealing member (not shown). As a result, the discharge opening 164 of the toner cartridge 162 is opened, and the toner in the toner cartridge 162 is supplied to the toner holding chamber 160 through the discharge opening 164. The toner holding chamber 160 is now ready for feeding the toner. In the illustrated embodiment, the discharge opening 164 extends substantially from one end to the other end of the toner holding chamber 160 in the widthwise direction above the toner feed roller 168. Hence, the fresh toner in the cartridge 162 is supplied substantially uniformly to the toner holding chamber 160 from its one end to the other in the widthwise direction. The above operation enables the developing device 34 to develop the latent electrostatic image. In performing the development, the agitating means 174 is rotated in the direction of arrow 184 in the developing chamber 156 to agitate the developer and charge the toner to a particular polarity. The developer is delivered toward the applicator means 172. The sleeve 180 in the applicator means 172 is rotated in the direction shown by an arrow 178. The developer delivered by the action of the agitating means 174 is held onto the surface of the sleeve 180 by the magnetic attracting force of the magnet 182 within the sleeve 180 and conveyed in the direction shown by an arrow 178 as the sleeve 180 rotates. The excess of the developer held onto the surface of the sleeve 180 is removed by the action of the brush cutting means 188. The removed developer is moved upwardly along the inner surface of the wall 154, then caused to flow down over the guide plate 176 toward the agitating means 174, and again agitated by the agitating means 174. In the meantime, the developer held onto the surface of the sleeve 180 and conveyed in the direction of arrow 178 is brought into contact with the photosensitive material disposed on the surface of the rotating drum 28. The toner in the developer is applied to a latent electrostatic image on the photosensitive material to develop the latent electrostatic image to a toner image. When the toner concentration of the developer decreases as a result of the developing action, the detector 190 produces a signal which in turn causes the toner feed roller 168 to rotate in the direction of arrow 170 and supply the toner in the toner holding chamber 160 to the developing chamber 156. The illustrated cleaning device 36 has a pair of end walls (not shown) disposed in spaced-apart relationship in the front-rear direction in the inside of the unit frame 22, and walls 192 and 194 extending in the aforesaid front-rear direction are provided between these end walls. An elastic blade 198 is attached to the upper surface of the wall 192 of the cleaning device 36 by a fixing member 198. The elastic blade 198 constitutes toner removing means, and its free end portion is kept in press contact with the peripheral surface of the rotating drum 28 under a predetermined pressure. The cleaning device 36 is provided with a toner recovery chamber 200 defined by the walls 192 and 194. The toner recovery chamber 200 is open at that site which faces the rotating drum 28, and a sealing member 202 is disposed in the opening portion. The sealing member 202 is attached to the outside surface of the wall 194, and its free end is kept in contact with, or in proximity to, the peripheral surface of the rotating drum 28. When the rotating drum 28 is rotated in the direction of arrow 30, the residual toner on the surface of the photosensitive material is removed by the elastic blade 198. The removed toner is guided by the sealing member 202 and the inside surface of the wall 194 and recovered into the toner recovery chamber 200. The copying machine described above is further constructed such that the toner recovered into the toner recovery chamber 200 is again fed to the toner holding chamber 160. With reference to Figures 3, 5, 6 and 8, the process unit 16 further includes toner feed means 203 for conducting the toner recovered and received in the toner recovery chamber 200 to the toner holding chamber 156. The illustrated toner feed means 203 comprises a hollow cylindrical member 204 communicating with the toner recovery chamber 202 and the toner holding chamber 156, and toner transfer means for transferring the toner through the hollow cylindrical member 204. In the illustrated embodiment, the toner transfer means is constructed of a slender helical member 208. An opening is formed at a required site of one end wall (the end wall positioned at a front site in the front-rear direction) of the cleaning device 36, and an opening corresponding to the above opening is also formed at a required site of the front wall 126 of the unit frame 22. Also, an opening is formed at a required site of the front wall 126 of the unit frame 22 corresponding to the toner holding chamber 160 of the developing device 34. One end portion 206a of the hollow cylindrical member 204 is connected to the opening formed in one end wall of the cleaning device 36 through the above one opening formed in the front wall 126 of the unit frame 22. Its intermediate portion 206b extends laterally from left to right ahead of the front wall 126, and its other end portion 206c is connected to the other opening formed in the front wall 126 of the unit frame 22. In the illustrated embodiment, the toner cartridge 162 is detachably loaded into the upper space of the toner holding chamber 16 as shown in Figures 6 and 8, and a hollow cylindrical guide member 207 is disposed below the discharge opening 164 of the toner cartridge 162. The hollow guide member 207 extends from one end to the other of the toner holding chamber 160 in the widthwise direction. Namely, it extends from the inside surface of the front wall 126 of the unit frame 22 to the inside surface of the rear wall 128, and the other end portion 206c of the hollow cylindrical member 204 is caused to communicate with one end of the hollow guide member 207. Instead of providing the hollow guide member 207 separately, it is possible to extend the other end portion 206c of the hollow cylindrical memer 204 from the front wall 126 to the rear wall 128 of the unit frame 22 within the toner holding chamber 160 and utilize the other end portion 206c as a hollow guide member. It is critical that at least part of the hollow cylindrical member 204 should be transparent or semitransparent. In the illustrated embodiment, a short cylindrical member 210 made from a transparent or semi-transparent synthetic resin is connected to part of the intermediate portion 206b (a part to be gripped as described hereinafter) of the hollow cylindrical member 204. An intermediate portion 212a of the helical member 208 is situated within the intermediate portion 206b of the hollow cylindrical member 204, and its one end portion 212b is positioned within the toner recovery chamber 200 of the cleaning device 36 via the one end portion 206a of the hollow cylindrical member 204. Its other end portion 212c is positioned within the hollow guide member 207 via the other end portion 206c of the hollow cylindrical member 204 (Figure 8). In the toner recovery chamber 200, one end portion 212b of the helical member 208 extends in the widthwise direction, namely in the aforesaid front-rear direction, in its bottom portion, and a shaft portion 214 provided at its one end is rotatably mounted on the other end wall (the end wall positioned rearwardly in the front-rear direction) of the cleaning device 36. The shaft portion 214 projects rearwardly through the aforesaid other end wall, and a gear 216 is mounted on its projecting end. The gear 216 meshes with a large gear 218 provided in the rear end portion of the rotating drum 28. Rotation of the rotating drum 28 in the direction of arrow 30 causes the gear 216 to rotate in the direction shown by an arrow 220 via the large gear 218. Within the hollow guide member 207, the other end portion 212c of the helical member 208 extends axially of the hollow guide member 207, namely in the aforesaid front-rear direction, and a shaft portion 222 provided at its other end is rotatably mounted on the rear wall 128 of the unit frame 22. As can be seen from Figure 8, the helical member 208 has the shaft portions 214 and 222 at its both ends, but the remainder has no shaft portion and is hollow. Furthermore, the helical member 208 is helically wound such that when the gear 216 is rotated in the direction of arrow 220, it transfers the toner in the direction shown by an arrow 224 (Figure 8). As shown in Figure 8, in the applicator means 172, shaft portions 228a and 228b provided at its opposite end portions are rotatably mounted on the front wall 126 (Figure 5) and the rear wall 128 (Figure 2) of the unit frame 22. In the agitating means 174, shaft portions 230a and 230b provided at its opposite end portions are rotatably mounted on the front wall 126 and the rear wall 128. A shaft portion 228b of the sleeve 180 projects rearwardly through the rear wall 128, and a gear 232 is mounted on this projecting end. The shaft portion 230b of the agitating means 174 projects rearwardly through the rear wall 128, and a gear 234 is mounted on its projecting end. The gears 232 and 234 are drivingly connected to each other via a small gear 236. Hence, when the gear 232 is turned in the direction shown by an arrow 238 by the aforesaid driving source (not shown) of the copying machine (whereby the sleeve 180 is rotated in the direction shown by arrow 178), the gear 234 is rotated in the direction shown by an arrow 240 via the gear 236 (whereby the agitating means 174 is rotated in the direction shown by arrow 184). When the rotating drum 28 is rotated in the direction of arrow 30 in the copying machine provided with the feed means 203 described above, the helical member 208 is rotated properly via the large gear 218 and the gear 216. Specifically, its one end portion 212b positioned within the toner recovery chamber 200 is rotated in the direction shown by an arrow 242 (Figures 6 and 8) to transfer the toner in the direction of arrow 224 from the rear end of the toner recovery chamber 200 toward its front end. The toner so transferred is fed to the toner holding chamber 160 via the hollow cylindrical member 204. In the hollow guide member 207, the other end portion 212c of the helical member 208 is rotated in the direction shown by an arrow 244 (Figures 6 and 8), and the toner fed to the toner holding chamber 160 as above is transferred from one end of the hollow guide member 207 toward its other end in the direction of arrow 224 by the action of the other end portion 212c rotating in the direction of arrow 244. While being transferred within the hollow guide member 207, the toner from the toner recovery chamber 200 is fed into the toner holding chamber 160 through a plurality of openings 226 (Figures 6 and 7). Preferably, the plurality of openings 226 are formed in spaced-apart relationship axially of the hollow guide member 207 as shown in Figure 7. Preferably, the openings 226 are progressively smaller one way in the widthwise direction of the toner holding chamber 156 (namely, frontwardly in the frontrear direction), and progressively larger the other way in the widthwise direction of the toner holding chamber 156 (i.a., rearwardly in the front-rear direction). Since the openings 226 are progressively smaller toward the front end side of the hollow guide member 207, the proportion of the toner to be supplied is small in spite of the relatively large amount of the toner in the front end portion. On the other hand, since the openings 226 are progressively larger toward the rear end side, the proportion of the toner supplied is large in spite of the relatively small amount of the toner in the rear end portion. Consequently the toner from the recovery chamber 200 can be supplied substantially uniformly in the widthwise direction of the toner holding chamber 160. The copying machine described above has the following noteworthy features. With reference mainly to Figures 6 and 8, a first holding chamber is defined by the detachably loaded toner cartridge 162 in the upper portion of the toner holding chamber 160. A mixing chamber is defined in the lower portion of the toner holding chamber 160, and a second holding chamber is defined by the hollow guide member 207 in the upper portion of the mixing chamber. Accordingly, fresh toner in the toner cartridge 162 is fed into the mixing chamber through the discharge opening 164. The toner recovered from the cleaning device 36 is fed to the lower portion of the mixing chamber through the openings 226 formed in the hollow guide member 207. The toner from the toner cartridge 162 and the toner from the hollow guide member 207 are mixed in the lower portion of the mixing chamber in the toner holding chamber 160, or in other words, near the toner feed roller 168. The mixed toner is fed to the developing chamber 156 through the discharge opening 166. Hence, the toner for reuse from the cleaning device 36 is mixed in a substantially constant proportion with the fresh unused toner from the toner cartridge 162, and the mixed toner is again fed to the developing chamber 156. Accordingly, stable images can be obtained over a relatively long period of time while inhibiting marked degradation of image quality. In relation to the fact that the hollow cylindrical member 204 is partly transparent or semi-transparent, the illustrated copying machine further has a window portion 248 at a required site of the front cover member 10, as shown in Figure 1. In the illustrated embodiment, the window portion 248 is constructed by covering the opening formed in the front cover member 10 with a member 250 formed of a transparent or semitransparent material. Instead of this structure, an opening may simply be formed in the front cover member 10. In this case, it is preferred that the front surface of the front cover member 10 and the intermediate portion 212a acting as a gripping portion of the hollow cylindrical member 204 should define nearly the same plane. Because of the above structure, part of the toner transferred from the toner recovery chamber 200 to the toner holding chamber 160 via the hollow cylindrical member 204 can be viewed through the member 210 of the hollow cylindrical member 204. Furthermore, the member 210 can be viewd through a member 250 attached to the front cover member 10. When, therefore, part of the hollow cylindrical member 204 is rendered transparent or semi-transparent the color of the toner in the developing chamber 156 and being in use can be easily determined without performing the copying cycle by removing the front cover member 10. Furthermore, when the window portion 248 is provided in the front cover member 10 at a site corresponding to the transparent or semi-transparent portion of the hollow cylindrical member 204, the color of the toner in use can be easily determined from outside without removing the front cover member 10. With reference mainly to Figures 1 to 4, when the process unit 16 is to be mounted on the upper supporting frame 6 in the housing 2, the upper supporing frame 6 is held at the open position as shown in Figures 3 and 4 by properly pivoting it. Then, the front cover attached to the upper supporting frame 6 is pivoted forwardly with its lower end portion as a fulcrum to open the front surface of the upper supporting frame 6. It is also possible to hold the front cover member 10 in the open state and then bring the upper supporting frame 6 to the open position. Thereafter, the portions 24 and 26 provided in the unit frame 22 are engaged with the supporting rails 18 and 20, and the unit frame 22 is mounted in position by moving it rearwardly in the front-rear direction (the direction perpendicular to the sheet surface in Figures 1 to 4). When the portions 24 and 26 to be supported are engaged with the supporting rails 18 and 20 while the upper supporting frame 6 is at the open position, the intermediate portion 206b, located ahead of the front wall 126 of the unit frame 22, of the hollow cylindrical member 204 is positioned substantially horizontally. Therefore, in moving the unit frame 22 rearwardly, the intermediate portion 206b of the hollow cylindrical member 204 can be easily grasped. Furthermore, as a result of this engagement, the supporting rail portions 18 and 20 support the portions 24 and 26 in a substantially perpendicular direction. Hence, by grasping the intermediate portion 206b of the hollow cylindrical member 204 serving as a gripping portion, the unit frame 22 can be moved easily and smoothly. After the mounting operation, the front cover member 10 is held in the closed state, and the upper supporting frame 6 is pivoted to the closed position shown in Figures 1 and 2 (alternatively, the upper supporting frame 6 may first be held at the closed position, and then the front cover member 10 may be held in the closed state). As a result, various constituent elements (such as the illuminating lamp 46) mounted on the upper supporting member 6, various constituent elements (the rotating drum 28, the developing device 34, the cleaning device 36, etc.) mounted on the unit frame 22, and various constituent elements mounted on the lower supporting frame 4 (such as the paper conveying system 76) are maintained in the positional relation shown in Figure 2, and the copying machine is ready for performing a copying operation. On the other hand, when paper which has jammed up in the paper conveying system 76 is to be removed or the process unit 16 is to be removed from the upper supporting frame 6 in the housing 2, the upper supporting frame 6 is pivoted as above to the open position. It will be easily understood from Figure 4 that as a result, a greater part of the paper conveying passage defined by the paper conveying system 76 is opened, and the jamming paper can be easily removed from the paper conveying system 76. To detach the process unit 16 from the upper supporting frame 6, the upper supporting frame 6 is held at the open position and then the front cover member 10 is pivoted and held in the open state shown in Figure 3. The unit frame 22 is then moved forwardly in the front-rear direction and detached from the upper supporting frame 6. Since the intermediate portion 206b of the hollow cylindrical member 204 is positioned substantially horizontally and the supporting portions 18 and 20 support the portions 24 and 26 in a substantially perpendicular direction, the intermediate portion 206b can be easily grasped and smoothy moved forwardly, and by so doing, the unit frame 22 can be easily detached in the required manner. The present invention can be applied to such a type of image forming machine which is provided with an ordinary supporting structure with no pivotable upper supporting frame and it can be applied to the type of image forming machine which is provided with a supporting structure consisting of a lower supporting frame and an upper supporting frame mounted on the lower supporting frame for free pivoting between an open position and a closed position (the type shown in Figures 1 to 4). The present invention can be applied to an image forming machine provided with a developing device of the type which uses a one-component developer composed only of toner, and it can be applied to an image forming machine provided with a developing device of the type which uses a two-component developer composed of carrier and toner.

Claims: An image forming machine comprising an image bearing member (28) having a photosensitive material on its surface, a developing device (34) for developing a latent electrostatic image formed on the surface of the photosensitive material, a cleaning device (36) for removing toner remaining on the surface of the photosensitive material, toner feed means for feeding the toner present in the cleaning device (36) to the developing device (34), the toner feed means including a hollow cylindrical member (204) connecting the cleaning device (36) to the developing device (34) and toner transfer means (208) disposed within the hollow cylindrical member, characterized in that at least a part of the hollow cylindrical member (204) is transparent or semi-transparent. The image forming machine of claim 1 wherein the image bearing member (28), the developing device (34) and the cleaning device (36) are mounted on a unit frame (22) adapted to be detachably mounted on a supporting structure; the hollow cylindrical member (204) is provided in the unit frame (6); and the hollow cylindrical member is arranged as a gripping portion when the unit frame is mounted on, and detached from, the supporting structure (2). The image forming machine of claim 2 wherein the supporting structure (2) is comprised of a lower supporting frame (4) and an upper supporting frame (6) mounted on the lower supporting frame (4) for free pivoting between an open position and a closed position; the unit frame is mounted detachably on the upper supporting frame (6); and the hollow cylindrical member (204) is positioned substantially horizontally when the upper supporting frame (6) is held at the open position. The image forming machine of claim 3 wherein a pair of supporting portions (18, 20) are provided in the upper supporting frame (6), and portions (24, 26) to be detachably mounted on the pair of supporting portions (18, 20) are provided in the unit frame (22). The image forming machine of claim 4 wherein the image bearing member is a drum (28), and the supporting portions (18, 20) and the portions (24, 26) provided in the unit frame are disposed parallel to the drum axis. The image forming machine of claim 3 wherein an openable and closable front cover member (10) is disposed ahead of the upper supporting frame (6), and a window (248) is so disposed in the front cover member (10) as to permit viewing of the transparent or semi-transparent part (210) of the hollow cylindrical member from outside while the front cover member (10) is in the closed state. The image forming machine of any preceding claim wherein the developing device (34) has a developing chamber (156), applicator means (172) disposed in the developing chamber (156) for applying toner to the latent electrostatic image to be developed, and a toner holding chamber (160) communicating with the developing chamber (156) through a toner discharge opening (166), the cleaning device (36) has toner removing means (198) which acts on the surface of the photosensitive material and removes the residual toner, and a toner recovery chamber (200) for recovering the toner removed by the action of the toner removing means (198), the hollow cylindrical member (204) permits communication between the toner recovery chamber (200) and the toner holding chamber (160), and the toner recovered in the toner recovery chamber (200) is fed to the toner holding chamber (160) through the hollow cylindrical member (204) by the action of the toner transfer means (208).

Inventors: AKIYAMA, KAZUNORI, TAKAMATSU, JUNICHI
Applicants: MITA INDUSTRIAL CO. LTD.
Application year: 1987
Main classification: G03G21
IPC codes: G03G21, G03G15