Patent Document

This application is a divisional of U.S. patent application Ser. No. 11/625,558, filed Jan. 22, 2007, issued as U.S. Pat. No. 7,715,746, issued May 11, 2010. 
    
    
     FIELD OF THE INVENTION AND RELATED ART 
     The present invention relates to a process cartridge used by a copying machine, a printer, or the like which employs an electrophotographic method, and an image forming apparatus which uses a process cartridge. 
     Here, an image forming apparatus is an apparatus which forms an image on a recording medium with the use of an electrophotographic image forming method. As examples of an electrophotographic image forming apparatus, there are an electrophotographic copying machine, an electrophotographic printer (for example, a laser beam printer, an LED printer, etc.), a facsimile machine, a word processor, etc. 
     A process cartridge is: a cartridge in which a charging means, a developing means or a cleaning means, and an electrophotographic photosensitive drum are integrally disposed, and which is removably mountable in the main assembly of an electrophotographic image forming apparatus; a cartridge in which at least one among a charging means, a developing means, and a cleaning means, and an electrophotographic photosensitive drum are integrally disposed, and which is removably mountable in the main assembly of an electrophotographic image forming apparatus; or a cartridge in which at least an developing apparatus and an electrophotographic photosensitive drum are integrally disposed, and which is removably mountable in the main assembly of an electrophotographic image forming apparatus. 
     A process cartridge removably mountable in an image forming apparatus, and an image forming apparatus which employs a process cartridge, are required to be designed so that the contact pressure between the electrical contacts of the process cartridge and the electrical contacts of the image forming apparatus remains stable when the process cartridge is in its image forming position in the main assembly of the image forming apparatus. Thus, it has been a common practice to provide an image forming apparatus with a backup member for keeping a cartridge under pressure (Japanese Laid-open Patent Application 2004-45857). 
     SUMMARY OF THE INVENTION 
     The present invention is one of the results of further development of the above described prior art. 
     The primary object of the present invention is to further improve a process cartridge, and an image forming apparatus employing a process cartridge, in terms of the stability in the state of contact between the electrical contacts of the process cartridge and the electrical contacts of the main assembly of the image forming apparatus. 
     According to an aspect of the present invention, there is provided a process cartridge detachably mountable to a main assembly of the apparatus of an image forming apparatus. The image forming apparatus includes a main assembly urging member and a main assembly positioning portion. The process cartridge comprises: a photosensitive drum; a portion-to-be-positioned for positioning the process cartridge by engaging with the main assembly positioning portion when the process cartridge is mounted to the main assembly of the apparatus; a first portion-to-be-urged for being urged to a first urging portion of the main assembly urging member to urge the portion-to-be-positioned to the main assembly positioning portion when the process cartridge is mounted to the main assembly of the apparatus; a second portion-to-be-urged for being urged to a second urging portion of the main assembly urging member to urge the portion-to-be-positioned to the main assembly positioning portion when the process cartridge is mounted to the main assembly of the apparatus; a cartridge electrical contact, provided between the first portion-to-be-urged and the second portion-to-be-urged with respect to a horizontal direction crossing with an axis of the photosensitive drum, for connecting electrically to a main assembly electrical contact portion provided in the main assembly urging member, when the process cartridge is mounted to the main assembly of the apparatus. 
     These and other objects, features, and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an external perspective view of the image forming apparatus in one of the preferred embodiments of the present invention. 
         FIG. 2  is a vertical sectional view of the image forming apparatus shown in  FIG. 1 , as seen from the left side of the apparatus. 
         FIG. 3  is an enlargement of a part of  FIG. 2 . 
         FIG. 4  is an external perspective view of the image forming apparatus, the door of which is open. 
         FIG. 5  is a vertical sectional view of the image forming apparatus, the door of which is open, as seen from the left side of the apparatus main assembly. 
         FIG. 6  is an external perspective view of the image forming apparatus, the cartridge tray of which is in its most outward position. 
         FIG. 7  is a vertical sectional view of the image forming apparatus, the cartridge tray of which is in its most outward position, as seen from the left side of the apparatus. 
         FIG. 8  is an external perspective view of the cartridge, as seen from the side from which the cartridge is not driven. 
         FIG. 9  is an external perspective view of the cartridge, as seen from the side from which the cartridge is driven. 
         FIG. 10  is a cross-sectional view of the cartridge, as seen from the lengthwise end on the left side. 
         FIG. 11  is an external perspective view of the cartridge tray, as seen from the side from which the cartridge is driven. 
         FIG. 12  is an external perspective view of the cartridge tray, as seen from the side from which the cartridge is not driven. 
         FIG. 13  is a side view of the cartridges, cartridge tray, cartridge pressing members and cartridge pressing member holding member of the apparatus main assembly, and cartridge positioning member of the apparatus main assembly, as seen from the side from which the cartridges are not driven, in which the cartridges are firmly held in the correct positions in the tray, on the non-driven side. 
         FIG. 14  is a side view of the cartridges, the cartridge tray, the cartridge pressing members and the cartridge pressing member holding member of the apparatus main assembly, and cartridge positioning member of the apparatus main assembly, as seen from the side from which the cartridges are driven, in which the cartridges are firmly held in the correct positions in the tray, on the driven side. 
         FIG. 15  is a side view of the cartridges, the cartridge tray, the cartridge pressing members and the cartridge pressing member holding member of the apparatus main assembly, and the cartridge positioning member of the apparatus main assembly, as seen from the side from which the cartridges are not driven, in which the cartridges are free from the cartridge pressing members and cartridge positioning member of the apparatus main assembly. 
         FIG. 16  is a side view of the cartridges, the cartridge tray, the cartridge pressing members and the cartridge pressing member holding member of the apparatus main assembly, and the cartridge positioning member of the apparatus main assembly, as seen from the side from which the cartridges are driven, in which the cartridges are free from the cartridge pressing members and cartridge positioning member of the apparatus main assembly. 
         FIG. 17  is a perspective view of the substrate of the memory chip of the cartridge, which has the fourth electrical contact of the cartridge. 
         FIG. 18  is an exploded view of the protrusions of the cartridge, and the substrate which has the fourth electrical contact of the cartridge. 
         FIG. 19  is a side view of the cartridge positioning portion, and the substrate having the fourth electrical contact of the cartridge, showing the relationship between the cartridge positioning portion and substrate. 
         FIG. 20(   a ) is a top view of the substrate of the memory chip of the cartridge, and protrusions  50  and  50  of the cartridge, and  FIG. 20(   b ) is a bottom view of the cartridge pressing member of the apparatus main assembly  1 A. 
         FIG. 21  is a perspective view of the electrical contact of the apparatus main assembly, and the fourth electrical contact of the cartridge, which are not in contact with each other. 
         FIG. 22  is a perspective view (as seen from an angle different from the angle from which they are seen in  FIG. 21 ) of the electrical contact of the apparatus main assembly, and the fourth electrical contact of the cartridge, which are not in contact with each other. 
         FIG. 23  is a perspective view of the electrical contact of the apparatus main assembly, and the fourth electrical contact of the cartridge, which are in contact with each other. 
         FIGS. 24(   a ) through  24 ( c ) are schematic drawings of the elastic (springy) electrical contact of the apparatus main assembly, and its adjacencies, depicting the conforming capability and wiping function of the springy electrical contact of the apparatus main assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Embodiment 1 
     (General Structure of Image Forming Apparatus) 
       FIG. 1  is an external perspective view of the image forming in this embodiment, and  FIG. 2  is a vertical sectional view of the image forming apparatus, as seen from the left side of the apparatus.  FIG. 3  is an enlargement of a part of  FIG. 2 . 
     This image forming apparatus  1  is a full-color laser printer based on four primary colors. It uses an electrophotographic process. It forms an image on a recording medium S (for example, a recording paper, an OHP sheet, a label, etc.) in response to electrical picture signals inputted from an external host apparatus (unshown), such as a personal computer, an image reader, etc. 
     In the following description of the preferred embodiment of the present invention, the front side (front surface side) of the image forming apparatus is the side which has a door  3 . The rear side of the image forming apparatus is the side opposite to the front side. “Fore-and-after direction” includes both the frontward and rearward directions. “The left and right sides of the apparatus main assembly” means the left and right sides of the apparatus main assembly as seen from the front side of the apparatus main assembly. “Side to side direction” includes both the leftward and rightward directions. 
     The lengthwise end of an electrophotographic photosensitive drum (the end of a photosensitive drum in terms of a direction parallel to its axial line), from which the photosensitive drum is driven, will be referred to as the driven side, and the lengthwise end opposite thereto will be referred to as the non-driven side. 
     In the main assembly  1 A of the image forming apparatus  1 , four process cartridges (first to fourth), that is, PY, PM, PC, and PK are contained. The four cartridges PY, PM, PC, and PK are horizontally arranged in the listed order in the rear-to-front direction of the apparatus main assembly  1 A (which may be referred to as inline or tandem arrangement). The four cartridges are the same in structure, although they are different in the color of the developers they store. 
     Each cartridge in this embodiment is an assembly which has: a drum unit  31  (first unit) made up of an electrophotographic photosensitive drum, and processing means, more specifically, a charging means  5  and a cleaning means  7 , which perform processes on the drum  4 ; and a development unit  6  (second unit) having a developing means as a processing means. As the charging means  5 , a charge roller is used. As the cleaning means  7 , a cleaning blade is used. As a developing means, a development roller  6   a  is used. 
     The developer container of the first cartridge PY stores yellow (Y) developer. On the peripheral surface of the drum  4 , a developer image of a yellow (Y) color is formed. The developer container of the second cartridge PM stores magenta (M) developer. On the peripheral surface of the drum  4 , a developer image of a magenta (M) color is formed. The developer container of the third cartridge PC stores cyan (C) developer. On the peripheral surface of the drum  4 , a developer image of a cyan (C) color is formed. The developer container of the fourth cartridge PK stores black (K) developer. On the peripheral surface of the drum  4 , a developer image of a black (K) color is formed. 
     In the area above the cartridges PY, PM, PC, and PK, a laser scanner unit  8  is disposed. This scanner unit  8  exposes the peripheral surface of the drum  4  in each cartridge. That is, the picture information regarding the image to be formed by each cartridge is inputted into a control circuit  2  from the external host apparatus (unshown), and the scanner unit  8  outputs a beam of laser light L while modulating it with the picture information, so that the peripheral surface of the photosensitive drum  4  in each cartridge is scanned (exposed) by the beam of laser light L through an exposure window  9 , with which the top wall of the cartridge is provided. 
     In the area below the cartridge PY, PM, PC, and PK, an intermediary transfer belt unit  10 , as a transferring member, is disposed, which has a flexible endless belt  12  (transfer belt), a driver roller  13 , a turn roller  14 , and tension roller  15 . The endless belt  12  is stretched around the driver roller  13 , the turn roller  14 , and the tension roller  15 , being thereby suspended by them, so that it can be circularly driven. The driver roller  13  and tension roller  15  are disposed in the rear portion of the apparatus main assembly  1 A, whereas the turn roller  14  is disposed in the front portion of the apparatus main assembly  1 A. Each cartridge is disposed so that the downwardly facing portion of the peripheral surface of the drum  4  remains in contact with the upwardly facing portion of the external surface of the endless belt  12  (primary transfer nip). On the inward side of the loop, which the belt  12  forms, primary transfer rollers  16  are disposed. Each transfer roller  16  is disposed so that it opposes the drum  4  in the corresponding cartridge, with the portion of the endless belt  12 , which corresponds to the top portion of the loop, pinched between the transfer roller  16  and drum  4 . A secondary transfer roller  17  is disposed outside the belt loop so that it opposes the driver roller  13 , with the belt  12  pinched between the two rollers. 
     In the area below the belt unit  10 , a paper feeder unit  18  is disposed, which has a paper tray  19 , a paper feeder roller  20 , a paper separation pad  21 , etc. The paper tray  19  is removably mountable in the apparatus main assembly  1 A from the front side (front loading). 
     In the top portion of the rear portion of the apparatus main assembly  1 A, a fixation unit  22  and a paper discharging unit  23  are disposed. Further, the top wall of the apparatus main assembly  1 A is shaped so that a part of the wall is utilized as a delivery tray  24 . The fixation unit  22  has a fixation film assembly  22   a  and a pressure application roller  22   b . The paper discharging unit  23  has rollers  23   a  and  23   b.    
     When each cartridge is correctly situated in its image forming position in the apparatus main assembly  1 A, it remains securely held to the cartridge positioning portion of the apparatus main assembly  1 A by the pressure applied from above by a cartridge pressing mechanism (which will be described later in detail), being thereby correctly positioned relative to the apparatus main assembly  1 A. Further, the driving force input portion of the cartridge is engaged with the driving force output portion of the apparatus main assembly. Further, the input electrical contact of the cartridge is connected to the power supply system with which the apparatus main assembly  1 A is provided. 
     The operation carried out by this image forming apparatus to form a full-color image is as follow: The drum  4  in each of the first to fourth cartridges PY, PM, PC, and PK is rotationally driven at a preset velocity in the counterclockwise direction indicated by an arrow mark. Further, the belt  12  is circularly driven in the clockwise direction indicated by an arrow mark (the subordinate direction with respect to the rotational direction of photosensitive drum) at a velocity which corresponds to the peripheral velocity of the drum  4 . The scanner unit  8  is also driven. In synchronization with the driving of the scanner unit  8 , the charge roller  5  in each cartridge uniformly charges the peripheral surface of the drum  4  to a preset polarity and potential, with a preset (controlled) timing. The scanner unit  8  scans (exposes) the peripheral surface of each drum  4  with the beam of laser light L while modulating the beam of laser light L with the picture signals for forming a monochromatic image of the primary color assigned to each cartridge. As a result, an electrostatic latent image, which reflects the picture signals corresponding to the primary color assigned to the cartridge, is formed on the peripheral surface of the drum  4 . This electrostatic latent image is developed by the development unit  6  into a visible image (image formed of development). 
     Through the above described electrophotographic image formation process, a yellow developer image, which corresponds to the yellow color component of an intended full-color image, is formed on the drum  4  of the first cartridge PY. This yellow developer image is transferred (primary transfer) onto the belt  12 . 
     On the drum  4  of the second cartridge PM, a magenta developer image, which corresponds to the magenta color component of the full-color image, is formed, and this developer image is transferred (primary transfer) onto the belt  12  so that it is layered on the yellow developer image which is already on the belt  12 . 
     On the drum  4  of the third cartridge PC, a cyan developer image, which corresponds to the cyan color component of the full-color image, is formed, and this developer image is transferred (primary transfer) onto the belt  12  so that it is layered on the yellow and magenta developer images which are already on the belt  12 . 
     On the drum  4  of the fourth cartridge PK, a black developer image, which corresponds to the black color component of the full-color image is formed, and this developer image is transferred (primary transfer) onto the belt  12  so that it is layered on the yellow, magenta, and cyan developer images which are already on the belt  12 . 
     Consequently, an unfixed full-color developer image is formed on the belt  12  by the four monochromatic color developer images, that is, the yellow, magenta, cyan, and black color development images. 
     After the primary transfer of the developer image onto the belt  12 , the developer remaining on the peripheral surface of the drum  4  in each cartridge is removed by the cleaning means  7 . 
     Meanwhile, the paper feeder roller  20  is driven with the preset (controlled) timing. As the paper feeder roller  20  is driven, one of the sheets of recording medium S stacked in the paper tray  19  is separated from the rest of the sheets of recording medium S by the coordination of the sheet feeder roller  20  and separation pad  21 , and is fed into the apparatus main assembly  1 A by the sheet feeder roller  20 . Then, the recording medium S is introduced into the nip (secondary transfer nip), that is, the interface between the secondary transfer roller  17  and the belt  12 , and then, is conveyed through the nip while remaining pinched by the secondary transfer roller  17  and the belt  12 . While the recording medium S is conveyed through the nip, the four layers of developer images, different in color, on the belt  12  are transferred together onto the recording medium S as if they were peeled away from the belt  12 , starting at their leading edges. 
     The recording medium S is separated from the surface of the belt  12 , and is introduced into the fixation unit  22 , and is subjected to heat and pressure in the fixation nip of the fixation unit  22 . As a result, the four layers of developer images different in color are fixed to the recording medium S. Thereafter, the recording medium S is moved out of the fixation unit  22 , and then, is discharged as a full-color copy onto the delivery tray  24  by the paper discharging unit  23 . 
     After the separation of the recording medium S from the belt  12 , the secondary transfer residual developer, that is, the developer remaining on the surface of the belt  12  after the separation of the recording medium S from the belt  12 , is removed by a belt cleaning device  25 . The belt cleaning device  25  can be eliminated by utilizing the cleaning means  7 . That is, the secondary transfer residual developer may be electrostatically adhered to the peripheral surface of the drum  4  in the primary transfer nip of the first cartridge PY, for example, so that it is removed from the drum  4  by the cleaning means  7 . 
     (Method for Replacing Cartridge) 
     As an image forming operation is carried out by each of the first to fourth cartridges PY, PM, PC, and PK, the developer stored in the development unit  6  of each cartridge is consumed. 
     Thus, the image forming apparatus is provided with a means (unshown) for detecting the amount of the developer remaining in each cartridge. The detected amount of the developer in each cartridge is compared, by the control circuit portion  2 , with a threshold value preset for issuing a warning, such as the cartridge is near the end of its service life, or the cartridge has reached the end of its service life. If the detected amount of the residual developer in the cartridge is smaller than the preset threshold value, the message which warns the user that the cartridge is close to the end of its life or has reached the end of its life is displayed on the screen of the monitor portion (unshown); in other words, the image forming apparatus prompts the user to prepare a replacement cartridge, or to replace the cartridge, in order to maintain a preset level of image quality. 
     In order to improve the image forming apparatus in usability, the image forming apparatus in this embodiment is provided with a cartridge tray (cartridge drawer: movable member which is movable while holding cartridges), which can be pulled out frontward to make it easier for a user to access the cartridges from the front side of the apparatus, in order to replace the cartridge. 
     When the cartridge tray is in the most outward position relative to the apparatus main assembly  1 A, all the cartridges in the tray are outside the apparatus main assembly  1 A, making it easier for the user to replace any cartridge in the tray. 
     More specifically, the front wall of the image forming apparatus  1  is provided with an opening  26 , through which the cartridge can be inserted into, or removed from, the apparatus main assembly  1 A. That is, the apparatus main assembly  1 A has the opening  26 , through which the cartridge is allowed to pass. 
     Further, the apparatus main assembly  1 A is provided with a door  3 , which can be rotationally moved between the closed position in which it covers the opening  26 , and the open position in which it exposes the opening  26 . 
     In this embodiment, this door  3  is rotationally movable relative to the apparatus main assembly  1 A about a shaft  27  (door hinge shaft) located at one of the horizontal edges of the door  3 . That is, the door  3  is rotatable about the hinge shaft  27  in a manner to be raised upward so that it can be moved into the closed position, in which it remains shut against the apparatus main assembly  1 A, covering the opening  26 , as shown in  FIGS. 1 and 2 , and also, so that it can be rotated frontward about the hinge shaft  27  into the open position, in a manner to be laid down, as shown in  FIGS. 4 and 5 , widely exposing the opening  26 . Designated by reference characters  3   a  is a handle, with which the door  3  is provided. Incidentally, the opening  26  is on the front side of the apparatus main assembly  1 A. 
     The apparatus main assembly  1 A is provided with a pair of tray supporting members  28 L and  28 R (tray moving means) ( FIG. 4 ), which are attached one for one to the inward side of the left and right panels of the main frame of the apparatus main assembly  1 A, opposing each other. The tray  29  is supported between the pair of holding members  28 L and  28 R, and by the pair of holding members  28 L and  28 R, being enabled to horizontally slide in the fore-and-after direction of the apparatus main assembly  1 A. The cartridges PY, PM, PC, and PK are supported by the tray  29 . 
     The door  3  and the pair of holding members  28 L and  28 R are connected by a door linkage  30 , so that as the door  3  is opened, the holding members  28 L and  28 R are moved both frontward and upward of the apparatus main assembly  1 A, that is, slantingly upward, by preset distances, by the movement of the door  3  transmitted to the holding members  28 L and  28 R through the door linkage  30 , while being guided by a guiding member (unshown). As a result, the holding members  28 L and  28 R are pulled out of the apparatus main assembly  1 A through the opening  26  so that the front end portion of each holding member  28 L,  28 R extends outward of the apparatus main assembly  1 A by a preset distance, as shown in  FIGS. 4 and 5 . 
     As the holding members  28 L and  28 R are moved outward, the driving force output portions (which will be described later) of the apparatus main assembly are disengaged from the corresponding driving force input portions (which will be described later) of the cartridges PY, PM, PC, and PK, respectively (disengagement of driving force transmitting means). Further, the pressure applied to each cartridge by the pressure application mechanism to secure and correctly position the cartridge is removed from the cartridge (pressure removal). Further, the tray  29  is freed from its positional restriction. Further, the electrical contacts of each cartridge are disengaged from the power supply system of the apparatus main assembly, making it thereby impossible for electric power to be supplied to the cartridge from the power supplying system on the apparatus main assembly side (electrical disengagement). Moreover, the upward movement of the holding members  28 L and  28 R moves upward the tray  29 , which is holding the cartridges PY, PM, PC, and PK, causing the cartridges to be lifted from the corresponding cartridge positioning portions of the apparatus main assembly  1 A. As a result, the downwardly facing area of the peripheral surface of the drum  4  in each cartridge is separated from the surface of the belt  12  ( FIG. 5 ), making it possible for the tray  29  to be pulled out of the apparatus main assembly  1 A. 
     At this point, the user is to grasp the handle  29   a  exposed through the opening  26 , and pull the tray  29  in the horizontal and frontward direction to slide the tray  29  relative to the pair of holding members  28 L and  28 R so that the tray  29  comes out of the apparatus main assembly  1 A through the opening  26 , and moves into its preset most outward position shown in  FIGS. 6 and 7 . 
     As the tray  29  is pulled out to the abovementioned preset position, the first-fourth cartridges PY, PM, PC, and PK held in the tray  29  are all moved out of the apparatus main assembly  1 A through the opening  26 , being exposed from the apparatus main assembly  1 A; the top surface of each cartridge is exposed. The apparatus main assembly  1 A is structured so that as the tray  29  is pulled out by a preset distance which is sufficient to expose all the cartridges, it is prevented by a pair of stoppers (unshown) from being pulled out further, and also, so that once the tray  29  is pulled out to the preset most outward position, it is securely retained in this most outward position by the holding members  28 L and  28 R. 
     This structure makes it unnecessary for the belt  12  to be moved in order for a user to replace the cartridge from the front side of the apparatus main assembly  1 A. 
     The tray  29  is structured to loosely hold each cartridge so that each cartridge can be moved out straight upward from the tray  29 , and also, so that the replacement cartridge for each of the first to fourth cartridges can be mounted into the tray  29  from directly above. Thus, the user is to extract from the tray  29  the cartridge or cartridges, which are to be replaced, that is, the cartridge or cartridges, the life of which has expired, by simply lifting it, and then, fit a brand-new cartridge or cartridges, from directly above, into the vacated space or spaces, one for one, in the tray  29 , as indicated by a double-dot chain line in  FIG. 7 . 
     In this embodiment, the tray  29  holds the cartridges PK, PC, PM, and PY, in which the developers of K, C, M, and Y colors, respectively, are stored. The order in which the cartridges PK, PC, PM, and PY are arranged in the tray  29  is the same as they are listed above. Namely, in terms of the upstream to downstream direction, that is, the direction in which the tray  29  is moved into the apparatus main assembly  1 A from outside of the apparatus main assembly  1 A, the cartridges PK, PC, PM, and PY are arranged in the listed order. In other words, in this embodiment, the cartridges are arranged according to the amount of developer consumption, so that the cartridge highest in developer consumption, that is, the cartridge highest in replacement frequency, is placed closest to the side from which the user operates the image forming apparatus. Therefore, the distance by which the tray  29  must be pulled out of the apparatus main assembly to expose the cartridge PK is very small. Thus, the image forming apparatus  1  in this embodiment is superior in operability to an image forming apparatus in accordance with the prior art, in terms of the efficiency with which the cartridge PK can be replaced. 
     After the user replaces the cartridge or cartridges in the tray  29  with a brand-new cartridge or cartridges, the user is to perform in reverse the above described sequence for placing a cartridge in the tray  29  or replacing the cartridge in the tray  29 . That is, the user is to horizontally slide the tray  29 , which is in its most outward position at this point in time, relative to the holding members  28 L and  28 R, in the rearward direction of the apparatus main assembly  1 A so that the tray  29  is moved back into the apparatus main assembly  1 A through the opening  26 . The tray  29  is to be pushed back into the apparatus main assembly  1 A to the point at which the stopper portion prevents the tray  29  from being pushed further back into the apparatus main assembly  1 A; in other words, the tray  29  is returned into the position shown in  FIGS. 4 and 5 . 
     Then, the user is to rotate the door  3  in the direction to close the door  3 . As the door  3  is operated in the direction to be closed as described, the door linkage  30  is moved by the movement of the door  3 , and the holding members  28 L and  28 R are moved by the door linkage  30 , in both the inward and downward direction, that is, slantingly downward direction, of the apparatus main assembly  1 A, while being guided by the guiding member (unshown). As the holding means  28 L and  28 R are moved, the movement of the holding means  28 L and  28 R causes the cartridge pressing mechanism to press each cartridge. As a result, each cartridge is pressed against the corresponding cartridge positioning portion of the apparatus main assembly  1 A, being thereby securely and correctly positioned relative to the apparatus main assembly  1 A. Further, the driving force input portion of each of the cartridges PY, PM, PC, and PK is connected with the corresponding driving force output portion of the apparatus main assembly, and the input electrical contacts of the cartridge are connected to the power supply system of the apparatus main assembly, enabling the cartridges to be supplied with the power from the power supply system of the apparatus main assembly  1 A. Further, the tray  29  is securely and correctly positioned relative to the apparatus main assembly  1 A, and the downwardly facing area of the peripheral surface of the drum  4  in each cartridge is placed in contact with the surface of the belt  12 . That is, the state of the image forming apparatus, shown in  FIGS. 1 and 2 , in which each of the cartridges PY, PM, PC, and PK is in its preset image formation position in the apparatus main assembly  1 A, is restored. In other words, the image forming apparatus  1  is readied for an image forming operation. 
     The tray  29  is a drawer movable in a straight line in the practically horizontal direction, which is perpendicular to the lengthwise direction of the drum  4 , while holding multiple cartridges. The tray  29  can be moved into or out of the apparatus main assembly  1 A; the tray  29  is enabled to take the most inward position, that is, the image forming position, relative to the apparatus main assembly  1 A, and the most outward position, relative to the apparatus main assembly  1 A, in which it allows the cartridges to be mounted into, or dismounted from, the tray  29 . 
     The holding members  28 L and  28 R also function as a cartridge moving means, which moves the tray  29  upward from the abovementioned latent image formation position before it moves the tray  29  into the abovementioned most outward position, in which the tray  29  allows the cartridges to be mounted or dismounted, or moves the tray  29  downward into the latent image formation position. In other words, the holding members  28 L and  28 R are members for supporting the tray  29 , and are enabled to take the first position, in which they allow the tray  29  to be moved between the abovementioned most outward position and transitional position, and the second position, in which they retain the tray  29  in the abovementioned latent image formation position. As the door  3  is closed, the holding members  28 L and  28 R are moved from the first position to the second position by the movement of the door  3 . Further, as the door  3  is opened, the holding members  28 L and  28 R are moved from the second position to the first position by the movement of the door  3 . 
     &lt;Cartridge&gt; 
     The first to fourth cartridges PY, PM, PC, and PK in this embodiment are the same in structure. Next, referring to  FIGS. 8-10 , the cartridge structure in this embodiment will be described. 
       FIG. 8  is a perspective view of the cartridge, as seen from the aforementioned non-driven side, and  FIG. 9  is a perspective view of the cartridge, as seen from the aforementioned driven side.  FIG. 10  is a cross-sectional view of the cartridge, as seen from the right side of the cartridge. 
     The leftward or rightward direction of each cartridge is the direction parallel to the axial line a-a of the drum  4 . The cartridge is an assembly, the lengthwise direction of which is the same as its leftward or rightward direction. 
     Referring to  FIG. 10 , the drum unit  31  has a cleaning means container  31   a  (cleaning means housing), in which the drum  4 , the charge roller  5 , and the cleaning blade  7  are disposed. The drum  4  is rotatably held by, and between, the left and right panels of the container  31   a , with bearings  32 L and  32 R (portions-to-be-positioned or portions-to-be-supported) placed between the drum  4  and the panels. The charge roller  5  is placed in contact with, and in parallel to, the drum  4 , and is rotatably attached to, and between, the left and right panels, with bearings placed between the charge roller  5  and the left and right panels. The blade  7  is formed of elastic rubber. The blade  7  is fixed to the container  31   a  by its base portion, in contact with the drum  4 , being tilted in the direction to counter the rotational direction of the drum  4 . The blade  7  plays the role of removing the developer remaining on the drum  4 . The developer removed from the peripheral surface of the drum  4  by the blade  7  is stored in the container  31   a.    
     The development unit  6  is provided with a developing means container  6   e  (developing means housing). It also has a development roller  6   a , and a developer coating roller  6   b , and a developer regulating member  6   c  (development blade), which are disposed in the container  6   e . The developer (unshown) is stored in the container  6   e . The development roller  6   a  is a roller formed of elastic rubber. It is located between the left and right panels of the container  6   e , and is rotatably supported by the left and right panels, with bearings placed between the development roller  6   a  and left and right panels. The developer supply roller  6   b  is a roller for coating the development roller  6   a  with developer. It is disposed, in contact with the development roller  6   a , between the left and right panels of the container  6   e , and is rotatably supported by the left and right panels, with bearings placed between the development supply roller  6   b , and left and right panels. The developer regulating member  6   c  is a piece of thin elastic plate, and is fixed to the container  6   e  by one of its edge portions. It is placed in contact with the development roller  6   a . It is on the downstream side of the developer supply roller  6   b , in terms of the rotational direction of the development roller  6   a , and is tilted in the direction to counter the rotational direction of the development roller  6   a . The regulating member  6   c  regulates in thickness the body of developer coated on the development roller  6   a  by the supply roller  6   b ; it forms a developer layer with a preset thickness, on the development roller  6   a . It also plays the role of giving a preset amount of electrical charge to the developer while the developer is coated on the development roller  6   a.    
     Each cartridge is provided with a drum driving coupling  33  (drum driving force receiving portion), a development roller driving coupling  34  (developer roller driving force receiving portion), and a cartridge holding portion  35 R, which are located at one of the lengthwise ends of the cartridge, that is, the lengthwise end on the driven side. The cartridge holding portion  35 R is located close to the top edge of the cartridge. The axial line of the drum driving coupling  33  coincides with that of the drum  4 . When the cartridge is in the preset image formation position in the apparatus main assembly, the drum driving coupling  33  receives from the apparatus main assembly the force for driving the drum  4 , whereas the development roller driving coupling  34  receives from the apparatus main assembly  1 A the force for driving the development roller  6   a . The cartridge holding portion  35 R is the portion by which the cartridge is held by the tray  29 , and is located close to the top edge of the cartridge. Further, as the cartridge is mounted into the apparatus main assembly  1 A, the bearing  32 R, that is, the bearing on the driven side, engages with the cartridge positioning portion of the apparatus main assembly, on the driven side; in other words, the bearing  32 R plays the role of a portion which is to be supported by the apparatus main assembly to correctly position the driven end of the cartridge relative to the apparatus main assembly  1 A. The bearing  32 R is located at the bottom end of the cartridge. 
     The lengthwise end of the cartridge, on the non-driven side, is provided with the cartridge supporting portion  35 L. The cartridge supporting portion  35 L is the portion by which the non-driven end of the cartridge is supported by the tray  29  as the driven end of the cartridge is supported by the cartridge supporting portion on the driven side. It is located close to the top edge of the cartridge. As the cartridge is mounted into the apparatus main assembly  1 A, the bearing  32 L, that is, the bearing on the non-driven side, engages with the cartridge positioning portion of the apparatus main assembly, on the non-driven side; in other words, the bearing  32 L plays the role of a portion which is to be supported by the apparatus main assembly to correctly position the non-driven end of the cartridge relative to the apparatus main assembly  1 A. The bearing  32 L is located at the bottom end of the cartridge. 
     As the cartridge is moved into its preset image forming position in the apparatus main assembly  1 A, the drum driving couplings  33  and development roller driving coupling  34  are engaged with the first and second driving force output portions (unshown) of the apparatus main assembly, respectively; when the cartridge is in its preset image formation position, the couplings  33  and  34  are in engagement with the first and second driving force output portions. As driving force is transmitted from the first driving force output portion to the drum driving coupling  33 , the drum  4  is rotationally driven by the transmitted driving force in the counterclockwise direction ( FIG. 10 ) at a preset peripheral velocity. The charge roller  5  is rotated by the rotation of the drum  4 . 
     It is from the second driving force output portion that driving force is transmitted to the development roller driving coupling  34 . The development roller driving coupling  34  is provided with a stepped gear (unshown), which is a part of the rotational axle of the development roller  6   a , and is integrally formed with the rotational axis. The stepped gear is directly in mesh with the development roller  6   a , and a gear (unshown) for driving the developer coating roller  6   b . Thus, in order to rotate the development roller  6   a  and developer coating roller  6   b  in the clockwise direction of  FIG. 10 , a rotational driving force is inputted into the development roller driving coupling  34  from the second driving force output portion of the apparatus main assembly  1 A in the direction to rotate the coupling  34  in the counterclockwise direction of  FIG. 10 . 
     The developer in the container  6   e  is coated on the development roller  6   a , which is being rotationally driven, by the rotating supply roller  6   b , which is being rotationally driven. The body of developer coated on the development roller  6   a  is regulated in thickness by the developer regulating member  6   c , forming a developer layer with a preset thickness, on the development roller  6   a , while being give an electrical charge. Then, the developer on the development roller  6   a  is conveyed by the rotation of the development roller  6   a  to a development area, that is, the contact area between the development roller  6   a  and the drum  4 , in which the developer is used for developing the latent image on the drum  4 . The developer remaining on the peripheral surface of the development roller  6   a  after the development of the latent image is returned by the rotation of the development roller  6   a  to the container  6   e , in which the developer is removed by the supply roller  6   b  from the peripheral surface of the development roller  6   a  at the same time as the peripheral surface of the development roller  6   a  is coated with a fresh supply of developer, that is, the developer in the container  6   e , by the supply roller  6   b.    
     Each cartridge is provided with first to fourth electrical contacts  36 - 39  (cartridge electrical contacts), which are located at the left end, that is, the non-driven end, of the cartridge. The first electrical contact  36  is electrically in contact with the charge roller  5 , and receives from the apparatus main assembly  1 A the charge bias which is supplied to the charge roller. The second electrical contact  37  is electrically in contact with the development roller  6   a , and receives from the apparatus main assembly  1 A the development bias which is supplied to the development roller  6   a . The third electrical contact  38  is electrically in connection with the developer coating roller  6   b , and receives from the apparatus main assembly  1 A the developer coating bias which is supplied to the developer coating roller  6   b . The fourth electrical contact  39  is an electrical contact having a memory chip. It is electrically connected to the control portion  2  of the apparatus main assembly  1 A, being thereby enabled to communicate with the control portion  2 . 
     The first and second electrical contacts  36  and  37  are exposed at the outward surface of the left end wall of the cartridge. The third electrical contact  38  is exposed at the front surface of the cartridge, in terms of the direction in which the tray  29  is moved into the apparatus main assembly. The fourth electrical contact  38  is exposed at the top surface of the cartridge. 
     &lt;Cartridge Tray&gt; 
     Next, referring to  FIGS. 11 and 12 , the tray  29  will be described. The tray  29  has a rectangular main frame, which is made up of four sections  29   b ,  29   c ,  29   d , and  29   e , that is, front, rear, left, and right sections, which are joined at their lengthwise ends. The space within the rectangular main frame is partitioned into four rectangular sub-spaces of roughly the same size by three partition plates  29   k . The four sub-spaces are arranged in the fore-and-after direction, and their long edges are parallel to the side-to-side direction of the apparatus main assembly  1 A. Hereafter, these four sub-spaces will be referred to as first-fourth cartridge compartments  29 ( 1 )- 29 ( 4 ), listing from the rear section  29   c  side toward the front section  29   b . These cartridge compartments  29 ( 1 )- 29 ( 4 ) of the tray  29  are the compartments into which the first to fourth cartridges PY, PM, PC, and PK are inserted to be held therein one for one (cartridge storage space; cartridge slot). The tray  29  loosely holds the cartridges PY, PM, PC, and PK, in its four cartridge compartments  29 ( a )- 29 ( 4 ), the long edges of which are parallel to the side-to-side direction of the apparatus main assembly  1 A. 
     The lengthwise end wall of each of the cartridge compartments  29 ( 1 )- 29 ( 4 ), which corresponds to the right section  29   e  (driven side) of the main frame of the tray  29 , is provided with holes  29   f  and  29   g , through which the first and second driving force output portions of the apparatus main assembly move into, or out of, the cartridge compartment (tray  29 ). The lengthwise end wall of each cartridge compartment, which corresponds to the left section  29   d  (non-driven side) of the main frame of the tray  29 , is provided with first to third intermediary electrical contacts  41 - 43 , which will become connected to the first to third electrical contacts  36 - 38  of the cartridge. The intermediary electrical contacts  36 - 38  are formed of an elastic (springy) substance. 
     Each of the intermediary electrical contacts  41 - 43  has an inward portion (a), which is exposed on the inward side of the corresponding cartridge compartment of the tray  29 , and an outward portion (b), which is exposed on the outward side of the corresponding cartridge compartment of the tray  29 . The inward portion (a) and outward portion (b) are electrically connected to each other. The inward portions (a) of the intermediary electrical contacts  41 - 43  are electrically connectible with the first to third input electrical contacts  36 - 38  of the cartridge, respectively. Further, the outward portions (b) of the intermediary electrical contacts  43 - 45  are electrically connectible with the output electrical contacts of the bias application circuit of the apparatus main assembly  1 A (main assembly electrical contacts (unshown)), one for one. 
     As for the method for inserting the cartridges PY, PM, PC, and PK into the cartridge compartments  29 ( 1 )- 29 ( 4 ), respectively, the cartridges may be released into the cartridge compartments from above. As the cartridges are released, the cartridge supporting portions  35 R and  35 L of each cartridge, which are on the driven and non-driven sides, respectively, are caught by the top surfaces of the right and left sections  29   e  and  29   d  of the tray frame; the bottom surfaces of the cartridge supporting portions  35 R and  35 L come into contact with the top surfaces of the right and left sections  29   e  and  29   d . As a result, the cartridge rests on the tray  29 ; the cartridge is supported by the tray  29 . That is, at this point, the tray  29  is supporting the cartridge so that the cartridge can be removed from the tray  29  by simply lifting the cartridge straight upward; the cartridge is supported by the tray  29  by being simply lowered into the tray  29  from straight above. Further, as the cartridge is lowered into the tray  29 , the first to third input electrical contacts  36 - 38  of the cartridge come into contact, and remain elastically in contact, with the inward portions (a) of the intermediary electrical contacts  41 - 43  of the tray  29 , respectively, establishing thereby an electrical connection between the cartridge and tray  29 . As the tray  29  is moved into the apparatus main assembly  1 A, the movement of the tray  29  moves each cartridge into the preset latent image forming position of the cartridge, in the apparatus main assembly  1 A, and the outward portions (b) of the intermediary electrical contacts  41 - 43  of the tray  29  come into contact with the output electrical contacts of the bias application circuit of the apparatus main assembly  1 A, establishing an electrical connection between the tray  29  and apparatus main assembly  1 A. As a result, the first to third input electrical contacts  36 - 38  of the cartridge become electrically connected to the power supply system of the apparatus main assembly  1 A through the intermediary electrical contacts  41 - 43  of the tray  29 . The intermediary electrical contacts  41 - 43  play the role of supplying the cartridge with the electrical biases that they receive from the output electrical contacts of the apparatus main assembly  1 A. 
     In the above described embodiment, the electrical contacts and the like are attached to the lengthwise end of the cartridge, on the non-driven side, and the lengthwise end of the tray  29 , on the non-driven side. However, this embodiment is not intended to limit the present invention in scope. That is, they may be attached to the lengthwise end of the cartridge, and the lengthwise end of the tray  29 , on the driven side. 
     &lt;Correct and Firm Positioning of Cartridge&gt; 
       FIG. 13  is a side view of the cartridges correctly positioned in the tray, as seen from the side from which the cartridges are not driven, showing how the cartridges are firmly held in the correct positions in the tray, on the non-driven side.  FIG. 14  is a side view of the cartridges correctly positioned in the tray, as seen from the side from which the cartridges are driven, showing how the cartridges are firmly held in the correct positions in the tray. 
     As each cartridge is moved into the apparatus main assembly  1 A while being held in the tray  29 , the cartridge holding portions  32 L and  32 R, that is, cartridge holding portions on the non-driven and driven sides, respectively, of the cartridge engage with the cartridge positioning portions  44 L and  44 R, that is, cartridge positioning portions on the non-driven and driven sides, respectively, of the apparatus main assembly  1 A. As a result, the apparatus main assembly  1 A supports the cartridge by the cartridge holding portions  32 L and  32 R from under the cartridge. That is, the cartridge is supported in the apparatus main assembly, at a minimum of two points in terms of the lengthwise direction of the drum  4 . 
     In this embodiment, the cartridge positioning portions  44 L and  44 R, that is, the cartridge positioning portions on the non-driven and driven sides, are grooves with which the left and right stays  45 L and  45 R are provided, respectively. The left and right stays  45 L and  45 R are solidly fixed to the inward sides of the left and right panels of the apparatus main assembly  1 A, and extend in the fore-and-after direction of the apparatus main assembly  1 A. The cartridge positioning portions  44 L and  44 R, or the left and right grooves of the stays  45 L and  45 R, are V-shaped in cross-section, and extend in the fore-and-after direction of the apparatus main assembly  1 A. As the downwardly arcuate portion of each of the left and right cartridge supporting portions  32 L and  32 R of the cartridge fit into these grooves, one for one, the cartridge is correctly positioned relative to the apparatus main assembly  1 A. More specifically, the cartridge supporting portions  32 L and  32 R of the cartridge are in the form of a segment of a circle, and the centers of their arcs coincide with the axial line of the drum  4 . Thus, as the cartridge is moved into the apparatus main assembly  1 A, the arcuate surface of each cartridge supporting portion  32  comes into contact with the inward surface (opposing two surfaces) of the corresponding cartridge positioning groove  44  of the apparatus main assembly  1 A, at two locations. 
     Further, as each cartridge is moved into the apparatus main assembly  1 A, the non-driven and driven ends of the top surface of the cartridge are pressed downward by the cartridge pressing members  46 L and  46 R, that is, the cartridge pressing members on the non-driven and driven sides, respectively, of the apparatus main assembly  1 A, causing the cartridge supporting portions  32 L and  32 R, on the non-driven and driven sides, respectively, to be pressed upon the cartridge positioning portions  44 L and  44 R, on the non-driven and driven sides, respectively, of the apparatus main assembly  1 A. As a result, not only is the cartridge correctly positioned relative to the apparatus main assembly  1 A, but also, is firmly held to the apparatus main assembly  1 A. 
     The apparatus main assembly  1 A is provided with four pairs of cartridge pressing members  46 L and  46 R, that is, a pair for each cartridge, and a pair of cartridge pressing member holding members  47 L and  47 R, which are on the non-driven and driven sides, respectively. The cartridge pressing members  46 L are held to the under side of the cartridge pressing member holding member  47 L, being aligned in the lengthwise direction of the member  47 L. More specifically, each cartridge pressing member  46 L is held to the cartridge pressing member holding member  47 L, with an elastic member  48 L (compression coil spring) placed between the cartridge pressing member holding member  47 L and cartridge pressing member  46 L so that the cartridge pressing member  46 L vertically slides relative to the apparatus main assembly  1 A. 
     The cartridge pressing members  46 R are held to the under side of the cartridge pressing member holding member  47 R, being aligned in the lengthwise direction of the member  47 R. More specifically, each cartridge pressing member  46 R is held to the cartridge pressing member holding member  47 R with an elastic member  48 R (compression coil spring) placed between the cartridge pressing member holding member  47 R and cartridge pressing member  46 R so that the cartridge pressing member  46 R vertically slides relative to the apparatus main assembly  1 A. 
     The abovementioned cartridge pressing member holding members  47 L and  47 R, on the non-driven and driven sides, respectively, are vertically moved in parallel to each other by the opening or closing movement of the door  3  (that is, movement of door linkage  30 ) (drawing does not show door linkage). More specifically, as the door  3  is moved in the direction to be completely shut against the apparatus main assembly  1 A, the cartridge pressing member holding members  47 L and  47 R are pushed down by the movement of the door  3  through the door linkage  30 , causing the bottom surfaces of the cartridge pressing members  46 L and  46 R of the apparatus main assembly  1 A to come into contact with the top surface of the corresponding cartridge. Then, the elastic members  48 L and  48 R are compressed between the cartridge pressing member holding members  47 L and  47 R and the cartridge pressing members  46 L and  46 R of the apparatus main assembly  1 A by the subsequent downward movement of the cartridge pressing member holding members  47 L and  47 R. Consequently, the portions of the top surface of the cartridge, which are in contact with the cartridge pressing members  46 L and  46 R of the apparatus main assembly  1 A, are pressed by the reactive force generated by the compression of the elastic members  48 L and  48 R. As a result, the cartridge supporting portions  32 L and  32 R of the cartridge, on the non-driven and driven sides, respectively, are pressed on the cartridge positioning portions  44 L and  44 R of the apparatus main assembly  1 A, on the non-driven and driven sides, respectively, correctly and securely positioning the cartridge relative to the apparatus main assembly  1 A. 
     As the door  3  is opened, the cartridge pressing member holding members  47 L and  47 R move upward in parallel to each other, separating thereby the cartridge pressing members  46 L and  46 R of the apparatus main assembly  1 A from the cartridge as shown in  FIGS. 15 and 16 ; the pressure applied on the cartridge by the cartridge pressing members  46 L and  46 R is removed. 
     &lt;Relationship Between Fourth Electrical Contact  39  of Cartridge and Cartridge Pressing Member  46 L of Apparatus Main Assembly&gt; 
     In this embodiment, the abovementioned fourth electrical contact  39  ( FIG. 8 ) of each cartridge, that is, the electrical contact located at the top surface of the lengthwise end on the non-driven side, is the electrical contact for the memory chip. More specifically, referring to  FIG. 17 , the electrical contact  39  is made up of a pair of contact points  39   a  and  39   b , which are exposed at one of the primary surfaces of the substrate  49  of the memory chip. The memory M is on the opposite surface of the substrate  49  from the contact points  39   a  and  39   b . The electrical contacts  39   a  and  39   b  are electrically in connection with the memory M. 
     Referring to  FIG. 18 , the drum unit  31  (first frame) is provided with a pair of protrusions  50  and  50 , which are on the non-driven side of the top surface of the drum unit  31 . The protrusions  50  and  50  are aligned in the direction perpendicular to the axial line of the drum  4 , with the provision of a gap which corresponds to the length of the abovementioned substrate  49 . The substrate  49  is fitted between the protrusions  50  and  50  so that its top surface, that is, the surface having the electrical contact points  39   a  and  39   b , faces upward, and also so that its lengthwise direction is parallel to the axial line of the drum  4 . The substrate is glued to the top surface of the drum unit  31 . 
     Referring to  FIG. 19 , when the cartridge is in its image forming position in the apparatus main assembly  1 A, the center line of the substrate  49  coincides with the perpendicular bisector N of the line connecting the two points at which the arcuate cartridge supporting portion  32 L of the cartridge is supported by the cartridge positioning portion  44 L of the apparatus main assembly  1 A, which is in the form of a groove with the V-shaped cross-section. That is, the cartridge supporting portions  32 L and  32 R of the cartridge serve as bearings which support the drum  4  so that the rotational center (axial line a-a) of the drum  4  coincides with the abovementioned perpendicular bisector N. 
     The cartridge pressing member  46 L of the apparatus main assembly  1 A, which is on the non-driven side, corresponds in position to the substrate  49  and protrusions  50  and  50  on the cartridge. The bottom surface of the cartridge pressing member  46 L has a groove  46   a , which is rectangular in cross-section, and into which the substrate  49  and protrusions  50  and  50  on the top surface of the cartridge fit.  FIG. 20(   a ) is a top view of the substrate  49  and protrusions  50  and  50  of the cartridge, and  FIG. 20(   b ) is a bottom view of the cartridge pressing member  46 L of the apparatus main assembly  1 A. The cartridge pressing member  46 L of the apparatus main assembly  1 A is provided with an electrical contact  51 , which is on the bottom surface of the groove  46   a  of the cartridge pressing member  46 L. The electrical contact  51  of the apparatus main assembly  1 A is made up of a pair of contact points  51   a  and  51   b  (end portions of electrical contact), which are exposed at the top surface of a substrate  52  and are electrically in connection to the control portion  2  through a pair of lead wires (unshown). 
     When the cartridge is in the image forming position in the apparatus main assembly  1 A, the cartridge pressing member  46 L of the apparatus main assembly  1 A, the substrate  49 , and protrusions  50  and  50  of the cartridge, are in the groove  46   a  of the apparatus main assembly  1 A, and the areas  46   b  (first urging portion) and  46   c  (second urging portion) of the downwardly facing surface of the cartridge pressing member  46 L of the apparatus main assembly  1 A is in contact with the areas  31   b  (first portion-to-be-urged) and  31   c  (second portion-to-be-urged) of the upwardly facing surface of the cartridge. Thus, the cartridge remains pressured by the cartridge pressing member  46 L of the apparatus main assembly  1 A which is under the pressure applied thereto by the reactive force generated by the compression of the elastic member  48 L. 
     The areas  46   b  and  46   c  of the bottom surface of the cartridge pressing member  46 L of the apparatus main assembly  1 A are the bottom surfaces of the lengthwise end portions of the cartridge pressing member  46 L, in terms of the direction perpendicular to the axial line of the drum  4 . They oppose each other across the gap in which the substrate  52  fits. The area  46   b  is the first pressing portion, and the area  46   c  is the second pressing portion. 
     Further, the areas  31   b  and  31   c  of the top surface of the cartridge, which are pressed by the first and second pressing portions  46   b  and  46   c , are the first and second portions of the cartridges, by which the cartridge is pressed by the cartridge pressing member  46 L of the apparatus main assembly  1 A. The substrate  49  having the electrical contact  39  (which has contact points  39   a  and  39   b ) of the cartridge, and the protrusions  50  and  50  of the cartridge, are located between the abovementioned first and second areas  31   b  and  31   c.    
     When the cartridge is in the image forming position in the apparatus main assembly  1 A, the electrical contact  39  (which has contacts points  39   b  and  39   c ) are electrically in contact with the electrical contact  51  (which has contact points  51   a  and  51   b ), respectively, making it possible for the control portion  2  of the apparatus main assembly  1 A and the memory chip M of the cartridge to communicate with each other. 
     The protrusions  50  and  50  of the cartridge have first positioning portions  50   a  and  50   a , one for one, which are for correctly positioning the cartridge pressing member  46 L of the apparatus main assembly  1 A, in terms of the direction parallel to the axial line of the drum  4 , by fitting into the groove  46   a  of the cartridge pressing member  46 L of the apparatus main assembly  1 A. They also have second positioning portions  50   b  and  50   b , one for one, which are for correctly positioning the cartridge pressing member  46 L of the apparatus main assembly  1 A in terms of the direction perpendicular to the axial line of the drum  4 . The height of the first positioning portion  50   a  and the height of the second positioning portion  50   b  are such that they correctly position the cartridge pressing member  46 L of the apparatus main assembly  1 A before the electrical contact  51  (which has contact points  51   a  and  51   b ) comes into contact with the electrical contact  39  (which has contact points  39   a  and  39   b ). 
     As the door  3  is opened, the cartridge pressing member holding member  47 L is moved upward by the movement of the door  33 . As a result, the cartridge pressing members  46 L of the apparatus main assembly  1 A are separated from the cartridge; the cartridge is freed from the pressure applied by the cartridge pressing member  46 L, and the electrical contact  51  (which has contact points  51   a  and  51   b ) of the apparatus main assembly  1 A is disconnected from the electrical contact  39  (which has contact points  39   a  and  39   b ). 
       FIGS. 21 and 22  are perspective views of the cartridge pressing member  46 L of the apparatus main assembly  1 A, the electrical contact  51  (which has contact points  51   a  and  51   b ) of the apparatus main assembly  1 A, the electrical contact  39  (which has contact points  39   a  and  39   b ) of the cartridge, and their adjacencies, in which the cartridge pressing member  46 L is not in contact with the cartridge, and the electrical contact  51  is not in contact with the electrical contact  39 .  FIG. 23  is a perspective view of the cartridge pressing member  46 L of the apparatus main assembly  1 A, the electrical contact  51  (which has contact points  51   a  and  51   b ) of the apparatus main assembly  1 A, the electrical contact  39  (which has contact points  39   a  and  39   b ) of the cartridge, and their adjacencies, in which the cartridge pressing member  46 L is in contact with the cartridge, and therefore, the electrical contact  51  is electrically in contact with the electrical contact  39 . 
     In consideration of the positioning of the electrical contacts of the cartridge and the electrical contacts of the apparatus main assembly  1 A, and the positioning of the areas of the cartridge, which are to be pressed by the cartridge pressing portions of the apparatus main assembly  1 A, relative to the apparatus main assembly  1 A, the image forming apparatus is structured so that the cartridge pressing portions of the apparatus main assembly  1 A follow the movement of the cartridge. The electrical contact  39  of the cartridge is placed between the first and second areas  31   b  and  31   c  of the cartridge, which are pressed by the cartridge pressing portions of the apparatus main assembly  1 A. Therefore, the distance between the electrical contact  39  of the cartridge and the electrical contact  51  of the apparatus main assembly  1 A remains stable. Therefore, the changes in the contact pressure between the electrical contact  39  of the cartridge and the electrical contact  51  of the apparatus main assembly  1 A is minimized, making it possible to stabilize the state of contact between the electrical contact of the cartridge and the electrical contact of the apparatus main assembly  1 A. 
     Further, the pressure applied to press the cartridge is utilized to keep the electrical contact  39  of the cartridge pressed on the electrical contact  51  of the apparatus main assembly  1 A, making it possible to reduce an image forming apparatus in size. 
     The image forming apparatus is structured so that the cartridge pressing member  46 L of the apparatus main assembly  1 A is effective to keep the electrical connection by the electrical contact position regulating portion of the cartridge with respect to the axial direction of the drum  4  and to the direction perpendicular to the axial line of the drum  4 . That is, the image forming apparatus is structured so that as the cartridge moves (as electrical contact of cartridge moves), the electrical contact  51  of the cartridge pressing member  46 L of the apparatus main assembly  1 A follows the movement of the cartridge (movement of electrical contact of cartridge). This structural arrangement makes it possible to reduce the positional deviation of the electrical contact  39  of the cartridge and the electrical contact  51  of the apparatus main assembly  1 A relative to each other, in terms of the direction in which the electrical contacts  39  and  51  are possibly sheared by the friction between the electrical contacts  39  and  51 , making it therefore possible to minimized the amount by which the electrical contacts  39  and  51  are shaved by each other due to the presence of the friction between the electrical contacts  39  and  51  in the direction in which the electrical contacts  39  and  51  are possibly sheared. Therefore, it is possible to stabilize the state of contact between the electrical contact  39  of the cartridge and the electrical contact  51  of the apparatus main assembly  1 A. 
     Further, referring to  FIG. 24 , the end portions  51   a  and  51   b  (contact points) of the electrical contact  51  of the apparatus main assembly  1 A are rendered elastic (springy), being therefore capable of conforming to the end portion  39   a  and  39   b  (contact points) of the electrical contact  39  of the cartridge. Further, as the end portions  51   a  and  51   b  (contact points) of the electrical contact  51  of the apparatus main assembly  1 A come into contact with the end portions  39   a  and  39   b  (contact points) of the electrical contact  39  of the cartridge, the former slide on the latter, functioning as a wiper for removing the foreign substances on the surfaces of the end portions  39   a  and  39   b  (contact points) of the electrical contact  39  of the cartridge.  FIG. 24(   b ) is a sectional enlargement of the portion of  FIG. 24(   a ), indicated by a line (b)-(b) in  FIG. 24(   a ), at a plane which coincides with, and is perpendicular to, the line (b)-(b).  FIG. 24(   c ) is an enlargement of the portion of  FIG. 24(   b ) that is surrounded by a broken line in  FIG. 24(   b ). 
     As described above, in this embodiment, the electrical contact  49  of the cartridge is placed between the first and second areas of the top surface of the cartridge, which catch the pressure applied to the cartridge by the apparatus main assembly  1 A. Therefore, the image forming apparatus is improved in terms of the stability in the state of contact between the electrical contact  49  of the cartridge and the electrical contact  51  of the apparatus main assembly  1 A. Further, it is possible to reduce in size the cartridge and the image forming apparatus. 
     Incidentally, in the above described embodiment of the present invention, the image forming apparatus is structured so that the tray  29  is moved in a straight line in the direction parallel to the surface on which the apparatus main assembly  1 A was set. However, the direction in which the movable member, or the tray  29 , is moved does not need to be limited to the abovementioned direction. For example, the image forming apparatus may be structured so that the tray  29  moves in a straight line in the upwardly or downwardly slanting direction relative to the surface on the apparatus main assembly  1 A is set. Needless to say, even in such a case, the image forming apparatus is structured so that the tray  29  is moved downward after being moved in a straight line. 
     As described above, according to the present invention, a process cartridge and an image forming apparatus can be improved in terms of the stability in the state of contact between the electrical contacts of the cartridge and the electrical contacts of the apparatus main assembly. 
     Further, according to the present invention, a process cartridge and an image forming apparatus can be reduced in size. 
     While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth, and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims. 
     This application claims priority from Japanese Patent Application No. 355651/2006 filed Dec. 28, 2006 which is hereby incorporated by reference.

Technology Category: 3