Abstract:
A color electrophotographic image forming apparatus having a main assembly, to which a process cartridge is detachably mountable, for forming a color image on a recording material, wherein the process cartridge includes an electrophotographic photosensitive drum and process means actable on the electrophotographic photosensitive drum, the apparatus includes an opening provided in the main assembly of the apparatus; a movable member which is linearly movable between an inside and an outside of the opening in a direction crossing with a longitudinal direction of the electrophotographic photosensitive drum while carrying plurality of such process cartridges; an accommodating portion for accommodating the process cartridges; and an urging member, provided above a movement path of the process cartridges, while being carried on the movable member, from the opening to the accommodating portion, for contacting the process cartridge passing therebelow to urge the process cartridge toward the movable member.

Description:
FIELD OF THE INVENTION AND RELATED ART 
       [0001]    The present invention relates to an electrophotographic color image forming apparatus which employs a process cartridge (or cartridges) removably mountable in the main assembly thereof. 
         [0002]    As examples of an electrophotographic color image forming apparatus, there are an electrophotographic color copying machine, an electrophotographic color printer (color laser printer, color LED printer, etc.), etc. 
         [0003]    A process cartridge means a cartridge in which an electrophotographic photosensitive member, and one or more processing means for processing the electrophotographic photosensitive member, are integrally disposed so that they can be removably mountable in the main assembly of the image forming apparatus. More specifically, a process cartridge is a cartridge in which an electrophotographic photosensitive member, and at least one among the abovementioned processing members, such as a developing means, a charging means, and a cleaning means, are integrally disposed. 
         [0004]    A process cartridge is removably mountable in the main assembly of an image forming apparatus by a user himself. Therefore, a process cartridge makes it possible for a user to maintain an image forming apparatus without relying on service personnel. 
         [0005]    There have been known various structural arrangements for accurately positioning a process cartridge relative to the main assembly of an electrophotographic image forming apparatus. 
         [0006]    For example, the apparatus main assembly is provided with pressure application springs, which are disposed along the cartridge guiding surface of the main assembly. Each of these springs is fitted around a spring supporting member, and is wound so that it applies pressure to the dowel with which a process cartridge is provided. 
         [0007]    This structural arrangement prevents a cartridge from rotating when it receives rotational driving force from the main assembly of an image forming apparatus (Japanese Laid-open Patent Application 2000-132069 ( FIGS. 14 and 15 ; Page 8, right column, lines 1-11). 
         [0008]    According to this structural arrangement, it is possible to precisely position a cartridge relative to the apparatus main assembly when forming an image. 
         [0009]    In recent years, in the field of an electrophotographic color image forming apparatus, it has been thought of structuring an image forming apparatus so that multiple process cartridges are supported in a movable member which is movable relative to the apparatus main assembly. This structural arrangement makes it possible to insert all at once multiple cartridges in the main assembly of an image forming apparatus by pushing the abovementioned movable member into the apparatus main assembly. 
         [0010]    The present invention is a further development of the above described structural arrangement in accordance with the prior art. 
       SUMMARY OF THE INVENTION 
       [0011]    The primary object of the present invention is to provide an electrophotographic color image forming apparatus structured so that multiple process cartridges can be smoothly inserted into its main assembly. 
         [0012]    Another object of the present invention is to provide an electrophotographic image forming apparatus which is substantially superior in operability to an electrophotographic color image forming apparatus in accordance with the prior art, in terms of the insertion of multiple cartridges into the apparatus main assembly. 
         [0013]    Another object of the present invention is to provide an electrophotographic color image forming apparatus which employs a cartridge-holding movable member which can be pulled out of its main assembly or retracted into the main assembly; and which is characterized in that when the movable member is retracted into the main assembly while holding multiple process cartridges, the cartridges do not accidentally collide with the other structural components of the main assembly. 
         [0014]    Another object of the present invention is to provide an electrophotographic color image forming apparatus which employs a cartridge-holding movable member which can be pulled out of its main assembly or retracted into the main assembly; and which is characterized in that even if a cartridge or cartridges are upwardly deviated from the cartridge-holding movable member, they are moved by a pressing member into the correct cartridge supporting position in the cartridge-holding movable member. 
         [0015]    Another object of the present invention is to provide an electrophotographic color image forming apparatus which employs a cartridge-holding movable member and a cartridge pressing member; and which is characterized in that the cartridge pressing member is disposed in the top portion of the path of the cartridge-holding movable member so that when multiple cartridges are moved through the space (path of cartridge-holding movable member) under the cartridge pressing member, the cartridges are pressed down by the pressure applied by the elastic pressing members. 
         [0016]    According to an aspect of the present invention, there is provided a color electrophotographic image forming apparatus having a main assembly, to which a process cartridge is detachably mountable, for forming a color image on a recording material, wherein said process cartridge includes an electrophotographic photosensitive drum and process means actable on said electrophotographic photosensitive drum, said apparatus comprising an opening provided in said main assembly of the apparatus; a movable member which is linearly movable between an inside and an outside of said opening in a direction crossing with a longitudinal direction of said electrophotographic photosensitive drum while carrying plurality of such process cartridges; an accommodating portion for accommodating said process cartridges; and an urging member, provided above a movement path of said process cartridges, while being carried on said movable member, from said opening to said accommodating portion, for contacting said process cartridge passing therebelow to urge said process cartridge toward said movable member. 
         [0017]    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 THE DRAWINGS 
         [0018]      FIG. 1  is an external perspective view of the image forming apparatus in one of the preferred embodiment of the present invention. 
           [0019]      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. 
           [0020]      FIG. 3  is an enlargement of a part of  FIG. 2 . 
           [0021]      FIG. 4  is an external perspective view of the image forming apparatus, shown in  FIG. 1 , the door of which is open. 
           [0022]      FIG. 5  is a vertical sectional view of the image forming apparatus in the preferred embodiment, the door of which is open, as seen from the left side of the apparatus main assembly. 
           [0023]      FIG. 6  is an external perspective view of the image forming apparatus in the preferred embodiment, the cartridge tray of which is in its most outward position. 
           [0024]      FIG. 7  is a vertical sectional view of the image forming apparatus in the preferred embodiment, the cartridge tray of which is in its most outward position, as seen from the left side of the apparatus. 
           [0025]      FIG. 8  is an external perspective view of the cartridge, as seen from the side from which the cartridge is driven. 
           [0026]      FIG. 9  is an external perspective view of the cartridge, as seen from the side from which the cartridge is not driven. 
           [0027]      FIG. 10  is an external perspective view of the cartridge, as seen from the angle different from the angle from which the cartridge is seen in  FIG. 9 . 
           [0028]      FIG. 11  is a plan view of the lengthwise end of the cartridge, from which the cartridge is driven. 
           [0029]      FIG. 12  is a plan view of the lengthwise end of the cartridge, from which the cartridge is not driven. 
           [0030]      FIG. 13  is a cross-sectional view of the cartridge, (in which drum is in contact with development roller). 
           [0031]      FIG. 14  is a cross-sectional view of the cartridge, (in which drum is not in contact with development roller). 
           [0032]      FIG. 15  is an external perspective view of the cartridge tray, as seen from the side from which the cartridge is driven. 
           [0033]      FIG. 16  is an external perspective view of the cartridge tray, as seen from the side from which the cartridge is not driven. 
           [0034]      FIG. 17  is a schematic drawing showing the positional relationship between the third intermediary electrical contact of the cartridge tray, and the third input electrical contact of the cartridge. 
           [0035]      FIG. 18  is a perspective view of the left and right cartridge pressing members and their supporting plates. 
           [0036]      FIG. 19(   a ) is an enlarged side view of the inward side of the left cartridge pressing member and its supporting plate, and  FIG. 19(   b ) is an enlarged side view of the inward side of the right cartridge pressing member and its supporting plate. 
           [0037]      FIG. 20  is a schematic sectional view of the image forming apparatus, the tray of which is in the most outward position, and the second cartridge of which is upwardly deviant from the tray. 
           [0038]      FIG. 21  is a schematic sectional view of the image forming apparatus, the tray of which is being moved back into the main assembly from the position shown in  FIG. 20 . 
           [0039]      FIG. 22  is an enlargement of the pressing member portion, and its adjacencies, of  FIG. 21 . 
           [0040]      FIG. 23  is a sectional view of the more effective version of the cartridge pressing member supporting member in the preferred embodiment of the present invention, and its adjacencies. 
           [0041]      FIG. 24(   a ) is an enlarged side view of the inward side of the more effective version of the left cartridge pressing member supporting member in the preferred embodiment, shown in  FIG. 23 , and FIG.  24 ( b ) is an enlarged side view of the inward side of the more effective version of the right cartridge pressing member supporting member. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiment 1  
     (General Structure of Image Forming Apparatus) 
       [0042]      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 . 
         [0043]    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 recording medium S (for example, recording paper, OHP sheet, label, etc.) in response to electric picture signals inputted from an external host apparatus (unshown) such as a personal computer, an image reader, etc. That is, the image forming apparatus  1  is an apparatus structured so that cartridges are removably mountable in its main assembly  1 A to form a color image on the recording medium S. 
         [0044]    In the following description of the preferred embodiment of the present invention, the front side (front surface side) of the image forming apparatus means 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. 
         [0045]    The lengthwise end of a photosensitive drum (end of a photosensitive drum in terms of direction parallel to its axial line), from which the photosensitive drum is driven, will be referred to as driven side, and the lengthwise end opposite thereto will be referred to as non-driven side. 
         [0046]    Designated by a referential character  1 B is a cartridge chamber, which is in the main assembly  1 A of the image forming apparatus  1 . There are four process cartridges (first to fourth), that is, PY, PM, PC, and PK, in the cartridge chamber  1 B. 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. The cartridge chamber  1 B is a chamber into which multiple cartridges are installed while being held in cartridge tray. To each cartridge in this chamber  1 B, rotational driving force is transmitted from the apparatus main assembly  1 A, as will be described later in detail. Further, to each cartridge in this chamber  1 B, bias is supplied from the apparatus main assembly  1 A. 
         [0047]    Each cartridge in this embodiment has: an electrophotographic photosensitive drum  4  (which hereafter will be referred to as drum); and a drum unit  31  (first unit) made up of processing means, more specifically, a charging means  5  and a cleaning means  7 , which process the drum  4 . Further, each cartridge has a development unit  6  (second unit) having a developing means as a processing means. The abovementioned drum and development units  31  and  6 , respectively, are joined so that they are allowed to rotationally move relative to each other. 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. 
         [0048]    The developer container of the first cartridge PY stores yellow (Y) developer. On the peripheral surface of the drum  4 , a developer image of 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 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 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 black (K) color is formed. 
         [0049]    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 the 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 the exposure window  9 , with which the top wall of the cartridge is provided. 
         [0050]    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 , turn roller  14 , and 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. 
         [0051]    In the area below the belt unit  10 , a paper feeder unit  18  is disposed, which has a tray  19 , a paper feeder roller  20 , a paper separation pad  21 , etc. The tray  19  is removably mountable in the apparatus main assembly  1 A from the front side (front loading). 
         [0052]    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.    
         [0053]    Each cartridge in the cartridge chamber  1 B is under the pressure applied from above by a pressure application mechanism (unshown), being thereby correctly positioned relative to the cartridge positioning portion (unshown) of the apparatus main assembly, and also, being thereby securely held to the apparatus main assembly. 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. This structural arrangement will be described later in more detail. 
         [0054]    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 (subordinate direction to 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 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 an 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 effected on the peripheral surface of the drum  4 . This electrostatic latent image is developed by the development roller  6 a. 
         [0055]    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 . 
         [0056]    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 . 
         [0057]    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 . 
         [0058]    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 . 
         [0059]    Consequently, an unfixed full-color developer image is effected on the belt  12  by the four monochromatic color developer images, that is, the yellow, magenta, cyan, and black color development images. 
         [0060]    After the primary transfer of the developer image onto the belt  12 , the toner remaining on the peripheral surface of the drum  4  in each cartridge is removed by the cleaning means  7 . 
         [0061]    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 tray  19  is separated from the rest of the sheets of recording medium 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 . The recording medium S is introduced into the nip (secondary transfer nip), that is, the interface between the secondary transfer roller  17  and belt  12 , and then, is conveyed through the nip while remaining pinched by the secondary transfer roller  17  and 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. 
         [0062]    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 . 
         [0063]    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 . 
       (Method for Replacing Cartridge) 
       [0064]    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. 
         [0065]    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 of the apparatus main assembly  1 A, 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. 
         [0066]    In order to improve the image forming apparatus in usability, the image forming apparatus in this embodiment is provided with a cartridge tray (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. 
         [0067]    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. 
         [0068]    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. 
         [0069]    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 . 
         [0070]    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. That is, the door  3  is rotatable about the hinge shaft  27  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, as shown in  FIGS. 4 and 5 , widely exposing the opening  26 . Designated by a referential character  29   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. 
         [0071]    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 . Incidentally, the main frame constitutes the skeletal structure of the apparatus main assembly  1 A. The tray  29  supports the cartridges so that they are horizontally juxtaposed in the fore-and-after direction. 
         [0072]    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 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  extends outward of the apparatus main assembly  1 A by a preset distance, as shown in  FIGS. 4 and 5 . 
         [0073]    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 tray  29  which is holding the cartridges PY, PM, PC, and PK is moved upward with the holding members  28 L and  28 R, 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. 1-FIG .  5 ), making it possible for the tray  29  to be pulled out of the apparatus main assembly  1 A. 
         [0074]    At this point, the user is to grasp the handle  29   a  exposed through the opening  29 , 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 , into its preset most outward position shown in  FIGS. 6 and 7 . 
         [0075]    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 S 1  and S 2  from being pulled out further ( FIG. 7 ), 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. 
         [0076]    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 . 
         [0077]    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 the most outward position, relative to the holding members  28 L and  28 R, in the rearward direction of the apparatus main assembly  1 A (direction indicated by arrow mark H in  FIG. 17 ), 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 Si 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 . 
         [0078]    Then, the user is to rotate the door  3  relative to the apparatus main assembly  1 A to shut the door  3  against the apparatus main assembly  1 A. 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 pushed by the door linkage  30 , in both the inward and 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 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 electric 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 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; each cartridge is placed in the cartridge chamber  1 B. In other words, the image forming apparatus  1  is readied for an image forming operation. 
         [0079]    As described above, the tray  29  is movable in a straight line in the direction perpendicular to the lengthwise direction (which is parallel to axial line) of the drum  4  of each cartridge, while holding multiple cartridges so that they are horizontally arranged in the fore-and-after direction, with their lengthwise direction being parallel to the side-to-side direction of the apparatus main assembly  1 A. 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 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 , a transitional position from which the tray  29  is moved into the apparatus main assembly in the slantingly downward direction, and a latent image formation position in which it allows an electrostatic latent image to be formed on the drum  4  of each cartridge. Incidentally, the tray  29  is a movable member. 
         [0080]    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 inward of the apparatus main assembly  1 A from outward of the apparatus main assembly  1 A, the cartridges PY, PM, PC, and PK 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; if the cartridge to be replaced is the cartridge PK, it is unnecessary to pull out the tray  29  to the point at which the pair of stoppers S 1  and S 2  prevents the tray  29  from being further pulled out. Thus, the image forming apparatus  1  in this embodiment is superior to an image forming apparatus in accordance with the prior art, in terms of the efficiency with which the cartridge PK can be replaced. Incidentally, the stopper S 1  is a part of the tray  29 , whereas the stopper S 2  is a part of the apparatus main assembly  1 A. When the tray  29  is pulled out of the apparatus main assembly  1 A, the stopper S 1  comes into contact with the stopper S 2 , preventing the tray  29  from being pulled out further, as shown in  FIG. 7 . When pushing the tray  29  back into the apparatus main assembly  1 A, the stopper S 1  comes into contact with the stationary counterpart (unshown) of the apparatus main assembly  1 A, preventing the tray  29  from being pushed further into the apparatus main assembly  1 A. 
         [0081]    Before the left and right holding members  28 L and  28 R allow the tray  29  to be moved into the abovementioned most outward position, in which the tray  29  allows the cartridges to be mounted or dismounted, they move the tray  29  upward from the abovementioned latent image formation position (they move tray  29  downward from transitional position as door  3  is closed). 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 . The holding members  28 L and  28 R constitute the moving means. 
       &lt;Cartridge&gt; 
       [0082]    The first to fourth cartridges PY, PM, PC, and PK in this embodiment are the same in structure. Next, referring to  FIGS. 8-14 , the cartridge structure in this embodiment will be described. 
         [0083]      FIG. 8  is a perspective view of the cartridge, as seen from the aforementioned driven side, and  FIG. 9  is a perspective view of the cartridge, as seen from the aforementioned non-driven side.  FIG. 10  is also a perspective view of the cartridge, as seen from the non-driven side, as is  FIG. 9 , but is different in the viewing angle.  FIG. 11  is a plan view of the driven side (right-hand) end surface of the cartridge, and  FIG. 12  is a plan view of the non-driven side (left-hand) end surface of the cartridge.  FIG. 13  is a cross-sectional view of the cartridge in which the development roller  6   a  is in contact with the drum  4 , and  FIG. 14  is a cross-sectional view of the cartridge in which the development roller  6   a  is not in contact with the drum  4 . 
         [0084]    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. The cartridge has a drum unit  31  (first unit), a development unit  6  (second unit), left panel  32 L, and right panel  32 R. 
         [0085]    The drum unit  31  has a cleaning means container  31   a  (cleaning means housing), in which the drum  4 , the charge roller  5 , the cleaning blade  7 , and a developer leakage prevention sheet  7   a  are disposed ( FIG. 13 ). The drum  4  is rotatably held by, and between, the left and right panels of the container  31   a,  with bearings placed between the drum  4  and the panels. The charge roller  5  is placed in contact with 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 so that, in terms of the rotational direction of the drum  4 , the base portion of the blade  7  is on the downstream side of the cleaning edge portion of the blade  7 . 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  is stored in the container  31   a.  The sheet  7   a  is located below the blade  7 , and is placed in contact with the drum  4 , being tilted so that, in terms of the rotational direction of the drum  4 , the edge portion of the sheet  7   a,  which is in contact with the drum  4 , is on the downstream side of the edge portion of the sheet  7   a,  by which the sheet  7   a  is attached to the container  31   a.  The sheet  7   a  prevents the developer from leaking from the container  31   a  through the gap between the container  31   a  and drum  4 . 
         [0086]    The development unit  6  is provided with a developing means container  6   e  (developing means housing). It also has a development roller  6   a,  a developer supply roller  6   b  (developer coating roller), a developer regulating member  6   c,  and a developer leak prevention sheet  6   d,  which are disposed in the container  6   e.  The developer 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 supplying (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 so that the contact area between the regulating member  6   c  and development roller  6   a  is on the upstream side of its portion by which it is fixed to the container  6   e.  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.  The sheet  6   d  is placed in contact with the development roller  6   a.  It is tilted so that, in terms of the rotational direction of the development roller  6   a,  the contact area between the sheet  6   d  and development roller  6   a  is on the downstream side of its portion by which it is anchored to the container  6   e.  The sheet  6   d  prevents the developer from leaking from the container  6   e  through the gap between the development roller  6   a  and container  6   e.    
         [0087]    The left panel  32 L is solidly attached to the outward surface of the left end wall of the container  31   a,  with a part of the left panel  32 L extending rearward from the container  31   a.  The right panel  32 R is solidly attached to the outward surface of the right end wall of the container  31   a,  with a part of the right panel  32 R extending rearward from the container  31   a.  The development unit  6  is positioned between the abovementioned rearwardly extending portions of the left and right panels  32 L and  32 R, respectively, and is supported so that it is enabled to rotate, in the oscillatory fashion, about an axis b-b, which is parallel to the axial line a-a of the drum. That is, the development unit  6  is joined with the drum unit  31  so that the two units are allowed to rotationally move relative to each other. The cartridge is structured so that the rotational axis b-b of the development unit  6  coincides with the axial line of the development roller driving coupling (second driving force input portion, that is, developer roller driving force receiving portion, which will be described later in detail), which is on the right panel  32 R side, and also, so that the rotational axis b-b of the development unit  6  coincides with the axial line of the development roller supporting shaft  35 , which is on the left panel  32 L side, that is, the non-driven side. The cartridge is structured so that, in terms of the coordinate on a plane perpendicular to the lengthwise direction of the cartridge, the cross-sectional center of the supporting shaft  35  practically coincides with the axial line of the coupling  34 . That is, the axial line of the coupling  34  practically coincides with the axial line of the supporting shaft  35 . 
         [0088]    Each cartridge is provided with the drum driving coupling  33  (first driving force input portion, that is, drum driving force receiving portion), the development roller driving coupling  34 , and a cartridge rotation preventing portion  36 R (protrusion: first rotation controlling portion or first portion-to-be-regulated), which are located at one of the lengthwise ends of the cartridge, that is, the lengthwise end on the driven side. Each cartridge is also provided with a rib  37 R (first rib or first portion=to-be-supported) by which the cartridge is supported by the cartridge chamber  1 B, on the driven side, and a cartridge positioning portion  38 R (first cartridge positioning portion of cartridge or first portion-to-be-positioned, which is on driven side). The axial line of the drum driving coupling  33  coincides with that of the drum. 
         [0089]    The lengthwise end wall of the cartridge, on the non-driven side, is provided with a cartridge rotation preventing portion  36 L (channel: second rotation controlling portion or second portion-to-be-regulated) and a rib  37 L (second portion or second portion-to-be-supported by which cartridge is supported by cartridge tray), and a cartridge positioning portion  38 L (second cartridge positioning portion of cartridge or second portion-to-be-positioned). 
         [0090]    As the cartridge is moved into its preset image forming position in the apparatus main assembly  1 A (cartridge chamber  1 B), the couplings  33  and  34  are engaged with the first and second driving force output portions (unshown) of the apparatus main assembly side, respectively; when the cartridge is in its preset image formation position, the coupling  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 coupling  33 , the drum  4  is rotationally driven by the transmitted driving force in the counterclockwise direction ( FIG. 13 ) at a preset peripheral velocity. The charge roller  5  is rotated by the rotation of the drum  4 . As driving force is transmitted from the second driving force output portion to the coupling  34 , the transmitted driving force is transmitted to the development roller  6   a  and developer supply roller  6   b  (developer coating roller) through a driving force transmission gear train (unshown), causing each of the development roller  6   a  and developer supply roller  6   b  to rotate in the clockwise direction ( FIG. 13 ) at a preset peripheral velocity. The developer in the container  6   e  is supplied to (coated on) the rotating development roller  6   a  by the rotating supply roller  6   b.  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.  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 drum  4 , in which the developer is used for developing the electrostatic latent image on the drum  4 . The developer remaining on the peripheral surface of the development roller  6   a  after the development of the electrostatic 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.    
         [0091]    As each cartridge is inserted into the tray  29 , the cartridge rotation preventing portions  36 R and  36 L of the cartridge, which are on the driven and non-driven sides, respectively, engage with the cartridge rotation preventing portions ( 29   h  and  29   i ) of the tray  29 , respectively, as will be described later in detail. The cartridge rotation preventing portions  36 R and  36 L prevent the cartridge from rotating when the cartridge is correctly positioned relative to the apparatus main assembly  1 A. That is, they prevent the cartridge from rotating when the cartridge receives rotational driving force from the apparatus main assembly  1 A. Incidentally, after the cartridge is dropped into the tray  29 , that is, immediately after the cartridge is placed in the tray  29 , each of the cartridge rotation preventing portion  36 R and  36 L may be, or may not be, in contact with the inward surface of the corresponding cartridge rotation preventing portion ( 29   h  or  29   i ) of the main assembly side. However, as the cartridge receives rotational driving force from the apparatus main assembly  1 A, they come into contact with the inward surfaces of the cartridge rotation preventing portions ( 29   h  and  29   i ), respectively, preventing thereby the cartridge from rotating. 
         [0092]    The ribs  37 R and  37 L, by which the cartridge is supported on the driven and non-driven sides, respectively, protrude outward from the top edge portions of the right and left end panels  32 R and  32 L, respectively, in the direction parallel to the lengthwise direction of the cartridge. The ribs  37 R and  37 L extend in the width direction of the cartridge; they are in the form of a long and narrow rectangular parallelepiped. As the cartridge is inserted into the tray  29 , the ribs  37 R and  37 L rest on the areas  29   m  and  29   n  of the top surface  29   x  ( FIG. 15 ) of the tray  29 , preventing thereby cartridge from falling through the tray  29 . 
         [0093]    Designated by referential characters  72 R and  72 L are right and left cartridge pressing members, respectively. The cartridge pressing members  72 R and  72 L are members which move an upwardly deviant cartridge (cartridges) in the tray  29  into its correct position in the tray  29 , when the tray  29  is pushed into the apparatus main assembly  1 A. That is, the right pressing member  72 R presses on the right rib  38 R of the cartridge to press the rib  38 R upon the top surface  29   x  of the tray  29 , and the left pressing member  72 L presses on the left rib  38 L of the cartridge to press the rib  38 L on the top surface  29   x  of the tray  29 . Designated by referential characters  73 R and  73 L are right and left plates for supporting the right and left pressing members  72 R and  72 L, respectively. That is, the supporting plate  73 R is the member to which the pressing member  72 R is attached. It is attached to the holding member  28 R. The supporting plate  73 L is the member to which the pressing member  72 L is attached. It is attached to the holding member  28 L ( FIGS. 3 and 4 ). 
         [0094]    The first rib  38 R, as one the cartridge positioning members of the cartridge, which is on the driven side, is an arcuate downward protrusion. It protrudes from the bottom edge of the right panel  32 R, and the center of its arcuate portion coincides with the axial line of the drum  4 . The second rib  38 L, as the other cartridge positioning members of the cartridge, which is on the non-driven side, is also an arcuate downward protrusion. It protrudes from the bottom edge of the right panel  32 L, and the center of its arcuate portion also coincides with the axial line of the drum  4 . As the tray  29  is pushed into the apparatus main assembly  1 A while holding a cartridge, the cartridge positioning (supporting) portions  38 R and  38 L engage with the cartridge positioning portions (unshown), one for one, with which the apparatus main assembly  1 A is provided, correctly positioning the cartridge relative to the cartridge chamber  1 B. Then, while the cartridge is in the correct position in the cartridge chamber  1 B of the apparatus main assembly  1 A, they remain engaged with the cartridge positioning portions of the apparatus main assembly  1 A, keeping thereby the cartridge correctly positioned relative to the cartridge chamber  1 B. More specifically, the positioning portions  38 R and  38 L of the cartridge are correctly positioned relative to the cartridge positioning portions (unshown) of the apparatus main assembly while the tray  29  (movable member) is lowered toward the transfer belt  12 . 
         [0095]    The left panel  32 L is provided with a first input electrical contact  39 , which is on the outward surface of the left panel  32 L. The container  6   e  is provided with a second input electrical contact  40  and a third electrical contact  41 , which are on the outward surface of the lengthwise end wall of the container  6   e,  on the non-driven side. The second input electrical contact  40  is exposed outward through a window  32   a,  with which the left panel  32 L is provided. The third input electrical contact  41  is slanted downward relative to the horizontal plane, as shown in  FIG. 12 . 
         [0096]    The first input electrical contact  39  is the electrical contact through which charge bias is applied to the charge roller  5  (charge roller bias application electrical contact). This electrical contact  39  is placed, and kept, in contact with one of the lengthwise end surfaces of the shaft of the charge roller  5 , by its elastic extension. Thus, it maintains electrical contact between the charge roller  5  and the power supply on the apparatus main assembly side while sliding on the abovementioned end surface of the charge roller shaft. 
         [0097]    The second input electrical contact  40  is the electrical contact through which development bias is applied to the development roller  6   a  (developer bias application electrical contact). This electrical contact  40  is placed, and kept, in contact with one of the lengthwise end surfaces of the shaft of the development roller  6   a,  by its elastic extension. Thus, it maintains electrical contact between the development roller  6   a  and the power supply on the apparatus main assembly side while sliding on the abovementioned end surface of the development roller shaft. 
         [0098]    The third input electrical contact  41  is the electrical contact through which bias is applied to the developer supply (coating) roller  6   b  (developer supplying (coating) roller bias application electrical contact). This electrical contact  41  is placed, and kept, in contact with one of the lengthwise end surfaces of the shaft of the developer supplying roller  6   b,  by its elastic extension. Thus, it maintains electrical contact between the developer supplying roller  6   b  and the power supply on the apparatus main assembly side while sliding on the abovementioned end surface of the developer supplying roller shaft. 
         [0099]    The development unit  6  is kept pressed by pressure application springs (unshown) in the direction, indicated by an arrow mark F ( FIG. 13 ), to rotate about the axial line b-b so that the development roller  6   a  is placed, and kept, in contact with the drum  4 . The cartridge is provided with a pressure removal cam  42 , which is rotatable to rotate the development unit  6 , against the abovementioned pressure application springs, about the axial line b-b, in the direction, indicated by an arrow mark G ( FIG. 14 ), to cause the development roller  6   a  to separate from the drum  4 . The pressure removal cam  42  can be kept in the position in which it keeps the development roller  6   a  separated from the drum  4 . It can be selectively rotated by its knob  42   a  in the direction to allow the pressure application springs to keep the development roller  6   a  in contact with the drum  4 , or in the direction to keep the development roller  6 a separated from the drum  4  by removing the pressure from the pressure application springs. While the cartridge is distributed or kept stored, the cam  42  is kept in the pressure removal position into which the cam  42  is rotatable, to keep the development roller  6 a separated from the drum  4  by a distance a ( FIG. 14 ), in order to prevent the development roller  6   a  from sustaining permanent deformation or the like. Thus, before the cartridge is used for image formation for the first time, or after it has been stored, the cam  42  is to be rotated in the direction to allow the pressure application springs to apply pressure to the development unit  6 , in order to place the development roller  6   a  in contact with the drum  4  ( FIG. 13 ), so that the cartridge is readied for image formation. As the cam  42  is rotated into the position ( FIG. 13 ) in which it allows the pressure application springs to apply pressure to the development unit  6 , a gap is created between the drum unit  31  and development unit  6 . This gap serves as the exposure window  9 . 
       &lt;Cartridge Tray&gt; 
       [0100]    Next, referring to  FIGS. 15 and 16 , 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,  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 plate  29   f.  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 compartment; 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. That is, as described above, the ribs  37 R and  37 L of each cartridge rest on the top surface (top surface of tray  29 ) of the frame portion of the corresponding cartridge compartment, preventing the cartridge from falling through the tray  29 . 
         [0101]    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 on the apparatus main assembly side move into, or out of, the cartridge compartment (tray  29 ). It is also provided with a recess  29   h  into which the cartridge rotation preventing portion  36 R on the driven side fits. 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 a rib  29   i,  which fits into the cartridge rotation preventing portion  36 L on the non-driven side. It is also provided with the first to third intermediary electrical contacts  43 - 45 , which will become connected to the first to third input electrical contacts  39 - 41  of the cartridge, as the cartridge is moved into the preset image forming position in the apparatus main assembly  1 A. 
         [0102]    Each of the intermediary electrical contacts  43 - 45  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. When the cartridge is in its proper position in the tray  29 , the inward portions (a) of the intermediary electrical contacts  43 - 45  are electrically in contact with the first to third input electrical contacts  39 - 41  of the cartridge, respectively. Further, when the cartridge is in the proper position in the cartridge chamber  1 B in the apparatus main assembly  1 A, the outward portions (b) of the intermediary electrical contacts  43 - 45  are electrically in contact with the output electrical contacts of the apparatus main assembly  1 A (main assembly electrical contacts (unshown)), one for one. 
         [0103]    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 rotation preventing portions  36 R and  36 L of each cartridge, which are on the driven and non-driven side, engage with the recess  29   h  and rib  29   i  of the tray  29 , respectively. That is, the cartridge rotation preventing portion  36 R fits into the recess  29   h,  and the cartridge rotation preventing portion  36 L fits around the rib  29   i  ( FIG. 15 ). As each cartridge falls further into the corresponding cartridge compartment of the tray  29 , the bottom surface of the rib  37 R is caught by the top surface of the left section  29   e  of the tray frame, and the bottom surface of the rib  37 L is caught by the top surface of the section  29   d  of the tray frame ( FIG. 15 ). 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 lowed into the tray  29 , the first to third input electrical contacts  39 - 41  of the cartridge come into contact, and remain in contact, with the inward portions (a) of the intermediary electrical contacts  43 - 45  of the tray  29 , respectively, establishing thereby 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  43 - 45  of the tray  29  come into contact with the output electrical contacts of the apparatus main assembly  1 A, establishing electrical connection between the tray  29  and apparatus main assembly  1 A. As a result, the first to third input electrical contacts  39 - 41  of the cartridge become electrically connected to the power supply system of the apparatus main assembly  1 A through the intermediary electrical contacts  43 - 45  of the tray  29 . The intermediary electrical contacts  43 - 45  supply the cartridge with the biases which they receive from the output electrical contacts of the apparatus main assembly  1 A. 
       &lt;Relationship Between Intermediary Electrical Contacts and Cartridge&gt; 
       [0104]    Next, referring to  FIGS. 15 ,  16 , and  17 , the relationship between the intermediary electrical contacts  43 - 45  with which the tray  29  is provided, and each cartridge, will be described. 
         [0105]    In this embodiment, the first to third intermediary electrical contacts  43 - 45  of each of the first to fourth cartridge compartments  29 ( 1 )- 29 ( 4 ) of the tray  29  are located at the lengthwise end of the cartridge compartment, on the non-driven side. The inward portions (a) of the first and second intermediary electrical contacts  43  and  44  are on the inward surface of the left portion  29   d  of the tray frame, and the inward portion (a) of the third intermediary electrical contact  45  is at the bottom of the cartridge compartment ( 29 ( 1 )- 29 ( 4 )), and is at the most downstream end of the cartridge compartment ( 29 ( 1 )- 29 ( 4 )) in terms of the direction, indicated by an arrow mark H ( FIG. 17 ), in which the tray  29  moves when it is pushed into the apparatus main assembly  1 A. 
         [0106]    The inward portion (a) of each of the first to third intermediary electrical contacts  43 - 45  is rendered elastic. The inward portions (a) of the first and second intermediary electrical contacts  43  and  44  elastically deform toward the non-driven side, whereas the inward portion (a) of the third intermediary electrical contact  45  elastically deforms in the abovementioned direction H. 
         [0107]    The first input electrical contact  39  of each cartridge is on the outward surface of the left end panel  32 L of the cartridge. The second input electrical contact  40  is on the outward surface of the lengthwise end wall of the development means container  6   c,  on the non-driven side, and is exposed outward through the window  32   a  with which the left panel  32 L is provided. 
         [0108]    The third input electrical contact  41  is positioned so that when the cartridge is properly supported by the tray  29 , it is at the leading end of the cartridge in terms of the abovementioned tray movement direction H. Further, it is attached to the cartridge so that when the cartridge is properly supported by the tray  29 , it is downwardly tilted ( FIGS. 12 and 17 ). Each cartridge is supported by the tray  29  so that the axial line a-a of the drum  4  intersects with the abovementioned tray movement direction H. The third input electrical contact  41  is on the outward side of the cartridge in terms of the width direction of the cartridge. 
         [0109]    When the cartridge is properly supported in the corresponding cartridge compartment of the tray  29 , the first input electrical contact  39  of the cartridge is in contact with the inward portion (a) of the first intermediary electrical contact  43 , with the latter kept elastically deformed by the former; the two remain electrically connected. The second input electrical contact  40  of the cartridge is in contact with the inward portion (a) of the second intermediary electrical contact  44 , with the latter kept elastically deformed by the former; the two remain electrically connected. The third input electrical contact  41  of the cartridge is in contact with the inward portion (a) of the third intermediary electrical contact  45 , with the latter kept elastically deformed by the former; the two remain electrically connected. 
         [0110]    The reactive force resulting from the abovementioned elastic deformation of the inward portions (a) of the first and second intermediary electrical contacts  43  and  44  keeps the cartridge in the tray  29  pressed upon the lengthwise end wall of the cartridge compartment, on the driven side, from the non-driven side, enabling thereby the cartridge to precisely receive the driving force transmitted from the apparatus main assembly  1 A. 
         [0111]    The third input electrical contact  41  of the cartridge is in contact with the inward portion (a) of the third intermediary electrical contact  45  ( FIG. 17 ). The third input electrical contact  41  is tilted relative to the horizontal plane. Therefore, the third input electrical contact  41  is pressed obliquely upward (direction indicated by arrow mark J in  FIG. 21 ) by the reactive force generated by the elastic deformation of the inward portion (a) of the third internal electrical contact  45 . This direction in which the third input electrical contact  41  is pressed is the same as the direction in which force is to be applied to the development unit  6  (second unit of cartridge) to rotate the development unit  6  about the rotational axis b-b of the development unit  6  to place the development roller  6   a  in contact with the drum  4  in the drum unit  31  (first unit of cartridge). This pressure applied to the third input electrical contact  41  by the elasticity of the third intermediary electrical contact  45  presses the cartridge toward the cartridge rotation preventing portion  36 L. As a result, the cartridge stabilizes within the range of play afforded between the rotation preventing portion  36  L and the surface of the rib  29   i.    
         [0112]    That is, the elasticity of the electrical contact  45  keeps the internal surface of the rotation preventing portion  36 L in contact with the rotation preventing rib  29   i.    
         [0113]    In this embodiment, the third input electrical contact  41  contacts the inward portion (a) of the third intermediary electrical contact  45 . With the cartridge kept pressed by the elasticity of this inward portion (a), the inward surface of the rotation preventing portion  36 L is kept in contact with the cartridge rotation preventing rib  29   i  of the tray  29 . The rotation preventing portion  36 L is the cartridge rotation preventing contact portion on the cartridge side. The rotation preventing portion  36 L, which is the cartridge rotation preventing contact portion on the cartridge side, is on the upstream side of the cartridge in terms of the abovementioned tray movement direction H. 
         [0114]    Further, as the third input electrical contact  41  strikes the inward portion (a) of the third intermediary electrical contact  45 , the force which upwardly presses the cartridge is generated in the inward portion (a) by the elasticity of the inward portion (a). In other words, the inward portion (a) of the third intermediary electrical contact  45  functions as a shock absorber when the cartridge falls into the corresponding cartridge compartment in the tray  29 . 
         [0115]    Referring to  FIGS. 6 and 7 , the operation for replacing the cartridge (cartridges) in the tray  29  with a new cartridge (cartridges) is to be carried out when the tray  29  is in the most outward position relative to the apparatus main assembly  1 A. Thus, in order to place the cartridges in the apparatus main assembly  1 A, the tray  29  must be moved back into the apparatus main assembly  1 A. 
         [0116]    If a user moves the tray  29  into the apparatus main assembly  1 A too fast, a shock occurs when the tray  29  settles into its home position in the apparatus main assembly. More specifically, the cartridges are shocked as the stopper Si collides with the solid bumper portion (unshown) of the apparatus main assembly  1 A. In this embodiment, however, each cartridge remains stabilized in its cartridge compartment in the tray  29  by the elasticity of the inward portion (a) of the third intermediary electrical contact  45 , as described above. That is, the cartridge is supported in its cartridge compartment ( 29 ( 1 )- 29 ( 4 )), being prevented from moving in the cartridge compartment, in the tray movement direction H. Therefore, even when the tray  29  is subjected to the abovementioned shock, it does not occur that the cartridge substantially move in the tray  29 . Therefore, the amount of shock to which the cartridge in this embodiment is subjected when the tray  29  is moved into the apparatus main assembly  1 A in this embodiment at an excessive speed is substantially smaller than that to which a cartridge in accordance with the prior art is moved into the apparatus main assembly in accordance with the prior art. In this embodiment, in order to achieve the above described effect, the inward portion (a) of the third intermediary electrical contact  45  is located on the downstream side in terms of the tray movement direction H. Further, the third input electrical contact  41 , which comes into contact with the inward portion (a), is located on the downstream side in terms of the tray movement direction H. That is, in this embodiment, the third input electrical contact  41 , which is for supplying the supply roller with bias is attached to the leading end of the cartridge in terms of the tray movement direction H. The inward portion (a) of the third intermediary electrical contact  45  is located on the downstream side in the corresponding cartridge compartment ( 29 ( 1 )- 29 ( 4 )) in terms of the tray movement direction H, and is positioned so that it elastically deforms in the tray movement direction H. In addition, a structural arrangement is made so that as the third input electrical contact  41  is pressed by the elastic inward portion (a) of the electrical contact  45  (intermediary electrical contact), the inward surface of the abovementioned cartridge rotation preventing portion  36 L (cartridge rotation preventing portion on cartridge side) comes into contact with the cartridge rotation preventing portion (rib)  29   i  of the tray  29 . 
         [0117]    Also in this embodiment, the weight of each cartridge was in a range of 500 g-650 g, whereas the amount of elasticity of the intermediary electrical contact  45  was set to a value in a range of 1.5 N-3.5 N (newton). 
         [0118]    Therefore, it was possible for the cartridge to receive a pressure large enough for the inward surface of the rotation preventing portion  36 L (rotation preventing portion on cartridge side) to be placed, and kept, in contact with the cartridge rotation preventing portion  29   i  of the tray  29 . 
         [0119]    In this embodiment, a torsional coil spring is used as the intermediary electrical contact  45 . 
         [0120]    The above given numerical values are not intended to limit this embodiment in scope; the cartridge weight and the amount of elasticity of the intermediary electrical contacts are optional. 
         [0121]    With the employment of the above described structural arrangement in this embodiment, the amount of impact and vibrations to which the cartridge in this embodiment is subject when the tray  29  in this embodiment strikes the stopper S 2  is substantially smaller than the amount of impact and vibrations to which a cartridge in accordance with the prior art is subjected when a tray in accordance with the prior art strikes the stopper S 2 . 
         [0122]    Also in this embodiment, the third input electrical contact  41 , which is for supplying bias to the supply roller  6   b  which is located on the downstream side of the charge roller  5  and development roller  6   a  in terms of the abovementioned tray movement direction H, when the cartridge is in the tray  29 , is attached to the leading end of the cartridge in terms of the tray movement direction H. Therefore, it was possible to substantially reduce in length the wiring between the third input electrical contact  41  and supply roller  6   b,  compared to the case in which other electrical contacts are attached to the leading end of the cartridge in terms of the tray movement direction H. 
         [0123]    Further, in this embodiment, the third input electrical contact  41  is attached to the cartridge so that when the cartridge is in the tray  29 , the contact area of the third input electrical contact  41  is downwardly tilted. Therefore, the third input electrical contact  41  is pressed obliquely upward by inward portion (a) of the electrical contact  45 . Therefore, the cartridge is pressed obliquely upward from below, ensuring that the inward surface of the cartridge rotation preventing portion  36 L (cartridge rotation preventing portion on cartridge side) comes into contact, and kept in contact, with the cartridge rotation preventing portion  29   i.  Moreover, not only do the rotation preventing portion  36 L and rotation preventing portion  29   i  function to prevent the cartridge from rotating, but also, they function as shock absorbers. 
         [0124]    Further, the play between the cartridge and tray  29  is nullified by the elasticity of the electrical contacts. That is, the cartridge is secured in the tray  29  by the elasticity of the electrical contacts. Thus, even if the user abruptly moves outward the tray  29  in the apparatus main assembly  1 A (direction opposite to direction indicated by arrow mark H in  FIG. 17 ), the shock and vibrations to which the cartridge is subjected are substantially smaller than those to which the cartridge in accordance with the prior art is subjected in the same situation. 
         [0125]    In this embodiment, the cartridge is provided with the developer leak prevention sheets  6   d  and  7   a,  which are located on the underside of the development roller  6   a  and cleaning blade  7 , respectively. However, the reduction in vibrations and shock can further reduce the possibility of developer leak. 
         [0126]    In this embodiment, the function of cushioning the shock to which the cartridges are subjected when the tray  29 , which can be moved into, or out of, the apparatus main assembly  1 A while holding the cartridges, is moved, is assigned to the intermediary electrical contact  45 . That is, in this embodiment, the intermediary electrical contact  45  was given the function of supplying electricity, and the function of cushioning shocks. Therefore, not only was it possible to reduce the component count of the image forming apparatus, but also, to simplify the structure of the image forming apparatus. 
         [0127]    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. 
         [0128]    Also in this embodiment, one of the intermediary electrical contacts is positioned at the leading end of each compartment of the tray  29 , in terms of the tray movement direction. However, the positioning of the intermediary electrical contacts does not need to be limited to the one in this embodiment. For example, the intermediary electrical contacts may be positioned at both the leading and trailing ends in terms of the tray movement direction H. 
         [0129]    However, positioning one of the intermediary electrical contact at the leading end in terms of the tray movement direction H is more effective to cushion the shock which occurs when the tray  29  is moved into the apparatus main assembly  1 A than positioning it at the trailing end. That is, the former arrangement can better cushion the shock to which the cartridge is subjected immediately prior to its usage, being therefore more practical, than the latter arrangement. 
       &lt;Cartridge Pressing Member&gt; 
       [0130]    Next, referring to  FIGS. 18-24 , the cartridge pressing member will be described. 
         [0131]    The apparatus main assembly  1 A is provided with a pair of cartridge pressing members  72 L and  72  R (left and right members), which are disposed on the front side of the left and right tray holding members  28 L and  28 R, respectively, and immediately above the path of the tray  29  (that is, cartridge path), opposing each other across the path. The pressing members  72 L and  72 R are solidly attached to the left and right pressing member supporting plates  73 L and  73 R, which are solidly attached to the aforementioned left and right tray supporting member  28 L and  28 R, respectively.  FIG. 18  is a perspective view of the left pressing member  72 L, left supporting plate  73 L, right pressing member  72 R and right supporting plate  73 R. 
         [0132]    The pressing members  72 L and  72 R are positioned so that when the cartridges PY, PM, PC, and PK held in the tray  29  are moved into the cartridge chamber  1 B through the opening  26  of the apparatus main assembly  1 A, the pressing members  72 L and  72 R will be immediately above the paths of the ribs  37 L and  37 R (cartridge supporting members on cartridge side), respectively. That is, the pressing member  72 L is positioned immediately above the path of the rib  72 L, and the pressing member  72 R is positioned immediately above the path of the rib  72 R. 
         [0133]    Referring to  FIG. 19 , each of the pressing members  72 L and  72 R is disposed so that its bottom portion protrudes into the path of the corresponding rib  37  so that a gap g is provided between the tray  29  and the bottom edge of the pressing member  72 . The gap g is greater than the thickness y of rib  72  ( 72 L and  72 R). It is set to a value which ensures that the rib  37  ( 37 L and  37 R) of a cartridge in the tray  29 , which is upwardly deviant by more than a preset distance, comes into contact with the pressing member  72 . The pressing member  72  is provided with slanted surfaces a and b. The surface a is on the opening  26  side, and is slanted at an angle θ, in terms of the abovementioned tray movement direction H, whereas the surface b is on the opposite side of the pressing member  72  from the opening  26 , and is downwardly slanted at an angle θ, in terms of the direction, indicated by an arrow mark I, in which the tray  29  is pulled out of the apparatus main assembly  1 A. When the cartridges are moved into the apparatus main assembly  1 A, the upwardly deviant cartridge can be smoothly guided downward by the slanted surface a, whereas when the cartridges are moved out of the apparatus main assembly  1 A, the upwardly deviant cartridge can be smoothly guided downward by the slanted surface b. 
         [0134]    Next, referring to  FIGS. 20-22 , the functions of the pressing members  72 L and  72 R will be described.  FIG. 20  is a sectional view of the image forming apparatus, the tray of which is in the most outward position, and in which the second cartridge PM is upwardly deviant from the correct position in the tray  29 .  FIG. 21  is a sectional view of the image forming apparatus, the tray of which is being moved in the abovementioned tray movement direction H from the most outward position shown in  FIG. 20 .  FIG. 22  is an enlargement of the pressing member  72 R portion, and its adjacencies, of  FIG. 21 . The pressing member  72 R is provided with the surface a slanted at the angle θ, as described above. If a cartridge, for example, the cartridge PM, in the tray  29  is upwardly deviant from the correct position in the tray  29  when the tray  29  is outside the apparatus main assembly  1 A, the rib  37 R (cartridge supporting portion on cartridge side) of the cartridge PM comes into contact with the pressing member  72 R when the tray  29  is moved into the apparatus main assembly  1 A. Thus, as the tray  29  is moved further into the apparatus main assembly  1 A, the rib  37  R is pressed downward by the slanted surface a of the pressing member  72 R. As a result, the flat portion  72 R 1  of the pressing member  72 R comes into contact with the top surface of the rib  37 R. The pressing member  72 L functions in the same manner as the pressing member  72 R functions as described above. That is, the rib  37 L of the cartridge PM is pressed downward by the slanted surface a, and then, the flat portion  72 L 1  of the pressing member  72 L comes into contact with the top surface of the rib  37 L. Thus, the cartridge PM is moved into the correct position in the tray  29 . That is, the ribs  37 R and  37 L are supported by the top surface of the tray  29 . 
         [0135]    As described above, while the tray  29  is moved into the apparatus main assembly  1 A, the pressing members  72 L and  72 R press down the upwardly deviant cartridge (cartridges) in the tray  29 , moving thereby the cartridge (cartridges) into the correct position in the tray. Further, as the ribs  37 L and  37  R move through the gap between the pressing members  72 L and  72 R and the tray  29 , the cartridge (cartridges) is pressed into the normal position in the tray  29 . 
         [0136]    When the tray  29  is pulled out of the apparatus main assembly  1 A, the slanted surface  b,  instead of the slanted surface a, presses the ribs  37 R and  37  L downward. 
         [0137]    With the presence of the slanted surface a, the cartridge can be smoothly guided downward when the tray (cartridges) is moved into the apparatus main assembly  1 A. The slanted surface b makes it possible to smoothly guide the cartridge downward when the tray  29  (cartridges) are moved out of the apparatus main assembly  1 A. 
         [0138]    The height of the pressing members  72 L and  72 R, and the angle of the slanted surfaces a and b, in this embodiment, are optional. 
         [0139]      FIGS. 23 and 24  are drawings of more effective versions of pressing members  72 L and  72 R. The pressing members  72 L and  72 R have supporting plates  73 L and  73 R, which are rotatable relative to the left and right tray supporting members  28 L and  28 R, about fulcrums  74 L and  74 R, respectively. Further, the supporting plates  73 L and  73 R are kept pressured by tensional springs  75 L and  75 R, respectively, in the direction to rotate toward the tray  29 . This structural arrangement, that is, the presence of elastic members (tensional springs  75 L and  75 R), ensures that the ribs  37 L and  37 R of each cartridge are pressed downward by the pressing members  72 L and  72 R. Further, the elasticity of the tensional springs  75 L and  75 R can soften the shock which occurs as the ribs  37 L and  37 R collide with the pressing members  72 L and  72 R. In other words, this structural arrangement improves the image forming apparatus in the operability of the tray  29  by a user. 
         [0140]    In the embodiment described above, the image forming apparatus  1  is structured so that the pressing members  72 L and  72 R come into contact with the ribs  37 L and  37 R, respectively, of the cartridge (cartridges) in the tray  29 , which is upwardly deviant from the correct position in the tray  29 . However, this embodiment is not intended to limit the presence invention in scope. For example, the image forming apparatus  1  may be structured as shown in  FIGS. 23 and 24 . 
         [0141]    In the case of the structural arrangement shown in  FIGS. 23 and 24 , the pressing members  72 L and  72 R come into contact with the top surfaces of all the cartridges which are moved by being supported by the tray  29 . Further, they elastically presses the cartridges toward the tray  29  which supports the cartridges. This structural arrangement achieves effects similar to those achieved by the above described preferred embodiment. 
         [0142]    The number of pressing members may be one; the image forming apparatus may be provided with only one of the pressing members  72 L or  72 R. However, providing the apparatus with both the pressing members  72 L and  72 R is more effective. 
         [0143]    As described above, in this embodiment, the pressing members  72 L and  72 R are positioned in the top portion of the path through which the cartridges are moved into the cartridge chamber  1 B through the opening  26  while being supported by the tray  29  (movable member), so that the when the cartridges are moved below the pressing members  72 L and  72 R, the pressing members  72 L and  72 R come into contact with the cartridges, and press the cartridges toward the tray  29  by which the cartridges are supported. Therefore, it is possible to prevent the problem that when multiple cartridges are moved into the apparatus main assembly  1 A while being supported by the movable member, they accidentally collides with the other internal structural components of the apparatus main assembly  1 A; it is possible to smoothly move the cartridges into the apparatus main assembly  1 A. Further, placing the pressing members  72 L and  72 R in the top portion of the tray path makes it possible to use a single pair of pressing members, that is, the pressing members  72 L and  72 R, as the common pressing members, to elastically press all the multiple cartridges which are moved below the pressing members. 
         [0144]    Further, the image forming apparatus  1  may be structured so that the pressing members  72 L and  72 R contact the top surfaces of all the cartridges which move below the pressing members, and elastically press all the cartridge toward the tray  29  by which they are supported. This arrangement ensures that the multiple process cartridges are more smoothly moved into the main assembly of the electrophotographic color image forming apparatus. 
         [0145]    Also in the embodiment described above, when multiple cartridges supported by the tray  29  are moved below the pressing members  72 L and  72 R, the pressing members  72 L and  72 R come into contact with the cartridge (cartridges) which is upwardly deviant from the tray  29  by a distance greater than a value which allows the pressing members  72 L and  72 R to contact the cartridge, and press the upwardly deviant cartridge toward the top surface of the tray  29 , by which the cartridges are to be supported. Therefore, the cartridge(s) which is upwardly deviant from the correct cartridge position in the tray  29  is moved into the correct cartridge position in the tray  29 . That is, even if the cartridge(s) in the tray  29  is upwardly deviant from the correct cartridge position in the tray  29 , it is moved into the correct cartridge position in the tray  29  by the pressing member  72 L and  72 R. 
         [0146]    Also in the embodiment described above, the pressing members  72 L and  72 R are positioned at opposing ends of the apparatus main assembly  1 A in terms of the direction perpendicular to the direction in which the cartridge(s) is moved through its path. Therefore, the pressing members  72 L and  72 R contact the opposing ends of the cartridge(s), in terms of the direction perpendicular to the cartridge movement direction, when the cartridge(s) moves below the pressing members  72 L and  72 R. Therefore, it is ensured that multiple cartridges are smoothly moved into the apparatus main assembly  1 A. 
         [0147]    The number of pressing members may be only one. That is, in terms of the direction perpendicular to the direction in which the cartridge(s) moves through the cartridge path, it may be at only one end of the apparatus main assembly  1 A that the pressing member is provided; it may be either the pressing member  72 L or  72 R. This arrangement can reduce component count of the image forming apparatus, and therefore, can reduce the cost of the apparatus. 
         [0148]    Further, the pressing members  72 L and  72 R are solidly attached to the apparatus main assembly  1 A so that they protrude downward into the cartridge path. Each pressing member  72  has the slanted surface a, which is on the opening  26  side of the pressing member  72 , and is downwardly slanted in terms of the downstream direction, that is, the direction in which the tray  29  is moved into the apparatus main assembly  1 A (direction H in  FIG. 19 ). Therefore, when multiple cartridges are moved into the apparatus main assembly  1 A while being supported by the movable member, they can be smoothly moved into the apparatus main assembly  1 A. 
         [0149]    Further, each pressing member  72  has the slanted surface b, which is on the opposite side of the pressing member  72  from the opening  26  and is downwardly slanted in terms of the direction (direction I in  FIG. 19 ; downstream direction) in which the tray  29  is moved out of the apparatus main assembly  1 A. 
         [0150]    Further, the pressing members  72 L and  72 R may be kept downwardly pressured by elastic pressing means to ensure that the multiple cartridges are more smoothly moved into the apparatus main assembly  1 A. 
         [0151]    The pressing members  72 L and  72 R are disposed next to the opening  26 . 
         [0152]    In the embodiment described above, the image forming apparatus was structured so that the pressing members  72 L and  72 R downwardly press the ribs  37 L and  37 R. However, the above described embodiment is not intended to limit the present invention in scope. For example, the image forming apparatus may be structured so that the pressing members  72 L and  72 R press the top surface of the cartridge, or the center portion of the top surface of the cartridge. 
         [0153]    Also in the embodiment described above, the tray  29  was movable in a straight line in the direction parallel to the surface on which the apparatus main assembly  1 A is set. However, the embodiment is not intended to limit the present invention in scope. For example, the image forming apparatus may be structured so that the tray  29  is movable in a straight line in the obliquely upward direction, or obliquely downward direction, relative to the surface on which the apparatus main assembly  1 A is set. 
         [0154]    According to an aspect of the present invention, there is provided an electrophotographic color image forming apparatus which is characterized in that multiple process cartridges can be smoothly inserted into the main assembly of the apparatus. 
         [0155]    According to another aspect of the present invention, there is provided an electrophotographic color image forming apparatus which is characterized in that it is superior in operability to an electrophotographic color image forming apparatus in accordance with the prior art, in terms of the insertion of multiple process cartridges into the apparatus main assembly. 
         [0156]    According to a further aspect of the present invention, there is provided an electrophotographic color image forming apparatus which is characterized in that when multiple cartridges are inserted into the apparatus main assembly, while being held by the movable member, the cartridges do not accidentally collide with the other structural components in the apparatus main assembly. 
         [0157]    According to the present invention, it is possible to provide an electrophotographic color image forming apparatus which is characterized in that even if a cartridge in the cartridge-holding movable member is upwardly deviant from the correct cartridge position in the cartridge-holding movable member, the cartridge can be moved into the correct cartridge position in the cartridge-holding movable member by a pressing member. 
         [0158]    According to a yet further aspect of the present invention, there is provided an electrophotographic color image forming apparatus which is characterized in that the apparatus main assembly is provided with a pressing member which is positioned in the top portion of the path of the abovementioned cartridge-holding movable member, and therefore, multiple cartridges can be elastically pressed one by one by a single pressing member (common pressing member) when the cartridges move below the pressing member. 
         [0159]    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. 
         [0160]    This application claims priority from Japanese Patent Application No. 355652/2006 filed Dec. 28, 2006 which is hereby incorporated by reference.