Abstract:
An electrophotographic image forming apparatus for forming an image on a recording material in the state that cartridge is detachably mounted to a main assembly of the electrophotographic image forming apparatus, the electrophotographic image forming apparatus comprising an opening; a cartridge supporting member linearly movable through the opening between an inside position, in the main assembly of the apparatus, for forming an image using the cartridge and an outside position which is outside the main assembly of the apparatus; retracting means for retracting the cartridge supporting member from a region in which the cartridge supporting member faces the opening, in the state that cartridge supporting member is in the outside position; and locking means for releasably locking the cartridge supporting member at the retracted position.

Description:
FIELD OF THE INVENTION AND RELATED ART 
     The present invention relates to an electrophotographic image forming apparatus which forms an image on recording medium while the image formation cartridge, or cartridges, therefor remain removably mounted in the main assembly of the image forming apparatus. 
     There has been proposed a structural arrangement for mounting two or more process cartridges on a cartridge supporting member which is movable relative to the main assembly of an image forming apparatus (U.S. Laid-open Patent Application 2007-77087). This structural arrangement makes it possible to simultaneously insert two or more development cartridges into the main assembly of an image forming apparatus. 
     Next, an example of image forming apparatus, which is conventional in structure, will be described. 
     A conventional image forming apparatus is structured so that a development cartridge, that is, a cartridge having a development roller, is removably mountable in the image assembly of the image forming apparatus. 
     More concretely, a development cartridge is removably mounted in a cartridge tray, which is supported by the main assembly of the image forming apparatus so that it can be moved relative to the main assembly. The cartridge tray is supported by a tray holding member so that it is slidingly movable in the direction intersectional to the lengthwise direction of a photosensitive drum. 
     After the opening of the cartridge mounting door of the main assembly of the image forming apparatus, the cartridge tray can be pulled out of the main assembly of the image forming apparatus. When the cartridge tray is outside the main assembly while holding the development cartridges, there is nothing on and above the cartridges, making it possible for the cartridges to be removed from the main assembly in the upward direction. 
     The image forming apparatus described above is provided with a recording medium feeder tray, in which multiple sheets of recording medium are storable in layers, and which can be pulled out of the main assembly. The sheets of recording medium in the recording medium feeder tray are fed into the main assembly by a feed roller, which makes up a part of the recording medium feeding portion of the main assembly. As each sheet of recording medium is conveyed into the interface between each process cartridge and a transfer belt, an image is transferred onto the sheet of recording medium. Then, the sheet of recording medium is discharged from the main assembly by a pair of discharge rollers  22  and  23 , which makes up the recording medium discharging portion of the main assembly. 
     SUMMARY OF THE INVENTION 
     If an electrophotographic color image forming apparatus which is conventional in structure becomes jammed with a sheet, or sheets, of paper (recording medium), or the like, it is reasonable to think of pulling the jammed paper from the recording medium feeding portion and/or the recording medium discharging portion after pulling the recording medium feeder tray. If it is impossible to remove the jammed paper from the recording medium feeding portion or/and recording medium discharging portion, it is reasonable to think of removing the jammed paper after disengaging the cartridge tray from the main assembly to secure an operational space for removing the jammed paper. 
     It is also reasonable to think that in order to remove the cartridge tray from the main assembly of the image forming apparatus structured as described above, however, it is necessary to carry out the operation for disengaging the cartridge tray from the main assembly. 
     Thus, the primary object of the present invention is to improve in usability an electrophotographic image forming apparatus, which employs a cartridge supporting member, by making it unnecessary to remove the cartridge supporting member in order to secure an operational space for such an operation as removing jammed paper or the like. 
     According to an aspect of the present invention, there is provided An electrophotographic image forming apparatus for forming an image on a recording material in the state that cartridge is detachably mounted to a main assembly of said electrophotographic image forming apparatus, said electrophotographic image forming apparatus comprising an opening; a cartridge supporting member linearly movable through said opening between an inside position, in said main assembly of the apparatus, for forming an image using said cartridge and an outside position which is outside said main assembly of the apparatus; retracting means for retracting said cartridge supporting member from a region in which said cartridge supporting member faces said opening, in the state that cartridge supporting member is in the outside position; and locking means for releasably locking said cartridge supporting member at the retracted position. 
     As described above, the present invention makes it possible to move the cartridge supporting member of an electrophotographic image forming apparatus away from the area, in which the cartridge supporting member squarely faces the cartridge mounting opening of the apparatus, after moving the cartridge supporting member from its inward position (image forming position) to its outward position. Thus, the present invention can create the operational space for taking care of paper jam or the like without disengaging the cartridge supporting member from the main assembly of the image forming apparatus. 
     These and other objects, features, and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1(   a ) and  1 ( b ) are sectional views of the image forming apparatus in the first preferred embodiment of the present invention. 
         FIGS. 2(   a ) and  2 ( b ) are sectional views of the image forming apparatus in the first preferred embodiment of the present invention. 
         FIGS. 3(   a ) and  3 ( b ) are perspective views of the cartridge tray in the first preferred embodiment. 
         FIGS. 4(   a ) and  4 ( b ) are perspective views of the image forming apparatus in the first preferred embodiment. 
         FIGS. 5(   a ) and  5 ( b ) are sectional views of the cartridge tray in the first preferred embodiment of the present invention, which are for describing the method for supporting the cartridge tray after the cartridge tray is rotationally moved into the displacement position. 
         FIG. 6(   a ) is a perspective view of the cartridge tray guiding member in the first preferred embodiment of the present invention, which is for describing the structure of the cartridge tray guiding member, and  FIG. 6(   b ) is a sectional view of the essential portions of the cartridge tray stopper portion of the main assembly in the first preferred embodiment of the present invention. 
         FIG. 7  is a perspective view of the image forming apparatus in the first preferred embodiment. 
         FIG. 8(   a ) is a sectional view of the image forming apparatus in the second preferred embodiment of the present invention, and  FIG. 8(   b ) is a sectional view of the essential portions of the image forming apparatus, which is for describing the method for moving the cartridge tray. 
         FIG. 9(   a ) is a sectional view of the image forming apparatus in the second preferred embodiment of the present invention, and  FIG. 9(   b ) is a sectional view of the essential portions of the image forming apparatus, which is for describing the method for moving the cartridge tray. 
         FIG. 10  is a perspective view of the main assembly and cartridge tray of the image forming apparatus in the second preferred embodiment of the present invention, which is for describing the method for moving the cartridge tray. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereafter, the present invention will be described in detail with reference to some of the preferred embodiments of the present invention. However, the measurement, materials, shapes, and relative positioning of the structural components in these embodiment are to be modified based on the structure of the image forming apparatus to which the present invention is applied, and/or the conditions under which the image forming apparatus is operated. That is, the preferred embodiments of the present invention, which will be referred to in the following detailed description of the present invention, are not intended to limit the present invention is scope. 
     Embodiment 1 
     First, referring to  FIGS. 1-7 , the first preferred embodiment of the electrophotographic image forming apparatus in accordance with the present invention will be described. This embodiment of the electrophotographic image forming apparatus is in the form of a full-color laser beam printer. Hereafter, the overall structure and functions of this laser beam printer will be described. Incidentally, not only is the present invention applicable to a full-color image forming apparatus, but also, a monochromatic laser printer, that is, a laser printer having only one photosensitive member. Further, not only is the present invention applicable to printers, but also, other electrophotographic image forming apparatuses, such as a copying machine, a facsimile machine, etc. 
     [Description of General Structure of Image Forming Apparatus] 
     First, referring to  FIG. 1(   a ), this embodiment of electrophotographic image forming apparatus in accordance with the present invention will be described in general structure.  FIG. 1(   a ) is a sectional view of the first embodiment of the electrophotographic image forming apparatus in accordance with the present invention, and shows the general structure of the apparatus. 
     This electrophotographic image forming apparatus has: a sheet feeder tray  13  in which multiple sheets of recording medium  14  (paper) are stored in layers; a feeding-and-conveying roller  15 , which makes up a recording medium feeding-and-conveying portion of the apparatus; a transfer belt  18 ; a fixation film  20  and a pressure roller  21 , which make up a fixing apparatus; a laser scanner; etc. These components are in the shell of the main assembly A of the image forming apparatus (which hereafter may be referred to simply as main assembly A). The main assembly A is provided with a cartridge tray  26 , which is a cartridge supporting member and is removably supported by the main assembly A. The cartridge tray  26  removably supports process cartridges  9 ,  10 ,  11 , and  12 . Each of the process cartridges  9 ,  10 ,  11 , and  12  has an electrophotographic photosensitive drum ( 1 ,  2 ,  3 , and  4 , respectively), a development roller ( 5 ,  6 ,  7 , and  8 , respectively, etc. The development roller is a processing means, which is for processing the photosensitive drum. Each of the process cartridges  9 ,  10 ,  11 , and  12  is removably supported by the abovementioned cartridge tray  26  so that as the cartridge tray  26  is moved into the preset position in the main assembly A, each process cartridge is precisely placed in its preset position (image formation position) in the main assembly A. Incidentally, in the case of this image forming apparatus, the process cartridges  9 ,  10 ,  11 , and  12  contain yellow, magenta, cyan, and black developers, respectively. The cartridge tray  26  is structured so that the process cartridges  9 ,  10 ,  11 , and  12  are held in parallel by the cartridge tray  26 . The electrophotographic image forming apparatus is a color image forming apparatus capable of forming a full-color image on recording medium. 
     The sheets of recording paper  14 , which are stored in layers in the feeder tray  13 , are fed out of the feeder tray  13  by the feed roller  15 , which is being rotated in the counterclockwise direction in the drawing, into the main assembly A, and then, is sent to the transfer belt  18 . 
     The photosensitive drums  1 ,  2 ,  3 , and  4  are being rotated in the clockwise direction in the drawing. As they are rotated, an electrostatic latent image is sequentially formed on each of the photosensitive drums  1 ,  2 ,  3 , and  4 , across their peripheral surfaces, by beams of laser light from the laser scanner  25 . Then, the electrostatic latent images are developed by the development rollers  5 ,  6 ,  7 , and  8 , into images formed of toner (which hereafter will be referred to simply as toner images). 
     The toner images are transferred onto the sheet of recording paper  14 . After the transfer of the toner images onto the recording paper  14 , the recording paper  14  is sent to the nip between the fixation film  20  and pressure roller  21 , and is conveyed through the nip. While the recording paper  14  is conveyed through the nip, the recording paper  14  and the toner images thereon are subjected to heat and pressure. As a result, the toner images become fixed to the recording paper  14 . 
     After the fixation of the toner images to the recording paper  14 , the recording paper  14  is discharged into a delivery tray  24  by a pair of discharge rollers  22  and  23 , which make up the recording paper discharging portion of the main assembly A. 
     [General Description of Process Cartridge Replacement Method] 
       FIGS. 1(   b ),  2 ( a ), and  2 ( b ) are sectional views of the first preferred embodiment of the electrophotographic image forming apparatus in accordance with the present invention, which is for describing the method for replacing the process cartridges in the cartridge tray  26 . Next, the method for replacing the process cartridge in this image forming apparatus will be described. 
     The cartridge tray  26  is held to the main assembly A of the image forming apparatus by a tray supporting member  27 , so that it can be slidably moved in a straight line in the horizontal direction in  FIG. 1(   b ). The cartridge tray  26  removably supports the process cartridges  9 ,  10 ,  11 , and  12 . It is enabled to linearly move between its inward position I, that is, its preset position in the main assembly A, and its outward position O, that is, its preset position outside the main assembly A, through the opening B. That is, the cartridge tray  26  is enabled to take the abovementioned inward position I and outward position O by being moved in the direction perpendicular to the lengthwise direction of the process cartridges which are held in parallel by the cartridge tray  26 . More specifically, referring to  FIG. 1 , the inward position I is a position in the main assembly A, and is the position in which the cartridge tray  26  places the process cartridges  9 ,  10 ,  11 , and  12  in their image forming positions. Next, referring to  FIG. 2 , the outward position O is the position outside the main assembly A. Further, the cartridge tray  26  has intermediary electrical contacts, which make electrical contact with the electrical contacts of the process cartridges. The intermediary electrical contacts are enabled to make electrical contact with the electrical contacts, with which the main assembly A is provided. 
     The above-described electrical contacts and the like are on the lengthwise end of the cartridge tray  26 , from which the process cartridges in the tray are not driven. The position of the electrical contacts does not need to be limited to the lengthwise end of the cartridge tray  26 , from which the process cartridges in the tray are not driven. That is, they may be placed on the lengthwise end of the cartridge tray  26 , from which the process cartridge in the tray are driven. Incidentally,  FIG. 3(   a ) shows the cartridge tray  26  and one of the process cartridges, as seen from the side from which the cartridge is driven, whereas  FIG. 3(   b ) shows the cartridge tray  26  and one of the process cartridges, as seen from the side from which the cartridge is not driven, that is, the side where the electrical contacts and the like are present. 
     A door  28  is attached to the main assembly A of the image forming apparatus, and is rotationally movable relative to the main assembly A. It is the member that is to be opened or closed to expose or cover, respectively, the opening B of the main assembly A to carry out such operations as removing jammed paper or the like, or replacing the process cartridge(s).  FIG. 1(   b ) shows the image forming apparatus when the door  28  of the apparatus is open (door  28  is in its open position). The door  28  is indirectly attached to the tray supporting member  27  by the door linkage  29 , so that the door  28  can be rotationally moved relative to the tray supporting member  27 . As the door  28  is opened, the door linkage  29  pulls the tray supporting member  27  out of the main assembly A, and moves the tray supporting member  27  into the tray supporting position, shown in  FIG. 1(   b ), which is right- and upward of the tray supporting member position, which is shown in  FIG. 1(   a ). The movement of this tray supporting member  27  causes the cartridge tray  26  to move upward, whereby the photosensitive drums  1 ,  2 ,  3 , and  4  are separated from the transfer belt  18 . As a result, it becomes possible for the cartridge tray  26  to be pulled out of the main assembly A. 
       FIG. 2(   a ) is a sectional view of the image forming apparatus, the cartridge tray  26  of which is in its outward position O of the main assembly A, into which the cartridge tray  26  was pulled out from the inside of the main assembly A, which was exposed by the opening of the door  28 . When the cartridge tray  26  is in the position shown in  FIG. 2(   a ), the process cartridges  9 ,  10 ,  11 , and  12  in the cartridge tray  26  are exposed upward, being enabled to be removed from the cartridge tray  26  as shown in  FIG. 2(   b ). When the cartridge tray  26  is in the position shown in  FIG. 2(   b ), a stopper claw  84 , which the main assembly A has, is in engagement with (temporarily locked with) a stopper boss  85  ( FIG. 6(   b )), which the cartridge tray  26  has, preventing thereby the cartridge tray  26  from being pulled out further. Referring to  FIG. 6(   b ), the stopper claw  84 , which temporarily locks the cartridge tray  26  in place, has a surface which is tilted in the direction in which the cartridge tray  26  is pulled out of the main assembly A. Therefore, the cartridge tray  26  can be easily unlocked in position by a cartridge tray rotating operation, which will be described later. 
     Next, referring to  FIG. 4(   a ), the main assembly A is provided with a means for temporarily displacing the cartridge tray, which is made up of a rotational shaft  74 , with which the cartridge tray  26  is provided, and a cartridge tray engaging portion  75 , with which the main assembly A is provided. The cartridge tray displacing means will be described later. As the cartridge tray  26  is pulled out of the main assembly A and moved into its outward position O, the rotational shaft  74  of the cartridge tray  26  engages with the cartridge tray engaging portion  75  of the main assembly A. As a result, it becomes possible for the cartridge tray  26  to be rotationally moved about the rotational shaft  74  to be displaced leftward of the opening B. The method for rotationally moving the cartridge tray  26  will be described later in detail. Incidentally, the opening B is the opening with which the main assembly A is provided to store the cartridge tray  26  in the main assembly A. 
     The operation for mounting the process cartridges  9 ,  10 ,  11 , and  12  into the main assembly A is opposite in procedure from the operation for removing the process cartridges from the main assembly A. That is, first, the cartridge tray  26  is to be pulled out of the main assembly A, and moved into its outward position O ( FIG. 2(   b )). Then, the process cartridges  9 ,  10 ,  11 , and  12  are to be placed on the cartridge tray  26  while the cartridge tray  26  is in its outward position O. Then, the cartridge tray  26  is to be put back into the main assembly A. Then, the door  28  is to be closed. As the door  28  is closed, the closing movement of the door  28  causes the door linkage  29  to push the tray supporting member  27  diagonally left- and downward, causing thereby the cartridge tray  26  to move left- and downward. As a result, the process cartridges  9 ,  10 ,  11 , and  12  held by the cartridge tray  26  are moved into their preset positions (image forming positions), in which the photosensitive drums  1 ,  2 ,  3 , and  4  remain in contact with the transfer belt  18 . 
       FIG. 4(   a ) is a perspective views of the main assembly A of the image forming apparatus, the door  28  of which is open, and the cartridge tray  26  of which is in its preset outward position O.  FIG. 4(   a ) shows the same condition of the image forming apparatus as that in  FIG. 2(   b ). When the image forming apparatus is in this condition, the process cartridges  9 ,  10 ,  11 , and  12  can be pulled out of, or mounted into the cartridge tray  26 , and the cartridge tray  26  is rotationally movable. 
     [General Description of Cartridge Tray Rotating Method] 
     Next, referring to  FIGS. 3-7 , the method for rotationally moving the cartridge tray  26  will be described. 
     Referring to  FIG. 6(   a ), this embodiment of image forming apparatus in accordance with the present invention has a guiding member  73 , which is a means for displacing the cartridge tray  26  into a displacement position T ( FIG. 4(   b )) from the area in which the cartridge tray  26  squarely faces the opening B of the main assembly A, after the cartridge tray  26  is moved into its outward position O ( FIG. 4(   a )). 
     The guiding member  73  is a member for guiding the cartridge tray  26  leftward or rightward of the abovementioned opening B, relative to the direction in which the cartridge tray  26  is moved out of, or into, the main assembly A, while keeping the cartridge tray  26  horizontal, after the cartridge tray  26  is moved out of the main assembly A and into its preset outward position O. Incidentally,  FIG. 4(   b ) shows the image forming apparatus structured so that the cartridge tray  26  is displaced leftward (side from which cartridges are not driven; side where electrical contacts are present) of the opening B. 
     Next, referring to  FIG. 6(   a ), the guiding member  73  has the abovementioned rotational shaft  74  and a shaft engaging portion  75 . The rotational axle  74  functions as the rotational axis of the cartridge tray  26 , and the shaft engaging portion  75  engages with the rotational shaft  74 . Next, referring to  FIGS. 3(   a ) and  3 ( b ), the rotational shaft  74  is provided on the same side of the cartridge tray  26  as the side from which the cartridges are not driven. The rotational shaft  74  is in a position in which the rotational shaft  74  does not interfere with the main assembly A, etc., when the cartridge tray  26  is rotationally moved. Next, referring to  FIGS. 4(   a ) and  4 ( b ), the shaft engaging portion  75  is attached to the main assembly A, on the side from which the cartridges are not driven. 
     Referring to  FIG. 4(   a ), as the cartridge tray  26  is pulled out of the main assembly A from its inward position I in the main assembly A through the opening B, and moved into its outward position O, the cartridge tray  26  is temporarily locked in the outward position O by the above described stopper claw  84  and stopper boss  85 . 
     Further, as the cartridge tray  26  is moved into the outward position O, the rotational shaft  74  of the cartridge tray  26  engages with the shaft engaging portion  75  of the main assembly A, whereby the cartridge tray  26  becomes rotatably supported by the main assembly A. The rotational shaft  74  and shaft engaging portion  75  are shaped so that they mesh with each other, as shown in  FIG. 6(   a ). 
     If it is wanted to rotationally move the cartridge tray  26  leftward of the opening B (leftward of main assembly A), the cartridge tray  26  is to be pulled out of the main assembly A, and moved into its outward position O shown in  FIG. 4(   a ). Then, the cartridge tray  26  is to be rotationally moved about the rotational shaft  74  so that the cartridge tray  26  is displaced leftward of the opening B. This operation causes the stopper claw  84  to be pushed up by the stopper boss  85 , causing thereby the cartridge tray  26  unlocked from the outward position O. Thus, it becomes possible for the cartridge tray  26  to be rotationally moved. 
     Referring also to  FIG. 4(   a ), the main assembly A and door  28  are provided with tray bearing surfaces  76 , which bear the weight of the cartridge tray  26 . The tray bearing surfaces  76  function as a means for preventing the cartridge tray  26  from tilting downward after being displaced from the area in which it squarely faces the opening B. That is, not only does the door  28  have the function of keeping the opening B covered, but also, the above described function of preventing the cartridge tray  26  from tilting downward. Thus, as the cartridge tray  26  is rotationally moved, the weight of the cartridge tray  26 , or the combined weight of the cartridge tray  26  and process cartridges, is borne by the tray bearing surfaces  76 , whereby the combined weight is prevented from concentrating upon the rotational shaft  74  and shaft engaging portion  75 . 
     Next, referring to  FIG. 4(   b ), the rotational movement of the cartridge tray  26  is regulated by the contact between the cartridge tray  26 , and the adjacency of the opening B of the main assembly A. Further, the cartridge tray  26  is provided with a tray locking member  92 , which is for temporarily locking the cartridge tray  26  in the displacement position. Thus, as the cartridge tray  26  is rotationally moved into its displacement position, the tray locking member  92  temporarily engages with the main assembly A, through an engagement process, which will be described later. 
     Referring also to  FIG. 5(   b ), the cartridge tray  26  is provided with a tray supporting member  90 , which supports the cartridge tray  26  when the cartridge tray  26  is in its displacement position. The tray supporting member  90  is a part of the cartridge tray  26 . When the cartridge tray  26  is in the outward position O, it remains retracted. It is movable into the position, shown in  FIG. 5(   a ), when the cartridge tray  26  is out of the area in which it faces the opening B. As the tray supporting member  90  is moved into the position shown in  FIG. 5(   b ), the cartridge tray  26  is prevented from tilting downward, by the surface on which the electrostatic image forming apparatus is sitting. 
     Moving the cartridge tray  26  into its displacement position (shown in  FIG. 4(   b )), which is away from the area in which the cartridge tray  26  squarely faces the opening B, makes it possible to carry out such operations as taking care of the paper jam or the like in the main assembly A through the opening B. 
     Next, referring to  FIGS. 5(   a ) and  5 ( b ), the locking means for temporarily locking the cartridge tray  26  in the abovementioned displacement position will be described. 
       FIG. 5(   a ) is a sectional view of the cartridge tray  26  which is remaining temporarily locked in the displacement position by the tray locking member  92  after being rotationally moved into the displacement position. 
     Referring to  FIG. 5(   a ), the cartridge tray  26  has the tray locking member  92  described above, and a tray handle  93  which is used for the operation for rotational moving the cartridge tray  26 . It is also provided with a connective member  91 , the movement of which causes the tray locking member  92  and handle  93  to move together. As for the main assembly A, it has a tray locking member engaging portion  95 , which is positioned so that as the cartridge tray  26  is moved into the displacement position, it engages with the tray locking member  92 . 
     Referring also to  FIG. 5(   a ), the cartridge tray  26  is provided with a tray lock spring  94 , which keeps the tray locking member  92  pressured upward of the main assembly A (direction indicated by arrow mark in  FIG. 5(   a )). Further, the cartridge tray  26  is provided with a handle spring  96 , which keeps the tray handle  93  pressured rightward (direction indicated by arrow mark in  FIG. 5(   a )). 
     Referring also to  FIG. 5(   a ), in order to ensure that when the tray handle  93  is not operated, that is, when the tray handle  93  is not moved leftward in  FIG. 5(   a ), the tray locking member  92  remains in its bottom position, the handle spring  96  is made greater in resiliency than the tray lock spring  94 . Therefore, as the tray handle  93  is released, the connective member  91  is moved rightward in  FIG. 5(   a ), whereby the tray locking member  92  is moved downward by the connective member  91 . Thus, as the cartridge tray  26  is rotationally moved into the displacement position, the cartridge tray  26  becomes temporarily locked in the displacement position. 
       FIG. 5(   b ) is a side view of the portions of the cartridge tray  26 , which are essential to the present invention, after the operation of the tray handle  93 , that is, after the completion of the leftward movement (in  FIG. 5(   b )) of the tray handle  93 . 
     Referring to  FIG. 5(   b ), after the completion of the leftward movement of the tray handle  93 , the connective member  91  is movable in the leftward in  FIG. 5(   b ). As the linking member  91  is moved leftward, the tray locking member  92  is allowed to be moved upward of the main assembly A by the resiliency of the tray locking spring  94 . As a result, the cartridge tray  26  becomes unlocked. 
     If it is wanted to return the cartridge tray  26  from the displacement position T to the outward position O, the cartridge tray  26  is to be rotated about the rotational shaft  74  in the direction opposite from the abovementioned direction. As the cartridge tray  26  is rotated in the opposite direction, the cartridge tray  26  moves back into the outward position O, from which the cartridge tray  26  can be moved back into its preset position I (image forming position) in the main assembly A, and the stopper boss  85  of the cartridge tray  26  engages with the stopper claw  84  of the main assembly A. 
     When the cartridge tray  26  is rotationally moved back into the outward position O, the tray handle  93  is moved in the direction indicated by the arrow mark in  FIG. 5(   a ). Therefore, the tray locking member  92  moves upward relative to the main assembly A, making it possible for the cartridge tray  26  to be rotationally moved. Further, also when the cartridge tray  26  is moved back from the outward position O into the inward position I (image forming position) in the main assembly A, the tray handle  93  is moved in the direction (leftward) indicated by the arrow mark in  FIG. 5(   a )). Therefore, the tray locking member  92  is allowed to move upward. Therefore, it does not occur that the tray locking member  92  hinders the movement of the cartridge tray  26 . 
     Referring to  FIG. 5(   b ), the tray supporting member  90  can be folded back to one of the lateral walls of the cartridge tray  26  so that it becomes roughly parallel to the lateral wall. Thus, as the cartridge tray  26  is moved back into its inward position I (image forming position) in the main assembly A from the outward position O, the tray supporting member  90  is stored in the tray supporting member  27 . 
     As described above, in this embodiment of the present invention, after the cartridge tray  26  is moved from its inward position I to its outward position O, it can be rotationally moved about the rotational shaft  74 , while remaining supported by the main assembly A, so that it can be displaced away from the area in which it squarely faces the opening B. Therefore, the operational space for taking care of paper jam or the like in the main assembly A can be created without disengaging the cartridge tray  26  from the main assembly A. That is, this embodiment of the present invention can improve an electrophotographic image forming apparatus in usability. 
     Embodiment 2 
     Next, referring to  FIGS. 8-10 , the second preferred embodiment of an image forming apparatus in accordance with the present invention will be described. This embodiment of image forming apparatus is structured so that after the cartridge tray  26  is pulled out of its inward position I (preset inward position) in the main assembly A and moved into its outward position O, it can be vertically moved upwardly out of the area (outward position O), in which it squarely faces the aforementioned opening B, while remaining horizontal. Hereafter, the method for moving the cartridge tray  26  in this embodiment will be described. 
       FIG. 8(   a ) is a sectional view of the image forming apparatus when the cartridge tray  26  of the apparatus is in its outward position O. The image forming apparatus in this embodiment also has a tray guiding member  76  shown in  FIG. 8(   a ), which is a means for displacing the cartridge tray  26  into a displacement position T ( FIG. 10)  from the area in which the cartridge tray  26  squarely faces the opening B of the main assembly A, after the cartridge tray  26  is moved into its outward position O ( FIG. 8(   a )), as does the counterpart the first preferred embodiment. 
     The tray guiding member  76  is a member for displacing the cartridge tray  26  straight upward or downward of the abovementioned opening B, from the area in which it squarely faces the opening B, after the cartridge tray  26  is moved into its preset outward position O. Incidentally, the image forming apparatus in this embodiment is an example of an image forming apparatus, which is structured so that the cartridge tray  26  is displaced in the upward direction of the opening B. 
     Next, referring to  FIG. 8(   a ), the tray guiding member  76  has a pair of auxiliary rails  77 , and rail linkages  78 . The auxiliary rails  77  are the rails for supporting the cartridge tray  26  in such a manner that the cartridge tray  26  can be moved from the inward position I in the main assembly A to the outward position O. The tray linkages  78  are linkages for upwardly displacing the cartridge tray  26  from the auxiliary rails  77 , that is, from the area in which the cartridge tray  26  squarely faces the opening B. 
     Referring to  FIG. 8(   a ), as the cartridge tray  26  is pulled out of the main assembly A, the auxiliary rails  77  and tray linkages  78  are pulled out of the main assembly A along with the cartridge tray  26 . There are a total of four tray linkages  78 . More specifically, the two tray linkages  78  are on the side from which the process cartridges on the cartridge tray  26  are not driven, and are connected to one of the auxiliary rails  77 , whereas the other two tray linkage  78  are on the side from which the process cartridges on the cartridge tray  26  are driven, and are connected to the other auxiliary rail  77 . Each auxiliary rail  77  and corresponding tray linkages  78  are connected to each other with auxiliary rail bosses  79 . The cartridge tray  26  and each tray linkage  78  are connected to each other with a tray boss  80 . Further, the auxiliary rails  77  are attached to the main assembly A so that they cannot be pulled out the main assembly A beyond the auxiliary rail position shown in  FIG. 8(   a ). 
     Next, referring to  FIG. 8(   b ), the main assembly A is provided with a pair of locking members  82  for locking the auxiliary rails  77  in the outward positions for the auxiliary rails  77  after the auxiliary rails  77  are pulled out of the main assembly A along with the cartridge tray  26 . Each locking member  82  is positioned so that before the cartridge tray  26  is moved upward, the position of the locking member  82  coincides with that of the inward end of the inward tray linkage  78 . Further, each locking member  82  is kept pressured upward by a locking spring  83 . When the auxiliary rails  77  and cartridge tray  26  are in their outermost positions, the tray linkages  78  and the weight of the cartridge tray  26  itself prevents the locking member  82  from being made to protrude upward by the locking spring  83 .  FIG. 8(   b ) shows in detail how the locking member  82  is being prevented from protruding. 
     If it is necessary to move the cartridge tray  26  from its outward position O to the displacement position T, which is on the upward side of the opening B, all that is necessary is to pull the cartridge tray  26  in the same direction as the direction in which the cartridge tray  26  is to be pulled to be moved out of the main assembly A and placed in the outward position O. As the cartridge tray  26  is pulled as described above, it moves into the above described displacement position T. More specifically, referring to  FIG. 9(   a ), as the cartridge tray  26  is pulled as described above, the tray linkages  78  rotate in the clockwise direction about the auxiliary rail bosses  79 . The movement of the cartridge tray  26  is regulated by the contact between a linkage guide  81  (regulating means), with which each auxiliary rail  77  is provided, and the corresponding tray linkage  78 . Further, while the tray linkages  78  are in contact with the linkage guides  81 , the cartridge tray  26  remains temporarily locked in the displacement position T by a linkage claw  86  (engaging means), being prevented from returning to the outward position O. 
     Next, referring to  FIG. 9(   b ), as the cartridge tray  26  is moved into the displacement position T, the locking members  82  are allowed to be made to upwardly protrude by the locking springs  83 , and engage with the auxiliary rails  77 . Therefore, the auxiliary rails  77  are prevented from moving back into the main assembly A.  FIG. 9(   b ) shows in detail the portions of the image forming apparatus, which are related to the control of the auxiliary rails  77  by the locking members  82 . 
       FIG. 10  is a perspective view of the image forming apparatus when the cartridge tray  26  of the apparatus is in its displacement position T, into which it was displaced after being pulled out to its outward position O. Upwardly displacing the cartridge tray  26  from the area in which the cartridge tray  26  squarely faces the opening B makes it possible to carry out such an operation as taking care of paper jam or the like through the opening B without disengaging the cartridge tray  26  from the main assembly A. 
     Further, the portion of the linkage claw  86 , which actually locks the tray linkage  78 , is slanted. Therefore, the tray linkages  78  can be unlock by pushing the cartridge tray  26  toward the main assembly A with a proper amount of force. In other words, when the cartridge tray  26  is in the abovementioned displacement position T, it can be returned to the outward position O by pushing the cartridge tray  26  toward the main assembly A with a reasonable amount of force. 
     As described above, in this embodiment, the cartridge tray  26  is attached to the auxiliary rails  77  with the tray linkages  78 . When it is necessary to carry out such an operation as taking care of the paper jam or the like, the cartridge tray  26  is upwardly moved away, while being kept parallel to the main assembly A by the tray linkages  78 , from the area in which it squarely faces the opening B, after it is moved from the inward position I in the main assembly A to the outward position O. Therefore, the operational space for taking care of the paper jam or the like in the main assembly A can be created without removing the cartridge tray  26  from the main assembly A. In other words, this embodiment also can improve an electrophotographic image forming apparatus in usability. 
     Miscellaneous Embodiments 
     In the first preferred embodiment, the image forming apparatus was structured to support the cartridge tray so that the cartridge tray can be moved out of the area, in which it squarely faces the opening B, in the leftward direction after being moved from the inward position I to the outward position O. This embodiment, however, is not intended to limit the present invention in terms of the direction in which the cartridge tray is to be moved out of the area in which it squarely faces the opening B. That is, even if an image forming apparatus is structured so that the cartridge tray can be moved out of the area, in which it squarely faces the opening B, in the rightward direction, after being pulled out of the main assembly A, the same effects as those described above can be achieved. 
     Also in the first preferred embodiment, the image forming apparatus was structured so that the cartridge tray is provided with the rotational shaft, about which the cartridge tray can be rotationally moved, and the means for displacing the cartridge tray away from the area in which the cartridge tray squarely faces the opening B, after the cartridge tray is moved from the inward position to the outward position, whereas the main assembly is provided with the tray locking member engaging portion. However, this embodiment of the present invention is not intended to limit the present invention in scope. That is, an electrophotographic image forming apparatus may be structured so that the main assembly is provided the means for displacing the cartridge tray away from the abovementioned area, and the cartridge tray is provided with the tray locking member engaging portion. Such a structural arrangement can also provide the same effects as those achieved by the first preferred embodiment. 
     Further, in the second preferred embodiment described above, the image forming apparatus was structured so that the cartridge tray was supported to allow the cartridge tray to be upwardly displaced after being moved from the inward position to the outward position. This embodiment, however, is not intended to limit the present invention is scope. That is, an electrostatic image forming apparatus may be structured so that the cartridge tray can be downwardly displaced from the area in which it squarely faces the opening B, after being pulled out of the main assembly A and moved into the outward position. Such a structural arrangement also can provide the same effects as those described above. 
     Further, in the preceding preferred embodiments described above, the process cartridges were removably mountable in the main assembly of the image forming apparatus. The preceding embodiments, however, are not intended to limit the present invention in scope. That is, the present invention is also applicable to electrophotographic image forming apparatuses structured so that process cartridges are removably mountable in the cartridge supporting member which is movably supported by the main assembly. Further, the process cartridges in the preceding embodiments were such process cartridges that have a photosensitive drum, a development roller, etc. However, the preceding embodiments are not intended to limit the present invention in terms of the process cartridge design. That is, the present invention is applicable to any process cartridge which integrally comprises an electrophotographic photosensitive drum, and one or more processing means which process the electrophotographic photosensitive drum, and which are removably mountable in the main assembly of an electrophotographic image forming apparatus. More concretely, all that is necessary for the present invention to be applicable to a given process cartridge is that the process cartridge is made up of an electrophotographic photosensitive drum, at least one among the abovementioned processing means, that is, the developing means, charging means, and cleaning means, and a cartridge (shell) in which the photosensitive drum and processing means are integrally placed. 
     Further, in the preceding embodiments, the image forming apparatuses used four removably mountable process cartridges. However, the preceding embodiments are not intended to limit an image forming apparatus in the number of process cartridges. That is, the present invention is applicable regardless of the process cartridge count. 
     Further, in the preceding embodiments of the present invention, the image forming apparatuses were printers. However, the preceding embodiments are not intended to limit the present invention in terms of image forming apparatus type. That is, not only is the present invention applicable to various printers, but also, image forming apparatuses other than printers, that is, copying machines, facsimile apparatuses, multi-functional image forming apparatuses capable of performing two or more functions of the preceding apparatuses. Further, the image forming apparatuses in the preceding preferred embodiments were those which uses a transfer belt as their recording medium, and which sequentially transfer in layers toner images, different in color, onto the transfer belt. However, the preceding embodiments are not intended to limit the application of the present invention to those in the preceding embodiments. That is, the present invention is also applicable to image forming apparatuses which use an intermediary transfer member, transfer toner images, different in color, onto the intermediary transfer member, and transfer all at once the toner images from the intermediary transfer member, onto final recording medium. The effects similar to those described above can be achieved by the application of the present invention to the cartridge supporting member of any of these image forming apparatuses. Further, the recording medium may be OHP sheets, labels, etc., in addition to sheets of recording paper. 
     While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth, and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims. 
     This application claims priority from Japanese Patent Applications Nos. 249590/2008 and 191927/2009 filed Sep. 29, 2008 and Aug. 21, 2009, respectively, which are hereby incorporated by reference.