Patent Publication Number: US-8116660-B2

Title: Image forming apparatus

Description:
FIELD OF THE INVENTION AND RELATED ART 
     The present invention relates to an image forming apparatus, to which a cartridge is detachably mountable, for forming an image on a recording material (medium). 
     The image forming apparatus includes, e.g., those of an electrophotographic type, an electrostatic recording type, a magnetic recording type, and the like, such as a copying machine, a printer (a laser beam printer, an LED printer, or the like), a facsimile machine, a word processor, and the like. 
     The cartridge includes at least one of an image bearing member on which a latent image is to be formed and a developing means for developing the latent image formed on the image bearing member with a developer and is detachably mountable to an apparatus main assembly. The apparatus main assembly is a portion of the image forming apparatus except the cartridge and a movable member for moving the cartridge. The cartridge is mountable to and demountable from the apparatus main assembly by a user himself (herself). For that reason, maintenance of the apparatus main assembly can be easily performed. 
     The image bearing member is a member on which the latent image (such as an electrostatic latent image, a potential latent image, a resistance latent image, or a magnetic latent image) is to be developed with the developer is formed. Examples of the image bearing member may include an electrophotographic photosensitive member (photoconductor) in an electrophotographic process, an electrostatic recording dielectric member in an electrostatic recording process, and a magnetic recording magnetic member in a magnetic recording process. 
     As an exchanging method of the cartridge with respect to the apparatus main assembly of the image forming apparatus, U.S. Pat. No. 5,608,498 discloses the following constitution. That is, a cartridge  30  is supported through a guide member  70  capable of elongating and contracting in two steps with respect to an ascending/descending board  61  which is moved forward and backward and up and down in interrelation with a side surface cover  80 . The cover  80  is opened to raise and move the cartridge  30  from an image forming position (I) to a pull-out position (II), and then the cartridge  30  is directly pulled out. By the pulling-out, the cartridge  30  is optionally moved to a position including a stopping position (III) so as to perform mounting/demounting of each device and jammed paper processing. 
     Further, U.S. Patent Application Publication No. 2007/0147890 discloses a constitution in which a plurality of cartridges is supported by a movable member movable with respect to the apparatus main assembly. According to this constitution, by inserting the movable member into the apparatus main assembly, the plurality of cartridges can be inserted simultaneously into the apparatus main assembly. Further, the movable member is pulled out from the apparatus main assembly and then a desired cartridge can be demounted from the member and can be replaced with a fresh cartridge. 
     SUMMARY OF THE INVENTION 
     The present invention have further developed the above-described conventional constitutions. 
     A principal object of the present invention is to improve usability in a cartridge exchange constitution and to improve operativity of maintenance such as jam clearance. 
     According to an aspect of the present invention, there is provided an image forming apparatus for forming an image on a recording material, comprising: 
     a cartridge including at least one of an image bearing member on which a latent image is to be formed and developing means for developing with a developer the latent image formed on the image bearing member; 
     a main assembly including a positioning portion for positioning the cartridge and an urging member for urging the cartridge so that the cartridge is positioned to the positioning portion; 
     a movable member movable, with respect to the main assembly in a state in which the movable member supports the cartridge, between a pulled-out position in which the movable member is pulled out to an outside of the main assembly to position the cartridge outside the main assembly and an inside position in which the cartridge is positioned inside the main assembly; and 
     a grip member, which is mounted to the movable member and which is to be gripped for pulling out the movable member, movable between a reference position and an outward position located outwardly the reference position with respect to a pull-out direction in which the movable member is pulled out from the inside position to the pulled-out position; 
     wherein in a state in which the movable member is located at the inside position, the cartridge is positioned to the positioning portion by the urging member to be placed in a positioning state when the grip member is located at the reference position, and 
     wherein in the state in which the movable member is located at the inside position, the positioning state of the cartridge is released by moving the grip member from the reference position to the outward position. 
     These and other objects, features and advantages of the present invention will become more apparent upon a 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 
         FIG. 1  is a perspective view of an outer appearance of an image forming apparatus in Embodiment 1. 
         FIG. 2  is a longitudinal left side view of the image forming apparatus. 
         FIG. 3  is a perspective view of an outer appearance of the image forming apparatus in a state in which a front door is opened. 
         FIG. 4  is a perspective view of an outer appearance of the image forming apparatus in a state in which the front door is opened and then a grip member of a tray is rotated forward to be placed in an opened state. 
         FIG. 5  is a longitudinal left side view of the image forming apparatus shown in  FIG. 4 . 
         FIG. 6  is a perspective view of an outer appearance of the image forming apparatus in a state in which the tray is pulled out from the state shown in  FIG. 4 . 
         FIG. 7  is a longitudinal left side view the image forming apparatus shown in  FIG. 6 . 
         FIG. 8(   a ) is an outer appearance perspective view of a cartridge as seen from a driving side and  FIG. 8(   b ) is an outer appearance perspective view of the cartridge as seen from a non-driving side. 
         FIG. 9  is an outer appearance perspective view of the tray. 
         FIGS. 10(   a ) and  10 ( b ) are schematic views for illustrating an outer surface portion of a left side tray holding member. 
         FIG. 11  is an outer appearance perspective view of left and right tray holding members, a left side interrelating mechanism, and the tray place in a state in which the grip member is in a closed state. 
         FIG. 12  is an outer appearance perspective view of the left and right tray holding members, the left side interrelating mechanism, and the tray placed in the state in which the grip member is in the opened state. 
         FIGS. 13(   a ),  13 ( b ) and  13 ( c ) are partly enlarged views each for illustrating the left side interrelating mechanism. 
         FIGS. 14(   a ),  14 ( b ) and  14 ( c ) are schematic views each for illustrating movement of the tray holding member in interrelation with rotational movement of the grip member. 
         FIGS. 15(   a ) and  15 ( b ) are schematic views for illustrating a tray movement preventing means (a pin and a U-shaped groove portion). 
         FIGS. 16 ,  17 , and  18 ( a ) and  18 ( b ) are schematic views each for illustrating interface portions, located adjacent to the cartridge, for releasing pressure application to and engagement with the cartridge in interrelation with the tray holding member. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiment 1 
     General Structure of Image Forming Apparatus 
       FIG. 1  is a perspective view of an outer appearance of an image forming apparatus  100  in this embodiment, and  FIG. 2  is a longitudinal left side sectional view of the image forming apparatus  100 . The image forming apparatus  100  is a four color-based full-color electrophotographic laser printer using an electrophotographic process. That is, the image forming apparatus  100  forms an image on a recording material (hereinafter referred to as a sheet) S on the basis of an electrical image signal input from an external host device (not shown) such as a personal computer, an image reader, or a remote facsimile machine into a control circuit portion (not shown). 
     In the following description, a front side (front surface side) of the image forming apparatus  100  means the side on which an apparatus opening/closing door (front door or openable door)  31  is provided. A rear side of the image forming apparatus  100  is the side opposite to the front side. A front-rear direction includes a frontward direction toward front as seen from the rear side of the image forming apparatus  100  and a rearward direction opposite to the frontward direction. The left and right sides means the left and right sides as seen from the front side of the image forming apparatus  100 . A left-right direction includes a leftward direction toward left as seen from the front side and a rightward direction opposite to the leftward direction. 
     In an apparatus main assembly  100 A of the image forming apparatus  100 , four (first to fourth) process cartridges P (PY, PM, PC and PK) are horizontally arranged in the listed order in terms of the rear-to-front direction (inline or tandem arrangement). The four cartridges have the same constitution except that colors of developers (toners) accommodated therein are different from each other. Each cartridge in this embodiment includes an electrophotographic photosensitive drum  1  as an image bearing member and further includes a charging device  2 , developing device  3 , and a cleaning device  4  which are used as image forming process means acting on the drum  1 . Further, each cartridge is prepared by integrally mounting the above-described drum  1 , the charging device  2 , the developing device  3 , and the cleaning device  4  in a cartridge frame  5 . The charging device (charging means)  2  in this embodiment is a contact charging roller. The developing device (developing means)  3  includes a developing roller  3   a  and a developer container in which the developer (toner) is accommodated. The cleaning device (cleaning means)  4  is of a blade type. 
     The developing device  3  of the first cartridge PY stores yellow (Y) toner. On the surface of the drum  1  of the cartridge PY, a toner (developer) image of yellow (Y) is formed. The developing device  3  of the second cartridge PM stores magenta (M) toner. On the surface of the drum  1  of the cartridge portion PM, a toner image of magenta (M) is formed. The developing device  3  of the third cartridge PC stores cyan (C) toner. On the surface of the drum  1  of the cartridge PC, a toner image of cyan (C) is formed. The developing device  3  of the fourth cartridge PK stores black (K) toner. On the surface of the drum  1  of the cartridge PK, a toner image of black (K) is formed. 
     In the area above the first to fourth cartridges PY, PM, PC, and PK, a laser scanner unit  11  is disposed. This scanner unit  11  outputs a beam of laser light modulated correspondingly to image (picture) information for each color input from the external host device. The output laser light enters each cartridge through an exposure window  6  provided at an upper surface of the cartridge frame  5 . Thus, laser scanning exposure is performed on the surface of the drum  1 . 
     A belt unit  12  is disposed below the cartridges PY, PM, PC, and PK. The belt unit  12  includes an endless belt  13  having flexibility, a driving roller  14 , a follower roller  15 , an auxiliary roller  16 , and a tension roller  17  around which the belt  13  is stretched and circulatively moved. The driving roller  14  and tension roller  17  are disposed on the front side of the apparatus main assembly  100 A. The follower roller  15  and the auxiliary roller  16  are disposed on the rear side of the apparatus main assembly  100 A. A lower surface of the drum  1  of each cartridge P contacts an upper surface of an upper belt portion of the belt  13 . Inside the belt  13 , four transfer rollers  18  are disposed. Each transfer roller  18  is disposed opposite to the drum  1  of the corresponding cartridge P through the upper belt portion of the belt  13 . 
     Below the belt unit  12 , a sheet feeding unit  19  is disposed, which includes a sheet feeding tray  20 , a sheet feeding roller  21 , and a separation pad  22 , and the like. The sheet feeding tray  20  is detachably mountable in the apparatus main assembly  100 A from the front side of the image forming apparatus  100  (front loading). 
     At an upper portion on the rear side of the apparatus main assembly  100 A, a fixing device  24  and a sheet discharging roller pair  25  are disposed. Further, at an upper surface of the apparatus main assembly  100 A, a sheet discharging tray  27  is provided. The fixing device  24  includes a fixation film assembly  24   a  and a pressing roller  24   b . The sheet discharging roller pair  25  includes sheet discharging rollers  25   a  and  25   b.    
     Each cartridge P placed in a state in which it is set at a set position in the apparatus main assembly  100 A is urged by an urging member (described later) to be held in a state in which each cartridge P is fixed (locked) to a predetermined positioning portion. To a drive input portion of each cartridge P, a drive output portion of the apparatus main assembly  100 A is connected. Further, to electrical contacts of each cartridge P, an electric energy supplying system of the apparatus main assembly  100 A is electrically connected. 
     An operation for forming a full-color image is as follows. With predetermined control timing, the drum  1  of each of the respective cartridges PY, PM, PC and PK is rotationally driven at the predetermined speed in the clockwise direction indicated by the arrow. Further, the belt  13  is rotationally driven in the counterclockwise direction indicated by an arrow (the (normal) rotational direction of the drum  1 ) at a speed which corresponds to the speed of the drum  1 . The scanner unit  11  is also driven with predetermined control timing. In synchronization with the driving of the scanner unit  11 , the charging roller  2  in each cartridge P uniformly electrically charges the surface of the drum  1  to predetermined polarity and potential with predetermined control timing. The scanner unit  11  scans (exposes) the surface of each drum  1  with the beam of laser light modulated correspondingly to the picture (image) signal for an associated color. As a result, an electrostatic latent image corresponding to the picture signal for the associated color is formed on the surface of the drum  1 . The thus formed electrostatic latent image is developed by the developing device  3  into a toner image. 
     Through the above described electrophotographic image forming process operation, a yellow toner image, which corresponds to the yellow (Y) color component of a full-color image is formed on the drum  1  of the first cartridge PY. On the drum  1  of the second cartridge PM, a magenta (M) toner image, which corresponds to the magenta component of the full-color image is formed. On the drum  1  of the third cartridge PC, a cyan (C) toner image, which corresponds to the cyan component of the full-color image is formed. On the drum  1  of the fourth cartridge PK, a black (K) toner image, which corresponds to the black component of the full-color image is formed. 
     Meanwhile, the sheet feeding roller  21  is driven with predetermined control timing. As a result, sheets S (recording material) stacked on the sheet feeding tray  20  are separated and fed one by one by cooperation of the sheet feeding roller  21  and the separation pad  22  to be introduced into a nip between registration roller pair  26   a  and  26   b . The sheet S is stopped in the nip between the registration roller pair  26   a  and  26   b  at its leading end to be subjected to oblique movement correction. Then, with predetermined control timing, the registration roller pair  26   a  and  26   b  is driven, so that the sheet S is sent to a nip between the belt  13  and an electrode roller  23  disposed oppositely to the driving roller  14  of the belt unit  12  with respect to the belt  13 . The sheet S is electrostatically held on the surface of the upper-side belt portion of the belt  13  and is conveyed from the front side to the rear side in the apparatus main assembly  100 A. That is, the sheet S is conveyed while successively passing through positions (transfer portions) of respective transfer rollers  18  of the fourth cartridge PY, the third cartridge PC, the second cartridge PM, and the first cartridge PY. As a result, onto the surface of the sheet S, the black (K) toner image, a the cyan (C) toner image, the magenta (M) toner image, and the yellow (Y) toner image are successively transferred in a predetermined superposition manner. Thus, on the surface of the sheet S conveyed by the belt  13 , unfixed full-color toner image of four colors of K, C, M and Y are synthetically formed. 
     In each cartridge P, untransferred toner remaining on the drum  1  surface after the transfer of the toner images onto the sheet S is removed by the cleaning device  4 . 
     The sheet S having passed through the transfer portion of the last cartridge (first cartridge) PY is separated from the surface of the belt  13  at a position of the follower roller  15  and is then guided by a guide  27  to be introduced into the fixing device  24 . The sheet S is subjected to heat and pressure in a fixation nip of the fixing device  24 . As a result, color mixing of the respective color toner images and fixation thereof on the sheet S are performed. Thereafter, the sheet S is moved out of the fixing device  24 , and then is discharged as a full-color image formation product onto the sheet discharge tray  27  by a sheet discharge roller pair  25 . 
     (Cartridge Exchange) 
     As each cartridge (PY, PM, PC, PK) is used for image formation, the developer (toner) stored in the developing device  3  is consumed. Then, when the developer is consumed to such an extent that an image of a quality satisfactory to a user who has purchased the cartridge cannot be formed, the exchange of the cartridge  3  is required. 
     For this reason, e.g., the image forming apparatus is provided with a means (not shown) for detecting an amount of the developer remaining in each cartridge. The detected amount of the developer in each cartridge is compared, by the control circuit portion, with a threshold value preset for providing a prewarning or warning of the lifetime of the cartridge. When the detected amount of the residual developer in the cartridge is smaller than the preset threshold value, the prewarning or warning of the lifetime of the cartridge is displayed on a display portion (not shown). As a result, the image forming apparatus prompts the user to prepare a cartridge for exchange, or to replace the cartridge with a fresh cartridge, in order to maintain an output image quality. 
     In this embodiment, the exchange (replacement) of the cartridge with respect to the image forming apparatus is performed through a method in which the cartridge P is placed on a cartridge tray  35  as a pull-out type frame-like movable member and is replaced in a front-access manner in order to improve usability. 
     On the front side of the apparatus main assembly  100 A, an opening  30  through which the tray  35  (cartridge P) passes when the cartridge P is pushed in the inside of the apparatus main assembly  100 A or is pulled out from the apparatus main assembly  100 A is provided. 
     Further, on the front side of the apparatus main assembly  100 A, a rotatable and openable door  31  is provided. This door  31  is an openable member locatable at a closed position in which the opening  30  is covered with the door  31  and at an open position in which the opening  30  is exposed. 
     In this embodiment, the door  31  can be opened and closed and can be rotationally moved relative to the apparatus main assembly  100 A about a hinge position  31   b  provided at a lower portion of the door  31 . That is, the door  31  is rotated about the hinge portion  31   b  so that it can be moved into the closed position (roughly vertical position) to place the opening  30  in a closed state as shown in  FIGS. 1 and 2 , and also, so that it can be rotated frontward about the hinge portion  31   b  into the open position (roughly horizontal position), as shown in  FIG. 3 , to place the opening  30  in an opened state. To the door  31 , a holding portion (finger placement portion)  31   a  for opening/closing the door  31  is provided. 
     The door  31  is also opened during maintenance for jam clearance or the like in addition to the cartridge exchange specifically described later. After the jam clearance, when the door  31  is closed, the cartridge is still urged against the apparatus main assembly by the urging member. Therefore, there is no need to adjust (correct) color misregistration. 
     Inside left and right frames  80 L and  80 R of a main frame  80  of the apparatus main assembly  100 A, a pair of left and right tray holding members (movable means or rail members)  34 L and  34 R is disposed, respectively. These tray holding members  34 L and  34 R oppose each other. A longitudinal (lengthwise) direction of each of the tray holding members  34 L and  34 R coincides with the front-rear direction of the apparatus main assembly  100 A. Between the left and right tray holding members  34 L and  34 R, the tray  35  is held horizontally slidably in the front-rear direction of the apparatus main assembly  100 A. The tray  35  supports each cartridge P. That is, the tray  35  includes mounting portions to which the plurality of cartridges PY, PM, PC and PK are detachably mountable. 
     To a front frame  35   b  of the tray  35 , a grip member  36  which is shaft-supported rotatably and is capable of being rotated forward (forward rotation) and rotated backward (backward rotation) is provided. In this embodiment, the grip member  36  can be rotated about a shaft-supporting portion to be placed in a closed state (a reference position) in which the grip member  36  is erected substantially vertically to face (contact) the front surface of the front frame portion of the tray  35  as shown in  FIGS. 2 and 3 . Further, the grip member  36  can be rotated about the shaft-supporting portion to be placed in an opened state (an outward position) in which the grip member is tilted forward substantially horizontally from the front surface of the front frame  35   b  of the tray  35  as shown in  FIGS. 4 and 5 . In this embodiment, the forward rotation of the grip member  36  means an operation for rotating the grip member  36  substantially 90 degrees from the above-described closed state to the above-described opened state (forward rotation with a predetermined rotation angle). On the other hand, the backward rotation of the grip member  36  means an operation for rotating the grip member substantially 90 degrees from the opened state to the closed state (backward rotation with a predetermined rotation angle). 
     An operation for exchanging the cartridge is as follows. The door  31  which covers the opening  30  of the apparatus main assembly  100 A as shown in  FIGS. 1 and 2  is opened as shown in  FIG. 3 . As a result, the opening  30  is exposed considerably, so that the front frame  35   b  of the tray  35  is also exposed. At this time, the grip member  36  located on the front side of the front frame  35   b  is in the closed state. The user grips a grip portion  36   a  of the grip member  36  and rotates 90 degrees forward the grip member  36 , thus placing the grip member  36  in the opened state in which the grip member  36  is substantially horizontally located. In this case, by an interrelating mechanism described later operating in interrelation with the forward rotation of the grip member  36 , the tray holding members  34 L and  34 R are moved by a predetermined distance. That is, the tray holding members  34 L and  34 R are moved from a first position to a second position. Here, the first position is a position of the tray holding members  34 L and  34 R in which the tray  35  (cartridge P) is moved to a transfer contact position (inside position) shown in  FIG. 2 , and the second position is a position of the tray holding members  34 L and  34 R in which the tray  35  is moved between a pushed-in position ( FIG. 5 ) and a pulled-out position ( FIGS. 6 and 7 ) with respect to the apparatus main assembly  100 A. The pushed-in position is a position in which the tray  35  is pushed in the inside of the apparatus main assembly  100 A until the tray  35  runs against and is stopped by a stopper portion (not shown) provided to the tray holding members  34 L and  34 R. The pulled-out position is a position in which the tray  35  is pulled out to the outside of the apparatus main assembly  100 A and each cartridge P is detachably mountable to the above-described mounting portion. 
     In interrelation with the upward movement of the tray holding members  34 L and  34 R, drive output portions on the apparatus main assembly side are disengaged from corresponding drive input portions of each of the cartridges PY, PM, PC and PK (driven portion disengagement). Further, the urging by the urging member which positions and fixes (locks) each cartridge with respect to the positioning portion of the apparatus main assembly  100 A is released (urging release or locking release). Further, electrical conduction of the electric energy supplying system on the apparatus main assembly  100 A side to the electrical contacts of each cartridge is ceased (electrical disconnection). Further, the positioning of the tray  35  with respect to the apparatus main assembly  100 A is released. These are also described specifically later. 
     As described above, when the tray holding members  34 L and  34 R are moved from the first position to the second position, the tray  35  and each cartridge P are also moved upward together with the tray holding members  34 L and  34 R, so that the drum  1  is separated from the belt  13  ( FIG. 5 ). That is, the tray  35  is moved from the transfer contact position (inside position shown in  FIG. 2 ) in which the drum  1  and the belt  13  contact each other to the transfer separation position (pushed-in position) ( FIG. 5 ) in which the drum  1  and the belt  13  are separated from each other. 
     Then, the grip member  36  placed in the opened state is gripped and the tray  35  is slid along the tray holding members  34 L and  34 R so as to be pulled out, thus being slidably moved horizontally and frontward. Then, as shown in  FIGS. 6 and 7 , the tray  35  is sufficiently pulled out through the opening  30  to a predetermined pulled-out position located outside the apparatus main assembly  100 A. 
     In this pull-out movement of the tray  35 , the drum  1  of each cartridge P and the belt  13  are separated from each other, so that friction therebetween is not caused to occur. 
     As a result, the entire first to fourth (four) cartridges PY, PM, PC and PK held by the tray  35  pass through the opening  30  to be exposed to the outside of the apparatus main assembly  100 A, so that the upper surfaces of all the cartridges are exposed. When the tray  35  is pulled out with a predetermined sufficient distance, further pull-out movement of the tray  35  is prevented by a stopper portion (not shown). Further, the tray  35  is held, in the state in which it is horizontally pulled out to the predetermined pulled-out position, by the tray holding members  34 L and  34 R. At this time, the tray  35  located at the considerably pulled-out position from the apparatus main assembly  100 A can be supported by the supporting portion  31   a  of the door  31  as shown in  FIGS. 6 and 7 . As a result, it is possible to prevent damage of the drum surface by considerably downward bending of the tray  35  on the main assembly front side due to the weight of the tray  35  and the cartridges and to prevent the apparatus main assembly  100 A from toppling over forward due to off-balance weight of the apparatus main assembly  100 A by the pulling out of the tray  35 . The door  31  is rotationally moved, the door  31  can be provided so that the supporting portion  31   a  is located inside the apparatus main assembly during the door closing and is located outside the apparatus main assembly during the door opening. Therefore, the tray  35  can be stably held at the pulled-out position to improve usability during the cartridge exchange without increasing the size of the apparatus main assembly. 
     The tray  35  supports each cartridge P so as to be detachably movable directly above. The tray  35  supports each cartridge P by moving each cartridge P directly below. As shown by chain double-dashed lines in  FIG. 7 , a spent cartridge P to be replaced is raised and removed above from the tray  35 . Then, a fresh cartridge is engaged in and placed on the tray from above. 
     In the case where the cartridge having an openable drum cover (not shown) for protecting the lower surface of the drum  1 , the cover is manually closed after the cartridge is demounted from the tray  35 . Further, with respect to a fresh cartridge, the cover is manually opened before the fresh cartridge is placed on the tray  35 . In another embodiment, in the process in which the cartridge is demounted by upwardly raising the cartridge from the tray  35 , the cover is automatically closed. Further, in the process in which the cartridge is engaged in and placed on the tray  35  from above, the cover is automatically opened. 
     As shown in  FIGS. 6 and 7 , when the tray  35  is pulled out to the pulled-out position and then a cartridge, to be exchanged, of the cartridges held on the tray  35  is exchanged, the user sufficiently pushes and moves the tray  35  into the apparatus main assembly to be accommodated at the pushed-in position. That is, the tray  35  is returned to the state before the pulling out as shown in  FIGS. 4 and 5 . Also during the push-in movement of the tray  35 , the drum  1  of each cartridge P and the belt  13  are separated from each other, so that friction therebetween is not caused to occur. 
     After the tray  35  is sufficiently pushed in to the pushed-in position, the grip member  36  is rotated backward from the opened state of  FIG. 4  to be returned to the closed state of  FIG. 3 . By the interrelating mechanism operating in interrelation with the backward rotation of the grip member  36 , the tray holding members  34 L and  34 R are moved downwardly by a predetermined distance. That is, the tray holding members  34 L and  34 R are moved from the second position to the first position. When the tray holding members  34 L and  34 R are moved from the second position to the first position, the tray and each cartridge P are also moved downwardly together with the tray holding members  34 L and  34 R, so that the drum  1  contacts the belt  13  ( FIG. 2 ). That is, the tray  35  is moved from the transfer separation position (pushed-in position) ( FIG. 5 ) in which the drum  1  and the belt  13  are separated from each other to the transfer contact position ( FIG. 2 : inside position) in which the drum  1  and the belt  13  are brought into contact with each other. 
     Further, in interrelation with the downward movement of the tray holding members  34 L and  34 R, each cartridge is urged by the urging member to be held in the state in which the cartridge is fixed (locked) to the predetermined positioning portion. To the drive input portion of the cartridge, the drive output portion on the apparatus main assembly side is connected. To the electrical contacts of the cartridge, the electric energy supplying system on the apparatus main assembly side is electrically connected. Further, the tray  35  is positioned to the apparatus main assembly  100 A by the tray movement preventing means. 
     Finally, the opened door  31  is closed as shown in  FIGS. 1 and 2  to complete the cartridge exchanging operation. 
     (Cartridge P) 
       FIG. 8(   a ) is a perspective view of the cartridge P as seen from the driving side and  FIG. 4  is a perspective view of the cartridge P as seen from the non-driving side. 
     The cartridge P is an elongated box-type assembly extending in the axial direction of the drum  1  as the left-right direction (longitudinal direction). The drum  1  is rotatably supported between shaft supporting portions  51  and  52  provided at left and right side surface portions of the cartridge frame  5 . To the right shaft supporting portion  51 , a coupling engaging portion  53  as the drum drive force input portion is provided. To the right side surface portion of the cartridge frame  5 , a coupling engaging portion  54  as the developing device drive input portion for driving the developing roller  3   a  is provided. To the left side surface portion of the cartridge frame  5 , a cartridge electrical contact  55  is provided. At upper portions of the left and right side surface portions of the cartridge frame  5 , eaves  56  are provided by extending and projecting the upper surface portion of the cartridge frame  5  in the left-right direction. With respect to the cartridge, the right side surface portion side provided with the coupling engaging portions  53  and  54  is the driving side and the left side surface portion side opposite from the right side surface portion side is the non-driving side. 
     (Tray  35 ) 
     The tray  35  is a movable member provided movably in a direction intersecting the axial direction of the drum  1  of each cartridge. Further, the tray  35  is movable between the pulled-out position in which the tray  35  having passed through the opening  30  is located outside the apparatus main assembly and each cartridge is mountable to and demountable from the apparatus main assembly and a latent image forming position (inside position) in which the electrostatic latent image can be formed on the drum  1 . 
       FIG. 9  is a perspective view of an outer appearance of the tray  35 . 
     The tray  35  includes a rectangular main frame portion prepared by connecting a front frame  35   b , a rear frame  35   c , a left frame  35   d , and a right frame  35   e . The inside of the main frame portion is substantially equally partitioned into four areas by three partitioning plates  35   f  with respect to the front-rear direction of the main frame portion, so that first to fourth elongated small frame portions  35 ( 1 ) to  35 ( 4 ) from the rear frame  35   c  side to the front frame  35   b  side are formed in this order in parallel to each other. The small frame portions  35 ( 1 ),  35 ( 2 ),  35 ( 3 ) and  35 ( 4 ) are mounting portions to which the first to fourth cartridges PY, PM, PC and PK are held, respectively. With respect to each of the small frame portions  35 ( 1 ) to  35 ( 4 ), the right frame  35   e  is provided with a hole  35   g  though which a developing device driving coupling passes. 
     Further, the tray  35  includes an intermediary electric contact  77  to be electrically connected to the electric contact  55  ( FIG. 8 ) of each cartridge. The intermediary electric contact  77  is electrically connectable to a main assembly side electric contact (not shown) provided to the apparatus main assembly  100 A. 
     Each of the cartridges PY, PM, PC and PK is inserted from above into an associated small frame portion of the tray  35 . Then, lower surfaces of the left and right eaves  56  are stopped by the upper surfaces  61   a  of the left and right frames  35   d  and  35   e , so that each cartridge (PY, PM, PC or PK) is accommodated in and supported by the tray  35 . That is, the tray  35  supports each cartridge demountably right above and supports each cartridge by moving each cartridge right below. The tray  35  roughly supports each of the cartridges. As a result, it is possible to easily perform exchange of each cartridge. 
     The grip member  36  is an elongated portal-shaped member extending in the left-right direction and is shaft-supported rotatably between shaft supporting portions  34   h L and  34   h R provided to front-side left and right side end portions of the front frame  35   b  of the tray  35 . That is, a left side leg portion  36   b L of the grip member  36  is located inside the left shaft supporting portion  35   h L which is provided with a shaft supporting hole. Into the shaft supporting hole, a shaft portion  36   c L which is provided integrally with the left side leg portion and extends in the left-right direction is inserted. The shaft portion  36   c L is projected outwardly from the left shaft supporting portion  35   h L and with the projected shaft portion  36   c L, a first left spur gear  51 L is integrally engaged. Further, a right side leg portion  36   b R of the grip member  36  is located inside the right shaft supporting portion  35   h R which is provided with a shaft supporting hole. Into the shaft supporting hole, a shaft portion  36   c R which is provided integrally with the right side leg portion and extends in the left-right direction is inserted. The shaft portion  36   c R is projected outwardly from the right shaft supporting portion  35   h R and with the projected shaft portion  36   c R, a first right spur gear  51 R is integrally engaged. As a result, the grip member  36  can be placed in the closed state as indicated by a solid line by being rotated backward about the shaft supporting portions to face (contact) the front surface of the front frame  35   b  of the tray  35 . Further, the grip member  36  can be placed in the opened state as indicated by a chain double-dashed line by being rotated forward from the front frame  35   b  about the shaft supporting portions. The first left spur gear  51 L and the first right spur gear  51 R are rotated forward together by the forward rotation of the grip member  36  and are rotated backward together by the backward rotation of the grip member  36 . 
     (Tray Holding Members  34 L and  34 R) 
     The left and right tray holding members  34 L and  34 R are movable means for moving the tray  35  from the latent image forming position (image forming position) to the set position in the upward direction before the tray  35  as the movable member is moved to the pulled-out position in which each cartridge is detachably mountable. Alternatively, the left and right tray holding members  34 L and  34 R are movable means for moving the tray  35  from the set position to the latent image forming position in the downward direction. In other words, the tray holding members  34 L and  34 R are a supporting member for supporting the tray  35  and can take the second position for permitting movement of the tray  35  between the pulled-out position and the set position and can take the first position for permitting positioning of the tray  35  at the latent image forming position. Further, by the interrelating mechanism operating in interrelation with the forward rotation of the grip member  36 , the tray holding members  34 L and  34 R are moved from the first position to the second position. The tray holding members  34 L and  34 R are moved from the second position to the first position by the interrelating mechanism operating in interrelation with the backward rotation of the grip member  36 . 
       FIG. 10(   a ) is an outer surface view of the left side tray holding member  34 L. On the other surface side of the tray holding member  34 L, two pins  34   c   1  and  34   c   2  are provided at front and rear portions with a spacing with respect to the front-rear direction. Further, two vertical racks  34   d   1  and  34   d   2  are provided at front and rear portions with spacing. The pins  34   c   1  and  34   c   2  of the left tray holding member  34 L are, as shown in  FIG. 10(   b ), engaged with elongated vertical guide holes  91 L 1  and  91 L 2  provided at front and rear portions of a stationary member  91 L provided integrally with a left frame  80 L of a main frame of the apparatus main assembly. By the engagement between the pin  34   c   1  and the guide hole  91 L 1  and the engagement between the pin  34   c   2  and the guide hole  91 L 2 , the tray holding member  34 L is supported vertically movably within a range of a hole length of each of the guide holes  91 L 1  and  91 L 2  with respect to the stationary member  91 L. 
     The right side tray holding member  34 R is not shown but has the same constitution as that of the left side tray holding member  34 L described above. That is, the right side tray holding member  34 R is also provided with front and rear pins and front and rear racks in an asymmetrical manner with respect to those of the left side tray holding member  34 L. The front and rear pins are engaged with elongated vertical guide holes provided at front and rear portions of a stationary member provided integrally with a right frame  80 R of the apparatus main assembly main frame. By the engagement between the pins and associated guide holes, the right side tray holding member  34 R is also supported vertically movably within a range of a hole length of each of the guide holes with respect to the stationary member. 
     That is, each of the left and right tray holding members  34 L and  34 R has latitude in vertical movement with the guide ranges of the associated guide holes with respect to the associated stationary member provided integrally with the left or right tray holding member  34 L or  34 R. 
     (Interrelating Mechanism Between Grip Member  36  and Tray Holding Members  34 L and  34 R) 
     The interrelating mechanism between the grip member  36  and the left tray holding member  34 L and the interrelating mechanism between the grip member  36  and the right tray holding member  34 R are symmetrically provided to the left tray holding member  34 L and the right tray holding member  34 R, respectively, and similarly function and operate. Therefore, with reference to  FIGS. 11 to 14 , the interrelating mechanism on the left tray holding member  34 L side will be described and thus the interrelating mechanism on the right tray holding member  34 L side will be omitted from illustration and description. 
     To a stationary member (not shown) on the left frame  80 L side of the apparatus main assembly main frame, a shaft  55  is rotatably provided through a shaft supporting member (not shown) with respect to the front-rear direction as an axial direction thereof. To front and rear ends of the shaft  55 , a second level bevel gear  54  and a third bevel gear  56  are fixed, respectively. On the second bevel gear  54  side, to a member (not shown) on the left frame  80 L side, a first bevel gear  53  and a second spur gear  52  and rotatably provided as a two-stepped gear through a shaft supporting member (not shown). The first bevel gear  53  engages with the second bevel gear  54 . The second spur gear  52  engages with the front rack  34   d   1  of the tray holding member  34 L. On the third bevel gear  56  side, to a stationary member (not shown) on the left frame  80 L side, a fourth bevel gear  57  and a third spur gear  58  are rotatably provided as a two-stepped gear through a shaft supporting member (not shown). The fourth bevel gear  57  engages with the third bevel gear  56 . The third spur gear  58  engages with the rear rack  34   d   1  of the tray holding member  34 L. To a rear end of the third bevel gear  56 , a bifurcated member  59  is fixed coaxially with the third bevel gear  56 . In the neighborhood of the bifurcated member  59 , an L-shaped stopper member  60  engageable with the bifurcated member  59 . The stopper member  60  is rotatably provided about a vertical shaft  60   a  with respect to the stationary member (not shown) on the left frame  80 L side. The stopper member  60  is rotationally urged by a tension spring  61  so that one arm portion  60   b  of the L-shaped stopper member  60  is moved toward the bifurcated member  59 . A reference numeral  60   c  represents the other arm portion of the L-shaped stopper member  60 . 
       FIG. 11  and  FIG. 14(   a ) show a state in which the tray  35  is moved to the pushed-in position inside the apparatus main assembly and the grip member  36  and the door  31  are closed as shown in  FIG. 2 . In this state, the left and right tray holding members  34 L and  34 R are moved through the interrelating mechanism in the downward direction within the apparatus main assembly. The pins  34   c   1  and  34   c   2  are located at lower portions of the guide holes  91 L 1  and  91 L 2 . The right tray holding member  34 R is configured similarly as in the left tray holding member. For that reason, each of the left and right tray holding members  34 L and  34 R are held at a predetermined lower portion (the first position) with respect to the stationary member  91 L ( 91 R: not shown) of the left frame  80 L (or the right frame  80 R). Therefore, the tray  35  held by the tray holding members  34 L and  34 R is also held at a predetermined lower position (the latent image forming position). 
     Each of the cartridges PY, PM, PC and PK held by the tray  35  is urged by the urging member at each of the left and right upper surface portions thereof. As a result, lower surface portions (portions to be positioned) of the driving-side shaft supporting portion  51  and the non-driving-side shaft supporting portion  52  are fixed to positioning portions  41  provided to stay members (inner side plates)  81 L and  81 R of the apparatus main assembly  100 A, so that each cartridge is held in a predetermined positioning state with respect to the apparatus main assembly  100 A. In this state, the lower surface of the drum of each cartridge stably contacts the upper surface of the upper-side belt portion of the belt unit  12 . 
     The coupling engaging portions  53  and  54  of each cartridge are placed in a state in which the drum driving coupling and the developing device driving coupling which are provided on the apparatus main assembly side are engaged therein, respectively. 
     To the electric contact  55  of each cartridge, electric power can be supplied from the apparatus main assembly through the intermediary electric contact. 
     Further, the tray  35  is positioned to the stay member  81  of the apparatus main assembly by a tray movement preventing means. In this embodiment, the positioning of the tray  35  is performed by the tray movement preventing means described below. That is, as shown in  FIGS. 15(   a ) and  15 ( b ), a downward pin  110  is provided to either one or both of the left and right frames  35   d  and  35   e  of the tray  35 . Further, a U-shaped groove  111  is provided to either one or both of the left and right stay members  81 L and  81 R of the apparatus main assembly. In the state in which the tray  35  is moved to the transfer contact position, the downward pin  110  engages with the U-shaped groove  111  as shown in  FIG. 15(   a ), so that movement of the tray  35  in the front-rear direction is prevented and thus the tray  35  is positioned to the apparatus main assembly  100 A. 
     A first left spur gear  51 L and a first right spur gear  51 R of the tray  35  are engaged with the second spur gear  52  ( FIG. 11 ) of the left side interrelating mechanism and the second spur gear of the right side interrelating mechanism (not shown). The other arm portion  60   c  of the stopper member  60  of each of the left and right interrelating mechanisms is urged rearward at the rear end surface of the rear frame  35   c  of the tray  35  located at the pushed-in position. As a result, each of the stopper portions  60  of the left and right interrelating mechanisms is held in a rotation angle state (disengaged state) in which one arm portion  60   b  is escaped from the bifurcated member  59  against a pulling force of the spring  61  with the vertical shaft  60   a  as a center. Further, each of the shafts of the left and right interrelating mechanisms is in such a rotation angle state that a bifurcated portion  59   a  of the bifurcated member  59  is vertically directed. 
     The image forming apparatus can perform an image forming operation in the above-described state. 
       FIG. 14(   b ) shows a state in which the door  31  placed in the state shown in  FIG. 13(   a ) is opened as also shown in  FIG. 3 . When jam occurs on the front surface side of the image forming apparatus, the user is not required to operate the grip member  36  for jam clearance but is only required to open the door  31  as shown in  FIG. 14(   b ). 
       FIG. 14(   c ) shows a state in which the grip member  36  placed in the state shown in  FIG. 14(   b ) is rotated forward substantially 90 degrees to be placed in the opened state. In the process of the forward rotation of the grip member  36  from the closed state to the opened state, the first left spur gear  51 L and the first right spur gear  51 R are also rotated forward together with the grip member  36 . Further, in interrelation with the forward rotation of the first left spur gear  51 L, the second spur gear  52 , the first bevel gear  53 , the second bevel gear  54 , the shaft  55 , the third bevel gear  56 , the fourth spur gear  58 , and the bifurcated member  59  of the left side interrelating mechanism are rotated forward. A final forward rotation angle of these members is substantially 90 degrees corresponding to that of the forward rotation of the grip member  36 . Hereinafter, a forward rotation operation of these members is referred to as a forward rotation operation of the left side interrelating mechanism By the forward rotation of the second spur gear  52  and the fourth spur gear  58 , the racks  34   d   1  and  34   d   2  are upwardly moved. As a result, the left side tray holding member  34 L is upwardly moved with the pins  34   c   1  and  34   c   2  guided by the guide holes  91 L 1  and  91 L 2 . That is, the tray holding member  34 L is moved from the first position to the second position. The pins  34   c   1  and  34   c   2  are located at the upper portion of the guide holes  91 L 1  and  91 L 2  by the upward movement of the tray holding member  34 L. 
     Further, in interrelation with the forward rotation of the first right spur gear  51 R, the right side interrelating mechanism performs the forward rotation operation similarly as the left side interrelating mechanism. As a result, the right side tray holding member  34 R is also upwardly moved similarly as the left side tray holding member  34 L. That is, the tray holding member  34 R is also moved from the first position to the second position. 
     The above-described upward movement state of the left and right tray holding members  34 L and  34 R is retained so long as the grip member  36  is held in the opened state. 
     Further, by the forward rotation operation of the left and right interrelating mechanisms, the bifurcated member  59  of each of the left and right interrelating mechanisms is placed in the rotation angle state in which the bifurcated portion  59   a  is horizontally directed as shown in  FIG. 12 . 
     In the above-described upward movement process of the left and right tray holding members  34 L and  34 R, with respect to each cartridge, the drum driving coupling and the developing device driving coupling are disengaged. Further, the urging positioning of each cartridge by the urging member is also released. 
     Further, electrical connection between the electrical contact  55  and the electric energy supplying system on the apparatus main assembly side is released. 
     Further, when the tray holding members  34 L and  34 R are moved from the first position to the second position, the tray  35  and each cartridge P are also moved upward together with the tray holding members  34 L and  34 R, so that the drum  1  is separated from the belt  13  ( FIG. 5 ). That is, the tray  35  is moved from the transfer contact position (inside position shown in  FIG. 2 ) in which the drum  1  and the belt  13  contact each other to the transfer separation position (pushed-in position) ( FIG. 5 ) in which the drum  1  and the belt  13  are separated from each other. Further, by the upward movement of the tray  35 , the pin  111  is completely disengaged from the U-shaped groove as shown in  FIGS. 14(   c ) and  15 ( b ), so that the positioning state of the tray  35  is released. Therefore, the tray  35  can be freely subjected to the horizontal slide movement operation in the front-rear direction with respect to the left and right tray holding members  34 L and  34 R placed in the state in which the members  34 L and  34 R are moved to the second position. 
     The groove  110  and the pin  111  constitute the tray movement preventing means for preventing the tray  35  as the movable member from moving from the set position in the apparatus main assembly to a direction intersecting the direction in which the drum  1  of each cartridge and the belt  13  contact each other. The prevention of the movement of the tray  35  by the tray movement preventing means  110  and  111  is released after the tray  35  follows the movement of the left and right tray holding members  34 L and  34 R as the movable means in the direction. In this state, the tray  35  is horizontally slid and moved in the front-rear direction with respect to the tray holding members  34 L and  34 R to take the pulled-out position in which each cartridge is exchangeable and the set position in which each cartridge is set inside the apparatus main assembly. 
     From the state of  FIG. 14(   c ), the opened-state grip member  36  is gripped and the tray  35  is pulled out to slide with respect to the tray holding members  34 L and  34 R, so that the tray  35  is horizontally slid and moved in the front direction. By the forward movement of the tray  35 , the rear frame  35   c  of the tray  35  is escaped from the other arm  60   c  of the stopper member  60  of each of the left and right interrelating mechanisms. As a result, the stopper member  60  is rotated about the vertical shaft  60   a  by the pulling force of the spring  61 , so that one arm  61   b  of the stopper member  60  enter the bifurcated portion  59   a  of the bifurcated member  59  to engage with the bifurcated member  59  as shown in  FIG. 13(   c ). By this engagement, the shaft  55  of each of the left and right interrelating mechanisms is placed in a state in which the shaft  55  is prevented from being rotated, so that the state of the movement of the left and right tray holding members  34 L and  34 R to the second position is retained. That is, even when the first left spur gear  51 L and the first right spur gear  51 R are separated from the second left spur gear and the second spur gears of the left and right interrelating mechanisms, respectively, the state of the movement of the left and right tray holding members  34 L and  34 R to the second position is retained. The bifurcated member  59  is urged toward the stopper member  60  by an urging means (not shown), so that a time required for engagement between the arm portion  61   b  and the bifurcated member  59  is shorter than a time required for disengagement between the spur gear  51 L ( 51 R) and the spur gear  52 . 
     As shown in  FIGS. 6 and 7 , the tray  35  is sufficiently pulled out to the predetermined pulled-out position outside the apparatus main assembly  100 A. When a cartridge, to be exchanged, of the cartridges held on the tray  35  is exchanged, the user sufficiently pushes and moves the tray  35  into the apparatus main assembly to be accommodated at the pushed-in position. That is, the tray  35  is returned to the state before the pulling out as shown in  FIGS. 4 and 5 . 
     A first left spur gear  51 L and a first right spur gear  51 R of the tray  35  are engaged with the second spur gear  52  ( FIG. 14(   c )) of the left side interrelating mechanism and the second spur gear of the right side interrelating mechanism (not shown). The other arm portion  60   c  of the stopper member  60  of each of the left and right interrelating mechanisms is urged rearward by the rear end surface of the rear frame  35   c  of the tray  35  located at the pushed-in position. As a result, each of the stopper portions  60  of the left and right interrelating mechanisms is held in a rotation angle state (disengaged state) in which one arm portion  60   b  is escaped from the bifurcated member  59  against a pulling force of the spring  61  with the vertical shaft  60   a  as a center. That is, prevention of the rotation of the shafts of the left and right interrelating mechanisms is released. 
     The grip member  36  placed in the opened state is rotated backward substantially 90 degrees to be returned to the closed state. In the process of the backward rotation of the grip member  36  from the opened state to the closed state, the first left spur gear  51 L and the first right spur gear  51 R are also rotated backward together with the grip member  36 . Further, in interrelation with the backward rotation of the first left spur gear  51 L, the second spur gear  52 , the first bevel gear  53 , the second bevel gear  54 , the shaft  55 , the third bevel gear  56 , the fourth spur gear  58 , and the bifurcated member  59  of the left side interrelating mechanism are rotated backward. A final backward rotation angle of these members is substantially 90 degrees corresponding to that of the backward rotation of the grip member  36 . Hereinafter, a backward rotation operation of these members is referred to as a backward rotation operation of the left side interrelating mechanism. By the backward rotation of the second spur gear  52  and the fourth spur gear  58 , the racks  34   d   1  and  34   d   2  are downwardly moved. As a result, the left side tray holding member  34 L is downwardly moved with the pins  34   c   1  and  34   c   2  guided by the guide holes  91 L 1  and  91 L 2 . That is, the tray holding member  34 L is moved from the second position to the first position. The pins  34   c   1  and  34   c   2  are located at the lower portion of the guide holes  91 L 1  and  91 L 2  by the downward movement of the tray holding member  34 L. 
     Further, in interrelation with the backward rotation of the first right spur gear  51 R, the right side interrelating mechanism performs the backward rotation operation similarly as the left side interrelating mechanism. As a result, the right side tray holding member  34 R is also downwardly moved similarly as the left side tray holding member  34 L. That is, the tray holding member  34 R is also moved from the second position to the first position. 
     Further, the shaft  55  of each of the left and right interrelating mechanisms is placed in the rotation angle state in which the bifurcated portion  59   a  of the bifurcated member  59  is upwardly directed ( FIG. 13(   b )). 
     When the tray holding members  34 L and  34 R are moved from the second position to the first position, the tray and each cartridge P are also moved downwardly together with the tray holding members  34 L and  34 R, so that the drum  1  contacts the belt  13  ( FIG. 2 ). That is, the tray  35  is moved from the transfer separation position (pushed-in position) ( FIG. 5 ) in which the drum  1  and the belt  13  are separated from each other to the transfer contact position ( FIG. 2 ) in which the drum  1  and the belt  13  are brought into contact with each other. 
     Further, in interrelation with the downward movement of the tray holding members  34 L and  34 R, each cartridge is urged by the urging member to be held in the state in which the cartridge is fixed (locked) to the predetermined positioning portion. To the drive input portion of the cartridge, the drive output portion on the apparatus main assembly side is connected. To the electrical contacts of the cartridge, the electric energy supplying system on the apparatus main assembly side is electrically connected. Further, by the downward movement of the tray  35 , the pin  111  is engaged in the U-shaped groove  110  as shown in  FIGS. 14(   b ) and  15 ( a ). As a result, the movement of the tray  35  in the front-rear direction is prevented, so that the tray  35  is positioned to the apparatus main assembly  100 A. 
     Finally, the opened door  31  is closed to complete the cartridge exchanging operation. 
     In this embodiment, an unshown latch mechanism is used, so that when the grip member  36  is operated from the opened state to the closed state, the grip member  36  can be placed in a partly opened state which is an intermediary state therebetween in some cases. In such cases, the following effect can be achieved by disposing the rotation center  31   b  of the door  31  outside the rotation centers  36   c L and  36   c R of the grip member  36 . That is, in the state of  FIG. 14(   c ), by closing the door  31 , the grip member  36  is interrelated with the door  31  and can also be closed at the same time. Therefore, the user can return the tray holding members from the state of the  FIG. 14(   c ) to the state of  FIG. 14(   a ) only by the operation of the door  31 . 
     The constitutions of the grip member and the left and right interrelating mechanisms are not limited to those described above but may also be replaced with various appropriate constitutions. Further, the constitution for retaining the state of the movement of the left and right tray holding members  34 L and  34 R to the second position is not limited to the above-described combination of the L-shaped stopper member  60  and the bifurcated member  59 . For example, by providing the guide range of the guide holes  91  with latitude with respect to the horizontal direction, the left and right tray holding members  34 L and  34 R may also be prevented from being downwardly moved from the second position to the first position. 
     As described above, in order to improve the usability, the cartridge is placed on the movable member (the tray) and is exchanged and the movable member is upwardly and downwardly moved by the vertical movement of the movable means (the tray holding member). The movable means is moved in interrelation with the forward and backward rotations of the tray grip member and is supported by the door  31  at the pulled-out position on the front side of the apparatus main assembly. 
     As a result, it is possible to provide an image forming apparatus, provided with a pull-out type process cartridge exchange constitution, having prevented an occurrence of damage and memory caused by rubbing between the belt  13  and the drum  1  of each cartridge P without increasing a size and cost of the apparatus main assembly  100 A. 
     (Interface Portions) 
     Interface portions will be described. 
       FIGS. 16 to 18  are schematic views for illustrating the interface portions in the neighborhood of each cartridge, which are interrelated with the tray holding members  34 L and  34 R to perform disengagement or release operation. 
       FIG. 16  is a perspective view showing a state (closed state) in which the grip member  36  is rotated backward and no cartridge is in the tray  35 .  FIG. 17  is a perspective view showing a state (opened state) in which the grip member  36  is rotated forward and the tray  35  has been pulled out. 
     On the right side in the apparatus main assembly, the drum driving (force transmitting) couplings  39  and the developing device driving (force transmitting) couplings  40  as the drive output portions on the apparatus main assembly side, which are connected with the drive input portions  53  and  54  ( FIG. 8(   a )) on the cartridge side, in order to rotationally drive the drum  1  and developing roller  3   a , respectively, in each cartridge. 
     On both the left and right sides in the apparatus main assembly  100 A, positioning portions for receiving the lower surface portions (to be positioned) of driving-side shaft-supporting portions  51  and non-driving-side shaft-supporting portions  52  of each cartridge are provided to the stay members  81 L and  81 R. 
     Also on both the left and right sides in the apparatus main assembly, urging members  42  for urging the left and right side upper surfaces of the corresponding cartridge so that the driving-side shaft-supporting portions  51  and the non-driving-side shaft-supporting portions can be engaged and fixed in the positioning portions  41  (the left side urging member is not shown). Each urging member  42  is provided with a spring for generating a pressing force. 
       FIG. 18(   a ) is an enlarged view of the urging member  42 , the drum driving coupling  39 , and the developing device driving coupling  40 , which are in the state shown in  FIG. 16 .  FIG. 18(   b ) is an enlarged view of the urging member  42 , the drum driving coupling  39 , and the developing device driving coupling  40 , which are in the state shown in  FIG. 17 . 
     The urging member  42  is rotatably provided to the apparatus main assembly  100 A with a supporting point  44 , and urges the right (or left) end upper surface of the corresponding cartridge by a spring force of an urging spring  43 . That is, the positioning portion  41  is provided along the movement direction of the tray  35  and at the positioning portion  41 , the cartridge P is urged by the urging member  42  in a direction substantially perpendicular to the movement direction of the tray  35  to be placed in the positioned state (locked state). In an urge-released state shown in  FIG. 18(   b ), a lever portion  45  of the urging member  42  has been pushed up by an urging member raising portion  46  provided to the tray holding member  34 R, so that the pressure applied to the cartridge is removed in interrelation with the movement of the tray holding member  34 R (lock-released state). 
     Further, a release lever pin  47  is provided to a release lever  48  (means for removing a driving force transmitted to cartridge) provided around the drum driving coupling  39  so as to retract the driving coupling  39 . In interrelation with the movement of the tray holding member  34 R, the release lever pin  47  is moved from the position shown in  FIG. 18(   a ) to the position shown in  FIG. 18(   b ). By the operation of the release lever  48 , the drum driving coupling  39  and the developing device driving coupling  40  are retracted to the position shown in  FIG. 18(   b ). That is, the drum driving coupling  39  and the developing device driving coupling  40  of each cartridge are released. 
     In the state shown in  FIG. 17 , that is, in a state in which the drum driving couplings  39 , the developing device driving couplings  40 , and the urging members  42  are released in interrelation with the motion of the tray holding members  34 L and  34 R, the tray  35  is slidable. Accordingly, the tray  34  is placed in such a state that it can be accommodated in and pulled out from the apparatus main assembly  100 A while holding the cartridges thereon. 
     As described above, the left and right tray holding members  34 L and  34 R are operated in interrelation with the forward and backward rotation of the grip member  36 . In this case, in order to reduce an operating force of the forward and backward rotation of the grip member  36 , the image forming apparatus may be structured so that the timing of the urge release is slightly different from the timing of the release of the driving couplings. 
     That is, the drum driving coupling  39 , the developing device driving coupling  40 , and the urging member  42  are made slightly different in releasing timing. More specifically, the pin  47  and the urging member raising portion  46  are made different in position to render the coupling and the urging member slightly different in releasing timing for the drive and the urging, and the four cartridges are rendered slightly different in releasing timing for the drive and the urging. Thus, a load exerted on the grip member  36  is distributed. As a result, it is possible to reduce the peak load and reduce the operating force during operation of the grip member  36  by the user. 
     As described above, the retraction of the driving means (couplings  39  and  40 ) and the vertical movement of the tray  35  are performed by the movement of the tray holding members  34 L and  34 R, so that it is possible to integrate the mechanisms to realize a compact size of the apparatus main assembly. 
     The image forming apparatus  100  in this embodiment is summarized as follows. 
     (1) The image forming apparatus  100  forms the image on the recording material S. The image forming apparatus  100  includes the movable member  35  for supporting the cartridge P including at least one of the image bearing member  1  on which the latent image is to be formed and the developing means  3  for developing with the developer the latent image formed on the image bearing member  1 . The movable member  35  can take the pulled-out position in which the movable member  35  having been pulled out to the outside of the apparatus main assembly  100 A of the image forming apparatus  100  permits mounting and demounting of the cartridge outside the apparatus main assembly  100 A and the inside position in which the cartridge is moved to the inside of the apparatus main assembly  100 A. Further, the grip member  36  capable of being rotated forward rotated backward is provided to the movable member  35 . The image forming apparatus  100  further includes the urging member  42  for placing the cartridge P in the positioned state (locked state) with respect to the positioning portion  41  of the apparatus main assembly  100 A. In the state in which the movable member  35  is located in the inside position, when the grip member  36  is rotated forward by the predetermined distance, the positioned state of the cartridge P with respect to the position portion  41  by the urging member  42  is released. Further, when the grip member  36  is rotated backward by the predetermined distance, the cartridge P is positioned to the positioning portion  41  by the urging member  42 . 
     (2) The positioning portion  41  is provided along the movement direction of the movable member  35 , and the cartridge P is urged by the urging member  42  in the direction substantially perpendicular to the movement direction of the movable member  35  to be placed in the positioned state. 
     (3) In the state in which the movable member  35  is located at the inside position and the grip member  36  is rotated forward by the predetermined distance, when the openable door  31  is closed with respect to the apparatus main assembly  100 A, the grip member  36  is rotated backward by the predetermined distance in interrelation with the motion of the openable door  31 . 
     (4) The movable member  35  can support the plurality of the cartridges PY, PM, PC and PK side by side with respect to the movement direction thereof. 
     In this embodiment, the cartridges P can be easily replaced in the front access manner. The image forming apparatus is of the type in which the cartridge can be replaced in a state in which it is mounted in the tray and in which the members on the apparatus main assembly side, the cartridges can be positioned during mounting thereof, and in which the tray roughly holds the cartridge and moves between the pulled-out position and the pushed-in position. As a result, the user can set the cartridge into the tray from right above with respect to the direction of gravitation without paying attention to the positioning at the pulled-out position of the tray. Thereafter, the user pushes the tray in to the pushed-in position and rotates backward the grip member  36  to face the front surface of the tray, so that it is possible to effect the positioning of the cartridge with reliability. As a result, it is possible to provide an image forming apparatus which allows a simple operation by the user and is capable of ensuring positional accuracy for each cartridge. 
     When the tray  35  is operated in such a state that the tray  35  is not completely raised, e.g., in a half-open state of the grip member  36 , there is a possibility of an occurrence of an image problem caused by rubbing of the drum  1  of each cartridge with the belt  13 . However, in this embodiment, it is possible to realize a state in which the tray  35  cannot be operated until the user completely rotates the grip member  36 , by providing the members (tray movement preventing means  110  and  111 ) for preventing the movement of the tray  35  by the forward and backward rotation of the grip member  36 . 
     As described above, the image forming apparatus of this embodiment can easily perform the exchange of the cartridge by the moving operation of the tray. 
     In the above-described embodiment, the cartridge P is the process cartridge prepared by integrally supporting the image bearing member  1  and the process means, acting on the image bearing member  1 , consisting of the charging means  2 , the developing means  3  and the cleaning means  4  into a cartridge but is not limited thereto. That is, the cartridge P may only be required to include at least the image bearing member on which the latent image is to be formed and the developing means for developing the latent image, formed on the image bearing member, with the developer. The process means is, e.g., at leas one of the charging means, the developing means, and the cleaning means. The image bearing member is the member on which the latent image to be developed with the developer is to be formed. The image bearing member may also be the electrostatic recording dielectric member in the electrostatic recording process, the magnetic recording magnetic member in the magnetic recording process, and the like, in addition to the electrophotographic photosensitive member in the electrophotographic process as in the embodiment. 
     In the above-described embodiment, the tray  35  as the movable member is configured to support the four cartridges PY, PM, PC and PK disposed in parallel to each other with respect to the movement direction of the tray  35 . However, the cartridges to be supported by the tray  35  may also be a single cartridge. Further, it is also possible to constitute the image forming apparatus in which two, three or five or more cartridge are supportable side by side on the tray  35 . 
     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 purpose of the improvements or the scope of the following claims. 
     This application claims priority from Japanese Patent Application No. 271781/2008 filed Oct. 22, 2008, which is hereby incorporated by reference.