Abstract:
A cartridge detachably mountable to a main assembly of the image forming apparatus, wherein the main assembly including an opening, an urging portion, a positioning portion and a regulating portion, the cartridge includes a portion to be urged by the urging portion so as to be moved in a crossing direction which crosses an inserting direction in which the cartridge is inserted, after the cartridge is inserted into the main assembly of the apparatus through the opening; a portion to be positioned by contacting to the positioning portion by the cartridge being moved by the urging portion in the crossing direction to position the cartridge relative to the main assembly of the apparatus; and a portion to be regulated by the regulating portion so as to prevent the cartridge from moving toward an outside through the opening in a state that portion to be positioned is in contact to the positioning portion, wherein the portion to be regulated is provided at a rear end of the cartridge and is brought, by movement of the cartridge in the crossing direction by the urging portion, to a regulating position where the portion to be regulated is behind the regulating portion with respect to the inserting direction to prevent the cartridge from moving toward the outside through the opening.

Description:
FIELD OF THE INVENTION AND RELATED ART 
       [0001]    The present invention relates to a cartridge removably mountable in the main assembly of an image forming apparatus. It also relates to an image forming apparatus which employs a cartridge removably mountable in the main assembly of an image forming apparatus. 
         [0002]    One of the examples of an image forming apparatus is an electrophotographic image forming apparatus, which is an apparatus for forming an image on recording medium with the use of an electrophotographic image forming process. These apparatuses include an electrophotographic copying machine, an electrophotographic printer (LED printer, laser beam printer, etc.), an electrophotographic facsimile apparatus, and an electrophotographic word processor, for example. 
         [0003]    A recording medium is a medium on which an image is formed. As for examples of a recording medium, there are recording sheet, OHP sheet, etc. 
         [0004]    A cartridge means a container, which is removably mountable in the main assembly of an image forming apparatus, and in which some of the substances, devices, etc., which are necessary for image formation, are placed. One of the examples of a cartridge is a process cartridge, in which an electrophotographic photosensitive member, and at least one among a charging means, a developing means, and a cleaning means, is integrally disposed. 
         [0005]    In many cases where a combination of the main assembly of an image forming apparatus, and a cartridge (cartridges) for the image forming apparatus, are transported (in particular, commercially distributed) in a single box, the main assembly and cartridge are separately wrapped, and then, are packed together in the single box for shipment. This arrangement requires a shipment box to be greater in size, making greater the shipment cost for the pair, than in a case where the main assembly of an image forming apparatus and the cartridge(s) therefor are packaged in a single shipment box. Further, it takes more time and effort for a user to take the pair out of the box and unwrap them after purchasing the image forming apparatus; it increases the amount of load to which the user is subjected before the user can actually use the product. 
         [0006]    Thus, there has been devised an image forming apparatus, the door of the main assembly of which can be kept shut with a process cartridge (cartridges) mounted in its main assembly while it is transported (Japanese Laid-open Patent application 2006-171407). More specifically, this image forming apparatus is structured so that an elastic member can be placed between the main assembly and process cartridge to prevent the problem that during the transportation of the image forming apparatus, the process cartridge in the main assembly is damaged because it shifts in position in the main assembly. Thus, this structural arrangement makes it possible to use a substantially smaller shipment box than the shipment box which has been used. In other words, this structural arrangement can improve the combination of an image forming apparatus and a cartridge therefor, in the efficiency with which they can be transported. 
         [0007]    There has also been devised a color image forming apparatus, which is structured so that a process cartridge can be mounted into, or removed from, its main assembly in the direction parallel to the axial line of the photosensitive drum in the process cartridge, and the main assembly of which is provided with a door for covering or exposing the opening of the main assembly, through which a cartridge is to be mounted or removed (U.S. Pat. No. 6,453,136). In the case of image forming apparatuses such as this image forming apparatus, one end of the rotational axle of the photosensitive drum of a process cartridge is supported and positioned by the rear wall of the main assembly of an image forming apparatus, whereas the other end is supported and positioned by the door unit of the main assembly, which is at the front of the apparatus main assembly. Therefore, the process cartridge can be easily regulated in its position relative to the main assembly in terms of the direction in which it is mounted into the main assembly. 
         [0008]    However, in the case of the above-described technology disclosed in the Japanese Laid-open Patent Application 2006-171407, the door is subjected to the reactive force which is generated by the elastic member, and which is equal in strength to the amount of the pressure applied to the elastic member by the cartridge (and main assembly). Therefore, the door has to be made more rigid than necessary to withstand the amount of the force to which it is subjected when it is opened or closed. Further, it makes larger the amount of force necessary to close the door. 
         [0009]    Further, in the case of the above described technology disclosed in U.S. Pat. No. 6,453,136, when opening the door unit to replace the cartridge in the main assembly, the door unit has to unlocked by operating a lever, whereas when closing the door unit after the replacement of the cartridge, the door unit has to be locked by operating the level. 
       SUMMARY OF THE INVENTION 
       [0010]    The primary object of the present invention is to provide a cartridge or an image forming apparatus which is simple in structure, and yet, can ensure that the cartridge properly positioned in the main assembly of the image forming apparatus does not move out of the main assembly through the opening with which the main assembly is provided to mount or remove the cartridge. 
         [0011]    According to an aspect of the present invention, there is provided a cartridge detachably mountable to a main assembly of the image forming apparatus, wherein the main assembly including an opening, an urging portion, a positioning portion and a regulating portion, said cartridge comprising a portion to be urged by the urging portion so as to be moved in a crossing direction which crosses an inserting direction in which said cartridge is inserted, after said cartridge is inserted into the main assembly of the apparatus through said opening; a portion to be positioned by contacting to the positioning portion by said cartridge being moved by the urging portion in the crossing direction to position said cartridge relative to the main assembly of the apparatus; and a portion to be regulated by the regulating portion so as to prevent said cartridge from moving toward an outside through said opening in a state that portion to be positioned is in contact to said positioning portion, wherein said portion to be regulated is provided at a rear end of said cartridge and is brought, by movement of said cartridge in the crossing direction by said urging portion, to a regulating position where said portion to be regulated is behind said regulating portion with respect to the inserting direction to prevent said cartridge from moving toward the outside through said opening. 
         [0012]    According to another aspect of the present invention, there is provided an image forming apparatus for forming an image on a recording material, said apparatus comprising a main assembly including an opening, an urging portion, a positioning portion and a regulating portion; a cartridge dismountably mounted to said main assembly, said cartridge including, a portion to be urged by the urging portion so as to be moved in a crossing direction which crosses an inserting direction in which said cartridge is inserted, after said cartridge is inserted into the main assembly of the apparatus through said opening; a portion to be positioned by contacting to the positioning portion by said cartridge being moved by the urging portion in the crossing direction to position said cartridge relative to the main assembly of the apparatus; and a portion to be regulated by the regulating portion so as to prevent said cartridge from moving toward an outside through said opening in a state that portion to be positioned is in contact to said positioning portion, wherein said portion to be regulated is provided at a rear end of said cartridge and is brought, by movement of said cartridge in the crossing direction by said urging portion, to a regulating position where said portion to be regulated is behind said regulating portion with respect to the inserting direction to prevent said cartridge from moving toward the outside through said opening. 
         [0013]    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 
         [0014]      FIG. 1  is a sectional view of the image forming apparatus in the first preferred embodiment of the present invention, and shows the image forming operation of the apparatus. 
           [0015]      FIG. 2  is an external perspective view of the image forming apparatus in the first embodiment. 
           [0016]      FIG. 3  is an external perspective view of the image forming apparatus, the door of which is open, and one of the four cartridges for which is being inserted or pulled out. 
           [0017]      FIGS. 4(   a ) and  4 ( b ) are external perspective views of the cartridge in the first preferred embodiment, as seen from the rear and front sides, respectively, of the cartridge in terms of the direction in which it is mounted into the main assembly of the image forming apparatus. 
           [0018]      FIG. 5  is a sectional view of the cartridge in the first preferred embodiment. 
           [0019]      FIG. 6  is a combination of the drawings of the cartridge and the main assembly  3 , as seen from the left side of the main assembly  3 , which is for describing the operation for mounting the cartridge  11  into the main assembly  3 . 
           [0020]      FIG. 7  is a perspective view of the tray raising mechanism which is in its second position. 
           [0021]      FIG. 8  is a side view of the tray raising mechanism, which is for describing how the tray is raised or lowered by the mechanism. 
           [0022]      FIG. 9  is a partially sectional and vertical side view of a combination of the tray, tray raising mechanism in its first position, and cartridge on the tray. 
           [0023]      FIG. 10  is a combination of four drawings of the mechanism for pulling the cartridge into the deepest end of the main assembly of the image forming apparatus, when mounting the cartridge into the main assembly, which is for describing the operation of the mechanism. 
           [0024]      FIG. 11  is a combination of three drawings of the mechanism for preventing the cartridge from popping out of the main assembly of the image forming apparatus after being precisely positioned in its second position, which is for describing the operation of the mechanism. 
           [0025]      FIG. 12  is a perspective view of the tray raising mechanism in the second preferred embodiment of the present invention. 
           [0026]      FIG. 13  is a combination of three drawings of the mechanism, in the second embodiment, for preventing the cartridge from popping out of the main assembly of the image forming apparatus after being precisely positioned in its second position, which is for describing the operation of the mechanism. 
           [0027]      FIG. 14  is an external perspective view of the cartridge in the third preferred embodiment of the present invention, as seen from the front side of the cartridge in terms of the direction in which the cartridge is mounted. 
           [0028]      FIG. 15  is a combination of three drawings of the mechanism, in the third embodiment, for preventing the cartridge from popping out of the main assembly of the image forming apparatus after being precisely positioned in its second position, which is for describing the operation of the mechanism. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiment 1 
     General Description of Image Forming Apparatus 
       [0029]    First, referring to  FIG. 1 , the image forming apparatus in the first preferred embodiment will be described regarding its overall structure.  FIG. 1  is a sectional view of the image forming apparatus in the first embodiment. 
         [0030]    The image forming apparatus  1  shown in  FIG. 1  employs four process cartridges  11  ( 11 Y,  11 M,  11 C, and  11 K). It is structured so that as the four process cartridges are mounted into its main assembly, they are aligned horizontally in a straight line (they horizontally align in tandem). Further, the main assembly of the image forming apparatus  1 , and the four process cartridges  11  (which hereafter will be referred to simply as cartridges), are structured so that the cartridges  11  can be independently mounted into, or removed from, the main assembly, from each other. 
         [0031]    The main assembly  3  of the image forming apparatus is what remains after the removal of all of the process cartridges  11  from the image forming apparatus  1 . 
         [0032]    The front side (surface or wall) of the image forming apparatus  1  is the side (surface or wall) provided with a door  2  for covering or exposing the entrance of the cartridge chamber of the main assembly  3 . The rear side is the opposite side from the front side. The left and right sides of the image forming apparatus  1  are the left and right sides as seen from the front side. 
         [0033]    Referring again to  FIG. 1 , the cartridges  11 Y,  11 M,  11 C, and  11 K make up the first-fourth image formation stations of the image forming apparatus, which correspond to monochromatic yellow, magenta, cyan, and black images, into which an intended full-color image is separated. The cartridges  11 Y,  11 M,  11 C, and  11 K contain yellow, magenta, cyan, and black developers (which hereafter may be referred to as toners), respectively. Each cartridge  11  has an electrophotographic photosensitive drum  12 . It also has electrophotographic processing means, more specifically, a charge roller  13  (charging means), a development unit  14  (developing means), a cleaning means, which are disposed in a manner to surround the peripheral surface of the photosensitive drum  12  in the circumferential direction of the photosensitive drum  12 . The main assembly  3  of the image forming apparatus  1  is provided with a laser scanner unit  16 , which is disposed so that it will be under the cartridges  11  after the mounting of the cartridges  11  into the main assembly  3 . The main assembly  3  is also provided with an intermediary transfer belt unit  4  (transferring means in the form of a belt; transferring-and-conveying means), which is disposed so that it will be on the top side of each photosensitive drum  12 . The belt unit  4  is for transferring an image (formed of developer) from the photosensitive drum  12  onto a recording medium P after the formation of the image on the photosensitive drum  12 . The belt unit  4  has an intermediary transfer belt  4   a , a secondary transfer roller  5  (transfer roller on the inward side of belt loop), a follower roller  6 , and a tension roller  7 . The secondary transfer roller  5  and follower roller  6  are disposed in the right and left end portions, respectively, of the main assembly  3 . The tension roller  7  is disposed near the follower roller  6 . The intermediary transfer belt  4   a  is suspended by the three rollers  5 ,  6 , and  7 . The intermediary transfer belt  4   a  (which hereafter will be referred to simply as belt  4   a ) is a flexible and endless belt. The abovementioned three rollers  5 ,  6 , and  7  are disposed in parallel, with their rotational axial lines extending in the front-to-rear direction. The tension roller  7  is kept pressured upward to provide the intermediary transfer belt  4   a  with tension. There are the first to fourth primary transfer rollers  9  (primary transferring means), which are disposed on the inward side of the loop which the belt  4   a  forms. In terms of the direction parallel to the front (rear) wall of the main assembly  3 , the four primary transfer rollers  9  are disposed in tandem between the follower roller  6  and secondary transfer roller  5 , in contact with the belt  4   a , and with preset amount of intervals. There is also a belt cleaning unit  10  for cleaning the belt  4   a , which is on the outward side of the abovementioned belt loop, corresponding in position to the follower roller  6 . 
         [0034]    Further, a secondary transfer roller  22  (transfer roller on the outward side of belt loop) is disposed in contact with the belt  4   a , on the outward side of the portion of the belt loop curved by the secondary transfer roller  22 . The interface between the belt  4   a  and secondary transfer roller  22  is the secondary transfer portion T 2 . 
         [0035]    The main assembly  3  of the image forming apparatus  1  is provided with a cassette chamber, which is in the bottom portion of the main assembly  3 , and in which a cassette  17 , in which the recording mediums P (sheets of recording paper, for example) are stored, is mounted. The main assembly  3  is also provided with a recording medium conveying means, which extends from the cassette chamber to the top portion of the main assembly  3 . The recording medium conveying means is made up of a pickup roller  18  (which corresponds in position to recording medium outlet of cassette  17 ), a recording medium passage  20 , a pair of registration rollers  21 , and a recording medium conveyance guide  23 , listing from the upstream side in terms of the direction in which the recording medium P is conveyed. 
         [0036]    The image forming operation of this image forming apparatus is as follows: First, each photosensitive drum  12  begins to be rotated with its own image formation timing, and is uniformly charged by the charge roller  13  across its peripheral surface. Then, the numerous points of the uniformly charged portion of the peripheral surface of the photosensitive drum  12  are selectively exposed by the laser scanner unit  16 . As a result, an electrostatic latent image is formed on the photosensitive drum  12 . The development unit  14  develops the electrostatic latent image by adhering toner to the latent image. Then, a bias which is opposite in polarity from the toner image is applied to the primary transfer roller  9 . As a result, the image formed of toner on the photosensitive drum  12  is transferred onto the belt  4   a . The above described steps of the image forming process are sequentially carried out in the first to fourth image formation stations. Thus, four monochromatic toner images, different in color, are transferred in layers onto the belt  4   a , composing (synthetically effecting) thereby an unfixed full-color toner image on the belt  4   a . Then, the unfixed full-color toner image is conveyed to the secondary transfer portion T 2  by the rotation of the belt  4   a.    
         [0037]    Meanwhile, the recording mediums P in the cassette  17  are sequentially sent out into the recording medium conveyance passage  20  (which hereafter will be referred to simply as recording medium passage  20 ) by the pickup roller  18  while being separated so that only the top one will be sent into the recording medium passage  20 . After each recording medium P is sent into the recording medium passage  20 , it is conveyed to the secondary transfer portion T 2  by the pair of registration rollers  21  with a preset timing. Then, while the recording medium P is conveyed through the second transfer portion T 2 , the application of a transfer bias to the second transfer roller  22  (roller outside belt loop) is started with a preset timing. As a result, the monochromatic toner images, different in color, on the belt  4   a , are transferred all at once (secondary transfer) onto the recording medium P, forming an unfixed multi-color image on the recording medium P. Then, the recording medium P is conveyed out of the secondary transfer portion T 2 , is separated from the belt  4   a , and is conveyed further by the recording medium conveyance guide  23  to the fixation unit  24 . While the recording medium P is conveyed through the fixation unit  24 , the recording medium P and the multi-color image thereon are subjected to heat and pressure by the heat roller  24   a  and pressure roller  24   b  of the fixation unit  24 . As a result, the unfixed multi-color image is fixed to the surface of the recording medium P. Then, the recording medium P is conveyed further by a pair of first discharge rollers  25  through a recording medium passage  26 , and then, is discharged from a delivery opening  28  onto a delivery tray  29 , which is a part of the top surface of the frame (shell) of the main assembly  3 . Meanwhile, the toner remaining on the peripheral surface of the photosensitive drum  12  after the transfer (primary transfer) of the toner image from the photosensitive drum  12  onto the belt  4   a  is removed by a cleaning member  70  to prepare the photosensitive drum  12  for the next image formation cycle. Similarly, the toner remaining on the belt  4   a  after the transfer (secondary transfer) of the toner images from the belt  4   a  onto the recording medium P is removed by the belt cleaning unit  10  to prepare the belt  4   a  for the next image formation cycle. 
       (Cartridge) 
       [0038]    Next, referring to  FIGS. 4 ,  5 , and  7 , the cartridge  11  in this embodiment will be described.  FIGS. 4(   a ) and  4 ( b ) are external perspective views of the cartridge in the first preferred embodiment, as seen from the rear and front sides, respectively, of the cartridge in terms of the direction in which it is mounted into the main assembly of the image forming apparatus.  FIG. 5  is an enlarged sectional view of the cartridge  11  after the proper positioning of the cartridge  11  in the main assembly  3  of the image forming apparatus  1 , and the adjacencies of the cartridge  11 . That is,  FIG. 5  shows the cartridge  11  which is ready for image formation. Incidentally, the cartridges  11 Y,  11 M,  11 C, and  11 K, which contain yellow, magenta, cyan, and black toners, respectively, are the same in structure. Referring to  FIG. 4 , each cartridge  11  is an assembly, the lengthwise direction of which is parallel to the rotational axis of its photosensitive drum  12 . Each cartridge  11  is provided with a drum driving coupling  34  and a development roller driving coupling  35 , which are located at the front (deepest) end of the cartridge  11  in terms of the direction in which the cartridge  11  is inserted into the main assembly  3  of the image forming apparatus  1 . Further, each cartridge  11  is provided with a cartridge position regulating portion  31   a  (cartridge displacement preventing portion) and a thrust lever catching portion  31   b , which are the front end portion of the cleaning unit frame  31  in terms of the direction in which the cartridge  11  is inserted into the main assembly  3 . In terms of the direction perpendicular to the direction in which the cartridge  11  is inserted, the cartridge position regulating portion  31   a  is located roughly at the middle of the cleaning unit frame  35 . Therefore, it is ensured that the cartridge  11  is kept properly positioned in the main assembly  3  by the cartridge position regulating portion  31   a  is rigid. 
         [0039]    The drum driving coupling  34  is the coupling with which the cartridge  11  receives the force for driving its photosensitive drum  12  from the apparatus main assembly  3 . The development roller driving coupling  35  is the coupling with which the cartridge  11  receives the force for driving its development roller  71  ( FIG. 5 ) from the main assembly  3 . 
         [0040]    Referring to  FIG. 5 , the cartridge  11  has an electrostatic latent image formation unit  15  (which hereafter will be referred to as latent image formation unit) and the development unit  14 . 
         [0041]    The latent image formation unit  15  has the photosensitive drum  12 , charge roller  13 , cleaning member  70 , and cleaning means frame  31 . It is the cleaning unit frame  31  that the photosensitive drum  12  is rotatably attached with the bearings ( 32 F and  32 F) positioned as the photosensitive drum supporting members between the photosensitive drum  12  and cleaning unit frame  31 . There are disposed the charge roller  13  and cleaning member  70  in the adjacencies of the peripheral surface of the photosensitive drum  12  as described above. The abovementioned transfer residual toner is removed from the peripheral surface of the photosensitive drum  12  by the cleaning member  70 , and falls into a chamber  31   g  for the removed toner. The photosensitive drum  12  is rotated, in coordination with the progression of an image forming operation, by transmitting driving force from a motor (unshown source for driving photosensitive drum  12 ) to the photosensitive drum  12  through the drum driving coupling  34 . A pair of bearings  36  for the charge roller  13  are attached to the cleaning unit frame  31  so that they can be moved relative to the cleaning unit frame  31  in the direction indicated by an arrow mark A. More concretely, the shaft  13   a  of the charge roller  13  is rotatably borne by the charge roller bearings  36 . Each bearing  36  is kept pressured toward the photosensitive drum  12  by a charge roller pressing member  37 . The charge roller  13  is rotated by the rotation of the photosensitive drum  12 . 
         [0042]    The development unit  14  (developing apparatus) has the development roller  71  (developer bearing member) and a development unit frame  38 . The development roller  71  rotates in contact with the photosensitive drum  12  in the direction indicated by an arrow mark B. It is rotatably supported by the development unit frame  38  with the interposition of a pair of development roller bearings (unshown) between the lengthwise ends of the development roller shaft and the development unit frame  38 , respectively. The development unit  14  is provided with a toner supply roller  72  and a development blade  73 , which are disposed in contact with the peripheral surface of the development roller  71 . The toner supply roller  72  rotates in contact with the development roller  71  in the direction indicated by an arrow mark C. The development blade  73  is for regulating in thickness the layer of toner as the layer of toner is formed on the peripheral surface of the development roller  71 . The development unit frame  38  also has a toner storage portion  38   a , in which a toner stirring member  74  is disposed, which is for conveying the toner in the toner storage portion  38   a  to the abovementioned toner supply roller  72  while stirring the toner. 
         [0043]    Further, the development unit  14  has a pair of bearings  33 F and  33 R, which have holes  33 Fa and  33 Ra, respectively. Further, the development unit  14  is provided with a pair of shafts  75 F and  75 R, which are fitted in the holes  33 Fa and  33 Ra, respectively, connecting thereby the development unit  14  and latent image formation unit  15  in such a manner that the development unit  14  and latent image formation unit  15  are allowed to rotationally move about the pair of shafts  75 F and  75 R. During an image forming operation, the development unit  14  of the cartridge  11  is kept under the pressure from a pair of compression springs  76 , and therefore, the development roller  71  remains in contact with the photosensitive drum  12 . 
         [0044]    The bottom portion  31   h  of the cleaning unit frame  31  is provided with a pressure catching portion  31   c  (cartridge pressing member catching portion), which extends in the lengthwise direction of the cartridge  11 . It is also provided with a cartridge guiding portion  31   e  (which hereafter will be referred to simply as guiding rib  31   e ). Incidentally, the cartridge  11  is provided with a slit  31   d , which is a gap between the bottom portion of the development unit  14  and the bottom portion of the latent image formation unit  15 , through which a beam of laser light is allowed to enter the cartridge  11 . In terms of the widthwise direction of the cartridge  11 , the slit  31   d  and guiding rib  31   e  are roughly at the middle of the cartridge  11 . Further, the latent image formation unit  15  is provided with a cartridge regulating upper rib  31   f , which is the right end portion of the bottom portion of the latent image formation unit  15  in terms of the direction in which the cartridge  11  is inserted into the apparatus main assembly  3  (which hereafter will be referred to simply as cartridge insertion direction). 
       (Method for Mounting Cartridge) 
       [0045]    Next, the method for mounting the cartridge  11  into the main assembly  3  of the image forming apparatus  1  will be described. 
         [0046]      FIG. 2  is an external perspective view of the image forming apparatus  1 .  FIG. 3  is an external perspective view of the image forming apparatus  1  when the door  2  of the main assembly  3  is open and one of the four cartridges  11  for the image forming apparatus is being inserted into, or pulled out of, the main assembly  3 . 
         [0047]    Referring to  FIG. 2 , in the case of the image forming apparatus  1  in this embodiment, the door  2 , and the opening  61   a  of the cartridge chamber of the apparatus main assembly  3 , are on the front side of the apparatus main assembly  3 . The door  2  is for exposing or covering up the opening  61   a . The door  2  is provided with a handhold  2   a . The opening  61   a  can be accessed by opening the door  2  in the direction indicated by an arrow mark A to replace the cartridge  11  or cartridges  11  in the main assembly  3 . 
         [0048]      FIGS. 6(   a )- 6 ( c ) are drawings of the main assembly  3  and cartridge  11 , as seen from the left side of the main assembly  3 , and are for describing the operation for mounting the cartridge  11  into the main assembly  3 . 
         [0049]      FIG. 6(   a ) is for describing the state of the cartridge  11  and apparatus main assembly  3  prior to the mounting of the cartridge  11  into the apparatus main assembly  3 . In the case of this image forming apparatus  1 , the opening  6   a  is a part of the front wall  61  of the frame of the apparatus main assembly  3 . The apparatus main assembly  3  is provided with a cartridge holding member  41  (which hereafter will be referred to simply as tray), which has a rail  48  and a pair of cartridge pressing members  43  and  44 . While the apparatus main assembly  3  and cartridge  11  are in the state shown in  FIG. 6(   a ), the top portions of the rail  48  and cartridge pressing members  43  and  44  are above the top surface of the tray  41 . 
         [0050]    The cartridge  11  is inserted into the apparatus main assembly  3  through the opening  61   a  in the direction indicated by an arrow mark E. In other words, the cartridge  11  is inserted into the apparatus main assembly  3  in the direction parallel to the rotational axis of the photosensitive drum  12 . As the cartridge  11  is inserted into the apparatus main assembly  3 , it comes to be supported, and remains supported thereafter, by the rail  48  and pressing members  43  and  44 , by the pressure catching portion  31   c  of the cartridge  11 . During the insertion of the cartridge  11  into the apparatus main assembly  3 , the cartridge  11  is guided in the following manner ( FIG. 5 ). That is, in terms of the vertical direction, the cartridge  11  is guided by the cartridge position regulating upper rib  31   f , with which the cartridge  11  is provided, and the cartridge guiding top groove  41   f , with which the tray  41  is provided. In terms of the left-to-right direction (horizontal direction), the cartridge  11  is guided by the guide rib  31   e  of the cartridge  11 , and the cartridge guiding rib  41   b  with which the tray  41  is provided. 
         [0051]      FIG. 6(   b ) is for describing the state of the cartridge  11  and apparatus main assembly  3  after the insertion of the cartridge  11  into the apparatus main assembly  3  all the way (deepest position in apparatus main assembly  3 ). As the cartridge  11  is inserted in the direction indicated by the arrow mark E, a main assembly contacting portion  31   j , which is an integral part of the cleaning unit frame  31 , comes into contact with the inward surface  62   c  of the rear wall  62  of the main assembly frame of the apparatus main assembly  3 , preventing thereby the cartridge  11  from being further moved in the cartridge insertion direction; the cartridge  11  is positioned in its deepest position in the apparatus main assembly  3 . When the cartridge  11  is in this deepest position in the apparatus main assembly  3 , the tray  41  is under the cartridge  11 . This contact between the inward surface of the rear wall  62  of the frame of the apparatus main assembly  3  and the main assembly contacting portion  31   j  of the cartridge  11  determines the position of the cartridge  11  relative to the apparatus main assembly  3  in terms of the lengthwise direction of the cartridge  11 . However, when the cartridge  11  is in the above described position, the operation for properly positioning the cartridge  11  relative to the apparatus main assembly  3  has not been completed, and further, the photosensitive drum  12  has not come into contact with the belt  4   a  of the intermediary transfer belt unit  4 . 
         [0052]      FIG. 6(   c ) is for describing the state of the cartridge  11  and apparatus main assembly  3  after the completion of the operation for mounting the cartridge  11  into the apparatus main assembly  3 . After the cartridge  11  is inserted into its deepest position in the apparatus main assembly  3  in terms of the cartridge insertion direction, through the opening  61   a , the tray  41 , which is holding the cartridge  11 , is moved in the direction perpendicular to the cartridge insertion direction by a tray raising mechanism, which will be described later; the tray  41  is moved upward while remaining horizontal. This upward movement of the tray  41  causes the rail  48  to downwardly displace relative to the tray  41 . As a result, the cartridge supporting portions (tray  31  and cartridge pressing members  43  and  44 ) press the pressure catching portion  31   c  of the cleaning unit frame  31  in the direction indicated by an arrow mark F (direction perpendicular to cartridge insertion direction). Not only do the bearings  32  ( 32   f  and  32 R), with which the lengthwise ends, one for one, of the cleaning unit frame  31  are provided, have the function of supporting the photosensitive drum  12  as described above, but also, they function as the portions for accurately positioning the cartridge  11  relative to the apparatus main assembly  3 . Further, in order to accurately position the cartridge  11  relative to the apparatus main assembly  3 , the front and rear walls  61  and  62  of the main assembly frame are provided with cartridge positioning portions  61   b  and  62   a , respectively. Thus, as the abovementioned pressure applying portions press the pressure catching portion  31   c  in the direction indicated by the arrow mark F, the bearings  32  come into contact with the cartridge positioning portions  61   b  and  62   a , one for one, and further, the photosensitive drum  12  comes into contact with the belt  4   a ; in other words, the operation for accurately positioning the cartridge  11  relative to the apparatus main assembly  3  ends (cartridge mounting operation is completed). 
         [0053]    That is, the inward surface  62   c , with which the main assembly contacting portion  31   j  is placed in contact, and the cartridge positioning portions  61   b  and  62   a , with which the bearings  32 F and  32 R are placed in contact, are the cartridge positioning portions of the apparatus main assembly  3 . 
         [0054]    The tray  41  is enabled to take a first position ( FIGS. 6(   a ) and  6 ( b )), and a second position (FIG.  6 ( c )). The first position ( FIGS. 6(   a ) and  6 ( b )) is the position which allows the cartridge  11  to be inserted into the apparatus main assembly  3 , whereas the second position ( FIG. 6(   c )) is the position into which the cartridge  11  is moved, in the direction (upward) perpendicular to the cartridge insertion direction, to accurately position the cartridge  11  relative to the cartridge positioning portions of the apparatus main assembly  3 . 
       (Structures of Tray Raising Mechanism and Tray) 
       [0055]    Next, the tray  41  and tray raising mechanism  50  of the apparatus main assembly  3  will be described in terms of their structure.  FIG. 7  is a perspective view of the tray raising mechanism when the tray  41  is in its second position.  FIG. 8  is a side view of the tray  41 , tray raising mechanism, and its adjacencies, and is for describing the operation for raising or lowering the tray  4 . In  FIGS. 7 and 8 , the first positions of the tray  41 , tray arms  101  and  102 , and door  2  are indicated by solid lines, whereas the second positions of the tray  41 , tray arms  101  and  102 , and door  2  are indicated by double-dot chain lines.  FIG. 9  is a side view of the tray raising mechanism and cartridge  11 , as seen from the direction perpendicular to the lengthwise direction of the cartridge  11 , when they are in their second positions. 
         [0056]    First, the structure of the tray  41  will be described. All trays  41  ( 41 Y,  41 M,  41 C, and  41 K), which support the cartridges  11  ( 11 Y,  11 M,  11 C, and  11 K), respectively, are the same in structure. 
         [0057]    Referring to  FIG. 5 , the tray  41  roughly matches in shape and size the bottom portion  31   h  of the cartridge  11 . Referring to  FIG. 7 , the tray  41  is provided with an opening  41   h  for allowing a beam of laser light (which hereafter will be referred to as exposure opening) to enter the cartridge  11 . The exposure opening  41   h  is roughly at the center of the tray  41 , in terms of the widthwise direction of the tray  41 , and extends in the direction parallel to the lengthwise direction of the tray  41 . When the cartridge  11  is in its designated position on the tray  41 , the exposure opening  41   h  aligns with the opening  31   d  (exposure opening) of the cartridge  11  ( FIG. 5 ). Thus, a beam of laser light L projected upward from the laser scanner unit  16  located below the tray  41  is allowed to reach the peripheral surface of the photosensitive drum  12  through the exposure openings  41   h  and  31   d.    
         [0058]    The tray  41  is provided with a guiding groove  41   b , which is parallel to the exposure opening  41   h . Referring to  FIG. 5 , the abovementioned guiding rib  31   e  of the cartridge  11  fits in the guiding groove  41   b  so that when the cartridge  11  is mounted into the apparatus main assembly  3 , it is properly guided into the apparatus main assembly  3 . In this embodiment, the guiding groove  41   b  and guiding rib  31   e  are matched in cross-sectional shape and dimension. That is, the cross section of the guiding rib  31   e  is such that its top surface is parallel to the cartridge insertion direction and its vertical surfaces are perpendicular to the cartridge insertion direction, whereas the cross section of the guiding groove  41   b  is such that its bottom surface is parallel to the cartridge insertion direction and its lateral surfaces are perpendicular to the cartridge insertion direction (top surface of the tray  41 ). 
         [0059]    The tray  41  is provided with the abovementioned pair of pressing members  43  and  44 , which are located on the front and rear sides, respectively, in terms of the cartridge insertion direction. Referring to  FIG. 9 , each of the pressing members  43  and  44  has a coil spring  46  and pressing portion  47 , which are in one of the vertical holes  41   g  of the tray  41 , with the pressing portion  47  placed on top of the coil spring  46  so that the pressing portion  47  is allowed to protrude above the top surface  41   a  of the tray  41 . 
         [0060]    Further, the tray  41  is provided with a recess  41   j , and an auxiliary rail  48 . The auxiliary rail  48  is in the recess  41   j . Referring to  FIG. 6(   b ), the auxiliary rail  48  is provided with a pair of support portions  48   a  and  48   b . Further, the tray  41  is provided with a pair of through holes  41   n   1  and  41   n   2 , in which the supporting portions  48   a  and  48   b  are fitted. Thus, the auxiliary rail  48  is supported by the tray  41  in such a manner that it is allowed to vertically side relative to the tray  41 . When the tray  41  is in its first position, the rail supporting surfaces  48   a   1  and  48   b   1 , that is, the bottom surfaces of the support portions  48   a  and  48   b , respectively, of the auxiliary rail  48 , are kept in contact with the bottom wall  63  of the apparatus main assembly  3  (which connects the front and rear walls  61  and  62  of the apparatus main assembly  3 ), by the weight of the auxiliary rail  48  itself; the auxiliary rail  48  is not allowed to move downward beyond where the bottom surface of the support portions  48   a  and  48   b  come into contact with the bottom wall  63  of the apparatus main assembly  3 . Thus, when the tray  41  is in its first position, the top surface of the auxiliary rail  48  is roughly level with the top surface  41   a  of the tray  41 , and the top of each of the pressing portions  47  of the pressing members  43  and  44 . Therefore, as the cartridge  11  is inserted into, or taken out of, the apparatus main assembly  3  while the tray  41  is in its first position, the auxiliary rail  48  and pressing member  43  and  44  support the cartridge  11 , by the pressure catching portions  31   c  of the cartridge  11 . 
         [0061]    On the other hand, referring to  FIG. 6(   c ), when the tray  41  is in its second position, that is, its highest position, the bottom surfaces  48   a   1  and  48   b   1  of the rail supporting portions  48   a  and  48   b , respectively, of the auxiliary rail  48  are not in contact with bottom wall  63  of the apparatus main assembly. Thus, the auxiliary rail  48  is supported by the bottom surface of the recess  41   j  of the tray  41 , being completely fitted in the recess  41   j  of the tray  41 . Thus, while the tray  41  is in the second position, each pressing portion  47  remains in contact with the corresponding pressure catching portion  31   c , and keeps the bearings  32 F and  32 R pressed upon the positioning portions  61   b  and  62   a , respectively, of the apparatus main assembly  3 . Thus, while the tray  41  is in the second position, the photosensitive drum  12  and belt  4   a  remain in contact with each other. 
         [0062]    Next, the structure of the tray raising mechanism will be described. 
         [0063]    Referring to  FIG. 7 , the tray raising mechanism  50  is made up of the tray  41 , the tray arms  101  and  102 , a linking shaft  120 , and a linking lever  121 . The tray arm  101  is attached to the linking shaft  120 , which is fitted in the first hole  101   a , with which the tray arm  101  is provided. Thus, the tray arm  101  is supported by the front wall  61  of the apparatus main assembly so that it can be rotated about the axial line of the linking shaft  120 . Further, the shaft  41   j   1  of the tray  41 , which is on the front side of the tray, is fitted in the second hole  101   b , with which the tray arm  101  is provided. That is, the shaft  41   j   1  is rotatably supported by the tray arm  101 . 
         [0064]    Further, the tray arm  102  is provided with the first hole  102   a , and a supporting shaft  132  is fitted in the first hole  102  of the tray arm  102 . Thus, the tray arm  102  is rotatably supported by the rear wall  62  of the apparatus main assembly  3 . Further, the tray arm  102  is provided with a second hole  102   b , and a shaft  41   j   2 , with which the rear portion of the tray  41  is provided. Thus, the shaft  41   j   2  is rotatably supported by the tray arm  102 . 
         [0065]    Further, the linking shaft  120  is in connection to an unshown tray arm, which supports the tray  41  by the front side of the tray, like the linking shaft  120  of each of the other trays  41 . Further, the linking shaft  120  is provided with the linking lever  121 , which also corresponds to the counterpart of each of the other tray  41 . Thus, as the linking lever  121  is rotated, the linking shaft  120  is rotated, whereby the tray arms  101  and  102  are synchronously rotated. 
         [0066]    Next, referring to  FIG. 8 , L 1  stands for the distance from the center of the first hole  101   a , which coincides with the rotational axis of the tray arm  101 , to the center of the second hole  101   b , which coincides with the axial line of the shaft  41   j   1  of the tray  41 . L 2  stands for the distance from the center of the first hole  102   a , which coincides with the rotational axis of the tray arm  101 , to the center of the second hole  102   b , in which the shaft  41   j   2  of the tray  41  is fitted. In this embodiment, L 1  is equal to L 2  (L 1 =L 2 ). 
         [0067]    Also referring to  FIG. 8 , θ 1  stands for the angle between the straight line which connects the center of the first hole  101   a  of the tray arm  101  and the center of the second hole  101   b  of the tray arm  101 , and the horizontal direction. Similarly, the θ 2  stands for the angle between the straight line which connects the center of the first hole  102   a  of the tray arm  102  and the center of the second hole  102   b  of the tray arm  102 , and the horizontal direction. In this embodiment, θ 1  equals θ 2  (θ 1 =θ 2 ). Further, the main assembly  3  of this image forming apparatus  1  is structured so that while the tray  41  is in its second position, the top surface  41   a  of the tray  41  remains horizontal; the front and rear sides of the tray  41  remain at the same height. 
         [0068]    As the linking lever  121  attached to the linking shaft  120  is rotated in the direction indicated by an arrow mark G, the tray arm  101  rotates about the axial line of the first hole  101   a  and the axial line of the linking shaft  120 . This rotation of the tray arm  101  causes the tray  41  to move, causing thereby the tray arm  102  to rotate about the axial line of the first hole  102   a  and the axial line of the supporting shaft  132  in the direction indicated by an arrow mark H. Thus, the tray  41  supported by the tray arms  101  and  102  moves upward from its first position to its second position while remaining horizontal. On the other hand, as the linking lever  121  is rotated in the opposite direction, that is, the direction indicated by an arrow mark G′, the tray arm  101  rotates about the axial line of the first hole  101   a  and the axial line of the linking shaft  120  in the direction indicated by the arrow mark G′. This rotation of the tray arm  101  causes the tray  41  to move, causing thereby the tray arm  102  to rotate about the axial line of the first hole  102   a  and the axial line of the supporting shaft  132  in the direction indicated by an arrow mark H′. Thus, the tray  41  supported by the tray arms  101  and  102  moves downward from the second position to the first position while remaining horizontal. 
         [0069]    In this embodiment, the tray raising mechanism is structured so that in order to raise the tray  41  into its second position, the tray arm  101  has to be rotated far enough for the straight line, which connects the center of the first hole  101   a  and the center line of the second hole  102   b , moves past the vertical line, which coincides with the center line of the first hole  101   a , by an angle of α. This structural arrangement causes the combination of the weight of the cartridge  11  and the weight of the tray  41  to work in the direction to rotate the linking shaft  120  in the direction indicated by the arrow mark G ( FIG. 8 ). Thus, it prevents the problem that the tray  41  moves down into the first position due to vibrations, falls, etc., which occur during the transportation (shipment) of the packaged image forming apparatus  1 . In other words, it ensures that the tray  41  remains stable in the second position. 
         [0070]    Also in this embodiment, the door  2  is connected to the linking lever  121  by a connecting means (unshown). Thus, the opening or closing of the door  2  causes the linking lever  121  to rotate. That is, as the door  2  is closed, the movement of the door  2  causes the linking lever  121  to be rotated in the direction indicated by the arrow mark G, causing thereby the tray  41  to move from the first position to the second position, whereas as the door  2  is opened, the movement of the door  2  causes the linking lever  121  to rotate in the direction indicated by the arrow mark G′, causing thereby the tray  41  to move from the second position to the first position. 
       (Mechanism for Giving Pulling Cartridge During Mounting of Cartridge) 
       [0071]    Next, referring to  FIG. 10 , the mechanism for pulling the cartridge  11  when the cartridge  1  is mounted into the apparatus main assembly  3 , will be described.  FIGS. 10(   a )- 10 ( c ) are drawings for describing the mechanism for pulling a pull to the cartridge  11  when the cartridge  11  is mounted into the apparatus main assembly  3 , regarding the movements of various components of the mechanism. 
         [0072]      FIG. 10(   a ) is a side view of the cartridge pulling mechanism prior to the mounting of the cartridge  11  into the apparatus main assembly  3 . The tray  41  is provided with a thrust lever  145  and a thrust spring  146 , which are located at the front end of the tray  41  in terms of the cartridge insertion direction. The thrust lever  145  is rotatably supported by the thrust lever supporting portion  41   e  of the tray  41 . The thrust spring  146  is a tension spring, and functions as a pressure applying member. One end of the thrust spring  146  is attached to the shaft  41   m  of the tray  41 , and the other end is attached to the shaft portion  145   c  of the thrust lever  145 . Thus, the resiliency of the thrust spring  146  works in the direction to reduce the distance between the shaft portion  41   m  of the tray  41  and the shaft portion  145   c  of the thrust lever  145 . In other words, the thrust lever  145  is under the moment, which works in the direction to rotate the thrust lever  145  in the direction indicated by an arrow mark M about the thrust lever supporting portion  41   e . When the cartridge pulling mechanism is in the state shown in  FIG. 10(   a ), the first arm portion  145   a  of the thrust lever  145  is above the top surface  41   a  of the tray  41 , and the second arm portion  145   b  of the thrust lever  145  is within the tray  41  (below top surface  41   a  of tray  41 ). The cartridge  11  is inserted into the apparatus main assembly  3  from the front side of the apparatus main assembly  3  (as indicated by arrow mark N in  FIG. 10(   a )). 
         [0073]      FIG. 10(   b ) is a side view of the cartridge pulling mechanism when the cartridge  11  is being mounted into the apparatus main assembly  3 . As the cartridge  11  is inserted in the direction indicated by the arrow mark N, the front end surface  31   i  of the cleaning unit frame  31  presses the first arm portion  145   a . As a result, the thrust lever  145  rotates about the supporting portion  41   e  in the direction indicated by an arrow mark M 2 , against the resiliency of the thrust spring  146 . Thus, the first arm portion  145   a  rotates about the supporting portion  41   e  by ε° from the position in which it has been before the mounting of the cartridge  11  into the apparatus main assembly  3 . During this rotation of the first arm portion  145   a , the axial line of the supporting portion  41   e , which is the rotational axis of the thrust lever  145 , coincides with the straight line L 3  (double-dot chain line in drawing), which connects the axial line of the shaft portion  41   m  of the tray  41  and the axial line of the shaft portion  145   c  of the thrust lever  145 . Also during this rotation of the first arm portion  145   a , the thrust lever  145  is in the neutral position, that is, the position in which it is not under the moment attributable to the resiliency of the thrust spring  146 . 
         [0074]      FIG. 10(   c ) is a side view of the cartridge pulling mechanism after the insertion of cartridge  11  into the deepest end of the apparatus main assembly  3 . When the cartridge pulling mechanism is in the state shown in  FIG. 10(   c ), the thrust lever  145  is under the pressure generated by the resiliency of the thrust spring  145  in the direction to place the shaft portion  41   m  of the tray  41  closer to the shaft portion  145   c  of the thrust lever  145 . In other words, the thrust lever  145  is under the moment which acts in the direction indicated by the arrow mark M 2 . When the cartridge pulling mechanism is in this state, the second arm portion  145   b  of the thrust lever  145  comes into contact with the thrust lever catching portion  31   b  of the cartridge frame  31 . As a result, the cartridge  11  is kept pressed toward the rear wall  62  of the apparatus main assembly  3  (in cartridge insertion direction). 
         [0075]      FIG. 10(   d ) is a side view of the cartridge pulling mechanism after the completion of the operation for inserting the cartridge  11  into the apparatus main assembly  3 . After the insertion of the cartridge  11  into the deepest end of the apparatus main assembly  3 , the cartridge  11  is raised by the tray  41  in the direction indicated by an arrow mark I as described above, whereby it is properly position for image formation, relative to the apparatus main assembly  3 . The thrust lever  145  remains under the force generated by the resiliency of the thrust spring  146  in the direction to reduce the distance between the shaft portion  41   m  of the tray  41  and the shaft portion  145   c  of the thrust lever  145 . Therefore, the thrust lever  145  remains under the moment which acts in the direction indicated by the arrow mark M 2 . When the cartridge pulling mechanism is in this state, the second arm portion  145   b  of the thrust lever  145  is in contact with the thrust lever catching portion  31   b  of the cartridge frame  31 , and keeps the cartridge  11  pressed toward the rear wall  62  of the frame of the apparatus main assembly  3  (keep cartridge  11  pressed in cartridge insertion direction). 
         [0076]    That is, during the mounting of the cartridge  11  into the apparatus main assembly  3  by a user, while the thrust lever  145  is in between the state shown in  FIG. 10(   a ) and the state shown in  FIG. 10(   b ), the thrust lever  145  is under the pressure which works in the opposite direction from the cartridge insertion direction, whereas while the thrust lever  145  is in between the state shown in  FIG. 10(   b ) and the state shown in  FIG. 10(   c ), the thrust lever  145  is under the pressure which works in the same direction as the cartridge insertion direction. In other words, after the insertion of the cartridge  11  into its deepest position in the apparatus main assembly  3 , the cartridge  11  remains under the pressure that works in the cartridge insertion direction. 
         [0000]    (Mechanism for Preventing Cartridge from being Displaced (Popping Out)) 
         [0077]    Next, the mechanism for preventing the problem that the cartridge  11  popping out of the apparatus main assembly  3  after it is properly mounted into the apparatus main assembly  3 , will be described.  FIGS. 11(   a )- 11 ( c ) are for describing the mechanism for preventing the problem that the cartridge  11  is displaced after it is properly mounted into the main assembly  3 . 
         [0078]    First, the reason why the mechanism for preventing the cartridge  11  from being displaced after the cartridge  11  is properly mounted into the apparatus main assembly  3  is provided even though the apparatus main assembly  3  is provided with the thrust lever  145  described above, will be described. As described above, while the cartridge  11  is inserted into the apparatus main assembly  3 , the thrust lever  145  remains under the pressure which works in the opposite direction from the cartridge insertion direction until the cartridge  11  reaches virtually the deepest end of the apparatus main assembly  3 . Thus, if it is only with the thrust lever  145  that the image forming apparatus  1  is provided to prevent the cartridge  11  from being displaced after its proper insertion into the apparatus main assembly  3 , the force necessary to insert the cartridge  11  into the apparatus main assembly  3  has to be greater than otherwise. In this embodiment, therefore, in order to prevent the cartridge  11  from being displaced after its proper mounting into the apparatus main assembly  3 , the image forming apparatus  1  is provided with the cartridge displacement (pup-out) prevention mechanism. 
         [0079]    Referring to  FIG. 11 , the cartridge  11  is provided with a cartridge displacement prevention portion  31   a  (cartridge position regulating portion), which is on the outward surface of the front wall of the cartridge frame  31  in terms of the cartridge insertion direction. The cartridge displacement prevention portion  31   a  is in the form of a letter L. That is, it horizontally extends in the cartridge insertion direction from the outside surface of the cartridge wall  31 , and then, vertically extends upward. Further, the rear wall  62  of the main assembly  3  is provided with a cartridge displacement prevention portion  49  (cartridge position regulating portion), which is on the inward surface of the rear wall  62 . The cartridge displacement prevention portion  46  also is in the form of a letter L. It horizontally extends from the rear wall  62 , and then, vertically extends downward. 
         [0080]      FIG. 11(   a ) is a drawing for describing the relationship between the cartridge displacement preventing portions  31   a  and  49  prior to the insertion of the cartridge  11  into the apparatus main assembly  3 . The cartridge  11  is inserted into the apparatus main assembly  3  through the opening  61   a  of the front wall  61  of the apparatus main assembly  3  in the direction indicated by an arrow mark P in  FIG. 11(   a ). Until the cartridges  11  reaches virtually the deepest end of the apparatus main assembly  3 , the cartridge displacement preventing portions  31   a  and  49  of the cartridge  11  and apparatus main assembly  3 , respectively, do not overlap with each other in terms of the cartridge insertion direction. Further, while the cartridge  11  is inserted into the apparatus main assembly  3 , the cartridge  11  is prevented by the above described auxiliary rail  48 , pressing members  43  and  44 , and cartridge movement regulating upper rib  31   f , from moving in the vertical direction. Therefore, the cartridge displacement preventing portions  31   a  and  49  do not come into contact with each other until the cartridge  11  reaches virtually the deepest end of the apparatus main assembly  3  in terms of the cartridge insertion direction. 
         [0081]      FIG. 11(   b ) is a drawing for describing the relationship between the cartridge displacement preventing portions  31   a  and  49  at the moment when the cartridge  11  has just reached the deepest end of the apparatus main assembly  3  in terms of the cartridge insertion direction. When the cartridge  11  is in the position shown in  FIG. 11(   b ), the vertical surface  31   a   1  of the cartridge displacement preventing portion  31   a  is deeper in the apparatus main assembly  3  than the vertical surface  49   a  of the cartridge displacement preventing portion  49 , in terms of the cartridge insertion direction. Also when the cartridge  11  is in the position shown in  FIG. 11(   b ), the cartridge displacement preventing portions  31   a  and  49  of the cartridge  11  and apparatus main assembly  3 , respectively, do not overlap with each other as seen from the front side of the main assembly  3 . Therefore, while the cartridge  11  is in the position shown in  FIG. 11(   b ), it can be taken out of the apparatus main assembly  3  without causing the cartridge displacement preventing portions  31   a  and  49  to come into contact with each other. 
         [0082]      FIG. 11(   c ) is a drawing for describing the relationship between the cartridge displacement preventing portions  31   a  and  49  of the cartridge  11  and apparatus main assembly  3 , respectively, after the completion of the mounting of the cartridge  11  into the apparatus main assembly  3 . After the cartridge  11  is inserted into the deepest end of the apparatus main assembly  3  in terms of the cartridge insertion direction, the tray  41  is raised (from first position to second position) by the tray raising mechanism while remaining horizontal. Thus, the cartridge  11  is moved upward (in other words, cartridge  11  moves in direction perpendicular to cartridge insertion direction). While the cartridge is in the position shown in  FIG. 11(   c ), the cartridge displacement preventing portions  31   a  and  49  of the cartridge  11  and apparatus main assembly  3 , respectively, overlap with each other as seen from the cartridge insertion direction. That is, as the tray  41  is raised, the vertical portion of the cartridge displacement preventing portion  31   a  is placed into the space between the vertical portion of the cartridge displacement preventing portion  49  and the rear wall  61  of the apparatus main assembly  3 . Thus, while the tray  41  is in the position shown in  FIG. 11(   c ), the cartridge  11  cannot move in the direction indicated by an arrow mark Q more than a distance equivalent to the size of the gap R 1  between the vertical surface  31   a   1  of the vertical portions of the cartridge displacement preventing portion  31   a , and the vertical surface  49   a  of the vertical portion of the cartridge displacement preventing portion  49 . That is, even if the cartridge  11  is moved in the direction indicated by the arrow mark Q by the vibrations and/or impacts which occur during the transportation of the image forming apparatus, the contact between the abovementioned vertical surfaces  31   a   1  and  49   a  prevents the cartridge  11  from moving more than the distance equivalent to the size of the gap R 1 . In other words, while the tray  41  is in the position shown in  FIG. 11(   c ), that is, while the bearings  32  and cartridge positioning portion  61   b  are in contact with each other, the cartridge  11  is not allowed to move outward of the opening  61   a ; the cartridge  11  does not pop out of the apparatus main assembly  3 . On the other hand, if the cartridge  11  and apparatus main assembly  3  are not provided with the cartridge displacement preventing portions  31   a  and  49 , respectively, the cartridge  11  is likely to be made to pop out of the apparatus main assembly  3 , by the abovementioned impacts or the like, because the bearing  32  remains in contact with only the cartridge positioning portion  61   b  of the apparatus main assembly  3 , which is a part of the edge of the cartridge insertion opening  61   a , while the cartridge  11  is in the second position in the main assembly  3 . 
         [0083]    The image forming apparatus  1  in this embodiment is structured so that after the cartridge  11  is properly positioned for image formation in the apparatus main assembly  3 , there is the gap R 1  between the cartridge displacement preventing portions  31   a  and  49  of the cartridge  11  and apparatus main assembly  3 , respectively, in terms of the cartridge insertion direction. Further, because the cartridge  11  is moved by the pressing members  43  and  44 , the vertical portion of the cartridge displacement preventing portion  31   a  of the cartridge  11  moves deeper into the apparatus main assembly  3  than the cartridge displacement preventing portion  49 , in terms of the cartridge insertion direction, without coming into contact with the cartridge displacement preventing portion  49 . Therefore, the amount of the load to which a user of the image forming apparatus  1  in this embodiment is subjected when mounting the cartridge  11  into the apparatus main assembly  3  is smaller than that to which a user is subjected when mounting a conventional cartridge ( 11 ) into the apparatus main assembly  3  of a conventional image forming apparatus. However, the image forming apparatus  1  may be structured so that while the tray  41  is in its first position, the cartridge displacement preventing portions  31   a  and  49  remains in contact with each other; there is no gap between the two portions  31   a  and  49 . 
         [0084]    As described above, the image forming apparatus in this embodiment is structured so that as the tray  41  is raised into its second position, the cartridge  11  is positioned so that its cartridge displacement preventing portion  31   a  overlaps with the cartridge displacement preventing portion  49  of the apparatus main assembly  3  in terms of the cartridge insertion direction. Therefore, even if the image forming apparatus  1  is transported with the cartridge  11  mounted in the apparatus main assembly  3 , it does not occur that the cartridge  11  is made to pop out of its image forming position in the direction opposite to the cartridge insertion direction, by the impacts, vibrations, etc., which are transmitted thereto from outside. Further, the provision of the cartridge displacement preventing portions  49  and  31   a  makes it possible to reduce in amount the pressure to be applied to the thrust lever  141 , making thereby it possible to reduce in amount the force necessary to insert the cartridge  11  into the apparatus main assembly  3 . 
         [0085]    That is, the present invention makes it possible to transport the image forming apparatus  1  with the cartridge  11  mounted in the apparatus main assembly  3 , making it thereby possible to reduce in size the box in which the combination of the main assembly of an image forming apparatus, and a cartridge (cartridges) therefore are packed when the apparatus main assembly  3  and cartridge  11  are transported together. In other words, the present invention can improve the image forming apparatus  1  in the efficiency with which it can be transported. 
         [0086]    Further, the present invention makes it unnecessary to provide the image forming apparatus  1  with an elastic member for filling the gap between the door  2  and cartridge  11  in order to prevent the cartridge  11  from rattling in the apparatus main assembly  3  while the image forming apparatus  1  is transported with the cartridge  1  mounted in the apparatus main assembly  3 . Without the presence of the elastic member, there is no reactive force which would have occurred as the elastic member were pressed (compressed) by the door  4  and cartridge  11 . Thus, the door  2  does not need to be made more rigid than necessary for the door to withstand being opened or closed as a part of the external cover of the apparatus main assembly  3 . Therefore, it is possible to simplify the door  2 , which in turn makes it possible to reduce in amount the force necessary to operate the door  2 . 
         [0087]    Further, the cartridge displacement preventing portion  31   a  is positioned at the front end of the cartridge  11  in terms of the cartridge insertion direction. Therefore, more latitude is afforded in terms of the positioning of the cartridge displacement preventing portion  31   a  relative to a plane perpendicular to the cartridge insertion direction (plane perpendicular to axial line of photosensitive drum  12 ). Therefore, it is possible to place the cartridge displacement preventing portion  31  at roughly the center of the cartridge  11 , in terms of the direction perpendicular to the cartridge insertion direction. Incidentally, the roughly center portion of the cartridge  11  in terms of the direction perpendicular to the cartridge insertion direction is higher in rigidity than the edge portion of the cartridge  11 . 
         [0088]    On the other hand, in a case where the cartridge displacement preventing portion  31   a  is placed at the rear end of the cartridge  11  in terms of the cartridge insertion direction, the cartridge displacement preventing portion  31   a  has to be placed near the edge portion of the cartridge  11  in terms of the direction perpendicular to cartridge insertion direction. Placing the cartridge displacement preventing portion  31   a  near the edge of the cartridge  11  is likely to make the cartridge displacement preventing portion  31   a  less rigid than placing the cartridge displacement preventing portion  31   a  at the center of the cartridge  11 . 
         [0089]    Further, when the tray raising mechanism is moved from the first position to the second position, it moves upward while moving inward of the apparatus main assembly  3 . Therefore, while the tray  41  is raised by the tray raising mechanism from the first position to the second position, the tray raising mechanism remains in contact with the bottom surface of the cartridge  11 , with the cartridge  11  remaining under the pressure which works in the direction to press the cartridge  11  inward of the apparatus main assembly  3 . Therefore, when the cartridge  11  is mounted into the apparatus main assembly  3 , it is precisely positioned relative to the apparatus main assembly  3 . 
       Embodiment 2 
       [0090]    Next, referring to  FIGS. 12 and 13 , the second preferred embodiment of the present invention will be described in detail. 
         [0091]      FIG. 12  is a perspective view of the essential portions of the cartridge regulating portion of the image forming apparatus in the second preferred embodiment of the present invention, and is for describing the structures of the essential portions, and in which the tray  41  is in its first position (which allows cartridge to be inserted).  FIGS. 13(   a )- 13 ( c ) are side views of one of the cartridge chambers of the apparatus main assembly  3 , and the cartridge  11  which is being mounted into the chamber. They are for describing how the cartridge displacement preventing mechanism operates as the cartridge  11  is mounted in the apparatus main assembly  3 . 
         [0092]    This embodiment is different from the first embodiment only in the structure of the cartridge regulating portion of the image forming apparatus. Referring to  FIG. 12 , unlike the cartridge regulating portion in the first embodiment described above, the cartridge regulating portion in this embodiment is a part of the edge portion of the opening  62   b  of the rear wall  62  of the apparatus main assembly  3 . 
         [0093]      FIG. 13(   a ) is for describing the state of the cartridge regulating mechanism prior to the insertion of the cartridge  11  into the apparatus main assembly  3 . Referring to  FIG. 13(   a ), the cartridge  11  is inserted into the apparatus main assembly  3  through the opening  61   a  of the front wall  61  of the apparatus main assembly  3  in the direction indicated by an arrow mark T. When the cartridge  11  is in the state shown in  FIG. 13(   a ), the cartridge displacement preventing portion  31   a  of the cartridge frame  31  is within the opening  62   b  of the rear wall  62  of the apparatus main assembly  3 , as seen from the direction parallel to the cartridge insertion direction. Thus, the cartridge regulating portion  31   a  does not come into contact with the rear wall  62  while the cartridge  11  is advanced to the deepest end of the apparatus main assembly  3  in terms of the cartridge insertion direction. 
         [0094]      FIG. 13(   b ) is for describing the state of the cartridge regulating mechanism immediately after the cartridge  11  has just been inserted to the deepest end of the apparatus main assembly  3  in terms of the cartridge insertion direction. When the cartridge regulating mechanism is in this state, the cartridge regulating vertical surface  31   a   1  of the cartridge regulating portion  31   a  of the cartridge  11  is beyond the rear wall  61  of the apparatus main assembly  3  in terms of the cartridge insertion direction. Also when the cartridge regulating mechanism is in this state, the cartridge regulating portion  31   a  of the cartridge frame  31  is within the opening  62   b , as seen from the direction parallel to the cartridge insertion direction. Therefore, the cartridge regulating portions  31   a  and rear wall  62  do not come into contact with each other even if the cartridge  11  is removed. 
         [0095]      FIG. 13(   c ) is for describing the state of the cartridge regulating mechanism after the completion of the cartridge insertion into the apparatus main assembly  3 . After the cartridge  11  is inserted to the deepest end of the apparatus main assembly  3  in terms of the cartridge insertion direction, the tray  41  is raised by the tray raising mechanism while remaining horizontal. Thus, the cartridge  11  is vertically moved upward. While the tray  41  is in its second position, the cartridge regulating portion  31   a  overlaps with the rear wall  62  of the apparatus main assembly  3  as seen from the direction parallel to the cartridge insertion direction. Thus, as long as the tray  41  is in its second position, the cartridge  11  is kept in its second position, and therefore, it does not occur that the cartridge  11  is made to pop out of the apparatus main assembly  3  by the vibrations and/or impacts, which occur during the transportation of the image forming apparatus and the cartridge  11  therein, because, as the cartridge  11  is pushed in the direction indicated by an arrow mark U by the abovementioned vibration and/or impacts, the cartridge regulating vertical surface  31   a   1  of the cartridge regulating portion  31   a  comes into contact with the rear wall  62  of the apparatus main assembly  3 , and therefore, the movement of the cartridge  11  in the direction indicated by the arrow mark U is limited to no more than a distance equivalent to the gap R 2  between the rear wall  62  and cartridge regulating vertical surface  31   a   1 . Further, while the cartridge  11  is in its second position, it can be removed. In other words, this embodiment achieves the same effects as those achievable by the first embodiment. In addition, in this embodiment, the rear wall  62  plays the role of the cartridge displacement preventing portion  49  in the first embodiment, making it unnecessary to provide the apparatus main assembly  3  with the cartridge displacement preventing portion  49 , that is, an additional component for regulating the cartridge  11 . 
         [0096]    In this embodiment, the apparatus main assembly  3  and cartridge  11  are structured so that while the tray  41  is in its second position, there is the gap R 2  between the rear wall  62  of the apparatus main assembly  3 , and the cartridge position regulating portion  31   a  of the cartridge  11 . However, the apparatus main assembly  3  and cartridge  11  may be structured so that while the tray  41  is in the second position, the rear frame  62  and cartridge position regulating portion  31   a  remain in contact with each other; that is, there is no gap between them. Further, in this embodiment, the cartridge position regulating portion of the cartridge  11  is in the form of a letter L, whereas the cartridge position regulating portion of the apparatus main assembly  3  is a part of the edge portion of the cartridge insertion opening of the apparatus main assembly  3 . However, the apparatus main assembly  3  and cartridge  11  may be structured so that the cartridge position regulating portion of the cartridge  11  is a part of the edge of a hole with which the frame of the cartridge  11  is provided, and the cartridge position regulating portion of the apparatus main assembly  3  is in the form of a letter L. 
       Embodiment 3 
       [0097]    Next, referring to  FIGS. 14 and 15 , the third preferred embodiment of the present invention will be described.  FIG. 14  is an external perspective view of the cartridge in the third preferred embodiment of the present invention, and depicts the cartridge regulating structure of the cartridge.  FIGS. 15(   a )- 15 ( c ) are side views of the cartridge  11 , and one of the cartridge chambers of the main assembly  3  of the image forming apparatus in this embodiment, which are for describing how the cartridge displacement preventing mechanism operates as the cartridge  11  is mounted in the apparatus main assembly  3 . 
         [0098]    The third preferred embodiment of the present invention is different from the first one only in the positioning of the cartridge regulating portion of the cartridge  11 . Referring to  FIG. 14 , the cartridge position regulating portions in this embodiment also are made up of the cartridge position regulating portion  38   a  with which the cartridge is provided, and the cartridge position regulating portion  49   a  with which the apparatus main assembly  3  is provided. Also in this embodiment, the cartridge position regulating portions  38   a  and  49   a  are in the form of a letter L. However, unlike the cartridge position regulating portions in the first embodiment, the cartridge position regulating portion  38   a  of the cartridge  11  is a part of the development unit frame  38 , which is roughly at the center of the development unit frame  38  in terms of the direction perpendicular to the cartridge insertion direction. The cartridge position regulating portion  38   a  in this embodiment is also rigid because of its positioning described above. 
         [0099]      FIG. 15(   a ) is for describing the state of the cartridge position regulating mechanism prior to the insertion of the cartridge  11  into the apparatus main assembly  3 . Referring to  FIG. 15(   a ), the cartridge  11  is inserted into the apparatus main assembly  3  through the opening  61   a  of the front wall  61  of the apparatus main assembly  3  in the direction indicated by an arrow mark V. When the cartridge  11  is in the state shown in  FIG. 15(   a ), the cartridge displacement preventing portion  31   a  of the development unit frame  38  does not overlap with the cartridge position regulating portion  49  of the apparatus main assembly  3 , as seen from the direction parallel to the cartridge insertion direction. Thus, the cartridge regulating portion  31   a  does not come into contact with the rear wall  62  while the cartridge  11  is advanced to the deepest end of the apparatus main assembly  3  in terms of the cartridge insertion direction. 
         [0100]      FIG. 15(   b ) is for describing the state of the cartridge position regulating mechanism immediately after the cartridge  11  has just been inserted to the deepest end of the apparatus main assembly in terms of the cartridge insertion direction. When the cartridge regulating mechanism is in this state, the cartridge position regulating vertical surface  31   a   1  of the cartridge position regulating portion  31   a  of the cartridge  11  is on the inward side of the cartridge position regulating vertical surface  49   a  of the cartridge position regulating portion  49  of the apparatus main assembly  3  in terms of the cartridge insertion direction. Also when the cartridge regulating mechanism is in this state, the cartridge regulating portion  31   a  of the cartridge frame  31  does not overlap with the cartridge position regulating portion  49 , as seen from the direction parallel to the cartridge insertion direction. Therefore, the cartridge position regulating portions  31   a  and cartridge position regulating portion  49  do not come into contact with each other even if the cartridge  11  is removed. 
         [0101]      FIG. 15(   c ) is for describing the state of the cartridge regulating mechanism immediately after the completion of the cartridge insertion into the apparatus main assembly  3 . After the cartridge  11  is inserted to the deepest end of the apparatus main assembly  3  in terms of the cartridge insertion direction, the tray  41  is raised by the tray raising mechanism while remaining horizontal. Thus, the cartridge  11  is vertically moved upward. While the tray  41  is in its second position, the cartridge position regulating portion  31   a  overlaps with the cartridge position regulating portion  49 , as seen from the direction parallel to the cartridge insertion direction. Thus, while the tray  41  is in its second position, the cartridge  11  is kept in its second position, and therefore, it does not occur that the cartridge  11  is made to pop out of the apparatus main assembly  3  by the vibrations and/or impacts, which occur during the transportation of the image forming apparatus and the cartridge  11  therein, because, as the cartridge  11  is pushed in the direction indicated by an arrow mark W by the abovementioned vibration and/or impacts, the cartridge regulating vertical surface  31   a   1  of the cartridge regulating portion  31   a  comes into contact with the cartridge position regulating surface  49   a  of the cartridge position regulating portion  49 , and therefore, the movement of the cartridge  11  in the direction indicated by the arrow mark W is limited to no more than a distance equivalent to the gap R 3  between the cartridge regulating vertical surfaces  31   a   1  and  49   a . Further, while the cartridge  11  is in its second position, it cannot be removed. In other words, this embodiment can achieve the same effects as those achievable by the first embodiment. In addition, the cartridge position regulating portion  38   a  in this embodiment is formed as a part of the development unit. Thus, the vibrations and/or impacts which occur during the transportation of the image forming apparatus are caught by the development unit, which is heavier than the latent image formation unit. Therefore, it is unnecessary for the development unit supporting portion of the latent image formation unit to be rigid enough to withstand the abovementioned vibrations and/impacts. 
         [0102]    In this embodiment, the apparatus main assembly  3  and cartridge  11  are structured so that there is the gap R 3  between the cartridge position regulating portion  49  of the apparatus main assembly  3  and the cartridge position regulating portion  38   a  of the cartridge  11  in terms of the direction in which the cartridge  11  is moved out of the apparatus main assembly  3 . However, the apparatus main assembly  3  and cartridge  11  may be structured so that while the tray  41  is in the second position, the cartridge position regulating portions  49  and  38   a  remain in contact with each other; that is, there is no gap between them. 
         [0103]    In the first to third preferred embodiments of the prevent invention described above, the cartridge was a process cartridge. However, the present invention is applicable to any cartridge which is removably mountable in the main assembly of an apparatus. That is, the present invention is applicable to a developer cartridge (which stores at least developer), a development cartridge (which has at least developer bearing member), or a latent image formation cartridge (which has at least electrophotographic photosensitive member). 
         [0104]    As will be evident from the above given description of the first to third embodiments of the present invention, the present invention makes it possible to place a combination of the main assembly of an image forming apparatus and a cartridge (cartridges) in a significantly smaller box than a box which has been conventionally used, when transporting the combination. Thus, the present invention can increase the efficiency with which the combination is transported. Further, the present invention can prevent the problem that in a case where an image forming apparatus is transported with a cartridge(s) for the apparatus mounted in the main assembly of the apparatus, the cartridge(s) becomes displaced relative to the main assembly. Further, the present invention can make significantly smaller the amount of force necessary to mount a cartridge into the main assembly of an image forming apparatus than the amount of force necessary to mount a conventional process cartridge into the main assembly of a conventional image forming apparatus. 
         [0105]    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. 
         [0106]    This application claims priority from Japanese Patent Application No. 135683/2008 filed May 23, 2008 which is hereby incorporated by reference.