PATENT ABSTRACT
A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, includes an electrophotographic photosensitive drum; developing roller for developing an electrostatic latent image formed on the electrophotographic photosensitive drum; drum frame supporting the electrophotographic photosensitive drum; a developing frame supporting the developing roller, the developing frame is movable relative to the drum frame and is capable of taking a contacting position in which the developing roller is in contact with the electrophotographic photosensitive drum; and a force receiving device including a first force receiving portion for receiving a first external force and a second force receiving portion for receiving a second external force, wherein the second force receiving portion is movable relative to the developing frame, wherein the second force receiving portion is placed in a stand-by position retracted from an operating position by the first force receiving portion receiving the first external force, and is movable from the stand-by position to the operating position for moving the developing frame from the contacting position to the spacing position, wherein a distance through which the second force receiving portion moves from the stand-by position to the operating position is larger than a distance through which the first force receiving portion is moved by the first external force.

PATENT DESCRIPTION
FIELD OF THE INVENTION AND RELATED ART 
       [0001]    The present invention relates to a process cartridge made up of an electrophotographic photosensitive drum and a development roller (which processes photosensitive drum), in particular, a process cartridge, the electrophotographic photosensitive drum and development roller of which can be placed in contact with, or separated from, each other. The present invention also relates to an electrophotographic image forming apparatus employing the above described process cartridge. 
         [0002]    In recent years, a process cartridge system has come to be widely used in the field of an image forming apparatus which uses an electrophotographic image forming process. A process cartridge system is one of the electrophotographic image forming systems. It uses a cartridge in which an electrophotographic photosensitive drum, and a development roller, that is, a roller for processing an electrophotographic photosensitive drum, are integrally disposed to make them removably mountable in the main assembly of an image forming apparatus. Thus, the employment of a process cartridge system makes it possible for a user to maintain an electrophotographic image forming apparatus without relying on a service person. This is why a process cartridge system has come to be widely used in the field of an electrophotographic image forming apparatus. 
         [0003]    A process cartridge is structured so that its development roller is kept pressured toward its electrophotographic photosensitive drum with the application of a preset amount of pressure, in order to keep the development roller in contact with the photosensitive drum when forming an image. In a case of a so-called contact development method, that is, a development method which places a development roller in contact with a photosensitive drum to develop a latent image on the photosensitive drum, the elastic layer of the development roller is kept pressed upon the peripheral surface of the photosensitive drum so that a preset amount of contact pressure is maintained between the peripheral surface of the development roller and that of the photosensitive drum. 
         [0004]    Therefore, if a process cartridge is left unused in the main assembly of an image forming apparatus for a substantial length of time, the elastic layer of the development roller sometimes deforms. Thus, if an image forming apparatus in which a process cartridge has been left unused for a substantial length of time is used for the first time thereafter, it is possible that a latent image will be nonuniformly developed. Further, in the case of a so-called contact development method, a development roller is in contact with a photosensitive drum during development. Therefore, developer sometimes transfers from a development roller onto the points of the peripheral surface of a photosensitive drum, to which developer is not supposed to adhere. Further, not only do a photosensitive drum and a development roller rotate in contact with each other during development, but also, during processes other than development. Therefore, a so-called contact development method exacerbates the deterioration of a photosensitive drum, a development roller, and developer. 
         [0005]    One of the solutions to the above described problem is proposed in Japanese Laid-open Patent Application 2003-167499. According to this patent application, an image forming apparatus is provided with a mechanism which acts on a process cartridge to keep an electrophotographic photosensitive drum and a development roller separated from each other when an image is not actually being formed (Patent Document 1). 
         [0006]    In the case of the image forming apparatus proposed in Patent Document 1, its main assembly is structured so that four process cartridges are removably mountable in the main assembly. Each cartridge is made up of a photosensitive member unit and a development unit. The photosensitive member unit has a photosensitive member. The development unit supports a development unit, and is connected to the photosensitive member unit so that it can be rotationally moved relative to the photosensitive member unit. Further, the main assembly of the image forming apparatus is provided with a separation plate, whereas the process cartridge is provided with a force receiving portion. As the separation plate is moved, the force receiving portion receives the force from the separation plate, causing the development unit to move relative to the photosensitive member unit. As a result, the development roller, which was in contact with the photosensitive drum, separates from the photosensitive drum. 
         [0007]    According to the prior art, the force receiving portion, that is, the portion which catches the force for separating a development roller and a photosensitive member from each other, remains projecting beyond the external contour of the development unit. Therefore, it is liable to be damaged while a user handles a process cartridge, or a process cartridge is conveyed alone. Further, the presence of the above described force receiving portion has been one of the major problems which arose when studies were made to reduce in size a process cartridge structured so that its electrophotographic photosensitive member and development roller can be placed in contact with, or separated from, each other, and also, when studies were made to reduce in size the main assembly of an image forming apparatus in which such a process cartridge as the one described above is removably mountable. 
       SUMMARY OF THE INVENTION 
       [0008]    The primary object of the present invention is to provide a process cartridge, the electrophotographic photosensitive drum and development roller of which can be placed in contact with, or separated from, each other, and which is significantly smaller in size than a counterpart in accordance with the prior art, and also, to provide an electrophotographic image forming apparatus which is compatible with a process cartridge in accordance with the present invention, is removably mountable and is significantly smaller in size than a counterpart in accordance with the prior art. 
         [0009]    Another object of the present invention is to provide a process cartridge, the electrophotographic photosensitive member and development roller of which can be placed in contact with, or separated from, each other, and the development unit moving force receiving portion of which is significantly less liable to be damaged while the process cartridge is handled by a user, or transported alone, than a counterpart in accordance with the prior art. 
         [0010]    These and other objects, features, and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]      FIG. 1  is a schematic sectional view of the electrophotographic image forming apparatus in the first embodiment of the present invention, showing the general structure of the apparatus. 
           [0012]      FIG. 2  is a schematic sectional view of the process cartridge in the first embodiment of the present invention. 
           [0013]      FIG. 3  is also a schematic sectional view of the electrophotographic image forming apparatus in the first embodiment of the present invention, showing the general structure of the apparatus. 
           [0014]      FIG. 4  is another schematic sectional view of the electrophotographic image forming apparatus in the first embodiment of the present invention, showing how the process cartridges therein are replaced. 
           [0015]      FIG. 5  is a schematic sectional view of one of the process cartridges, and its adjacencies, in the electrophotographic image forming apparatus in the first embodiment of the present invention, at a plane perpendicular to the axial line of the photosensitive drum. 
           [0016]      FIG. 6  is a schematic sectional view of the process cartridge in the first embodiment of the process cartridge, showing the movement of the structural components of the cartridge, which is related to the mounting of the process cartridge into the apparatus main assembly. 
           [0017]      FIG. 7  is a schematic side view (as seen from the side from which it receives cartridge driving force) of the process cartridge in the first embodiment of the present invention, which is being mounted into the apparatus main assembly, showing the movement the structural components of the cartridge, which is related to the mounting of the process cartridge into the apparatus main assembly. 
           [0018]      FIG. 8  is also a schematic sectional view (as seen from the side from which it receives cartridge driving force) of the process cartridge in the first embodiment of the present invention, which is being mounted into the apparatus main assembly, showing the movement of the structural components of the cartridge, which is related to the mounting of the process cartridge into the apparatus main assembly. 
           [0019]      FIG. 9  is an exploded perspective view of the process cartridge in the first embodiment of the present invention. 
           [0020]      FIG. 10(   a ) is a perspective view of the process cartridge in the first embodiment of the present invention, as seen from the side from which the cartridge is driven, and  FIG. 10(   b ) is a perspective view of the process cartridge in the first embodiment of the present invention, as seen from the side opposite from the side from which the cartridge is driven. 
           [0021]      FIG. 11  is a perspective view of the process cartridge in the first embodiment of the present invention, as seen from the side from which the cartridge is driven. 
           [0022]      FIG. 12  is a schematic drawing of the process cartridge in the second embodiment of the process cartridge, showing the movement of the structural components of the cartridge. 
           [0023]      FIG. 13  is an exploded perspective view of the process cartridge in the second embodiment of the present invention. 
           [0024]      FIG. 14  is a schematic drawing of the process cartridge in the third embodiment of the process cartridge, showing the movement of the structural components of the cartridge, which is related to the mounting of the process cartridge into the apparatus main assembly. 
           [0025]      FIG. 15  is an exploded perspective view of the process cartridge in the third embodiment of the present invention. 
           [0026]      FIG. 16  is a schematic drawing of the cartridge tray guiding hole of the electrophotographic image forming apparatus in the first embodiment of the present invention. 
           [0027]      FIG. 17  is a partially cutaway perspective view of the electrophotographic image forming apparatus in the first embodiment of the present invention. 
           [0028]      FIG. 18  is a schematic drawing of the pressing member, and the components related to the operation of the pressing member, in the first embodiment of the present invention, showing the movement of the pressing member. 
           [0029]      FIG. 19  is a schematic drawing of the force applying first member, and the components related to the operation of the force applying first member, in the first embodiment of the present invention, showing the operation of the force applying first member. 
           [0030]      FIG. 20  is a perspective view of the force receiving apparatus of the process cartridge in the first embodiment of the present invention. 
           [0031]      FIG. 21  is a schematic drawing of the process cartridge in the first embodiment of the present invention, the force receiving second member of which has been just been moved by the force applying second member of the cartridge. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiment 1 
       [0032]    Next, referring to  FIGS. 1-4 , the process cartridges and electrophotographic image forming apparatuses in this preferred embodiment of the present invention will be described. 
         [0033]      FIG. 1  is a schematic sectional view of the electrophotographic image forming apparatus  100  (which hereafter will be referred to simply as apparatus main assembly), in which multiple (four) process cartridges  50   y,    50   m,    50   c,  and  50   k  (which hereafter may be referred to simply as cartridges  50 ) which have been removably mounted. The multiple (four) cartridges  50  store yellow, magenta, cyan, and black toners (developers), one for one.  FIG. 2  is a schematic sectional view of the cartridge itself.  FIGS. 3 and 4  are schematic sectional drawings of the electrophotographic image forming apparatus in this embodiment, which are for showing how the any cartridge or cartridges  50  are removed from the main assembly of the image forming apparatus. 
       {General Structure of Electrophotographic Image Forming Apparatus} 
       [0034]    The electrophotographic image forming apparatus in this embodiment is structured to carry out the following image forming operation. Referring to FIG.  1 , first, the uniformly charged area of the peripheral surface of each of the electrophotographic photosensitive drums (which hereafter will be referred to as photosensitive drums)  30   y,    30   m,    30   c,  and  30   k  is scanned by a beam of laser light  11  projected by a laser scanner  10 , with which the apparatus main assembly  100  is provided, while being modulated with pictorial signals. As a result, an electrostatic latent image is effected on the peripheral surface of each photosensitive drum  30 . This electrostatic latent image is developed by a development roller  42 , into a visible image; an image is formed of toner (developer) on the peripheral surface of the photosensitive drum  30 . In other words, yellow, magenta, cyan, and black toner images are formed on the photosensitive drums  30   y,    30   m,    30   c,  and  30   k,  respectively. Then, these toner images are sequentially transferred by the voltages applied to transfer rollers  18   y,    18   m,    18   c,  and  18   k,  onto a transfer belt  19  supported and stretched by rollers  20 - 22 . Thereafter, the toner images on the transfer belt  19  are transferred by a transfer roller  3 , onto a sheet of recording medium P delivered by a recording medium conveyance roller  1  as a recording medium conveying means. Then, the recording medium P is conveyed to a fixation unit  6  made up of a driver roller, and a fixation roller having an internal heater. In the fixation unit  6 , heat and pressure is applied to the recording medium P and the toner images thereon. As a result, the toner images on the recording medium P are fixed to the recording medium P. Then, the recording medium P is discharged onto a delivery tray  9  by a pair of discharge rollers  7 . 
       {General Structure of Process Cartridge} 
       [0035]    Next, referring to  FIGS. 1 ,  2  and  10 , the cartridges  50  in this embodiment will be described. The multiple (four) cartridges  50  in this embodiment are the same in structure although they are different in the color of the toner T they store. Thus, the structure of the cartridges  50  will be described with reference to the cartridge  50   y.    
         [0036]    The cartridge  50   y  is provided with a photosensitive drum  30 , and processing means which process the photosensitive drum  30 . The processing means in this embodiment are a charge roller  32  which is the charging means for charging the photosensitive drum  30 , a development roller  42  which is the developing means for developing a latent image formed on the photosensitive drum  30 , a blade  33  which is the cleaning means for removing the residual toner remaining on the peripheral surface of the photosensitive drum  30 , etc. The cartridge  50   y  is made up of a drum unit  31  and a development unit  41 . 
       {Structure of Drum Unit} 
       [0037]    Referring to  FIGS. 2 and 10 , the drum unit  31  includes the abovementioned photosensitive drum  30 , charge roller  32 , and blade  33 . It also includes a waste toner storing portion  35 , a drum unit main frame  34 , and lateral covers  36  and  37  (which hereafter will be referred to simply as cover). Referring to  FIG. 9 , one of the lengthwise end portions of the photosensitive drum  30  is rotatably supported by the supporting portion  36   b  of the cover  36 , whereas the other lengthwise end of the photosensitive drum  30  is rotatably supported by the supporting portion  37   b  of the cover  37  as shown in  FIGS. 10(   a ) and  10 ( b ). The covers  36  and  37  are attached to the lengthwise ends of the drum unit main frame  34 . Next, referring to  FIG. 10(   b ), the lengthwise end portion of the photosensitive drum  30 , which is supported by the cover  36 , is provided with a coupling member  30   a  for transmitting driving force to the photosensitive drum  30 . The coupling member  30   a  engages with a first coupling member  105  of the apparatus main assembly  100 , shown in  FIGS. 4 and 7 , as the cartridge  50   y  is mounted into the apparatus main assembly  100 . Thus, as driving force is transmitted from a motor (unshown) with which the apparatus main assembly  100  is provided, to the coupling member  30   a,  the photosensitive drum  30  rotates in the direction indicated by an arrow mark U in  FIG. 2 . The charge roller  32  is supported by the drum unit main frame  34  so that it is rotated in contact with the photosensitive drum  30  by the rotation of the photosensitive drum  30 . The blade  33  is supported also by the drum unit main frame  34  so that it remains in contact with the peripheral surface of the photosensitive drum  30  with the presence of a preset amount of pressure between the blade  33  and the peripheral surface of the photosensitive drum  30 . The covers  36  and  37  are provided with holes  36   a  ( FIG. 9) and 37   a  ( FIGS. 10(   b )) for supporting the development unit  40  in such a manner that the development unit  40  is rotationally movable relative to the drum unit  31 . 
       {Structure of Development Unit} 
       [0038]    Referring to  FIGS. 2 and 9 , the development unit  41  has the abovementioned development roller  42 . It also has a development blade  43 , a development unit main frame  48 , a bearing unit  45 , and a pair of lateral covers  46 . The development unit main frame  48  has a toner storage portion  49  in which the toner to be supplied to the development roller  42  is stored. It supports the development blade  34  which regulates the thickness to which toner is coated on the peripheral surface of the development roller  42 . Referring to  FIG. 9 , the bearing unit  45  is firmly attached to one of the lengthwise end portions of the development unit main frame  48 . It rotatably supports the development roller  42 , one of the lengthwise end portions of which has a development roller gear  69 . Further, the bearing unit  45  is provided with an idler gear  68 , which transmits driving force from a coupling member  67  to the development roller bear  69 . The cover  46  is securely attached to the outward side of the bearing unit  45 , in terms of the lengthwise direction of the bearing unit  45 , in a manner to cover the coupling member  67  and idler gear  68 . Further, the cover  46  is provided with a cylindrical portion  46   b,  which protrudes outward from the outward surface of the cover  46 . The coupling member  67  is exposed through the hollow of the cylindrical portion  46   b.  The apparatus main assembly  100  and process cartridge  50   y  are structured so that as the process cartridge  50   y  is mounted into the apparatus main assembly  100 , the coupling member  67  engages with the second coupling  106  of the apparatus main assembly  100 , which is shown in  FIG. 17 , transmitting thereby driving force from the motor (unshown) with which the apparatus main assembly  100  is provided, to the process cartridge  50   y.    
       {Connection of Development Unit to Drum Unit} 
       [0039]    Referring to  FIGS. 9-11 , the development unit  41  and drum unit  31  are connected in the following manner: First, at one end of the process cartridge  50   y,  the cylindrical portion  46   b  is fitted into the supporting hole  36   a.  At the other end, a projection  48   b  which projects from the development unit main frame  48  is fitted into the supporting hole  37   a.  As a result, the development unit  41  is connected to the drum unit  31  in such a manner that the development unit  41  is rotationally movable relative to the drum unit  31 . Next, referring to  FIG. 2 , the development unit  41  is kept pressured by a pair of compression springs  95 , which are elastic members, in the direction to be rotated about the axial line of the cylindrical portion  46   b  so that the development roller  42  is kept in contact with the photosensitive drum  30 . That is, the development unit  41  is kept pressed by the resiliency of the compression springs  95  in the direction indicated by a narrow mark G, generating a moment H which acts in the direction to rotate the development unit  41  about the cylindrical portion  46   b  and projection  48   b.  Thus, the development roller  42  is kept in contact with the photosensitive drum  30  with the presence of the preset amount of contact pressure between the development roller  42  and photosensitive drum  30 . The position in which the development unit  41  is when it is kept in contact with the photosensitive drum  30  is referred to as “contact position”. 
         [0040]    Referring to  FIG. 10(   a ), the compression spring  95  in this embodiment is located on the opposite side from one of the lengthwise end portions, where the coupling member  30   a  of the photosensitive drum  30 , and the coupling member  67  which transmits driving force to the development roller gear  69 , are located. 
       {Force Receiving Apparatus} 
       [0041]    Referring to  FIG. 2 , the cartridge  50   y  is provided with a force receiving apparatus  90  for placing the development roller  42  and photosensitive drum  30  in contact with each other, or separating them from each other, in the apparatus main assembly  100 . 
         [0042]    Referring to  FIGS. 6 and 8 , which are schematic side views of the cartridge  50   y,  the cover  36  of which has been removed, as seen from the side from which the cartridge  50   y  is driven, the force receiving apparatus  90  is made up of a force receiving first member  71  and a force receiving second member  70 . Until the cartridge  50   y  begins to be positioned relative to the apparatus main assembly  100  in a preset manner, the force receiving second member  70  remains in its standby position, that is, the position in which the force receiving second member  70  does not project beyond the external contour of the cartridge  50   y,  as shown in  FIG. 10(   a ). As the cartridge  50   y  is advanced into the apparatus main assembly  100  in the direction indicated by an arrow mark Z 2  (shown in  FIG. 1)  by a cartridge tray  13  (which will be described later), the cartridge  50   y  is positioned in the apparatus main assembly  100  by a cartridge positioning portion  101   a  of the apparatus main assembly  100 . As the cartridge  50   y  is pressed against the cartridge positioning portion  101   a,  the force receiving first member  71  is pressed upward by a projection  180  (force receiving first member pressing member) of the apparatus main assembly  100 , which will be described later. That is, the force receiving first member  71  receives a first external force from the projection  180 . As a result, the force receiving portion  70  is moved out of its standby position, projecting outward of the cartridge  50   y  beyond the external contour of the cartridge  50   y,  as shown in  FIG. 11 . 
         [0043]    Next, referring to  FIGS. 6 ,  7 , and  9 , while the cartridge  50   y  is kept in its accurate positioned (image forming position) in the apparatus main assembly  100  by the positioning portion  101   a,  the force receiving first member  71  is below the force receiving second member  70 . The force receiving first and second members  71  and  70  are in connection with each other. More specifically, the force receiving second member  70  is rotatably supported by its rotational axle  70   b,  and is provided with an elongated hole  70   a.  The top end portion (in drawings) of the force receiving first portion  71  is provided with a projection (connective pin), which is fitted in the elongated hole of the force receiving second member  70 . Thus, as force is applied to the force receiving second member  70  by the force receiving first member  71 , more specifically, the projection (connective pin) of the force receiving first member, which is in the elongated hole  70   a  of the force receiving second member  70 , the force receiving first member  70  is rotationally moved about its rotational axle  70   b.    
         [0044]    Referring to  FIG. 7 , since the elongated hole  70   a  is located between the rotational axle  70   b  and the force catching surface  70   c,  a distance h 2  by which the force receiving second member  70  moves can be made greater than a distance h 1  ( FIG. 7 ) by which the force receiving first member  71  moves, by properly setting the leverage ratio of the force receiving second member  70 . Here, the distances by which the force receiving first and second members  71  and  70  move are the distances measured in terms of the vertical direction, that is, the direction parallel to the direction in which the force receiving member  71  is moved toward the force applying member  60  (which will be described later). That is, with the employment of the above described structural arrangement, the distance h 2  by which the force receiving second member  70  moves can be increased without increasing the projection  180  in the distance by which it projects, making it thereby possible to reduce in size the apparatus main assembly  100  shown in  FIG. 1 . Incidentally, the force receiving apparatus is movably supported by the cover  46 . 
       {Cartridge Tray of Electrophotographic Image Forming Apparatus Main Assembly} 
       [0045]    Next, the cartridge tray  13 , which is in the form of a drawer, will be described. 
         [0046]    Referring to  FIG. 4 , the cartridge tray  13  is attached to the apparatus main assembly  100  in such a manner that, in practical terms, it can be horizontally and linearly moved relative to the apparatus main assembly  100 . That is, the cartridge tray  13  can be pushed into, or pulled out of, the apparatus main assembly  100  in the direction indicated by an arrow mark Z 2  or Z 1 , respectively. The apparatus main assembly  100  is structured so that the cartridge tray  13  can be locked in the innermost position (image forming position, shown in  FIG. 1 , in the apparatus main assembly  100 ), and the outermost position (cartridge replacement position: cartridge mounting or removing position), shown in  FIG. 4 , which is the farthest position to which the cartridge tray  13  can be pulled out). The cartridge  50  is mounted into the cartridge tray  13  by an operator in the direction indicated by an arrow mark C, which is virtually parallel to the direction of gravity, as shown in  FIG. 4 . The cartridge tray  13  is structured so that as the cartridges  50  are mounted into the cartridge tray  13 , the cartridges  50  become arranged in tandem, in the direction parallel to the direction in which the cartridge tray  13  is movable, with their lengthwise direction (which is parallel to axial lines of photosensitive drum  30  and development roller  42 ) being perpendicular to the moving direction of the cartridge tray  13 . As the cartridge  13  is pushed into the apparatus main assembly  100 , the cartridges  50  in the cartridge tray  13  enter the apparatus main assembly  100 , with the presence of a preset amount of gap f 2  ( FIG. 5 ) between the photosensitive drum  30  in each cartridge  50 , and an intermediary transfer belt  19  located below the cartridge path. Then, as the cartridge tray  13  is moved into its innermost position in the apparatus main assembly  100 , each cartridge  50  is positioned in the apparatus main assembly  100  by the cartridge positioning portion  101   a  provided in the apparatus main assembly  100  ( FIGS. 5 and 7 ). The cartridge positioning operation will be described later in detail. A user is to close a door  12  after pushing the cartridge tray  13  all the way into the apparatus main assembly  100 . Closing the door  12  ensures that each cartridge  50  is properly mounted into the apparatus main assembly  100 . Therefore, in terms of operability, this structural arrangement for the apparatus main assembly  100  and cartridges  50  is superior to the structural arrangement of an electrophotographic image forming apparatus in accordance with the prior art, which requires the cartridges  50  to be individually mounted into the apparatus main assembly  100  by a user. 
         [0047]    Next, referring to  FIGS. 1 ,  3 ,  4 , and  17 , the operation of the cartridge tray  13  will be described.  FIG. 17  does not show the cartridges  50 , in order to make it easier to understand the operation of the cartridge tray  13 . 
         [0048]    The cartridge tray  13  is supported by a pair of tray supporting members  14  in such a manner that the cartridge tray  13  can be pulled out of the apparatus main assembly  100  while remaining supported by the tray supporting members  14 . The tray supporting members  14  are moved by the movement of the door  12 , which can be opened or closed by an operator (user). The door  12  is attached to the apparatus main assembly  100  so that it can be rotationally moved about its rotational axis  12   a.  The door  12  is rotationally movable between a position (shut position) in which it completely covers an opening  80 , as shown in  FIG. 1 , and a position (open position) in which it fully exposes the opening  80  as shown in  FIG. 3 . 
         [0049]    When it is necessary to take out any cartridge or cartridge  50  in the apparatus main assembly  100 , the door  12  is to be rotationally moved from the shut position to the open position. As the door  12  is rotationally moved, a pair of projections  15  (connective pins) with which the door  12  is provided moves in the clockwise direction about the rotational axis  12   a,  while moving in a pair of elongated holes  14   c,  one for one, with which the tray supporting member  14  is provided, from the bottom end of the elongated hole  14   c  toward the top end of the elongated hole  14   c,  as shown in  FIG. 3 . As a result, the tray supporting members  14  are moved by the projections  15  in the direction indicated by the arrow mark Z 1 . As the tray supporting members  14  are moved in the abovementioned direction, the projections  14   d   1  and  14   d   2 , which project from each of the tray supporting members  14  are guided by the guiding holes  107  with which the apparatus main assembly  100  is provided, as shown in  FIG. 4 . Referring to  FIG. 16 , each guiding hole  107  has three sections, that is, two horizontal sections  107   a   1  and  107   a   3 , and one diagonal section  107   a   2 . The diagonal section  107   a   2  extends diagonally upward from the horizontal section  107   a   1  to the horizontal section  17   a   3 . Therefore, as the door  12  is moved from the shut position, shown in  FIG. 1 , to the open position, shown in  FIG. 3 , the projections  14   d    1  and  14   d    2  are guided by the guiding hole  107 , sequentially through the horizontal portion  107   a   1 , diagonal portion  107   a   2 , and horizontal portion  107   a   3 . Thus, the tray supporting members  14  are first moved in the direction indicated by the arrow mark Z 1 , and then, are moved in the direction indicated by an arrow mark Y 1 , that is, direction to move away from the transfer belt  19 . With the tray supporting members  14  moved all the way in the direction indicated by the arrow mark Y 1 , the cartridge tray  13  can be pulled out of the apparatus main assembly  100  through the opening  80  in the direction indicated by the arrow mark Z 1 , as shown in  FIG. 4 .  FIG. 17  is a partially cutaway perspective view of the image forming apparatus after the cartridge tray  13  has been pulled out of the apparatus main assembly  100  to its outermost position. 
         [0050]    Next, the case in which any cartridge or cartridges  50  are mounted into the apparatus main assembly  100  will be described. Referring to  FIG. 4 , the cartridge tray  13  is to be pushed into the apparatus main assembly  100  in the direction of the arrow mark Z 2  through the opening  80 , with the door  12  kept in the open position. Thereafter, the door  12  is to be moved into the shut position as shown in  FIG. 2 . As the door  12  is moved, each of the projection  15  of the door  12  moves in the counterclockwise direction about the rotational axis  12   a,  while moving in the corresponding elongated hole  14   c  of the tray supporting member  14 , toward the bottom end  14   c   2  of the elongated hole  14   c,  as shown in  FIG. 1 . Thus, the tray supporting member  14  is moved in the direction of the arrow mark Z 2  by the pair of projections  15 . Therefore, as the door  12  is moved into the shut position as shown in  FIG. 1 , the projections  14   d   1  and  14   d   2  ( FIG. 4 ) are guided by the horizontal portion  107   a   1 , diagonal portion  107   a   2 , and horizontal portion  107   a   3 , in the listed order, as shown in  FIG. 16 . Therefore, the tray supporting members  14  move, first, in the direction of the arrow mark Z 2 , and then, in the direction of the arrow mark Y 2 , that is, the direction to move closer to the transfer belt  19 , as shown in  FIG. 1 . 
       {Positioning of Process Cartridge Relative to Electrophotographic Image Forming Apparatus Main Assembly} 
       [0051]    Next, referring to  FIGS. 5 ,  17 , and the positioning of the cartridge  50  in the apparatus main assembly  100  will be described. Referring to  FIG. 17 , the apparatus main assembly  100  is provided with multiple pairs (four pairs in this embodiment) of cartridge positioning portions  101   a  for positioning a cartridge  50  relative to the apparatus main assembly  100 . That is, each cartridge compartment of the cartridge tray  13  is provided with a pair of cartridge positioning portions  101   a,  which are located at the lengthwise ends of the corresponding compartment, one for one, in terms of the direction parallel to the lengthwise direction of the cartridge  50 , in a manner to sandwich the transfer belt  19 . Referring to FIGS.  18 ( a ) and  18 ( b ), there are pressing members  61  ( 61   y,    61   m,    61   c,  and  61   k ) above each of the tray supporting members  14 . Each pressing member  61  is provided with a hole  61   d,  through which a pressing member supporting shaft  55 , with which the apparatus main assembly  100  is provided, is put to rotatably support the pressing member  61 . 
         [0052]    Referring again to  FIGS. 18(   a ) and  18 ( b ), as the door  12  is moved from the open position to the shut position (in X direction), the pressing member  61  is moved in the direction indicated by an arrow mark Z, pressing thereby on the top surface of the drum unit main frame  34  as shown in  FIG. 20 . Therefore, the cartridge  50   y  is pressed in the direction indicated by an arrow mark P in  FIG. 7 , causing the cartridge positioning portion  31   b,  with which the drum unit  31   y  is provided, to come into contact with the cartridge positioning portion  101   a  of the apparatus main assembly  100 . As a result, the cartridge  50   y  is properly positioned in the apparatus main assembly  100 . Similarly, the cartridges  50   m,    50   c,  and  50   k  are properly positioned in the apparatus main assembly  100 . 
         [0053]    Further, as the cartridge  50  is made to descend toward the positioning portion  101   a  by the movement of the door  12 , the projection  180  of the apparatus main assembly  100  comes into contact with the force receiving portion  71   c  of the force receiving first member  71 , which is in the bottom portion of the cartridge  50 . That is, the force receiving member  71  receives force from the projection  180 , from the bottom side of the cartridge  50 . In comparison, when the door  12  is moved from the shut position to the open position (Y direction), the pressing member  61  moves in the direction indicated by an arrow mark J. As a result, the pressing member  61  separates from the top surface of the drum unit main frame  34  as shown in  FIG. 5 . 
       {Development Roller Separating Mechanism of Electrophotographic Image Forming Apparatus Main Assembly} 
       [0054]    Next, the operation of the force applying first portion  60  will be described. 
         [0055]    Referring to  FIGS. 1 ,  3  and  19 , in terms of the vertical direction of the apparatus main assembly  100 , the force applying member  60  is positioned so that after the proper positioning of the cartridge  50 , the force applying member  60  is above the cartridge  50 . In terms of the axial line of the photosensitive drum  30 , the force applying member  60  is positioned so that it is enabled to come into contact with the force receiving second member  70  which is at the corresponding lengthwise ends of the cartridge  50 . 
         [0056]    Driving force is transmitted from a motor  110  (mechanical power source) with which the apparatus main assembly  100  is provided, to a gear  112  through a gear  111 . As the driving force is transmitted to the gear  112 , the gear  112  rotates in the direction indicated by an arrow mark L, rotating thereby the cam portion  112   a,  which is integral with the gear  112 , in the arrow L direction. The cam portion  112   a  is in contact with the moving force receiving portion  60   b,  with which the force applying member  60  is provided. Therefore, as the cam portion  112   a  rotates, the moving force receiving member  60  is moved in the direction indicated by an arrow mark E or B. 
         [0057]    Referring to  FIG. 19(   a ), as the force applying member  60  moves in the direction indicated by the arrow mark E, a rib  60   y  of the force applying member  60  separates from the force receiving second member  70 , as shown in  FIG. 7 , allowing thereby the development roller  42  to come into contact with the photosensitive drum  30 . This position of the development unit  41 , which allows the development roller  42  to remain in contact with the photosensitive drum  30 , will be referred to as the contact position. 
         [0058]    Referring to  FIG. 19(   b ), as the force applying member  60  is moved in the direction indicated by the arrow mark B, the rib  60   y  comes into contact with the force receiving second member  70 , subjecting the force receiving second member  70  to external force (second external force) through the rib  60   y.  Therefore, the development unit  41  is rotated (rotationally moved) about the cylindrical portion  46   b  (rotational axle), separating thereby the development roller  42  from the photosensitive drum  30 . This position of the development unit  41 , which keeps the development roller  42  separated from the photosensitive drum  30 , will be referred to as the separation position. 
         [0059]    Similarly, the force applying member  60  is positioned above the path of the cartridge  50 , through which the cartridge  50  is moved into the apparatus main assembly  100  by the cartridge tray  13 . The force receiving second member  70  is attached to the cartridge  50  in such a manner that until the cartridge  50  is moved into the apparatus main assembly  100 , the force receiving second member  70  remains in its standby position ( FIG. 5 ). Therefore, the force applying member  60  can be positioned significantly closer to the cartridge path, without allowing the force applying member  60  and cartridge  50  to interfere with each other during the mounting of the cartridge  50 , compared to the force applying member of an image forming apparatus in accordance with the prior art, making it possible to minimize wasted space, making it thereby possible to significantly reduce the cartridge  50   y  in terms of its dimension in terms of its lengthwise direction (axial direction of photosensitive drum  30 ) as well as the vertical direction of the apparatus main assembly  100 . The detailed description of the force applying member  60  will be given later. 
         [0000]    {Description of Mounting of Process Cartridge into Electrophotographic Image Forming Apparatus Main Assembly, and Operation of Force Receiving Apparatus} 
         [0060]    Next, the operational sequence from the beginning of the mounting of the cartridge  50  into the apparatus main assembly  100 , to the separation of the development roller  42  from the photosensitive drum  30 , will be described. 
         [0061]    Referring to  FIG. 4 , after the cartridge tray  13  is pulled out of the apparatus main assembly  100  to its outermost position, each cartridge  50  can be mounted into, or removed from, the cartridge tray  13  in the vertical direction, which is indicated by the arrow mark C. 
         [0062]    After the mounting of the cartridge(s)  50  into the cartridge tray  13 , the cartridge tray  13  is to be moved into the apparatus main assembly  100  in the direction indicated by the arrow Z 2 , through the opening  80 . That is, in this embodiment, each cartridge  50  is horizontally moved into the apparatus main assembly  100 , from the direction which is intersectional (roughly perpendicular) to the axial line of the photosensitive drum  30 . 
         [0063]    Referring to  FIG. 3 , the cartridge  50   y  is mounted in the downstream end of the cartridge tray  13  in terms of the direction in which the cartridge tray  13  is moved into the apparatus main assembly  100 . That is, the cartridge  50   y  moves below the ribs  60   k    60   c,  and  60   m  of the force applying member  60  from upstream to downstream. 
         [0064]    If the apparatus main assembly  100  and cartridge  50   y  are structured so that the force receiving second member  70  remains projecting when the cartridge  50   y  is moved into the apparatus main assembly  100 , the pressing member  61  and force applying member  60  must be positioned significantly higher than they are positioned in this embodiment. In this embodiment, however, the apparatus main assembly  100  and cartridge  50   y  are structured so that the force receiving second member  70  remains in the above described standby position when the cartridge  50   y  is moved into the apparatus main assembly  100 . Therefore, the pressing member  61  and force applying member  60  can be positioned as closely as possible, without taking into consideration the distance by which the force receiving second member  70  projects beyond the external contour of the cartridge  50   y.  In other words, the pressing member  61  and force applying member  60  can be positioned significantly closer to the path of the cartridge  50   y,  making it possible to reduce the cartridge  50   y  in dimension in terms of the direction parallel to the vertical direction of the apparatus main assembly  100 , compared to the counterparts of a process cartridge in accordance with the prior art. Further, referring to  FIG. 20 , in terms of the direction parallel to the axial line of the drum  30 , the force receiving apparatus  90 , pressing member  61 , and force applying member  60  overlap, making it possible to reduce thereby the cartridge  50   y  in dimension in terms of the lengthwise direction of the cartridge  50   y.    
         [0065]    Next, referring to  FIG. 5 , the image forming apparatus in this embodiment is structured to ensure that when the cartridge tray  13  is moved into the apparatus main assembly  100 , there remain a gap f 1  between the force applying member  60  and force receiving second member  70 , and a gap f 2  between photosensitive drum  30  and transfer belt  19 . Therefore, the cartridge  50  and apparatus main assembly  100  do not interfere with each other when the cartridge  50  is moved into the apparatus main assembly  100 . 
         [0066]    After the cartridge tray  13  is pushed all the way into the apparatus main assembly  100 , the door  12  is to be moved into the shut position as shown in  FIGS. 1 and 18(   b ). As the door  12  is moved into the shut position, the tray supporting members  14  are moved toward the transfer belt  19  (direction indicated by arrow mark Y 2 ). Hereafter, the vertical component of this movement of the tray supporting members  14  in the direction indicated by the arrow mark Y 2  will be referred to as a distance f 2 . As the tray supporting members  14  are moved in the direction indicated by the arrow mark Y 2 , the cartridges  50  are moved toward the transfer belt  19  by the movement of the tray supporting members  14 , causing thereby the peripheral surface of the photosensitive drum  30  in each cartridge  50  to come into contact with the surface of the transfer belt  19 . By the time the peripheral surface of the photosensitive drum  30  comes into contact with the surface of the transfer belt  19 , the gap f 1  between the force receiving apparatus  90  and force applying member  60  widens to the sum of the gaps f 1  and f 2 , as shown in  FIG. 5 . 
         [0067]    Further, as the door  12  is moved into the shut position, the pressing member  61  is moved by the movement of the door  12 , pressing thereby on the top surface of the drum unit main frame  34 . Therefore, the cartridge positioning portion  31   b  of each cartridge  50  is placed in contact with the cartridge positioning portion  101   a  of the apparatus main assembly  100 . Consequently, each cartridge  50  is properly positioned relative to the apparatus main assembly  100 , as shown in  FIG. 7 . 
         [0068]    Further, a shaft  36   d,  shown in  FIG. 10 , with which the cover  36  of each cartridge  50  is provided, engages with the cartridge rotation stopping portion  13   a  ( FIG. 17 ), with which the cartridge tray  13  is provided. Therefore, the cartridge  50  is prevented from moving further in the direction indicated by an arrow mark a in  FIG. 1 , in the apparatus main assembly  100 . 
         [0069]    Next, referring to  FIG. 6 , the home position of the force applying member  60  in this embodiment is made to be where the force applying member  60  keeps the development roller  42  separated from the photosensitive drum  30 . This is for the following reason. That is, while the image forming apparatus is not used for image formation after the mounting of the cartridges  50 , each cartridge  50  remains in the state shown in  FIG. 8 . That is, the force applying member  60  has moved in the direction indicated by the arrow mark B, and the force receiving second member  70  has been moved by the rib  60   y  as far as it can be moved. While the cartridge  50  is in this state, the photosensitive drum  30  and development roller  42  remain separated from each other. It is in this state, shown in  FIG. 8 , in which the photosensitive drum  30  and development roller  42  remain separated from each other, that the cartridge  50  is removed from the apparatus main assembly  100 . Thus, when the cartridge  50  is mounted into the apparatus main assembly  100  next time, the force applying member  60  is in the position shown in  FIG. 8 . Therefore, as the cartridge  50  is mounted, the force receiving second member  70  comes into contact with the rib  60   y,  because the force receiving second member  70  is out of its standby position, as shown in  FIG. 6 . Thus, the force receiving first portion  71  is provided with an elastic portion  71   b,  which is formed as an integral part of the force receiving first portion  71 , as shown in  FIG. 6 . Therefore, as the contact between the force receiving second member  70  and rib  60   y  begins to interfere with the inward movement of the cartridge  50 , the elastic portion  71   b  gives in (is compressed), preventing thereby the force receiving apparatus  90  from being damaged. 
         [0070]    As the force applying member  60 , which is in the state shown in  FIG. 6 , is moved in the direction indicated by an arrow mark E as shown in  FIG. 7 , the force receiving second member  70  projects outward farther from the cartridge  50   y,  entering thereby the path of the rib  60   y.  This position of the force receiving second member  70 , that is, the position in which the force receiving second member  70  is in the path of the rib  60   y,  will be referred to as the outermost position (active position). That is, when the force receiving second member  70  is in its outermost position, the distance of the projection of the force receiving second member  70  is greater than that when the force receiving second member  70  is in the abovementioned standby position, which is obvious. In order for the force receiving second member  70  to engage with the force applying member  60 , the distance of the projection of the force receiving second member  70  at the outermost position must be greater than the sum of the gaps f 1  and f 2 . Further, the action of the force applying member  60  is triggered in a period between the completion of the mounting of the cartridges  50  into the apparatus main assembly  100  and the starting of an image forming operation. 
         [0071]    Next, referring to  FIG. 8 , as the force applying member  60  is moved in the direction indicated by the arrow mark B, the lateral surface  70   c,  which is the force receiving second portion of the force receiving second portion  70 , receives external force (second external force) through the rib  60   y   3 , since the force receiving second member  70  (lateral surface  70   c ) is in the path of the force applying member  60 . Therefore, the development unit  41  is rotationally moved about its rotational axis  46   b  (shaft), causing thereby the development roller  42  to separate by a gap α from the photosensitive drum  30 . It is in its outermost position that the force receiving second member  70  receives the external force (second external force) from the force applying member  60 . Therefore, this structural arrangement is greater in the distance between the force applying member  60  and the rotational axis  46   b  of the development unit  41  than a structural arrangement which moves the force applying member toward the process cartridge to separate the development roller from the photosensitive drum. Therefore, the employment of this structural arrangement makes it possible to reduce the amount of torque necessary to separate the development roller  42  from the photosensitive drum  30 . 
         [0072]    In this embodiment, the elastic portion  71   b  is an integral part of the force receiving first member  71 . However, as long as it is enabled to absorb the force applied to the force receiving first member  70  by the abovementioned change in the position of the cartridge  50 , it may be formed as a part of another component, or as an independent component. For example, the force applied to the force receiving first member  71  by the change in the position of the cartridge  50  may be absorbed by placing an absorbing member independent from the force receiving second and first members  70  and  71 , between the force receiving second and first members  70  and  71 , or by forming the force receiving second member of an elastic material so that the above described force can be absorbed by the deformation of the force receiving second member  71  itself. 
         [0073]    Before the starting of an image forming operation, the force applying member  60  is moved in the direction indicated by the arrow mark E to place the development roller  42  in contact with the photosensitive drum  30 . As the force applying member  60  is moved in the abovementioned direction, the force receiving second member  70  stops receiving force from the rib  60   y,  as shown in  FIG. 7 . Therefore, the development roller  42  is placed in contact with the photosensitive drum  30  by the resiliency of the compression springs  95  provided between the development unit  41  and drum unit  31 , readying thereby the process cartridge  50  for image formation. It is before the development roller  42  comes into contact with the photosensitive drum  30  that the photosensitive drum  30  begins to be rotated, and the development roller  42  begins to be rotated, by the driving force which the cartridge  50  receives from the apparatus main assembly  100  through the coupling portion  67 . This is for the following reason. That is, referring to  FIG. 10(   a ), the coupling portion  67  is made coaxial with the cylindrical portion  46   b  so that even when the development unit  41  moves about the cylindrical portion  46   b,  the coupling portion  67  does not change in position. That is, in this embodiment, it is before the development roller  42  is placed in contact with the photosensitive drum  30  that the development roller  42  and photosensitive drum  30  begin to be rotated. This arrangement makes it possible to minimize the difference in peripheral velocity between the photosensitive drum  30  and development roller  42  when the development roller  42  comes into contact with the photosensitive drum  30 . Therefore, it can minimize the amount of the wear that occurs to the photosensitive drum  30  and development roller  42  when the two come into contact with each other. After the completion of the image forming operation, the development roller  42  is separated from the photosensitive drum  30  by moving the force applying member  60  in the direction indicated by the arrow mark B as described above. It is after the separation of the development roller  42  from the photosensitive drum  30  that the development roller  42  and photosensitive drum  30  are stopped. Thus, this arrangement minimizes the difference in the peripheral velocity between the development roller  42  and photosensitive drum  30 , which occurs when the two become separated. Therefore, it minimizes the amount by which the development roller  42  and photosensitive drum  30  wear when they are separated from each other. Consequently, this arrangement improves an image forming apparatus in image quality. 
         [0074]    Next, the operation for removing the cartridge  50  from the apparatus main assembly  100  will be described. 
         [0075]    First, the door  12  is to be moved from its shut position to the open position. As the door  12  is moved, the tray supporting members  14  are raised in the direction to separate from the transfer belt  19  as shown in  FIGS. 3 and 4 . Therefore, the cartridges  50  are moved upward, causing the photosensitive drum  30  in each cartridge  50  to separate from the transfer belt  19 . Further, the pressing member  61  is rotated in the direction indicated by the arrow mark J in  FIG. 5 , being separated from the drum unit  31 , as described above. Thus, the force receiving first member  71  separates from the projection  180 , being thereby deprived of the force to keep the force receiving second member  70  projecting beyond the external contour of the development unit  41 . 
         [0076]    As for the force receiving second member  70 , its slant surface  70   y   2  comes into contact with the slant surface  60   y   2  of the force applying  60 , as shown in  FIG. 21 . Thus, the force receiving second member  70  is rotationally moved about its rotational axis  70   a,  back into its standby position (inaction position), by the component of the force to which the slant surface  70   y   2  is subjected as the cartridge  50  (cartridge tray  13 ) is pulled out. Incidentally, a spring may be employed, as in another embodiment of the present invention, as the means for generating the force for returning the force receiving second member into its standby position. That is, the first embodiment, in which the abovementioned spring is not employed, was presented as the embodiment which is smallest in the components count. 
         [0077]    As described above, in this embodiment, the apparatus main assembly  100  and cartridge  50  are structured so that as the door  12  is moved into its shut position after the cartridge  50  is mounted into the apparatus main assembly  100 , the force receiving second member  70  for moving the development unit  41  projects beyond the outward surface of the development unit  41 . Therefore, the cartridge  50  in this embodiment is significantly smaller in height than a cartridge ( 50 ) in accordance with the prior art. Further, the force receiving second member  70  remains in its standby position while the cartridge  50  is mounted. Therefore, the space necessary, in the apparatus main assembly  100  in this embodiment, for the movement of the cartridge(s)  50  does not need to be as large as that in the main assembly of an image forming apparatus in accordance with the prior art. That is, the present invention makes it possible to reduce the opening  80  in size, and also, makes it possible to place the force applying member  60  significantly closer to the path of the cartridge  50  than the prior art, making it thereby possible to reduce the apparatus main assembly  100  in vertical dimension. Further, the force receiving apparatus  90 , pressing member  61 , and force applying member  60  are positioned so that they overlap in terms of the direction parallel to the axial line of the drum, as shown in  FIG. 20 , making it possible to reduce the cartridge in its lengthwise dimension. 
         [0078]    Further, when the cartridge  50  is handled by a user, or is transported alone, the force receiving second member  70  remains in its standby position, being therefore unlikely to be damaged. 
         [0079]    In this embodiment, the apparatus main assembly  100  is structured so that its projection  180  is below the path of the cartridge  50 . However, as long as the projection  180  comes into contact with the force receiving first member  71  while the cartridge  50  is mounted into the apparatus main assembly  100 , it does not matter where the projection  180  is positioned. Moreover, the shape of the projection  180  is optional, as long as the projection  180  is enabled to move the force receiving portion  71   c  by coming into contact with the force receiving portion  71   c.  In other words, the force receiving portion  71   c  may be a stationary projection which projects from the cover  46 . However, if the force receiving portion  71   c  is made stationary, the force receiving portion  71   c  must be adjusted in height to prevent the force receiving portion  71   c  from coming into contact with the apparatus main assembly  100  while the cartridge  50   y  is mounted into the apparatus main assembly  100 . 
       Embodiment 2 
       [0080]    Next, referring to  FIGS. 12 and 13 , another preferred embodiment of the present invention will be described. In this embodiment, the cartridge  50  is provided with a first lever  471 , a second lever  470 , and a gear  472 . The first lever  471  has a force receiving first portion  471   c.  The second lever  470  has a force receiving second portion  470   c,  and meshes with the gear  472 . This structural arrangement can move the second lever by a greater distance than the distance by which the first lever is moved. 
         [0081]    The gear  472  is a step gear made up of a portion (first portion) which engages with the first lever  471  and is n 1  in tooth count, and a portion (second portion) which engages with the second lever  470  and is n 2  in tooth count. Thus, it is possible to amplify the distance by which the first level  471  is moved by making the tooth count n 2  of the second portion of the gear  472  greater than the tooth count n 1  of the first portion of the gear  472  (n 2 &gt;n 1 ). To concretely described the operation of the force receiving apparatus in this embodiment, referring to  FIG. 12(   a ), while the cartridge  50  is inserted into the apparatus main assembly  100 , the second lever  470  remains within the cartridge  50 . Then, when the cartridge  50  is properly positioned relative to the apparatus main assembly  100  by the cartridge positioning portion  101   a,  the force receiving first portion  471   c  begins to receive external force (first external force) from the projection  180 , being thereby moved upward as indicated by an arrow mark F 2 . As the force receiving first portion  471   c  moves upward as indicated by the arrow mark F 2 , the gear  472  is rotated, and this rotation of the gear  472  causes the second lever  470  to move upward. Thus, immediately after the cartridge  50  is properly positioned by the cartridge positioning portion  101   a,  the second lever  470  is in its outermost position as shown in  FIG. 12(   b ). When the second lever  470  is in its outermost position, the force receiving portion  470   c  of the lever  470  receives the external force (second external force) from the rib  60   y   3  in the same manner as the force receiving second portion  70   c  of the force receiving second member  70  receives external force from the rib  60   y   3  in the first embodiment. 
         [0082]    Further, in this structural arrangement, a coil spring  473  is provided to ensure that the second lever  470  always returns to its standby position. The reason therefor is as follows: It is assumed that from the standpoint of apparatus design, it is difficult to ensure that the component of the force which the slant surface  60   y   1  receives is large enough to return the force receiving portion  470   c  to its original position (for example, if the amount of the force necessary to pull cartridges (cartridge tray) increases). In other words, the provision of the coil spring  473  is not mandatory, as it is not in the first embodiment. 
         [0083]    This embodiment, however, will be described with reference to a case where the coil spring  473  is provided. In this case, unless the resiliency of the coil spring  473  is smaller than the resilience of the elastic portion  471   b  which is an integral part of the lever  471 , the force receiving first member  470  is not allowed to move. Therefore, all that is necessary is to set the relationship between a force F 1  which is generated by the coil spring  473 , and a force F 2  which is generated by the elastic member  471   b,  to be F 1 &lt;F 2 . 
         [0084]    In this embodiment, the cartridge  450  is designed to be assembled in the following manner: First, the gear  472  is rotatably supported by the cover  446  which is firmly attached to the bearing unit  445 , and then, the second lever  470  and first lever  471  are attached so that the two levers mesh with the corresponding portions of the gear  472 . The shape of the apparatus main assembly in this embodiment is the same as that of the apparatus main assembly in the first embodiment. Therefore, the force receiving portion which is necessary to place the development roller in contact with the photosensitive drum, or separating the development roller from the photosensitive drum, is the tip  470   c  of the second lever  470 . Otherwise, this embodiment is the same as the first embodiment. 
         [0085]    As described above, the force receiving apparatus in this embodiment is the same in effectiveness as that in the first embodiment. In this embodiment, however, the distance by which the second lever is moved can be easily changed by changing the gear ratio between the first and second portions of the gear  472 . 
         [0086]    Also in this embodiment, when the cartridge tray is pulled out, the force receiving member  470  comes into contact with the slant surface  60   y   2 . Then, as the cartridge tray is pulled out further, the force receiving second member  470  is pushed back into the development unit, and stored therein, by being moved in the direction indicated by an arrow mark F 2  by the slanted surface  60   y   2 . Therefore, the provision of the return spring  473  is not mandatory. 
       Embodiment 3 
       [0087]    Next, referring to  FIGS. 14 and 15 , the third embodiment of the present invention will be described with reference to a case where the force receiving first member belongs to a drum unit  531 . First, the method for assembling the cartridge in this embodiment will be described. The cartridge in this embodiment is designed so that a force receiving first member  571  belongs to a drum unit  531 . A force receiving second member  570  and a connective rod  574  are attached to a cover  546 . Then, the cover  536  is joined with a bearing member  545 . Lastly, the development unit  541  and drum unit  531  are connected by the cover  536  to complete the cartridge  550 . 
         [0088]    To describe in more detail the cartridge  550  in this embodiment with reference to  FIGS. 14 and 15 , first, referring to  FIG. 14 , a projection  5180  of the apparatus main assembly is located so that it opposes the drum unit. Thus, the force receiving first member  571  is placed in the drum unit  531 . 
         [0089]    The drum unit is provided with the force receiving first member  571 , which has a force receiving first portion  571   c  and is movable. Further, the drum unit is provided with a rod  571  and a connective rod  574 . The connective rod  574  is rotationally movable about the rotational axis  574   a  while remaining in contact with the rod  571 . The development unit is provided with a force receiving second member  570 , which has an elongated hole  570   b  and is rotationally movable about a rotational axis  570   a.  Further, the opposite lengthwise end of the connective rod  574  from the rod  571  is provided with a projection (connective pin) which fits in the elongated hole of the force receiving second member  570 . 
         [0090]    When the cartridge  550  is properly positioned relative to the apparatus main assembly  101  by the cartridge positioning portion  101   a,  the force receiving first portion  571   c  begins to receive external force (first external force) from the projection  5180 . Therefore, the force receiving first member  571  begins to be moved in the direction indicated by an arrow mark I as shown in  FIG. 14(   b ), causing the connective rod  574  to rotationally move in the direction (clockwise direction) indicated by an arrow mark m. Thus, the force receiving second member  570  is rotationally moved about the rotational axis  570   a  in the direction to move the opposite end portion of the  570  from the elongated hole  570   b,  arcuately upward, as indicated by an arrow mark n. Since the curvature of the elongated hole  570   b  is such that while the development roller is not in contact with the photosensitive drum, the center of the curvature of the elongated hole  570   b  coincides with the rotational axis of the development unit  541 . Therefore, while the development unit  541  is separated from the drum unit  531 , the connective rod  574  is subjected to no load. Also in this embodiment, a return spring ( 573 ) is provided. However, the return spring  573  may be eliminated by a design change. 
         [0091]    Also in this embodiment, the distance by which the force receiving second member is moved can be made greater than the distance by which the force receiving first member is moved, by properly selecting the leverage ratio of the connective rod. 
         [0092]    Further, in this embodiment, when the cartridge tray is pulled out, the force receiving member  570  comes into contact with the slant surface  60   y   2  as does the force receiving first member  70  in the first embodiment. Then, as the cartridge tray is pulled out further, the force receiving second member  570  is pushed back into the development unit  541  to be stored therein, by being moved in the direction opposite from the direction indicated by the arrow mark n. Therefore, the provision of the return spring  573  is not mandatory. 
         [0093]    According to the present invention, it is possible to reduce in size a process cartridge, the electrophotographic photosensitive drum and development roller of which can be placed in contact with, or separated from, each other. It is also possible to reduce in size an electrophotographic image forming apparatus which employs the abovementioned process cartridge. Further, it is possible to structure an electrophotographic image forming apparatus so that its force receiving apparatus for separating the development roller from the electrophotographic photosensitive drum is unlikely to be damaged while the abovementioned process is handled by a user, or is transported alone. 
         [0094]    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. 
         [0095]    This application claims priority from Japanese Patent Applications Nos. 172742/2007 and 162311/2008 filed Jun. 29, 2007 and Jun. 20, 2008, respectively, which are hereby incorporated by reference.