Abstract:
A color electrophotographic image forming apparatus includes plural cartridge mounting portions for demountably mounting independently removable cartridges, a moving unit that includes the cartridge mounting portions and is movable between an image forming position and a mounting and demounting position for mounting and demounting the cartridges, and a mounting and demounting position locking member for locking the moving unit in the mounting and demounting position to prevent movement to the image forming position when at least one of the cartridges is not mounted in the corresponding cartridge mounting portion. The mounting and demounting position locking member is movable from an unlocking position to a locking position in interrelation with demounting of any one of the cartridges from its corresponding cartridge mounting portion, and to the unlocking position when all of the plurality of cartridges are mounted in their corresponding plurality of cartridge mounting portions.

Description:
[0001]    This application is a divisional of U.S. patent application Ser. No. 12/713,408, filed Feb. 26, 2010. 
     
    
     FIELD OF THE INVENTION AND RELATED ART 
       [0002]    The present invention relates to a color electrophotographic image forming apparatus, wherein a plurality of cartridges are dismountably mounted to a main assembly, and an image is formed on a recording material. 
         [0003]    Here, the color electrophotographic image forming apparatus forms a color image on the recording material using an electrophotographic image forming process. The examples of the color electrophotographic image forming apparatus include a color electrophotographic copying machine, a color electrophotographic printer (color laser beam printer, color LED printer, for example), a color facsimile device, and a color word processor. The image is formed by the electrophotographic image forming apparatus on a recording material, and the recording material is paper or an OHP sheet, for example. The cartridge is a process cartridge, a developing cartridge or the like and contributes to an image forming process for forming the image on the recording material in the state that it is mounted to the main assembly of the electrophotographic image forming apparatus. Here, the process cartridge contains at least one of the charging means, developing means, and cleaning means as process means, and the electrophotographic photosensitive drum as a unit integrally, and it is dismountably mountable to the main assembly. The process cartridge may contain the developing means as the process means and the electrophotographic photosensitive drum as a unit, and it is dismountably mounted to the main assembly of the electrophotographic image forming apparatus. The process cartridge may contain the charging means, the developing means, or the cleaning means as the process means and the electrophotographic photosensitive drum as a unit, and it is dismountably mounted to the main assembly. The process cartridge which is provided integrally with the electrophotographic photosensitive drum and the developing means is called an integral-type process cartridge. The process cartridge which is provided integrally with the electrophotographic photosensitive drum and the process means other than the developing means is called a discrete type process cartridge. In this case, the developing means is provided in a developing unit not integrally with the process cartridge, and the discrete type process cartridge forms the image using the combination with such a developing unit. The process cartridge is mounted and demounted relative to the main assembly by a user. For this reason, the maintenance of the apparatus is easy. The process means acts on the electrophotographic photosensitive drum. The developing cartridge is provided with a developing roller, and an electrostatic latent image formed on the electrophotographic photosensitive drum is developed by the developing roller. It contains a developer (toner) for the development, and is dismountably mounted to the main assembly. In the case of the developing cartridge, the electrophotographic photosensitive drum is mounted to the main assembly or a cartridge supporting member. Or, the electrophotographic photosensitive drum is provided in a so-called discrete type process cartridge. In this case, the process cartridge is not provided with the developing means. The developing cartridge is also mounted and demounted relative to the main assembly by the user. For this reason, the maintenance of the device is easy. Therefore, the cartridge in this invention includes the process cartridges of a so-called integral type or a so-called discrete type. The cartridge includes the combination of the so-called process cartridge of the discrete type and the developing cartridge. In another example of the cartridge, the electrophotographic photosensitive drum is mounted fixedly to the main assembly or the cartridge supporting member and the detachably mountable developing cartridge act on the electrophotographic photosensitive drum. As has been described hereinbefore, the electrophotographic image forming apparatus for forming the image on the recording material using the electrophotographic image forming process is known. In this electrophotographic image forming apparatus, the process cartridge type described above is known. In addition, the developing cartridge type which comprises only the developing unit that is not integral with the photosensitive drum is known. In the present invention, the process cartridge type and the developing cartridge type are usable. The process cartridge and the developing cartridge are provided with a developer accommodating portion which contains the developer (toner) for developing the electrostatic latent image. 
         [0004]    A color electrophotographic image forming apparatus is known (U.S. Pat. No. 5,428,426) which includes an intermediary transfer drum as an intermediary transfer member, wherein the cartridges each including a developer and a photosensitive drum are provided therearound. With this structure, in mounting the process cartridge in the main assembly, the photosensitive drum is positioned relative to the intermediary transfer drum, and therefore the mounting and demounting of the process cartridge are easy. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention further develops the conventional structure described above. It is a principal object of the present invention to provide a color electrophotographic image forming apparatus with which the mounting operativity upon mounting and dismounting a cartridge to a main assembly of the color electrophotographic image forming apparatus is improved. 
         [0006]    According to an aspect of the present invention, there is provided a color electrophotographic image forming apparatus for forming a color image on a recording material comprising a plurality of cartridge mounting portions for demountably mounting cartridges; a single intermediary transfer member provided opposed to said electrophotographic photosensitive member drums, wherein developed images formed on said electrophotographic photosensitive member drums are to be transferred; an image forming unit including said cartridge mounting portions and said intermediary transfer member, wherein said image forming unit is movable between a transfer position for transferring to the recording material a developed image transferred onto said intermediary transfer member from said electrophotographic photosensitive member drums and a mounting and demounting position for mounting and demounting said cartridges relative to said cartridge mounting portions; and a mounting and demounting position locking member for locking said image forming unit in the mounting and demounting position relative to a main assembly of said color electrophotographic image forming apparatus when at least one of said cartridges mounted to said cartridge mounting portions is removed in a state in which image forming unit is placed in the mounting and demounting position. 
         [0007]    According to the present invention the operativity at the time of mounting and demounting the cartridge on the main assembly is improved. 
         [0008]    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 
         [0009]      FIG. 1  is an outer appearance perspective view of the image forming apparatus of Embodiment 1. 
           [0010]      FIG. 2A  is a schematic right side sectional view of the image forming apparatus of  FIG. 1 . 
           [0011]      FIG. 2B  is a partial enlarged view of a part of  FIG. 2A . 
           [0012]    In  FIG. 3 , (a) is a schematic view of a non-contact type developing system, and (b) is a schematic view of a contact type developing system. 
           [0013]      FIG. 4A  is a right-hand side outer appearance perspective view of an image forming unit in the state that the developing cartridges of the first and second cartridges are dismounted, and  FIG. 4B  is a left-hand side outer appearance perspective view of the image forming unit. 
           [0014]      FIG. 5A  shows a right side view of the image forming unit in the state that all the developing cartridges  33  are dismounted from the respective mounting portions, and  FIG. 5B  is a left-hand side longitudinal sectional view of the image forming apparatus. 
           [0015]      FIG. 6A  is an enlarged cross-sectional view taken along ( 9 )-( 9 ) of  FIG. 5B , and  FIG. 6B  is a right side longitudinal sectional view of the image forming apparatus in the state that a cover is in an open position. 
           [0016]      FIG. 7A  is a left-hand side longitudinal sectional view of the image forming apparatus in the state that the cover is in the open position, and  FIG. 7B  is a perspective view of the image forming unit in the state that the locking of the image forming unit relative to a main assembly is released by a locking lever being operated in a lock releasing direction. 
           [0017]      FIG. 8A  is a right side longitudinal sectional view of the image forming apparatus in the state that the image forming unit is in a mounting and dismounting position, and  FIG. 8B  is a left-hand side longitudinal sectional view of the image forming apparatus in the state that the image forming unit is in the mounting and dismounting position. 
           [0018]      FIG. 9A  is a left side view of the image forming unit in the state that it is in the mounting and dismounting position and in which the developing cartridge of the second cartridge is dismounted, and  FIG. 9B  is an enlarged cross-sectional view taken along ( 16 )-( 16 ) of  FIG. 9A . 
           [0019]      FIG. 10A  is a left side view of the image forming unit partway of returning from the mounting and dismounting position to the transfer position, and  FIG. 10B  is an enlarged cross-sectional view taken along ( 18 )-( 18 ) of  FIG. 10A . 
           [0020]      FIG. 11  is an illustration of a releasing member which releases the lock made by a mounting and dismounting position locking member. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0021]    The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings. The dimensions, the materials, the configurations, the relative positions, and so on of the constituent parts which will be described hereinafter may be properly changed by one skilled in the art depending on the structures and the various conditions of a device to which this invention is applied, and the scope of this invention is not limited to specific dimensions, materials, configurations, relative positions and so on of the embodiments which will be described below. 
       Embodiment 1 
       [0022]      FIG. 1  is an outer appearance perspective view of the color electrophotographic image forming apparatus (image forming apparatus)  100  according to this embodiment.  FIG. 2A  is a right side longitudinal sectional view of the image forming apparatus  100 . The image forming apparatus  100  is a laser printer of a full-color type which uses the electrophotographic process. In more detail, the image forming apparatus  100  forms a full-color image on a recording material (paper) S on the basis of an electrical image signal inputted to a control circuit portion  300  from an external host device  400  of a personal computer, an image reader, a receiving part of a facsimile device or the like. In the following descriptions of the image forming apparatus  100 , a front side is a side, wherein a feeding cassette  19  which stacks a recording material S is drawn. A backside is the opposite side from it. An upper side is a side where a maintenance cover  10  is opened. Front-rear directions are a direction to the front side from the backside of the image forming apparatus and the reverse direction thereof. The left and right are the left and right, as seen from the front side of the image forming apparatus. The left-right directions are a direction to the left from the right, and the reverse direction thereof. A main assembly  100 A is a portion of an image forming apparatus other than the cartridge. The image forming apparatus  100  is placed on a substantially horizontal installation surface F such as a mounting base, the desk or floor. The main assembly  100 A includes an image forming unit  200 .  FIG. 2B  is an enlarged view of a unit  200  portion of the image forming apparatus  100  shown in  FIG. 2B . The unit  200  is provided with a plurality of cartridges  33  and a single intermediary transfer member  34  (in this embodiment, four process cartridges P (PY, PM, PC, PK)). In the image forming apparatus  100 , a plurality of cartridges  33  are dismountably mounted to main assembly  100 A, and a color image is formed on recording material S. The unit  200  will be described in the detail hereinafter. In this embodiment, each process cartridge (cartridge) P is a discrete type which includes a photosensitive unit  32  and developing cartridge  33  as a pair. Each cartridge P has a similar structure except in having different color developers (toner) contained in the developing cartridges  33 . In this embodiment, although the cartridge is a separation type developing cartridge, the present invention is not limited to this. The photosensitive unit  32  is provided with an electrophotographic photosensitive drum photoconductivity member (drum type; hereinafter, drum)  32   a . The unit  32  includes the charging roller  32   b  and the cleaning blade  32   c  for removing the developer which remained on the surface of the drum  32   a , as the process means which acts on the drum  32   a . The drum  32   a , the charging roller  32   b , and the cleaning blade  32   c  are assembled in predetermined arrangement relations relative to a photosensitive member case  32   d . The developing cartridge  33  is provided with a developing device case  33   a  and a developing roller  33   b , provided at one end portion of this case  33   a , for developing an electrostatic latent image formed on the drum  32   a  into a developer image by supplying the developer to the drum  32   a . The cartridge  33  includes the developing device  33   c  as the developer accommodating portion for accommodating the developer to be used for a development of the electrostatic latent image and a supplying roller  33   d  for supplying the developer from the developing device  33   c  to the developing roller  33   b . A first cartridge PY accommodates a yellow (Y) developer in the developing device  33   c  of the cartridge  33 , and forms a Y color developer image on the surface of the drum  32   a . A second cartridge PM accommodates a magenta (M) developer in the developing device  33   c  of the cartridge  33 , and forms an M color developer image on the surface of the drum  32   a . A third cartridge PC accommodates a cyan (C) developer in the developing device  33   c  of the cartridge  33 , and forms a C color developer image on the surface of the drum  32   a . A fourth cartridge PK accommodates a black (K) developer in the developing device  33   c  of the cartridge  33 , and forms a K color developer image on the surface of the drum  32   a . In this embodiment, the intermediary transfer member  34  is a cylindrical drum (intermediary transfer drum) that horizontally extends along an axis of a rotation axis  34   a . Each cartridge  33  is provided on a front side of the transfer member  34 , and extends substantially parallel with the installation surface F of the main assembly  100 A. They are provided adjacent to each other with respect to the substantially vertical direction. In the image forming apparatus of this embodiment, the first cartridge PY takes a top most stage position, and the second cartridge PM is placed therebelow. The third cartridge PC is placed further below. The fourth cartridge PK takes a bottom most stage position. As shown in (a) of  FIG. 3 , the developing roller  33   b  of each cartridge P may be spaced by a predetermined small gap (predetermined distance) x from the drum  32   a , as a non-contact developing system. As shown in (b) of  FIG. 3 , it may be in contact with the drum  32   a , as a contact type developing system. In the non-contact type developing system of (a), in order to maintain the predetermined gap x, the spacers  33 s provided on the left and right end portions of the developing roller  33   b  are contacted to the drum  32   a . The front side of each cartridge P is provided with a laser scanner unit  11  as an image exposure device. The unit  11  is disposed between a front frame  110   a  of a main frame  110  which is a frame of the main assembly and the cartridges P, in the main assembly  100 A. The unit  11  includes a laser diode, a polygonal mirror, an Fθ lens, a reflection mirror, and so on. The unit  11  outputs laser beams L (LY, LM, LC, LK) which are modulated correspondingly to the image information for the Y, M, C, K color inputted to the control circuit portion  300  from the external host device  400  to scan the drums  32   a  of the cartridges P for the corresponding colors (image exposure). A lower part of the unit  200  includes a feeding unit  18 . The feeding unit  18  includes a feeding cassette  19  for stacking recording material S, a feeding roller  20 , a separation pad  21 , and so on. The cassette  19  can go into and out of the front side of the main assembly  100 A (front loading). In the main assembly  100 A, between the transfer member  34  and a rear frame  110   b  of the main frame  110 A, there is provided an upper recording material feeding path extended from the feeding roller  20  to the upper rear portion in the main assembly  100 A. A registration roller couple  18   a, a  secondary transfer roller  22 , a fixing device  23 , and a discharging roller pair  24  are provided vertically along this feeding path. The fixing device  23  includes a fixing film unit  23   a  and a pressing roller  23   b . The discharging roller pair  24  includes a discharging roller  24   a  and a discharging roller  24   b.    
         [0023]    An upper surface of the main assembly  100 A is provided with a maintenance cover  10  which functions as a discharging tray for receiving a recording material S on which the image has been formed. The cover  10  opens and closes an opening  100 B provided in the upper surface of the main assembly  100 A (opening and closing member). A rear side of the cover  10  is rotatably coupled through a hinge shaft  10   a  to the main assembly  100 A. The cover  10  is movable between the closed position for closing a top opening  100 B of the main assembly  100 A and the open position for opening the opening portion  100 B. The cover  10  is an opening and closing member for opening and closing the opening  100 B in the upper portion of the main assembly  100 A about the hinge shaft  10   a . A user touches the fingers on a grip portion  10   d  provided on a front side of the cover  10 , and an opening and closing of the cover  10  is effected manually. Through the opening  100 B, as will be described hereinafter, the developing cartridge is mounted and demounted relative to a developing cartridge mounting portion  31   c  of the unit  200  placed in the mounting and dismounting position. In the state of  FIGS. 2A and 2B , a drive inputting portion (unshown) of the transfer member  34  of the unit  200  is coupled with a drive outputting portion (unshown) of a main assembly ( 100 A). The drive inputting portions (unshown) of a photosensitive unit  32  and the developing cartridge  33  of each cartridge couple with the drive outputting portions (unshown) provided in the main assembly  100 A, respectively. The electrical contacts (unshown) of the photosensitive unit  32  and the developing cartridge  33  of each cartridge P are electrically connected with an electric power supply system (unshown) of the main assembly ( 100 A). The driving force transmission system and a bias voltage application system of the transfer member  34  and each cartridge P are not illustrated, for the sake of simplicity, since they may be the same as those in the ordinary image forming apparatus. 
         [0024]    The operation for forming a full-color image will be described. The drum  32   a  of each cartridge P is rotationally driven at a predetermined controlled speed in a clockwise direction indicated by an arrow in  FIG. 2B . The charging roller  32   b  is rotated by the rotation of the drum  32   a . The transfer member  34  is rotationally driven at the speed corresponding to the speed of the drum  32   a  in the counterclockwise direction (codirectional with the rotation of the drum  32   a ) of the arrow. In the cartridge  33 , the developing roller  33   b  and the supplying roller  33   d  are rotationally driven at a predetermined controlled speed in the counterclockwise direction of the arrow. The scanner unit  11  also is driven. In synchronism with this drive, a predetermined charging bias voltage is applied to the charging roller  32   b  at the predetermined controlled timing in each cartridge P. By this, the surface of the drum  32   a  is uniformly charged by the charging roller  32   b  to the predetermined polarity and predetermined potential. In each cartridge P, the electrostatic latent image formed on the surface of the drum  32   a  is developed into a developer image by the developing roller  33   b  of the developing cartridge  33 . The developing roller  33   b  is supplied with a predetermined developing bias voltage at the predetermined controlled timing. Through the above-described electrophotographic image forming process operation, a Y color developer image corresponding to a yellow component of the full-color image is formed on the drum  32   a  of the first cartridge PY. The developer image is transferred (primary transfer) onto the transfer member  34  in a primary transfer nip which is the contact portion between the drum  32   a  and the intermediary transfer member  34 . An M color developer image corresponding to a magenta component of the full-color image is formed on the drum  32   a  of the second cartridge PM. The developer image is transferred (primary transfer) onto the transfer member  34  in a primary transfer nip which is the contact portion between the drum  32   a  and the transfer member  34  superimposedly on the already transferred Y color developer image. On the drum  32   a  of the third cartridge PC, a C color developer image corresponding to a C color component of the full-color image is formed. The developer image is transferred (primary transfer) onto the transfer member  34  in the primary transfer nip which is the contact portion between the drum  32   a  and the intermediary transfer member  34  superimposedly on the already transferred Y color+M color developer image. A K color developer image corresponding to a black component of the full-color image is formed on the drum  32   a  of the fourth cartridge PK. The developer image is transferred (primary transfer) onto the transfer member  34  in the primary transfer nip which is the contact portion between the drum  32   a  and the intermediary transfer member  34  superimposedly on the already transferred Y color+M color+C color developer images. In this way, a full-color developer image of the Y color+M color+C color+K color is synthetically formed on the transfer member  34 . The order of the colors of the developer images sequentially superimposedly transferred onto the transfer member  34  is not limited to the above described order. 
         [0025]    The untransferred developer remaining on the drum surface after the primary transfer of the developer image relative to the transfer member  34  is removed by the cleaning blade  32   c  in each cartridge. On the other hand, the feeding roller  20  is driven at the predetermined controlled timing. In this manner, by a cooperation of the feeding roller  20  and the separation pad  21 , the separation and feeding of the sheet-like recording materials S stacked in the cassette  19  is carried out one by one. The recording material S is introduced into the secondary transfer nip which is the contact portion between the transfer member  34  and the secondary transfer roller  22 , at the predetermined controlled timing by the registration roller couple  18   a . The secondary transfer roller  22  is supplied with the secondary transfer bias voltage of the predetermined potential having the polarity opposite to that of the charge polarity of the developer at the predetermined controlled timing. By this, while the recording material S is nipped and fed by the secondary transfer nip, the developer image on the intermediary transfer member  34  on which it is superimposed is sequentially transferred (secondary transfer) onto the surface of recording material S. The recording material S which passed the secondary transfer nip is separated from the surface of the transfer member  34  and is introduced into the fixing device  23  in which it is heated and pressed by a fixing nip. By this, the color developer images are mixed and fixed on recording material S. The recording material S is discharged out of the fixing device  23 , and is discharged on the cover  10  which functions as a discharging tray by discharging roller pair  24  as a full-color print. In the case of this embodiment, the toner remaining after the secondary transfer on the surface of the transfer member after the separation of the recording material  34  is electrostatically deposited on the surface of the drum  32   a  in the primary transfer nip of the first cartridge PY, for example, and it is removed by the cleaning blade  32   c . In the case of a monochromatic image forming mode, only the fourth cartridge PK for forming a black K image is used. In this embodiment, the secondary transfer roller  22  is movable between a first position in which it contacts the transfer member  34  and forms the secondary transfer nip and a second position spaced from the transfer member  34  by a shifting mechanism (unshown). At the time of an image forming operation of the image forming apparatus  100 , the secondary transfer roller  22  is moved to the first position, and at the time of then on-image formation, it is moved to the second position. The transfer roller  22  may normally be contacted with the intermediary transfer member  34 . 
       (Image Forming Unit) 
       [0026]      FIG. 4A  is a right-hand side outer appearance perspective view of the image forming unit  200 . In  FIG. 4A , the developing cartridge  33  of the first cartridge PY and the developing cartridge  33  of the second cartridge PM are dismounted from the respective mounting portions  31   c .  FIG. 4B  is a left-hand side outer appearance perspective view of the unit  200 .  FIG. 5A  is the right side view of the unit  200  in the state where all the cartridges  33  are dismounted from the respective mounting portion  31   c .  FIG. 5B  is a left side longitudinal sectional view of the image forming apparatus  100 . The unit  200  has the sub-frame  31  which is rotatably supported between the left-hand side frame  110 L and the right-hand side frame  110 R. The frame  31  is provided with an intermediary transfer frame  31   a  rotatably supporting the transfer member  34 . The transfer member  34  is provided with a shaft (rotation axis)  34   a , and the left-hand end portion and right-hand end portion thereof are supported rotatably between a left side plate  31   a -L of the frame  31   a  and a right side plate  31   a -R thereof. Outer sides of the left side plate  31   a -L and the right side plate  31   a -R are provided with a left shaft portion  45 L and a right shaft portion  45 R co-axial with the center axis  34   a  of the frame  31   a , respectively. The sub-frame  31  is provided with a photosensitive member supporting unit  31   b  ( FIG. 2B  and  FIG. 5B ) for supporting the photosensitive unit  32  of each cartridge P. A photosensitive member case  32   d  of the photosensitive unit  32  is coupled to a unit  31   b . By this, a photosensitive drum  32   a  is in contact, with a predetermined urging force, to the transfer member  34 . The sub-frame  31  is provided with the cartridge mounting portions  31   c  ( FIG. 5A ) for mounting the cartridge dismountably. In this embodiment, the cartridge mounting portions  31   c  are the developing cartridge mounting portions (developing device coupling unit for tentatively holding developing cartridges  33 ) for mounting the first to fourth cartridges P dismountably. A mounting portion  31   c  has such a guiding configuration that the cartridge  33  is coupled to the photosensitive unit  32  mounted to the unit  31   b . The developing device case  33   a  of the cartridge  33  is coupled to the mounting portion  31   c . A handle  31   e  is provided in the left-hand end portion of the upper surface of the frame  31 . The locking lever  35  is provided at the outer side of left side plate  31   a -L of the frame  31 . The lever  35  is provided swingably about the boss  31   d  implanted to the outer surface of left side plate  31   a -L. The front side  35   e  of the lever  35  is formed into a convex surface having a center at the shaft portion  45 L, and extends from the bottom side to the top side of the sub-frame  31 . A boss  31   d  is positioned in the substantially central portion with respect to the up-down direction of the lever  35 . A bottom end of the front side  35   e  of the lever  35  is provided with a projection  35   a . A top end  35   b  of the lever  35  is in the position of a grip portion  31   d  of the sub-frame  31 . The lever  35  is normally urged to the counterclockwise direction indicated by the arrow rotationally about the boss  31   d  in  FIG. 5B , by a spring force of a compression spring  37  compressed between the lever  35  and the left side plate  31   a -L. 
         [0027]    The left shaft portion  45 L and the right shaft portion  45 R of the unit  200  are supported rotatably by the bearing portions (unshown) provided on a left frame ( 110 L) and a right ( 110 R), respectively. More particularly, the unit  200  is rotatable about the shaft portions  45 L,  45 R, i.e., a rotational center  34   a  of the intermediary transfer member  34 , in the main assembly  100 A. By this, as shown in  FIG. 2B , the unit  200  is movable between the transfer position (first orientation) and the mounting and dismounting position (second orientation) B as shown in  FIG. 8A . The transfer position A is the position for transferring the developer image transferred onto the transfer member  34  from the drum  32   a  onto the recording material S. Here, the mounting and dismounting position B is the position for mounting and demounting the cartridge  33  relative to the mounting portion  31   c . In the state that the unit  200  is placed in the transfer position A, as shown in  FIG. 5A , the projection  35   a  of the locking lever  35  is in engagement with a first recess  36   a  of a locking base  36  fixed to a stationary member of the main assembly ( 100 A) side. By this, the unit  200  is locked to the main assembly  100 A in the transfer position A (locking). According to this embodiment, the projection  35   a  of the locking lever  35  and the first recess  36   a  of a locking base  36  are a transfer position locking means for locking the unit  200  to the main assembly  100 A in the transfer position A. The base  36  is provided with a concave surface  36   c  opposed to an arcuate surface of the front side  35   e  of the lever  35 . The bottom end of the concave surface  36   c  is provided with the first recess  36   a , and a top end thereof is provided with a second recess  36   b . As for the lever  35 , the projection  35   a  of the bottom end is normally rotationally urged about the boss  31   d  toward the base  36  by the spring force of the compression spring  37 . 
         [0028]      FIG. 6A  shows an enlarged cross-sectional view taken along ( 9 )-( 9 ) of  FIG. 5B . Designated by  38  is a plunger  38  supported to be linearly movable by a left side plate portion corresponding to the mounting portion  31   c  of the frame  31 . Designated by  33   e  is a development bearing for supporting the developing roller  33   b  pivotally by the developing device case  33   a . The plunger  38  is pressed and urged toward the developing cartridge  33  by a compression spring  40  provided between a confinement plate  39  fixed to the lever  35  by a screw  39   a  and the plunger  38 . In the state that the cartridge  33  is mounted to the mounting portion  31   c, a  free end portion  38   a  of the plunger  38  presses an inclined surface of a development bearing  33   e . As shown in  FIG. 3A , the spacers  33 s of the developing roller  33   b  are in contact to the drum  32   a , or, as shown in  FIG. 3B , by this, the developing roller  33   b  is in contact to the drum  32   a . In more detail, the cartridge  33  is positioned in the predetermined relation relative to the mounting portion  31   c  to be stably supported. The positioning structure for the cartridge  33  which includes the plunger  38 , the compression spring  40 , and the confinement plate  39  is provided in the mounting portion  31   c  of each cartridge P. By this, each cartridge  33  is positioned in predetermined relation to the corresponding mounting portion  31   c , and is stably supported. 
       (Exchanging System of Developing Cartridge) 
       [0029]    The developer contained in developing device  33   c  in each cartridge P (PY, PM, PC, PK) is consumed with the image forming operation. In view of this, for example, the means (unshown) for detecting a remaining amount of the developer of each developing cartridge  33  is provided. The control circuit portion  300  compares a detected remaining amount value with the threshold for a lifetime forenotice and a lifetime warning of the cartridge preset beforehand. The lifetime forenotice or the lifetime warning of the cartridge  33  is displayed on the display portion  102  of an operating portion  101  or a display ( 400 ) of an external host device of the image forming apparatus  100  for the cartridge  33  exhibiting the detected remaining amount value less than the threshold. This prompts a preparation of the developing cartridge for the exchange to the user, or prompts the exchange of the developing cartridge. In the image forming apparatus  100  of this embodiment, in an exchange of each developing cartridge  33  mounted to the unit  200 , the opening  100 B of the top side of the main assembly  100 A is opened. Then, the user manually operates a grip portion  10   d  of the cover  10 , to sufficiently rotate the cover  10  to the predetermined open position for opening the opening portion  100 B from the closing position for closing the opening  100 B about the hinge shaft  10   a .  FIG. 6B  and  FIG. 7A  are a right-hand side longitudinal sectional view and a left-hand side longitudinal sectional view of the image forming apparatus  100  in the state that the cover  10  is opened to a predetermined open position. When the cover  10  is opened to the predetermined open position, the open state is maintained by locking means (unshown). By this, even if the user lifts the hand from the cover  10  thereafter, the cover  10  returns automatically and is not rotated. As for the locking means, the proper means of a click stop mechanism, for example, or the like can be used. By the interrelating mechanism (unshown) in interrelation with the partially opening rotation of the cover  10 , the coupling of the drive outputting portion of the main assembly side with the drive inputting portion of the transfer member  34  is released. The coupling of the drive outputting portion of the main assembly ( 100 A) side with the photosensitive unit  32  of each cartridge and the drive inputting portion of the developing cartridge  33  is released. The electrical connection of the electric power supply system in the main assembly ( 100 A) with the photosensitive unit  32  and the electrical contact of the developing cartridge  33  are released. By the cover  10  being opened, the opening portion  100 A is opened greatly. By this, in the main assembly  100 A, the top side of the unit  200  placed in the transfer position A is exposed. The top ends  35   b  of the handle  31   e  and the lever  35  which are in the left-hand end portion of the top side of the frame  31  are exposed, so that the user can access the handle  31   e  thereof and the top end  35   b.    
         [0030]    In view of this, the user catches the left hand or the right hand on the handle  31   e  and the top end  35   b , and first, the user pushes the top end  35   b  of the lever  35  in the direction (front side) of an arrow G of  FIG. 7A . By this, the lever  35  is rotated in the clockwise direction in  FIG. 7A  about the boss  31   d  against elasticity of the compression spring  37 . As shown in  FIG. 7B , by this, the projection  35   a  of the bottom end of the lever  35  separates from the first recess  36   a  of the locking base  36 , so that the locking relative to the main assembly  100 A of the unit  200  in the transfer position A is released. In this state, the user pushes the handle  31   e  rearwardly to rotate the unit  200  manually in the clockwise direction in  FIG. 7A  and the counter-clockwise direction in  FIG. 6B  about the shaft portions  45 L,  45 R. After slightly rotating the unit  200 , a pressing force, in a direction of the arrow G, of the top end  35   b  of the lever  35  is released. The projection  35   a  of the bottom end of the lever  35  is normally rotationally urged by the spring force of the compression spring  37  about the boss  31   d  toward the base  36 . By this, the projection  35   a  disengaging from the first recess  36   a  is in contact with the concave surface  36   c  of the base  36 . In this state, the unit  200  is continuously rotated in the counter-clockwise direction in  FIG. 7A . By this, the projection  35   a  is moved toward the upside second recess  36   b , while sliding on the concave surface  36   c . When the unit  200  is rotated in the clockwise direction in  FIG. 7B  by approx. 45 degrees from the transfer position A, the projection  35   a  of the lever  35  reaches the second recess  36   b  of the upper portion of the base  36 . The projection  35   a  elastically engages with a recess  36   b  with a click feeling. The user rotates the unit  200  until this click feeling is provided. By this, the unit  200  rotates upwardly by approx. 45 degrees from the transfer position A of  FIG. 6B  and  FIG. 7A  to shift the cartridge  33  to an angular attitude faced to the opening portion  100 B ( FIG. 8A ,  FIG. 8B ). This angular attitude is temporarily confined by the engagement between the projection  35   a  and the second recess  36   b . In other words, the unit  200  rotates to the mounting and dismounting position B for mounting and demounting the cartridge  33  relative to the mounting portion  31   c , and the dismounting of the cartridge  33  from the opening portion  100 B is enabled. In the state that the unit  200  is placed in a mount position B, each cartridge  33  is pulled out against the urging force by the compression spring  40  of the plunger  38  from the mounting portion  31   c  upwardly and obliquely. By this, each cartridge  33  can be dismounted from the mounting portion  31   c . On the contrary, in the state that the unit  200  is placed in the mount position B, each cartridge  33  is inserted angularly downwardly against the urging force by the compression spring  40  of the plunger  38  into the mounting portion  31   c . By this, each cartridge  33  can be mounted to the mounting portion  31   c . By the structure described above, the cartridge  33  can be exchanged without retracting the scanner unit  11 . By this, the user can exchange the cartridge  33  easily. 
         [0031]      FIG. 9A  illustrates the state that the unit  200  is placed in the mounting and dismounting position B and the cartridge  33  of the second cartridge PM is dismounted.  FIG. 9B  is an enlarged cross-sectional view taken along ( 16 )-( 16 ) of  FIG. 9A . The plunger  38  of each mounting portion  31   c  is urged by the compression spring  40 . The plunger  38  of the mounting portion  31   c  which does not have the cartridge  33  is not in engagement with the development bearing  33   e  of the cartridge ( 33 ) side. Therefore, the plunger  38  is advanced by the spring force of the compression spring  40 . The flange  38   b  of the plunger  38  engages with the recess  35   c  of the lever ( 35 ), so that the plunger  38  stops. In this state, the rotation of the lever  35  about the boss  31   d  is prohibited by an outer periphery  38   c  of the flange  38   b  abutting to an inner surface  35   d  of the recess  35   c  of the locking lever ( 35 ). In more detail, in the state that the unit  200  is placed in the mounting and dismounting position B, when even one of the cartridges  33  mounted to the mounting portions  31   c  is taken out, the unit  200  is locked by the mounting and dismounting position locking member relative to the main assembly  100 A in the mounting and dismounting position B. According to this embodiment, the mounting and dismounting position locking mechanism is constituted by a flange  38   b  (locking portion) of the plunger ( 38 ) and a recess  35   c  (locking portion) of the lever ( 35 ). By the structure described above, the engagement between the projection  35   a  and the second recess  36   b  is maintained, so that the user is prevented from closing the unit  200  inadvertently in the exchange of the cartridge  33 . Therefore, in the mounting and demounting of the cartridge  33 , it does not occur that the cartridge  33  is nipped between the opening portion  100 B of the main assembly  100 A and the unit  200 . 
         [0032]    When the cartridge  33  is mounted to the mounting portion  31   c  which does not have the cartridge  33 , the development bearing  33   e  contacts to the free end portion  38   a  of the plunger  38 , by which the plunger  38  retracts against the spring force of the compression spring  40 . By this, flange (locking portion)  38   b  disengages from the recess (locking portion)  35   c  of the lever ( 35 ). In more detail, the unit  200  is released from the lock relative to the main assembly  100 A by mounting and dismounting position locking members  38   b ,  35   c . The free end portion  38   a  of the plunger  38  presses the inclined surface of the bearing  33   e . By this, to the photosensitive drum  32   a , the spacer  33 s of the developing roller  33   b  is in contact ((a) of  FIG. 3 ) or the developing roller  33   b  is in contact ((b) of  FIG. 3 ). Thus, the cartridge  33  is positioned relative to the mounting portion  31   c , and is stably supported there. When the cartridges  33  are mounted to all the mounting portions  31   c , the mounting and dismounting position locking members  38   b ,  35   c  release the lock of the unit  200  relative to the main assembly  100 A. In this state, the user catches the handle  31   e  and the lever  35  of the unit  200  temporarily confined by temporary confinement members  35   a ,  36   b  to the mounting and dismounting position B with the left hand or right hand at the top end  35   b  thereof. First, the user pulls the top end  35   b  of the lever  35  to the front (arrow G of  FIG. 8A ). In more detail, the user rotates the lever  35  about the boss  31   d  against the elasticity of the compression spring  37  (clockwise direction in  FIG. 8B ). By this, the projection (locking portion)  35   a  of the bottom end of the lever  35  disengages from the second recess (locking portion)  36   b  of the base  36 . By this, the temporary confinement by the temporary confinement members  35   a ,  36   b  relative to the main assembly  100 A in the mounting and dismounting position B of the unit  200  is released. In the released state, the user pulls the handle  31   e  to the front to rotate the unit  200  manually about the shaft portions  45 L,  45 R in the counter-clockwise direction in  FIG. 8A , and in the clockwise direction in  FIG. 8B . After rotating slightly the unit  200 , the pressing, in the direction of the arrow G, of the top end  35   b  releases. The lever  35  is normally rotationally urged by the spring force of the compression spring  37  which presses against the projection  35   a  about the boss  31   d  toward the base  36 . By this, the projection  35   a  having disengaged from the second recess  36   b  is in contact with the concave surface  36   c  of the base  36 . In this state, the unit  200  is continuously rotated (clockwise direction in  FIG. 8B ). By this, while the projection  35   a  slides along the concave surface  36   c  of the locking base  36 , it is moved toward the lower recess  36   a . When the unit  200  is rotated by approx. 45 degrees from the mounting and dismounting position B (clockwise direction in  FIG. 8B ), the projection  35   a  of the lever  35  reaches a recess  36   a . The projection (locking portion)  35   a  engages into the recess (locking portion)  36   a . This provides the click feeling. The user rotates the unit  200  until this click feeling is provided. By this, the unit  200  rotates by approx. 45 degrees from the mounting and dismounting position B ( FIG. 8A ,  FIG. 8B ) to return to the previous transfer position A ( FIG. 6B ,  FIG. 7A ). The angular attitude is maintained by the engagement between the projection  35   a  and the recess  36   a . Thereafter, the user rotates the cover  10  in the closed position manually. By the interrelating mechanism (unshown) in interrelation with a closing operation of the cover  10 , the drive outputting portion of the main assembly side couples with the drive inputting portion of the transfer member  34 . The drive outputting portions of the main assembly ( 100 A) side are coupled to the drive inputting portions of each of the photosensitive units  32  and each of the developing cartridges  33 . The electrical contacts of the unit  32  and the cartridge  33  are electrically connected to the electric power supply system in the main assembly ( 100 A) side. By this, the image forming apparatus  100  returns to the state shown in  FIGS. 2A and 5B  to enable the image forming operation. 
         [0033]      FIG. 10A  illustrates the state in the course of the unit  200  being returned from the mounting and dismounting position B to the transfer position A.  FIG. 10B  is an enlarged cross-sectional view taken along ( 18 )-( 18 ) of  FIG. 10A . As shown in  FIG. 10B , when the cartridge  33  is in the mounting portion  31   c , the plunger  38  is pushed against the compression spring  40 . By this, a flange portion (locking portion)  38   b  is exposed from the recess (locking portion)  35   c . For this reason, the lever  35  can be rotated. As shown in  FIG. 10A , the projection  35   a  of the locking lever  35  urged by the compression spring  37  has a sliding resistance relative to a surface  36   c  of the base  36 , and therefore the movement of the unit  200  is retarded. Therefore, when the user returns the unit  200  from the mounting and dismounting position B to the transfer position A, the unit  200  is moved with a suppressed impact.  FIG. 11  is a right perspective view of the unit  200  from which the developing cartridges  33  of the first cartridge PY and the second cartridge PM are dismounted. In the manufacturing and service of the image forming apparatus  100 , it may be required that even if the cartridge  33  is not mounted, the unit  200  is returned to the transfer position A. In such an occasion, while the plungers  38  which project into the inside of a mounting portion from the first-fourth mounting portions (developing device coupling units)  31   c  are pushed, the unit  200  is rotated. In this manner, even if the cartridge is not mounted to the mounting portion  31   c, a  releasing member  38  is provided and it releases the lock by the mounting and dismounting position locking members  38   b ,  35   c . By the user operating the releasing member  38  thereof manually, the lock by the mounting and dismounting position locking members  38   b ,  35   c  can be released. 
         [0034]    The structure of the image forming apparatus  100  of the above-described embodiment is summarized as follows. The apparatus is an electrophotographic color image forming apparatus  100  for forming a color image on recording material S. It includes two or more cartridge mounting portions  31   c  for mounting the cartridge  33  dismountably. It further includes a single transfer member  34  opposed to drums  32   a , and the developer images formed on the drums  32   a  are transferred onto the transfer member. The apparatus includes an image forming unit  200  including two or more cartridge mounting portions  31   c  and the transfer member  34 . The unit  200  is movable between the transfer position A for transferring the developer image transferred onto the transfer member  34  from drums  32   a  onto the recording material S, and the mounting and dismounting position B for mounting and demounting the cartridge  33  relative to the mounting portion  31   c . In the state that the unit  200  is placed in the mounting and dismounting position B, the cartridges  33  are taken out of the mounting portions  31   c . The mounting and dismounting position locking members  38   b ,  35   c  for locking the unit  200  relative to the main assembly  100 A in the mounting and dismounting position B are provided when even one of the cartridges  33  is taken out of the mounting portion  31   c . Furthermore, the temporary confinement members  35   a ,  36   b  for temporarily confining the unit  200  in the mounting and dismounting position B are provided when the unit  200  moves from the transfer position A to the mounting and dismounting position B. The user takes out a first cartridge from the unit  200  temporarily confined in the mounting and dismounting position B by the temporary confinement members  35   a ,  36   b . When the cartridges  33  are mounted to all the mounting portions  31   c , locking members  38   b ,  35   c  release the unit  200  relative to the main assembly  100 A. The cartridge  33  mounted to the mounting portion  31   c  which does not have the cartridge  33  may be the very cartridge that has been dismounted from the mounting portion  31   c . Or, it may be a different cartridge  33 . By the mounted cartridge, the lock by the mounting and dismounting position locking members  38   b ,  35   c  is released. Furthermore, the transfer position locking members  35   a ,  36   a  for locking the unit  200  relative to the main assembly  100 A is provided in the transfer position A. The unit  200  is movable between the transfer position A and the mounting and dismounting position B by the user&#39;s manual operation. Furthermore, even if the cartridge  33  is not mounted to the mounting portion  31   c , the lock by the locking members  38   b ,  35   c  can be released by the releasing member  38 . The lock by the locking members  38   b  and  35   c  can be released by the user operating the releasing member  38  manually. The unit  200  is moved between the mounting and dismounting position B and the transfer position A about the rotation axis  34   a  of the transfer member  34 . A plurality of drums  32   a  are provided in the unit  200 . In this embodiment, the cartridge  33  is a developing cartridge which is provided with the developing roller  33   b  for developing the electrostatic latent image formed on the drum  32   a . The cartridge  33  is mounted to the mounting portions  31   c , so that the developing roller  33   b  is placed opposed to the drums  32   a , respectively. In the state that the unit  200  is placed in transfer position A, the developing roller  33   b  develops the electrostatic latent image in the state that it is spaced with the gap x from the drum  32   a . According to the embodiments, the mounting and dismounting operativity of the cartridge  33  to the main assembly  100 A can be improved. Furthermore, the color electrophotographic image forming apparatus can be provided in which at the time of the mounting and dismounting of the cartridge, the cartridge can be replaced without retracting the scanner unit (image exposure device)  11 . The color electrophotographic image forming apparatus can be provided, wherein at the time of the mounting and demounting of the cartridge  33 , the cartridge  33  is not nipped between the opening portion  100 B of the main assembly and the image forming unit  200 . 
         [0035]    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. 
         [0036]    This application claims priority from Japanese Patent Application No. 048102/2009 filed Mar. 2, 2009, which is hereby incorporated by reference herein.