Abstract:
In order to provide a process cartridge which has a simple mechanism and can be easily positioned with respect to an apparatus body and securely mounted on the apparatus body even in a half-locked state or a half-inserted condition, the process cartridge  200  includes a unit  201,  a positioning member  202,  a holding member  203  and a restricting and releasing mechanism  204.  The unit  201  includes an element used for an image forming process. The positioning member  202  has a positioning member which engages with an engagement portion  125, 126  formed on the image forming apparatus to position the process cartridge  200  at a predetermined mount position in the image forming apparatus. The holding member  203  holds the unit  201  to allow displacement of the unit  201  relative to the positioning member  202.  The restricting and releasing mechanism  204  is arranged to restrict or release the displacement of the unit  201  relative to the positioning member  202.

Description:
This application is based on application Ser. No. 2000-45858 filed in Japan on Feb. 23, 2000, the contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a process cartridge and an image forming apparatus using the same. 
     In an image forming apparatus used in a copying machine, a printer or the like, for the purposes of exchanging or repairing elements necessary for image forming processes, treating a jam or the like, process cartridges including the elements are detachably mounted on the image forming apparatus. Such process cartridges are necessary to be securely mounted and positioned on the image forming apparatus so as not to cause a maloperation. 
     U.S. Pat. No. 5,066,976 proposes such a mechanism that if a process cartridge is not perfectly push into an apparatus body, a part of holding member for holding the process cartridge protrudes out of an opening portion of grip, whereby it can be possible to judge whether or not the process cartridge is pushed into a predetermined position. Japanese Utility Model Laid-open publication No. 63-100736 proposes such a mechanism that when a cover is closed, a stopper mechanism provided on the cover pushes and fixes a process unit. Japanese Utility Model Laid-open publication No. 62-149046 proposes such a mechanism that a process unit detachably mounted so as to approach to and separate from a photosensitive is moved by a lever to position in place. 
     However, the positioning mechanisms of process cartridges proposed above have a disadvantage that when the process cartridges are positioned in a half-locked state or a half-inserted condition, or when the operation of the lever is omitted, the positioning of the process cartridges has to be conducted again, and also have a disadvantage that the push-fixation mechanism is complicated. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a process cartridge which has a simple mechanism and can be easily positioned with respect to an apparatus body and securely mounted on the apparatus body even in a half-locked state or a half-inserted condition, and also provide an image forming apparatus using the process cartridge. 
     According to a first aspect of the present invention, there is provided a process cartridge which can be mounted on and dismounted from an image forming apparatus, the process cartridge comprising: 
     a unit comprising an element used for an image forming process; 
     a positioning member having a positioning member which engages with an engagement portion formed on the image forming apparatus to position the process cartridge at a predetermined mount position in the image forming apparatus; 
     a holding member for holding the unit to allow displacement of the unit relative to the positioning member; and 
     a restricting and releasing mechanism for restricting or releasing the displacement of the unit relative to the positioning member. 
     In the first aspect of the present invention, when the process cartridge is mounted on the image forming apparatus, the unit is secured by restricting the displacement of the unit relative to the positioning member, it is possible to stably surely mount the process unit. The term “displacement” in this specification of the present invention includes pivot, vibration, movement, swing and so on. 
     It is preferable that the engagement portion of the image forming apparatus comprises a recess or projection, and wherein the positioning member comprises a projection or recess which engages with the recess or projection of the engagement portion. In this case, the projection or recess of the positioning member may comprise a plurality of projections or recesses which are disposed around the holding member. 
     Preferably, the holding member comprises a screw member. 
     Preferably, the process cartridge further comprises a cover member for interlocking with the restricting and releasing mechanism to cover or open a specific portion of the unit. In this case, the element may comprise a toner container and a developing roller, and cover member may cover or open the developing roller. 
     Preferably, the restricting and releasing mechanism comes into contact with a member provided on the image forming apparatus and operates. In this case, the restricting and releasing mechanism may operate when the process cartridge is mounted on and dismounted from the image forming apparatus. Alternately, the restricting and releasing mechanism mat operate when the process cartridge is mounted on the image forming apparatus. 
     According to a second aspect of the present invention, there is provided a process cartridge which can be mounted on and dismounted from an image forming apparatus, the process cartridge comprising: 
     a unit comprising an element used for an image forming process; 
     a positioning member having a first positioning member which engages with an engagement portion formed on the image forming apparatus to position the process cartridge at a first predetermined position in the image forming apparatus; and 
     a first pressed portion which is pressed by a first press portion provided on the image forming apparatus when the process cartridge is moved from the first predetermined position to a second predetermined position to position the process cartridge at the second predetermined position. 
     In the second aspect of the present invention, when the process cartridge moves in the image forming apparatus, the first pressed portion of the process cartridge is pressed by the first press portion of the image forming apparatus and positioned in place, whereby the process cartridge can be securely mounted in the predetermined position even in an incompletely mounted condition. 
     It is preferable that the engagement portion of the image forming apparatus comprises a recess or projection, and wherein the positioning member comprises a projection or recess which engages with the recess or projection of the engagement portion. 
     Preferably, the first pressed portion is provided on the positioning member. 
     preferably, the process cartridge further comprises a second pressed portion which is pressed by a second press portion provided on a cover of the image forming apparatus when closing the cover, the process cartridge is positioned at the first predetermined position by pressing the second press portion on the second pressed portion. In this case, the second pressed portion may be provided on the positioning member. The second pressed portion may be the first pressed portion. 
     Preferably, the process cartridge may further comprises a third pressed portion which is pressed by a third press portion provided on the image forming apparatus when the process cartridge is moved from the second predetermined position to a third predetermined position to position the process cartridge at the third predetermined position. In this case, the pressing direction by the third press portion may be substantially perpendicular to the pressing direction by the first press portion. When the process cartridge is positioned at the third predetermined position, the first and second pressed portions are not pressed by the first and second press portion. 
     Preferably, the pressing direction by the first and second press portions may be identical to the direction that the process cartridge is mounted on the image forming apparatus. 
     According to a third aspect of the present invention, there is provided an image forming apparatus, comprising: 
     a process cartridge comprising: 
     a unit comprising an element used for an image forming process; 
     a positioning member having a positioning member; 
     a holding member for holding the unit to allow displacement of the unit relative to the positioning member; and 
     a restricting and releasing mechanism for restricting or releasing the displacement of the unit relative to the positioning member; 
     an image forming unit for forming an image using the element of the process cartridge; and 
     an engagement portion which engages with the positioning member of the process cartridge to position the process cartridge at a predetermined mount position in the image forming apparatus. 
     According to a fourth aspect of the present invention, there is provided an image forming apparatus, comprising: 
     a process cartridge comprising: 
     a unit comprising an element used for an image forming process; 
     a positioning member having a first positioning member; and 
     a first pressed portion; 
     an image forming unit for forming an image using the element of the process cartridge; 
     an engagement portion which engages with the positioning member of the process cartridge to position the process cartridge at a first predetermined position in the image forming apparatus; and 
     a first press portion for pressing the first pressed portion of the process cartridge when the process cartridge is moved from the first predetermined position to a second predetermined position to position the process cartridge at the second predetermined position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further objects and advantages of the present invention will become clear from the following description taken in conjunction with the preferred embodiments thereof with reference to the accompanying drawings, in which: 
     FIG. 1 is a schematic structural view of a color printer as an embodiment of an image forming apparatus; 
     FIG. 2 is a perspective view showing a state of closing a cover of an apparatus body to mount a toner cartridge; 
     FIG. 3 is a perspective view viewed from the inside of the front wall of the apparatus body; 
     FIG. 4 is a perspective view of a rotation rack and the toner cartridge; 
     FIG. 5 is a perspective view of the toner cartridge; 
     FIG. 6 is a perspective view of the toner cartridge with a positioning member removed; 
     FIG. 7 is a front view of the color printer with a toner recovery box mounted; 
     FIG. 8 is a perspective view of the toner recovery box; 
     FIG. 9 is a front view showing a relation between the toner cartridge and an opening portion; 
     FIG. 10 is a front view showing a relation between the toner cartridge and the opening portion; 
     FIGS. 11A-11E are schematic plan views sequentially showing states when mounting the toner cartridge; 
     FIG. 12 is a schematic side view showing a first positioning state of the toner cartridge; 
     FIG. 13A is a side view of the rotation rack showing a state before mounting the toner cartridge; 
     FIG. 13B is a schematic side view showing a final positioning state of the toner cartridge; and 
     FIG. 14 is a schematic front view showing the final positioning state of the toner cartridge. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a general structural view of a color printer  10  according to the present invention. The color printer  10  is provided with a developing unit  20 , a photosensitive unit  30 , a laser print head  40 , an intermediate transfer unit  50  and a fixing unit  60 . 
     The developing unit  20  has a rotation rack  22  driven to rotate in a direction of arrow “a”. On the rotation rack  22 , four developing vessels  24 Y,  24 M,  24 C and  24 K are held in a juxtaposed condition in a circumferential direction. In the developing vessels  24 Y,  24 M,  24 C and  24 K are contained toners with colors of yellow, magenta, cyan and black, respectively. The developing vessels  24 Y,  24 M,  24 C and  24 K have developing rollers  26 Y,  26 M,  26 C and  26 K, respectively, which turn and convey the respective toners carried on the outer peripheries of the rollers. 
     The photosensitive unit  30  has a photosensitive drum  32  driven to rotate in a direction of arrow “b”. The photosensitive drum  32  is arranged to oppose to the developing roller  26 Y,  26 M,  26 C or  26 K of the developing vessel  24 Y,  24 M,  24 C or  24 K which arrives at a developing position by the rotation of the rotation rack  22 . In FIG. 1, the developing position is a position where the developing vessel  24 Y is positioned. Around the photosensitive drum  32 , there are disposed an electrostatic charger  34  for uniformly charging the surface of the photosensitive drum  32  and a cleaner  36  for removing the toner remaining on the surface of the photosensitive drum  32  after the first transfer. 
     The laser print head  40  irradiates a laser beam  42  on the uniformly charged surface of the photosensitive drum  32  in accordance with an image information input from the outside. Thus, on the surface of the photosensitive drum  32  are formed a latent image for each color toner image. 
     The intermediate transfer unit  50  has an intermediate transfer belt  56  which is supported on four rollers  51 ,  52 ,  53  and  54  and driven to rotate in a direction of arrow “c”. Adjacent to the roller  54  is disposed a first transfer roller  58 . In the vicinity of the first transfer roller  58 , the intermediate transfer belt  56  is opposed to the photosensitive drum  32 . The intermediate transfer belt  56  is also opposed to a second transfer roller  59  at a portion supported by the roller  51 . A portion where the second transfer roller  59  and the intermediate transfer belt  56  are opposed to each other is an image forming portion A. On the outer surface of the intermediate transfer belt  56 , a cleaner  57  for removing the toner remaining on the surface of the intermediate transfer belt  56  after the second transfer. The intermediate transfer member is not limited to a belt type but may be another type, for example, a drum type. 
     The fixing unit  60  has a fixing roller  62  and two pairs of discharge rollers  64 ,  66  which constitute a discharge portion. A sheet on which an image is fixed by passing through the fixing roller  62  is discharged on a discharge tray  68  by the rotation of the discharge rollers  64 ,  66 . The discharge portion may comprise a pair of rollers or a pair of belts. 
     Under the color printer  10 , a feed cassette  70  as a feed portion is disposed. The feed cassette  70  contains sheets S such as recording papers in a stacked condition. Rotation of a feed roller  72  causes the uppermost sheet S to be fed out one by one. 
     A sheet conveying path  74  is formed to extend in a substantially vertical direction from the feed cassette  70 . The sheet conveying path  74  extends from the feed cassette  70  to the pairs of discharge rollers  64 ,  66  through the image forming portion A and the fixing roller  62 . Rotation of conveyance roller pairs  76 ,  78 ,  80  and  82  causes the sheet S fed out of the feed cassette  70  to be upwardly conveyed along the sheet conveying path  74 . 
     In a space between the sheet conveying path  74  and a substantially flat side wall  12  of the printer body is formed a refeed path  86 , having conveyance roller pairs  92  and  94 , for stopping the sheet on one side surface of which an image is formed at the image forming portion A as shown in FIG. 1, switchbacking and refeed it to the image forming portion A in a reversed state. 
     The upper portion of the refeed path  86  extends to the inside of the fixing unit  60  and meets with the sheet conveying path  74  in front of the pair of discharge rollers  64 . The lower portion of the refeed path  86  meets with the sheet conveying path  74  in front of the conveyance roller pair  78 . 
     Referring to FIG. 1 again, a manual feed tray  96  is attached on the outside surface of the side wall  12  of the printer body. The manual feed tray  96  is possible to pivot around a shaft  97  to open and close. With the manual feed tray  96  opened (in a state as shown in FIG.  1 ), the sheets S are set on the tray. Rotation of the feed roller  98  causes the uppermost one of the sheets S set on the manual feed tray  96  to be fed to the sheet conveying path  74  one by one. 
     AS the developing vessels  24 Y,  24 M,  24 C and  24 K are detachably mounted on the printer body, these developing vessels are referred to as toner cartridges  200  (one embodiment of the process cartridge according to the present invention). 
     A structure of printer body for mounting and positioning the toner cartridge  200  on the printer body will be explained first. As shown in FIG. 2, the front wall  14  of the printer body is formed with an opening  101  for dismounting and mounting the toner cartridge  200  and an opening  102  for dismounting and mounting the photosensitive unit  30  and the intermediate transfer unit  50 . On the back side surface of the front wall  14 , as shown in FIG. 3, there are formed two arcuate ribs  104 ,  105  (corresponding to the first press portions according to the present invention) which have a center at an shaft aperture  103  for supporting the rotation rack  22  and radiuses of r 1 , r 2  respectively. The upstream end portions of the ribs  104 ,  105  with respect to the rotational direction “a” of the rotation rack  22  are formed with inclined surfaces  104   a,    105   a.  On the downstream side of the ribs  104 ,  105  with respect to the rotational direction “a” of the rotation rack  22 , a press lever  106  (corresponding the third press portion according to the present invention) is pivotably attached by a shaft  107  at a position apart from the shaft aperture  103  of the rotation rack  22  with a radius of r 3  (r 1 &gt;r 2 &gt;r 3 ). The press lever  106  is urged by a spring  108  toward the inside from the front wall  14  so that the end of the lever  106  comes into contact with a reverse U-shape of stopper  109 . Outside of the front wall  14  of the printer body is provided with a cover  110  for covering the openings  101 ,  102 . Inside the cover  110  is provided with a projection  111  (corresponding to the second press portion according to the present invention) for pressing the toner cartridge  200  inserted into the opening  101  when closing the cover  110 . 
     The rotation rack  22  comprises as shown in FIG. 4 a rotation shaft  121 , a circular end plate  122  positioned at an end of the rotation shaft  121  and four wing plates  123  disposed around the rotation shaft  121  which are integrally formed as an integral part. The rotation rack  22  is possible to be rotated around the rotation shaft  121 . On an area of the end plate  122  surrounded by two wing plates  123  is formed with a pivot shaft portion  124  comprising a pin which projects parallel to the rotation shaft  121 . On the end surface of each wing plate  123 , there are formed a first positioning recess  125 , a second positioning recess  126  and a V-shaped cutout  127  in order from the outside to the inside. The first positioning recess  125  of one first wing plate  123  and the second positioning recess  126  of the other wing plate  123  adjacent to the one first wing plate  123  constitute a positioning member of the toner cartridge  200  to be inserted therebetween. 
     On the edge of one side surface of each wing plate  123  is formed a first guide ridge  128  which extends parallel to the rotation shaft  121 . On the other side surface is formed a second guide ridge  129  which is disposed more inside than the first guide ridge  128  and extends parallel to the rotation shaft  121  in the same manner as the first guide ridge  128 . The first guide ridge  128  of one first wing plate  123  and the second guide ridge  129  of the other wing plate  123  adjacent to the one first wing plate  123  constitute a guide portion of the toner cartridge  200  to be inserted therebetween. Inside the second guide ridge  129  of each wing plate  123  are provided a positioning lever  130 , a first press lever  131  and a second press lever  132  which are possible to pivot around a shafts  133 ,  134  and  135  respectively and urged toward the second guide ridge  129  by means of springs  136 ,  137  and  138  as shown in FIG.  13 A. 
     Consequently, construction of the toner cartridge  200  itself will be explained. As shown in FIG. 5, the toner cartridge  200  comprises a unit member  201 , a positioning member  202 , a holding portion  203 , a restricting and releasing mechanism  204  and a protection cover  205 . 
     The unit member  201  has as shown in FIG. 6 a toner container  25  and a developing roller  26  as elements necessary to the image forming process. The toner container  25  has an elongated shape and contains toner of predetermined color. The toner can be replenished through a replenishment port  27  formed on the one end of the toner container  25 . The developing roller  26  is rotatably provided so that a part thereof can be revealed from an opening  28  of the toner container  25 , whereby the toner is carried on the outer surface of the developing roller  26 . On both ends of the developing roller  26  are provided runners  206 . The runners  206  come into press contact with the photosensitive drum  32  at the developing position so that a gap between the developing roller  26  and the photosensitive drum  32  can be precisely maintained to keep high image quality. 
     On the outer surface of the toner container  25  are formed a guide surface  207  and a guide ridge  208  which cooperate with the first and second guide ridges  128 ,  129  of the aforementioned rotation rack  22  respectively. On the outer surface of the toner container  25  are also formed a press ridge  209  parallel to the guide ridge  208 . To the press ridge  209  comes into pressure contact with the first and second press lever  131  and  132  of the rotation rack  22 . The press ridge  209  is as shown in FIG. 12 formed with an engagement portion  210  with which the positioning lever  130  of the rotation rack  22  engages. 
     On one end surface of the toner container  25  on which the replenishment port  27  is positioned, a pivot shaft portion  211  and a pivot range restricting projection  212  are formed. The pivot shaft portion  211  constitutes the holding portion  203 . The pivot range restricting projection  212  restricts pivot of the unit member  201  with respect to the positioning member  202 . The pivot shaft portion  211  is formed with a screw hole  213 . On the other end surface of the toner container  25  on which the replenishment port  27  is not positioned, as shown in FIG. 5, a shaft hole  214  is formed at a position corresponding to the pivot shaft portion  211 . The shaft hole  214  is arranged so as to engage with the pivot shaft portion  124  of the end plate  122  of the rotation rack  22 . 
     The positioning member  202  has a substantially plate-like shape and covers the end portion of the toner container  25  on which the replenishment port  27  is positioned. On the inside surface of both ends of the positioning member  202 , there are formed first and second positioning projections  215  and  216  extending to the longitudinal direction of the toner container  25 . The first and second positioning projections  215 ,  216  (corresponding to the positioning member of the present invention) are arranged to engage with the first and second positioning recesses  125 ,  126 . On the center of the positioning member  202 , there is formed a holding aperture  217  at a position corresponding to the pivot shaft portion  211  of the toner container  25 . On the inside surface of the positioning member  202 , a segment shape of pivot range restricting rib  218  and a V shape of restriction rib  219  are formed. The pivot range restricting rib  218  is arranged so that the pivot range restricting projection  212  of the toner container  25  can enter into the pivot range restricting rib  218 . The restriction rib  219  is arranged so that a restricting and releasing pin  228  explained hereinafter of the restricting and releasing mechanism  204  can engage with the restriction rib  219 . On the other hand, on the outer surface of the positioning member  202 , as shown in FIG. 5, there are formed a first step portion  220 , a second step portion  221  and a third step portion  222  (corresponding to first, second and third pressed portions according to the present invention). The first step portion  220  has a segment shape with a predetermined width and is located at a position most departing from the center of the rotation shaft  121  of the rotation rack  22  by a radius of r 1 . The second step portion  221  has a segment shape with a predetermined width and is located inside the first step portion  220  at a position departing from the center of the rotation shaft  121  of the rotation rack  22  by a radius of r 2 . The third step portion  222  has a segment shape with a predetermined width and is located inside the second step portion  221  at a position departing from the center of the rotation shaft  121  of the rotation rack  22  by a radius of r 3 . 
     The holding portion  203  comprises the pivot shaft portion  211  of the toner container  25  and the holding aperture  217  of the positioning member  202  into which the pivot shaft portion  211  is fitted. The holding portion  203  is arranged to pivotably hold the unit member  201  with respect to the positioning member  202 . A screw  223  is screwed into the screw hole  213  of the pivot shaft portion  211  through the holding aperture  217 , preventing the positioning member  202  from coming away from the unit member  201 . The pivot range restricting projection  212  of the toner container  25  enters into pivot range restricting rib  218  of the positioning member  202 , restricting the pivot of the unit member  201  within a predetermined pivot range. 
     The restricting and releasing mechanism  204  comprises a restricting and releasing lever  225  provided on the toner container  25  and a restriction rib  219  formed on the positioning member  202 . The restricting and releasing lever  225  is arranged to pivot around a shaft  226  on the end portion of the toner container  25  on which the replenishment port  27  is formed. On one end of the restricting and releasing lever  225  is formed a projection  227  projecting in a direction coming away from the positioning member  202 . On the other end of the restricting and releasing lever  225  is formed a restricting and releasing pin  228  projecting toward the positioning member  202 . The restricting and releasing lever  225  is urged by a spring  229  in a direction that the restricting and releasing pin  228  engages with the restriction rib  219  of the positioning member  202 . The projection  227  of the restricting and releasing lever  225  is so arranged that the projection  227  comes into contact with the cutout  127  of the wing plate  123  of the rotation rack  22  when mounting the toner cartridge  200  to rotate the restricting and releasing lever  225  around the shaft  226  in a direction of an arrow, disengaging the restricting and releasing pin  228  from the restriction rib  219 . 
     The protection cover  205  has a plate-like shape which covers the developing roller  26  of the unit member  201 . The protection cover  205  has first wire levers  231  and a second wire lever  233 . The first wire levers  231  extend from the both ends of the protection cover  205  and are fitted into shaft holes  230  formed on the both ends of the toner container  25 . The second wire lever  233  extends form the end of the protection cover  205  on a side which the replenishment port  27  of the toner container  25  is formed and is fitted into a shaft hole  232  formed on the end of the toner container  25 . Thus, the protection cover  205  is possible to substantially translate between a cover position where the protection cover  205  covers the developing roller  26  and a retreat position where the protection cover  205  retreats from the developing roller  26  to expose the latter. 
     The translation of the protection cover  205  is interlocked with the pivot of the restricting and releasing lever  225  via an interlocking mechanism. The interlocking mechanism comprises a link lever  234  and a link wire  235 . The link lever  234  is attached coaxially with the shaft hole  230  of the first wire lever  231 . One end of the link wire  235  is curled around the first wire lever  231 , while the other end of the link wire  235  curled around a restricting and releasing pin  228  of the restricting and releasing lever  225 . On the shaft side of the link lever  234  is formed an engaging portion  236  with which the link wire  235  engages, while on the tip end side of the link lever  234  is formed a through hole  237  into which the second wire lever  233  is inserted. 
     By the way, as shown in FIG. 2, in the present embodiment of the color printer  10  a toner recovery box  300  is provided between the front wall  14  and the cover  110 . The toner recovery box  300 , as shown in FIGS. 7,  8 , has a substantially rectangular shape and is partitioned by a partition wall  301  into an upper part and a lower part. The lower part of the toner recovery box  300  has a first receiving port  302  for receiving the remaining toner conveyed by an unshown conveyor screw after being removed by the cleaner  36  of the photosensitive drum  32  and a second receiving port  303  for receiving the remaining toner conveyed by an unshown conveyor screw after being removed by the cleaner  57  of the intermediate transfer belt  56 . The upper part of the toner recovery box  300  has a smoke toner inlet port  304  and a discharge port  305 , between which a filter  306  is filled in. The smoke toner inlet port  304  is connected to a suction box  308  via a suction duct  307 . The suction box  308  has an elongated rectangular shape so that it is disposed along the photosensitive drum  32 . The suction box  308  is formed with a plurality of suction port  309  on the surface opposing to the photosensitive drum  32 . The discharge port  305  is connected to a fan provided on an unshown rear wall via a discharge duct  310 . 
     Thus, the remaining toner removed by both the cleaner  36  of the photosensitive drum  32  and the cleaner  57  of the intermediate transfer belt  56  is recovered into the lower part of the toner recovery box  300 . The smoke toner generating at a developing region is conveyed by the suction air stream in a direction of an arrow caused by the rotation of the fan to enter into the upper part of the toner recovery box  300  and then collected and recovered by the filter  306 . Thus, both the recovery of the remaining toner on the photosensitive drum  32  and the intermediate transfer belt  56  and the recovery of the smoke toner at the developing region are carried out in the same toner recovery box  300 , simplifying the recovery work. In addition, the smoke toner at the developing region is removed by the suction air stream, reducing an image failure such as fogging. 
     Hereinafter, mounting and dismounting operations of the toner cartridge  200  in the color printer  10  having a above described construction will be explained. 
     In FIG. 9, when the developing roller  26  crosshatched is positioned at the developing position, the toner cartridge  200  is offset from the opening  101  so that the toner cartridge  200  can not be dismounted. This prevents the runners  206  of the developing roller  26  positioned at the developing position from being damaged due to vibration and impact when mounting and dismounting the toner cartridge  200  and prevents the photosensitive drum  32  from being damaged by the runners  206 . For example, in order to remove the toner cartridge  200  having the crosshatched developing roller  26  for the purpose of toner replenishment, repair or the like, the cover  110  is opened and the rotation rack  22  is rotated in a direction of an arrow by an unshown handle to position the toner cartridge  200  at the opening  101  as shown in FIG.  10 . At this time, the developing roller  26  of the other toner cartridge  200  is shifted from the photosensitive drum  32  and therefore never comes into contact with the latter. Thus, the toner cartridge  200  concerned can be safely dismounted. The toner cartridge  200  can be dismounted by pulling out the toner cartridge  200  in an axial direction of the rotation rack  22  after protruding a part of the toner cartridge  200  by an unshown pulling out mechanism. 
     When the toner cartridge  200  is pulling out, the projection  227  of the restricting and releasing lever  225  as shown in FIG. 6 disengages from the cutout of the wing plate  123  of the rotation rack  22 , whereby the restricting and releasing lever  225  pivots in a reverse-clockwise direction in FIG. 6 by the urging force of the spring  229 . As a result, the first wire lever  231  and the second wire lever  233  pivot in a clockwise direction in FIG. 6 via the link lever  234  and the link wire  235  so that the protection cover  205  moves to the cover position. Thus, the developing roller  26  is protected, preventing hands or clothes of an operator from being fouled with the toner carried on the developing roller  26 . Pivot of the restricting and releasing lever  225  in a reverse-clockwise direction in FIG. 6 causes the restricting and releasing pin  228  to engage with the restriction rib  219  of the positioning member  202 , restricting the pivot of the positioning member  202  around the holding portion  203 . Thus, the toner cartridge  200  after being removed becomes a state that the unit member  201  and the positioning member  202  are secured to each other, preventing the positioning member from becoming loose. 
     Next, in order to mount the toner cartridge  200  with the toner replenished, the toner cartridge  200  repaired or a new toner cartridge  200 , the cover  110  is opened and the rotation rack  22  is rotated by the unshown handle to position a blank storing portion of the rotation rack  22  at the opening  101 . Consequently, as shown in FIG. 2, with the positioning member  202  directed to this side, the end of the unit member  201  is inserted into the opening  101 . At this time, the guide surface  207  and the guide ridge  208  of the unit member  201  are guided by the first and second guide ridges  128 ,  129  respectively, whereby the unit member  201  is smoothly surely housed into the rotation rack  22 . Even if the toner cartridge  200  is in a half-inserted state, closure of the cover  110  as shown in FIG. 2 allows the projection  111  of the cover  110  to push the outer surface of the positioning member  202  of the toner cartridge  200 , causing the toner cartridge  200  to be inserted into the rotation rack  22  (refer to FIGS. 11A,  11 B). 
     Thus, the toner cartridge  200  inserted into the rotation rack  22  is in a first positioned state (corresponding to the first predetermined position of the present invention) as shown in FIG.  12 . In the first positioned state, into the shaft hole  214  of the unit member  201  is slightly fit the pivot shaft portion  124  of the rotation rack  22 , while the first and second positioning projections  215  and  216  of the positioning member  202  are slightly fit into the first and second positioning recesses  125 ,  126  of the rotation rack  22 . The positioning lever  130  of the rotation rack  22  is not engaged with the engagement portion  210  of the toner cartridge  200  yet. As described above, as the pivot of the positioning member  202  around the holding portion  203  is restricted so that the unit member  201  and the positioning member  202  are secured to each other, the first and second positioning projections  215  and  216  of the positioning member  202  of the toner cartridge  200  can be surely inserted into the first and second positioning recesses  125 ,  126  of the rotation rack  22  without deviating. 
     At the time when the toner cartridge  200  is inserted in the first positioned state, the projection  227  of the restricting and releasing lever  225  as shown in FIG. 6 comes into contact with the inclined surface of the cutout  127  of the wing plate  123  of the rotation rack  22  and is pushed, whereby the restricting and releasing lever  225  pivots against the urging force of the spring  229 . As a result, the first and second wire levers  231 ,  233  pivot via the link lever  234  and the link wire  235 , causing the protection cover  205  to move to the retreat position. Thus, the developing roller  26  is exposed as shown in FIG.  6 . 
     Pivot of the restricting and releasing lever  225  causes the restricting and releasing pin  228  to disengage from the restriction rib  219  of the positioning member  202 , whereby pivot of the positioning member  202  around the holding portion  203  is released. Thus, the unit member  201  of the toner cartridge  200  is possible to pivot around a fulcrum defined by the holding aperture  217  of the positioning member  202  and the pivot shaft portion  124  of the rotation rack  22 . At this time, the pivot range restricting projection  212  of the unit member  201  comes into contact with the pivot range restricting rib  218  of the positioning member  202 , whereby the pivot range of the unit member  201  is restricted to an extent of ±30°. 
     From the first positioned state, when the rotation rack  22  is rotated by the unshown handle in the direction of the arrow, the first and second step portions  220 ,  221  of the positioning member  202  of the toner cartridge  200  are stepwise pushed by the ribs  104 ,  105  of the front wall  14 . As a result, the toner cartridge  200  can be further pushed in the axial direction of the rotation rack  22  (refer to FIGS. 11C,  11   d ), being in a second positioned state (corresponding to the second predetermined position of the present invention). In the second positioned state, the positioning lever  130  of the rotation rack  22  is not engaged with the engagement portion  210  of the toner cartridge  200  yet. 
     From the second positioned state, when the rotation rack  22  is rotated in the direction of the arrow, the second step portion  221  (alternatively, the third step portion  222 ) of the positioning member  202  of the toner cartridge  200  is pushed by the lever  106  of the front wall  14 . As a result, the toner cartridge  200  can be further pushed in the axial direction of the rotation rack  22  (refer to FIG.  11 E), being in a final positioned state (corresponding to the third predetermined position of the present invention). In this final positioned state, as shown in FIGS. 12 to  13 B, to the shaft hole  214  of the unit member  201  of the toner cartridge  200  is perfectly fit the pivot shaft portion  124  of the rotation rack  22 , while the first and second positioning projections  215  and  216  of the positioning member  202  are perfectly fit into the first and second positioning recesses  125 ,  126  of the rotation rack  22 . The positioning lever  130  of the rotation rack  22  engages with the engagement portion  210  of the toner cartridge  200 , preventing the toner cartridge  200  from coming away from the rotation rack  22 . 
     In this final positioned state, as the positioning member  202  of the toner cartridge  200  comes away from the ribs  104 ,  105  of the front wall  14 , rotation of the rotation rack  22  is not obstructed. In addition, in the final positioned state, the positioning lever  130  and the first and second press levers  131 ,  132  press the press ridge  209  of the unit member  201  of the toner cartridge  200  due to the urging forces of the springs  136 ,  137  and  138 . As a result, the unit member  201  which is pivotable around the holding portion  203  is urged as shown in FIG. 14 in the rotation direction as shown by the arrow around the holding portion  203 . Thus, when the developing roller  26  of the toner cartridge  200  reaches developing position opposing to the photosensitive drum  32 , the runners  26  of the developing roller  26  come into contact with the photosensitive drum  32 , causing the toner cartridge  200  to be pressed down against the urging forces of the springs  136 ,  137  and  138 . As a result, press contacts between the photosensitive drum  32  and the runners  206  are generated, whereby a gap s between the developing roller  26  and the photosensitive drum  32  is highly accurately maintained, resulting in high image quality. 
     In the aforementioned embodiment, the toner cartridge  200  of the developing unit  20  has been described as the process cartridge of the present invention. However, the present invention is not limited to this and may be applied to the photosensitive unit  30 , the intermediate transfer unit  50  and the fixing unit  60 . The present invention can be also applied to cartridges of charging, transferring, cleaning, fixing, exposing, erasing or other exchangeable members. 
     In the aforementioned embodiment, the color printer has been described as an example but the present invention can be applied to a monochrome printer. The present application is not limited to the printer but can be also applied to other image forming apparatuses such as a copying machine, a facsimile, a composite machine thereof and a printing machine. The present invention is not limited to the electrophotographic type of image forming apparatus but can be applied to a direct recording type, an electrostatic recording type and an ink jet type of image forming apparatuses. 
     Although the present invention has been fully described by way of the examples with reference to the accompanying drawings, it is to be noted here that various changes and modifications will be apparent to those skilled in the art. Therefore, unless such changes and modifications otherwise depart from the spirit and scope of the present invention, they should be construed as being included therein.