Abstract:
A unit detachably mountable to a main assembly of the electrophotographic image forming apparatus, the electrophotographic image forming apparatus including a main assembly electrical contact and a rotatable electrical contact supporting member for supporting the main assembly electrical contact, the unit including a unit electrical contact for electrically connecting with the main assembly electrical contact when the unit is mounted to the main assembly of the apparatus; and an engaging portion for engagement with the electrical contact supporting member when the unit is inserted into the main assembly of the apparatus, the engaging portion being effective to cause a rotational motion of the electrical contact supporting member in a direction crossing with an engaging direction in which the engaging portion is brought into engagement with the electrical contact supporting member, when the unit is being inserted into the main assembly of the apparatus, wherein a sliding motion is imparted between the unit electrical contact and the main assembly electrical contact by the engaging portion causing the rotational motion of the electrical contact supporting member, with the unit electrical contact and the main assembly electrical contact being contacted to each other.

Description:
FIELD OF THE INVENTION AND RELATED ART  
       [0001]     The present invention relates to an electrophotographic image forming apparatus, and it also relates to a unit and a process cartridge, which are removably mountable in an electrophotographic image forming apparatus.  
         [0002]     Here, an electrophotographic image forming apparatus means an apparatus which forms an image on recording medium (for example, recording paper, OHP sheet, etc.) with the use of one of the electrophotographic image forming processes. As for examples of an electrophotographic image forming apparatus, there are electrophotographic copying machines, electrophotographic printers (for example, laser printers, LED printers, etc.), facsimileing machines, etc.  
         [0003]     A unit means a developing means or a developer container, which is unitized to be removable in the main assembly of an electrophotographic image forming apparatus. A process cartridge means one of various types of units, and is a cartridge in which at least one among a charging means, a developing means and a cleaning means, as processing means, and an electrophotographic photosensitive drum, are integrally disposed, and which is removably mountable in the main assembly of an image forming apparatus, or a cartridge in which at least a developing means and an electrophotographic photosensitive drum are integrally disposed, and which is removably mountable in the main assembly of an image forming apparatus.  
         [0004]     A process cartridge system which integrally places an electrophotographic photosensitive member, and a single or plurality of processing means which act on the electrophotographic photosensitive member, in a cartridge removably mountable in the main assembly of an electrophotographic image forming apparatus has long been used in the field of an electrophotographic image forming apparatus. A process cartridge system makes it possible for a user to maintain an electrophotographic image forming apparatus without relying on a service person, drastically improving an electrophotographic image forming apparatus in operational efficiency. Thus, it is widely used in the field of an electrophotographic image forming apparatus.  
         [0005]     In order to form an image with the use of an electrophotographic image forming apparatus which employs a process cartridge system, voltage must be applied to the charging member for charging the electrophotographic photosensitive member in the process cartridge, and the developing member for developing an electrostatic latent image formed on the electrophotographic photosensitive member in the process cartridge. Also, communication must be possible between the storage elements in the process cartridge and the main assembly of the image forming apparatus. Therefore, electrical connection must be established between the process cartridge and the main assembly.  
         [0006]     Conventionally, the main assembly of an electrophotographic image forming apparatus is provided with electrical contacts designed for the main assembly, whereas a process cartridge is provided with electrical contacts designed for a unit (cartridge) to be connected with the electrical contacts on the main assembly side. Thus, as a process cartridge is mounted into the main assembly of an electrophotographic image forming apparatus, the electrical contacts on the main assembly side become connected to the electrical contacts on the process cartridge side, allowing the process cartridge to be supplied with voltage, and the main assembly and process cartridge to communicate with each other.  
         [0007]     More concretely, the following structural arrangement has been known. The main assembly of an electrophotographic image forming apparatus is provided with electrical contacts for the main assembly, and a unit, which is to be mounted in the main assembly of an electrophotographic image forming apparatus is provided with electrical contacts for the unit, that is, electrical contacts which will be connected to the electrical contacts on the main assembly side, as the unit is mounted into the main assembly. Each of the electrical contacts on the main assembly side is provided with an area across which the corresponding electrical contact on the unit side is allowed to slide. With the employment of this structural arrangement, even if spots of scattered developer, or the like, are present on the electrical contacts on the main assembly and/or unit sides, they are removed (wiped away) as the unit is mounted into the main assembly. Therefore, it is assured that reliable electrical connection is established between the electrical contacts on the main assembly side and those on the unit side as the unit is mounted into the main assembly (Japanese Laid-open Patent Application 2003-330335, p. 4-p. 6, p. 10, and  FIGS. 6 and 13 ).  
         [0008]     The present invention is one of the further developments of the above described prior art.  
       SUMMARY OF THE INVENTION  
       [0009]     The primary object of the present invention is to provide a unit, a process cartridge and an electrophotographic image forming apparatus, which is superior to the prior art unit and apparatus, in terms of the level of reliability at which the electrical contact is established between the electrical contacts on the unit side and those on the main assembly side of the electrophotographic image forming apparatus, as the unit is mounted into the main assembly.  
         [0010]     Another object of the present invention is to provide a unit, a process cartridge and an electrophotographic image forming apparatus, in which each of the electrical contacts on the unit side (cartridge side) slides on the corresponding electrical contact on the main assembly side, and vice versa, so that the contaminants, such as foreign substances, on the electrical contacts on both sides are removed by the sliding movement of the electrical contacts.  
         [0011]     Another object of the present invention is to provide a unit, a process cartridge and an electrophotographic image forming apparatus, in which the electrical circuits, on the main assembly side of the electrophotographic image forming apparatus, to which the electrical contacts on the main assembly are connected, are more reliably protected than those in a combination of a unit and an electrophotographic image forming apparatus in accordance with the prior art.  
         [0012]     According to an aspect of the present invention, there is provided a unit detachably mountable to a main assembly of the electrophotographic image forming apparatus, the electrophotographic image forming apparatus including a main assembly electrical contact and a rotatable electrical contact supporting member for supporting the main assembly electrical contact, said unit comprising a unit electrical contact for electrically connecting with the main assembly electrical contact when said unit is mounted to said main assembly of the apparatus; and an engaging portion for engagement with the electrical contact supporting member when said unit is inserted into the main assembly of the apparatus, said engaging portion being effective to cause a rotational motion of the electrical contact supporting member in a direction crossing with an engaging direction in which said engaging portion is brought into engagement with the electrical contact supporting member, when said unit is being inserted into the main assembly of the apparatus, wherein a sliding motion is imparted between said unit electrical contact and the main assembly electrical contact by said engaging portion causing the rotational motion of said electrical contact supporting member, with said unit electrical contact and the main assembly electrical contact being contacted to each other.  
         [0013]     According to another aspect of the present invention, there is provided a process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, the electrophotographic image forming apparatus including a main assembly electrical contact and a rotatable electrical contact supporting member for supporting the main assembly electrical contact, said process cartridge comprising an electrophotographic photosensitive member; process means actable on said electrophotographic photosensitive member; a cartridge electrical contact for electrically connecting with the main assembly electrical contact when said process cartridge is mounted to said main assembly of the apparatus; and an engaging portion for engagement with the electrical contact supporting member when said process cartridge is inserted into the main assembly of the apparatus, said engaging portion being effective to cause a rotational motion of the electrical contact supporting member in a direction crossing with an engaging direction in which said engaging portion is brought into engagement with the electrical contact supporting member, when said process cartridge is being inserted into the main assembly of the apparatus, wherein a sliding motion is imparted between said cartridge electrical contact and the main assembly electrical contact by said engaging portion causing the rotational motion of said electrical contact supporting member, with said cartridge electrical contact and the main assembly electrical contact being contacted to each other.  
         [0014]     According to a further aspect of the present invnetion, there is provided an electrophotographic image forming apparatus for forming an image on a recording material, wherein a unit is detachably mountable to a main assembly of said electrophotographic image forming apparatus, said apparatus comprising (i) a main assembly electrical contact; (ii) a rotatable electrical contact supporting member for supporting said main assembly electrical contact; (iii) mounting means for detachably mounting said unit, said unit including, a cartridge electrical contact for electrically connecting with said main assembly electrical contact when said process cartridge is mounted to said main assembly of the apparatus, and an engaging portion for engagement with the electrical contact supporting member when said unit is inserted into the main assembly of the apparatus, said engaging portion being effective to cause a rotational motion of the electrical contact supporting member in a direction crossing with an engaging direction in which said engaging portion is brought into engagement with the electrical contact supporting member, when said unit is being inserted into the main assembly of the apparatus, wherein a sliding motion is imparted between said unit electrical contact and the main assembly electrical contact by said engaging portion causing the rotational motion of said electrical contact supporting member, with said unit electrical contact and the main assembly electrical contact being contacted to each other; and feeding means for feeding the recording material.  
         [0015]     According to an aspect of the present invention, there is provided an electrophotographic image forming apparatus for forming an image on a recording material, wherein a process cartridge is detachably mountable to a main assembly of said electrophotographic image forming apparatus, said apparatus comprising (i) a main assembly electrical contact; (ii) a rotatable electrical contact supporting member for supporting said main assembly electrical contact; (iii) mounting means for detachably mounting said process cartridge, said process cartridge including, a cartridge electrical contact for electrically connecting with the main assembly electrical contact when said process cartridge is mounted to said main assembly of the apparatus, and an engaging portion for engagement with the electrical contact supporting member when said unit is inserted into the main assembly of the apparatus, said engaging portion being effective to cause a rotational motion of the electrical contact supporting member in a direction crossing with an engaging direction in which said engaging portion is brought into engagement with the electrical contact supporting member, when said process cartridge is being inserted into the main assembly of the apparatus, wherein a sliding motion is imparted between said cartridge electrical contact and the main assembly electrical contact by said engaging portion causing the rotational motion of said electrical contact supporting member, with said cartridge electrical contact and the main assembly electrical contact being contacted to each other; and feeding means for feeding the recording material.  
         [0016]     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  
       [0017]      FIG. 1  is a sectional view of the electrophotographic image forming apparatus in the first embodiment of the present invention, showing the general structure thereof.  
         [0018]      FIG. 2  is a sectional view of the process cartridge in the first embodiment of the present invention, showing the general structure thereof.  
         [0019]      FIG. 3  is a schematic perspective view (No. 1) of the process cartridge.  
         [0020]      FIG. 4  is a schematic perspective view (No. 2) of the process cartridge.  
         [0021]      FIG. 5  is a schematic perspective view (No. 1) of the development unit of the process cartridge.  
         [0022]      FIG. 6  is a schematic perspective view (No. 2) of the development unit of the process cartridge.  
         [0023]      FIG. 7  is a drawing for describing the method for mounting the process cartridge.  
         [0024]      FIG. 8  is a side view of the cartridge positioning mechanism of the main assembly of the electrophotographic image forming apparatus, which is for precisely positioning the process cartridge in terms of the widthwise direction of the process cartridge, in the main assembly of the electrophotographic image forming apparatus.  
         [0025]      FIG. 9  is a side view of the connective (coupling) portion of the process cartridge, and the corresponding portion of the main assembly of the electrophotographic image forming apparatus, showing how the former is connected to the latter.  
         [0026]      FIG. 10  is a schematic perspective view of the connective (coupling) portion of the process cartridge, and the electrical contact supporting member, on the main assembly side, which corresponds to the connective portion of the process cartridge.  
         [0027]     FIGS.  11 ( a ) and  11 ( b ) are enlarged frontal and perspective views of the connective (coupling) portion of the process cartridge.  
         [0028]      FIG. 12  is an enlarged plan view of the electrical contact supporting member on the main assembly side of the electrophotographic image forming apparatus, and the substrative plate which supports this electrical contact supporting member.  
         [0029]      FIG. 13  is a perspective drawing (No. 1) for describing the rotational movement of the electrical contact supporting member on the main assembly side of the electrophotographic image forming apparatus, which occurs as the connective (coupling) portion of the process cartridge engages with the electrical contact supporting member on the main assembly side.  
         [0030]      FIG. 14  is a perspective drawing (No. 2) for describing the rotational movement of the electrical contact supporting member on the main assembly side of the electrophotographic image forming apparatus, which occurs as the connective portion of the process cartridge engages with the electrical contact supporting member on the main assembly side.  
         [0031]      FIG. 15  is a perspective drawing (No. 3) for describing the rotational movement of the electrical contact supporting member on the main assembly side of the electrophotographic image forming apparatus, which occurs as the connective portion of the process cartridge engages with the electrical contact supporting member on the main assembly side.  
         [0032]      FIG. 16  is a perspective view (No. 1) of the electrical contacts connected to the memory element of the unit, and the electrical contacts on the main assembly side of the electrophotographic image forming apparatus.  
         [0033]      FIG. 17  is a perspective view (No. 2) of the electrical contacts connected to the storage means of the unit, and the electrical contacts on the main assembly side of the electrophotographic image forming apparatus.  
         [0034]      FIG. 18  is a schematic drawing of the electrical wiring for the electrical contacts on the main assembly side of the electrophotographic image forming apparatus.  
         [0035]      FIG. 19  is a chart of the R/W circuit.  
         [0036]      FIG. 20  is a schematic perspective view of one of the modifications of the first embodiment, regarding the connective (coupling) portion of the process cartridge, and the electrical contact supporting member, on the main assembly side, which corresponds to the connective portion of the process cartridge.  
         [0037]      FIG. 21  is a perspective drawing for describing the rotational movement of the electrical contact supporting member on the main assembly side of the electrophotographic image forming apparatus, which occurs as the connective (coupling) portion of the process cartridge engages with the electrical contact supporting member on the main assembly side. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0038]     Hereinafter, the electrophotographic image forming apparatus in accordance with the present invention, and the process cartridge, that is, a form of the unit removably mountable in the electrophotographic image forming apparatus, will be described in detail with reference to the appended drawings.  
       EMBODIMENT 1  
     (1) General Structure of Electrophotographic Image Forming Apparatus  
       [0039]      FIG. 1  is a sectional view of the electrophotographic image forming apparatus (which hereinafter may be referred to simply as image forming apparatus), showing the general structure thereof. The image forming apparatus in this embodiment is a full-color laser beam printer, which employs one of the electrophotographic processes of the transfer type, and is of the so-called tandem type.  
         [0040]     Referring to  FIG. 1 , designated by referential symbols Y, M, C, and Bk are first to fourth image formation stations, which form, one for one, yellow, magenta, cyan, and black toner images, the colors of which match, one for one, the four color components into which the optical image of a full-color image is separated. The four image formation stations are stacked in the main assembly  100  of the image forming apparatus, in the listed order starting from the bottom.  
         [0041]     Each of the four image formation stations Y, M, C, and Bk comprises a set of devices for the electrophotographic process, for example, an electrophotographic photosensitive drum (which hereinafter may be referred to as photosensitive drum) as an image bearing member  1  ( a - d ), a charging means  2  ( a - d ), a scanner unit  3  ( a - d ) as an exposing means, a development roller  40  ( a - d ), a cleaning member  6  ( a - d ), etc.  
         [0042]     The scanner unit  3  ( a - d ) is an exposing means for forming an electrostatic latent image on the peripheral surface of the photosensitive drum  1  by projecting a beam L of light onto the uniformly charged peripheral surface of the photosensitive drum  1  while modulating the beam L of light with image formation data. It is positioned at the same level as the photosensitive drum  1  ( a - d ). It has a laser diode (unshown), a scanner motor (unshown), a polygon mirror ( a - d ), a focal lens  10  ( a - d ), etc.  
         [0043]     Designated by a referential number  5  is an electrostatic transferring means for transferring the toner image formed on the peripheral surface of each of the photosensitive drums  1  ( a - d ) onto recording medium S (transfer medium). This electrostatic transferring means  5  comprises: an endless transfer belt  11 ; a driver roller  13 ; two follower rollers  14   a  and  14   b;  and a tension roller  15 . The endless transfer belt  11  is stretched around the four rollers  13 ,  14   a,    14   b,  and  15 , being vertically extended with its outward surface placed in contact with the peripheral surface of each of the photosensitive drums  1  ( a - d ), and is circularly driven. Designated by referential numbers  12  ( a - d ) are transfer rollers, which are positioned so that the transfer belt  11  remains pinched between the photosensitive drums  1  ( a - d ) and transfer rollers  12  ( a - d ), respectively, during the formation of an image.  
         [0044]     Designated by a referential number  16  is a recording medium conveying portion, which is located in the bottom portion of the main assembly  100  of the image forming apparatus (which hereinafter may be referred to simply as apparatus main assembly), and conveys the recording medium S onto the transfer belt  11  of the electrostatic transferring means  5 . The recording medium conveying portion  16  comprises a feeding cassette  17 , in which a plurality of recording mediums S are stored. Designated by referential numbers  18 ,  19 , and  22  are a conveyance roller, a pair of registration rollers, and an electrostatic adhesion roller, respectively.  
         [0045]     Designated by a referential number  20  is a fixation station which is in the top portion of the apparatus main assembly  100 . The fixation station  20  is a station for fixing to the recording medium S, a plurality of unfixed toner images different in color, which have just been transferred onto the recording medium S. It comprises: a heat roller  21   a,  which is rotationally driven; a pressure roller  21   b,  which is kept pressed against the heat roller  21   a  to apply pressure to the recording medium S; a pair of discharge rollers  23 ; a sheet outlet portion  24 ; etc. Designated by a referential number  25  is a delivery tray which is located on top of the apparatus main assembly  100  to catch the recording medium S on which a permanent full-color image has just been formed.  
         [0046]     The image formation stations Y, M, C, and Bk are sequentially driven in synchronism with the predetermined control timing of the image formation sequence, so that the photosensitive drum  1  ( a - d ) in each image formation station rotates in the counterclockwise direction. The transfer belt  11  of the electrostatic transferring means  5  is circularly driven by the driver roller  13  in the clockwise direction, indicated by an arrow mark D, at a peripheral velocity equal to that of each photosensitive drum  1  ( a - d ).  
         [0047]     As each photosensitive drum  1  ( a - d ) is rotationally driven, its peripheral surface is uniformly charged (primary charge) to predetermined polarity (negative polarity in this embodiment) and potential level by a charging means  2  ( a - d ). The charged peripheral surface of the photosensitive drum  1  is exposed to the beam L of laser light outputted from the scanner unit  3  ( a - d ) while being modulated with the image formation data. As a result, an electrostatic latent image in accordance with the image formation data is formed on the peripheral surface of each of the photosensitive drums  1  ( a - d ). More specifically, the beam L of light modulated with video signals is outputted by the laser diode (unshown) of the unit  3  ( a - d ), toward the polygon mirror  9  ( a - d ) being rotated at a high velocity. After being deflected (reflected) by the polygon mirror  9 , the beam L of light is focused on the charged peripheral surface of the photosensitive drum  1 , selectively exposing numerous points of the charged surface of the photosensitive drum  1 . As a result, an electrostatic latent image is formed on the peripheral surface of each of the photosensitive drums  1 .  
         [0048]     The electrostatic latent image is developed by the development roller  40  ( a - d ) into a visible image (image formed of toner). In this embodiment, the latent image is reversely developed with the use of toner with the negative polarity. In other words, a visible image is formed on the peripheral surface of the photosensitive drum  1  in each image formation station; yellow, magenta, cyan, and black toner images are formed on the photosensitive drums  1   a,    1   b,    1   c,  and  1   d  in the image formation stations Y, M, C, and Bk, respectively, with the predetermined control timing for the image formation sequence. The yellow, magenta, cyan, and black colors are the color components into which the optical image of an intended full-color image is separated.  
         [0049]     Meanwhile, the feed roller  18  of the sheet feeding portion  16  begins to be rotated with predetermined timing. As a result, the recording mediums S in the cassette  17  begin to be fed into the apparatus main assembly  100  while being separated one by one. After being fed into the apparatus main assembly  100 , each recording medium S is temporarily held by the pair of registration rollers  19  as the leading edge of the recording medium S comes into contact with the nip between the pair of registration rollers  19 , which are not rotating when the recording medium S comes into contact with the nip. Then, the pair of registration rollers  19  begins to be rotated in synchronism with the rotation of the transfer belt  11  and the formation of the toner image on the peripheral surface of the photosensitive drum  1  ( a - d ), allowing thereby the recording medium S to be conveyed to the nip between the electrostatic adhesion roller  22  and transfer belt  11 , and conveyed through the nip. While the recording medium S is conveyed through the nip between the electrostatic adhesion roller  22  and transfer belt  11 , the recording medium S is pressed onto the outward surface of the endless transfer belt  11 . In addition, while the recording medium S is conveyed through the nip between the adhesion roller  22  and transfer belt  11 , voltage is applied between the transfer belt  11  and adhesion roller  22 , inducing thereby electric charge between the recording medium S, which is formed of dielectric substance, and the dielectric layer of the transfer belt  11 . As a result, the recording medium S is electrostatically adhered to the outward surface of the transfer belt  11 , and therefore, it remains flatly adhered to the transfer belt  11  while it is conveyed to the most downstream point of the most downstream transfer station by the movement of the transfer belt  11 .  
         [0050]     To describe in more detail, the pair of registration rollers  19  are rotated to release the recording medium S with such timing that the recording medium S is conveyed to the transfer belt  11  so that the point in time, at which the leading edge of the toner image on the peripheral surface of the photosensitive drum  1   a  in the first image formation station Y, or the most upstream image formation station in terms of the moving direction of the transfer belt  11 , arrives at the nip between the photosensitive drum  1   a  and transfer belt  11 , coincides with the point in time at which the print-start line of the recording medium S arrives at the nip between the photosensitive drum  1   a  and transfer belt  11 . With the provision of this arrangement, the recording medium S is conveyed upward from the transfer station of the first image formation station Y, or the most upstream image formation station, to the fourth image formation station Bk, or the most downstream image formation station, while remaining perfectly flatly adhered to the transfer belt  11 .  
         [0051]     While the recording medium S is conveyed as described above, the toner image on each of the photosensitive drums  1  ( a - d ) is sequentially transferred in layers onto the recording medium S by the electric field generated between each of the photosensitive drums  1  ( a - d ) and the corresponding transfer roller  12  ( a - d ). In this embodiment, positive electric charge is given to the recording medium S from each of the photosensitive drums  1  ( a - d ) through the transfer belt  11 . By the electric field generated by this electric charge, the toner image on each photosensitive drum  1 , which is negative in polarity, is transferred onto the recording medium S, which is in contact with the photosensitive drum  1 .  
         [0052]     To summarize, the recording medium S is held to the transfer belt  11  by being electrostatically adhered thereto, and is conveyed upward by the rotation of the transfer belt  11  through the transfer station of each of the first to fourth image formation stations Y, M, C, and Bk. While the transfer medium S is sequentially conveyed upward through the image formation stations Y, M, C, and Bk, the yellow, magenta, cyan, and black toner images formed on the photosensitive drums  1   a,    1   b,    1   c,  and  1   d,  respectively, are sequentially transferred in layers onto the recording medium S. As a result, an unfixed full-color toner image is synthesized on the surface of the recording medium S.  
         [0053]     After receiving in layers the four color toner images, the recording medium S is separated from the transfer belt  11  by its resiliency and the curvature of the drive roller  13 , and then, is conveyed into the fixation station  20 . In the fixation station  20 , the recording medium S is conveyed through the nip formed by the rotating heat roller  21   a  and the pressure roller  21   b  kept pressed against the heat roller  21   a.  As a result, heat and pressure are applied to the recording medium S by the heat roller  2   a  and pressure roller  2   b.  Consequently, the plurality of unfixed toner images different in color, on the recording medium S, are fixed to the surface of the recording medium S. After the fixation of the toner images to the recording medium S, the recording medium S is discharged by the pair of discharge rollers  23  from the sheet outlet portion  24 , into the delivery tray  25  located outside the apparatus main assembly  100 .  
         [0054]     In each of the first to fourth image formation stations Y, M, C, and Bk, after the transfer of the toner image onto the recording medium S, the residues on the peripheral surface of the photosensitive drum  1 , such as the toner remaining the photosensitive drum  1  ( a - d ) after the transfer, are removed by the cleaning member  6  ( a - d ), and the photosensitive drum  1  is used for the following image forming process.  
       (2) Process Cartridge  
       [0055]     In the first to fourth image formation stations Y, M, C, and Bk, process cartridge  7  ( a - d ) as image formation units are removably mounted, one for one. The process cartridges  7  ( a - d ) comprise photosensitive drums  1  ( a - d ), charging means  2  ( a - d ), development rollers  40  ( a - d ), and cleaning members  6  ( a - d ), respectively. Each process cartridge  7  is removably mountable in the apparatus main assembly  100 .  
         [0056]     The procedure for mounting each of the above described cartridges  7  ( a - d ) into the apparatus main assembly  100  or dismounting it therefrom is as follows. That is, each cartridge  7  is mounted or dismounted by exposing the cartridge insertion opening in the apparatus main assembly  100  by fully opening the front door  26  of the apparatus main assembly  100 .  
         [0057]     More specifically, the front cover of the apparatus main assembly  100  is in the form of the door  26  hinged to the apparatus main assembly  100  so that it can be open or closed, along with the electrostatic transferring means  5 , relative to the main assembly  100 . Thus, the door  26  can be rotated about the hinge  27  ( FIG. 7 ) located at the bottom portion of the apparatus main assembly  100 , into the position outlined by the double-dot chain line in  FIG. 1 , or the solid line in  FIG. 7 , by pulling the door  26  toward an operator. In other words, by pulling the door  26  toward an operator, the door  26  can be placed into the position in which it fully exposes the cartridge insertion opening  21  ( FIG. 7 ) in the apparatus main assembly  100 . Thus, by closing the door  26 , the cartridge insertion opening  91  is covered (as outlined by solid line in  FIG. 1 ). The procedure for mounting the cartridges  7  ( a - d ) into the apparatus main assembly  100  or removing them from the apparatus main assembly  100  will be described in detail in the following Item (3).  
         [0058]     In the following description of the present invention, the widthwise direction of the process cartridge or a given member thereof means the direction in which the process cartridge is mounted into, or removed from, the apparatus main assembly  100 . The lengthwise direction of the process cartridge or a given member thereof means the direction intersectional to the direction in which the process cartridge is mounted into, or removed from, the apparatus main assembly  100 . Further, the rear side of the cartridge means the rear side as seen from the front side of the the apparatus main assembly  100  when the cartridge is in the apparatus main assembly  100 . The left or right side of a cartridge means the left or right side which will be on the left or right side as seen from the fron side of the apparatus when the cartridge is in the apparatus main assembly  100 . The top surface of a cartridge means the surface which will be the top surface when the cartridge is in the apparatus main assembly  100 , and the bottom surface is the surface which will be the bottom surface when the cartridge is in the apparatus main assembly  100 .  
         [0059]      FIG. 2  is a sectional view of the cartridge  7 , and  FIGS. 3 and 4  are schematic perspective views of the cartridge  7 .  FIGS. 5 and 6  are schematic perspective views of the development unit of the cartridge  7 .  
         [0060]     As for the developer stored in the toner container of the developing means in each of the cartridges  7  ( a - d ) in the first to fourth image formation stations Y, M, C, and Bk, respectively, the developer in the cartridge  7   a  in the first image formation station Y is toner with yellow color; the developer in the cartridge  7   b  in the second image formation station M is toner with magenta color; the developer in the cartridge  7   c  in the third image formation station C is toner with cyan color; and the developer in the cartridge  7   d  in the fourth image formation station Bk is toner with black color. The four process cartridges are identical in structure, although they are different in the color of the toner therein. Therefore, the structure of only one of the process cartridges  7  will be described.  
         [0061]     Referring primarily to  FIG. 2 , each cartridge  7  has a cleaning unit  50 , or a first unit, and a development unit  4 , or a second unit. The cleaning unit  50  comprises the photosensitive drum  1 , charging means  2 , and cleaning means  6 , whereas the development unit  4  comprises the developing means.  
         [0062]     To the unit  50 , the photosensitive drum  1  is rotatably attached. In the adjacencies of the peripheral surface of the photosensitive drum  1 , the charging means  2  and cleaning member  6  are disposed in contact therewith as described above. After being removed from the peripheral surface of the photosensitive drum  1  by the cleaning member  6 , the residual toner is sent to a toner chamber  53  for removed toner, which is located behind the cleaning unit frame  51 . As the charging means  2 , one of the charging means of the contact type is employed. The charging member is in the form of an electrically conductive roller, and is placed in contact with the peripheral surface of the photosensitive drum  1 . As charge bias voltage is applied to the charge roller, the peripheral surface of the photosensitive drum  1  is uniformly charged.  
         [0063]     The development unit  4  comprises the toner container  41  and a development unit frame  45 . The toner in the toner container  41  is sent to a toner supply roller  43  by a toner conveyance mechanism  42 , and then, is uniformly coated on the peripheral surface of the development roller  40  by the abovementioned toner supply roller  43 , and the development blade  44  as a developing member kept pressed upon the peripheral surface of the development roller  40 , while being frictionally charged. Then, as development bias is applied to the development roller  40 , the latent image formed on the peripheral surface of the electrophotographic photosensitive drum  1  is developed. Incidentally, the development roller  40  is disposed opposing the photosensitive drum  1 .  
         [0064]     The photosensitive drum  1  is rotatably supported by its lengthwise ends by a pair of supporting members  64  and  65  ( FIG. 3 ), which are supported by the cleaning unit frame  51 . One of the lengthwise ends of the photosensitive drum  1  is provided with a coupling member  70  to which driving force is transmitted from a motor (unshown) with which the apparatus main assembly  100  is provided. With the provision of this structural arrangement, the photosensitive drum  1  can be rotationally driven in the counterclockwise direction with reference to  FIG. 2 . The rotation of the photosensitive drum  1  is transmitted through a gear train (unshown) to the toner conveyance mechanism  52  in the toner chamber  53  for removed toner, to drive the toner conveyance mechanism  52 .  
         [0065]     The pair of supporting members  64  and  65  are supported by a pair of handles  82  and  83  to be used for mounting the cartridge  7  into the main assembly  100  of an image forming apparatus, and also, are supported by the cleaning unit frame  51 . The cleaning unit frame  51  is provided with a shutter  72  for protecting the photosensitive drum  1 . The shutter  72  is enabled to be closed into the position (FIGS.  2  and  3 ) in which it covers the drum exposure window, and also, is enabled to be opened upward (or downward) into the position (outlined by double-dot chain line in  FIG. 2 ) in which it exposes the drum exposure opening, by a opening and closing mechanism  97 . When the cartridge  7  is out of the apparatus main assembly  100 , the shutter  72  is held in the closed position, covering thereby the drum exposure opening to protect the peripheral surface of the photosensitive drum  1 . Further, as the front door  26  ( FIG. 1 ) of the apparatus main assembly  100  is closed after the insertion of the cartridge  7  into the apparatus main assembly  100 , the shutter  72  is moved into the open position by a means which is moved by the closing movement of the front door  26 . As a result, the transfer belt  11  comes into contact with the peripheral surface of the photosensitive drum  1 .  
         [0066]     The development unit  4  is connected to the cleaning unit  50  as if it is suspended from the cleaning unit  50  so that it can be pivoted about the axial line of the joint between the two units. More specifically, referring to  FIGS. 5 and 6 , the development unit  4  is provided with a pair of bearing members  47  and  48 , which are attached to the lengthwise ends of the unit  4 , one for one, and are provided with holes  47   a  and  48   a,  respectively, the axial lines of which coincide with the pivotal axes of the unit  4 . A pair of connective shafts  62  and  63  are inserted into the holes  47   a  and  48   a,  respectively, through the corresponding connective holes of the cleaning unit frame  51 . As a result, the development unit  4  is pivotally connected to the cleaning unit frame  51  ( FIG. 2 ).  
         [0067]     The cartridge  7  is structured so that when it is not in the main assembly of an image forming apparatus, the development unit  4  remains under the pressure which acts in the direction to rotate the development unit  4  about the connective shafts  62  and  63  inserted in the hole  47   a  and  48   a,  the rotational axes of which coincide with the rotational axes of the bearing members  47  and  48 , so that the development roller  40  is kept in contact with the photosensitive drum  1 . For this purpose, the lengthwise end of the cartridge  7 , on the bearing  47  side, is provided with a compression spring  54 , as a means for pressing the development unit  4 , which is positioned between the development unit  4  and cleaning unit  50 , at the widthwise end, on the opposite side of the connective shafts  62  and  63  from the photosensitive drum  1 , and the lengthwise end of the cartridge  7 , on the bearing  48  side, is provided with a tension spring  90  ( FIG. 6 ) as a means for pulling the development unit  4 , which also is positioned between the unit  50  and development unit  4 .  
         [0068]     Designated by a referential number  71  ( FIGS. 4-6 ) is a cartridge driving gear (helical gear) with which the development unit  4  is provided. When the cartridge  7  is in the apparatus main assembly  100 , the cartridge driving gear  71  is in mesh with the driving gear (unshown helical gear) on the main assembly side, and receives driving force from the driving gear on the main assembly side. By the rotation of this driving gear  71 , the development roller  40 , toner conveyance mechanism  42 , and toner supply roller  43  are driven through the gear train (unshown).  
         [0069]     Designated by referential numbers  94  and  102  ( FIGS. 2 and 4 ) are a memory (which will be described later), and the connective (coupling) member attached to the rear surface of the cleaning unit frame  51 . The connective member  102  is to be engaged with the electrical contact supporting member on the main assembly side. These members will be described in detail in Item (4).  
       (3) Method for Mounting Process Cartridge  
       [0070]     Next, referring to  FIGS. 7 and 8 , the method for mounting the cartridge  7  into the apparatus main assembly  100  will be described.  
         [0071]     Referring primarily to  FIG. 7 , as described above, the operation for mounting each of the cartridges  7  ( a - d ) into the apparatus main assembly  100 , or removing it therefrom, is carried out after the cartridge insertion opening  91  in the apparatus main assembly  100  is widely exposed by opening the front door  26  of the apparatus main assembly  100 . When the door  26  is in the closed position, it is locked to the apparatus main assembly  100  with a latching mechanism (unshown). Thus, when opening the front door  26 , first, the door  26  is to be unlocked by unlatching the latching mechanism, and the door  26  is to be opened toward an operator by rotating the door  26  about the hinge shaft  27  located at the bottom edge of the door  26 . As the front door  26  is opened all the way, the cartridge insertion opening  91  in the apparatus main assembly  100  becomes fully exposed.  
         [0072]     Inward of the cartridge insertion opening  91 , there are four pairs of guides  80  and  81  attached to the inward surfaces of the side plates  31  and  32  of the apparatus main assembly  100  in order to guide the cartridges  7  into the image formation positions. The cartridge insertion opening  91  is tall enough to expose all four cartridge compartments all at once. The cartridge compartments are vertically stacked. The bottommost cartridge compartment is for the cartridge containing yellow developer (toner), and the rest are stacked in the order of magenta, cyan, and black cartridges on top of the bottommost compartment.  
         [0073]     The compartments for the cartridges  7  for yellow, magenta, cyan, and black color are identical in structure. Thus; the method for mounting the cartridge  7  into the apparatus main assembly  100  will be described with reference to the bottommost cartridge compartment, or the compartment for the cartridge  7   a  for yellow color.  
         [0074]     First, an operator is to lift the cartridge  7  by grasping with his left and right hands the left and right handles  82  and  83  located at the lengthwise ends of the cartridge  7 , more specifically, the lengthwise ends of the cleaning unit  50 , and to insert the cartridge  7  into the cartridge compartment inside the cartridge insertion opening  91  in the direction indicated by an arrow mark Q, with the rear side of the cartridge, that is, the opposite side of the cartridge  7  from the photosensitive drum  1 , in terms of the widthwise direction of the cartridge  7 , facing forward.  
         [0075]     The guides  80  and  81  of the main assembly  100  are provided with rough guides  86  and  87 , respectively, which support the cartridge  7  by the bottom surfaces of the lengthwise end portions of the cartridge  7 . The operator is to insert the cartridge into the cartridge compartment so that the bottom surface  48   c  of the bearing member  48  of the cartridge  7 , and the bottom surface  51   f  of the cleaning unit frame  51 , rest on the rough guides  86  and  87 , respectively. The guides  80  and  81  of the apparatus main assembly  100  are also provided with boss guides  88  and  89 , respectively, into which the bosses  51   d  and  51   e,  with which the lengthwise end walls of the cleaning unit frame  51  are provided, fit to regulate the rotation of the cartridge  7  in the apparatus main assembly  100 . As the cartridge  7  is further inserted, the bosses  51   d  and  51   e  come into contact with the boss guides  88  and  89 , and ride onto them, being thereby guided, respectively.  
         [0076]     Further, the guide  81  of the main assembly  100  is provided with a pressing means  84  ( 84   d - 84   g,  listing from bottom side) for pressing the cartridge  7  in the lengthwise direction. The cartridge pressing means  84  comes into contact with the right end surface of the cartridge  7 , more specifically, the guiding portion  85  ( FIG. 3 ) on the right end surface of the cleaning unit frame  51  in this embodiment, and presses the cartridge  7  in the lengthwise direction, that is, toward the left side plate  31  of the apparatus main assembly  100 .  
         [0077]     Then, as the cartridge  7  is further inserted into the apparatus main assembly  100 , the abovementioned guiding portion  85  of the cartridge  7  comes under the pressure from the pressing means  84 . Therefore, while the cartridge  7  is further inserted, the cartridge  7  remains pressured toward the left side plate  31  of the apparatus main assembly  100 , that is, the opposite side plate from the right side plate  32  to which the pressing means  84  is attached. Further, one of the lengthwise ends of the cleaning unit frame  51  is provided with a positioning portion  51   c  for accurately positioning the cartridge  7  in the apparatus main assembly  100 . That is, as this positioning portion  51   c  comes into contact with the end surface of the insert guide  80  of the apparatus main assembly  100 , the position of the cartridge  7  in the apparatus main assembly  100  becomes fixed in terms of the lengthwise direction.  
         [0078]     There is extended a center plate  93  between the side plates  31  and  32  of the apparatus main assembly  100 . The center plate  93  is provided with four exposure windows which allow the beam L of laser light from each scanner  3  to pass. Also, the center plate  93  is fitted with four electrical contact supporting rotatable members  105  for supporting the electrical contacts on the main assembly side. The electrical contact supporting members  105  are protruding into the cartridge compartments  200  through the four holes  96 , one for one, with which the center plate  93  is provided. The electrical contacts on the main assembly side come into contact with the electrical contacts on the unit side, which are electrically connected with the memory  94  which stores the information regarding the cartridge  7 ; they are for establishing electrical connection between the memory  94  of the cartridge  7  and the apparatus main assembly  100 .  
         [0079]     Referring to  FIG. 8 , the bearings  64  and  65  which support the photosensitive drum  1  are inserted along the guiding grooves  34   a  and  34   h,  respectively, until the bearings  64  and  65  are pressed against the contact areas  37  and  38  of the guiding grooves  34   a  and  34   h  so that the position of the cartridge  7  relative to the apparatus main assembly  100  in terms of the widthwise direction becomes fixed. That is, when the bearings  64  and  65  are in contact with the contact areas  37  and  38  of the guiding grooves  34   a  and  34   h,  the bearings  64  and  65 , and the bosses  51   d  and  51   e  protruding, one for one, from the lengthwise end surfaces of the cleaning unit frame  51 , are precisely positioned relative to the apparatus main assembly  100  by the boss guides  88  and  89 .  
         [0080]     The cartridge  7  is inserted until the bearings  64  and  65  are caught by the contact areas of the guiding grooves  34   a  and  34   h  by coming into contact with the contact areas  37  and  38  of the guiding grooves  34   a  and  34   h.  Then, at the very end of the process of mounting the cartridge  7  into the apparatus main assembly  100 , the connective (coupling) portion  102  located on the rear surface of the cartridge  7  fully engages with the electrical contact supporting member  105  protruding into the cartridge compartment  200  through the aforementioned hole  96 . In this embodiment, the electrical contacts, on the unit side, which are in electrical connection with the memory  94  of the cartridge  7 , are placed in contact with the electrical contacts on the main assembly side, establishing thereby the electrical connection between the memory  94  and the apparatus main assembly  100 . This arrangement will be described later.  
         [0081]     Further, the electrical contact of the development bias unit (unshown), with which the cartridge  7  is provided for development bias application is placed in contact with the electrical contact (unshown) with which the apparatus main assembly  100  is provided for development bias application, establishing thereby electrical connection between the two electrical contacts.  
         [0082]     Further, the driving gear  71  of the cartridge  7  is meshed with the driving gear (unshown) of the apparatus main assembly  100 .  
         [0083]     As for the cartridges  7   b,    7   c,  and  7   d,  they are inserted into the corresponding cartridge compartments in the same manner as the cartridge  7   a  is inserted into the bottommost cartridge compartment as described above.  
         [0084]     Next, the open front door  26  is to be closed against the apparatus main assembly  100 , and the door is to be locked with the latching mechanism (unshown). This closing movement of the front door  26  causes the following actions through a means, the movement of which is caused by the movement of the front door  26 : 
        1) positioning of each of the cartridges  7  within the apparatus main assembly  100  in terms of the widthwise direction;     2) moving the shutter  72  of each cartridge  7  into the open position; and     3) engaging the coupling  70  of each cartridge  7  with the corresponding driving force transmission coupling of the apparatus main assembly  100 .        
 
         [0088]     More specifically, 1) positioning of the shutter  72  of each cartridge  7  in terms of the widthwise direction is done by a pressing means  30 , the movement of which is caused by the movement of the mechanism for opening or closing the door  26  to the inward side of which the electrostatic transferring means  5  is attached. The pressing member  30  is rotatably attached to a shaft  39  crimped to the side plate  31 . It is engaged with a connective member  29 , the movement of which is caused with the opening or closing movement of the door  26 . Thus, when the door  26  is open, in other words, when the apparatus main assembly  100  is in the state in which the process cartridges  7  are mountable into the apparatus main assembly  100  or dismountable, the pressing member  30  is in a position  30   a,  into which the pressing member  30  is retracted. While the cartridge  7  is inserted, the pressing member  30  does not come into contact with the cartridge  7 . However, as the door  26  is closed after the insertion of the cartridge  7 , the connective member  29  is moved in the direction indicated by an arrow mark R by the closing movement (in direction indicated by arrow mark T) of the door  26 , and the pressing member  30  is moved into the position  30   b  by the movement of the connective member  29 , in which it presses on the slanted surface  51   s  of the cleaning unit frame  51 , located near the bearing  64 , in the direction indicated by an arrow mark S. As a result, the cartridge  7  is precisely positioned in the apparatus main assembly  100  in terms of its widthwise direction. There is also provided a similar mechanism on the side plate  32  side. In other words, the cartridge  7  is pressed by its lengthwise ends by the pair of pressing members  30 .  
         [0089]     After the mounting of each of the cartridges  7  into the apparatus main assembly  100 , the coupling  70  of each cartridge  7  is in engagement with the corresponding driving force transmission coupling on the main assembly  100  side. Therefore, the driving force from the motor (unshown) on the apparatus main assembly  100  side can be transmitted to the coupling  70  on the cartridge  7  side to rotationally drive the photosensitive drum  1  of the cartridge  7  in the counterclockwise direction in  FIG. 1 , and the toner conveyance mechanism  52  in the toner chamber  53  for removed toner can be driven by the rotation of the photosensitive drum  1  through the unshown gear train.  
         [0090]     Further, the cartridge driving gear  71  of each cartridge  7  is in mesh with the driving gear (unshown) on the main assembly  100  side. Therefore, the driving gear  71  can receive driving force from the driving gear on the main assembly  100  side, and the development roller  40 , toner conveyance mechanism  42 , and toner supply roller  43  in each cartridge  7  are driven by the rotation of the driving gear  71  through a gear train (unshown).  
         [0091]     Further, the development bias application electrical contact (unshown) of each cartridge  7  is in contact with the electrical contact on the apparatus main assembly  100  side, establishing thereby electrical contact between the development bias application electrical contact on the cartridge  7  side and the power source (unshown) on the main assembly  100  side, making it therefore possible for the development bias to be applied to the development roller  40  in each cartridge  7  from the power source on the main assembly  100  side.  
         [0092]     Further, the connective (coupling) portion  102  on the rear surface of each cartridge  7  is in engagement with the electrical contact supporting member  105 , on the main assembly side, which is protruding through the hole  96  of the center plate  93 , establishing electrical contact between the electrical contacts on the unit side and the electrical contacts on the main assembly  100  side, making it possible for electrical data to be exchanged between the memory  9  of the cartridge  7  and the control circuit portion  113  on the main assembly  100  side.  
         [0093]     As for the removal of each cartridge  7  from the apparatus main assembly  100 , it is done by performing in reverse the above described procedure for mounting the cartridge  7  into the apparatus main assembly  100 . That is, first, the aforementioned latching mechanism (unshown) is to be disengaged, and then, the door  26  is to be opened toward the operator by rotating it downward about the hinge shaft  27  located at the bottom edge of the door  26 . As the door  26  is opened, the process cartridges  7  are relieved by the means, which is moved by the movement of the door  26 , of the pressure being applied thereto by the pressing means  30 , and also, the driving force transmission coupling on the main assembly  100  side is disengaged from the coupling  70  on the cartridge  7  side by the opening movement of the door  26 . Further, the shutter  72  is moved into the closed position. Thereafter, the operator is to grasp the handles  82  and  83  of the process cartridge  7 , and pull the cartridge  7  in the opposite direction from the direction in which the cartridge  7  is inserted into the apparatus main assembly  100 . This makes the cartridge  7  come out of the apparatus main assembly  100 .  
       (4) Description of Mechanical Structure of Electrical Contacts  
       [0094]     Next, the mechanical structure of the electrical contacts on the main assembly side will be described.  
         [0095]     As described before, each cartridge  7  is provided with the memory  94  and connective (coupling) member  102 , which are attached to the rear surface of the cartridge  7 , more specifically, the rear surface of the cleaning unit frame  51 . The connective (coupling) member  102  engages with the electrical contact supporting member on the main assembly side. As for the apparatus main assembly  100 , it provided with the rotatable electrical contact supporting members  105 , which support the electrical contacts  103  and  104  on the main assembly side, and which protrude into the cartridge compartments through the holes  96  of the center plate  93 . As described before, the process cartridge  7  is to be inserted into the cartridge compartment  200  of the apparatus main assembly  100 , with the rear surface of the cartridge  7  facing forward through the opening  91 , until the bearings  64  and  65  of the cartridge  7  are caught by the contact areas of the  37  and  38  of the guiding grooves  34 , respectively ( FIG. 8 ). As the cartridge  7  is inserted into the apparatus main assembly  100  as described above, the connective (coupling) member  102  of the cartridge  7  engages with the electrical contact supporting member  105  on the apparatus main assembly  100  side; the electrical contacts on the unit side are placed physically in contact with the electrical contacts on the main assembly side, establishing thereby electrical connection between the electrical contacts on two sides ( FIG. 8 , and  FIG. 9 ( a )- 9 ( b )- 9 ( c )). The connective (coupling) member  102  is provided at a leading end of the cartridge  7  with respect to the mounting direction in which the cartridge  7  is mounted to the main assembly  100  of the apparatus.  
         [0096]     The connective (coupling) member  102  is located at the forward surface of the cartridge  7  in terms of the direction in which the cartridge  7  is inserted into the apparatus main assembly  100 .  
         [0097]      FIG. 10  is a perspective view of the connective (coupling) member  102 , and the electrical contact supporting member  105  which corresponds with the connective (coupling) member  102 , and FIGS.  11 ( a ) and  11 ( b ) are enlarged plan and perspective views of the connective (coupling) member  102 .  FIG. 12  is an enlarged plan view of the combination of the electrical contact supporting member  105  and the substrative plate  106  which supports the electrical contact supporting member  105 .  FIGS. 13-15  are drawings for describing the rotational movement of the electrical contact supporting member  105 , which occurs when it engages with the connective (coupling) member  102 .  FIGS. 16 and 17  are drawings for describing the electrical contacts on the unit side, and the electrical contacts on the main assembly side.  FIG. 18  is a circuit diagram related to the electrical contacts on the main assembly side, and  FIG. 19  is the chart of the R/W circuit.  
         [0098]     Each cartridge  7  is provided with electrical contacts  101   a  and  101   b  electrically connected to the memory  94  of the cartridge  7 . The memory  94  is located on the rear surface of the of connective (coupling) member  102 , being solidly fixed thereto with the use of two-sided adhesive tape, hot melt or ordinary adhesive, by thermal crimping, or the like method. The connective (coupling) member  102  has a twisted or spiralled hole  102   a,  which is polygonal in cross section. In this embodiment, the cross section of the spiralled hole  102   a  is rectangular.  
         [0099]     More specifically, the connective (coupling) member  102  has a recess (hole)  102   a,  into which the end portion (contacting portion) of the electrical contact supporting member  105  engages. The electrical contact supporting member  105  will be described later in more detail. The aforementioned electrical contacts  101   a  and  101   b  are on the bottom surface of this recess  102   a.  The provision of this structural arrangement makes it difficult for a finger to come into contact with the electrical contacts  101   a  and  101   b,  preventing thereby such electrical problems that the electrical contacts  101   a  and  101   b  are contaminated, and/or the memory  94  is adversely affected by static electricity.  
         [0100]     The center plate  93  is provided with four rotatable supporting members  105 , which support the corresponding electrical contacts  103  and  104  on the main assembly side, which are to be electrically connected to the electrical contacts  101   a  and  101   b  on the unit side. Each supporting member  105  is attached to the substrative plate  106  for supporting the supporting member  105 , in such a manner that the supporting member  105  can be rotated about its axis (unshown). Also to the substrative plate  106 , the ground contacts  107  and  108  are attached, which are electrically connected to the electrical contacts  103  and  104 , respectively, on the main assembly side. The ground contacts  107  and  108  are also connected to the ground of the apparatus main assembly  100 . Also to the substrative plate  106 , electrical contacts  109  and  110  of the control circuit of the apparatus main assembly  100 , are connected. In this embodiment, four electrical contacts are attached to the substrative plate  106 : the contacts  107 ,  108 ,  109  and  110  connected to the R/W circuit  111  ( FIG. 18 ) which carries out the reading and writing functions, and electrical contacts  103  and  104 . The R/W circuit  111  will be described later.  
         [0101]     The substrative plate  106  is attached to the opposite surface of the center plate  93  from the cartridge compartment  200 , with fastening jigs  106   a  ( FIG. 9 ) such as screws, with the supporting member  105  protruding into the cartridge compartment  200  through the hole  96  of the center plate  93 .  
         [0102]     Before the mounting of the cartridge  7  into the apparatus main assembly  100 , sliding portion  103   a  and  104   a  of the electrical contacts  103  and  104  on the main assembly side are in connection to the ground contacts  107  and  108 , which are connected to the ground G ( FIG. 18 ) of the apparatus main assembly  100 . Also before the mounting of the cartridge  7 , the electrical contacts  103  and  104  on the main assembly side are always in contact with the ground G, and the electrical contact supporting member  105  is always under the pressure generated by the return spring (unshown) placed in the supporting member  105 , in the direction to keep the electrical contacts  103  and  104  on the main assembly side in contact with the ground contacts  107  and  108 .  
         [0103]     To describe in more detail with reference to the schematic drawing of the supporting member  105  in  FIG. 18 , before the mounting of the cartridge  7 , the sliding portions  103   a  and  104   a,  that is, one end of the electrical contact  103  on the main assembly side, and one end of the electrical contact  104  on the main assembly side, are electrically in contact with the ground contacts  107  and  108 , which are electrically in contact with the ground G. As the cartridge  7  is mounted into the apparatus main assembly  100 , the sliding portions  103   a  and  104   a  are moved in the directions indicated by arrow marks T 1  and T 2 , respectively, being thereby electrically connected to the electrical contacts  109  and  110 , which are connected to the R/W circuit  111  for reading from, or writing into, the memory  94 . The R/W circuit  111  is also connected to the control circuit  113 . Thus, as the cartridge u is mounted into the apparatus main assembly  100 , the electrical contacts  103  and  104  on the main assembly side are electrically connected to the electrical contacts  101   a and  101   b  on the unit side, allowing the memory  94  and apparatus main assembly  100  to communicate with each other.  
         [0104]     That is, as the cartridge (unit)  7  is inserted into the apparatus main assembly  100 , the connective (coupling) member  102  engages with the electrical contact supporting member  105 , causing thereby the electrical contact supporting member  105  to rotate. As the electrical contact supporting member  105  is rotated, the electrical contacts  103  and  104  on the main assembly side are moved by the rotation of the electrical contact supporting member  105  from the position in which they are electrically in contact with the ground contacts  107  and  108 , into the position in which they will be electrically in contact with the electrical contacts  109  and  110 . The direction in which the electrical contact supporting member  105  is rotated is intersectional to the direction in which the connective (coupling) member  102  engages with the electrical contact supporting member  105 . The direction in which the connective (coupling) member  102  engages with the electrical contact supporting member  105  is parallel to the rotational axis of the electrical contact supporting member  105 , and also, is parallel to the axial line of the recess (hole)  102   a.  Therefore, it is ensured that as the cartridge  7  is mounted into the apparatus main assembly  100 , the R/W circuit is connected to the memory  94 . Further, the electrical connection of the sliding portions  103   a  and  104   a  can be switched by the insertion of the cartridge  7 .  
         [0105]     Next, referring to  FIG. 18 , and the chart given in  FIG. 19 , the signal exchange between the R/W circuit  111  and memory  94  will be described. When writing data into the memory  94  from the control circuit  113 , the control circuit  113  raises the R/W switching signal to the H level to send data  119  to be written. Then, the data  119  to be written are sent from the differential driver  116  of the R/W circuit  118  to the DA′ signal  121  and DA signal  122 . When reading data from the memory  94 , the control circuit  113  lowers R/W switching signal  118  to the L level, and receives the data  120  sent from the memory  94  to the DA′ signal  121  and DA signal  122 , from the signal  120 , that is, the output of the differential receiver  117  of the R/W circuit  111 .  
         [0106]     Next, referring to  FIGS. 13-15 , the engagement between the connective (coupling) member  102  and supporting member  105  will be described. In  FIGS. 13-15 , the connective (coupling) member  102  is the only component illustrated from the cartridge side; the structural components on the cartridge side other than the connective (coupling) member  102  are not shown.  
         [0107]     Referring to  FIG. 13 , as the cartridge  7  is inserted into the apparatus main assembly  100 , the end portion (contact area)  105   a  of the supporting member  105 , which is rectangular in cross section, enters the entrance of the spiral recess (hole)  102   a  of the connective (coupling) member  102 . As a result, the end portion  105   a  comes into contact with the twisted internal surfaces  102   b  of the spiral recess of the connective (coupling) member  102 .  
         [0108]     Next, referring to  FIG. 14 , as the cartridge  7  is inserted further into the apparatus main assembly  100 , the end portion  105   a  of the supporting member  105  enters further into the recess  102   a,  with the end portion (contact area)  105   a  of the supporting member  105  sliding on the twisted internal surfaces  102   b  of the spiral recess  102   a  of the connective (coupling) member  102 . In other words, while the end portion  105   a  of the supporting member  105  enters the recess  102   a  of the connective (coupling) member  102 , the supporting member  105  is guided by the twisted surface  102   b  of the recess  102   a  of the connective (coupling) member  102 . Therefore, the supporting member  105  is rotated in the direction indicated by an arrow mark P against the aforementioned return spring (unshown) in the supporting member  105 . The direction indicated by the arrow mark P is intersectional to the direction in which the connective (coupling) member  102  is engaged with the electrical contact supporting member  105  (direction parallel to rotational axis of electrical contact supporting member  105 ).  
         [0109]     The end portion  105   a,  or engaging portion, may be formed as the mid portion of the supporting member  105  as shown in  FIG. 21 . Forming the engaging portion  105   a  as the mid portion of the supporting member  105  makes the supporting member  105  stronger against torsional force.  
         [0110]     Referring to  FIG. 15 , the rotation of the supporting member  105  stops at the end of the mounting of the cartridge  7  into the apparatus main assembly  100 , with the sliding portions  103   a  and  104   a  of the electrical contacts  103  and  104  on the main assembly side electrically connected to the electrical contacts  109  and  110 , respectively.  
         [0111]     In other words, as the cartridge  7  is mounted into the apparatus main assembly  100 , the connective (coupling) member  102  engages with the supporting member  105 , causing the supporting member  105  to rotate in the direction indicated by the arrow mark P against the aforementioned return spring (unshown) in the supporting member  105 . Thus, the sliding portions  103   a  and  104   a  of the electrical contacts  103  and  104  on the main assembly side rotate with the supporting member  105 , coming into contact with the electrical contacts  109  and  110 , respectively.  
         [0112]     Also as the cartridge  7  is inserted into the apparatus main assembly  100 , the electrical contacts  103  and  104  of the main assembly become electrically connected to the electrical contacts  101   a  and  101   b  of the unit. The electrical contacts  103  and  104  of the main assembly are elastically supported, being enabled to move, while remaining in contact with the electrical contacts  101   a  and  101   b  on the unit side, in the direction parallel to the lateral wall of the supporting member  105 . Thus, when the electrical contacts  103  and  104  on the main assembly side are in contact with the electrical contacts  101   a  and  101   b  connected to the memory  94  of the unit, a certain amount of contact pressure is always maintained between the electrical contacts  103  and  104  and the electrical contacts  101   a  and  101   b,  respectively, by the structural arrangement which elastically supports the electrical contacts  103  and  104 .  
         [0113]     Next, referring to  FIG. 16 ( a ), the contact point potions  103   b  and  104   b  of the electrical contacts  103  and  104 , respectively, on the main assembly side, which are to come into contact with the electrical contacts  101   a  and  101   b,  on the unit side, leading to the memory  94 , come into contact with the  101   a  and  101   b,  by the contact points  103   c  and  104   c  during the mounting of the cartridge  7  into the apparatus main assembly  100 . Then, as the cartridge  7  is further inserted (direction indicated by arrow mark Q in drawing), the supporting member  105  is rotated about the rotational axis  112  of the supporting member  105 . As a result, the contact point portions  103   b  and  104   b  on the main assembly side are moved, in relative terms, to the positions  103   d  and  104   d,  respectively, as shown in  FIG. 16 ( b ). In other words, the electrical contacts  103  and  104  on the main assembly side are moved into the positions in which they remain in contact with the electrical contacts  101   a  and  101   b  on the unit side. In this embodiment, a structural arrangement is made so that the rotational angle of the supporting member  105  becomes 45°. With the provision of the above described structural arrangement, as the cartridge  7  is mounted into the apparatus main assembly  100 , a pair of slide marks  114  and  115 , or traces of the sliding of the electrical contacts  103  and  104 , on the main assembly side, are formed on surfaces of the electrical contacts  101   a  and  101   b  on the unit side.  
         [0114]     As the electrical contacts  103  and  104  on the main assembly side slide on the electrical contacts  101   a  and  101   b  on the unit side, the contamination, such as dust, having adhered to the electrical contacts on the two sides is removed, ensuing that the satisfactory electrical connection is established between the two sides, that is, between the electrical contacts  101   a  and  103 , and between the electrical contacts  101   b  and  104 .  
         [0115]     Referring to  FIG. 17 , the electrical contacts  103  and  014  on the main assembly side are positioned away from the rotational axis of the supporting member  105 . Therefore, they are caused to slide on the electrical contacts  101   a  and  101   b,  respectively, on the unit side, by the rotation of the supporting member  105 .  
         [0116]     Incidentally, the portions of the supporting member  105 , which are to come into contact with the internal surfaces of the recess of the connective (coupling) member  102 , are rectangular in terms of the cross section perpendicular to the axial line of the supporting member  105 . However, it does not need to be rectangular as long as it is polygonal and capable of engaging into the recess of the connective (coupling) member  102 .  
         [0117]     This embodiment of the present invention can bring forth the following effects. 
        1) Even if a user, who is charged with static electricity, happens to place his hand by mistake in the entrance of the cartridge compartment of the apparatus main assembly  100 , in which the cartridge  7  is not present, the electrostatic noises, which are applied to the electrical contacts  103  and  104  on the main assembly side as the hand comes into contact with the electrical contacts  103  and  104 , are discharged to the ground G ( FIG. 18 ), protecting thereby the R/W circuit  111 . In other words, this embodiment can ensure that the electrical circuit, on the main assembly side of the electrophotographic image forming apparatus, to which the electrical contacts on the main assembly side are connected, are protected.     2) When the cartridge (unit)  7  is inserted into the main assembly of the electrophotographic image forming apparatus, the connective (coupling) member  102  engages with the electrical contact supporting member  105 , and rotates the electrical contact supporting member  105 , causing thereby the electrical contacts  103  and  104  on the main assembly side to be switched in position from the position in which they are electrically in connection to the ground contacts  107  and  108 , respectively, into the position in which they will be electrically connected to electrical contacts  109  and  110 , ensuring that the R/W circuit is protected. The connection of the electrical contacts  103  and  104  on the main assembly side can be switched by the insertion of the cartridge  7  into the apparatus main assembly  100 .     3) The movement of the cartridge  7  which occurs during the insertion of the cartridge  7  into the apparatus main assembly  100  causes the electrical contacts  103  and  104  on the main assembly side to slide on the electrical contacts  101   a  and  101   b,  respectively, on the unit side, as indicated by the lines  114  and  115  in  FIGS. 14 and 15 . Therefore, even if such contaminants that interfere with electrical conduction are on the electrical contacts  103 ,  104 ,  101   a,  and  101   b,  they are removed by the sliding of the electrical contacts  103  and  104  on the electrical contacts  101   a  and  101   b,  ensuring that satisfactory electrical connection is established between the electrical contacts  103  and  104  on the main assembly side and the electrical contacts  101   a  and  101   b  on the unit side, respectively.     4) The removal of contaminants to be accomplished by causing the electrical contacts on the main assembly side to slide on the electrical contacts on the unit side as described in Paragraph 3) is achieved by the insertion of the cartridge  7  into the apparatus main assembly  100 . Therefore, it is unnecessary for a user to perform a specific operation dedicated to the removal of the contaminants from the electrical contacts.     5) The memory  94  of the cartridge  7  is placed on the rear surface of the connective (coupling) member  102 . Therefore, a user is prevented from unintentionally touching the electrical contacts  101   a    101   b  connected to the memory  94 , being therefore prevented from adhering contaminants or the like to the electrical contacts  101   a  and  101   b,  when handling the cartridge  7 .        
 
       (5) Structural Modifications  
       [0000]    
       
         
           
              1) Regarding the shapes of the connective (coupling) member  102  and electrical contact supporting member  105 , the relationship between the connective (coupling) member  102  and electrical contact supporting member  105  in terms of which of the two is given a projection (or recess) may be reversed as shown in  FIG. 20 .  
           
         
       
     
         [0124]     More specifically, the end portion of the supporting member  105  may be provided with a member  105   a  having a spiral hole (recess)  105   b  which has a polygonal cross section, and the internal surfaces  105   c  of which are twisted, whereas the connective (coupling) member  102  may be provided with a projection which engages into the hole  105   b  of the member  105   a  of the supporting member  105 . This structural arrangement also can rotate the supporting member  105 . 
        2) The preceding embodiment was described with reference to the electrophotographic color image forming apparatus employing one of the developing methods of the contact type, and the process cartridge therefor. However, the present invention is also applicable to an electrophotographic monochromatic image forming apparatus employing one of the developing methods of the non-contact type as well as the contact type, a development unit mountable in the main assembly of electrophotographic image forming apparatus, and a developer unit which holds developer.     3) Further, the preceding embodiment was described with reference to the mechanism for establishing electrical connection between the memory of the process cartridge and the main assembly of the electrophotographic image forming apparatus. However, the present invention is also applicable to the mechanism for applying voltage to the charging member and the mechanism for applying voltage to the developing member.        
 
         [0127]     Moreover, it is feasible to apply this embodiment to the fixation unit for fixing an unfixed image on the recording medium to the recording medium. 
        4) Also, the preceding embodiment was described with reference to the structural arrangement in which the internal surfaces of the coupler portion of the process cartridge were twisted. However, the embodiment is not intended to limit the scope of the present invention. In other words, all that is necessary is for the internal surfaces of the coupler portion of the process cartridge to be shaped so that they can rotate the electrical contact supporting member. For example, they may be shaped so that their lateral edges are simply angled relative to the axial line of the electrical contact supporting member.        
 
         [0129]     As described above, according to the present invention, when a unit (process cartridge) is mounted into the main assembly of an electrophotographic image forming apparatus, electrical connection is more reliably established between the electrical contacts which the main assembly of the electrophotographic image forming apparatus has, and the electrical contacts which the unit (process cartridge) has, than according to the prior art.  
         [0130]     Also according to the present invention, when a unit (process cartridge) is mounted into the main assembly of an electrophotographic image forming apparatus, the electrical contacts on the main assembly side slide on the electrical contacts of the unit (cartridge), removing thereby the contaminants on the both sides.  
         [0131]     Further, the present invention ensures that the electrical circuit, on the main assembly side of an electrophotographic image forming apparatus, to which the electrical contacts on the main assembly side are connected, is protected.  
         [0132]     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.  
         [0133]     This application claims priority from Japanese Patent Application Nos. 024341/2004 and 014097/2005 filed Jan. 30, 2004 and Jan. 21, 2005, respectively, which are hereby incorporated by reference.