Abstract:
A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, includes a developing member for developing an electrostatic latent image formed on an electrophotographic photosensitive drum, a toner accommodation frame having a developer accommodating portion for accommodating a developer to be used by a developing member to develop the electrostatic latent image, a drum frame for supporting the electrophotographic photosensitive drum, a developing frame for supporting the developing member, the developing frame being swingably coupled with the toner accommodation frame, a first end cover connected with the drum frame and the developing frame at one longitudinal end of each of the drum frame and the developing frame, and a second end cover connected with the drum frame and the developing frame at the other longitudinal end of the drum frame and the developing frame.

Description:
FIELD OF THE INVENTION AND RELATED ART 
     The present invention relates to a process cartridge, an assembling method therefor and an electrophotographic image forming apparatus. 
     Here, the electrophotographic image forming apparatus forms an image on a recording material through an electrophotographic image-formation type process. Examples of electrophotographic image forming apparatus include an electrophotographic copying machine, an electrophotographic printer (a laser beam printer, an LED printer or the like), a facsimile machine and a word processor. 
     The above-described process cartridge contains as a unit an electrophotographic photosensitive member and a charging means, a developing means or a cleaning means in the form of a cartridge that is detachably mountable to a main assembly of an image forming apparatus. The process cartridge may contain an electrophotographic photosensitive member and at least one of a charging means, a developing means and a cleaning means in the form of a cartridge that is detachably mountably to a main assembly of an image forming apparatus. The process cartridge may contain an electrophotographic photosensitive member and at least developing means in the form of a cartridge that is detachably mountably to a main assembly of an image forming apparatus. 
     With a process cartridge type apparatus, the servicing or maintenance operations can be in effect carried out by the users, so that the operativity is significantly improved, and therefore, the process cartridge type is widely used in the electrophotographic field. 
     As shown in FIG. 23, the process cartridge  45  comprises a developing device frame  43  supporting a developing roller  18  and a toner accommodating container  46 , which are welded with each other by ultrasonic welding. To the developing unit, a cleaning frame  47  which supports a photosensitive drum  11 , a charging roller  12  and a cleaning blade  14 , is coupled by a pin  49 . A compression coil spring  42  is provided between the cleaner frame  47  and developing device frame  43 . By this, the photosensitive drum  11  and the developing roller  18  are urged toward each other with spacer rollers therebetween. 
     In the electrophotographic image forming apparatus of the process cartridge type, there is a demand is for a large capacity developer (toner) accommodating container and a large removed toner container to extend the time period until the necessity of exchange of the process cartridge. 
     However, when the capacity of the developer accommodating container is increased, the weight of the developer increases. As a result, the loads imparted to the developing roller and the photosensitive drum are increased correspondingly. 
     Additionally, the loads change with consumption of the developer. Furthermore, the developer per se adjacent the developing roller  48  are influenced by the weight of the developer. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a solution to the problem. 
     Accordingly, it is a principal object of the present invention to provide a process cartridge and an electrophotographic image forming apparatus wherein the image quality is stabilized even if the accommodation capacity of the developer (toner) is increased. 
     It is another object of the present invention to provide a process cartridge, an assembling method for the process cartridge and an electrophotographic image forming apparatus in which the load imparted by the weight of a developer to a developing member and an electrophotographic photosensitive drum is reduced. 
     It is a further object of the present invention to provide a process cartridge, an assembling method for the process cartridge and an electrophotographic image forming apparatus in which the change in the load imparted by the weight of the developer to a process cartridge, the developing member, and the electrophotographic photosensitive drum, can be reduced. 
     According to an aspect of the present invention, there is provided a process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, comprising: 
     a developing member for developing an electrostatic latent image formed on the electrophotographic photosensitive drum; 
     a toner accommodation frame having an developer accommodating portion for accommodating a developer to be used by the developing member to develop the electrostatic latent image; 
     a drum frame for supporting the electrophotographic photosensitive drum; 
     a developing frame for supporting the developing member, the developing frame being swingably coupled with the toner accommodation frame; 
     a first end cover connected with the drum frame and the developing frame at one longitudinal end of each of the drum frame and the developing frame; and 
     a second end cover connected with the drum frame and the developing frame at the other longitudinal end of the drum frame and the developing frame. 
     These and other objects, features and advantages of the present invention will become more apparent upon a 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 
     FIG. 1 is a sectional view of the process cartridge in the preferred embodiment of the present invention, at a plane perpendicular to the longitudinal direction of the cartridge. 
     FIG. 2 is a schematic vertical sectional view of the image forming apparatus in the preferred embodiment of the present invention, at a plane perpendicular to the process cartridge. 
     FIG. 3 is a schematic, perspective, and exploded view of the process cartridge in the preferred embodiment of the present invention, and depicts the general structure of the cartridge. 
     FIG. 4 is a schematic perspective view of the process cartridge in the preferred embodiment of the present invention, and shows the general structure of the cartridge. 
     FIG. 5 is a schematic perspective view of a disassembled essential portion of the process cartridge in the preferred embodiment of the present invention. 
     FIG. 6 is a schematic side view of the process cartridge in the preferred embodiment of the present invention. 
     FIG. 7 is a schematic side view of the process cartridge in the preferred embodiment of the present invention. 
     FIGS. 8 a  and  8   b  are schematic side views of an essential portion of the process cartridge in the preferred embodiment of the present invention. 
     FIG. 9 is a diagram which depicts the driving system of the process cartridge in the preferred embodiment of the present invention. 
     FIG. 10 is a vertical sectional view of the process cartridge in another embodiment of the present invention. 
     FIG. 11 is a plan view of the disassembled process cartridge in another embodiment of the present invention. 
     FIG. 12 is a horizontal sectional view of a portion of the process cartridge in another embodiment of the present invention. 
     FIG. 13 is a side view of the process cartridge in another embodiment of the present invention. 
     FIG. 14 is a front view of the sealing member in the preferred embodiment of the present invention. 
     FIG. 15 is a perspective view of the sealing member in another embodiment of the present invention. 
     FIG. 16 is a vertical sectional view of the process cartridge in another embodiment of the present invention. 
     FIG. 17 is a vertical sectional view of the process cartridge in another embodiment of the present invention. 
     FIG. 18 is a vertical sectional view of the process cartridge in another embodiment of the present invention. 
     FIG. 19 is a perspective drawing which shows the installation and removal of the process cartridge into and from the main assembly of an image forming apparatus. 
     FIG. 20 is a perspective view of the impeller equipped gear of the process cartridge. 
     FIG. 21 is a sectional view of the impeller equipped gear, at a plane B—B in FIG.  20 . 
     FIG. 22 is a sectional view of the impeller equipped gear, at a plane A—A in FIG.  20 . 
     FIG. 23 is a vertical sectional view of an example of a conventional process cartridge. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments of the present invention will be described with reference to FIGS. 1-9. 
     In these embodiments, the term “longitudinal direction” refers to the direction which is perpendicular to the recording medium conveyance direction, and is parallel to the plane of the recording medium. 
     Process Cartridge ad Main Assembly of Electro-photographic Image Forming Apparatus 
     FIG. 1 is a sectional view of the essential portion of the process cartridge in accordance with the present invention. FIG. 2 is a sectional view of the essential portion of an image forming apparatus in accordance with the present invention. This process cartridge is provided with an electrophotographic photosensitive member, and a processing means that acts on the electrophotographic photosensitive member. The processing means can comprise for example, a charging means for charging the peripheral surface of the electrophotographic photosensitive member, a developing means for developing an electrostatic latent image formed on the electro-photographic photosensitive member, and a cleaning means for removing the toner remaining on the peripheral surface of the electrophotographic photosensitive member. 
     As shown in FIG. 1, the process cartridge  15  in this embodiment comprises: an electrophoto-graphic photosensitive member  11  (hereinafter, “electrophotographic photosensitive drum”) in the form of a drum; a charge roller  12  as a charging member; a developing apparatus comprising a development roller  18  as a developing member, and a development blade  26 ; a cleaning blade  14  as a cleaning member; and a housing in which the preceding components are integrally disposed. The process cartridge  15  is removably installable in the main assembly  27  of an electrophotographic image forming apparatus (hereinafter, “apparatus main assembly”). 
     The development roller  18  is a cylindrical member formed of metallic material such as aluminum, stainless steel, or the like, and contains a nonconducting magnetic roller (unillustrated). 
     Referring to FIG. 2, this process cartridge  15  is installed in an electrophotographic image forming apparatus C, for image formation. 
     A sheet S is fed out of a sheet cassette  6  in the bottom portion of the apparatus, by a conveyer roller  7 . In synchronism with the conveyance of this sheet S, the photosensitive drum  11  is exposed by an exposing apparatus  8  according to the image data. As a result, an electrostatic latent image is formed on the photosensitive drum  11 . Thereafter, the developer (hereinafter, “toner”) stored in a toner storage container  16  is triboelectrically charged by a development blade  26 , and this developer is borne on the peripheral surface of the development roller  18 . Then, as development bias is applied to the development roller  18  as a developing member, the toner is supplied to the photosensitive drum  11 . As a result, an image formed of toner (hereinafter, “toner image”) is formed on the photosensitive drum  11 , corresponding to the electrostatic latent image. Next, this toner image is transferred onto the sheet S, as a recording medium, by applying bias (voltage) to a transfer roller  9 . Then, the sheet S is conveyed to a fixing apparatus  10 , in which the toner image is fixed. Next, the sheet S is discharged by a discharge roller  1  into a delivery portion  2  provided on the top side of the apparatus. Meanwhile, the toner which remained on the photosensitive drum  11  after the image transfer is removed by a cleaning blade  14  as a cleaning member. The removed toner is moved rearward of a removed toner storage bin  5  by a removed toner conveying member  115 . It should be noted here that prior to the above-described, photosensitive-drum exposure, the photosensitive drum  111  is charged by a charge roller as a charging member. 
     Structure of Process Cartridge Frame 
     FIGS. 3 and 4 are perspective views which show the structure of the process cartridge frame. FIG. 3 shows the process cartridge frame prior to its assembly, and FIG. 4 shows the process cartridge after its assembly. 
     The process cartridge  15  comprises three frame pieces: a cleaning-means frame  13  as a drum frame that integrally supports the photosensitive drum  11 , a charge roller  12 , and a cleaning blade  14 ; a developing-means frame  17  that integrally supports the development roller  18 , and a development blade (unillustrated in FIG. 3, and designated by a reference code  26  in FIG.  4 ); and a toner-storage frame  16  provided with a toner-storage portion  16   d  in which toner is stored. Further, the process cartridge  15  in this embodiment comprises a pair of side covers  19  and  20  that are fixed to the longitudinal ends of the cleaning-means frame  13  and toner-storage frame  16  to hold the frames  13  and  16  together. The development-means frame  17  is supported by the cleaning-means frame  13 . 
     To the cleaning-means frame  13 , the cleaning blade  14  is fixed with the use of small screws. The charge roller  12  is rotatably supported by the longitudinal ends, by bearings (unillustrated). Referring again to FIG. 1, in the cleaning-means frame  13 , the removed toner conveying member  115  for conveying the toner removed by the cleaning blade  14 , into the removed toner bin  5 , is rotatably disposed. In addition, in the cleaning-means frame  13 , the photosensitive drum  11  is rotatably supported, with the flange portions, that is, the longitudinal end portions, of the photosensitive drum  11 , supported by a pair of bearings  22   a  and  22   b . The toner-storage frame  16  stores toner therein, and comprises a pair of toner conveying members  113  and  114  (FIG. 1) for conveying the stored toner toward the development roller  18 . These toner conveying members may be provided with a toner stirring function. 
     The detailed description of the development means frame  17  will be given later. 
     The aforementioned side covers  19  and  20  are large enough to match in size the primary cross section (cross section at a plane perpendicular to the longitudinal direction of the photosensitive drum  11 ) of the process cartridge  15 . They are positioned at the longitudinal ends of the process cartridge  15  (end portion in terms of the longitudinal direction of the photosensitive drum  11 ), one for one, covering, and being fixed to, both the cleaning-means frame  13  and the toner-storage frame  16 . With this arrangement, the side covers  19  and  20  integrally hold together the cleaning-means frame  13  and the toner-storage frame  16 . The holes  19   a  and  20   a  with which the side covers  19  and  20  are provided, respectively, are aligned with the rotational axis of the photosensitive drum  11  in the the cleaning-means frame  13 . In the hole  13   a  of the side cover  19 , that is, the side cover illustrated on the front side of the drawing, with which cleaning-means frame  13  is provided, the bearing  22   a  is press fitted. Also, a shaft  25  is put through the hole  19   a  of the side cover  19 , the bearing  22   a , and the center hole  11   a   1  of the flange  11   a , to rotatably support one of the longitudinal encls of the photosensitive drum  11  by the cleaning-means frame  13 . With this arrangement, the side cover  19  is precisely positioned by the bearing  22   a , improving the accuracy in terms of the positional relationship of the side cover  19  with respect to the photosensitive drum  11 . Further, a positioning member  19   b , with which the side cover  19  is provided, and which is located so that its position becomes as far away as possible from the photosensitive drum  11  after the attachment of the side cover  19 , is engaged with a positioning portion  13   b  with which the side wall  13   c  of the cleaning means frame  13  is provided. As a result, the position of the side cover  19 , in terms of the rotational direction of the side cover  19  with respect to the center, or the axial line, of the photosensitive drum  11 , is fixed. Then, the side cover  19  is fixed to the side wall  13   c , that is, the wall at the longitudinal end, of the cleaning-means frame  13 . The toner-storage frame  16  is provided with a pair of cylindrical positioning portions  16   a  and  16   b , which project from one of the side walls  16   d , that is, the wall at the longitudinal end, of the toner-storage frame  16 , in the longitudinal direction of the toner-storage frame  16 . These positioning portions  16   a  and  16   b  are fitted in the positioning portion  19   c  and  19   d , that is, holes, respectively, with which the side cover  19  is provided, accurately positioning the toner-storage frame  16  relative to the side cover  19 . Then, the toner-storage frame  16  and side cover  19  are fixed to each other. The other side cover  20  is similarly fixed to the toner-storage frame  16  and the cleaning-means frame  13 , being accurately positioned relative to each other. The developing-means frame  17  is positioned using a method that will be described later. The bearings  22  ( 22   a  and  22   b ) double as members for positioning the process cartridge  15  relative to the apparatus main assembly  27 . 
     Joining of Toner Storage Frame and Developing Means Frame 
     In order to supply toner from the toner-storage frame  16  to the development roller  18 , the toner-storage frame  16  and the development-means frame  17  are provided with opening  16   c  (FIG. 1) and  17   a . Further, the development-means frame  17  and the toner-storage frame  16  are joined with each other in such a manner that their internal spaces become connected to each other through the openings  17   a  and  16   c , with a sealing means  21  as a flexible sealing means disposed between the two frames. As described above, the position of the toner-storage frame  16  is fixed relative to the side covers  19  and  20 , whereas the position of the development-means frame  17  is fixed relative to the cleaning-means frame  13 . Therefore, the frames  16  and  17  are attached to each other in a manner to allow them to pivot relative to each other to absorb the dimensional errors of the two frames. When installed into the apparatus main assembly  17 , the position of the process cartridge  15  is fixed relative to the cartridge installation space of the apparatus main assembly  27 , by the cleaning-means frame  13 , which supports the photosensitive drum  11 . The toner-storage frame  16  is substantially different in weight between the beginning of its usage when it contains toner, and the end of its usage when it is empty. Therefore, flexible material is used as the material for the sealing member  21 . With this setup, even if a deformation occurs to the toner-storage frame  16 , or one or both of the side covers  19  and  20 , the deformation can be absorbed. 
     FIG. 18 is a vertical sectional view of a process cartridge equipped with a flexible sealing member different from the above described sealing member  21 . 
     A sealing member  60  as a flexible sealing means is formed of elastic material such as foamed synthetic resin (for example, foamed urethane), rubber with a low degree of hardness, silicon rubber, or the like. This sealing member  60  is in the form of a piece of plate with a large opening  60   a . After the installation of the sealing member  60 , the opening  60   a  aligns with both the openings  17   a  and  16   c . The size of the opening  60   a  is approximately the same as those of the openings  17   a  and  16   c . The sealing member  60  is pasted to either to the surface of the development-means frame  17  or the surface of the toner-storage frame  16 , which face each other, or both of the surfaces. The sealing member  60  is not pasted to the portion of the toner-storage frame  16 , corresponding to the area through which the toner seal  24  is passed when the toner seal  24  is pulled out. 
     The thickness of the sealing member  60  is greater than the distance, after the completion of the assembly of the process cartridge  15 , between the surface  17   g  of the developing-means frame  17  and the surface  16   f  of the toner-storage frame  16 . 
     Therefore, after the completion of the assembly of the process cartridge  15 , the sealing member  60  is compressed by the mutually facing surfaces  17   g  and  16   f  as shown in FIG.  18 . The reactive force generated by the compression of the sealing member  60  acts as the pressure which keeps the spacer rollers  18   b  of the development roller  18  pressed upon the photosensitive drum  11 . Therefore, the reactive force which the sealing member  60  generates is desired to be as small as possible. 
     With the provision of the above described structure, the load generated by the weight of the toner applies to the side covers  19  and  20 , instead of applying to the development roller supported by the development means frame  17 . Thus, the photosensitive drum  11  is not subjected to the load generated by the weight of the toner, and therefore, a stable image can be formed, even if the amount of the toner in the toner-storage frame  16  increases. 
     Structure of Developing Means Frame 
     Referring to FIGS. 3,  5 ,  6  and  7 , the structure of the developing means frame will be described. FIG. 3 represents the state of the developing-means frame prior to assembly. FIGS. 5,  6  and  7  are drawings for describing the structure of the developing-means frame involved in the pressure application to the developing-means frame. 
     To the development-means frame  17 , the development roller  18 , which contains the magnetic roller  18   a , the development blade  26  (FIG.  1 ), and a magnetic seal (unillustrated) are attached. A magnetic roller  18   a  is put through the longitudinal center hole of the development roller  18 , and is nonrotationally supported by a developing-means frame  17 , at each of the longitudinal ends. There is maintained a gap between the development roller  18  and magnetic roller  18   a . The development roller  18  is rotationally supported by the developing-means frame  17 , at each of the longitudinal ends. For the power supply to the development roller  18 , electrical contacts are provided within the development roller  18 . Further, both of the longitudinal end portions of the development roller  18  are fitted with a ring  18   b  (spacer rig) (FIG. 3) for maintaining a predetermined distance between the peripheral surfaces of the photosensitive drum  11  and development roller  18 . 
     The developing-means frame  17  is provided with an arm portion  17   c , which is on the driven side, that is, one of the longitudinal ends of the development roller  18 , from which the development roller  18  is driven. The end portion of this arm portion  17   c  is provided with a hole  17   d , the center of which functions as the pivotal center. The developing-means frame  17  is pivotally supported by a cleaning-means frame  13 , in such a manner that the central axes of the photosensitive drum  11  and development roller  18  remain parallel to each other. More specifically, a pin  17   d   1  is fitted in the hole  17   d  of the development-means frame  17  and the hole (unillustrated) of the cleaning-means frame  13 , so that the development-means frame  17  becomes pivotable about the center of the hole  17   d . In addition, as described above, the cleaning-means frame  13  and toner-storage frame  16  are immovably fixed to each other. Thus, the development-means frame  17  is movable relative to the toner-storage frame  16 . Next, referring to FIG. 16, the hooks of a tensional coil spring  36  are fitted around the spring anchoring projections  13   d  and  17   f  of the cleaning-means frame  13  and development-means frame  17 , respectively, to provide such force that keeps the development roller  18  pressed toward the photosensitive drum  11 , by their longitudinal ends. It should be noted here that in terms of the longitudinal direction of the photosensitive drum  11 , the hole  17   d  is located on the driven side of the photosensitive drum  11 . The drive side means the side by which the driving force is received when the process cartridge  15  is in the apparatus main assembly  27 . The non-driven side means the side opposite to the driven side in terms of the longitudinal direction of the electrophotographic photosensitive drum  11 . 
     Furthermore, the non-driven side of the developing-means frame  17  is provided with a projecting member  17   e , which is fixed to the development-means frame  17  with the use of screws  17   e   2  and projects in the direction of the rotational axis of the development roller  18 . This projecting member  17   e  is under the pressure which keeps it pressed toward the photosensitive drum  11  while keeping the rotational axes of the photosensitive drum  11  and development roller  18  parallel to each other. The longitudinal ends of the cleaning-means frame  13  and toner-storage frame  16 , on the non-driven side, are covered with a side cover  19 , which is attached thereto with the use of screws  100 . 
     The longitudinal ends of the cleaning means frame  13  and toner storage  16 , on the other side, or the driven side, are covered with a side cover  20 , which is attached thereto with the use of screws  100  (FIG.  3 ). 
     Conversely, the cleaning-means frame  13  and toner-storage frame  16  are fixed to the side covers  19  and  20 . Further, the development-means frame  17  is movable relative to the cleaning-means frame  13  and the toner-storage frame  16 , with one of the longitudinal ends of the development-means frame  17  being supported by the cleaning-means frame  13  and the other being supported by the side cover  19 . 
     Development Roller Pressing System 
     The end  17   e   1  of the projecting member  17   e  is inserted in a groove  19   e , as a guiding portion, with which the side cover  19  is provided. The groove  19   e  extends toward the rotational axis of the photosensitive drum  11 , allowing the projecting member  17   e  to move toward the rotational axis of the photosensitive drum  11 . In the groove  19   e , a compression coil spring  23   b  as an elastic member, and a slide piece  23   a  as a pressing member, slidable in the longitudinal direction of the groove  19   e , are disposed so that pressure is applied to the projecting member  17   e  through the slide piece  23   a.    
     Further, this groove  19   e  functions as a positioning member for regulating the direction in which the development roller  18  (developing means frame  17 ) is allowed to move. In other words, the development roller  18  is allowed to displace only in the direction parallel to the longitudinal direction of this groove  19   e , since the moving direction of the projecting member  17   e  is regulated by the internal surface of the groove  19   e.    
     As the process cartridge  15  receives a driving force from the apparatus main assembly  27 , the force is applied to the gears  105   b  and  107   b  (FIG.  9 ), which are attached to the longitudinal ends of the photosensitive drum  11  and development roller  18 , respectively, in a direction parallel to the central axis of the hole  17   e  to move the gears  105   b  and  107   b  so that they engage each other (it does not occur that the force is applied in the direction to separate the gears  105   b  and  107   b  from each other). In other words, the gears  105   b  and  107   b  are disposed so that the extension of the transverse line of action between the gears  105   b  and  107   b  runs adjacent to the hole  17 d. Further, the center line of the hole  17   d  and the rotational axis of the photosensitive drum  11  are disposed on the same side with respect to the transverse line of action. Furthermore, the development roller  18  is under the force from the aforementioned compression coil spring  23   b , being kept pressed toward the photosensitive drum  11 . 
     The above description of this embodiment may be summarized as follows. 
     The process cartridge  15  removably installable in the main assembly  27  of an image Forming apparatus comprises: the electrophotographic photosensitive drum  11 ; the development roller  18  as a developing member for developing the electrostatic latent image formed on the electrophotographic photosensitive drum  11 ; the cleaning-means frame  13  as a frame for supporting the electrophotographic photosensitive drum  11 ; and the developing-means frames  17  for supporting the development roller  18 . The developing-means frame  17  is provided with the projecting member  17   e , which is attached to one of the longitudinal ends of the development roller  18 , and projects in the longitudinal direction of the development roller  18 . The projecting member  17   e  is fitted in the groove  19   e  as a guiding portion, being enabled to move in the groove  19   e  toward, or away from, the cleaning-means frame  13 . The developing-means frame  17  is pivotally joined with the cleaning-means frame  13 , at the other longitudinal end of the development roller  18 . The development roller  18  is supported by the development-means frame  17 , being enabled to move in the direction perpendicular to its rotational axis. The process cartridge  15  further comprises the compression coil spring  23   b  as an elastic member for generating such pressure that keeps the projecting member  17   e  pressed toward the cleaning-means frame  13  while allowing the projecting member  17   e  to move in the groove  19   e  in a direction perpendicular to the central axis of the projecting member  17   e.    
     The groove  19   e  as a guiding member is provided with a recess  19   e   1 , in which the end  17   e   1  of the projecting member  17   e  is fitted. Within the recess  19   e   1 , the coil spring  23   b , as an elastic member, is fitted in such a manner that the projecting member  17   e  is kept pressed toward the cleaning means frame  13  by the elastic force of the coil spring  23   b . With this arrangement, the development roller  18  is pressed upon the electrophotographic photosensitive drum  11  with the interposition of a pair of spacer rollers  18   b  between the peripheral surfaces of the development roller  18  and the electrophotographic photosensitive drum  11 . The spacer rollers are fitted around the longitudinal ends of the development roller  18 , one for one. 
     To the end of the coil spring  23   b , the slide piece  23   a  as a pressing member is attached. The slide piece  23   a  makes contact with the flat portion  17   e   3  of the projecting member  17   e , pressing the projecting member  17   e  due to the elastic force of the coil spring  23   b . The coil spring  23   b  is fitted in the groove  19   e , being allowed to slide within the groove  19   e.    
     The projecting member  17   e  is disposed so that its axial line approximately aligns with the rotational axis of the development roller  18 . 
     The development-means frame  17  is rotationally supported by the cleaning-means frame  13 , by the other longitudinal end of the development roller  18 , at a position away from the rotational axis of the development roller  18  rotationally supported also by the developing-means frame  17 , with the pin  17   d   1  fitted through the developing means frame  17  and cleaning-means frame  18 . 
     Further, at the other longitudinal end of the development roller  18 , the tension spring  36  is stretched between the development-means frame  17  and cleaning-means frame  13 , with one end of the tension spring  36  attached to the development-means frame  17  and the other end attached to the cleaning-means frame  13 . 
     The groove  19   e  is provided in the inwardly facing surface of the side cover  19 , as a first side cover, attached to the longitudinal ends of the cleaning-means frame  13  and development-means frame  17 , at each of their longitudinal ends. 
     It is necessary that the toner-storage frame  16  and development-means frame  17  are joined so that toner does not leak from the joint between the opening  16   c  of the toner-storage frame  16  and the opening  17   a  of the development-means frame  17 . On the other hand, the development-means frame  17  and the toner-storage frame  16  need to be pivotable relative to each other. Therefore, in this embodiment, a sealing member  21 , the size of which matches the size of the moving ranges of both opening portions, is placed between the opening portion of the toner-storage frame  16  and the opening portion of the development-means frame  17 , to prevent the toner leakage. This sealing member  21  is pinched between the two opening portions, with the opening of the sealing member  21  aligning with the openings  16   c  and  17   a . The sealing member  21  is desired to be shaped not to generate such force that impedes the movement of the development means frame  17 ; more specifically, it is provided with at least one fold, or it is in the form of a bellows. It is possible that the surface surrounding the opening  16   c  or  17   a  is provided with a groove which surrounds the opening, and in which an O-ring is fitted to seal the joint between the toner-storage frame  16  and the development-frames frame  17  while allowing the gap between the two frames to be variable. 
     In this embodiment, the sealing member  21  is formed of elastomer, and is provided with two folds (unillustrated), to reduce the overall resiliency of the sealing member  21 . However, the material for the sealing member  21  does not need to be limited to the elastomer. It may be any material superior in flexibility, for example, foamed urethane, rubber with a low degree of hardness, silicone rubber, or the like. If the material used for the sealing member  21  is small in reactive force, the same effects at those obtained with the provision of the folds, that is, the shaping of the sealing member  21  in the form of a bellows, can be obtained without such provision or shaping. 
     Driving System 
     FIG. 9 is a diagram which depicts the drive train in this embodiment. 
     An arrow mark X indicates the direction in which the process cartridge  15  is installed into the apparatus main assembly  27 . 
     The driving force sources  101  and  102  (for example, an electric motor) provided in the apparatus main assembly  27  are connected to couplings  103  and  104 . As the process cartridge  15  is installed into the apparatus main assembly  27 , the couplings  103  and  104  are engaged with couplings  105   a  and  16   a , respectively, with which the process cartridge  15  is provided. The couplings  105   a  and  106   a  rotate with the input gears  105   b  and  106   b , respectively. The coupling  106   a  is supported by a bearing  116   c . The coupling  105   a  is integral with the gear  105   b , or is an integral part of a gear flange  105 . The gear flange  105  is supported by a bearing  116   b.    
     Next, the driving system of the process cartridge will be described. 
     To one of the longitudinal ends of the photosensitive drum  11 , the gear flange  105  is fixed. To one of the longitudinal ends of the development roller  18 , a gear flange  107  is fixed. The gear flanges  105  is integrally formed with the gear  105   b . Similarly, the gear flange  107  is integrally formed with the gear  107   b . To the other longitudinal end of the photosensitive drum  11 , a bearing flange  119  is fixed, and to the other longitudinal end of the development roller  18 , a bearing flange  120  is fixed. The photosensitive drum  11  are development roller  18  being to their own units. The gear  105   b  is in mesh with the sleeve gear  107   b.    
     As the coupling  103  is rotated by the driving force from the driving force source  101  provided in the apparatus main assembly  27 , the photosensitive drum  11  and development roller  18  are rotated. The photosensitive drum unit is rotationally supported by the bearings  116   b  and  117   b . The development roller  18  is rotationally supported by the development-means frame  17 . Further, the development roller  18  is rotated while maintaining an optimal gap, which is provided by the aforementioned spacer rollers  18   b , from the peripheral surface of the photosensitive drum  11 . The bearings  116   b  and  117   b  are the surfaces themselves of the holes with which the cleaning-means frame  13  is provided, or the bearings  22  (FIG. 3) fixed to the cleaning-means frame  13 . In the bearings  116   b  and  117   b , the journal portions  105   c  and  119   b  of the flanges  105  and  109 , respectively, are fitted. 
     Next, the driving of toner conveying members  113  and  114  will be described. 
     To the toner conveying member  114 , a driving force is transmitted from the input gear  106   b . The toner conveying member  114  is directly connected to the shaft of the gear  106   b . The driving force is transmitted to the toner conveying member  113  through an idler gear  108  meshed with the input gear  106   b , and a toner conveyance gear  109  meshed with the idler gear  108 . The idler gear  108  is rotationally supported by the shaft  108   a . Thus, as the input gear  106   b  rotates, the toner conveyance gear members  114  and  113  follow the rotation of the input gear  106   b  because their journal portions are rotationally supported by the bearings  116   b  and  116   e , and the bearings  117   c  and  117   d , respectively. 
     Further, in a removed toner bin  5 , with which the cleaning means frame  13  is provided to collect the removed toner, a feather-shaped toner conveying member  115  for conveying the toner removed from the photosensitive drum  11  is disposed. This removed toner conveying member  115  is rotationally supported by the cleaning means frame  13 , with the use of bearings  116   a  and  117   a . To one of the longitudinal ends of the toner conveying member  115 , an input gear  112  fixed. This gear  112  is indirectly meshed with an output gear  110 , through idler gears  111   c ,  111   b  and  111   a.    
     To the other longitudinal end (non-driven side) of the toner conveying member  114 , the output gear  110  is fixed. The idler gears  11   a ,  11   b  and  11   c  are rotationally supported by the bearing portions  117   e ,  117   f ,  117   g , by their shaft portions. Thus, as the toner conveying member  114  rotates, the removed toner conveying member  115  follows the rotation of the toner conveying member  114 . In other words, the driving force received by the gear  106   b  is transmitted to the other longitudinal end of the toner conveying member through the toner conveying member  114 . Then, it is transmitted to the conveying member  115  through the gears  111   a ,  111   b ,  111   c  and  112 , at the other longitudinal end (on the non-driven side). The above positional arrangement of the components of the driving system assures that the driving force is efficiently delivered to both the driven and non-driven sides through the driving system. 
     As described above, the transmission of the driving force throughout the process cartridge  15  is separately shared by a driving system for transmitting the driving force to the photosensitive drum  11  and development roller  18 , and another driving system for transmitting the driving force to the toner conveying members and removed toner conveying members, to which the driving force is delivered from the driving force source  101  and  102 , respectively. 
     In addition to the above described structural arrangement, according to which the driving force is transmitted from the output portion of the toner conveying member  114  to the removed toner conveying member  115 , the following arrangements are conceivable: (1) the removed toner conveying member  115  is driven by transmitting the driving force by way of the toner conveying member  113  with the provision of the similar structure; (2) the removed toner conveying member  115  is driven by transmitting the driving force by way of any of the input gears  106   b  and  109 , and the idler gear  108 , through the gear trains; or (3) the removed toner conveying member  115  is driven by an idler gear attached to the end of the shaft of the idler gear  108  extended to the non-driven side. 
     The above described embodiment may be summarized as follows. 
     The process cartridge  15  removably installable in the main assembly  27  of an electrophotographic image forming apparatus comprises: the electrophotographic photosensitive drum  11 ; the development roller  18  as a developing member for developing the electrostatic latent image formed on the electrophotographic photosensitive drum  11 ; the toner-storage portion  16   d  as a developer storage portion for storing the developer t used for developing the electrostatic latent image; the toner conveying members  113  and  114  as a developer conveying member for conveying the toner t stored in the toner-storage portion  16   d , toward where the development roller  18  is disposed; a combination of the coupling  105   a  and input gear  105   b  as the first driving force transmitting means for receiving the driving force for rotating the electrophotographic photosensitive drum  11  from the apparatus main assembly  27  and transmitting the received driving force to the electrophotographic photosensitive drum  11 , as the process cartridge  15  is installed into the electrophotographic photosensitive member main assembly  27 ; and a combination of the coupling  106   a  and input gear  106   b  as the second driving force transmitting means for receiving the driving force for driving the toner conveying member from the apparatus main assembly  27  and transmitting the received driving force to the toner conveying member, as the process cartridge  15  is installed into the electrophotographic image forming apparatus main assembly  27 , wherein the driving system for driving the coupling  106   a  and gear  106   b , and the driving system for driving the coupling  105   a  and gear  106   b , are independent from each other. 
     The position at which the coupling  105   a  and coupling  106   a  receive the driving force from the apparatus main assembly  27  is the leading end of the process cartridge in terms of the direction in which the process cartridge  15  is installed into the apparatus main assembly  27 , provided that the process cartridge  15  is installed into the apparatus main assembly  27  in the direction parallel to the longitudinal direction of the electrophotographic photosensitive drum  11 . 
     Further, the process cartridge  15  comprises the cleaning blade  114  as a cleaning member for removing the developer remaining on the electro-photographic photosensitive drum  11 , and the removed toner conveying member  115  as a removed developer conveying member for conveying the developer removed from the electrophotographic photosensitive drum  11  by the cleaning blade  114 . The removed toner conveying member  115  is rotated by the driving force which the coupling  106   a  received from the apparatus main assembly  27 . 
     The driving force which the coupling  106   a  received from the apparatus main assembly  27  is transmitted to the other longitudinal end of the toner conveying member  114  through the toner conveying member  114 , and then, is transmitted to the removed toner conveying member  115 , at the other longitudinal end of the toner conveying member  114 . 
     At the other longitudinal end of the toner conveying member  114 , the plurality of gears  111   a ,  111   b ,  111   c  and  112  are disposed, and the driving force which was transmitted to this side through the toner conveying member  114  is transmitted to the removed toner conveying member  115  through the plurality of gears  111   a ,  111   b ,  111   c  and  112 . 
     The driving force which the coupling  105   a  received from the apparatus main assembly  27  is transmitted to the development roller  18  through the gear  107   b . By this driving force, the development roller  18  is rotationally driven. Further, as the process cartridge  15  is installed into the apparatus main assembly  27 , the coupling  106   a  as the aforementioned cartridge coupling engages with the coupling  104  as the main assembly coupling of the apparatus main assembly  27  to receive the driving force, whereas the coupling  105   a  as the aforementioned cartridge coupling engages the coupling  103  as the main assembly coupling of the apparatus main assembly  27  to receive the driving force. 
     The apparatus main assembly  27  is provided with the coupling  103  as the first driving force transmitting member of the main assembly, and the coupling  104  as the second driving force transmitting member of the main assembly. 
     With the provision of the above structural arrangement, it does not occur that the rotational irregularity and vibration of the driving system involved in the conveyance of the toner for development, and the removed toner, are directly transmitted to the driving system for rotationally driving the photosensitive drum and development roller directly involved in image formation. Therefore, it is possible to prevent the formation of an image which suffers from irregularities traceable to pitch irregularity or vibration, or blurring. 
     In particular, as the capacity of the toner storage container is increased (for example, to a capacity equivalent to the amount of toner sufficient to produce approximately 30000 A4 type standard copies), the amount of load that is applied to the system for driving the toner conveying member increases. Further, there is a possibility that as the number of the toner conveying members is increased to three, four, and so on, it becomes easier for the irregularities traceable to driving force transmission to occur. Thus, a driving system structure such as the above described one in which the driving system is divided into a plurality of sub-systems is advantageous. 
     Further, with the increase in the capacity of the toner storage container, the load that is applied to the removed toner conveying member also increases. Also, the driving system in which the driving system is divided into a plurality of sub-systems becomes advantageous as the cleaning-means frame becomes virtually filled up with the removed toner. 
     Furthermore, the driving force input system for driving the removed toner conveying member and the driving force input system for driving the developmental toner, are integrated into a single unit, simplifying the structure of the coupling for connecting the apparatus main assembly and the process cartridge, which in turn makes it easier to arrange the gears and the like, providing an advantage from the viewpoint of space saving. 
     Conventionally, the toner conveying system and toner stirring system are driven by directly meshing the gear of the development roller with the gears of the toner conveying system and toner stirring system. However, in this embodiment, such direct engagement between the gears of the former and latter does not occur. Therefore, even if the load that is applied to the toner conveying system and toner stirring system increases due to the increase in the toner storage container capacity, it is unnecessary to increase the strength of the gears  105   b  and  107   b  for driving the development roller  18 . Therefore, it is possible to use low module gears for driving force transmission. With this arrangement, it does not occur that an image suffering from the aforementioned irregularities is produced due to the irregularity in the pitch that occurs as the drum gear  105   b  and sleeve gear  107   b  mesh with each other. 
     Further, in this embodiment the cleaning-means frame and the toner-storage frame are integrally fixed to each other by the side covers. Therefore, the removed toner conveying member and developmental toner conveying member can be precisely connected and driven. 
     Further, only the developing means frame which supports the developing member such as the development roller is pivotally supported so that it is enabled to pivot following the photosensitive drum. Therefore, it is easy to connect the drum gear  105   b  and sleeve gear  107   b  to each other by driving them. 
     The force for rotationally driving the removed toner conveying member  115  is transmitted from the driving system for driving the toner conveying member. Therefore, even when the photosensitive drum is rotated at a high velocity, it is easy to continue to convey the removed toner at the conventional rotational velocity. 
     Structure of Air Passage for Cooling 
     FIG. 8 is a schematic drawing of the gear train positioned along the photosensitive drum. FIG. 8, ( a ) is a side view of the process cartridge, with the side cover removed, and FIG. 8, ( b ) is a side view of the process cartridge, in which the contour of the side cover is indicated by an imaginary line. Within the cleaning means frame  13 , the conveying member  115  for conveying the recovered removed toner toward the rear of the removed toner bin  5  is disposed. When the structural arrangement of the process cartridge  15  is such that the conveying member  115  receives the driving force from photosensitive drum  11 , and the rotational velocity must be reduced by a large ratio. However, if the arrangement is such that the driving force is transmitted from the toner conveying member  114 , the velocity reduction by a large ratio is unnecessary. Therefore, it is easy to attain a proper rotational velocity. In this case, the gears  111   b  and  111   c  are disposed in the adjacencies of the photosensitive drum  11 , penetrating the toner storage frame  16  and developing-means frame  17  (FIG. 8 ( a )). 
     In this embodiment, in order to prevent the temperature increase in the adjacencies of the photosensitive drum, it is assured that an air passage  19   f  is secured in the side cover  16 , in the adjacencies of the photosensitive drum (FIG. 8 ( b )). More specifically, the gear  111   b  and  111   c  are provided with a plurality of slits  24   a  and  24   b , respectively, the interval portions of which form a plurality of axial flow vanes, to forcefully exhaust, or take in, the air through an air passage  19   b . With this arrangement, it does not occur that the air passage  19  for cooling the interior is blocked by the gears  111   b  and  111   c.    
     Next, referring to FIGS. 20,  21  and  23 , the structure of the cooling air passage will be described. FIG. 20 is a perspective view of the gear  11   c . The structure of the gear  111   b  is the same as that of the gear  111   c , except that the former is opposite to the latter in the direction of the helical teeth, and the direction of the helical air passages. Therefore, the air passage structure is described referring to the gear  111   c  as an example. FIG. 21 is a development of the section of the B—B portion of the gear  111   c  illustrated in FIG. 20, at a cylindrical plane perpendicular to the rotational axis of the gear  111   c , and FIG. 22 is a sectional view of the gear  111   c  illustrated in FIG. 20, at a plane A—A. 
     The gear  111   c  is a helical gear. In a disk portion  111   c   3 , which connects the rim portion  11   c   2  comprising the helical teeth, and the hub portion  111   c   1 , a plurality of through slits  24   a  are provided, which extend in the radial direction of the gear  111   c , at equal intervals. There is also provided a certain amount of distance between the surface of the disk portion  111   c   3  and the inwardly facing surface  19   h  of the side cover  19 . Thus, the air passage  19   f  of the side cover  19  and the slits  24   a  are rendered continuous through the space  29 . The gear  111   c  is rotationally supported by a shaft  19 G, which extends inward from the inwardly facing surface of the side cover  19 , perpendicular to the longitudinal direction of the photosensitive drum  15 ; the shaft  19 G is put through the center hole of the hub  111   c   1 . The end portion of the shaft  19 G is fitted with a retainer ring (unillustrated) to prevent the gear  111   c  from moving in the shaft direction. The outwardly facing surface  111   c   4  of the rim portion  111   c   2  is very close to the inwardly facing surface  19   h  of the side cover  19 . The inwardly facing surface  19   h  of the side cover  19 , and the outwardly facing surface  111   c   4  of the rim portion, are required to make the amount of the air flow between them as small as possible. Thus, they may be intricately formed in such a manner that the gap between them forms a labyrinth. 
     The length and position of each slit  24   a  in terms of the radial direction of the gear  111   c  matches those of the air passage  19   f.    
     Referring to FIG. 21, the interval between the adjacent two slits  24   a  is occupied by a helical vane  24   g ; the adjacent two slits  24   a  are separated by a helical vane. The slit  24   a  is desired to be shaped like an interval space between adjacent two vanes of an axial flow fan so that the gear  111   c  is rendered aerodynamically effective in moving air. However, the gear  111   c  is relatively slow in rotational velocity, and therefore, the vanes of the gear  111   c  may be simply angled. With the provision of these slits  24   a , the disk portion  111   c   3  of the gear  111   c , that is, the portion of the gear  111   c  on the inward side of the rim  111   c   2  in terms of the radial direction of the gear  111   c , constitutes an impeller. 
     Referring to FIGS. 20 and 21, as the gear  111   c  rotates in the direction indicated by an arrow mark  24   c , air flows in the axial direction as indicated by an arrow mark  24   d . Then, the air moves toward the air passage  19   f  through the space  29 , and is exhausted out of the process cartridge  15  through the air passage  19   f  of the side cover  19 . 
     As is evident from the drawings, the cooling air passage is structured so that the air currents from all the slits  24   a  are allowed to simultaneously flow through the space  29 . Therefore, all the vanes  24   d  contribute to the generation of the air flow. 
     If the direction of the surface  24   f  of the vane  24   g  is reversed, the direction of the air flow reverses even if the rotational direction of the gear  111   c  is kept the same. Thus, the direction of the surface  24   f  should be determined to be advantageous in terms of cooling efficiency, in consideration of the positional arrangement of the components, and the general configuration of the cooling air passage. 
     The twist angle of teeth  24   e  of the helical gear  111   c  is rendered parallel to the twist angle of the surfaces  24   f  of the vanes  24   g . With this arrangement, the teeth  24   e  and vanes  24   g  become the same in terms of the air flow in the axial direction of the gear  111   c . Further, such an arrangement is advantageous in terms of mode formation, in a case that the gear  111   c  is molded of resin. In a case that the teeth  24   e  and vanes  24   g  of the gear  111   c  are constructed so that they become the same in terms of in which direction they send air in terms of the axial direction of the gear  111   c , a gap for allowing the air to pass is provided between the outwardly facing surface of the rim  111   c   2  and the inwardly facing surface of the side cover  119 . Also, a cover which follows the peripheral surface of the gear  111   c , except for the portion where the gear  111   c  meshes with its counterpart, is provided as a member which functions like the casing of an air blower. 
     As described above, during an image forming operation, the gears  111   b  and  111   c  rotate, and therefore, the internal space of the process cartridge  15  is ventilated. Also, the heat generated by the fixing apparatus and the like is removed. Further, the apparatus main assembly  27  is provided with ventilation holes through which the apparatus main assembly  27  is naturally ventilated, or ventilating means such as a fan (unillustrated), or the like is provided. 
     Other Embodiments of Process Cartridge 
     Referring to FIGS. 10,  11  and  21 , the embodiments of the process cartridge in accordance with the present invention, different from the preceding embodiment, will be described. 
     FIGS. 11 and 12 are schematic drawings of one of the embodiments of a process cartridge in accordance with the present invention, and show the structure of the cartridge as seen from above. 
     Referring to FIG. 11, a toner storage frame  116  provided with a toner storage portion is accurately positioned relative to side covers  119   a  and  119   b , and fixed thereto, by fitting the pins  119   c  of the side covers  119  ( 119   a  and  119   b ) into the holes or corresponding positioning bosses  116   a  of the toner-storage frame  116 . The cleaning-means frame  113  is accurately positioned relative to the side covers  119   a  and  119   b , and fixed thereto, by engaging the positioning bosses  113   b  with the positioning pins  119   d  of the side covers  119   a  and  119   b . Consequently, the cleaning-means frame  113  and toner-storage frame  116  are integrally fixed to each other. 
     Referring to FIG. 10, the developing-means frame  117  of a developing apparatus D is supported by the pins inserted in the holes  113   a  of the cleaning-means frame  113 , being enabled to pivot about the center of the holes  113   a  while holding a development roller  118  and a development blade  112 . Between the spring anchoring projection  113   c  of the cleaning-means frame  113 , and the spring anchoring projection  117   f  of the developing-means frame  117 , a tensional coil spring  112  is stretched as shown in FIG.  13 . With the resiliency of the tensional coil spring  122 , the spacer rings  118   b  are kept pressed upon the photosensitive drum  11 , outside the image formation region. The spacer rings  18   b  are provided at the longitudinal ends of the development roller  118 , one for one, and are greater in radius by a value equivalent to a development gap (approximately 300 μm) than the development roller  118 . 
     With this arrangement, a gap is provided between the developing-means frame  117  and toner-storage frame  116 . Further, the toner-storage frame  116  is structured so that its bottom well is approximately horizontal when the process cartridge is in the apparatus main assembly. 
     In this embodiment, the gap between the developing apparatus D and toner storage frame  116  is sealed. More specifically, the openings  117   b  and  116   c  of the developing apparatus D and frame  116 , respectively, for allowing toner to pass, are connected by a flexible member  120 , as a sealing member, shaped like a bellows. The flexible member  120  as a flexible seal is welded or glued to the frames  116  and  117 , by the connective portions  120   a  and  120   b , respectively. 
     The flexible member  120  has to be connected only to prevent toner from leaking while toner is passing between the openings  116   c  of the frame  116 , and the opening  117   b  of the frame  117 . Therefore, the frames  116  and  117  may be provided with a male and a female coupler, which surround the openings  116   c  and  117   b , respectively, and the joint between them is sealed with a sealing member, provided that the couplers can absorb the displacement of the frames  116  and  117  relative to each other. 
     Referring to FIG. 14, the flexible member  120  is shaped like a belt which surrounds the openings  117   b  and  116   c.    
     The surfaces  116   d  and  117   c  of the frames  116  and  117 , respectively, which face each other, are flat surfaces approximately parallel to each other. They surround the openings  116   c  and  117   b , respectively. To the surface  116   d , a connective portion  120   a  of the flexible member  120  is fixed, and to the surface  117   c , the connective portion  120   b  of the flexible member  120  is fixed. The method used to fix these connective portions  120   a  and  120   b  to the surfaces  116   d  and  117   c  is thermal welding, or gluing. It is also possible to clasp the connective portions  120   a  and  120   b  with the use of clasping members (unillustrated), for example, a wear plate, and screw the clasping members to the surfaces  116   d  and  117   c.    
     The flexible member  120  is uniform in terms of the shape of the cross section perpendicular to the surfaces  120   a  and  120   b . More specifically, referring to FIGS. 10 and 15, in terms of cross section, the L-shaped outward sheath portion  120   c  and L-shaped inward sheath portion  120   d  of the flexible member  120  are connected by a zigzag portion. Further, the inward sheath portion  120   d  and outward sheath portion  120   c  overlap each other in terms of the direction parallel to the planes of the openings  116   d  and  117   c . In other words, the flexible member  120  has two folds k. With the provision of this structural arrangement, even if the distance between the mutually facing surfaces  116   d  and  117   c  varies, or the surfaces  116   d  and  117   c  become displaced relative to each other in the direction parallel to their planes, or the surfaces  116   d  and  117   c  become nonparallel to each other, or the preceding displacements occur in combination, the flexible member  120  bends like a bellows, absorbing the displacements to keep sealed the passage between the openings  116   c  and  117   d . Further, since the flexible member  120  is in the form of a bellows, it is very small in the resistance it generates as one or a plurality of the aforementioned displacements occur. Therefore, the flexible member  120  does not affect the contact pressure generated between the spacer rings  118   b  and photosensitive drum  111  by the tensional coil spring  122 . 
     Further, when the frame  116  is full of toner, there is a possibility that the weight of the toner within the frame  116  will deform the side cover  119 , and as a result, the mutually facing surfaces  116   d  and  117   c  will be displaced relative to each other. The flexible member  120  is capable of dealing with this type of situation. This type of deformation changes as the amount of the toner within the frame  116  is reduced. As a result, the positional relationship between the opposing surfaces  116   d  and  117   c  also changes. However, this displacement can also be dealt with by the flexible member  120 . 
     The front and rear walls of the apparatus main assembly  27  are provided with a guide (unillustrated). 
     On the other hand, the process cartridge  115  is provided with a pair of shaft-like, cylindrical projections (unillustrated), which project outward from the cleaning-means frame  113  through the holes  119   e  and  119   f  of the side covers  119 , one for one, and the axial lines of which are in alignment with the rotational axis of the photosensitive drum  111 . When the process cartridge  115  is installed into the apparatus main assembly  27 , the position of the process cartridge  15  relative to the apparatus main assembly  27  is fixed as these cylindrical projections engage with the positioning portions (unillustrated) of the apparatus main assembly  27 . Since the frame  116  is relatively large, and the distance from the center of the photosensitive drum  111  to the center of gravity of the frame  116  is relatively large, a large amount of moment is generated in the direction to rotate the process cartridge  115  about the rotational axis of the photosensitive drum  111  in the clockwise direction. As a result, the point of the process cartridge  115 , indicated by an arrow mark A in FIG. 10, comes into contact, and remains in contact, with the apparatus main assembly  27 , fixing the maintaining the attitude of the process cartridge  115 . 
     Regarding the preceding description, the material for the flexible member  120  is desired to be such elastomer that is similar in properties to the material used for the frames  113  and  116 . In this embodiment, styrene resin was used as the frame material, and styrene elastomer was used as the material for the flexible member  120 . This combination was excellent in terms of bonding. Other material such as rubber, urethane, silicon rubber, and the like may be also used as the material for the flexible member  120 . As for the means for attaching the flexible member  120 , adhesive or double-shaped adhesive tape may be used. Instead of these adhering means, a mechanically attaching means may be used. For example, the flexible member  120  may be clasped by a clasping member. Obviously, both connective means may be used in combination. 
     As for the molding method for the flexible member, injection molding or compression molding may be used. Further, material in the form of a sheet may be heat-pressed. 
     In order to minimize the reactive force of the flexible member  120 , the direction of which is approximately parallel to the conveyance direction of the sheet S, the flexible member  120  is structured so that the portion between the folds k and k, the portion between the fold k and the connective portion  120   a , and the portion between the fold k and the connective portion  120   b , become parallel to the sheet conveyance direction, as shown in FIG.  10 . However, the flexible member  120  may be folded so that the above described portions become perpendicular to the sheet conveyance direction. 
     Further, a fold width W, or the distance between the opposing two folds, of the flexible member  120  is determined so that the flexibility of the flexible member is not lost within a range in which the frames  117  and  116  are allowed to move relative to each other. The opening of the flexible member  120 , which faces the opening  116   c , is greater in both the horizontal and vertical directions than the opening  116   c , and the opening of the flexible member  120 , which faces the opening  117   b , is smaller in both the horizontal and vertical direction than the opening  117   b.    
     FIG. 17 shows an example of the flexible member  120 , which has only a single fold k. Even if the flexible member  120  is provided with only one fold k, it can deal with the displacement of the frames  116  and  117  relative to each other, as long as the width W from the connective portion  120   b  to the fold k is rendered generous. 
     In the preceding description of the embodiments of the present invention, the bellows portion of the flexible member  120  was described with reference to its vertical sectional view. However, when shown in a horizontal sectional view, the direction in which the fold k projects is opposite to the direction in which it projects in the vetical sectional view. For example, the fold projecting inward in FIG. 16 projects ouward when seen in the horizontal sectional view. 
     The above described embodiments of the present invention may be summarized as follows. 
     The process cartridge  15  ( 115 ) removably installable in the main assembly  27  of an electrophotographic image forming apparatus, comprises: 
     the electrophotographic photosensitive drum  11  ( 111 ); 
     the development roller  18  ( 118 ) as a developing member for developing an electrostatic latent image formed on the electrophotographic photosensitive member  11  ( 111 ); 
     the toner storage frame  16  ( 116 ) provided with the toner storage portion  16   a  ( 116   a ) as a developer storing portion for storing the developer used for developing the electrostatic latent image with the use of the development roller  18  ( 118 ); 
     the cleaning means frame  13  ( 113 ) as a drum frame for supporting the electrophotographic photosensitive drum  11  ( 111 ); 
     the developing means frame  17  ( 117 ) which supports the development roller  18  ( 118 ) and is pivotally attached to the toner storage frame  16  ( 116 ); 
     the side covers  19  ( 119   a ) as the first end cover for holding together the cleaning means frame  13  ( 113 ) and developing means frame  17  ( 117 ), at each of the longitudinal ends of the cleaning means frame  13  ( 113 ) and developing means frame  17  ( 117 ); and 
     the side cover  20  ( 119   b ) as the second end cover for holding together the cleaning means frame  13  ( 113 ) and developing means frame  17  ( 117 ), at each of the other longitudinal ends of the cleaning means frame  13  ( 113 ) and developing means frame  17  ( 117 ). 
     The developing-means frame  17  ( 117 ) and toner-storage frame  16  ( 116 ) are connected to each other, with the interposition of the sealing member  21  to  60 , or the flexible member  120 , and the flexible sealing member is pasted to the developing-means frame  17  ( 117 ) and toner-storage frame  16  ( 116 ). 
     The sealing member  60  is a hollow member and has a through hole  60   a . One end of the through hole  60   a  faces the opening  16   c , as a supply outlet, with which the toner-storage frame  16  is provided, and the other end of the through hole  60   a  faces the opening  17   a , as a supply inlet, with which the developing-means frame  17  is provided. The opening  16   c  is an opening through which the developer t stored in the toner storage portion  16   a  is conveyed toward the development roller  18 . The opening  17   a  is an opening through which the developer t is received into the developing means frame  17  after passing through the opening  16   c . As for the sealing member  60 , one end of its through hole  60   a  is pasted to the toner-storage frame  16 , by the surface that surrounds the opening of the hole  60   a , and the other end of the through hole  60   a  is pasted to the developing-means frame  17  by the surface that surrounds the opening of the hole  60   a.    
     The sealing member  21  and flexible member  120  have at least one fold k between the surface b which they are pasted to the developing-means frames  17  and  117 , respectively, and the surface by which they are pasted to the toner-storage frame  16  and  116 , respectively. The sealing member  21  and flexible member  120  are in the form of a bellows, one end of which is pasted to the toner-storage frame  16  and  116 , respectively, and the other end of which is pasted to the developing-means frame  17  and  117 , respectively. 
     The flexible sealing members  21  and  60  are formed of elastic material, sheet, or film. 
     The material for the sealing members  21  and  60 , and the material for the flexible member  120 , are foamed urethane, ester resin, or polyurethane resin. 
     The side cover  19  is provided with a handle  29 , which is grasped by an operator when the process cartridge  15  ( 115 ) is installed into, or removed from, the apparatus main assembly. The process cartridge  15  ( 115 ) is installed into, or removed from, the apparatus main assembly  27  in a direction parallel to the longitudinal direction of the electrophotographic photosensitive drum  11  ( 111 ). 
     The side cover  19  ( 119 ) is provided with the hole  19   a  ( 119   f ), through which the shaft  25  ( 125 ) of the electrophotographic photosensitive member  11  ( 111 ) projects. One of the longitudinal ends of the electrophotographic photosensitive member  11  ( 111 ) is supported by the cleaning-means frame  13  ( 113 ), by the shaft  25  ( 125 ). The position of the process cartridge  15  ( 115 ) relative to the apparatus main assembly  27  is fixed as the process cartridge  15  ( 115 ) is installed into the apparatus main assembly  27 . 
     The top surface of the toner-storage frame  16  ( 116 ) is provided with a handle  30 . The top surface refers to the surface that faces upward when the process cartridge  15  ( 115 ) is in the apparatus main assembly  27 . The handle  30  is a portion that is grasped by an operator when the process cartridge  15  ( 115 ) is moved. 
     The side covers  19  and  20  ( 119   a  and  119   b ) are fixed to the cleaning-means frame  13  ( 113 ) and toner-storage frame  16  ( 116 ) with the use of screws  100 . 
     The cleaning means frame  13  ( 113 ) has an exposure opening  131  ( 1131 ), which is an opening through which a beam of light modulated with image formation data is projected onto the electro-photographic photosensitive drum  11  ( 111 ) from the apparatus main assembly  27  after the installation of the process cartridge  15  ( 115 ) into the apparatus main assembly  27 . 
     In the cleaning means frame  13  ( 113 ), the charge roller  12  ( 112 ), as a charging member for charging the electrophotographic photosensitive drum  11  ( 111 ), and the cleaning blade  14  ( 114 ) as a cleaning member for removing the developer remaining on the electrophotographic photosensitive drum  11  ( 111 ), are disposed. 
     The side covers  19  and  20  ( 119   a  and  119   b ) are fixed to the cleaning-means frame  13  ( 113 ) and toner-storage frame  16  ( 116 ) with the use of resin. 
     The side cover  19  is provided with the groove  19   e  in which the projecting member  17   e , provided at one of the longitudinal ends of the developing means frame  17 , is movably supported. The projecting member  17   e  formed of resinous material is an integral portion of the developing-means frame  17 . The toner storage portion  16  ( 116 ) contains the developer t. 
     The assembly method for the process cartridge  15  ( 115 ) is as follows. 
     The assembly method for the process cartridge  15  ( 115 ) removably installable in the main assembly  27  of an electrophotographic image forming apparatus comprises: 
     (a) a drum attachment step for attaching the electrophotographic photosensitive drum  11  ( 111 ) to the cleaning-means frame  13  ( 113 ) as a drum frame; 
     (b) a frame joining step for joining the developing-means frame  17  ( 117 ) and toner storage frame  16  ( 116 ) in a manner to allow them to pivot relative to each other; 
     (c) a developing member attachment step for attaching the development roller  18  ( 118 ) as a developing means to the development means frame  17  ( 117 ), the development roller  18  ( 118 ) being a means for developing an electrostatic latent image formed on the electrophotographic photosensitive drum  11  ( 111 ); 
     (d) a developer filling step for filling the toner-storage frame  16  ( 116 ) with the developer t; 
     (e) a first end cover joining step for attaching the side cover  19  ( 119   e ) as the first end cover to the cleaning-means frame  13  ( 113 ) and the development-means frame  17  ( 117 ), at each of the longitudinal ends of the frames  13  ( 113 ) and  17  ( 117 ); 
     (f) a second end cover joining step for attaching the side cover  20  ( 119   b ) as the second end cover to the cleaning-means frame  13  ( 113 ) and the development-means frame  17  ( 117 ), at each of the other longitudinal ends of the frame  13  ( 113 ) and  17  ( 117 ). 
     In the frame joining step, the development-means frame  17  ( 117 ) and toner-storage frame  16  ( 116 ) are joined with each other in a manner to allow them to pivot relative to each other, with the interposition of the sealing member  21  ( 60 ) or the flexible sealing member  120 , as a flexible member, between the two frames, so that one end of the flexible member is attached to the development-means frame  17  ( 117 ) and the other end of the flexible member is attached to the toner-storage frame  16  ( 116 ). 
     In the first end cover joining process and second end cover joining step, the side covers  19  ( 119   a ) and side cover  20  ( 119   b ) are attached to the cleaning-means frame  13  ( 113 ) and development-means frame  17  ( 117 ) with the use of screws. 
     In the first end cover joining step and second end cover joining step, the side covers  19  ( 119   a ) and side cover  20  ( 119   b ) are attached to the cleaning-means frame  13  ( 113 ) and development-means frame  17  ( 117 ) with the use of resin. 
     In the developer filling step, the developer t is filled into the developer storage portion of the toner-storage frame  16  ( 116 ) through the developer filling opening (unillustrated) provided at one of the longitudinal ends of the toner storage frame  16  ( 116 ). 
     Cartridge Installing Space in Main Assembly 
     FIG. 19 is a perspective view of the cartridge installing space provided in the apparatus main assembly  17 . As the front door (unillustrated) of the apparatus main assembly  17  is opened, the entrance to the cartridge installing space  71  becomes visible. 
     In the opposing sidewalls of this cartridge installing space  71 , a pair of guide rails  72  and  73  are provided one for one, which extend in a direction perpendicular to the direction in which the sheet S is conveyed, and parallel to the surface of the sheet S. The guide rails  72  and  73  are disposed virtually parallel to each other, and also at virtually the same levels, that is, in a virtually horizontal plane. 
     The process cartridge  15  ( 115 ) is advanced into, or retracted out of, the above described cartridge installing space  71 , in the longitudinal direction of the process cartridge  15  ( 115 ); the process cartridge  15  ( 115 ) is removably installed into the apparatus main assembly  17 , with the guide portions  15   a  ( 115   a ) and  15   b  ( 115   b ) engaged in the corresponding guide rails  72  and  73  of the cartridge installing space  71 . 
     As described in the foregoing, according to the present invention, the image quality is stabilized. 
     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.