Patent Publication Number: US-6336017-B1

Title: Mounting member for mounting a flange to an end of a cylindrical member of an electrophotographic photosensitive drum of a process cartridge, such a flange, such a drum, and such a process cartridge

Description:
FIELD OF THE INVENTION AND RELATED ART: 
     The present invention relates to a mounting member, a drum flange, an electrophotographic photosensitive drum and a process cartridge. 
     Here, the term “electrophotographic image forming apparatus” refers to an apparatus which forms images on a recording medium, using an electrophotographic image forming process. It includes an electrophotographic copying machine, an electrophotographic printer (for example, LED printer, laser beam printer), an electrophotographic facsimile machine, an electrophotographic word processor, and the like. 
     The term “process cartridge” refers to a cartridge having, as a unit, an electrophotographic photosensitive member, and charging means, developing means and cleaning means, which is detachably mountable to a main assembly of an image forming apparatus. It may include, as a unit, an electrophotographic photosensitive member and at least one of charging means, developing means and cleaning means. It may include, as a unit, developing means and an electrophotographic photosensitive member. 
     An image forming apparatus using an electrophotographic process is known, which is used with the process cartridge. This is advantageous in that the maintenance operation can be, in effect, carried out by the users thereof without expert service persons, and therefore, the operativity can be remarkably improved. Therefore, this type of device is now widely used. 
     In such an electrophotographic image forming apparatus, the electrophotographic photosensitive member is supported on a cartridge frame at opposite longitudinal ends to stably rotate the photosensitive drum. 
     SUMMARY OF THE INVENTION 
     It is a principal object of the present invention to provide a further improvement in the prior art structure. 
     It is a principal object of the present invention to provide a mounting member, a drum flange using the mounting member, an electrophotographic photosensitive drum and a process cartridge. 
     It is an object of the present invention to provide a mounting member, a drum flange using the mounting member, and an electrophotographic photosensitive drum and a process cartridge wherein the flange can be mounted to a cylindrical member using elastic force. 
     According to an aspect of the present invention, there is provided a mounting member for mounting a flange to an end of a cylindrical member of an electrophotographic photosensitive drum, comprising: a base plate; a hole provided at a center portion of the base plate; a plurality of first projected portions provided projected outwardly from an edge of the base plate, for elastic contact to an inner surface of the flange; a plurality of second projected portions provided to project outwardly from an edge of the base plate, for elastic contact to an inner surface of the flange. 
     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 longitudinal sectional view of an electrophotographic image forming apparatus using a process cartridge. 
     FIG. 2 is a longitudinal sectional view of a process cartridge usable with the electrophotographic image forming apparatus shown in FIG.  1 . 
     FIG. 3 is a side view illustrating a supporting structure for a photosensitive drum. 
     FIG. 4 is a sectional view of a drum flange at a non-driving side of a drum unit. 
     FIG. 5 is a side view of a body of the drum flange. 
     FIG. 6 is a rear view of a body of the drum flange. 
     FIG. 7 is a front view of the body of the drum flange. 
     FIG. 8 is a front view of a drum grounding plate. 
     FIG. 9 is a front view of a drum grounding plate before shaping. 
     FIG. 10 is a top plan view of a drum grounding plate. 
     FIG. 11 is a side view of a drum grounding plate. 
     FIG. 12 is a front view of a clamping plate. 
     FIG. 13 is a side view of a clamping plate. 
     FIG. 14 is a side view of a drum flange. 
     FIG. 15 is a sectional view of a drum flange. 
     FIG. 16 is an illustration illustrating a mounting method of the drum flange to the main body. 
     FIG. 17 is a front view of a drum flange. 
     FIG. 18 is a front view showing a painted surface of the photosensitive drum. 
     FIG. 19 is an illustration of the relation between the diameters of the drum flange and the photosensitive drum. 
     FIG. 20 shows the drum flange inserted into the photosensitive drum. 
     FIG. 21 is an illustration when a cylinder clamping pawl of a clamping plate is inserted by a pawl pushing tool. 
     FIG. 22 shows a drum flange as seen from the center of the photosensitive drum toward outside. 
     FIG. 23 is a sectional view of a drum flange mounted to the photosensitive drum  7 . 
     FIG. 24 is a side view showing a relation between the clamping plate and the grounding plate in the drum flange after assembling. 
     FIG. 25 is a detailed illustration showing a relation between the clamping plate and the grounding plate. 
     FIG. 26 illustrates the deterioration of circularity of the photosensitive drum when there is no press-fitting engagement portion, nor flange clamping pawl of the clamping plate. 
     FIG. 27 shows a circularity of the photosensitive drum when the drum flange according to the present invention is used, wherein (a) shows an outer diameter circularity of the photosensitive drum at the position where a flange clamping pawl of the clamping plate contacts to the photosensitive drum, (b) shows an outer diameter circularity of the photosensitive drum at a position approximately 3 mm away from the position where the flange clamping pawl of the clamping plate contacts to the photosensitive drum. 
     FIG. 28 is a front view of a drum flange according to another embodiment of the present invention. 
     FIG. 29 is a side view of a drum flange shown in FIG.  28 . 
     FIG. 30 is a front view of a clamping plate according to another embodiment of the present invention. 
     FIG. 26 illustrates the deterioration of a circularity of a photosensitive drum  7  when there is no engaging portion  52  of the main body  50  and pawls  92   a - 92   h  of the clamping plate  90 . In this figure, a thickness of a wall of the photosensitive drum  7  is 1 mm. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. 
     FIG. 1 schematically illustrates an electrophotographic image forming apparatus (printer) which employs a process cartridge in accordance with the present invention. This electrophotographic image forming apparatus (hereinafter, “image forming apparatus”) is a laser beam printer, which is based on an electrophotographic process, and employs a removably installable process cartridge. 
     In other words, this image forming apparatus is constituted of the main assembly and a removably installable process cartridge. The main assembly comprises a structural frame constituted of two pieces: a top portion  2  and a bottom portion  1 . The top portion  2  is hinged to the rear side (left side in FIG. 1) of the bottom portion  1  with the use of a hinge pin  3 , so that it can be rotated in the direction indicated by an arrow mark (I), about the hinge pin  3  to enable it to take two positions: an open position (outlined by double dot chain line) and a closed position (outlined by solid line). When the top portion  2  is at the open position, a process cartridge B (which will be described later in detail) can be installed into, or removed from, the main assembly in the direction indicated by an arrow mark (YO). The top portion  2  is provided with a pair of guides  2   a  as an installation-removal means along which the process cartridge B is installed or removed in the arrow (YO) direction. The guide  2   a  is in the form of a long groove, whereas the cartridge frame  12  of the process cartridge B. guided by the guide  2   a  is provided with a pair of guides (unillustrated) in the form of a tongue, which fit in the pair of guides  2   a , one for one. The cartridge frame  12  will be described later in detail. 
     As the top portion  2  of the structural frame of the apparatus main assembly is closed, the process cartridge B is placed at a predetermined position in the main assembly. With the process cartridge B at the predetermined position in the main assembly, a laser scanner unit  6 , which constitutes the main portion of an exposing apparatus, is located on the front side (right-hand side in FIG. 1) of the process cartridge B, and a sheet cassette  27 , in which a plurality of sheets P, that is, image media, are held, is located below the process cartridge B. On the downstream side of the sheet cassette  27  in terms of the direction in which the sheet P is conveyed, a sheet feeder roller  34 , a registration roller pair  35 , a transfer guide  36 , a transfer charger  26  as a transferring means, a sheet conveyer  37 , a fixing device  29 , and the like are arranged in the listed order. These components are all disposed in the bottom portion  1  of the structural frame of the main assembly, whereas a sheet discharge roller  31 , a delivery tray  32 , and a reflection mirror  33 , which are on the downstream side of the fixing device  29  are disposed, along with the process cartridge B, in the top portion  2  of the structural frame of the main assembly. 
     In this embodiment, the sheet feeder roller  34 , the registration roller pair  35 , the transfer guide  36 , the sheet conveyer  37 , the sheet discharge roller  31 , and the like constitute a conveying means  13  for conveying the sheet P as recording medium. 
     Referring to FIG. 2, the process cartridge B comprises a structural frame  12  constituted of a toner frame  12   a , a cleaning frame  12   b , and a development frame  2   c . The toner frame  12   a  stores toner. The development frame  12   c  is attached to the toner frame  12   a , and the cleaning frame  12   b  is attached to the development frame  12   c . This cartridge frame  12  integrally contains four processing devices: a photosensitive drum (electrophotographic photosensitive member)  7 , a charging means  8 , a developing means  10 , and a cleaning means  11 . The photosensitive drum  7  is a rotative cylindrical member, and the charging member  8  comprises a rotative roller  8   a . The developing means  10  rotatively supports a development roller  10   c , and the cleaning means  11  comprises a cleaning blade lla and a waste toner bin  11   c . The top wall of the cartridge frame  12  is provided with an exposure window  9 , which is formed by cutting or drilling. The bottom wall of the cartridge frame  12  is provided with a cover  5 , which can be opened to expose, or closed to cover, the opening  4  through which an image formed on the photosensitive drum  7  is transferred onto the recording medium. The cover  5  moves to the closed position to cover the opening  4 , protecting the photosensitive peripheral surface of the photosensitive member  7  as the process cartridge B is removed from the main assembly of the printer (electrophotographic image forming apparatus), or the top portion  2  of the structure frame of the main assembly is opened. 
     Next, an image forming process will described in general terms. Upon reception of a process start signal, the photosensitive drum  7  is rotatively driven in the direction indicated by an arrow mark RI at a predetermined peripheral velocity (process speed). The peripheral surface of the photosensitive drum  7  is in contact with the charge roller  8   a  of the charging means  8 , to which a bias voltage is applied. Thus, as the photosensitive drum  7  is rotatively driven, the peripheral surface of the photosensitive drum  7  is uniformly charged by this charging means  8 . 
     From the laser scanner unit  6 , a laser beam L modulated with sequential digital electric signals, which reflect image data, is outputted. The laser beam L is reflected by the reflection mirror  33 , and enters the cartridge frame  12  through the exposure window  9  of the top wall of the cartridge frame  12 , exposing the charged peripheral surface of the photosensitive drum  7  in a scanning manner. As a result, an electrostatic latent, image which reflects the image data, is formed on the peripheral surface of the photosensitive drum  7 . This electrostatic latent image is developed by a layer of developer (toner) coated on the peripheral surface of the development roller  10   c . The thickness of the layer of the toner is regulated by the development blade  10   b  of the developing means  10 . The toner is sent from the toner frame  12   a  into the development frame  12   c  by the toner sending member  10   a  disposed in the toner frame  12   a.    
     Meanwhile, the plurality of sheets P stored in the sheet cassette  27  are sent out, one by one, from the sheet cassette  27  by the sheet feeder roller  34 . Then, the sheet P is delivered to the transfer station, that is, the interface between the peripheral surfaces of the photosensitive drum  7  and transfer charger  26 , by the registration roller pair  35 , through the transfer guide  36 , with a timing coordinated with the timing for the outputting of the laser beam L. In the transfer station, the toner image on the photosensitive drum  7  is transferred onto the sheet P starting from the downstream end. 
     After the toner image is transferred onto the sheet P, the sheet P is separated from the photosensitive drum  7 , and then is conveyed to the fixing device  29  by the sheet conveyer  37 . in the fixing device  29 , the sheet P is put through the nip formed by the fixing roller  29   a  and pressure roller  29   b . While the sheet P is put through the nip, the toner image is fixed to the sheet P. Then, the sheet P with the fixed toner image is discharged into the delivery tray  32  by the sheet discharge roller  31 . After the image transfer, the photosensitive drum  7  is cleaned by the cleaning means; and the toner particles remaining on the peripheral surface of the photosensitive drum  7  are removed by the cleaning blade  11   a  of the cleaning means  11 . The removed toner particles are guided into the waste toner bin  11   c  by a scooping sheet  11   b . Thereafter, the cleaned portion of the peripheral surface of the photosensitive drum  7  is used for the next cycle of the image forming process, which starts from the charging of the photosensitive drum  7 . 
     Supporting Structure for Photosensitive Drum  7   
     FIG. 3 is a side view of the structure for supporting the photosensitive drum . 7 . 
     Referring to FIG. 3, referential characters  7   b  and  7  designate a drum unit and a photosensitive drum  71  respectively. A referential character  45  designates a drum flange assembly, which is attached to one of the longitudinal ends, that is, the driving side end, of the photosensitive drum  7  (cylindrical drum  600 ), by crimping or the like method. 
     A reference character  41  designates a cover member of the cleaning frame  12   b , which is located on the driving side. A reference character  43  designates a means for transmitting a driving force, which is constituted of a certain type of coupler. This driving force transmitting means  43  is engaged with an unillustrated axial member fixed to the drum flange  45  by insert molding or the like method, and transmits the driving force from the printer main assembly to rotate the photosensitive drum  7 . 
     A reference character  501  designates a drum flange assembly attached to the other end, that is, the end opposite to the driving end, of the photosensitive drum  7 . A reference character  50  designates the drum flange of the drum flange assembly  501 , and a reference character  42  designates the cover of the cleaning frame  12   b , on the side opposite to the driving side. 
     The drum unit  7   b  comprises the photosensitive drum  7  and drum flange assemblies  45  and  501 . 
     Structure of Drum Flange  7   b    
     FIG. 4 is sectional view of one of the longitudinal end portions of the drum unit  7   b , on the side opposite to the driving side, adjacent to the drum flange assembly  501 . 
     In FIG. 4, a reference character  42   b  designates an electrically conductive axial shaft as the central axis, which is fixed to the cover  42  on the side opposite to the driving side by insert molding or the like method. It is made of steel, being formed by turning, and is plated with nickel. 
     The electrically conductive shaft  42   b , which is the axial member, is put through a hole  12   b   1  of the cleaning frame  12   b , so that it doubles as the member which fixes the positional relationship between the cleaning frame  12   b  and the photosensitive drum  7 . 
     A reference character  70  designates a plate for grounding the photosensitive drum  7 . This drum grounding member  70  is attached to the drum flange  50  of the drum flange assembly  501  with the use of an anchoring or clamping plate  90  which functions as a mounting member for mounting the flange  70 , constituted of a piece of elastic plate, being pinched between the drum flange  50  of the drum flange assembly  501  and the clamping plate  90 . 
     The drum grounding plate  70  is provided with an elastic arm portion  75 , or the first springy arm portion, which will be described later. It is electrically connected to the electrically conductive shaft  42   b , and grounds the photosensitive drum  7  through the ground contact portions  73   a  and  73   b  of cylinder contact springs  77   a  and  77   b  as the second plate sprints, which also will be described later. 
     Structure of Drum Flange  50  of Drum Flange Assembly  501   
     FIG. 5 is a side view of the drum flange  50  of the drum flange assembly  501  illustrated in FIG.  4 . 
     The drum flange  50  of the drum flange assembly  501  is formed of resin. Its peripheral wall portion comprises a stopper portion  65 , and a portion  51 , a portion  52 , and a guide portion  53 , which are to be fitted into the photosensitive drum  7 . The stopper portion  65  is portion which fixes the positional relation between the drum flange  50  and the photosensitive drum  7  in the longitudinal direction of the photosensitive drum  7 . The fitting portion  51  is a portion which is pressed into the photosensitive drum  7 , and the fitting portion  52 , or the second portion, is a portion which also is pressed into the photosensitive drum  7 . The pressure applied to the portion  52  to fit it into the photosensitive drum  7  is lighter than the pressure applied to the portion  51  to insert it into the photosensitive drum  7 . The insert guide portion  53  is a portion which is fitted into the photosensitive drum  7 , perfectly or with some play. 
     Referring to FIG. 19, the external diameter D 501  of the fitting portion  51  is 1.0005 to 1.005 times the internal diameter D 705  of the photosensitive drum  7 . The external diameter D 502  of the fitting portion  52  is 0.999 to 1.002 times the internal diameter D 707  of the photosensitive drum  7 . The external diameter D 503  of the fitting guide portion  53  is exactly matched to the internal diameter D 707  of the photosensitive drum  7  so that it perfectly fits into the photosensitive drum  7 , that is, without leaving any gap. 
     The fitting portion  52  is provided with an edge portion  52   a , which is located on the fitting guide portion  53  side. The edge portion  52   a  is constituted of a rib which circles the peripheral surface of the drum flange  50 . It projects 0.5 mm to 3 mm in the radial direction of the drum flange  50 . The internal diameter D 502  of the fitting portion  52  is smaller than the diameter D 902  of the circumcircle of the flange gripping extensions  92   a - 92   h.    
     FIG. 6 is an illustration of the drum flange  50  as seen from the direction indicated by an arrow mark A 2  in FIG.  5 . 
     In FIG. 6, reference characters  55   a - 55   h  designate through holes for a pressing tool  631  for pressing the cylinder gripping extensions or cylinder clamping pawls  91   a - 91   h  of the clamping plate  90 . Reference characters  56   a - 56   h  designate holes with which the circular flat wall  62  of the drum flange  50  is provided for positioning the pressing tool  631  in terms of the rotational direction of the photosensitive drum  7 ; the pressing tool  631  is accurately positioned relative to the drum flange  50  by the holes  56   a - 56   h , assuring that the clamping plate  90  is pressed, on the correct points  99 . 
     A reference character  57  designates a hole through which the electrically conductive shaft  42   b  is put, as tightly as possible while allowing the photosensitive drum  7  to rotate about the shaft  42   b.    
     FIG. 7 is a front view of the drum flange  50  of the drum flange assembly  501  illustrated in FIG. 4 as seen from the direction indicated by an arrow mark B 21  in FIG.  5 . 
     In FIG. 7, a reference character  58  designates a rectangular boss that accurately fixes the positional relationship between the drum grounding plate  70  and the clamping plate  90  in terms of the rotational direction of the photosensitive drum  7 . In other words, with the presence of this boss  58 , the pressing tool  631  is accurately aligned with the cylinder gripping rectangular radial extensions  91   a - 91   h  of the clamping plate  90 , assuring that the correct points  99  of the clamping plate  90  are pressed. 
     A reference character  59  designates the inward end surface of the drum flange  50 , or the hatched portion in the drawing. This is the surface to which the drum grounding plate  70  is attached. It is precisely formed. 
     Reference characters  54   a - 54   h  designate bosses for holding the drum grounding plate  70  and clamping plate  90  to the drum flange  50 . They are melted after these plates  70  and  90  are mounted. 
     Reference characters  60   a - 60   h  designate slots cut in the fitting portion  52  and fitting guide portion  53  of the drum flange  50 . As described before, the elastic contact portions  73   a  and  73   b  of the grounding plate  70 , and the rectangular, radial, cylinder clamping pawls  91   a - 91   h  of the clamping plate  90 , are put through these slots, being placed in contact with the inside surface  7   i  of the photosensitive drum  7 . 
     A reference character  61  designates a cylindrical boss for centering the drum grounding plate  70  and clamping plate  90  relative to the drum flange  50 . This boss  61  makes it possible for the eight cylinder clamping pawls  91   a - 91   h  of the clamping plate  90  to make contact with the inside surface  7   i  of the photosensitive drum  7 , on the predetermined points, with uniform pressure. 
     A reference character  64  designates a slot for the elastic shaft contact arm portion  75  of the drum grounding plate  70 . The slot  64  affords the elastic arm portion  75  of the drum grounding plate  70  a sufficient stroke range, so that an accurate amount of pressure is generated by the elastic shaft contact portion  75 . 
     A reference character  63  designates a rib, which presses down on the drum grounding plate  70 , engaging with the bend portion  76  of the drum grounding plate  70 . The bend portion  76  will be described later. More specifically, the rib  63  presses down on the end portion of the bend portion  76  of the drum grounding plate  70 , assuring that a proper amount of pressure is applied to the electrically conductive shaft  42   b  by the elastic arm portion  75  of the drum grounding plate  70 , and therefore assuring electrical conductivity. 
     Structure of Drum Grounding Plate  70   
     FIG. 8 is a front view of the drum grounding plate  70 . 
     The drum grounding plate  70  is formed of phosphor bronze or the like, which is electrically conductive and also elastic. It comprises the first elastic contact portions  75   a , and the second elastic contact portions  73   a  and  73   b , which will be described later. The first elastic contact portion  75   a  makes contact with the electrically conductive shaft  42   b  of the cover  42 , which is placed in contact with the ground portion (unillustrated) of the printer main assembly. The second contact portions  73   a  and  73   b  are placed in contact with the inside surface  7   i  of the photosensitive drum  7 . With the presence of the above described structure, the photosensitive drum  7  is grounded to the ground portion of the printer main assembly. 
     The contact portion  75   a  is provided at the end of the elastic arm portion  75  of the drum grounding plate  70  (FIGS.  9  and  10 ), and the second Lcontact portions  73   a  and  73   b  are provided at the end portions of the cylinder springs  77   a  and  77   b , respectively. The first contact portion  75   a  and the second contact portions  73   a  and  73   b  are angularly shaped. 
     The springs  77   a  and  77   b  are identically shaped, and are symmetrically positioned relative to the center line ( 750 ) of the elastic arm portion  75  of the drum grounding plate  70 , that is, the line drawn through the point of contact between the contact portion  75   a  and the electrically conducive shaft  42   b  and the center of the elastic arm portion  75 . 
     Reference characters  72   a  and  72   b  designate through holes, which are cut through the springs  77   a  and  77   b . Cutting these holes  72   a  and  72   b  through the spring portions  77   a  and  77   b  reduces the widths of the spring portions  72   a  and  72   b  in terms of material, reducing thereby their resiliency, without reducing the widths of the spring portions  72   a  and  72   b  in terms of structure, maintaining thereby virtually the same structural strength as that provided when no hole is cut. 
     Reference characters  71   a - 71   h  designate holes, through which the aforementioned thermally deformable bosses  54   a - 54   f  are put, one for one; they are aligned in a circle, which has the same center and diameter as those of the circle in which the thermally deformable bosses  54   a - 54   h  of the drum flange  50  are aligned, and also are aligned with the same pitch as those bosses. The holes  71   b  and  71   c  are symmetrically positioned to each other relative to the center line  77   o   1  of the spring portion  77   a , and the holes  71   d  and  71   e  are symmetrically positioned to each other relative to the center line of the spring portion  77   b . The thermally deformable bosses  54   b ,  54   c ,  54   f  and  54   g  are put through these holes  71   b ,  71   c ,  71   d  and  71   e , one for one in the listed order, and then, are melted to hold the drum grounding plate  70  to the drum flange  50 . As a result, it is assured that pressure is uniformly applied to the spring portions  77   a  and  77   b  by the two pairs of deformed bosses  54   b ,  54   c ,  54   f  and  54   g . The above arrangement assures that the drum grounding plate  70  remains correctly positioned relative to the drum flange assembly  501  when the drum flange assembly  501  is inserted into the photosensitive drum  7 , and that the spring portions  77   a  and  77   b  are prevented from being easily twisted. 
     The contact portions  73   a  and  73   b  of the  701  are angularly shaped as described before, and therefore, the angular tips and finned edges of the contact portions  73   a  and  73   b  assure that sufficient electrical conductivity is maintained between the inside surface  7   i  of the photosensitive drum  7  and the contact portions  73   a  and  73   b.    
     A reference character  74  designates a slot for fixing the position of the drum grounding plate  70  relative to the drum flange  50  in terms of the rotational direction of the photosensitive drum  7 . The slot  74  engages with the rectangular positioning boss  58  to fix the angle of the drum grounding plate  70  relative to the drum flange  50 . 
     FIG. 9 is a development of the drum grounding plate  70 . The drum grounding plate  70  is constituted of a single piece of approximately 0.2 mm thick metallic plate. As for the manufacturing method for the drum grounding plate  70 , pressing or the like method is used so that a strong drum grounding plate with high strength can be economically manufactured. 
     FIG. 10 is a top view of the drum grounding plate  70  as seen from the direction indicated by an arrow mark A 31  in FIG.  8 . 
     Referring to FIG. 9, the drum grounding plate  70  is a single piece of metallic plate formed by pressing or the like method as described above. It is constituted of a portion  701 , which is flat and substantially round, and a smaller portion  76 , which extends almost perpendicularly from the flat and round portion  701 . The flat and round portion  701  is provided with a hole  78 , through which the electrically conductive shaft  42   b  is put, and the slot  701   a . It is placed flatly in contact with the drum flange  50 . The perpendicular smaller portion  76  is provided with the elastic arm portion  75 , which is tilted toward the flat and round main portion  701   a  so that it makes contact with the electrically conductive shaft  42   b . The smaller portion  76 , substantially perpendicular to the flat and round main portion  701 , also makes contact with the rib  63  of the drum flange  50 , assuring that the elastic arm portion  75  of the drum grounding plate  70  generates a contact pressure of 50 g to 100 g. 
     With the above described arrangement, it is possible to provide the drum grounding plate  70  with a longer elastic arm portion  75 , which has a smaller constant of elasticity. 
     The drum grounding plate  70  is formed by pressing so that the fins are created on the side  330  indicated by an arrow mark  330 . Therefore, the drum grounding plate  70  makes contact with the inside surface  7   i  of the photosensitive drum  7 , by the finned side of the edge, assuring reliable contact. 
     FIG. 11 is side view of the drum grounding plate  70  as seen from the direction indicated by an arrow mark B 31  in FIG.  4 . 
     As the drum unit  7   b  is assembled into the structural frame of the process cartridge B, the elastic arm portion  75  for the first contact point  75   a  is pressed in the direction indicated by an arrow mark E by the electrically conductive shaft  42   b , being elastically bent from the position outlined by a double dot chain line  751  to the position outlined by the solid line  752 , causing the contact point  75   a  to come in contact with the electrically conductive shaft  42   b . The contact point  75   a , placed in contact with the electrically conductive shaft  42   b , is kept in contact with the shaft  42   b  by the resiliency of the elastic arm portion  75  while being allowed to slide on the peripheral surface of the shaft  42   b . When the elastic arm portion  75  is at the position outlined by the solid line  752 , the contact point  75   a  is at a position  75   a   2 , having been moved from a position  75   a   1  at which it was before the elastic arm portion  75  was pressed by the electrically conductive shaft  42   b . Thus, after the assembly, the contact point  75   a  remains in contact with the rotational center portion of the electrically conductive shaft  42   b , and yet, it is prevented from being easily worn by friction. 
     Structure of Clamping Plate  90   
     FIG. 12 is a front view of the clamping plate  90  as a means for clamping the drum flange  50  to the photosensitive member  7 . 
     The clamping plate  90  is a plate-like member formed of approximately 0.1 mm-0.5 mm thick plate of SUS (stainless steel), phosphor bronze, or the like material. go Here, an clamping plate  90  formed of 0.2 mm thick SUS304P will be described as an example. 
     In FIG. 12, referential characters  91   a - 91   h  are radial rectangular, cylinder clamping pawls of the clamping plate  90  as the second extensions. As the drum flange assembly  501  is inserted into the photosensitive drum  7  after the clamping plate  90  is attached to the drum flange  50 , the extensions  91   a - 91   h  come in contact with the inside surface  7   i  of the photosensitive drum  7 , and firmly anchor themselves to the inside surface  7   i . The extensions  91   a - 91   h  are tilted toward the bottom end surface  62  of the drum flange  50  so that it becomes easier for the clamping plate  90  to be inserted into the photosensitive drum  7 . Further, tilting the extensions  91   a - 91   h  as described above causes them to bite into the inside surface  7   i  of the photosensitive drum  7  as force applies to the clamping plate  90  in the direction to push the drum flange assembly  501  out of the photosensitive drum  7 . Therefore, the clamping plate  90  is prevented from easily coming out of the photosensitive drum  7 . The diameter D 901  (FIG. 13) of the circumcircle of the extensions  91   a - 91   h  is made to be 1.01-1.05 times the internal diameter D 707  (FIG. 19) of the photosensitive drum  7 , assuring that a sufficient amount of force is generated to cause the extensions  91   a - 91   h  to come in contact with the inside surface  7   i  of the photosensitive drum  7 , and anchor themselves to the inside surface  7   i.    
     The tip of each of the cylinder clamping pawls  91   a - 91   h  is shaped square, and makes contact with the inside surface  7   i  of the photosensitive drum  7  across its entire edge. In other words, the tip of each extension makes contact with the inside surface  7   i  of the photosensitive drum  7 , across the wide area of the surface  7   i , preventing thereby the cylinder from deteriorating in terms of circularity. Further, the extensions  91   a - 91   h  cause the coating on the inside surface  7   i  of the photosensitive drum  7  to be stripped across the wide area. 
     Referential characters  92   a - 92   h  designate the first rectangular, radial, drum flange clamping pawls of the clamping plate  90 . The extensions  92   a - 92   h  make contact with the inside surface  52   b  of the fitting portion  52  of the drum flange  50 . They are tilted in the direction opposite to the tilt of the cylinder clamping pawl  91   a - 91   h . This makes it easier for the clamping plate  90  to be inserted into the drum flange  50 , while making it difficult for the clamping plate  90  to come out of the drum flange  50 . 
     A reference character  93  designates a slot, which engages with the square boss  58  of the drum flange  50 ; engagement between the slot  93  and the boss  58  fixes the positional relationship between the drum flange  50  and the clamping plate  90  in terms of the rotational direction of the photosensitive drum  7 . This makes it possible to accurately align the cylinder clamping pawls  91   a - 91   h  with the through holes  55   a - 55   h  for the pressing tool  631 . Therefore, each cylinder clamping pawl  91   a - 91   h  can be pressed, on the precise spot, which will be described later. Further, the cylinder clamping pawl  91   a - 91   h  press themselves upon the inside surface  7   i  of the photosensitive drum  7  in a direction perpendicular to the inside surface  7   i , anchoring themselves to the photosensitive drum  7  with maximum effectiveness. 
     Reference characters  95   a - 95   h  designate holes for the thermally deformable bosses  54   a - 54   h . The holes  95   a - 95   h  are aligned in a circle with the same diameter as the circle in which the thermally deformable bosses  54   a - 54   h  are aligned, at the same pitch as the pitch at which the thermally deformable bosses  54   a - 54   h  are aligned. 
     FIG. 13 is a side view of the clamping plate  90  as seen from the direction indicated by an arrow mark A 41  in FIG.  12 . 
     As illustrated in FIG. 13, the cylinder clamping pawls  91   a - 91   h  and the drum flange clamping pawl  92   a - 92   h  are tilted in the opposite directions. When the clamping plate  90  is assembled onto the drum flange  50 , the clamping plate  90  is lined up so that the extensions  91   a - 91   h  tilt toward the circular inside surface  62  of the drum flange  50 . 
     A reference character  96  designates the flat portion of the clamping plate  90 . When the clamping plate  90  is assembled onto the drum flange  50 , this flat portion  96  is placed in contact with the flat portion of the drum grounding plate  70 , and then, the bosses  54   a - 54   h  are thermally deformed to retain the clamping plate  90 . The flat portion  96  minimizes the deformation of the drum grounding plate  70  which occurs when the drum flange assembly  501  is inserted into the photosensitive drum  7 . 
     FIG. 14 is a side view of the drum flange assembly  501 . 
     The drum flange assembly  501  is constituted of the drum flange  50 , which has been described so far, the drum grounding plate  70 , and the clamping plate  90 . 
     The clamping plate  90  is attached to drum flange  50  so that the extension  91   a - 91   h  tilt toward the circular inside surface  62  of the drum flange  50 . 
     Lining up the clamping plate  90  as described above makes it easier to insert the drum flange assembly  501  into the photosensitive drum  7 . 
     Internal Structure of Drum Flange Assembly  501   
     FIG. 15 is a sectional view of the drum flange assembly  501  illustrated in FIG.  14 . 
     The drum grounding plate  70  is attached to the drum flange  50  so that the bosses  54   a - 54   f  (unillustrated) are put through the holes  71   a - 71   f  (unillustrated) of the drum grounding plate  70 , one for one. Then, the clamping plate  90  is attached to the drum flange  50 , through the drum grounding plate  70 . 
     FIG. 16 is a drawing which depicts how the clamping plate  90  is attached to the drum flange  50 . 
     As depicted by FIG. 16, the clamping plate  90  is pressed into the drum flange  50  with the use of the pressing jig  521  after the drum grounding plate  70  is placed in the drum flange  50 . As for the pressing jig  521 , its diameter equals the diameter b 52  of the circle drawn by connecting the points at which the extensions  92   a - 92   h  are to be bent. The jig surface, which makes contact with the clamping plate  90  when pressing the clamping plate  90 , is flat. Therefore, the springiness of the extensions  92   a - 92   h  of the clamping plate  90  is not adversely effected as the clamping plate  90  is pressed into the drum flange  50 . The bosses  54   a - 54   h  fit into the holes  95   a - 95   h  of the clamping plate  90  as the clamping plate  90  is pressed into the drum flange  50 . 
     After the attachment of the clamping plate  90 , the bosses  54   a - 54   h  of the drum flange  50  are melted to permanently hold the drum grounding plate  70  and clamping plate  90  to the drum flange  50 , completing the drum flange assembly  501 . 
     The clamping plate  90  is attached to the drum flange  50  as described above. Then, the bosses  54   a - 54   h  of the drum flange  50  are melted, being positioned so that the cylinder clamping pawls  91   a - 91   h  are positioned on a line drawn through the midpoint between the adjacent two bosses and the center of the clamping plate  90 . 
     As the drum grounding plate  70  is placed in the drum flange  50  in the above described manner, the tilted portion  76  of the drum grounding plate  70  engages with the rib  63  of the drum flange  50 . More specifically, as the drum grounding plate  70  is placed in the drum flange  50 , the tilted portion  76  comes in contact with the electrically conductive shaft  42   b , and is pushed backward by the shaft  42   b , coming in contact with the rib  63 , while a certain amount of stress, or resilient pressure, is generated in the elastic arm portion  75 . In this state, the tilted arm portion  76  is supported by the lateral surface of the rib  63 . 
     FIG. 17 is a front view of the flange assembly  501 , that is, the completed flange assembly  501 , illustrated in FIG. 14, as seen from the side of bosses  54   a - 54   h.    
     As illustrated in FIG. 17, the eight bosses  54   a - 54   h  of the drum flange  50  are aligned in a circle at the base portions of the drum flange clamping pawls  92   a - 92   h , with the cylinder clamping pawls  91   a - 91   h  being positioned on a line drawn through the midpoint between the adjacent two bosses and the center of the clamping plate  90 . More specifically, the thermally deformable bosses  54   a - 54   h  are aligned in a circle so that any adjacent two bosses are symmetrically positioned relative to the center line of a corresponding clamping extension. For example, the bosses  92   a  and  92   h  are symmetrically positioned relative to the center line  91   o  of the clamping extension  91   h . Further, the bosses  54   a - 54   h  are aligned in a circle so that they do not align with extensions  91   a - 91   h  of the clamping plate  9  in the radial direction of the clamping plate  90 , while the adjacent two bosses are positioned symmetrically relative to the center line of the corresponding clamping extension. 
     Further, as depicted in FIG. 17, the springy arm portion  77   a  and  77   b  of the drum grounding plate  70 , which are positioned in symmetrically across the drum grounding plate  70 , are held to the drum flange  50  by thermally deforming the pair of bosses  54   b  and  54   c  and the pair of bosses  54   f  and  54   g . With this arrangement, the elastic arm portion  75  is firmly held down by the clamping plate  90 , and therefore, the tilted elastic arm portion  75  is prevented from being pulled in the left or right direction, even though a certain amount of stress is generated in the elastic arm portions  77   a  and  77   b  when the drum flange assembly  501  is inserted into the photosensitive drum  7 . Further, the contact point  75   a  of the drum grounding plate  70  makes contact with the center portion of the end of the electrically conductive shaft  42   b  (FIG.  4 ), and therefore, the wearing of the contact point  75   a  is minimized. Further, the flat portion  701  of the drum grounding plate  70  is firmly held to the drum flange  70  by the clamping plate  90 , being prevented from deforming, and therefore, it is assured that the elastic arm portion  75  reliably generates a pressure of 50 g-100 g. 
     Further, according to the present invention, the number of the bosses of the drum flange  50  is eight, or the most appropriate number, so that the stress generated in the drum grounding plate  70  when the cylinder clamping pawls  91   a - 91   h  are pressed is borne by the drum flange clamping pawls  92   a - 92   h , preventing thereby the bosses  54   a - 54   h  from being damaged. 
     In this embodiment, the drum flange  50  is provided with eight bosses  54   a - 54   h . However, it may be provided with only two bosses. In such a case, the two bosses are symmetrically positioned relative to the longitudinal central axis of the photosensitive drum  7 , and the clamping plate  90  is easily held to the drum flange  50  by melting the symmetrically positioned bosses. 
     FIG. 18 is a front view of the photosensitive drum  7 , in particular, the coated peripheral surface thereof. 
     In FIG. 18, a reference character  600  designates a hollow aluminum cylinder which constitutes the base member of the photosensitive drum  7 . The photosensitive layer is coated on the peripheral surface of this aluminum cylinder  600 . 
     A reference character  601  designates the photosensitive layer portion (image bearing portion) on the aluminum cylinder  600 , and reference characters  602  and  603  each designate a portion of the aluminum cylinder where the peripheral surface of the aluminum cylinder  600  is exposed. 
     One of the commonly used methods for coating the photosensitive drum  7  is as follows. The aluminum cylinder  600  is dipped in a pot (unillustrated) which contains a melted photosensitive layer material, so that the aluminum cylinder  600  is dipped as deep as a line  605  between the coated and uncoated areas illustrated in FIG.  18 . Then, the photosensitive material having adhered to the inside surface of the aluminum cylinder  600  is removed by solvent, a blade (unillustrated), or the like. 
     Next, the photosensitive material having adhered to the outside of the aluminum cylinder  600  is removed from the end portion opposite to the end portion covered with the photosensitive material, up to the line  606  between the portion  603  and the photosensitive layer portion  601 , by a blade or the like. 
     Hereinafter, a method for assembling the drum unit  7   b  will be described. 
     The order in which the drum unit  7   b  is assembled is as follows. First, the drum flange assembly  501  is inserted into the photosensitive drum  7  (FIG.  21 ). Next, the cylinder clamping pawls  91   a - 91   h  of the clamping plate  90  are bent toward the center of the photosensitive drum  7  with the use of a pressing tool  631 . 
     FIG. 19 is a drawing which shows the dimensional relationship between the drum flange assembly  501  and photosensitive drum  7 . 
     The dimensional relationship between the internal diameter D 707  of the photosensitive drum  7 , and the measurements of the flange assembly  501  to be pressed into the photosensitive drum  7 , is as follows. The external diameter D 501  of the portion  51  of the drum flange  50  is 1.0005-1.005 times the internal diameter D 707  of the photosensitive drum  7 , and the external diameter D 502  of the fitting portion  52  of the drum flange  50  is 0.999-1.002 times the internal diameter D 707  of the photosensitive drum  7 . The external diameter D 503  of the fitting guide portion  53  of the drum flange  50  is perfectly matched with the internal diameter D 707  of the photosensitive drum  7  so that the fitting guide portion  53  perfectly fits in the photosensitive drum  7 , that is, without any gap. 
     The fitting portion  52  of the drum flange  50  is provided with an edge  52   b , which is on the fitting guide portion  53  side of the drum flange  50  (FIG.  5 ). 
     The relationship among the external diameters D 501 , D 502  and D 503  of the fitting portions  51  and  52 , and fitting guide portion  53 , respectively, of the drum flange  50 , and the internal diameter D 707  of the photosensitive drum  7 , in terms of the central value within a tolerance range is: 
     
       
         D 501 &gt;D 502 &gt;D 707 &gt;D 503 .  
       
     
     Further, the external diameter D 501  of the portion  51  of the drum flange  50  is definitely larger in terms of the central value in the tolerance range than the internal diameter D 707  of the photosensitive drum  7 . 
     The external diameter D 503  of the fitting guide portion  53  is definitely smaller in terms of the central value in the tolerance range than the internal diameter D 707  of the photosensitive drum  7 . 
     The external diameter D 502  of the portion  52  is larger than the internal diameter D 707  of the photosensitive drum  7 , only in terms of the central value within the tolerance range. Thus, some gap may be present between the portion  52  and the inside surface of the photosensitive drum  7  after the insertion of the drum flange  50  into the photosensitive drum  7 . 
     FIG. 20 is a sectional view of the drum flange assembly  501  after its insertion into the photosensitive drum  7 . 
     In this embodiment, the drum flange assembly  502 , complete with clamping plate  90 , is inserted into the photosensitive drum  7 , on the side  602  where the aluminum cylinder is exposed. 
     As the drum flange assembly  501  is inserted into the photosensitive drum  7 , the insertion stopper  65  of the drum flange  50  functions to stop the insertion of the drum flange assembly  502 , accurately positioning the drum flange assembly  502  relative to the photosensitive drum  7  in terms of the longitudinal direction of the photosensitive drum  7 . 
     FIG. 21 is an explanatory drawing which depicts how the cylinder clamping pawls  91   a - 91   h  of the clamping plate  90  are inserted into the photosensitive drum  7  up to the predetermined positions with the use of the pressing tool  631 . 
     The pressing tool  631  presses the cylinder clamping pawls  91   a - 91   h  of the clamping plate  90 , on the pressure application points  99  located adjacent to the base portions of the extensions  91   a - 91   h , by its pressing prongs F 63 , until the extensions  91   a - 91   h  settle in the positions illustrated in FIG. 23, at which they are caused to firmly grip the photosensitive drum  7 . With the extensions  91   a - 91   h  settled in the positions illustrated in FIG. 23, the contact points  651  between the extensions  91   a - 91   h  and the photosensitive drum  7  are substantially the same as the location of the edge  52   a  of the fitting portion  52  of the drum flange  50 . As the cylinder clamping pawl  91   a - 91   h  are pressed inward the photosensitive drum  7 , the photosensitive material layer adhering to the inside surface of the photosensitive drum  7  is scraped away by them. 
     With the structure described above, the cylinder clamping pawls  91   a - 91   h  and the edge  52   a  of the fitting portion  52  of the drum flange  50  press upon the photosensitive drum  7  from inside, minimizing the loss of the circularity of the photosensitive drum  7  caused by the cylinder clamping pawls  91   a - 91   h.    
     Further, the extensions  92   a - 92   h  are tilted toward the longitudinal center (inward) of the photosensitive drum  7  relative to the inside surface  52   b  of the fitting portion  52 . Therefore, pressing UA the cylinder clamping pawls  91   a - 91   h  causes the drum clamping pawls  92   a - 92   h  to push the fitting portion  52  in the radially outward direction, creating the synergistic effect of preventing the circularity of the photosensitive drum  7  from being adversely affected. 
     Further, the extensions  91   a - 91   h  tilt outward of the photosensitive drum  7 , that is, in the direction opposite to the extensions  92   a - 92   h , in terms of the longitudinal direction of the photosensitive drum  7 . Therefore, the synergistic effect is created also in terms of their resilient force generated by being elastically deformed, increasing the force with which the extensions  91   a - 91   h  grip the photosensitive drum  7 . In other words, the above described structure improves reliability. 
     FIG. 22 is a view of the drum flange assembly  501  as seen from the inward side of the photosensitive drum  7 . 
     In FIG. 22, the pressing points  99  of the cylinder clamping pawls  91   a - 91   h  of the clamping pate  90 , which are pressed by the pressing tool  631 , are illustrated as if they are on the same plane as the plane of this drawing. The pressing prongs F 63  of the pressing tool  631  press the back side (in this drawing) of the clamping plate  90  toward the longitudinal center of the photosensitive drum  7 . The pressing points  99  are located at the approximate centers of the extensions  91   a - 91   h  in terms of the radial direction of the clamping plate  90 , and outward of the circles drawn through the bosses  54   a - 54   h , in terms of the radial direction of the clamping plate  90 . 
     With the above arrangement, the extensions  91   a - 91   h  can be bent perpendicularly to the direction in which they are inserted. Therefore, the photosensitive drum  7  is better in circularity, and the drum flange assembly  501  is more reliably clamped to the photosensitive drum  7 . 
     Further, as the clamping plate  90  is pressed by the pressing tool  631 , on the pressing points  99 , the cylinder clamping pawls  91   a - 91   h  are bent at points  91   a   2 - 91   h   2  (FIG. 23) which are adjacent to the original bent points  91   a   1 - 91   h   1  (FIG.  21 ). 
     FIG. 23 is a sectional view of the drum flange assembly  501  after its insertion into the photosensitive drum  7 . 
     The cylinder clamping pawls  91   a - 91   h  of the clamping plate  90  contact the inside surface  7   i  of the photosensitive drum  7 , at the points  651 , being bent as illustrated in FIG.  23 . These points  651  correspond to the border line  606  between the portion  603  where the aluminum cylinder is exposed, and the photosensitive layer portion, on the outer surface of the photosensitive drum  7 . At these points  651 , the circularity of the photosensitive drum  7  is not a serious concern. Therefore, the drum unit  7   b  is improved in yield. In other words, productivity is improved along with quality. 
     FIG. 24 is a side view of the assembled drum unit  7   b . It depicts the relationship between the clamping plate  90  and drum grounding plate  70 . More specifically, it is a transparent view of the assembled drum unit  7   b , and shows the state of the drum flange assembly  501  in the completed drum unit  7   b , through the photosensitive drum  7 . 
     As the pressing tool  631  illustrated in FIG. 21 is pressed, the cylinder clamping pawls  91   a - 91   h  of the clamping plate  90  come in contact with the inside surface  7   i  of the photosensitive drum  7 , and wedge themselves against the inside surface  7   i , on the spots away from the contact points  73   a  and  73   b  of the drum grounding plate  70 . 
     FIG. 25 is an enlarged view of the portions of the clamping plate  90  and drum grounding plate  70 , and shows in detail the relationship between the clamping plate  90  and drum grounding plate  70  illustrated in FIG. 24, in particular, the portions designated by a reference character K 66  in FIG.  24 . It depicts the contact points  73   a  and  73   b  of the drum grounding plate  70 , and the cylinder clamping pawls  91   a - 91   h  of the clamping plate  90 . 
     Referring to FIG. 12, the cylinder clamping pawls  91   a - 91   h  of the clamping plate  90  have a square tip. Further, the clamping plate  90  is formed of electrically conductive material, and therefore, the square edge portions  911  of the tips of the extensions  91   a - 91   h  further assure reliability in terms of electrical conductivity. Also, as the clamping plate  90  is pressed, the distance between the edge portions  911  of the extensions  91   a - 91   h  and the contact points  73   a  and  73   b  of the drum grounding plate  70  increases, increasing thereby the size of the contact area. Therefore, the reliability of the electrical contact points is drastically improved. In addition, the extensions  91   a - 91   h  reliably bite into the inside surface of the photosensitive drum  7 , further improving electrical conductivity. The area  911   a  covered with diagonal lines is the area from which the photosensitive material layer adhering to the inside surface  7   i  of the photosensitive drum  7  has been scraped away by the cylinder clamping pawls  91   a - 91   h  of the clamping plate  90 . 
     FIG. 26 shows the deterioration of the circularity of the photosensitive drum  7  when the flange  501  does not have the clamping pawls  92   a - 92   h  and the engaging portion  52 . The thickness of the cylinder wall is 1 mm. 
     In FIG. 26, the contact portion between the photosensitive drum  7  and the pawls  91   a - 91   h  of the clamping plate  90  is indicated by a chain line. As will be understood from the figure, the outer surface is not smooth, and the circularity is 14.9 μm. 
     FIG. 27 shows the circularity of the photosensitive drum  7  using the drum flange  501  according to this embodiment. (a) shows the outer diameter circularity of the photosensitive drum at the position where the pawl  92   a - 92   h  of the clamping plate  9  contacts to the photosensitive drum  7 , and (b) shows the outer diameter circularity of the photosensitive drum  7  at the position approximately 3 mm away from the position where the pawls  92   a - 92   h  of the clamping plate  90  contacts to the photosensitive drum. 
     In (a) of FIG. 27, chain line indicates the contact portion between the clamping plate  90  of the photosensitive drum and the pawls  91   a - 91   h . As will be understood from the figure, the outer surface of the photosensitive drum  7  is smooth, and the circularity is 10.4 μm because of the provision of the engaging portion  52  of the body  50  of the flange and the pawls  92   a - 92   h  of the clamping plate  90 . 
     In (b) of FIG. 27, chain line indicates the contact portion between the clamping plate  90  of the photosensitive drum and the pawls  91   a - 91   h . As will be understood from the figure, the influence of the pawls  91   a - 91   h  of the clamping plate  90  is removed, and the circularity is 8.8 μm. 
     Although not shown here, the contact position of the pawls  91   a - 91   h  of the clamping plate  90  to the photosensitive drum  7  is between an abutment reference position for a spacer for maintaining a gap between the photosensitive drum  7  and the developing roller(developing means)  10   c  and a printing region (photosensitive layer portion  601  of the aluminum cylinder  600 , as described above), and is away from the abutment reference position by not less than 3 mm, and is away from the printing region by not less than 15 mm. 
     By doing so, the yield of the drum unit  7   b  is raised, and the image quality of the formed image is improved, so that quality and productivity of the drum unit  7   b  is improved. 
     (Another Embodiment of the Drum Flange) 
     FIG. 28 is a front view of an above-described drum flange  501  according to another embodiment of the present invention, and FIG. 29 a side view of a drum flange shown in FIG.  28 . 
     In FIGS. 28 and 29, designated by  801  is an electroconductive clamping plate of stainless steel, Sphosphor bronze or the like having a structure similar to that of the clamping plate  90 ;  802  is a body of the drum flange press-fitted into the end of the photosensitive drum  7 ;  803  is an electroconductive center shaft of SUS (stainless steel) or the like unified with the body  802  of the drum flange by insertion molding or the like;  804  is a radial pawl-as a third pawl radially extended from the clamping plate  801  toward the inside of the circle. The flange  800  of this embodiment, similarly to the drum flange  501  of the above-described embodiment, assuredly contacts the inner wall  7   i  of the photosensitive drum  7 , by the cylinder clamping pawls  801   a - 801   h  of the clamping plate  801 , by way of the conduction shaft  803  from the ground portion of the main assembly of the printer (not shown), which is contacted to the electroconductive center shaft  803 . 
     By this, there is no need to provide a grounding plate  70  as in the drum flange  501  of the above-described embodiment, so that number of parts is reduced, and the assembling property is improved with cost reduction and improved quality. 
     (Another Embodiment of Clamping Plate) 
     FIG. 30 is a front view of a clamping plate  90  according to another embodiment of the present invention. 
     In this embodiment, the clamping plate  901  is of electroconductive material such as bronze, stainless steel or the like. The structure is the same as with the clamping plate  901  of the above-described embodiment except that grounding contact  902  is constituted by a center portion of the engaging hole  901   a  of the conduction shaft  42   b . In this figure, designated by  902   a - 902   h  are cylinder clamping pawls; and  903   a - 903   h  are flange clamping pawls. 
     With such structure, similar to the drum flange  501  of the above-described embodiment, there is no need to provide the drum grounding plate  70 , so that so that number of parts of the drum flange  501  is reduced, and the assembling property is improved with a cost reduction and improved quality. 
     As described in the foregoing, according to this embodiment, each of the pawls  91   a - 91   h  of the clamping plate  90 , secured to the fixing of the engaging portion  51  of the body  50 , is provided with bent portion  91   a   2 - 91   h   2  elastically bent toward the longitudinally central portion (inside) of the photosensitive drum  7 , and bites into the inner surface of the wall of the photosensitive drum  7 . Additionally, it urges the body  50  of the flange toward the longitudinally central portion of the photosensitive drum  7 . By this, the connection force between the body  50  of the flange and the photosensitive drum  7  is made firmer, thus improving the quality of the drum unit  7   b.    
     By limiting the diameter D 901  of the circumscribed circle of the pawls  91   a - 91   h  of the clamping plate  90  such that lengths of the pawls  91   a - 91   h  are within the range of 1.01-1.05 times the inner diameter D 707  of the photosensitive drum  7 , the productivity of the clamping plate  90  is improved, and the connection strength relative to the photosensitive drum  7  is assured, and therefore, the quality of the drum unit  7   b  and the productivity are improved. 
     By provision of through-holes  55   a - 55   h  in the circular disk surface  62  of the body  50 , corresponding to the pawls  91   a - 91   h  of the clamping plate  90 , it can be inspected whether the pawls  91   a - 91   h  of the clamping plate  90  are bent assuredly, that is, whether the connection with the photosensitive drum  7  is satisfactory, so that the quality of the drum unit  7   b  can be improved. 
     By using eight pawls  91   a - 91   h  in the clamping plate  90 , the expansion in the radially outward direction can be distributed properly, so that circularity of the photosensitive drum  7  is improved, and therefore, the image quality of the formed image and the quality of the drum unit  7   b  are improved. 
     By using a tool  631  through through-holes  55   a - 55   h  formed in the circular disk surface  62  of the body  50  of the drum flange, the pawls  91   a - 91   h  of the clamping plate  90  can be assuredly and easily bent, and therefore, the mass-productivity and the quality of the drum unit  7   b  can be improved. 
     The body  50  of the drum flange is made of resin material having a low melting point, and the clamping plate  90  is made of a material having a high melting point such as stainless steel, phosphor bronze or the like. At least two bosses  54   a - 54   h  provided in the body  50  of the drum flange are engaged in the holes  95   a - 95   h  of the clamping plate  90 , and are melted and solidified. Because of these features, the clamping plate  90  can be easily fastened relative to the body  50  of the drum flange, and the mass-productivity and a cost reduction of the drum flange  501  can be accomplished. 
     At least two bosses  54   a - 54   h  of the body  50  of the drum flange are disposed at a line symmetrical position, that is, equidistant from the center line  91   o  of the pawls  91   a - 91   h , respectively, by which twisting of the pawl  91   a - 91   h  upon elastic deformation can be suppressed, and the connection relative to the photosensitive drum  7  can be stabilized, and therefore, the quality of the drum unit  7   b  can be improved. 
     At least two bosses  54   a - 54   h  of the body  50  of the drum flange are disposed outside the width of the pawl  91   a - 91   h  of the clamping plate  90 , and are opposed to the center line  91   o  of the pawls  91   a - 91   h , by which the twisting of the pawls  91   a - 91   h  upon the elastic deformation can be further suppressed, and the connection relative to the photosensitive drum  7  is further stabilized, and therefore, the quality of the drum unit  7   b  can be improved. 
     By using not less than  8  bosses  54   a - 54   h , the connection of the pawl  91   a - 91   h  of the clamping plate  90  relative to the photosensitive drum  7  is stabilized, and the mass-productivity and the quality of the drum unit  7   b  is improved, and cost reduction is accomplished. 
     The engaging portion  51  of the body  50  of the flange is provided with an engaging portion  52 , and is provided with cut-away portions  60   a - 60   h  for contacting the pawls  91   a - 91   h  of the clamping plate  90  to the inner wall  7   i  of the photosensitive drum  7 , and the pawls  91   a - 91   h  of the clamping plate  90  are mounted to the inner wall  7   i  of the photosensitive drum  7  at a position of the edge portion  52   a  of the engaging portion  52  of the body  50  of the drum flange. By this, the pawls  91   a - 91   h  and the engaging portion  52  are pressed to the photosensitive drum  7 . Therefore, the pressing force applies uniformly to the photosensitive drum  7 , so that deterioration of the circularity of the photosensitive drum  7  is suppressed, and the image quality of the formed image and the quality of the drum unit  7   b  are improved. 
     The outer diameter D 501 , D 502  of the engaging portion  51  and the engaging portion  52  of the body  50  of the flange is within the range of 0.999 times-1.005 times of the inner diameter D 707  of the photosensitive drum  7 , so that mass-productivity property of the drum unit  7   b  and the quality of the drum unit  7   b  can be improved. 
     The pawls  92   a - 92   h  of the clamping plate  90  are bent toward the central portion (inside) to contacts the inner wall  52   b  of the engaging portion  52  of the body  50  of the flange, and the pawls  91   a - 91   h  of the clamping plate  90  are pressed toward the center side of the photosensitive drum  7 . By doing so, the pawls  92   a - 92   h  press against the inner wall  7   i  of the photosensitive drum  7  through the inner wall  52   b  of the engaging portion  52 . Thus, the connecting force between the drum flange  501  and the photosensitive drum  7  are further improved, and the deformation of the clamping plate  90  per se by the pawls  91   a - 91   h , can be suppressed, the deterioration of the circularity of the photosensitive drum  7  can be further suppressed, and the quality of the drum unit  7   b  and the image quality can be further improved. 
     The pawls  92   a - 92   h  of the clamping plate  9  are disposed adjacent the at least two bosses  54   a - 54   h  of the body  50  of the flange. By doing so, the force in the direction of urging the pawls  91   a - 91   h  toward the longitudinally inside of the photosensitive drum  7  (inside), is received by the pawls  92   a - 92   h . Therefore, the load applied on the at least two bosses  54   a - 54   h  of the body  50  of the flange can be reduced, so that the heat crimp boss is not easily broken, and therefore, the mass-productivity property of the drum unit  7   b  and the quality of the drum unit  7   b  can be improved. 
     By using  8  pawls  92   a - 92   h  for the clamping plate  90 , the number of the pawls  91   a - 91   h  which directly urge the photosensitive drum  7 , and the number of the pawls  92   a - 92   h  which urge the photosensitive drum  7  through the inner wall  52   b  of the engaging portion  52  of the body  50  of the flange, can be increased. Therefore, the circularity of the photosensitive drum  7  can be improved, and the number of the bosses  54   a - 54   h  of the engaging portion  52  of the body  50  of the flange can be minimized, so that the connection with the photosensitive drum  7  can be stabilized, and the drum-unit mass-productivity and the quality of the drum unit  7   b  are improved, and the cost reduction can be accomplished. 
     The center portions (widthwise) of the pawls  91   a - 91   h  of the clamping plate  90  are deformed and bent toward the longitudinally inside (inside) of the photosensitive drum  7  by bosses  54   a - 54   h  of the body  50  of the flange, using a tool  631 . By this, the pawls  91   a - 91   h  are easily deformed elastically without twisting, and therefore, the drum-unit mass-productivity and quality are improved. 
     The contact portions between the drum and the pawls  91   a - 91   h  of the clamping plate  90 , which may cause the circularity of the photosensitive drum  7  to deteriorate, are disposed adjacent the coating boundary portion  606  between the image carrying portion  601  and the metal exposed portion  603 , which does not require high accuracy. Therefore, a cause of deterioration of the circularity of the photosensitive drum  7  can be avoided, and the drum-unit mass-productivity and quality can be improved, and the image quality of the formed image can be improved. 
     The contact portions between the clamping plate  90  and the cylinder clamping pawl  91   a - 91   h , which may cause the circularity of the photosensitive drum  7  to deteriorate, are sufficiently away from the abutment portion, which is a contact reference between the image region(printing region  601 ) of the photosensitive drum  7  and the developing roller  10   c , by which the quality of the drum unit  7   b  and the image quality of the formed image can be improved. 
     As described with respect to another embodiment of the drum flange, when the body  802  of the flange is integrally formed with the electroconductive center shaft  803 , the clamping plate  801  is made electroconductive. By doing so, the grounding plate is not required, and a sufficient connection force and assured electroconduction can be accomplished, so that assembling operativity, product quality and the mass-productivity are improved. 
     By using an electroconductive material as the material of the clamping plate  90 , electroconduction with the conduction shaft  42   b  is improved, and the quality of the drum unit  7   b  is improved. 
     By using a stainless steel plate, and phosphor bronze, which are readily available, as the material of the clamping plate  90 , a drum unit  7   b  which is inexpensive, highly reliable, and which has high quality, can be provided. 
     [Other Embodiments]. 
     In the foregoing embodiments, a description has been provided with respect to the drum flange used for the electrophotographic photosensitive member as a cylindrical member, but the drum flange of the present invention is preferably usable for a developing roller of a developing means wherein the circularity is improved. Therefore, the cylindrical member in the present invention includes a developing roller as well as the photosensitive drum. 
     Further, the process cartridge B in the first embodiment was of a type which formed a monochromatic image. However, the present invention is preferably applicable not only to a process cartridge which forms a monochromatic image, but also to a process cartridge which comprises multiple developing means and forms a multi-color image (for example, two-color image, three-color image, or full-color image). 
     Also, the electrophotographic photosensitive member is not limited to the photosensitive drum alone. For example, the following may be included. First, as for the photosensitive material, photoconductive material such as amorphous silicon, amorphous selenium, zinc oxide, titanium oxide, or organic photoconductive material may be included. As for the configuration of the base on which the photosensitive material is coated, a rotary configuration, such as a drum shape, or a flat configuration, such as a belt shape, may be included. 
     Also, the present invention is preferably usable with various known developing methods such as the magnetic brush developing method using two component toner, the cascade developing method, the touch-down developing method, the cloud developing method. 
     The structure of the charging means has been described as a contact charging method, but a conventional structure is usable wherein a tungsten wire is enclosed by a metal shield of a material such as aluminum at three sides, and a high voltage is applied to the tungsten wire to generate positive or negative ions, which are sent to the surface of the photosensitive drum, thus uniformly charging the surface of the drum. 
     Further, the charging means may be of a blade type (charge blade), a pad type, a block type, a rod type, or a wire type, in addition to the aforementioned roller type. 
     The means for cleaning the toner remaining on the photosensitive drum may be of a blade type, a fur brush type, a magnetic brush type, or the like. 
     The process cartridge may be the one containing the electrophotographic photosensitive member, the developing means and at least one of process means for example. Therefore, the process cartridge may be the ones disclosed as the embodiment, the one containing the electrophotographic photosensitive member, the developing means and the charging means as a unit which is detachably mountable relative to the image forming apparatus, the one containing the electrophotographic photosensitive member, the developing means, and the cleaning means as a unit, which is detachably mountable relative to the image forming apparatus, or the one containing the electrophotographic photosensitive member and the developing means, as a unit, which is detachably mountable relative to the image forming apparatus, for example. 
     In the description of the embodiments, the laser beam printer is discussed, but the present invention is not limited to this, and is usable with an electrophotographic copying machine, a facsimile machine, a word processor, or another electrophotographic image forming apparatus. 
     As described in the foregoing, according to the present invention, there is provided a drum flange having a plurality of pawls in the form of elastic plate members fixed to a press-fitting engagement portion of the body, and each of the pawls is elastically deformed toward a longitudinally central portion (inside) of the cylindrical member to form bent portions, which bite in the inner wall of the cylindrical member. By this, the body of the flange is urged toward the center side in the longitudinal direction of the cylindrical member, so that the connecting force between the flange body and the cylindrical member are made firmer. According to the cylindrical member of the embodiments of the present invention, there is provided a flange having a plurality of pawls in the form of an elastic plate members fixed to a press-fitting engagement portion of the body, and each of the pawls is elastically deformed toward a longitudinally central portion (inside) of the cylindrical member to form bent portions, which bite in the inner wall of the cylindrical member By this, the body of the flange is urged toward the center side in the longitudinal direction of the cylindrical member, so that the connecting force between the flange body and the cylindrical member is firm enough to survive high speed rotation, and a long service life. 
     For process cartridge having a drum flange of an electrophotographic photosensitive drum supported on a cartridge frame, there is provided a drum flange having a plurality of pawls in the form of elastic plate members fixed to a press-fitting engagement portion of the body, and each of the pawls is elastically deformed toward a longitudinally central portion (inside) of the electrophotographic photosensitive member to form bent portions, which bite in the inner wall of the electrophotographic photosensitive member. By this, the body of the flange is urged toward the center side in the longitudinal direction of the electrophotographic photosensitive drum, so that the connecting force between the flange body and the electrophotographic photosensitive drum is firm enough to survive high speed rotation, and a long service life. 
     As described in the foregoing, according to the present invention, the flange can be clamped to a cylindrical member assuredly. 
     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.