Patent Publication Number: US-6212343-B1

Title: Developing device, process cartridge and image forming apparatus that prevent toner leakage

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a developing device, a process cartridge in which a developing device and a photoconductor unit are integrated, and an image forming apparatus, and more particularly relates to an improved mechanism to prevent toner from leaking out of the developing device. 
     2. Discussion of the Background 
     There is known a developing device for developing an electrostatic latent image formed on a photoconductor in which a developing roller to supply toner to the photoconductor and a blade contacting a surface of the developing roller are mounted to a developing case containing toner therein. In such a developing device, the blade restricts the thickness of toner adhering to the developing roller. When single-component toner is used, the blade is pressed to contact the developing roller such that toner passing between the blade and the developing roller is charged by friction. When the blade is made of an elastically deformable metal plate the blade is fixed to the developing case and is pressed to the developing roller while being bent. In this case, because the rigidity of the blade is low, the blade is sandwiched between a blade holder with high rigidity and a supporting member so as to be laminated with each other, and the laminated blade, blade holder and supporting member are attached to the developing case. 
     If the developing device as described above is dropped during transportation, the developing roller and the blade vibrate and thereby toner intrudes into a gap between the backside of the blade and a blade attaching surface of the developing case and leaks out of the developing case. To prevent such leakage of toner, an opening of the developing case is sealed by a tape, which is peeled off when the developing device is used. This method of sealing an opening of a developing case with a tape requires an operation of taking off the seal when attaching the developing case to an image forming apparatus, which is troublesome. 
     In order to attach a blade made of a metal plate to a developing case, while laminating the blade with a long blade holder having high rigidity, a blade attaching surface corresponding to the long blade holder must be formed in the developing case. It is hard to form a blade attaching surface having a length corresponding to the long blade holder in a precise manner in the developing case. Generally, the blade attaching surface is formed partly uneven in the longitudinal direction and thereby the blade holder bends in the longitudinal direction together with the blade. Because of this bending of the blade holder and the blade, a contact line between the blade and the developing roller deviates from a line parallel to an axial line of the developing roller and thereby the contact pressure of the blade against the developing roller becomes uneven, causing an undesirable effect on the quality of a resulting image. 
     It may be conceivable to form protruding blade attaching surfaces in the vicinity of both ends of the developing case so as to support both ends of the blade holder, together with the blade, with the protruding blade attaching surfaces. However, the airtightness between the blade holder and the developing case is lost at the center part of the developing case, i.e., at a part between the blade attaching surfaces at both side ends of the developing case, and thereby toner tends to leak therefrom. 
     When a developing device is configured such that the amount of toner adhering to a developing roller is restricted by a blade, a roller part of the developing roller is disposed at a toner exit formed in a developing case and axial parts of the developing roller protruding from both ends of the roller part respectively are rotatably supported by supporting walls formed at both sides of the developing case. A lower edge of the blade contacts the roller part of the developing roller such that the blade seals a gap between an upper edge of the toner exit and an upper outer circumferential surface of the developing roller. Further, in order to prevent leakage of toner through a gap between an outer circumferential surface of the developing roller and the toner exit, side seals are provided at both longitudinal ends of the toner exit so as to contact outer circumferential surfaces of both ends of the roller part of the developing roller and an exit seal is provided at a flat surface of the developing case, which is formed in the developing case extending from a lower edge of the toner exit toward a photoconductor, so as to elastically contact the roller part of the developing roller. 
     In order to decrease the load to the developing roller when the developing roller is driven, the exit seal is generally formed with a thin plastic sheet having low compressibility and is configured such that a part of the exit seal is supported by the flat surface of the developing case and a free end part of the exit seal extending toward the toner exit from the flat surface is pressed against the outer circumferential surface of the developing roller by its own elasticity. The exit seal is generally stuck to the flat surface of the developing case by double-sided adhesive tape. 
     As described above, because the exit seal contacts the developing roller by its own elasticity and the part of the exit seal stuck to the flat surface of the developing case does not contact the developing roller, both ends of the exit seal tend to be peeled off. If both ends of the exit seal peel off, toner intruded under the exit seal intrudes toward both ends of the exit seal and may leak through a gap between the inner surfaces of the supporting walls formed at both sides of the developing case and the ends of the exit seal. 
     Further, in order to prevent leakage of toner through a gap between the outer circumferential surface of the developing roller and the toner exit, it is practiced that a free end side of an exit seal attached to a lower part of a developing case elastically contacts a lower outer circumferential surface of the developing roller and outer circumferential surfaces of both ends of a roller part of the developing roller are supported by side seals disposed at both longitudinal ends of the toner exit of the developing case. 
     When a blade is formed with a thin metal plate having elasticity and is configured such that the blade is bent by a developing roller so as to contact the developing roller by its reacting force when the blade is assembled in the developing device, as described above, the axial center of the developing roller is determined by a bearing of a developing case. In the above configuration, in order to bend the metal blade by pressure of the developing roller, the blade must be shorter than the interval between inner surfaces of side seals arranged at both sides of the developing roller. If the blade is made shorter than the interval between the inner surfaces of the side seals, a gap is generated between both ends of the blade and both inner surfaces of a toner exit, causing leakage of toner through the gap. If the blade is made longer than the interval between the inner surfaces of the side seals, the blade contacts the side seals due to pressure of the developing roller and thereby the blade cannot be bent any further. Such loss in the freedom of bending in the blade causes deformation of the blade and inferior sealing of a gap between the roller part of the developing roller and the side seals. 
     A known developing device includes a stirring device to stir toner in a developing case, a developing roller and a toner supplying roller to supply toner to the developing roller. In such a developing device, in order to transmit power to the toner stirring device and the toner supplying roller from the outside, rotation axes of these rotating devices protrude from a side wall of the developing case and gears are provided to ends of the protruded axes respectively to transmit rotation power to the axes. 
     In such a developing device, if sealing around the rotation axes of the stirring device and the toner supplying roller is insufficient, toner tends to leak out of the developing case around the rotation axes when the developing device falls and is shocked. The sealing effect around the rotation axes may be sufficiently increased by arranging a seal member having a rubber lip at respective inner circumferential parts of ring-shaped metal bearings supporting the rotation axes. However, the seal member having such a configuration is expensive and therefore increases the cost of a developing device using the sealing member. 
     In an image forming apparatus such as a copying machine or printer, it is widely practiced that a photoconductor unit, in which a photoconductor and a used toner collecting device to collect residual toner on an outer circumferential surface of the photoconductor are assembled in a body, and a developing device, in which a developing roller is provided to a developing case, are assembled to a unit known as a process cartridge. 
     FIGS. 19 and 20 illustrate an example of such a photoconductor unit. FIG. 19 is a side vertical cross section of a photoconductor unit  200 . A photoconductor  9  is rotatably supported by the photoconductor unit  200  and a used toner collecting part  101  to collect used toner remaining on an outer circumferential surface of the photoconductor  9  is formed in the photoconductor unit  200 . 
     FIG. 20 is a front view of the photoconductor unit  200  when the photoconductor  9  is removed. A collecting inlet  102  is formed in the used toner collecting part  101  at a position near an outer circumferential surface of the photoconductor  9 . The collecting inlet  102  is formed in a long and narrow rectangular shape extending substantially over the entire length of the photoconductor  9 . Side seals  103  formed with a teflon felt or the like are stuck at edges of both longitudinal sides of the collecting inlet  102 . The side seals  103  slidably contact outer circumferential surfaces of both ends of the photoconductor  9 . 
     A long blade  104  that scrapes off residual used toner on an outer circumferential surface of the photoconductor  9  is fixed to one longitudinal edge of the collecting inlet  102  and a long inlet seal  105  is stuck to the other longitudinal edge of the collecting inlet  102 . The inlet seal  105  slidably contacts an outer circumferential surface of the photoconductor  9  so as to prevent used toner scraped off by the blade  104  from leaking through the collecting inlet  102 . Both longitudinal ends of the inlet seal  105  contact the side seals  103  by pressure respectively. 
     The photoconductor  9  rotates in a direction indicated by an arrow in FIG.  19  and an electrostatic latent image is formed on an outer circumferential surface of the photoconductor  9  by exposure with a latent image forming part (not shown). The latent image is developed to a visible toner image with toner supplied by a developing roller (not shown), and the toner image is then transferred to a transfer sheet (not shown) at a transfer position. When the toner image is transferred to the transfer sheet, a part of the toner of the toner image is not transferred to the transfer sheet and remains on the outer circumferential surface of the photoconductor  9  as residual used toner. The residual toner is scraped off the outer circumferential surface of the photoconductor  9  with the blade  104  and is collected to the used toner collecting part  101 . When collecting used toner, the inlet seal  105  slidably contacts the outer circumferential surface of the photoconductor  9  and thereby leakage of the collected used toner from the collecting inlet  102  is prevented. Also, leakage of toner from both sides of the inlet seal  105  is prevented by bringing both longitudinal ends of the inlet seal  105  into contact with the side seals  103  by pressure. 
     However, when the photoconductor  9  is rotated in the direction of the arrow in FIG. 19, a pulling force is applied to the inlet seal  105 , which is slidably contacting the outer circumferential surface of the photoconductor  9 , in the rotation direction of the photoconductor  9 . The pulling force acts on both longitudinal ends of the inlet seal  105  in a direction to peel off the inlet seal  105  and thereby both ends of the inlet seal  105  are moved toward the center of the inlet seal  105  and thereby a part of the inlet seal  105  slidably contacting the outer circumferential surface of the photoconductor  9  waves. Because of this waving, a gap is created between the inlet seal  105  and the outer circumferential surface of the photoconductor  9  and collected used toner leaks through the gap. 
     Further, if a gap is created between the inlet seal  105  and the side seals  103 , which are overlaid with each other, as a result of the both end parts of the inlet seal  105  being pulled toward the center of the inlet seal  105  as described above, collected used toner intrudes into the gap and the intruded toner leaks from the sides of the inlet seals  105 . 
     SUMMARY OF THF INVENTION 
     The present invention has been made in view of the above-discussed and other problems and addresses and resolves the above-discussed and other problems. A preferred embodiment of the present invention provides a novel developing device, a novel process cartridge using the developing device and a novel image forming apparatus using the developing device or the process cartridge, in which leakage of toner from a developing case of the developing device is prevented without having inconvenience of taking off a tape sealing an opening of the developing case when using the developing device or the process cartridge. 
     Another preferred embodiment of the present invention provides a novel developing device, a novel process cartridge using the developing device and a novel image forming apparatus using the developing device or the process cartridge, in which a blade can be disposed so as to contact a developing roller straight, leakage of toner due to a drop of the developing device or the process cartridge is prevented, and inconvenience of taking off a tape sealing an opening of a developing case of the developing device is avoided. 
     Further, another preferred embodiment of the present invention provides a novel developing device, a novel process cartridge using the developing device and a novel image forming apparatus using the developing device or the process cartridge, in which leakage of toner from both sides of an exit seal of a developing case of the developing device is prevented. 
     Another preferred embodiment of the present invention provides a novel developing device, a novel process cartridge using the developing device and a novel image forming apparatus using the developing device or the process cartridge, in which leakage of toner from both sides of a developing roller and a blade is prevented. 
     Furthermore, another preferred embodiment of the present invention provides a novel developing device and a novel process cartridge using the developing device and a novel image forming apparatus using the developing device or the process cartridge with an inexpensive and simple configuration, in which toner is prevented from leaking out of a developing case of the developing device, at a part where rotation axes of a toner stirring device and a toner supplying roller provided in the developing case of the developing device pass through a side wall of the developing case, from around the rotation axes, and in which, even when toner leaks from around the rotation axes toward the outside of the developing case, scattering of the toner is prevented. 
     Another embodiment of the present invention provides a novel photoconductor unit, a novel process cartridge using the developing device and a novel image forming apparatus using the developing device or the photoconductor unit, in which, when residual toner on an outer circumferential surface of a photoconductor is collected to a used toner collecting part, leakage of the collected used toner is prevented. 
     According to an embodiment of the present invention, in a developing device, a developing roller opposed to a photoconductor is rotatably mounted to a developing case of the developing device. A blade mounting surface is formed in an outer wall of the developing case, that is opposed to the photoconductor, and a blade holder, a blade and a supporting plate, that are laminated with each other, are mounted to the blade mounting surface of the developing case. A part of the blade opposite to a part of the blade sandwiched between the blade holder and the supporting member is elastically bent so as to contact an outer circumferential surface of the developing roller, and seal members are arranged at least along an edge of a longitudinal side of the blade holder at the side of the developing roller and along an edge of another longitudinal side of the blade holder at the opposite side of the developing roller, respectively, so as to increase airtightness of gaps between the blade holder and the outer wall of the developing case. 
     The seal members may be made longer than a longitudinal length of the blade holder, so that both longitudinal ends of the seal members are bent along sides of both ends of the blade holder, respectively. 
     According to another embodiment of the present invention, in a developing device, blade mounting surfaces and a recessed surface are formed in an outer wall of the developing case, that is opposed to the photoconductor, in vicinity of both longitudinal ends and at a center part of the outer wall, respectively, and a surface of the recessed surface is recessed from surfaces of the blade mounting surfaces. A blade holder, a blade and a supporting plate, that are laminated with each other, are mounted to the blade mounting surfaces, and a part of the blade opposite to a part of the blade sandwiched between the blade holder and the supporting member is elastically bent so as to contact an outer circumferential surface of the developing roller. Seal members are arranged at least along an edge of a longitudinal side of the blade holder at the side of the developing roller and along an edge of another longitudinal side of the blade holder at the opposite side of the developing roller, respectively, so as to increase airtightness of gaps between the blade holder and the outer wall of the developing case, and a packing member is arranged in a gap between the center part of the blade holder and the recessed part. 
     The seal members may be formed with a material that has a density finer than that of toner particles and a rigidity that will not cause any deformation of the blade. 
     According to still another embodiment of the present invention, a developing device includes a developing case in which a toner exit opposed to a photoconductor and a flat surface extended from a lower edge of the toner exit toward the photoconductor are formed. A developing roller includes an axial part rotatably supported by supporting walls provided at both sides of the developing case and a roller part disposed at the toner exit. A blade is configured such that a lower edge thereof contacts the roller part of the developing roller so as to seal a gap between an upper edge of the toner exit and an upper outer circumferential surface of the roller part of the developing roller. A thin exit seal is supported by the flat surface of the developing case with a free end side thereof, which is extended toward the inside of the toner exit, elastically contacting the roller part of the developing roller, and corner seals seal corners where edges of longitudinal ends of the exit seal and the supporting walls of the developing case contact each other, respectively. 
     According to still another embodiment of the present invention, a developing device includes a developing case in which a toner exit opposed to a photoconductor and a flat surface extended from a lower edge of the toner exit toward the photoconductor are formed. A developing roller includes an axial part rotatably supported by supporting walls provided at both sides of the developing case and a roller part disposed at the toner exit. A blade is configured such that a lower edge thereof contacts the roller part of the developing roller so as to seal a gap between an upper edge of the toner exit and an upper outer circumferential surface of the roller part of the developing roller. A thin exit seal is supported by the flat surface of the developing case with a free end side thereof, which is extended toward the inside of the toner exit, elastically contacting the roller part of the developing roller, and clips elastically sandwich longitudinal ends of the exit seal and the flat surface of the developing case, respectively. 
     According to still another embodiment of the present invention, a developing device includes a developing case, in which a toner exit opposed to a photoconductor and a flat surface extended from a lower edge of the toner exit toward the photoconductor are formed, and a developing roller including an axial part rotatably supported by supporting walls provided at both sides of the developing case and a roller part disposed at the toner exit. A blade is configured such that a lower edge thereof contacts the roller part of the developing roller so as to seal a gap between an upper edge of the toner exit and an upper outer circumferential surface of the roller part of the developing roller. A thin exit seal is supported by the flat surface of the developing case with a free end side thereof, which is extended toward the inside of the toner exit, elastically contacting the roller part of the developing roller. Corner seals seal corners where longitudinal ends of the exit seal and the supporting walls of the developing case contact each other, respectively, and clips elastically sandwich longitudinal ends of the exit seal and the flat surface of the developing cover, respectively. 
     According to still another embodiment of the present invention, a developing device includes a developing case, in which a toner exit opposed to a photoconductor is formed, and a developing roller including an axial part rotatably supported by supporting walls provided at both sides of the developing case and a roller part disposed at the toner exit. Side seals are arranged at both longitudinal ends of the toner exit so as to contact outer circumferential surfaces of longitudinal ends of the roller part of the developing roller. A blade that is formed with a thin metal plate having elasticity is configured such that a lower edge thereof contacts the roller part of the developing roller so as to seal a gap between an upper edge of the toner exit and an upper outer circumferential surface of the roller part of the developing roller. The blade includes a wide-width part having a length such that both longitudinal ends thereof face the side seals respectively and a narrow-width part extended from the wide-width part toward upstream of a rotation direction of the developing roller and configured to have a length that enables the narrow-width part to be bent in a direction orthogonal to a longitudinal direction of the developing roller between the side seals arranged at both sides of the toner exit, and a step part forming a boundary between the wide-width part and the narrow-width part is disposed downstream of a contact point of the blade and the roller part of the developing roller in the rotation direction of the developing roller. 
     The length of the narrow-wide part may be made longer than an interval between inside surfaces of the side seals such that, when the blade is pressed by the developing roller, the narrow-wide part bends toward a rear side of the toner exit by pressure of the developing roller even after the wide-width part contacts the side seals. 
     According to still another embodiment of the present invention, in a developing device, a toner accommodating part is formed in a developing case of the developing device and a rotating member is rotatably housed in the toner accommodating part. A rotating axis of the rotating member passes through a wall of the developing case to protrude outside of the wall of the developing case and a flexible stopping claw formed at an end of the rotating axis protruded outside of the wall of the developing case is inserted into an insertion hole formed in a gear and is stopped by being engaged with the gear. A seal is stuck to an outside surface of the gear so as to seal the insertion hole. 
     According to still another embodiment of the present invention, in a developing device, a toner accommodating part is formed in a developing case of the developing device and a rotating member is rotatably housed in the toner accommodating part. A rotating axis of the rotating member passes through a wall of the developing case to protrude outside of the wall of the developing case and an end of the rotating axis protruded outside of the wall of the developing case is engaged with a gear. An engaging hole is formed in the wall of the developing case, a bearing is fit into the engaging hole, a bearing seal formed with foaming polyurethane in a donut shape so as to pass through the rotating axis is fixed to an end of the bearing facing the toner accommodating part. An outer diameter of the bearing seal is larger than an inner diameter of the engaging hole by about 0.2-1.0 mm in the radius. 
     According to still another embodiment of the present invention, in a developing device, a toner accommodating part is formed in a developing case of the developing device and a rotating member is rotatably housed in the toner accommodating part. A rotating axis of the rotating member passes through a wall of the developing case to protrude outside of the wall of the developing case and an end of the rotating axis protruded outside of the wall of the developing case is engaged with a gear. An engaging hole is formed in the wall of the developing case, a bearing is fit into the engaging hole, a bearing seal formed with foaming polyurethane in a donut shape so as to pass through the rotating axis is fixed to an end of the bearing facing the toner accommodating part. An inner diameter of the bearing seal is smaller than an inner diameter of the bearing by about 0.2-1.0 mm in the radius. 
     In the immediately above developing device, a D-shaped part may be formed at a part of the rotating axis engaging with the gear and a chamfer may be formed between a part of the rotating member where the D-shaped part is formed and a part of the rotating member where the D-shaped part is not formed. 
     According to still another embodiment of the present invention, in a photoconductor unit, a photoconductor is rotatably supported and a used toner collecting unit to collect residual used toner on the photoconductor is formed. A narrow and long collecting inlet is formed in the used toner collecting unit at a position adjacent to an outer circumferential surface of the photoconductor, extending along substantially an entire length of the photoconductor. Side seals are disposed at longitudinal ends of the collecting inlet so as to slidably contact an outer circumferential surface of ends of the photoconductor. A long blade is provided at one longitudinal edge of the collecting inlet so as to scrape off residual used toner on an outer circumferential surface of the photoconductor, and a long inlet seal is stuck to the other longitudinal edge of the collecting inlet so as to slidably contact the outer circumferential surface of the photoconductor. Support parts are formed at longitudinal ends of the inlet seal protruding in a direction orthogonal to a longitudinal direction of the inlet seal to increase a sticking area of the inlet seal to the edge of the collecting inlet. 
     Both longitudinal ends of the inlet seal may be overlaid with the side seals with respective outer edges of the inlet seal and the side seals aligned with each other, and pressing seals that are formed in a substantially L-shape with a fixing part and a leakage preventing part may be disposed such that the fixing part of the pressing seals is stuck on end parts of the inlet seal and the leakage preventing part is stuck at a position to contact outer end surfaces of the side seals and the inlet seal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
     FIG. 1 is a side cross section illustrating an exemplary construction of an image forming apparatus having a process cartridge according to an embodiment of the present invention; 
     FIG. 2 is a side view of the process cartridge; 
     FIG. 3 is a side cross section of the process cartridge; 
     FIG. 4 is a front cross section of the process cartridge at a Y—Y line of FIG. 3; 
     FIG. 5 is a horizontal cross section illustrating an exemplary structure of supporting a blade to a developing case; 
     FIG. 6 is a front view of the developing case when the blade and a developing roller are removed; 
     FIG. 7 is a schematic front view explaining a relation between a blade holder and a seal member; 
     FIG.  8 ( a ) and FIG.  8 ( b ) are schematic drawings illustrating a support structure of the blade and seal members, FIG.  8 ( a ) being a cross section at an end of the developing case and FIG.  8 ( b ) being a cross section at a center of the developing case; 
     FIG. 9 is a side cross section of a process cartridge according to another embodiment of the present invention; 
     FIG. 10 is a schematic drawing illustrating an exemplary structure of mounting an exit seal and a corner seal to a developing case; 
     FIG. 11 is a schematic drawing illustrating a state where the exit seal and the corner seal are mounted to the developing case; 
     FIG. 12 is a front view of the developing case illustrating a relation between the blade and the side seal; 
     FIG. 13 is a side view of a process cartridge according to another embodiment of the present invention; 
     FIG. 14 is a front cross section illustrating an exemplary structure of attaching a toner stirring device to the developing case; 
     FIG. 15 is a front cross section illustrating an exemplary construction of attaching a toner supply roller to the developing device; 
     FIG. 16 is a side cross section of a photoconductor unit according to another embodiment of the present invention; 
     FIG. 17 is a front view of the photoconductor unit when a photoconductor is removed; 
     FIG. 18 is a bottom view of the photoconductor unit, illustrating a shape of a support part formed in an inlet seal and a position of sticking the inlet seal; 
     FIG. 19 is a side cross section of a photoconductor unit of a prior art; and 
     FIG. 20 is a front view of the photoconductor unit when a photoconductor is removed. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views. 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, the preferred embodiments of the present invention are described. 
     Referring more particularly to FIG. 1, an exemplary construction of an image forming apparatus P incorporating a process cartridge according to the first embodiment of the present invention is first described. 
     Numeral  1  denotes a main body of the image forming apparatus P. An image reading device  2  is provided at an upper part of the main body  1  to read an image of an original document, and a process cartridge  3  is provided inside the main body  1 . A sheet conveying path  4  for guiding a transfer sheet is formed below the process cartridge  3 . 
     The image reading device  2  includes a reading unit  5  that reads an image of an original document and an original document tray  6  that accommodates original documents to be fed toward the reading unit  5 . The original document tray  6  is supported at a support axis  7  so as to be rotatable from a horizontal position A indicated by a solid line to a standing position B indicated by a two-dot chain line. The original document tray  6  is configured so as to be kept in a stable condition by stoppers (not shown) at the horizontal position A and the standing position B, respectively. 
     The process cartridge  3  includes a photoconductor case  8  which is formed in a shape of a case, a photoconductor  9 , a charging roller  10  and a developing device  11 . The photoconductor  9  is rotatably mounted to the photoconductor case  8 . The charging roller  10  and the developing device  11  are arranged around the photoconductor  9 . A transfer unit  12  is provided at the side of the main body  1  so as to face a circumferential surface of a lower part of the photoconductor  9 . The developing device  11  includes a developing case  13  that is detachably attached to the photoconductor case  8 , a rotatable developer stirring device  14  that stirs developer contained inside the developing case  13 , i.e., inside a toner container unit  13   e , a developing roller  15  contacting the photoconductor  9 , a toner supply roller  16  that supplies developer to the developing roller  15 , and a blade  17  contacting the developing roller  15 . In addition, a latent image forming unit  18  is provided above the process cartridge  3  to form a latent image on the photoconductor  9  by scanning a charged part of the photoconductor  9  with a laser light modulated according to an image signal. 
     At one side of the main body  1 , a tray  19  is provided to support a transfer sheet S in a slanted condition. The tray  19  also supports original documents which are read by the image reading device  2  and fed out therefrom. Below the tray  19 , a feeding roller  20  that is rotatably driven and a pressure plate  21  that is pressed to one direction such that a transfer sheet S on the tray  19  is pressed to the feeding roller  20  are provided. Further, a separating pad  22  and a separating roller  23  are provided so as to elastically contact the feeding roller  20 , respectively, such that double feeding of transfer sheets S is prevented. 
     The feeding roller  20 , the separating pad  22  and the separating roller  23  are arranged at the entrance side of the sheet conveying path  4 . A bottom path  24  is provided downstream of the conveying roller  20  in a direction in which a transfer sheet S is conveyed so as to communicate with the sheet conveying path  4 . Further, a fixing unit  25  is arranged downstream of the sheet conveying path  4  to fix a toner image on a transfer sheet S. 
     A sheet stacker  26  is arranged between the original document tray  6  and the fixing unit  25 . The stacker  26  includes a sheet receiving plate  27  that is positioned to align with a line extending from a lower end of the original document tray  6  when the original document tray  6  is rotated to the standing position B so as to receive a transfer sheet S exited from the fixing unit  25 . A discharging exit  28  that discharges a transfer sheet S, which is exited from the fixing unit  25 , in a horizontal direction and a reversed discharging path  29  that reverses and guides a transfer sheet S to the stacker  26  are provided in the vicinity of a side surface of the main body  1 , which is opposite to the side where the tray  19  is provided. A pair of rollers  30  is provided at each of upper and lower end parts of the reversed discharging path  29 . A switching claw  31  is rotatably arranged at a dividing point of the reversed discharging path  29  and the discharging exit  28  so as to switch the direction of discharging a transfer sheet S. 
     Next, the operation of reading an image of an original document and the operation of recording the image on a transfer sheet S are described. When reading an image of an original document, the original document is fed to the reading unit  5  while the original document tray  6  is kept in the horizontal position A as indicated by the solid line in FIG.  1 . The image of the original document thus fed to the reading unit  5  is read by the reading unit  5 , and then the original document is supported by an upper part of the tray  19  while being stood against the tray  19 . The image thus read is transmitted to an external facsimile equipment when the image forming apparatus P is operated in a facsimile transmission mode or recorded on a transfer sheet S fed from the tray  19  when operated in a copying mode. The image forming apparatus P can also record an image received from the outside on a transfer sheet S in a facsimile reception mode. 
     When recording an image on a transfer sheet S, the surface of the photoconductor  9  is charged by the charging roller  10  while the photoconductor  9  is rotated in the clockwise direction, and an electrostatic latent image is formed on a charged part of the photoconductor  9  by the latent image forming unit  18  according to an image of an original document read by the image reading device  5  or an image received from the outside. The latent image is then developed with the developing device  11 . The developed image is then transferred to a transfer sheet S, which is fed from the tray  19  by the feeding roller  20 . The image transferred to the transfer sheet S is fixed to the sheet S when the sheet S passes through the fixing unit  25 . The transfer sheet S carrying the image is then discharged to either the discharging exit  28  or the sheet stacker  26  according to the direction of the switching claw  31 . 
     Next, the construction of the process cartridge  3 , in particular, that of the developing device  11 , is described. As illustrated in FIG. 2, the photoconductor case  8  includes a handle  32  to hold when attaching the process cartridge  3  to the main body  1  (FIG.  1 ). A shutter  33  is configured so as to cover the bottom surface of the photoconductor  9  when the process cartridge  3  is detached from the main body  1  and open the bottom surface of the photoconductor  9  when the process cartridge  3  is attached to the main body  1 . The developing case  13  is detachably mounted between outer walls  8   a  and  8   b  at both sides of the photoconductor case  8 . The wall  8   b  is not shown in FIG.  2  and is illustrated in FIG.  4 . 
     FIG. 3 is a side vertical cross section of the developing device  11  and FIG. 4 is a front vertical cross section of the developing device  11  at a Y—Y line in FIG.  3 . As illustrated in FIG. 4, the developing roller  15  includes a roller part  34  and a metal axial part  35  passing through the center of the roller part  34 . The outer circumferential part of the roller part  34  is formed of an elastic material having a low friction coefficient, such as rubber, for charging single component toner by friction. The developing case  13 , which is detachably mounted between the outer walls  8   a  and  8   b , includes supporting walls  13   a  and  13   b  that face each other at a predetermined interval, inside the outer walls  8   a  and  8   b . A bearing  36  is formed by opening a hole in the supporting wall  13   a  to rotatably support one end of the axial part  35  and a bearing  37  is formed by mounting a bushing in the supporting walls  13   b . A plastic gear  38  that is driven by a motor (not shown) is engaged with an end of the axial part  35  protruding from the bearing  36 . 
     As illustrated in FIG. 3, the developing case  13  is provided with a cover  40  that is adhered to an upper opening of a toner containing room  39 . Further, a blade holder  42 , a blade  17  and a support member or plate  43 , that are laminated with each other, are attached to an outer wall  41  of the developing case  13  at the side of the photoconductor  9 . The blade holder  42  has a relatively high rigidity and the blade  17  is formed with a metal plate that is elastically deformable, such as stainless steel. The blade  17  is sandwiched by the blade holder  42  and the support plate  43  at the upper half part of the blade  17 , and the lower half part of the blade  17  extends downward from the laminated part so as to contact the developing roller  15  with pressure. 
     FIG. 5 is a horizontal cross section illustrating the support structure of the blade  17  relative to the developing case  13 . As illustrated in the drawing, a blade mounting surface  44  is formed in the vicinity of both ends of the outer wall  41  and a recessed surface  45  is formed at the center part of the outer wall  41 . The surface of the recessed surface  45  is slightly recessed from the surface of the blade mounting surface  44 . A screw hole  46  and an axially-formed protrusion  47  for positioning are formed at the blade mounting surface  44 . A bent piece  48  that opposes to the cover  40  of the developing case  13  and a protrusion piece  50  that passes through a hole formed on the supporting wall  13   b  (not shown) at one side of the developing case  13  are formed in the blade holder  42 . A bent piece  51  that contacts the bent piece  48  of the blade holder  42  is formed at an upper edge of the supporting plate  43 . The blade  17  includes a bent piece  52  that is bent in a L shape at a lower end of the blade  17 , and thereby it is avoided that an edge of the end of the blade  17  contacts a surface of the developing roller  15 . Further, positioning holes  53  and screw mounting holes  55  are formed at both end sides of the blade holder  42 , the blade  17  and the supporting plate  43 . The protrusion  47  at the blade mounting surface  44  is inserted into the positioning holes  53  and a mounting screw  54  is passed through the screw mounting holes  55  so as to be engaged with the screw hole  46 . 
     The shape of the positioning hole  53  of the blade  17  at one side of the blade  17  is different from that of the positioning hole at the other side of the blade  17 . In more detail, the positioning hole  53  at one side of the blade  17  is shaped in a circle having an internal diameter identical to the outer diameter of the protrusion  47 , and the positioning hole  53  at the other side of the blade  17  is shaped in a hole elongated in the axial direction of the developing roller  15  with a width corresponding to the outer diameter of the protrusion  47 . By this arrangement, the mounting position of the blade  17  relative to the developing case  13  can be adjusted. Therefore, the shape of the mounting hole  55  can be any shape. The shape of the positioning hole  53  and the mounting hole  55  of the blade holder  42  and the supporting plate  43  are made substantially the same as those of the blade  17 . 
     When the developing case  13  is made in plastic molding, it is very hard to form the surface of the blade mounting surface  44 , which is formed in the outer wall  41  of the developing cover  13 , in a completely flat shape over the entire length thereof so as to correspond to the blade  17 . For this reason, the blade mounting surface  44  is formed in a limited area of the outer wall  41  in the vicinity of both ends of the outer wall  41  and the recessed surface  45  is formed at the center part of the outer wall  41 . It is desirable that no gap exists between the recessed surface  45  and the blade holder  42 . Therefore, a thin sheet  56  having elasticity, such as a polyethylene film, is arranged between the recessed surface  45  and the blade holder  42 . The thickness of the outer wall  41  is made the same for the blade mounting surface  44  and the recessed surface  45  and the blade mounting surface  44  and the recess plane are both formed by a group of ribs  44   a  and  45   a  so as to avoid forming sink marks when molded (FIGS.  5  and  6 ). 
     Further, as illustrated in FIG. 6, a seal member  57  is attached to the outer wall  41  of the developing case  13 . Both end parts of the seal member  57  are bent downward so as to form contact parts  58 , which contact the outer circumferential surface of the developing roller  15 . 
     In addition, as illustrated in FIG. 7, a seal member  59  is attached to the bent piece  48  of the blade holder  42  so as to contact the outer wall  41  and the lower surface of the cover  40 . The seal member  59  is longer than the entire length of the blade holder  42  except the protrusion  50 , and both end parts of the seal member  59  are bent so as to form bent parts  60 . The bent parts  60  seal the gap between the supporting walls  13   a  and  13   b  (FIGS. 4 and 6) of the developing case  13  and the blade holder  42 . 
     FIGS.  8 ( a ) and  8 ( b ) illustrate the support structure of the blade  17  and the seal members  57  and  59 . FIG.  8 ( a ) is a vertical cross side view at the blade mounting surface  44  of the developing case  13  and FIG.  8 ( b ) is a similar view at the recessed surface  45 . As illustrated in the drawings, the seal member  57  is disposed along the longitudinal edge of the blade holder  42  at the side of the developing roller  15  and is sandwiched by the backside of a deformable part of the blade  17  (i.e., a part not sandwiched by the blade holder  42  and the supporting plate  43 ) and the outer wall  41  of the developing case  13 . The seal member  59  is disposed along the edge of the blade holder  42  at the opposite side of the seal member  57 . 
     When a latent image is developed with the above-described developing device  11 , toner in the developing case  13  is charged by friction between the developing roller  15  and the toner supply roller  16  and further by friction between the developing roller  15  and the blade  17 . The developing roller  15  rotates in the counterclockwise direction in FIGS. 1,  3  and  8  and the toner passed under the blade  17  adheres to the developing roller  15 . A latent image on the photoconductor  9  is developed with the toner supplied to the developing roller  15 . 
     When the process cartridge  3  or the developing device  11  is handled by itself and if the process cartridge  3  or the developing device  11  falls, for example, the developing cover  13  may be shocked and thereby the developing roller  15  and the blade  17  may vibrate. However, because the seal member  57  is provided along the lower edge of the blade holder  42  to seal the gap between the blade  17  and the outer wall  41  and the seal member  59  is provided along the upper edge of the blade holder  42  to seal the gap between the lower surface of the cover  40  and the outer wall  41 , toner in the developing case  13  is prevented from passing the backside of the blade holder  42  and the blade  17  and leaking to the outside of the developing cover  13 . 
     Further, when the blade holder  42 , the blade  17  and the supporting plate  43  are metal, if each length of the blade holder  42 , the blade  17  and the supporting plate  43  is longer than the interval between the supporting walls  13   a  and  13   b  of the developing case  13 , the blade holder  42 , the blade  17  and the supporting plate  43  cannot be assembled inside of the supporting walls  13   a  and  13   b . Therefore, each length of the blade holder  42 , the blade  17  and the supporting plate  43  is required to be at least shorter than the interval between the supporting walls  13   a  and  13   b  of the developing case  13 . However, due to manufacturing tolerance of the blade holder  42 , the blade  17  and the supporting plate  43 , a gap may exist between both ends of the blade holder  42 , the blade  17  and the supporting plate  43  and the supporting walls  13   a  and  13   b . However, the seal member  59  is made longer than the longitudinal length of the blade holder  42  and is supported by the blade holder  42  with both end parts of the seal member  59  bent along the sides of both ends of the blade holder  42 . Therefore, the gap between the both longitudinal ends of the blade  17 , the blade holder  42  and the supporting plate  43  and the inside surface of the supporting walls  13   a  and  13   b  is sealed by the bent parts  60  of the seal member  59 . 
     Further, both end parts of the blade holder  42  are attached to the blade mounting surface  44  and the sheet  56  is disposed between the recessed surface  45  at the center of the developing case  13  and the blade holder  42 . Therefore, even when the developing case  13  is shocked, the seal member  57  will never intrude, even partly, between the blade holder  42  and the recessed surface  45 , and toner is prevented from being leaked through the recessed surface  45 . 
     In addition, by attaching both end parts of the blade holder  42  to the blade mounting surface  44 , the blade holder  42 , the blade  17  and the supporting plates  43  can be supported by the outer wall  41  without causing a curvature in the longitudinal direction, and thereby the blade  17  can contact the developing roller  15  with the contact line between the blade  17  and the developing roller  15  made straight. 
     Further, by making the seal member  57  with a material that has a finer (or higher) density than the toner particles and a rigidity that will not cause any deformation of the blade  17 , the sealing property of the sealing member  57  for the gap between the backside of the blade  17  and the seal member  57  can be enhanced with the load given to the developing roller  15  by the seal member  57  made relatively small. The seal member  57  can be formed with, for example, a material of a foaming urethane system. 
     Specifically, when the process cartridge  3  is tested for a drop, in which the seal member  57  having the hardness of 30 kgf or less (according to 6.3 (A method) of Japanese Industrial Standard K 6400), the density of 0.07 g/cm 3  or less (14 times or more in the foaming coefficient), and the permeability of 5 cc/cm 2 /sec or less (according to 13.1 (A method) of Japanese Industrial Standard K 6400) is used, no leakage of toner has been observed at the backside of the blade  17 . No undesirable effect due to deformation of the blade  17  caused by pressure from the seal member  57  has been observed either. The effect of deformation of the blade  17  was determined by measuring the amount of toner adhered on the developing roller  15 . 
     Now, another developing device according to the second embodiment of the present invention is described. The parts substantially the same as those illustrated in FIG.  1  through FIG. 8 are denoted by the same numerals or codes and the description thereof is omitted. The structure of a seal that prevents toner from leaking from around the developing roller  15  is specifically described. As illustrated in FIG.  9  through FIG. 11, in the developing case  13 , a toner exit  61  in which the roller part  34  of the developing roller  15  is disposed and a flat surface  62  extending from a lower edge of the toner exit  61  toward the photoconductor  9  are formed. An exit seal  63 , that is made of an elastic plastic film such as polyester, is stuck to the flat surface  62  by adhesion or the like. The free end side of the exit seal  63 , i.e., the toner exit  61  side of the exit seal  63 , that extends beyond the edge of the flat surface  62 , elastically contacts the outer circumferential surface of the roller part  34  of the developing roller  15  by its own elasticity. 
     As illustrated in FIG.  10  through FIG. 12, side seals  64  are stuck to both sides of the toner exit  61  so as to contact the outer circumferential surfaces of both end parts of the roller part  35 , respectively. Both longitudinal ends of the exit seal  63  are laid over the side seals  64 , respectively. 
     Further, although only one side of the developing device  11  is illustrated in the drawings, corner seals  65  and clips  66  are provided so as to seal corners where both longitudinal ends of the exit seal  63  and the supporting walls  13   a  and  13   b  contact each other, respectively. The clip  66  is formed with a metal plate having elasticity and includes a contact piece  67  which is brought into contact with the lower surface of the flat surface  62  and a pressure piece  68  which elastically presses the corner seal  65  from the above. Both ends of the flat surface  62  and the exit seal  63 , and the corner seals  65 , are elastically sandwiched between the contact piece  67  and the pressure piece  68  of the clip  66 . 
     Further, in this embodiment, the supporting walls  13   a  and  13   b  do not extend to the position aligning with the tip end of the flat surface  62 . Therefore, the corner seal  65  to be placed on the exit seal  63  and the pressure piece  68  of the clip  66  are both formed in a L-shape, as illustrated in FIG. 10, so as to contact an inner surface  13   c  and an end surface  13   d  (orthogonal to the inner surface  13   c ) of the supporting walls  13   a  and  13   b . The corner seal  65  is configured such that two sides of the corner seal  65  forming a L-shape contact the inner surface  13   c  and the end surface  13   d  with the two sides rolled up. 
     As illustrated in FIGS. 8 and 9, the blade  17  is configured such that the part extending downward beyond the blade holder  42  bents toward the rear side of the developing case  13  by being pressed with the roller part  34  of the developing roller  15  and the bent piece  52  contacts the roller part  34 . Therefore, as indicated by a one-dot chain line in FIG. 12, the contact position C of the roller part  34  and the blade  17  is located in a position slightly above the lower edge of the blade  17 . 
     Further, as illustrated in FIGS. 10 through 12, the blade  17  includes a wide-width part  69  with both longitudinal ends thereof faced the side seals  64  (i.e., overlaid with the side seals  64 ), a narrow-width part  70  located below the wide-width part  69  in the drawings and a step part  71  forming the boundary between the wide-width part  69  and the narrow-width part  70 . As illustrated in FIG. 12, the step part  71  is located above the contact position C of the blade  17  and the roller part  34  (downstream of the contact position C in the rotating direction of the developing roller  15 ). The length of the narrow-width part  70  located below the step part  71  in the drawings is made such that, when the blade  17  is pressed by the roller part  34  of the developing roller  15 , the narrow-width part  70  can be bent toward the rear side of the toner exit  61  by pressure of the developing roller  15 , even after the wide-width part  69  contacts the side seals  64 . More specifically, in FIG. 12, the length L2 of the narrow-wide part  70  is set to a length ΔL longer than an interval L1 between the inside surfaces of the side seals  64  and the narrow-width part  70  is overlapped with the side seals  64  by a distance ΔL/2 (for example, 0.1-0.5 mm) at both ends of the narrow-width part  70 , respectively. When the overlapping distance is about ΔL/2, the narrow-wide part  70  of the blade  17  can be bent toward the rear side of the toner exit  61  by pressure of the developing roller  15  by elastically deforming the edges of the side seals  64  which are overlaid with the narrow-width part  70 . 
     Thus, the blade  17  can be put into contact with the roller part  34  over the entire length of the roller part  34  and further the both sides of the roller part  34  can be securely put into contact with the side seals  64  by bending action of the narrow-width part  70  below the step part  71 . 
     Further, the corners where the longitudinal ends of the exit seals  63  and the supporting walls  13   a  and  13   b  contact each other can be sealed by the corner seals  65 , respectively. Also, both ends of the exit seals  63  and the corner seals  65  can be pressed together against the flat surface  62  with the clip  66 , respectively. The corner seals  65  are condensed by being pressed by the clip  66  and thereby leakage of toner is prevented more effectively. 
     Furthermore, because the wide-width parts  69  are formed at both longitudinal ends of the blade  17  so as to face the side seals  64  respectively, intrusion of toner toward both sides of the toner exit  61  is suppressed. In addition, when the narrow-width part  70  is pressed by the developing roller  15  and the narrow-width part  70  is pressed against the side seals  64 , bending of the narrow-width part  70  will not be hampered. Thus, the outer circumferential surfaces of the roller part  34  of the developing roller  15  can be securely put into contact with the side seals  64 . Because the length L2 of the narrow-width part  70  is slightly longer than the interval L1 between the side seals  64 , intrusion of toner toward both sides of the blade  17  can be also suppressed. Thus, toner leakage around the developing roller  15  is effectively prevented. 
     Next, another developing device  11  according to the third embodiment of the present invention is described in reference to FIG.  13  through FIG.  15 . The parts substantially the same as those in the previous embodiments are denoted by the same numerals or codes and the description thereof is omitted. This embodiment relates to a seal construction for a part of the developing case  13 , in which respective ends of the stirring device  14  and the toner supplying roller  16  at one side protrude outside of the developing case  13  so that a power is transmitted thereto. As illustrated in FIG. 15, an engaging hole  80  is formed in a wall of a case of the developing device  11 , i.e., in the supporting wall  13   a  of the developing case  13 , and a bearing  81  is fit into the engaging hole  80 . When the bearing  81  is fit into the engaging hole  80 , a bearing seal  82 , which is formed in a donut shape with foaming polyurethane, is fixed by adhesion to one end of the bearing  81  at the side of the toner container part  13   e . A rotating axis  16   a  of the toner supply roller  16  is inserted into the bearing seal  82  and the bearing  81  so as to protrude outside of the developing case  13 . The end of the rotating axis  16   a  protruded outside of the developing case  13  engages with a gear  84  of a power transmitting mechanism  83  (FIG.  13 ). 
     The outer diameter “a” of the bearing seal  82  is larger than the inner diameter “b” of the engaging hole  80  by 0.2-1.0 mm in the radius. That is, (a−b)/2=0.2-1.0 mm. The inner diameter “d” of the bearing seal  82  is smaller than the inner diameter “c” of the bearing  81  by 0.2-1.0 mm in the radius. That is, (d−c)/2=−0.2-−1.0 mm. 
     A D-shaped part  85 , in which the cross section is shaped like the character “D”, is formed at the tip end of the rotating axis  16   a  for stopping rotation of the engaged gear  84 . A chamfer  86  is formed between a part of the rotating axis  16   a  where the D-shaped part  85  is formed and a part where the D-shaped part  85  is not formed. 
     Further, as illustrated in FIG. 14, an insertion hole  87  is formed in the supporting walls  13   a  and a rotating axis  14   a  of the stirring device  14  is inserted through the insertion hole  87 . A donut-shaped inner seal  88  is engaged at a part of the rotation axis  14   a  which is located inside of the toner container part  13   e  and the side of the inner seal  88  is in contact with the inner surface of the supporting wall  13   a.    
     The end of the rotation axis  14   a  protruded outside of the developing case  13  engages with a gear  89  of the power transmission  83 . The gear  89  is prevented from being released from the rotation axis  14   a  by inserting a flexible stopping claw  90 , that is formed at the end of the rotation axis  14   a , into an insertion hole  91  formed in the gear  89  and by engaging a tip end of the stopping claw  90  with a stepped part  92  formed in the gear  89 . 
     An outer seal  93  is stuck to the outside surface of the gear  89 , at which the stopping claw  90  is engaged, so as to seal the insertion hole  91 . An opening (not shown) for supplying toner is formed in the supporting wall  13   a  of the developing cover  13  and the opening is tightly closed by a closing cap  94  as illustrated in FIG.  13 . 
     In FIG. 13, numeral  100  denotes a photoconductor unit, which is formed by assembling a photoconductor case  8 , a photoconductor  9 , a charging roller  10  and a shutter  33  into an integrated unit. A process cartridge  3  is assembled by connecting the photoconductor unit  100  and the developing unit  11 . The process cartridge  3  is attached to the main body  1  (FIG. 1) in a detachable manner. 
     When the developing device  11  is assembled, the bearing  81  is fit into the engaging hole  80  by thrusting the bearing  81  having the bearing seal  82  attached at one end thereof by adhesion into the engaging hole  80  from the outside of the supporting wall  13   a . The outer diameter “a” of the bearing seal  82  is made larger than the inner diameter “b” of the engaging hole  80  by 0.2-1.0 mm in the radius. However, because the bearing seal  82  is made of foaming polyurethane, the bearing seal  82  has high compressibility. Therefore, when the bearing  81  is fit into the engaging hole  80  from the outside of the supporting walls  13   a , the bearing seal  82  can be easily compressed to a size with an outer diameter smaller than the inner diameter of the engaging hole  80  such that the bearing  81  can be easily fit into the engaging hole  80 . Once the bearing seal  82  passes through the engaging hole  80 , the bearing seal  82  is decompressed to the original size and the part of the bearing seal  82  extending beyond the inner diameter of the engaging hole  80  contacts a circumference of the engaging hole  80  at an inner surface of the supporting wall  13   a.    
     Accordingly, with the provision of the bearing seal  82 , toner is prevented from intruding into a gap between the inner circumferential surface of the engaging hole  80  and the outer circumferential surface of the bearing  81  and thereby toner leakage through the gap between the inner circumferential surface of the engaging hole  80  and the outer circumferential surface of the bearing  81  is prevented. Further, because the bearing seal  82  made of foaming polyurethane is inexpensive, a relatively inexpensive seal mechanism can be realized by using the bearing seal  82  made of foaming polyurethane. 
     Further, although the inner diameter “d” of the bearing seal  82  is made shorter than the inner diameter “c” of the bearing  81  by 0.2-1.0 mm in the radius, because the bearing seal  82  made of foaming polyurethane has high compressibility, in assembling the developing device  11 , when the rotation axis  16   a  of the toner supply roller  16  is inserted through the bearing seal  82 , the bearing seal  82  is easily compressed to a size having an inner diameter through which the rotation axis  16   a  can be easily inserted, and thereby the operation of inserting the rotation axis  16   a  through the bearing seal  82  and the bearing  81  can be easily performed. 
     In addition, a sharp drop is not formed in the longitudinal outer circumferential surface of the rotation axis  16   a  because the chamfer  86  is formed between a part of the rotating axis  16   a  where the D-shaped part  85  is formed and a part where the D-shaped part  85  is not formed. Accordingly, when the rotation axis  16   a  is inserted through the bearing seal  82 , the chamfer  86  contacts the inner circumferential part of the bearing seal  82  and thereby the inner circumferential part of the bearing seal  82  is gradually compressed in the radial direction. Thus, the chamfer  86  contacts the inner circumferential part of the bearing seal  82  along the insertion direction of the rotation axis  16   a  and thereby damaging of the bearing seal  82  is avoided. 
     Further, in assembling the developing device  11 , the rotation axis  14   a  of the stirring device  14  is inserted through the insertion hole  87  formed in the supporting wall  13   a  so as to protrude the stopping claw  91  outside of the developing case  13 . The protruded stopping claw  91  is inserted into the insertion hole  91  of the gear  89  and the stopping claw  90  is engaged with the stepped part  92  of the gear  89 . Further, the outer seal  93  is stuck to the outer surface of the gear  89  so as to seal the insertion hole  91 . 
     Therefore, when toner leaks outside of the developing device  11  through a gap between the inner circumferential surface of the insertion hole  87  and the outer circumferential surface of the rotation axis  14   a , the toner passes around the stopping claw  90  and intrudes into the insertion hole  91  of the gear  89 . The toner intruded into the insertion hole  91  is sealed by the outer seal  93  and is prevented from being scattered from the insertion hole  91  to the circumference. Thus, the circumference of the developing device  11  is prevented from being soiled by scattering toner. In particular, in this embodiment, scattering of toner is prevented by a simple and inexpensive construction, as described above, to stick the outer seal  93  to the outer surface of the gear  89 . 
     Now, another photoconductor unit according to the fourth embodiment of the present invention is described with reference to FIGS. 16-18. The parts substantially the same as those in the previous embodiments are denoted by the same numerals or codes and the description thereof will be omitted. As in FIG. 13, a photoconductor unit  100  is formed by assembling a photoconductor case  8 , a photoconductor  9 , a charging roller  10  and a shutter  33  into an integrated unit. A process cartridge  3  is assembled by connecting the photoconductor unit  100  and the developing unit  11 . The process cartridge  3  is attached to the main body  1  (FIG. 1) in a detachable manner. 
     The fourth embodiment relates to a construction to prevent leakage of collected used toner in the inside of the photoconductor unit  100 . As illustrated in FIG. 16, a used toner collecting unit  101  is formed in the photoconductor case  8 . A long and narrow collecting inlet  102  is formed in the used toner collecting unit  101  at a position adjacent to the outer circumferential surface of the photoconductor  9 . The collecting inlet  102  is formed along substantially the entire length of the photoconductor  9 . Side seals  103  made of teflon felt are stuck to both longitudinal ends of the used toner collecting inlet  102  and the outer circumferential surfaces of both ends of the photoconductor  9  slidably contacts the side seals  103 . A long blade  104  is fixed to one longitudinal edge of the collecting inlet  102  so as to scrape off residual used toner on the outer circumferential surface of the photoconductor  9 . A long inlet seal  105  is stuck to the other longitudinal edge of the collecting inlet  102  so as to slidably contact the outer circumferential surface of the photoconductor  9 . 
     Support parts  106  are formed at both longitudinal ends of the inlet seal  105  so as to increase the sticking area of the inlet seal  105  to the edges of the collecting inlet  102  and thereby to make the inlet seal  105  hard to be peeled off. The support parts  106  are formed in a rectangle shape protruded in the direction orthogonal to the longitudinal direction of the inlet seal  105 . 
     The longitudinal ends of the inlet seal  105  are laid over the side seals  103  with respective outer edges aligned with each other. Further, pressing seals  107  formed, for example, with foaming polyurethane, are stuck to the both longitudinal ends of the inlet seal  105 . The pressing seal  107  is formed substantially in a L-shape by a fixing part  107   a  and a leakage preventing part  107   b . The fixing part  107   a  is stuck on a part of the inlet seal  105 , which is stuck to the longitudinal edge of the collecting inlet  102  at the longitudinal end of the inlet seal  105 , and the leakage preventing part  107   b  is stuck to the circumferential edge of the collecting inlet  102  while contacting the outer end surfaces of the side seal  103  and the inlet seal  105 . 
     With the above-described configuration, the photoconductor  9  is rotated in the direction indicated by an arrow in FIG. 16, and residual used toner on the outer circumferential surface of the photoconductor  9  is scraped off the surface of the photoconductor  9  by the blade  104 . The scraped off used toner is collected into the used toner collecting part  101  through the collecting inlet  102 . When the photoconductor  9  is rotated as above, the inlet seal  105  is slidably contacting the outer circumferential surface of the photoconductor  9 , and therefore a pulling force along the rotating direction of the photoconductor  9  is applied to the inlet seal  105  from the photoconductor  9 . However, because the supporting parts  106  are formed at both longitudinal ends of the inlet seal  105  so as to increase the sticking area of the inlet seal  105  to the edges of the collecting inlet  102  and thereby the supporting parts  105  are firmly stuck to the edges of the collecting inlet  105 , even when the pulling force is applied to the inlet seal  105  according to the rotation of the photoconductor  9 , the both ends of the inlet seal  105  will not be pealed off. Therefore, it will not occur that both ends of the inlet seal  105  are peeled off and are thereby shifted toward the center of the inlet seal  105 . Accordingly, waving of the inlet seal  105  will not occur at a part of the inlet seal  105  slidably contacting the outer circumferential surface of the photoconductor  9 . Therefore, leakage of toner through a nip portion of the inlet seal  105  and the outer circumferential surface of the photoconductor  9  is prevented. 
     Further, the pressing seals  107  are stuck to both longitudinal ends of the inlet seal  105  and the leakage preventing parts  107   b  of the pressing seal  107  are stuck to the edges of the collecting inlet  102  while contacting the outer end surfaces of the side seal  103  and the inlet seal  105 . Therefore, even if collected used toner intrudes into a part where the side seal  103  and the inlet seal  105  are overlaid, the collected used toner is prevented from leaking toward the ends of the inlet seal  105  by the leakage preventing part  107   b  of the pressing seal  107  and thereby leakage of collected used toner from the end sides of the inlet seal  105  is securely prevented. 
     Numerous additional modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than specifically described herein. 
     This document claims priority and contains subject matter related to Japanese patent applications No. 10-301326, No. 10-301327, No. 10-301329, No. 10-303848, No. 10-308454, No. 10-308456, No. 10-367439, No.10-367440 and No. 11-184687 filed in the Japanese Patent Office on Oct. 22, 1998, Oct. 22, 1998, Oct. 22, 1998, Oct. 26, 1998, Oct. 29, 1998, Oct. 29, 1998, Dec. 24, 1998, Dec. 24, 1998, and Jun. 30, 1999, respectively, and the entire contents of which are hereby incorporated by reference.