Abstract:
A developing device includes: a casing; a developing roller mounted on the casing, and having a rotational axis extending in an axis direction and a peripheral surface on which a developer is carried, the developing roller being configured to rotate in a rotational direction about the rotational axis; and a seal provided between the casing and the developing roller to prevent the developer from leaking between peripheral surface and the casing. The seal includes: a film member opposed to the peripheral surface of the peripheral surface of the developing roller; and an elastic member provided between the film member and the casing to press the film member against the peripheral surface of developing member. The casing includes a restricting wall provided downstream of the seal member in the rotational direction to restrict the seal from moving in the rotational direction.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2011-167284 filed Jul. 29, 2011. The entire content of this application is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a developing device provided with a seal. 
     BACKGROUND 
     There is conventionally known a developing device including a casing having an opening portion, a developing roller provided so as to be opposed to the opening portion, and a lower film for preventing toner leakage from between a lower portion of the developing roller and the casing. More specifically, in this technique, the lower film is formed into an elongated shape extending in an axial direction of the developing roller, one end of the lower film positioned upstream side of a rotational direction of the developing roller being attached to the casing by a double-stick tape, the other end thereof being brought into sliding contact with the outer peripheral surface of the developing roller as a free end. 
     SUMMARY 
     However, in the above-described technique, the lower film is bent toward the developing roller to be pressed against the developing roller with an adequate pressing force. Therefore, the one end of the lower film may come off from the casing by a reaction force against the bending. Further, if the double-stick tape gets wrinkles when attached to the casing, toner may leak from a gap formed by the wrinkles. Therefore, the attachment work needs to be done in a careful manner, which makes the attachment work cumbersome and complicated. 
     In view of the foregoing, it is an object of the present invention to provide a developing device capable of preventing toner (developer) leakage with a simple mounting work while preventing a seal provided between the lower side of the developing roller and the casing from coming off. 
     In order to attain the above and other objects, the invention provides a developing device including: a casing; a developing roller mounted on the casing, and having a rotational axis extending in an axis direction and a peripheral surface on which a developer is carried, the developing roller being configured to rotate in a rotational direction about the rotational axis; and a seal provided between the casing and the developing roller to prevent the developer from leaking between peripheral surface and the casing. The seal includes: a film member opposed to the peripheral surface of the peripheral surface of the developing roller; and an elastic member provided between the film member and the casing to press the film member against the peripheral surface of developing member. The casing includes a restricting wall provided downstream of the seal member in the rotational direction to restrict the seal from moving in the rotational direction. 
     Another aspect of the present invention provides a developing device including: a casing configured to accommodate developer and formed with an opening; a developing roller mounted on the casing and opposing the opening, and having a rotational axis extending in an axis direction and a peripheral surface on which the developer is carried, the developing roller being configured to rotate in a rotational direction about the rotational axis; and a seal for preventing the developer from leaking from between the peripheral surface of the developing roller and the casing. The seal includes: a film member extending in the axis direction and configured to contact the peripheral surface of developing roller; and an elastic member provided between the film member and the casing to press the film member against the peripheral surface of developing roller. The casing includes a restricting wall positioned at a downstream of the seal in the rotational direction to restrict the seal from moving in the rotational direction. The seal is supported between the peripheral surface of the developing roller and the casing while contacting the restricting wall. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The particular features and advantages of the invention as well as other objects will become apparent from the following description taken in connection with the accompanying drawings, in which: 
         FIG. 1  is a cross-sectional view of a laser printer provided with a developing cartridge according to an embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of the developing cartridge. 
         FIG. 3  is an enlarged perspective view of the developing cartridge near an opening portion. 
         FIG. 4  is an explanation view of attachment of a lower seal to the developing cartridge. 
         FIG. 5  is a cross-sectional view of  FIG. 4 . 
         FIG. 6  is an explanation view of insertion of a developing roller into a guide groove. 
         FIG. 7  is an explanation view of attachment of a lower seal to the developing cartridge according to a variation. 
         FIG. 8  is an explanation view of a side seal member according to a variation. 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. 
     In the following description, the entire configuration of a laser printer will be described briefly first, followed by characteristic portions of the present invention. 
     Further, in the following description, directions are defined as viewed from a user who operates a printer  1 . That is, right side in  FIG. 1  is defined as “front side,” left side therein as “rear side,” far side therein as “right side,” and near side therein as “left side.” Further, vertical direction in  FIG. 1  is defined as “up-and-down direction.” 
     As illustrated in  FIG. 1 , the laser printer  1  includes, in a main body casing  2 , a feeder section  4  for feeding a paper sheet  3 , and an image forming section  5  for forming an image on the paper sheet  3 . 
     The feeder section  4  includes a paper supply tray  6  detachably mounted to a bottom portion of the main body casing  2  and a paper pressing plate  7  provided in the paper supply tray  6 . The feeder section  4  further includes various rollers  11  for feeding the paper sheet  3  and removing paper powder. In this feeder section  4 , a plurality of paper sheets  3  in the paper supply tray  6  are pressed upward by the paper pressing plate  7  and then fed one by one by the various rollers  11  to the image forming section  5 . 
     The image forming section  5  includes a scanner unit  16 , a process cartridge  17 , and a fixing section  18 . 
     The scanner unit  16  is provided in an upper portion of the main body casing  2  and includes a laser emitting section (not illustrated), a rotation-driven polygon mirror  19 , lenses  20  and  21 , reflecting mirrors  22 ,  23 , and  24 . In the scanner unit  16 , a laser beam passes through a path denoted by a long dashed double-dotted line in the drawing and is irradiated in a high-speed scanning operation onto a surface of a photosensitive drum  27 . 
     The process cartridge  17  is detachably attached to the main body casing  2  from the front side of the main body casing  2  by opening a front cover  2   a . The process cartridge  17  includes mainly a developing cartridge  28  (one example of the developing device) and a drum unit  39 . 
     The developing cartridge  28  is detachably attached to the main body casing  2  in a state where the developing cartridge  28  is attached to the drum unit  39 . As illustrated in  FIG. 2 , the developing cartridge  28  includes a developing roller  31 , a layer-thickness regulating blade  32 , a supply roller  33 , and a toner containing chamber  34 . 
     In the developing cartridge  28 , toner (one example of the developer) contained in the toner containing chamber  34  is agitated by an agitator  34 A and is supplied to the developing roller  31  by the supply roller  33 . At this time, the toner is charged by friction between the supply roller  33  and developing roller  31 . Then, with the rotation of the developing roller  31 , the toner carried on the outer peripheral surface of the developing roller  31  enters between the layer-thickness regulating blade  32  and developing roller  31  and is then carried on the developing roller  31  as a thin layer of a predetermined thickness while being charged by friction. 
     The drum unit  39  includes the photosensitive drum  27 , a scorotron charger  29 , and a transfer roller  30 . In the drum unit  39 , the surface of the photosensitive drum  27  is uniformly positively charged by the scorotron charger  29  and is thereafter exposed by the high-speed scanning operation of the laser beam from the scanner unit  16 . As a result, electric potential at the exposed portion decreases and thus an electrostatic latent image based on image data is formed. 
     Subsequently, the toner carried on the developing roller  31  is supplied, by rotation of the developing roller  31 , to the electrostatic latent image formed on the surface of the photosensitive drum  27 , whereby a toner image is formed on the surface of the photosensitive drum  27 . Thereafter, the paper sheet  3  is fed between the photosensitive drum  27  and transfer roller  30 , whereby the toner image carried on the surface of the photosensitive drum  27  is transferred onto the paper sheet  3 . 
     As illustrated in  FIG. 1 , the fixing section  18  includes a heating roller  41  and a pressure roller  42  disposed opposite to the heating roller  41  so as to pressurize the heating roller  41 . In the fixing section  18  having the above configuration, the toner transferred onto the paper sheet  3  is thermally fixed during the passage of the paper sheet  3  between the heating roller  41  and the pressure roller  42 . The paper sheet  3  onto which the toner has been thermally fixed in the fixing section  18  is fed to a paper discharge tray  46  by a paper discharge roller  45  disposed on the downstream side of the fixing section  18 . 
     &lt;Detailed Configuration of Developing Cartridge&gt; 
     Next, a configuration of the developing cartridge  28  according to the embodiment of the present invention will be described in detail.  FIG. 3  illustrates a state where the developing roller  31  and supply roller  33  have been removed from a casing  50 . 
     As illustrated in  FIG. 3 , the developing cartridge  28  includes, in addition to the above-described developing roller  31 , the casing  50  that rotatably supports the developing roller  31 , a pair of side seal members  61 , a pair of blade seal members  62 , and a lower seal  63  (one example of the seal member). The pair of side seal members  61  is brought into sliding contact with both axial direction end portions of the developing roller  31 , respectively. Further, the pair of blade seal members  62  is also brought into sliding contact with both axial direction end portions of the developing roller  31 , respectively. The developing roller  31  rotates in a rotational direction shown by an arrow in the drawing, that is, rotates in the direction from the side seal member  61  toward the blade seal member  62 . 
     In the casing  50 , there are formed a support portion  51  that rotatably supports the developing roller  31 , an opening portion  52  for supplying the toner from the toner containing chamber  34  inside the casing  50  to the developing roller  31 , a side seal attachment surface  53  to which the side seal member  61  is attached, and an attachment groove  57  in which the lower seal  63  goes. 
     The support portion  51  is formed as a circular hole penetrating, in a left-right direction, a side wall  55  protruding rearward from a left-right direction outside end portion of the side seal attachment surface  53  so as to support both end portions of a rotary shaft of the developing roller  31  directly or through a bearing. A guide groove  56  protruding rearward and opened rearward is formed on the rear side of the support portion  51  so as to communicate with the support portion  51 . 
     Thus, as described later, when the rotary shaft of the developing roller  31  is inserted into the developing cartridge  28  along the guide groove  56  from outside the casing  50 , the rotary shaft of the developing roller  31  is guided from outside the casing  50  to the support portion  51 . The developing roller  31  supported in the support portion  51  is disposed at a position opposite to the opening portion  52  and can receive supply of the toner through the opening portion  52 . 
     The opening portion  52  is formed into a rectangular hole elongated along the axial direction of the developing roller  31 , and the layer-thickness regulating blade  32  is fixed to the upper portion of the opening portion  52 . 
     As illustrated in  FIG. 2 , the layer-thickness regulating blade  32  includes a metal plate  32 A, reinforcing plates  32 B and  32 C that sandwich an upper portion of the metal plate  32 A for reinforcing purpose, and a pressing member  32 D made of rubber which is fixed to a lower portion (leading end portion) of the metal plate  32 A and which is smaller in left-right direction width than the metal plate  32 A. The layer-thickness regulating blade  32  is fixed to the casing  50  at the upper portion of the metal plate  32 A sandwiched by the reinforcing plates  32 B and  32 C. The pressing member  32 D at the leading end of the layer-thickness regulating blade  32  is brought into sliding contact with the developing roller  31  by a biasing force of the metal plate  32 A. In  FIG. 3 , the outside reinforcing plate  32 C has been removed from the metal plate  32 A. 
     A blade back seal  64  is provided between the layer-thickness regulating blade  32  and casing  50 . More specifically, as schematically illustrated in  FIG. 4(   a ), the blade back seal  64  is formed into a reverse U-like shape surrounding an upper side portion of the opening portion  52  and attached, at both ends thereof, to an upper portion of the side seal attachment surface  53 . 
     The blade back seal  64  is formed longer than the layer-thickness regulating blade  32  in the left-right direction (longitudinal direction), and both end portions  64 A of the blade back seal  64  in the left-right direction protrude from both end portions  32 E of the layer-thickness regulating blade  32  in the left-right direction, respectively. As a result, when the layer-thickness regulating blade  32  is fixed to the casing  50  so as to compress the blade back seal  64 , the both end portions  32 E of the layer-thickness regulating blade  32  are covered by the end portions  64 A of the blade back seal  64  that are not compressed. Thus, as shown in  FIG. 5  in which (a) is an X-X cross sectional view of  FIG. 4(   c ) and ( b ) is a Y-Y cross sectional view of  FIG. 4(   c ), a minor gap G 1  formed between the compressed blade back seal  64  and a level difference (level difference between the metal plate  32 A and inner reinforcing plate  32 B) of the layer-thickness regulating blade  32  is filled with the both end portions  64 A of the blade back seal  64  (in  FIG. 5(   b ), a lower end of the layer-thickness regulating blade  32  is covered by a lower end portion of the blade back seal  64 ), thereby preventing toner leakage. 
     As illustrated in  FIG. 3 , the side seal attachment surface  53 , which is an arc-like surface, is formed on both the left and right sides (axial direction both sides of the developing roller  31 ) of the opening portion  52 . 
     As illustrated in  FIG. 2 , the attachment groove  57  is formed on a lower side of the opening portion  52  (see  FIG. 3 ) of the casing  50  and includes mainly a restricting wall  57 A, an inclined wall  57 B disposed at the upstream of the restricting wall  57 A, and a bottom wall  57 C connecting the restricting wall  57 A to the inclined wall  57 B. 
     The restricting wall  57 A is formed substantially perpendicular to the bottom wall  57 C, which brings the restricting wall  57 A into close surface contact with the front surface of the rectangular solid lower seal  63  when the lower seal  63  is placed on the bottom wall  57 C. 
     The inclined wall  57 B is inclined relative to the bottom wall  57 C so as to be away from the restricting wall  57 A toward the developing roller  31  side. Thus, the lower seal  63  is guided to the restricting wall  57 A along the inclined wall  57 B so that the front surface of the lower seal  63  is brought into close surface contact with the restricting wall  57 A. 
     As illustrated in  FIG. 3 , each of the side seal members  61  is provided between each of the both end portions of the developing roller  31  and the side seal attachment surface  53  of the casing  50 . 
     The side seal member  61  includes a substrate  61 A having elasticity and a sliding contact member  61 B provided on the substrate  61 A so as to be brought into slide contact with the developing roller  31 . The substrate  61 A is formed of elastically-deformable urethane sponge which is softer than a material of the slide contact member  61 B and is fitted in a concave portion and a plurality of ribs formed in the side seal attachment surface  53  of the casing  50 . The substrate  61 A may be attached to the side seal attachment surface  53  of the casing  50  by a double-stick tape or an adhesive. 
     The sliding contact member  61 B is formed of a felt material thinner than the substrate  61 A and is attached to the substrate  61 A by a double-stick tape. The front, rear, left, and right surfaces of the sliding contact member  61 B are flush with those of the substrate  61 A. 
     The blade seal members  62  are provided at both end portions of the layer-thickness regulating blade  32  in the left-right direction, respectively, so as to tightly contact left and right both end edges of the layer-thickness regulating blade  32  and each positioned adjacent to the side seal member  61  in the rotational direction of the developing roller  31 . As illustrated in  FIG. 5(   a ), the blade seal member  62  is formed by attaching, by a double-stick tape, a substrate  62 A and a sliding contact member  62 B thinner than the substrate  62 A, likewise the above-described side seal member  61 . The substrate  62 A is attached by a double-stick tape to the metal plate  32 A of the layer-thickness regulating blade  32 , whereby the blade seal member  62  is fixed to the layer-thickness regulating blade  32 . 
     The sliding contact member  62 B is formed longer than the substrate  62 A in the rotational direction of the developing roller  31 , and is bent at the leading end of the layer-thickness regulating blade  32  (metal plate  32 A) so as to wrap the layer-thickness regulating blade  32  from the lower side. This prevents the blade seal member  62  from coming off due to rotation of the developing roller  31 . 
     Further, the configuration in which only the thin sliding contact member  62 B is bent to attach the blade seal member  62  to the layer-thickness regulating blade  32  (metal plate  32 A) can significantly reduce a level difference which is formed by the metal plate  32 A and the sliding contact member  62 B. Thus, the blade back seal  64  compressed toward the metal plate  32 A and the sliding contact member  62 B can be deformed so as to follow the reduced level difference, thereby preventing toner leakage from around the level difference. 
     As shown in  FIG. 5(   a ), the bent portion of the sliding contact member  62 B contacts an upper end portion of its adjacent side seal member  61  (upper ends of the substrate  61 A and sliding contact member  61 B). This prevents toner leakage from between the side seal member  61  and blade seal member  62 . 
     As illustrated in  FIG. 3 , the lower seal  63  is a member that prevents the toner from leaking from between the outer peripheral surface of the developing roller  31  and casing  50  and includes a substrate  63 A formed of urethane sponge (one example of the elastic member) and a film member  63 B provided on the substrate  63 A so as to contact the outer peripheral surface of the developing roller  31 . As illustrated in  FIG. 2 , the lower seal  63  is held by being sandwiched between the developing roller  31  and casing  50  in a state of being merely placed in the attachment groove  57  without using an adhesive. 
     More specifically, the lower seal  63  is placed in the attachment groove  57 , and then the developing roller  31  is mounted in the casing  50 , whereby the lower seal  63  is held by being sandwiched between the developing roller  31  and casing  50  in a state of being adjacent to the restricting wall  57 A. Upon rotation of the developing roller  31 , a force directed in the rotation (downstream) direction is applied from the developing roller  31  to the lower seal  63  to press the lower seal in the downstream direction; however, the downstream direction movement of the lower seal  63  is restricted by the restricting wall  57 A. 
     As a result, the lower seal  63  is pressed against the restricting wall  57 A to tightly contact the restricting wall  57 A, thereby preventing the lower seal  63  from coming off from the casing  50 . 
     Further, since the lower seal  63  can be attached to the casing  50  simply by placing the lower seal  63  in the attachment groove  57  and sandwiching the same between the developing roller  31  and casing  50 , the attachment work of the lower seal  63  can be made simpler than that in a configuration in which the seal member is fixed to the casing by, e.g., a double-stick tape. The absence of the double-stick tape between the lower seal  63  and the casing  50  can prevent a gap from being formed at the attachment work of the lower seal  63  due to formation of wrinkles in the double-stick tape, thereby preventing toner leakage without fail. Note that such wrinkles are likely to occur particularly when an elongated lower seal is used. 
     In a state where the lower seal  63  abuts against the restricting wall  57 A, the developing roller  31  contacts a portion of the lower seal  63  that is positioned downstream in the rotational direction relative to the center (center of the developing roller  31  in the rotational direction) thereof. Thus, the developing roller  31  can be separated more away from the leading end (upstream side end portion in the rotational direction) of the film member  63 B than in a configuration in which the developing roller is made to contact the center of the lower seal, thereby preventing the leading end of the film member  63 B raised due to deformation of the substrate  63 A from being brought into sliding contact with the outer periphery of the developing roller  31 . 
     As illustrated in  FIG. 3 , the substrate  63 A of the lower seal  63  is formed into a rectangular solid extending in the left-right direction and is provided between the film member  63 B and casing  50  so as to press the film member  63 B against the developing roller  31 . A length L 1  of the substrate  63 A before attachment to the casing  50  is longer than a distance L 2  between the pair of side seal members  61  attached to the casing  50 . 
     When the substrate  63 A and the side seal members  61  are attached to the casing  50 , the substrate  63 A is first placed on the attachment groove  57  with the both end portions thereof protruding from the left and right both ends of the attachment groove  57  of the casing  50 , as illustrated in  FIG. 4(   a ). Thereafter, while contracting the substrate  63 A in the left-right direction with the surface of the substrate  63 A held using a jig, the side seal members  61  are attached to the side seal attachment surfaces  53  on both the left and right sides of the substrate  63 A. 
     As a result, both the left and right end surfaces of the substrate  63 A are brought into press contact with the left-right direction inner surfaces of the respective side seal members  61 , thereby preventing toner leakage from between the substrate  63 A and side seal members  61 . 
     As illustrated in  FIG. 4(   c ), the film member  63 B is a sheet-like member formed of polyethylene terephthalate and extends in the axial direction of the developing roller  31  so as to be brought into sliding contact with the developing roller  31  over substantially the entire axial length thereof. More specifically, the both end portions of the film member  63 B protrude outward in the left-right direction (toward the side seal member  61  side) from the substrate  63 A, and the protruding both end portions thereof are put on (overlap) the respective side seal members  61 . 
     In the conventional configuration, the film member is provided between the both side seal members. Therefore, the film member may hit the inner surface of the side seal member at the attachment time of the lower seal or side seal member, thereby bending the film member. As a result, toner may leak from between the film member and the developing roller. 
     However, the protruding end portions of the film member  63 B are put on (overlap) the respective side seal members  61  in the present embodiment. Therefore, toner leakage from between the film member  63 B and developing roller  31  can be prevented since the film member  63 B is not bent. 
     As illustrated in  FIG. 6 , the above-described guide groove  56  of the casing  50  is formed at a position and angle such that the developing roller  31  abuts against an upper surface  631  (developing roller  31  side surface) of the lower seal  63  when the developing roller  31  is mounted to the support portion  51 . In other words, the guide groove  56  is formed at a position and angle such that a trajectory T of the developing roller  31  upon mounting of the developing roller  31  to the support portion  51  intersects the upper surface  631  of the lower seal  63 . 
     This configuration prevents the developing roller  31  from abutting against an upper rear side corner of the lower seal  63  upon mounting of the developing roller  31  to the support portion  51 , thereby preventing the lower seal  63  from swaying and coming off from the attachment groove  57 . 
     While the invention has been described in detail with reference to the embodiment thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention. 
     For example, although the lower seal  63  (substrate  63 A) is attached to the casing  50  by press contact with the inner surfaces of the respective side seal members  61  in the above embodiment, a configuration shown in  FIG. 7  may be employed. In  FIG. 7 , the same reference numerals are used for components substantially the same as those in the first embodiment, and the descriptions thereof are omitted. 
     As illustrated in  FIG. 7 , a lower seal  70  includes a substrate  71  formed of the same material as the lower seal  63  in the above embodiment but having a shape different therefrom and a film member  63 B substantially the same as that in the above embodiment. The substrate  71  includes a main body  71 A having a length shorter than a distance between a pair of side seal members  80  that have been attached to the casing  50  and a pair of protruding portions  71 B extending outward in the left-right direction respectively from both left and right end portions of the main body  71 A. 
     As illustrated in  FIG. 7(   b ), in the casing  50 , a pair of ribs  58  is disposed upstream of the pair of side seal members  80  in the rotational direction, respectively, so as to be spaced apart from the pair of side seal members  80 . Each protruding portion  71 B is sandwiched between the corresponding rib  58  and side seal member  80 , thereby bringing the protruding portion  71 B into press contact with the side seal member  80 . 
     More specifically, as illustrated in  FIG. 7(   a ), a substrate  81  of the side seal member  80  before attachment to the casing  50  protrudes downward from a lower end of a sliding contact member  82  of the side seal member  80  in the rotational direction. Further, the substrate  81  before attachment to the casing  50  is longer than a length between the protruding portion  71 B and blade back seal  64  in the rotational direction. 
     Since the lower side end portion of the substrate  81  is not restrained by the sliding contact member  82 , the crush amount of the lower side end portion of the substrate  81  can be increased. Therefore, as shown in  FIG. 7(   b ), when the side seal member  80  is attached to the casing  50 , the substrate  81  is contracted and brought into press contact with the protruding portion  71 B, thereby bringing the end portion into tight contact with the protruding portion  71 B. 
     Further, although, as shown in  FIG. 4 , the inner surface of the sliding contact member  61 B in the left-right direction is flush with that of the substrate  61 A in the above embodiment, the inner surface of the sliding contact member  61 B in the left-right direction may be positioned outward of that of the substrate  61 A, as shown in  FIG. 8 . 
     This construction suppresses restriction of deformation of the left-right direction inner portion of the substrate  61 A by the sliding contact member  61 B. Therefore, when the base material  63 A of the lower seal  63  and substrate  61 A of the side seal member  61  are brought into press contact with each other, the crush amount of the substrate  61 A is increased, thereby increasing contact between the lower seal  63  and side seal member  61 . 
     Note that, in  FIG. 8 , the film member  63 B is formed so as to protrude toward the side seal member  61  side from the substrate  63 A, and the protruding portions thereof are put on (overlap) the sliding contact members  61 B of the side seal member  61 . 
     Further, although the sliding contact member  62 B of the blade seal member  62  is formed thinner than the substrate  62 A in the above embodiment, the sliding contact member may be formed thicker than the substrate. 
     Further, although the urethane sponge has been taken as an example of an elastic member in the above embodiment, other sponge materials may be employed. Further, other resin materials may be employed as a material of the film member instead of the polyethylene terephthalate mentioned in the above embodiment. Further, materials of the substrate and sliding contact member which constitute the side seal member are not limited to those mentioned in the above embodiment, but may be changed according to need. 
     Further, although the lower seal  63  is put into the attachment groove  57  in the above embodiment, a configuration may be adopted in which only the restricting wall  57 A is formed in the casing  50 , and the lower seal  63  is sandwiched between the developing roller  31  and casing  50  in a state of being adjacent to the restricting wall  57 A. 
     Although the present invention has been applied to the developing cartridge  28  in the above embodiment, the present invention is not limited to this. For example, the present invention may be applied to other developing device such as a process cartridge obtained by combining the developing cartridge and drum unit or a developing unit receiving supply of toner from a toner cartridge for containing the toner.