Abstract:
A developer cartridge includes a developer roller, a support member and a first seal member. The developer roller has a rotational axis and a peripheral surface. The peripheral surface includes a center zone and an end zone at one end portion in an axial direction. The support member supports the developer roller to be rotatable about the rotational axis. The support member has an opposing surface opposed to the end zone. A protrusion protrudes from the opposing surface, and extends in a direction crossing with the axial direction. The first seal member is disposed between the end zone and the opposing surface in order to prevent developer from leaking out of a space formed between the end zone and the opposing surface.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims priority to Japanese Patent Application No. 2005-130200 filed on Apr. 27, 2005, the contents of which are hereby incorporated by reference into the present application. 
   TECHNICAL FIELD 
   The present invention relates to an image-forming device such as a laser printer, and a developer cartridge and process cartridge mounted in the image-forming device. 
   BACKGROUND 
   Image-forming devices such as laser printers have conventionally been provided with a developer cartridge detachably mounted therein for supplying a developer to the surface of a photosensitive drum in the image-forming device. 
   The developer cartridge is commonly configured of a casing for accommodating developer, and a developing roller rotatably supported in the casing for carrying developer within the casing. The casing also has an elongated opening formed therein. The developing roller is disposed so that a portion of the roller is exposed through the opening to confront the surface of a photosensitive drum disposed in the image-forming device. As the developing roller rotates, developer from the casing carried on the surface of the developing roller comes into contact with the surface of the photosensitive drum. At this time, the developer is attracted to an electrostatic latent image formed on the surface of the photosensitive drum in order to develop the image into a developer image. Subsequently, the developer image is transferred onto a sheet of paper, forming an image on the paper. 
   This type of developer cartridge has been conventionally provided with sealing members disposed between each end of the developing roller and the casing to prevent developer from leaking therethrough. When the sealing member are fixed to the casing with double-sided tape or adhesive, remnants of the double-sided tape or adhesive remain on the casing after the sealing members are peeled therefrom. Accordingly, extra effort is required when recycling (reusing) the developing cartridge as the sealing members are replaced with new members. 
   Therefore, Japanese unexamined patent application publication No. HEI-9-269657 proposes a technique for mounting sealing members on the housing of the developing device. According to this technique, fitting parts are formed in the housing such that the sealing members can be fittingly inserted into the fitting parts. Protruding parts extending in a direction parallel to the axial direction of the developing roller (a direction orthogonal to the rotating direction of the developing roller) are formed on each fitting part to prevent the sealing members from shifting from the mounted position as the developing roller rotates. 
   However, in the proposed structure described above, since the sealing members are not fixed to the fitting parts with double-sided tape or adhesive, a gap may be formed between the sealing member and the fitting part as the developing roller rotates, risking the chance that developer may enter this gap and leak out of the housing along the protruding parts. 
   SUMMARY 
   In view of the foregoing, it is an object of the present invention to provide a developer cartridge, process cartridge, and image-forming device capable of reliably preventing developer from leaking between the ends of the developing roller and the casing. 
   In order to attain the above and other objects, the present invention provides a developer cartridge includes a developer roller, a support member and a first seal member. The developer roller has a rotational axis and a peripheral surface. The peripheral surface includes a center zone and an end zone at one end portion in an axial direction. The support member supports the developer roller to be rotatable about the rotational axis. The support member has an opposing surface opposed to the end zone. A protrusion protrudes from the opposing surface, and extends in a direction crossing with the axial direction. The first seal member is disposed between the end zone and the opposing surface in order to prevent developer from leaking out of a space formed between the end zone and the opposing surface. 
   Another aspect of the present invention provides a process cartridge including the above-described developer cartridge and an image-bearing member on which the toner is provided from the developer cartridge. 
   Another aspect of the present invention provides an image-forming device including the above-described developer cartridge and a body mountable the developer cartridge. 
   Another aspect of the present invention provides an image-forming device including the above-described process cartridge and a body mountable the process cartridge. 
   Another aspect of the present invention provides a developer cartridge including a developer roller, a support member and a first seal member. The developer roller has a rotational axis and a peripheral surface. The peripheral surface includes a center zone and an end zone at one end portion in an axial direction. The support member supports the developer roller to be rotatable about the rotational axis. The support member has an opposing surface opposed to the end zone. The opposing surface is formed with a protrusion having a first end and a second end farther from the central zone than the first end in the axial direction. The first end of the protrusion is formed in an upstream side of the second end of the protrusion with respect to a rotational direction of the developer roller. The first seal member is disposed between the end zone and the opposing surface in order to prevent developer from leaking out of a space formed between the end zone and the opposing surface. 
   Another aspect of the present invention provides a process cartridge including the above-described developer cartridge and an image-bearing member on which the toner is provided from the developer cartridge. 
   Another aspect of the present invention provides an image-forming device including the above-described developer cartridge and a body mountable the developer cartridge. 
   Another aspect of the present invention provides an image-forming device including the above-described process cartridge and a body mountable the process cartridge. 
   Another aspect of the present invention provides a developer cartridge including a developer roller, a support member and a first seal member. The developer roller has a rotational axis and a peripheral surface. The peripheral surface includes a center zone and an end zone at one end portion in an axial direction. The support member supports the developer roller to be rotatable about the rotational axis. The support member has an opposing surface opposed to the end zone. The opposing surface is formed with a protrusion having a first end and a second end. A virtual straight line connecting the first end to the second end is orthogonal to the axial direction. The first seal member is disposed between the end zone and the opposing surface in order to prevent developer from leaking out of a space formed between the end zone and the opposing surface. 
   Another aspect of the present invention provides a process cartridge including the above-described developer cartridge and an image-bearing member on which the toner is provided from the developer cartridge. 
   Another aspect of the present invention provides an image-forming device including the above-described developer cartridge and a body mountable the developer cartridge. 
   Another aspect of the present invention provides an image-forming device including the above-described process cartridge and a body mountable the process cartridge. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the invention will become more apparent from reading the following description of the preferred embodiments taken in connection with the accompanying drawings in which: 
       FIG. 1  is a side cross-sectional view of a laser printer according to a preferred embodiment of the present invention, when a cover is in a closed state; 
       FIG. 2  is a side cross-sectional view of the laser printer in  FIG. 1  when the front cover is in an open state; 
       FIG. 3  is a side cross-sectional view of a developer cartridge provided in the laser printer of  FIG. 1 ; 
       FIG. 4  is a perspective view of the developer cartridge in  FIG. 3  from the rear side (side on which the developing roller is provided); 
       FIG. 5  is a perspective view of the developer cartridge in  FIG. 3  when the developing roller has been removed; 
       FIG. 6  is a perspective view showing the rear side of the developer cartridge in  FIG. 3  on one widthwise end thereof; 
       FIG. 7  is a perspective view showing a rear side of a developer side casing of the developer cartridge in  FIG. 3  on one widthwise end thereof; and 
       FIG. 8  is a perspective view showing protruding parts in the developer side casing according to a variation of the preferred embodiment. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A developer cartridge, a process cartridge and an image-forming device according to preferred embodiments of the present invention will be described while referring to the accompanying drawings wherein like parts and components are designated by the same reference numerals to avoid duplicating description. 
   1. General Structure of a Laser Printer 
     FIGS. 1 and 2  are side cross-sectional views of a laser printer  1  serving as the image-forming device of the present invention. The laser printer  1  includes a main casing  2  and, within the main casing  2 , a feeder unit  4  for supplying sheets of a paper  3 , an image-forming unit  5  for forming images on the paper  3  supplied from the feeder unit  4 , and the like. 
   &lt;Main Casing&gt; 
   An access opening  6  is formed in one side surface of the main casing  2  for inserting and removing a process cartridge  18  described later. A front cover  7  is disposed on the side surface of the main casing  2  and is capable of opening and closing over the access opening  6 . 
   The front cover  7  is rotatably supported by a cover shaft (not shown) inserted through a bottom end of the front cover  7 . When the front cover  7  is rotated closed about the cover shaft, the front cover  7  covers the access opening  6 , as shown in  FIG. 1 . When the front cover  7  is rotated open about the cover shaft (rotated downward), the access opening  6  is exposed, as shown in  FIG. 2 , enabling the process cartridge  18  to be mounted into or removed from the main casing  2  via the access opening  6 . 
   In the following description, the side of the laser printer  1  on which the front cover  7  is provided will be referred to as the “front side,” while the opposite side will be referred to as the “rear side.” Further, a direction orthogonal to both of the front-to-rear direction and the vertical direction will be referred to as the “width direction.” In addition, the front, rear, left, right, top, and bottom sides of the process cartridge  18  (and a developer cartridge  26 ) described later will be described based on the state of the process cartridge  18  mounted in the main casing  2 . 
   &lt;Feeding Unit&gt; 
   The feeder unit  4  includes a paper tray  8  detachably mounted in a lower section of the main casing  2 , a feeding roller  9  and separating pad  10  disposed above a front end of the paper tray  8 , a pickup roller  11  disposed to the rear side of the feeding roller  9 , a pinch roller  12  disposed in confrontation with the feeding roller  9  at the lower front surface thereof, and a pair of registration rollers  13  disposed above and rearward of the feeding roller  9 . 
   A paper-pressing plate  14  is provided inside the paper tray  8  for supporting the paper  3  in a stacked state. The paper-pressing plate  14  is pivotably supported on the rear end thereof, so that the front end can pivot downward to a resting position in which the paper-pressing plate  14  rests on a bottom plate of the paper tray  8  and can pivot upward to a supplying position in which the paper-pressing plate  14  is at a slope. 
   A lever  15  is provided in the front section of the paper tray  8  for lifting the front end of the paper-pressing plate  14  upward. The lever  15  has a substantially L-shaped cross section in order to bend around the front end of the paper-pressing plate  14  and extend under the bottom surface of the same. The top end of the lever  15  is attached to a lever shaft  16  disposed on the front end of the paper tray  8 , while the rear end of the lever  15  contacts the bottom surface of the paper-pressing plate  14  near the front end thereof. When a driving force is inputted into the lever shaft  16 , the lever  15  rotates about the lever shaft  16  so that the rear end of the lever  15  lifts the front end of the paper-pressing plate  14  upward, shifting the paper-pressing plate  14  from the resting position to the supplying position. 
   When the paper-pressing plate  14  is in the supplying position, the topmost sheet of the paper  3  stacked on the paper-pressing plate  14  is pressed against the feeding roller  11 . The rotating feeding roller  11  begins feeding the sheets of paper  3  between the separating roller  9  and separating pad  10 . 
   When the paper tray  8  is removed from the main casing  2 , the front end of the paper-pressing plate  14  drops downward of its own accord into the resting position. In this state, the paper  3  can be loaded in a stacked state on the paper-pressing plate  14 . 
   When the pickup roller  11  conveys a sheet of the paper  3  between the feeding roller  9  and separating pad  10 , the paper  3  becomes interposed between the feeding roller  9  and separating pad  10  by the rotation of the feeding roller  9  and is reliably separated and fed one sheet at a time. The fed sheets of paper  3  pass between the feeding roller  9  and pinch roller  12  and are conveyed to the registration rollers  13 . 
   After adjusting the registration of the paper  3 , the registration rollers  13  convey the sheet of paper  3  to a transfer position in the image-forming unit  5  (a position between a photosensitive drum  28  and a transfer roller  30  described later at which a toner image formed on the photosensitive drum  28  is transferred onto the paper  3 ). 
   &lt;Image-Forming Unit&gt; 
   The image-forming unit  5  includes a scanning unit  17 , the process cartridge  18 , and a fixing unit  19 . 
   (1) Scanning Unit 
   The scanning unit  17  is disposed in the top section of the main casing  2  and includes a laser light source (not shown), a polygon mirror  20  that can be driven to rotate, a fθ lens  21 , a reflecting mirror  22 , a lens  23 , and a reflecting mirror  24 . The laser light source emits a laser beam based on image data. As illustrated by a dotted line in  FIG. 1 , the laser beam is deflected by the polygon mirror  20 , passes through the fθ lens  21 , is reflected by the reflecting mirror  22 , passes through the lens  23 , and is reflected downward by the reflecting mirror  24  to be irradiated on the surface of the photosensitive drum  28  described later of the process cartridge  18  in a high-speed scan. 
   (2) Process Cartridge 
   The process cartridge  18  is detachably mounted in the main casing  2  beneath the scanning unit  17 . The process cartridge  18  includes a drum cartridge  25 , and the developer cartridge  26  that is detachably mounted on the drum cartridge  25 . 
   The developer cartridge  26  can be mounted in or removed from the main casing  2  together with the drum cartridge  25 , or can be mounted in or removed from the main casing  2  by itself while the drum cartridge  25  is mounted in the main casing  2 . 
   The drum cartridge  25  includes a drum side casing  27 . The developer cartridge  26  is mounted on the front portion of the drum side casing  27 . In the rear portion of the drum side casing  27 , the drum cartridge  25  includes the photosensitive drum  28 , a Scorotron charger  29 , the transfer roller  30 , and a cleaning brush  31 . 
   The photosensitive drum  28  includes a main drum body  32  that is cylindrical in shape and has a positive charging photosensitive layer formed of polycarbonate or the like on the outer surface thereof, and a metal drum shaft  33  extending along the axial center of the main drum body  32  in the longitudinal direction thereof. The drum shaft  33  is rotatably supported in the drum side casing  27  so that the photosensitive drum  28  can rotate in the drum side casing  27  about the drum shaft  33 . During an image-forming process, the photosensitive drum  28  rotates clockwise in  FIG. 1 . 
   The charger  29  is supported on the drum side casing  27  diagonally above and rearward of the photosensitive drum  28 . The charger  29  is disposed in opposition to the photosensitive drum  28  from a prescribed distance so as not to contact the same. The charger  29  includes a discharge wire and a grid for controlling the amount of corona discharge from the discharge wire that reaches the surface of the photosensitive drum  28  to charge the surface with a uniform positive polarity. 
   The transfer roller  30  is disposed in the drum side casing  27  beneath the photosensitive drum  28  and opposes and contacts the photosensitive drum  28  to form a nip part therewith. The transfer roller  30  is configured of a metal transfer roller shaft  34  that is covered with a roller  35  formed of an electrically conductive rubber material. The roller shaft  34  is rotatably supported in the drum side casing  27 . During a transfer operation, the transfer roller  30  is driven to rotate counterclockwise in  FIG. 1 , while a transfer bias is applied to the transfer roller  30 . 
   The cleaning brush  31  is disposed rearward of the photosensitive drum  28  so that a tip of the brush is in contact with the surface of the main drum body  32  of the photosensitive drum  28 . 
     FIG. 3  is a side cross-sectional view of the developer cartridge  26 . The developer cartridge  26  includes a developer side casing  36  and, within the developer side casing  36 , a supply roller  37 , a developing roller  38 , and a thickness-regulating blade  39 . 
   The developer side casing  36  is formed in a box shape having an elongated opening  40  formed in the rear side thereof. A partitioning wall  41  is provided in the developer side casing  36  for partitioning the interior of the developer side casing  36  into a toner-accommodating chamber  42 , and a developing chamber  43 . 
   The toner-accommodating chamber  42  is filled with a nonmagnetic, single-component toner having a positive charge. The toner used in the preferred embodiment is a polymerized toner obtained by copolymerizing a polymerized monomer using a well-known polymerization method such as suspension polymerization. The polymerized monomer may be, for example, a styrene monomer such as styrene or an acrylic monomer such as acrylic acid, alkyl (C1-C4) acrylate, or alkyl (C1-C4) meta acrylate. The polymerized toner is formed as particles substantially spherical in shape in order to have excellent fluidity for achieving high-quality image formation. 
   This type of toner is compounded with a coloring agent, such as carbon black, or wax, as well as an additive such as silica to improve fluidity. The average diameter of the toner particles is about 6-10 μm. 
   An agitator shaft  45  is disposed in the center of the toner-accommodating chamber  42  and extends in the width direction. An agitator  44  is supported on the agitator shaft  45  for rotating about the agitator shaft  45  to stir toner inside the toner-accommodating chamber  42 . While agitating toner in the toner-accommodating chamber  42 , the agitator  44  discharges some of the toner through an opening  46  formed below the partitioning wall  41 . 
   The supply roller  37  is disposed diagonally rearward and below the opening  46 . The supply roller  37  includes a metal supply roller shaft  47  that is covered by a sponge roller  48  formed of an electrically conductive foam material. The supply roller shaft  47  is rotatably supported in both side walls of the developer side casing  36  in the developing chamber  43 . 
   The developing roller  38  is disposed rearward of the supply roller  37  and contacts the supply roller  37  with pressure so that both are compressed. The developing roller  38  includes a metal developing roller shaft  49 , and a roller  50  formed of an electrically conductive rubber material that covers the developing roller shaft  49 . The developing roller shaft  49  is rotatably supported in the developing chamber  43  in both side walls of the developer side casing  36 . The roller  50  is more specifically formed of an electrically conductive urethane rubber or silicon rubber containing fine carbon particles or the like, the surface of which is coated with urethane rubber or silicon rubber containing fluorine. A developing bias is applied to the developing roller  38  during a developing operation. 
   The thickness-regulating blade  39  includes a main blade member  51  configured of a metal leaf spring member, a pressing part  52  provided on a distal end of the main blade member  51 , and a blade holder  53  for holding the main blade member  51 . The pressing part  52  has a semicircular cross section and is formed of an insulating silicon rubber. The blade holder  53  is mounted in a blade mounting part  64  described later of the developer side casing  36 , while the elastic force of the main blade member  51  causes the pressing part  52  to contact the surface of the developing roller  38  with pressure at a position above the supply roller  37 . 
   During a developing operation, the supply roller  37  rotates counterclockwise in  FIG. 2 , while the developing roller  38  also rotates counterclockwise in  FIG. 2 . 
   Toner discharged toward the developing chamber  43  through the opening  46  is supplied onto the roller  50  of the developing roller  38  by the rotating supply roller  37 . At this time, the toner is positively tribocharged between the sponge roller  48  of the supply roller  37  and the roller  50  of the developing roller  38 . As the developing roller  38  rotates, toner supplied to the surface of the roller  50  passes between the roller  50  and the pressing part  52  of the thickness-regulating blade  39 , thereby maintaining a uniform thickness of toner on the surface of the developing roller  38 . 
   In the meantime, as shown in  FIG. 1 , the charger  29  charges the surface of the photosensitive drum  28  with a uniform positive polarity. Subsequently, a laser beam emitted from the scanning unit  17  is scanned at a high speed over the surface of the photosensitive drum  28 , forming an electrostatic latent image on the photosensitive drum  28  corresponding to an image that will be formed on the paper  3 . 
   Next, positively charged toner carried on the surface of the developing roller  38  comes into contact with the photosensitive drum  28  as the developing roller  38  rotates and is supplied to areas on the surface of the positively charged photosensitive drum  28  that were exposed to the laser beam and, therefore, have a lower potential. In this way, the latent image on the photosensitive drum  28  is transformed into a visible image according to a reverse development process so that a toner image is carried on the surface of the photosensitive drum  28 . 
   As the registration rollers  13  convey a sheet of the paper  3  through a transfer position between the photosensitive drum  28  and transfer roller  30 , the toner image carried on the surface of the photosensitive drum  28  is transferred onto the paper  3  by a transfer bias applied to the paper  3 . 
   Toner remaining on the surface of the photosensitive drum  28  after the transfer operation is recovered by the developing roller  38 . Further, paper dust deposited on the photosensitive drum  28  from the paper  3  is removed from the surface of the photosensitive drum  28  by the cleaning brush  31 . 
   (3) Fixing Unit 
   The fixing unit  19  is disposed rearward of the process cartridge  18  and includes a fixed frame  54 ; and a heating roller  55  and a pressure roller  56  provided within the fixed frame  54 . 
   The heating roller  55  includes a metal tube, the surface of which has been coated with a fluorine resin, and a halogen lamp disposed inside the metal tube for heating the same. The heating roller  55  is driven to rotate clockwise in  FIG. 1 . 
   The pressure roller  56  is disposed below and in opposition to the heating roller  55  and contacts the heating roller  55  with pressure. The pressure roller  56  is configured of a metal roller shaft covered with a roller that is formed of a rubber material. The pressure roller  56  follows the rotational drive of the heating roller  55 . 
   In the fixing unit  19 , toner transferred onto the paper  3  at the transfer position is fixed to the paper  3  by heat as the paper  3  passes between the heating roller  55  and pressure roller  56 . After the fixing process, the paper  3  is conveyed along a discharge path  57  that extends in a sloped direction toward the top surface of the main casing  2 . Discharge rollers  58  are provided at the top end of the discharge path  57 . The discharge rollers  58  receive the paper  3  conveyed along the discharge path  57  and discharge the paper  3  onto a discharge tray  59  formed on the top surface of the main casing  2 . 
   2. Detailed Structure of the Developer Side Casing for the Developer Cartridge 
     FIG. 4  is a perspective view of the developer cartridge  26  from the rear side (side on which the developing roller  38  is provided).  FIG. 5  is a perspective view of the developer cartridge  26  when the developing roller  38  has been removed.  FIG. 6  is a perspective view showing the rear side of the developer cartridge  26  on one widthwise end thereof.  FIG. 7  is a perspective view showing a rear side of the developer side casing  36  of the developer cartridge  26  on one widthwise end thereof. 
   &lt;Developer Side Casing&gt; 
   The developer side casing  36  of the developer cartridge  26  includes a top wall  60  and bottom wall  61  that oppose each other vertically; a pair of side walls  62  for closing off the widthwise sides of the developer side casing  36  between the top wall  60  and bottom wall  61 ; and a front wall  63  (see  FIG. 3 ) for closing off the front side of the developer side casing  36  between the top wall  60  and bottom wall  61 . 
   The top wall  60  is plate-shaped and wider than the distance between the opposing side walls  62  so as to span between the upper edges of the side walls  62 . The blade mounting part  64  is provided on the rear end of the top wall  60  for mounting the thickness-regulating blade  39 . The opening  40  elongated in the width direction is defined by the blade mounting part  64 , bottom wall  61 , and side walls  62 . 
   The blade mounting part  64  is L-shaped in cross section. More specifically, the blade mounting part  64  is integrally formed of a plate-shaped upper mounting part  65  opposing the bottom wall  61  of the developer side casing  36 , and a lattice-shaped front mounting part  66  bent downward substantially at a right angle from the front edge of the upper mounting part  65 . The upper mounting part  65  occupies a horizontal plane and is elongated in the width direction, while the front mounting part  66  occupies a vertical plane and is also elongated in the width direction. 
   As shown in  FIG. 3 , the front end of the bottom wall  61  extends diagonally upward and forward and is formed continuously with the front wall  63 . A film mounting part  67  is formed on the upper rear surface of the bottom wall  61  extending in the axial direction of the developing roller  38 . A lower film  68  is provided on the film mounting part  67 . The lower film  68  is formed of polyethylene terephthalate for sliding against the peripheral surface of the roller  50  on the developing roller  38  while contacting this surface uniformly across the entire width of the roller  50 . By sliding uniformly over the peripheral surface of the roller  50  at a position above the bottom wall  61 , the lower film  68  can prevent toner from leaking through the bottom wall  61  and the developing roller  38 . 
   As shown in  FIG. 4 , each of the side walls  62  includes a supporting plate  69  for supporting the developing roller shaft  49  of the developing roller  38  so that the developing roller  38  is exposed in the opening  40 ; and a seal mounting part  70  for mounting seals described later. 
   Each supporting plate  69  is plate-shaped and extends vertically. As shown in  FIGS. 5 through 7 , a bearing hole  71  is formed in each supporting plate  69  for receiving the developing roller shaft  49  of the developing roller  38 . The bearing hole  71  is U-shaped in a side view. The bearing hole  71  opens on the rear side in order to receive the developing roller shaft  49  of the developing roller  38  through this opening. 
   The seal mounting part  70  is disposed adjacent to the supporting plate  69  and inside the supporting plate  69  in the width direction (the inner side in the axial direction of the developing roller  38 ). The seal mounting part  70  has a roller-confronting surface  72  that opposes the peripheral surface of the roller  50  on a widthwise end of the developing roller  38  and extends in a curved shape along the peripheral surface of the roller  50 . 
   As shown in  FIG. 7 , a recessed part  73  is formed in a vertical midpoint of the roller-confronting surface  72  for receiving the supply roller shaft  47  of the supply roller  37 . The recessed part  73  is recessed in the roller-confronting surface  72  in a direction obliquely forward. A sponge member (not shown) is disposed on the recessed part  73  to fill a gap between the supply roller shaft  47  and a surface of the recessed part  73  when the supply roller shaft  47  is received. 
   A plurality of rib-shaped protruding parts  74  is formed in the upper and lower parts of the roller-confronting surface  72  separated by the recessed part  73 . The protruding parts  74  are parallel to one another and spaced at prescribed intervals. The protruding parts  74  are slanted with respect to the width direction, angling inward in the width direction from the upstream side to the downstream side in the rotating direction of the developing roller  38 , that is, upward in  FIG. 7 . Further, a downstream contact part  75  protrudes from the top end of the roller-confronting surface  72  for contacting a side seal  77  described later from the top (from the downstream side in the rotating direction of the developing roller  38 ). 
   Each side wall  62  also has an axial contact part  76  for contacting the side seal  77  described later from the inner side in the axial direction of the developing roller  38 . The axial contact part  76  is disposed on the opposite side of the seal mounting part  70  from the supporting plate  69  and extends in the front-to-rear direction so that the rear end (free end) protrudes farther rearward than the roller-confronting surface  72 . The axial contact part  76  does not protrude over the side seal  77 . 
   &lt;Side Seal&gt; 
   As shown in  FIG. 6 , the side seal  77  mentioned above is disposed on the roller-confronting surface  72  of the seal mounting part  70  to prevent toner from leaking between the roller-confronting surface  72  and an end of the roller  50 . 
   The side seal  77  is formed of a sponge material such as urethane foam. The side seal  77  is fitted between the downstream contact part  75  and a rear corner part  67   a  of the film mounting part  67 , and between the supporting plate  69  and the axial contact part  76 . 
   More specifically, the side seal  77  extends vertically along the rotating direction of the developing roller  38  over the roller-confronting surface  72 . The upper endface of the side seal  77  contacts the downstream contact part  75 . A rectangular-shaped corner part is cut out from the inner axial side of the side seal  77  on the lower end thereof. The rear corner part  67   a  of the film mounting part  67  is inserted into this cutout part such that a small gap is formed between the side seal  77  and the rear corner part  67   a  in the front-to-rear direction. The outer endface of the side seal  77  in the width direction contacts the supporting plate  69 , while the axial contact part  76  contacts the inner endface of the side seal  77  in the width direction. The rear corner part  67   a  does not protrude over the side seal  77 . 
   Accordingly, the downstream contact part  75  and the rear corner part  67   a  position the side seal  77  in the rotating direction of the developing roller  38 , while the supporting plate  69  and the axial contact part  76  position the side seal  77  in the axial direction of the developing roller  38  (width direction). 
   The side seal  77  slides along the peripheral surface of the roller  50  in order to prevent toner from leaking between the roller  50  and roller-confronting surface  72 . 
   &lt;Blade Seal&gt; 
   In the developer cartridge  26  of the preferred embodiment, a blade seal  78  is disposed over the front mounting part  66  of the blade mounting part  64  and the upper ends of the seal mounting parts  70 . 
   The blade seal  78  is formed of a sponge material, such as urethane foam. As shown in  FIG. 5 , the blade seal  78  is integrally formed of side parts  79  disposed on the upper ends of the roller-confronting surfaces  72  on the seal mounting parts  70 ; and a connecting part  80  for linking the side parts  79 . 
   The blade seal  78  is formed shorter in the width direction than the gap between the downstream contact parts  75  disposed on each widthwise end so that a small gap is formed between each side part  79  of the blade seal  78  and the corresponding downstream contact part  75 . Lower endfaces of the side parts  79  are in contact with upper endfaces of the side seals  77 . More specifically, each side part  79  contacts an upper endface of the side seal  77  from the downstream side in the rotating direction of the developing roller  38  and at a region separated from the region of the side seal  77  contacting the downstream contact part  75 . 
   The thickness-regulating blade  39  is mounted on the blade mounting part  64  by placing the blade holder  53  against the front mounting part  66  of the blade mounting part  64  with the blade seal  78  interposed therebetween, inserting screws  81  (see  FIG. 4 ) through the thickness-regulating blade  39  and blade seal  78  from the rear side of the blade holder  53 , and screwing the screws  81  into screw holes  82  formed in the developer side casing  36 . In this state, the blade seal  78  is interposed between the blade holder  53  of the thickness-regulating blade  39  and the front mounting part  66  of the blade mounting part  64 , thereby sealing the gap therebetween. 
   3. Operations and Effects of the Preferred Embodiment 
   By providing the side seals  77  on the roller-confronting surfaces  72  of the seal mounting parts  70  opposing the peripheral surface of the roller  50  on both ends of the developing roller  38 , it is possible to prevent toner from leaking between the ends of the roller  50  and the roller-confronting surfaces  72 . Further, a plurality of protruding parts  74  extending in a direction that crosses the axial direction of the developing roller  38  is formed on the roller-confronting surfaces  72 . Accordingly, even if toner gets between the roller-confronting surface  72  and side seal  77 , the protruding parts  74  block passage of the toner therethrough, thereby reliably preventing toner from leaking between the end portions of the roller  50  and the roller-confronting surfaces  72 . 
   Further, the protruding parts  74  extend at an angle to the width direction that slants inward in the width direction (the axial direction of the developing roller  38 ) from the upstream to the downstream side in the rotational direction of the developing roller  38 . Hence, the force that the side seal  77  receives from the roller  50  as the developing roller  38  rotates can be converted to a force sloping inward in the width direction. Hence, the portion of the side seals  77  on the inner widthwise side can be firmly pushed against the roller-confronting surfaces  72  of the developer side casing  36 . Further, even if toner works between the roller-confronting surface  72  and side seal  77 , the protruding parts  74  can guide the toner toward the inside of the developer side casing  36 , thereby more reliably preventing toner from leaking between the roller-confronting surface  72  and side seal  77 . 
   The downstream contact parts  75  are also provided for contacting the side seals  77  disposed on the roller-confronting surfaces  72  from the downstream end in the rotating direction of the developing roller  38 . Accordingly, the side seals  77  are easily positioned on the roller-confronting surfaces  72  with reference to the downstream contact parts  75 . Further, the downstream contact parts  75  can prevent the side seals  77  from shifting downstream in the rotating direction. 
   Further, the rear corner part  67   a  of the film mounting part  67  opposes the side seal  77  over a small gap from the upstream side in the rotating direction of the developing roller  38 . Accordingly, the side seal  77  is easily positioned on the roller-confronting surface  72  with reference to the rear corner part  67   a  of the film mounting part  67 , as well as the downstream contact part  75 . Further, the rear corner part  67   a  of the film mounting part  67  and the downstream contact part  75  can position the side seal  77  in the rotating direction of the developing roller  38 . 
   Further, the supporting plate  69  of the side walls  62  and the axial contact part  76  are disposed on both sides of the side seal  77  in the width direction for positioning the side seal  77  in the width direction. 
   The side seal  77  is mounted on the roller-confronting surface  72  so as to be fitted between the downstream contact part  75  and the rear corner part  67   a  and between the supporting plate  69  and the axial contact part  76 . Further, the small gap is formed between the side seal  77  and the rear corner part  67   a.  Accordingly, the side seal  77  can easily be removed from the roller-confronting surface  72  when recycling the developer cartridge  26 , thereby making the developer cartridge  26  more suitable for recycling. 
   Further, the blade seal  78  is provided for preventing toner from leaking between the blade holder  53  of the thickness-regulating blade  39  and the front mounting part  66  of the blade mounting part  64 . If a gap is formed between the side seals  77  and blade seal  78 , toner can escape through the gap. However, the blade seal  78  in the preferred embodiment circumvents the downstream contact part  75  and contacts a portion of the side seal  77  that is not in contact with the downstream contact part  75 , thereby preventing toner from leaking between the side seal  77  and blade seal  78 . 
   Since the process cartridge  18  of the preferred embodiment is provided with the developer cartridge  26 , which is capable of reliably preventing toner from leaking between both ends of the roller  50  on the developing roller  38  and the roller-confronting surfaces  72 , the process cartridge  18  can also prevent toner from leaking from the developer cartridge  26 . Further, the laser printer  1  in which the process cartridge  18  is mounted can prevent toner from leaking from the developer cartridge  26  and process cartridge  18 . 
   4. Variations of the Embodiment 
   While the invention has been described in detail with reference to the specific 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, in the preferred embodiment described above, the protruding parts  74  extend at an angle to the width direction that slants inward in the width direction from the upstream to the downstream side in the rotating direction of the developing roller  38 . However, the protruding parts  74  may be formed to extend in a direction along the rotating direction of the developing roller  38  (a direction orthogonal to the width direction), as shown in  FIG. 8 . In other words, toner that has worked between the roller-confronting surface  72  and side seal  77  can be prevented from passing through when the protruding parts  74  extend in a direction along the rotating direction of the developing roller  38 , or any direction crossing the axial direction of the developing roller  38  (the width direction). 
   Accordingly, the protruding parts  74  can reliably prevent toner from leaking between the roller-confronting surfaces  72  and both ends of the roller  50  on the developing roller  38 . 
   In addition, the protruding part  74  has only to include one part crossing the rotating direction.