Abstract:
An arrangement of sealing members seals developer in a developer device. The sealing members minimize or eliminate developer from leaking around the sides of a developer carrier.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from Japanese Patent Application No. 2005-282634 filed on Sep. 28, 2005, the entire subject matter of which is incorporated herein by reference. 
     FIELD 
     Aspects of the present invention relate to developing devices for storing developer, such as toner, therein. Aspects of the invention also relate to process cartridges having the developing devices as well as image forming apparatuses having the process cartridges. 
     BACKGROUND 
     Laser printers print on recording media (for example, sheets of paper) using developers. The laser printer includes a case that stores developer. The case that stores the developer includes a case body. The case body has been formed with an opening. A developing roller is rotatably attached to the case body at a position facing the opening. The developing roller is configured to carry the developer stored within the case body. The laser printer includes a photosensitive member that contacts the developing roller. An electrostatic latent image is formed on a surface of the photosensitive member. The developing roller and the photosensitive member contact each other while rotating, so that the developer carried by the developing roller adheres to the electrostatic latent image on the photosensitive member. Thus, the electrostatic latent image on the photosensitive member is developed with the developer to form a visible image. The developer of the visible image is transferred from the photosensitive member to a recording medium, so that the recording medium is then printed with the developer in the shape of the visible image. 
     If the developer contained in the case body leaks outside of the case body, devices disposed around the case body may become contaminated. The case body needs to be designed such that the design prevents the leakage of the developer. In a related area, side seal members are used to protect the leakage of the developer from both ends of the developing roller with respect the axial direction of the developing roller. The case body includes an area facing a surface of the developing roller at each end with respect to an axial direction thereof. The side seal members are affixed to the area of the case body and contact the developing roller. Thus, each end of the developing roller is sealed in the developing roller&#39;s axial direction. 
     During operation, the side seal member contacts the developing roller, and a rotation force of the developing roller is transmitted to the side seal member. When the developing roller rotates, the side seal member is pressed inward with respect to the axial direction of the developing roller, and the side seal member is then moved inward. If the side seal member is moved inward, the ability of the side seal member to adequately seal the case may deteriorate. This deterioration increases the likelihood that the developer may leak from the case body. 
     SUMMARY 
     Aspects of the invention provide a developing device having higher sealing ability than conventional developing devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects of the invention will be described in detail with reference to various example structures and the following figures, wherein: 
         FIGS. 1A and 1B  are sectional views showing a part of a developing device; 
         FIG. 2  is a sectional view of a laser printer according to at least one embodiment of the invention; 
         FIG. 3  is an enlarged sectional view of a process cartridge in accordance with one or more aspects of the present invention; 
         FIG. 4  is a sectional view of a photosensitive member cartridge in accordance with one or more aspect of the present invention; 
         FIG. 5  is a front view of a developer cartridge viewed in a direction V of  FIG. 3  in accordance with one or more aspect of the present invention; 
         FIG. 6  is a perspective view showing an end of the developer cartridge in accordance with one or more aspect of the present invention; 
         FIG. 7  is a perspective view of side seal members in accordance with one or more aspect of the present invention; 
         FIG. 8  is a sectional view of the developer cartridge taken along the line VIII-VIII of  FIG. 5  in accordance with one or more aspect of the present invention; 
         FIG. 9  is a front view of the inside surface  150   c  of the case-side side seal member  150  in accordance with one or more aspect of the present invention; 
         FIG. 10  is a sectional view taken along the line X-X of  FIG. 9  in accordance with one or more aspect of the present invention; 
         FIG. 11  is a front view of a developer cartridge according to at least a second embodiment of the invention; 
         FIG. 12  is a perspective view of a part of a developer cartridge according to at least a third embodiment of the invention; and 
         FIG. 13  is a perspective view of a part of a developer cartridge according to at least a fourth embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Aspects of the invention relate to a developing device that includes an improved design, thereby minimizing the likelihood of developer leaks. 
     It is noted that various connections are set forth between elements in the following description. It is noted that these connections in general and, unless specified otherwise, may be direct or indirect and that this specification is not intended to be limiting in this respect. 
     In accordance with one or more aspects of the present invention, as long as a contact member is provided in a case body so as to contact an inside surface of a side seal member, the side seal member can be prevented from moving inward even when it is pressed by a developing roller disposed in rotating contact with the side seal member. The inside surface of a side seal member is a side surface of the side seal member facing inward with respect to an axial direction of a developing roller. Referring to  FIGS. 1A and 1B , one or more aspects of the present invention is described.  FIG. 1A  is a sectional view of a part of a developing device. The developing device has a case body  500  that is formed with an elongated opening and configured to store developer therein. The developing device includes a developing roller  502  disposed in the opening of the case body  500  and rotatably supported on the case body  500  at both ends. The developing roller  502  is configured to transport the developer. A side seal member  504  is affixed on the case body  500 . The case body  500  includes an area  500   a  at each end of the case body  500 . The area  500   a  faces each end portion of the circumferential surface of the developing roller  502  with respect to the developing roller  502 &#39;s axial direction. The side seal member  504  is attached in the area  500   a  of the case body  500  and contacts the developing roller  502 . The case body  500  includes a contact member  506  disposed in contact with an inside surface  504   a  of the side seal member  504  (with respect to the axial direction of the developing roller  502 ) at each end. Because of the contact member  506 , the side seal member  504  can be prevented from moving inward (leftward in  FIG. 1A ). 
     The side seal member  504  is not rigid because the side seal member  504  needs to provide a sealing effect. The side seal member  504  can be manufactured by cutting a material that is not rigid. It is not easy to accurately make a straight cut in a material that is not rigid. Thus, the inside surface  504   a  of the side seal member  504  may be formed on a slant. The inside surface  504  of the side seal member  504  may be inclined outward (rightward in  FIG. 1A ), in a direction from the area  500   a  toward the developing roller  502 , like a phantom line M in  FIG. 1A . If the contact member  506  as shown in  FIG. 1A  is used for the side seal member  504  having the inside surface  504  inclined outward, a lower part of the side seal member  504  (a part close to the area  500   a  of the case body  500 ) and the contact member  506  may significantly interfere with each other. As a result, the side seal member  504  is greatly shifted outward (rightward in  FIG. 1A ). In this case, the side seal member contacts the developing roller at an unintended position, which may lower the sealing effect. 
     To prevent the lower part of the side seal member  504  and the contact member  506  from interfering with each other, a clearance N may be provided between the contact surface  506   a  of the contact member  506  and the area  500   a  of the case body  500  as shown in  FIG. 1B . By providing clearance N in this way, if the inside surface  504   a  of the side seal member  504  is inclined like a phantom line M in  FIG. 1B , the lower part of the side seal member  504  and the contact member  506  can be prevented from interfering with each other. Thus, the side seal member  504  can be prevented from moving outward. 
     According to one or more aspects of the invention, as the contact member is provided, the side seal can be prevented from moving inward. Furthermore, clearance can be provided between the contact surface of the contact member and the area of the case body, so as to prevent the side seal member from moving outward. According to one or more aspects of the invention, the side seal member can be prevented from contacting the developing roller in an unintended position. In this regard, the developing device may have a high sealing effect. 
       FIGS. 1A and 1B  are views that describe the relative relationships between components in accordance with one or more aspects of the present invention. Each component should not be limited to shape and position shown in the figures. The technical scope of the invention should be interpreted based on the scope of the invention. 
     The case body of the developing device may include a layer thickness regulating member that is configured to regulate a thickness of developer carried on the developing roller. The layer thickness regulating member extends in the axial direction of the developing roller and regulates the thickness of developer on the developing roller over a substantially full range (or length) of the developing roller with respect to the axial direction. By regulating the thickness of the developer on the developing roller, a uniform thickness of developer can be supplied from the developing roller to the photosensitive member. Thus, a density of the developer to be transferred from the photosensitive member to a recording medium may be substantially uniform. The layer thickness regulating member may include an area facing the circumferential surface of each end portion of the developing roller with respect to the axial direction. Here, the side seal member may be affixed to cover fully from the area of the case body to the area of the layer thickness regulating member. A regulating member-side side seal member may or may not be provided independently from the side seal member. The regulating member-side side seal member may be affixed to the area of the layer thickness regulating member and contact the developing roller. Here, the side seal member and the regulating member-side side seal member contact each other so as to minimize or eliminate any gap between them in the rotation direction of the developing roller. 
     With any one of the above configurations, the side seal member may be affixed even to the area of the layer thickness regulating member, so that a wide range with respect to the rotation direction of the developing roller can be sealed, and thus the sealing effect may be improved. 
     The inside surface of the case-side seal member may shift inward toward a downstream side with respect to the rotational direction of the developing roller. 
     With this configuration, the sealing effect can be improved compared with a case where the inside surface of the case-side seal member shifts in an opposite direction of the above configuration. 
     One or more approaches described above may be embodied in the following developing device. The developing device may include a case body, a developing roller, a layer thickness regulating member, a regulating member-side seal member, and a contact member. The case body may be formed with an elongated opening and configured to contain developer therein. The developing roller may be disposed in the opening of the case body and rotatably supported on the case body at each end, with the developing roller configured to hold a layer of the toner thereon. The layer thickness regulating member may be fixed to the case body, extend in the axial direction of the developing roller, and be configured to regulate a thickness of the layer of the developer on the developing roller. The regulating member-side seal member may be attached to the layer thickness regulating member. The contact member is formed in the case body and has a contact surface contacting an inside surface of the regulating member-side seal member. The layer thickness regulating member includes an area facing a circumferential surface of the developing roller at an end portion of the case body with respect to an axial direction of the developing roller. The regulating member-side seal member is attached to the area of the layer thickness regulating and contacts the developing roller. A clearance is provided between the contact surface of the contact member and the area of the layer thickness regulating member. 
     With this configuration, the regulating member-side seal member can be prevented from shifting inward or outward. In addition, the regulating member-side seal member can be prevented contacting the developing roller in an unintended position. The developing device has high sealing effect. 
     When the contact member contacts the developing roller, it may be deformed during rotation of the developing roller. Thus, a clearance is provided between the contact member and the developing roller. 
     Non-magnetic, single-component polymerized toner easily leaks. The above developing device effectively functions as a case for storing such a toner that minimizes or eliminates leaks. 
     The developing device may be a developer cartridge configured to be received in and removed from an image forming apparatus, such as a copier, a laser printer, a facsimile, and a multifunction apparatus, which is configured to form an image using the developer. 
     A process cartridge may include the developing device. The process cartridge is configured to be received in and removed from an image forming apparatus configured to form an image using a developer. The process cartridge includes a photosensitive member and the developing device. The developer carried on the developing roller is supplied to a surface of the photosensitive member. 
     The process cartridge has high sealing effect, thereby minimizing or preventing leaks of the developer. 
     An image forming apparatus may include the developing device. The developer conveyed by the developing roller of the developing device is supplied to a surface of the photosensitive member. Next, the developer supplied to the surface of the photosensitive drum is transferred onto a recording medium. 
     In the image forming apparatus, as the developing device has high sealing effect, toner leakage can be minimized or prevented, and contamination by leaked developer may be minimized. 
     A first embodiment of the invention will be described with reference to the accompanying drawings.  FIG. 2  is a sectional view of a laser printer  10  according to one or more embodiments of the invention. In the following description, the right side in  FIG. 2  indicates a front side of the printer  10 . 
     The printer  10  has a casing  12 . The casing  12  is made up of a plurality of plate members. In  FIG. 2 , a rear cover member  14  and a front cover member  16  are shown as members constituting a part of the casing  12 . The front cover member  16  is pivotal on a shaft  18  in directions of arrows R 1  and R 2 . When the front cover member  16  is pivoted in the direction of arrow R 1 , the casing  12  is opened. In this state, a process cartridge  40 , which will be described later, can be replaced. When the front cover member  16  is pivoted in the direction of arrow R 2 , the casing  12  is closed. 
     The printer  10  includes a sheet supply device  20 , a process cartridge  40 , a light exposure device  70 , a toner fixing device  90 , and other devices. The devices  20 ,  40 ,  70 , and  90  are disposed inside the casing  12 . 
     The sheet supply device  20  includes a paper tray  22  and four rollers  28 ,  30 ,  32 ,  34 . Print sheets (sheets onto which the developer will deposited) (not shown) are loaded in the paper tray  22 . The paper tray  22  has a bottom plate  24  on which a stack of print sheets is loaded. An uppermost sheet of the stack of the sheets loaded on the bottom plate  24  makes contact with a pick up roller  28 . With the paper tray  22  set in the casing  12 , a front end portion (on the right side of  FIG. 2 ) of the bottom plate  24  is urged upward by a mechanism (not shown). Thus, when the stack of print sheets decreases in quantity, the bottom plate  24  is raised only at its front end portion. With this configuration, the uppermost sheet is allowed to normally contact the pickup roller  28 . 
     The pickup roller  28  is connected to a drive source, not shown. The pickup roller  28  is capable of rotating counterclockwise. When the pickup roller  28  rotates, the uppermost sheet of the stack of the sheets loaded in the paper tray  22  is fed in the direction of arrow D 1 . The sheet fed in the direction of arrow D 1  contacts a separation roller  30 . The separation roller  30  is not connected to the drive source. The separation roller  30  is rotated counterclockwise by contact with the sheet. The separation roller  30  is configured to separate a single sheet from the stack when the stack reaches the separation roller  30  so as to feed the single sheet only to a downstream side. The sheet passed the separation roller  30  is fed to between the pinch roller  32  and the paper dust removing roller  34 . 
     The pinch roller  32  and the paper dust removing roller  34  are not connected to the drive source. The pinch roller  32  is urged toward the paper dust removing roller  34  by an urging mechanism, not shown. The sheet interposed between the pinch roller  32  and the paper dust removing roller  34  is pressed toward the paper dust removing roller  34  by the pinch roller  32 . A surface of the paper dust removing roller  34  is specially treated to remove foreign matter such as paper dust from the sheet in contact. The sheet from which paper dust is removed is fed along a rail  36  toward between two registration rollers  38 . 
     The lower registration roller  38  is connected to the drive source, not shown. As the lower registration roller  38  rotates counterclockwise, the sheet is fed in the direction of arrow D 2 . The upper registration roller  38  is moved in contact with the sheet fed by the lower registration roller  38 , and rotated clockwise. 
     When the sheet is fed in the direction of arrow D 2  by the registration rollers  38 , letters or images are printed on the sheet. Specifically, printing is made by the process cartridge  40 , the light exposure device  70 , and the toner fixing device  90 . 
     The process cartridge  40  is detachable from the casing  12 . When the front cover member  16  is opened in the direction of arrow R 1 , the process cartridge  40  can be removed from the casing  12 . An old process cartridge  40  can be replaced with a new one. 
     The configuration of the process cartridge  40  will be described briefly. The process cartridge  40  has a casing  42 . The casing  42  includes a through hole  42   a  at the top surface. A toner chamber  45  is formed on the right side inside the casing  12 . Toner is contained in the toner chamber  45 . On the left side inside the casing  42 , three rollers  48 ,  50 ,  52 , and a photosensitive drum  54  are disposed. Each of these rollers  48 ,  50 ,  52 , and the photosensitive drum  54  is connected to the drive source, not shown. The rightmost roller  48  is a supply roller. On the left of the supply roller  48 , a developing roller  50  is disposed. On the left of the developing roller  50 , the photosensitive drum  54  is disposed. Under the photosensitive drum  54 , a transfer roller  52  is disposed. The sheet fed by the registration rollers  38  in the direction of arrow D 2  goes in between the photosensitive drum  54  and the transfer roller  52 . The photosensitive drum  54  rotates clockwise and the transfer roller  52  rotates counterclockwise. With the rotation of the photosensitive drum  54  and the transfer roller  52 , the sheet is fed further to the left in the direction of arrow D 2 . While the sheet is fed to the left, toner adhered on the photosensitive drum  54  is transferred onto the sheet. 
     The light exposure device  70  is disposed above the process cartridge  40 . The light exposure device  70  is fixed to the casing  12 . The light exposure device  70  has a casing  72 . The casing  72  is formed at its lower surface with a through hole  72   a . The light exposure device  70  includes a polygon mirror  74 , a reflecting mirror  76 , a lens  78 , a reflecting mirror  80  and other optical elements in the casing  72   a . The light exposure has a light source, not shown. A laser beam is emitted from the light source based on print data. The laser beam supplied from the light source is polarized at the polygon mirror  74 , and directed to the reflecting mirror  76 . The laser beam is reflected at the reflecting mirror  76 , and passes through the lens  78 . The laser beam passing through the lens  78  is further reflected at the reflecting mirror  80 . The laser beam reflected at the reflecting mirror  80  comes from the through hole  72   a  outside the casing  72   a  and is directed downward. The laser beam coming out from the through hole  72   a  passes the through hole  42   a  and reaches the photosensitive drum  54 . Thus, the photosensitive drum  54  is exposed to light with a predetermined pattern. Arrow L of  FIG. 2  indicates a path of the laser beam. 
     The configuration of the toner fixing device  90  will be described. The toner fixing device  90  is disposed behind the process cartridge  40  (on the left side of  FIG. 2 ). The toner fixing device  90  includes a frame  92 , a heat roller  94 , and a pressure roller  96 . The heat roller  94  and the pressure roller  96  are rotatably supported in the frame  92 . 
     The heat roller  94  has a metal tube  94   a  and a halogen lamp  94   b  disposed inside the metal tube  94   a . The halogen lamp  94   b  heats the metal tube  94   b . The heat roller  94  is connected to the drive source, not shown. When the drive source operates, the pressure roller  96  rotates clockwise. The pressure roller  96  is urged to the heat roller  94  by a mechanism, not shown. The pressure roller  96  is not connected to the drive source. When the heat roller  94  rotates clockwise, the pressure roller  96  follows the rotation of the heat roller  94  and rotates counterclockwise. 
     When the sheet passes through the process cartridge  40 , it goes in between the heat roller  94  and the pressure roller  96 . When the heat roller  94  rotates clockwise, the sheet, which is in between the heat roller  94  and the pressure roller  96 , is fed to the left. The sheet is heated by the heat roller  94  that is heated to high temperature. Thus, toner transferred onto the sheet is fixed to the sheet by heat. The sheet passing through the toner fixing device  90  is fed in the direction of arrow D 3 . 
     A feed roller  97  is disposed just under the left end of the frame  92 . The feed roller  97  is rotatably supported by the casing  12 . The feed roller  97  is connected to the drive source, not shown. The feed roller  97  rotates counterclockwise. The feed roller  97  feeds the sheet passing through the toner fixing device  90  further toward the upper left. The sheet fed toward the upper left by the feed roller  97  is fed toward the right along rails  98 . 
     Two ejection rollers  100  are disposed on the right side of the rail  98 . The lower ejection roller  100  is connected to the drive source, not shown. The lower ejection roller  100  rotates clockwise. The upper ejection roller  100  is not connected to the drive source. When the lower ejection roller  100  rotates clockwise, the upper ejection roller  100  follows the rotation of the lower ejection roller  100  and rotates counterclockwise. 
     The sheet fed by the feed roller  97  goes in between the two ejection rollers  100 . When the lower ejection roller  100  rotates clockwise, the sheet, which is in between the two ejection rollers  100 , is fed toward the right. The sheet is fed outside the casing  12 . An output tray  110  is formed on the upper surface of the casing  12 . The sheet fed outside the casing  12  is ejected onto the output tray  110 . 
     With reference to  FIG. 3 , the configuration of the process cartridge  40  will be described in detail.  FIG. 3  shows an enlarged sectional view of the process cartridge  40 . 
     The process cartridge  40  is made up of two cartridges  43  and  44 . The right cartridge  43  is a developer cartridge. The left cartridge  44  is a photosensitive member cartridge. The developer cartridge  43  and the photosensitive member cartridge  44  are detachably connected to each other.  FIG. 4  shows a sectional view of the photosensitive member cartridge  44  after the developer cartridge  43  is removed. According to the process cartridge  40 , only the developer cartridge  43  can be replaced with a new one whereas only the photosensitive member cartridge  44  can be replaced with a new one. The process cartridge  40  can be replaced as a whole with a new one. 
     The configurations of the two cartridges  43  and  44  will be described. First, the configuration of the photosensitive member cartridge  44  will be described. The photosensitive member cartridge  44  has a casing  44   a . The casing  44   a  is formed at its upper surface with a through hole  42   a  through which a laser beam passes. The casing  44   a  is formed at its lower surface with an incoming hole  44   b  through which a sheet goes in the photosensitive member cartridge  44 . The casing  44   a  is formed at its left side surface with an outgoing hole  44   c  through which the sheet goes out from the photosensitive member cartridge  44 . The sheet goes in the photosensitive member cartridge  44  from the incoming hole  44   b , passes between the photosensitive drum  54  and the transfer roller  52 , and goes out from the outgoing hole  44   c.    
     The photosensitive drum  54 , the transfer roller  52 , and the charger  66  are disposed in the casing  44   a  of the photosensitive member cartridge  44 . 
     The photosensitive drum  54  is disposed in contact with the developing roller  50  at the left thereof. The photosensitive drum  54  includes a photosensitive drum body  54   a  and a photosensitive drum shaft  54   b . The photosensitive drum body  54   a  has a cylindrical shape, and is a positively charged photosensitive member. The surface of the photosensitive drum body  54   a  is made of polycarbonate. The photosensitive drum shaft  54   b  is made of metal. The photosensitive drum shaft  54   b  is fixed to the casing  44   a  of the photosensitive member cartridge  44 . The photosensitive drum body  54   a  is rotatably attached to the photosensitive drum shaft  54   b . The photosensitive drum body  54   a  is connected to the drive source, not shown. The photosensitive drum body  54   a  rotates clockwise. 
     The transfer roller  52  is disposed in contact with the photosensitive drum  54  from beneath. The transfer roller  52  includes a transfer roller body  52   a  and a transfer roller shaft  52   b . The transfer roller body  52   a  is made of a conductive rubber material. The transfer roller shaft  52   b  is made of metal. The transfer roller shaft  52   b  is rotatably attached to the casing  44   a  of the photosensitive drum  44 . The transfer roller shaft  52   b  is connected to the drive source, not shown. The transfer roller  52  rotates counterclockwise. The transfer roller shaft  52   b  is connected to a voltage supply circuit, not shown. During image transfer (when toner adhered to the photosensitive drum  54  is transferred onto the sheet), a bias is applied from the voltage supply circuit to the transfer roller  52 . 
     The charger  66  is disposed above the photosensitive drum  54 . There is a clearance between the charger  66  and the photosensitive drum  54 . The charger  66  is a scorotron charger. The charger  66  has a charging wire  66   a  and a grid  66   b . The charging wire  66   a  extends in a direction perpendicular to the sheet of  FIG. 3 . The charging wire  66   a  receives a high voltage. The grid  66   b  is disposed between the charging wire  66   a  and the photosensitive drum  54 . The grid  66   b  receives a bias voltage to adjust a discharge of the charging wire  66   a . A high voltage is applied to the charging wire  66   a  causing it to produce a corona discharge, whereas a bias voltage is applied to the grid  66   b . Thus, the surface of the photosensitive drum  54  or photosensitive drum body  54   a  is positively charged. 
     The configuration of the developer cartridge  43  will be described. The developer cartridge  43  has a case body  43   a . The toner chamber  45  is formed in the case body  43   a . Toner is contained in the toner chamber  45 . In this embodiment, a nonmagnetic single-component polymerized toner positively charged is used. For example, a polymerized toner, which is obtained through copolymerization of styrene-based monomers and acryl-based monomers, is used. As acryl-based monomers, acrylic acid, alkyl (C1-C4) acrylate, and alkyl (C1-C4) methacrylate may be used. The polymerized toner has substantially spherical particles, and has excellent flowability. A coloring agent and wax may be added to the polymerized toner. Additives such as silica can also added to the polymerized toner to improve flowability. An agitator  46  is accommodated in the toner chamber  45 . The agitator  46  is rotatable on the shaft  46   a  and is attached to the case body  43   a . When the agitator  46  rotates clockwise, toner in the toner chamber  45  is agitated. Thus, toner is supplied to the supply roller  48 . 
     An opening  43   b  is formed on the left side of the case body  43   a . The opening  43   b  extends in a direction perpendicular to the sheet of  FIG. 3 . On the right side of the opening  43   b , the supply roller  48  is disposed. On the left side of the opening  43   b , the developing roller  50  is disposed. 
     The supply roller  48  includes a supply roller body  48   a  and a supply roller shaft  48   b . The supply roller body  48   a  is made of a conductive foaming material. The supply roller shaft  48   b  is made of metal. The supply roller  48  is rotatably supported in the case body  43   a  of the developer cartridge  43 . The supply roller  48  is connected to the drive source, not shown. The supply roller  48  rotates clockwise. 
     The developing roller  50  strongly contacts the supply roller  48  at the left thereof. The developing roller  50  includes a developing roller body  50   a  and a developing roller shaft  50   b . The developing roller body  50   a  is made of a conductive rubber material. As the rubber material, urethane rubber or silicone rubber, which contains carbon particles, may be used. The surface of the urethane rubber or silicone rubber is covered with urethane rubber or silicone rubber, which contains fluorine. The developing roller shaft  50   b  is made of metal. The developing roller shaft  50   b  is connected to the voltage supply circuit, not shown. During image formation (when the toner is adhered to the photosensitive drum  54 ), a bias is applied from the voltage supply circuit to the developing roller  50 . The developing roller  50  is rotatably supported in the case body  43   a  at a position facing the opening  43   b . The developing roller  50  is connected to the drive source, not shown. The developing roller  50  rotates counterclockwise. 
     A layer-thickness regulating member  47  is fixed to the case body  43   a . The layer-thickness regulating member  47  is disposed on the left of the opening  43   b . The layer-thickness regulating member  47  extends in a direction perpendicular to the sheet of  FIG. 3 , and contacts the developing roller  50 . With this configuration, the layer-thickness regulating member  47  regulates (adjusts) thickness of a developer layer formed on the surface of the developing roller  50 . 
       FIG. 5  is a front view of the developer cartridge  43  when viewed in a direction V of  FIG. 3 . In  FIG. 5 , the developing roller  50  is indicated with a broken line. The developing roller  50  extends in the left-right direction at the position facing the opening  43   b  of the case body  43 . The layer-thickness regulating member  47  is fixed to the upper portion of the case body  43   a . The layer-thickness regulating member  47  extends in the left-right direction. 
     In both end portions of the case body  43   a , areas  140  face the left and right ends of the circumferential surface of the developing roller  50 . Case-side side seal members  150  are attached to the areas  140  of the case body  43   a . In both end portions of the layer-thickness regulating member  47 , areas  142  face the developing roller  50 . Regulating member-side side seal members  152  are attached to the areas  142 . 
     The areas  140  of the case body  43   a  and the areas  142  of the layer-thickness regulating member  47  are arranged vertically. The areas  140  of the case body  43   a  are formed on an upstream side of the developing roller  50  with respect the rotation direction of the developing roller  50 , whereas the areas  142  of the layer-thickness regulating member  47  are formed on a downstream side of the developing roller  50  with respect to the rotation direction of the developing roller  50 . 
       FIG. 6  is a perspective view showing surroundings of a right end portion of the developer cartridge  43  (the right end portion of  FIG. 5 ). The following description describes the right end portion of the developer cartridge  43 . As a left portion of the developer cartridge  43  mirrors to the right end portion, a description of the left end portion of the developer cartridge is omitted. In  FIG. 6 , a part of a frame member  160   a  is cut away for a better understanding of the configuration of the layer-thickness regulating member  47 . 
     In  FIG. 6 , the developing roller  50  is not shown. In the right end portion of the case body  43   a , a hole  143   a  for rotatably supporting the developing roller  50  is provided. The developing roller shaft  50   b  ( FIG. 3 ) extends outward through the hole  143   a  (rightward in  FIG. 6 ). 
     In a lower portion of the case body  43   a , a front-side frame  143   b  is formed. An axial-direction seal member  156  is connected to the front-side frame  143   b . The axial-direction seal member  156  has a first seal portion  156   a  and a second seal portion  156   b . The first seal portion  156   a  is thin like a film, and is made of polyethylene terephthalate (PET). The first seal portion  156   a  extends in an axial direction of the developing roller  50  or in the left-right direction as shown in  FIG. 5 . The first seal portion  156   a  has a width having a range S indicated with a double-headed arrow of  FIG. 6 . The front-side frame  143   b  is bent downward (in the down direction of  FIG. 5 ) toward a rear side beyond dotted line  143   c  (in an upper left direction in  FIG. 6 ). The first seal portion  156   a  extends rearward beyond dotted line  143   c  of the front-side frame  143   b . Namely, the first seal member  156   a  includes a floating portion that is not affixed to the front-side frame  143   b . The second seal portion  156   b  is short in the axial direction of the developing roller  50  and long in the rotation direction of the developing roller  50 . The second seal portion  156   b  is disposed between the first seal portion  156   a  and the front-side frame  143   b . The second seal portion  156   b  is affixed on the front-side frame  143   b . An outer surface of the second seal portion  156   b  (the right surface of  FIG. 6 ) protrudes outward (rightward in  FIG. 6 ) from an outer surface of the first seal portion  156   a . The outer surface of the second seal portion  156   b  contacts an inner surface of the case-side side seal member  150 . The circumferential surface of the developing roller  50  contacts the first seal portion  156   a . The circumferential surface of the developing roller  50  also contacts a part of the second seal portion  156   b  that protrudes from the first seal portion  156   a . As the first seal portion  156   a  and the second seal portion  156   b  contact each other, the lower portion of the developing roller  50  and the case body  43   a  are sealed. 
     The case-side side seal member  150  and the regulating member-side side seal member  152  can be shaped like a circular arc as shown in  FIG. 7 . 
       FIG. 7  is a perspective view of the case-side side seal member  150  and the regulating member-side side seal member  152 . The case-side side seal member  150  has a two-layer structure. A lower layer  150   a  of the case-side side seal member  150  is connected to the area  140  ( FIG. 5 ) provided in each end portion of the case body  43   a . The lower layer  150   a  is made of a sponge. An upper layer  150   b  of the case-side side seal member  150  is joined to the lower layer  150   a . The upper layer  150   b  can be made of felt. The upper layer  150   b  contacts the circumferential surface of the developing roller  50 . 
     The regulating member-side side seal member  152  also has a two-layer structure. A lower layer  152   a  of the regulating member-side side seal member  152  is joined to the area  142  ( FIG. 5 ) provided in each end portion of the layer-thickness regulating member  47 . The lower layer  152   a  can be made of a sponge. An upper layer  152   b  of the regulating member-side side seal member  152  is joined to the lower layer  152   a . The upper layer  152   b  is made of a felt. The upper layer  152   b  contacts the circumferential surface of the developing roller  50 . 
     The lower layer  150   a  of the case-side side seal member  150  and the lower layer  152   a  of the regulating member-side side seal member  152  are made of a sponge, which is elastically deformable, so that the corresponding upper layers  150   b  and  152   b  can be strongly pressed against the developing roller  50 . Thus, a high sealing ability can be obtained. 
     As is evident from  FIG. 7 , a part of the regulating member-side side seal member  152  overlaps the upper surface of the case-side side seal member  150 . In addition, the inside surface  150   c  (left side surface of  FIG. 7 ) of the case-side side seal member  150  is located inward more than the inner surface  152   c  of the regulating member-side side seal member  152 . 
       FIG. 8  is a sectional view taken along the line VIII-VIII of  FIG. 6 . With reference to  FIG. 8 , the configuration of the layer-thickness regulating member  47  will be described. In  FIG. 8 , the developing roller  50  is indicated by a broken line. An arrow of a broken line indicates a rotational direction of the developing roller  50 . 
     The layer-thickness regulating member  47  has a holding member  160 . The holding member  160  is configured to hold a contact member  162  ( FIG. 6 ) in contact with the developing roller  50 . The contact member  162  extends in the axial direction of the developing roller  50  and is in contact with the developing roller  50  substantially throughout with respect to the axial direction thereof. The contact member  162  is made of a rubber. The holding member  160  is made up of two frame members  160   a ,  160   b , and a stainless plate  160   c . A front-side (left side of  FIG. 8 ) frame member  160   a  has substantially an L-shape. The stainless plate  160   c  is interposed between the front-side frame member  160   a  and a rear-side frame member  160   b . The two frame member  160   a ,  160   b , and the stainless plate  160   c  each extend in the axial direction of the developing roller  50  (in a direction perpendicular to the sheet of  FIG. 8 ). As shown in  FIG. 6 , the contact member  162  is joined to the stainless plate  160   c . The contact member  162  is not joined to right and left end portions of the stainless plate  160   c . The regulating member-side side seal member  152  is joined to the right and left end portion of the stainless plate  160   c . The regulating member-side side seal member  152  extends downward over the stainless plate  160   c . The extending part of the regulating member-side side seal member  152  overlaps the case-side side seal member  150 . The case-side side seal member  150  and the regulating member-side side seal member  152  are joined at the overlapping part. 
     A sponge material  164  is interposed between the case body  43   a  and the rear-side frame member  160   b . The sponge material  164  extends in the axial direction of the developing roller  50 . The sponge material  164  is configured to create a seal between the case body  43   a  and the rear-side frame member  160   b . A sponge material  166  is interposed between the sponge material  164  and the stainless plate  160   c . The sponge material  166  also extends in the axial direction of the developing roller  50  and functions as a seal. 
     An elastic member (e.g. a sponge)  168  is disposed in a lower portion of the case body  43   a  to fill around the supply roller  48   b . The case-side side seal member  150  is joined to the sponge  168 . 
     As shown in  FIG. 6 , the case body  43   a  has a contact member  170  that contacts the inside surface  150   c  (left side surface of  FIGS. 6 and 7 ) of the case-side side seal member  150 . The contact member  170  is formed as a part of the case body  43   a  by injection molding. The contact member  170  includes a part  170   a  that extends inward from the inner surface  43   d  of the case body  43   a , a part  170   b  that bends 90 degrees from the part  170   a , and a part  170   c  that bends 90 degrees from the part  170   b  and extends outward. The part  170   c  contacts the inside surface  150   c  of the case-side side seal member  150 . A contact surface  170   d  ( FIGS. 9 and 10 ) of the contact member  170 , which contacts the case-side side seal member  150 , is disposed on a downstream side from a middle portion of the case-side side seal member  150  with respect to the rotational direction of the developing roller  50 . 
       FIG. 9  is a front view of the inside surface  150   c  of the case-side side seal member  150 . In  FIG. 9 , the developing roller  50  is only shown in cross section, and the contact surface  170   d  of the contact member  170  is indicated with a hatched portion. As is evident from  FIG. 9 , the contact surface  170   d  of the contact member  170  contacts only the central portion of the inside surface  150   c  of the case-side side seal member  150 . Namely, a clearance N 1  exists between the contact surface  170   d  of the contact member  170  and the area  140  of the case body  43   a . The clearance N 1  is preferably set to 0.2 mm or greater. A clearance N 2  exists between the contact surface  170   d  of the contact member  170  and the developing roller  50 . The clearance N 2  is preferably set to 0.2 mm or greater. The contact surface  170   d  of the contact member  170  contacts the upper layer  150   b  and the lower layer  150   a  of the case-side side seal member  150 . 
       FIG. 10  is a sectional view taken along the line X-X of  FIG. 9 . It is apparent from  FIG. 10  how the contact member  170  is contacts the case-side side seal member  150 . 
     With reference to  FIG. 3  again, the operation of the process cartridge  40  having a configuration as described above will be described. 
     Toner contained in the toner chamber  45  is adhered to the supply roller  48 . Toner on the supply roller  48  is positively charged by friction between the supply roller  48  and the developing roller  50 . Toner positively charged covers the surface of the developing roller  50 . A contact member  162  ( FIG. 6 ) of the layer-thickness regulating member  47  contacts a toner layer formed on the surface of the developing roller  50 . Thus, the toner layer is regulated to a specified thickness. 
     The surface of the photosensitive drum body  54   a  is positively charged by the charger  66 . The surface of the photosensitive drum body  54   a , which is positively charged, receives a laser beam emitted from the light exposure device  70  ( FIG. 2 ). Thus, a specified area of the surface of the photosensitive drum body  54   a  is exposed to the laser beam, and the potential becomes low in the exposed area of the photosensitive drum body  54   a . The exposed area varies depending on print contents. An electrostatic latent image based on the print contents is formed on the photosensitive drum body  54   a.    
     Toner covering the developing roller  50  is adhered to the exposed area of the photosensitive drum body  54   a . Toner does not adhere to an area of the photosensitive drum body  54   a  that is not exposed to the laser beam. Thus, the electrostatic latent image formed on the photosensitive drum body  54   a  is developed with the toner into a visible image. As the thickness of the toner layer on the developing roller  50  is maintained constant by the layer-thickness regulating member  47 , a visible image of the same thickness is developed on the photosensitive drum  54   a.    
     The visible image carried on the photosensitive drum body  54   a  is transferred onto a sheet between the photosensitive drum  54  and the transfer roller  52 . At this time, a bias is applied to the transfer roller  52 . Toner is transferred onto the sheet by the difference in potential between the photosensitive drum  54  and the transfer roller  52 . As the visible image of the same thickness is developed on the photosensitive drum body  54   a , toner is transferred onto the sheet with the same density. Thus, the printing density is maintained constant. 
     An image, such as text and drawing, is printed on a sheet as each process is undergone. 
     The above printer  10  is provided with the contact member  170  ( FIG. 6 ) that contacts the inside surface  150   c  of the case-side side seal member  150 . Even when the developing roller  50  rotates, the contact member  170  can prevent the case-side side seal member  150  from moving inward (leftward in  FIG. 10 ). Furthermore, as shown in  FIG. 10 , the clearance N 1  is provided between the contact surface  170   d  of the contact member  170  and the area  140  of the case body  43   a . Thus, even if the case-side side seal member  150  is formed on a slant like a phantom line M 1 , the lower portion of the case-side side seal member  150  and the contact surface  170   d  of the contact member  170  do not interfere much with each other. Without the clearance N 1 , the lower portion of the case-side side seal member  150  and the contact surface  170   d  of the contact member  170  greatly interfere with each other. In this case, the case-side side seal member  150  will be moved to the right further from the position shown in  FIG. 10 , and can not be disposed at an intended position. In the embodiment, as the lower portion of the case-side side seal member  150  and the contact surface  170   d  of the contact member  170  do not interfere much with each other, the case-side side seal member  150  can be disposed at the intended position. 
     The clearance N 2  is provided between the contact surface  170   d  of the contact member  170  and the developing roller  50 . Thus, if the case-side side seal member  150  is formed on a slant like a phantom line M 2 , the upper portion of the case-side side seal member  150  and the contact surface  170   d  of the contact member  170  do not interfere much with each other. Thus, the case-side side seal member  150  can be disposed at an intended position. When the clearance N 2  is provided between the contact member  170  and the developing roller  50 , the contact member  170  and the developing roller  50  do not contact each other. Thus, deformation of the contact member  170  due to the rotation of the developing roller  50  can be prevented. 
     According to one or more embodiments, the case-side side seal member  150  can be prevented from moving inward and can be disposed at an intended position. Thus, the developer cartridge  43  of the embodiment can provide high sealing ability. With the use of the developer cartridge  43  of the embodiment, the inside of the printer  10  can be effectively prevented from getting contaminated due to toner leakage. 
     A second embodiment of the invention will be described with reference to  FIG. 11 .  FIG. 11  is a front view of a part of a developer cartridge  243  of the second embodiment. The following description will be made as to a difference from the first embodiment. As shown in  FIG. 11 , the case-side side seal members  150  are disposed so that the inside surfaces  150   c  shift inward as they head toward the downstream side of the developing roller  50  with respect to its rotational direction. 
     If the inside surfaces  150   c  of the case-side side seal members  150  shift outward (in the opposite direction to that of this embodiment) as they head toward the downstream side of the developing roller  50  with respect to its rotational direction, toner, which is adhered to the axial-direction seal members  156  ( FIG. 6 ), moves toward the downstream side along the inside surfaces  150   c  of the case-side side seal members  150 . Thus, the toner adhered to the axial-direction seal members  156  tends to remain outwardly at the downstream side. Toner remaining outwardly may be adhered to the developing roller  50 . If the developing roller  50  rotates with toner adhered to the end portions, the toner may go in between the upstream end of each case-side side seal member  150  and the case body  43   a , and may easily leak out from the case body  43   a.    
     When the inside surfaces  150   c  of the case-side side seal members  150  shift inward as described in this embodiment, toner adhered to the axial-direction seal members  156  is likely to remain inwardly at the downstream side. Thus, the toner is adhered to the developing roller  50  in a more inward direction than the above case. Namely, the toner is adhered to the developing roller  50  inside more than inner ends of the upstream ends of the case-side side seal members  150 . Thus, even when the developing roller  50  rotates, toner will not drift in between the each case-side side seal member  150  and the case body  43   a . According to the embodiment, the developer cartridge  243  can improve sealing ability compared with the case where the seals  150  shift outward. 
     A third embodiment of the invention will be described with reference to  FIG. 12 .  FIG. 12  is a perspective view of a part of a developer cartridge  343  of the third embodiment. The following description will be made as to one or more differences from the first embodiment. 
     In the first embodiment, the case-side side seal member and the regulating member-side side seal member are independently provided. In the third embodiment, only a case-side side seal member  350  is used. The case-side side seal member  350  includes a case-side elastic member  350   a , a regulating member-side elastic member  350   b , and a felt member  350   c . The case-side elastic member  350   a  is joined to the case body  43   a . The regulating member-side elastic member  350   b  is joined to the layer-thickness regulating member  47 . The felt member  350   c  is joined to the case-side elastic member  350   a  and the regulating member-side elastic member  350   b . In this embodiment, the case-side side seal member  350  is disposed to extend from the case body  43   a  to the layer-thickness regulating member  47 . 
     The contact member  170  contacts the case-side elastic member  350   a . Even with the configuration of this embodiment, the case-side side seal member  350  can be prevented from moving inward and can be disposed at an intended position. The developer cartridge  343  of this embodiment can provide high sealing ability. 
     A fourth embodiment of the invention will be described with reference to  FIG. 13 .  FIG. 13  is a perspective view of a part of a developer cartridge  443  of the fourth embodiment. The following description will be made as to a difference from the first embodiment. 
     A regulating member-side side seal member  452  of the embodiment is longer downward than the regulating member-side side seal member  152  of the first embodiment. The stainless plate  160   c  is provided longer in a downward direction than that of the first embodiment to join the regulating member-side side seal member  452  fully. The contact member  170  contacts the regulating member-side side seal member  452 . In this embodiment, a clearance is provided between the contact surface  170   d  ( FIG. 9 ) of the contact member  170  and the stainless plate  160   c.    
     With the configuration of this embodiment, the regulating member-side side seal member  452  can be prevented from moving inward and can be disposed at an intended position. 
     While the various aspects of the invention have been described in conjunction with the example structures and methods described above, various alternatives, modifications, variations, improvements and/or substantial equivalents, whether known or that are or may be presently unforeseen, may become apparent to those having at least ordinary skill in the art. Accordingly, the example structures and methods, as set forth above, are intended to be illustrative of the invention, not limiting it. Various changes may be made without departing from the spirit and scope of the invention. Therefore, aspects of the invention are intended to embrace all known or later developed alternatives, modifications, variations, improvements and/or substantial equivalents.