Patent Publication Number: US-7899367-B2

Title: Toner cartridge, agitating member, and image forming apparatus for use therewith

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2006-042675, filed on Feb. 20, 2006, the entire subject matter of which is incorporated herein by reference. 
     FIELD 
     Aspects of the invention relate to an image forming apparatus such as a laser printer, and a toner cartridge, with an agitating member, which may be disposed in the image forming apparatus. 
     BACKGROUND 
     In a known image forming apparatus such as a laser printer, an electrostatic latent image is formed on a surface of a photosensitive drum, toner is supplied from a toner cartridge to the latent image, and the electrostatic latent image is developed into a toner image on the surface of the photosensitive drum. Then, the toner image is transferred to a sheet, so that image is formed on the sheet. 
     The toner cartridge includes a toner chamber, a developing chamber, and an agitating member. The toner chamber contains toner therein. The developing chamber communicates with the toner chamber via a toner supply opening. The agitating member is rotatably disposed in the developing chamber, and is configured to stir toner in the toner chamber. Toner in the toner chamber is stirred and moved toward the toner supply opening by rotation of the agitating member. The toner is supplied to the developing chamber via the toner supply opening. Toner supplied into the developing chamber is formed into and carried as a thin layer on a surface of a developing roller. The thin layer of toner on the surface of the developing roller is brought in contact with the surface of the photosensitive drum by rotation of the developing roller, and thus is supplied to the electrostatic latent image formed on the surface of the photosensitive drum. 
     Thus, the agitating member is required to efficiently convey toner in the toner chamber to the toner supply opening. 
     For example, there has been proposed an agitating member in which a plurality of flexible sheet pieces is arranged on a shaft. In the agitating member, flexibility of the sheet pieces disposed at both ends of the shaft is less than that of other sheet pieces, so as to improve the stirring force at both ends of the container where toner is stored. 
     Another agitating member is proposed that includes a flexible member that is rotatably and freely disposed within a toner supply container in order to carry toner to a toner supply port. The flexible member has a plurality of slits to define separate areas, each having a hole therein. Thus, toner can be collected toward the middle in the toner supply container, so that toner can be used efficiently. 
     However, in the first proposed structure, a direction of toner conveyance by a center sheet piece is the same as the direction of toner conveyance of each end piece, and it is difficult to provide a component along the rotation shaft to the direction of toner conveyance by the agitating member. 
     On the contrary, in the second proposed structure, the flexible member includes a hole and thus stiffness around the hole is weak. It may be possible to give the component along the rotation shaft to the direction of toner conveyance by the agitating member, however, with the provision of the hole, toner conveyance force by the flexible member may be reduced and an adequate quantity of toner cannot be conveyed to the toner supply port. 
     SUMMARY 
     One or more embodiments of the invention provide a toner cartridge, an agitating member, and an image forming apparatus, which are capable of adding a component including the axial direction to a direction where toner is conveyed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Illustrative aspects of the invention will be described in detail with reference to the following figures in which like elements are labeled with like numbers and in which: 
         FIG. 1  is a side sectional view of a general structure of a laser printer as an image forming apparatus according to an embodiment of the invention; 
         FIG. 2  is a sectional view of a developer cartridge shown in  FIG. 1 ; 
         FIG. 3  is a sectional view of the developer cartridge taken along the line A-A of  FIG. 2 ; 
         FIG. 4  is a perspective view of an agitator shown in  FIG. 2  viewed from a film side; 
         FIG. 5  is a perspective view of the opposite side of the agitator from that shown in  FIG. 4 ; 
         FIG. 6  is a front view of the agitator shown in  FIG. 4 ; 
         FIG. 7  is a rear view of the agitator shown in  FIG. 4 ; 
         FIG. 8  is a sectional view of a developer cartridge according to another embodiment of the invention; 
         FIG. 9  is a sectional view of the developer cartridge taken along the line B-B of  FIG. 8 ; 
         FIG. 10  is a perspective view of an agitator having three slits shown in  FIG. 8  viewed from a film side; 
         FIG. 11  is a perspective view of the opposite side of the agitator from that shown in  FIG. 10 ; 
         FIG. 12  is front view of the agitator shown in  FIG. 10 ; 
         FIG. 13  is a rear view of the agitator shown in  FIG. 10 ; 
         FIG. 14  is a perspective view of an agitator having a slit viewed from a film side according to another embodiment of the invention; 
         FIG. 15  is a perspective view of the opposite side of the agitator from that shown in  FIG. 14 ; 
         FIG. 16  is a front view of the agitator shown in  FIG. 14 ; 
         FIG. 17  is a rear view of the agitator shown in  FIG. 14 ; 
         FIG. 18  is a perspective view of an agitator to which rectangle shaped thickness regulating sheets are adhered, viewed from a film side, according to another embodiment of the invention; 
         FIG. 19  is a perspective view of an agitator to which right triangle shaped thickness regulating sheets are adhered, viewed from a film side, according to another embodiment of the invention; 
         FIG. 20  is a perspective view of an agitator including two films according to another embodiment of the invention; 
         FIG. 21  is a perspective view of the opposite side of the agitator from that shown in  FIG. 20 ; 
         FIG. 22  is a front view of the agitator shown in  FIG. 20 ; 
         FIG. 23  is a rear view of the agitator shown in  FIG. 20 ; and 
         FIG. 24  is a rear side of an agitator having different length supporting plates in each area according to another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Aspects of the invention relate to a toner cartridge, an agitating member, and an image forming apparatus for use with the toner cartridge. 
     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. 
     For purposes herein, aspects of the invention are shown in relation to an image carrier and developer carrier. In various aspects, the image carrier may include a photosensitive drum, photosensitive belt, or the combination of one of a photosensitive drum or belt and an intermediate transfer drum or belt. Further, the developer carrier may include a developer roller or other systems for conveying developer to the image carrier. 
     Various embodiments will be described in detail with reference to the accompanying drawings. 
     As shown in  FIG. 1 , a laser printer  1  includes in a main body casing  2 , a feeder unit  4  for feeding sheets  3 , which serves as recording mediums, and an image forming unit  5  for forming a specified image on a sheet  3  fed by the feeder unit  4 . 
     In the following description of the illustrated embodiments of the invention, a side of the laser printer  1  on which a front cover  7  is arranged will be referred to as the front or front side (the right side of  FIG. 1 ), and a side opposite the side on which the front cover  7  is arranged will be referred to as the rear or rear side (the left side of  FIG. 1 ). With regard to various individual objects of the laser printer  1  and/or a process cartridge  19 , the six sides as front, rear, left, right, top and bottom of the individual objects will be similarly identified based on the arranged/attached position of the object on/in the main body casing  2  of the laser printer  1 , unless otherwise specified. A direction from the front to the rear or from the rear to the front will be referred to as a front-rear direction. A direction from the top to the bottom or from the bottom to the top will be referred to as a top-bottom direction or a vertical direction. A direction from the left to the right or from the right to the left, that is orthogonal to the front-rear direction and the top-bottom direction, will be referred to as a left-right direction or a width direction. 
     The main body casing  2  has an attachment/detachment cavity  6  and a front cover  7  at the front side (right side in  FIG. 1 ). The process cartridge  19  is attached to and removed from the main body casing  2  via the attachment/detachment cavity  6 . The front cover  7  is supported by the main body casing  2  so as to pivot on a cover shaft  8  inserted into the front cover  7  at a lower end portion thereof. When the front cover  7  is closed on the cover shaft  8 , the attachment/detachment cavity  6  is closed by the front cover  7 . When the front cover  7  is opened (tilted) on the cover shaft  8 , the attachment/detachment cavity  6  is opened by the front cover  7 , so that the process cartridge  19  can be inserted in or removed from the main body casing  2  via the attachment/detachment cavity  6 . 
     The feeder unit  4  is disposed at a bottom portion in the main body casing  2  and includes a sheet supply tray  9 , a separation roller  10 , a separation pad  11 , a pickup roller  12 , a paper dust removing roller  13 , a pinch roller  14 , and a pair of resister rollers  15 . The sheet supply tray  9  is removably attachable along the front-rear direction. The separation roller  10  and the separation pad  11  are disposed at the upper front end of the sheet supply tray  9  to face each other. The pickup roller  12  is disposed behind the separation roller  10  or at an upstream side from the separation roller  10  with respect to a sheet feeding direction. The paper dust removing roller  13  is disposed in an upper front portion of the separation roller  10  or at a downstream side from the separation roller  10  with respect to the sheet feeding direction. The pinch roller  14  is disposed facing the paper dust removing roller  13 . The resist rollers  15  are disposed in an upper rear portion of the separation roller  10 . 
     The sheet supply tray  9  includes a sheet pressing plate  16  therein. The sheet pressing plate  16  is capable of loading a stack of sheets  3  thereon. The sheet pressing plate  16  is pivotally supported at its rear end. The sheet pressing plate  16  is vertically movable at its front end between a loading position and a conveying position. When in the loading position, the sheet pressing plate  15  is disposed such that its front end is positioned down and aligned with a bottom plate of the sheet supply tray  9 . When in the conveying position, the sheet pressing plate  16  is disposed such that its front end is inclined upward from the bottom plate. 
     A lever  17  for raising the front end of the sheet pressing plate  16  is provided at a front end portion of the sheet supply tray  9 . The lever  17  is supported under the front end portion of the sheet pressing plate  16  so as to move vertically. 
     When the front end portion of the sheet supply tray  9  is raised by the lever  17  and the sheet pressing plate  16  is disposed in the conveying position, an uppermost sheet  3  of the stack loaded on the sheet pressing plate  16  is pressed by the pickup roller  12  from underneath and is conveyed between the separation roller  10  and the separation pad  11  upon rotation of the pickup roller  12 . The sheet  3  passes between the separation roller  10  and the separation pad  11  and then between the paper dust removing roller  13  and the pinch roller  14 , where foreign matter such as dust is removed from the sheet  3  by the paper dust removing roller  13 . The sheet  3  is inverted along a U-shaped sheet feed path and conveyed to the resist rollers  15 . 
     The resist rollers  15  are disposed in a substantially horizontally extending portion of the U-shaped sheet feed path and configured to temporarily stop a sheet  3  fed in the sheet feed path and feed it to a transfer position between a photosensitive drum  27  and the transfer roller  30  during image formation in the image forming unit  5 . 
     When the sheet supply tray  9  is removed from the main body casing  2 , the sheet pressing plate  16  is located in the loading position, so that a stack of sheets  3  can be loaded on the sheet pressing plate  16 . 
     The image forming unit  5  includes a scanner unit  18 , a process cartridge  19 , and a fixing unit  20 . 
     The scanner unit  18  is disposed at an upper portion in the main body casing  2 . The scanner unit  18  includes a laser light source (not shown), a polygon mirror  21 , a first lens  22 , a first reflecting mirror  23 , a second lens  24 , and a second reflecting mirror  25 . In the scanner unit  18 , as shown in a broken/dotted line, a laser beam emitted from the laser light source, based on print data, is deflected by the polygon mirror  21 , passes through the first lens  22 , is folded by the first reflecting mirror  23 , passes through the second lens  24 , is bent downward by the second reflecting mirror  25 , and then directed to a surface of the photosensitive drum  27  of the process cartridge  19 . 
     The process cartridge  19  is mounted below the scanner unit  18  in the main body casing  2 . The process cartridge  19  is detachably attachable to the main body casing  2  via the attachment/detachment cavity  6 . 
     The process cartridge  19  includes, in a drum frame  26 , the photosensitive drum  27  serving as a photosensitive member, a scorotron charger  28 , a developing cartridge  29  serving as a toner cartridge, a transfer roller  30 , and a cleaning brush  31 . 
     The drum frame  26  is provided with an inlet  32  and an outlet  33 . A sheet  3  being fed in the sheet feed path enters the process cartridge  19  from the inlet  32  and exits the process cartridge  19  from the outlet  33 . 
     The photosensitive drum  27  includes a metal drum shaft  34  and a cylindrical shaped drum body  35 . The drum shaft  34  extends in the width direction, and is supported at both ends by the drum frame  26  so as not to rotate. The drum body  35  is formed such that its outermost layer is a positively charged photosensitive layer made of polycarbonate. 
     The scorotron charger  28  is supported by the drum frame  26  and disposed away from the photosensitive drum  27 , so as to face the photosensitive drum  27  diagonally rearward from above. The scorotron charger  28  is configured to charge the surface of the photosensitive drum  27  uniformly and positively by corona discharge. 
     The developing cartridge  29  includes, in a case  36 , a supply roller  37 , a developing roller  38 , serving as a toner carrying member, a layer-thickness regulating member  39 , and an agitator  40  serving as an agitating member. The developing cartridge  29  may be designed to be detachably attachable to the drum frame  26 . The developing cartridge  29  can be attached to and removed from the main body casing  2  along with the drum frame  26  when the developing cartridge  29  is kept in the drum frame  26 . In addition, in one example, the developing cartridge  29  can only be attached to and removed from the main body casing  2  with the drum frame  26  remaining in the main body casing  2 . With the developing cartridge  29  attached to the main casing  2 , the developing roller  38  contacts the photosensitive drum  27  diagonally from front and from above. In other examples, a drum may be removed with developing cartridge  29 . 
     The transfer roller  30  may be disposed below the photosensitive drum  27  in the drum frame  26 , contacting the photosensitive drum  27  in a generally vertical direction. The transfer roller  30  includes a metal transfer roller shaft  41  and a transfer roller body  42  made of a conductive rubber material covering the transfer roller shaft  41 . The transfer roller shaft  41  extends in the width direction, and is rotatably supported by the drum frame  26 . During image transfer, a transfer bias is applied to the transfer roller  30 . 
     The cleaning brush  31  is attached to the drum frame  26 , and disposed facing the photosensitive drum  27  behind. The cleaning brush  31  is disposed in contact with the photosensitive drum  27  to scrape foreign matter such as dust adhering the surface of the photosensitive drum  27 . 
     During image formation, the photosensitive drum  27  is rotatably driven, and the surface of the photosensitive drum  27  is uniformly charged by the scorotron charger  28 . A laser beam from the scanner unit  18  is scanned at high speed at an area charged on the surface of the photosensitive drum  29 , thereby forming an electrostatic latent image corresponding to an image to be formed on the sheet  3 . Simultaneously, the developing roller  38  is rotatably driven and a thin layer of positively charged toner is formed on the surface of the developing roller  38 . The thin layer of toner formed on the surface of the developing roller  38  is supplied to the photosensitive drum  29  with the electrostatic latent image, the electrostatic latent image is an exposure portion where the potential has become low due to exposure to the laser beam. The toner is then formed on the surface of the photosensitive drum  27  when the developing roller  38  contacts the photosensitive drum  27 . As a result, the latent image on the photosensitive drum  27  becomes visible. Thus, toner image is formed on the surface of the photosensitive drum  27 . 
     The toner image formed on the surface of the photosensitive drum  27  is transferred to a sheet  3  being fed by the resist rollers  15 . In other words, while the sheet  3  having entered from the inlet  32  and passing through a transfer position between the photosensitive drum  27  and the transfer roller  30 , the toner image is transferred from the surface of the photosensitive drum  27  to the sheet  3  via a bias applied to the transfer roller  30 . The sheet  3  to which the toner image has been transferred is discharged from the outlet  33  and fed to the fixing unit  20 . 
     The fixing unit  20  is disposed to the rear of the process cartridge  19 . The fixing unit  20  includes a heat roller  44  and a pressure roller  45  in a fixing unit frame  43 . 
     In the fixing unit  20 , the toner image transferred onto the sheet  3  at the transfer position is fixed onto the sheet  3  by heat while the sheet  3  passes between the heat roller  44  and the pressure roller  45 . The sheet  3 , with the toner image having been fixed by heat, is fed to a discharge tray  46  formed on the top surface of the main body casing  2 . 
     On a sheet discharge side from the fixing unit  20  to the discharge tray  46 , the sheet feed path is inverted frontward in a substantially U shape. A feed roller  47  is disposed in the middle of the sheet feed path on the sheet discharge side. The sheet  3  fed from the fixing unit  20  is fed in the sheet feed path by the feed roller  47  and discharged onto the discharge tray  46  by ejection rollers  48 . 
     The structure of the developing cartridge  29  will be described with reference to  FIGS. 2 and 3 . 
     The case  36  of the developing cartridge  29  includes a pair of sidewalls  51  facing each other in the width direction, a top wall  52  disposed between upper ends of the sidewalls  51 , a bottom wall  53  disposed between lower ends of the sidewalls  51 , and a front wall  54  disposed between front ends of the sidewalls  54 . The case  36  can be in a box shape at the rear. 
     The bottom wall  53  integrally may include a front-side bottom wall  55 , a middle bottom wall  56 , and a rear-side bottom wall  57 . 
     The front-side bottom wall  55  may be formed continuously from a lower end of the front wall  54 , and is shaped in a substantially arc protruding downward in cross section. 
     The middle bottom wall  56  is formed continuously from a rear end of the front-side bottom wall  55 , and may be shaped in a substantially arc protruding downward in cross section. 
     The rear-side bottom wall  57  is formed continuously from the middle bottom wall  56  and inclined downward to the rear side. 
     A boundary portion  58  between the front-side bottom wall  55  and the middle bottom wall  56  is substantially inverse V-shaped in cross section protruding upward. A partition wall  59  extends downward toward the boundary portion  58  and fully across the inside of the case  36  in a middle portion of the top wall  52  with respect to the front-rear direction. The inside of the case  36  is divided into a toner chamber  60  serving as a toner storing portion and a developing chamber  61  with the partition wall  59 . The toner chamber  60  is disposed at the front of the partition wall  59 , and the developing chamber  61  is disposed at the rear of the partition wall  59 . The lower end of the partition wall  59  does not reach the boundary portion  58 . Between the lower end of the partition wall  59  and the boundary portion  58 , a toner supply opening  62  serving as a developer supply port is provided. The toner supply opening  62  extends fully across the inside of the case  36  and is substantially rectangular shaped. Toner stored in the toner chamber  60  is fed to the developing chamber  61  via the toner supply opening  62 . 
     The toner chamber  60  is defined by the front part of each sidewall  51 , the front part of the top wall  52 , the front-side bottom wall  55  and the partition wall  59 , while the developing chamber  61  is defined by the rear part of each sidewall  51 , the rear part of the top wall  52 , the middle bottom wall  56 , the rear-side bottom wall  57 , and the partition wall  59 . The toner chamber  60  and the developing chamber  61  communicate with each other via the toner supply opening  62 . 
     The toner chamber  60  contains positively charged nonmagnetic single-component toner as a developing agent. The toner chamber  60  is provided with an agitator  40  for mixing toner. The agitator  40  includes an agitator rotating shaft  63  serving as the axis of rotation and a film  64  serving as a flexible member. The film  64  is circularly moved in the toner chamber  61  by rotation of the agitator rotating shaft  63 . The agitator rotating shaft  63  extends in the width direction and is rotatably supported by the sidewalls  51 . When the agitator rotating shaft  63  is driven, the film  64  is circularly moved in the toner chamber  60 , and toner in the toner chamber  60  is mixed and fed to the developing chamber  61  via the toner supply opening  62 . 
     In the developing chamber  61 , the supply roller  37  is disposed along the middle bottom wall  56 . The supply roller  37  is configured to supply toner, which is fed into the developing chamber  61 , to the developing roller  38 . The supply roller  37  includes a metal supply roller shaft  65  and a supply roller body  66  made of a conductive foaming material. The supply roller shaft  65  is covered with the supply roller body  66 . The supply roller shaft  65  extends in the width direction, and is rotatably supported by the sidewalls  51 . 
     The developing roller  38  is disposed behind the supply roller  37  in the developing chamber  61 . The developing roller  38  is configured to supply toner to the photosensitive drum  27  ( FIG. 1 ) and develop an electrostatic latent image formed on the photosensitive drum  27 . The developing roller  38  includes a metal developing roller shaft  67  and a developing roller body  68  made of a conductive rubber material. The developing roller shaft  67  is covered with the developing roller body  68 . The developing roller shaft  67  extends in the width direction and is rotatably supported by the sidewalls  51 . Both ends of the developing roller shaft  67  protrude outwardly in the width direction from the corresponding sidewalls  51  and are covered with collar members  69 . 
     The layer-thickness regulating member  39  is disposed in an upper portion of the developing roller  38 . The layer-thickness regulating member  39  is configured to regulate toner carried on the developing roller  38  to a thin layer. The layer-thickness regulating member  39  is attached to a blade attaching portion  70  extending between upper ends at the rear ends of the sidewalls  51 . More specifically, the layer-thickness regulating member  39  may include of a metal plate spring member, and its base end fixed between the blade attaching portion  70  and a fixing member  72  with a sealing member  71 , for prevention of toner leakage, interposed therebetween. A free end of the layer-thickness regulating member  39  is provided with a pressing portion  73  having a generally semicircular shape in cross section and made of insulative silicone rubber. The pressing portion  73  is elastically pressed against the developing roller  38 . 
     Toner fed into the developing roller  61  is supplied to the developing roller  38  through the rotation of the supply roller  37 , while being positively and frictionally charged between the supply roller  37  and the developing roller  38 . Toner supplied onto the developing roller  38  passes between the pressing portion  73  of the layer-thickness regulating member  39  and the developing roller  38  along with the rotation of the developing roller  38 , while the toner is uniformly regulated to a specified thickness as a thin layer and carried on the developing roller  38 . 
     The structure of the agitator  40  will be described with reference to  FIGS. 4 to 7 . 
     The agitator rotating shaft  63  can be made of hard resin such as ABS resin, and may include a round rod-like shaft body  80 , a film holding member  81 , and wiper holding members  82 . The shaft body  80  extends in the width direction, which is a longitudinal direction, of the case  36  ( FIG. 3 ). The film holding member  81  is fixed on one side of the shaft body  80  with respect to a radial direction thereof. The wiper holding members  82  are fixed on the opposite side of the shaft body  80  from the film holding member  81 . 
     The film holding member  81  includes a film adhering plate  83 , a plurality of connecting rods  84 , and a closing plate  85 . The film adhering plate  83  is a thin-plate like member extending in an axial direction of the shaft body  80 , which is equal to the longitudinal direction of the case  36  (or a film  64 , which will be described later), and hereinafter referred to as “the axial direction”. The connecting rods  84  are spaced in the axial direction, and disposed between the film adhering plate  83  and the shaft body  80 . The closing plate  85  is provided so as to close a space between the film adhering plate  83  and the shaft body  80  from one side. 
     The film adhering plate  83  is disposed away from the shaft body  80  so that one side of the film adhering plate  83  is parallel to the shaft body  80 . The other side of the film adhering plate  83 , which is far from the shaft body  80 , is a surface to which a film  64  is adhered. 
     The film  64  may be made of polyethylene terephthalate (PET) and may have a rectangular shape elongated in the axial direction. A base end of the film  64 , which is one end with respect to the direction orthogonal to the axial direction, is adhered to the film adhering plate  83 . The film  64  extends in a direction opposite from the closing plate  85 . Although the film  64  is shaped in a rectangle, it may be designed in any shape such as a polygon or curve and may or may not be chamfered at its free end opposite to the base end have the base end may be elongated in the axial direction. 
     The film  64  is formed with two slits  86 . Each slit  86  extends from a free end of the film  64  (where the film  64  is not adhered to the film adhering plate  83 ) near to the film adhering plate  83 . The free end of the film  64  is divided into three areas  64 A,  64 B,  64 C which are substantially equal with respect to the axial direction. 
     The wiper holding portions  82  are provided at both ends of the shaft body  80 . Each wiper holding portion  82  includes a wiper  87  having a substantially rectangular shape. The wiper  87  is made of an elastic material such as urethane rubber. 
     Each wiper  87  protrudes outward from the corresponding wiper holding member  82  with respect to the axial direction of the shaft body  80  or the longitudinal direction of the case  36 , and an edge of each wiper  87  elastically contacts the inner surface of the sidewall  51  of the case  36 . Thus, while the wiper  87  moves around the shaft body  80  upon the rotation of the agitator rotating shaft  63 , it slides on the inner surface of the sidewall  51 , and wipes a toner detection window  74  ( FIG. 3 ) provided on the corresponding sidewall  51 . The toner detection window  74  is configured to allow light to pass through, where the light is used detecting toner remaining in the toner chamber  61 , is the light being directed from a light-emitting device disposed on one side outside of the case  36  to a photoreceptor disposed on the other side. The accuracy to detect remaining toner can be improved by wiping the toner detection window  74 . 
     The film  64  is shaped so that a length of the film  64 , measured in the direction orthogonal to its longitudinal direction, is longer than a distance between the shaft body  80  and each point on the inner wall surface of the toner chamber  60  ( FIG. 2 ). 
     In the agitator  40 , support plates  88  serving as supporting members are provided at both ends of the film holding member  81  with respect to its longitudinal direction. Each support plate  88  is disposed between the outermost connecting rod  84  and the immediately inwardly adjacent connecting rod  84 , and extends toward the free end of the film  64  in the direction orthogonal to the axial direction. Each support plate  88  is made of the same hard resin as that of the film holding member  81  and integrally formed with the film holding member  81 . 
     A side of film  64  faces each support plate  88 . Each support plate  88  contacts a side of film  64  near an outer end of the film  64 , with respect to its longitudinal direction, in each end area  64 A,  64 C. Each support plate  88  may have a rectangular shape that may or may not be gently chamfered at its free end when viewed in the axial direction. A length of each support plate  88  measured in the direction orthogonal to the axial direction is shorter than the distance between the shaft body  80  and each point on the inner wall surface of the toner chamber  60  ( FIG. 2 ). 
     Thus, as shown in  FIG. 2 , the film  64  is curved in the toner chamber  60  so that a surface of the film  64  opposite from the support plates  88  contacts the inner wall surface of the toner chamber  60 . When the agitator rotating shaft  63  is rotated clockwise in  FIG. 2 , the film  64  is moved around the shaft body  80  of the agitator rotating shaft  63  while remaining in contact with the inner wall surface of the toner chamber  60 . 
     At this time, the film  64  is brought in a state shown by a broken line of  FIG. 6  when viewed from a downstream side of the rotation direction. As the outer ends of the film  64 , with respect to the longitudinal direction thereof, in both end areas  64 A,  64 C are supported by the support plates  88  from an upstream side of the rotation direction, the flexibility at the outer ends is small, and thus the outer ends move ahead of the inner ends of the areas  64 A,  64 C and the area  64 B. In other words, as the inner ends of the areas  64 A,  64 C and the whole of the area  64 B of the film  64  are not supported by the support plates  88 , the flexibility at the inner ends of the areas  64 A,  64 C and the whole of the area  64 B is great, and they move behind the outer ends in both end areas  64 A,  64 C. In still other words, in the film  64 , stress (or resistance to toner) generated in the outer ends in both end areas  64 A,  64 C becomes greater than that generated in the inner ends of the areas  64 A,  64 C and the whole of the area  64 B. Thus, as shown by arrows in  FIG. 6 , a flow of toner takes place inwardly in each end area  64 A,  64 C, and in a direction orthogonal to the axial direction in the area  64 B. As a result, toner stored in the toner chamber  60  is agitated by the agitator  40  and collected in the middle of the toner chamber  60 , and then efficiently fed to the developing chamber  61  via the toner supply opening  62 . 
     The film  64  has the areas divided by the slits  86 . Thus, stress produced in at least one of the areas can differ between one end and the other end of the area with respect to the axial direction, while the film  64  is rotated. Thus, the area produces a flow of toner having a direction going from a place where greater stress is produced to a place where less stress is produced. The other area enables toner to be moved in the direction orthogonal to the axial direction. Thus, the film  64  can maintain force enough to convey toner. That is, the film  64  can convey an adequate amount of toner while adding a component including the axial direction to a direction where toner is conveyed by the agitator  40 . Thus, a thin layer of toner can be preferably formed on the developing roller  38 , and the developing roller  38  can preferably develop the electrostatic latent image. 
     With a simple structure that the film  64  is provided with the support plates  88 , special processing to the film  64  can be eliminated. Different levels of stress can be produced between the outer end and the inner end, with respect to the axial direction, in each end area  64 A,  64 C of the film  64  during rotation of the film  64 . 
     The support plates  88  may be shorter than the film  64  in the direction orthogonal to the axial direction, so that the film  64  extends beyond the support plates  88  (or exists on a continuation of each support plate  88 ) and can be curved at the extended portion. Thus, the film  64  can be set so that the free end thereof can contact the inner wall surface of the toner chamber  60 . The film  64  can slide on the inner wall surface of the toner chamber  64  upon the rotation, and thus can deliver better agitation of the toner. 
     The support plates  88  can be provided in the same number as the slits  86 , and the number of the support plates  88  may be, for example one fewer than the number of the areas  64 A,  64 B,  64 C divided by the slits  86 . Thus, the area  64 B, which is not supported by the support plates  88 , can be provided. In the area  64 B, which is not supported by the support plates  88 , toner can be favorably moved in the direction orthogonal to the axial direction. Thus, the performance of the agitator  40  to convey toner can be further improved. 
     A second embodiment of the invention will be described with reference to  FIGS. 8 and 9 . In  FIGS. 8 and 9 , a developing cartridge  129  is a variant of the developing cartridge  29  of the first embodiment, where parts substantially equivalent to those described above are denoted by the same reference numerals, and descriptions therefor will be omitted. 
     The developing cartridge  129  includes a partition wall  91  configured to partition the internal space of the case  36  into the toner chamber  60  and the developing chamber  61 . The partition wall  91  extends vertically in the case  36 , so that a bottom end of the partition wall  91  reaches the boundary portion  58  between the front-side bottom wall  55  and the middle bottom wall  56 , and a top end of the partition wall  91  reaches the inner wall surface (bottom surface) of the top wall  52 . As shown in  FIG. 9 , the partition wall  91  is disposed in a middle portion of the case  36  with respect to the longitudinal direction thereof, and spaces are provided outside both ends of the partition wall  91  between both sidewalls  51 . The spaces may open vertically in the case  36 . One of the spaces provided facing the area  164 A functions as a toner supply opening  92  through which toner stored in the toner chamber  60  is fed to the developing chamber  61 . The other space provided facing the area  164 D functions as a toner return opening  93  through which toner excessively fed in the developing chamber  61  is returned to the toner chamber  60 . 
     With reference to  FIGS. 10 to 13 , an agitator  140  included in the developer cartridge  129  of the second embodiment shown in  FIG. 8  will be described. In  FIGS. 10 to 13 , parts substantially equivalent to those described above are denoted by the same reference numerals, and descriptions therefor will be omitted. In  FIGS. 10 to 13 , the wipers  87  are not shown. 
     A film  164  is formed with three slits  186  extending from a free end of the film  164  near to the film adhering plate  83 . Two of the three slits  86  are made in positions where the film  164  is divided into three equal areas in the axial direction, and the remaining one is made in a position where one of the three equal areas located on one end is divided into two equal areas. With the arrangement of the slits  186 , the film  164  is divided into two narrow areas  164 A,  164 B, which are relatively narrow with respect to the axial direction, and two broad areas  164 C,  164 D, which are relatively broad with respect to the axial direction. 
     The agitator  140  is provided with four support plates  88 . Two of the four support plates  88  are disposed on both ends of the film holding member  81  with respect to the longitudinal direction thereof, facing outer ends in the corresponding end areas  164 A,  164 D of the film  164 , and extending in a direction orthogonal to the axial direction from the film holding member  81  toward the free end of the film  164 . The remaining two support plates  88  are disposed in positions facing the ends on the area  164 D side in the areas  164 B,  164 C, and extending in the direction orthogonal to the axial direction from the film holding member  81  toward the free end of the film  164 . 
     With this structure, as shown in  FIG. 8 , the film  164  is curved in the toner chamber  60  so that a surface of the film  164  opposite from the support plates  88  contacts the inner wall surface of the toner chamber  60 . When the agitator rotating shaft  63  is rotated clockwise in  FIG. 8 , the film  164  is moved around the shaft body  80  of the agitator rotating shaft  63  while remaining in contact with the inner wall surface of the toner chamber  60 . 
     At this time, the film  164  is brought into a state shown by a broken line of  FIG. 12  when viewed from a downstream side of the rotation direction. In the areas  164 A,  164 B of the film  164 , as the respective outer ends, with respect to the axial direction, are supported by the support plates  88 , they may receive relatively small deflections, and thus move ahead of the inner ends. In other words, in the areas  164 A,  164 B of the film  164 , as the inner ends are not supported by the support plates  88 , they may receive relatively great deflections, and lag behind the outer ends. In other words, in the areas  164 A,  164 B of the film  164 , stress generated in the outer ends becomes greater than stress generated in the inner ends. In the areas  164 C,  164 D, as ends on the area  164 D side (as opposed to the  164 A side) are supported by the support plates  88 , they receive relatively small deflection, and thus move ahead of the opposite ends on the area  164 A side. In other words, in the areas  164 C,  164 D, as the ends on the area  164 A side are not supported by the support plates  88 , they receive relatively greater deflections, and thus lag behind the ends on the area  164 D side. In still other words, in the areas  164 C,  164 D, stress generated on the face of film  164  on the area  164 D side increases greater than stress generated on the face of film  164  on the area  164 A side. 
     Thus, as shown by arrows in  FIG. 12 , in the vicinity of each area  164 A,  164 B, a flow of toner directed between the areas  164 A,  164 B takes place. In the vicinity of each area  164 C,  164 D, a flow of toner directed from the area  164 D to the area  164 A occurs. Thus, toner stored in the toner chamber  60  is mixed by the agitator  140 , collected on moving paths in the areas  164 A,  164 B, and fed in the direction orthogonal to the axial direction toward the developing chamber  61 . With this structure, toner stored in the toner chamber  60  can be efficiently fed to the developing chamber  61  via the toner supply opening  92 . Excess toner fed to the developing chamber  61  is returned to the toner chamber  60  via the toner return opening  93 . 
     A third embodiment of the invention will be described with reference to  FIGS. 14 to 17 . In  FIGS. 14 to 17 , an agitator  240  is a variant of the agitator  40  of the first embodiment shown in  FIGS. 4 to 7 , parts substantially equivalent to those described above are denoted by the same reference numerals, and descriptions therefor will be omitted. 
     The agitator  240  may be used instead of the agitator  40  of the first embodiment. In the agitator  240  of the third embodiment, a film  264  is formed with a slit  286  extending from the free end of the film  264  to at least near to the film adhering plate  83 . The free end of the film  264  is divided into two areas  264 A,  264 B, which are substantially equal in the axial direction. 
     In the agitator  240 , support plates  88  are disposed on both ends of the film holding member  81  with respect to its axial direction. The support plates  88  extend in the direction orthogonal to the axial direction from the film holding member  81  to the free end of the film  264 . The support plates  88  face the outer ends of the areas  264 A,  264 B. 
     Thus, the film  264  may be curved in the toner chamber  60  ( FIG. 2 ) so that a surface of the film  264  opposite from the support plates  88  contacts the inner wall surface of the toner chamber  60 . When the agitator rotating shaft  63  is rotated, the film  264  is moved around the shaft body  80  of the agitator rotating shaft  63  while remaining in contact with the inner wall surface of the toner chamber  60 . 
     At this time, the film  264  is brought in a state shown by a broken line of  FIG. 16  when viewed from a downstream side of the rotation direction. In each area  264 A,  264 B, the outer end with respect to the axial direction is supported by the support plate  88  from an upstream side of the rotation direction, it receives a relatively small deflection, and thus moves ahead of the inner end. In other words, in each area  264 A,  264 B, as the inner end is not supported by the support plate  88 , it receives a relatively greater deflection, and thus moves behind the outer end. In other words, in each area  264 A,  264 B, stress (or resistance to toner) generated in the outer end becomes greater than that in the inner end. 
     Thus, as shown by arrows in  FIG. 16 , a flow of toner directed between the areas  264 A,  264 B takes place in the toner chamber  60 . As a result, toner stored in the toner chamber  60  is mixed by the agitator  240  and moves toward the middle of the toner chamber  60 , and then is efficiently fed to the developing chamber  61  via the toner supply opening  62 . 
     A fourth embodiment of the invention will be described with reference to  FIG. 18 . In  FIG. 18 , an agitator  340  is a variant of the agitator  40  of the first embodiment shown in  FIGS. 4 to 7 , parts substantially equivalent to those described above are denoted by the same reference numerals, and descriptions therefor will be omitted. 
     The agitator  340  may be used instead of the agitator  40  of the first embodiment. The agitator  340  further includes thickness regulating sheets  101  bonded onto both end areas  364 A,  364 C of the film  364  in addition to the structure of the agitator  40  of the first embodiment. The thickness regulating sheets  101  function as thickness regulating members. 
     The thickness regulating sheets  101  are made of the same film material as the film  364  with the same thickness as the film  364 . Film  364  may have slits  386 . Each thickness regulating sheet  101  is rectangular shaped so that it may have half the width of the corresponding one of the areas  364 A,  364 C, and has the same length as the film  364  in the direction orthogonal to the axial direction. Each thickness regulating sheet  101  is bonded at the outer end of the corresponding one of the areas  364 A,  364 C, with respect to the axial direction, on a surface of the film  364  opposite from the support plates  88 . 
     With this structure, during rotation of the film  364 , greater stress can be produced in outer ends of both end areas  364 A,  364 C of the film  364 , with respect to the axial direction. Thus, the stress can be produced differently in size between the outer ends and the inner ends of both end areas  364 A,  364 C. As a result, the performance of the agitator  340  to convey toner can be further improved. 
     The support plates  88  may be omitted from the agitator  340  shown in  FIG. 18 . Even in this case, the agitator  340  can exhibit substantially similar effects as the agitator  40  of the first embodiment. 
     In the fourth embodiment, the thickness regulating sheets  101  are attached to the film  364  to change stress to be produced therein. However, instead of the thickness regulating sheets  101 , thickness of the film  340  may be changed in the areas  364 A and  364 C. 
     A fifth embodiment of the invention will be described with reference to  FIG. 19 . In  FIG. 19 , an agitator  440  is a variant of the agitator  40  of the first embodiment shown in  FIGS. 4 to 7 , parts substantially equivalent to those described above are denoted by the same reference numerals, and descriptions therefor will be omitted. 
     The agitator  440  may be used instead of the agitator  40  of the first embodiment. In the agitator  440 , the thickness regulating sheets  101  are substantially triangular shaped. Each thickness regulating sheet  101  is configured so that one side of two sides orthogonal to each other has the same width as the width of the corresponding area  464 A,  464 C in the axial direction, and the other side has the same length as the length of the film  464  in the direction orthogonal to the axial direction. The film  464  may have slits  486 . Each thickness regulating sheet  101  is disposed in the corresponding area  464 A,  464 C so that the one end is aligned with the base end of the film  464  and the other end is flush with the outer edge of the corresponding area  464 A,  464 C with respect to the axial direction. Each thickness regulating sheet  101  can be affixed to a surface of the film  464  opposite from the support plates  88 . 
     With this structure, upon the rotation of the film  464 , greater stress can be produced on the faces of the outer ends in the areas  464 A,  464 C of the film  464 . In addition, stiffness in the inner ends of the areas  464 A,  464 C of the film  464  at the base end can be improved. Thus, the performance of the agitator  440  to convey toner can be improved. 
     The thickness regulating sheets  101  alone are enough to produce greater stress in the outer ends than in the inner ends of the areas  464 A,  464 C upon the rotation of the agitator  440 . Thus, the support plates  88  may be omitted from the agitator  440  shown in  FIG. 19 . Even in this case, the agitator  440  can exhibit substantially similar effects as the agitator  40  of the first embodiment. 
     In the fifth embodiment, the thickness regulating sheets  101  are attached to the film  464  to change stress to be produced therein. However, instead of the thickness regulating sheets  101 , thickness of the film  464  may be changed in the areas  464 A and  464 C. 
     A sixth embodiment of the invention will be described with reference to  FIGS. 20 to 23 . In  FIGS. 20 to 23 , an agitator  540  is a variant of the agitator  40  of the first embodiment shown in  FIGS. 4 to 7 , parts substantially equivalent to those described above are denoted by the same reference numerals, and descriptions therefor will be omitted. 
     The agitator  540  may be used instead of the agitator  40  of the first embodiment. The agitator rotating shaft  63  of the agitator  540  includes a round rod-like shaft body  80 , a film holding member  81 , a second film holding member  111 , and a wiper holding member  82 . The shaft body  80  extends in the longitudinal direction of the case  36 . The film holding member  81  is fixed on one side of the shaft body  80  with respect to its radial direction. The second film holding member  111  is fixed on the other side of the shaft body  80 , which is opposite from the film holding member  81 . The wiper holding member  82  is fixed to the second film holding member  111 . 
     As with the film  64  of the first embodiment, a film  564  is attached to the film adhering plate  83  of the film holding member  81 . The film  564  is divided into three areas  564 A,  564 B,  564 C partitioned by two slits  586 . 
     The second film holding member  111  includes a film adhering plate  112 , a plurality of connecting rods  113 , and a closing plate  115 . The film adhering plate  112  is a thin-plate like member extending in the axial direction of the shaft body  80 . The connecting rods  113  are spaced in the axial direction of the shaft body  80 , and disposed between the film adhering plate  112  and the shaft body  80 . The closing plate  115  is provided so as to close a space between the film adhering plate  112  and the shaft body  80 . 
     The film adhering plate  112  is disposed symmetrical to the film adhering plate  83  of the film holding member  81  on the shaft body  80  and so that one side of the film adhering plate  112  is parallel to the shaft body  80 . The other side of the film adhering plate  112 , which is far from the shaft body  80 , is a surface to which a film  114  is adhered. The film  114  functions as a flexible member. 
     The film  114  is made of polyethylene terephthalate (PET) and has a rectangular shape extending in the axial direction of the shaft body  80 . A base end of the film  114 , with respect to the direction orthogonal to the axial direction of the shaft body  80 , is adhered to the film adhering plate  112 . The film  114  and the film  564 , held by the film holding member  81 , extend in opposite directions from each other. 
     The film  114  is formed with two slits  116 . Each slit  116  extends from a free end of the film  114  (where the film  114  is not adhered to the film adhering plate  112 ) to near the film adhering plate  112 . The free end of the film  114  is divided into three areas  114 A,  114 B,  114 C, which are substantially equal in the axial direction. 
     The film  114  is shaped so that a width of the film  114 , which is a distance measured in the direction orthogonal to the axial direction, is longer than a distance between the shaft body  80  of the agitator rotating shaft  63  and the each point on the inner wall surface of the toner chamber  60  ( FIG. 2 ). 
     Support plates  117  are disposed in a middle portion of the film holding member  111  so as to face the inner ends of the areas  114 A,  114 C with respect to the axial direction. The support plates  117  function as a supporting member and extend toward the free end of the film  114  in the direction orthogonal to the axial direction. The support plates  117  are made of the same hard resin as that of the second film holding member  111  and shaped integrally with the second holding member  111 . The support plates  117  have a rectangular shape gently chamfered at their free ends when viewed in the axial direction. A length of each support plate  117  in the direction orthogonal to the axial direction is shorter than the distance between the shaft body  80  and each point on the inner wall surface of the toner chamber  60  ( FIG. 2 ). 
     With this structure, the films  564 ,  114  are curved in the toner chamber  60  so that a surface of each film  564 ,  114  opposite form the shaft body  80  contacts the inner wall surface of the toner chamber  60 . When the agitator rotating shaft  63  is rotated, the films  564 ,  114  are moved around the shaft body  80  of the agitator rotating shaft  63  while remaining contacting the inner wall surface of the toner chamber  60 . 
     At this time, the film  564  is brought in a state shown by a broken line of  FIG. 22  when viewed from a downstream side of the rotation direction. As the outer ends of the areas  564 A,  564 C of the film  564 , with respect to the axial direction, are supported by the support plates  88  from an upstream side of the rotation direction, they receive less deflection, and thus move ahead of the inner ends of the areas  564 A,  564 C and the area  564 B. On the other hand, the film  114  is brought in a state shown by a broken line of  FIG. 23  when viewed from the downstream side of the rotation direction. As the inner ends of the areas  114 A,  114 C, with respect to the axial direction, are supported by the support plates  117  from the upstream side of the rotation direction, they receive less deflection, and thus move ahead of the outer ends of the areas  114 A,  114 C, and the area  114 B. In other words, as the outer ends of the areas  114 A,  114 C and the area  114 B of the film  114  are not supported by the support plates  117 , they receive greater deflection, and lags behind the inner ends of the areas  114 A,  114 C. In still other words, in the film  114 , stress (or resistance to toner) generated at the inner ends of the areas  114 A,  114 C becomes greater than that generated in the outer ends of the areas  114 A,  114 C and the area  114 B. 
     Thus, as shown by arrows in  FIG. 22 , in the vicinity of each area  564 A,  564 C of the film  564 , a flow of toner directed from the outer end to the inner end in the axial direction takes place. In the vicinity of the area  564 B, a flow of toner directed in the direction orthogonal to a surface of the area  564 B axial direction takes place. On the other hand, as shown by arrows in  FIG. 23 , in the vicinity of each area  114 A,  114 C, a flow of toner directed from the inner end to the outer end takes place. In the vicinity of the area  114 B, a flow of toner directed in the direction orthogonal to a surface of the area  114 B takes place. 
     As a result, toner is collected at the middle in the toner chamber  60  by the film  564 , and dispersed in the longitudinal direction of the toner chamber  60  by the film  117 . Thus, the agitator  540  of  FIGS. 20 to 23  can retain the performance to convey toner same or more than that of the agitator  40  of the first embodiment, as well as disperse toner stored in the toner chamber  60  in the longitudinal direction of the toner chamber  60 . With this structure, the performance to mix toner can be improved. 
     A seventh embodiment of the invention will be described with reference to  FIG. 24 . In  FIG. 24 , an agitator  640  is a variant of the agitator  40  of the first embodiment shown in  FIGS. 4 to 7 , parts substantially equivalent to those described above are denoted by the same reference numerals, and descriptions therefor will be omitted. 
     The agitator  640  may be used instead of the agitator  40  of the first embodiment. The agitator  640  further includes a film  664  with slits  686  and support plates  121  in addition to the structure of the agitator  40  of the first embodiment. The support plates  121  are disposed in a middle portion in the axial direction of the film holding member  81  to face the inner ends of end areas  664 A,  664 C of the film  664 . The support plates  121  extend in the direction orthogonal to the axial direction from the film holding member  81  to the free end of the film  564 . 
     The support plates  121  are made of the same hard resin as the film holding member  81  and are shaped integrally with the film holding member  81 . Each support plate  121  has a substantially rectangular shape that may be gently chamfered at its free end when viewed in the axial direction. A length of each support plate  121  is shorter than the support plate  88  with respect to the direction orthogonal to the axial direction. 
     With this structure, the inner ends in the end areas  664 A,  664 C of the film  664  are supported by the support plates  121  and stress can be produced differently in size between the outer end and the inner end, with respect to the axial direction, in each end area  664 A,  664 C of the film  664  during rotation of the film  664 . 
     While the invention has been described in connection with various example structures and illustrative aspects, it will be understood by those skilled in the art that other variations and modifications of the structures and aspects described above may be made without departing from the scope of the invention. Other structures and aspects will be apparent to those skilled in the art from a consideration of the specification or practice of the invention disclosed herein. It is intended that the specification and the described examples only are illustrative with the true scope of the invention being defined by the following claims. 
     For instance, in the fourth and fifth embodiments, the thickness regulating sheets  101  are attached to the film  340 ,  440  to change stress to be produced therein. However, instead of the thickness regulating sheets  101 , thickness of the film  340 ,  440  may be changed in the areas  64 A and  64 C.