Abstract:
In a developer cartridge, the base portion is fixed to an outer surface of the one side of the frame, and extends from one end thereof to another end thereof in a second direction orthogonal to the first direction. The first extending portion extends from one end thereof to another end thereof in the first direction. The one end of the first extending portion is connected to the another end of the base portion. The second extending portion extends from one end thereof to another end thereof in a direction opposite to the second direction. The one end of the second extending portion is connected to the another end of the first extending portion. The input portion is connected to the another end of the second extending portion and inputs electrical power from an external device. The electrode is deformable such that a distance between the base portion and the second extending portion becomes smaller.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2010-072621 filed Mar. 26, 2010. The entire content of the priority application is incorporated herein by reference. 
     TECHNICAL FIELD 
     The invention relates to a developer cartridge provided in an image forming device such as a laser printer. 
     BACKGROUND 
     A tandem-type color laser printer, as a color printer using an electrophotography method, provided with a plurality of photoconductors and a plurality of developer cartridges are well known in the art. In the tandem type color laser printer, the plurality of photoconductors are arranged in parallel in correspondence with toners of four colors of yellow, magenta, cyan, and black. The plurality of developer cartridges are arranged in correspondence with the photoconductors so as to feed toners to the photoconductors. 
     A following developer cartridge is proposed as an example of a developer cartridge provided in such a tandem-type color laser printer. That is, the developer cartridge includes a developing roller and a feed roller brought into contact with the developing roller. When the developer cartridge is attached to a drum cartridge that rotatably supports the photosensitive drum, the developer cartridge is configured to be pressed elastically against a photosensitive drum such that the developing roller is brought into elastic press-contact with the photosensitive drum. 
     The developer cartridge has a bias electrode brought into contact with a relay electrode provided in the drum cartridge. The bias electrode is formed of a plate spring and has a protruding portion protruding outward in the width direction of the developer cartridge toward the relay electrode of the drum cartridge. 
     When the developer cartridge is mounted on the drum cartridge, the protruding portion of the bias electrode is brought into press-contact with the relay electrode of the drum cartridge. 
     As a result, bias voltage applied from a high voltage power supply provided in a main body casing is applied to the bias electrode of the developer cartridge through the relay electrode of the drum cartridge. 
     SUMMARY 
     In the conventional developer cartridge, the bias electrode is formed as a plate spring and is brought into press-contact with the relay electrode by biasing force of the plate spring. 
     Thus, the press-contact of the bias electrode against the relay electrode causes friction force between the bias electrode and the relay electrode. 
     Meanwhile, the cross-section of the photosensitive drum is not a true circle but is eccentric within a predetermined range of tolerance. Therefore, when the photosensitive drum is rotated, the developing roller is pressed by the photosensitive drum with periodically changing pressing force of the photosensitive drum. 
     At this time, the developer cartridge is moved by the pressing force from the photosensitive drum so as to be away from the photosensitive drum against the pressing force to the photosensitive drum or come close to the photosensitive drum by the pressing force to the photosensitive drum, such that the developing roller follows the outer periphery of the photosensitive drum while the contacting state of the developing roller with the photosensitive drum is maintained. 
     However, when the friction force occurs between the bias electrode and relay electrode as described above, the abovementioned movement of the developer cartridge may be inhibited at the side in the axial direction of the developing roller at which the bias electrode is provided. 
     As a result, the pressing force of the developing roller to the photosensitive drum may become nonuniform in the axial direction of the developing roller. 
     An object of the invention is to provide a developer cartridge capable of allowing the developing roller to uniformly press the photosensitive drum, a process unit provided with the developing roller, and an image forming device provided with the process unit. 
     In order to attain the above and other objects, the invention provides a developer cartridge. The developer cartridge includes a frame, a carrying member, and an electrode. The frame has one side in a first direction. The carrying member carries a toner and is rotatably supported by the frame, the carrying member extending in the first direction. The electrode is supported by one side of the frame. The electrode includes a base portion, a first extending portion, a second extending portion, and an input portion. The base portion is fixed to an outer surface of the one side of the frame, and extends from one end thereof to another end thereof in a second direction orthogonal to the first direction. The first extending portion extends from one end thereof to another end thereof in the first direction. The one end of the first extending portion is connected to the another end of the base portion. The second extending portion extends from one end thereof to another end thereof in a direction opposite to the second direction. The one end of the second extending portion is connected to the another end of the first extending portion. The input portion is connected to the another end of the second extending portion and inputs electrical power from an external device. The electrode is deformable such that a distance between the base portion and the second extending portion becomes smaller. 
     According to another aspect, the invention provides a process unit includes a contact part and a developer cartridge. The contact part is configure to supply electrical power. The developer cartridge includes a frame, a carrying member, and an electrode. The frame has one side in a first direction. The carrying member carries a toner and is rotatably supported by the frame, the carrying member extending in the first direction. The electrode is supported by one side of the frame. The electrode includes a base portion, a first extending portion, a second extending portion, and an input portion. The base portion is fixed to an outer surface of the one side of the frame, and extends from one end thereof to another end thereof in a second direction orthogonal to the first direction. The first extending portion extends from one end thereof to another end thereof in the first direction. The one end of the first extending portion is connected to the another end of the base portion. The second extending portion extends from one end thereof to another end thereof in a direction opposite to the second direction. The one end of the second extending portion is connected to the another end of the first extending portion. The input portion is connected to the another end of the second extending portion. The input portion contacts the contact part and inputs electrical power from the contact part. The electrode is deformable such that a distance between the base portion and the second extending portion becomes smaller. 
     According to still another aspect, the invention provides an image forming device. The image forming device includes a power supply and a process unit. The power supply is configured to supply electrical power. The process unit includes a contact part and a developer cartridge. The contact part is configure to supply electrical power. The developer cartridge includes a frame, a carrying member, and an electrode. The frame has one side in a first direction. The carrying member carries a toner and is rotatably supported by the frame, the carrying member extending in the first direction. The electrode is supported by one side of the frame. The electrode includes a base portion, a first extending portion, a second extending portion, and an input portion. The base portion is fixed to an outer surface of the one side of the frame, and extends from one end thereof to another end thereof in a second direction orthogonal to the first direction. The first extending portion extends from one end thereof to another end thereof in the first direction. The one end of the first extending portion is connected to the another end of the base portion. The second extending portion extends from one end thereof to another end thereof in a direction opposite to the second direction. The one end of the second extending portion is connected to the another end of the first extending portion. The input portion is connected to the another end of the second extending portion. The input portion contacts the contact part and inputs electrical power from the contact part. The electrode is deformable such that a distance between the base portion and the second extending portion becomes smaller. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The particular features and advantages of the invention as well as other objects will become apparent from the following description taken in connection with the accompanying drawings, in which: 
         FIG. 1  is a cross sectional side view of a color laser printer according to an embodiment; 
         FIG. 2  is an upper-right perspective view of a process unit of the color laser printer shown in  FIG. 1 ; 
         FIG. 3  is a left side view showing a right side plate of a process frame; 
         FIG. 4  is a perspective view showing a top-rear-right side of a developer cartridge seeing from; 
         FIG. 5  is a perspective view showing a top-rear-right side of a developer cartridge when an electrode cover is detached; 
         FIG. 6  is a right side view of the developer cartridge; 
         FIG. 7(   a ) is a right side view showing a right side of an electrode plate of the developer cartridge shown in  FIG. 6 ; 
         FIG. 7(   b ) is a view showing a front bottom side of the electrode; 
         FIG. 8(   a ) is a perspective view showing a right-rear-bottom side of the electrode cover; 
         FIG. 8(   b ) is a perspective view showing a left-bottom side of the electrode cover; 
         FIG. 8(   c ) is a cross sectional view of the electrode cover taken along a line C-C shown in  FIG. 8(   a ); 
         FIG. 9  is a cross sectional view of the developer cartridge taken along a line A-A shown in  FIG. 6 ; and 
         FIG. 10  is a cross sectional view of the developer cartridge taken along the line A-A shown in  FIG. 6  when the electrode cover is mounted. 
     
    
    
     DETAILED DESCRIPTION 
     1. Entire Configuration of Color Laser Printer 
     As shown in  FIG. 1 , a color laser printer  1  is a direct tandem type color laser printer and is laid horizontally. The color laser printer  1  has a main-body casing  2  and, within the main-body casing  2 , a paper feeding section  3  for feeding a paper P, an image forming section  4  for forming an image on the fed paper P. 
     (1) Main-Body Casing 
     The main-body casing  2  has a box shape that is substantially rectangular in a side view and accommodates the paper feeding section  3  and the image forming section  4 . A front cover  5  is provided on one side wall of the main-body casing  2  so as to mount or remove a process unit  9  to be described later. 
     The terms “upward”, “downward”, “upper”, “lower”, “above”, “below”, “beneath”, “right”, “left”, “front”, “rear” and the like will be used throughout the description assuming that the color laser printer  1  is disposed in an orientation in which it is intended to be used. In use, the color laser printer  1  is disposed as shown in  FIG. 1 . That is, the front cover  5  is provided at the front side of the color laser printer  1 . In the following description, the left-right direction is referred to as a longitudinal direction. 
     (2) Paper Feeding Section 
     The paper feeding section  3  has a paper feeding tray  6  provided at the bottom of the main-body casing  2  and a pair of registration rollers  7  disposed above the front end portion of the paper feeding tray  6 . 
     The papers P accommodated in the paper feeding tray  6  are fed one by one between the registration rollers  7  and then fed to the image forming section  4  (between a photosensitive drum  14  (to be described later) and a conveying belt  22  (to be described later)) at a predetermined timing. 
     (3) Image Forming Section 
     The image forming section  4  has a scanning unit  8 , a process unit  9 , a transfer unit  10 , and a fixing unit  11 . 
     (3-1) Scanning Unit 
     The scanning unit  8  is disposed in the upper portion of the main-body casing  2 . The scanning unit  8  irradiates laser beams toward four photosensitive drums  14  (to be described later) based on image data so as to expose the photosensitive drums  14  as indicated by broken lines. 
     (3-2) Process Unit 
     (3-2-1) Configuration of Process Unit 
     The process unit  9  is disposed below the scanning unit  8  and above the transfer unit  10 . The process unit  9  has a single process frame  12  and four developer cartridges  13  corresponding to four colors. The process unit  9  is detachably mounted on the main body casing  2  by being slid in the front-rear direction relative to the main-body casing  2 . 
     The process frame  12  is slidably movable in the front-rear direction relative to the main-body casing  2  and supports the four photosensitive drums  14 , four scorotron chargers  15 , and four drum cleaning rollers  16 . 
     The four photosensitive drums  14  extend in the left-right direction and are arranged parallel to and spaced apart from one another in the front-rear direction. Specifically, the photosensitive drums  14  include a cyan photosensitive drum  14 C, a magenta photosensitive drum  14 M, a yellow photosensitive drum  14 Y, and a black photosensitive drum  14 K arranged in this order from front to rear. 
     The scorotron chargers  15  are disposed diagonally above and rearward of the respective photosensitive drums  14  and face the photosensitive drums  14 . The scorotron chargers  15  separate from the photosensitive drums by a gap. 
     The drum cleaning rollers  16  are disposed rearward of the respective photosensitive drums  14  and face and contact the photosensitive drums  14 . 
     The developer cartridges  13  are detachably supported by the process frame  12  above the corresponding photosensitive drums  14  and face the corresponding photosensitive drums  14 . Specifically, a cyan developer cartridge  13 C, a magenta developer cartridge  13 M, a yellow developer cartridge  13 Y, and a black developer cartridge  13 K are arranged in this order from front to rear. Each of the developer cartridges  13  is also provided with a developing roller  17 . 
     Although details will be described later, each developing roller  17  is rotatably supported at the lower end of the corresponding developer cartridge  13  so as to expose the bottom rear end of the developing roller  17  through a lower edge of the developer cartridge  13 . The bottom rear end of each developing roller  17  contacts a top of the corresponding photosensitive drum  14 . 
     Each of the developer cartridges  13  also has a feed roller  18  for feeding toner to the corresponding developing roller  17  and a layer thickness regulating blade  19  for regulating the thickness of the toner fed to the developing roller  17 . Toner corresponding to each of the four colors is accommodated above the feed roller  18  and the layer thickness regulating blade  19 . 
     (3-2-2) Developing Operation of Process Unit 
     The toner accommodated in each of the developer cartridges  13  is fed to the feed roller  18 , which in turn feeds the toner to the developing roller  17 . The toner is positively triboelectrically charged between the feed roller  18  and the developing roller  17 . 
     As the developing roller  17  rotates, the layer thickness regulating blade  19  regulates the toner fed to the developing roller  17  to a prescribed thickness, so that the developing roller  17  carries a uniform thin layer of toner thereon. 
     The scorotron charger  15  applies a uniform charge of positive polarity to a surface of the corresponding photosensitive drum  14  while the photosensitive drum  14  rotates. Subsequently, the surface of the photosensitive drum  14  is exposed by laser beam (refer to the broken line of  FIG. 1 ) emitted from the scanning unit  8  in a high-speed scan. As a result, an electrostatic latent image corresponding to an image to be formed on the paper P is formed on the surface of the respective photosensitive drum  14 . 
     As the photosensitive drum  14  continues to rotate, the positively charged toner carried on the surface of the developing roller  17  is supplied to the electrostatic latent image formed on the surface of the photosensitive drum  14 , thereby developing the electrostatic latent image into a visible toner image through reverse development. 
     (3-3) Transfer Unit 
     The transfer unit  10  is disposed in the main-body casing  2  above the paper feeding section  3  and below the process unit  9  and extends in the front-rear direction. The transfer unit  10  has a drive roller  20 , a driven roller  21 , the conveying belt  22 , and four transfer rollers  23 . 
     The drive roller  20  and the driven roller  21  are arranged spaced apart from each other in the front-rear direction. The conveying belt  22  is winded around the drive roller  20  and the driven roller  21 , with a top portion of the conveying belt  22  contacting each of the photosensitive drums  14  from below. When the drive roller  20  rotates, the conveying belt  22  circulates such that the top portion of the conveying belt  22  moves from the front side to rear side. 
     The transfer rollers  23  are disposed at positions opposing corresponding photosensitive drums  14 , with the top portion of the conveying belt  22  interposed therebetween. 
     When the paper P is fed from the paper feeding section  3 , the conveying belt  22  conveys the paper P from the front side to the rear side such that the paper P passes sequentially through each transfer position between the photosensitive drums  14  and the corresponding transfer rollers  23 . As the paper P is conveyed on the conveying belt  22 , the toner images of each color carried on the respective photosensitive drums  14  are sequentially transferred onto the paper P to form a color image. 
     (3-4) Fixing Unit 
     The fixing unit  11  is disposed rearward of the transfer unit  10  and has a heating roller  24  and a pressure roller  25  arranged opposite to the heating roller  24 . While the paper P passes between the heating roller  24  and the pressure roller  25 , the color image transferred onto the paper P in the transfer unit  10  is fixed to the paper P by heat and pressure. 
     (4) Paper Discharge 
     The paper P onto which the toner image has been fixed is conveyed along a U-shaped discharge path (not shown) by paper discharge rollers  26 . The paper discharge rollers  26  discharge the paper P onto a paper discharge tray  27  disposed above the scanning unit  8 . 
     2. Detailed Description of Process Unit 
     (1) Process Frame 
     As illustrated in  FIG. 2 , the process frame  12  has substantially a rectangular frame shape elongated in the front-rear direction, as viewed from above. The process frame  12  has a pair of side plates  31 . The side plates  31  are respectively positioned at the left and right sides of the process frame  12 . 
     The side plates  31  are arranged spaced apart from each other and opposite each other in the left-right direction. As shown in  FIG. 3 , the both side plates  31  have substantially a rectangular shape elongated in the front-rear direction and has guide grooves  32 . 
     In the present embodiment, a process-side electrode  46  (to be described later) is formed only in the right side plate  31 . Thus, hereinafter, only the right side plate  31  will be described in detail, and the description of the left side plate  31  will be omitted. Further, the right side plate  31  is hereinafter referred to merely as the side plate  31 . 
     The side plate  31  has four guide grooves  32  which are formed in the left surface (inner surface in the left-right direction) equally spaced apart from one another in the front-rear direction. Each guide groove  32  is formed between the upper edge of the side plate  31  and corresponding photosensitive drum  14 . 
     Each guide groove  32  has a first guide groove  32 A diagonally extending in the lower-rear direction (first inclined direction X) from the upper end portion of the side plate  31  and a second guide groove  32 B which is formed continuing from the first guide groove  32 A so as to extend, at a different angle from the first guide groove  32 A, in the lower-rear direction (second inclined direction Y) from the lower end portion of the first guide groove  32 A. That is, the guide groove  32  is bent at the boundary between the first and second guide grooves  32 A and  32 B. The second inclined direction Y is more inclined to the rear direction than the first inclined direction X. 
     A process-side electrode  46  is formed at the rear side of the boundary between the first and second guide grooves  32 A and  32 B. The substantially rectangular portion of the process-side electrode  46  is exposed through the left surface of the side plate  31 . 
     The process-side electrode  46  integrally has a power receiving portion (not illustrated) exposed through the right surface of the side plate  31 . When the process unit  9  is attached to the main-body casing  2 , the power receiving portion (not illustrated) is electrically connected to a power supply (not illustrated) provided in the main-body casing  2 . 
     Further, pressure cams  36  are formed in the left surface of the side plate  31  in correspondence with the respective guide grooves  32 . Each pressure cam  36  has substantially a fan-like shape in the side view. 
     Each of the pressure cams  36  is pivotally supported about a pivot shaft  40  and is biased by a biasing member (not shown) in the counterclockwise direction as viewed from the left side. 
     (2) Developer Cartridge 
     (2-1) Configuration of Developer Cartridge 
     As shown in  FIG. 4 , each developer cartridge  13  has a frame  51 , an electrode unit  52 , and a drive unit  65 . 
     The frame  51  is formed into substantially a box shape elongated in the left-right direction. In the side view, the frame  51  has an isosceles triangular cross-section having an apex angle that is directed in the lower-rear direction. 
     The frame  51  has a handle  60 , a pair of left and right side outer surfaces  61 , and a pair of left and right bosses  64 . The handle  60  is positioned at the front side upper end portion of the frame  51 . The side surfaces  61  are located at both ends of the frame  51  in the left-right direction. Each bosses  64  protrudes outward from the respective side surface  61 . Further, the frame  51  has an opening portion  53  in the rear-side lower end portion. 
     The bosses  64  are formed on the left and right end surfaces  61  of the frame  51  in substantially cylindrical shapes protruding outside in the left and right directions. 
     The opening portion  53  extends over the entire left-right direction of the frame  51  and is opened rearward. 
     Further, as shown in  FIGS. 5 and 6 , a developing roller shaft inserting groove  47 , a communication groove  49 , a feed roller shaft inserting groove  48 , and a feed roller bearing fitting portion  50  are formed in the right wall of the frame  51 . 
     In the side view, the developing roller shaft inserting groove  47  is formed in a substantial U-shape at the lower end portion of the frame  51 . The developing roller shaft inserting groove  47  cutouts to extend from the rear edge of the frame  51  toward the front side thereof and is opened rearward. 
     In the side view, the communication groove  49  is formed in a substantially linear shape continuing from the front end portion of the developing roller shaft inserting groove  47  and extend in the front-rear direction. 
     In the side view, the feed roller shaft inserting groove  48  is formed in a substantial U-shape continuing from the front end portion of the communication groove  49  and being opened at the rear side thereof. 
     In the side view, the feed roller bearing fitting portion  50  is formed in a substantially rectangular shape that is recessed to the left from the right surface of the frame  51 . When projected in the left-right direction, the feed roller bearing fitting portion  50  is disposed such that the front end portion of the feed roller shaft inserting groove  48  is located at substantially the center of the feed roller bearing fitting portion  50 . 
     Further, a pair of electrode positioning bosses  41  and a pair of cover positioning bosses  43  are formed on the right wall of the frame  51 . Further, a cover engaging through-hole  44 , a screw hole  42 , and a receiving portion  45  are formed on the right wall of the frame  51 . 
     The electrode positioning bosses  41  are apart from each other above the developing roller shaft inserting groove  47  and the feed roller shaft inserting groove  48  such that the interval between the electrode positioning bosses  41  corresponds to the lengths of a base portion  56  of an electrode plate  54  (to be described later) in the front-rear direction. Further, both of the electrode positioning bosses  41  are substantially formed in a cylindrical shape protruding to the right side from the right wall of the frame  51 . 
     The cover positioning bosses  43  sandwich the front side portion of the developing roller shaft inserting groove  47  therebetween in the upper-lower direction. Further, the cover positioning bosses  43  are formed in a substantially cylindrical shape protruding to the right side from the right wall of the frame  51 . 
     In the side view, the cover engaging through-hole  44  is formed in a substantially rectangular shape at the front side of the lower-side cover positioning boss  43 . 
     The screw hole  42  is formed above the feed roller bearing fitting portion  50  at the lower-rear side of the front-side electrode positioning boss  41  and at the lower-front side of the rear-side electrode positioning boss  41 . 
     In the side view, the receiving portion  45  is formed in a substantially rectangular shape above the upper-side cover positioning boss  43 . The receiving portion  45  is recessed to the left from the right surface of the frame  51 . When projected in the left-right direction, the receiving portion  45  is formed at a position overlapping an engagement portion  75  (to be described later) of an electrode plate  54  (to be described later). Further, when projected in the left-right direction, the receiving portion  45  is disposed between the developing roller  17  and the layer thickness regulating blade  19 . 
     The electrode unit  52  is provided on the right end portion of the frame  51  and has an electrode plate  54  and an electrode cover  55  (refer to  FIG. 4 ). 
     As shown in  FIGS. 7(   a ) and  7 ( b ), the electrode plate  54  is formed from a metal plate and has a substantially rectangular shape as viewed from the right side. 
     More specifically, the electrode plate  54  integrally has a base portion  56 , a pair of first extending portions  57 , a second extending portion  58 , and an input portion  59 . 
     In the side view, the base portion  56  is formed in a substantially rectangular flat plate shape extending in an extending direction that is orthogonal to the longitudinal direction and that is oriented from the upper-front side to the lower-rear side. The base portion  56  has a predetermined width in a width direction that is orthogonal to the longitudinal direction and the extending direction and that is therefore oriented from the lower-front side to the upper-rear side. Further, a positioning through-hole  71 , a positioning groove  72 , and a screw insertion through-hole  73  are formed at a bottom rear end portion of the base portion  56 . 
     In the side view, the positioning through-hole  71  is formed in a substantially rectangular shape at the rear end portion of the base portion  56  and penetrates the base portion  56 . The positioning groove  72  is formed in a substantially rectangular shape at the front end portion of the base portion  56  and extends from the lower-front side to the upper-rear side. In the side view, the screw insertion through-hole  73  is formed in a substantially circular shape at the lower end portion of the base portion  56  and penetrates the base portion  56 . 
     The pair of first extending portions  57  and located and formed in a substantially flat plate shape. Each of the first extending portions  57  is connected to the respective width end of the base portion  56  in the width direction. Each of the first extending portion  57  extends to the right direction from the upper-front side end portion of the base portion  56 . 
     In the side view, the second extending portion  58  is formed substantially U-shaped and extending from the right end portions of the both first extending portions  57  to the lower-rear side. The upper-front side of the second extending portion  58  is opened so as to connect the both first extending portions  57 . The upper-rear side end portion of the second extending portion  58  is cut out so as to expose the positioning through-hole  71  to the right side. The lower-front side end portion of the second extending portion  58  is cut out so as to expose the screw insertion through-hole  73 . Further, the second extending portion  58  is opposed to the base portion  56  in the left-right direction. 
     As viewed form the side, the input portion  59  is substantially located at a center of the second extending portion  58  in the width direction. The input portion  59  is formed in a substantially rectangular shape extends from the lower-rear side end portion of the second extending portion  58  to the lower-rear side. Further, the input portion  59  has a contact portion  74  and an engagement portion  75 . 
     As shown in  FIG. 7(   b ), the contact portion  74  is curved substantially in a U-shape continuing from the lower-rear side end portion of the second extending portion  58  and protruding to the right with the left side thereof is opened. More specifically, the contact portion  74  extends from the lower-rear side end portion of the second extending portion  58  to the right and curved in substantially a U-shape toward the lower-rear side. 
     As shown in  FIG. 7(   a ), the engagement portion  75  is formed in a substantially rectangular shape extending from the lower-rear side end portion of the contact portion  74  to the lower-rear side. Further, as shown in  FIG. 7(   b ), the engagement portion  75  is inclined to the right as the engagement portion  75  extends from the lower-rear end portion of the contact portion  74  to the lower-rear side. 
     As shown in  FIGS. 8(   a ) and  8 ( b ), the electrode cover  55  is formed of a conductive material such as a conductive resin and integrally has a bearing portion  81 , an electrode supporting portion  82  that is provided above the bearing portion  81  and supports the electrode plate  54 . 
     The bearing portion  81  has an electrode side developing bearing portion  83  and an electrode side feed bearing portion  84 . 
     The electrode side developing bearing portion  83  is provided at the rear end portion of the bearing portion  81 , and has a developing roller shaft insertion thorough-hole  85  and a developing roller shaft supporting portion  86 . 
     In the side view, the developing roller shaft insertion through-hole  85  is formed in a substantially circular shape and penetrates the bearing portion  81  in the left-right direction. 
     The developing roller shaft supporting portion  86  is formed in a substantially cylindrical shape around the developing roller shaft insertion through-hole  85  and extends from the left surface of the bearing portion  81  to the left. The inner diameter of the developing roller shaft supporting portion  86  is substantially the same as the diameter of the developing roller shaft insertion through-hole  85 . The outer diameter of the developing roller shaft supporting portion  86  is made slightly smaller than the diameter of the developing roller shaft inserting groove  47  ( FIG. 6 ) and is fitted to the front side portion of the developing roller shaft inserting groove  47 . 
     The electrode side feed bearing portion  84  is disposed in parallel to and spaced apart from the electrode side developing bearing portion  83  at the front side of the electrode side developing bearing portion  83  and has a feed roller shaft supporting portion  87 , a feed roller shaft insertion hole  88 , and a feed roller shaft collar portion  89 . 
     As shown in  FIG. 8(   b ), the feed roller shaft supporting portion  87  is formed in a substantially prism shape protruding from the left surface of the bearing portion  81  to the left direction. Further, the feed roller shaft supporting portion  87  is formed in a substantially rectangular shape in the side view, so as to have a size corresponding to the feed roller bearing fitting portion  50  for fitting to the feed roller bearing fitting portion  50 . 
     The feed roller shaft insertion hole  88  is formed in a substantially circular shape in the side view, is located at substantially the center of the feed roller shaft supporting portion  87 , and penetrates the feed roller shaft supporting portion  87  in the left-right direction. 
     As shown in  FIG. 8(   a ), the feed roller shaft collar portion  89  is located at a peripheral side of the feed roller shaft insertion hole  88 . The feed roller shaft collar portion  89  is formed in a substantially cylindrical shape extending from the right surface of the bearing portion  81  to the right direction. The inner diameter of the feed roller shaft collar portion  89  is substantially the same as the diameter of the feed roller shaft insertion hole  88 . 
     Further, the bearing portion  81  has a pair of cover positioning through-holes  90 . Further, the bearing portion  81  has an engaging claw  80 . 
     The cover positioning through-holes  90  sandwiches the developing roller shaft insertion through-hole  85  in the upper-lower direction. Further, the cover positioning through-holes  90  penetrate the bearing portion  81  and are formed in a substantially rectangular shapes in the side view such that the cover positioning bosses  43  of the frame  51  (see  FIG. 5 ) are inserted to the cover positioning through-holes  90 . 
     As shown in  FIG. 8(   b ), the engaging claw  80  is formed at the front side of the lower-side cover positioning through-hole  90 . The engaging claw  80  protrudes from the left surface of the bearing portion  81  to the left direction and is curved in a hook-like manner at the left end portion. 
     The electrode supporting portion  82  is disposed above the electrode side developing bearing portion  83  and has a covering portion  91 , an exposing portion  92 , and a screw thread portion  93 . 
     The covering portion  91  is formed in a substantially rectangular frame shape whose right side is closed and whose left side is opened. The covering portion  91  covers the first extending portions  57  and the second extending portion  58  ( FIGS. 7  ( a ) and  7 ( b )). Specifically, the covering portion  91  has a length in the left-right direction longer than the length of the first extending portions  57  in the left-right direction. Further, the covering portion  91  has a length in the width direction longer than the length of the second extending portion  58  in the width direction and a length in the extending direction longer than the length of the second extending portion  58  in the extending direction. Further, the right wall of the covering portion  91  is formed such that a front side half portion of the covering portion  91  extends along the front-rear direction and a remaining rear side portion of the covering portion  91  continuing from the front side half portion is inclined with respect to the left rear direction. 
     The exposing portion  92  is formed in a substantially rectangular frame shape elongated in the front-rear direction at the rear side of the covering portion  91  and continues from substantially the center in the width direction of the covering portion  91 . The right side of the exposing portion  92  is closed and the left side of the exposing portion  92  is opened. 
     The electrode supporting portion  82  has an exposing thorough-hole  96 . 
     The exposing thorough-hole  96  is formed in a substantially rectangular shape extending in the front-rear direction in the side view and penetrates the right wall of the exposing portion  92  in the left-right direction. Further, the exposing thorough-hole  96  has a length in the front-rear direction capable of receiving (inserting) the contact portion  74  (see  FIG. 4 ). 
     As shown in  FIGS. 3 and 4 , the drive unit  65  is provided at the left end portion of the frame  51  and has a drive side developing bearing portion  66 , a drive side feed bearing portion  67 , and a coupling member  68 . 
     The drive side developing bearing portion  66  is formed in a substantially cylindrical shape at the lower end portion of the drive unit  65  and extends in the left-right direction. The drive side developing bearing portion  66  has an inner diameter capable of receiving a developing roller shaft  62  (described later). 
     As shown in  FIG. 3 , the drive side feed bearing portion  67  is formed in substantially annular shape in the side view and is disposed in parallel to and spaced apart from the drive side developing bearing portion  66  at the upper-front side of the drive side developing bearing portion  66 . The inner diameter of the drive side feed bearing portion  67  is smaller than that of the drive side developing bearing portion  66 . The drive side feed bearing portion  67  has an inner diameter capable of receiving (inserting) a feed roller shaft  63  (described later). 
     The coupling member  68  is a substantially cylindrical shaped coupling female member and is rotatably supported at the left wall of the frame  51 . When the developer cartridge  13  is mounted to the main-body casing  2 , a coupling male member (not shown) is coupled from the left to the left end portion of the coupling member  68 , whereby drive force is input to the drive unit  65  from the a drive source (not shown) of the main-body casing  2 . Further, in the drive unit  65 , the coupling member  68  transmits the drive force to the developing roller  17  and the feed roller  18  through gears (not shown). 
     As shown in  FIG. 3 , the left end portion of the developing roller shaft  62  is rotatably supported by the drive side developing bearing portion  66 , and as shown in  FIG. 4 , the right end portion of the developing roller shaft  62  is rotatably supported by the electrode side developing bearing portion  83  of the electrode unit  52 . With the above configuration, the developing roller  17  is rotatably supported by the frame  51 . 
     Further, as shown in  FIG. 3 , the left end portion of the feed roller shaft  63  is rotatably supported by the drive side feed bearing portion  67 , and as shown in  FIG. 4 , the right end portion of the feed roller shaft  63  is rotatably supported by the electrode side feed bearing portion  84  of the electrode unit  52 . With the above configuration, the feed roller  18  is rotatably supported by the frame  51 . 
     (2-2) Assembing Electrode Unit 
     When the electrode unit  52  is mounted to the frame  51 , the electrode plate  54  is mounted to the frame  51 . 
     When the electrode plate  54  is mounted to the frame  51 , the electrode plate  54  is disposed on the right side of the frame  51  with the base portion  56  positioned on the left side. Then, the electrode plate  54  is mounted to the frame  51  from the right such that the electrode positioning through-hole  71  of the electrode plate  54  is fitted around the rear-side electrode positioning boss  41  of the frame  51  ( FIG. 6 ), and the electrode positioning groove  72  of the electrode plate  54  is fitted around the front-side electrode positioning boss  41  of the frame  51 . That is, the bottom rear end portion of the base portion  56  is fixed to the frame  51 . 
     Next, the electrode cover  55  is mounted to the frame  51  for covering the electrode plate  54 . 
     When the electrode cover  55  is mounted to the frame  51 , the electrode cover  55  is disposed on the right side of the frame  51 . 
     Then, the electrode supporting portion  82  is positioned relative to the frame  51  such that the covering portion  91  covers the second extending portion  58  and the exposing thorough-hole  96  receives the contact portion  74  (that is, the contact portion  74  is inserted to the exposing through-hole  96 ). Simultaneously, the bearing portion  81  is positioned relative to the frame  51  such that the both cover positioning through-holes  90  are fitted around the corresponding cover positioning bosses  43  of the frame  51  and such that the engaging claw  80  engages the cover engaging through-hole  44  of the frame  51 . After that, the electrode cover  55  is mounted to the frame  51  from the right. 
     At this time, as shown in  FIG. 10 , the rear end portion of the exposing portion  92  contacts to and is pressed by the engagement portion  75  from the right. The rear end portion of the covering portion  91  contacts to and is pressed by the second extending portion  58  from the right. As a result, the second extending portion  58  and the input portion  59  are bent against the biasing force of the electrode plate  54  so as to be brought close to the base portion  56  and are moved to the left. 
     At this time, the front side portion of the covering portion  91  is opposed to the second extending portion  58  with a predetermined interval therefrom in the left-right direction. Further, the screw hole  42  of the frame  51  is exposed through the screw insertion hole  98 . 
     Then, the screw  94  is screwed into the screw hole  42  through the screw insertion hole  98  and the screw insertion through-hole  73 . As a result, the mounting of the electrode unit  52  to the frame  51  is completed. 
     3. Mount of Developer Cartridge to Main-Body Casing 
     (1) Attachment/detachment of Developer Cartridge to/from Process Unit 
     As shown in  FIG. 3 , for mounting the developer cartridge  13  to the main-body casing  2 , the developer cartridge  13  is mounted to the process frame  12 . 
     When the developer cartridge  13  is mounted to the process frame  12 , the developer cartridge  13  is disposed above the process frame  12  pulled out of the main-body casing  2  at a position corresponding to the corresponding photosensitive drum  14  in the front-rear direction. Then, the developer cartridge  13  is inserted down into the process frame  12  from the lower end portion thereof. 
     Then, as the developer cartridge  13  is inserted into the process frame  12 , the both end portions of the developing roller shaft  62  in the left-right direction are fitted from the above to the first guide groove  32 A of the corresponding guide groove  32  formed in the both side plates  31  of the process frame  12 . 
     As a result, the developer cartridge  13  is inserted into the process frame  12 , with the both end portions of the developing roller shaft  62  in the left-right direction guided by the first guide groove  32 A in the first inclined direction X. That is, the developer cartridge goes slightly rearward as the developer cartridge  13  goes downward. 
     When the developer cartridge  13  is further inserted into the process frame  12  after the both end portions of the developing roller shaft  62  in the left-right direction reaches the lower end portion of the first guide groove  32 A, the both end portions of the developing roller shaft  62  in the left-right direction is guided by the second guide groove  32 B in the second inclined direction Y, and reaches the deepest portion of the second guide groove  32 B. At this time, the bosses  64  are opposed to the pressure cams  36  from the upper-rear side. 
     Then, the developer cartridge  13  is pivoted to the front side. As a result, the developer cartridge  13  pivots to the front side about the developing roller shaft  62 . Then, the bosses  64  go into the lower side of the pressure cams  36  such that the pressure cams  36  pivot to the front side. 
     When the bosses  64  have gone into the lower side of the pressure cams  36  (indicated by the broken line in  FIG. 3 ), the pressure cams  36  are engaged with the bosses  64  from the above and press the bosses  64  to the lower-rear side by the biasing force of a biasing means (not shown). That is, the developer cartridge  13  is pressed to the lower-rear side by the pressure cams  36 . 
     Thus, the developer cartridge  13  is completely mounted to the process frame  12 . Subsequently, other developer cartridges  13  are mounted to the process frame  12  according to the same procedure. 
     The cross-section of the photosensitive drum  14  is not a true circle but is eccentric within a predetermined range of tolerance. Therefore, when the photosensitive drum  14  is rotated, the developing roller  17  is pressed by the photosensitive drum  14  with periodically changing pressing force. 
     On the other hand, the pressure cams  36  press the bosses  64  of the developer cartridge  13  allowing the developer cartridge  13  to move in accordance with the pressing force from the photosensitive drum  14 . 
     As shown in  FIG. 10 , when the developer cartridge  13  is completely mounted to the process frame  12 , the contact portion  74  contacts the process-side electrode  46  from the left. 
     Thus, when the developer cartridge  13  is pressed to the right, the contact portion  74  is moved to the left by the reactive force from the process-side electrode  46  (indicated by the dotted line in  FIG. 10 ). Further, when projected in the pressing force direction of the pressure cams  36  (lower-rear direction), the pressure cam  36  presses a portion of the boss  64  that overlaps a moving range S within which the right end portion of the contact portion  74  moves. The process-side electrode  46  moves in the moving range S between the outward end of the boss  64  and the right side surface  61 . In the embodiment, the pressure cam  36  partially presses the portion of the boss  64  within the moving region S. However, the pressure cam  36  may press all the portion of the boss  64  within the moving region S. 
     The developer cartridge  13  is detached from the process frame  12  according to a procedure reverse to the abovementioned procedure for mounting the developer cartridge  13  to the process frame  12 . 
     (2) Attachment/detachment of Process Unit to/from Main-Body Casing 
     The process unit  9  (that is, the process frame  12  to which all the developer cartridges  13  have been mounted) is mounted to the main-body casing  2 . When the process unit  9  is mounted to the main-body casing  2 , the process unit  9  is inserted into the main-body casing  2  toward the rear side. 
     Then, when the process unit  9  is completely inserted into the main-body casing  2  as shown in  FIG. 1 , the photosensitive drums  14  contact the conveying belt  22  from the above. Thereafter, the front cover  5  is swingably moved rearward to close the inner space of the main-body casing  2 . 
     Thus, the attachment of the process unit  9  to the main-body casing  2  is completed. 
     When the process unit  9  mounted to the main-body casing  2  is detached therefrom, the front cover  5  is swingably moved frontward, and the process unit  9  is pulled out frontward. 
     (3) Supply of Power 
     When the developer cartridge  13  is mounted to the main-body casing  2 , a coupling male member (not shown) provided in the main-body casing  2  is coupled from the left to the left end side of the coupling member  68 . The developer cartridge  13  is pressed to the right by the coupling male member (not shown), and then the contact portion  74  of the developer cartridge  13  is pressed toward the process-side electrode  46  of the side plate  31 . At this time, as shown in  FIG. 10 , the input portion  59  is moved to the left within a range between the right end portion of the boss  64  and the right end portion of the frame  51  (right side surface  61 ) by the reactive force from the process-side electrode  46 . 
     Further, power is supplied to a power receiving portion (not shown) of the process-side electrode  46  from a power supply  99  ( FIG. 3 ) of the main-body casing  2 . Then, the power is supplied from the process-side electrode  46  to the electrode plate  54 . 
     The power supplied to the electrode plate  54  is then supplied to the developing roller shaft  62  and the feed roller shaft  63  through the electrode cover  55 . Thus, the same bias is applied to the developing roller  17  and the feed roller  18  simultaneously. 
     4. Effect 
     (1) According to the developer cartridge  13 , as shown in  FIGS. 7(   a ),  7 ( b ), the electrode plate  54  has the base portion  56  which is fitted to the frame  51 , the first extending portions  57 , the second extending portion  58  extending from the right end portion of the first extending portions  57  to the lower-rear side, and the input portion  59 . The electrode plate  54  is bended (deformed) such that the base portion  56  and the second extending portion  58  are brought closer to each other in the left-right direction. 
     The electrode plate  54  can be deformed largely in the left-right direction by an extension of the first extending portion  57  to the right. That is, the electrode plate  54  can be reduced in rigidity and increased in deformation amount. 
     Thus, because the biasing force of the electrode plate  54  is reduced, the friction force occurring between the electrode plate  54  and the process unit  9  can be reduced after the developer cartridge  13  is mounted to the process unit  9 . 
     As a result, even if the photosensitive drum  14  presses the developing roller  17  with the pressing force changing periodically due to the eccentricity of the photosensitive drum  14 , and the developer cartridge  13  is moved such that the developing roller  17  follows the outer periphery of the photosensitive drum  14  while the developing roller  17  keeps contacting with the photosensitive drum  14 , the friction force does not inhibit the movement of the developer cartridge  13 . As a result, the developer roller  17  can uniformly and constantly be pressed against the photosensitive drum  14 . 
     (2) Further, according to the developer cartridge  13 , shown in  FIG. 6 , the base portion  56  is fitted to (is fixed to) the frame  51  at the lower-rear end portion thereof. 
     Thus, when the input portion  59  is moved to the left, the upper-front end portion of the base portion  56  can be separated from the frame  51 . 
     Thus, the biasing force of the electrode plate  54  can be reduced further by the separation of the upper-front end portion of the base portion  56 , so that the friction force occurring between the electrode plate  54  and the process unit  9  after the developer cartridge  13  is mounted to the process unit  9  can be reduced further. 
     As a result, the developer roller  17  can be pressed against the photosensitive drum  14  more uniformly. 
     (3) Further, according to the developer cartridge  13  shown in  FIG. 7(   b ), the engagement portion  75  is inclined with respect to the right as the engagement portion  75  extends to the lower-rear side. 
     Thus, the movement amount of the electrode plate  54  in the left-right direction can be increased at the engagement portion  75 . That is, the electrode plate  54  can be reduced in rigidity and increased in deformation amount. 
     As a result, the biasing force of the electrode plate  54  can be reduced further. 
     (4) Further, according to the developer cartridge  13 , as shown in  FIGS. 5 and 6 , the receiving portion  45  receives (is inserted by) the engagement portion  75  (that is the engagement portion  75  enters the receiving portion  45 ) when the electrode plate  54  is deformed. 
     Thus, the movement amount of the engagement portion  75  can be increased further because the engagement portion  75  is received by the receiving section  45 . That is, with the configuration in which the engagement portion  75  is received by the receiving section  45 , the electrode plate  54  can be reduced in rigidity and increased in deformation amount. As a result, the biasing force of the electrode plate  54  can be reduced further. 
     (5) Further, according to the developer cartridge  13 , as shown in  FIG. 10 , the input portion  59  is moved in the left-right direction within a range between the right end portion of the boss  64  and the right end portion of the frame  51  (the right side surface  61 ) when the electrode plate  54  is bended. 
     Therefore, the pressing force applied to the boss  64  can reliably be transmitted to the contacting region between the contact portion  74  and the process-side electrode  46 . 
     As a result, the friction force occurring between the contact region between the contact portion  74  and the process-side electrode  46  can be canceled by the pressing force applied to the boss  64 . 
     As a result, the developer cartridge  13  can reliably be pressed by pressing the boss  64 . 
     (6) Further, according to the developer cartridge  13 , as shown in  FIG. 7(   a ), the first extending portions  57  extend from the both end portions of the base portion  56  in the width direction of the electrode plate  54 , and the input portion  59  extends from the width direction center of the second extending portion  58 . 
     Thus, when the input portion  59  contacts the process-side electrode  46 , the input portion  59  can be supported by the first extending portions  57  at both widthwise ends of the electrode plate  54 . 
     As a result, the input portion  59  can contacts uniformly with the process-side electrode  46  in the width direction. 
     (7) Further, according to the developer cartridge  13 , as shown in  FIG. 8(   a ), the electrode cover  55  can cover the base portion  56 , the first extending portions  57  and the second extending portion  58  while exposing the input portion  59 . 
     (8) Further, according to the developer cartridge  13 , as shown in  FIG. 10 , the electrode cover  55  has the covering portion  91  which is opposed to the second extending portion  58  with a predetermined interval in the left-right direction. 
     Thus, when the input portion  59  is moved to the left, the second extending potion  58  can reliably be separated from the frame  51 . 
     (9) Further, according to the process unit  9  and the color laser printer  1 , the developer cartridge  13  having the above configuration is provided, so that the developer roller  17  can be pressed against the photosensitive drum  14  uniformly.