Patent Publication Number: US-9417558-B2

Title: Development cartridge, process cartridge, and image forming apparatus having the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of prior U.S. application Ser. No. 14/546,069, filed Nov. 18, 2-014, which claims priority under 35 U.S.C. §119 from Japanese Patent Applications No. 2013-238353 filed on Nov. 18, 2013 and No. 2013-238347 filed on Nov. 18, 2013. The entire subject matters of the applications are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Technical Field 
     The following description relates to aspects of a development cartridge and a process cartridge attached to an electrophotographic image forming apparatus. 
     2. Related Art 
     As an electrophotographic image forming apparatus, a printer has been known that includes a development cartridge detachably attached to the printer. The development cartridge includes a development roller and a supply roller. 
     As an example of the development cartridge, a development cartridge has been known that includes a development gear, a supply gear, and a gear cover configured to collectively cover the development gear and the supply gear. The development gear is disposed at an end portion of a development roller and configured to receive an externally-transmitted driving force. Further, the supply gear is disposed at an end portion of a supply roller and configured to receive an externally-transmitted driving force. 
     SUMMARY 
     In the aforementioned development cartridge, the gear cover collectively covers the development gear and the supply gear. Therefore, the gear cover needs to be large in size. Thus, the development cartridge is as well required to be large in size. 
     Aspects of the present disclosure are advantageous to provide one or more improved techniques, for a development cartridge, which make it possible to realize miniaturization of the development cartridge with a first gear and a second gear collectively covered. 
     According to aspects of the present disclosure, a development cartridge is provided, which includes a housing configured to store developer (i.e., development agent) therein, a developer carrying body configured to rotate around a first axis extending in a first direction, a supply member configured to rotate around a second axis along the first axis, and to contact the developer carrying body and supply the developer to the developer carrying body, a first gear connected with an end portion of the developer carrying body, a second gear connected with an end portion of the supply member, and a gear cover configured to cover the first gear and the second gear, the gear cover including a first cover portion extending in a second direction perpendicular to the first direction, and a second cover portion connected with the first cover portion, the second cover portion extending in the first direction, the second cover portion having an opening through which a part of the second gear protrudes from the second cover portion and is exposed. 
     According to aspects of the present disclosure, further provided is a process cartridge that includes a photoconductive body cartridge, and a development cartridge detachably attached to the photoconductive body cartridge, the development cartridge including a housing configured to store developer therein, a developer carrying body configured to rotate around a first axis extending in a first direction, a supply member configured to rotate around a second axis along the first axis, and to contact the developer carrying body and supply the developer to the developer carrying body, a first gear connected with an end portion of the developer carrying body, a second gear connected with an end portion of the supply member, and a gear cover configured to cover the first gear and the second gear, the gear cover including a first cover portion extending in a second direction perpendicular to the first direction, and a second cover portion connected with the first cover portion, the second cover portion extending in the first direction, the second cover portion having an opening through which a part of the second gear protrudes from the second cover portion and is exposed, the housing including a projection protruding in a direction in which the part of the second gear protrudes from the second cover portion, the projection being disposed adjacent to the second gear in the first direction, the photoconductive body cartridge including a photoconductive body configured to rotate around a rotational axis along the first direction, and a cartridge attachment portion configured such that the development cartridge is attached thereto, the cartridge attachment portion including a bottom portion disposed to face the second gear in a direction in which the part of the second gear protrudes from the second cover portion, the bottom portion having an engagement hole configured such that the projection of the housing of the development cartridge is inserted therethrough. 
     According to aspects of the present disclosure, further provided is an image forming apparatus that includes a casing having an opening, and a process cartridge configured to be inserted into and removed from the casing through the opening, the process cartridge including a photoconductive body cartridge, and a development cartridge detachably attached to the photoconductive body cartridge, the development cartridge including a housing configured to store developer therein, a developer carrying body configured to rotate around a first axis extending in a first direction, a supply member configured to rotate around a second axis along the first axis, and to contact the developer carrying body and supply the developer to the developer carrying body, a first gear connected with an end portion of the developer carrying body, a second gear connected with an end portion of the supply member, and a gear cover configured to cover the first gear and the second gear, the gear cover including a first cover portion extending in a second direction perpendicular to the first direction, and a second cover portion connected with the first cover portion, the second cover portion extending in the first direction, the second cover portion having an opening through which a part of the second gear protrudes from the second cover portion and is exposed, the housing including a projection protruding in a direction in which the part of the second gear protrudes from the second cover portion, the projection being disposed adjacent to the second gear in the first direction, the photoconductive body cartridge including a photoconductive body configured to rotate around a rotational axis along the first direction, and a cartridge attachment portion configured such that the development cartridge is attached thereto, the cartridge attachment portion including a bottom portion disposed to face the second gear in a direction in which the part of the second gear protrudes from the second cover portion, the bottom portion having an engagement hole configured such that the projection of the housing of the development cartridge is inserted therethrough. 
    
    
     
       BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
         FIG. 1  is a cross-sectional side view of a development cartridge in an illustrative embodiment according to one or more aspects of the present disclosure. 
         FIG. 2  is a cross-sectional side view of an image forming apparatus with the development cartridge attached thereto in the illustrative embodiment according to one or more aspects of the present disclosure. 
         FIG. 3A  is a left side view of the development cartridge in the illustrative embodiment according to one or more aspects of the present disclosure. 
         FIG. 3B  is a left side view of the development cartridge from which a gear cover is removed, in the illustrative embodiment according to one or more aspects of the present disclosure. 
         FIG. 4  is a perspective view showing the development cartridge when viewed from a lower left side, in the illustrative embodiment according to one or more aspects of the present disclosure. 
         FIG. 5  is an exploded perspective view showing the development cartridge and the gear cover removed from the development cartridge when viewed from a lower left side, in the illustrative embodiment according to one or more aspects of the present disclosure. 
         FIG. 6  is a bottom view of the development cartridge in the illustrative embodiment according to one or more aspects of the present disclosure. 
         FIG. 7  is a perspective view showing a drum cartridge and the development cartridge when viewed from an upper right side to illustrate how the development cartridge is attached to the drum cartridge, in the illustrative embodiment according to one or more aspects of the present disclosure. 
         FIG. 8  is a perspective view showing a process cartridge when viewed from an upper right side, in the illustrative embodiment according to one or more aspects of the present disclosure. 
         FIG. 9  is a cross-sectional side view of the process cartridge along line A-A shown in  FIG. 8 , in the illustrative embodiment according to one or more aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     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. 
     Hereinafter, an illustrative embodiment according to aspects of the present disclosure will be described with reference to the accompanying drawings. 
     1. General Configuration of Development Cartridge 
     As shown in  FIG. 1 , a development cartridge  1  includes a development frame  2 , an agitator  3 , a development roller  4 , a supply roller  5 , and a layer thickness regulating blade  6 . 
     In the following description, directions of the development cartridge  1  will be defined as shown in the accompany drawings. Specifically, a side at which the development roller  4  is disposed will be defined as a rear side of the development cartridge  1 , and an opposite side will be defined as a front side of the development cartridge  1 . In other words, a left side on a paper surface of  FIG. 1  is the rear side of the development cartridge  1 , and a right side on the paper surface of  FIG. 1  is the front side of the development cartridge  1 . Further, an upside on the paper surface of  FIG. 1  is an upper side of the development cartridge  1 , and a downside on the paper surface of  FIG. 1  is a lower side of the development cartridge  1 . Further, a left side and a right side of the development cartridge  1  will be defined on the basis of a front view of the development cartridge  1  (i.e., when the development cartridge  1  is viewed from the front). Specifically, a near side with respect to the paper surface of  FIG. 1  is a left side of the development cartridge  1 , and a far side with respect to the paper surface of  FIG. 1  is a right side of the development cartridge  1 . 
     The development frame  2  is formed substantially in a box shape extending in the left-to-right direction. A rear end portion of the development frame  2  is open in the front-to-rear direction. Further, the development frame  2  includes therein a toner storing chamber  7  and a development chamber  8 . The toner storing chamber  7  is configured to store toner. 
     The agitator  3  is disposed at a substantially middle portion of the toner storing chamber  7  in the front-to-rear direction. The agitator  3  includes an agitator shaft  9  and an agitator blade  10 . 
     The agitator shaft  9  is formed substantially in a cylindrical shape extending in the left-to-right direction. Two end portions of the agitator shaft  9  in the left-to-right direction protrude outward from a below-mentioned left wall  32  and a below-mentioned right wall  33  in the left-to-right direction, respectively. 
     The agitator blade  10  extends outward from the agitator shaft  9  in a radial direction of the agitator shaft  9 . 
     The agitator  3  is configured to rotate around an agitator rotational axis A 1  as a center axis of the agitator shaft  9 . 
     The development roller  4  is disposed at a rear end portion of the development chamber  8 . The development roller  4  includes a development roller shaft  11  and a development roller main body  12 . 
     The development roller shaft  11  is made of metal. The development roller shaft  11  is formed substantially in a cylindrical shaft extending in the left-to-right direction. Two end portions of the development roller shaft  11  in the left-to-right direction protrude outward from the below-mentioned left wall  32  and the below-mentioned right wall  33  in the left-to-right direction, respectively. 
     The development roller main body  12  is made of electrically-conductive rubber. The development roller main body  12  is formed substantially in a cylindrical shape extending in the left-to-right direction. The development roller main body  12  does not cover the two end portions of the development roller shaft  11  in the left-to-right direction, and covers a substantially middle portion of the development roller shaft  11  in the left-to-right direction. Further, an upper portion and a rear portion of the development roller main body  12  are exposed out of the development frame  2 . 
     The development roller  4  is configured to rotate around a development roller rotational axis A 2  as a center axis of the development roller shaft  11 . 
     The supply roller  5  is disposed on a lower front side relative to the development roller  4 , in the development chamber  8 . More specifically, the supply roller  5  is disposed in front of and below the development roller rotational axis A 2 . The supply roller  5  includes a supply roller shaft  13  and a supply roller main body  14 . 
     The supply roller shaft  13  is made of metal. The supply roller shaft  13  is formed substantially in a cylindrical shape extending in the left-to-right direction. Two end portions of the supply roller shaft  13  in the left-to-right direction protrude from the below-mentioned left wall  32  and the below-mentioned right wall  33  in the left-to-right direction, respectively. 
     The supply roller main body  14  is made of electrically-conductive sponge. The supply roller main body  14  is formed substantially in a cylindrical shape extending in the left-to-right direction. The supply roller main body  14  does not cover the two end portions of the supply roller shaft  13  in the left-to-right direction, and covers a substantially middle portion of the supply roller shaft  13  in the left-to-right direction. Further, an upper rear end portion of the supply roller main body  14  is in pressure contact with a lower front end portion of the development roller main body  12  of the development roller  4 . A diameter of the supply roller main body  14  is smaller than a diameter of the development roller main body  12 . 
     The supply roller  5  is configured to rotate around a supply roller rotational axis A 3  as a center axis of the supply roller shaft  13 . 
     The layer thickness regulating blade  6  is disposed on an upper front side relative to the development roller  4 , in the development chamber  8 . More specifically, the layer thickness regulating blade  6  is disposed in front of and above the development roller rotational axis A 2 . The layer thickness regulating blade  6  includes a first clamping member  60 , a second clamping member  61 , and a blade member  62 . 
     The first clamping member  60  is formed substantially in an L-shaped bent plate in a cross-sectional side view, and extends in the left-to-right direction. Specifically, the first clamping member  60  includes a horizontal portion  60 A extending in the front-to-rear direction and a vertical portion  60 B bending downward from a rear end portion of the horizontal portion  60 A. Namely, the vertical portion  60 B extends in the vertical direction in a side view. 
     The second clamping member  61  is disposed on the first clamping member  60 . The second clamping member  61  is formed substantially in an L-shaped bent plate in a cross-sectional side view, and extends in the left-to-right direction. Specifically, the second clamping member  61  includes a horizontally-extending portion extending in the front-to-rear direction on the first clamping member  60 , and a downward-extending rear end portion that bends downward from a rear end portion of the horizontally-extending portion so as to face a rear end portion of the first clamping member  60  from behind. The rear end portion of the second clamping member  61  is slanted to the front (i.e., slanted to the vertical portion  60 B of the first clamping member  60 ) toward a lower end thereof, so as to clamp the blade member  62 . 
     The blade member  62  is formed substantially in a rectangular plate shape having a longitudinal direction along the left-to-right direction, in a front view. The blade member  62  extends in the vertical direction in a side view. In other words, an extending direction of the blade member  62  is the vertical direction. An upper end portion of the blade member  62  is supported so as to be clamped between the vertical portion  60 B of the first clamping member  60  and the rear end portion of the second clamping member  61 . A lower end portion of the blade member  62  is in contact with an upper front end portion of the development roller  4 . 
     The toner storing chamber  7  and the development chamber  8  are defined as adjacent different chambers by a boundary line B. The boundary line B is a tangential line that touches a front end of the supply roller main body  14  of the supply roller  5 . Further, the boundary line B extends along the vertical direction in which the layer thickness regulating blade  6  extends. 
     2. Overall Configuration of Printer 
     The development cartridge  1  configured as above is attached inside the printer  15 , as shown in  FIG. 2 . 
     The printer  15  is an electrophotographic monochrome printer. The printer  15  includes a main body casing  16 , a process cartridge  17 , a scanning unit  18 , and a fuser unit  19 . 
     The main body casing  16  is formed substantially in a box shape. The main body casing  16  has an opening  20 . Further, the main body casing  16  includes a front cover  21 , a feed tray  22 , and a catch tray  23 . 
     The opening  20  penetrates a front wall of the main body casing  16 . The opening  20  is configured to allow the process cartridge  17  to pass through the opening  20 . 
     The front cover  21  is configured to open and close the opening  20 . 
     The feed tray  22  is disposed at a bottom portion of the main body casing  16 . The feed tray  22  is configured to support sheets P placed thereon. 
     The catch tray  23  is disposed on an upper surface of the main body casing  16 . 
     The process cartridge  17  is configured to be inserted into and removed from the main body casing  16  through the opening  20 . The process cartridge  17  includes a drum cartridge  24  and the development cartridge  1 . 
     The drum cartridge  24  includes a photoconductive drum  25 , a scorotron charger  26 , and a transfer roller  27 . 
     The photoconductive drum  25  is disposed at a rear end portion of the drum cartridge  24 . The photoconductive drum  25  is formed substantially in a cylindrical shape extending in the left-to-right direction. The photoconductive drum  25  is rotatably supported by a frame of the drum cartridge  24 . 
     The scorotron charger  26  is disposed behind and apart from the photoconductive drum  25 . 
     The transfer roller  27  is disposed under the photoconductive drum  25 . The transfer roller  27  is configured to contact a lower end portion of the photoconductive drum  25 . 
     The development cartridge  1  is detachably attached to the drum cartridge  24 . Further, when the development cartridge  1  is attached to the drum cartridge  24 , a rear end portion of the development roller  4  is brought into contact with a front end portion of the photoconductive drum  25 . 
     The scanning unit  18  is disposed above the process cartridge  17 . As indicated by a dashed line in  FIG. 2 , the scanning unit  18  is configured to emit a laser beam based on image data to the photoconductive drum  25 . 
     The fuser unit  19  is disposed behind the process cartridge  17 . The fuser unit  19  includes a heating roller  28  and a pressing roller  29 . The pressing roller  29  is disposed on a lower rear side relative to the heating roller  28 . The pressing roller  29  is in pressure contact with a lower rear end portion of the heating roller  28 . 
     When the printer starts an image forming operation under control by a controller (not shown), the scorotron charger  26  evenly charges a surface of the photoconductive drum  25 . Thereafter, the scanning unit  18  exposes the surface of the photoconductive drum  25 . Thereby, an electrostatic latent image based on the image data is formed on the surface of the photoconductive drum  25 . 
     Further, the supply roller  5  supplies the toner stored in the development frame  2  to the development roller  4 . Thereby, the toner is positively charged by friction between the development roller  4  and the supply roller  5 . Then, the toner is carried on the development roller  4 . The layer thickness regulating blade  6  regulates a thickness of the toner carried on the development roller  4  to be constant. 
     The development roller  4  supplies the toner having a constant thickness to the electrostatic latent image formed on the surface of the photoconductive drum  25 . Thereby, a toner image is carried on the surface of the photoconductive drum  25 . 
     By rotation of various rollers, the sheets P are fed from the feed tray  22  to a position between the photoconductive drum  25  and the transfer roller  27 , on a sheet-by-sheet basis at respective predetermined moments. The toner image on the photoconductive drum  25  is transferred onto a sheet P, when the sheet P passes between the photoconductive drum  25  and the transfer roller  27 . 
     Afterward, when passing between the heating roller  28  and the pressing roller  29 , the sheet P is heated and pressed therebetween. Thereby, the toner image on the sheet P is thermally fixed onto the sheet P. Thereafter, the sheet P is discharged onto the catch tray  23 . 
     3. Details about Development Cartridge 
     As shown in  FIGS. 3A and 4 , the development cartridge  1  includes the aforementioned development frame  2  and a driving unit  31 . 
     (1) Development Frame 
     The development frame  2  includes a left wall  32 , a right wall  33 , a front wall  34 , a lower wall  35 , and an upper wall  36 . 
     The left wall  32  is disposed at a left end portion of the development frame  2 . The left wall  32  is formed substantially in a rectangular plate shape extending in the front-to-rear direction, in a side view. As shown in  FIGS. 3B and 5 , the left wall  32  includes a first screw portion  38 , a second screw portion  39 , a third screw portion  40 , a hook portion  41 , a caulking portion  37 , and a frame projection  42 . 
     The first screw portion  38  is disposed at an upper rear portion of the left wall  32 . The first screw portion  38  is formed substantially in a cylindrical shape protruding leftward from a left surface of the left wall  32 . The first screw portion  38  includes a first screw hole  38 A and a first engagement portion  38 B. 
     The first screw hole  38 A is formed substantially in a circular shape in a side view. The first screw hole  38 A is recessed rightward from a left end face of the first screw portion  38 . 
     The first engagement portion  38 B is disposed at a left end portion of the first screw portion  38 . The first engagement portion  38 B is formed substantially in a cylindrical shape extending leftward from a peripheral portion of the first screw hole  38 A. 
     The second screw portion  39  is disposed at a lower end portion of a substantially middle portion of the left wall  32  in the front-to-rear direction. The second screw portion  39  is formed substantially in a cylindrical shape protruding leftward from the left surface of the left wall  32 . The second screw portion  39  includes a second screw hole  39 A and a second engagement portion  39 B. 
     The second screw hole  39 A is formed substantially in a circular shape in a side view. The second screw hole  39 A is recessed rightward from a left end face of the second screw portion  39 . 
     The second engagement portion  39 B is disposed at a left end portion of the second screw portion  39 . The second engagement portion  39 B is formed substantially in a cylindrical shape extending leftward from a peripheral portion of the second screw hole  39 A. 
     As shown in  FIG. 3B , the third screw portion  40  is disposed at an upper front end portion of the left wall  32 . The third screw portion  40  is formed substantially in a cylindrical shape protruding leftward from the left surface of the left wall  32 . The third screw portion  40  includes a third screw hole  40 A and a third engagement portion  40 B. 
     The third screw hole  40 A is formed substantially in a circular shape in a side view. The third screw hole  40 A is recessed rightward from a left end face of the third screw portion  40 . 
     The third engagement portion  40 B is disposed at a left end portion of the third screw portion  40 . The second engagement portion  40 B is formed substantially in a cylindrical shape extending leftward from a peripheral portion of the third screw hole  40 A. 
     As shown in  FIGS. 3B and 5 , the caulking portion  37  is disposed at a lower rear end portion of the left wall  32 . The caulking portion  37  is formed substantially in a cylindrical shape protruding leftward from the left surface of the left wall  32 . 
     The hook portion  41  is disposed at a substantially middle portion of the left wall  32  in the front-to-rear direction, on a lower front side relative to the second screw portion  39 . The hook portion  41  is formed substantially in a U-shaped plate in a bottom view. 
     The frame projection  42  is disposed between the caulking portion  37  and the second screw portion  39 , on the left wall  32 . The frame projection  42  is formed substantially in a rectangular plate shape protruding downward from a lower end portion of the left wall  32 , in a side view. It is noted that the frame projection  42 , together with a below-mentioned bearing projection  49 , forms an engagement projection  64 . 
     As shown in  FIGS. 1 and 7 , the right wall  33  is disposed at a right end portion of the development frame  2 . In the same manner as the left wall  32 , the right wall  33  is formed substantially in a rectangular plate shape extending in the front-to-rear direction, in a side view. 
     The front wall  34  is configured to bridge a distance between a front end portion of the left wall  32  and a front end portion of the right wall  33 . The front wall  34  is formed substantially in a plate shape extending in the left-to-right direction. 
     As shown in  FIGS. 1 and 4 , the lower wall  35  is configured to bridge a distance between a lower end portion of the left wall  32  and a lower end portion of the right wall  33 . The lower wall  35  is formed substantially in a plate shape extending in a curved manner rearward from a lower end portion of the front wall  34 . The lower wall  35  includes a curved wall  43  and a bent wall  44 . 
     The curved wall  43  extends rearward continuously from a lower end portion of the front wall  34 , over a range from a substantially central portion to a front portion of the lower wall  35 . The curved wall  43  is formed substantially in an arc shape along a rotational trajectory of the agitator  3 , in a cross-sectional side view. 
     The bent wall  44  is formed substantially in a W-shape that extends rearward continuously from a rear end portion of the curved wall  43  at a rear portion of the lower wall  35 , in a cross-sectional side view. A front portion of the bent wall  44  is formed substantially in an arc shape along a rotational trajectory of the supply roller  5 . A rear portion of the bent wall  44  extends rearward. 
     As shown in  FIGS. 1 and 7 , the upper wall  36  is disposed above an upper end portion of the left wall  32 , an upper end portion of the right wall  33 , and an upper end portion of the front wall  34 . The upper wall is formed substantially in a plate shape extending in the left-to-right direction. The upper wall  36  includes a blade supporting wall  45 . 
     The blade supporting wall  45  is configured to support the layer thickness regulating blade  6 . The blade supporting wall  45  is disposed at a rear end portion of the upper wall  36 . The blade supporting wall  45  is formed substantially in a rectangular plate shape extending in the left-to-right direction, in a plane view. A rear surface of the blade supporting wall  45  extends in the vertical direction in a side view. Namely, the rear surface of the blade supporting wall  45  extends in the same direction as the extending direction of the layer thickness regulating blade  6 . 
     A peripheral portion of the upper wall  36  other than the blade supporting wall  45  is fixed, by a method such as welding, to the upper end portion of the left wall  32 , the upper end portion of the right wall  33 , and the upper end portion of the front wall  34 . 
     (2) Detailed Dispositions of Development Roller, Supply Roller, Layer Thickness Regulating Blade, and Agitator 
     Subsequently, referring to  FIG. 1 , explanations will be provided about detailed dispositions of the agitator  3 , the development roller  4 , the supply roller  5 , and the layer thickness regulating blade  6 . 
     As described above, the agitator  3  is disposed at the substantially middle portion of the toner storing chamber  7  in the front-to-rear direction. The development roller  4  is disposed at the rear end portion of the development chamber  8 . The supply roller  5  is disposed on the lower front side relative to the development roller  4 , in the development chamber  8 . The layer thickness regulating blade  6  is disposed on the upper front side relative to the development roller  4 , in the development chamber  8 . 
     A first partition line D 1  is defined as a virtual line extending along the vertical direction and passing through the supply roller rotational axis A 3 . Further, a second partition line D 2  is defined as a virtual line passing through the development roller rotational axis A 2  and the agitator rotational axis A 1 . In other words, the second partition line D 2  is along an extending direction of the vertical portion  60 B of the first clamping member  60  that contacts the blade member  62 . 
     Moreover, of areas sectioned by the first partition line D 1  and the second partition line D 2 , an upper front area is defined as a first quadrant T 1 , a lower front area is defined as a second quadrant T 2 , a lower rear area is defined as a third quadrant T 3 , and an upper rear area is defined as a fourth quadrant T 4 . 
     Further, in a side view, a nipping point N between the development roller main body  12  and the supply roller main body  14  is defined as a point where a straight line (not shown) connecting the development roller rotational axis A 2  with the supply roller rotational axis A 3  intersects a circumferential surface of the development roller main body  12  of the development roller  4 . Additionally, a first virtual line V 1  is defined as a line passing through the development roller rotational axis A 2  and a contact point C between the development roller main body  12  of the development roller  4  and the layer thickness regulating blade  6 . A second virtual line V 2  is defined as a tangential line that touches the development roller main body  12  of the development roller  4  and passes through the nipping point N. 
     At this time, the agitator  3 , the development roller  4 , the supply roller  5 , and the layer thickness regulating blade  6  are supported by the development frame  2 , in respective positions such that the first virtual line V 1  and the second virtual line V 2  intersect each other in the first quadrant T 1 . 
     Further, the layer thickness regulating blade  6  is disposed between the development roller  4  and the blade supporting wall  45  of the development frame  2 . 
     (3) Driving Unit 
     As shown in  FIGS. 3B and 5 , the driving unit  31  includes a bearing member  46 , a gear train  47 , and a gear cover  48 . 
     (3-1) Bearing Member 
     The bearing member  46  is formed substantially in a rectangular plate shape in a side view. The bearing member  46  is attached to the left surface of the left wall  32 . The bearing member  46  is configured to rotatably support a left end portion of the supply roller shaft  13  and rotatably support a left end portion of the development roller shaft  11 . Namely, the respective left end portions of the supply roller shaft  13  and the development roller shaft  11  are supported to be rotatable relative to the left wall  32  via the bearing member  46 . Further, the respective left end portions of the supply roller shaft  13  and the development roller shaft  11  protrude leftward from the bearing member  46 . In addition, the bearing member  46  includes a bearing projection  49 . 
     The bearing projection  49  is formed substantially in a rectangular plate shape protruding downward from a lower end portion of the bearing member  46 , in a side view. When projected in the left-to-right direction, an external form of the bearing projection  49  is coincident with an external form of the frame projection  42  of the left wall  32 . A right surface of the bearing projection  49  is in contact with a left surface of the frame projection  42 . Thereby, the bearing projection  49  and the frame projection  42  form the engagement projection  64  that protrudes downward from the development cartridge  1 . 
     (3-2) Gear Train 
     The gear train  47  is disposed at a left portion of the left wall  32 . The gear train  47  includes a development coupling  50 , a development gear  51 , a supply gear  52 , an idle gear  53 , an agitator gear  54 , and a detection gear  55 . 
     (3-2-1) Development Coupling 
     The development coupling  50  is disposed at a rear portion of the left surface of the left wall  32 . The development coupling  50  is configured to transmit a driving force from a driving source (not shown) to the agitator  3 , the development roller  4 , and the supply roller  5 . The development coupling  50  is supported to be rotatable around a shaft (not shown) extending in the left-to-right direction. The shaft is fixed to the left wall  32  to be un-rotatable relative to the left wall  32 . A rotational axis of the development coupling  50  is defined as a coupling rotational axis A 4 . The development coupling  50  is formed substantially in a cylindrical shape extending in the left-to-right direction. The development coupling  50  is provided integrally with a coupling gear  56  and a coupling portion  57 . 
     The coupling gear  56  is a right part of the development coupling  50 . The coupling gear  56  includes gear teeth provided all over a circumferential surface thereof. 
     The coupling portion  57  is a left part of the development coupling  50 . The coupling portion  57  is formed substantially in a cylindrical shape that has a rotational axis positionally coincident with a rotational axis of the coupling gear  56 . Further, an outer diameter of the coupling portion  57  is smaller than an outer diameter of the coupling gear  56 . The coupling portion  57  includes a recessed portion  58  and two projections  59 . 
     The recessed portion  58  is recessed rightward from a left end face of the coupling portion  57 , substantially in a circular shape in a side view. 
     Each of the two projections  59  protrudes inward from an inner circumferential surface of the recessed portion  58  in a radial direction of the recessed portion  58 . The two projections  59  are disposed to face each other in the radial direction of the recessed portion  58 . Each of the two projections  59  is formed substantially in a rectangular column shape extending in the left-to-right direction. 
     As shown in  FIGS. 3A and 3B , when a third virtual line V 3  is defined as a straight line that extends in the vertical direction and passes through the coupling rotational axis A 4 , the supply roller shaft  13  is disposed behind the third virtual line V 3 . 
     (3-2-2) Development Gear 
     As shown in  FIGS. 3B and 5 , the development gear  51  is configured to transmit a driving force from the driving source (not shown) to the development roller  4  via the development coupling  50 . The development gear  51  is disposed behind the development coupling  50 . The development gear  51  is formed substantially in a cylindrical shape extending in the left-to-right direction. The development gear  51  includes gear teeth all over a circumferential surface thereof. The development gear  51  is attached to a left end portion of the development roller shaft  11  to be un-rotatable relative to the development roller shaft  11 . Further, a front end portion of the development gear  51  engages with a right part of a rear end portion of the coupling gear  56  of the development coupling  50 . 
     (3-2-3) Supply Gear 
     The supply gear  52  is configured to transmit a driving force from the driving source (not shown) to the supply roller  5  via the development coupling  50 . The supply gear  52  is disposed adjacent to a left side of the bearing projection  49 , on a lower rear side relative to the development coupling  50 . The supply gear  52  is formed substantially in a cylindrical shape extending in the left-to-right direction. The supply gear  52  includes gear teeth over an entire circumferential surface thereof. The supply gear  52  is attached to a left end portion of the supply roller shaft  13  to be un-rotatable relative to the supply roller shaft  13 . Further, an upper front end portion of the supply gear  52  engages with a substantially middle portion, in the left-to-right direction, of a lower rear end portion of the coupling gear  56 . Namely, as shown in  FIG. 6 , the supply gear  52  engages with a portion of the coupling gear  56  that is positionally different in the left-to-right direction from a portion of the coupling gear  56  that engages with the development gear  51 . In other words, an engagement portion between the coupling gear  56  and the development gear  51  is in a different position in the left-to-right direction from an engagement portion between the coupling gear  56  and the supply gear  52 . 
     (3-2-4) Idle Gear 
     As shown in  FIGS. 3B and 5 , the idle gear  53  is disposed in front of the development coupling  50 . The idle gear  53  is supported to be rotatable around a shaft (not shown) extending in the left-to-right direction. The shaft is fixed to the left wall  32  to be un-rotatable relative to the left wall  32 . The idle gear  53  is provided integrally with an idle large-diameter gear  53 A, an idle medium-diameter portion  53 B, and an idle small-diameter gear  53 C. 
     The idle large-diameter gear  53 A is a left part of the idle gear  53 . The idle large-diameter gear  53 A is formed substantially in a circular ring shape having a thickness in the left-to-right direction. The idle large-diameter gear  53 A includes gear teeth over an entire circumferential surface thereof. A rear end portion of the idle large-diameter gear  53 A engages with a front end portion of the coupling gear  56  of the development coupling  50 . 
     The idle medium-diameter portion  53 B is a substantially middle part of the idle gear  53  in the left-to-right direction. The idle medium-diameter portion  53 B protrudes rightward from a right surface of the idle large-diameter gear  53 A. The idle medium-diameter portion  53 B is formed substantially in a cylindrical shape having a closed right end. An outer diameter of the idle medium-diameter portion  53 B is smaller than an outer diameter of the idle large-diameter gear  53 A. An inner diameter of the idle medium-diameter portion  53 B is as large as an inner diameter of the idle large-diameter gear  53 A. 
     The idle small-diameter gear  53 C is a right part of the idle gear  53 . The idle small-diameter gear  53 C is formed substantially in a cylindrical shape extending rightward from a right surface of the idle medium-diameter portion  53 B. An outer diameter of the idle small-diameter gear  53 C is smaller than the inner diameter of the idle medium-diameter portion. An inner diameter of the idle small-diameter gear  53 C is slightly larger than an outer diameter of the shaft (not shown) of the idle gear  53 . The idle small-diameter gear  53 C includes gear teeth over an entire circumferential surface thereof. 
     In the idle gear  53 , respective rotational axes of the idle large-diameter gear  53 A, the idle medium-diameter portion  53 B, and the idle small-diameter gear  53 C are positionally coincident with each other. 
     (3-2-5) Agitator Gear 
     The agitator gear  54  is disposed on a lower front side relative to the idle gear  53 . The agitator gear  54  is fixed to a left end portion of the agitator shaft  9  to be un-rotatable relative to the agitator shaft  9 . The agitator gear  54  is provided integrally with an agitator large-diameter gear  54 A and an agitator small-diameter gear  54 B. 
     The agitator large-diameter gear  54 A is a right part of the agitator gear  54 . The agitator large-diameter gear  54 A is formed substantially in a circular ring shape having a thickness in the left-to-right direction. The agitator large-diameter gear  54 A includes gear teeth over an entire circumferential surface thereof. An upper rear end portion of the agitator large-diameter gear  54 A engages with a lower front end portion of the idle small-diameter gear  53 C. 
     The agitator small-diameter gear  54 B is a left part of the agitator gear  54 . The agitator small-diameter gear  54 B is formed substantially in a cylindrical shape that has a rotational axis positionally coincident with a rotational axis of the agitator large-diameter gear  54 A. Further, an outer diameter of the agitator small-diameter gear  54 B is smaller than an outer diameter of the agitator large-diameter gear  54 A. An inner diameter of the agitator small-diameter gear  54 B is as large as an inner diameter of the agitator large-diameter gear  54 A. The agitator small-diameter gear  54 B includes gear teeth over an entire circumferential surface thereof. 
     (3-2-6) Detection Gear 
     The detection gear  55  is disposed in front of the agitator gear  54 . The detection gear  55  is supported to be rotatable around a shaft (not shown). The shaft extends in the left-to-right direction from a cap for closing a toner filling opening (not shown) of the left wall  32 . The detection gear  55  is formed substantially in a cylindrical shape that extends in the left-to-right direction and has a closed left end. The detection gear  55  includes gear teeth over half a circumferential surface thereof. Namely, the detection gear  55  is a tooth-missing gear. Further, a rear end portion of the detection gear  55  is configured to engage with a front end portion of the agitator small-diameter gear  54 B of the agitator gear  54 . The detection gear  55  includes a contact portion  63 . 
     The contact portion  63  protrudes leftward from a left end face of the detection gear  55 . The contact portion  63  extends over an angle range of 60 degrees in a circumferential direction of the detection gear  55 . The contact portion  63  is formed substantially in a curved plate shape. 
     (3-3) Gear Cover 
     The gear cover  48  is attached to the left wall  32  so as to entirely cover the gear train  47 . As shown in  FIGS. 3A and 5 , the gear cover  48  is provided integrally with a rear cover  66  and a front cover  67 . 
     (3-3-1) Rear Cover 
     The rear cover  66  is a rear part of the gear cover  48 . The rear cover  66  is provided integrally with a first portion  68  and a second portion  69 . 
     The first portion  68  is an upper part of the rear cover  66 . The first portion  68  is provided integrally with a first base plate  70  and a first peripheral wall  71  that protrudes rightward from a peripheral end portion of the first base plate  70 . Namely, the first portion  68  is formed substantially in a box shape having an open right end and a closed left end. Further, the first portion  68  includes a coupling cover portion  72 , a development roller cover portion  73 , and a first fixed portion  74 . 
     The coupling cover portion  72  is disposed at a substantially middle part of the first base plate  70  in the vertical direction and the front-to-rear direction. The coupling cover portion  72  includes a drive input opening  75  and a cylinder portion  76 . 
     The drive input opening  75  penetrates the first base plate  70 , and is formed substantially in a circular shape in a side view. 
     The cylinder portion  76  is formed substantially in a cylindrical shape that extends leftward from a left surface of the first base plate  70  at a peripheral portion of the drive input opening  75 . An inner diameter of the cylinder portion  76  is as large as a diameter of the drive input opening  75 . Further, a dimension of the cylinder portion  76  in the left-to-right direction is as large as a dimension, in the left-to-right direction, of the coupling portion  57  of the development coupling  50 . 
     The development roller cover portion  73  is disposed at a rear end portion of a substantially middle part of the first base plate  70  in the vertical direction, behind the coupling cover portion  72 . The development roller cover portion  73  includes a color portion  77 . 
     The color portion  77  is formed substantially in a cylindrical shape that extends in the left-to-right direction and has a closed left end. An inner diameter of the color portion  77  is slightly larger than an outer diameter of the development roller shaft  11 . 
     The first fixed portion  74  is disposed at an upper rear end portion of the first base plate  70 , above the development roller cover portion  73 . The first fixed portion  74  is slightly recessed rightward from the development roller cover portion  73 . The first fixed portion  74  has a first insertion hole  78 . 
     The first insertion hole  78  penetrates the first base plate  70 , and is formed substantially in a circular shape in a side view. An inner diameter of the first insertion hole  78  is slightly larger than the first engagement portion  38 B of the first screw portion  38 . 
     The second portion  69  is a lower part of the rear cover  66 . The second portion  69  is disposed below the first portion  68  so as to be continuous from a right end portion of the first peripheral wall  71 . Namely, the second portion  69  is disposed on a right side relative to the first base plate  70  of the first portion  68 . The second portion  69  is provided integrally with a second base plate  79  and a second peripheral wall  80 . The second peripheral wall  80  protrudes rightward from a peripheral end portion of the second base plate  79 . Namely, the second portion  69  is formed substantially in a box shape having an open right end and a closed left end. The second portion  69  includes a supply roller cover portion  81 , a locking portion  83 , and a cutout portion  84 . 
     The supply roller cover portion  81  is disposed at a substantially middle portion of the second base plate  79  in the front-to-rear direction, below the coupling cover portion  72 . The supply roller cover portion  81  includes a semicircular portion  82 . 
     The semicircular portion  82  is formed substantially in a semicircular shape protruding downward from the supply roller cover portion  81 , in a side view. A radius of an arc of the semicircular portion  82  is slightly larger than a radius of the supply gear  52 . 
     In a state where the gear cover  48  is attached to the left wall  32 , when the supply roller cover portion  81  is projected in the left-to-right direction, the semicircular portion  82  protrudes downward from the supply gear  52 . 
     Thereby, the supply roller cover portion  81  is configured to entirely cover a left surface of the supply gear  52  from the left. It is noted that the supply roller cover portion  81  and the development roller cover portion  73  are configured to cover the supply gear  52  and the development gear  51  from the left. 
     The lock portion  83  is disposed at a rear end portion of the second base plate  79 , below the development roller cover portion  73 , behind the supply roller cover portion  81 . The lock portion  83  is formed substantially in a bottomed-frame shape having a closed right end. The lock portion  83  has a lock insertion hole (not shown) that penetrates a right end portion of the lock portion  83 , and is formed substantially in a circular shape in a side view. 
     Further, the lock portion  83  includes a protection wall  85 . 
     The protection wall  85  is formed substantially in an L-shaped plate protruding leftward from a lower right end portion and a front right end portion of the lock portion  83 , in a side view. 
     As shown in  FIGS. 5 and 6 , the cutout portion  84  is formed by cutting out a specific portion that is a lower portion of the supply roller cover portion  81  and a substantially middle portion, in the front-to-rear direction, of a lower portion of the second peripheral wall  80 . In other words, the cutout portion  84  is defined as a space that is below the supply roller cover portion  81  and in front of the lock portion  83 . 
     (3-3-2) Front Cover 
     As shown in  FIGS. 3A and 5 , the front cover  67  extends forward continuously from a front end portion of the rear cover  66 , and forms a front part of the gear cover  48 . The front cover  67  is provided integrally with a third portion  86 , a fourth portion  87 , and a fifth portion  88 . 
     The third portion  86  is an upper rear part of the front cover  67 . The third portion  86  is provided integrally with a third base plate  89  and a third peripheral wall  90  that protrudes rightward from a peripheral end portion of the third base plate  89 . Namely, the third portion  86  is formed substantially in a box shape having an open right end and a closed left end. Although the following state is not shown in any drawings, in the state where the gear cover  48  is attached to the left wall  32 , the third portion  86  is inserted into the idle gear  53  and supports an idle gear supporter configured to pivotally support the idle gear  53 . 
     The fourth portion  87  is a lower rear part of the front cover  67 . The fourth portion  87  is disposed below the third portion  86  so as to be continuous from a right end portion of the third peripheral wall  90 . Namely, the fourth portion  87  is disposed on a right side relative to the third base plate  89  of the third portion  86 . The fourth portion  87  includes a fourth base plate  91  and a fourth peripheral wall  92  that protrudes rightward from a lower end portion of the fourth base plate  91 . Namely, the fourth portion  87  is formed substantially in a L-shaped plate in a cross-sectional front view. The fourth portion  87  further includes a second fixed portion  93  and a locking claw  94 . 
     The second fixed portion  93  is disposed at a rear end portion of the fourth base plate  91 . The second fixed portion  93  has a second insertion hole (not shown) that penetrates the second fixed portion  93 , and is formed substantially in a circular shape in a side view. An inner diameter of the second insertion hole (not shown) is slightly larger than an outer diameter of the second engagement portion  39 B of the second screw portion  39 . 
     The locking claw  94  is formed substantially in a hook shape that protrudes rightward from a right end portion of a substantially middle portion of the fourth peripheral wall  92  in the front-to-rear direction and is bent upward from a right end portion of the protrusion. 
     The fifth portion  88  is a front part of the front cover  67 . The fifth portion  88  protrudes leftward continuously from front end portions of the third portion  86  and the fourth portion  87 . The fifth portion  88  includes a detection gear cover portion  95  and a third fixed portion  96 . 
     The detection gear cover portion  95  is formed substantially in a cylindrical shape that protrudes leftward continuously from the front end portions of the third portion  86  and the fourth portion  87  and has a closed left end. Namely, a left end portion of the detection gear cover portion  95  is positioned on a left side relative to the third portion  86  and the fourth portion  87 . The detection gear cover portion  95  includes a contact-portion opening  97  and a detection gear regulating portion  98 . 
     The contact-portion opening  97  penetrates a left end wall of the detection gear cover portion  95 , and is formed substantially in a C-shape having an open lower end in a side view. Thereby, the contact-portion opening  97  is configured such that the contact portion  63  of the detection gear  55  protrudes therethrough. 
     The detection gear regulating portion  98  is formed substantially in a cylindrical shape protruding rightward from a central part of a right surface of a right wall of the detection gear cover portion  95 . An outer diameter of the detection gear regulating portion  98  is slightly smaller than an inner diameter of the detection gear  55 . 
     As shown in  FIG. 3A , the third fixed portion  96  protrudes forward from an upper right end portion of a front part of the detection gear cover portion  95 . The third fixed portion  96  is formed substantially in a box shape having an open right end and a left closed end. Further, a left end wall of the third fixed portion  96  is positioned on a right side relative to the third base plate  89  and substantially in plane with (a left end face of) the fourth base plate  91 . The third fixed portion  96  has a third insertion hole (not shown) that penetrates the first fixed portion  96 , and is formed substantially in a circular shape in a side view. An inner diameter of the third insertion hole (not shown) is slightly larger than an outer diameter of the third engagement portion  40 B of the third screw portion  40 . 
     4. Attaching Gear Cover to Development Frame and Detaching Gear Cover from Development Frame 
     The gear cover  48  configured as above is attached by an operator to the development frame  2 . 
     In order to attach the gear cover  48  to the development frame  2 , as shown in  FIGS. 4 and 5 , first, the gear cover  48  is attached to the left wall  32  having the gear train  47  attached thereto, from the left. More specifically, in the rear cover  66 , the color portion  77  accepts insertion of the development roller shaft  11  thereinto, and the cylinder portion  76  accepts insertion of the coupling portion  57  thereinto. Further, in the front cover  67 , an idle gear supporting portion (not shown) is inserted into the agitator gear  54 , and the detection gear regulating portion  98  is inserted into the detection gear  55 . Further, the contact-portion opening  97  accepts insertion of the contact portion  63  of the detection gear  55  therethrough. 
     Thereby, in the rear cover  66 , the first insertion hole  78  accepts insertion of the first engagement portion  38 B of the first screw portion  38  therethrough. The lock insertion hole (not shown) of the lock portion  83  accepts insertion of the caulking portion  37  therethrough. Further, in the front cover  67 , the second insertion hole (not shown) accepts insertion of the second engagement portion  39 B of the second screw portion  39  therethrough. The third insertion hole (not shown) accepts insertion of the third engagement portion  40 B of the third screw portion  40  therethrough. The locking claw  94  is hooked to the hook portion  41 , and locks the hook portion  41 . 
     Thus, the gear cover  48  is attached to the left wall  32  from the left. 
     Thereby, a left end face of the supply gear  52  and a right surface of the supply roller cover portion  81  are disposed to face each other across a distance. Further, the third base plate  89  covers the idle gear  53  and the agitator gear  54 . The detection gear cover portion  95  covers the detection gear  55 . The idle gear  53  and the detection gear  55  are rotatably supported by the left wall  32  in such a manner that the rotational axes of the idle gear  53  and the detection gear  55  are not positionally shifted relative to the left wall  32 . 
     Subsequently, a first screw member  101  is screwed into the first screw hole  38 A via the first insertion hole  78 . A second screw member  102  is screwed into the second screw hole  39 A via the second insertion hole (not shown) of the second fixed portion  93 . A third screw member  103  is screwed into the third screw hole  40 A via the third insertion hole (not shown) of the third fixed portion  96 . 
     Thus, the gear cover  48  is attached to the left wall  32  with the rear cover  66  covering the development coupling  50 , the development gear  51 , and the supply gear  52 , and the front cover  67  covering the agitator gear  54  and the detection gear  55 . 
     As shown in  FIGS. 4 and 6 , in a view from a lower side, a lower end portion of the supply gear  52  is exposed through the cutout portion  84  of the supply roller cover portion  81  and protrudes downward from the cutout portion  84 . 
     In the above procedure, the development cartridge  1  is completely attached inside the printer  15 . 
     Further, the gear cover  48  is detached from the left wall  32  in a reverse procedure of the aforementioned procedure. 
     Specifically, first, the first screw member  101  is removed from the first screw hole  38 A. The second screw member  102  is removed from the second screw hole  39 A. The third screw member  103  is removed from the third screw hole  40 A. 
     Then, when the locking state where the locking claw  94  is hooked to the hook portion  41  is released, and the gear cover  48  is moved leftward, the gear cover  48  is detached from the left wall  32 . 
     Thus, the gear cover  48  is completely removed from the left wall  32 . 
     5. Details about Process Cartridge 
     The process cartridge  17  is configured with the development cartridge  1  attached to the drum cartridge  24 . 
     As shown in  FIGS. 7 and 8 , the drum cartridge  24  includes a drum frame  105 , the aforementioned photoconductive drum  25 , and the aforementioned scorotron charger  26 . 
     The drum frame  105  is formed substantially in a shape of a rectangular bottomed frame having a closed lower end. The drum frame  105  includes a drum container  106  as a rear part of the drum frame  105 , and a development cartridge attachment portion  107  as a front part of the drum frame  105 . 
     The drum container  106  is configured to support the photoconductive drum  25  and the scorotron charger  26 . 
     The development cartridge attachment portion  107  is configured such that the development cartridge  1  is attached thereto and detached therefrom. The development cartridge attachment portion  107  includes a drum bottom wall  108 . 
     The drum bottom wall  108  is a lower end part of the development cartridge attachment portion  107 . The drum bottom wall  108  is formed substantially in a plate shape extending in the front-to-rear direction and the left-to-right direction. The drum bottom wall  108  has an engagement hole  109 . 
     The engagement hole  109  penetrates a left rear portion of the drum bottom wall  108 , and is formed substantially in a rectangular shape having a longitudinal direction along the front-to-rear direction in a plane view. A dimension of the engagement hole  109  in the front-to-rear direction is slightly longer than a dimension of the engagement projection  64  of the development cartridge  1  in the front-to-rear direction. A dimension of the engagement hole  109  in the left-to-right direction is slightly longer than a dimension of the engagement projection  64  in the left-to-right direction. 
     When the development cartridge  1  is attached to the development cartridge attachment portion  107  of the drum frame  105 , as shown in  FIG. 1 , a rear end portion of the development roller  4  of the development cartridge  1  is brought into contact with a front end portion of the photoconductive drum  25 . Further, as shown in  FIG. 9 , the lower wall  35  of the development frame  2  of the development cartridge  1  is positioned to face the drum bottom wall  108  of the drum frame  105 . At this time, the engagement projection  64  is inserted through the engagement hole  109  of the drum bottom wall  108  from above. Further, a left rear end portion of the drum bottom wall  108  is disposed below the supply gear  52 . Thereby, the left rear end portion of the drum bottom wall  108  covers the supply gear  52  so as to face upward and be opposed to the supply gear  52 . 
     Thus, the process cartridge  17  is configured as described above. 
     6. Operations and Advantageous Effects 
     According to the development cartridge  1 , as shown in  FIGS. 4 and 6 , both the development gear  51  and the supply gear  52  are covered with the development roller cover portion  73 , the supply roller cover portion  81 , and the second peripheral wall  80 . Further, the supply gear  52  protrudes from the cutout portion  84  of the second peripheral wall  80  so as to expose a lower end portion of the supply gear  52 . 
     Therefore, since the second peripheral wall  80  has the cutout portion  84  configured such that the supply gear  52  protrudes therefrom, it is possible to attain miniaturization of the gear cover  48  in the vertical direction. 
     Consequently, it is possible to realize miniaturization of the development cartridge  1  while protecting both the development gear  51  and the supply gear  52  with the gear cover  48 . 
     In addition, according to the development cartridge  1 , as shown in  FIG. 4 , the lower end portion of the supply gear  52  protrudes from the second peripheral wall  80 , whereas the left surface of the supply gear  52  is entirely covered with the supply roller cover portion  81 . 
     Therefore, it is possible to certainly protect all the left surface of the supply gear  52  while attaining miniaturization of the development cartridge  1 . 
     Further, according to the development cartridge  1 , as shown in  FIG. 6 , it is possible to apply grease to the supply gear  52  through the cutout portion  84  of the second peripheral wall  80 . 
     Further, the development gear  51  and the supply gear  52  are disposed in their respective different positions in the left-to-right direction. Therefore, it is possible to apply grease to the development gear  51  through the cutout portion  84  of the second peripheral wall  80 . 
     Hence, it is possible to efficiently apply grease to both the development gear  51  and the supply gear  52  through the cutout portion  84  of the second peripheral wall  80 . 
     Further, according to the development cartridge  1 , as shown in  FIG. 3B , the supply roller shaft  13  is disposed closer to the development roller  4  than the third virtual line V 3  in the front-to-rear direction (i.e., when viewed along the left-to-right direction). Therefore, the development gear  51  connected with the development roller  4  is allowed to be disposed in a position relatively close to the supply gear  52  connected with the supply roller  5 . 
     Hence, in the development cartridge  1 , it is possible to dispose the development roller  4  and the supply roller  5  in respective proper positions thereof, and to realize miniaturization of the development cartridge  1 . 
     Further, according to the development cartridge  1 , as shown in  FIGS. 3B and 4 , it is possible to protect a right surface of the supply gear  52  with the engagement projection  64 . 
     Therefore, even though the lower end portion of the supply gear  52  protrudes from the cutout portion  84  of the second peripheral wall  80 , it is possible to surely protect the supply gear  52 . 
     According to the drum cartridge  24 , as shown in  FIGS. 7 and 9 , when the development cartridge  1  is attached to the development cartridge attachment portion  107 , it is possible to protect the lower end portion of the supply gear  52  that protrudes from the cutout portion  84  and is exposed, with the drum bottom wall  108 . Further, it is possible to easily position the development cartridge  1  relative to the drum cartridge  24 , by engaging the engagement projection  64  with the engagement hole  109 . 
     As the engagement projection  64  protrudes from the development cartridge  1 , the development cartridge  1  might be enlarged in size in a direction in which the supply gear  52  protrudes (i.e., in a downward direction). Nevertheless, according to the illustrative embodiment, when the development cartridge  1  is attached to the drum cartridge  24 , the engagement projection  64  is inserted through the engagement hole  109 . Thus, it is possible to prevent enlargement of the process cartridge  17 . 
     Hereinabove, the illustrative embodiment according to aspects of the present disclosure has been described. The present disclosure can be practiced by employing conventional materials, methodology and equipment. Accordingly, the details of such materials, equipment and methodology are not set forth herein in detail. In the previous descriptions, numerous specific details are set forth, such as specific materials, structures, chemicals, processes, etc., in order to provide a thorough understanding of the present disclosure. However, it should be recognized that the present disclosure can be practiced without reapportioning to the details specifically set forth. In other instances, well known processing structures have not been described in detail, in order not to unnecessarily obscure the present disclosure. 
     Only an exemplary illustrative embodiment of the present disclosure and but a few examples of their versatility are shown and described in the present disclosure. It is to be understood that the present disclosure is capable of use in various other combinations and environments and is capable of changes or modifications within the scope of the inventive concept as expressed herein. For instance, according to aspects of the present disclosure, the following modifications are possible. 
     7. Modifications 
     In the aforementioned illustrative embodiment, the first virtual line V 1  and the second virtual line V 2  intersect each other in the first quadrant T 1 . Nevertheless, the development roller  4 , the supply roller  5 , and the layer thickness regulating blade  6  may be disposed such that the first virtual line V 1  and the second virtual line V 2  intersect each other in the third quadrant T 3 . 
     In the aforementioned illustrative embodiment, the gear cover  48  is provided integrally with the rear cover  66  and the front cover  67 . Nevertheless, the rear cover  66  and the front cover  67  may be separatable from each other. 
     In the aforementioned illustrative embodiment, in the gear cover  48 , the second portion  69  of the rear cover  66  is provided integrally with the second base plate  79  and the second peripheral wall  80 . Nevertheless, the second base plate  79  and the second peripheral wall  80  may be separatable from each other. 
     Further, for instance, instead of the aforementioned development roller  4 , a developer carrying body such as a brush roller and a magnetic roller may be employed. 
     Further, for instance, instead of the aforementioned supply roller  5 , a brush-like supply member may be employed. 
     In the aforementioned illustrative embodiment, the process cartridge  17  is configured such that the drum cartridge  24  and the development cartridge  1  are separatable from each other. Nevertheless, the process cartridge  17  may be provided integrally with the drum cartridge  24  and the development cartridge  1 . 
     Furthermore, the development cartridge  1  may be configured such that a toner cartridge for storing toner is detachably attached to a frame supporting the development roller  4 .