Patent Publication Number: US-9423769-B2

Title: Process cartridge

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2013-150925, filed on Jul. 19, 2013, which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     Aspects disclosed herein relate to a process cartridge for use in an electrophotographic image forming apparatus. 
     BACKGROUND 
     A known process cartridge for use in an electrophotographic image forming apparatus includes, for example, a drum cartridge and a developing cartridge. The drum cartridge includes a photosensitive drum. The developing cartridge includes a developing roller and is configured to be detachably installed in the drum cartridge. 
     SUMMARY 
     The drum cartridge and the developing cartridge each may include a handle. In the known process cartridge in which the developing cartridge is installed in the drum cartridge, the handle of the developing cartridge may be positioned over the handle of the drum cartridge. 
     Nevertheless, this configuration may cause difficulty in reducing a size of such a process cartridge in an upper-lower direction by thickness corresponding to a total thickness of the overlapping handles, i.e., may cause difficulty in making the process cartridge have a thinner body. 
     Accordingly, aspects of the disclosure provide for a process cartridge whose size in a second direction may be reduced while accessibility to the developing cartridge is ensured. 
     According to one or more aspects of the disclosure, a process cartridge may include an image carrying member cartridge and a developing cartridge. The image carrying member cartridge may include an image carrying member configured to rotate, and a first frame configured to support the image carrying member at one end portion of the first frame in a first direction perpendicular to an axial direction of the image carrying member and including a first handle at the other end portion of the first frame in the first direction. The developing cartridge may be configured to be attached to the image carrying member cartridge and includes a developing agent carrying member, and a second frame configured to support the developing agent carrying member at one end portion of the second frame in the first direction and including a second handle at the other end portion of the second frame in the first direction. In a state where the developing cartridge is attached to the image carrying member cartridge, a one edge of the first handle in a second direction perpendicular to the axial direction and perpendicular to the first direction may be located at substantially the same position as a one edge of the second handle in the second direction with respect to the second direction. In the state where the developing cartridge is attached to the image carrying member cartridge, the second handle may be spaced apart from the first handle in the first direction. 
     According to one or more other aspects of the disclosure, a process cartridge may include an image carrying member cartridge and a developing cartridge. The image carrying member cartridge may include an image carrying member and a first handle positioned at an end portion thereof the image carrying member cartridge. The developing cartridge may be configured to be attached to the image carrying member cartridge and includes a developing agent carrying member, a developing agent chamber, and a second handle positioned at an end portion, of a side of the first handle, of the developing cartridge. When the developing cartridge is accommodated in the image carrying member cartridge, the second handle may be spaced apart from the first handle between the image carrying member and the first handle. 
     According to the aspects of the disclosure, the size of the process cartridge may be reduced in the second direction while accessibility to the developing cartridge is ensured. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure, needs satisfied thereby, and the objects, features, and advantages thereof, reference now is made to the following descriptions taken in connection with the accompanying drawings. 
         FIG. 1  is a central sectional view depicting a process cartridge including a drum cartridge and a developing cartridge in an illustrative embodiment according to one or more aspects of the disclosure. 
         FIG. 2  is a central sectional view depicting an image forming apparatus in which the process cartridge depicted in  FIG. 1  is installed in the illustrative embodiment according to one or more aspects of the disclosure. 
         FIG. 3  is an upper rear perspective view depicting the drum cartridge depicted in  FIG. 1  in the illustrative embodiment according to one or more aspects of the disclosure. 
         FIG. 4  is an upper rear perspective view depicting the developing cartridge depicted in  FIG. 1  in the illustrative embodiment according to one or more aspects of the disclosure. 
         FIG. 5  is a lower front perspective view depicting the developing cartridge depicted in  FIG. 4  in the illustrative embodiment according to one or more aspects of the disclosure. 
         FIG. 6  is a plan view depicting the process cartridge depicted in  FIG. 1  in the illustrative embodiment according to one or more aspects of the disclosure. 
         FIG. 7A  is a cross-sectional view taken along line A-A in  FIG. 6  for explaining one step in a procedure to install the developing cartridge in the drum cartridge in the illustrative embodiment according to one or more aspects of the disclosure, wherein a rear end portion of the developing cartridge is positioned in a developing cartridge mount of the drum cartridge and the developing cartridge is located at a non-restricted position. 
         FIG. 7B  is a cross-sectional view taken along line A-A in  FIG. 6  for explaining another step subsequent to the step of  FIG. 7A  in the procedure to install the developing cartridge in the drum cartridge in the illustrative embodiment according to one or more aspects of the disclosure, wherein a developing roller is in contact with a photosensitive drum. 
         FIG. 7C  is a cross-sectional view taken along line A-A in  FIG. 6  for explaining other step subsequent to the step of  FIG. 7B  in the procedure to install the developing cartridge in the drum cartridge in the illustrative embodiment according to one or more aspects of the disclosure, wherein the developing cartridge is installed in the drum cartridge and is located at a restricted position. 
         FIG. 8A  is an explanatory diagram for explaining one step in a procedure to detach the developing cartridge from the drum cartridge in the illustrative embodiment according to one or more aspects of the disclosure, wherein the developing cartridge is located at the restricted position and a lock member is located at a restricting position. 
         FIG. 8B  is an explanatory diagram for explaining another step subsequent to the step of  FIG. 8A  in the procedure to detach the developing cartridge from the drum cartridge in the illustrative embodiment according to one or more aspects of the disclosure, wherein the developing cartridge is located at the non-restricted position and the lock member is located at a non-restricting position. 
     
    
    
     DETAILED DESCRIPTION 
     1. Overview of Process Cartridge 
     As depicted in  FIG. 1 , a process cartridge  1  includes a drum cartridge  2  and a developing cartridge  3 . The drum cartridge  2  is an example of an image carrying member cartridge. 
     In the description below, an upper-lower direction is defined with reference to an orientation of the process cartridge  1  that is disposed in a horizontal position. That is, the process cartridge  1  depicted in  FIG. 1  is disposed in the horizontal position and the orientation of the process cartridge  1  is defined as indicated by arrows in  FIG. 1 . A right-left direction is defined with respect to the process cartridge  1  as viewed from its front. A right-left direction is an example of an axial direction. A front-rear direction is an example of a first direction. An upper-lower direction is an example of a second direction. A forward direction is an example of one direction of the first direction. A rearward direction is an example of the other direction of the first direction. An upper direction is an example of one direction of the second direction. A lower direction is an example of the other direction of the second direction. 
     The drum cartridge  2  includes a photosensitive drum  4 , a scorotron charger  5 , and a transfer roller  6 . The photosensitive drum  4  is an example of an image carrying member. 
     The photosensitive drum  4  is rotatably supported at a rear end portion of the drum cartridge  2 . 
     The scorotron charger  5  is disposed behind the photosensitive drum  4  and spaced apart from the photosensitive drum  4 . 
     The transfer roller  6  is disposed below the photosensitive drum  4 . The transfer roller  6  is in contact with a lower end portion of the photosensitive drum  4 . 
     The developing cartridge  3  is installed in the drum cartridge  2  and is positioned in front of the photosensitive drum  4 . The developing cartridge  3  includes a developing roller  7 , a supply roller  8 , a layer-thickness regulating blade  9 , and a toner chamber  10 . The developing roller  7  is an example of a developing agent carrying member. The toner chamber  10  is an example of a developing agent chamber. 
     The developing roller  7  is rotatably supported at a rear end portion of the developing cartridge  3 . The developing roller  7  is in contact with a front end portion of the photosensitive drum  4 . 
     The supply roller  8  is disposed below and in front of the developing roller  7 . The supply roller  8  is rotatably supported by the developing cartridge  3 . The supply roller  8  is in contact with a lower-front end portion of the developing roller  7 . 
     The layer-thickness regulating blade  9  is disposed above and in front of the developing roller  7 . The layer-thickness regulating blade  9  is in contact with a front end portion of the developing roller  7 . 
     The toner chamber  10  is disposed in front of the supply roller  8  and the layer-thickness regulating blade  9 . The toner chamber  10  is configured to store toner therein. Toner is an example of a developing agent. The toner chamber  10  includes an agitator  11 . 
     The agitator  11  is rotatably supported inside the toner chamber  10 . 
     2. Usage of Process Cartridge 
     As depicted in  FIG. 2 , the process cartridge  1  is configured to be installed in an image forming apparatus  21  and to be used therein. 
     The image forming apparatus  21  is an electrophotographic monochrome printer. The image forming apparatus  21  includes a main casing  22 , the process cartridge  1 , a scanner unit  23 , and a fixing unit  24 . 
     The main casing  22  has a substantially box shape. The main casing  22  has an opening  25  defined therein and includes a front cover  26 , a sheet supply tray  27 , and a sheet discharge tray  28 . 
     The opening  25  is defined in a front end portion of the main casing  22 . The opening  25  provides communication between the inside and the outside of the main casing  22  in the front-rear direction to allow the process cartridge  1  to pass therethrough. 
     The front cover  26  is disposed at the front end portion of the main casing  22 . The front cover  26  has a substantially flat plate shape. The front cover  26  extends in the upper-lower direction and is supported by a front wall of the main casing  22  so as to be rotatable about its lower end portion. The front cover  26  is configured to expose or close the opening  25 . 
     The sheet supply tray  27  is disposed at a bottom portion of the main casing  22 . The sheet supply tray  27  is configured to accommodate therein one or more sheets P. 
     The sheet discharge tray  28  is disposed at a front half portion of an upper wall of the main casing  22 . The sheet discharge tray  28  is recessed than an upper surface of the main casing  22  for supporting one or more sheets P thereon. 
     The process cartridge  1  is positioned at a substantially middle position of the main casing  22  in the upper-lower direction. The process cartridge  1  is configured to be installed in and detached from the main casing  22 . 
     The scanner unit  23  is disposed above the process cartridge  1 . The scanner unit  23  is configured to irradiate the photosensitive drum  4  with a laser beam based on image data. 
     The fixing unit  24  is disposed behind the process cartridge  1 . The fixing unit  24  includes a heat roller  29  and a pressure roller  30 . The pressure roller  30  is in pressure contact with a lower-rear end portion of the heat roller  29 . 
     As the image forming apparatus  21  starts an image forming operation, the scorotron charger  5  charges a surface of the photosensitive drum  4  uniformly and the scanner unit  23  exposes the surface of the photosensitive drum  4  with light. Thus, an electrostatic latent image based on image data is formed on the surface of the photosensitive drum  4 . 
     The agitator  11  agitates toner stored in the toner chamber  10  and supplies toner to the supply roller  8 . The supply roller  8  further supplies toner to the developing roller  7  from the agitator  11 . Meanwhile, toner is positively charged between the developing roller  7  and the supply roller  8  and is then carried by the developing roller  7 , and the layer-thickness regulating blade  9  regulates a layer thickness of toner carried by the developing roller  7 . 
     The toner carried by the developing roller  7  is then supplied onto the electrostatic latent image formed on the surface of the photosensitive drum  4 . Thus, a toner image is carried by the surface of the photosensitive drum  4 . 
     The sheets P are fed, one by one, to between the photosensitive drum  4  and the transfer roller  6  at a predetermined timing from the sheet supply tray  27  by rotation of the rollers. The toner image formed on the surface of the photosensitive drum  4  is transferred onto the sheet P while the sheet P passes between the photosensitive drum  4  and the transfer roller  6 . 
     Then, the sheet P is applied with heat and pressure while the sheet P passes between the heat roller  29  and the pressure roller  30 , whereby the toner image transferred onto the sheet P is thermally fixed thereon. After the toner image is fixed on the sheet P, the sheet P is discharged onto the sheet discharge tray  28 . 
     3. Details of Drum Cartridge 
     As depicted in  FIGS. 1 and 3 , the drum cartridge  2  includes a drum frame  31  that is an example of a first frame. 
     The drum frame  31  includes a base frame  32  and a cover frame  33 . 
     The base frame  32  has a substantially rectangular shape in plan view and has a bottom. The base frame  32  includes a pair of side walls  34 , a bottom wall  35 , a rear wall  36 , a front wall  37 , and a strengthening rib  61  that are integral with each other. 
     The side walls  34  are disposed at both end portions, respectively, of the bottom wall  35  of the base frame  32  in the right-left direction. The side walls  34  each have a substantially rectangular flat plate shape in side view and extend in the front-rear direction, respectively. The left side-wall  34  includes a lock member  38  that is an example of a regulating member. 
     The lock member  38  includes a rotating shaft  39 , a lever portion  40 , and a lifting portion  41  that are integral with each other. 
     The rotating shaft  39  has a generally cylindrical shape and extends in the right-left direction. A left end portion of the rotating shaft  39  is rotatably supported by a front end portion of the left side-wall  34 . 
     The lever portion  40  extends upward from a right end portion of the rotating shaft  39  beyond an upper edge of the left side-wall  34 . The lever portion  40  has a substantially flat plate shape. The lever portion  40  includes a regulating portion  42 . 
     The regulating portion  42  is disposed at an upper end portion of the lever portion  40  (see  FIG. 8A ). The regulating portion  42  has a substantially flat plate shape and extends in the right-left direction. A right end portion of the regulating portion  42  protrudes rightward relative to the right end portion of the rotating shaft  39 . 
     The lifting portion  41  extends downward and rearward from the right end portion of the rotating shaft  39 . The lifting portion  41  has a substantially rod shape. 
     The bottom wall  35  is disposed between lower end portions of the side walls  34  and extends in the front-rear direction. The bottom wall  35  has a substantially rectangular flat plate shape in plan view. The bottom wall  35  includes a plurality of, for example, two, pressing-member supporting portions  43 , a plurality of, for example, two, pressing members  44 , and a plurality of, two, contact protrusions  45 . 
     As depicted in  FIGS. 3 and 7C , the pressing-member supporting portions  43  are disposed at right and left end portions, respectively, of the bottom wall  35 . The pressing-member supporting portions  43  each include a pair of side plates  46  and a front plate  47 . 
     In each of the pressing-member supporting portions  43 , the side plates  46  are spaced apart from each other in the right-left direction. The side plates  46  each protrude upward from an upper surface of the bottom wall  35 . The side plates  46  are bent toward each other and further extend in the right-left direction from their upper ends, respectively, where they are bent. 
     The front plate  47  is disposed in front of the pair of side plates  46 . The front plate  47  protrudes upward from the upper surface of the bottom wall  35 . 
     The pressing member  44  is disposed between the side plates  46  of each of the pressing-member supporting portions  43  so as to be slidable in the front-rear direction. The pressing members  44  have the same configuration and each include a pressing portion  48  and a protruding portion  49 . 
     The pressing portion  48  has a substantially rectangular column shape. The pressing portion  48  extends in the front-rear direction and has a closed rear end. A rear face  48 A of the pressing portion  48  has a substantially arc shape in side view. The pressing portion  48  includes a compression spring  54 . 
     The compression spring  54  is disposed inside the pressing portion  48 . The compression spring  54  is a coil spring that extends in the front-rear direction. A front end portion of the compression spring  54  is in contact with the front plate  47  of the pressing-member supporting portion  43 . A rear end portion of the compression spring  54  is in contact with a rear wall of the pressing portion  48 . The compression spring  54  urges the pressing member  44  rearward. 
     The protruding portion  49  is disposed above the pressing portion  48 . The protruding portion  49  has a substantially triangular flat plate shape in side view. The protruding portion  49  extends from a substantially middle portion of the pressing portion  48  in the right-left direction and further extends upward beyond the upper ends of the side plates  46  while passing between the upper end portions of the side plates  46 . A rear face  49 A of the protruding portion  49  continuously extends to an upper end of the rear face  48 A of the pressing portion  48  and is included forward toward the upper direction. 
     As depicted in  FIG. 3 , the contact protrusions  45  are disposed behind the pressing-member supporting portions  43 , respectively. The contact protrusions  45  each have a substantially semisphere shape. The contact protrusions  45  protrude upward from the upper surface of the bottom wall  35  at the respective positions. 
     As depicted in  FIGS. 1 and 3 , the rear wall  36  protrudes upward from a rear end portion of the bottom wall  35  and extends in the right-left direction. The rear wall  36  has a substantially rectangular flat plate shape in front view. 
     The front wall  37  extends upward continuously from a front end portion of the bottom wall  35 . The front wall  37  has a substantially rectangular flat plate shape in front view. Right and left end portions of the front wall  37  are contiguous to the front end portions of the side walls  34 , respectively. The front wall  37  includes a drum cartridge handle  50  that is an example of a first handle. 
     The drum cartridge handle  50  is disposed at a substantially middle portion of the front wall  37  in the right-left direction. The drum cartridge handle  50  has a substantially rectangular flat plate shape in plan view. The drum cartridge handle  50  extends forward from an upper end portion of the front wall  37 . The drum cartridge handle  50  has a recess portion  51 . 
     The recess portion  51  is defined in a substantially middle portion of a rear end portion of the drum cartridge handle  50 . The recess portion  51  is recessed downward than an upper surface of the drum cartridge handle  50  and is open to the rear. A bottom wall of the recess portion  51  is inclined upward toward the front. The recess portion  51  includes a plurality of ribs  52 . 
     Each of the plurality of ribs  52  slightly protrudes upward from a bottom wall of the recess portion  51  and extends in the right-left direction. The ribs  52  are spaced apart from each other in the front-rear direction. 
     A strengthening rib  61  is disposed between the pressing-member supporting portions  43 . The strengthening rib  61  includes a rib portion  62  and a plurality of connecting portions  63 . The plurality of connecting portions  63  is an example of a strengthening portion. 
     The rib portion  62  is disposed behind the front wall  37  and spaced apart from the front wall  37 . The rib portion  62  includes a plurality of first ribs  62 A and a plurality of second ribs  62 B. 
     Each of the plurality of first ribs  62 A protrudes upward from the bottom wall  35  and extends in the right-left direction. The plurality of first ribs  62 A each have a substantially flat plate shape. The first ribs  62 A are spaced apart from each other in the front-rear direction. 
     Each of the plurality of second ribs  62 B protrudes upward from the bottom wall  35  and extends in the front-rear direction. The plurality of second ribs  62 B each have a substantially flat plate shape. Each second rib portion  62 B and each first rib portion  62 A intersect with each other and are contiguous to each other. The second ribs  62 B are spaced apart from each other in the front-rear direction. 
     The connecting portions  63  are disposed between the rib portion  62  and the front wall  37 . Each of the plurality of connecting portions  63  protrudes upward from the bottom wall  35  and extends in the front-rear direction. The plurality of second ribs  62 B each have a substantially flat plate shape. Each of the plurality of connecting portions  63  is contiguous to the rib portion  62  and the front wall  37 . Of the plurality of connecting portions  63 , one or more connecting portions  63  that are disposed more outside than the drum cartridge handle  50  in the right-left direction each have an upper edge portion that are inclined downward toward the rear. 
     The cover frame  33  is disposed above a rear end portion of the base frame  32  so as to cover the photosensitive drum  4 . The cover frame  33  supports the scorotron charger  5 . 
     In the drum cartridge  2 , a portion defined in front of the photosensitive drum  4  by the photosensitive drum  4 , the pair of side walls  34 , and the front wall  37  serves as a developing cartridge mount  53  where the developing cartridge  3  is to be installed therein. 
     4. Details of Developing Cartridge 
     As depicted in  FIGS. 4 and 5 , the developing cartridge  3  includes a developing frame  71  and a drive portion  70 . The developing frame  71  is an example of a second frame. 
     The developing frame  71  has a substantially box shape. The developing frame  71  includes a pair of side walls  72 , a bottom wall  74 , a front wall  73 , and an upper wall  75 . 
     The side walls  72  are disposed at both end portions, respectively, of the bottom wall  74  of the developing frame  71  in the right-left direction. 
     The bottom wall  74  has a substantially flat plate shape and extends in the front-rear direction. Right and left end portions of the bottom wall  74  are contiguous to lower end portions, respectively, of the side walls  72 . 
     The front wall  73  is contiguous to a front end portion of the bottom wall  74  and extends upward from the front end portion of the bottom wall  74 . The front wall  73  has a substantially rectangular flat plate shape in front view. Right and left end portions of the front wall  73  are contiguous to the front end portions, respectively, of the side walls  72 . The front wall  73  includes a developing cartridge handle  76  that is an example of a second handle. 
     The developing cartridge handle  76  is disposed at a substantially middle portion of an upper end portion of the front wall  73  in the right-left direction. The developing cartridge handle  76  includes an upper plate  77  and side plates  78  that are integral with each other. The upper plate  77  is an example of a first wall and the side plates  78  are an example of a pair of second walls. 
     The upper plate  77  is disposed at an upper end portion of the developing cartridge handle  76 . The upper plate  77  has a substantially rectangular flat plate shape in plan view. The upper plate  77  protrudes forward and upward from the upper end portion of the front wall  73  and extends in the right-left direction. The upper plate  77  is inclined upward toward the front (see  FIG. 7C ). The upper plate  77  includes a plurality of upper ribs  79  and a plurality of lower ribs  80 . 
     Each of the plurality of upper ribs  79  slightly protrudes upward from an upper surface of the upper plate  77  and extends in the right-left direction. The upper ribs  79  are spaced apart from each other in the front-rear direction. 
     Each of the plurality of lower ribs  80  slightly protrudes downward from a lower surface of the upper plate  77  and extends in the right-left direction. The lower ribs  80  are spaced apart from each other in the front-rear direction. 
     The side plates  78  are disposed at right and left end portions, respectively, of the upper plate  77  of the developing cartridge handle  76 . The side plates  78  each have a substantially rectangular flat plate shape in side view. Each of the side plates  78  protrudes forward from the front wall  73  of the developing frame  71  and extends in the upper-lower direction. Upper end portions of the side plates  78  are contiguous to right and left end portions, respectively, of the upper plate  77 . 
     The upper wall  75  has a substantially rectangular flat plate shape in plan view. A front end portion of the upper wall  75  is contiguous to the upper end portion of the front wall  73 . Right and left end portions of the upper wall  75  are contiguous to the upper end portions, respectively, of the side walls  72 . 
     The drive portion  70  is disposed to the left of the developing frame  71 . The drive portion  70  includes a gear train (not depicted) and a gear cover  81  that covers the gear train. The gear train transmits a driving force from the main casing  22  to the developing roller  7 , the supply roller  8 , and the agitator  11 . 
     The gear cover  81  has a substantially rectangular cylindrical shape and extends in the right-left direction. The gear cover  81  includes a lock portion  82 . 
     The lock portion  82  is disposed at a front end portion of the gear cover  81 . The lock portion  82  has a substantially rectangular flat plate shape in front view. The lock portion  82  protrudes leftward from a left surface of the gear cover  81  and extends in the upper-lower direction. 
     5. Installation and Detachment of Developing Cartridge in and from Drum Cartridge 
     (1) Installation Procedure of Developing Cartridge in Drum Cartridge 
     As depicted in  FIGS. 1 and 6 , the developing cartridge  3  is installed in the developing cartridge mount  53  of the drum cartridge  2 . 
     In an installation procedure of the developing cartridge  3  in the drum cartridge  2 , an operator holds the developing cartridge handle  76 . 
     When the operator holds the developing cartridge handle  76 , for example, the operator holds the upper plate  77  between a thumb and the other fingers such that the index finger, the middle finger, the ring finger and the little finger are in contact with the lower surface of the upper plate  77  with touching the lower ribs  80  and the thumb is in contact with the upper surface of the upper plate  77  with touching the upper ribs  79 . 
     Subsequently, as depicted in  FIG. 7A , the operator puts the rear end portion of the developing cartridge  3  into the developing cartridge mount  53  of the drum cartridge  2  from above while holding the developing cartridge handle  76 . 
     In response to this, the front end portions of the side walls  72  of the developing cartridge  3  come into contact with the rear faces  49 A of the protruding portions  49  of the pressing members  44 , respectively, of the drum cartridge  2  from above. 
     Subsequent to that, the operator moves his/her hand off the developing cartridge handle  76  and presses the front end portion of the developing cartridge  3  downward and rearward. 
     In response to this, the developing cartridge  3  moves downward and rearward while the front end portions of the side walls  72  slide over the rear faces  49 A of the protruding portions  49  of the pressing members  44 , respectively. The position of the developing cartridge  3  that is located after pressed downward and rearward is referred to as a non-restricted position. 
     As depicted in  FIG. 7B , as the developing roller  7  comes into contact with the photosensitive drum  4  from the front, the further downward and rearward movement of the developing cartridge  3  is restricted. 
     The operator further presses the front end portion of the developing cartridge  3  downward. 
     In response to this, the developing cartridge  3  rotates about its rear end portion in a clockwise direction in left side view. At that time, the front end portions of the side walls  72  of the developing cartridge  3  move downward while pressing the rear faces  48 A of the pressing portions  48  of the pressing members  44 , respectively, toward the front. 
     Then, the pressing members  44  move forward against urging force of the compression springs  54 . The front end portions of the side walls  72  slide downward over the rear faces  48 A of the pressing portions  48  of the pressing members  44 , respectively, and thus are positioned behind the respective pressing members  44 . 
     As depicted in  FIG. 7C , as the lower surfaces  72 B of the front end portions  72 A of the side walls  72  come into contact with the respective contact protrusions  45  of the drum frame  31  from above, the further upward rotation of the developing cartridge  3  is restricted. The position of the developing cartridge  3  that is restricted for the rotation is referred to as a restricted position. 
     In this state, front faces  72 C of the front end portions  72 A of the side walls  72  are in contact with the rear faces  48 A of the pressing portions  48  of the pressing members  44 , respectively. 
     Thus, the pressing members  44  press the side walls  72 , respectively, rearward due to urging force from the compression springs  54 . In response to this, the developing roller  7  is pressed against the photosensitive drum  4  by the pressing force from the pressing members  44 . 
     As described above, the developing cartridge  3  is thus installed in the drum cartridge  2 . 
     After the developing cartridge  3  is installed in the drum cartridge  2 , as depicted in  FIGS. 1 and 6 , the front wall  73  of the developing frame  71  is positioned behind the front wall  37  of the drum frame  31  while at least a clearance D 1  is left between the front wall  73  of the developing frame  71  and the front wall  37  of the drum frame  31  throughout the right-left direction. More specifically, in the developing frame  71 , a portion, where the developing cartridge handle  76  is disposed, of the front wall  73  is located closest to the front wall  37  of the drum frame  31  and behind the front wall  37  of the drum frame  31  while the clearance D 1  is left between the front wall  73  of the developing frame  71  and the front wall  37  of the drum frame  31 . In the developing frame  71 , a portion, where the developing cartridge handle  76  is not disposed and that is disposed more outside than the developing cartridge handle  76  in the right-left direction, of the front wall  73  is located behind the front wall  37  of the drum frame  31  while a clearance D 2  is left between the portion of the front wall  73  of the developing frame  71  and the front wall  37  of the drum frame  31 . The clearance D 2  is greater than the clearance D 1 . 
     In this state, the developing cartridge handle  76  of the developing frame  71  is positioned behind the drum cartridge handle  50  of the drum frame  31  so as to face the drum cartridge handle  50  of the drum frame  31  while clearance is left therebetween. As indicated by a double-dotted and dashed line in  FIG. 1 , an upper edge  77 A of the upper plate  77  of the developing cartridge handle  76  of the developing frame  71  is located at substantially the same position in the upper-lower direction as an upper edge  50 A of the drum cartridge handle  50  of the drum frame  31 . 
     The pressing members  44  are positioned between the front wall  73  of the developing frame  71  and the front wall  37  of the drum frame  31  in plan view. 
     The connecting portions  63  of the strengthening rib  61  are also positioned between the front wall  73  of the developing frame  71  and the front wall  37  of the drum frame  31  in plan view. 
     The rib portion  62  of the strengthening rib  61  is positioned below the lower end portions of the side plates  78  of the developing cartridge handle  76  and faces the lower end portions of the side plates  78  of the developing cartridge handle  76 . 
     (2) Detachment Procedure of Developing Cartridge from Drum Cartridge 
     As depicted in  FIG. 8A , in the state where the developing cartridge  3  is installed in the drum cartridge  2 , i.e., in the state where the developing cartridge  3  is located at the restricted position, the regulating portion  42  of the lock member  38  is located above the lock portion  82  of the developing cartridge  3 . The position of the lock member  38  that is located above the lock portion  82  of the developing cartridge  3  is referred to as a restricting position. When the lock member  38  is located at the restricting position, the lever portion  40  extends upward from the rotating shaft  39 . When the lock member  38  is located at the restricting position, the lifting portion  41  extends rearward and downward from the rotating shaft  39  such that a lower end portion of the lifting portion  41  is positioned below the front end portion of the gear cover  81 . 
     If the front end portion of the developing cartridge  3  moves upward while the lock member  38  is located at the restricting position, the lock portion  82  of the developing cartridge  3  comes into contact with the regulating portion  42  of the lock member  38 . Thus, further upward movement of the front end portion of the developing cartridge  3  is restricted, whereby the separation of the developing cartridge  3  from the drum cartridge  2  is restricted. 
     In a detachment procedure of the developing cartridge  3  from the drum cartridge  2 , as a first step, the operator presses the lever portion  40  of the lock member  38  forward and downward. 
     In response to this, the lock member  38  rotates about the rotating shaft  39  in the clockwise direction in left side view. As the lock member  38  rotates in the clockwise direction, a lower-rear end portion of the lifting portion  41  comes into contact with the front end portion of the gear cover  81  from below while the regulating portion  42  moves inclinatory forward to the front of the lock portion  82  of the developing cartridge  3 . 
     The operator further presses the lever portion  40  of the lock member  38  downward and forward. 
     In response to this, as depicted in  FIG. 8B , the gear cover  81  is pressed upward by the lifting portion  41  and the front end portion of the developing cartridge  3  thus moves upward. The position of the lock member  38  that is located under this situation is referred to as a non-restricting position. 
     At that time, as depicted in  FIG. 7A , the front end portions  72 A of the side walls  72  of the developing cartridge  3  are in contact with the rear faces  49 A of the protruding portions  49  of the pressing members  44  of the drum cartridge  2 , respectively, from above. Thus, the developing cartridge  3  is supported while the front end portion of the developing cartridge  3  is positioned at an upper position. The position of the developing cartridge  3  under this situation is referred to as a non-restricted position. 
     At that time, as indicated by a double-dotted and dashed line in  FIG. 7A , the upper edge  77 A of the upper plate  77  of the developing cartridge handle  76  of the developing frame  71  is located at a higher position than the upper edge  50 A of the drum cartridge handle  50  of the drum frame  31 . 
     Subsequently, the operator holds the developing cartridge handle  76 . 
     At that time, to hold the developing cartridge handle  76 , for example, the operator inserts his/her index finger, middle finger, ring finger and little finger into between the drum cartridge handle  50  and the developing cartridge handle  76 , and holds the upper plate  77  between the thumb and the other fingers such that the index finger, the middle finger, the ring finger and the little finger are in contact with the lower surface of the upper plate  77  with touching the lower ribs  80  and the thumb is in contact with the upper surface of the upper plate  77  with touching the upper ribs  79  as described above. 
     Subsequent to this, while holding the developing cartridge handle  76 , the operator pulls up the developing cartridge  3  from the developing cartridge mount  53  of the drum cartridge  2  to separate the developing cartridge  3  from the drum cartridge  2 . 
     As described above, the drum cartridge  2  is thus completely detached from the developing cartridge  3 . 
     6. Installation and Detachment of Process Cartridge in and from Main Casing 
     For installing or detaching the drum cartridge  2  in which the developing cartridge  3  is installed, i.e., the process cartridge  1 , in or from the main casing  22 , the operator holds the drum cartridge handle  50 . 
     When the operator holds the drum cartridge handle  50 , for example, the operator holds the drum cartridge handle  50  between the thumb and the other fingers such that the index finger, the middle finger, the ring finger and the little finger are in contact with the lower surface of the drum cartridge handle  50  and the thumb is in contact with the bottom surface of the recess portion  51  of the drum cartridge handle  50  with touching the ribs  52 . 
     As depicted in  FIG. 2 , the operator opens the front cover  26  to expose the opening  25  and installs or detaches the process cartridge  1  in or from the main casing  22  via the opening  25 . 
     7. Effects 
     (1) According to the process cartridge  1 , as depicted in  FIG. 1 , the developing cartridge handle  76  of the developing cartridge  3  is positioned behind the drum cartridge handle  50  and is spaced apart from the drum cartridge handle  50  in the state where the developing cartridge  3  is installed in the drum cartridge  2 . 
     This configuration may enable the operator to insert his/her fingers between the developing cartridge handle  76  and the drum cartridge handle  50  and readily hold the developing cartridge handle  76  of the developing cartridge  3  for detaching the developing cartridge  3  from the drum cartridge  2 . 
     The upper edge of the drum cartridge handle  50  is located at substantially the same position as the upper edge of the developing cartridge handle  76  in the upper-lower direction in the state where the developing cartridge  3  is installed in the drum cartridge  2 . 
     The developing cartridge handle  76  of the developing cartridge  3  therefore may not greatly protrude upward relative to the drum cartridge handle  50  of the drum cartridge  2 . 
     Consequently, the size of the process cartridge  1  may be reduced in the upper-lower direction while accessibility to the developing cartridge  3  is ensured. 
     (2) According to the process cartridge  1 , as depicted in  FIG. 6 , the developing cartridge handle  76  and the drum cartridge handle  50  face each other in the state where the developing cartridge  3  is installed in the drum cartridge  2 . 
     That is, the developing cartridge handle  76  is located at substantially the same position as the drum cartridge handle  50  in the right-left direction. 
     This configuration may, therefore, ensure accessibility to the developing cartridge handle  76  as well as accessibility to the drum cartridge handle  50 . 
     (3) According to the process cartridge  1 , as depicted in  FIG. 3 , the recess portion  51  of the drum cartridge handle  50  is recessed downward than the upper surface of the drum cartridge handle  50  and is open to the rear. 
     This configuration may, therefore, enable the operator to insert his/her fingers into between the developing cartridge handle  76  and the drum cartridge handle  50  via the recess portion  51  for detaching the developing cartridge  3  from the drum cartridge  2 . 
     Consequently, the configuration may enable the operator to hold the developing cartridge handle  76  readily. 
     (4) According to the process cartridge  1 , as depicted in  FIG. 5 , the developing cartridge handle  76  includes the upper plate  77  that extends in the right-left direction and the side plates  78  that extend downward from the right and left end portions, respectively, of the upper plate  77 . 
     That is, the upper plate  77  extends in the direction perpendicular to the direction that the side plates  78  extend. 
     This configuration may, therefore, enable the upper plate  77  to reduce or prevent deformation of the side plates  78  while enabling the side plates  78  to reduce or prevent deformation of the upper plate  77 . 
     Consequently, the stiffness of the entire developing cartridge handle  76  may be ensured, thereby enabling the operator to hold the developing cartridge handle  76  stably. 
     (5) According to the process cartridge  1 , as depicted in  FIG. 1 , the rib portion  62  of the strengthening rib  61  of the drum frame  31  is positioned below the side plates  78  in the state where the developing cartridge  3  is installed in the drum cartridge  2 . 
     With this configuration, therefore, even if the process cartridge  1  is deformed due to application of an excessive pressing force during the installation of the developing cartridge  3  into the drum cartridge  2 , the side plates  78  may come into contact with the rib portion  62 , thereby restricting further deformation of the process cartridge  1 . 
     This configuration may therefore prevent breakage of the process cartridge  1  when the excessive pressing force is applied on the process cartridge  1 . 
     (6) According to the process cartridge  1 , as depicted in  FIG. 1 , the bottom wall of the recess portion  51  and the upper plate  77  both extend on an upward and forward inclination. 
     This configuration may, therefore, provide clearance between the bottom wall of the recess portion  51  and the upper plate  77 , thereby enabling the operator to hold the developing cartridge handle  76  further readily. 
     (7) According to the process cartridge  1 , as depicted in  FIG. 7C , the upper plate  77  of the developing cartridge  3  that is located at the non-restricted position is located at the position higher than the upper plate  77  of the developing cartridge  3  that is located at the restricted position. 
     This configuration may, therefore, enable the operator to hold the developing cartridge handle  76  further readily when the developing cartridge  3  is located at the non-restricted position. 
     (8) According to the process cartridge  1 , as depicted in  FIG. 6 , there is clearance between the front wall  73  of the developing cartridge  3  and the front wall  37  of the drum cartridge  2  throughout the right-left direction. 
     This configuration may, therefore, enable the operator to hold the developing cartridge handle  76  without restraint using the clearance provided throughout the right-left direction. 
     (9) According to the process cartridge  1 , as depicted in  FIG. 6 , the pressing members  44  are disposed between the front wall  73  of the developing cartridge  3  and the front wall  37  of the drum cartridge  2 . 
     This configuration may, therefore, enable the operator to visually observe the condition of the pressing members  44  that are pressing the developing cartridge  3 . 
     Consequently, the developing cartridge  3  may be surely pressed by the pressing members  44 . 
     (10) According to the process cartridge  1 , as depicted in  FIG. 6 , the connecting portions  63  of the strengthening rib  61  are disposed between the front wall  73  of the developing cartridge  3  and the front wall  37  of the drum cartridge  2 . 
     With this configuration, the drum frame  31  may be reinforced through the use of the space provided between the front wall  73  of the developing cartridge  3  and the front wall  37  of the drum cartridge  2 . 
     As depicted in  FIG. 3 , the pressing-member supporting portions  43  are disposed at the respective positions more outside than the strengthening rib  61  in the right-left direction. 
     With this configuration, in the drum frame  31 , the pressing members  44  may be supported by the respective portions reinforced by the strengthening rib  61 , thereby allowing the pressing members  44  to slide stably. 
     As depicted in  FIG. 3 , of the plurality of connecting portions  63 , the one or more connecting portions  63  that are disposed more outside than the drum cartridge handle  50  in the right-left direction each have the upper edge portion that are inclined downward toward the rear. 
     With this configuration, the developing cartridge  3  may be attached to the drum cartridge  2  smoothly along the inclination of the upper end portions of the connecting portions  63 . 
     8. Variations 
     In the illustrative embodiment, the photosensitive drum  4  is adopted as the image carrying member. Nevertheless, in other embodiments, the image carrying member may include a photosensitive belt as well as the photosensitive drum  4 . 
     In the illustrative embodiment, the developing roller  7  is adopted as the developing agent carrying member. Nevertheless, in other embodiments, the developing agent carrying member may include a developing sleeve, a developing belt, and a brush roller as well as the developing roller  7 .