Patent Publication Number: US-8995877-B2

Title: Process cartridge having cover for protecting photosensitive drum

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2011-261253 filed Nov. 30, 2011. The entire content of the priority application is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a process cartridge that is mountable in an electrophotographic image forming apparatus. 
     BACKGROUND 
     As a process cartridge mountable in an electrophotographic printer, there has been known a process cartridge including a photosensitive member for carrying a developer image, and a developing roller for supplying developer to the photosensitive member. 
     For example, there is proposed a process cartridge including: a process casing having a photosensitive drum; and a developing unit having a developing roller and detachably attachable to the process casing. 
     In this process cartridge, the developing unit is urged toward the photosensitive drum so that the developing roller is constantly in pressure contact with the photosensitive drum. 
     When this process cartridge is not mounted on a main body of a printer, a cover is put thereon so as to cover the photosensitive drum. The cover is provided with a pair of separation members designed to separate the developing roller from the photosensitive drum. 
     SUMMARY 
     In the above-described process cartridge, in order to separate the developing roller from the photosensitive drum, a user needs to place each separation member between the developing roller and the photosensitive drum before putting the cover over the photosensitive drum, making attachment of the cover complicated and cumbersome. 
     In view of the foregoing, it is an object of the present invention to provide a process cartridge and a covering member easily attachable thereto in a state where a developing roller is separated from a photosensitive member. 
     In order to attain the above and other objects, there is provided a process cartridge including a photosensitive member unit having a photosensitive member; a developing unit detachably mountable on the photosensitive member unit and having a developing roller; a movable member configured to move between a first position and a second position when the developing unit is mounted on the photosensitive member unit; and a covering member configured to cover the photosensitive member, the movable member being at the second position in a state where the covering member covers the photosensitive member. The movable member at the first position permits the photosensitive member and the developing roller to be in contact with each other and the movable member at the second position permits the photosensitive member and the developing roller to be in separation from each other. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The particular features and advantages of the invention as well as other objects will become apparent from the following description taken in connection with the accompanying drawings, in which: 
         FIG. 1  is a central cross-sectional view of a printer that accommodates therein a process cartridge according to an embodiment of the present invention; 
         FIG. 2  is a perspective view of the process cartridge of  FIG. 1  as viewed from its rear side and left side, the process cartridge including a drum cartridge having a bearing member and a photosensitive drum; 
         FIG. 3  is an enlarged view of an essential portion of the process cartridge of  FIG. 2 , the drum cartridge being formed with a second engagement portion and the bearing member having a first engagement portion; 
         FIG. 4A  is a perspective view of a drum cover according to the embodiment as viewed from its rear side and left side, the drum cover including a first engaging portion and a second engaging portion; 
         FIG. 4B  is a perspective view of the drum cover according to the embodiment as viewed from its front side and right side; 
         FIG. 5  is an explanatory view illustrating how the drum cover according to the embodiment is attached to the process cartridge of  FIG. 2 , wherein the bearing member is at a first position and the first engaging portion of the drum cover is engaged with the first engagement portion of the bearing member; 
         FIG. 6  is an explanatory view illustrating how the drum cover according to the embodiment is attached to the process cartridge of  FIG. 2  after the state of  FIG. 5 , wherein the drum cover is moved downward to bring the bearing member at its second position; 
         FIG. 7  is an explanatory view illustrating how the drum cover according to the embodiment is attached to the process cartridge of  FIG. 2  after the state of  FIG. 6 , wherein the second engaging portion of the drum cover is brought into abutment with the second engagement portion of the drum cartridge; and 
         FIG. 8  is an explanatory view illustrating how the drum cover according to the embodiment is attached to the process cartridge of  FIG. 2  after the state of  FIG. 7 , wherein the drum cover has been mounted on the process cartridge. 
     
    
    
     DETAILED DESCRIPTION 
     1. Overall Structure of the Printer 
     As shown in  FIG. 1 , a printer  1  is a horizontal direct tandem color printer. The printer  1  accommodates therein a plurality of process cartridges  5  according to an embodiment of the present invention. 
     In the following description, terms “upward”, “downward”, “upper”, “lower”, “above”, “below”, “beneath”, “right”, “left”, “front”, “rear” and the like will be used assuming that the printer  1  is disposed horizontally. Specifically, in  FIG. 1 , the right side is a front side, and a left side is a rear side of the printer  1 . Further, “right side” and “left side” will be used when viewing the printer  1  from its front side. That is, the near side in  FIG. 1  is the left side, and the far side in  FIG. 1  is the right side of the printer  1 . 
     Referring to  FIG. 1 , the printer  1  includes a main casing  2  having a substantially box-like shape. A top cover  4  is swingably provided at an upper end portion of the main casing  2  so as to open and cover a main body opening  3  formed in the main casing  2 . The top cover  4  is pivotally movable about its rear end portion functioning as a fulcrum. 
     In the present embodiment, the printer  1  accommodates therein four process cartridges  5 . 
     All the process cartridges  5  are detachably provided in the main casing  2 . Each of the process cartridges  5  corresponds to one of four colors (black, yellow, magenta, and cyan) for use in the printer  1 . From the front side to the rear side, the process cartridges  5  are juxtaposedly arrayed at intervals in an order of a black process cartridge  5 K, a yellow process cartridge  5 Y, a magenta process cartridge  5 M, and a cyan process cartridge  5 C. 
     Each process cartridge  5  includes a drum cartridge  6  and a developing cartridge  7  detachably mountable on the drum cartridge  6 . 
     Each drum cartridge  6  includes a photosensitive drum  8 . The photosensitive drum  8  is formed in a cylindrical shape extending in a left-right direction (or a lateral direction). The photosensitive drum  8  defines a central axis extending in the left-right direction and is rotatably supported to a drum frame  31  (described later) of the drum cartridge  6 . 
     Each developing cartridge  7  includes a developing roller  9 . The developing roller  9  is also cylindrical-shaped extending in the left-right direction and is rotatable supported to a cartridge frame  51  (described later) of the developing cartridge  7 . The developing roller  9  is disposed at a rear end portion of the developing cartridge  7  so as to be exposed rearward therefrom. The developing roller  9  is in contact with the photosensitive drum  8  at a position frontward and upward thereof when the developing cartridge  7  is mounted on the drum cartridge  6 . 
     Each developing cartridge  7  also includes a supply roller  10 , a thickness regulation blade  11  and a toner container (shown without a reference numeral) disposed above the supply roller  10  and the thickness regulation blade  11 . The supply roller  10  supplies toner to the developing roller  9 , and the thickness regulation blade  11  regulates a thickness of the toner supplied to the developing roller  9 . 
     Toner stored in the toner container of the developing cartridge  7  is positively tribocharged between the supply roller  10  and the developing roller  9 , and is carried on a peripheral surface of the developing roller  9  as a thin layer of a uniform thickness by the thickness regulation blade  11 . 
     A scorotron charger  12  and an LED unit  13  are disposed to oppose each photosensitive drum  8 . Specifically, the scorotron charger  12  is disposed to face the corresponding photosensitive drum  8  from rear-upper side thereof, and the LED unit  13  is disposed to face the corresponding photosensitive drum  8  from above. The scorotron charger  12  applies a uniform charge to an outer peripheral surface of the photosensitive drum  8 , and the LED unit  13  then exposes the outer peripheral surface to light based on image data, thereby forming an electrostatic latent image on the outer peripheral surface of the photosensitive drum  8 . 
     As the developing roller  9  rotates, the toner carried on the peripheral surface of the developing roller  9  is supplied to the electrostatic latent image formed on the outer peripheral surface of the corresponding photosensitive drum  8 . A toner image (developer image) is thus borne on the outer peripheral surface of each photosensitive drum  8 . 
     Sheets P of paper are stacked in a sheet cassette  14  disposed at a bottom end portion of the main casing  2 . A pickup roller  15 , a sheet supply roller  16 , and a pair of registration rollers  17  convey the sheets P upward and rearward one sheet at a time along a U-shaped sheet conveying path. Each sheet P is then supplied at a predetermined timing between the photosensitive drums  8  and an endless conveying belt  18  opposing the same. Four transfer rollers  19  are disposed at an internal space defined by the conveying belt  18  such that each transfer roller  19  opposes each photosensitive drum  8  via the conveying belt  18 . While the sheet P is conveyed on the conveying belt  18  from the front side to the rear side between the photosensitive drums  8  and the transfer rollers  19 , the toner image of each color is sequentially superimposed and transferred onto the sheet P. A color image is thus formed on each sheet P. 
     Subsequently, the sheet P passes between a heat roller  20  and a pressure roller  21  that are disposed rearward of the conveying belt  18 , at which time the color image transferred onto the sheet P is thermally fixed thereto by heat and pressure. 
     The sheet P is then conveyed upward and frontward along a U-shaped sheet conveying path, and is discharged onto a discharge tray  22  formed on the top cover  4 . 
     2. Process Cartridge 
     In the following description, orientations of the process cartridge  5  will be referred to assuming that the process cartridge  5  is disposed on a horizontal plane as shown in  FIG. 2  such that a lower wall  34  of the drum cartridge  6  corresponds to the lower side of the process cartridge  5 . The side on which the photosensitive drum  8  is disposed is defined as the rear side of the process cartridge  5 . 
     (1) Drum Cartridge 
     As shown in  FIG. 2 , the drum cartridge  6  includes the drum frame  31 , a pair of pressing members  42  (see  FIG. 5 ), and a pair of bearing members  30 . 
     (1-1) Drum Frame 
     The drum frame  31  is formed in a frame-like shape having a generally rectangular shape in a plan view, and is closed on its bottom side. More specifically, the drum frame  31  includes: left and right side walls  32 ; a front wall  33  spanning between front end portions of the two side walls  32 ; a lower wall  34  spanning between lower end portions of the two side walls  32 ; and an upper wall  35  spanning between upper-rear end portions of the two side walls  32 . 
     Each side wall  32  has a substantially rectangular shape in a side view and extends in a front-rear direction. Each side wall  32  has a rear end portion in which a coupling hole  36  and a frame-side engaged portion  40  are formed. The bearing members  30  are coupled to the respective coupling holes  36 , and second engagement portions  84  (described later) of a drum cover  81  (described later) are engaged with the respective frame-side engaged portions  40 . 
     The coupling holes  36  are formed in a substantially circular shape in a side view to penetrate through the respective side walls  32  in the left-right direction. The coupling hole  36  has an inner diameter substantially equal to (or slightly larger than) an outer diameter of a bearing portion  37  (described later) of the corresponding bearing member  30 . 
     The frame-side engaged portion  40  is formed in a generally rectangular columnar shape at a position frontward and downward of the coupling hole  36 . The frame-side engaged portion  40  extends outward from an outer surface of the side wall  32  in the left-right direction. More specifically, each frame-side engaged portion  40  includes a sloped surface  44  and an engaging surface  45 . 
     Referring to  FIGS. 3 and 5 , the sloped surface  44  constitutes a lower surface of the frame-side engaged portion  40  and extends in the front-rear direction. The sloped surface  44  slopes such that, as extending in a counterclockwise direction in a left side view with respect to the central axis of the photosensitive drum  8 , the sloped surface  44  extends outward in a radial direction of the photosensitive drum  8 . 
     The engaging surface  45  constitutes an upper-front surface of the frame-side engaged portion  40 , and extends in the radial direction of the photosensitive drum  8 . 
     The front wall  33  is formed in a substantially flat plate-like shape extending in the left-right direction. 
     The lower wall  34  is connected to a lower end portion of the front wall  33  and has a substantially flat plate-like shape extending in the front-rear direction and in the left-right direction. 
     The upper wall  35  is formed in a substantially flat plate-like shape extending in the left-right direction for covering the photosensitive drum  8  from above. The scorotron charger  12  is supported on a lower surface of the upper wall  35  (see  FIG. 1 ). 
     In the drum frame  31 , a developing cartridge accommodating portion  39  is defined for accommodating the developing cartridge  7  therein. Specifically, the developing cartridge accommodating portion  39  is defined by: a front-half portion of the lower wall  34 ; portions of the two side walls  32  corresponding to the front-half portion of the lower wall  34 ; the front wall  33 ; and a front edge portion of the upper wall  35 . 
     (1-2) Pressing Members 
     As shown in  FIG. 5 , the pair of pressing members  42  are disposed on the front wall  33  of the drum frame  31  such that the pressing members  42  come into contact with a front wall  55  (described later) of the developing cartridge  7  from front side thereof. 
     The pressing members  42  are formed in a rectangular columnar shape extending in the front-rear direction. The pressing members  42  are supported on a rear surface of the front wall  33  so as to be slidable in the front-rear direction. The pressing members  42  are arranged on left and right end portions of the rear surface of the front wall  33 . 
     A compression coil spring  43  is interposed between a front end portion of each pressing member  42  and the rear surface of the front wall  33 . The compression coil springs  43  can expand and contract in a direction in which the pressing members  42  are slidable (i.e., the front-rear direction). With this structure, the pressing member  42  is constantly biased toward the rear side, thereby biasing the developing cartridge  7  rearward toward the photosensitive drum  8 . 
     (1-3) Bearing Members 
     As shown in  FIGS. 3 and 5 , each bearing member  30  integrally includes the bearing portion  37 , a bearing-side engaged portion  41 , and a pressing portion  38 . 
     The bearing portion  37  has a substantially cylindrical shape extending in the left-right direction. The bearing portion  37  has an inner diameter substantially equal to (or slightly larger than) an outer diameter of each lateral end portion of the photosensitive drum  8 . The bearing portion  37  rotatably supports each lateral end portion of the photosensitive drum  8 . 
     The bearing-side engaged portion  41  is formed in a substantially hook-like shape in a side view. The bearing-side engaged portion  41  extends diagonally upward and rearward from an upper-rear end portion of the bearing portion  37 , and has an upper-rear end portion that is bent diagonally upward and frontward therefrom. The bearing-side engaged portion  41  is engageable with a first engagement portion  83  (described later) of the drum cover  81  (described later). 
     The pressing portion  38  is formed in a flat plate-like shape, having a certain thickness in the left-right direction. The pressing portion  38  protrudes frontward from a front end portion of the bearing portion  37 . The pressing portion  38  has a front end portion that is curved downward toward the front side and is abuttable with a separation engagement portion  66  (described later) of the developing cartridge  7 . The front end portion of the pressing portion  38  is thus adapted to press the developing cartridge  7  frontward. 
     The bearing portions  37  of the bearing members  30  are coupled to the right and left end portions of each photosensitive drum  8  from laterally outward thereof so as to be capable of rotating relative to the same. At the same time, the bearing portions  37  of the bearing members  30  are inserted into the respective coupling holes  36  of the both side walls  32  of the drum frame  31  such that the bearing members  30  can rotate relative to the coupling holes  36 . 
     With this structure, the bearing members  30  are rotatable about the central axis of the photosensitive drum  8  to be movable between a first position (shown in  FIG. 5 ) and a second position (shown in  FIG. 6 ). At the first position, the front end portion of the pressing portion  38  is positioned to oppose the separation engagement portion  66  (described later) of the developing cartridge  7  from rearward and downward thereof. At the second position, the front end portion of the pressing portion  38  is in abutment with the separation engagement portion  66  of the developing cartridge  7  and pushes the same frontward. 
     (2) Developing Cartridge 
     As shown in  FIG. 2 , the developing cartridge  7  includes the cartridge frame  51 , a drive unit  52 , and a detection unit  53 . The drive unit  52  is placed on the left side of the cartridge frame  51 , and the detection unit  53  is positioned on the right side of the cartridge frame  51 . 
     (2-1) Cartridge Frame 
     The cartridge frame  51  is formed in a substantially box-like shape extending in the left-right direction. The cartridge frame  51  integrally includes left and right side walls  54 , the front wall  55  (see  FIG. 1 ), a lower wall  56  (see  FIG. 1 ), and an upper wall  57 . In the following description, the side wall  54  on the left side is referred to as “left side wall  54 L” and the side wall  54  on the right side is referred to as “right side wall  54 R”. 
     The two side walls  54 L,  54 R are formed in a substantially rectangular shape in a side view and extend in the front-rear direction and in a top-down direction. The two side walls  54 L,  54 R are disposed in opposition to and in separation from each other in the left-right direction. 
     The front wall  55  extends in the left-right direction, and spans between front end portions of the two side walls  54 L,  54 R. 
     The lower wall  56  extends in the left-right direction, and spans between lower end portions of the two side walls  54 L,  54 R so as to be continuous with a lower end portion of the front wall  55 . 
     The upper wall  57  is formed in a flat plate-like shape having a substantially rectangular shape in a plan view. The upper wall  57  is connected to frontward portions of the two side walls  54 L,  54 R and an upper end portion of the front wall  55 . The upper wall  57  has a rear end portion on which the thickness regulation blade  11  is disposed to contact the developing roller  9  from above. 
     (2-2) Drive Unit 
     The drive unit  52  includes a developing coupling  61  and a drive-side gear cover  62 . 
     The developing coupling  61  has a substantially columnar shape extending in the left-right direction. The developing coupling  61  is rotatably supported to the left side wall  54 L. The developing coupling  61  has a left surface on which a coupling recessed portion  63  is formed. 
     The coupling recessed portion  63  is depressed rightward from the left surface of the developing coupling  61 . The coupling recessed portion  63  has a generally elongated shape in a side view, extending in a radial direction of the developing coupling  61  and having a diametrically center portion which is narrow in width (see  FIGS. 3 and 5 ). When the process cartridge  5  is mounted in the main casing  2 , a tip end of a main body coupling (not shown) provided in the main casing  2  is inserted into the coupling recessed portion  63  so as to be incapable of rotating relative to the same. Thus, via the main body coupling (not shown), a rotational driving force is inputted into the developing coupling  61  from the main casing  2 . The rotational driving force inputted into the developing coupling  61  is transmitted to the developing roller  9  and the supply roller  10  via a gear train (not shown). 
     The drive-side gear cover  62  is formed in a substantially rectangular cylindrical shape extending in the left-right direction. The drive-side gear cover  62  has its left end portion closed. The drive-side gear cover  62  includes a coupling collar  65  and the separation engagement portion  66 . 
     The coupling collar  65  has a generally cylindrical shape, protruding leftward from a left wall of the drive-side gear cover  62  at a position substantially center thereof in the front-rear direction. The coupling collar  65  has a right end portion that is in communication with inside of the drive-side gear cover  62 . 
     The separation engagement portion  66  is provided in a form of a rib, protruding rearward from a rear end portion of the coupling collar  65  and extending in the left-right direction. The separation engagement portion  66  has a rear surface extending in the top-down direction. 
     The drive-side gear cover  62  is screw-fixed to the left side wall  54 L such that a left end portion of the developing coupling  61  is fitted with the coupling collar  65 . The coupling recessed portion  63  is exposed from a left end portion of the coupling collar  65 . 
     (2-3) Detection Unit 
     The detection unit  53  includes a detection-side gear cover  72 . 
     The detection-side gear cover  72  is formed in a rectangular cylindrical shape extending in the left-right direction. The detection-side gear cover  72  has its right end portion closed. The detection-side gear cover  72  has a rear end portion on which provided is a separation engagement portion (not shown) having the same shape as that of the separation engagement portion  66  of the drive-side gear cover  62 . The detection-side gear cover  72  is screw-fixed to the right side wall  54 R such that the detection-side gear cover  72  accommodates therein a new-product detection gear (not shown). The new-product detection gear (not shown) is partially exposed from the detection-side gear cover  72 . 
     When a new (unused) developing cartridge  7  is mounted in the main casing  2 , the new-product detection gear (not shown) is configured to be rotated, by a predetermined amount, upon receipt of the rotational driving force transmitted from the developing coupling  61  via the gear train (not shown). This rotation of the new-product detection gear (not shown) is detected by detection means (not shown) disposed in the main casing  2 . Specifically, a portion of the new-product detection gear exposed from the detection-side gear cover  72  is detected by the detection means (not shown). Based on the detection results, information on the developing cartridge  7  is determined at the printer  1 , such as whether the mounted developing cartridge  7  is new, and specifications of the mounted developing cartridge  7 . 
     3. Protection of the Photosensitive Drum 
     (1) Drum Cover 
     The drum cover  81  is attached to a rear end portion of the drum frame  31  (see  FIG. 8 ) for covering the photosensitive drum  8  to protect the same when the drum cartridge  6  is not mounted in the main casing  2 . 
     In the following description, directions with regard to the drum cover  81  will be referred to, assuming that the drum cover  81  is attached to the drum frame  31  (the states shown in  FIGS. 4 and 8 ). 
     The drum cover  81  is made of a resiliently deformable resin. Referring to  FIG. 4 , the drum cover  81  integrally includes a covering portion  82  and a pair of flange portions  80 . 
     The covering portion  82  extends in the left-right direction and has a curved plate-like shape so as to be in conformance with an outer profile of the photosensitive drum  8 . The covering portion  82  is formed so as to generally completely cover the photosensitive drum  8  from lower-rear side thereof when the drum cover  81  is attached to the process cartridge  5 . 
     The flange portions  80  have a substantially flat plate-like shape. The flange portions  80  protrude frontward and upward from left and right end portions of the covering portion  82 . Each flange portion  80  includes a first engagement portion  83  and a second engagement portion  84 . 
     The first engagement portion  83  is formed in a substantially hook-like shape in a side view. The first engagement portion  83  extends frontward from an upper-end portion of the flange portion  80 , and has a front end that is bent downward. 
     The second engagement portion  84  is formed in a substantially flat plate-like shape, extending frontward and upward from a lower end portion of the flange portion  80 . The second engagement portion  84  has a width in the left-right direction and has a thickness in a direction parallel to a line connecting the upper-rear side and the lower-front side. The second engagement portion  84  is so configured as to be resiliently deformable in its thickness direction. Each second engagement portion  84  has a tip end portion (upper-front end portion) from which a claw portion  85  protrudes rearward and upward. 
     More specifically, the claw portion  85  is formed in a substantially right-angled triangular shape in a side view having an apex oriented upward and rearward. The claw portion  85  includes a sloped plane  86  and an engagement plane  87 . 
     The sloped plane  86  extends rearward from the upper-front end portion of the second engagement portion  84 . More specifically, the sloped plane  86  is sloped downward and rearward as extending upstream (toward the lower-rear side) in the extending direction of the second engagement portion  84  (or in the direction toward the upper-front side from the lower-rear side). 
     The engagement plane  87  extends frontward and downward from a rear end portion of the sloped plane  86 . That is, the engagement plane  87  extends in the direction perpendicular to the extending direction of the second engagement portion  84 . 
     (2) Attachment of the Drum Cover 
     Next, how the drum cover  81  is attached to the process cartridge  5  will be described with reference to  FIGS. 5 to 8 . Hereinafter, for simplifying explanation, mounting operations of the drum cover  81  will be described only on the left side of the process cartridge  5 , since the same operations will be performed on the right side. 
     It should be noted that, when the drum cover  81  is not attached to the process cartridge  5  (see  FIG. 2 ), the bearing member  30  is at the first position (see  FIG. 5 ). When the bearing member  30  is at the first position, the developing roller  9  is in pressure-contact with the photosensitive drum  8  from frontward thereof due to a biasing force of the pressing members  42 . 
     In order to attach the drum cover  81  to the process cartridge  5 , as shown in  FIG. 5 , the first engagement portion  83  of the drum cover  81  is first engaged with the bearing-side engaged portion  41  of the bearing member  30  from above. 
     Then, as shown in  FIG. 6 , the drum cover  81  is moved downward, thereby angularly rotating the bearing member  30  about the central axis of the photosensitive drum  8  in the counterclockwise direction in a left side view. 
     Accordingly, the front end portion of the pressing portion  38  of the bearing member  30  comes into contact with a rear end portion of the separation engagement portion  66  of the developing cartridge  7  from below. 
     As the bearing member  30  is further rotated counterclockwise in a left side view as the drum cover  81  is further moved downward, the separation engagement portion  66  of the developing cartridge  7  is pushed frontward while slidingly moves on and along the curved front end portion of the pressing portion  38 . The bearing member  30  is thus displaced to the second position from the first position. 
     As a result, the developing cartridge  7  is moved frontward against the biasing force applied from the pressing members  42  and the developing roller  9  is separated from the photosensitive drum  8 . In other words, when the bearing member  30  is at the second position, the photosensitive drum  8  and the developing roller  9  are separated from each other. A separation direction of the developing cartridge  7  from the corresponding photosensitive drum  8  is indicated by an arrow in  FIG. 6 . 
     Subsequently, in order to complete mounting of the drum cover  81  on the process cartridge  5 , as shown in  FIG. 7 , the drum cover  81  is then pivotally moved counterclockwise in a left side view about the central axis of the photosensitive drum  8 , while the bearing member  30  is kept at the second position. 
     The claw portion  85  of the second engagement portion  84  of the drum cover  81  thus comes into contact with the frame-side engaged portion  40  of the drum frame  31  from reward and downward thereof. 
     As the drum cover  81  is further pivotally moved counterclockwise in a left side view, the second engagement portion  84  is deformed outward in the radial direction of the photosensitive drum  8  such that the sloped plane  86  of the claw portion  85  slidingly moves on and along the sloped surface  44  of the frame-side engaged portion  40 . The second engagement portion  84  thus climbs over the frame-side engaged portion  40 . 
     After having climbed over the frame-side engaged portion  40 , the second engagement portion  84  is restored to its original state because of resiliency thereof. 
     As a result, as shown in  FIG. 8 , the engagement plane  87  of the second engagement portion  84  faces the engaging surface  45  of the frame-side engaged portion  40 , by which the second engagement portion  84  is engaged with the frame-side engaged portion  40 . 
     In that manner, the bearing member  30  is fixed in position relative to the drum frame  31  through the drum cover  81 , while being maintained at the second position. At this time, the photosensitive drum  8  is covered, from below and rearward thereof, by the covering portion  82  of the drum cover  81 . 
     Attachment of the drum cover  81  to the process cartridge  5  is thus completed. 
     4. Operations and Technical Advantages 
     (1) In the process cartridge  5  according to the present embodiment, as shown in  FIG. 8 , the photosensitive drum  8  and the developing roller  9  can be separated from each other by the bearing members  30  displaced to the second position by the drum cover  81 . Hence, the drum cover  81  can be easily attached to the process cartridge  5  while keeping the developing roller  9  separated from the photosensitive drum  8 . 
     (2) According to the process cartridge  5  of the present embodiment, as shown in  FIGS. 4 and 8 , the drum cover  81  can be sized in the front-rear direction to interfere with the bearing members  30  disposed to oppose the developing cartridge  7  from rearward thereof (or from upstream in the separation direction). In other words, due to interposition of the bearing members  30  between the drum cover  81  and the separation engagement portion  66 , the drum cover  81  is not necessary to be made large enough to directly contact with the separation engagement portion  66  of the developing cartridge  7 . 
     Therefore, unlike the conventional drum cover having separation members, the drum cover  81  of the present embodiment can be made smaller at least in the front-rear direction. 
     (3) According to the process cartridge  5  of the present embodiment, as shown in  FIGS. 4 and 8 , the bearing members  30  are disposed at both lateral end portions of the developing cartridge  7  so as to face each other in the left-right direction. The first engagement portions  83  are also provided at the both end portions of the drum cover  81  in the left-right direction. 
     Therefore, with help of the drum cover  81 , the developing cartridge  7  can be separated from the photosensitive drum  8  in a stable and balanced manner in the left-right direction. 
     (4) According to the process cartridge  5  of the present embodiment, as shown in  FIG. 2 , the bearing members  30  are provided on the drum cartridge  6 . 
     Therefore, with such a simple structure, the bearing members  30  are able to reliably act on the developing cartridge  7  that is mounted on the drum cartridge  6 . 
     (5) According to the process cartridge  5 , as shown in  FIGS. 5 and 6 , the bearing members  30  are angularly rotatable to move between the first position (see  FIG. 5 ) and the second position (see  FIG. 6 ). 
     In other words, such compact angular rotational movement of the bearing members  30  enables the bearing member  30  to move between the first position and the second position. 
     (6) According to the process cartridge  5 , as shown in  FIG. 8 , during the operation of covering the photosensitive drum  8  with the drum cover  81 , the bearing members  30  are displaced to the second position by engagement of the bearing-side engaged portions  41  with the first engagement portions  83 . After being displaced to the second position, the bearing member  30  can be maintained at the second position by engagement of the second engagement portions  84  with the frame-side engaged portions  40 . 
     (7) According to the process cartridge  5  of the present embodiment, the drum cover  81  is made of a resin having a resiliency. 
     Therefore, due to the resiliency of the drum cover  81  (specifically, the resiliency of the second engagement portions  84 ), the drum cover  81  is permitted to resiliently deform to be easily mounted on the process cartridge  5  to cover the photosensitive drum  8 . 
     While the invention has been described in detail with reference to the embodiments thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention.