Patent Publication Number: US-7715755-B2

Title: Image forming apparatus and developing cartridge with deformable handle

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application claims priority from Japanese Patent Application No. 2006-077269, filed on Mar. 20, 2006, the entire subject matter of which is incorporated herein by reference. 
   FIELD 
   Aspects of the invention relate to an image forming apparatus, such as a laser printer and a developing cartridge for use in the image forming apparatus. 
   BACKGROUND 
   A known tandem image forming apparatus is provided with image carriers corresponding to yellow, magenta, cyan and black toner. Such a tandem image forming apparatus can print in color at substantially the same speed as printing in monochrome, because a toner image of each color is formed at substantially the same time on each corresponding one of the image carriers and each of the different colored images is sequentially laid on top of a sheet while the sheet passes the image carriers. 
   As disclosed in one example of this type of tandem image forming apparatus, an image carrier cartridge supports image carriers, each associated with one color. The image carrier cartridge is slidably installed in or removed from a body casing of the image forming apparatus. A developing cartridge for developing an electrostatic latent image formed on each of the image carriers is removably set in the image carrier cartridge. 
   In one example of an image forming apparatus, four developing cartridges are installed in a frame of the image carrier cartridge with little space. Therefore, it is not easy to install in or remove the developing cartridges from the image carrier cartridge. 
   SUMMARY 
   Accordingly, one aspect of the invention is to provide an image forming apparatus in which a plurality of developing cartridges may be installed in or removed from an image carrier unit that is configured to hold the developing cartridges. Another aspect of the invention is to provide a developing cartridge that is easily installed into and/or removed from an image carrier unit that is configured to hold a plurality of the developing cartridges. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     One or more aspects of the invention will be described in detail with reference to the following figures in which like elements are labeled with like numbers and in which: 
       FIG. 1  is a sectional side view showing a general structure of a color laser printer as an image forming apparatus according to an embodiment of the invention; 
       FIG. 2  is a right-side view of a process unit shown in  FIG. 1 ; 
       FIG. 3  is a perspective view of a developing cartridge viewed from the upper front right side; 
       FIG. 4  is a rear-side view of the developing cartridge shown in  FIG. 3 ; 
       FIG. 5  is a left side view of the developing cartridge shown in  FIG. 3 ; 
       FIG. 6  is a right side view of a body casing of the printer and the process unit shown in  FIG. 1 , illustrating the process unit withdrawn from the body casing; 
       FIG. 7  is a right side view of the body casing of the printer and the process unit shown in  FIG. 1 , illustrating the process unit being inserted into the body casing; 
       FIG. 8  is a right side view of the body casing of the printer and the process unit shown in  FIG. 1 , illustrating the process unit installed in the body casing; 
       FIG. 9  is a perspective view of a contact/separation mechanism provided in the color laser printer shown in  FIG. 1  viewed from an upper front right side; 
       FIG. 10  is a perspective view of a rear end of a left contact/separation member shown in  FIG. 9 , viewed from a rear right side; 
       FIG. 11  is a right side view of the developing cartridges shown in  FIG. 3  and the contact/separation member shown in  FIG. 9 , illustrating four developing cartridges are pressed against corresponding photosensitive drums; 
       FIG. 12  is a right side view of the developing cartridges shown in  FIG. 3  and the contact/separation member shown in  FIG. 9 , illustrating three developing cartridges being separated from the corresponding photosensitive drums and one developing cartridge as pressed against the corresponding photosensitive drum; and 
       FIG. 13  is a right side view of the developing cartridges shown in  FIG. 3  and the contact/separation member shown in  FIG. 9 , illustrating four developing cartridges being separated from the corresponding photosensitive drums. 
   

   DETAILED DESCRIPTION 
   An illustrative embodiment of the invention will be described in detail below with reference to the accompanying drawings. 
   It is noted that various connections are set forth between elements in the following description. It is noted that these connections in general and, unless specified otherwise, may be direct or indirect and that this specification is not intended to be limiting in this respect. 
   For purposes herein, aspects of the invention are shown in relation to an image carrier and developer carrier. In various aspects, the image carrier may include a photosensitive drum, photosensitive belt, or the combination of one of a photosensitive drum or belt and an intermediate transfer drum or belt. Further, the developer carrier may include a developer roller or other systems for conveying developer to the image carrier. 
   As shown in  FIG. 1 , a color laser printer  1  is a tandem color laser printer in which a plurality of sub units  25  are arranged in tandem in a horizontal direction, as handling yellow, magenta, cyan and black toner. 
   The color laser printer  1  includes a body casing  2 , a sheet supply section  4  that supplies a sheet  3 , an image forming section  5  that forms an image on the sheet  3  fed therein, and a sheet ejection section  6  that ejects the sheet  3 , where the image is formed on sheet  3 . The sections  4 ,  5 ,  6  are disposed in the body casing  2 . 
   In the following description, the left side in  FIG. 1  is referred to as the front side of the printer  1 , and an opposite side (the right side in  FIG. 1 ) is referred to as the rear side of the printer  1 , as shown by arrows in  FIG. 1 . The right and left sides of the printer  1  are defined when the printer  1  is viewed from the front side. Unless otherwise specified, the front, rear, left, right, top and bottom of a drum unit  23  and a developing cartridge  24  are defined in conjunction with an orientation in which the drum unit  23  and the developing cartridge  24  are installed in the body casing  2 . 
   At the front wall of the body casing  2 , a front cover  7  is disposed to cover or uncover a space in the body casing  2 . The front cover  7  is pivotally supported about a lower end thereof by the front wall of the body casing  2 . With the front cover  7  open, a process unit  18  can be withdrawn from the body casing  2  to a withdrawal position and inserted into an installation position. 
   As shown in  FIGS. 1 and 8 , the installation position refers to a position where the process unit  18  is placed during an image formation. As shown in  FIGS. 6 and 7 , the withdrawal position refers to a position where the process unit  18  is or is being withdrawn through the front cover  7 . In the withdrawal position, the handles  83  of at least one of developing cartridges  24  are out of contact with a bottom surface of a supporting plate  21  of an exposure unit  17  (described below). 
   The sheet supply section  4  is provided at a bottom portion of the body casing  2 . The sheet supply section  4  is inserted in or removed from the body casing  2  while being slid along the front-rear direction. The sheet supply section  4  includes a sheet supply tray  8 , a separation roller  9 , a separation pad  10 , a pickup roller  11 , and a sheet supply path  13 . The sheet supply tray  8  holds sheets  3  therein. The separation roller  9  and the separation pad  10  oppose each other at the upper front end of the sheet supply tray  8  when the sheet supply tray  8  is installed in the body casing  2 . The pickup roller  11  is disposed behind the separation roller  9 . The sheets  3  are fed along the sheet supply path  13 . 
   A sheet dust removing roller  14  and a pinch roller  15  opposing each other are disposed in front of and above the separation roller  9  in the sheet supply path  13 . A pair of register rollers  16  is disposed above the sheet dust removing roller  14  and the pinch roller  15 . 
   The image forming section  5  includes an exposure unit  17 , a process unit  18 , a transfer unit  19 , and a fixing unit  20 . 
   The exposure unit  17  is disposed at an upper portion of the body casing  2 . The exposure unit  17  includes a support plate  21  extending in the front-rear and right-left directions above the process unit  18  placed in the installation position, and a casing  22  supported on the upper surface of the support plate  21 . A laser beam emitting portion and a polygon mirror are disposed in the casing  22 . 
   The exposure unit  17  emits laser beams from the laser beam emitting portion, with the laser beams corresponding to image data for each yellow, magenta, cyan, and black color. The laser beams are scanned by the polygon mirror. The laser beams pass through a window formed in the support plate  21  to irradiate surfaces of photosensitive drums  31  (described below). 
   The process unit  18  includes a drum unit  23 , as an example of an image carrier unit, and four developing cartridges  24  for each color. 
   Referring to  FIGS. 1 and 2 , the drum unit  23  will be described. The drum unit  23  includes four sub units  25 , each corresponding to one color, a pair of side plates  26  sandwich the four drum units  25  from the right and left sides ( FIG. 2  only showing right side plate  26 ), a front beam  27  disposed between the front ends of the side plates  26 , a front holding portion  28  disposed at the front beam  27 , a rear beam  29  disposed between the rear ends of the side plates  26 , and a rear holding portion  30  disposed at the rear beam  29 . 
   As shown in  FIG. 1 , the sub units  25  include a yellow sub unit  25 Y, a magenta sub unit  25 M, a cyan sub unit  25 C and a black sub unit  25 K that are arranged in this order from the front side along the front-rear direction with some distance between adjacent sub units  25 . 
   Each sub unit  25  holds a photosensitive drum  31 , as an example of an image carrier, a scorotron charger  32 , and a cleaning brush  33 . 
   The photosensitive drum  31  is of a cylindrical shape and is rotatable. The surface of the photosensitive drum  31  is uniformly and positively charged by the charger  32  during an image formation. The cleaning brush  33  is disposed to remove paper dust or fibers left on the photosensitive drum  31  after the image is transfer to the sheet  3 . The cleaning brush  33  is disposed behind the photosensitive drum  31 . 
   The four developing cartridges  24  are configured to be detachably mounted in the corresponding sub units  25  provided for each color, as shown in  FIG. 1 . More specifically, the developing cartridges  24  include a yellow developing cartridge  24 Y detachably mountable in the yellow sub unit  25 Y, a magenta developing cartridge  24 M detachably mountable in the magenta sub unit  25 M, a cyan developing cartridge  24 C detachably mountable in the cyan sub unit  25 C, and a black developing cartridge  24 K detachably mountable in the black sub unit  25 K. 
   Each developing cartridge  24  includes a box-shaped case  36  with an opening at its lower end. Each developing cartridge  24  further includes an agitator  37 , a supply roller  38 , a developing roller  39 , as an example of a developer carrier, and a layer thickness regulating blade  40  that are disposed in the case  36 . 
   Toner as a developer is contained in the case  36 . More specifically, the yellow developing cartridge  24 Y contains yellow toner, the magenta developing cartridge  24 M contains magenta toner, the cyan developing cartridge  24 C contains cyan toner, and the black developing cartridge  24 K contains black toner. Each developing cartridge  24  contains, for example, positively chargeable non-magnetic single component polymerized toner. 
   The agitator  37  agitates the toner in the case  36 . The supply roller  38  includes a metal supply roller shaft  41  rotatably supported by the case  36  and a conductive sponge roller  42  covering a peripheral surface of the supply roller shaft  41 . The developing roller  39  includes a metal developing roller shaft  43  rotatably supported by the case  36  and a conductive rubber roller  44  covering a peripheral surface of the developing roller shaft  43 . The layer thickness regulating blade  40  is supported by the case  36  at its end opposite to the free end of the blade  40 . 
   The toner contained in the case  36  of each developing cartridge  24  is supplied due to its own weight to the supply roller  38  while being agitated by the agitator  37 . The toner supplied to the supply roller  38  is then supplied to the developing roller  39  while the supply roller  38  is rotating. At this time, the toner is positively charged by friction between the developing roller  39  to which developing bias is applied and the supply roller  38 . The toner supplied to the developing roller  39  passes between the blade  40  and the developing roller  39  while the developing roller  39  rotates. The toner is carried on the surface of the developing roller  39  as a thin layer whose thickness has been uniformly regulated. 
   In the sub unit  25 , the surface of the photosensitive drum  31  is uniformly and positively charged by the corresponding charger  32  while the drum  31  is rotating. The positively-charged drum  31  surface is selectively exposed to the laser beam emitted from the exposure unit  17  at high speed, to form on the surface of the drum  31  an electrostatic latent image corresponding to an image to be formed on the sheet  3 . 
   As the toner, which is carried on the developing roller  39  and is positively charged, is brought into confrontation with the corresponding photosensitive drum  31  by the rotation of the developing roller  39  while the drum  31  is rotated, the toner is supplied to the electrostatic latent image formed on the surface of the photosensitive drum  31 . Thus, the electrostatic latent image on the drum  31  is made visible and a toner image of each color is formed on the relevant photosensitive drums  31 . 
   The transfer unit  19  is disposed above the sheet supply section  4  and below the process unit  18  in the body casing  2 , along the front-rear direction, as shown in  FIG. 1 . The transfer unit  19  includes a drive roller  46 , a driven roller  47 , a conveying belt  48 , transfer rollers  49 , and a cleaning unit  50 . 
   The sheet  3  supplied from the sheet supply section  4  is fed from the front side to the rear side by the conveying belt  48  circulated by the drive roller  46  and the driven roller  47 , so as to sequentially pass through transfer positions between the conveying belt  48  and the photosensitive drums  31 . The color toner images carried on the photoconductive drums  31  are transferred onto the sheet  3  while the sheet  3  passes between the transfer positions. Thus, a color image is formed on the sheet  3 . 
   More specifically, as the yellow toner image carried on the surface of the photoconductive drum  31  of the yellow sub unit  25 Y is transferred on the sheet  3 , the magenta toner image carried on the surface of the photoconductive drum  31  of the magenta process units  25 M is then transferred on the sheet  3  having the yellow toner image transferred thereon. Similarly, the cyan and black toner images carried on the surfaces of the photoconductive drums  31  of the cyan and black process units  25 C,  25 K, respectively, are transferred on the sheet  3 . Thus, each of the different colored images is laid on top of each other. 
   The fixing unit  20  is disposed behind the black sub unit  25 K in the body casing  2  to face, in the front-rear direction, the transfer position between the photosensitive drum  31  and the conveying belt  48 . The fixing unit  20  includes a heat roller  55  and a pressure roller  56 . 
   The sheet  3  is fed to the fixing unit  20  where the color toner images transferred onto the sheet  3  are thermally fixed while the sheet  3  passes between the heat roller  55  and the pressure roller  56 . Thus, a color image is formed on the sheet  3 . 
   In the sheet ejection section  6 , the sheet  3  is fed from the fixing unit  20  along a sheet ejection path  57  to a feed roller  59  and a pinch roller  60 , and ejected by a pair of ejection rollers  61  onto a sheet ejection tray  58 . 
   The case  36  of each developing cartridge  24  will be described in detail below. 
   As shown in  FIGS. 3-5 , the case  36  may include a pair of sidewalls  71  facing each other in the left and right direction, a top wall  72  disposed between the sidewalls  71  at their top ends, a front wall  73  disposed between the sidewalls  71  at their front ends, and a rear wall  74  disposed between the sidewalls  71  at their rear ends. The sidewalls  71 , the front wall  73 , and the rear wall  74  define, at their bottom ends, an opening from which the developing roller  39  is exposed. 
   Each sidewall  71  has a window  75  for detecting the amount of toner stored in the case  36 . The windows  75  are disposed opposite to each other in the left and right direction. The windows  75  allow light to pass therethrough along the left and right direction. 
   As shown in  FIG. 5 , the left sidewall  71  is provided with a gear mechanism (not shown) covered with a gear cover  76 . The gear mechanism includes a driven coupling gear  77  and a gear train (not shown). Drive force input to the driven coupling gear  77  is transmitted via the gear train to the agitator  37 , the supply roller  38 , and the developing roller  39 . 
   A bearing member  80  that rotatably supports the right end of the developing roller shaft  43  is disposed at a lower side of the right sidewall  71 , as shown in  FIGS. 3 and 4 . The right end of the developing roller shaft  43  is rotatably inserted into a hole formed in the bearing member  80 . The left end of the developing roller shaft  43  is rotatably inserted in a hole formed in the left sidewall  71 . Thus, the developing roller shaft  43  is rotatably supported by the case  36 . The left end and right end of the developing roller shaft  43  extend outward from the gear cover  76  and the bearing member  80 , respectively. A part of the end of the shaft  43  extending from the gear cover  76  or the bearing member  80  is covered by a collar member  81 , as shown in  FIG. 4 . 
   As shown in  FIGS. 3-5 , a separation projection  82  is provided so as to extend outwardly in the left and right direction from an upper end of each sidewall  71 . The separation projection  82  is of a substantially cylindrical shape. 
   An elastic handle  83  is disposed at right and left ends of the top wall  72 . The handle  83  may be formed of an elastic material, such as rubber. The handle  83  may have a substantially triangular shape in a side view extending upward. In other examples, the handle  83  may have other shapes including ovals, circles, multi-sided shapes, combinations thereof, and the like. 
   As shown in  FIG. 3 , the handle  83  is provided substantially across the width of the top wall  72  in the front-rear direction. The handle  83  includes a fixed portion  84  that is fixed on the top wall  72 , a front portion  85  that extends from the front end of the fixed portion  84  toward an upward and rearward direction, and a rear portion  86  that extends from the rear end of the fixed portion  84  toward an upward and frontward direction. Upper ends of the front portion  85  and the rear portion  86  are connected. The fixed portion  84 , the front portion  85  and the rear portion  86  define a substantially triangular opening  87  in side view. The opening  87  passes through in the left and right direction, which is a thickness direction of the handle  83 . 
   When a user installs the developing cartridge  24  in the drum unit  23 , the user holds the handles  83  with his/her hands. The developing cartridge  24  is inserted into the corresponding sub unit  25  from above, such that the developing roller  39  is brought into contact with an upper front portion of the corresponding photosensitive drum  31 . When a user takes the developing cartridge  24  out of the drum unit  23 , the user holds the handles  83  with his/her hands and pulls the developing cartridge  24  upwardly. 
   Pressing of the developing roller  39  against the corresponding photosensitive drum  31  will be described with reference to  FIGS. 6-8 . 
   To place the process unit  18  in the installation position in the body casing  2 , the process unit  18  is slidably inserted along the front-rear direction from the front side of the body casing  2  toward the rear side when the front cover  7  is open. 
   As shown in  FIG. 6 , when the process unit  18  is in the withdrawal position, the handles  83  of the developing cartridges  24  do not contact the bottom surface of the support plate  21  of the exposure unit  17  disposed in the body casing  2 . 
   When the process unit  18  is further inserted inward/rearward, the handles  83  of the developing cartridges  24  contact, sequentially from the rearmost black developing cartridge  24 K, the bottom surface of the support plate  21 . The handles  83  elastically deform in the vertical direction between the bottom surface of the support plate  21  and the top wall  72  of the case  36 , as shown in  FIG. 7 . 
   When the process unit  18  is placed in the installation position, the handles  83  of all developing cartridges  24  contact the bottom surface of the support plate  21  and elastically deform in the vertical direction between the bottom surface of the support plate  21  and the top wall  72  of the case  36 , as shown in  FIG. 8 . 
   When the handles  83  are elastically deformed, its restoring force is applied to the bottom surface of the support plate  21 . With the force acting on the support plate  21 , the case  36  of the developing cartridge  24  is urged downward. Thus, the developing roller  39  can be pressed against the corresponding photosensitive drum  31 . 
   A contact/separation mechanism  91  for making the developing roller  39  contact to or separate from the corresponding photosensitive drum  31  will be described with reference to  FIGS. 9-13 . 
   As shown in  FIG. 9 , the contact/separation mechanism  91  of the color laser printer  1  may include a pair of linear cam members  92  and a synchronous moving mechanism  93 . The linear cam members  92  are disposed so as to interpose therebetween the process unit  18  placed in the installation position. The linear cam members  92  are configured to move linearly in the front-rear direction. The synchronous moving mechanism  93  is configured to linearly move the linear cam members  92  in synchronization with each other. 
   Each linear cam member  92  is of a substantially plate shape elongated in the front-rear direction. As shown in  FIG. 10 , each linear cam member  92  is slidably held by a substantially L-shaped holder  94  in a cross section that extends in the front-rear direction. Each holder  94  (only left holder  94  shown in  FIG. 10 ) is fixed on an inner surface of one of a pair of frames  95  (only left frame  95  shown in  FIG. 10 ). The frames  95  are disposed within the body casing  2  opposite to each other in the left and right direction. The linear cam members  92  contact protrusions  82  ( FIG. 4 ), which extend from the sidewalls  71 , from underneath when the process unit  18  is placed in the installation position. 
   As shown in  FIG. 9 , each linear cam member  92  includes cam portions  96  of a substantially trapezoidal shape in a side view. Four cam portions  96  are provided on an upper surface of each linear cam member  92  in association with the protrusions  82 . Each cam portion  96  includes a slide surface  97  provided at an angle from the lower front side to the upper rear side, and a flat separation surface  98  that extends rearward from a rear end of the slide surface  97 . 
   In association with the positions of the linear cam members  92 , the four cam portions  96  take states as shown in  FIGS. 11-13 , i.e., a state where all protrusions  82  are positioned in the front of the corresponding cam portions  96  as shown in  FIG. 11 ; a state where the protrusion  82  of the black developing cartridge  24 K only is positioned in the front of the corresponding cam portion  96  and other protrusions  82  are disposed on the corresponding cam portions  96  as shown in  FIG. 12 ; and a state where all protrusions  82  are disposed on the corresponding cam portions  96  as shown in  FIG. 13 . 
   More specifically, the first three cam portions  96 A,  96 B,  96 C from the front side are formed into the substantially same shape and are disposed equidistantly. The distance between the last (rearmost) cam portion  96 D and the third cam portion  96 C is greater than a distance between each of the other three cam portions  96 A,  96 B,  96 C. The rearmost cam portion  96 D has the separation surface  98  shorter that that of other three cam portions  96 A,  96 B,  96 C in the front-rear direction. 
   The synchronous moving mechanism  93  is configured to transmit drive force from the left linear cam member  92  to the right linear cam member  92 . 
   More specifically, as shown in  FIGS. 9 and 10 , the synchronous moving mechanism  93  includes a left rack gear  99 , a left pinion gear  100 , a right rack gear  101 , a right pinion gear  102 , a connecting shaft  103 , a transmission gear  104 , a crank gear  105 , and a conversion member  106 . The left rack gear  99  is formed on an upper rear surface of the left linear cam member  92 . The left pinion gear  100  is configured to engage with the left rack gear  99 . The right rack gear  101  is formed on an upper rear surface of the right linear cam member  92 . The right pinion gear  102  is configured to engage with the right rack gear  101 . The connecting shaft  103  mounts the left pinion gear  100  and the right pinion gear  102  on each end thereof such that the left pinion gear  100  and the right pinion gear  102  do not rotate relative to the shaft  103 . The transmission gear  104  is fixed on the left frame  95  and is configured to transmit drive force from a motor (not shown). The crank gear  105  is rotated in one direction (e.g., in the counterclockwise direction in  FIG. 10 ) with the rotating force of the transmission gear  104 . The conversion member  106  is configured to convert the rotation of the crank gear  105  into linear movement for the left linear cam member  92 . 
   The left pinion gear  100  and the right pinion gear  102  engage with the left rack gear  99  and the right rack gear  101 , respectively, at their front ends when the linear cam members  92  are moved to the rearmost positions, as shown in  FIG. 11 . When the linear cam members  92  are moved to the foremost positions as shown in  FIG. 13 , the left pinion gear  100  and the right pinion gear  102  engage with the left rack gear  99  and the right rack gear  101 , respectively, at their rear ends. 
   The connecting shaft  103  is disposed between the holders  94 , and rotatably supported by the holders  94 , as shown in  FIG. 10 . 
   The crank gear  105  is rotatably supported by a central shaft, which extends in the left and right direction and is supported by the frame  95 . A gear  107  that engages with the transmission gear  104  is formed on the perimeter of the crank gear  105 . The crank gear  105  is provided with a rear-side protruding shaft  108  that protrudes toward the right side. 
   The rearmost end of the left linear cam member  92  is provided with a front-side protruding shaft  109  that protrudes toward the right side. When the linear cam member  92  is in the rearmost position or the foremost position, as shown in  FIGS. 11 and 13 , the front-side protruding shaft  109  faces the rear-side protruding shaft  108  in the front-rear direction in parallel with each other. 
   The conversion member  106  is disposed between the rear-side protruding shaft  108  and the front-side protruding shaft  109 , such that an end of the conversion member  106  moves along a movement path of the rear-side protruding shaft  108  when the crank gear  105  is rotated. 
   As shown in  FIG. 11 , when the linear cam members  92  are moved to the rearmost position, each protrusion  82  of the developing cartridges  24  is placed in front of the corresponding cam portion  96 , and contacts an upper surface of the linear cam members  92 . The developing roller  39  of each developing cartridge  24  is pressed against the corresponding photosensitive drum  31  with the elastic force (restoring force) of the handles  83 . 
   As the transmission gear  104  is rotated by drive force from the motor (not shown) in the state as shown in  FIG. 11 , the crank gear  105  is rotated counterclockwise in  FIG. 11 . Accordingly, the rear-side protruding shaft  108  moves frontward, and the left linear cam member  92  moves frontward. With the movement of the left linear cam member  92 , the left pinion gear  100  rotates clockwise in  FIG. 11 , and the rotation of the left pinion gear  100  is transmitted to the right pinion gear  102  via the connecting shaft  103 . The right pinion gear  102  rotates in the same direction as the left pinion gear  100 , and consequently, the right linear cam member  92  moves frontward. 
   As shown in  FIG. 12 , when the crank gear  105  rotates approximately 90 degrees from the state shown in  FIG. 11 , the protrusions  82  of the yellow, magenta and cyan developing cartridges  24 Y,  24 M,  24 C slide on the sliding surfaces  97  of the corresponding cam portions  96  and are raised on the separation surfaces  98  of the corresponding cam portions  96 . The protrusions  82  of the black developing cartridge  24 K are positioned in the front of the corresponding cam portions  96 . Thus, the yellow developing cartridge  24 Y, the magenta developing cartridge  24 M, and the cyan developing cartridge  24 C are moved upward, and their developing rollers  39  separate from the corresponding photosensitive drums  31 . Only the developing roller  39  of the black developing cartridge  24 K is in contact with the corresponding photosensitive drum  31 . 
   As shown in  FIG. 13 , when the crank gear  105  is rotated counterclockwise approximately 180 degrees from the state shown in  FIG. 11 , by driving the motor, the linear cam members  92  are moved to the foremost position, the protrusions  82  of all developing cartridges  24  are raised on the separation surfaces  98  of the corresponding cam portions  96 . Thus, all the developing cartridges  24  are moved up and the developing rollers  39  of the developing cartridges  24  separate from the corresponding photosensitive drums  31 . 
   When the motor is further driven to rotate the crank gear  105  counterclockwise in  FIG. 13 , the rear-side protruding shaft  108  is moved rearward and accordingly the pair of linear cam members  92  is moved rearward. When the crank gear  105  is rotated 180 degrees from the state shown in  FIG. 13 , all the developing cartridges  24  are placed in the state as shown in  FIG. 11  where the developing rollers  39  are pressed against the corresponding drums  31 . 
   As described above, the case  36  of each developing cartridge  24  has the handles  83 . A user can install or remove the developing cartridge  24  in or from the drum unit  23  (the corresponding sub unit  25 ) while holding the handles  83 . At least some parts of the handles  83  are elastically deformable. For instance, all of the handles  83  may be elastically deformable or less than all of the handles  83  may be elastically deformable. Therefore, as being deformable, even when a space between the support plate  21  of the exposure unit  17  and the process unit  18  placed in the installation position is small, the handles  83  may be fitted, due to their elastic deformation in the small space. Thus, the developing cartridges  24  may be readily installed in or removed from the drum unit  23  with the handles  83 . Further, the handles  83  may not hinder the installation or removal of the process unit  18  in or from the body casing  2 . 
   Before insertion into color laser printer  1 , the handles  83  may be in an undeformed state. In  FIGS. 11-13 , the handles  83  are shown in one or more deformed states. For instance, in  FIG. 11 , where all developing cartridges  24  are supported by the drum unit  23  that results in the developing rollers  39  being pressed against the photosensitive drums  31 , the handles  83  may be in a first deformation state. In  FIG. 12 , one of the handles  83  is in the first deformation state while the other handles  83  are in a second deformation state. In  FIG. 13 , where all developing cartridges  24  are separated from the drum unit  23 , the handles  83  may be in the second deformation state. Although not shown, it is appreciated that additional states of deformation and no deformation may exist when the developing cartridges  24  are inserted into the color laser printer  1 . For instance, the support plate  21  may possibly be raised and lowered inside the color laser printer  1  to deform and not to deform the handles  83 . 
   When the process unit  18  is moved from the withdrawal position to the installation position, the handles  83  elastically deform between the top wall  72  of the developing cartridge  24  and the support plate  21  of the exposure unit  17 . With the elastic force (restoring force) of the handles  38  applied to the bottom surface of the support plate  21 , the developing roller  39  may be pressed against the corresponding photosensitive drum  31 . Thus, additional device to press the developing roller  39  against the corresponding photosensitive drum  31  may not be required, reducing costs and the number of components to be used. 
   Every time the developing cartridge  24  is replaced with new one, the handles  83  may be also replaced with new ones. Thus, the handles  83  may not be continuously used in a condition where the elasticity of the handles  83  is reduced. Thus, favorable pressing of the developing roller  39  against the corresponding photosensitive drum  31  may be continued. Accordingly, development failures may be reduced that are attributable to shortage of toner supply from the developing roller  39  to the photosensitive drum  31  due to the reduced pressing force of the developing roller  39 . Thus, a quality image may be produced. 
   For example, when specifications of the toner or the developing roller  39  are changed, the handles  83  may be formed of one or more materials having elasticity that meets the specification changes. Thus, pressing force of the developing roller  39  against the corresponding photosensitive drum  31  may be properly controlled to ensure the appropriate toner supply from the developing roller  39  to the corresponding photosensitive drum  31 . Accordingly, an electrostatic latent image formed on the photosensitive drum  31  may be made visible or developed favorably, leading to quality image formation. 
   The handle  83  is provided at each end, with respect to the left and right direction, of the case  36  of the developing cartridge  24 . While holding the handles  83 , a user may stably handle the developing cartridge  24 . Each end of the case  36  where the handle  83  is disposed corresponds to an end of the developing roller  39  in its axial direction. Therefore, when the process unit  18  in which the developing cartridges  24  are installed in the drum unit  23  is placed in the installation position, the developing roller  39  may be pressed against the corresponding photosensitive drum  31  in a well-balanced manner in the axial direction of the roller  39  through the case  36 , with the elastic force of the handles  83  applied to the bottom surface of the support plate  21 . Thus, toner may be supplied from the developing roller  39  to the corresponding photosensitive drum  31  uniformly in the axial direction of the drum  31 . Consequently, an electrostatic latent image formed on the photosensitive drum  31  may be made visible or developed favorably. 
   The support plate  21  of the exposure unit  17  has the window, as described above, that passes laser beams therethrough to irradiate the photosensitive drum  31  with the laser beams. The length of the window in the axial direction of the developing roller  39  (left and right direction) is shorter than the length of the rubber roller  44  of the developing roller  39  and the length of the case  36 . Because the handle  83  is disposed on each end of the case  36  in the left and right direction, the handles  83  may not get caught in the window when the process unit  18  is moved between the installation position and the withdrawal position. Consequently, the process unit  18  may be smoothly moved. 
   The handle  83  has the opening  87  that passes through in its thickness direction, so that the handle  83  may readily elastically deform. Thus, the handles  83  may not interfere with the installation of the process unit  18  in the body casing  2 . 
   The handle  83  extends along an insertion/withdrawal direction of the process unit  18  into/from the body casing  2 . The opening  87  is provided in a direction perpendicular to the insertion/withdrawal direction. When the handles  83  contact the bottom surface of the support plate  21  while the process unit  18  is moved in the insertion/withdrawal direction, the handles  83  may be elastically and reliably deformed. 
   While the invention has been described in connection with various example structures and illustrative aspects, it will be understood by those skilled in the art that other variations and modifications of the structures and aspects described above may be made without departing from the scope of the invention. Other structures and aspects will be apparent to those skilled in the art from a consideration of the specification or practice of the invention disclosed herein. It is intended that the specification and the described examples are illustrative with the true scope of the invention being defined by the following claims.