CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from Japanese Patent Application No. 2010-171999 filed Jul. 30, 2010. The entire content of the priority application is incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to an image forming device such as a color printer. 
       BACKGROUND 
       [0003]    In well-known tandem image forming devices, photosensitive drums for colors of yellow, magenta, cyan and black are juxtaposed, and a toner image of each color is formed on the corresponding photosensitive drum substantially at the same time with one another. In case of a direct transferring system, each toner image formed on each photosensitive drum is sequentially superimposed onto a sheet passing beneath each photosensitive drum due to a circular movement of a conveyor belt. In case of an intermediate transferring system, each toner image is sequentially superimposed on an intermediate transfer belt to form a colored toner image, and the colored toner image is then transferred onto a sheet. 
         [0004]    Some of the toner carried on each photosensitive drum may sometimes remain deposited thereon without being transferred onto the sheet or the intermediate transfer belt. To this effect, some tandem image forming devices are provided with a drum cleaner for collecting remaining toner from each photosensitive drum. 
         [0005]    A belt cleaner has also been proposed for collecting toner remained on the conveyor belt or the intermediate transfer belt. Such belt cleaner includes a waste toner box in which the toner collected by the belt cleaner (waste toner) is stored. 
         [0006]    When both of the drum cleaner and the belt cleaner are provided, the toner collected by the drum cleaner is ejected onto a belt, and the toner on the belt is then collected by the belt cleaner. 
       SUMMARY 
       [0007]    However, conventionally, the photosensitive drums are disposed upward of the belt, while the belt cleaner is disposed below the belt. This configuration inevitably requires a large dimension in height, resulting in a large image forming device. Furthermore, when the waste toner box becomes full, the belt needs to be removed first in order to take out the waste toner box from the image forming device. 
         [0008]    In view of the foregoing, it is an object of the present invention to provide a compact image forming device capable of facilitating disposal of waste toner. 
         [0009]    In order to achieve the above and other objects, the present invention provides an image forming device including a plurality of photosensitive drums, a plurality of developer cartridges, an endless belt, a plurality of first collecting units, a plurality of first conveying units, a second collecting unit, a second conveying unit, and a plurality of communication portions. The plurality of photosensitive drums is juxtaposedly arrayed in a first direction to form a drum array including a leading photosensitive drum and a trailing photosensitive drum in the first direction, each photosensitive drum extending in a second direction perpendicular to the first direction. Each of the plurality of developer cartridges is detachably mountable on each of the plurality of photosensitive drums, each developer cartridge having a developer accommodating chamber in which developer to be supplied to each photosensitive drum is stored and a waste developer accommodating chamber in which waste developer to be disposed is stored. The endless belt extends in the first direction and in the second direction and facing each of the plurality of photosensitive drums. Each of the plurality of first collecting units is disposed for each of the plurality of photosensitive drums, each first collecting unit collecting the waste developer on the corresponding photosensitive drum. Each of the plurality of first conveying units is disposed for each of the first collecting units and conveys the waste developer collected by the each first collecting unit toward the waste developer accommodating chamber of the corresponding developer cartridge. The second collecting unit is disposed adjacent to the leading photosensitive drum and collects the waste developer on the endless belt. The second conveying unit conveys the waste developer collected by the second collecting unit toward the waste developer accommodating chamber of the developer cartridge corresponding to the leading photosensitive drum. Each of the plurality of communication portions allows fluid communication between the first conveying unit and the waste developer accommodating chamber, wherein among the plurality of communication portions a specific communication portion in association with the leading photosensitive drum also allows fluid communication between the second conveying unit and the waste developer accommodating chamber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    In the drawings: 
           [0011]      FIG. 1  is a cross-sectional view of a color printer according to an embodiment of the present invention, wherein a drawer frame is accommodated in the color printer, the drawer frame including drum units and toner cartridges; 
           [0012]      FIG. 2  is a cross-sectional view of the color printer of  FIG. 1 , wherein the drawer frame according to the embodiment is in a pull-out state where the drawer frame is being pulled out; 
           [0013]      FIG. 3  is a cross-sectional view of the color printer of  FIG. 1 , wherein one of the drum units is removed from the drawer frame in the pull-out state; 
           [0014]      FIG. 4  is a cross-sectional view of the color printer of  FIG. 1 , wherein one of the toner cartridges is removed from the drawer frame in the pull-out state; 
           [0015]      FIG. 5  is an elevation view (front side view) of the drum unit and the toner cartridge shown in  FIG. 1 , the drum unit including a communication unit; 
           [0016]      FIG. 6  is an elevation view (front side view) of the drum unit shown in  FIG. 1 ; 
           [0017]      FIG. 7  is a cross-sectional view of the drum unit and the toner cartridge shown in  FIG. 1 , wherein a toner accommodation chamber of the toner cartridge and a developing chamber of the drum unit are in fluid communication with each other; 
           [0018]      FIG. 8  is a cross-sectional view of the drum unit and the toner cartridge shown in  FIG. 1 , wherein the toner accommodation chamber of the toner cartridge and the developing chamber of the drum unit are prevented from communicating with each other; 
           [0019]      FIG. 9  is a cross-sectional view of the drum unit taken along a line A-A shown in  FIG. 7 ; 
           [0020]      FIG. 10  is a cross-sectional view of the drum unit taken along a line B-B shown in  FIG. 7 ; 
           [0021]      FIG. 11  is a left side view of the drum unit shown in  FIG. 1 ; 
           [0022]      FIG. 12  is a cross-sectional view of the drum unit shown in  FIG. 11 ; 
           [0023]      FIG. 13  is a cross-sectional view of the toner cartridge and the communication unit shown in  FIG. 5 , wherein the communication unit is not connected to the toner cartridge; and 
           [0024]      FIG. 14  is a cross-sectional view of the toner cartridge and the communication unit shown in  FIG. 5 , wherein the communication unit is connected to the toner cartridge. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    First, a general configuration of a tandem color printer  1  according to an embodiment of the present invention will be described with reference to  FIGS. 1 through 4 . In the color printer  1 , a drawer frame  3  according to the embodiment is mountable. 
         [0026]    In the following description, a right side in  FIG. 1  will be referred to as a front side, while a left side in  FIG. 1  will be referred to as a rear side. The terms “upward”, “downward”, “upper”, “lower”, “above”, “below”, “beneath”, “right”, “left”, “front”, “rear” and the like will be used assuming that the color printer  1  is viewed from its front side. Also, directions with respect to the drawer frame  3  will be referenced based on an assumption that the drawer frame  3  is accommodated within the color printer  1 . 
         [0027]    As shown in  FIG. 1 , the color printer  1  includes a main casing  2  within which the drawer frame  3  can be accommodated. The drawer frame  3  has a square frame shape in a plan view. A front cover  4  is pivotably movably provided at the front side of the main casing  2 . When the front cover  4  is opened, the drawer frame  3  is movable relative to the main casing  2  with respect to a horizontal direction. More specifically, the drawer frame  3  is movable between an accommodated position in which the drawer frame  3  is accommodated within the main casing  2  (shown in  FIG. 1 ), and a pull-out position in which the drawer frame  3  is pulled out from the main casing  2  (shown in  FIG. 2 ). 
         [0028]    In the drawer frame  3 , four drum units  5  are supported. The four drum units  5  are provided respectively for four colors of black, yellow, magenta and cyan to be used in the color printer  1 . The drum units  5  are juxtaposed in a front-to-rear direction according to the order of colors given above such that the drum unit  5  for black is positioned rearmost in the front-to-rear direction. 
         [0029]    Each drum unit  5  is detachably mountable on the drawer frame  3  from above when the drawer frame  3  is in the pull-out position, as shown in  FIG. 3 . More specifically, as shown in  FIG. 3 , the drawer frame  3  includes a left side frame (not shown) and a right side frame  302  disposed in opposition to each other in a left-to-right direction. On inner surfaces of the left side frame and the right side frame  302  (on a right side surface of the left side frame and a left side surface of the right side frame  302 ), four guide grooves  7  are formed respectively in correspondence with the four drum units  5 . Each guide groove  7  extends diagonally downward and frontward in the front-to-rear direction. A shaft  801  of a photosensitive drum  8  (described later) is inserted into the corresponding pair of guide grooves  7  from upward thereof, such that each drum unit  5  is being mounted in the drawer frame  3  along the guide grooves  7 , while the shaft  801  is slidingly moved downward within the guide grooves  7 . Likewise, when the drum unit  5  is removed from the drawer frame  3 , the drum unit  5  is pulled upward along the corresponding guide grooves  7 . 
         [0030]    Each drum unit  5  includes the photosensitive drum  8 , a charging roller  9 , a developing device  10  and a drum cleaner  11 . The photosensitive drum  8  is rotatable about its axis extending in the left-to-right direction and is rotatably supported to the drum unit  5 . During image formation, the photosensitive drum  8  is rotated in a counterclockwise direction when viewed from its left side (i.e., in a counterclockwise direction in  FIG. 1 ). The charging roller  9 , the developing device  10  and the drum cleaner  11  are disposed to surround the photosensitive drum  8 . More specifically, as shown in  FIG. 1 , the charging roller  9  is disposed at a position diagonally upward and frontward of the photosensitive drum  8  and in contact with the photosensitive drum  8 . The developing device  10  has a lower end portion that opposes the photosensitive drum  8  at a position rearward of the same. The drum cleaner  11  confronts the photosensitive drum  8  at a position frontward of the photosensitive drum  8 . The drum unit  5  for the color of black positioned rearmost in the front-to-rear direction (hereinafter to be referred to as the drum unit  5 K) is further provided with a belt cleaner  12 . 
         [0031]    A toner cartridge  13  for storing toner therein is detachably mountable on the developing device  10  from above. As shown in  FIG. 3 , when the drawer frame  3  is in the pull-out position, the toner cartridge  13  is integrally detachable with the drum unit  5  relative to the drawer frame  3 . Further, when the drawer frame  3  is in the pull-out position, the toner cartridge  13  alone is also removable from the drawer frame  3 , while the drum unit  5  remains mounted on the drum unit  5 , as shown in  FIG. 4 . 
         [0032]    Within the main casing  2 , an exposure device  14 , an intermediate transfer belt  15 , a sheet feed cassette  22  and a fixing unit  23  are also provided, as shown in  FIG. 1 . 
         [0033]    The exposure device  14  is disposed at an uppermost portion of the main casing  2 . The exposure device  14  is configured to irradiate four laser beams corresponding to the four colors used in the color printer  1  toward surfaces of the photosensitive drums  8 . Instead of the exposure device  14 , four LED arrays may be provided for the photosensitive drums  8 . 
         [0034]    As each photosensitive drum  8  rotates, the corresponding charging roller  9  applies a uniform charge to the surface of the photosensitive drum  8 . 
         [0035]    Subsequently, the laser beams irradiated from the exposure device  14  selectively expose the surfaces of the photosensitive drums  8  to light. As a result of exposure to light, an electrostatic latent image is formed on the surface of each photosensitive drum  8 . When toner is supplied to the electrostatic latent image from the developing device  10 , the electrostatic latent image is developed into a toner image. 
         [0036]    The intermediate transfer belt  15  is disposed below the drawer frame  3  in the accommodated position. The intermediate transfer belt  15  is an endless belt, and mounted around three rollers  16 ,  17  and  18  in a taut state. The two rollers  16 ,  17  are disposed so as to oppose each other in the front-to-rear direction and at positions identical to each other with respect to a vertical direction. The two rollers  16 ,  17  are separated from each other in the front-to-rear direction by a prescribed distance that is substantially identical to a length of the drawer frame  3  in the front-to-rear direction. The remaining roller  18  is disposed diagonally downward and frontward of the roller  17  that is positioned at the rear side in the main casing  2 . The intermediate transfer belt  15  thus defines a planar portion  19  between the rollers  16 ,  17  (upper portion of the endless intermediate transfer belt  15 ), the planar portion  19  extending in the front-to-rear direction and the left-to-right direction. The planar portion  19  is in contact with each of the photosensitive drums  8  and a first cleaning roller  75  (to be described later). 
         [0037]    Four primary transfer rollers  20  are disposed within a loop of the intermediate transfer belt  15  such that each primary transfer roller  20  is in confrontation with each photosensitive drum  8  via the planar portion  19 . 
         [0038]    During image formation, the intermediate transfer belt  15  circularly moves in a clockwise direction when viewed from its left side. Due to the primary transfer rollers  20 , the toner images formed on the surfaces of the photosensitive drums  8  are superimposed onto the intermediate transfer belt  15 , sequentially from the black toner image. A colored toner image is thus formed on the intermediate transfer belt  15 . 
         [0039]    A secondary transfer roller  21  is disposed rearward of the roller  17  so as to oppose the same via the intermediate transfer belt  15 . The secondary transfer roller  21  is in contact with the intermediate transfer belt  15 . 
         [0040]    The sheet feed cassette  22  is disposed at a lower portion of the main casing  2 . The sheet feed cassette  22  accommodates therein sheets of paper P. The paper P accommodated in the sheet feed cassette  22  is conveyed toward a position where the intermediate transfer belt  15  is in contact with the secondary transfer roller  21  by various rollers. Due to the secondary transfer roller  21 , the colored toner image formed on the intermediate transfer belt  15  is transferred onto the paper P passing between the intermediate transfer belt  15  and the secondary transfer roller  21 . 
         [0041]    The fixing unit  23  is disposed rearward of the drawer frame  3  in the accommodated position. The paper P on which the colored toner image has been transferred is then conveyed to the fixing unit  23  whereby the toner image is fixed to the paper P by heat and pressure. After the toner image has been fixed to the paper P in the fixing unit  23 , various rollers discharge the paper P onto a discharge tray  24  formed on a top surface of the main casing  2 . 
         [0042]    Next, a detailed configuration of the drum unit  5 K will be described with reference to  FIGS. 5 through 14  as an example for explaining a configuration of the drum unit  5 . The drum unit  5 K has a configuration identical to those of other three drum units  5  (for yellow, magenta and cyan) except that the belt cleaner  12  and a second conveyor unit  101  (described later) are provided only in the drum unit  5 K. 
         [0043]    As shown in  FIGS. 5 and 6 , the drum unit  5 K includes a left side plate  31  and a right side plate  32  arranged in opposition to each other in the left-to-right direction. The charging roller  9 , the developing device  10 , the drum cleaner  11  and the belt cleaner  12  (shown in  FIG. 1 ) are interposed between the left side plate  31  and the right side plate  32  and integrally held to the left side plate  31  and the right side plate  32 . The left side plate  31  extends upward and has an upper end portion facing the toner cartridge  13  from leftward of the same. The right side plate  32  extends upward and has an upper end portion facing the developing device  10  from rightward of the same such that a space above the developing device  10  is exposed rearward so as to be used as a space for accommodating the toner cartridge  13  therein. 
         [0044]    The developing device  10  includes a developing device frame  41  extending between the left side plate  31  and the right side plate  32 , as shown in  FIGS. 5 and 6 . A developing chamber  42  is formed in the developing device frame  41 , as shown in  FIGS. 7 and 8 . The developing chamber  42  has a lower end portion that is open toward the photosensitive drum  8 . 
         [0045]    Within the developing chamber  42 , a developing roller  43 , a supply roller  46 , a thickness-regulating blade  49  and an auger  50  are disposed. 
         [0046]    The developing roller  43  is positioned at the lower end portion of the developing chamber  42 . The developing roller  43  includes a cylindrical-shaped developing roller main body  44  and a developing roller shaft  45  extending in the left-to-right direction. The developing roller main body  44  has an axis extending in the left-to-right direction, and the developing roller shaft  45  penetrates through the developing roller main body  44  along the axis thereof. The developing roller main body  44  has an outer circumferential surface a portion of which is exposed outside of the developing chamber  42  and is in contact with the surface of the photosensitive drum  8 . The developing roller shaft  45  penetrates through left and right side plates (not shown) of the developing device frame  41  and is rotatably supported to the same. The developing roller shaft  45  has widthwise ends in the left-to-right direction that are supported to the left side plate  31  and the right side plate  32  respectively. 
         [0047]    The supply roller  46  includes a cylindrical-shaped supply roller main body  47  and a supply roller shaft  48  extending in the left-to-right direction. The supply roller main body  47  has an axis extending in the left-to-right direction, and the supply roller shaft  48  penetrates through the supply roller main body  47  along the axis of the supply roller main body  47 . The supply roller  46  is disposed diagonally upward and rearward of the developing roller  43  such that the supply roller main body  47  is in contact with the developing roller main body  44 . The supply roller shaft  48  is rotatably supported to the left and side plates of the developing device frame  41 . 
         [0048]    The thickness-regulating blade  49  has a thin plate-like shape. The thickness-regulating blade  49  has a base end held to the developing device frame  41  and another free end that is movable due to resilient deformation of the thickness-regulating blade  49 . The free end of the thickness-regulating blade  49  is in contact with the developing roller main body  44  from upward of the same. 
         [0049]    The auger (feeder screw)  50  is disposed at a position diagonally upward and frontward of the supply roller  46 . The auger  50  includes an auger shaft  51  extending in the left-to-right direction and an auger screw  52  formed on and along the auger shaft  51  in a spiral manner. The auger shaft  51  is rotatably supported to the left side plate  31  and the right side plate  32 . 
         [0050]    As the auger  50  rotates, toner supplied within the developing chamber  42  from the toner cartridge  13  is conveyed in the left-to-right direction and dispersed along the auger  50 . As the supply roller  46  rotates, the toner is supplied onto the developing roller main body  44  from the supply roller main body  47 . As the developing roller  43  rotates, the toner on the developing roller main body  44  enters between the free end of the thickness-regulating blade  49  and the developing roller main body  44 , and is maintained on the developing roller main body  44  as a thin layer of uniform thickness. 
         [0051]    The developing device frame  41  is further formed with a plate-shaped partitioning wall  53  positioned between the developing chamber  42  and the space for accommodating the toner cartridge  13 . The partitioning wall  53  curves in an arcuate shape, with its convex side facing the developing chamber  42 . 
         [0052]    The partitioning wall  53  is formed with a communication port  54  at a position circumferentially center of the partitioning wall  53 . The communication port  54  penetrates through the partitioning wall  53  so as to allow the communication port  54  to be in fluid communication with the developing chamber  42 . The auger  50  is positioned within the developing chamber  42  at a position in confrontation with the communication port  54 . 
         [0053]    A plate-shaped developing-side shutter  55  is provided on the partitioning wall  53 . The developing-side shutter  55  has an accurate shape protruding toward the developing chamber  42  substantially in conformance with the arcuate-shaped outline of the partitioning wall  53 . The developing-side shutter  55  is formed with a shutter opening  56  at a position corresponding to the position of the communication port  54  formed on the partitioning wall  53 . The developing-side shutter  55  is movable along the partitioning wall  53  between an open position where the shutter opening  56  is in communication with the communication port  54  and a closed position where the shutter opening  56  is prevented from communicating with the communication port  54 . 
         [0054]    The drum cleaner  11  includes a drum cleaner casing  61  extending in the left-to-right direction. The drum cleaner casing  61  spans across the left side plate  31  and the right side plate  32 , as shown in  FIG. 9 . The drum cleaner casing  61  includes a cleaner opening  62  and a waste toner chamber  63 . The cleaner opening  62  spans an entire width of the photosensitive drum  8  in the left-to-right direction so as to face the same. The waste toner chamber  63  is formed within the drum cleaner casing  61  and in fluid communication with the cleaner opening  62 . 
         [0055]    As shown in  FIGS. 7 through 9 , an auger  64  is disposed within the waste toner chamber  63 . The auger  64  includes an auger shaft  65  extending in the left-to-right direction and an auger screw  66  provided on and along the auger shaft  65  in a spiral manner. The drum cleaner casing  61  has a right side wall  67  that closes (covers) the waste toner chamber  63  at a right side thereof, as shown in  FIG. 9 . The auger shaft  65  has a right end portion penetrating the right side wall  67  and is rotatably supported to the same. The auger shaft  65  has a left end portion that is rotatably supported to an opposing wall  92  (described later). 
         [0056]    The drum cleaner  11  further includes a scraper  69  as shown in  FIGS. 7 and 8 . The scraper  69  has a plate-like shape extending in the left-to-right direction and in the vertical direction. The scraper  69  has an upper en portion that is fixed to the drum cleaner casing  61 , and a lower portion that is in contact with the surface of the photosensitive drum  8  within the cleaner opening  62 . 
         [0057]    In accordance with the rotation of the photosensitive drum  8 , the toner remaining deposited on the surface of the photosensitive drum  8  after the toner image is transferred onto the intermediate transfer belt  15  is scraped off from the surface of the photosensitive drum  8  by the scraper  69  as waste toner. The waste toner scraped off from the photosensitive drum  8  is received within the waste toner chamber  63  via the cleaner opening  62 . Subsequently, as the auger  64  rotates, the auger  64  (the auger screw  66 ) conveys the waste toner leftward within the waste toner chamber  63 . 
         [0058]    The belt cleaner  12  includes a belt cleaner casing  71 . As shown in  FIGS. 7 and 8 , the belt cleaner casing  71  includes a first peripheral wall  72  and a second peripheral wall  73 . The first peripheral wall  72  curves in an arcuate shape in cross-section, with its convex side facing upward. The first peripheral wall  72  has a front end portion from which the second peripheral wall  73  extends downward. The second peripheral wall  73  has a substantially U-shape in cross-section, whose bottom end portion projecting downward. As shown in  FIG. 10 , each of the first peripheral wall  72  and the second peripheral wall  73  has a left end portion connected to the left side plate  31 . The belt cleaner casing  71  also includes a right side wall  74  (see  FIG. 10 ) defining right end portions of the first peripheral wall  72  and the second peripheral wall  73 . The right side wall  74  is spaced away from the right side plate  32  of the drum unit  5 K. 
         [0059]    As shown in  FIGS. 7 and 8 , the first cleaning roller  75  is disposed within the drum cleaner casing belt cleaner casing  71  at a position between rear end portions of the first peripheral wall  72  and the second peripheral wall  73 . The first cleaning roller  75  includes a cylindrical-shaped cleaning roller main body  76  and a cleaning roller shaft  77  extending in the left-to-right direction. The cleaning roller main body  76  has an axis extending in the left-to-right direction, and the cleaning roller shaft  77  penetrates through the cleaning roller main body  76  along the axis of thereof The cleaning roller shaft  77  is rotatably supported to the belt cleaner casing  71 . 
         [0060]    The belt cleaner casing  71  is formed with a roller accommodation chamber  78  surrounded by the first peripheral wall  72 , and a waste toner chamber  79  surrounded by the second peripheral wall  73 . 
         [0061]    A second cleaning roller  80  is further disposed within the roller accommodation chamber  78 . The second cleaning roller  80  includes a cylindrical-shaped cleaning roller main body  81  and a cleaning roller shaft  82  extending in the left-to-right direction. The cleaning roller main body  81  has an axis extending in the left-to-right direction, and the cleaning roller shaft  82  penetrates through the cleaning roller main body  81  along the axis thereof The cleaning roller main body  81  is in contact with the cleaning roller main body  76  of the first cleaning roller  75  at a position diagonally upward and frontward of the cleaning roller main body  76 . As shown in  FIG. 10 , the cleaning roller shaft  82  has a right end portion that is rotatably supported to the right side plate  32 , and a left end portion that is rotatably supported to the belt cleaner casing  71 . 
         [0062]    Within the waste toner chamber  79 , an auger  83  is rotatably disposed, as shown in  FIGS. 7 ,  8 ,  10 . The auger  83  includes an auger shaft  84  extending in the left-to-right direction and an auger screw  85  formed on and along the auger shaft  84  in a spiral manner. As shown in  FIG. 10 , the auger shaft  84  has a right end portion penetrating through the right side wall  74  and rotatably supported to the right side plate  32 , and a left end portion rotatably supported to an opposing wall  102  (described later). 
         [0063]    Further, as shown in  FIGS. 7 and 8 , a scraper  86  is disposed at a boundary area between the roller accommodation chamber  78  and the waste toner chamber  79 . The scraper  86  has a plate-like shape extending in the left-to-right direction. The scraper  86  has an upper en portion that is fixed to the belt cleaner casing  71 , and a lower portion that is in contact with a surface of the cleaning roller main body  81  of the second cleaning roller  80  at a position diagonally downward and frontward of the cleaning roller main body  81 . 
         [0064]    The cleaning roller main body  76  of the first cleaning roller  75  is in contact with the intermediate transfer belt  15 , as described earlier (see  FIG. 1 ). Further, as also shown in  FIG. 1 , a backup roller  87  is disposed within the loop of the intermediate transfer belt  15  at a position in confrontation with the first cleaning roller  75  via the intermediate transfer belt  15 . 
         [0065]    Toner still remaining on the intermediate transfer belt  15  after the toner image has been transferred to the paper P (i.e., waste toner) is carried on a surface of the cleaning roller main body  76  of the first cleaning roller  75  when the cleaning roller main body  76  confronts the intermediate transfer belt  15  in accordance with the circular movement of the intermediate transfer belt  15 . The waste toner is then transferred from the surface of the cleaning roller main body  76  of the first cleaning roller  75  to the surface of the cleaning roller main body  81  of the second cleaning roller  80 . The waste toner is scraped off from the surface of the cleaning roller main body  81  by the scraper  86 , and is received within the waste toner chamber  79 . Subsequently, as the auger  83  rotates, the auger  83  (the auger screw  85 ) conveys the waste toner leftward within the waste toner chamber  79 . 
         [0066]    Incidentally, instead of the belt cleaner  12 , a scraper may be provided so as to be in slidingly contact with the intermediate transfer belt  15 . In this configuration, the waste toner on the intermediate transfer belt  15  can be scraped off therefrom by the scraper. 
         [0067]    As shown in  FIG. 11 , on an outer surface (left side surface) of the left side plate  31  of the drum unit  5 K, a first conveying unit  91  is provided. The first conveying unit  91  has an elongated shape, extending diagonally upward and rearward from a lower front end portion to an upper end portion of the left side plate  31 . The first conveying unit  91  includes the opposing wall  92  and a peripheral wall  93 . The opposing wall  92  is disposed in opposition to the left side plate  31  and is spaced away therefrom. The peripheral wall  93  is formed along an entire periphery of the opposing wall  92 . As shown in  FIGS. 9 and 12 , a space  94  is defined by the outer surface of the left side plate  31 , the opposing wall  92  and the peripheral wall  93 , and serves as a waste toner chamber through which waste toner is conveyed. 
         [0068]    Belt shafts  95 ,  96  are respectively disposed at upper and lower end portions within the waste toner chamber  94 . The belt shafts  95 ,  96  extend in the left-to-right direction and are rotatably supported to the opposing wall  92 . An endless toner conveying belt  98  is mounted on the belt shafts  95 ,  96 . The toner conveying belt  98  has an outer circumferential surface on which a plurality of ribs  97  is formed at regular intervals. The toner conveying belt  98  is circularly moved in a clockwise direction in a left side view, as indicated by an arrow in  FIG. 12 . 
         [0069]    The belt shaft  95  has a left end protruding leftward from the opposing wall  92 . The left end of the belt shaft  95  protruding from the opposing wall  92  is fitted with a gear  99 , as shown in  FIG. 11 . 
         [0070]    As shown in  FIG. 9 , the waste toner chamber  94  is in fluid communication with the waste toner chamber  63  of the drum cleaner  11 . Therefore, the waste toner conveyed leftward within the waste toner chamber  63  by the auger  64  flows into the waste toner chamber  94 . The waste toner flowing into the waste toner chamber  94  is then conveyed upward by the ribs  97  of the toner conveying belt  98  in accordance with the circular movement of the toner conveying belt  98 . 
         [0071]    Further, as shown in  FIG. 11 , on the outer surface (left side surface) of the left side plate  31  of the drum unit  5 K, the second conveyor unit  101  is provided. The second conveyor unit  101  has an elongated shape, extending diagonally upward and frontward from a lower rear end portion to the upper end portion of the left side plate  31 . 
         [0072]    The second conveyor unit  101  includes an opposing wall  102  and a peripheral wall  103 . The opposing wall  102  is disposed in opposition to the left side plate  31  and is spaced away therefrom. The peripheral wall  103  is formed along an entire periphery of the opposing wall  102 . As shown in  FIGS. 10 and 12 , a space  104  is defined by the outer surface of the left side plate  31 , the opposing wall  102  and the peripheral wall  103 , and serves as a waste toner chamber through which waste toner is conveyed. 
         [0073]    Belt shafts  105 ,  106  are respectively disposed at upper and lower end portions within the waste toner chamber  104 . The belt shafts  105 ,  106  extend in the left-to-right direction and are rotatably supported to the opposing wall  102 . An endless toner conveying belt  108  is mounted on the belt shafts  105 ,  106 . The toner conveying belt  108  has an outer circumferential surface on which a plurality of protrusions  107  is formed at regular intervals. The toner conveying belt  108  is circularly moved in a clockwise direction in a left side view, as indicated by an arrow in  FIG. 12 . 
         [0074]    The belt shaft  105  has a left end protruding leftward from the opposing wall  102 . The left end of the belt shaft  105  protruding from the opposing wall  102  is fitted with a gear  109 , as shown in  FIG. 11 . 
         [0075]    As shown in  FIG. 10 , the waste toner chamber  104  is in fluid communication with the waste toner chamber  79  of the belt cleaner  12 . Therefore, the waste toner conveyed leftward within the waste toner chamber  79  by the auger  83  flows into the waste toner chamber  104 . The waste toner flowing into the waste toner chamber  104  is then conveyed upward by the protrusions  107  in accordance with the circular movement of the toner conveying belt  108 . 
         [0076]    As shown in  FIG. 12 , a communication unit  111  is provided between upper end portions of the first conveying unit  91  and the second conveyor unit  101 . The communication unit  111  has a hollow cylindrical shape, extending in the left-to-right direction and penetrating through the left side plate  31 , as shown in  FIG. 13 . That is, the communication unit  111  has a left-side portion protruding leftward from the left side plate  31 , and a right-side portion protruding rightward from the left side plate  31 . 
         [0077]    As shown in  FIG. 12 , the left-side portion of the communication unit  111  has a peripheral wall on which communication ports  112 ,  113  are formed, the communication ports  112 ,  113  penetrating through the peripheral wall. The communication port  112  is in fluid communication with the waste toner chamber  94  of the first conveying unit  91 , while the communication port  113  is in fluid communication with the waste toner chamber  104  of the second conveyor unit  101 . 
         [0078]    The right-side portion of the communication unit  111  has a peripheral wall on whose bottom portion a connecting port  114  is formed, the connecting port  114  penetrating through the peripheral wall, as shown in  FIG. 13 . 
         [0079]    As shown in  FIGS. 9 and 13 , a cylindrical-shaped shutter  115  is externally coupled to the peripheral wall of the right-side portion of the communication unit  111 . The shutter  115  is movable in the left-to-right direction along the peripheral wall of the right-side portion of the communication unit  111 . The shutter  115  is biased rightward by a coil spring  116  disposed between the shutter  115  and the left side plate  31 . 
         [0080]    Within the communication unit  111 , an auger  117  is rotatably disposed. The auger  117  includes an auger shaft  118  extending in the left-to-right direction and an auger screw  119  formed on and along the auger shaft  118  in a spiral manner. The auger shaft  118  has a left end portion protruding leftward from the communication unit  111 . The left end of the auger shaft  118  protruding from the communication unit  111  is fitted with a gear  120 , as shown in  FIG. 11 . 
         [0081]    The gear  120  is in meshing engagement with the gears  99 ,  109 . Hence, when a driving fore is inputted to the gear  120 , the driving force is transmitted to the respective gears  99 ,  109 , thereby rotating the same. The rotation of the gears  99 ,  109  enables the toner conveying belts  98 ,  108  to circularly move. 
         [0082]    The waste toner conveyed upward by the toner conveying belt  98  within the waste toner chamber  94  flows into the communication unit  111  via the communication port  112 . The waste toner conveyed upward by the toner conveying belt  108  within the waste toner chamber  104  flows into the communication unit  111  via the communication port  113 . As the auger  117  rotates in response to input of the driving force to the gear  120 , the auger  117  (auger screw  119 ) conveys the waste toner rightward within the communication unit  111 . 
         [0083]    As shown in  FIGS. 7 and 8 , the toner cartridge  13  includes a hollow cylindrical-shaped inner casing  121  and an outer casing  122  that accommodates therein the inner casing  121 . The outer casing  122  also has a hollow cylindrical shape. 
         [0084]    A partitioning wall  123  is formed within the inner casing  121 . The partitioning wall  123  partitions an internal space of the inner casing  121  into a toner accommodation chamber  124  and a waste toner accommodation chamber  125 . Toner to be supplied to the developing device  10  is stored within the toner accommodation chamber  124 , while collected waste toner is stored within the waste toner accommodation chamber  125 . 
         [0085]    On the inner casing  121 , an inner outlet  126  is formed for allowing fluid communication between inside and outside of the toner accommodation chamber  124 . The inner outlet  126  is positioned such that the inner outlet  126  is in coincidence with the communication port  54  of the partitioning wall  53  when the toner cartridge  13  is mounted on the partitioning wall  53  of the developing device frame  41 . 
         [0086]    As shown in  FIGS. 13 and 14 , the inner casing  121  has a left end face on which a recessed portion  127  is formed. The recessed portion  127  is protruding inward (toward the inner space of the inner casing  121 ) from the left end face of the inner casing  121 . The recessed portion  127  has a circular-shaped side view, having an inner diameter greater than an outer diameter of the communication unit  111  but smaller than an outer diameter of the shutter  115 . The recessed portion  127  has a bottom end on which a discharging port  128  is formed. The discharging port  128  opens downward and is in fluid communication with the waste toner accommodation chamber  125 . 
         [0087]    Within the recessed portion  127 , a shutter  129  is movably disposed for opening and closing the discharging port  128 . The shutter  129  is movable in the left-to-right direction, and integrally includes a cylindrical portion  130  and an abutment portion  131 . The cylindrical portion  130  has an outer diameter substantially identical to the inner diameter of the recessed portion  127 . The abutment portion  131  covers a left end of the cylindrical portion  130 . A coil spring  132  is disposed between the abutment portion  131  and the recessed portion  127  such that the shutter  129  is biased leftward by the coil spring  132 . 
         [0088]    Within the toner accommodation chamber  124 , an agitator  133  is disposed, as shown in  FIGS. 7 and 8 . The agitator  133  includes an agitator shaft  134  extending in the left-to-right direction, and an agitating film  135  held to the agitator shaft  134 . 
         [0089]    Within the waste toner accommodation chamber  125 , an auger  136  is rotatably disposed. As shown in  FIG. 13 , the auger  136  includes an auger shaft  137  extending in the left-to-right direction and an auger screw  138  formed on and along the auger shaft  137  in a spiral manner. 
         [0090]    As shown in  FIGS. 7 and 8 , on an outer circumferential surface of the outer casing  122 , an outer outlet  139  is formed. The outer outlet  139  is positioned such that the outer outlet  139  is in coincidence with the inner outlet  126  with respect to the left-to-right direction. Hence, as the outer casing  122  is made to rotate (slidingly move) relative to the inner casing  121 , the inner outlet  126  takes either a position where the inner outlet  126  confronts the outer outlet  139  and is in communication with the same, or another position where the inner outlet  126  is not in confrontation with the outer outlet  139 . The outer outlet  139  is also positioned such that the outer outlet  139  is in confrontation with the shutter opening  56  of the developing-side shutter  55  and in communication with the same when the toner cartridge  13  is mounted on the partitioning wall  53  of the developing device frame  41 . 
         [0091]    The toner cartridge  13  is mounted within the space above the partitioning wall  53  of the developing device frame  41  (see  FIG. 6 ) from a right side of the space. That is, at the time of installation of the toner cartridge  13 , the toner cartridge  13  is moved from the right side toward a left side of the space above the partitioning wall  53 . Subsequently, as shown in  FIG. 13 , the recessed portion  127  and the communication unit  111  are positionally-aligned with each other such that the communication unit  111  is inserted within the recessed portion  127  provided on the left end face of the inner casing  121 . At this time, the shutter  115  coupled to the communication unit  111  is in confrontation with a peripheral end portion of the recessed portion  127 . 
         [0092]    As the toner cartridge  13  moves further leftward, the shutter  115  is brought into contact with the peripheral end portion of the recessed portion  127  and is prevented from being inserted within the recessed portion  127 , while, in the mean time, the communication unit  111  is inserted into the recessed portion  127 . As the communication unit  111  is inserted into the recessed portion  127 , the communication unit  111  pushes the shutter  129  rightward. In response, the shutter  129  is moved rightward against a biasing force of the coil spring  132 . When the shutter  129  moves to reach an inner right end portion of the recessed portion  127 , the toner cartridge  13  is stopped from moving further, the installation of the toner cartridge  13  being completed. At this time, the connecting port  114  of the communication unit  111  is in confrontation with the discharging port  128  of the toner cartridge  13 . That is, an internal space of the communication unit  111  and the waste toner accommodation chamber  125  of the toner cartridge  13  are in fluid communication with each other via the connecting port  114  and the discharging port  128 . 
         [0093]    With this configuration, the waste toner conveyed rightward by the auger  117  within the communication unit  111  flows into the waste toner accommodation chamber  125  via the connecting port  114  and the discharging port  128 . In accordance with rotation of the auger  136  disposed within the waste toner accommodation chamber  125 , the auger  136  conveys the incoming waste toner rightward. The waste toner is thus uniformly dispersed within the waste toner accommodation chamber  125  in the left-to-right direction. 
         [0094]    As shown in  FIG. 8 , when the toner cartridge  13  has just been mounted within the space above the partitioning wall  53 , the communication port  54  of the partitioning wall  53  and the shutter opening  56  of the developing-side shutter  55  do not confront each other. Further, the inner outlet  126  of the inner casing  121  and the outer outlet  139  of the outer casing  122  do not confront each other, either. 
         [0095]    From this state, the outer casing  122  is then made to rotate in a counterclockwise direction in  FIG. 8 . When the toner cartridge  13  is mounted on the space above the partitioning wall  53 , the outer casing  122  is connected to the developing-side shutter  55 . Therefore, when the outer casing  122  is rotated, the developing-side shutter  55  is also moved in conjunction with the rotation of the outer casing  122 . The outer casing  122  is rotated to a position where the outer outlet  139  opposes the inner outlet  126 . As a result, as shown in  FIG. 7 , the outer outlet  139  is in opposition to the inner outlet  126 , and the shutter opening  56  formed on the developing-side shutter  55  is in opposition to the communication port  54  formed on the partitioning wall  53 . Thus, the toner accommodation chamber  124  and the developing chamber  42  are brought into fluid communication with each other, and the toner accommodated within the toner accommodation chamber  124  is supplied to the developing chamber  42 . 
         [0096]    As described above, the drum cleaner  11  is disposed for each photosensitive drum  8  for collecting waste toner deposited on the surface of the photosensitive drum  8 . The belt cleaner  12  for collecting waste toner on the intermediate transfer belt  15  is provided rearward of the rearmost photosensitive drum  8  for black. The toner cartridge  13  includes the toner accommodation chamber  124  for accommodating toner to be supplied to the photosensitive drum  8 , and the waste toner accommodation chamber  125  for accumulating the waste toner to be disposed. 
         [0097]    The waste toner collected at the drum cleaner  11  is conveyed toward the waste toner accommodation chamber  125  of each toner cartridge  13  by the first conveying unit  91 . The waste toner collected at the belt cleaner  12  is conveyed toward the waste toner accommodation chamber  125  of the toner cartridge  13  corresponding to the rearmost photosensitive drum  8  positioned adjacent to the belt cleaner  12 . Each waste toner accommodation chamber  125  is in fluid communication with the communication unit  111  of each drum unit  5 . The communication unit  111  that is in fluid communication with the waste toner accommodation chamber  125  of the toner cartridge  13  corresponding to the rearmost photosensitive drum  8  for black also serves to allow fluid communication between the first conveying unit  91  and the waste toner accommodation chamber  125 , and between the second conveyor unit  101  and the waste toner accommodation chamber  125 . 
         [0098]    With this configuration, the waste toner collected from the photosensitive drum  8  for black by the drum cleaner  11  is conveyed, via the first conveying unit  91  and the communication unit  111 , to the waste toner accommodation chamber  125  that is in fluid communication with the communication unit  111 . To this waste toner accommodation chamber  125 , the waste toner collected from the intermediate transfer belt  15  by the belt cleaner  12  is also conveyed via the second conveyor unit  101  and the communication unit  111 . Therefore, a separate waste toner box for storing the waste toner collected from the intermediate transfer belt  15  is not necessary. The color printer  1  can be thus made compact. 
         [0099]    Further, the waste toner collected from both of the photosensitive drum  8  and the intermediate transfer belt  15  can be disposed at a time just by replacing the toner cartridge  13  corresponding to the black photosensitive drum  8 . Furthermore, since the intermediate transfer belt  15  is not required to be removed for replacing each toner cartridge  13 , efforts required to dispose the waste toner can be greatly reduced. 
         [0100]    Further, the communication unit  111  is connected to the left end face of the toner cartridge  13 . The waste toner collected by the drum cleaner  11  and the belt cleaner  12  is conveyed first leftward by the augers  64 ,  83 , then upward by the first conveying unit  91  and the second conveyor unit  101 , and finally to the waste toner accommodation chamber  125  from its left side via the communication unit  111 . 
         [0101]    The auger  136  provided within the waste toner accommodation chamber  125  conveys the waste toner flowing from the communication unit  111  into the waste toner accommodation chamber  125  rightward. Therefore, the waste toner can be dispersed in the left-to-right direction within the waste toner accommodation chamber  125 . As a result, the waste toner is prevented from accumulating at an area in the vicinity of the communication unit  111  within the waste toner accommodation chamber  125 . The flow of the waste toner from the communication unit  111  into the waste toner accommodation chamber  125  can be made smooth and secured. 
         [0102]    Further, each photosensitive drum  8 , the drum cleaner  11 , the communication unit  111 , the first conveying unit  91  and the second conveyor unit  101  are integrally supported to the left side plate  31  and the right side plate  32 . More specifically, the side plates  31 ,  32  retaining the rearmost photosensitive drum  8  for black integrally support the drum cleaner  11 , the belt cleaner  12 , the first conveying unit  91  and the second conveyor unit  101 . The pair of side plates  31 ,  32  retaining each of the remaining three photosensitive drums  8  supports the drum cleaner  11  corresponding to the photosensitive drum  8 , and the first conveying unit  91 . Therefore, the black photosensitive drum  8 , the drum cleaner  11 , the belt cleaner  12 , the first conveying unit  91  and the second conveyor unit  101  can be treated as an integral unit, while each of the other three photosensitive drums  8 , its drum cleaner  11  and first conveying unit  91  can be treated as an integral unit. 
         [0103]    Further, the four toner cartridges  13  can be integrally pulled out from the main casing  2  via the drawer frame  3 . Therefore, replacement of the toner cartridge  13  for black that is positioned rearmost in the front-to-rear direction can be facilitated. 
         [0104]    Although the present invention has been described with respect to the specific embodiment thereof, it will be appreciated by one skilled in the art that a variety of changes may be made without departing from the scope of the invention.
An image forming device includes photosensitive drums, developer cartridges, an endless belt, first collecting units, first conveying units, a second collecting unit, a second conveying unit and communication portions. The photosensitive drums form a drum array including a leading photosensitive drum. Each developer cartridge has a waste developer accommodating chamber. Each first collecting unit collects waste developer on the corresponding photosensitive drum. Each first conveying unit conveys the waste developer toward the waste developer accommodating chamber. The second collecting unit collects waste developer on the endless belt. The second conveying unit conveys the waste developer toward the waste developer accommodating chamber. Each communication portion allows fluid communication between the first conveying unit and the waste developer accommodating chamber. One of the communication portions associated with the leading photosensitive drum also allows fluid communication between the second conveying unit and the waste developer accommodating chamber.