Patent Publication Number: US-8538288-B2

Title: Toner box and developing device for image forming device

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2010-113667 filed May 17, 2010. The entire content of this priority application is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a toner box and a developing device for an image-forming device. 
     BACKGROUND 
     Some conventional image-forming devices, such as laser printers, are provided with a photosensitive drum, a developing device, and a toner box mounted on the case of the developing device for accommodating toner. 
     The toner box has an arc-shaped peripheral surface, for example, with a toner outlet formed in the arc-shaped peripheral surface for discharging toner into the developing device. A sealing member is provided around the toner outlet to prevent toner from leaking from the toner box. A shutter is slidably disposed on the outside of the arc-shaped peripheral surface for opening and closing the toner outlet. 
     After the toner box is mounted on the case of the developing device, the toner outlet is opened by sliding the shutter to a position not opposing the toner outlet. Through this operation, toner in the toner box can be supplied to the developing device through the toner outlet. 
     In an image-forming operation, the conventional image-forming device having the structure described above forms an electrostatic latent image on the surface of the photosensitive drum. A developing unit of the developing device develops the latent image into a toner image. When the toner box begins to run out of toner as the toner is consumed in image-forming operations, an operator removes this toner box from the case of the developing device and mounts a new toner box in its place. 
     Before the operator removes the toner box from the case of the developing device, the operator slides the shutter to a position opposing the toner outlet so that the shutter closes the toner outlet. In this state, the shutter is in close contact with the sealing member, which seals the gap between the shutter and the periphery of the toner outlet. Thus, this construction prevents toner in the toner box from leaking out through the toner outlet after the toner box has been removed from the case of the developing device. 
     Both lateral ends of the shutter along a direction orthogonal to the direction in which the shutter moves are wrapped around the side surfaces of the toner box and are rotatably supported on these side surfaces. With this construction, the shutter can easily deform so that its center portion relative to the direction orthogonal to the moving direction expands outward. When the shutter deforms in this way, the seal formed between the shutter and the peripheral portion of the toner outlet may be compromised, allowing toner to leak out through the shutter and the toner outlet. 
     SUMMARY 
     In view of the foregoing, it is an object of the present invention to provide a toner box and a developing device equipped with the toner box having structures capable of preventing deformation of the shutter. 
     In order to attain the above and other objects, the present invention provides a toner box including: a main body; a shutter; a shutter cover; and a toner seal. The main body is configured to accommodate toner therein and has a main-body-side communication through-hole, through which an interior and an exterior of the main body communicate. The shutter is disposed so as to be capable of moving between an open position in which the shutter opens the main-body-side communication through-hole, and a closed position in which the shutter closes the main-body-side communication through-hole. The shutter cover is configured to cover part of the shutter. The shutter cover has a cover-side communication through-hole at a position corresponding to the main-body-side communication through-hole to allow communication of toner through the main-body-side communication through-hole. The toner seal is configured to be disposed between the main body and the shutter and surround a perimeter of the main-body-side communication through-hole when the shutter is in the closed position. A leading edge of the shutter defined in a closing direction, in which the shutter is moved from the open position to the closed position, is positioned on an upstream side of the main-body-side communication through-hole in the closing direction when the shutter is in the open position. Part of the shutter is covered by a portion of the shutter cover surrounding the cover-side communication through-hole when the shutter is in the closed position. 
     According to another aspect, the present invention provides a developing device including: a developing unit; and the above-described toner box. The toner box is detachably mounted in the developing unit. The developing unit is configured so as to be capable of being disposed in a device body of an image-forming device. The developing unit is provided with a shutter drive member that is configured to move the shutter of the toner box between the open position and the closed position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a cross-sectional view of a color printer according to an embodiment of the present invention; 
         FIG. 2  is a perspective view of the color printer in  FIG. 1  showing a drawer unit that has been pulled outward from a main frame of the printer; 
         FIG. 3  is a perspective view of the drawer unit in  FIG. 2  when toner boxes have all been removed; 
         FIG. 4A  is a right side view of the drawer unit in  FIG. 2  when opening members are in a second position and shutters are in an open position; 
         FIG. 4B  is a left side view of the drawer unit when a closing members are in a third position and the shutters are in the open position; 
         FIG. 5A  is a right side view of the drawer unit when the opening members are in a first position and the shutters are in a closed position; 
         FIG. 5B  is a left side view of the drawer unit when the closing members are in a fourth position and the shutters are in the closed position; 
         FIG. 6  is a perspective view of a mechanism for interlocking the opening member shown in  FIG. 4A  with the closing member shown in  FIG. 4B ; 
         FIG. 7  is a plan view of the drawer unit in  FIG. 3 ; 
         FIG. 8  is a cross-sectional view of the drawer unit taken along the cross-sectional line VIII-VIII shown in  FIG. 7 ; 
         FIG. 9  is a perspective view of a shutter drive member shown in  FIG. 8 ; 
         FIG. 10  is a perspective view of a main body part of the shutter drive member shown in  FIG. 9 ; 
         FIG. 11  is a perspective view of one of the toner boxes shown in  FIG. 1 ; 
         FIG. 12  is an exploded perspective view of the toner box in  FIG. 11 ; 
         FIG. 13  is a side view of a toner seal shown in  FIG. 12 ; 
         FIG. 14  is a partial perspective view of the surface of a mesh layer shown in  FIG. 13 ; 
         FIG. 15  is a cross-sectional view of the mesh layer; 
         FIG. 16A  is a bottom view of the toner box in  FIG. 11  when the shutter is in the open position; 
         FIG. 16B  is a bottom view of the toner box when the shutter is in the closed position; 
         FIG. 17A  is a cross-sectional view of the toner box in  FIG. 11  and the shutter drive member in  FIG. 7  when the shutter is in the open position; 
         FIG. 17B  is a cross-sectional view of the toner box in  FIG. 11  and the shutter drive member in  FIG. 7  when the shutter is in the closed position; 
         FIG. 18A  is a left side view of the toner box in  FIG. 11  and the shutter drive member in  FIG. 7  showing the state of a locking mechanism before the toner box has been coupled with the shutter drive member; 
         FIG. 18B  is a left side view of the toner box in  FIG. 11  and the shutter drive member in  FIG. 7  showing the state of the locking mechanism after the toner box has been coupled with the shutter drive member; 
         FIG. 19  is a partial perspective view of the locking mechanism shown in  FIGS. 18A and 18B ; 
         FIG. 20A  is a cross-sectional view of the shutter and locking mechanism when the shutter is fixed by the locking mechanism; 
         FIG. 20B  is a cross-sectional view of the shutter and locking mechanism when the shutter is not fixed by the locking mechanism; 
         FIG. 21A  illustrates how toner on the shutter is scraped off by the toner seal and an annular frame seal when the shutter enters between the toner seal and the annular frame seal; 
         FIG. 21B  illustrates how toner on an edge of a shutter according to a comparative example enters between the toner seal and the annular frame seal when the shutter enters between the toner seal and the annular frame seal; 
         FIG. 22  illustrates how air flows out of the toner box; 
         FIG. 23  is a perspective view showing a variation of the shutter according to the embodiment; 
         FIG. 24  is a cross-sectional view of the shutter according to the variation in  FIG. 23  taken along the cross-sectional line XXIV-XXIV in  FIG. 23 ; 
         FIG. 25  is a side view showing a variation of the toner seal according to the embodiment; 
         FIG. 26  is a side view showing another variation of the toner seal; 
         FIG. 27A  illustrates how the toner seal is bonded to the shutter according to a variation; 
         FIG. 27B  is a cross-sectional view taken along a line XXVIIB-XXVIIB in  FIG. 27A ; 
         FIG. 28A  illustrates how one toner seal is bonded to a main body of the toner box and another toner seal is bonded to the shutter, according to another variation; 
         FIG. 28B  is a cross-sectional view taken along a line XXVIIIB-XXVIIIB in  FIG. 28A ; and 
         FIG. 29  is a bottom view of a toner box according to a variation of the embodiment that employs a shutter of a different shape. 
     
    
    
     DETAILED DESCRIPTION 
     Next, an embodiment of the present invention will be described while referring to the accompanying drawings. 
     1. Structure of a Color Printer 
     As shown in  FIG. 1 , the image-forming device according to the embodiment is a tandem-type color printer  1 . As shown in  FIGS. 1 and 2 , the color printer  1  includes a main casing  2 . A drawer unit  3  is mounted inside the main casing  2 . A front cover  4  is provided on the front surface of the main casing  2  and is capable of being opened and closed thereon. When the front cover  4  is open, the drawer unit  3  can be moved horizontally between an accommodated position inside the main casing  2 , as indicated by solid lines in  FIG. 1 , and a withdrawn position outside the main casing  2 , as depicted virtually by dotted lines in  FIG. 1  and shown in  FIG. 2 . 
     In the following description, the side of the color printer  1  on which the front cover  4  is provided (right side in  FIG. 1 ) will be referred to as the front side of the color printer  1 . The top, bottom, left, and right sides of the color printer  1  in the following description will be based on the reference point of a user viewing the color printer  1  from the front side. Directions related to the drawer unit  3  and toner boxes  11 , described later, that are mounted in the drawer unit  3  will be referenced based on their positions when mounted in the main casing  2 , unless otherwise specified. Note that the front cover  4  has been omitted from  FIG. 2 . 
     As shown in  FIG. 1 , four photosensitive drums  5  are rotatably retained in the drawer unit  3 . The photosensitive drums  5  are capable of rotating about axes extending in the left-to-right direction. The four photosensitive drums  5  are respectively provided for the colors black, yellow, magenta, and cyan. The photosensitive drums  5  are arranged parallel to each other at regular intervals in the front-to-rear direction in the order black, yellow, magenta, and cyan. 
     Four chargers  6  are also retained in the drawer unit  3 . The chargers  6  have a one-on-one correspondence to the four photosensitive drums  5  and are disposed at positions diagonally upward and rearward from the corresponding photosensitive drums  5 . Each charger  6  is a Scorotron charger that includes a discharge wire and grid, for example. 
     Four developing units  7  are also retained in the drawer unit  3 . The four developing units  7  also have a one-on-one correspondence to the four photosensitive drums  5  and are disposed diagonally above and forward of the corresponding photosensitive drums  5 . Each developing unit  7  includes a developing unit frame  8 , and a developing roller  9  accommodated in the developing unit frame  8 . The developing roller  9  is disposed in contact with the photosensitive drum  5  and is capable of rotating about an axis extending in the left-to-right direction. 
     Four cleaners  10  are also retained in the drawer unit  3 . The cleaners  10  are provided with a one-on-one correspondence to the four photosensitive drums  5  and are positioned rearward of the corresponding photosensitive drums  5 . The cleaners  10  function to move paper dust and the like deposited on the surfaces of the photosensitive drums  5 . 
     A space  12  is provided in the drawer unit  3  above each developing unit  7 . A toner box  11  that accommodates toner is mounted in the space  12  formed above each developing unit  7 . Sufficient room above the drawer unit  3  for mounting the toner boxes  11  in the spaces  12  is acquired by pulling the drawer unit  3  outward to the withdrawn position. The toner boxes  11  supply toner to the corresponding developing units  7 . 
     An exposure device  13  is provided in the main casing  2  above the drawer unit  3 . The exposure device  13  irradiates four laser beams corresponding to the four colors used by the color printer  1 . 
     As each photosensitive drum  5  rotates, the corresponding charger  6  applies a uniform charge to the surface of the photosensitive drum  5  through corona discharge. Subsequently, the exposure device  13  irradiates laser beams for selectively exposing the surfaces of the photosensitive drums  5 . This exposure selectively removes charge from the surfaces of the photosensitive drums  5 , forming electrostatic latent images thereon. When the electrostatic latent image carried on the surface of a photosensitive drum  5  rotates to a position opposite the corresponding developing roller  9 , the developing roller  9  supplies toner to the latent image, developing the image into a toner image. That is, the developing roller  9  executes a developing operation. 
     Here, four LED arrays may be provided for the four photosensitive drums  5  in place of the exposure device  13 . 
     A paper cassette  14  accommodating sheets of a paper P is disposed in a bottom section of the main casing  2 . The paper P accommodated in the paper cassette  14  is conveyed onto a conveying belt  15  by various rollers. The conveying belt  15  confronts the four photosensitive drums  5  from below. Four transfer rollers  16  are disposed inside the conveying belt  15  at positions confronting each of the photosensitive drums  5  through the upper portion of the conveying belt  15 . When a sheet of paper P is conveyed onto the conveying belt  15 , the conveying belt  15  carries the sheet sequentially through positions between the conveying belt  15  and each of the photosensitive drums  5 . As the sheet passes beneath each photosensitive drum  5 , the toner image carried on the surface of the photosensitive drum  5  is transferred onto the paper P. 
     A fixing unit  17  is provided on the downstream end of the conveying belt  15  with respect to the direction that the paper P is conveyed. After toner images are transferred onto a sheet of paper P, the sheet is conveyed to the fixing unit  17 , where the toner images are fixed to the sheet by heat and pressure. After the toner images are fixed in the fixing unit  17 , various rollers discharge the sheet onto a discharge tray  18  formed on the top surface of the main casing  2 . 
     2. Drawer Unit 
     (1) Drawer Frame 
     As shown in  FIG. 3 , the drawer unit  3  has a drawer frame  21 . The drawer frame  21  is configured of a pair of side plates  22  and  23  arranged parallel to each other and separated in the left-to-right direction, a front beam  24  bridging the front ends of the side plates  22  and  23 , and a rear beam  25  bridging the rear ends of the side plates  22  and  23 . The overall structure of the drawer frame  21  is square-shaped in a plan view. 
     The respective groups of four photosensitive drums  5 , chargers  6 , developing units  7 , and cleaners  10  (see  FIG. 1 ) are all held together between the side plates  22  and  23  on the left and right sides thereof. The spaces  12  in which the toner boxes  11  are mounted are formed between the side plates  22  and  23  above the corresponding developing units  7 . In other words, the side plates  22  and  23  hold the photosensitive drums  5 , chargers  6 , developing units  7 , and cleaners  10 . Further, the side plates  22  and  23  oppose each other in the left-to-right direction, with gaps formed therebetween to allocate the spaces  12  in which the toner boxes  11  are mounted. 
     (2) Opening Members 
     As shown in  FIGS. 4A and 5A , four opening members  26  are disposed on the right side surface (outer surface) of the right side plate  23  at positions corresponding to the spaces  12 . Each opening member  26  includes a rotating support part  27  configured of a shaft extending in the left-to-right direction, and a lever part  28  coupled to the rotating support part  27 . 
     The rotating support part  27  is rotatably supported in the side plate  23 . 
     The lever part  28  is integrally configured of a coupling part  29  having a circular shape in a side view, and an arm part  30  that has a narrow elongated plate shape extending forward from the coupling part  29 , for example. The lever part  28  is coupled to the rotating support part  27  by inserting the rotating support part  27  into the coupling part  29  so that the rotating support part  27  cannot rotate relative to the coupling part  29 . 
     By pivoting the opening member  26  with the rotating support part  27  serving as the fulcrum, the opening member  26  can be shifted between a first position in which the arm part  30  of the lever part  28  slopes diagonally forward and downward, as shown in  FIG. 5A , and a second position in which the arm part  30  extends horizontally, as shown in  FIG. 4A . Hence, the direction in which the opening member  26  moves from the first position to the second position (i.e., the rotating direction) is clockwise when viewing the opening member  26  from the right side. 
     A first cover  31  is disposed above the opening members  26  on the right side surface of the right side plate  23  for covering all four opening members  26  in the second position. In a cross-sectional view, the first cover  31  is L-shaped, extending rightward, then bending and extending downward. As shown in  FIG. 4A , most of the upper half of the coupling part  29  and most of the entire arm part  30  constituting the lever part  28  are accommodated inside the first cover  31  (between the first cover  31  and the side plate  23 ) when the opening member  26  is in the second position. The first cover  31  is integrally formed with the side plate  23 . 
     (3) Closing Members 
     As shown in  FIGS. 4B and 5B , four closing members  32  are disposed on the left side surface (outer surface) of the left side plate  22  at positions corresponding to the spaces  12 . Each closing member  32  includes a rotating support part  33  configured of a shaft extending in the left-to-right direction, and a lever part  34  coupled to the rotating support part  33 . 
     The rotating support part  33  is rotatably supported in the side plate  22 . 
     The lever part  34  is integrally configured of a coupling part  35  having a circular shape in a side view, and an arm part  36  that has a narrow elongated plate shape extending forward from the coupling part  35 , for example. The lever part  34  is coupled to the rotating support part  33  by inserting the rotating support part  33  into the coupling part  35  so that the rotating support part  33  cannot rotate relative to the coupling part  35 . 
     By pivoting the closing member  32  with the rotating support part  33  serving as the fulcrum, the closing member  32  can be shifted between a third position in which the arm part  36  of the lever part  34  slopes diagonally forward and downward, as shown in  FIG. 4B , and a fourth position in which the arm part  36  extends horizontally, as shown in  FIG. 5B . Hence, the direction in which the closing member  32  moves from the third position to the fourth position (i.e., the rotating direction) is opposite the direction in which the opening member  26  moves from the first position to the second position, i.e., counterclockwise when viewing the closing member  32  from the left side. 
     A second cover  37  is disposed above the closing members  32  on the left side surface of the left side plate  22  for covering all four closing members  32  in the fourth position. In a cross-sectional view, the second cover  37  is L-shaped, extending leftward, then bending and extending downward. As shown in  FIG. 5B , most of the upper half of the coupling part  35  and most of the entire arm part  36  constituting the lever part  34  are accommodated inside the second cover  37  (between the second cover  37  and the side plate  22 ) when the closing member  32  is in the fourth position. The second cover  37  is integrally formed with the side plate  22 . 
     (4) Lever Interlocking Mechanism 
     As shown in  FIG. 6 , the rotating support part  33  of the closing member  32  penetrates the left side plate  22  (see  FIG. 3 ) and extends between the side plates  22  and  23  in the left-to-right direction. As shown in  FIG. 7 , a left pinion gear  38  is mounted on the left end of the rotating support part  33  to the right (inside) of the side plate  22  and is not capable of rotating relative to the rotating support part  33 . A small gap is formed between the left pinion gear  38  and side plate  22  so that rotation of the left pinion gear  38  is not hindered. Similarly, a right pinion gear  39  is mounted on the right end of the rotating support part  33  to the left (inside) of the side plate  23  and is not capable of rotating relative to the rotating support part  33 . The right pinion gear  39  is longer than the left pinion gear  38  in the left-to-right direction. A small gap is formed between the right pinion gear  39  and side plate  23  so that rotation of the right pinion gear  39  is not hindered. 
     The rotating support part  27  of each opening member  26  penetrates the right side plate  23  (see  FIG. 3 ). As shown in  FIG. 6 , the left end of the rotating support part  27  opposes the right pinion gear  39  from the upper rear side. A pinion gear  40  is mounted on the left end of the rotating support part  27  and is incapable of rotating relative to the rotating support part  27 . The pinion gear  40  is engaged with the right pinion gear  39 . 
     As shown in  FIGS. 4A ,  4 B, and  6 , the positions of the opening members  26  and closing members  32  mounted on the drawer frame  21  are adjusted so that the closing members  32  are in their third positions when the opening members  26  are in their second positions. 
     When a closing member  32  is moved from the third position to the fourth position, the corresponding rotating support part  33 , left pinion gear  38 , and right pinion gear  39  rotate counterclockwise when viewed from the left. The rotation of the right pinion gear  39  is transferred to the pinion gear  40 , rotating the pinion gear  40  and the rotating support part  27  clockwise in a left side view. Through the rotation of the rotating support part  27 , the opening member  26  is moved from the second position to the first position. 
     Similarly, when an opening member  26  is moved from the first position to the second position, the rotating support part  27  and pinion gear  40  rotate counterclockwise in a left side view. The rotation of the pinion gear  40  is transferred to the right pinion gear  39 , rotating the right pinion gear  39 , rotating support part  33 , and left pinion gear  38  clockwise in a left side view. The rotation of the rotating support part  33  moves the closing member  32  from the fourth position to the third position. 
     Accordingly, the opening member  26  moves from the second position to the first position in association with movement of the closing member  32  from the third position to the fourth position. Similarly, the closing member  32  moves from the fourth position to the third position in association with movement of the opening member  26  from the first position to the second position. 
     (5) Developing Unit Frame 
     As shown in  FIGS. 3 and 7 , the developing unit frames  8  are disposed at regular intervals in the front-to-rear direction and span between the side plates  22  and  23 . The developing unit frames  8  define the spaces  12  provided for mounting the toner boxes  11 . 
     As shown in  FIG. 8 , a developing chamber  41  is formed in each developing unit frame  8  for accommodating the developing roller  9 . The side of the developing chamber  41  opposing the corresponding photosensitive drum  5  is open. The developing roller  9  is disposed in the bottom of the developing chamber  41  near the open side thereof. 
     The developing unit frame  8  also has a plate-shaped partitioning wall  42  positioned between the developing chamber  41  and the space  12 . The partitioning wall  42  curves in an arc shape with its convex side facing the developing chamber  41 . The partitioning wall  42  partitions the interior of the developing unit frame  8  into the developing chamber  41  and the space  12  formed above the developing chamber  41 . As shown in  FIG. 3 , three rectangular openings  43  are formed in the circumferential center of the partitioning wall  42 . The rectangular openings  43  are formed at positions opposing three main-body-side communication through-holes  58  (described later with reference to  FIG. 12 ) formed in the toner box  11  when the toner box  11  is mounted in the space  12 . 
     (6) Shutter Drive Member 
     As shown in  FIGS. 7 and 8 , a shutter drive member  44  is movably disposed above the partitioning wall  42  for driving a shutter  73  described later. 
     As shown in  FIG. 9 , the shutter drive member  44  includes a main body part  111  (resin plate) formed of a resin, and a reinforcing plate  112  (metal plate) formed of a thin metal plate that is affixed to the main body part  111 . 
     As shown in  FIG. 10 , the main body part  111  is integrally configured of four plate-shaped parts  441 ,  442 ,  443 , and  444  arranged at intervals in the left-to-right direction; and a coupling part  445  having a bar shape that extends in the left-to-right direction for coupling the front edges of the plate-shaped parts  441 - 444 . Each of the plate-shaped parts  441 - 444  is formed of a plate curved in an arc, with the convex side facing the developing chamber  41 . The curved arc of the plate-shaped part substantially conforms to the shape of the partitioning wall  42 . 
     The shutter drive member  44  is provided above the partitioning wall  42  of each developing unit frame  8 . For simplification, only the shutter drive member  44  disposed above one partitioning wall  42  is shown in  FIGS. 7 and 8 . 
     As shown in  FIG. 7 , the plate-shaped part  444  on the left end confronts the top of the left pinion gear  38 . A left rack gear  46  is formed on the bottom surface of the plate-shaped part  444  (the surface opposing the left pinion gear  38 ) for engaging with the left pinion gear  38 . 
     As shown in  FIG. 7 , the plate-shaped part  441  on the right end confronts the top of the right pinion gear  39 . More specifically, the pinion gear  40  is engaged in the right end portion of the right pinion gear  39 , and the right pinion gear  39  extends farther leftward than the pinion gear  40 , as shown in  FIG. 6 . The plate-shaped part  441  opposes from above the portion of the right pinion gear  39  extending leftward from the pinion gear  40 . A right rack gear  45  is formed on the bottom surface of the plate-shaped part  441  opposing the right pinion gear  39  and is engaged with the right pinion gear  39 . 
     When a user operates one of the opening members  26  or closing members  32  to rotate the respective left pinion gear  38  or right pinion gear  39 , the rotations of the left pinion gear  38  and right pinion gear  39  are transferred to the left rack gear  46  and right rack gear  45 . As a result, the shutter drive member  44  moves between a position opposing the rectangular openings  43  (the position shown in  FIG. 7 ) and a position forward of the rectangular openings  43 . More specifically, when one of the opening members  26  is moved from the first position to the second position, the corresponding shutter drive member  44  moves forward from the position opposing the rectangular openings  43  along with the rotations of the left pinion gear  38  and right pinion gear  39  and is placed in a position not opposing the rectangular openings  43 . 
     From this state, if the closing member  32  is moved from the third position to the fourth position, the shutter drive member  44  moves rearward along with the rotations of the left pinion gear  38  and right pinion gear  39  from the position not opposing the rectangular openings  43  to the position opposing the rectangular openings  43 . 
     Shutter drive protrusions  47  are formed on the top surfaces of the plate-shaped parts  441 - 444  at positions corresponding to shutter drive openings  88  described later. 
     The reinforcing plate  112  covers the entire region of the main body part  111 , excluding the right edge of the plate-shaped part  441  and the left edge of the plate-shaped part  444 . Insertion through-holes  113  are formed in the reinforcing plate  112  at positions overlapping the shutter drive protrusions  47 . Each of the shutter drive protrusions  47  is inserted through a corresponding insertion through-hole  113  and protrudes upward from the reinforcing plate  112 . 
     By overlaying the reinforcing plate  112  on the main body part  111  in this way, it is possible to ensure sufficient rigidity of the shutter drive member  44  so that the shutter drive member  44  can move the shutter  73  described later with reference to  FIG. 12  with sufficient stability. 
     Further, by inserting the shutter drive protrusions  47  through the insertion through-holes  113  in the reinforcing plate  112 , the position of the reinforcing plate  112  relative to the main body part  111  remains fixed with the shutter drive protrusions  47  protruding from the reinforcing plate  112 . 
     Since the three rectangular openings  43  formed in the partitioning wall  42  are opened and closed by the reinforcing plate  112  moving in association with the shutter drive member  44 , the reinforcing plate  112  functions as a developing-device-side shutter for opening and closing the rectangular openings  43 . 
     3. Toner Box 
     (1) Main Body 
     As shown in  FIGS. 11 and 12 , the toner box  11  includes a main body  51  for accommodating toner. The main body  51  is formed of a resin material in a substantially hollowed-out semicircular column shape and is elongated in the left-to-right direction. More specifically, the main body  51  has an internal space for accommodating toner that is formed by: a rectangular top surface  52  elongated in the left-to-right direction; an arcing surface  53  that is connected to the front edge of the top surface  52  and that has a substantially semicircular arc shape in a cross section with the convex side facing downward; a fixing surface  54  extending parallel to the top surface  52  and protruding rearward from the rear edge of the arcing surface  53 ; a rear surface  55  bridging the rear edge of the top surface  52  and the rear edge of the fixing surface  54 ; a left side surface  56  bridging the respective left edges of the top surface  52 , arcing surface  53 , fixing surface  54  and rear surface  55 ; and a right side surface  57  bridging the respective right edges of the top surface  52 , arcing surface  53 , fixing surface  54 , and rear surface  55 . 
     As shown in  FIG. 12 , three main-body-side communication through-holes  58  are formed in the arcing surface  53  of the main body  51  at positions slightly rearward of the lowest end thereof. The main-body-side communication through-holes  58  are rectangular in shape and elongated in the left-to-right direction and are spaced at intervals in the left-to-right direction. The main-body-side communication through-holes  58  provide communication between the interior and exterior of the main body  51 . 
     Narrow slit-shaped relief grooves (escape grooves)  59  are also formed in the arcing surface  53 . The relief grooves  59  extend in the peripheral direction of the arcing surface  53  and are formed one on each of the left and right sides of each main-body-side communication through-hole  58 . 
     As shown in  FIGS. 16A and 16B , a plurality of positioning protrusions  60  is formed on the front edge of the arcing surface  53 . The positioning protrusions  60  are spaced at intervals in the left-to-right direction. As shown in  FIGS. 17A and 17B , each positioning protrusion  60  has a hook shape, extending forward, then bending and extending upward. 
     As shown in  FIG. 12 , recessions  61  and  62  are respectively formed in the left and right ends of the main body  51  in the lowest portion of the arcing surface  53 . The recession  61  on the left side is open in the left side surface  56  of the main body  51 , while the recession  62  on the right side is open in the right side surface  57  of the main body  51 . 
     The toner box  11  further includes toner seals  71  affixed to the arcing surface  53  of the main body  51 , a shutter cover  72  disposed so as to cover the arcing surface  53 , and a shutter  73  disposed between the arcing surface  53  and shutter cover  72 . 
     (2) Toner Seals 
     As shown in  FIG. 12 , one of the toner seals  71  is provided for each main-body-side communication through-hole  58 . The toner seal  71  has a sheet-like form with an opening  74 . The area of the opening  74  is greater than the area of the corresponding main-body-side communication through-hole  58 . Thus, the toner seals  71  are fixed to the arcing surface  53  of the main body  51  so that the openings  74  are aligned and in communication with the corresponding main-body-side communication through-holes  58  and, hence, encircle the main-body-side communication through-holes  58 . 
     As shown in  FIG. 13 , each toner seal  71  has a laminated structure (two-layer structure) configured of an elastic layer  75 , and a mesh layer  76  disposed on one surface of the elastic layer  75 . 
     The elastic layer  75  is formed of a resilient foam material, such as the product PORON® (trade name, registered trade mark) manufactured by Rogers Inoac Corporation. The elastic layer  75  is formed much thicker than the mesh layer  76 . A fixing surface  77  constituting the surface of the elastic layer  75  opposite the mesh layer  76  is fixed to the arcing surface  53  of the main body  51  with adhesive as shown in  FIG. 22 . 
       FIG. 14  shows a surface portion of the mesh layer  76 , while  FIG. 15  shows a cross-sectional portion of the same. As shown in the drawings, the mesh layer  76  includes warp fibers  78  and weft fibers  79  interlaced in a plain weave (an alternating over and under pattern). The gaps between adjacent warp fibers  78  and the gaps between adjacent weft fibers  79  are greater than or equal to 15 μm and smaller than or equal to 50 μm and preferably greater than or equal to 25 μm and smaller than or equal to 40 μm. 
     As shown in  FIGS. 16A and 16B , the portion of the toner seal  71  disposed forward of the main-body-side communication through-hole  58  (on the front end side of the arcing surface  53 ) has a width D 1  along the circumferential direction of the arcing surface  53 . The portion of the toner seal  71  disposed rearward of the main-body-side communication through-hole  58  (on the rear end side of the arcing surface  53 ) has a width D 2  along the circumferential direction of the arcing surface  53 . The width D 1  is greater than the width D 2 . 
     (3) Shutter Cover 
     The shutter cover  72  is curved to conform to the arcing surface  53  of the main body  51 . The shutter cover  72  is formed of a resin film that is thinner than the thickness of the shutter  73 . More specifically, the shutter cover  72  has a thickness greater than or equal to 0.03 mm and smaller than or equal to 0.3 mm, and preferably greater than or equal to 0.08 mm and smaller than or equal to 0.2 mm. The left-to-right dimension of the shutter cover  72  is approximately equal to the same dimension of the arcing surface  53 , so that the shutter cover  72  covers the arcing surface  53  across substantially the entire width in the left-to-right direction. 
     As shown in  FIG. 12 , a plurality of positioning openings  80  is formed in the front edge portion of the shutter cover  72  at intervals in the left-to-right direction. As shown in  FIGS. 17A and 17B , the positioning protrusions  60  formed on the arcing surface  53  of the main body  51  are engaged in the positioning openings  80 . More specifically, the positioning openings  80  are formed in the front edge portion of the shutter cover  72  at positions in the left-to-right direction corresponding to the positioning protrusions  60  and of a sufficient size for inserting the positioning protrusions  60 . After the positioning protrusions  60  are inserted into the corresponding positioning openings  80 , the top edges of the positioning openings  80  engage the positioning protrusions  60 . 
     The rear edge part of the shutter cover  72  is folded back to conform to the fixing surface  54  of the main body  51 . A plurality of screw insertion through-holes  81  are formed in this rear edge portion of the shutter cover  72  at intervals in the left-to-right direction, as shown in  FIG. 12 . As shown in  FIGS. 16A and 16B , the shutter cover  72  is attached to the main body  51  by engaging the positioning protrusions  60  in the respective positioning openings  80 , and by inserting screws  82  through all of the screw insertion through-holes  81  and screwing the tips of the screws  82  into the fixing surface  54  of the main body  51 . 
     As shown in  FIGS. 11 and 12 , cover-side communication through-holes  83  are formed in the shutter cover  72  at positions corresponding to the toner seals  71 . Each of the cover-side communication through-holes  83  has a rectangular shape and is elongated in the left-to-right direction. Further, the cover-side communication through-hole  83  has a greater open area than the area of the main-body-side communication through-hole  58  so as to expose the main-body-side communication through-hole  58  in its entirety. The size of each cover-side communication through-hole  83  is such that when the shutter  73  is in an open position (described later), as shown in  FIG. 16A , a gap is formed between the rear edge of the corresponding toner seal  71  and the rear edge of the cover-side communication through-hole  83 , gaps are formed between the left and right edges of the corresponding toner seal  71  and the left and right edges of the cover-side communication through-hole  83 , and the front edge of the corresponding toner seal  71  is interposed between the shutter cover  72  and the arcing surface  53  of the main body  51 . Consequently, when the shutter  73  is in the open position, the shutter cover  72  does not cover the rear edge and both left and right edges of the toner seal  71 , allowing these edges to protrude outward through the cover-side communication through-hole  83 . 
     As shown in  FIG. 12 , slanted parts  84  having portions angled relative to the circumferential direction of the shutter cover  72  are formed on the shutter cover  72  in both rear side corners of each cover-side communication through-hole  83  as part of the peripheral edge of the cover-side communication through-hole  83 . With the slanted parts  84 , the left-to-right width of each cover-side communication through-hole  83  grows narrower toward the rear edge of the shutter cover  72 . 
     The part of each slanted part  84  forming a peripheral edge portion of each cover-side communication through-hole  83  may extend in a straight line or follow a gentle curve, provided that the portion is slanted relative to the circumferential direction of the shutter cover  72 . These portions of the slanted parts  84  are shaped in a gentle curve in the example of  FIG. 12 . 
     Guide slits  85  elongated in the front-to-rear direction (circumferential direction of the shutter cover  72 ) are formed in the shutter cover  72  at positions corresponding to the relief grooves  59  formed in the main body  51 . The guide slits  85  have a front-to-rear length that is greater than or equal to the front-to-rear length of the relief grooves  59 . The left-to-right width of the guide slits  85  is also greater than or equal to the left-to-right width of the relief grooves  59 . Each guide slit  85  confronts the corresponding relief groove  59  in its entirety. 
     Locking member insertion through-holes  86  and  87  are also formed in the shutter cover  72  at positions corresponding to the recessions  61  and  62  formed in the main body  51 . 
     (4) Shutter 
     As shown in  FIG. 12 , the shutter  73  curves along the arcing surface  53  of the main body  51 . The shutter  73  is formed of a resin film having a width in the left-to-right direction slightly smaller than the left-to-right width of the shutter cover  72 . The dimension of the shutter  73  along the circumferential direction of the arcing surface  53  is greater than the same dimension of the toner seals  71  and is set such that the shutter  73  does not contact the fixing surface  54  and the positioning protrusions  60  when moving between an open position and a closed position described later. 
     The shutter  73  may not be formed of a resin film. However, the shutter  73  is preferably made from a film-shaped material that has a thickness smaller than or equal to 250 micrometers (μm) and that has a sufficient degree of flexibility or pliability so that the film-shaped material can be rolled up. 
     Two shutter drive openings  88  separated by a prescribed interval in the circumferential direction of the shutter  73  are formed in the shutter  73  at positions opposing each relief groove  59  in the main body  51 . The distance between the two shutter drive openings  88  at each position is set such that all shutter drive openings  88  confront a corresponding relief groove  59  and confront and communicate with a corresponding guide slit  85  formed in the shutter cover  72 , regardless of whether the shutter  73  is in the open position or the closed position. 
     V-shaped notches  89  are formed in the rear edge of the shutter  73  (the edge of the shatter  73  on the rear edge side of the arcing surface  53 ) at positions in the left-to-right direction corresponding to the main-body-side communication through-holes  58  formed in the main body  51 . The V-shaped notches  89  open toward the rear edge side of the arcing surface  53 . Forming the V-shaped notches  89  in this way, produces sloped parts (slanted parts)  90  in the rear edge of the shutter  73  that are angled relative to the circumferential direction of the shutter  73 . 
     Locking openings  91  and  92  are also formed in the shutter  73  at positions opposing the recessions  61  and  62  formed in the main body  51  when the shutter  73  is in the closed position. Hence, when the shutter  73  is in the closed position, the locking openings  91  and  92  confront the recessions  61  and  62 , respectively, and also confront the respective locking member insertion through-holes  86  and  87  formed in the shutter cover  72 . Accordingly, the recession  61  and locking member insertion through-hole  86  are in communication via the locking opening  91 , and the recession  62  and locking member insertion through-hole  87  are in communication via the locking opening  92 . 
     The shutter  73  is interposed between the arcing surface  53  of the main body  51  and the shutter cover  72 . While held between the arcing surface  53  and shutter cover  72 , the shutter  73  can move between an open position and a closed position described next. 
     (5) Open Position of the Shutter 
     In the open position shown in  FIG. 16A , the shutter  73  is positioned on the front side of the cover-side communication through-holes  83  formed in the shutter cover  72 . More specifically, when the shutter  73  is in the open position, the rear edge of the shutter  73  is positioned farther forward than the front edges of the cover-side communication through-holes  83 , and the rear edge portion of the shutter  73  is interposed between the front edge portion of the toner seal  71  and the shutter cover  72 . Therefore, each main-body-side communication through-hole  58  formed in the main body  51  and the opening  74  formed in the corresponding toner seal  71  are made open, while being in communication with each other. This provides communication between the interior and exterior of the main body  51 . Further, since the rear edge and both left and right edges of the toner seal  71  are exposed, these edges protrude outward through the cover-side communication through-hole  83 . 
     (6) Closed Position of the Shutter 
     In the closed position shown in  FIG. 16B , the shutter  73  is positioned farther rearward than the open position. When the shutter  73  is in the closed position, the rear edge of the shutter  73  is positioned slightly rearward than the rear edges of the cover-side communication through-holes  83 . Accordingly, the shutter  73  opposes nearly the entire area of the cover-side communication through-holes  83 , excluding the regions opposite the V-shaped notches  89  formed in the shutter  73 , and contacts the shutter cover  72  in the peripheral portions of the cover-side communication through-holes  83 . The toner seals  71  are entirely interposed between the shutter  73  and the arcing surface  53  of the main body  51 . As a result, the shutter  73  covers the main-body-side communication through-holes  58  formed in the main body  51  and the openings  74  formed in the toner seals  71  in their entirety, blocking communication between the interior and exterior of the main body  51 . 
     4. Mounting the Toner Box 
     Each toner box  11  is mounted in or removed from the corresponding space  12  formed above the partitioning wall  42  of the developing unit frame  8  (see  FIG. 7 ) when the corresponding shutter  73  is in the closed position. 
     When a toner box  11  is not mounted in the corresponding space  12 , the opening member  26  is in the first position shown in  FIG. 5A  and the closing member  32  is in the fourth position shown in  FIG. 5B . The corresponding shutter drive member  44  above the partitioning wall  42  is positioned opposite the rectangular openings  43  formed in the partitioning wall  42 , as shown in  FIGS. 7 and 8 . 
     With the drawer unit  3  (drawer frame  21 ) pulled out of the main casing  2  to the withdrawn position (see  FIG. 1 ), the toner box  11  is mounted into the corresponding space  12  from above. At this time, the shutter drive protrusions  47  positioned closer to the front side among the pairs of shutter drive protrusions  47  formed in the shutter drive member  44  protrude upward along a substantially vertical direction, while the shutter drive protrusions  47  positioned closer to the rear protrude in a direction angled upward and forward, as shown in  FIG. 17B . When the toner box  11  is mounted in the space  12 , each of the shutter drive protrusions  47  engages in a corresponding shutter drive opening  88  through the corresponding guide slit  85 . 
     While the drawer unit  3  remains in the withdrawn position, an operator next moves the opening member  26  from the first position shown in  FIG. 5A  to the second position shown in  FIG. 4A , causing the shutter drive member  44  to move from a position confronting the rectangular openings  43  to a position not confronting the rectangular openings  43  (see  FIG. 17A ). In association with the movement of the shutter drive member  44 , the shutter  73  moves forward from the closed position to the open position. 
     As shown in  FIG. 8 , annular frame seals  93  are disposed on top of the partitioning wall  42  at positions corresponding to each of the toner seals  71 . That is, the annular frame seals  93  are disposed on a surface of the partitioning wall  42  confronting the corresponding space  12  at positions corresponding to each of the toner seals  71 . The annular frame seals  93  surround the periphery or perimeter of each rectangular opening  43 . When the shutter  73  is in the open position, the rear edge and both left and right edges of each toner seal  71  protrudes outward through the corresponding cover-side communication through-hole  83 . The protruding portions of the toner seal  71  directly press against the corresponding frame seal  93 , and portions of the frame seal  93  that do not contact the toner seal  71  contact the shutter cover  72 . Therefore, the opening  74  formed in each toner seal  71  is in communication with the corresponding rectangular opening  43  through the opening region in the corresponding frame seal  93 , while the toner seal  71  and frame seal  93  seal any gaps formed between the partitioning wall  42  and shutter cover  72 . 
     After all toner boxes  11  have been mounted in the corresponding spaces  12 , all opening members  26  have been shifted from their first positions to their second positions, and the shutters  73  of all toner boxes  11  are in their open positions, the toner boxes  11  supply toner to all corresponding developing units  7 . Subsequently, the operator pushes the drawer unit  3  to the accommodated position within the main casing  2  and closes the front cover  4  (see  FIG. 1 ). At this time, the user can begin performing image-forming operations with the color printer  1 . 
     In order to remove a toner box  11  from the drawer unit  3 , the operator opens the front cover  4  and pulls the drawer unit  3  outward from the accommodated position to the withdrawn position. Next, the operator shifts the closing member  32  for the desired toner box  11  from the third position shown in  FIG. 4B  to the fourth position shown in  FIG. 5B . This movement of the closing member  32  moves the shutter drive member  44  from a position not confronting the rectangular openings  43  to a position confronting the rectangular openings  43  (see  FIG. 17B ). In association with the movement of the shutter drive member  44 , the shutter  73  moves rearward from the open position to the closed position. 
     Next, the operator removes the toner box  11  from the space  12 . Since the shutter  73  is in the closed position at this time, there is no risk of toner spilling out of the main body  51  when the toner box  11  is removed. 
     5. Locking Mechanism 
     Since the shutter drive protrusions  47  are not engaged in the shutter drive openings  88  when the toner box  11  has been removed from the drawer unit  3 , the shutter  73  can move freely relative to the main body  51  and shutter cover  72 . Therefore, if the toner box  11  were jolted, shaken, or the like, the shutter  73  could move out of the closed position. 
     In order to fix the shutter  73  in the closed position while the toner box  11  is removed from the drawer unit  3 , the toner box  11  in the embodiment has a locking mechanism  101  provided in each of the recessions  61  and  62 , as shown in  FIGS. 18A and 18B . Since the locking mechanism  101  disposed in the recession  61  and the locking mechanism  101  disposed in the recession  62  have the same structure, except in mirror image, the locking mechanism  101  disposed in the recession  61  will be used below for a collective description of the locking mechanisms  101 . 
     As shown in  FIG. 19 , the locking mechanism  101  includes an arm  102 , and a locking protrusion  103  attached to the arm  102 . 
     The arm  102  is configured of a flexible thin plate, such as a leaf spring. The arm  102  has the shape of a crank. That is, beginning from one end, the arm  102  extends downward within the recession  61 , then bends and extends leftward, and finally bends and extends downward. More specifically, as shown in  FIGS. 18A and 18B , the arm  102  is integrally formed of a fixing part  104  extending downward within the recession  61 , a holding part  105  extending leftward from the bottom edge of the fixing part  104 , and a contact part  106  extending downward from the left edge of the holding part  105 . The fixing part  104  is fixed to the leftward-facing surface of the main body  51  inside the recession  61  by a screw  107 . 
     As shown in  FIG. 19 , the locking protrusion  103  has a flattened square pillar shape and is fixed to the bottom surface of the holding part  105 . When the shutter  73  is in the closed position, the locking protrusion  103  on the bottom surface of the holding part  105  is disposed in a position opposing the locking opening  91  formed in the shutter  73 . 
     Accordingly, when the toner box  11  has been removed from the drawer unit  3 , the locking protrusions  103  of both locking mechanisms  101  are respectively inserted into the locking openings  91  and  92  formed in the shutter  73 , as shown in  FIGS. 18A and 20A , thereby preventing the shutter  73  from moving out of the closed position. Accordingly, the locking mechanisms  101  prevent the shutter  73  from moving out of the closed position while the toner box  11  has been removed from the drawer unit  3 . 
     When the toner box  11  is mounted in a corresponding space  12  provided in the drawer unit  3 , the bottom edge of the contact part  106  contacts the top surface of the shutter drive member  44  (the top surface of the plate-shaped part  441  or  444 ) during the mounting operation, as shown in  FIGS. 18B and 20B . Thus, as the toner box  11  is moved farther in the mounting direction, the force of resistance received from the shutter drive member  44  causes the holding part  105  of the arm  102  to deform, bending so that the left end of the holding part  105  rises upward. Consequently, the locking protrusions  103  are extracted from the locking openings  91  and  92 . At this time, the shutter  73  can move freely relative to the main body  51  and shutter cover  72  and can move together with the shutter drive member  44 . 
     6. Operations 
     (1) As described above, the toner box  11  is provided with a main body  51  for accommodating toner. The main-body-side communication through-holes  58  are formed in the main body  51  for allowing communication between the interior and exterior of the same. The shutter  73  is provided for opening and closing the main-body-side communication through-holes  58 . That is, the shutter  73  is capable of moving between an open position in which the shutter  73  does not block the main-body-side communication through-holes  58  and a closed position in which the shutter  73  blocks the main-body-side communication through-holes  58 . 
     Since the shutter  73  is formed of a relatively thin film, rather than a relatively thick product, such as those formed by molding or metalworking, any toner present in the main-body-side communication through-holes  58  does not come to rest on the edge of the shutter  73  when the shutter  73  is moved from the open position to the closed position. Hence, after the toner box  11  has been removed from the developing unit  7 , the configuration of the shutter  73  prevents toner from spilling out of the toner box  11  (off the edge of the shutter  73 ), thereby preventing toner from soiling the inside and outside of the main casing  2 . 
     More specifically, when the toner box  11  is mounted in the developing unit  7 , the toner seal  71  on the toner box  11  side and the annular frame seal  93  on the developing unit  7  side closely contact with each other to form a seal therebetween. When the shutter  73  is moved from the open position to the closed position, an edge of the shutter  73  enters between the toner seal  71  and the annular frame seal  93 . At that time, toner rest on the surfaces of the shutter  73  is scraped off by the toner seal  71  and the annular frame seal  93  because the shutter  73  is formed of a thin film shape as shown in  FIG. 21A . So, toner does not enter between the toner seal  71  and the annular frame seal  93 . This prevents toner from dropping off the shutter  73  of the toner box  11  when the toner box  11  is detached from the annular frame seal  93  of the developing unit  7 . On the other hand, now assume that the shutter  73  were formed of a relatively thick product, such as a molded resin or a metal plate, as indicated by a comparative shutter  173  shown in  FIG. 21B . In such a case, when the comparative shutter  173  enters between the toner seal  71  and the annular frame seal  93 , toner rest on the edge of the comparative shutter  173  will enter a space surrounded by the edge of the comparative shutter  173 , toner seal  71 , and annular frame seal  93 . So, toner enters between the toner seal  71  and the annular frame seal  93 . The toner will drop off the comparative shutter  173  when the toner box having the comparative shutter  173  is detached from the annular frame seal  93  of the developing unit  7 . 
     Additionally, being formed of a film, the shutter  73  is deformable for conforming to the shape of the main body  51  and can move along the surface of the main body  51  in this deformed state. Hence, only a small amount of space is required for opening and closing the shutter  73 . This allows for increased freedom in the peripheral shape of the main-body-side communication through-holes  58  and can help make the structure around the developing units  7  more compact. 
     Further, the shutter  73  contacts the toner seals  71  with general uniformity of pressure, rather than with strong pressure in specific areas. This structure ensures smooth movement of the shutter  73  and improves the close contact between the shutter  73  and toner seals  71 , thereby reliably preventing toner leakage. 
     Further, the shutter drive openings  88  are formed in the shutter  73  for engaging the shutter drive protrusions  47  provided on the developing unit  7 . When the shutter drive protrusions  47  are moved while engaged in the shutter drive openings  88 , the shutter  73  moves together with the shutter drive protrusions  47 . Hence, through a simple construction, it is possible to move the shutter  73  from the open position to the closed position. 
     It is also possible to configure the structure for moving the shutter  73  such that the shutter drive protrusions are disposed on the shutter  73  and the shutter drive openings that engage with these protrusions are formed in the developing unit  7 . However, when a toner box  11  having this structure is removed from the developing unit  7 , the operator might accidentally catch a finger on one of the shutter drive protrusions and could easily move the shutter  73  from the closed position into the open position. Since it is more difficult to catch a finger on one of the shutter drive openings  88 , forming the shutter drive openings  88  in the shutter  73  can prevent the shutter  73  from being moved from the closed position to the open position while the toner box  11  is out of the developing unit  7 . Accordingly, the structure of the embodiment can better prevent the leakage of toner from the toner box  11 . 
     (2) The shutter drive openings  88  are formed on both sides of each main-body-side communication through-hole  58  relative to a direction orthogonal to the direction in which the shutter  73  moves, i.e., both left and right sides of each main-body-side communication through-hole  58 . Accordingly, the shutter drive protrusions  47  can provide a drive force to the shutter  73  for moving the same, which force is balanced in the left-to-right direction, thereby achieving stable movement of the shutter  73 . 
     (3) Further, relief grooves  59  are formed in the main body  51  at positions corresponding to the shutter drive openings  88 . Accordingly, the tips of the shutter drive protrusions  47  inserted through the shutter drive openings  88  can be inserted into the corresponding relief grooves  59  to ensure reliable engagement between the shutter drive protrusions  47  and shutter drive openings  88 . Further, since the relief grooves  59  are elongated in the moving direction of the shutter  73 , the shutter  73  can be moved while maintaining the engaged state of the shutter drive protrusions  47  and shutter drive openings  88 . 
     (4) A plurality of the main-body-side communication through-holes  58  is formed in the main body  51  to facilitate the supply of toner from the interior of the main body  51  to the developing unit  7 , ensuring that a large quantity of toner is supplied to the developing unit  7 . 
     (5) The sloped parts  90  that are sloped at an angle to the moving direction of the shutter  73  are formed in a leading edge of the shutter  73  relative to the direction (closing direction) in which the shutter  73  moves from the open position to the closed position. Accordingly, the surface area of the shutter  73  contacting the toner seal  71  in the width direction increases gradually as the shutter  73  moves from the open position to the closed position. This configuration prevents a sudden increase in the width of the shutter  73  contacting the toner seal  71 , thereby preventing a sudden increase in resistance to the movement of the shutter  73 . As a result, the addition of the sloped parts  90  ensures motion of the shutter  73 . 
     With a comparative configuration in which the leading edge of the shutter  73  in the closing direction extends in a straight line (i.e., a structure having no sloped parts  90 ), there is a risk that this edge of the shutter  73  will catch on the toner seal  71  when the shutter  73  is moving from the open position to the closed position, hindering this movement. However, by providing the sloped parts  90  as described in the embodiment, the sloped parts  90  move diagonally to the toner seal  71  when the shutter  73  is moved from the open position to the closed position, preventing the edge of the shutter  73  from catching on the toner seal  71 . 
     (6) Further, locking protrusions  103  protrude from the main body  51  toward the shutter  73 , and locking openings  91  and  92  are formed in the shutter  73  at positions corresponding to the locking protrusions  103 . The locking protrusions  103  are engaged in the locking openings  91  and  92  when the shutter  73  is in the closed position, thereby preventing the shutter  73  from moving out of the closed position. Accordingly, this structure reliably prevents movement of the shutter  73  while the toner box  11  is detached from the developing unit  7  and can better prevent toner from leaking out of the toner box  11 . 
     (7) The shutter  73  is covered by the shutter cover  72 , which prevents the operator from directly touching the shutter  73  and moving the shutter  73  from the closed position to the open position while the toner box  11  is detached from the developing unit  7 . Accordingly, this structure can better prevent toner from leaking out of the toner box  11 . 
     (8) The guide slits  85  are formed in the shutter cover  72  at positions corresponding to the shutter drive openings  88 . Therefore, after the shutter drive protrusions  47  are inserted through the guide slits  85 , the portions of the shutter drive protrusions  47  protruding from the other side of the guide slits  85  can engage with the shutter drive openings  88 . Since the guide slits  85  extend in the moving direction of the shutter  73 , the shutter drive protrusions  47  can move within the guide slits  85  while remaining engaged with the shutter drive openings  88 . Accordingly, by providing the shutter cover  72 , the shutter  73  can be moved while maintaining the engaged state of the shutter drive protrusions  47  and shutter drive openings  88 . 
     (9) Further, the cover-side communication through-holes  83  are formed in the shutter cover  72  at positions corresponding to the main-body-side communication through-holes  58 . Hence, when the main-body-side communication through-holes  58  are open, toner can be supplied from the interior of the main body  51  to the developing unit  7  through the main-body-side communication through-holes  58  and the cover-side communication through-holes  83 . 
     (10) The area of each cover-side communication through-hole  83  is larger than the area of the corresponding main-body-side communication through-hole  58 , and thus, the main-body-side communication through-hole  58  can be exposed in its entirety in the corresponding cover-side communication through-hole  83 . Hence, this structure prevents the shutter cover  72  from hindering the supply of toner from the interior of the main body  51  to the developing unit  7 . 
     (11) Further, the slanted parts  84  formed on the shutter cover  72  have a portion that slants at an angle to the moving direction of the shutter  73  as part of the peripheral edge of the corresponding cover-side communication through-holes  83 . Consequently, the width of each cover-side communication through-hole  83  in the direction orthogonal to the moving direction of the shutter  73  grows narrower toward the downstream side of the closing direction, i.e., the direction in which the shutter  73  is moved from the open position to the closed position. Accordingly, the surface area of the shutter  73  that contacts the shutter cover  72  in the width direction gradually increases when the shutter  73  moves from the open position to the closed position, thereby preventing a sudden increase in the area of contact between the shutter  73  and shutter cover  72  and, hence, preventing a sudden increase in resistance to the movement of the shutter  73 . Therefore, this structure ensures smooth movement of the shutter  73 . 
     If the cover-side communication through-holes  83  were formed in a perfect rectangular shape without forming the slanted parts  84  on the shutter cover  72 , the leading edge of the shutter  73  relative to the closing direction could catch on the peripheral edges of the cover-side communication through-holes  83  formed in the shutter cover  72  when the shutter  73  moves from the open position to the closed position, thereby hindering movement of the shutter  73 . However, when the slanted parts  84  are formed on the shutter cover  72 , the slanted parts  84  move along a diagonal relative to the leading edge of the shutter  73  in the closing direction when the shutter  73  moves from the open position to the closed position. Hence, the slanted parts  84  can prevent the leading edge of the shutter  73  from catching on the peripheral edge of the cover-side communication through-holes  83 . 
     (12) The shutter cover  72  is formed thinner than the shutter  73 . Therefore, it is possible to provide the shutter cover  72  while still maintaining only a small gap between the main body  51  and developing unit  7 , thereby ensuring that toner is smoothly supplied from the interior of the main body  51  to the developing unit  7 . 
     (13) The shutter cover  72  is formed of a film having a thickness within a range between 0.03 and 0.3 mm, and preferably between 0.08 and 0.2 mm. By using a film of this thickness, the shutter cover  72  can be made elastically deformable. It is noted that the shutter cover  72  may not be formed of a film. 
     Since the shutter cover  72  is elastically deformable, the shutter cover  72  can deform to absorb a reaction force that the shutter  73  receives from the toner seal  71  when the shutter  73  compresses the toner seal  71  while advancing between the toner seal  71  and shutter cover  72  from the open position to the closed position. Thus, the elastically deformable shutter cover  72  allows the shutter  73  to move smoothly between the open position and closed position. Further, the shutter cover  72  can deform in order to conform to the shape of the developing unit  7  (shutter drive member  44 ). Hence, the shutter cover  72  having this structure can eliminate dead space between the toner box  11  and developing unit  7 , which is conducive to making the structure including the toner box  11  and developing unit  7  more compact and, thus, the color printer  1  more compact. 
     The shutter cover  72  can be made elastically deformable even though the shutter cover  72  is not formed of a film. For example, the shutter cover  72  can be made elastically deformable by being formed of a stainless steel plate of a thickness of 0.1 mm, for example. 
     (14) The positioning protrusions  60  formed on the main body  51  protrude from the main body  51  toward the shutter cover  72 . The positioning openings  80  are formed in the shutter cover  72  for engaging with the positioning protrusions  60 . Through the engagement between the positioning protrusions  60  and positioning openings  80 , the shutter cover  72  can be positioned relative to the main body  51 . Accordingly, the shutter cover  72  can be easily mounted on the main body  51  when assembling the toner box  11 . 
     In the shutter cover  72 , the positioning openings  80  are formed through the shutter cover  72  as through-holes. However, recessions may be formed in the shutter cover  72  instead of the through-holes so that an inlet of each recession functions as the positioning opening  80 . 
     (15) The right and left rack gears  45  and  46  are formed on the resinous plate-shaped parts  441  and  444  of the shutter drive member  44  for receiving a drive force for moving the shutter  73 . Providing the rack gears  45  and  46  on the resinous plate-shaped parts  441  and  444  simplifies formation of the rack gears  45  and  46 . By inputting a drive force into the rack gears  45  and  46 , the drive force can move the shutter drive member  44 , causing the shutter  73  to move between the open position and closed position in association with the movement of the shutter drive member  44 . 
     (16) The toner seals  71  encircle the main-body-side communication through-holes  58 . That is, the toner seals  71  surround the perimeters or peripheries of the main-body-side communication through-holes  58 . Each toner seal  71  has an elastic layer  75  provided with a fixing surface  77 , and a mesh layer  76  disposed on the side of the elastic layer  75  opposite the fixing surface  77 . The mesh layer  76  is configured to prevent the leakage of toner while allowing the passage of air so that air can escape from the main body  51  through the mesh layer  76  when the main body  51  deforms due to changes in temperature or the like. More specifically, as shown in  FIG. 22 , air comes out of the main body  51  through the main-body-side communication through-hole  58 , and passes through the mesh layer  76  in a direction along the main body  51 , before finally flowing out the outer edge of the toner seal  71 . So, air can readily escape from the toner box  11 . This can avoid an increase in the internal pressure of the main body  51  caused by deformation of the main body  51 . Thus, the integrity of seals formed by each of the toner seals  71  can be maintained, preventing toner from leaking out through gaps between the main body  51  and shutter  73 . 
     Since the shutter  73  slides over the mesh layer  76  of each toner seal  71  when moving between the open and closed positions, the shutter  73  can be moved with less torque than if the shutter  73  was sliding over the elastic layer  75  since the resistance generated by the mesh layer  76  is smaller. 
     (17) The mesh layers  76  are formed to allow air to pass in a direction along the main body  51 . Hence, air can escape out of the main body  51  through the mesh layers  76  of the toner seals  71  even though the toner seals  71  are compressed between the main body  51  and shutter  73 . Accordingly, this construction can maintain the integrity of the seals formed by the toner seals  71  while allowing air to escape from the main body  51 . 
     (18) The gaps between adjacent fibers forming the mesh layer  76  are preferably at least 15 μm and no greater than 50 μm. By setting the gaps between fibers within this range, the mesh layer  76  can form an adequate seal against toner, while allowing the passage of air. 
     The gaps between adjacent fibers forming the mesh layer  76  are more preferably at least 25 μm and no greater than 40 μm. Within this range, the mesh layer  76  can form a better seal against toner, while still allowing the smooth passage of air. 
     (19) Since the mesh layer  76  is formed in a plain weave, gaps can be maintained on both sides of the warp fibers  78  and weft fibers  79  when the toner seal  71  is compressed between the main body  51  and shutter  73 , allowing a uniform passage of air. Accordingly, air can adequately escape from the main body  51 . 
     (20) The area of the opening or space  74  surrounded or encircled by each toner seal  71  is greater than the area of the corresponding main-body-side communication through-hole  58 . Hence, the opening  74 , which is the space encircled by the toner seal  71 , exposes the corresponding main-body-side communication through-hole  58  in its entirety, thereby preventing the toner seal  71  from hindering the supply of toner from the interior of the main body  51  to the developing unit  7 . 
     (21) When the shutter  73  is in the open position, the rear edge of the shutter  73  (i.e., the leading edge of the shutter  73  in the direction that the shutter  73  moves from the open position to the closed position) is positioned farther forward than the front edges of the cover-side communication through-holes  83 . When the shutter  73  is in the closed position, the shutter  73  is covered by the portions of the shutter cover  72  encircling the cover-side communication through-holes  83 . Therefore, the shutter  73  is covered by the shutter cover  72  across its entire width in the left-to-right direction (the direction orthogonal to the closing direction), regardless of whether the shutter  73  is in the open position or the closed position. Hence, even when stress is exerted on the shutter  73  for deforming the same, the shutter cover  72  can restrain such deformation, preventing deformation of the shutter  73  and preventing potential toner leakage caused by such deformation. 
     (22) Further, gaps are formed between the rear edges of the toner seals  71  (the downstream edges in the closing direction) and the rear edges of the corresponding cover-side communication through-holes  83  (the downstream edges in the closing direction) when the shutter  73  is in the open position. In other words, the rear edges of the toner seals  71  protrude into the corresponding cover-side communication through-holes  83  and are not covered by the shutter cover  72  when the shutter  73  is in the open position. Therefore, at least the rear edges of the toner seals  71  protrude out through the cover-side communication through-holes  83  when the shutter  73  is in the open position. The toner seals  71  protruding out through the cover-side communication through-holes  83  can contact the developing unit  7  (annular frame seals  93 ) when the toner box  11  is mounted in the developing unit  7 , forming a seal between the toner box  11  and developing unit  7 . This construction can reduce the gap between the main body  51  and developing unit  7 , thereby further reducing the potential for toner leakage between these components. 
     (23) When the shutter  73  is in the open position, gaps are formed between both left and right side edges of each toner seal  71  (i.e., both edges of the toner seal  71  relative to a direction orthogonal to the closing direction) and both left and right edges of the corresponding cover-side communication through-hole  83 . Hence, in addition to its rear edge, both left and right edges of the toner seal  71  are not covered by the shutter cover  72  when the shutter  73  is in the open position, enabling these three edges of the toner seal  71  to protrude out through the corresponding cover-side communication through-hole  83 . Since this construction increases the contact surface area between the toner seals  71  and the developing unit  7  (annular frame seals  93 ) when the toner box  11  is mounted in the developing unit  7 , this structure improves the seal formed by the toner seals  71  between the toner box  11  and developing unit  7 . 
     (24) The portion of the toner seal  71  disposed forward of the main-body-side communication through-hole  58  (on the front end side of the arcing surface  53 ), that is, the portion of the toner seal  71  disposed on the upstream side of the main-body-side communication through-hole  58  in the closing direction has a width D 1  along the circumferential direction of the arcing surface  53 . The width D 1  is greater than a width D 2  along the circumferential direction of the arcing surface  53  for the portion of the toner seal  71  disposed on the rear side of the corresponding main-body-side communication through-hole  58  (the rear end side of the arcing surface  53 ), that is, for the portion of the toner seal  71  disposed on the downstream side of the main-body-side communication through-hole  58  in the closing direction. 
     Accordingly, when the front edge of the toner seal  71  is interposed between the shutter cover  72  and the main body  51 , the rear edge of the toner seal  71  can be reliably exposed from the shutter cover  72 . 
     (25) When the shutter  73  is in the open position, the rear edge of the shutter  73  (the leading edge in the closing direction) is interposed between the toner seals  71  and shutter cover  72  and, hence, this rear edge of the shutter  73  does not come off the toner seals  71  while the shutter  73  is in the open position. Accordingly, the shutter  73  can be moved smoothly from the open position to the closed position without catching on the toner seal  71 . 
     (26) The shutter drive member  44  includes the main body part  111  formed of a resin, and the reinforcing plate  112  formed of a thin metal plate. By overlaying the reinforcing plate  112  on the main body part  111 , it is possible to ensure sufficient rigidity of the shutter drive member  44  so that the shutter drive member  44  can move the shutter  73  with stability. 
     Further, the shutter drive protrusions  47  can be easily formed on the main body part  111  since the main body part  111  is formed of a resin material. 
     Further, by inserting the shutter drive protrusions  47  through the insertion through-holes  113  in the reinforcing plate  112 , the reinforcing plate  112  can be fixed in position relative to the main body part  111  with the shutter drive protrusions  47  protruding from the reinforcing plate  112 . 
     7. Variations of the Embodiment 
     (1) First Variation 
     The shutter  73  may have a structure as shown in  FIGS. 23 and 24 , instead of the structure shown in  FIG. 12 . 
     In the shutter  73  shown in  FIG. 12 , shutter drive openings  88  are formed through the shutter  73  for engaging the shutter drive protrusions  47  (see  FIG. 10 ). However, in the shutter  73  shown in  FIGS. 23 and 24 , shutter drive recessions  121  are formed in the shutter  73  for engaging the shutter drive protrusions  47 . With this construction, an inlet  122  for each shutter drive recession  121  functions as a shutter drive opening for being engaged with the corresponding shutter drive protrusion  47 . 
     (2) Second Variation 
     The toner seal  71  may also have the structure shown in  FIG. 25  and is not limited to the structure shown in  FIG. 13 . 
     The toner seal  71  described in the embodiment with reference to  FIG. 13  has a two-layer structure including the elastic layer  75  and mesh layer  76 . However, the toner seal  71  shown in  FIG. 25  has an additional mesh layer  131  laminated on the mesh layer  76 . 
     By providing the toner seal  71  with a plurality of mesh layers  76  and  131 , air can more readily escape from the main body  51  of the toner box  11  (see  FIG. 12 ). 
     (3) Third Variation 
     The toner seal  71  may also have the structure shown in  FIG. 26 . Here, the toner seal  71  has a laminated structure with four or more layers formed by alternately laminating the elastic layer  75  and mesh layer  76  one on the other. Also with this configuration, air can readily escape from the main body  51  of the toner box  11 . 
     (4) Fourth Variation 
     The toner seal  71  may be bonded to the shutter  73 , rather than to the main body  51 , as illustrated in  FIGS. 27A and 27B . That is, the fixing surface  77  of the elastic layer  75  is attached to the shutter  73  with adhesive at such a position that the toner seal  71  will be disposed between the shutter  73  and the main body  51  and the toner seal  71  will surround a perimeter of the main-body-side communication through-hole  58  when the shutter  73  is in the closed position.  FIG. 27A  shows the state where the shutter  73  is in the open position, in which the toner seal  71  is shifted together with the shutter  73  from the main-body-side communication through-hole  58  in the main body  51 .  FIG. 27B  shows the cross-section taken along a line XXVIIB-XXVIIB in  FIG. 27A . Also with this configuration, air can readily escape through the mesh layer  76  from the toner box  11 . Since the mesh layer  76  of the toner seal  71  slides over the main body  51  when the shutter  73  moves between the open and closed positions, the shutter  73  can be moved with less torque than if the elastic layer  75  was sliding over the main body  51  since the resistance generated by the mesh layer  76  is smaller. In addition, because the shutter  73  is made of a thin film, any toner present in the main-body-side communication through-hole  58  will not rest on the edge of the shutter  73  when the shutter  73  moves from the open position to the closed position. So, toner will not drop off the shutter  73  after the toner box  11  is removed from the developing unit  7 . 
     (5) Fifth Variation 
     As shown in  FIGS. 28A and 28B , separate toner seals  141  having the same structure as the toner seals  71  shown in  FIGS. 27A and 27B  may be bonded to the arcing surface  53  of the main body  51  in such positions that the toner seals  71  will oppose and contact the corresponding toner seals  141  when the shutter  73  is in the closed position. That is, the fixing surface  77  of the elastic layer  75  in the toner seal  71  is attached to the shutter  73  with adhesive and the fixing surface  77  of the elastic layer  75  in the toner seal  141  is attached to the main body  51  at such positions that the toner seal  71  and the toner seal  141  will be disposed between the shutter  73  and the main body  51  and the toner seals  71  and  141  will surround a perimeter of the main-body-side communication through-hole  58  when the shutter  73  is in the closed position.  FIG. 28A  shows the state where the shutter  73  is in the open position, in which the toner seal  71  is shifted together with the shutter  73  from the toner seal  141  that is attached on the main body  51 .  FIG. 28B  shows the cross-section taken along a line XXVIIIB-XXVIIIB in  FIG. 28A . Also with this configuration, air can readily escape through the layers  76  in the toner seals  71  and  141  from the toner box  11 . Because the shutter  73  is made of a thin film, any toner present in the main-body-side communication through-hole  58  will not rest on the edge of the shutter  73  when the shutter  73  moves from the open position to the closed position. So, toner will not drop off the shutter  73  after the toner box  11  is removed from the developing unit  7 . 
     (6) Sixth Variation 
     In the structure of the embodiment shown in  FIG. 16A , the rear edge of the shutter  73  is positioned farther forward than the front edges of the cover-side communication through-holes  83  when the shutter  73  is in the open position. However, the rear edge of the shutter  73  may be positioned farther to the rear than the front edges of the cover-side communication through-holes  83 , provided that the main-body-side communication through-holes  58  formed in the main body  51  (and preferably the main-body-side communication through-holes  58  and the openings  74  formed in the toner seals  71 ) are entirely open. In other words, it is sufficient that the rear edge of the shutter  73  is positioned farther forward than the front edges of the main-body-side communication through-holes  58  when the shutter  73  is in the open position. 
     (7) Seventh Variation 
     In the embodiment, when the shutter  73  is in the closed position, the shutter  73  contacts the shutter cover  72  around the entire peripheries of the cover-side communication through-holes  83 , as shown in  FIG. 16B . However, the shutter  73  may be formed in the shape shown in  FIG. 29  so that the shutter  73  does not contact the shutter cover  72  around the entire peripheries of the cover-side communication through-holes  83 , that is, so that the shutter  73  does not contact the shutter cover  72  on some part of the peripheries of the cover-side communication through-holes  83 . 
     While the invention has been described in detail with reference to the embodiment and variations thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention. 
     In the above-described embodiment, the toner box  11  is detachably mounted on the developing unit  7 . However, the toner box  11  may be detachably mounted in the image-forming device  1  at a position different from the developing unit  7 . A toner transferring unit, such as an auger, may be provided in the image-forming device  1  to transfer toner from the toner box  11  to the developing unit  7 .