Patent Publication Number: US-9841720-B2

Title: Image forming apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 14/813,542 filed Jul. 30, 2015 which claims priority from Japanese Patent Application No. 2014-156899, filed on Jul. 31, 2014, the entire subject matter of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     Technical Field 
     An aspect of the present invention relates to an image forming apparatus capable of forming images in an electro-photographic method. 
     Related Art 
     An image forming apparatus, such as a tandem-typed color printer, for forming colored images in an electro-photographic method is known. The tandem-typed color printer may have a plurality processing units, each of which contains a photosensitive drum for one of a plurality of colors (e.g., yellow, magenta, cyan, and black). 
     The tandem-typed color printer may be equipped with a cleaning system, in which residual toner remaining on surfaces of the photosensitive drums is scraped off by cleaning blades, and the residual toner removed from the photosensitive drums may be conveyed sideward along a direction of axes of the photosensitive drums by conveyer spirals in a toner collecting unit so that the collected residual toner is conveyed by a toner conveyer unit to be stored in a waste toner container disposed inside the image forming apparatus. 
     SUMMARY 
     While the plurality of processing units may be integrally supported by a supporting member in the image forming apparatus, the supporting member may be configured to further support the toner conveyer unit. Meanwhile, the waste toner container may be detachable from and attachable to the toner conveyer unit while the toner conveyer may be stationary inside the image forming apparatus. 
     The present disclosure is advantageous in that an image forming apparatus, in which a supporting member to support a plurality of processing unit may support a toner conveyer unit, and the toner conveyer unit may be detachably attached to the toner container unit, is provided. 
     According to an aspect of the present invention, an image forming apparatus, having a body including a first wall, the first wall having an aperture, and a second wall opposite to the first wall; and a processing unit movable between an inside position, in which the processing unit is inside the body, and an outside position, in which the processing unit is outside the body, through the aperture in the body, is provided. The processing unit includes a first drum cleaner configured to remove waste toner from a first photosensitive drum, the first drum cleaner including a first cleaning blade arranged to contact the first photosensitive drum, and a first screw longitudinally extending in an axial direction of the first photosensitive drum; a second drum cleaner configured to remove waste toner from a second photosensitive drum, the second drum cleaner including a second cleaning blade arranged to contact the second photosensitive drum, and a second screw longitudinally extending in an axial direction of the second photosensitive drum; and a waste toner conveyer configured to convey the waste toner removed by the first drum cleaner and the second drum cleaner, the waste toner conveyer including a conveyer tube longitudinally extending in a movable direction in which the processing unit is movable from the outside position to the inside position, the waste toner conveyer having a port, a conveyer screw located inside the conveyer tube, and a shutter movable between an opening position, in which the port is open, and a closed position, in which the port is closed, the port of the conveyer tube being arranged closer to the first wall of the body than to the second wall of the body when the processing unit is in the inside position. The image forming apparatus further has a transfer unit, including a belt unit with a belt arranged to contact the first photosensitive drum and the second photosensitive drum; and a belt cleaner including a container, the container having an opening which communicates with the port of the conveyer tube when the processing unit is in the inside position. 
    
    
     
       BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
         FIG. 1  is a cross-sectional view of an image forming apparatus, taken at a widthwise center, according to a first embodiment of the present disclosure. 
         FIG. 2  is a cross-sectional view of the image forming apparatus, taken at a line A-A shown in  FIG. 1 , according to the first embodiment of the present disclosure. 
         FIG. 3  is a cross-sectional view of the image forming apparatus, taken at a line B-B shown in  FIG. 2 , according to the first embodiment of the present disclosure. 
         FIG. 4A  illustrates engagement between a handle in a shutter and a shutter-restrictive part in a front cover in the image forming apparatus according to the first embodiment of the present disclosure.  FIG. 4B  illustrates the shutter in an opening position in the image forming apparatus according to the first embodiment of the present disclosure.  FIG. 4C  illustrates the shutter in a closable position in the image forming apparatus according to the first embodiment of the present disclosure. 
         FIG. 5A  is a cross-sectional view of a transfer unit in the image forming apparatus, taken at the line B-B shown in  FIG. 2 , according to the first embodiment of the present disclosure.  FIG. 5B  is a cross-sectional view of the transfer unit in the image forming apparatus, taken at a widthwise center, according to the first embodiment of the present disclosure. 
         FIG. 6A  is a cross-sectional view of the transfer unit in the image forming apparatus, taken at a line C-C shown in  FIG. 5A , according to the first embodiment of the present disclosure.  FIG. 6B  is a cross-sectional view of the transfer unit in the image forming apparatus, taken at a line D-D shown in  FIG. 5B , according to the first embodiment of the present disclosure. 
         FIG. 7  is a cross-sectional view of the image forming apparatus when a developer cartridge is to be exchanged, with the front cover being in an openable position and a processing unit being in a separated position, according to the first embodiment of the present disclosure. 
         FIG. 8  is a cross-sectional view of the image forming apparatus being in a same condition as the image forming apparatus shown in  FIG. 7 , at a position equivalent to the line B-B shown in  FIG. 1 , according to the first embodiment of the present disclosure. 
         FIG. 9  is a cross-sectional view of the image forming apparatus when the developer cartridge is to be exchanged, with the front cover being in the openable position and the processing unit being in an external position, according to the first embodiment of the present disclosure. 
         FIG. 10  is an illustrative view of a first modified example of the image forming apparatus, with the front cover being in a closable position and the shutter being in an opening position, according to the first embodiment of the present disclosure. 
         FIG. 11  is another illustrative view of the first modified example of the image forming apparatus, with the front cover being in the openable position and the shutter being in a closable position, according to the first embodiment of the present disclosure. 
         FIG. 12  is an illustrative view of a second modified example of the image forming apparatus, with the front cover being in the closable position and the shutter being in the opening position, according to the first embodiment of the present disclosure. 
         FIG. 13A  is an illustrative view of the second modified example of the image forming apparatus, with the shutter being in the opening position, according to the first embodiment of the present disclosure.  FIG. 13B  is a front view of the handle of the shutter being in the opening position, in the image forming apparatus of the second modified example, according to the first embodiment of the present disclosure.  FIG. 13C  is an illustrative view of the second modified example of the image forming apparatus, with the shutter being in the closable position, according to the first embodiment of the present disclosure.  FIG. 13D  is a front view of the handle of the shutter being in the closable position, in the image forming apparatus of the second modified example according to the first embodiment of the present disclosure. 
         FIG. 14  is another illustrative view of the second modified example of the image forming apparatus, with the front cover being in the openable position and the shutter being in the opening position, according to the first embodiment of the present disclosure. 
         FIG. 15  is a cross-sectional view of an image forming apparatus, taken at a widthwise center, according to a second embodiment of the present disclosure. 
         FIG. 16  is a cross-sectional view of the image forming apparatus, taken at a line E-E shown in  FIG. 15 , according to the second embodiment of the present disclosure. 
         FIG. 17  is a cross-sectional view of the image forming apparatus, taken at a line F-F shown in  FIG. 16 , according to the second embodiment of the present disclosure. 
         FIG. 18A  illustrates the shutter in the opening position in the image forming apparatus according to the second embodiment of the present disclosure.  FIG. 18B  illustrates the shutter in the closable position in the image forming apparatus according to the second embodiment of the present disclosure. 
         FIG. 19  is a cross-sectional view of the image forming apparatus when a developer cartridge is to be exchanged, with the front cover being in the openable position and the processing unit being in the separated position, according to the second embodiment of the present disclosure. 
         FIG. 20  is a cross-sectional view of the image forming apparatus being in a same condition as the image forming apparatus shown in  FIG. 19 , at a position equivalent to the line F-F shown in  FIG. 19 , according to the second embodiment of the present disclosure. 
         FIG. 21  is a cross-sectional view of the image forming apparatus when the developer cartridge is to be exchanged, with the front cover being in the openable position and the processing unit being in the external position, according to the second embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, illustrative embodiments of the present disclosure will be described with reference to the accompanying drawings. 
     1. Overall Configuration of Image Forming Apparatus 
     An image forming apparatus  1  according to a first embodiment of the present disclosure is a direct tandem-typed color laser printer (see  FIG. 1 ). In the following description, directions concerning the image forming apparatus  1  and elements included in the image forming apparatus  1  will be based on a user&#39;s ordinary usable posture and position to use the image forming apparatus  1 , when the image forming apparatus  1  is laid horizontally, and referred to in accordance with orientation indicated by arrows in each drawing. Therefore, for example, an upward direction and a downward direction in  FIG. 1  correspond to an upward direction and a downward direction respectively for the user, and a rightward direction and a leftward direction in  FIG. 1  correspond to a frontward direction and a rearward direction respectively for the user. A right-hand side and a left-hand side for the user facing a front face of the image forming apparatus  1  is defined as right and left respectively. Therefore, a nearer side in  FIG. 1  is the left-hand side, and a farther side in  FIG. 1  is the right-hand side. A right-to-left or left-to-right direction of the image forming apparatus  1  may also be referred to as a widthwise direction or a lateral direction. The front-to-rear or rear-to-front direction may be referred to as a front-rear direction or a direction of depth. Furthermore, directions of the drawings in  FIGS. 2-21  are similarly based on the orientation of the image forming apparatus  1  as defined above and correspond to those with respect to the image forming apparatus  1  shown in  FIG. 1  even when the image forming apparatus  1  in the drawings is viewed from different angles. 
     The image forming apparatus  1  includes a body  2 , a processing unit  3 , a scanner unit  4 , a transfer unit  5 , and a fixing unit  6 . 
     The body  2  is formed to have an approximate shape of a rectangular box and includes an aperture  21 , a front cover  22 , a feeder tray  7 , and a sheet outlet tray  8 . 
     The aperture  21  is located on a front face of the body  2  and is formed through the front face of the body  21  along the front-rear direction to allow communication between the interior and the exterior of the body  2  so that the processing unit  3  may be installed inside the body through the aperture  21 . 
     The front cover  22  is located at a frontward position of the body  2  and has an approximate shape of a flat plate. The front cover  22  may be arranged to stand along the vertical direction and supported by the front face of the body  2  at a lower end thereof to be swingable frontward about the lower end. Thus, the front cover  22  is swingable between an openable position (see  FIG. 7 ), at which the aperture  21  is exposed, and a closable position (see  FIG. 1 ), at which the aperture  21  is covered. 
     The feeder tray  7  is located at a lower position in the body  2  and may accommodate sheets P being transcription media therein. 
     The sheet outlet tray  7  is formed on an upper face of the body  2  to dent downward from the upper face so that the sheets P may be stacked thereon. 
     The processing unit  3  may be accommodated inside the body  2  through the aperture  21  to be located in a central area in the body  2 . The processing unit  3  is movable inside the body  2  between a contacting position (see  FIG. 1 ), at which a plurality of photosensitive drums  11  contact a conveyer belt  17 , and a separated position (see  FIG. 7 ), which is an upper position with respect to the contacting position and at which the photosensitive drums  11  are separated from the conveyer belt  17 , while the processing unit  3  is accommodated inside the body  2 . The photosensitive drums  11  and the conveyer belt  17  will be described later in detail. Further, the processing unit  3  is movable along the front-rear direction between the separated position and an external position (see  FIG. 9 ), which is a position extended frontward with respect to the separated position and outside the body  2 , through the aperture  21 . Thus, when the processing unit  3  is accommodated inside the body  2 , the processing unit  3  may be pushed rearward through the aperture  21 . The processing unit  3  includes a drum unit  9  and a plurality of developer cartridges  10 . 
     The drum unit  9  includes the plurality of photosensitive drums  11  and a plurality of charger rollers  12 . 
     The photosensitive drums  11  are rotatably supported by a lower part of the processing unit  3 . Each of the photosensitive drums  11  is arranged to correspond to one of the colors of yellow, magenta, cyan, and black. The photosensitive drums  11  are arranged to be spaced apart from one another to align along the front-rear direction, from the front toward the rear, in an order of, for example, yellow, magenta, cyan, and black, respectively. The photosensitive drums  11  are each formed to have a cylindrical shape, which longitudinally aligns along the widthwise direction. In other words, the axes of the photosensitive drums  11  extend in the widthwise direction. 
     Each of the charger rollers  12  is arranged to correspond to one of the photosensitive drums  11  and is arranged in an upper-rearward position with respect to the corresponding one of the photosensitive drums  11 . Each charger roller  12  is arranged to contact an upper-rear part of the corresponding one of the photosensitive drums  11 . 
     Each of the developer cartridges  10  is arranged to correspond to one of the photosensitive drums  11  in a frontward position with respect to the corresponding one of the photosensitive drums  11 . The developer cartridges  10  each includes a developer roller  13  and a supplier roller  14 , and contains toner in one of the corresponding colors in an upper area thereof with respect to the developer roller  13  and the supplier roller  14 . 
     The developer roller  13  is rotatably supported by a corresponding one of the developer cartridges  10  to be exposed rearward at a lower position in the developer cartridge  10 . The developer roller  13  is arranged to contact a frontward end of the corresponding one of the photosensitive drums  11 . 
     The supplier roller  14  is arranged in a frontward position with respect to the developer roller  13  to contact a frontward end of the developer roller  13 . 
     The scanner unit  4  is located in an upper position with respect to the processing unit  3 . The scanner unit  4  may emit laser beams, as indicated by solid lines in  FIG. 1 , toward the photosensitive drums  11  according to image data so that the photosensitive drums  11  are selectively exposed to the laser beams according to the image data. 
     The transfer unit  5  is located in a lower position with respect to the processing unit  3 . The transfer unit  5  includes a driving roller  15 , a driven roller  16 , the conveyer belt  17 , and a plurality of transfer rollers  18 . 
     The driving roller  15  is located in a rearward position in the transfer unit  5 . 
     The driven roller  16  is located in a frontward and spaced-apart position with respect to the driving roller  15  in the transfer unit  5  to face with the driving roller  15 . 
     The conveyer belt  17  is strained around the driving roller  15  and the driven roller  16 , and is arranged to contact each one of the photosensitive drums  11  at an upper part thereof. The conveyer belt  17  is rolled along with rotation of the driving roller  15  and the driven roller  16  to circulate in a direction to move the upper part rearward and a lower part frontward. 
     Each of the transfer rollers  18  is arranged to correspond to one of the photosensitive drums  11  in a lower position with respect to the corresponding one of the photosensitive drums  11  so that the upper part of the conveyer belt  17  is placed in between the photosensitive drums  11  and the transfer rollers  18 . 
     The fixing unit  6  is located in a rearward position with respect to the transfer unit  5 . The fixing unit  6  includes a heat roller and a pressure roller  20 . The pressure roller  20  is arranged to contact the heat roller  19 . 
     When the image forming apparatus  1  starts forming an image, the charger rollers  12  charge the surfaces of the photosensitive drums  11  evenly, and the scanner unit  4  emits the laser beams toward the photosensitive drums  11  selectively according to the image data so that electrostatic latent images are formed in the areas selectively exposed to the laser beams on the photosensitive drums  11 . 
     Meanwhile, the supplier rollers  14  supply the toner in the developer cartridges  10  to the developer rollers  13 . The toner supplied to each developer roller  13  is frictionally charged between the developer roller  13  and the supplier roller  14  and carried on the developer roller  13 . 
     The developer rollers  13  then supply the toner to the electrostatic latent images on the photosensitive drums  11 . Thus, toner images are formed on the surfaces of the photosensitive drums  11 . 
     In the meantime, sheets P in the feeder tray  7  are picked up one-by-one along with rotation of the rollers. Each sheet P is conveyed upper-frontward and turned upper-rearward to be conveyed to an intermediate position between the photosensitive drum  11  at a most frontward position and the conveyer belt  17 . Thereafter the sheet P is conveyed rearward by the conveyer belt  17 . The toner images on the photosensitive drums  11  are transferred onto the sheet P sequentially as the sheet P proceeds through an intermediate position between each photosensitive drum  11  and transfer roller  18 . 
     The sheet P is thereafter exposed to heat and pressure from the heat roller  19  and the pressure roller  20  when the sheet P passes through an intermediate position between the heat roller  19  and the pressure roller  20  so that the image is fixed thereon. The sheet P is thereafter discharged to the sheet outlet tray  8 . 
     2. Detailed Configuration of the Image Forming Apparatus 
     The body  2  of the image forming apparatus  1  includes, as shown in  FIGS. 2-3 , an outer frame  31 , an inner frame  32 , a pair of lifts  30 , a slide-restrictive piece  29 , and the front cover  22 . 
     The outer frame  31  forms an exterior housing of the image forming apparatus  1  and has an approximate shape of a box. The outer frame  31  may be made of, for example, hard resin. 
     The inner frame  32  is located inside the outer frame  31 . The inner frame  32  has an approximate shape of a sleeve, of which front end and rear end are open, and longitudinally aligns along the front-rear direction. The inner frame  32  includes a pair of lateral plates  33 , a pair of guide members  37 , an upper plate  34 , a lower plate  35 , and a pair of drum positioning members  36 . 
     The lateral plates  33  are arranged to be spaced apart from each other on a laterally inner side of right and left side walls of the outer frame  31 . The lateral plates  33  each has a shape of a plate standing vertically and may be made of metal such as stainless steel. 
     The guide members  37  are each supported on an inner surface of an upper part of each lateral plate  33 . Each guide member  37  has a shape of a plate standing vertically and may be made of, for example, hard resin. Each guide member  37  has a plurality of, for example, two (2), guide grooves  37 A. 
     The guide groove  37 A is formed on a frontward end and a rearward end of each guide member  37 . Each guide groove  37 A is formed to dent laterally outward from an inner surface of the guide member  37  and is extended to curve upper-frontward, or lower-rearward. 
     The upper plate  34  is located in a lower and spaced-apart position with respect to a top part of the outer frame  31 . The upper plate  34  may be made of metal such as stainless steel and has a shape of a flat plate spreading along the widthwise direction. The upper plate  34  is arranged to bridge a gap between upper ends of the paired lateral plates  33 . The upper plate  34  supports the scanner unit  4 , which is placed on the upper plate  34 . 
     The lower plate  35  is arranged in a lower position in the inner frame  32 . The lower plate  35  is located in an upper and spaced-apart position with respect to a bottom part of the outer frame  31 . The lower plate  35  may be made of metal such as stainless steel and has a shape of a flat plate spreading along the widthwise direction. The lower plate  34  is arranged in an upper position with respect to the feeder tray  7  to bridge a gap between lower ends of the paired lateral plates  33 . 
     The paired drum-positioning members  36  are arranged to be spaced apart from each other on a laterally inner side of the lateral plates  33 . Each drum-positioning member  36  has a shape of a plate standing vertically. The drum-positioning members  36  may be made of metal such as stainless steel. The drum-positioning members  36  are fixed to an upper surface of the lower plate  35  at lower ends thereof. The drum-positioning members  36  are each formed to have a plurality of positioning dents  36 A (see  FIG. 1 ). 
     The positioning dents  36 A in each drum-positioning member  36  are, as shown in  FIGS. 1-2 , arranged to be evenly spaced apart from each other along the front-rear direction in positions corresponding to the positions of the photosensitive drums  11 . The positioning dents  36 A are formed to dent downward from an upper edge of the drum-positioning member  36  in a shape of a U, which is open upward. The photosensitive drums  11  are each arranged to have widthwise ends thereof to fit in the corresponding ones of positioning dents  36 A. 
     The paired lifts  30  are, as shown in  FIGS. 2-3 , arranged on a laterally inner side of the paired guide members  37 . Each of the lifts  30  has a shape of a plate, which spreads along the front-rear direction. The lifts  30  each has a guide groove  30 A and an engageable boss  30 B. 
     The guide groove  30 A is formed to dent outward along the widthwise direction from an inner surface of each lift  30  and to stretch longitudinally along the front-rear direction. 
     The engageable bosses  30 B are each formed on a front end and a rear end of the lift  30  respectively. Each engageable boss  30 B has a cylindrical shape, which protrudes outward from an outer surface of the lift  30  along the widthwise direction. The engageable boss  30 B is arranged to slidably fit in the guide groove  37 A in the guide member  37 . 
     The slide-restrictive piece  29  is located in a frontward area in the body  2  at a frontward position with respect to the transfer unit  5 . The slide-restrictive piece  29  is in a shape of a block stretching vertically and has a slit  29 A. 
     The slit  29 A is formed and deepened to dent downward from a top surface of the slide-restrictive piece  29  to have a shape of a U, in a lateral view, which is open upward. A dimension (depth) of the slit  29 A in the vertical direction is greater than a distance for the drum unit  9  to move between the contacting position and the separated position. 
     The front cover  22  includes a pair of lift-restrictive pieces  38 , a shutter-restrictive piece  39 , and a pair of tension springs  40 . 
     The paired lift-restrictive pieces  38  are each arranged on a widthwise end of the front cover  22  at an intermediate height of the front cover  22  along the vertical direction. Each lift-restrictive piece  38  is formed to protrude rearward from a rearward face of the front cover  22 , when the front cover is in the closable position. The lift-restrictive pieces  38  each has a shape of a quadrilateral plate, in a lateral view, and is arranged to face with a front end of each lift  30 , when the front cover is in the closable position, to restrict the lift  30  from moving frontward. 
     The shutter-restrictive piece  39  is, as shown in  FIGS. 3 and 4A , located at a lower-leftward end of the front cover  22 . The shutter-restrictive piece  39  has a shape of a block and arranged to protrude rearward from the rear face of the front cover  22 . The shutter-restrictive piece  39  includes a grove  39 A and a blocker  39 B. 
     The groove  39 A is located in a widthwise central position in the shutter-restrictive piece  39 . The groove  39 A is formed to dent frontward from a rearward face of the shutter-restrictive piece  39  and to stretch longitudinally along the vertical direction. 
     The blocker  39 B is located at each widthwise end of the shutter-restrictive piece  39 . The blocker  39 B is formed to project rearward from the rear face of the front cover  22  and to stretch longitudinally along the vertical direction. The blockers  39 B form lateral walls of the groove  39 A. 
     The paired tension springs  40  are coiled springs and are supported by the front cover  22  at upper and widthwise ends of the front cover  22 . Each of the tension springs  40  is anchored to the upper and widthwise ends of the front cover  22  at one end thereof, and the other end of the tension spring  40  is anchored to a lower-front end of each lift  30 . 
     3. Detailed Configuration of the Drum Unit 
     The drum unit  9  has, as shown in  FIGS. 1-2 , a form of a frame, which is open upward, downward, and sideward. The drum unit  9  includes a pair of lateral plates  41 , a plurality of drum cleaners  42 , and a waste toner conveyer  43 . 
     3-1. Lateral Plates 
     The paired lateral plates  41  are located at widthwise ends of the drum unit  9 . Each lateral plate  41  has a shape of a plate, which stands vertically, and has a protrusive strip  41 A. 
     The protrusive strip  41 A is located at an upper end of each lateral plate  41  and is formed to protrude outward along the widthwise direction from an outer surface of the lateral plate  41  and to stretch longitudinally along the front-rear direction. The protrusive strips  41 A are placed to slidably fit in the guide grooves  30 A in the lifts  30 . 
     3-2. Drum Cleaners 
     Each of the drum cleaners  42  is arranged in a rearward position with respect to corresponding one of the photosensitive drums  11  between the paired lateral plates  41 . Each drum cleaner  42  includes a cleaner-frame  45 , a cleaning blade  46 , and a screw  47 . 
     The cleaner-frame  45  has a shape of a box, which stretches longitudinally in the widthwise direction and has an opening  45 A. 
     The opening  45 A is formed through a frontward part of the cleaner-frame  45  along the front-rear direction and is elongated along the widthwise direction. The opening  45 A is formed in a position to coincide with the rearward end of the photosensitive drum  11  along the front-rear direction. 
     The cleaning blade  46  is located in a frontward position with respect to the opening  45 A. The cleaning blade  46  has a shape of a plate, which stands along the vertical direction. An upper end of the cleaning blade  46  is fixed to an upper edge of the opening  45 A on a front face of the cleaner-frame  45 . The cleaning blade  46  is arranged to have a lower edge thereof to contact the rearward end of the photosensitive drum  11 . 
     The screw  47  is located in a lower position in the cleaner-frame  45 . The screw  47  is an auger screw, which aligns longitudinally along the widthwise direction. The screw  47  is arranged to have a rightward end thereof to penetrate through a right-side wall of the cleaner-frame  45  and through the lateral plate  41  of the drum unit  9  on the right to protrude further rightward than the lateral plate  41  on the right. The rightward end of the screw  47  is rotatably supported by the right-side wall of the cleaner-frame  45 . The screw  47  includes a gear  47 A. 
     The gear  47 A is supported on the rightward end of the screw  47  in an outward (rightward) position with respect to the lateral plate  41  on the right. The gear  47  is not rotatable with respect to the screw  47  but is rotatable integrally with the screw  47 . A driving force generated in the body  2  of the image forming apparatus  1  is transmitted to the gear  47 A through a gear train, which is not shown, to rotate the screw  47 . 
     3-3. Waste Toner Conveyer 
     The waste toner conveyer  43  is, as shown in  FIGS. 2-3 , located in a lower position in the drum unit  9  on an outer (leftward) side of one of the lateral plates  41  on the left. The waste toner conveyer  43  includes a conveyer tube  51 , a plurality of connectors  52 , a screw  53 , and a shutter  54 . 
     The conveyer tube  51  is arranged to longitudinally align along the front-rear direction and has a closed tubular form, of which front end and rear end are closed. The conveyer tube  51  is in an arrangement such that an upper part thereof overlaps lower ends of the photosensitive drums  11  when projected along the widthwise direction. The conveyer tube  51  includes a port  51 A. 
     The port  51 A is formed in a frontward position in the conveyer tube  51  to vertically bore through a bottom of the conveyer tube  51  and has a shape of a rectangle in a plan view seen from the bottom. 
     The connectors  52  are located in upper positions with respect to the conveyer tube  51  to be spaced apart from one another along the front-rear direction. The connectors  52  are arranged to each correspond to one of the plurality of drum cleaners  42 ; therefore, there may be four (4) connectors  52 . Each of the connectors  52  has a tubular shape, which is formed to extend upward continuously from a top of the conveyer tube  51  and curve rightward. A rightward end of the connector  52  is connected to a leftward end of the cleaner-frame  45  of the corresponding one of the drum cleaners  42 . 
     The conveyer screw  53  is located inside the conveyer tube  51  and is an auger screw arranged to longitudinally align along the front-rear direction. A front end and a rear end of the conveyer screw  53  are rotatably supported by a front wall and a rear wall that close the front and rear ends of the conveyer tube  51  respectively. The rearward part of the conveyer screw  53  penetrates through the rear wall of the conveyer tube  51  to protrude rearward from the rear wall of the conveyer tube  51 . The conveyer screw  53  includes a gear  53 A. 
     The gear  53 A is supported on the rear end of the conveyer screw  53  at rearward position with respect to the rear wall of the conveyer tube  51 . The gear  53  is not rotatable with respect to the conveyer screw  53  but is rotatable integrally with the conveyer screw  53 . A driving force generated in the body  2  of the image forming apparatus  1  is transmitted to the gear  53 A through a gear train, which is not shown, to rotate the conveyer screw  53 . 
     The shutter  54  is located at a front end of the waste toner conveyer  43 . The shutter  54  has a shape of a cylinder, which aligns longitudinally along the front-rear direction. The shutter  54  is, as shown in  FIGS. 4B and 4C , movable to rotate about a central axis A of conveyer tube  51  between an opening position (see  FIG. 4B ), in which the port  51 A of the conveyer tube  51  is exposed within the body  2 , and a closed position (see  FIG. 4C ), in which the port  51 A of the conveyer tube  51  is closed. In the following description, unless otherwise stated, the shutter  54  is described with reference to the opening position. The shutter  54  includes a sleeve  55  and a handle  56 , and an engageable part  57 . 
     The sleeve  55  is located at a rear end of the shutter  54 . The sleeve  55  has a cylindrical shape aligning longitudinally along the front-rear direction. A front end of the sleeve  55  is closed, and a rear end of the sleeve  55  is open. The sleeve  55  is placed over the front end of the conveyer tube  51  to cover an outer circumference of the front end of the conveyer tube  51 . The sleeve  55  includes a hole  55 A. 
     The hole  55 A is formed in a rearward position in the sleeve  55  to vertically bore through a bottom of the sleeve  55  and has a rectangular shape in a plan view seen from the bottom. The hole  55 A is formed in a vertically coincident position with the port  51 A of the conveyer tube  51 . 
     The handle  56  is located in a frontward position in the shutter  54  with regard to the front-rear direction. The handle  56  protrudes frontward from the closed front end of the sleeve  55  and is elongated in a radial direction of the sleeve  55 . The handle  56  has an approximate shape of a three-sided frame which is open rearward in a lateral view. The handle  56  may be placed in a first handling position, in which the handle  56  longitudinally aligns along the vertical direction in a front view, when the front cover  22  is in the closable position, to be accommodated in the groove  39 A of the shutter-restrictive piece  39  of the front cover  22 , as indicated by solid lines in  FIG. 4A . When the front cover  22  is in the openable position, the handle  56  may be placed in a second handling position, in which the handle  56  longitudinally aligns along the widthwise direction in the front view to contact the blocker  39 B of the shutter restrictive part  39  of the front cover, as indicated by dash-and-dot lines in  FIG. 4A . 
     The engageable part  57  is arranged to protrude downward from a lower circumference of the front end of the shutter  54  (see  FIG. 4B ). The engageable part  57  has a shape of a plate. In other words, the engageable part  57  is a piece of protrusive plate that protrudes downward from the lower circumference of the front end of the shutter  54 . A vertical dimension of the engageable part  57  is equal to the vertical dimension (depth) of the slit  29 A of the slide-restrictive piece  29  and is longer than the distance between the contacting position and the separated position for the drum unit  9  to move. Thus, the engageable part  57  may fit in the slit  29 A of the slide-restrictive piece  29 . 
     4. Detailed Configuration of the Transfer Unit 
     The transfer unit  5  includes, as shown in  FIGS. 5A-5B , a transfer-frame  60 , a belt unit  61 , and a belt cleaner  62 . 
     The transfer-frame  60  has, as shown in  FIGS. 5A and 6A , a shape of a box, which is open upward and has a bottom. The transfer-frame  60  includes a pair of lateral walls  63  and a bottom plate  64 . 
     The paired lateral walls  63  are arranged on widthwise ends of the transfer-frame  60 . Each of the lateral walls  63  has a shape of a rectangular plate, which stands vertically. Each lateral wall  63  has an elongated opening  63 A and a compression spring  63 B. One of the lateral walls  63  on the left further includes an exposable opening  65 . 
     The elongated openings  63 A are each formed in a frontward position in each of the lateral walls  63 . Each elongated opening  63 A has a rectangular shape elongated along the front-rear direction in a lateral view and bores through the lateral wall  63  sideward along the widthwise direction. 
     The compression springs  63 B are each located in each of the elongated openings  63 A. Each of the compression springs  63 B is a coil spring stretching along the front-rear direction. The compression spring  63 B is in an arrangement such that a front end thereof contacts a rear end of a rotation shaft  16 A of the driven roller  16 , and a rear end thereof contacts an inner and rear face of the elongated opening  63 A. Thus, the compression springs  63 B urge the rotation shaft  16 A of the driven roller  16  frontward constantly. 
     The exposable opening  65  is formed in a front area in the lateral wall  63  on the left and in a frontward position with respect to the elongated opening  63 A. The exposable opening  65  has a rectangular shape elongated along the vertical direction bored sideward through the lateral wall  63  on the left along the widthwise direction. 
     The bottom plate  64  is at a lower end of the transfer-frame  60 . The bottom plate  64  is a flat plate spreading along the widthwise direction. Widthwise ends of the bottom plate  64  are connected with lower ends of the lateral walls  63 . The bottom plate  64  includes a plurality of rollers  64 A. 
     The rollers  64 A are arranged at frontward and widthwise ends and rearward and widthwise ends of the bottom plate  64 . The rollers  64 A each has a shape of a disk in a lateral view and is rotatably supported on the bottom plate  64 . An upper end of each roller  64 A is in an upper position with respect to an upward surface of the bottom plate  64 . 
     The belt unit  61  is, as shown in  FIGS. 5B and 6B , located in an upper position in the transfer unit  5 . The belt unit  61  includes the driving roller  15 , the driven roller  16 , the conveyer belt  17 , and the transfer rollers  18 , which are mentioned earlier. A rotation shaft  15 A of the driving roller  15  is rotatably supported at a rearward position in the transfer-frame  60  of the transfer unit  5 . The rotation shaft  16 A of the driven roller  16  is arranged to penetrate through lateral walls of a cleaning unit  70  in the belt cleaner  62  and inserted in the elongated openings  63 A of the transfer-frame  60 . 
     The belt cleaner  62  is, as shown in  FIGS. 5A and 6A , located in a lower-frontward position in the belt unit  61 . The belt cleaner  62  includes a cleaner-frame  66  and a cleaning blade  67 . 
     The cleaner-frame  66  of the belt cleaner  62  includes the cleaner unit  70 , a container  68 , and a joint  69 . 
     The cleaning unit  70  is located in a frontward area in the belt unit  61  and in a frontward position with respect to the cleaner-frame  66 . The cleaning unit  70  has a shape of a box, which stands vertically and spreads along the widthwise direction. Lateral walls of the cleaning unit  70  stretch rearward beyond a rear wall of the cleaning unit  70 . The cleaning unit  70  includes an opening  70 A. 
     The opening  70 A is formed in an upper position on the rear wall of the cleaning unit  70 . The opening  70 A has a rectangular shape elongated along the widthwise direction in a front view and bores rearward through the rear wall of the cleaning unit  70  along the front-rear direction. 
     The container  68  is located in a lower position with respect to the belt unit  61 . The container  68  has a boxed shape, which stretches rearward continuously with a lower end of the cleaning unit  70 . 
     The joint  69  is located at a leftward end of the belt unit  61 . The joint  69  is formed to extend upper-leftward continuously from the leftward end of the belt unit  61 . The joint  69  is arranged to protrude leftward through the exposable opening  65  beyond the lateral wall  63  on the left. The joint  69  includes a dent  69 A and an opening  69 B. 
     The dent  69 A is formed on an upper-leftward end in the joint  69 . The dent  69 A has a shape of an arc, which dents downward. 
     The opening  69 B is formed at a central position in the dent  69 A with regard to the widthwise direction and the front-rear direction to bore through an upper face of the joint  69  vertically. 
     The cleaning blade  67  is arranged on an upper end of the rear wall of the cleaning unit  70 . The cleaning blade  67  has a shape of a plate stretching along the widthwise direction. The cleaning blade  67  is on a side opposite from the driven roller  16  across the cleaning belt  70  and is in an arrangement such that an upper end thereof is supported on an edge of the opening  70 A on the rearward face of the cleaning unit  70 , and a lower edge thereof contacts the conveyer belt  17 . 
     5. Behaviors in Drum Cleaning and Belt Cleaning 
     Behaviors to clean the photosensitive drums  11  and the conveyer belt  17  will be described below. 
     When the toner images are transferred to the sheet P during the image forming operation in the image forming apparatus  1  described above (see  FIG. 1 ), there may be residual toner, which is not transferred onto the sheet P but remains on the surfaces of the photosensitive drum  11 . Further, there may be paper dust, which is transferred from the sheet P to the surfaces of the photosensitive drums  11 . 
     Waste toner including such residual toner and paper dust may be scraped off from the surfaces of the photosensitive drums  11  by the cleaning blades  46  of the drum cleaners  42  as the photosensitive drums  11  rotate and stored inside the cleaner-frames  45  of the drum cleaners  42 . Thus, each of the cleaning blades  46  cleans the surface of the corresponding one of the photosensitive drums  11 . 
     The waste toner stored inside each cleaner-frame  45  is conveyed leftward by rotation of the screw  47  to the corresponding one of the connectors  52  of the waste toner conveyer  43  (see  FIG. 2 ). The waste toner reaching the connectors  52  may fall in the conveyer tube  51  by the effect of gravity. 
     The waste toner falling in the conveyer tube  51  is conveyed frontward inside the conveyer tube  51  by rotation of the conveyer screw  53 , and further through the port  51 A of the conveyer tube  51  and the hole  55 A of the shutter  54 , to the opening  69 B in the joint  69  of the belt cleaner  62  (see  FIG. 3 ). 
     The waste toner reaching the opening  69 B in the joint  69  passes through the opening  69 B and enters the joint  69  by the effect of gravity to be stored in the container  68  (see  FIGS. 5A and 6A ). 
     Meanwhile, when the toner images are transferred to the sheet P during the image forming operation in the image forming apparatus  1  (see  FIG. 1 ), there may be residual toner, which remains on the surface of the conveyer belt  17 , and paper dust transferred from the sheet P. Further, there may be periodic events to form the toner images of test patterns on the surface of the conveyer belt  17  directly before the image forming operation with the sheet P is conducted in order to avoid misalignment of the toner images in the plurality of colors. 
     The residual toner and the paper dust adhered to the surface of the conveyer belt  17  may be scraped off from the surface of the conveyer belt  17  by the cleaning blade  67  of the belt cleaner  62  as the conveyer belt  17  circulates and stored in the container  68 . 
     6. Exchanges of the Developer Cartridges 
     A flow to exchange the developer cartridges  10  will be described below. 
     First, a user removes the developer cartridge  10  from the body  2 . In order to remove the developer cartridge  10  from the body  2 , the user places the front cover  22  in the openable position (see  FIG. 7 ). As the front cover  22  swings open, the paired tension springs  40  are stretched frontward, and the pair of lifts  30  are pulled frontward by resilient force of the tension springs  40 . In this regard, the engageable bosses  30 B slide in the guide grooves  37 A of the guide members  37 , and the lifts  30  are moved upper-frontward. As the lifts  30  move upper-frontward, the processing unit  3  moves upward to the separated position, and the photosensitive drums  11  are moved upward to be separated from the conveyer belt  17 . 
     Meanwhile, as shown in  FIG. 8 , the waste toner conveyer  43  is moved upward to be separated from the dent  69 A in the joint  69  of the belt cleaner  62 . The shutter  54  being in the opening position is moved straight above with the lower part of the engageable part  57  maintained fitted in the slit  29 A of the slide-restrictive piece  29 . Thereby, the port  51 A in the shutter  54  of the waste toner conveyer  43  is moved upward to be separated from the opening  69 B in the connector  69  of the belt cleaner  61 . Thus, the channel between the waste toner conveyer  43  and the belt cleaner  62  through the hole  55 A of the shutter  54  and the opening  69 B of the joint  69  is disconnected. 
     In the meantime, the lower end of the engageable part  57  of the shutter  54  remains engaged with an upper area of the slit  29 A of the slide-restrictive piece  29  while the shutter  54  is in the opening position. In other words, the engageable part  57  remains partly coincident with the groove  29  in a view along the front-rear direction. Thereby, the processing unit  3  may be restricted from moving frontward while being placed in the separated position. In this regard, a distance D 1  between the port  51 A in the conveyer tube  51  and the opening  69 B in the joint  69  of the belt cleaner  62  is longer than a distance D 2 , which is between the port  51 A in the conveyer tube  51  and the opening  69 B in the joint  69  of the belt cleaner  62  when the processing unit  6  is in the contacting position (see  FIG. 3 ). 
     Next, the user may hold the handle  56  of the shutter  54  in the waste toner conveyer  43  and rotate the shutter  54  clockwise, in a front view, to place the shutter  54  in the closed position (see  FIG. 4C ). 
     When the shutter  54  is in the closed position, the hole  55 A in the shutter  54  coincides with a leftward circumference of the conveyer tube  51 . Meanwhile, the bottom of the sleeve  55  of the shutter  54  in the closed position coincides with the port  51 A of the conveyer tube  51 . In this regard, the engageable part  57  of the shutter  54  is moved upper-leftward to be separated from the slit  29 A of the slide-restrictive piece  29 . In other words, the engageable part  57  of the shutter  54  is disengaged from the slit  29   a  of the slide-restrictive piece  29  when the shutter  54  is in the closed position. Thereby, the processing unit  3  is released from the restriction from the slide-restrictive piece  29  and is allowed to move frontward. 
     Next, the user may pull the processing unit  3  frontward to place in the external position (see  FIG. 9 ). In this regard, the protrusive strips  41 A slide inside the guide grooves  30 A in the lifts  30 , and the photosensitive drums  11  being upwardly separated from the conveyer belt  17  are moved from the separated position to the external position. 
     Next, the user may pull a specific one or more of the developer cartridges  10  upward, as indicated by double-dotted lines in  FIG. 9 . Thereby, the developer cartridge(s)  10  may be fully separated from the body  2 . 
     Thereafter, in order to complete exchange of the developer cartridges  10 , the user may attach one or more of new developer cartridges  10  to the body  2 . In order to attach the new developer cartridge  10  to the body  2 , the user may follow the above-described process in a reversed order. 
     That is, the user may attach the new developer cartridge  10  to the processing unit  3  and push the processing unit  3  rearward into the body  2 . The processing unit  3  may be placed in the separated position (see  FIG. 7 ). 
     Next, the user may hold the handle  56 B of the shutter  54  in the waste toner conveyer  43  and rotate counterclockwise, in the front view, to place the shutter  54 B in the opening position (see  FIGS. 4B and 8 ). Accordingly the lower end of the engageable part  57  of the shutter  54  fits in the upper area of the slit  29 A of the slide-restrictive piece  29 . Thereby, the processing unit  3  is restricted from moving frontward while being in the separated position. 
     Next, the user may move the front cover  22  to swing from the openable position to the closable position. Accordingly, the tension springs  40  contract as the front cover  22  swings, and the lift-restrictive pieces  38  contact the front ends of the lifts  30 . 
     As the user moves the front cover  22  further to swing toward the closable position, the lifts  30  are pushed rearward by the lift-restrictive pieces  38 , and the engageable bosses  30 B are moved to slide in the guide grooves  37 A of the guide members  37  lower-rearward. Accordingly, the processing unit  3  is moved downward as the lifts  30  move lower-rearward to the contacting position. 
     After the processing unit  3  is set in the contacting position, the front cover  22  may be placed in the closable position. Thus, attachment of the developer cartridges  10  to the body  2  is completed. 
     7. Effects 
     According to the image forming apparatus  1  described above, the port  51 A in the conveyer tube  51  of the waste toner conveyer  43  may be arranged on the front end of the conveyer tube  51  (see  FIG. 3 ). Meanwhile, the port  51 A may be exposed or closed by the shutter  54  (see  FIGS. 4B and 4C ). 
     Thus, in order to move the processing unit  3  from the contacting position (see  FIG. 1 ) to the external position (see  FIG. 9 ), the shutter  54  on the front side may be moved so that the port  51 A is closed while the processing unit  3  is in the separated position (see  FIG. 7 ). Thereafter, with the engageable part  57  of the shutter  54  being outside the slit  29 A of the slide-restrictive piece  29 , the processing unit  3  may be allowed to move from the separated position to the external position. When the processing unit  3  is to be moved from the external position to the contacting position, the shutter  54  on the front side may be handled to be moved to open the port  51 A after the processing unit  3  is moved to the contacting position. 
     Thus, the user may handle the shutter  54  from the position on the same side, i.e., the front side, as the user moves the processing unit  3 . Therefore, within the simple configuration, the waste toner conveyer  43 , which is movable along with the processing unit  3 , may be connected to or separated from the belt cleaner  62 , which stays steady in the body  2 , smoothly. 
     According to the image forming apparatus  1  described above, as shown in  FIG. 3 , there may be the single port  51 A of the conveyer tube  51  while the plurality of cleaning blades  46  are provided. Therefore, the waste toner cleaned by the plurality of cleaning blades  46  may be collectively conveyed by the waste toner conveyer  43  to be stored through the single port  51 A in the belt cleaner  62 . Accordingly, the connection between the waste toner conveyer  43  and the belt cleaner  62  may be established or disconnected easily and smoothly by the opening or closing motion of the single port  51 A. 
     According to the image forming apparatus  1  described above, as shown in  FIG. 4C , the processing unit  3  may be moved from the separated position to the external position with the shutter  54  maintained in the closed position. Therefore, the waste toner in the waste toner conveyer  43  may be prevented from leaking while the processing unit  3  is being moved outward to the external position. 
     According to the image forming apparatus  1  described above, as shown in  FIGS. 3 and 4B , the shutter  54 , when in the opening position, may restrict the processing unit  3  from moving from the separated position to the external position. On the other hand, as shown in  FIG. 4C , when the shutter  54  is in the closed position, the processing unit  3  may be released from the restriction and allowed to move from the separated position to the external position. Therefore, it may be avoided that the processing unit  3  is moved to the external position with the port  51 A being open. Accordingly, leakage of the waste toner through the port  51 A while the processing unit  3  is moved outward to the external position may be prevented. 
     According to the image forming apparatus  1  described above, as shown in  FIGS. 4B and 4C , the engageable part  57  in the shutter  54  may be arranged to fit in the slit  29 A of the slide-restrictive piece  29  in the body  2  when the shutter  54  is in the opening position and to be separated from the slit  29 A of the slide-restrictive piece  29  when the shutter  54  is in the closed position. Therefore, when the shutter  54  is in the opening position, engagement of the shutter  54  with the slide-restrictive piece  29  may restrict the processing unit  3  from moving in the front-rear direction. Meanwhile, when the shutter  54  is in the closed position, engageable part  57  of the shutter  54  is disengaged from the slide-restrictive piece  29  of the body  2 ; therefore, the processing unit  3  may be released from the restriction. Accordingly, the processing unit  3  may be securely prevented from moving to the external position when the port  51 A is open. 
     According to the image forming apparatus  1  described above, as shown in  FIG. 4B , the engageable part  54  of the shutter  57  may be a piece of protrusive plate, which extends downward from the lower end of the shutter  54  when the shutter  54  is in the opening position. Meanwhile, the slide-restrictive piece  29  may be formed to have the slit  29 A, which is elongated along the vertical direction. Therefore, with the simple structure, in which the engageable part  57  of the shutter  54  is engaged with the slit  29 A of the slide-restrictive piece  29 , the processing unit  3  may be prevented from moving outward to the external position while the port  51 A is open. 
     According to the image forming apparatus  1  described above, as shown in  FIG. 8 , the lower end of the engageable part  57  stays engaged in the upper area of the slide-restrictive piece  29  when the processing unit  3  is in the separated position. Therefore, even when the processing unit  3  is in the separated position, as long as the shutter  54  is in the opening position, the engagement between the engageable part  57  of the shutter  54  and the slide-restrictive piece  29  may be maintained. Therefore, until the shutter  54  is placed in the closed position, the processing unit  3  may be securely restricted from moving. Accordingly, the processing unit  3  may be securely prevented from moving to the external position when the port  51 A is open. 
     According to the image forming apparatus  1  described above, as shown in  FIGS. 4B  and  4 C, the shutter  54  may be provided with the handle  56 , by which the shutter  54  is moved to the opening position and the closed position, on the front end of the shutter  54 . With the handle  56  on the front side, the shutter  54  may be manipulated from the front side to be moved easily. Accordingly, the connection between the waste toner conveyer  43  and the belt cleaner  62  may be established and disconnected easily. 
     According to the image forming apparatus  1  described above, as shown in  FIG. 4A , the handle  56  may be arranged to fit in the groove  39 A of the shutter-restrictive piece  39  on the front cover  22  when the shutter  54  is in the opening position. On the other hand, as shown in the dash-and-dot lines in  FIG. 4A , the handle  56  may not be placed to fit in the groove  39 A of the shutter-restrictive piece  39  on the front cover  22  when the shutter  54  is in the closed position; therefore, the handle  56  is interfered with by the blockers  39 B on the right and left sides so that the front cover  22  may be restricted from moving to the closable position. Accordingly, the front cover  22  may be restricted from moving toward the closable position while the shutter  54  is in the closed position. In other words, the front cover  22  may be allowed to move to the closable position after the shutter  54  is securely moved to the opening position. Thus, when the front cover  22  covers the aperture  21 , the connection between the waste toner conveyer  43  and the belt cleaner  62  may be securely established. Accordingly, the waste toner may be conveyed to the belt cleaner  62  securely. 
     According to the image forming apparatus  1  described above, as shown in  FIGS. 4B and 4C , the user may hold the handle  56 , which aligns along the radial direction of the sleeve  55 , to rotate the shutter  54  about the central axis of the sleeve  55 . Therefore, with the simple operation, the shutter  54  may be moved between the opening position and the closed position easily. 
     According to the image forming apparatus described above, as shown in  FIGS. 7 and 9 , the processing unit  3  may be moved from the contacting position to the separated position while being accommodated inside the body  2  so that the photosensitive drums  11  should not contact the conveyer belt  17  while being moved outward to the external position. Thus, when the processing unit  3  is moved, the photosensitive drums  11  may be prevented from being rubbed on the conveyer belt  17  or damaged by the conveyer belt  17 . 
     According to the image forming apparatus  1  described above, as shown in  FIGS. 3 and 8 , the port  51 A in the waste toner conveyer  43  may be connected with the opening  69 B of the belt cleaner  62  when the processing unit  3  moves from the separated position (see  FIG. 8 ) to the contacting position (see  FIG. 3 ) and may be disconnected from the opening  69 B of the belt cleaner  62  when the processing unit  3  moves from the contacting position (see  FIG. 3 ) to the separated position (see  FIG. 8 ). Thus, the behavior of the processing unit  3  to move between the contacting position and the separated position may be effectively used to connect or disconnect the port  51 A of the waste toner conveyer  43  to or from the opening  69 B of the belt cleaner  62 . 
     According to the image forming apparatus  1  described above, as shown in  FIGS. 3 and 8 , the distance D 1  between the port  51 A in the waste toner conveyer  43  and the opening  69 B in the belt cleaner  62  when the processing unit  3  is in the separated position may be greater than the distance D 2  between the port  51 A in the waste toner conveyer  43  and the opening  69 B in the belt cleaner  62  when the processing unit  3  is in the contacting position. Therefore, when the processing unit  3  is in the separated position, the port  51 A in the waste toner conveyer  43  may be disconnected from the opening  69 B in the belt cleaner  62  sufficiently. 
     According to the image forming apparatus  1  described above, as shown in  FIGS. 3, 8 , and  4 B, the processing unit  3  may be shifted from the contacting position straight above to the separated position with the engageable part  57  in the shutter  54  being engaged with the slit  29 A of the slide-restrictive piece  29 . Meanwhile, the port  51 A in the waste toner conveyer  43  may be moved straight above from the opening  62  of the belt cleaner  62  along with the shift of the processing unit  3 . Therefore, even if the waste toner falls from the waste toner conveyer  43  through the port  51 A, the waste toner may be caught in the belt cleaner  62 , which is in the straight below, through the  69 B. Therefore, it may be prevented that the area around the dent  69 A of the joint  69  in the belt cleaner  62  is blotted by the waste toner fallen from the waste toner conveyer  43  through the port  51 A. 
     According to the image forming apparatus described above, as shown in  FIGS. 1 and 7 , the processing unit  3  may be moved from the contacting position to the separated position in conjunction with the opening motion of the front cover  22  moving from the closable position to the openable position. Therefore, the behavior of the front cover  22  to shift from the closable position to the openable position may be effectively used to move the processing unit  3  from the contacting position to the separated position smoothly. 
     According to the image forming apparatus  1  described above, as shown in  FIGS. 2 and 3 , the waste toner conveyer  43  may overlap the lower ends of the photosensitive drums  11  when projected along the widthwise direction. Therefore, the space on the widthwise outer side of the photosensitive drums  11  may be used to arrange the waste toner conveyer  43  efficiently. Thereby, a volume of the processing unit  3  may be prevented from being increased. 
     According to the image forming apparatus  1  described above, as shown in  FIGS. 2 and 3 , the waste toner conveyer  43  may include the conveyer screw  53  aligning along the front-rear direction and the cylindrical conveyer tube  51 , which accommodates the conveyer screw  53  and has the port  51 A. Thereby, the waste toner may be conveyed within the conveyer tube  51  rearward by rotation of the conveyer screw  53 . Thus, with the simple complicated structure, the waste toner may be conveyed in the front-rear direction. 
     According to the image forming apparatus  1  described above, as shown in  FIGS. 4B and 4C , the shutter  54  may be movable to rotate about the central axis A of the conveyer tube  51  between the opening position and the closed position. Thus, with the simple structure, the shutter  54  may be movable between the opening position and the closed position. 
     According to the image forming apparatus  1  described above, as shown in  FIGS. 4B and 4C , the belt cleaner  62  may have the opening  69 B, which is connected with the port  51 A of the waste toner conveyer  43  when the shutter  54  is in the opening position. Therefore, when the shutter  54  is in the opening position, the waste toner conveyer  43  and the belt cleaner  62  may establish the communication through the port  51 A in the waste toner conveyer  43  and the opening  69 B of the shutter  54 . Thus, with the simple structure, the communication between the waste toner conveyer  43  and the belt cleaner  62  may be easily established. 
     8. Modified Examples 
     Examples modified from the embodiment will be described below with reference to  FIGS. 10-14 . In the following description, items or structures which are the same as or similar to the items or the structures described above in the above first embodiment will be referred to by the same reference signs, and description of those will be omitted. 
     8-1. First Modified Example 
     8-1-1. Configuration of the First Modified Example 
     In the first embodiment described above, the shutter  54  is rotatable between the opening position and the closed position. Meanwhile, in the first modified example, a shutter  80  is slidable between an opening position (see  FIG. 10 ) and a closed position (see  FIG. 11 ) being at a frontward position with respect to the opening position. 
     The shutter  80  aligns longitudinally along the front-rear direction and has a cylindrical shape, of which front end is closed. The shutter  80  is placed over the front end of the conveyer tube  51  to cover an outer circumference of the front end of the conveyer tube  51 . Unlike the shutter  54  described in the first embodiment, the shutter  80  does not have the handle  56  of the engageable part  57  but has a hole  80 A. 
     The hole  80 A is formed at a rearward position in the shutter  80  to vertically bore through a bottom of the conveyer tube  51 . The hole  80 A is formed in a vertically coincident position with the port  51 A of the conveyer tube  51 . 
     In a position between the front end of the conveyer tube  51  and a front wall of the shutter  80 , disposed is a compression spring  81 . The compression spring  81  is a coil spring stretching along the front-rear direction. The compression spring  81  is in an arrangement such that a rear end thereof contacts a frontward face of the conveyer tube  51 , and a front end thereof contacts an inner and rearward surface of the front wall of the shutter  80 . The compression spring  81  is compressed when the shutter  80  is in the opening position to urge the shutter  80  frontward. 
     The front cover  22  has a presser member  82 . The presser member  82  is located at a lower-leftward end of the front cover  22 . The presser member  82  protrudes rearward from the rear face of the front cover  22  and has a shape of a quadrangular plate in a lateral view. The presser member  82  presses the shutter  80  rearward when the front cover  22  is in the closable position and places the shutter  80  in the opening position against the urging force by the compression tension spring  81 . 
     8-1-2. Exchange of Developer Cartridges 
     In order to exchange the developer cartridges  10  in the first modified example, first, the user may move the front cover  22  to swing frontward to the openable position (see  FIG. 11 ). 
     As the front cover  22  swings open, the lifts  30  are pulled frontward by the resilient force of the tension springs  40  to move upper-frontward, and the processing unit  3  is placed in the separated position. 
     Meanwhile, the shutter  80  is shifted from the opening position to the closed position by the resilient force of the compression spring  81 . Thus, in conjunction with the shift of the front cover  22  from the closable position to the openable position, the shutter  80  is moved from the opening position to the closed position. 
     Next, the user may pull the processing unit  3  frontward and pull a specific one or more of the developer cartridges  10  upward, similarly to the previous embodiment. Thereby, the developer cartridge(s)  10  may be fully separated from the body  2 . 
     Thereafter, in order to complete exchange of the developer cartridges  10 , the user may attach one or more of new developer cartridges  10  to the body  2  and push the processing unit  3  rearward into the body  2  so that the processing unit  3  may be placed in the separated position. 
     Thereafter, the user may move the front cover  22  to swing from the openable position to the closable position. The lifts  30  are pushed rearward by the lift-restrictive pieces  38  to move lower-rearward to place the processing unit  3  to the contacting position. Thereafter, the front cover  22  may be placed in the closable position. 
     Meanwhile, the shutter  80  may be pressed rearward by the presser member  82  on the front cover  22  to move from the closed position to the opening position against the resilient force of the compression spring  81 . Thus, the shutter  80  may be moved from the closed position to the opening position in conjunction with the movement of the front cover  22  from the openable position to the closable position. Thus, attachment of the developer cartridges  10  to the body  2  is completed. 
     8-1-3. Effects 
     According to the first modified example, the shutter  80  may be moved to the closed position by handling the front cover  22  to move to the openable position and expose the aperture  21 . Therefore, without an additional action to the shutter  80 , the communication between the waste toner conveyer  43  and the belt cleaner  62  may be smoothly disconnected. 
     Further, the shutter  80  may be placed to the closed position securely as the front cover  22  is moved to the openable position and before the processing unit  3  is moved to the external position. Therefore, the waste toner in the waste toner conveyer  43  may be prevented from leaking while the processing unit  3  is being moved to the external position. 
     Meanwhile, the effects that may be caused by the first embodiment may be similarly achieved through the configuration of the first modified example. 
     8-2. Second Modified Example 
     8-2-1. Configuration of the Second Modified Example 
     In the first embodiment described above, the shutter  54  has the engageable part  57 , which may be fitted in the slide-restrictive piece  29  in the body  2 . Meanwhile, in the second modified example, as shown in  FIG. 12 , the shutter  90  may include a handle  91 , which is engageable with the front cover  22 . 
     The handle  91  may be, as shown in  FIGS. 13A-13B , located at the front end of the shutter  90 . The handle  91  may include a shaft  92  and a knob  93 . 
     The shaft  92  may have a cylindrical shape, which protrudes frontward from the front face of the sleeve  55 . 
     The knob  93  may be arranged to protrude frontward from a front end of the shaft  92 . The knob  93  may align along the widthwise direction when the shutter  90  is in an opening position (see  FIGS. 13A and 13B ). In this regard, a dimension of the knob  93  along the widthwise direction may be longer than a dimension of a slit  94  on the front cover  22 , which will be described later in detail, along the widthwise direction. The knob  93  may have a shape of a rectangular plate. 
     Meanwhile, the front cover  22  may have the slit  94 , through which the knob  91  may penetrate. The slit  94  is formed in a leftward position in the front cover  22 . As shown in  FIG. 13B , the slit  94  may be a through-hole, which has a rectangular shape in a front view elongated along the vertical direction. The slit  94  may include a shaft-penetration part  95  and a pair of alignment parts  96 . 
     The shaft-penetration part  95  is formed at an approximate center of a dimension the slit  94  along the vertical direction and has a round shape in a front view. A diameter of the shaft-penetration part  95  is larger than a diameter of the shaft  92  of the handle  91 . 
     The alignment parts  96  are each formed continuously to extend from the shaft-penetration part  95  upward and downward along the vertical direction. The alignment parts  96  each has a rectangular shape elongated along the vertical direction in the front view. A dimension of the alignment parts  96  along the widthwise direction is greater than a thickness of the knob  93 . 
     8-2-2. Exchange of the Developer Cartridges 
     In order to exchange the developer cartridges  10  in the second modified example, first, the user may hold the knob  93  of the shutter  90  and rotate counterclockwise in the front view, as shown in  FIGS. 13C and 13D , to place the shutter  90  in a closed position. 
     In this regard, the hole  55 A of the shutter  90  may coincide with a leftward circumference of conveyer tube  51 . Meanwhile, the bottom of the sleeve  55  in the shutter  90  may coincide with the port  51 A of the conveyer tube  51 . 
     In this regard, the knob  93  aligns with the slit  94  along the vertical direction, and the entire handle  91  fits in the slit  94  in the front view. Thereby, the front cover  22  may be released from the restriction and may be allowed to move from the closable position to the openable position. 
     Thereafter, the user may place the front cover  22  to the openable position, as shown in  FIG. 14 . In this regard, the knob  93  of the shutter  90  may pass through the slit  94 . 
     Thereby, similarly to the first embodiment, the lifts  30  may be pulled forward by the resilient force of the tension springs  40  to move upper-frontward, and the processing unit  3  may be placed in the separated position. 
     Thereafter, the user may move the processing unit  3  to the external position and pull a specific one or more of the developer cartridges  10  upward, similarly to the first embodiment. Thereby, the developer cartridge(s)  10  may be fully separated from the body  2 . 
     Thereafter, in order to complete exchange of the developer cartridges  10 , the user may attach one or more of new developer cartridges  10  to the body  2  and push the processing unit  3  rearward into the body  2  so that the processing unit  3  may be placed in the separated position. 
     Thereafter, the user may place the front cover  22  to the closable position, as shown in  FIG. 12 . In this regard, the lifts  30  may be pushed rearward by the lift-restrictive pieces  38  to move lower-rearward, and the processing unit  3  may be placed in the contacting position. Meanwhile, as shown in  FIGS. 13C and 13D , the knob  93  of the shutter  90  may pass through the slit  94  to protrude frontward from the slit  94  in the front cover  22 . The shaft  92  of the shutter  92  may be arranged to penetrate through the shaft-penetration part  95 . 
     Next, the user may hold the knob  93  and rotate the shutter  90  counterclockwise in the front view to place the shutter  90  in the opening position, as shown in  FIGS. 13A and 13B . 
     Thereby, the knob  93  is arranged to align along the widthwise direction and faces with peripheral areas of the slit  94  in the front cover  22  along the widthwise direction. Thus, the front cover  22  may be restricted from moving from the closable position to the openable position. Thus, attachment of the developer cartridges  10  to the body  2  is completed. 
     8-2-3. Effects 
     According to the second modified example, as shown in  FIGS. 12 and 13B , when the shutter  90  is in the opening position, the knob  93  of the shutter  90  may face with the widthwise peripheral areas of the slit  94 , and the front cover  22  may be restricted from moving from the closable position to the openable position. Further, as shown in  FIG. 13D , when the shutter  90  is in the closed position, the knob  93  of the shutter  90  may align with the alignment parts  96  of the slit  94 , and the front cover  22  may be allowed to move from the closable position to the openable position. 
     Therefore, with the port  51 A of the waste toner conveyer  43  being open, the aperture  21  may not be allowed to be exposed, and the processing unit  3  may not be allowed to move to the external position. 
     Accordingly, it may be prevented that the processing unit  3  is moved outward to the external position while the port  51 A of the waste toner conveyer  43  is open. 
     Therefore, the waste toner in the waste toner conveyer  43  may be prevented from leaking while the processing unit  3  is being moved to the external position 
     Meanwhile, the effects that may be caused by the previous embodiment may be similarly achieved through the configuration of the first modified example. 
     8-3 More Examples 
     Some more examples which may be modified from the previous embodiment will be described below. 
     The cleaning blades  46  in the drum cleaners  42  may be replaced with, for example, conductive cleaning brushes (not shown) or conductive cleaning rollers (not shown). With such cleaning brushes or cleaning rollers, scrapers such as blades may be additionally provided so that the toner adhered to the cleaning brushes or the cleaning rollers may be removed therefrom. 
     For another example, the screws  47  in the drum cleaners  42  and the screw  53  in the waste toner conveyer  43  may be replaced with another forms of conveyers. For example, a rotation shaft and fins made of thin films may be provided. Each fin may be attached to the rotation shaft at one end thereof, and the other end being a free end may be cut in a shape such that a distance between the rotation shaft and the free end may be shorter at a downstream part of the fin and longer at an upstream part of the fin with regard to the toner-conveying direction. For another example, the screws  42  and/or the screw  53  may be replaced with a belt-conveyer. 
     9. Second Embodiment 
     Referring to  FIGS. 15-22 , an image forming apparatus  101  according to a second embodiment will be described below. In the following description, items or structures which are the same as or similar to the items or the structures described in the previous embodiment will be referred to by the same reference signs, and description of those will be omitted. 
     The image forming apparatus  101  is a color laser printer capable of forming images in an intermediate transfer method. 
     9-1. Body 
     As shown in  FIGS. 15-16 , according to the second embodiment, a body  102  of the image forming apparatus  101  includes a pair of linkages  103 , a manual sheet inlet  109 , a manual sheet tray  108 , a manual sheet path  107 , an intermediate transfer unit  110 , a secondary transfer roller  111 , a belt cleaning unit  141 , a connecting member  140 , a second front cover  150 , and an image reading unit  104 . 
     9-1-1 Linkages 
     The paired linkages  103  each connects one of the paired lifts  30  with the front cover  22 . In the following description, unless otherwise stated, directions concerning the linkages  103  will be based on a condition, in which the front cover  22  is in the openable position (see  FIG. 19 ) and the linkages  103  are extended outward. Each linkage  103  includes a first link member  105  and a second link member  106 . 
     The first link member  105  has a shape of a bar extending lower-frontward from a lower-front end of the corresponding one of the lifts  30 . An upper-rear end of the first link member  105  is rotatably connected to the lower-front end of the corresponding one of the lifts  30 . 
     The second link member  106  has a shape of a bar extending lower-frontward from a lower-front end of the first link  105 . An upper-rear end of the second link member  106  is rotatably connected to a lower-front end of the first link member  105 . A lower-front end of the second link member  106  is rotatably connected to the front cover  22 . 
     9-1-2. Manual Sheet Inlet, Manual Sheet Tray, and Manual Sheet Path 
     The manual sheet inlet  109  is located at a lower end of the front cover  22 . The manual sheet inlet  109  is formed to longitudinally align with the widthwise direction to bore through the front cover  22  along the front-rear direction. 
     The manual sheet tray  108  has a shape of a plate and is located in a frontward position with respect to the front cover  22 . The manual sheet tray  108  is swingable about a lower end thereof between a standing position, in which the manual sheet tray  108  vertically aligns with the front cover  22  being in the closable position, and an inclined position, in which the manual sheet tray  108  leans frontward with respect to the front cover  22  being in the closable position to extend upper-frontward from the lower end thereof. The inclined position of the manual sheet tray  108  is indicated by double-dotted lines in  FIG. 15 . When the manual sheet tray  108  is in the standing position, the lower end of the manual sheet tray  108  is in a frontward position with respect to the manual sheet inlet  109  to close the manual sheet inlet  109 . When the manual sheet inlet  108  is in the inclined position, the lower end of the manual sheet tray  108  is in a frontward position with respect to the manual sheet path  107  across the manual sheet inlet  109 . 
     The manual sheet path  107  is located in a position between the feeder tray  7  and a processing unit  120 . The processing unit  120  will be described below in detail. The manual sheet path  107  is formed to extend rearward from the front end of the body  105  to a frontward position with respect to a pickup roller R, which picks up the sheet P from the feeder tray  7 . In other words, a rear end of the manual sheet path  107  is at the frontward position with respect to the pickup roller R. Thus, the sheet P set on the manual sheet tray  108  in the inclined position may be conveyed in the manual sheet path  107  to the pickup roller R. 
     9-1-3. Intermediate Transfer Unit, Belt Cleaning Unit, Connecting Member, and Second Cover 
     The intermediate transfer unit  110  is located in a position between the processing unit  120  and the manual sheet path  107 . The intermediate transfer unit  110  includes a driving roller  112 , a driven roller  113 , a tensile roller  116 , an intermediate transfer belt  114 , and a plurality of primary transfer rollers  115 . 
     The driving roller  112  is located at a rear end of the intermediate transfer unit  110 . 
     The driven roller  113  is located at a front end of the intermediate transfer unit  110  in a frontward and spaced apart position with respect to the driving roller  112 . The driven roller  113  is, unlike the driven roller  16  mentioned earlier in the first embodiment, maintained stationary with respect to the body  102 . 
     The tensile roller  116  is located in a lower-frontward and spaced apart position with respect to the driving roller  112 . The tensile roller  116  is resiliently movable in the vertical direction to maintain a tensile force in the intermediate transfer belt  114  constant. 
     The intermediate transfer belt  114  is strained around the driving roller  112 , the driven roller  113 , and the tensile roller  116  in an arrangement such that an outer surface of an upper part of the intermediate transfer belt  114  should contact each one of the photosensitive drums  11 . The intermediate transfer belt  114  is driven by rotation of the driving roller  112  and the driven roller  113  to circulate in a direction such that the upper part of the intermediate transfer belt  114  moves frontward and a lower part of the intermediate transfer belt  114  moves rearward. 
     Each of the primary transfer rollers  115  is located in a lower position with respect to a corresponding one of the photosensitive drums  11  across the upper part of the intermediate transfer belt  114 . 
     The secondary transfer roller  111  is located in a lower-rear position with respect to the driving roller  112  in the intermediate transfer unit  110  across the intermediate transfer belt  114 . 
     The belt cleaning unit  141  includes, as shown in  FIGS. 15 and 17 , a belt cleaner  142 , a waste toner container  143 , and a conveyer  145 . 
     The belt cleaner  142  is located in an upper position with respect to the rear end of the intermediate transfer unit  110 . The belt cleaner  142  includes a cleaner-frame  146 , a scraper blade  147 , a brush  148 , and an auger screw  149 . 
     The cleaner-frame  146  has an oval shape in a lateral view and includes a collecting hole  146 A. 
     The collecting hole  146 A is formed to bore through a bottom of the cleaner-frame  146 . 
     The scraper blade  147  is located in a lower position with respect to the collecting hole  146 A. The scraper blade  147  has a shape of a plate aligning longitudinally along the front-rear direction. An upper end of the scraper blade  147  is fixed to an upper edge of the collecting hole  146 A of the cleaner-frame  146 . The scraper blade  147  is arranged to have a rear edge thereof to contact the upper surface of the upper part of the intermediate transfer belt  114 . 
     The brush  148  is located in an upper position with respect to the collecting hole  146 A. The brush  148  is arranged to have a lower end thereof to contact an upper surface of the scraper blade  147 . 
     The auger screw  149  is located in a frontward position with respect to the brush  148  to align longitudinally along the widthwise direction. 
     The waste toner container  143  is, as shown in  FIGS. 16-17 , located in a lower-leftward position in the body  102  to be detachably attached between the outer frame  31  and the inner frame  32 . The waste toner container  143  has a shape of a box longitudinally aligning along the front-rear direction. 
     The conveyer  145  is, as shown in  FIG. 17 , located in a leftward position with respect to the belt cleaner  142 . The conveyer  145  is a tube longitudinally aligning along the vertical direction. The conveyer  145  is connected to a front end of the belt cleaner  142  at an upper end thereof and is detachably attached to a rear end of the waste toner container  143  at a lower end thereof. 
     The connecting member  140  is located in a lower position with respect to a front end of the waste toner conveyer  123 . The connecting member  140  is a tube longitudinally aligning along the vertical direction. The connecting member  140  is detachably attached to the front end of the waste toner container  143 . The connecting member  140  includes an opening  140 A. 
     The opening  140 A is formed in a central position with regard to the widthwise direction and the front-rear direction on an upper end of the connecting member  140 . The opening  140 A is a hole formed to bore through an upper wall of the connecting member  140  vertically. 
     The second front cover  150  is located in a lower-leftward position with respect to the front end of the body  102  and in a frontward position with respect to the waste toner container  143  to face with the waste toner container  143 . The second front cover  150  has a shape of a plate standing along the vertical direction and is supported by the front wall of the body  102  to be swingable about the lower end thereof. The second front cover  150  is swingable between an openable position, in which a lower-leftward area in the body  102  is exposed so that the waste toner container  143  may be detached or attached therethrough, and a closable position, in which the lower-leftward area in the body  102  is closed and the waste toner container  143  is restricted from being moved. The openable position of the second front cover  150  is indicated by double-dotted lines in  FIG. 17 , and the closable position of the second front cover  150  is indicated by solid lines in  FIG. 17 . 
     9-1-4. Image Reading Unit 
     The image reading unit  104  is located in an upper and spaced apart position with respect to the outlet tray  8 . The image reading unit  104  is capable of reading an image formed on a sheet and generate image data based on the read image. 
     9-2. Detailed Configuration of Processing Unit 
     The processing unit  120  is, as shown in  FIG. 15 , located in a central area in the body  102 . The processing unit  120  is movable inside the body  2  between a contacting position (see  FIG. 15 ), at which the plurality of photosensitive drums  11  contact an intermediate transfer belt  114 , and a separated position (see  FIG. 19 ), which is an upper position with respect to the contacting position and at which the photosensitive drums  11  are separated from the intermediate transfer belt  114 , while the processing unit  120  is accommodated inside the body  102 . Further, the processing unit  120  is movable between the separated position and an external position (see  FIG. 21 ), which is frontward with respect to the separated position and outside the body  2 , through the aperture  21 . The processing unit  120  includes a drawer unit  121  and a plurality of developer cartridges  122 . 
     9-2-1. Drawer Unit 
     The drawer unit  121  has, as shown in  FIGS. 15 and 16 , a form of a frame, which is open upward, downward, and sideward. The drum unit  121  includes a waste toner conveyer  123 . 
     The waste toner conveyer  123  is, as shown in  FIGS. 16 and 17 , located in a lower position in the drawer unit  121  on an outer (leftward) side of one of lateral walls on the left. The waste toner conveyer  123  includes a conveyer tube  124 , a plurality of connectors  125 , a conveyer screw  126 , and a shutter  127 . 
     The conveyer tube  51  is arranged to longitudinally align along the front-rear direction and has a closed tubular form, of which front and rear ends are closed. The conveyer tube  124  includes a port  124 A. 
     The port  124 A is formed in a frontward position in the conveyer tube  124  to vertically bore through a bottom of the conveyer tube  124  and has an approximate shape of a rectangle in a plan view from the bottom. 
     The connectors  125  are located in upper positions with respect to the conveyer tube  124  to be spaced apart from one another along the front-rear direction. The connectors  125  are arranged to each correspond to one of the plurality of processing cartridges  122 ; in other words, there are four (4) connectors  125 . Each of the connectors  125  is in a tubular shape, which is formed to extend upward continuously from a top of the conveyer tube  124  and curve rightward. A rightward end of each connector  125  is arranged to penetrate through a leftward one of the lateral plates  41  in the drawer unit  122  to be placed in an area laterally inward in the drawer unit  121  along the widthwise direction. 
     The conveyer screw  126  is similar to the conveyer screw  126  mentioned earlier in the first embodiment and is arranged inside the conveyer tube  124 . The conveyer screw  126  includes a gear  126 A. 
     The shutter  127  is located at a front end of the waste toner conveyer  123 . The shutter  127  is, as shown in  FIGS. 18A-18B , movable between an opening position (see  FIG. 18A ), in which the port  124 A of the conveyer tube  124  is exposed within the body  102 , and a closed position (see  FIG. 18B ), in which the port  124 A of the conveyer tube  124  is closed. In the following description, unless otherwise stated, the shutter  124  is described with reference to the opening position. The shutter  54  includes a main part  128 , a handle  129 , and a contact part  130 . 
     The main part  128  has a cylindrical shape aligning longitudinally along the front-rear direction. A front end of the main part  128  is closed, and a rear end of the main part  128  is open. The main part  128  is placed over the front end of the conveyer tube  124  to cover an outer circumference of the front end of the conveyer tube  124 . The main part  128  has a hole  128 A. 
     The hole  128 A is formed in a rearward position in the main part  128  to vertically bore through a bottom of the main part  128  and has an approximate shape of a rectangle in a plan view from the bottom. The hole  128 A is formed in a vertically coincident position with the port  124 A of the conveyer tube  124 . 
     The handle  129  is arranged in a frontward position in the shutter  127 . The handle  129  protrudes frontward from the front end of the main part  128  and extends along the vertical direction. The handle has a shape of an approximate shape of a three-sided frame which is open rearward in a lateral view. 
     The contact part  130  is arranged to protrude downward from a lower circumference of the rear end of the shutter  127 . The contact part  130  has a shape of a plate. In other words, the contact part  130  is a piece of protrusive plate that protrudes downward from the bottom of the rear end of the shutter  127 . A dimension of the contact part  130  along the vertical direction is longer than a distance for the processing unit  120  to move between the contacting position and the separated position. Thus, the contact part  130  may contact an upper end of the connecting member  140 . 
     9-2-2. Processing Cartridges 
     Each of the processing cartridges  122  includes, as shown in  FIG. 15 , a photosensitive drum  11 , a charger roller  12 , a developer unit  131 , and a drum cleaner  132 . 
     The photosensitive drum  11  is rotatably supported by a lower part of a corresponding one of the processing cartridges  122 . 
     The charger roller  12  is arranged in an upper-frontward position of the processing cartridge  122  to contact an upper-frontward end of the photosensitive drum  11 . 
     The developer unit  131  is located in a rearward position with respect to the photosensitive drum  11 . The developer unit  131  includes a developer roller  13  and a supplier roller  14  and contains toner in one of the corresponding colors in an upper area with respect to the developer roller  13  and the supplier roller  14 . 
     The developer roller  13  is rotatably supported by the developer unit  131  to be exposed frontward at a lower position in the developer unit  131 . The developer roller  13  is arranged to contact a rearward area of the corresponding one of the photosensitive drums  11 . 
     The supplier roller  14  is arranged in a rearward position with respect to the developer roller  13  to contact a rearward area of the developer roller  13 . 
     The drum cleaner  132  is located in a frontward position with respect to a corresponding one of the photosensitive drums  11  and includes, similarly to the drum cleaner  42  described earlier in the first embodiment, a cleaner-frame  45 , a cleaning blade  46 , and a screw  47 . An opening  45 A in the cleaner-frame  45  is formed to bore through a rear wall of the cleaner-frame  45  along the front-rear direction and coincides with the frontward end of the photosensitive drum  11  along the front-rear direction. The cleaning blade  46  is arranged to have a lower end thereof to contact the frontward end of the photosensitive drum  11 . 
     In the second embodiment, the cleaner-frame  45  of the drum cleaner  132  includes, as shown in  FIG. 16 , a connector  133 , which is connected with the connector  125  of the drawer unit  121 . 
     The connector  133  has an cylindrical shape extending leftward from a lower-leftward end of the cleaner-frame  45  of the drum cleaner  132 . 
     9-3. Image Forming Operation 
     When the image forming apparatus  101  starts forming an image, the charger rollers  12  charge the surfaces of the photosensitive drums  11  evenly, and the scanner unit  4  emits the laser beams toward the photosensitive drums  11  selectively according to the image data so that electrostatic latent images are formed in the areas selectively exposed to the laser beams on the photosensitive drums  11 . 
     Meanwhile, the supplier rollers  14  supply the toner in the developer cartridges  10  to the developer rollers  13 . The toner supplied to each developer roller  13  is frictionally charged between the developer roller  13  and the supplier roller  14  and carried on the developer roller  13 . 
     The developer rollers  13  then supply the toner to the electrostatic latent images on the photosensitive drums  11 . Thus, toner images are formed on the surfaces of the photosensitive drums  11 . 
     The toner images formed on the surfaces of the photosensitive drums  11  are sequentially transferred onto the outer surface of the upper part of the intermediate transfer belt  114  so that a multiple-colored image is formed on the outer surface of the intermediate transfer belt  114 . 
     Meanwhile, sheets P in the feeder tray  7  are picked up one-by-one along with rotation of the pickup roller R. Each sheet P is conveyed upper-rearward and conveyed to a position between the intermediate transfer belt  114  and the secondary transfer roller  111  at a predetermined timing. As the sheet P is conveyed upward to pass through the position between the intermediate transfer belt  114  and the secondary transfer roller  111 , the colored image is transferred onto the sheet P. 
     The sheet P is thereafter exposed to heat and pressure from the heat roller  19  and the pressure roller  20  when the sheet P passes through an intermediate position between the heat roller  19  and the pressure roller  20  so that the colored image should be fixed thereon. The sheet P is thereafter discharged to the sheet outlet tray  8 . 
     9-4. Behaviors in Drum Cleaning and Belt Cleaning 
     Behaviors to clean the photosensitive drums  11  and the intermediate transfer belt  114  in the image forming apparatus  101  in the second embodiment will be described below. 
     When the toner images are transferred to the sheet P during the image forming operation in the image forming apparatus  101  described above (see  FIG. 15 ), there may be residual toner, which is not transferred onto the intermediate transfer belt  114  but remains on the surfaces of the photosensitive drum  11  in the processing cartridges  122 . 
     Waste toner including such residual toner may be scraped off from the surfaces of the photosensitive drums  11  by the cleaning blades  46  of the drum cleaners  132  as the photosensitive drums  11  rotate and stored inside the cleaner-frames  45  of the drum cleaners  132 . 
     The waste toner stored inside each cleaner-frame  45  is conveyed by rotation of the screw  47  leftward to the connector  125  of the corresponding one of the waste toner conveyer  123  (see  FIG. 16 ). The waste toner reaching the connector  125  may fall in the conveyer tube  124  by the effect of gravity. 
     The waste toner falling in the conveyer tube  124  is conveyed frontward inside the conveyer tube  124  by rotation of the conveyer screw  126 , and further through the port  124 A of the conveyer tube  124  and the hole  128 A of the shutter  128 , to the opening  140 A in the connecting member  140 . 
     The waste toner reaching the opening  124 A in the connecting member  140  passes through the opening  124 A and enters the connecting member  140  by the effect of gravity to be stored in the waste toner container  143 . 
     Meanwhile, when the toner images are transferred to the sheet P during the image forming operation (see  FIG. 15 ), there may be residual toner, which remains on the surface of the intermediate transfer belt  114 . 
     The residual toner adhered to the surface of the intermediate transfer belt  114  may be scraped off from the surface of the intermediate transfer belt  114  by the cleaning blade  147  of the belt cleaner  142  as the intermediate transfer belt  114  circulates and stored in the frontward area in the cleaner-frame  146 . 
     The waste toner stored in the frontward area in the cleaner-frame  146  is, as shown in  FIGS. 15 and 17 , conveyed by the auger screw  149  to an upper area in the conveyer member  145  to pass through the conveyer member  145  and stored in the waste toner container  143 . 
     9-6. Exchanges of the Processing Cartridges 
     A flow to exchange the processing cartridges  122  will be described below. 
     First, a user may remove the processing cartridges  122  from the body  102 . In order to remove the processing cartridges  122  from the body  102 , the user may place the front cover  22  in the openable position (see  FIG. 19 ). 
     As the front cover  22  swings open, the linkages  103  are stretched frontward, and the lifts  30  are pulled frontward. In this regard, the engageable bosses  30 B slide in the guide grooves  37 A of the guide members  37 , and the lifts  30  are moved upper-frontward. 
     As the lifts  30  move upper-frontward, the processing unit  120  moves upward to the separated position, and the photosensitive drums  11  are moved upward to be separated from the intermediate transfer belt  114 . 
     Meanwhile, as shown in  FIG. 20 , the waste toner conveyer  123  is moved upward to be separated from the connecting member  140 . Thereby, the hole  128 A in the shutter  127  of the waste toner conveyer  123  is moved upward, and the channel between the waste toner conveyer  123  and the belt cleaner  62  through the hole  128 A of the shutter  127  and the opening  140 A of the connecting member  140  is disconnected. 
     In the meantime, the lower end of the contact part  130  of the shutter  127  remains faced with an upper-rearward end of the connecting member  140 . Thereby, the processing unit  120  may be restricted from moving frontward while being placed in the separated position. 
     Next, the user may hold the handle  129  of the shutter  127  in the waste toner conveyer  123  and rotate the shutter  127  clockwise, in a front view, to place the shutter  127  in the closed position (see  FIG. 18B ). 
     When the shutter  127  is in the closed position, the hole  128 A in the shutter  127  coincides with a leftward circumference of the conveyer tube  124 . Meanwhile, the bottom of the main part  128  of the shutter  127  in the closed position coincides with the port  124 A of the conveyer tube  124 . 
     In this regard, the contact part  130  of the shutter  127  is moved upper-leftward to be separated from the rearward position with respect to the connecting member  140 . Thereby, the contact prat  130  and the connecting member  140  are disengaged, and the processing unit  120  is released from the restriction and is allowed to move frontward. 
     Next, the user may pull the processing unit  120  frontward to place in the external position (see  FIG. 21 ). In this regard, the protrusive strips  41 A slide inside the guide grooves  30 A in the lifts  30 , and the photosensitive drums  11  being upwardly separated from the intermediate transfer belt  114  are moved from the separated position to the external position. 
     Next, the user may pull a specific one or more of the processing cartridges  122  upward, as indicated by double-dotted lines in  FIG. 21 . Thereby, the processing cartridge(s)  122  may be fully separated from the body  102 . 
     Thereafter, in order to complete exchange of the processing cartridges  122 , the user may attach one or more of new processing cartridges  122  to the body  102 . In order to attach the new processing cartridge  122  to the body  102 , the user may follow the above-described process in a reversed order. 
     That is, the user may attach the new processing cartridges  122  to the drawer unit  121  and push the processing unit  120  rearward into the body  102 . The processing unit  102  may be placed in the separated position (see  FIG. 19 ). 
     Next, the user may hold the handle  129  of the shutter  127  in the waste toner conveyer  123  and rotate the shutter  127  counterclockwise, in the front view, to place the shutter  127  in the opening position (see  FIGS. 18A and 20 ). Accordingly the lower end of the contact part  130  of the shutter  127  is placed in the rear area of the upper end of the connecting member  140 . Thereby, the processing unit  120  is restricted from moving frontward while being in the separated position. 
     Next, the user may move the front cover  22  to swing from the openable position to the closable position. Accordingly, the linkages  103  collapse at joints between the first link member  105  and the second link member  106  and push the lifts  30  rearward. 
     Further, as the user moves the front cover  22  further to swing toward the closable position, the lifts  30  are pushed rearward, and the engageable bosses  30 B are moved to slide in the guide grooves  37 A of the guide members  37  lower-rearward. Accordingly, the processing unit  120  is moved downward as the pair of lifts  30  moves lower-rearward to the contacting position. 
     After the processing unit  120  is set in the contacting position, the front cover  22  is placed in the closable position. Thus, attachment of the processing cartridges  122  to the body  102  is completed. 
     When the waste toner container  143  is filled up with the collected waste toner, as indicated by the double-dotted lines in  FIG. 17 , the second front cover  150  may be open, and the waste toner container  143  may be pulled outside the body  102  so that a replacing empty waste toner container  143  may be attached to the body  102 . 
     9-7. Effects 
     According to the image forming apparatus  101  of the second embodiment described above, the effects that may be caused by the first embodiment may be similarly achieved. 
     Although examples of carrying out the invention have been described, those skilled in the art will appreciate that there are numerous variations and permutations of the image forming apparatus that fall within the spirit and scope of the invention as set forth in the appended claims. It is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or act described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.