Patent Publication Number: US-9411269-B2

Title: Image forming apparatus and developing agent cartridge

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of prior U.S. application Ser. No. 14/456,735, filed Aug. 11, 2014, which is a continuation of prior U.S. application Ser. No. 14/060,259, filed Oct. 22, 2013, now U.S. Pat. No. 8,805,236, issued Aug. 12, 2014, which is a continuation of prior U.S. application Ser. No. 13/692,023, filed Dec. 3, 2012, now U.S. Pat. No. 8,571,441, issued Oct. 29, 2013, which is a continuation of prior U.S. application Ser. No. 13/411,878, filed Mar. 5, 2012, now U.S. Pat. No. 8,326,177, issued Dec. 4, 2012, which is a continuation of prior U.S. application Ser. No. 12/968,931, filed Dec. 15, 2010, now U.S. Pat. No. 8,139,978, issued Mar. 20, 2012, which is a continuation application of prior U.S. application Ser. No. 12/685,744, filed Jan. 12, 2010, now U.S. Pat. No. 7,877,039, issued Jan. 25, 2011, which is a continuation application of prior U.S. application Ser. No. 11/782,917, filed Jul. 25, 2007, now U.S. Pat. No. 7,657,206, issued Feb. 2, 2010, which claims priority to Japanese Patent Applications Nos. 2006-202611, 2006-202612 and 2006-202613 filed on Jul. 25, 2006, the disclosures of which are hereby incorporated into the present application by reference. 
    
    
     TECHNICAL FIELD 
     Aspects of the present invention relate to an image forming apparatus such as a color laser printer and a developing agent cartridge installed in the image forming apparatus. 
     BACKGROUND 
     Conventionally known is the so-called tandem-type color laser printer having photosensitive drums forming electrostatic latent images, developing rollers developing the electrostatic latent images and toner boxes accommodating toners fed to the developing rollers, arranged correspondingly to four colors, i.e. yellow, magenta, cyan and black, respectively. 
     The tandem-type color laser printer forms generally simultaneously toner images of the respective colors on the respective photosensitive drums and sequentially transfers the toner images of the respective colors from the photosensitive drums to a sheet sequentially passing through the photosensitive drums, and therefore can form color images at a speed generally identical to that of a monochromatic laser printer. 
     For example, there has been proposed a tandem-type color laser printer having image forming stations, each including a photosensitive member, a developing unit having a developing roller and storing a developing agent and a transfer unit, provided correspondingly to respective colors, and forming color images by passing a transfer medium through the image forming stations of the respective colors. 
     In the tandem-type color laser printer, a set of four photosensitive members as well as a coroner charger and a cleaner arranged around the photosensitive member can be drawn out and detached from the printer body, and mounted on and attached to the printer body, as an integral photosensitive cartridge. Further, developing devices belonging to the photosensitive members are detachably mountable to the photosensitive cartridge. 
     Also known is a color image forming apparatus in which a plurality of developing machines are arranged correspondingly to respective colors and toner hoppers for supplementing toners to the developing machines are parallelly provided above side portions of the developing machines in a detachably mountable manner to the developing machines respectively. 
     However, each of the developing devices storing the toners corresponding to the respective colors must be increased in size in order to ensure sufficient volumes of the toners. 
     In the tandem-type color laser printer, on the other hand, the each developing device is attached/detached to/from the photosensitive cartridge. Therefore, if the developing devices are increased in size in order to ensure sufficient volumes of toners, the photosensitive cartridge must also be increased in size. Then, the printer body to/from which the photosensitive cartridge is attached/detached is inevitably increased in size. 
     In order to exchange each developing device in the tandem-type color laser printer, further, the photosensitive cartridge must be drawn out and detached from the printer body to exchange each developing device with a new one in the detached photosensitive cartridge, and must thereafter be mounted on and attached to the printer body again. In other words, the photosensitive cartridge including the photosensitive bodies, the coroner charger and the cleaner must be detached from and then attached to the printer body, in order to exchange each developing device. Thus, much labor is required for detaching the photosensitive cartridge from the printer body and thereafter attaching the photosensitive cartridge to the printer body. 
     Further, while each developing device storing the toner is provided with members such as a feed roller, a developing roller and a regulation blade necessary for developing a toner image, the developing device must be exchanged when the toner is used up, even if these members are still operable. Therefore, the running cost is increased. 
     The color laser printer can be undesirably increased in size due to the aforementioned structure including the plurality of photosensitive drums, the plurality of developing rollers and the plurality of toner boxes corresponding to the respective colors. 
     If the toner boxes are reduced in size in order to miniaturize the color laser printer, the volumes of the toners that can be accommodated in the toner boxes are reduced, so that the toner boxes must be frequently exchanged, leading to troublesome maintenance. 
     On the other hand, when sufficient volumes of toners are ensured in the toner boxes while miniaturizing the color laser printer, the toner boxes are limited in size reduction to inevitably occupy a large volume ratio in the color laser printer. Thus, arrangement of other parts in the color laser printer is restricted. 
     When the toner boxes are respectively provided with agitators for agitating the toners accommodated therein, for example, it is difficult to provide mechanisms for supplying driving force to the agitators on all the toner boxes in the limited space of the color laser printer. 
     When the developing machines and the toner hoppers are formed independently of each other as in the color image forming apparatus, for example, shutter members must be provided on all the toner hoppers respectively such that the toner hoppers communicate with the developing machines by opening the shutter members for feeding the toners to the developing machines and the toner hoppers are sealed by closing the shutter members for preventing the toners from leaking. 
     In this case, it is difficult to provide mechanisms for opening/closing the shutter members on all the toner hoppers in the limited space of the color laser printer. 
     SUMMARY 
     One aspect of the present invention may provide an image forming apparatus reducible in size while ensuring a sufficient volume of developing agent in developing agent cartridge, excellent in operability and capable of reducing the maintenance cost. 
     Another aspect of the present invention may provide an image forming apparatus capable of reliably supplying driving force to an agitating member provided in each developing agent cartridge while ensuring a sufficient volume of developing agent in the developing agent cartridge when the image forming apparatus is reduced in size, and a developing agent cartridge installed in this image forming apparatus. 
     Still another aspect of the present invention may provide an image forming apparatus capable of reliably opening/closing a shutter member provided on each developing agent cartridge while ensuring a sufficient volume of developing agent in the developing agent cartridge when the image forming apparatus is reduced in size, and a developing agent cartridge installed in this image forming apparatus. 
     The same or different aspect of the present invention may provide an image forming apparatus including: a casing; a plurality of image carriers parallelly arranged along one direction in the casing, and formed with an electrostatic latent image; a plurality of developing agent carriers opposed to the image carriers, for visualizing the electrostatic latent image by feeding a developing agent to the image carriers; and a plurality of developing agent cartridges, parallelly arranged in the one direction to be opposed to the developing agent carriers in the longitudinal direction of the developing agent carriers, and configured to be together attachable/detachable to/from the casing along the one direction, for accommodating the developing agent fed to the developing agent carriers. 
     One or more aspects of the present invention provide an image forming apparatus including: a plurality of image carriers formed with an electrostatic latent image; a plurality of developing agent carriers visualizing the electrostatic latent image by feeding a developing agent to the image carriers; a plurality of developing agent cartridges accommodating the developing agent fed to the developing agent carriers; an agitating member provided in the developing agent cartridge and supplied with driving force to agitate the developing agent accommodated in the developing agent cartridges; a drive unit supplying the driving force to the agitating member of at least any developing agent cartridge; and a transmission unit transmitting the driving force supplied by the drive unit, from the agitating member of a first developing agent cartridge to the agitating member of a second developing agent cartridge adjacent to the first developing agent cartridge. 
     One or more aspects of the present invention provide a developing agent cartridge, accommodating a developing agent fed to a developing agent carrier, including: a first agitating member supplied with driving force to be rotated for agitating the accommodated developing agent; a first rotating shaft extending along one direction and provided with the first agitating member, for serving as the rotation center of the first agitating member; an input transmission portion provided on one end portion of the first rotating shaft in the one direction, for receiving the driving force; and an output transmission portion provided on the other end portion of the first rotating shaft in the one direction, for outputting the driving force received by the input transmission portion. 
     One or more aspects of the present invention provide an image forming apparatus including: a plurality of image carriers parallelly arranged along one direction and formed with an electrostatic latent image; a plurality of developing agent carriers visualizing the electrostatic latent image by feeding a developing agent to the image carriers; a plurality of developing agent cartridges provided correspondingly to the developing agent carriers and parallelly arranged along the one direction to be opposed to the developing agent carriers in a longitudinal direction of the developing agent carriers, for accommodating the developing agent fed to the developing agent carriers; an agitating member provided in the developing agent cartridge, supplied with driving force to be rotated for agitating the developing agent accommodated in the developing agent cartridge; and a rotating shaft extending along the one direction and provided with the agitating member, for serving as a rotation center of the agitating member. 
     One or more aspects of the present invention provide an image forming apparatus including: a plurality of image carriers formed with an electrostatic latent image; a plurality of developing agent carriers visualizing the electrostatic latent image by feeding a developing agent to the image carriers; a plurality of developing agent cartridges accommodating the developing agent fed to the developing agent carrier, and formed with a cartridge-side opening passing the developing agent therethrough; a first shutter member provided on the developing agent cartridge, for opening/closing the cartridge-side opening; and an opening/closing member collectively opening/closing all of the first shutter members. 
     One or more aspects of the present invention provide a developing agent cartridge, accommodating a developing agent fed to a developing agent carrier, and detachably mounted on a casing of an image forming apparatus, including: a cartridge case including a generally cylindrical portion, and formed with a cartridge-side opening passing the developing agent therethrough on a peripheral surface of the generally cylindrical portion; a first shutter member shaped along the generally cylindrical portion, for pivotably opening/closing the cartridge-side opening; a first projection engaging with an opening/closing member opening/closing the first shutter member, for opening/closing the first shutter member in association with operation of the opening/closing member; and a second projection engaging with a second shutter member opening/closing a casing-side opening formed in the casing to communicate with the cartridge-side opening, for opening/closing the second shutter member in association with the first projection, wherein the first projection and the second projection are provided on the first shutter member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a left-side sectional view showing an illustrative aspect of a color laser printer as an example of an image forming apparatus of one or more aspects of the present invention. 
         FIG. 2  is a left-side perspective view of the color laser printer. 
         FIG. 3  illustrates a state where only a second cover is opened in  FIG. 2 . 
         FIG. 4  illustrates a state where only a first cover is opened in  FIG. 2 . 
         FIG. 5  is a left-side sectional view of the color laser printer cut along a position where the left side surface of a partition wall is exposed. 
         FIGS. 6( a ) and 6( b ) , excerpting a cartridge receiving section accommodation space from the color laser printer in front elevation view, illustrate a closed state (partition-wall-side shutter closing position) and an opened state (partition-wall-side shutter opening position) of a partition-wall-side shutter respectively. 
         FIG. 7  is a left-side sectional view of the color laser printer cut along a position where a cartridge receiving section is exposed. 
         FIG. 8  is a left-side sectional view of the cartridge receiving section accommodating all toner cartridges. 
         FIG. 9  is a left-side elevation view of the cartridge receiving section accommodating all toner cartridges. 
         FIG. 10  is a right-side perspective view of the cartridge receiving section accommodating no toner cartridges. 
         FIGS. 11( a ) and 11( b )  are front elevation views of the cartridge receiving section, with an operation lever located on a lever closing position and a lever opening position respectively. 
         FIGS. 12( a ), 12( b ) and 12( c )  are a left-side elevation view, a front elevation view and a rear elevation view of each toner cartridge respectively. 
         FIGS. 13( a ) and 13( b )  are right-side perspective views of each toner cartridge, with an inner cylinder located on a cartridge-side shutter closing position and a cartridge-side shutter opening position respectively. 
         FIGS. 14( a ) and 14( b )  are front sectional views of each toner cartridge, with the inner cylinder located on the cartridge-side shutter closing position and the cartridge-side shutter opening position respectively.  FIGS. 14( a ) and 14( b )  show a first projection, a second projection, a first projection exposing hole, a second projection exposing hole, an inner-cylinder-side opening and an outer-cylinder-side opening on the same plane, for the convenience of illustration. 
         FIG. 15  is a right-side perspective view of the cartridge receiving section accommodating all the toner cartridges, with the inner cylinders located on the cartridge-side shutter closing position. 
         FIG. 16  is a right-side perspective view of  FIG. 15 , showing the inner cylinders of the toner cartridges located on the cartridge-side shutter opening position. 
         FIGS. 17( a ) and 17( b )  are front sectional views of the cartridge receiving section accommodating each toner cartridge, with the inner cylinder located on the cartridge-side shutter closing position and the cartridge-side shutter opening position respectively.  FIGS. 17( a )  and  17 ( b ) show the first projection, the second projection, the first projection exposing hole, the second projection exposing hole, the inner-cylinder-side opening, the outer-cylinder-side opening and an opening/closing main portion engaging hole on the same plane, for the convenience of illustration. 
         FIG. 18  is a left-side sectional view of  FIG. 5 , showing a cartridge receiving section drawn out from a main body casing to a position (attachment/detachment position) where all the toner cartridges are exposed frontward from the main body casing. 
         FIG. 19  is a front elevation view of the color laser printer, showing the cartridge receiving section accommodation space, the cartridge receiving section and the toner cartridge in a front sectional view. 
         FIGS. 20( a ) and 20( b )  excerpt the front sectional view of the cartridge receiving section accommodation space, the cartridge receiving section and the toner cartridge from  FIG. 19 , with the inner cylinder located on the cartridge-side-shutter closing position and the cartridge-side-shutter opening position respectively.  FIGS. 20( a ) and 20( b )  show the first projection, the second projection, the first projection exposing hole, the second projection exposing hole, the inner-cylinder-side opening, the outer-cylinder-side opening, the opening/closing main portion engaging hole, a partition-wall-side feed hole and a partition-wall-side return hole on the same plane, for the convenience of illustration. 
         FIG. 21  excerpts each processing section from  FIG. 1 . 
         FIG. 22  is a plan view of the processing section in a state where the upper sidewall of a developer casing is removed. 
         FIG. 23  is a left-side sectional view of  FIG. 1 , showing an intermediate stage of attaching/detaching the processing sections. 
         FIG. 24  is a left-side sectional view of  FIG. 18 , showing a second embodiment of one or more aspects of the present invention. 
         FIG. 25  is a left-side sectional view of  FIG. 18 , showing a third embodiment of one or more aspects of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of one or more aspects of the present invention are now described with reference to the drawings. 
     First Embodiment 
     1. General Structure of Color Laser Printer 
       FIG. 1  is a left-side sectional view showing an illustrative aspect of a color laser printer as an example of an image forming apparatus of one or more aspects of the present invention. 
     As shown in  FIG. 1 , this color laser printer  1  is a tandem-type color laser printer having a plurality of processing sections  62  horizontally arranged in parallel with each other. The color laser printer  1  includes a sheet feeding section  4  for feeding a sheet  3 , an image forming section  5  for forming images on the fed sheet  3  and a sheet ejecting section  6  for ejecting the sheet  3  formed with the images, in a boxy main body casing  2  as an example of a casing. The color laser printer  1  further includes a scanning unit  7  provided above the main body casing  2  as an example of an image reading unit for reading image information from a document, and is formed as the so-called composite printer. 
     In the following description, it is assumed that the right and left sides in the plane of  FIG. 1  are the front and rear sides of the color laser printer  1  respectively in a state where toner cartridges  69  and the processing sections  62  described later are mounted in the main body casing  2 . It is also assumed that this side and the other side of  FIG. 1  along the thickness thereof are the left and right sides of the color laser printer  1  respectively. The right-and-left direction may also be referred to as a width direction. 
     (1) Main Body Casing 
       FIG. 2  is a left-side perspective view of the color laser printer.  FIG. 3  illustrates a state where only a second cover is opened in  FIG. 2 .  FIG. 4  illustrates a state where only a first cover is opened in  FIG. 2 .  FIG. 5  is a left-side sectional view of the color laser printer cut along a position where the left side surface of a partition wall is exposed. 
     The main body casing  2  is in the form of a box as described above, the upper side surface of the front end of the upper sidewall thereof is inclined downward obliquely toward the front side, and an operation panel  8  including operation keys and an LED display section is embedded in this front end. The scanning unit  7  is arranged on a portion of the upper sidewall of the main body casing  2  rearward beyond the operation panel  8 . A cartridge receiving section mounting port  11  serving as an example of a first opening, a sheet ejection port  9 , a processing section mounting port  10  serving as an example of a second opening and a sheet feeding tray mounting port  50  are formed on the front wall, i.e., the front surface of the main body casing  2 . 
     (1-1) Cartridge Receiving Section Mounting Port 
     The cartridge receiving section mounting port  11  has a generally rectangular shape vertically longitudinal in front elevation view as shown in  FIG. 4 . The cartridge receiving section mounting port  11  is provided with the first cover  22  covering the cartridge receiving section mounting port  11  in an openable/closable manner. 
     The first cover  22  is rotatably supported by a hinge  23  connecting the proximal end portion of the first cover  22  and the lower end portion of the front wall of the main body casing  2  with each other. 
     When the first cover  22  is pivoted about the pivoting shaft (not shown) of the hinge  23  counterclockwise in left-side elevation view and closed, the cartridge receiving section mounting port  11  is closed with the first cover  22 , as shown in  FIG. 2 . 
     When the first cover  22  is pivoted about the pivoting shaft (not shown) of the hinge  23  clockwise in left-side elevation view and opened, on the other hand, the cartridge receiving section mounting port  11  is opened as shown in  FIG. 4 . 
     The main casing  2  is formed therein with a cartridge receiving section accommodation space  24 , serving as an example of a first accommodation space, defined generally in the form of a rectangular parallelepiped for communicating with the cartridge receiving section mounting port  11 . 
     The cartridge receiving section accommodation space  24  is defined by the upper, lower and left sidewalls of the main body casing  2  and the partition wall  15  in the up-and-down (vertical) and right-and-left (horizontal) directions. The partition wall  15  is provided in the main body casing  2 , to parallelly extend along the left sidewall of the main body casing  2  inside the left sidewall of the main body casing  2  in the width direction. The rear portion of the cartridge receiving section accommodation space  24  is closed with the rear wall of the main body casing  2 . The partition wall  15  is rightwardly separated from the left sidewall of the main body casing  2  by a distance corresponding to about ¼ of the width-directional size of the main body casing  2 , as described later in detail. The cartridge receiving section accommodation space  24  accommodates a cartridge receiving section  68  serving as an example of a receiving section described later. 
     (1-2) Sheet Ejection Port 
     The sheet ejection port  9 , adjacent to the right side of the cartridge receiving section mounting port  11  through the partition wall  15 , has a generally rectangular shape width-directionally longitudinal in front elevation view at the width-directional central position of the upper half of the front wall of the main body casing  2 . A sheet ejection space  12  defined generally in the form of a rectangular parallelepiped is formed in the main body casing  2  to communicate with the sheet ejection port  9 . 
     In the up-and-down direction, the sheet ejection space  12  is defined by the upper sidewall of the main body casing  2  and an ejection tray  13  (see  FIG. 1 ) opposed in the right-and-left direction to the upper sidewall of the main body casing  2  at an interval. In the right-and-left direction, the sheet ejection space  12  is defined by a first right-side inner wall  14  and the partition wall  15 . The first right-side inner wall  14  is provided in the main body casing  2 , to parallelly extend along the right sidewall of the main body casing  2  inside the right sidewall of the main body casing  2  in the width direction. The rear portion of the sheet ejection space  12  is closed with an ejection wall  51  extending upward from the rear end portion of the ejection tray  13  to a portion close to the lower side surface of the upper sidewall of the main body casing  2 , as shown in  FIG. 1 . This ejection wall  51  is arranged on a position separated frontward from the rear end of the main body casing  2  by a distance corresponding to about ¼ of the anteroposterior (horizontal) size of the main body casing  2 . 
     The ejection tray  13  is so formed as to loosely extend upward obliquely toward the front side from the rear end thereof. A rectangular ejection hole  16  width-directionally longitudinal in front elevation view is formed on a generally central position of the ejection wall  51  in the up-and-down direction. The width-directional size of the ejection hole  16  is set larger than that of the sheet  3 . The sheets  3  formed with color images is ejected frontward from the ejection hole  16  and placed on the ejection tray  13  in a stackable manner, as described later. Therefore, the user can take out the sheets  3  placed on the ejection tray  13  by accessing the sheet ejection space  12  through the sheet ejection port  9 . 
     (1-3) Processing Section Mounting Port 
     As shown in  FIG. 3 , the processing section mounting port  10  is adjacent to the right side of the cartridge receiving section mounting port  11  through the partition wall  15  and located under the sheet ejection port  9 , and has a generally rectangular shape width-directionally longitudinal in front elevation view. This processing section mounting port  10  is formed longer than the sheet ejection port  9  in the width direction so that the right edge thereof is located rightward beyond that of the sheet ejection port  9 . The processing section mounting port  10  has the second cover  18  provided adjacently to the first cover  22  for covering the processing section mounting port  10  in an openable/closable manner. 
     The second cover  18  is pivotably supported on a second cover pivoting shaft (not shown) inserted into the proximal end portion thereof. An L-shaped portion  19  bent counterclockwise in left-side elevation view is formed on the distal end of the second cover  18 , i.e., the radial outer end portion around the second cover rotating shaft (not shown). The width-directional size of the L-shaped portion  19  is formed smaller than that of the sheet ejection port  9 . A folding sheet stopper  20  is provided at the width-directional center of the L-shaped portion  19  in a swingable manner (see  FIG. 2 ). 
     When pivoted about the second cover pivoting shaft (not shown) counterclockwise in left-side elevation view, the second cover  18  closes the processing section mounting port  10 . At this time, the L-shaped portion  19  is accommodated in the sheet ejection space  12  from the sheet ejection port  9  as shown in  FIG. 2 , to come into contact and engage with the front end portion of the ejection tray  13  as shown in  FIG. 1 . Therefore, the pivot of the second cover  18  is restricted so that the second cover  18  keeps the state where the processing section mounting port  10  is closed. When the second cover  18  thus closes the processing section mounting port  10 , the upper side surfaces of the L-shaped portion  19  and the ejection tray  13  are continuous with each other. 
     When the tip end of the L-shaped portion  19  and the front end portion of the ejection tray  13  are disengaged from each other, the second cover  18  is allowed to pivot. When the second cover  18  is pivoted about the second cover pivoting shaft (not shown) clockwise in left-side elevation view, the processing section mounting port  10  is opened as shown in  FIG. 3 . 
     The main body casing  2  is further formed therein with a process accommodation space  17 , serving as an example of a second accommodation space, defined generally in the form of a rectangular parallelepiped to communicate with the processing section mounting port  10 . 
     In the up-and-down direction, the process accommodation space  17  is defined by the ejection tray  13 , a connecting wall  197  and a midway wall  52 , as shown in  FIG. 1 . The connecting wall  197  corresponds to a portion of the upper sidewall of the main body casing  2  located rearward beyond the ejection tray  13 . The midway wall  52 , located between the ejection tray  13  and the lower sidewall of the main body casing  2  in the up-and-down direction, extends parallelly along the lower sidewall of the main body casing  2 . In the right-and-left direction, on the other hand, the process accommodation space  17  is defined by the partition wall  15  and a second right-side inner wall  21  width-directionally opposed to the partition wall  15  at an interval on a position rightwardly under the first right-side inner wall  14 , as shown in  FIG. 3 . The rear side of the process accommodation space  17  is closed with the rear wall of the main body casing  2 , as shown in  FIG. 1 . More specifically, the process accommodation space  17  is defined generally in an L shape in left-side sectional view by the ejection wall  51 , the ejection tray  13 , the second cover  18 , the midway wall  52 , the rear sidewall of the main body casing  2  and the connecting wall  197 . The process accommodation space  17  accommodates the image forming section  5 . 
     (1-4) Sheet Feeding Tray Mounting Port 
     The sheet feeding tray mounting port  50 , adjacent to the lower portion of the processing section mounting port  10  through the midway wall  52 , has a generally rectangular shape width-directionally longitudinal in front elevation view. 
     The main body casing  2  is formed therein with a sheet feeding tray accommodation space  53  defined generally in the form of a rectangular parallelepiped communicating with the sheet feeding tray mounting port  50 . 
     The sheet feeding tray accommodation space  53  is defined by the midway wall  52 , the lower and right sidewalls of the main body casing  2  and the partition wall  15  in the up-and-down and right-and-left directions. The rear side of the feeding tray accommodation space  53  is closed with the rear wall of the main body casing  2 . This feeding tray accommodation space  53  accommodates a sheet feeding tray  54  described later. 
     (1-5) Partition Wall 
       FIGS. 6( a ) and 6( b ) , excerpting the cartridge receiving section accommodation space from the color laser printer in front elevation view, illustrate a closed state (partition-wall-side shutter closing position) and an opened state (partition-wall-side shutter opening position) of a partition-wall-side shutter respectively. 
     The partition wall  15  separates the sheet ejection space  12  and the process accommodation space  17  from the cartridge receiving section accommodation space  24  (see  FIG. 4 ) between the sheet ejection port  9  and the cartridge receiving section mounting port  11 , and between the processing section mounting port  10  and the cartridge receiving section mounting port  11 , as described above. 
     The partition wall  15  is generally rectangular in side elevation view as shown in  FIG. 5 , and bent at a generally central portion  25  in the up-and-down direction generally in the form of a crank in front elevation view as shown in  FIGS. 6( a ) and 6( b ) , and integrally includes a partition wall upper portion  26  and a partition wall lower portion  27  located upward and downward beyond the bent portion  25  respectively. The partition wall lower portion  27  is formed so as to extend parallelly along the partition wall upper portion  26  on the left side of the partition wall upper portion  26 . 
     As shown in  FIG. 5 , the partition wall  15  includes a guide rail  28 , a partition-wall-side shutter mechanism  29 , and a driving mechanism  30  serving as an example of a drive unit. The guide rail  28  is provided on a position of the left side surface of the partition wall upper portion  26  adjacent to the bent portion  25 . The partition-wall-side shutter mechanism  29  is provided on a generally central position of the left side surface of the partition wall lower portion  27  in the up-and-down direction while the driving mechanism  30  is provided at the back of the partition-wall-side shutter mechanism  29 . 
     The guide rail  28  is generally U-shaped in side elevation view with an open front side, and includes a pair of ridges  31  protruding leftward from the left side surface of the partition wall upper portion  26  to extend in the anteroposterior direction. The front edges of the pair of ridges  31  are located slightly rearward beyond the front end edge of the partition wall  15 , while the rear end portions thereof are curvedly connected with each other. The upper ridge  31  of the pair of ridges  31  is formed with an inclined surface obliquely inclined upward toward the front end edge, on the front end portion of a portion opposed to the lower ridge  31 . A pair of guide rail positioning projections  33  slightly projecting inward to face the pair of ridges  31  respectively are provided on positions of the opposed portions of the pair of ridges  31  located frontward beyond the portion (referred to as a connecting portion  32 ) connecting the rear end portions with each other as described above. Another guide rail  28  is provided on the right side surface of the left sidewall of the main body casing  2 , and opposed to the guide rail  28  of the partition wall  15  in the width direction (see  FIGS. 6( a ) and 6( b ) ). 
     As shown in  FIGS. 6( a ) and 6( b ) , the partition-wall-side shutter mechanism  29  is arranged slightly under a generally central portion of the partition wall lower portion  27  in the up-and-down direction, and includes a partition-wall-side toner passing portion  34  and the partition-wall-side shutter  35  serving as an example of a second shutter member. 
     The partition-wall-side toner passing portion  34 , having a generally prismatic shape longitudinal in the anteroposterior direction, has a left side surface provided in the form of an arc smoothly recessed rightward in front elevation view and a right side surface fixed to the left side surface of the partition wall lower portion  27 . Leftwardly protruding partition-wall-side shutter support portions  38  are respectively provided on both anteroposterior end portions (see  FIG. 5 ) of the left side surface of the partition-wall-side toner passing portion  34 . 
     As shown in  FIG. 5 , partition-wall-side feed holes  39  and partition-wall-side return holes  40  adjacent to the rear sides of the partition-wall-side feed holes  39  are respectively formed on four portions of the partition-wall-side toner passing portion  34  anteroposteriorly separated at the same intervals. The partition-wall-side feed holes  39  and the partition-wall-side return holes  40  are circular in side elevation view, and pass through the partition-wall-side toner passing portion  34  and the partition wall lower portion  27  in the width direction. The partition-wall-side feed holes  39  and the partition-wall-side return holes  40  serve as examples of partition-wall-side openings and casing-side openings respectively. Partition wall sealing members (not shown) of felt, sponge or the like are provided around the partition-wall-side feed holes  39  and the partition-wall-side return holes  40  to protrude leftward. 
     The partition-wall-side shutter  35  is in the form of an arcuate thin plate longitudinal in the anteroposterior direction along the left side surface (see  FIGS. 6( a ) and 6( b ) ) of the partition-wall-side toner passing portion  34  in front elevation view. Downwardly recessed upper notches  41  are respectively formed on four portions of the upper end edge of the partition-wall-side shutter  35  separated at the same intervals in the anteroposterior direction. More specifically, each upper notch  41  is located rearward beyond the corresponding partition-wall-side return hole  40 . Further, upwardly recessed lower notches  42  are respectively formed on positions of the lower end edge of the partition-wall-side shutter  35  opposed to the upper notches  41  in the up-and-down direction. 
     The partition-wall-side shutter support portions  38  support both anteroposterior end portions of the partition-wall-side shutter  35 , so that the partition-wall-side shutter  35  is slidable along the arcuate left side surface (see  FIGS. 6( a ) and 6( b ) ) of the partition-wall-side toner passing portion  34 . Therefore, the partition-wall-side shutter  35  is slidably movable between the partition-wall-side shutter closing position for closing all the partition-wall-side feed holes  39  and all the partition-wall-side return holes  40  from the left side as shown in  FIG. 6( a ) , and the partition-wall-side shutter opening position for opening all the partition-wall-side feed holes  39  and all the partition-wall-side return holes  40  from the left side as shown in  FIG. 6( b ) . The partition-wall-side shutter  35  is provided on both anteroposterior end portions (see  FIG. 5 ) thereof with engaging portions (not shown) engaging with the partition-wall-side shutter support portions  38  when the partition-wall-side shutter support portions  38  support both anteroposterior end portions of the partition-wall-side shutter  35 . Thus, the partition-wall-side shutter  35  is prevented from undesirable detachment from the partition-wall-side shutter support portions  38 . Clearances (see  FIG. 6( a ) ) formed between the partition-wall-side shutter  35  located on the partition-wall-side shutter closing position and the peripheral edges of the partition-wall-side feed holes  39  and the partition-wall-side return holes  40  are sealed with the aforementioned partition wall sealing members (not shown) in the right-and-left direction. 
     As shown in  FIG. 5 , the driving mechanism  30  is arranged slightly downward beyond a generally central position of the partition-wall-side toner passing portion  34  in the up-and-down direction and rearward beyond the partition-wall-side toner passing portion  34 , and includes a gear support portion  43 , a first gear  44  and a second gear  45 . 
     The gear support portion  43  is in the form of a thin plate generally L-shaped in plan view, and integrally includes a first support portion  46  and a second support portion  47 . 
     The first support portion  46  is generally rectangular in left-side elevation view, and the front side surface thereof is fixed to the left side surface of the partition wall lower portion  27 . A first support hole (not shown) passing through the first support portion  46  and the partition wall lower portion  27  in the width direction is formed at the central position of the first support portion  46  in the anteroposterior and up-and-down directions. 
     The second support portion  47  is generally rectangular in front elevation view, and the right end portion thereof is connected to the front end portion of the first support portion  46 . A second support hole  48  circular in front elevation view is formed at the central position of the second support portion  47  in the right-and-left and up-and-down directions, to pass through the second support portion  47  in the anteroposterior direction. 
     The first gear  44  is a bevel gear, and a portion (tooth portion) provided with teeth is exposed in the cartridge receiving section accommodation space  24  from the left side surface of the partition wall lower portion  27 . The rotating shaft of the first gear  44  is inserted into a first support hole (not shown) of the first support portion  46  along the width direction, and the first support portion  46  rotatably supports the first gear  44 . Another portion of the first gear  44  opposed to the tooth portion along the rotating shaft is arranged rightward beyond the partition wall lower portion  27 , and connected to an agitator driving motor (not shown). 
     The second gear  45  is a bevel gear, whose rotating shaft is inserted into the second support hole  48  of the second support portion  47  along the anteroposterior direction, and the second support portion  47  rotatably supports the second gear  45 . A portion (tooth portion) of the second gear  45  provided with teeth is arranged rearward beyond the second support portion  47 , and meshes with the tooth portion of the first gear  44  generally perpendicularly in plan view. A portion of the rotating shaft of the second gear  45  located frontward beyond the second support portion  47  is in the form of a cylinder having a larger diameter than that of the second support hole  48 , and a rearwardly recessed connecting hole  49  is formed on the front side surface thereof. The connecting hole  49  is formed generally in the figure of “8” in front elevation view. 
     When the agitator driving motor (not shown) is driven in the driving mechanism  30 , the first gear  44  is rotated clockwise in left-side elevation view while the second gear  45  is rotated counterclockwise (along the arrow in  FIG. 5 ) in rear elevation view following the rotation of the first gear  44 . 
     (2) Sheet Feeding Section 
     As shown in  FIG. 1 , the sheet feeding section  4  includes the sheet feeding tray  54  accommodating the sheets  3 , a sheet feeding roller  55  provided above the rear end portion of the sheet feeding tray  54 , and a separation roller  56  and a separation pad  57  opposed to each other at the back of the sheet feeding roller  55 . The sheet feeding section  4  further includes two assist rollers  58  opposed to the separation roller  56  above the separation pad  57 , a sheet feeding transport path  59  extending generally upward from the opposed portion between the upper assist roller  58  and the separation roller  56 , and a pair of transport rollers  60  provided on a midway of the sheet feeding transport path  59 . 
     The sheet feeding tray  54  is generally in the form of a box having an open upper portion, and anteroposteriorly slidably attached/detached to/from the sheet feeding tray accommodation space  53  of the main body casing  2  from the front side. When the sheet feeding tray accommodation space  53  accommodates the sheet feeding tray  54 , the front sidewall of the sheet feeding tray  54  closes the sheet feeding tray mounting port  50 . 
     The sheets  3  are stacked in the sheet feeding tray  54 , and the uppermost sheet  3  is fed to the opposed portion between the separation roller  56  and the separation pad  57  through rotation of the sheet feeding roller  55 , separated and thereafter guided by the assist rollers  58  to be fed generally upward along the outer circumferential surface of the separation roller  56 . This sheet  3  is delivered to the sheet feeding transport path  59  from the opposed portion between the upper assist roller  58  and the separation roller  56 . The sheet  3  delivered to the sheet feeding transport path  59  is advanced generally upward in the sheet feeding transport path  59  through the transport rollers  60 , and transported to a secondary transfer position between a secondary transfer roller  178  and an intermediate transfer belt  176  described later. 
     (3) Image Forming Section 
       FIG. 7  is a left-side sectional view of the color laser printer cut along a position where the cartridge receiving section  68  is exposed. 
     The image forming section  5  includes a scanner unit  61 , a toner feeding section  67  (see  FIG. 7 ), the processing sections  62 , a transferring section  63  and a fixing section  64 . 
     (3-1) Scanner Unit 
     As shown in  FIG. 7 , the scanner unit  61  is arranged in a lower portion of the process accommodation space  17  of the main body casing  2  under the plurality of processing sections  62  described later. This scanner unit  61  includes a scanner frame  65  fixed to the aforementioned midway wall  52  and a scanner casing  66  fixed to the scanner frame  65 . The scanner frame  65  and the scanner casing  66  are provided with exit windows (not shown) corresponding to the processing sections  62  respectively. Optical members such as a light source, a polygonal mirror  97 , an f□ lens, reflecting mirrors  98  and a face tangle error correcting lens are arranged in the scanner casing  66 , and a laser beam emitted from the light source on the basis of image data is deflected and scanned by the polygonal mirror  97 , passes through the f□ lens and the face tangle error correcting lens, is reflected by the reflecting mirrors  98  and thereafter applied onto the surface of a photosensitive drum  133  serving as an example of an image carrier, described later, of the processing section  62  through the exit window (not shown) by high-speed scanning, as shown by arrows in  FIG. 1 . 
     (3-2) Toner Feeding Section 
       FIG. 8  is a left-side sectional view of the cartridge receiving section accommodating all toner cartridges.  FIG. 9  is a left-side elevation view of the cartridge receiving section accommodating all toner cartridges.  FIG. 10  is a right-side perspective view of the cartridge receiving section accommodating no toner cartridges.  FIGS. 11( a ) and 11( b )  are front elevation views of the cartridge receiving section, with an operation lever located on a lever closing position and a lever opening position respectively. 
     The toner feeding section  67  is arranged in the cartridge receiving section accommodation space  24  of the main body casing  2  as shown in  FIG. 4 , and includes the cartridge receiving section  68  and the toner cartridges  69  serving as examples of developing agent cartridges as shown in  FIG. 8 . 
     (3-2-1) Cartridge Receiving Section 
     The cartridge receiving section  68  includes a receiving section casing  82 , roller support portions  76  (see  FIG. 9 ), an opening/closing member  75 , the operation lever  81  serving as an example of an operation member, a first transmission portion  88  and second transmission portions  89 . 
     The receiving section casing  82  is generally in the form of a box having an open upper portion. More specifically, the receiving section casing  82  generally has an inverted L shape with an upper half wider than the lower half, and the lower half has a generally arcuate lower end portion, in front elevation view, as shown in  FIGS. 11( a ) and 11( b ) . A triangular projection  70  generally triangularly protruding rearward in side elevation view is integrally formed on the upper half of the rear end portion of the receiving section casing  82 , as shown in  FIGS. 9 and 10 . The left and right side surfaces of the triangular projection  70  are flush with the corresponding left and side surfaces of the receiving section casing  82  respectively. An opening exposing the interior of the receiving section casing  82  is formed in the lower half of the right side surface of the receiving section casing  82 , as shown in  FIG. 10 . 
     Three receiving section partition walls  72  arranged at the same intervals along the anteroposterior direction are integrally provided in the receiving section casing  82 , to partition the interior of the receiving section casing  82  into four receiving chambers  73  along the anteroposterior direction. The receiving section partition walls  72  also partition the aforementioned opening provided in the lower half of the right side surface of the receiving section casing  82  into four receiving-section-side openings  74  along the anteroposterior direction. The receiving-section-side openings  74  serve as examples of passage-side openings. 
     Attachment/detachment guide grooves  77  are respectively formed on the same positions of side surfaces anteroposteriorly opposed to each other in the front and rear sidewalls of the receiving section casing  82  and in the receiving section partition walls  72 . The attachment/detachment guide grooves  77 , generally Y-shaped in front or rear elevation view, are so formed that the width thereof is gradually reduced downward from the upper end edges of the front and rear sidewalls of the receiving section casing  82  and of the side surfaces the receiving section partition walls  72  to reach a constant level in intermediate portions. The lower end portion of each attachment/detachment guide groove  77  is located on a position separated upward from the lower end of the receiving section casing  82  by a distance corresponding to about ⅕ of the up-and-down size of the receiving section casing  82 . In the groove walls of the attachment/detachment guide grooves  77 , receiving section positioning projections  78  slightly protruding in the direction where the groove walls are opposed to each other are respectively provided on positions slightly upward beyond the lower end edges of the groove walls. 
     The lower end portion of the receiving section casing  82  is generally arcuate in front elevation view as described above, whereby the lower sidewall of the receiving section casing  82  is also generally arcuate in front elevation view. The right end edge of the receiving section casing  82  defines the lower end edges of the receiving-section-side openings  74 . Receiving section penetration holes  79  longitudinal in the right-and-left direction in right-side elevation view are respectively formed on anteroposterior centers of portions of the lower sidewall of the receiving section casing  82  corresponding to the receiving chambers  73  respectively, to pass through the lower sidewall of the receiving section casing  82  along the thickness direction. 
     Leftwardly recessed receiving section notches  80  are respectively formed on portions of the right end edge of the lower sidewall of the receiving section casing  82  corresponding to the receiving chambers  73 . In the receiving chambers  73 , the receiving section notches  80  are respectively positioned rearward beyond the receiving section penetration holes  79 . 
     The roller support portions  76  are in the form of rails respectively extending from the rear end portions of the left and right side surfaces of the triangular projection  70  toward the front end portions of the corresponding left and right side surfaces of the receiving section casing  82  along the anteroposterior direction, as shown in  FIGS. 9 and 10 . A plurality of rollers  71  are rotatably provided on the width-directional outer side surface of each roller support portion  76 . More specifically, pairs of two rollers  71  are arranged on both anteroposterior end portions of each roller support portion  76  at intervals in the anteroposterior direction. 
     As shown in  FIG. 9 , the opening/closing member  75  is generally U-shaped in side elevation view to sandwich the lower end portion of the receiving section casing  82  in the anteroposterior direction, and integrally includes a front arm portion  83 , a rear arm portion  84  and an opening/closing main portion  85 . 
     The front and rear arm portions  83  and  84  are in the form of thin plates provided with swinging shafts (not shown) on first longitudinal end portions thereof respectively. The swinging shaft (not shown) of the front arm portion  83  is inserted into a support hole (not shown) formed in the front sidewall of the receiving section casing  82 , so that the front arm portion  83  is supported on the front sidewall of the receiving section casing  82  in a swingable manner. Further, the swinging shaft (not shown) of the rear arm portion  84  is inserted into a support hole (not shown) formed in the rear sidewall of the receiving section casing  82 , so that the rear arm portion  84  is supported on the rear sidewall of the receiving section casing  82  in a swingable manner. The rear arm portion  84  is so arcuately formed (not shown) as to avoid a connecting projection  92  of the first transmission portion  88 . The swinging centers of the front and rear arm portions  83  and  84  and the arc center of the lower sidewall of the receiving section casing  82  are on the same position in front sectional view. 
     The opening/closing main portion  85  is in the form of a thin plate generally arcuate in front sectional view and longitudinal in the anteroposterior direction along the lower sidewall of the receiving section casing  82 . As shown in  FIG. 10 , the opening/closing main portion  85  is formed with four opening/closing main portion engaging holes  86  passing through the opening/closing main portion  85  along the thickness direction at the same intervals in the anteroposterior direction. Each opening/closing main portion engaging hole  86  is rectangular in plan view, and the anteroposterior size thereof is set slightly smaller than that of each receiving section penetration hole  79 . The right-and-left size of each opening/closing main portion engaging hole  86  is set to about ⅕ of that of each receiving section penetration hole  79 . 
     The opening/closing main portion  85  extends between second longitudinal end portions of the front and rear arm portions  83  and  84  opposite to the aforementioned first longitudinal end portions provided with the swinging shafts (not shown). Therefore, the opening/closing main portion  85  is swingable along the lower sidewall of the receiving section casing  82  about a swinging center defined by the arc center of the lower sidewall of the receiving section casing  82 . More specifically, the opening/closing main portion  85  is swingable in the range where the opening/closing main portion engaging holes  86  is always exposed from the receiving section penetration holes  79 . 
     The operation lever  81  is discoidal in the front elevation view, and a grasp portion  87  generally arcuate in right-side elevation view protrudes frontward from the width-sectional center of the front side surface thereof. The rear side surface of the operation lever  81  is fixed to the front side surface of the front arm portion  83  of the opening/closing member  75 . In other words, the operation lever  81  is arranged on the front end portion of the cartridge receiving section  68 . Thus, the user can open/close the opening/closing member  75  by grasping the grasp portion  87  from the front side of the cartridge receiving section  68  and turning the operation lever  81  clockwise or counterclockwise in front elevation view. In the following description, it is assumed that the position of the operation lever  81  where the right end edge of each opening/closing main portion engaging hole  86  aligns with that of the corresponding receiving section penetration hole  79  as shown in  FIG. 11( a )  is the lever closing position. It is also assumed that the position of the operation lever  81  where the left end edge of each opening/closing main portion engaging hole  86  aligns with that of the corresponding receiving section penetration hole  79  as shown in  FIG. 11( b )  is the lever opening position. 
     The first transmission portion  88  integrally includes a first support shaft  90 , a first transmission gear  91  and the connecting projection  92 , as shown in  FIG. 8 . The first support shaft  90 , extending in the anteroposterior direction, is so provided as to pass through the rear sidewall of the receiving section casing  82  on a position downward beyond the attachment/detachment guide grooves  77  (see  FIG. 10 ), and rotatably supported on this rear sidewall. The front end portion of the first support shaft  90  is located frontward beyond the front side surface of the rear sidewall of the receiving section casing  82 , and provided with the first transmission gear  91 . The rear end portion of the first support shaft  90  is located rearward beyond the rear side surface of the rear sidewall of the receiving section casing  82 , and provided with the connecting projection  92 . The first transmission gear  91  is a spur gear provided with teeth on the outer circumferential surface thereof. The connecting projection  92 , protruding rearward from the rear end portion of the first support shaft  90 , is formed generally in the figure of “8” smaller than the aforementioned connecting hole  49  (see  FIG. 5 ) of the second gear  45  in rear elevation view. 
     Each of the three second transmission portions  89 , provided correspondingly to the receiving section partition walls  72  of the receiving section casing  82  respectively, includes a second support shaft  93 , an input transmission gear  94  serving as an example of an input portion, and an output transmission gear  99  serving as an example of an output portion. The second support shaft  93 , extending in the anteroposterior direction, is so provided as to pass through each receiving section partition wall  72  on a position downward beyond the attachment/detachment guide grooves  77  (see  FIG. 10 ), and rotatably supported on this receiving section partition wall  72 . The front end portion of the second support shaft  93  is located frontward beyond the front side surface of each receiving section partition wall  72 , and provided with the output transmission gear  99 . The rear end portion of the second support shaft  93  is located rearward beyond the rear side surface of each receiving section partition wall  72 , and provided with the input transmission gear  94 . The input and output transmission gears  94  and  99  are spur gears provided with teeth on the outer circumferential surfaces thereof, and identical in size to the first transmission gear  91 . 
     (3-2-2) Toner Cartridge 
       FIGS. 12( a ), 12( b ) and 12( c )  are a left-side elevation view, a front elevation view and a rear elevation view of each toner cartridge respectively.  FIGS. 13( a ) and 13( b )  are right-side perspective views of each toner cartridge, with an inner cylinder located on a cartridge-side shutter closing position and a cartridge-side shutter opening position respectively.  FIGS. 14( a ) and 14( b )  are front sectional views of each toner cartridge, with the inner cylinder located on the cartridge-side shutter closing position and the cartridge-side shutter opening position respectively.  FIGS. 14( a ) and 14( b )  show a first projection, a second projection, a first projection exposing hole, a second projection exposing hole, an inner-cylinder-side opening and an outer-cylinder-side opening on the same plane, for the convenience of illustration. 
     The four toner cartridges  69  are provided correspondingly to developing rollers  143  (see  FIG. 21 ) serving as examples of developing agent carriers, of the processing sections  62  provided correspondingly to toners of respective colors described later. Each toner cartridge  69  is formed generally in the figure of “8” in front elevation view and generally rectangular in right-side elevation view as shown in  FIGS. 12( a ) to 12( c ) , and includes an outer cylinder  95  serving as an example of a cartridge case, and the inner cylinder  96  serving as an example of a first shutter member, a feed-side shutter, a return-side shutter or a cartridge-side shutter, as shown in  FIGS. 14( a ) and 14( b ) . 
     The outer cylinder  95  is a hollow member formed generally in the figure of “8” in front elevation view and generally rectangular in right-side elevation view similarly to the toner cartridge  69 , and integrally includes a storage section  100  forming the upper portion thereof and a feed section  101  serving as an example of a generally cylindrical portion, forming the lower portion thereof. 
     The storage section  100  is in the form of an ellipse longitudinal in the up-and-down direction in front elevation view, and has a grip  103  provided on the upper end portion thereof, as shown in  FIG. 12( a ) . The grip  103  is generally in an inverted U shape in left-side elevation view, and distal end portions thereof are fixed to both anteroposterior end portions of the upper end portion of the storage section  100  respectively. 
     A storage chamber  102  defined in the form of an ellipse longitudinal in the up-and-down direction in front elevation view is formed in the storage section  100 , as shown in  FIGS. 14( a ) and 14( b ) . 
     The storage chamber  102  stores a toner of a corresponding color among black, cyan, magenta and yellow. The toner of each color is a positively chargeable nonmagnetic one-component polymerized toner as an example of developing agent. The toner cartridge  69  having the storage chamber  102  storing the black toner is hereinafter referred to as a black toner cartridge  69 K, while the remaining toner cartridges  69  are also referred to as yellow, magenta and cyan toner cartridges  69 Y,  69 M and  69 C according to the corresponding colors respectively. 
     A storage-side agitator rotating shaft  112  serving as an example of a second rotating shaft extends between the front and rear sidewalls of each storage section  100 , as shown in  FIG. 8 . More specifically, the storage-side agitator rotating shaft  112  so anteroposteriorly extends (see  FIG. 12( b ) ) as to pass through a portion close to the arc center of the lower arc of the elliptically formed storage section  100  in front elevation view, and is rotatably supported by the front and rear sidewalls of the storage section  100 . The storage-side agitator rotating shaft  112  is provided with a storage-side agitator  113  serving as an example of a second agitating member. 
     The storage-side agitator  113  is formed in a rectangular shape in left-side elevation view, by a bar rotating along the lower arc of the storage section  100  and a member holding the bar. This storage-side agitator  113  is arranged in the storage chamber  102 , and the proximal edge thereof is fixed to the storage-side agitator rotating shaft  112 . 
     As shown in  FIG. 12( a ) , the front and rear end portions of the storage-side agitator rotating shaft  112  protrude frontward and rearward from the front and rear sidewalls of the storage section  100  respectively. A storage-side agitator input gear  114  serving as an example of a storage-chamber-side input portion is provided on the portion of the storage-side agitator rotating shaft  112  protruding rearward from the rear sidewall of the storage section  100 . 
     The storage-side agitator input gear  114  is a spur gear provided with teeth on the outer circumferential surface thereof, and the diameter of this storage-side agitator input gear  114  is so set that the storage-side agitator input gear  114  is settled inside the contour of the storage section  100  in rear elevation view as shown in  FIG. 12( c ) . The anteroposterior size of the storage-side agitator input gear  114  is equalized to those of the input and output transmission gears  94  and  99 , as shown in  FIG. 8 . 
     The feed section  101  is circular in front elevation view as shown in  FIGS. 12( b ) and 12( c ) , and the upper end portion thereof is connected to the lower end portion of the storage section  100 . Connecting ribs  106  are respectively provided on both width-directional sides of the connecting portion between the storage section  100  and the feed section  101  for connecting the outer side surfaces of the storage section  100  and the feed section  101  with each other in the vicinity of the connecting portion. The connecting ribs  106 , each provided in the form of a generally triangular thin plate in front elevation view, are provided on both anteroposterior end portions of the storage section  100  and the feed section  101  respectively. These connecting ribs  106  ensure rigidity of the outer cylinder  95  in the connecting portion between the storage section  100  and the feed section  101 . 
     An inner cylinder accommodation chamber  104  defined generally in the form of a cylinder circular in front elevation view is formed in the feed section  101 , as shown in  FIGS. 14( a ) and 14( b ) . An outer cylinder connecting hole  105  passing through the connecting portion between the storage section  100  and the feed section  101  in the up-and-down direction is formed in this connecting portion. The outer cylinder connecting hole  105  is in the form of a rectangle anteroposteriorly longitudinal in plan view, and the inner cylinder accommodation chamber  104  communicates with the storage chamber  102  through the outer cylinder connecting hole  105 . 
     The feed section  101  is formed with the first projection exposing hole  107 , the second projection exposing hole  111 , and the outer-cylinder-side opening  108  serving as an example of a cartridge-side opening, as shown in  FIGS. 12( a ), 13( a ) and 13( b ) . 
     The first projection exposing hole  107  is generally rectangular in left-side elevation view, and formed over the range from the six o&#39;clock position (i.e., the lower end portion of the feed section  101 ) to about the eight o&#39;clock position in front elevation view at the anteroposterior center of the feed section  101  (see  FIGS. 12( a ), 13( b ), 14( a ) and 14( b ) ). 
     The second projection exposing hole  111  is generally rectangular in right-side elevation view as shown in  FIGS. 13( a ) and 13( b ) , and formed over the range from the six o&#39;clock position (i.e., the lower end portion of the feed section  101 ) to about the two o&#39;clock position in front elevation view (see  FIGS. 14( a ) and 14( b ) ) on a generally central portion of the feed section  101  in the anteroposterior direction, more specifically on a position rearward beyond the first projection exposing hole  107 . 
     The outer-cylinder-side opening  108  includes an outer-cylinder-side feed hole  109  serving as an example of a feed-side opening, and an outer-cylinder-side return hole  110  serving as an example of a return-side opening, as shown in  FIG. 13( b ) . The outer-cylinder-side feed hole  109  and the outer-cylinder-side return hole  110  are in the form of circles generally identical in size to each other in right-side elevation view, and formed on the front half of the right end portion of the feed section  101 . The outer-cylinder-side feed hole  109  and the outer-cylinder-side return hole  110  are adjacent to each other. More specifically, the outer-cylinder-side return hole  110  is adjacent to the rear side (more specifically, a portion slightly obliquely above the rear side) of the outer-cylinder-side feed hole  109 . 
     A feed-side agitator rotating shaft  120  serving as an example of a rotating shaft or a first rotating shaft extends between the front and rear sidewalls of each feed section  101 , as shown in  FIG. 8 . More specifically, the feed-side agitator rotating shaft  120  anteroposteriorly extends (see  FIG. 12( b ) ) to pass through the circle center of the circular feed section  101  in front elevation view, and is rotatably supported by the front and rear sidewalls of the feed section  101 . The feed-side agitator rotating shaft  120  is provided with a plurality of feed-side agitators  115  serving as examples of agitating members or first agitating members. 
     The plurality of feed-side agitators  115 , each formed by a flexible film or the like generally rectangular in left-side elevation view and generally in the form of an inverted L (see  FIGS. 14( a ) and 14( b ) ) in front elevation view, are arranged in the inner cylinder accommodation chamber  104 , and the proximal edges thereof are fixed to the feed-side agitator rotating shaft  120 . Each feed-side agitator  115  is so formed that the distal end thereof slidably comes into contact with the inner circumferential surface of the inner cylinder accommodation chamber  104  (feed chamber  121  described later) to be deflected upstream in the rotational direction. 
     As shown in  FIG. 12( a ) , the front and rear end portions of the feed-side agitator rotating shaft  120  protrude frontward and rearward from the front and rear sidewalls of the feed section  101  respectively. A feed-side agitator input gear  116  serving as an example of an input transmission portion is provided on the portion of the feed-side agitator rotating shaft  120  protruding rearward from the rear sidewall of the feed section  101 . A feed-side agitator output gear  117  serving as an example of an output transmission portion is provided on the portion of the feed-side agitator rotating shaft  120  protruding frontward from the front sidewall of the feed section  101 . The yellow toner cartridge  69 Y is provided with no feed-side agitator output gear  117  (see  FIG. 8 ). 
     The feed-side agitator input gear  116  and the feed-side agitator output gear  117  are spur gears, identical in size to each other, provided with teeth on the outer circumferential surfaces thereof, and the diameters thereof are set to about half of the diameter of the feed section  101  circularly formed in front elevation view, as shown in  FIGS. 12( b ) and 12( c ) . The anteroposterior size of the feed-side agitator input gear  116  and the feed-side agitator output gear  117  is equalized to that of the storage-side agitator input gear  114 . The feed-side agitator rotating shaft  120 , the feed-side agitator input gear  116  and the feed-side agitator output gear  117  serve as an example of a third transmission portion. Further, the first transmission portion  88 , the second transmission portion  89 , the feed-side agitator rotating shaft  120 , the feed-side agitator input gear  116  and the feed-side agitator output gear  117  serve as an example of a transmission unit. 
     In the rear sidewall of the feed section  101 , an intermediate gear support shaft  118  is provided on a position upward beyond the feed-side agitator input gear  116  to protrude rearward from the rear sidewall of the feed section  101 , as shown in  FIG. 12( c ) . The intermediate gear support shaft  118  is provided with an intermediate gear  119  serving as an example of an intermediate transmission portion. The storage-side agitator rotating shaft  112 , the storage-side agitator input gear  114  and the intermediate gear  119  serve as an example of a storage-chamber-side transmission portion. 
     The intermediate gear  119  is a spur gear provided with teeth on the outer circumferential surface thereof, and the diameter thereof is equalized to the opposition interval between the feed-side agitator input gear  116  and the storage-side agitator input gear  114 . The intermediate gear  119  meshes with the feed-side agitator input gear  116  and the storage-side agitator input gear  114 . The anteroposterior size of the intermediate gear  119  is equalized to that of the feed-side agitator input gear  116  (see  FIG. 12( a ) ). 
     The inner cylinder  96  is generally in the form of a hollow cylinder along the inner cylinder accommodation chamber  104  of the feed section  101  of the outer cylinder  95 , and accommodated in the inner cylinder accommodation chamber  104  coaxially with the feed-side agitator rotating shaft  120 , as shown in  FIGS. 14( a ) and 14( b ) . The aforementioned feed-side agitator rotating shaft  120  anteroposteriorly extends in the interior (referred to as the feed chamber  121 ) of the inner cylinder  96  accommodated in the inner cylinder accommodation chamber  104 , and the feed-side agitators  115  are arranged in the feed chamber  121 . The inner cylinder  96  is pivotable about the feed-side agitator rotating shaft  120  in sliding contact with the inner circumferential surface of the feed section  101  of the outer cylinder  95 . 
     An inner cylinder communication hole  122  and the inner-cylinder-side opening  125  (see  FIG. 13( b ) ) are formed in the inner cylinder  96 . 
     The inner cylinder communication hole  122  is formed on a portion of the circumference of the inner cylinder  96 , in the form of a rectangle generally identical in size to the outer cylinder connecting hole  105  as viewed from the center of the pivoting shaft of the inner cylinder  96 . 
     The inner-cylinder-side opening  125 , formed on a portion of the circumference of the front half of the inner cylinder  96  as shown in  FIG. 13( b ) , includes an inner-cylinder-side feed hole  126  and an inner-cylinder-side return hole  127 . The inner-cylinder-side feed hole  126  and the inner-cylinder-side return hole  127  are in the form of circles generally identical in size to the outer-cylinder-side feed hole  109  and the outer-cylinder-side return hole  110  as viewed from the center of the pivoting shaft of the inner cylinder  96 . The inner-cylinder-side feed hole  126  and the inner-cylinder-side return hole  127  are adjacent to each other. More specifically, the inner-cylinder-side return hole  127  is adjacent to the rear side (more specifically, a portion slightly obliquely above the rear side) of the inner-cylinder-side feed hole  126 . 
     The inner cylinder  96  is provided with the first and second projections  123  and  124 . 
     The first projection  123  is provided on a portion of the circumference of the anteroposterior center of the inner cylinder  96 , more specifically on a position (see  FIGS. 14( a ) and 14( b ) ) deviating from the inner-cylinder-side return hole  127  by about 135□ clockwise in front elevation view, and is generally in the form of a rectangular parallelepiped protruding outward in the radial direction of the inner cylinder  96 . The anteroposterior size of the first projection  123  is set slightly smaller than those of the first projection exposing hole  107  of the outer cylinder  95  and the opening/closing main portion engaging hole  86  (see  FIG. 10 ) of the opening/closing member  75  of the cartridge receiving section  68 . The peripheral size (along the circumferential surface of the inner cylinder  96 ) of the first projection  123  is set to about ¼ of the peripheral size (along the circumferential surface of the feed section  101  of the outer cylinder  95 ) of the first projection exposing hole  107  and slightly smaller than the right-and-left size of the opening/closing main portion engaging hole  86  (see  FIG. 10 ). When the inner cylinder  96  is accommodated in the inner cylinder accommodation chamber  104  of the outer cylinder  95  (see  FIGS. 14( a ) and 14( b ) ), the first projection  123  is exposed through the first projection exposing hole  107  of the outer cylinder  95  so that the distal end thereof protrudes outward in the radial direction of the feed section  101  beyond the outer side surface of the feed section  101 . 
     The second projection  124  includes an upper second projection  128  and a lower second projection  129  identical in size to each other. 
     The upper second projection  128  is generally in the form of a rectangular parallelepiped protruding outward in the radial direction of the inner cylinder  96  on the outer circumferential surface of the inner cylinder  96 , e.g., on a position obliquely under the rear side of the inner-cylinder-side return hole  127  in  FIG. 13( b ) . 
     The lower second projection  129  is formed on the outer circumferential surface of the inner cylinder  96  on a position deviating from the upper second projection  128  by about 50□ clockwise (see  FIGS. 14( a ) and 14( b ) ). 
     The anteroposterior size of the upper and lower second projections  128  and  129  is set slightly smaller than that of the second projection exposing hole  111  of the outer cylinder  95 . Further, the peripheral size (along the circumferential surface of the inner cylinder  96 ) of the upper and lower second projections  128  and  129  is set to about 1/10 of the peripheral size (along the circumferential surface of the feed section  101  of the outer cylinder  95 ) of the second projection exposing hole  111 . The upper and lower second projections  128  and  129  are respectively formed with shutter support grooves  130  recessed reversely to the direction of opposition in which the upper and lower second projections  128  and  129  are opposed to each other along the circumferential surface of the inner cylinder  96  in generally central portions thereof along the direction of protrusion. When the inner cylinder  96  is accommodated in the inner cylinder accommodation chamber  104  of the outer cylinder  95  (see  FIGS. 14( a ) and 14( b ) ), the upper and lower second projections  128  and  129  are exposed through the second projection exposing hole  111  of the outer cylinder  95  so that the distal ends thereof protrude outward in the radial direction of the feed section  101  beyond the outer side surface of the feed section  101 . The shutter support grooves  130  of the upper and lower second projections  128  and  129  are positioned slightly outward beyond the outer side surface of the feed section  101  in the radial direction of the feed section  101  (see  FIGS. 14( a ) and 14( b ) ). 
     A cartridge outside shutter  131  is mounted on the shutter support grooves  130  of the upper and lower second projections  128  and  129 . The cartridge outside shutter  131  is in the form of a thin plate arcuate along the outer peripheral surface of the feed section  101  and anteroposteriorly longitudinal in front elevation view. A peripheral end edge (upper end edge) of the cartridge outside shutter  131  is engaged to the shutter support groove  130  of the upper second projection  128 , while the other peripheral end edge (lower end edge) thereof is engaged to the shutter support groove  130  of the lower second projection  129 . Thus, the cartridge outside shutter  131  is sandwiched between the upper and lower second projections  128  and  129  on a position slightly outward beyond the outer side surface of the feed section  101  in the radial direction of the feed section  101 . 
     When accommodated in the inner cylinder accommodation chamber  104  of the outer cylinder  95 , the inner cylinder  96  is pivotable with respect to the inner circumferential surface of the feed section  101  of the outer cylinder  95  between the cartridge-side shutter closing position (see  FIG. 14( a ) ) inhibited from counterclockwise pivot in front elevation view, and the cartridge-side shutter opening position (see  FIG. 14( b ) ) inhibited from clockwise pivot. 
     When the inner cylinder  96  is located on the cartridge-side shutter closing position, the first projection  123  is in contact with the right end edge of the first projection exposing hole  107  while the upper second projection  128  of the second projection  124  is in contact with the upper end edge of the second projection exposing hole  111 , as shown in  FIG. 14( a ) . A portion of the inner cylinder  96  located downward beyond the inner-cylinder-side opening  125  closes the outer-cylinder-side opening  108  of the outer cylinder  95  from inside in the radial direction of the inner cylinder  96 , while the cartridge outside shutter  131  closes the outer-cylinder-side opening  108  from outside in the radial direction of the inner cylinder  96 . Further, another portion of the inner cylinder  96  located rightward beyond the inner cylinder communication hole  122  closes the outer cylinder connecting hole  105  of the outer cylinder  95  from inside in the radial direction of the inner cylinder  96 . Thus, the storage chamber  102  and the feed chamber  121  are isolated from each other. 
     When the inner cylinder  96  is located on the cartridge-side shutter opening position, on the other hand, the first projection  123  is in contact with the left end edge of the first projection exposing hole  107  while the lower second projection  129  of the second projection  124  is in contact with the lower end edge of the second projection exposing hole  111 , as shown in  FIG. 14( b ) . The inner-cylinder-side opening  125  of the inner cylinder  96  and the outer-cylinder-side opening  108  of the outer cylinder  95  are opposed to each other, and the cartridge outside shutter  131  opens the outer-cylinder-side opening  108  from outside in the radial direction of the inner cylinder  96 . More specially, when the inner-cylinder-side opening  125  and the outer-cylinder-side opening  108  are opposed to each other, the inner-cylinder-side return hole  127  and the outer-cylinder-side return hole  110  are opposed to each other while the inner-cylinder-side feed hole  126  and the outer-cylinder-side feed hole  109  are also opposed to each other. Thus, the feed chamber  121  of the inner cylinder  96  communicates with the exterior through the inner-cylinder-side opening  125  and the outer-cylinder-side opening  108 . Further, the inner cylinder communication hole  122  and the outer cylinder connecting hole  105  are opposed to each other. Thus, the storage chamber  102  of the outer cylinder  95  and the feed chamber  121  of the inner cylinder  96  communicate with each other. When the inner-cylinder-side return hole  127  and the outer-cylinder-side return hole  110  are opposed to each other, a clearance formed between the peripheral edges of the inner-cylinder-side return hole  127  and the outer-cylinder-side return hole  110  in the direction of opposition thereof is sealed with a cartridge sealing member (not shown) of felt, sponge or the like. Similarly, when the inner-cylinder-side feed hole  126  and the outer-cylinder-side feed hole  109  are opposed to each other, a clearance formed between the peripheral edges of the inner-cylinder-side feed hole  126  and the outer-cylinder-side feed hole  109  in the direction of opposition thereof is also sealed with the cartridge sealing member (not shown). 
     (3-2-3) Attachment/Detachment of Toner Cartridge to/from Cartridge Receiving Section 
       FIG. 15  is a right-side perspective view of the cartridge receiving section accommodating all the toner cartridges, with the inner cylinders of the toner cartridges located on the cartridge-side shutter closing position.  FIG. 16  is a right-side perspective view of  FIG. 15 , showing the inner cylinders of the toner cartridges located on the cartridge-side shutter opening position.  FIGS. 17( a ) and 17( b )  are front sectional views of the cartridge receiving section accommodating each toner cartridge, with the inner cylinder located on the cartridge-side shutter closing position and the cartridge-side shutter opening position respectively.  FIGS. 17( a ) and 17( b )  show the first projection, the second projection, the first projection exposing hole, the second projection exposing hole, the inner-cylinder-side opening, the outer-cylinder-side opening and the opening/closing main portion engaging hole on the same plane, for the convenience of illustration. 
     First, the user grasps the grip  103  of the toner cartridge  69  (see  FIG. 13( a ) ) having the inner cylinder  96  located on the cartridge-side shutter closing position. Then, the user mounts from above the toner cartridge  69  in the corresponding receiving chamber  73  (see  FIG. 10 ) of the cartridge receiving section  68  having the operation lever  81  located on the lever closing position while keeping the feed-side agitator output gear  117  on the front side. The receiving chambers  73 , corresponding to the colors of the toners similarly to the toner cartridges  69 , are hereinafter referred to as yellow, magenta, cyan and black receiving chambers  73 Y,  73 M,  73 C and  73 K respectively in this order from the front side, as shown in  FIG. 10 . 
     When each toner cartridge  69  is mounted in the corresponding receiving chamber  73 , the front end portions (see  FIGS. 12( a ) to 12( c ) ) of the storage-side agitator rotating shaft  112  and the feed-side agitator rotating shaft  120  are received in the attachment/detachment guide groove  77  positioned frontward in the receiving chamber  73 , while the rear end portions (see  FIGS. 12( a ) to 12( c ) ) of the storage-side agitator rotating shaft  112  and the feed-side agitator rotating shaft  120  are received in the attachment/detachment guide groove  77  positioned rearward in the receiving chamber  73 . Thus, the toner cartridge  69  moves generally downward in the receiving chamber  73  through the front and rear end portions of the storage-side agitator rotating shaft  112  and the feed-side agitator rotating shaft  120  (see  FIGS. 12( a ) to 12( c ) ) guided into the corresponding attachment/detachment guide grooves  77  respectively. When the front and rear end portions of the feed-side agitator rotating shaft  120  (see  FIGS. 12( a ) to 12( c ) ) come into contact with the lower end edge of the corresponding attachment/detachment guide grooves  77  beyond the receiving section positioning projections  78  thereof, each toner cartridge  69  is completely received in the corresponding receiving chamber  73 , as shown in  FIG. 15 . All the toner cartridges  69  received in the corresponding receiving chambers  73  respectively are parallelly arranged along the anteroposterior direction. 
     At this time, the first projection  123  of each toner cartridge  69  engages with the corresponding opening/closing main portion engaging hole  86  of the opening/closing member  75  of the cartridge receiving section  68  in the corresponding receiving chamber  73 . In each receiving chamber  73 , further, the feed-side agitator input gear  116  of the toner cartridge  69  meshes with the output transmission gear  99  of the second transmission portion  89  from above while the feed-side agitator output gear  117  meshes with the input transmission gear  94  of the second transmission portion  89  from above, as shown in  FIG. 8 . When all the toner cartridges  69  are accommodated in the corresponding receiving chambers  73  respectively, the second transmission portions  89  are positioned between the toner cartridges  69  adjacent to each other in the anteroposterior direction. 
     In the black receiving chamber  73 K, the feed-side agitator input gear  116  of the black toner cartridge  69 K meshes with the first transmission gear  91  of the first transmission portion  88 . 
     When each toner cartridge  69  is accommodated in the corresponding receiving chamber  73  as shown in  FIG. 15 , the lower half of the storage section  100  and the feed section  101  are exposed from the receiving-section-side opening  74  in the right side of the toner cartridge  69 . The exposed portion of the feed section  101  includes the outer-cylinder-side opening  108 , the inner-cylinder-side opening  125 , the second projection  124  and the cartridge outside shutter  131 , as shown in  FIG. 16 . 
     The user can detach each toner cartridge  69  from the cartridge receiving section  68  by grasping the grip  103  (see  FIGS. 12( a ) to 12( c ) ) and moving the toner cartridge  69  accommodated in the corresponding receiving chamber  73  generally upward as shown in  FIG. 15 , contrarily to the aforementioned procedure. 
     (3-2-4) Attachment/Detachment of Cartridge Receiving Section to/from Main Body Casing 
       FIG. 18  is a left-side sectional view of  FIG. 5 , showing a cartridge receiving section drawn out from the main body casing  2  to a position (attachment/detachment position) where all the toner cartridges are exposed frontward from the main body casing.  FIG. 19  is a front elevation view of the color laser printer, showing the cartridge receiving section accommodation space, the cartridge receiving section and the toner cartridge in a front sectional view.  FIGS. 20( a ) and 20( b )  excerpt the front sectional view of the cartridge receiving section accommodation space, the cartridge receiving section and the toner cartridge from  FIG. 19 , with the inner cylinder located on the cartridge-side-shutter closing position and the cartridge-side-shutter opening position respectively.  FIGS. 20( a ) and 20( b )  show the first projection, the second projection, the first projection exposing hole, the second projection exposing hole, the inner-cylinder-side opening, the outer-cylinder-side opening, the opening/closing main portion engaging hole, the partition-wall-side feed hole and the partition-wall-side return hole on the same plane, for the convenience of illustration. 
     When the partition-wall-side shutter  35  is located on the partition-wall-side shutter closing position in the main body casing  2  as shown in  FIG. 6( a ) , the first cover  22  is opened for opening the cartridge receiving section mounting port  11  as shown in  FIG. 4 . Then, the cartridge receiving section  68  accommodating all the toner cartridges  69  corresponding to the respective colors is inserted into the cartridge receiving section accommodation space  24  from the front side, as shown in  FIG. 18 . At this time, the rollers  71  provided on both width-directional sides of the cartridge receiving section  68  are received in the corresponding guide rails  28  of the main body casing  2 . More specifically, each roller  71  is sandwiched in the up-and-down direction between the pair of ridges  31  of the corresponding guide rail  28 . Thus, the cartridge receiving section  68  slidingly moves rearward in the cartridge receiving section accommodation space  24  through the rollers  71  guided by the corresponding guide rails  28 . When the rearmost ones of the rollers  71  provided on the both width-directional sides of the cartridge receiving section  68  come into contact with the inner peripheral surfaces of the rear end portions of the corresponding guide rails  28  beyond the guide rail positioning projections  33  thereof, the cartridge receiving section  68  is completely accommodated in the cartridge receiving section accommodation space  24 , as shown in  FIG. 4 . When the first cover  22  is closed, the cartridge receiving section  68  is completely mounted in the main body casing  2 . The anteroposterior position of the cartridge receiving section  68  completely mounted in the main body casing  2  is referred to as a mount position. In this state, the upper end portion of each toner cartridge  69 , more specifically the upper end portion of the storage section  100 , is located upward beyond the ejection tray  13 , as shown in  FIG. 7 . 
     When the cartridge receiving section  68  is mounted in the main body casing  2 , the connecting projection  92  of the first transmission portion  88  thereof is connected to the connecting hole  49  of the second gear  45  provided on the driving mechanism  30  of the main body casing  2 . When the aforementioned agitator driving motor (not shown) is driven in this state, the driving force thereof is transmitted to the first gear  44  of the driving mechanism  30 . This driving force is further transmitted to the second gear  45  meshing with the first gear  44 , thereby rotating the second gear  45  counterclockwise in rear elevation view. Therefore, the connecting projection  92  connected to the connecting hole  49  of the second gear  45  co-rotates with the second gear  45  counterclockwise in rear elevation view due to the transmitted driving force of the agitator driving motor (not shown). This driving force rotates the first support shaft  90  and the first transmission gear  91  in the same direction, as shown in  FIG. 8 . 
     The driving force rotating the first support shaft  90  and the first transmission gear  91  is transmitted to the feed-side agitator input gear  116  of the black toner cartridge  69 K meshing with the first transmission gear  91 . Thus, the feed-side agitator input gear  116  is rotated clockwise in rear elevation view (counterclockwise in front elevation view), thereby rotating the feed-side agitator rotating shaft  120  provided with the feed-side agitator input gear  116  as well as the feed-side agitators  115  and the feed-side agitator output gear  117  provided on the feed-side agitator rotating shaft  120  clockwise in rear elevation view (counterclockwise in front elevation view). Further, this driving force is transmitted to the storage-side agitator input gear  114  meshing with the intermediate gear  119  via the intermediate gear  119  meshing with the feed-side agitator input gear  116 . Thus, the storage-side agitator input gear  114  is rotated clockwise in rear elevation view (counterclockwise in front elevation view), thereby rotating the storage-side agitator rotating shaft  112  provided with the storage-side agitator input gear  114  and the storage-side agitator  113  provided on the storage-side agitator rotating shaft  112  clockwise in rear elevation view (counterclockwise in front elevation view). 
     This driving force is output from the feed-side agitator output gear  117  of the black toner cartridge  69 K and transmitted to the second transmission portion  89 , more specifically transmitted to the second support shaft  93  through the input transmission gear  94  meshing with the feed-side agitator output gear  117  in front of the black toner cartridge  69 K. Thus, the second support shaft  93  and the output transmission gear  99  are rotated counterclockwise in rear elevation view, similarly to the first support shaft  90  and the first transmission gear  91 . In the cyan toner cartridge  69 C, the driving force received from the output transmission gear  99  is transmitted to the feed-side agitator input gear  116  meshing with the output transmission gear  99  of the second transmission portion  89 , and is further transmitted to the feed-side agitator rotating shaft  120 , the feed-side agitator output gear  117 , the intermediate gear  119 , the storage-side agitator input gear  114  and the storage-side agitator rotating shaft  112 , thereby rotating the feed-side agitators  115  and the storage-side agitator  113 . 
     In other words, the driving force rotating the first support shaft  90  in the first transmission portion  88  rotates the feed-side agitator  115  and the storage-side agitator  113  of the black toner cartridge  69 K, and is thereafter successively transmitted to the feed-side agitators  115  and the storage-side agitators  113  of the cyan toner cartridge  69 C adjacent to the front side of the black toner cartridge  69 K, the magenta toner cartridge  69 M adjacent to the front side of the cyan toner cartridge  69 C and the yellow toner cartridge  69 Y adjacent to the front side of the magenta toner cartridge  69 M in this order. Thus, the feed-side agitator  115  and the storage-side agitator  113  of each toner cartridge  69  are so rotated as to agitate the toner in the feed chamber  121  and the storage chamber  102  of the toner cartridge  69 . When the inner cylinder  96  of each toner cartridge  69  is located on the cartridge-side shutter opening position as shown in  FIG. 17( b ) , the inner cylinder communication hole  122  and the outer cylinder connecting hole  105  are opposed to each other, and the storage chamber  102  and the feed chamber  121  communicate with each other, whereby the toner can be fed from the storage chamber  102  into the feed chamber  121  through the storage-side agitator  113  agitating the toner stored in the storage chamber  102  in addition to the own weight of the toner. 
     When each toner cartridge  69  is accommodated in the corresponding receiving chamber  73  as shown in  FIGS. 15 and 16 , the operation lever  81  located on the lever closing position is turned clockwise in front elevation view to move to the lever opening position, whereby the opening/closing member  75  also pivots clockwise about a swinging shaft (not shown) along with the movement of the operation lever  81 . Further, the first projection  123  of each toner cartridge  69  engaging with the opening/closing main portion engaging hole  86  of the opening/closing member  75  collectively moves in the first projection exposing hole  107  of the outer cylinder  95  in the same direction also along with the opening/closing member  75 . Due to this movement of the first projection  123 , the inner cylinder  96  provided with the first projection  123  also pivots from the cartridge-side shutter closing position (see  FIG. 15 ) to the cartridge-side shutter opening position (see  FIG. 16 ). Then, the upper and lower second projections  128  and  129  provided on the inner cylinder  96  move in the second projection exposing hole  111  in the same direction, and the lower second projection  129  is engaged to the corresponding receiving section notch  80  of the receiving section casing  82  and the first projection  123  comes into contact with the left end edge of the receiving section penetration hole  79  of the receiving section casing  82  as shown in  FIG. 16  when the inner cylinder  96  pivots to the cartridge-side shutter opening position (see  FIG. 17( b ) ). 
     When the cartridge receiving section  68  is mounted in the main body casing  2 , the upper and lower second projections  128  and  129  of each toner cartridge  69  accommodated in the cartridge receiving section  68  sandwich in the up-and-down direction the partition-wall-side shutter  35  located on the partition-wall-side shutter closing position in front elevation view, as shown in  FIG. 19 . More specifically, the aforementioned upper and lower notches  41  and  42  (see  FIG. 5 ) of the partition-wall-side shutter  35  correspond to the toner cartridge  69  of each color such that the upper second projection  128  engages with the foremost upper notch  41  (see  FIG. 5 ) and the lower second projection  129  engages with the foremost lower notch  42  (see  FIG. 5 ) in the yellow toner cartridge  69 Y (see  FIG. 15 ), for example. In each of the toner cartridges  69  of the remaining colors, the upper and lower second projections  128  and  129  similarly engage with the corresponding upper and second notches  41  and  42  respectively. 
     When the cartridge receiving section  68  is mounted in the main body casing  2 , the outer-cylinder-side feed hole  109  (see  FIG. 13( b ) ) of the outer-cylinder-side opening  108  of each toner cartridge  69  accommodated in the cartridge receiving section  68 , is width-directionally opposed to the partition-wall-side feed hole  39  (see  FIG. 5 ) of the partition-wall-side toner passing portion  34  with the partition-wall-side shutter  35  and the cartridge outside shutter  131  interposed therebetween, as shown in  FIG. 20( a ) . Similarly, the outer-cylinder-side return hole  110  (see  FIG. 13( b ) ) is width-directionally opposed to the partition-wall-side return hole  40  (see  FIG. 5 ) of the partition-wall-side toner passing portion  34  with the partition-wall-side shutter  35  and the cartridge outside shutter  131  interposed therebetween. 
     More specifically, the partition-wall-side feed hole  39  and the partition-wall-side return hole  40  (see  FIG. 5 ) also correspond to the toner cartridge  69  of each color similarly to the upper and lower notches  41  and  42  such that the outer-cylinder-side feed hole  109  is opposed to the foremost partition-wall-side feed hole  39  (see  FIG. 5 ) and the outer-cylinder-side return hole  110  is opposed to the foremost partition-wall-side return hole  40  (see  FIG. 5 ) in the yellow toner cartridge  69 Y (see  FIG. 15 ), for example. Similarly in each of the toner cartridges  69  corresponding to the remaining colors, the outer-cylinder-side feed hole  109  is opposed to the corresponding partition-wall-side feed hole  39  while the outer-cylinder-side return hole  110  is opposed to the partition-wall-side return hole  40  corresponding to the partition-wall-side feed hole  39 . Each toner cartridge  69  is opposed to the developing roller  143  of each processing section  62  described later in the width direction (longitudinal direction of the developing roller  143 ) on the right side surface provided with the outer-cylinder-side feed hole  109  and the outer-cylinder-side return hole  110 , as shown in  FIG. 7 . 
     When the operation lever  81  (see  FIG. 16 ) located on the lever closing position is moved to the lever opening position in this state as described above, the partition-wall-side shutter  35  sandwiched between the upper and lower second projections  128  and  129  slidingly moves from the partition-wall-side shutter closing position to the partition-wall-side shutter opening position following pivot of the inner cylinder  96  of the toner cartridge  69  from the cartridge-side shutter closing position to the cartridge-side shutter opening position. When the partition-wall-side shutter  35  reaches the partition-wall-side shutter opening position, the outer-cylinder-side feed hole  109  of each toner cartridge  69  and the corresponding partition-wall-side feed hole  39  communicate with each other while the outer-cylinder-side return hole  110  and the corresponding partition-wall-side return hole  40  also communicate with each other, as shown in  FIG. 20( b ) . When the driving force of the agitator driving motor (not shown) is so supplied as to rotate the feed-side agitators  115  counterclockwise in front elevation view as described above, therefore, the toner is fed from the feed chamber  121  to the inner-cylinder-side feed hole  126 , and transmitted rightward (toward a developer-side feed hole  171  describe later) beyond the partition wall  15  through the outer-cylinder-side feed hole  109  and the partition-wall-side feed hole  39 . The feed-side agitator  115  is notched on a portion opposed to the inner-cylinder-side return hole  127 , in order to feed no toner to the inner-cylinder-side return hole  127  while in order to feed the toner from the feed chamber  121  to the cylinder-side feed hole  126  during rotation. 
     When the outer-cylinder-side feed hole  109  communicates with the corresponding partition-wall-side feed hole  39  and the outer-cylinder-side return hole  110  communicates with the corresponding partition-wall-side return hole  40 , right-and-left clearances formed between the peripheral edges of the partition-wall-side feed hole  39  and the outer-cylinder-side feed hole  109  and between the peripheral edges of the partition-wall-side feed hole  40  and the outer-cylinder-side return hole  110 , are sealed with the aforementioned partition wall sealing member (not shown). Further, the right-and-left clearances formed between the peripheral edges of the inner-cylinder-side feed hole  126  and the outer-cylinder-side feed hole  109  in the direction of opposition and between the peripheral edges of the inner-cylinder-side return hole  127  and the outer-cylinder-side return hole  110 , are sealed with the cartridge sealing member (not shown), as described above. Therefore, the toner fed from the feed chamber  121  passes through the inner-cylinder-side feed hole  126 , the outer-cylinder-side feed hole  109  and the partition-wall-side feed hole  39  with no intermediate leakage. 
     Contrarily to the aforementioned procedure, when the first cover  22  is opened as shown in  FIG. 4  for moving the operation lever  81  (see  FIGS. 14( a ) and 14( b ) ) to the lever closing position while moving the inner cylinder  96  and the partition-wall-side shutter  35  to the cartridge-side-shutter closing position and the partition-wall-side shutter closing position (see  FIG. 20( a ) ) respectively and the cartridge receiving section  68  is drawn out frontward from the mount position, the cartridge receiving section  68  can be detached from the main body casing  2  in a sliding manner. When the rollers  71  provided on the rear end of the cartridge receiving section  68  are located on the front end portion of the corresponding guide rail  28  as shown in  FIG. 18 , all the toner cartridges  69  are exposed from the main body casing  2 . The current anteroposterior position of the cartridge receiving section  68  is referred to as the attachment/detachment position. When the cartridge receiving section  68  is located on the attachment/detachment position, each toner cartridge  69  can be attached/detached to/from the cartridge receiving section  68 . 
     When the cartridge receiving section  68  is further drawn out from the attachment/detachment position and the rollers  71  provided on the rear end of the cartridge receiving section  68  are displaced frontward from the front edges of the corresponding guide rail  28 , the cartridge receiving section  68  is completely detached from the main body casing  2 . 
     (3-3) Processing Section 
       FIG. 21  excerpts each processing section from  FIG. 1 .  FIG. 22  is a plan view of the processing section in a state where the upper sidewall of a developer casing is removed.  FIG. 23  is a left-side sectional view of  FIG. 1 , showing an intermediate stage of attaching/detaching the processing sections. 
     As shown in  FIG. 1 , the plurality of processing sections  62  is provided correspondingly to the toners of the respective colors. In other words, the processing sections  62  are formed by four sections, i.e., a yellow processing section  62 Y, a magenta processing section  62 M, a cyan processing section  62 C and a black processing section  62 K. The four processing sections  62  are parallelly arranged at intervals from the front side toward the rear side. More specifically, the yellow, magenta, cyan and black processing sections  62 Y,  62 M,  62 C and  62 K are arranged from the front side in this order. The four processing sections  62  are connected together with connecting members (not shown), and accommodated in the process accommodation space  17  of the main body casing  2 . When the second cover  18  of the main body casing  2  is opened to open the processing section mounting port  10  (see  FIG. 3 ) and thereafter the four processing sections  62  are anteroposteriorly moved, the four processing sections  62  are together slidably attached/detached to/from the main body casing  2 , as shown in  FIG. 23 . 
     Each processing section  62  includes a process casing  132 , the photosensitive drum  133 , a scorotron charger  134 , a cleaning roller  141  and a developing section  135 , as shown in  FIG. 21 . 
     The process casing  132  is in the form of a bottomed frame member generally U-shaped in left-side sectional view and width-directionally longitudinal, and provided on the lower end portion thereof with an irradiation window  136  passing through the lower sidewall of the process casing  132  in the thickness direction. The irradiation window  136  is generally in the form of a rectangle width-directionally longitudinal in bottom-side elevation view. 
     The photosensitive drum  133  includes a drum body  137  and a drum rotation shaft  138 . The drum body  137  has a hollow cylindrical shape and is formed by a positively chargeable photosensitive layer with an outermost layer of polycarbonate or the like. The drum rotation shaft  138  extends along the rotating shaft of the drum body  137  at the center of this rotating shaft. The drum rotation shaft  138  is unrotatably supported on both width-directional sidewalls of the process casing  132 . The drum body  137  is rotatable with respect to the drum rotation shaft  138 , and the upper half thereof is exposed upward from the upper end edge of the process casing  132 . As shown in  FIG. 22 , a gear portion (drum gear portion  154 ) is provided on the right end portion of the drum body  137 . The driving force of a process driving motor (not shown) of the main body casing  2  is transmitted through the drum gear portion  154  thereby to rotationally drive the drum body  137  counterclockwise in left-side elevation view, as shown in  FIG. 21 . 
     The scorotron charger  134  is a positively chargeable scorotron charger including a wire  139  and a grid  140  for generating corona discharge through application of a charging bias. This scorotron charger  134  is opposed to the photosensitive drum  133  from under the same at an interval, so as not to come into contact with the photosensitive drum  133 . 
     The cleaning roller  141  includes a cleaning roller shaft  152  of a metal and a cleaning foaming roller  153  of a conductive foamed material covering the cleaning roller shaft  152 . The cleaning roller shaft  152  is rotatably supported on the both width-directional sidewalls of the process casing  132  at the back of the photosensitive drum  133 . As shown in  FIG. 22 , a gear portion (cleaning gear portion  155 ) meshing with the drum gear portion  154  is provided on the right end portion of the cleaning roller shaft  152 . The cleaning foaming roller  153  is so arranged as to come into contact with the photosensitive drum  133  from behind. On this contact position, the cleaning foaming roller  153  is rotated along with the cleaning roller shaft  152  in the direction (clockwise) opposite to the rotational direction of the photosensitive drum  133  as shown in  FIG. 21 , due to the driving force of the aforementioned process driving motor (not shown) transmitted thereto through the drum gear portion  154  and the cleaning gear portion  155  as shown in  FIG. 22 . In image formation, a cleaning bias is applied to the cleaning roller  141  from a high-pressure substrate (not shown) provided in the main body casing  2 . 
     The developing section  135  is arranged in front of the photosensitive drum  133 , and includes the developer casing  142  as well as the developing roller  143 , a feed roller  144 , a layer-thickness regulating member  145 , a feed auger  156 , a return auger  157  and a developer seal  164  arranged in the developer casing  142 . 
     The developer casing  142  is in the form of a box generally triangular in left-side elevation view and width-directionally longitudinal. A rectangular developer connecting hole  158  width-directionally longitudinal in rear elevation view is formed on the rear end portion of the developer casing  142 . A developer partition wall  159  is formed in the developer casing  142 , and divides the interior of the developer casing  142  into a developing chamber  160  and a toner feed chamber  161 . The toner feed chamber  161  is positioned on the front end portion of the developer casing  142 , and defined generally in the form of a circle in left-side elevation view. The front end portion of the developer casing  142  is in the form of a hollow cylinder corresponding to the left-side sectional shape of the toner feed chamber  161 . The developing chamber  160  is positioned on the rear side of the toner feed chamber  161  with the developer partition wall  159  interposed, and defined generally in the form of a trapezoid in right-side sectional view. As shown in  FIG. 22 , the developer partition wall  159  is formed on the right end portion thereof with a toner connecting hole  162  passing through the developer partition wall  159  in the thickness direction, and the developing chamber  160  and the toner feed chamber  161  communicate with each other through the toner connecting hole  162 . The developing roller  143 , the feed roller  144 , the layer-thickness regulating member  145 , the return auger  157  and the developer seal  164  are arranged in the developing chamber  160  while the feed auger  156  is arranged in the toner feed chamber  161 , as shown in  FIG. 21 . 
     The developing roller  143  is arranged on a rear portion of the developing chamber  160 , and the rear end portion thereof is exposed rearward through the developer connecting hole  158  and brought into pressure contact with the photosensitive drum  133  from the front side. The developing roller  143  is formed by covering a developing roller rotation shaft  146  of a metal with a rubber roller  147  of an elastic member prepared from a conductive rubber material or the like. The developing roller rotation shaft  146  is rotatably supported on both width-directional sidewalls of the developer casing  142 , and provided with a gear portion (developer gear portion  163 ) on the right end portion thereof, as shown in  FIG. 22 . The driving force of the aforementioned process driving motor (not shown) is transmitted to the developer gear portion  163  to rotate the developing roller  143  in the direction (clockwise) opposite to the rotational direction of the photosensitive drum  133 , as shown in  FIG. 21 . In image formation, a developing bias is applied to the developing roller  143  from the high-pressure substrate (not shown) provided in the main body casing  2 . 
     The feed roller  144  is opposed to the developing roller  143  obliquely from under the front side, and brought into pressure contact with the developing roller  143 . This feed roller  144  is formed by covering a feed roller rotation shaft  148  of a metal with a sponge roller  149  formed by a conductive sponge member. The feed roller rotation shaft  148  is rotatably supported on the both width-directional sidewalls of the developer casing  142 , and a gear portion (not shown: feed gear portion) is provided on the right end portion thereof. The driving force of the aforementioned process driving motor (not shown) is transmitted to this feed gear portion (not shown) to rotate the feed roller  144  in the same direction (clockwise) as the rotational direction of the developing roller  143 . 
     The layer-thickness regulating member  145  includes a blade body  150  and a pressuring portion  151 . The blade body  150 , having a proximal edge supported on the rear end portion of the lower end portion of the developer casing  142 , is formed by a leaf spring member of a metal. The pressuring portion  151 , provided on the distal end of the blade body  150 , is prepared from insulating silicone rubber to be generally rectangular in sectional view. In the layer-thickness regulating member  145 , the pressuring portion  151  is brought into pressure contact with the surface of the developing roller  143  at the back of the feed roller  144 , due to the elastic force of the blade body  150 . 
     The feed auger  156  integrally includes a feed-side rotation shaft  165  longitudinal in the width direction and a feed-side transport portion  166 , as shown in  FIG. 22 . The feed-side rotation shaft  165  is rotatably supported on the both width-directional sidewalls of the developer casing  142 . The feed-side transport portion  166  is spirally formed on the outer circumferential surface of the feed-side rotation shaft  165  along the axial direction thereof. A gear portion (feed auger gear portion  167 ) is provided on the right end portion of the feed-side rotation shaft  165 , so that the driving force of the process driving motor (not shown) of the main body casing  2  is transmitted through this feed auger gear portion  167 . Thus, the feed auger  156  is rotationally driven in the toner feed chamber  161  clockwise in left-side elevation view, as shown in  FIG. 21 . The developer-side feed hole  171  is formed on a portion of the left sidewall of the developer casing  142  opposed to the feed auger  156 , for making the interior of the toner feed chamber  161  communicate with the exterior, as shown in  FIG. 22 . When the processing section  62  is mounted in the main body casing  2 , the developer-side feed hole  171  is opposed to and communicates with the partition-wall-side feed hole  39  (see  FIG. 5 ) corresponding to each toner. 
     The return auger  157  is arranged above the feed roller  144  at an interval in the developing chamber  160  as shown in  FIG. 21 , and integrally includes a return-side rotation shaft  168  longitudinal in the width direction and a return-side transport portion  169 , as shown in  FIG. 22 . The return-side rotation shaft  168  is rotatably supported on the both width-directional sidewalls of the developer casing  142 . The return-side transport portion  169  is spirally formed on the outer circumferential surface of the return-side rotation shaft  168  along the axial direction thereof. The spiral directions of the return-side transport portion  169  and the feed-side transport portion  166  are equalized to each other. A gear portion (return auger gear portion  170 ) meshing with the feed auger gear portion  167  is provided on the right end portion of the return-side rotation shaft  168 . The driving force of the process driving motor (not shown) of the main body casing  2  is transmitted to the return auger  157  through the feed auger gear portion  167  and the return auger gear portion  170 , thereby rotationally driving the return auger  157  counterclockwise in the developing chamber  160 , as shown in  FIG. 21 . A developer-side return hole  172  is formed on a portion of the left sidewall of the developer casing  142  opposed to the return auger  157 , for making the interior of the developing chamber  160  communicate with the exterior, as shown in  FIG. 22 . When the processing section  62  is mounted in the main body casing  2 , the developer-side return hole  172  is opposed to and communicates with the partition-wall-side return hole  40  (see  FIG. 5 ) corresponding to each toner. 
     In image formation, the toner accommodated in each toner cartridge  69  having the inner cylinder  96  located on the cartridge-side shutter opening position, is agitated by the feed-side agitator  115  in the feed chamber  121 , as described above and as shown in  FIG. 20( b ) . Then, the toner is fed through the inner-cylinder-side feed hole  126  to pass through the outer-cylinder-side feed hole  109 , the partition-wall-side feed hole  39  and the developer-side feed hole  171  (see  FIG. 22 ) and discharged into the toner feed chamber  161 , as shown in  FIG. 22 . 
     The toner discharged into the toner feed chamber  161  is transported rightward in the toner feed chamber  161  by the feed-side transport portion  166  of the rotationally driven feed auger  156 . This toner is transported into the developing chamber  160  and fed to the right end portion of the return auger  157  through the toner connecting hole  162  on the right end portion of the toner feed chamber  161 . The toner fed to the right end portion of the return auger  157  is transported leftward by the return-side transport portion  169  of the rotationally driven return auger  157 , and fed to the feed roller  144  (see  FIG. 21 ) arranged under the return auger  157 . 
     The toner reaching the developer-side return hole  172  without being fed to the feed roller  144  passes through the partition-wall-side return hole  40  and the outer-cylinder-side return hole  110  and thereafter enters the inner-cylinder-side return hole  127 , to be collected in the feed chamber  121  of the corresponding toner cartridge  69 , as shown in  FIGS. 20( a ) and 20( b ) . The toner reaching the developer-side return hole  172  is that transported leftward by the return-side transport portion  169  due to the aforementioned circulation of the toner, or that having been retained in the developing chamber  160  and transported leftward by the return-side transport portion  169  to reach the developer-side return hole  172 . 
     The toner fed to the feed roller  144  is then fed to the developing roller  143  due to the rotation of the feed roller  144 , as shown in  FIG. 21 . At this time, the toner is triboelectrically positively charged between the feed roller  144  and the developer roller  143  to which the developing bias is applied. The triboelectrically charged toner enters the space between the pressuring portion  151  of the layer-thickness regulating member  145  and the rubber roller  147  of the developing roller  143  following the rotation of the developing roller  143  to form a thin layer of a constant thickness, which in turn is carried on the rubber roller  147  of the developing roller  143 . 
     On the other hand, the scorotron charger  134  generates corona discharge through application of the charging bias, to uniformly positively charge the surface of the drum body  137  of the photosensitive drum  133 . The surface of the drum body  137 , uniformly positively charged by the scorotron charger  134  following the rotation thereof, is thereafter exposed by high-speed scanning of a laser beam emitted from the corresponding exit window (not shown) of the scanner unit  61  (see  FIG. 1 ) and received through the irradiation window  136 , thereby forming an electrostatic latent image of each color corresponding to the image to be formed on each sheet  3 . 
     Upon further rotation of the drum body  137 , the positively charged toner carried on the surface of the developing roller  143  is fed to the electrostatic latent image formed on the surface of the drum body  137  when facing and coming into contact with the photosensitive drum  133  due to the rotation of the developing roller  143 . Thus, the electrostatic latent image formed on the drum body  137  is visualized, and a toner image (developing agent image) resulting from reversal development is carried on the surface of the drum body  137  correspondingly to each color. 
     The developer seal  164  is in the form of a film longitudinal in the width direction and generally rectangular in plan view, and the upper end portion thereof is mounted on the upper sidewall of the developer casing  142 . The developer seal  164  is uniformly in sliding contact with the developing roller  143  from above along the axial direction thereof, and prevents the toner from leaking through the space between the upper sidewall of the developer casing  142  and the developing roller  143 . 
     The developing roller  143  collects the residual toner remaining on the surface of the photosensitive drum  133  after primary transfer described later. Further, the cleaning foaming roller  153  collects sheet dust coming from the sheet  3  and adhering onto the photosensitive drum  133  after the primary transfer. 
     (3-4) Transferring Section 
     As shown in  FIG. 1 , the transferring section  63  is arranged above the processing sections  62  along the anteroposterior direction in the process accommodation space  17  of the main body casing  2 . This transferring section  63  includes a driving roller  174 , a driven roller  175 , the intermediate transfer belt  176 , primary transfer rollers  177 , the secondary transfer roller  178 , a relay path  179  and a cleaning section  180 . 
     The driving roller  174  is arranged obliquely above the rear side of the photosensitive drum  133  of the black processing section  62 K. In image formation, the driving roller  174  is rotationally driven in the direction (clockwise in  FIG. 1 ) opposite to the rotational direction of the photosensitive drums  133 . 
     The driven roller  175  is arranged obliquely above the front side of the photosensitive drum  133  of the yellow processing section  62 Y, to be anteroposteriorly opposed to the driving roller  174 . This driven roller  175  is driven and rotated in the same direction (clockwise in  FIG. 1 ) as the rotational direction of the driving roller  174  upon the rotation of the driving roller  174 . 
     The intermediate transfer belt  176  is an endless belt of resin such as conductive polycarbonate or polyimide in which conductive particles of carbon or the like are dispersed. This intermediate transfer belt  176  is wound around the driving roller  174  and the driven roller  175 , and so arranged that the outer contact surface thereof oppositely comes into contact with all the photosensitive drums  133  of the processing sections  62 . 
     The driving roller  174  drives the driven roller  175 , and the intermediate transfer belt  176  circumferentially travels between the driving roller  174  and the driven roller  175  clockwise in  FIG. 1 . 
     Inside the intermediate transfer belt  176  wound around the driving roller  174  and the driven roller  175 , each primary transfer roller  177  is opposed to the photosensitive drum  133  of each processing section  62  to sandwich the intermediate transfer belt  176  between the same and the photosensitive drum  133 . This primary transfer roller  177  is formed by covering a roller rotating shaft of a metal with a rubber roller of an elastic member such as a conductive rubber material. The roller rotating shaft of the primary transfer roller  177  extends along the width direction and is rotatably supported on the main body casing  2 , and a primary transferring bias is applied to the primary transfer roller  177  in primary transfer described later. The primary transfer roller  177  rotates in the same direction (clockwise in  FIG. 1 ) as the direction of the circumferential travel of the intermediate transfer belt  176  on the position (primary transfer position) in opposing contact with the intermediate transfer belt  176 . 
     The secondary transfer roller  178  is opposed to the rear portion of the driving roller  174  to sandwich the intermediate transfer belt  176  between the same and the driving roller  174 . The roller rotating shaft of the secondary transfer roller  178  extends along the width direction and is rotatably supported on the main body casing  2 , and a secondary transferring bias is applied to the secondary transfer roller  178  in secondary transfer. The secondary transfer roller  178  rotates in the direction (counterclockwise in  FIG. 1 ) opposite to the direction of the circumferential travel of the intermediate transfer belt  176  on the position (secondary transfer position) in opposing contact with the intermediate transfer belt  176 . 
     The relay path  179  is so formed as to extend generally upward from the aforementioned secondary transfer position toward the fixing section  64 . 
     The intermediate transfer belt  176  circumferentially traveling around the driving roller  174  and the driven roller  175  sequentially passes through the contact positions (primary transfer positions) between the same and the photosensitive drums  133  of the processing sections  62  from the front side toward the rear side. In the process of this passage, the toner images corresponding to the respective colors and carried on the photosensitive drums  133  of the processing sections  62  are sequentially transferred to the intermediate transfer belt  176  through the primary transferring biases applied to the primary transfer rollers  177  respectively, so that a color image is formed on the intermediate transfer belt  176 . 
     That is, when the yellow toner image carried on the surface of the photosensitive drum  133  of the yellow processing section  62 Y is transferred to the intermediate transfer belt  176 , for example, the magenta toner image carried on the surface of the photosensitive drum  133  of the magenta processing section  62 M is thereafter transferred to the intermediate transfer belt  176 , to be superposed on the already transferred yellow toner image. Similarly, the cyan and black toner images carried on the surfaces of the photosensitive drums  133  of the cyan and black processing sections  62 C and  62 K are subsequently transferred to the intermediate transfer belt  176  to be superposed on the yellow and magenta toner images, so that the color image is formed on the intermediate transfer belt  176 . 
     The color image formed on the intermediate transfer belt  176  is collectively transferred to each sheet  3  transported from the sheet feeding section  4  to the secondary transfer position through the secondary transferring bias applied to the secondary transfer roller  178  when the intermediate transfer belt  176  passes through the contact position (secondary transfer position) between the same and the secondary transfer roller  178 . The sheet  3  having the color image transferred thereto is transported to the fixing section  64  along the relay path  179 . 
     The cleaning section  180  is arranged above the intermediate transfer belt  176 , and includes a primary cleaning roller  181 , a secondary cleaning roller  182 , a scraping blade  183  and a toner storage section  184 . 
     The toners adhering to the surface of the intermediate transfer belt  176  in the aforementioned transfer operation are first transferred from the surface of the intermediate transfer belt  176  to the primary cleaning roller  181  in the cleaning section  180  through a primary cleaning bias. The toners transferred to the primary cleaning roller  181  are then transferred to the secondary cleaning roller  182  through a secondary cleaning bias. Thereafter the toners transferred to the secondary cleaning roller  182  are scraped off by the scraping blade  183  to fall from the secondary cleaning roller  182 , and stored in the toner storage section  184 . 
     (3-5) Fixing Section 
     The fixing section  64  is arranged above the aforementioned secondary transfer position, and includes a heating roller  185  and a pressure roller  186  pressing the heating roller  185 . The color image transferred to the sheet  3  is heated and pressed in the fixing section  64  when the sheet  3  passes between the heating roller  185  and the pressure roller  186 , to be thermally fixed to the sheet  3 . 
     (4) Sheet Ejecting Section 
     The sheet ejecting section  6  includes a pair of transport rollers  187 , a sheet ejecting transport path  188 , sheet ejecting rollers  189  and the aforementioned ejection tray  13 . The pair of transport rollers  187  are so arranged as to come into contact with each other on a position obliquely above the front sides of the heating roller  185  and the pressure roller  186 . The sheet ejecting transport path  188  is so formed as to generally horizontally extend frontward from the contact position between the pair of transport rollers  187  toward the ejection hole  16  of the ejection wall  51 . The sheet ejecting rollers  189  include three rollers so arranged that two of these rollers are in contact with the remaining roller. This sheet ejecting rollers  189  are arranged in front of the sheet ejecting transport path  188  so that one of the rollers is exposed through the ejection hole  16  into the sheet ejection space  12 . 
     Each sheet  3  having the color image fixed thereon in the fixing section  64  is transported by the transport rollers  187  along the sheet ejecting transport path  188  in the sheet ejecting section  6 , and ejected onto the ejection tray  13  by the sheet ejecting rollers  189  through the ejection hole  16 . 
     (5) Scanning Unit 
     (5-1) General Structure of Scanning Unit 
     The scanning unit  7  includes a document board  190  connected to the upper sidewall of the main body casing  2  and a cover  191  supported on the document board  190  in an openable/closable manner. 
     The document board  190  is in the form of a thick plate rectangular in plan view, and a glass surface  192  for receiving a document is formed on the upper surface thereof. 
     The glass surface  192  is formed by embedding a glass plate in the document board  190  so that the upper surface of the document board  190  is flattened. This glass surface  192  is in the form of a rectangle similar to the document board  190  in plan view. 
     The document board  190  is provided therein with a CCD sensor  193  for reading the document and a scanning/driving motor (not shown) for driving the CCD sensor  193  to scan the document in a state of being opposed to the glass surface  192 . 
     The CCD sensor  193 , movably supported in the right-and-left direction inside (under) the glass surface  192 , is normally set on standby on the left end of the glass surface  192 , and driven by a scanning driving motor (not shown) in ordinary document reading to scan the document from the left side toward the right side in the state of being opposed to the glass surface  192 . 
     The cover  191  for pressing a document is in the form of a rectangular thin plate similar to the document board  190  in plan view, and provided with an ADF (auto document feeder) device  195  for automatically reading the document on the left upper end portion thereof, as shown in  FIG. 2 . This ADF device  195  includes a casing  196 , a document transport roller (not shown), a document transportation driving motor (not shown) and a document sensor (not shown). The casing  196  is in the form of an anteroposteriorly longitudinal box containing the document transport roller (not shown) and the document transportation driving motor (not shown), and is provided with a standby sheet tray  194  on the up-and-down center of the right sidewall thereof. The standby sheet tray  194  is in the form of a thin plate generally sectorial in plan view and has a left end portion supported by the ADF device  195  and a right end portion extending rightward, and documents can be set on the upper side surface thereof in a stacked manner. 
     A document inlet (not shown) for introducing each document into the casing  196  is formed on the right sidewall of the casing  196  above the standby sheet tray  194 , while a document outlet (not shown) for ejecting the document from the casing  196  is formed under the standby sheet tray  194 . The document inlet (not shown) and the document outlet (not shown) are in the form of anteroposteriorly longitudinal rectangles. 
     The rear end portion of the cover  191  is supported on the rear end portion of the document board  190  in a swingable manner through a hinge  199 , as shown in  FIG. 1 . 
     The front end portion of the cover  191  swings in the up-and-down direction about the hinge  199  provided on the rear end portion thereof. The glass surface  192  of the document board  190  is exposed when the user raises the front end portion of the cover  191 , and covered when the user lowers the front end portion of the cover  191 . Thus, the cover  191  covers the glass surface  192  of the document board  190  in an openable/closable manner. 
     (5-2) Ordinary Document Reading in Scanning Unit 
     In this scanning unit  7 , the user raises the front end portion of the cover  191  and sets the document on the glass surface  192 , thereafter lowers the front end portion of the cover  191  and operates any operation key of the operation panel  8  of the main body casing  2 . Then, the CCD sensor  193  is driven by the scanning/driving motor (not shown) to scan the document from the left side toward the right side in the state of being opposed to the document set on the glass surface  192 , thereby reading image information from the document. 
     When the image information is completely read from the document, the user raises the front end portion of the cover  191  again and removes the document from the glass surface  192 . When completely scanning the document, the CCD sensor  193  is driven by the scanning/driving motor (not shown) to automatically move to the left end of the glass surface  192  to return to the standby state. 
     (5-3) Automatic Document Reading in Scanning Unit 
     When the document sensor (not shown) senses a document set on the standby sheet tray  194  (see  FIG. 2 ) in automatic document reading with the ADF device  195 , the CCD sensor  193  is fixed onto an automatic document reading position (not shown), dissimilarly to the aforementioned ordinary document reading. Then, the user operates the operation key of the operation panel  8 , thereby driving the document transportation driving motor (not shown) of the ADF device  195  and rotating the document transport roller (not shown) by the driving force thereof, so that the document moves leftward due to the rotation of the document transport roller (not shown) and is introduced into the casing  196  through the document inlet (not shown). The introduced document passes through a document transport path (not shown) and is opposed to the CCD sensor  193 . At this time, the CCD sensor  193  reads image information by scanning the document, and thereafter the document is transported rightward from the document outlet (not shown) to be ejected onto the upper surface of the cover  191 . 
     (5-4) Image Formation Based on Image Information Read from Document 
     The image forming section  5  creates image data on the basis of the aforementioned image information read from the document by the CCD sensor  193 , and forms the image on each sheet  3  as described above. 
     2. Functions and Effects 
     (1) Function and Effect 1 
     In this color laser printer  1 , the plurality of toner cartridges  69  provided correspondingly to the developing rollers  143  as shown in  FIG. 7  are together attached/detached to/from the main body casing  2  independently of the photosensitive drums  133  and the developing rollers  143  along one direction, i.e., the anteroposterior direction, as shown in  FIG. 4 . When only the toner cartridges  69  are increased in size in order to ensure sufficient volumes of the toners, therefore, the main body casing  2  may not be correspondingly increased in size but can be compactly formed. 
     Further, the toner cartridges  69  are opposed to the developing rollers  143  along the longitudinal direction (width direction) of the developing rollers  143  when mounted on the main body casing  2 , as shown in  FIG. 7 . Assuming that the main body casing  2  has a constant size in the up-and-down direction intersecting with the longitudinal direction of the developing rollers  143 , therefore, the up-and-down size of the toner cartridges  69  can be increased by the length corresponding to the up-and-down size of the developing rollers  143  as compared with that in a case of opposing the toner cartridges  69  to the developing rollers  143  in the up-and-down direction. Further, assuming that the main body casing  2  also has a constant size in the anteroposterior direction intersecting with the longitudinal direction of the developing rollers  143 , the anteroposterior size of the toner cartridges  69  can be increased by the length corresponding to the anteroposterior size of the developing rollers  143  as compared with that in a case of anteroposteriorly opposing the toner cartridges  69  to the developing rollers  143 . 
     Thus, the volumes of the toners in the toner cartridges  69  can be sufficiently ensured. 
     Further, only the toner cartridges  69  can be together attached/detached to/from the main body casing  2  along the anteroposterior direction, whereby the operability can be improved and the running cost can be reduced. 
     Consequently, the volumes of the toners can be sufficiently ensured in the toner cartridges  69 , the color laser printer  1  can be miniaturized, the operability thereof can be improved, and the maintenance cost can be reduced. 
     The toner cartridges  69  are anteroposteriorly slidably attached/detached to/from the main body casing  2  in the state of being received in the cartridge receiving section  68 , as shown in  FIG. 18 . Therefore, the operability can be improved. 
     Further, the toner cartridges  69  are attached/detached to/from the cartridge receiving section  68  in the up-and-down direction intersecting with the anteroposterior and right-and-left directions. Therefore, the toner cartridges  69  can be smoothly attached/detached to/from the cartridge receiving section  68 , thereby further improving the operability. 
     In addition, the toner cartridges  69  are detachably mountable to the cartridge receiving section  68  generally along the up-and-down direction, whereby the cartridge receiving section  68  accommodating the toner cartridges  69  can be attached/detached to/from the main body casing  2  in the anteroposterior direction, i.e., the right-and-left direction, after the toner cartridges  69  are generally vertically attached to the cartridge receiving section  68 . Thus, the operability can be further improved. 
     The cartridge receiving section  68  is completely detachable from the main body casing  2 , whereby all toner cartridges  69  can be reliably attached/detached to/from the cartridge receiving section  68 . 
     In the main body casing  2 , the toner cartridges  69  protrude upward beyond the ejection tray  13 , as shown in  FIG. 7 . In other words, the upper end portion of the storage section  100  of each toner cartridge  69  is located upward beyond the ejection tray  13 , whereby the volume of the toner accommodated in the toner cartridge  69  can be sufficiently ensured. More specifically, the ejection tray  13  receiving the sheets  3  stacked thereon requires a space corresponding to the thicknesses of the stacked sheets  3 . Therefore, the main body casing  2  can protrude upward beyond the ejection tray  13  due to the space for receiving the sheets  3 . The space resulting from this protrusion of the main body casing  2  is so effectively utilized as to ensure sufficient volumes of the toners. 
     Each toner cartridge  69  is formed with the outer-cylinder-side feed hole  109  for feeding the toner and the outer-cylinder-side return hole  110  for receiving the toner on the position opposed to the developing roller  143 , is provided with the inner cylinder  96  covering the outer-cylinder-side feed hole  109  and the outer-cylinder-side return hole  110  in an openable/closable manner as shown in  FIGS. 14( a ) and 14( b ) . 
     Thus, as shown in  FIG. 14( a )  the inner cylinder  96  is closed (moved to the cartridge-side shutter closing position) when the toner cartridge  69  is attached/detached to/from the main body casing  2 , so that the toner can be prevented from leaking through the outer-cylinder-side feed hole  109  and the outer-cylinder-side return hole  110 . When the toner cartridge  69  is mounted to the main body casing  2 , the inner cylinder  96  is opened (moved to the cartridge-side shutter opening position) as shown in  FIG. 14( b ) , so that the toner can be fed to the developing roller  143  through the outer-cylinder-side feed hole  109  while the toner returned from the developing roller  143  can be recovered through the outer-cylinder-side return hole  110 . Therefore, the toner is prevented from leaking from the toner cartridge  69  in attachment/detachment and can be reliably fed from the toner cartridge  69  in mounting, so that defective development can be prevented by ensuring circulation of the toner between the toner cartridge  69  and the corresponding developing roller  143 . 
     The cartridge receiving section  68  is formed with the receiving-section-side opening  74 , through which each toner passes, on the position opposed to the outer-cylinder-side feed hole  109  and the outer-cylinder-side return hole  110 , as shown in  FIGS. 17( a ) and 17( b ) . 
     When each toner cartridge  69  is mounted on the cartridge receiving section  68 , therefore, the toner can be fed to the developing roller  143  from the outer-cylinder-side feed hole  109  of the toner cartridge  69  through the receiving-section-side opening  74  of the cartridge receiving section  68 . Thus, the toner can be reliably fed to the developing roller  143 . Further, the toner returned from the developing roller  143  can be recovered from the outer-cylinder-side return hole  110  through the receiving-section-side opening  74 , whereby the circulation of the toner between the toner cartridge  69  and the corresponding developing roller  143  can be reliably ensured to prevent defective development. 
     The plurality of developing rollers  143  and the plurality of photosensitive drums  133  are together attached/detached to/from the main body casing  2  as the processing sections  62  along the anteroposterior direction identical to the attachment/detachment direction (see  FIG. 18 ) for the toner cartridges  69 , as shown in  FIG. 23 . 
     Therefore, the plurality of developing rollers  143  and the plurality of photosensitive drums  133  as well as the toner cartridges  69  can be attached/detached along the same direction, for improving the operability. 
     As shown in  FIG. 2 , the main body casing  2  has the cartridge receiving section mounting port  11  (see  FIG. 4 ) formed on the position anteroposteriorly opposed to the toner cartridges  69  for passing the toner cartridges  69  therethrough, and the processing section mounting port  10  (see  FIG. 3 ) formed on the position anteroposteriorly opposed to the developing rollers  143  and the photosensitive drums  133  (processing sections  62 ) for passing the processing sections  62  therethrough. The main body casing  2  further has the first and second covers  22  and  18  provided adjacently to each other on the front side surface thereof for covering the cartridge receiving section mounting port  11  and the processing section mounting port  10  in an openable/closable manner respectively. 
     Thus, the toner cartridges  69  can be attached/detached through the cartridge receiving section mounting port  11  by opening the first cover  22  as shown in  FIG. 4 , while the developing rollers  143  and the photosensitive drums  133  (processing sections  62 ) can be attached/detached through the processing section mounting port  10  by opening the second cover  18  as shown in  FIG. 3 . Therefore, attachment/detachment of the toner cartridges  69  and that of the developing rollers  143  and the photosensitive drums  133  can be controlled on the same side surface of the main body casing  2 , thereby further improving the operability. 
     As shown in  FIGS. 3 and 4 , the main body casing  2  is provided with the partition wall  15  for separating the cartridge receiving section accommodation space  24  accommodating the plurality of toner cartridges  69  from the process accommodation space  17  accommodating the plurality of developing rollers  143  and the plurality of photosensitive drums  133  along the anteroposterior direction between the cartridge receiving section mounting port  11  and the processing section mounting port  10 . 
     Therefore, the plurality of toner cartridges  69  can be smoothly attached/detached to/from the cartridge receiving section accommodation space  24  along the anteroposterior direction, while the plurality of developing rollers  143  and the plurality of photosensitive drums  133  can also be smoothly attached/detached to/from the process accommodation space  17  along the anteroposterior direction. 
     As shown in  FIGS. 20( a ) and 20( b ) , the partition wall  15  has the partition-wall-side feed hole  39  formed between the toner cartridge  69  and the developing roller  143  for passing toner, and has the partition-wall-side shutter  35  provided on the side of the partition wall  15  closer to the cartridge receiving section accommodation space  24  for covering the partition-wall-side feed hole  39  in an openable/closable manner, and the partition-wall-side shutter  35  is opened/closed in association with opening/closing of the inner cylinder  96 . 
     When each toner cartridge  69  is attached/detached to/from the main body casing  2 , therefore, in case where the inner cylinder  96  is closed, the partition-wall-side shutter  35  is also closed (moved to the partition-wall-side shutter closing position) in association with closing of the inner cylinder  96  as shown in  FIG. 20( a ) , whereby the toner can be prevented from leaking through both sides of the toner cartridge  69  and the cartridge receiving section accommodation space  24 . When the toner cartridge  69  is mounted to the main body casing  2 , in case where the inner cylinder  69  is opened, the partition-wall-side shutter  35  is also opened (moved to the partition-wall-side shutter opening position) in association with opening of the inner cylinder  96  as shown in  FIG. 20( b ) , whereby the toner can be fed to the developing roller  143  from the outer-cylinder-side feed hole  109  through the partition-wall-side feed hole  39 . Therefore, the toner is prevented from leaking through the both sides of the toner cartridge  69  and the cartridge receiving section accommodation space  24  in attachment/detachment, and can be reliably fed from the toner cartridge  69  in mounting. 
     The color laser printer  1 , including the scanning unit  7  provided above the main casing  2  for reading the image information from the document as shown in  FIG. 1 , can form the image on each sheet  3  through the image information read by the scanning unit  7 , thereby implementing a composite apparatus also serving as a copying machine. 
     In this color laser printer  1 , further, the toner cartridges  69  can be together attached/detached to/from the main body casing  2  along the anteroposterior direction independently of the photosensitive drums  133  and the developing rollers  143 , regardless of the scanning unit  7  provided above the main body casing  2 . Therefore, the toner cartridges  69  can be increased in size for ensuring sufficient volumes of the toners while compactly forming the main body casing  2  of the color laser printer  1  serving as a composite apparatus. Further, the toner cartridges  69  (cartridge receiving section  68 ) are anteroposteriorly attached/detached to/from the main body casing  2 , so that the scanning unit  7  provided above the main body casing  2  may not be retracted in attachment/detachment of the toner cartridges  69 . In addition, the volumes of the toners accommodated in the toner cartridges  69  can be increased by approximating the upper portions of the toner cartridges  69  to the scanning unit  7 . 
     (2) Function and Effect 2 
     In the color laser printer  1 , the driving force of the agitator driving motor (not shown) is transmitted to the feed-side agitators  115  of the black toner cartridge  69 K through the first transmission portion  88  connected to the driving mechanism  30  (see  FIG. 5 ) as well as the feed-side agitator input gear  116  and the feed-side agitator rotating shaft  120  of the black toner cartridge  69 K, as shown in  FIG. 8 . This driving force is then transmitted to the feed-side agitators  115  of the cyan toner cartridge  69 C through the feed-side agitator output gear  117  of the black toner cartridge  69 K, the corresponding second transmission portion  89  as well as the feed-side agitator input gear  116  and the feed-side agitator rotating shaft  120  of the cyan toner cartridge  69 C adjacent to the front side of the black toner cartridge  69 K. Similarly, the driving force received by the feed-side agitators  115  of the cyan toner cartridge  69 C is transmitted to the feed-side agitators  115  of the magenta toner cartridge  69 M adjacent to the front side of the cyan toner cartridge  69 C, and further transmitted to the feed-side agitators  115  of the yellow toner cartridge  69 Y adjacent to the front side of the magenta toner cartridge  69 M. 
     Thus, the driving force supplied from the driving mechanism  30  to the feed-side agitators  115  of the black toner cartridge  69 K through the first transmission portion  88 , is sequentially transmitted from the feed-side agitators  115  of the rear toner cartridges  69  to those of the front toner cartridges  69  adjacent thereto through the feed-side agitator output gears  117 , the second transmission portions  89 , the feed-side agitator input gears  116  and the feed-side agitator rotating shafts  120 . Therefore, this driving force is also transmitted to the feed-side agitators  115  of the remaining three toner cartridges  69 C,  69 M and  69 Y, whereby the feed-side agitators  115  of all the toner cartridges  69  can be driven in a more compact structure as compared with a structure individually providing the driving mechanism  30  (see  FIG. 5 ) for each toner cartridge  69  or individually supplying the driving force from the driving mechanism  30  (see  FIG. 5 ) to the feed-side agitators  115  of each toner cartridge  69 . 
     Therefore, the structure (the first transmission portion  88 , the second transmission portions  89 , the feed-side agitator input gears  116 , the feed-side agitator rotating shafts  120  and the feed-side agitator output gears  117 ) supplying the driving force to all the feed-side agitators  115  can be arranged in the color laser printer  1  without reducing the size of the toner cartridges  69 . 
     Consequently, the driving force can be supplied to the feed-side agitators  115  provided on the respective toner cartridges  69  while ensuring sufficient volumes of the toners in the toner cartridges  69  when the color laser printer  1  is miniaturized. 
     The toner cartridges  69  are parallelly arranged along the anteroposterior direction, and the driving mechanism  30  supplies the driving force to the feed-side agitators  115  of the black toner cartridge  69 K arranged on the rear end side in the anteroposterior direction. The second transmission portions  89 , the feed-side agitator input gears  116 , the feed-side agitator rotating shafts  120  and the feed-side agitator output gears  117  sequentially transmit the driving force to the feed-side agitators  115  of the cyan, magenta and yellow toner cartridges  69 C,  69 M and  69 Y provided on the front end side in the anteroposterior direction. Thus, the driving force can be systematically supplied to the feed-side agitators  115  of all the toner cartridges  69 . 
     More specifically, the driving force of the driving mechanism  30  can be reliably transmitted to the feed-side agitators  115  of the black toner cartridge  69 K arranged on the rear end side through the first transmission portion  88 . 
     Further, the second transmission portions  89  are arranged between the toner cartridges  69 , so that the driving force transmitted to the feed-side agitators  115  of the rear toner cartridges  69  can be reliably transmitted to those of the front toner cartridges  69  adjacent thereto through the second transmission portions  89 . 
     In each toner cartridge  69 , the feed-side agitator input gear  116  provided on the rear end portion of the feed-side agitator rotating shaft  120  engages with the first transmission portion  88  or the second transmission portion  89 , thereby transmitting the driving force of the driving mechanism  30  to the feed-side agitator rotating shaft  120  from the first transmission portion  88  or the second transmission portion  89  through the feed-side agitator input gear  116 . 
     The feed-side agitator rotating shaft  120  is rotated by the driving force transmitted thereto, so that the feed-side agitators  115  provided thereon are rotated about the feed-side agitator rotating shaft  120 , thereby agitating the toner accommodated in the toner cartridge  69 . 
     The feed-side agitator output gear  117  provided on the front end portion of the feed-side agitator rotating shaft  120  engages with the second transmission portion  89  adjacent to the first transmission portion  88  engaging with the feed-side agitator input gear  116  or another second transmission portion  89  adjacent to the second transmission portion  89  engaging with the feed-side agitator input gear  116 . The second transmission portion  89  adjacent to the first transmission portion  88  is the second transmission portion  89  located between the black and cyan toner cartridges  69 K and  69 C, and the other second transmission portion  89  is the second transmission portion  89  provided in front of the second transmission portion  89  located between the black and cyan toner cartridges  69 K and  69 C. Thus, the driving force transmitted to the feed-side agitator rotating shaft  120  through the feed-side agitator input gear  116  is transmitted to the second transmission portion  89  adjacent to the first transmission portion  88  engaging with the feed-side agitator input gear  116  or the front-side second transmission portion  89  adjacent to the second transmission portion  89  engaging with the feed-side agitator input gear  116  through the feed-side agitator output gear  117 . 
     Therefore, the transmission of the driving force from the first transmission portion  88  to the second transmission portion  89  or from the second transmission portion  89  to the other second transmission portion  89 , and the rotation of the feed-side agitators  115  can be carried out through the feed-side agitator rotating shaft  120 , the feed-side agitator input gear  116  and the feed-side agitator output gear  117 , whereby the driving force can be efficiently transmitted and the number of the components can be reduced. 
     The second transmission portion  89  includes the input transmission gear  94  and the output transmission gear  99 , and in the second transmission portion  89  the driving force is transmitted to the input transmission gear  94  from the feed-side agitator output gear  117  of the rear-side toner cartridge  69  and further transmitted from the output transmission gear  99  to the feed-side agitator input gear  116  of the front-side toner cartridge  69  adjacent to the rear-side toner cartridge  69 . 
     Consequently, the second transmission portion  89  can reliably transmit the driving force received by the feed-side agitators  115  of the rear-side toner cartridge  69  to the feed-side agitator input gear  116  of the front-side toner cartridge  69  adjacent to the rear-side toner cartridge  69 . 
     Further, the cartridge receiving section  68  can move all the toner cartridges  69  together. 
     This cartridge receiving section  68  includes the aforementioned first and second transmission portions  88  and  89 , and the first transmission portion  88  is connected to the driving mechanism  30  when the cartridge receiving section  68  is located on the mount position. Therefore, the driving force can be supplied to the feed-side agitators  115  of all the toner cartridges by transmitting the driving force of the driving mechanism  30  to the feed-side agitators  115  of the black toner cartridge  69 K arranged on the rear end side and sequentially transmitting this driving force to the feed-side agitators  115  of the front-side toner cartridges  69  adjacent thereto through the operation of simply moving the cartridge receiving section  68  accommodating the toner cartridges  69  to the mount position. 
     Each toner cartridge  69  is opposed to the corresponding developing roller  143  in the longitudinal direction (width direction) of the developing roller  143 . 
     Assuming that the color laser printer  1  has a constant size in the up-and-down direction intersecting with the longitudinal direction of the developing rollers  143 , therefore, the up-and-down size of the toner cartridge  69  can be increased by the length corresponding to the up-and-down size of the developing roller  143  as compared with that in the case of opposing the toner cartridge  69  to the developing roller  143  in the up-and-down direction. Further, assuming that the color laser printer  1  also has a constant size in the anteroposterior direction intersecting with the longitudinal direction of the developing roller  143 , the anteroposterior size of the toner cartridge  69  can be increased by the length corresponding to the anteroposterior size of the developing roller  143  as compared with that in the case of anteroposteriorly opposing the toner cartridge  69  to the developing roller  143 . 
     Consequently, the volume of the toner in the toner cartridge  69  can be sufficiently ensured. 
     The toner cartridge  69  includes the storage chamber  102  and the feed chamber  121 , whereby the toner stored in the storage chamber  102  is fed to the feed chamber  121  and agitated by the feed-side agitators  115  in the feed chamber  121 , and a necessary volume of toner is thereafter fed from the feed chamber  121  to the developing roller  143 . Thus, the toner can be efficiently fed. 
     Further, the toner cartridge  69  is opposed to the corresponding developing roller  143  in the longitudinal direction (width direction) of the developing roller  143  as described above, whereby the feed-side agitator rotating shaft  120  serving as the rotation center of the feed-side agitators  115  is opposed to the developing roller  143  (see  FIG. 7 ). In other words, the developing roller  143  is positioned in the rotational direction of the feed-side agitators  115 , so that the toner can be more smoothly fed. 
     The storage chamber  102  includes the storage-side agitator  113 , which in turn agitates the toner stored in the storage chamber  102 . Therefore, the toner stored in the storage chamber  102  can be maintained in a state always feedable to the feed chamber  121 . 
     The toner cartridge  69  further includes the storage-side agitator rotating shaft  112 , the storage-side agitator input gear  114  and the intermediate gear  119 , and the intermediate gear  119  engages with the aforementioned feed-side agitator input gear  116  and the aforementioned storage-side agitator input gear  114 , whereby the driving force received by the feed-side agitator input gear  116  is transmitted to the storage-side agitator input gear  114  through the intermediate gear  119 . The storage-side agitator input gear  114  is provided on the rear end portion of the storage-side agitator rotating shaft  112 , so that the driving force received by the storage-side agitator input gear  114  is transmitted to the storage-side agitator rotating shaft  112 . 
     The storage-side agitator rotating shaft  112  is rotated by the driving force transmitted thereto, and the storage-side agitator  113  provided thereon is rotated about the storage-side agitator rotating shaft  112  to agitate the toner stored in the storage chamber  102 . 
     Consequently, no additional structure may be provided for supplying driving force to the storage-side agitator  113  but the driving force input in the feed-side agitator input gear  116  can be reliably transmitted to the storage-side agitator  113  in the simple structure, thereby agitating the toner stored in the storage chamber  102 . 
     (3) Function and Effect 3 
     In the color laser printer  1 , the inner cylinder  96  of each toner cartridge  69  is opened (moved to the cartridge-side shutter opening position) to open the outer-cylinder-side opening  108  as shown in  FIG. 16 , whereby the toner accommodated in the toner cartridge  69  can be fed to the corresponding developing roller  143  through the outer-cylinder-side opening  108 . On the other hand, the inner cylinder  96  is closed (moved to the cartridge-side shutter closing position) to close the outer-cylinder-side opening  108 , whereby the toner accommodated in the toner cartridge  69  can be prevented from leaking through the outer-cylinder-side opening  108  (see  FIG. 15 ). 
     In the color laser printer  1 , the single opening/closing member  75  collectively opens/closes all the inner cylinders  96  with no opening/closing mechanisms respectively provided on the toner cartridges  69  for opening/closing the inner cylinders  96 , whereby the structure for opening/closing all the inner cylinders  96  can be compactly designed. 
     Therefore, the opening/closing member  75  can be arranged in the color laser printer  1  without reducing the toner cartridges  69  in size. 
     Consequently, all inner cylinders  96  can be reliably opened/closed while sufficiently ensuring the volumes of the toners in the toner cartridges  69  when the color laser printer  1  is miniaturized. 
     Further, the cartridge receiving section  68  can move all the toner cartridges  69  together. 
     The operation lever  81  operated for opening/closing the opening/closing member  75  is provided on the front end portion of the cartridge receiving section  68  in the anteroposterior direction along which the toner cartridges  69  are parallelly arranged, whereby the inner cylinders  96  of all the toner cartridges  69  can be collectively opened/closed by operating the operation lever  81  to open/close the opening/closing member  75 . Consequently, the operability can be improved. 
     As shown in  FIG. 5 , the partition wall  15  of the main body casing  2  is formed with the partition-wall-side feed holes  39  and the partition-wall-side return holes  40  communicating with the outer-cylinder-side feed holes  109  and the outer-cylinder-side return holes  110  of the outer-cylinder-side openings  108  respectively, and is provided with the partition-wall-side shutter  35  opening/closing all the partition-wall-side feed holes  39  and all the partition-wall-side return holes  40 . 
     When the partition-wall-side shutter  35  is opened (moved to the partition-wall-side shutter opening position) as shown in  FIG. 20( b ) , therefore, each partition-wall-side feed hole  39  and each partition-wall-side return hole  40  are opened to communicate with the corresponding outer-cylinder-side feed hole  109  and the corresponding outer-cylinder-side return hole  110  respectively. Thus, the toner accommodated in each toner cartridge  69  can be fed to the corresponding developing roller  143  through the outer-cylinder-side opening  108 , the partition-wall-side feed hole  39  and the partition-wall-side return hole  40 . 
     When the partition-wall-side shutter  35  is closed (moved to the partition-wall-side shutter closing position) as shown in  FIG. 20( a ) , on the other hand, the partition-wall-side feed hole  39  and the partition-wall-side return hole  40  are closed and blocked from the corresponding outer-cylinder-side opening  108 . Thus, the toner accommodated in the toner cartridge  69  can be prevented from being fed to the developing roller  143 . 
     In the color laser printer  1 , the partition-wall-side shutter  35  opens/closes all the partition-wall-side feed holes  39  and all the partition-wall-side return holes  40  as shown in  FIG. 5 , whereby the structure for opening/closing all the partition-wall-side feed holes  39  and all the partition-wall-side return holes  40  can be compactly designed. Thus, the main body casing  2  provided with the partition-wall-side shutter  35  can be miniaturized. Consequently, the color laser printer  1  can be miniaturized. 
     The partition-wall-side shutter  35  is opened/closed by opening/closing each inner cylinder  96 . In other words, the partition-wall-side shutter  35  is opened by opening the inner cylinder  96 , and closed by closing the inner cylinder  96 , whereby the inner cylinder  96  and the partition-wall-side shutter  35  can be reliably opened/closed in association with each other. 
     More specifically, each toner cartridge  69  includes the first projection  123  engaging with the opening/closing member  75  for opening/closing the inner cylinder  96  in association with operation of the opening/closing member  75 , and the second projection  124  engaging with the partition-wall-side shutter  35  for opening/closing the partition-wall-side shutter  35  in association with the movement of the first projection  123 . 
     When the opening/closing member  75  is opened/closed, the first projection  123  engaging therewith opens/closes the inner cylinder  96  in association with the opening/closing of the opening/closing member  75 , and the second projection  124  engaging with the partition-wall-side shutter  35  opens/closes the partition-wall-side shutter  35  in association with operation of the first projection  123 . 
     Therefore, the inner cylinder  96  and the partition-wall-side shutter  35  can be reliably opened/closed in association with each other by simply providing the first and second projections  123  and  124  on the toner cartridge  69 . 
     Further, the first and second projections  123  and  124  are provided on the inner cylinder  96 , whereby the structure can be simplified. 
     Second Embodiment 
       FIG. 24  is a left-side sectional view of  FIG. 18 , showing a second embodiment of one or more aspects of the present invention. Referring to  FIG. 24 , members similar to the aforementioned ones are denoted by the same reference numerals, and the descriptions thereof are not repeated. 
     As shown in  FIG. 18 , the front end portions of the pair of ridges  31  are opposed to each other at an interval in the up-and-down direction in the guide rail  28 . When the cartridge receiving section  68  located on the attachment/detachment position is further drawn frontward as described above, therefore, the rollers  71  provided on the rear end of the cartridge receiving section  68  are displaced frontward from the front end edge of the corresponding guide rail  28 , so that the cartridge receiving section  68  is completely detached from the main body casing  2 . 
     Alternatively, the front end portions of a pair of ridges  31  may be connected with each other, as shown in  FIG. 24 . More specifically, a width-directionally thin connecting plate  200  extends between the front end portions of the right end edges of the pair of ridges  31  of a guide rail  28  provided on a partition wall  15 . Another connecting plate  200  of the same shape extends between the front end portions of the left end edges of a pair of ridges  31  of another guide rail  28  (see  FIG. 20 ) provided on the right side surface of the left sidewall of a main body casing  2 . The connecting plate  200  is generally rectangular in left-side elevation view, and the rear end edge thereof is in the form of a frontwardly recessed arc. 
     Further, only the aforementioned rollers  71  (see  FIG. 18 ) provided on the rear end are width-directionally increased in size as compared with the remaining rollers  71  located frontward beyond these rollers  71 . More specifically, the right one of the rollers  71  provided on the rear end is so formed as to protrude rightward beyond the connecting plate  200  in front elevation view in the state of being sandwiched between the corresponding pair of ridges  31 , while the left one of the rollers  71  provided on the rear end is so formed as to protrude leftward beyond the connecting plate  200  in front elevation view in the state of being sandwiched between the corresponding pair of ridges  31 . 
     In this case, the rollers  71  positioned frontward beyond the rollers  71  provided on the rear end move frontward through the front end portions of the corresponding pair of ridges  31  when the cartridge receiving section  68  located on the mount position is detached from the main body casing  2 , while the rollers  71  provided on the rear end are caught on the rear end edge of the corresponding connecting plate  20 . Thus, the cartridge receiving section  68  can be stopped on the position (attachment/detachment position) where all the toner cartridges  69  are exposed from the main body casing  2  to be detachable from the cartridge receiving section  68 . Therefore, all the toner cartridges  69  can be reliably attached/detached to/from the cartridge receiving section  68  without detaching the cartridge receiving section  68  from the main body casing  2 . 
     Third Embodiment 
       FIG. 25  is a left-side sectional view of  FIG. 18 , showing a third embodiment of one or more aspects of the present invention. Referring to  FIG. 25 , members similar to the aforementioned ones are denoted by the same reference numerals, and the descriptions thereof are not repeated. 
     As shown in  FIG. 18 , the guide rail positioning projections  33  are provided on the rear end portions of the opposed portions of the pair of ridges  31  of each guide rail  28  in the aforementioned embodiments, so that the rollers  71  provided on the rear end of the cartridge receiving section  68  go beyond the guide rail positioning projections  33  when the cartridge receiving section  68  is completely mounted on the cartridge receiving section accommodation space  24  of the main body casing  2 . Additionally, guide rail positioning projections  33  may be provided on the front end portions (referred to as front end projections  33 A) of opposed portions of a pair of ridges  31 , as shown in  FIG. 25 . 
     In this case, the aforementioned rollers  71  provided on the rear end are caught on the front end projections  33 A when the cartridge receiving section  68  located on the mount position is detached from the main body casing  2 , so that the cartridge receiving section  68  can be stopped on the position (attachment/detachment position) where all the toner cartridges  69  are exposed from the main body casing  2  to be detachable from the cartridge receiving section  68 . Therefore, all the toner cartridges  69  can be reliably attached/detached to/from the cartridge receiving section  68  without detaching the cartridge receiving section  68  from the main body casing  2 . 
     Fourth Embodiment 
     While the intermediate transfer type color laser printer  1  temporarily transferring the toner images of the respective colors from the photosensitive drums  133  to the intermediate transfer belt  176  and thereafter collectively transferring the toner images to each sheet  3 , is illustrated in the aforementioned embodiments, the present invention is not limited to this but is also applicable to a direct transfer type color laser printer directly transferring toner images of respective colors from the respective photosensitive drums  133  to each sheet  3 , for example. 
     The embodiments described above are illustrative and explanatory of the invention. The foregoing disclosure is not intended to be precisely followed to limit the present invention. In light of the foregoing description, various modifications and alterations may be made by embodying the invention. The embodiments are selected and described for explaining the essentials and practical application schemes of the present invention which allow those skilled in the art to utilize the present invention in various embodiments and various alterations suitable for anticipated specific use. The scope of the present invention is to be defined by the appended claims and their equivalents.