Abstract:
An image forming device includes a casing, photosensitive bodies, developing devices, developer accommodating devices, and a retaining member. The developer accommodating devices includes a first developer accommodating device that is individually replaceable and separable from the corresponding developing device and a second developer accommodating device that is replaceable together with the corresponding developing device. The retaining member retains the photosensitive bodies arranged in an arrangement direction, the developing devices, and the developer accommodating devices at fixed positions within the casing. The retaining member is capable of being pulled out from the casing and is movable between a housed position and a withdrawn position. One of the developer accommodating devices located at a most upstream side in the arrangement direction is the first developer accommodating device, and each of the developer accommodating devices other than the one of the developer accommodating devices is the second developer accommodating device.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from Japanese Patent Application No. 2010-012058 filed Jan. 22, 2010. The entire content of this priority application is incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The present invention relates in general to an image-forming device for forming images on recording sheets, and more particularly to an image-forming device having a plurality of photosensitive members arranged in tandem and retained together with corresponding developing devices and developer-accommodating devices at fixed positions in a retaining member that can be withdrawn from a body of the image-forming device along the juxtaposed direction of the photosensitive members. 
       BACKGROUND 
       [0003]    An image-forming device such as a laser printer for forming color images on recording sheets is well known in the art. One such image-forming device has a plurality of photosensitive members and a plurality of corresponding developer cartridges (each integrally formed of a developing device and a developer-accommodating device) arranged in tandem and held at fixed positions within a retaining member. Parts, consumables, and the like in the photosensitive members and the developer cartridges can be replaced by pulling the retaining member out from a body of the image-forming device along the direction in which the photosensitive members are juxtaposed. 
       SUMMARY 
       [0004]    In order to keep down running costs in a laser printer or other image-forming device, it is beneficial to be able to separate the developer-accommodating devices (toner cartridges) from the developing devices and the photosensitive members so that the developer-accommodating devices can be replaced individually. However, when developing devices having such individually detachable toner cartridges are employed in an image-forming device configured with a retaining member that is pulled out of the image-forming device in the direction of the juxtaposed photosensitive members, the force applied to the extracted retaining member as a result of operations performed to open and close shutters in the toner cartridge when mounting and removing the toner cartridge can potentially damage the retaining member or cause the image-forming device to overturn. 
         [0005]    It is an object of the present invention to provide an image-forming device having photosensitive members arranged in tandem in a retaining member that can be pulled out of a body of the image-forming device along the juxtaposing direction of this tandem arrangement, whereby one of the developing devices provided in the retaining member has an individually detachable toner cartridge for reducing running costs and the configuration eliminates the risk of damaging the retaining member and overturning the body of the image-forming device due to forces applied to the retaining member when the retaining member is partially withdrawn from the body. 
         [0006]    In order to attain the above and other objects, the invention provides an image forming device. The image forming device includes a casing, a plurality of photosensitive bodies, a plurality of developing devices, a plurality of developer accommodating devices, and a retaining member. The casing is formed with an opening. The plurality of developing devices respectively corresponds to the plurality of photosensitive bodies. The plurality of developer accommodating devices accommodates and supplies developer respectively to the plurality of developing devices. The plurality of developer accommodating devices includes a first developer accommodating device that is individually replaceable and separable from the corresponding developing device and a second developer accommodating device that is replaceable integrally together with the corresponding developing device. The retaining member retains the plurality of photosensitive bodies arranged in an arrangement direction, the plurality of developing devices, and the plurality of developer accommodating devices at fixed positions in the casing. The retaining member is capable of being pulled out from the casing in the arrangement direction through the opening and is movable between a first position where the plurality of photosensitive bodies, the plurality of developing devices, and the plurality of developer accommodating devices are inside the casing and a second position where one of the plurality of developer accommodating devices located at most upstream side in the arrangement direction is replaceable. The one of the plurality of developer accommodating devices located at the most upstream side in the arrangement direction is the first developer accommodating device accommodating black developer. Each of the developer accommodating devices other than the one of the plurality of developer accommodating devices is the second developer accommodating device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The particular features and advantages of the invention as well as other objects will become apparent from the following description taken in connection with the accompanying drawings, in which: 
           [0008]      FIG. 1  is a cross-sectional view showing a color multifunction device according to an embodiment of the present invention; 
           [0009]      FIG. 2  is a cross-sectional view illustrating a state in which a retaining case is at a first position where the retaining case is inside a main body of the color multifunction device; 
           [0010]      FIG. 3  is a cross-sectional view illustrating a state in which the retaining case is at a second position where the retaining case is pulled out from the main body; 
           [0011]      FIG. 4  is a cross-sectional view illustrating an operation in which process units are replaced; 
           [0012]      FIG. 5  is a perspective view showing a toner cartridge and a developing device when shutters are at a closed position; 
           [0013]      FIG. 6  is a perspective view showing the toner cartridge and the developing device when the shutters are at an open position; 
           [0014]      FIG. 7(   a ) is a explanatory diagram conceptually illustrating a configuration ambient to a rear end of the retaining case in the main body when the process units are replaced; and 
           [0015]      FIG. 7(   b ) is an explanatory diagram conceptually illustrating a configuration ambient to a front end of the retaining case in the main body when the process units are replaced. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Next, an embodiment of the present invention will be described while referring to the accompanying drawings. The following description first covers the overall structure of a color multifunction device of the embodiment according to the present invention and subsequently includes a detailed description of a process unit having a developer-accommodating device accommodating black developer. 
         [0017]    As shown in  FIG. 1 , a color multifunction device  1  has a main body  10  and a flatbed scanner.  20  disposed above the main body  10 . Within the main body  10 , the color multifunction device  1  primarily includes a sheet-feeding unit  30  for supplying sheets of a paper P, an image-forming unit  40  for forming images on sheets of paper P supplied by the sheet-feeding unit  30 , and a sheet-discharging unit  90  for discharging the sheets of paper P after images have been formed thereon. 
         [0018]    In the following description, directions related to the color multifunction device  1  will refer to directions seen from the perspective of an operator when operating the color multifunction device  1 . Specifically, the right side of the color multifunction device  1  in  FIG. 1  will be referred to as the “front” or the “near side”; the left side as the “rear” or the “far side”; the near side in  FIG. 1  as “left”; and the far side in  FIG. 1  as “right.” Also, the upper and lower sides along the vertical in  FIG. 1  will be referred to as “upper” and “lower” in the description. 
         [0019]    The flatbed scanner  20  disposed above the main body  10  is a document-reading device well known in the art. During a copy operation and the like, the flatbed scanner  20  generates image data by irradiating light onto an original document placed in the flatbed scanner  20  and reads the image from the original document. 
         [0020]    The sheet-feeding unit  30  is disposed in a bottom section of the main body  10  and includes a paper tray  31  for accommodating sheets of paper P, and a paper-feeding mechanism  32  for conveying sheets of paper P from the paper tray  31  to the image-forming unit  40 . The paper-feeding mechanism  32  separates and conveys the paper P accommodated in the paper tray  31  to the image-forming unit  40  one sheet at a time. 
         [0021]    The image-forming unit  40  primarily includes an exposure unit  50 , four process units including a process unit  61  and three process units  62 , a transfer unit  70 , and a fixing unit  80 . 
         [0022]    The exposure unit  50  is provided in a top section of the main body  10  and includes a laser light source, a polygon mirror, lenses, reflecting mirrors, and the like (not shown in the drawings). Laser beams emitted from the laser light source are reflected off the polygon mirror and the reflecting mirrors, pass through the lenses, and are scanned at a high speed over surfaces of photosensitive drums described later. 
         [0023]    The process unit  61  and the process units  62  are disposed between the sheet-feeding unit  30  and the exposure unit  50  and are juxtaposed (arranged in tandem) in the front-to-rear direction. The process units  61  and  62  are held in a retaining case  65 . 
         [0024]    The retaining case  65  has a bottomless frame-like structure, for example, and is capable of moving between a first position where the retaining case  65  is mounted in the main body  10  (see  FIG. 2 ) and a second position where the retaining case  65  is removed forwardly from the main body  10 , i.e., the process unit  61  is within the main body  10  and the process units  62  are outside the main body  10  while the retaining case  65  retains the process units  61  and  62  (see  FIG. 3 ). Guide rails  10 R (see  FIG. 3 ) are formed on inner sides of the main body  10  for guiding the retaining case  65  in the front-to-rear direction. A front cover  11  is provided on a front side of the main body  10  over an opening  11   a  formed in the main body  10  and can be pivotally rotated downward to expose the opening  11   a  or upward to cover the opening  11   a.  A handle  65 H is provided on a front end of the retaining case  65 . By opening the front cover  11  and pulling on the handle  65 H, an operator can pull the retaining case  65  out of the main body  10  in a pull-out direction through the opening  11   a,  i.e., moves the retaining case  65  to the second position, as illustrated in  FIG. 3 . Once the retaining case  65  has been positioned at the second position, the operator can replace components of the process units  61  and  62  that, during their normal operating state, are positioned far side (rearward) of the main body  10 . That is, the second position indicates the position of the retaining case  65  at which the developer-accommodating device (a toner cartridge  100 ) of the process unit  61  disposed farthest inward in the retaining case  65  among the four process units  61  and  62  with respect to the pull-out direction can be accessed and replaced. 
         [0025]    The structure for enabling the operation to pull the retaining case  65  outward with respect to the main body  10  and to support the retaining case  65  while maintaining the retaining case  65  in either the first position or the second position will be described later in greater detail. 
         [0026]    As shown in  FIG. 1 , the process unit  61  disposed on a farthest side of the retaining case  65  among the four process units  61  and  62  includes a photosensitive drum  61 A, a charger  61 B, the toner cartridge  100  accommodating black toner, and a developing device  200 . The developing device  200  includes a developing roller  61 C, a supply roller  61 D, and a thickness-regulating blade  61 E. The structure of the process unit  61  will be described later in greater detail. 
         [0027]    The photosensitive drum  61 A and the charger  61 B of the process unit  61  may be configured so that they are mounted in and removed from the retaining case  65  together (i.e., replaceable as a unit) or may be fixed to the retaining case  65  to form a single unit therewith. Alternatively, the developing roller  61 C, the supply roller  61 D, and the thickness-regulating blade  61 E constituting the developing device  200  may be configured as an integrated unit that is mounted in and removed from the retaining case  65 , or may be fixed to the retaining case  65  together with the photosensitive drum  61 A and the charger  61 B and formed as a single unit with the retaining case  65 . If the developing device  200  is detachably mounted in the retaining case  65 , the photosensitive drum  61 A and the charger  61 B may be configured to be detachably mounted as a unit or to be mounted and removed separately. 
         [0028]    Each of the three process units  62  among the four process units disposed nearer frontward in the retaining case  65  includes a photosensitive drum  62 A, a charger  62 B, a developing roller  62 C, a supply roller  62 D, a thickness-regulating blade  62 E, and a developer-accommodating device  62 G. The developer-accommodating devices  62 G of these process units  62  accommodate toner in one of the colors cyan, magenta, and yellow, respectively. A developing device  62 H of each process unit  62  is configured of the developing roller  62 C, the supply roller  62 D, and the thickness-regulating blade  62 E and is integrally configured with the developer-accommodating device  62 G and detachably mounted in the retaining case  65  (see  FIG. 4 ). 
         [0029]    As with the photosensitive drum  61 A and the charger  61 B of the process unit  61 , the photosensitive drum  62 A and the charger  62 B of the process unit  62  may be configured to be detachably mounted in the retaining case  65  (i.e., replaceable) or fixed to the retaining case  65  to form a single unit therewith. The process unit  62  (i.e., the photosensitive drum  62 A, the charger  62 B, the developing roller  62 C, the supply roller  62 D, the thickness-regulating blade  62 E, and the developer-accommodating device  62 G) may be detachably mounted in the retaining case  65  as a unit. 
         [0030]    The transfer unit  70  is disposed between the sheet-feeding unit  30  and the process units  61  and  62 . The transfer unit  70  primarily includes a drive roller  71 , a follow roller  72 , an endless conveying belt  73  stretched taut about the rollers  71  and  72 , and four transfer rollers  74 . The outer surface of the conveying belt  73  is in contact with each of the photosensitive drums  61 A and  62 A and is pinched between the transfer rollers  74  disposed on the inner side of the conveying belt  73  and the photosensitive drums  61 A and  62 A. 
         [0031]    A cleaning unit  75  is disposed beneath the conveying belt  73 . The cleaning unit  75  contacts the conveying belt  73  for removing toner, paper dust, and other deposited matter from the conveying belt  73  and for recovering this deposited matter. 
         [0032]    The fixing unit  80  is disposed rearward of the process units  61  and  62  and the transfer unit  70 . The fixing unit  80  primarily includes a heating roller  81 , and a pressure roller  82  disposed in confrontation with the heating roller  81  and applying pressure to the same. 
         [0033]    In the image-forming unit  40 , the chargers  61 B and  62 B apply a uniform charge to the respective surfaces of the photosensitive drums  61 A and  62 A, after which the surfaces are exposed to laser beams emitted from the. exposure unit  50  in a high-speed scan to form electrostatic latent images on the charged surfaces of the photosensitive drums  61 A and  62 A based on image data. Toner accommodated in the toner cartridge  100  and the developer-accommodating devices  62 G is supplied respectively to the developing rollers  61 C and  62 C via the supply rollers  61 D and  62 D. As the developing rollers  61 C and  62 C rotate, toner carried on the surfaces of the same is regulated to a prescribed thickness by the respective thickness-regulating blades  61 E and  62 E. 
         [0034]    The toner layers of uniform thickness carried on the developing rollers  61 C and  62 C are supplied to the electrostatic latent images formed on the photosensitive drums  61 A and  62 A, respectively, whereby the electrostatic latent images are developed into visible toner images on the photosensitive drums  61 A and  62 A. Subsequently, as a sheet of paper P carried on the conveying belt  73  is sequentially conveyed between the photosensitive drums  61 A and  62 A and the conveying belt  73  (the transfer rollers  74 ), the toner images carried on the photosensitive drums  61 A and  62 A are sequentially transferred onto and superposed on the sheet of paper P. When the sheet of paper P is then conveyed between the heating roller  81  and the pressure roller  82 , the toner images transferred on the sheet are fixed to the sheet by heat. 
         [0035]    The sheet-discharging unit  90  primarily includes a paper-discharge path  91  for guiding sheets of paper P upward in the main body  10  from the exit side of the fixing unit  80  while inverting the sheets, and a discharge roller  92  for discharging the inverted sheets onto a discharge tray  15  formed on top of the main body  10 . Thus, after the toner images are fixed to the sheet of paper P by heat in the fixing unit  80 , the sheet is conveyed from the fixing unit  80  into the paper-discharge path  91 , and the discharge roller  92  discharges the sheet onto the discharge tray  15 . 
         [0036]    Next, the structure of the process unit  61  (the toner cartridge  100  and the developing device  200 ) will be described in detail and contrasted with the process units  62  while referring primarily to  FIGS. 5 and 6 .  FIGS. 5 and 6  show a bottom view of the toner cartridge  100  and a top view of the developing device  200 . 
         [0037]    As shown in  FIGS. 3 and 4 , the toner cartridge  100  of the process unit  61  is detachably mounted on the developing device  200 . When mounted on the developing device  200 , the toner cartridge  100  is positioned above and adjacent to the developing device  200 . 
         [0038]    As shown in  FIGS. 5 and 6 , the toner cartridge  100  is a substantially cylindrical container with side walls  110  closing both left and right ends thereof. The cylindrically shaped wall of the toner cartridge  100  is formed with a first supply opening  111  for supplying toner from the toner cartridge  100  to the developing device  200 . 
         [0039]    A cylindrical first shutter  120  is provided on the toner cartridge  100  around the cylindrical wall of the toner cartridge  100 . By rotating the first shutter  120  in a circumferential direction relative to the toner cartridge  100 , the shutter  120  can open and close the first supply opening  111 . Specifically, a first shutter supply opening  121  is formed in the first shutter  120  at a position that perfectly overlaps the first supply opening  111  formed in the toner cartridge  100  when the first shutter  120  is in an open position illustrated in  FIG. 6 . When the first shutter  120  is rotated a prescribed stroke in the circumferential direction relative to the toner cartridge  100  to a closed position illustrated in  FIG. 5 , the first shutter  120  completely blocks the first supply opening  111 . 
         [0040]    A ridge part  110 P is provided on each of the left and right side walls  110  of the toner cartridge  100 . The ridge parts  110 P extend radially from the center of the side walls  110  to the outer edge thereof and have a rectangular cross section. Protruding parts  120 P having the same cross-sectional shape as the ridge parts  110 P are provided on longitudinal ends of the first shutter  120 . 
         [0041]    When the first shutter  120  is set in the closed position as shown in  FIG. 5 , the protruding parts  120 P are aligned with the outer ends of the corresponding ridge parts  110 P, forming continuous guide rails for guiding the toner cartridge  100  when the toner cartridge  100  is mounted on the developing device  200  described later. When the first shutter  120  is rotated to the open position while the toner cartridge  100  is attached to the developing device  200 , the protruding parts  120 P move circumferentially within second groove parts R 2  (described later in greater detail) formed in side walls of the developing device  200  so that the toner cartridge  100  is engaged (interlocked) with the developing device  200  (see  FIG. 6 ). 
         [0042]    A handle  120 H is provided on the peripheral surface of the first shutter  120 . The handle  120 H extends horizontally rearward from an upper portion of the first shutter  120  when the toner cartridge  100  is mounted on the developing device  200  (i.e., when the first shutter  120  is in the open position), as shown in  FIG. 1 . When the operator grips the handle  120 H and rotates the handle  120 H from this horizontal position upward relative to the mounted toner cartridge  100 , the first shutter  120  is rotated to the closed position, disengaging (unlocking) the toner cartridge  100  from the developing device  200  so that the toner cartridge  100  can be removed (see  FIG. 3 ). 
         [0043]    Further, an agitator  140  well known in the art is provided inside the toner cartridge  100  (see  FIG. 1 ). The agitator  140  is primarily configured of a rotational shaft rotatably supported in the left and right side walls  110 , and a plurality of sheet-like agitating blades. The agitating blades are formed of a flexible material and are fixed to the rotational shaft. 
         [0044]    A motor (not shown) provided in the main body  10  applies a drive force to the rotational shaft for rotating the agitator  140  in the toner cartridge  100 . When the rotational shaft rotates, the distal edges of the agitating blades slanted relative to the rotational shaft scrape against the inner surface of the toner cartridge  100 , agitating toner in the toner cartridge  100  and conveying this toner toward the first supply opening  111 . 
         [0045]    As shown in  FIG. 1 , the developing device  200  is provided with the developing roller  61 C, the supply roller  61 D, the thickness-regulating blade  61 E, and the like. The structure and arrangement of the developing device  200  is similar to the developing device  62 H of the process units  62 , except that the toner cartridge  100  is detachably mounted on the developing device  200  as the developer-accommodating device, and an accommodating recessed part  210 S (see  FIG. 6 ) for receiving the mounted toner cartridge  100  is formed in the developing device  200  at a position opposing the supply roller  61 D. 
         [0046]    As shown in  FIGS. 5 and 6 , a second supplying opening  211  is formed in a curved wall of the developing device  200  forming the arch shape (arc-shaped in a cross section) of the accommodating recessed part  210 S at a position corresponding to the first supply opening  111  formed in the toner cartridge  100 . The second supplying opening  211  functions to supply toner from the toner cartridge  100  to the developing device  200 . 
         [0047]    A second shutter  220  is also provided in the developing device  200  around the arch-shaped wall of the accommodating recessed part  210 S. By rotating in a circumferential direction relative to the accommodating recessed part  210 S, the second shutter  220  can open and close the second supplying opening  211  formed in the accommodating recessed part  210 S. More specifically, a second shutter supply opening  221  is formed in the second shutter  220  at a position that is perfectly aligned with the second supplying opening  211  formed in the developing device  200  when the second shutter  220  is in an open position (see  FIG. 6 ). By rotating the second shutter  220  a prescribed stroke in the circumferential direction relative to the developing device  200  to a closed position, the second shutter  220  completely blocks the second supplying opening  211  (see  FIG. 5 ). 
         [0048]    A grooved part  210 R is formed on the inside surface of each of the left and right walls of the accommodating recessed part  210 S. The grooved part  210 R includes a first groove part R 1  extending radially downward from the center of curvature of the accommodating recessed part  210 S, a second groove part R 2  following circumferential directions (both forward and rearward) from the bottom end of the first groove part R 1 , and a funnel-shaped part R 3  formed at the top of the first groove part R 1  in a funnel shape that widens toward the top in order to facilitate insertion of the ridge part  110 P and the protruding part  120 P when mounting the toner cartridge  100  in the accommodating recessed part  210 S. 
         [0049]    An inner circumferential protruding part  220 P is formed on each of the left and right ends of the second shutter  220  for slidably engaging in the second groove parts R 2 . A notched part  220 Q is formed in the inner circumferential protruding part  220 P in a portion opposing the bottom end of the first groove part. R 1  when the second shutter  220  is at the closed position so that the protruding part  120 P can be inserted into the notched part  220 Q when mounting the toner cartridge  100  (see  FIG. 5 ). 
         [0050]    While chemical toner is used for the color toner accommodated in the developer-accommodating devices  62 G of the process units  62  in the embodiment, pulverized toner is used for the black toner accommodated in the toner cartridge  100  of the process unit  61 . 
         [0051]    Here, “chemical toner” denotes toner that is manufactured according to chemical processes, in contrast to the traditional toners that are manufactured through a mechanical pulverizing process. Chemical toner can be produced through a variety of methods, including emulsion polymerization and aggregation, suspension polymerization, emulsion aggregation, and dissolution suspension. “Pulverized toner” includes not only traditional toner manufactured according to a mechanical pulverizing process, but also to the same toner that has been chemically treated to produce rounder toner particles. 
         [0052]    By employing pulverized toner, which has lower fluidity than chemical toner, it is possible to reduce the likelihood of toner leaking from the developing device  200  and to extend the service life of the developing device  200  in terms of the number of printed sheets, since the service life is greatly dependent on the lifespan of the toner leakage preventing seal. 
         [0053]    Next, the structure for enabling the retaining case  65  to be pulled outward from the main body  10  and for supporting the retaining case  65  in fixed positions will be described with reference to  FIGS. 2 through 4  and  FIGS. 7(   a ) and  7 ( b ).  FIGS. 7(   a ) and  7 ( b ) are explanatory diagrams conceptually illustrating a rear supporting structure SR and a front supporting structure SF when the retaining case  65  is at the second position shown in  FIG. 4 . 
         [0054]    A flange part  65 R is provided on each of the left and right walls of the retaining case  65 . The flange parts  65 R extend along the walls in the front-to-rear direction and are formed by bending the upper edges of the side walls outward. As shown in  FIG. 7(   a ), rollers  65 K are provided on the rear end of the retaining case  65  rearward of the flange parts  65 R. 
         [0055]    Guide rails  10 R are provided in the main body  10  on left and right sides of the space provided for accommodating the retaining case  65 . The guide rails  10 R serve to guide the retaining case  65  in the pull-out direction while maintaining the retaining case  65  in a horizontal orientation. As shown in  FIG. 7(   b ), a sloped part  10 S and a roller  10 K are provided on the front end of each guide rail  10 R, and a roller  10 J is disposed slightly rearward and above the sloped part  10 S and the roller  10 K on each side. 
         [0056]    As shown in  FIGS. 3 ,  4 , and  7 ( a ), a restricting frame  10 F is provided in the main body  10  on each of the left and right sides of the space accommodating the retaining case  65 . The restricting frames  10 F run parallel to the guide rails  10 R and restrict the retaining case  65  from moving the flange parts  65 R upward at least for the region of the rear supporting structure SR when the retaining case  65  is in the second position. 
         [0057]    As shown in  FIGS. 2 and 3 , a sloped part  10 N and a positioning part  10 M are provided on the rear end of each of the guide rails  10 R. 
         [0058]    When the retaining case  65  is in the first position shown in  FIG. 2 , the rollers  65 K on the rear end of the retaining case  65  are accommodated in the positioning parts  10 M provided on the main body  10  and are fixed in position by the same. At this time, the flange parts  65 R of the retaining case  65  rest on the guide rails  10 R of the main body  10  and are stably supported in a fixed position by the same. Operations of the color multifunction device  1  can be performed when the retaining case  65  is in this position. 
         [0059]    When the retaining case  65  is pulled outward from this position, the rollers  65 K provided on the rear end of the retaining case  65  roll up the sloped parts  10 N onto the guide rails  10 R, while the flange parts  65 R at the front end of the retaining case  65  slide up the sloped parts  10 S and pass over the rolling rollers  10 K, thereby guiding the retaining case  65  forward. 
         [0060]    When the retaining case  65  arrives at the second position shown in  FIG. 3 , leaf springs  65 S mounted on the flange parts  65 R contact the rollers  10 J on the main body  10 , and this contact halts movement of the retaining case  65  in the pull-out direction. In this position, the operator can replace the toner cartridge  100  of the process unit  61  and the developer-accommodating devices  62 G (and the developing rollers  62 C, the supply rollers  62 D, and the thickness-regulating blades  62 E) of the process units  62 . 
         [0061]    As shown in  FIGS. 3 and 4 , the process unit  61  is still positioned within the main body  10  when the retaining case  65  is in the second position. At the same time, the process unit  61  is positioned between the front supporting structure SF and the rear supporting structure SR, and the retaining case  65  is supported in the main body  10  at the front supporting structure SF and the rear supporting structure SR. 
         [0062]    Specifically, since the rollers  65 K are resting on the guide rails  10 R, as shown in  FIG. 7(   a ), downward movement of the retaining case  65  is restricted. Further, the restricting frames  10 F disposed above the rollers  65 K and the flange parts  65 R restrict upward movement of the retaining case  65 . 
         [0063]    As shown in  FIG. 7(   b ), downward movement of the retaining case  65  is restricted since the flange parts  65 R rest on the rollers  10 K, and upward movement is restricted since the rollers  10 J are positioned above the flange parts  65 R. 
         [0064]    The leaf springs  65 S serving to fix the retaining case  65  in the second position have center regions that bulge gently upward. The front ends of the leaf springs  65 S are embedded in the corresponding flange parts  65 R while the rear ends can slide into recessed parts formed in the top surfaces of the corresponding flange parts  65 R. Hence, if the user exerts greater force to pull the retaining case  65  farther forward from the state shown in  FIG. 7(   b ), the leaf springs  65 S are configured to elastically deform and pass beneath the rollers  10 J as the retaining case  65  moves forward. 
         [0065]    When the user pulls the retaining case  65  past the second position, the rollers  65 K on the rear end of the retaining case  65  pass over the corresponding sloped parts  10 S and the rollers  10 K, allowing the retaining case  65  to be completed removed from the main body  10 . Thus, the operator can repair or replace the photosensitive drums  61 A and  62 A, the chargers  61 B and  62 B, and the like after removing the retaining case  65  in this way. 
         [0066]    Next, operations for replacing the toner cartridge  100  in the process unit  61  having the above construction will be described. 
         [0067]    When the process unit  61  is positioned as shown in  FIGS. 1 and 2 , the toner cartridge  100  is engaged with the developing device  200 , and the first shutter  120  and the second shutter  220  are at the open position. In other words, as shown in  FIG. 6 , the protruding part  120 P of the first shutter  120  is at a position offset from the ridge part  110 P and is inset in the second groove part R 2 . Thus, the mounted toner cartridge  100  is firmly and inseparably fixed to the developing device  200 . 
         [0068]    When the toner cartridge  100  is out of black toner or needs to be replaced for any reason, the operator first opens the upper cover  12 , grips the handle  120 H, and then pulls the retaining case  65  forward until the retaining case  65  becomes fixed in the second position. When the handle  120 H is rotated rearward (counterclockwise direction in  FIG. 1 ), the first and second shutters  120  and  220  on the toner cartridge  100  and the developing device  200  are closed and the toner cartridge  100  is disengaged from the developing device  200  (see  FIG. 3 ). Next, the operator extracts the toner cartridge  100  upward through the opening  11   a.    
         [0069]    More specifically, the operation to rotate the handle  120 H rearward shifts the first shutter  120  and the second shutter  220  from the position shown in  FIG. 6  to the position shown in  FIG. 5 , causing the first shutter  120  and the second shutter  220  to shift to the closed position and the protruding parts  120 P of the first shutter  120  to arrive at a position aligned with the ridge parts  110 P. Consequently, the protruding parts  120 P can pass through the respective first groove parts R 1  which are the portion of the grooved parts  210 R that extend radially, thereby enabling the operator to pull the toner cartridge  100  upward, as illustrated in  FIG. 4 . 
         [0070]    To mount a new toner cartridge  100  in the process unit  61 , the operator first opens the front cover  11 , then pulls the retaining case  65  forward until the retaining case  65  becomes fixed in the second position shown in  FIG. 3 . Subsequently, the operator mounts the new toner cartridge  100 . 
         [0071]    During this operation, the operator aligns the ridge parts  110 P and the protruding parts  120 P on left and right sides of the toner cartridge  100  in the state shown in  FIG. 5  with the grooved parts  210 R on the left and right sides of the developing device  200  and inserts the ridge parts  110 P and the protruding parts  120 P in the corresponding grooved parts  210 R until the entire toner cartridge  100  is seated in the accommodating recessed part  210 S of the developing device  200 . Subsequently, the operator rotates the handle  120 H forward (clockwise direction in  FIG. 1 ), moving the first shutter  120  and the second shutter  220  to their open positions shown in  FIG. 6 . 
         [0072]    Through this operation, the protruding parts  120 P of the first shutter  120  enter the respective second groove parts R 2  of the grooved parts  210 R and move to a position offset from the respective ridge parts  110 P. Accordingly, the mounted toner cartridge  100  is firmly fixed to and inseparable from the developing device  200 . 
         [0073]    Since the second shutter  220  of the developing device  200  opens and closes the second supplying opening  211  in association with the handle  120 H opening and closing the first shutter  120 , both the first shutter  120  and the second shutter  220  are easily opened and closed through a single operation. Further, the toner cartridge  100  is disengaged from the developing device  200  in association with the operation of the handle  120 H to switch these shutters  120  and  220  to their closed positions and is engaged with the developing device  200  in association with the operation of the handle  120 H to switch the shutters  120  and  220  to their open positions, thereby achieving both safety and simplicity of operations. 
         [0074]    When one of the developer-accommodating devices  62 G of the process units  62  must be replaced together with the developing device  62 H (i.e., the developing roller  62 C, the supply roller  62 D, and the thickness-regulating blade  62 E) because the developer-accommodating device  62 G has run out of cyan, magenta, or yellow toner, for example, the operator opens the front cover  11 , grips the handle  65 H, and pulls the retaining case  65  forward to the second position and replaces the relevant components, as illustrated in  FIG. 4 . 
         [0075]    Here, the retaining case  65  may be completely separately removed from the main body  10  before replacing the components of the process units  61  and  62 . 
         [0076]    As shown in  FIG. 4 , guide grooves  65 G are formed in the inner surfaces of both side walls constituting the retaining case  65 . The guide grooves  65 G function to guide the vertical sliding movement of the developer-accommodating devices  62 G and the developing devices  62 H when they are mounted in the retaining case  65  and to maintain the mounted developing devices  62 H (particularly the developing rollers  62 C) at a fixed position in the bottom ends of the guide grooves  65 G. This construction for mounting and removing the developer-accommodating devices  62 G and the developing device  62 H facilitates the smooth replacement of components in the process units  62 . 
         [0077]    The color multifunction device  1  according to the embodiment having the construction described above primarily produces the following advantages and effects. 
         [0078]    As described above, the color multifunction device  1  has the drawer-like retaining case  65  for accommodating the plurality of developer-accommodating devices in tandem. Of these developer-accommodating devices, the toner cartridge  100  that accommodates black developer is detachably mounted in the process unit  61  disposed in the farthest position of the retaining case  65  relative to the pull-out direction. Since this position affords the most stable operations when the retaining case  65  is fixed in the second position, replacement of the toner cartridge  100  accommodating black developer is both easy and safe, and running costs can be reduced. 
         [0079]    Further, the process units  62  whose developing devices  62 H and corresponding developer-accommodating devices  62 G accommodating color toners can be integrally separated from the retaining case  65  as a unit are arranged toward the near side of the retaining case  65  relative to the pull-out direction. This structure of the process units  62  eliminates the opening and closing of shutters in the developer-accommodating devices  62 G, thereby making replacement of the process units  62  easy and safe. 
         [0080]    Among the developer accommodating devices  62 G and the toner cartridge  100 , the toner cartridge  100  can be replaced separately from the process unit  61 . Since the toner cartridge  100  accommodates black toner, which is generally consumed faster than the color toners, this configuration can greatly reduce running costs. 
         [0081]    The process unit  61  in which the toner cartridge  100  is detachably mounted is positioned inside the main body  10  when the retaining case  65  is pulled out to the second position. This arrangement greatly reduces the risk that forces applied to the retaining case  65  during operations to open and close shutters  120  and  220  when mounting and removing the toner cartridge  100  will cause damage to the retaining case  65  or overturn the main body  10  of the color multifunction device  1 . 
         [0082]    Further, when the retaining case  65  is pulled out and fixed in the second position, the process unit  61  in the retaining case  65  is supported in the main body  10  at two locations, i.e., the front side (the front supporting structure SF) and the rear side (the rear supporting structure SR). Therefore, operations for opening and closing the shutters  120  and  220  when mounting and removing the toner cartridge  100  can be performed more easily and safely. 
         [0083]    While the invention has been described in detail with reference to the embodiment thereof, it would be apparent to those skilled in the art that many modifications and variations may be made therein without departing from the spirit of the invention, the scope of which is defined by the attached claims. 
         [0084]    While the recording sheets described in the embodiment are paper P, such as normal paper or postcards, the recording sheets may also be transparencies or the like. 
         [0085]    The specific structure and arrangement of other components constituting the image-forming device, such as the exposure device, retaining member, photosensitive drums, developer-accommodating devices, and operating member (handle), may be modified as desired and are not limited to the description in the above-mentioned embodiment. 
         [0086]    Further, while the image-forming device with process units according to the present invention is the color multifunction device  1  in the embodiment, the image-forming device may also be a photocopier, printer, or the like. Also, the image-forming device of the embodiment includes four process units  61  and  62 , but the present invention may be applied to any image-forming device having a plurality of developer-accommodating devices, including one that accommodates black developer.