Abstract:
An arrangement for providing developer to process cartridges is described. Developer agent storing members may be insertable into a body containing the process cartridges through a front of the body. The developer agent storing members may be provided on two sides to reduce the stacked height of the developer agent storing members in the body.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2007-210462, filed on Aug. 10, 2007, the entire subject matter of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     Aspects of the invention relate to tandem-type image forming apparatuses. 
     BACKGROUND 
     A known tandem-type image forming apparatus includes a plurality of process cartridges spaced in a line, and is configured to print a color image at once. 
     The image forming apparatus is configured such that toner cartridges can be removed and replaced from the top of the apparatus. Thus, the image forming apparatus requires a space for toner cartridge replacement above, so that its installation site may be limited. When an image reading unit is provided on the top of the image forming apparatus, the toner cartridges cannot be removed from above, and the apparatus should undergo some design changes relating to toner cartridge replacement. 
     SUMMARY 
     Aspects of the invention provide an image forming apparatus configured to facilitate toner cartridge replacement without a need to involve design changes in the limitation of the installation site or the availability of an image reading unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Illustrative aspects of the invention will be described in detail with reference to the following figures in which like elements are labeled with like numbers and in which: 
         FIG. 1  is a side sectional view of an internal structure of a color laser printer as an illustrative example of an image forming apparatus according to an illustrative embodiment of the invention; 
         FIG. 2  is a perspective view of an appearance of the color laser printer of  FIG. 1  in which a frame accommodating process cartridges is pulled out; 
         FIG. 3  is a perspective view of the color laser printer where a toner cartridge is replaced; and 
         FIG. 4  is a front view of a color multifunction apparatus as another example of the image forming apparatus. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative embodiment of the invention will be described in detail with reference to the accompanying drawings. An image forming apparatus according to aspects of the invention applies to a color laser printer  1 . It will be appreciated that aspects of the invention apply to other types of image forming apparatuses as well. 
     It is noted that various connections are set forth between elements in the following description. It is noted that these connections in general and, unless specified otherwise, may be direct or indirect and that this specification is not intended to be limiting in this respect. 
     For purposes herein, aspects of the invention are shown in relation to an image carrier and developer carrier. In various aspects, the image carrier may include a photosensitive drum, photosensitive belt, or the combination of one of a photosensitive drum or belt and an intermediate transfer drum or belt. Further, the developer carrier may include a developer roller or other systems for conveying developer to the image carrier. 
     For ease of discussion, in the following description, directions are defined as viewed from a user who operates the color laser printer  1 . The top or upper side, the bottom or lower side, the left or left side, the right or right side, the front or front side, and the rear or rear side of the color laser printer  1  are identified as indicated by the arrows in  FIG. 2 . With regard to various individual objects of the color laser printer  1 , sides of the individual objects are similarly identified based on the arranged/attached position of the object on/in the color laser printer  1 . 
     As shown in  FIG. 1 , the color laser printer  1  may include a plurality of, e.g., four, photosensitive drums  3   a - 3   d  arranged in parallel to each other in a front-rear direction in a body case  2 . Surfaces of the photosensitive drums  3   a - 3   d  are regularly charged by corresponding scorotron chargers  4   a - 4   d  and irradiated by laser beams emitted from an exposure unit  5 , and electrostatic latent images are formed on the surfaces based on image data. The electrostatic latent images formed on the surfaces of the photosensitive drums  3   a - 3   d  are developed into toner images with corresponding colors of toner (developer) carried on developing rollers  6   a - 6   d.    
     A stack of sheets P is stored in a sheet supply cassette  7  disposed in a bottom portion of the body case  2 . A topmost sheet P is separated from the stack of sheets P by rollers in a sheet supply portion  8  disposed in a front portion of the body case  2  and conveyed upward to a conveyor belt  9  disposed above and rearward of the sheet supply portion  8 . The conveyor belt  9  is disposed facing the photosensitive drums  3   a - 3   d . Transfer rollers  10   a - 10   d  are disposed within the conveyor belt  9  to face the corresponding photosensitive drums  3   a - 3   d  via the conveyor belt  9 . By the action of the transfer rollers  10   a - 10   d  that are biased, toner images in each color on the photosensitive drums  3   a - 3   d  are successively overlapped each other and transferred onto the sheet P conveyed to the conveyor belt  9 . The sheet P having four-color toner images thereon is conveyed to a fixing unit  11 . The toner images transferred onto the sheet P are thermally fixed by the fixing unit  11 , and the sheet P is ejected upward to an output tray  12  by changing the sheet feeding direction from rear to front by rollers. 
     A plurality of, e.g., four, process cartridges  13   a - 13   d  are disposed between the sheet supply cassette  7  and the exposure unit  5  in the body case  2 . The process cartridges  13   a - 13   d  are arranged in tandem in the front-rear direction. The process cartridges  13   a - 13   d  are held in a frame  14  in a detachable manner. The frame  14  is configured to be attached to and removed from the body case  2 . 
     The process cartridges  13   a - 13   d  include the photosensitive drums  3   a - 3   d , the scorotron chargers  4   a - 4   d , the developing rollers  6   a - 6   d , supply rollers  15   a - 15   d , and toner hoppers  16   a - 16   d . The process cartridges  13   a - 13   d  are identical in structure except that they have different colors of toner supplied from toner cartridges  17   a - 17   d  to the toner hoppers  16   a - 16   d . Toner is supplied from the toner cartridges  17   a - 17   d  via the toner hoppers  16   a - 16   d  and the supply rollers  15   a - 15   d  to the developing rollers  6   a - 6   d.    
     As shown in  FIG. 2 , an operation unit  18  is disposed at a left front side on an upper surface of the body case  2 , so that a user can manipulate the operation unit  18  in front of the color laser printer  1 . A front surface of the body case  2  contains a front cover  19 . The front cover  19  is pivotally mounted at its lower end to the body case  2 . The frame  14  holding the process cartridges  13   a - 13   d  can be pulled toward the front through an opening formed when the front cover  19  is opened. With the frame  14  pulled toward the front, the process cartridges  13   a - 13   d  can be replaced. 
     As shown in  FIGS. 1 and 3 , the toner cartridges  17   a - 17   d  are disposed two by two on both sides of the exposure unit  5  above the process cartridges  13   a - 13   d  in the body case  2 . The toner cartridges  17   a ,  17   c  are vertically arranged on the left side and the toner cartridges  17   b ,  17   d  are vertically arranged on the right side. 
     The two vertically arranged toner cartridges  17   b ,  17   d  or  17   a ,  17   c  are shifted in a direction where the process cartridges  13   a - 13   d  are arranged in tandem or in the front-rear direction, as shown in  FIG. 1 . In other words, the rear end of the upper toner cartridge  17   d  or  17   c  is positioned slightly more rearward than the rear end of the lower cartridge  17   b  or  17   a . Toner supply tubes  20   a - 20   d  ( 20   a ,  20   c  not shown) are connected on rear sides of the corresponding toner cartridges  17   a - 17   d . Each toner supply tube  20   a - 20   d  extends vertically downward from the underside of the corresponding toner cartridge  17   a - 17   d . When the toner cartridge  17   a - 17   d  is removed from the body case  2 , it is disconnected from the corresponding toner supply tube  20   a - 20   d.    
     The toner cartridges  17   a - 17   d  are cylindrical in shape, and disposed to extend in the direction where the process cartridges  13   a - 13   d  are arranged in tandem, i.e., in the front-rear direction of the body case  2 . As shown in  FIG. 3 , toner cartridge covers  21 ,  22 , are disposed on the front surface of the body case  2 . The toner cartridges  17   a - 17   d  are configured to be pulled out from openings formed when the toner cartridge covers  21 ,  22  are opened. In this manner, the toner cartridges  17   a - 17   d  can be replaced from the front side where the user manipulates the operation unit  18 . 
     Toner contained in each toner cartridge  17   a - 17   d  is supplied via the toner supply tube  20   a - 20   d  to the toner hopper  16   a - 16   d  of the process cartridge  13   a - 13   d  as shown in  FIG. 1 . The toner cartridges  17   a - 17   d  are identical in structure except that they each contain different colors of toner. Preferably, each toner cartridge  17   a - 17   d  has a known conveying device (not shown), such as an auger, for agitating and conveying toner to the rear of the toner cartridge  17   a - 17   d  (rearward of the body case  2 ). 
     Advantages of aspects of the color laser printer  1  described above include the following. 
     As the toner cartridges  17   a - 17   d  can be pulled toward the front, they can be easily replaced, and the operability of the color laser printer  1  can be improved. 
     The toner cartridges  17   a - 17   d  are disposed above the process cartridges  13   a - 13   d.  Thus, through the use of gravitation, toner in the toner cartridges  17   a - 17   d  can be supplied via the toner supply tubes  20   a - 20   d  to the toner hoppers  16   a - 16   d  of the process cartridges  13   a - 13   d . Toner can be more efficiently supplied by provision of a conveying device such as an auger (not shown) inside each toner supply tube  20   a - 20   d.    
     The exposure unit  5  can be made in a width the same as or narrower than the image formation area width, but the developing rollers  6   a - 6   d  and the photosensitive drums  3   a - 3   d  should be made wider than the image formation area width. As a result, a space is formed on each side of the exposure unit  5 . In this embodiment, four toner cartridges  17   a - 17   d  are disposed two on each side of the exposure unit  5 , so that a space inside the body case  2  can be efficiently used. 
     In the body case  2 , a space under which each toner cartridge  17   a - 17   d  is disposed can accommodate a driving unit (now shown) for applying power to rollers including photosensitive drums  3   a - 3   d  and an electrode as a heating device of the fixing unit  11 . Thus, the space inside the body case  2  can be efficiently used and the body case  2  can be reduced in size. 
     As the toner cartridges  17   a - 17   d  are disposed on both sides of the exposure unit  5 , there is no need to provide a toner chamber having a certain capacity in each process cartridge  13   a - 13   d . Thus, the process cartridges  13   a - 13   d  can be reduced in size, especially in height. As the process cartridges  13   a - 13   d  can be reduced in height, the body case  2  also can be reduced in height, and the color laser printer  1  can be provided with a low-profile design. 
     The toner cartridges  17   a - 17   d  are disposed so that a direction of their length extends in the direction where the process cartridges  13   a - 13   d  are arranged in tandem, i.e., in the front-rear direction of the body case  2 . Thus, the size of each toner cartridge  17   a - 17   d  can be secured greatly in its longitudinal direction. In addition, the volume of each toner cartridge  17   a - 17   d  also can be increased. 
     The two vertically arranged toner cartridges  17   b ,  17   d  (or  17   a ,  17   c ) are disposed out of alignment with each other in the direction where the process cartridges  13   a - 13   d  are arranged in tandem, so that the toner supply tubes  20   a - 20   d  connected on lower parts on the rear of the corresponding toner cartridges  17   a - 17   d  can be extended vertically downward. In other words, as the upper and lower toner cartridges  17   b ,  17   d  (or  17   a ,  17   c ) are disposed out of alignment with each other in the front-rear direction, paths to supply toner from the toner cartridges  17   a - 17   d  to the toner hoppers  16   a - 16   d  (or an arrangement of the toner supply tubes  20   a - 20   d ) can be simplified. 
     As the frame  14  that holds the process cartridges  13   a - 13   d  detachably is configured to be capable of moving in the same direction as the toner cartridges  17   a - 17   d  are attached to or removed from the body case  2 , the toner cartridges  17   a - 17   d  and the process cartridges  13   a - 13   d  can be easily replaced. Thus, the operability of the color laser printer  1  can be improved. In addition, the process cartridges  13   a - 13   d  and the toner cartridges  17   a - 17   d  can be replaced from the front side where the operation unit  18  is manipulated, there is no need to provide a space for replacement above, and thus there is no restraint on the installation site. 
     In the above embodiment, each process cartridge  13   a - 13   d  integrally includes the photosensitive drum  3   a - 3   d  and the developing roller  6   a - 6   d . However, the process cartridge  13   a - 13   d  may be a separable combination of a cartridge including the photosensitive drum  3   a - 3   d  and a cartridge including the developing roller  6   a - 6   d.    
     In the above embodiment, the four toner cartridges  17   a - 17   d  are disposed two on each side of the exposure unit  17 . The number of toner cartridges is not limited to four. Three or more toner cartridges may be disposed on each side of the exposure unit  5 . Alternatively, the number of toner cartridge disposed on each side may be different. For example, one toner cartridge may be disposed on one side of the exposure unit  5  and three toner cartridges may be disposed on the other side of the exposure unit  5 . 
     In the above embodiment, the toner cartridges  17   a - 17   d  are identical in size. However, the toner cartridges  17   a - 17   d  may be different in size. For example, a toner cartridge containing black toner, which is relatively quickly used up, may be increased in size. 
     In the above embodiment, the color laser printer  1  is illustrated as an example of the image forming apparatus of the invention. The image forming apparatus according to aspects of the invention applies to a color multifunction apparatus  1 ′ shown in  FIG. 4 . The color multifunction apparatus  1 ′ may include a flatbed scanner  23  functioning as an image reading unit and a supporting member  24  on top of the body case  2 . The flatbed scanner  23  may be disposed on top of the supporting member  24  and include an operation unit  18 ′ for manipulation by a user standing in front of the color multifunction apparatus  1 ′. The supporting member  24  may be disposed between the flatbed scanner  23  and the body case  2  and configured to support the flatbed scanner  23 . In the color multifunction apparatus  1 ′, a sheet P having image thereon may be ejected through a space S enclosed between the body case  2 , the flatbed scanner  23  and the supporting member  24 , and located on the output tray  12 . 
     In the color multifunction apparatus  1 ′, all or part of the toner cartridges  17   a - 17   d  may be positioned inside the supporting member  24 . With this configuration, the inside space of the supporting member  24 , which may be substantially hollow in a known color multifunction apparatus, can be efficiently used. In addition, as the process cartridges  13   a - 13   d  and the toner cartridges  17   a - 17   d  can be replaced from the front side of the body case  2  where the operation unit  18 ′ is manipulated, there is no need to make a design change relating to replacement of the toner cartridges  17   a - 17   d  even if the flatbed scanner  23  is provided. Thus, the above described body case  2  can be used for both the color laser printer  1  and the color multifunction apparatus  1 ′, the color laser printer  1  and the color multifunction apparatus  1 ′ can be manufactured in the same manufacturing line, and thus the cost of manufacturing can be reduced. 
     The above embodiment shows the process cartridges  13   a - 13   d  and the toner cartridges  17   a - 17   d  are configured to be capable of moving together in the same direction as the toner cartridges  17   a - 17   d  are attached or removed. However, the invention is not limited to the embodiment. For example, the process cartridges  13   a - 13   d  may be configured to be capable of moving together in the left-right direction. Alternatively, the process cartridges  13   a - 13   d  may be configured to be capable of being replaced independently. 
     While the features herein have been described in connection with various example structures and illustrative aspects, it will be understood by those skilled in the art that other variations and modifications of the structures and aspects described above may be made without departing from the scope of the invention. Other structures and aspects will be apparent to those skilled in the art from a consideration of the specification or practice of the features disclosed herein. It is intended that the specification and the described examples only are illustrative with the true scope of the inventions being defined by the following claims.