Abstract:
An image forming apparatus includes an image forming mechanism for forming an image, at least one developer container replaceably provided in the image forming apparatus for containing developer, a housing for housing the image forming mechanism and the at least one developer container, and an operation device provided on the housing. The housing includes at least one openable portion opened for replacement of the at least one developer container. The operation device includes an instruction display part for indicating a message prompting opening of the at least one openable portion, and at least one developer-end display part for indicating depletion or near-depletion of the developer contained in any one of the at least one developer container. The at least one developer-end display part and the instruction display part are placed adjacent to each other and are viewable from a front side of the image forming apparatus.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese patent application no. 2004-335298 filed on Nov. 19, 2004, the entire contents of which are hereby incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image forming method and apparatus, such as a color printer, a color copier, a color facsimile machine, and a complex machine thereof, and more particularly to an image forming method and apparatus allowing convenient replacement of members included in the image forming apparatus, such as developer containers 
     2. Description of the Related Art 
     In recent years, color image forming apparatuses according to an electrographic method for forming a color image on a recording medium, such as a sheet and a film, have been widely used. This type of color image forming apparatus is increasingly used as a printer, for example, in connection with a personal computer. That is, the color image forming apparatus is increasingly personalized. For convenience, a user of such color image forming apparatus often prefers to place the color image forming apparatus close to the user&#39;s working space. In this case, it is preferable to reduce the height of the color image forming apparatus for enhancing the user&#39;s working efficiency, and to downsize the color image forming apparatus (e.g., reduce the width of the color image forming apparatus) for saving space. Further, from the viewpoint of personalization of the color image forming apparatus and reduction in maintenance cost of the color image forming apparatus, it is desirable for users that the color image forming apparatus is designed to be easy to perform replacement and maintenance works of consumable components, such as a toner which serves as a developer (i.e., development agent). 
     In this type of color image forming apparatus, a color image is generally formed by using toners of four colors as the developers. The color image forming apparatus, therefore, includes a larger number of components than a monochrome image forming apparatus and thus tends to be larger in size. Further, a per-unit-time number of recording mediums output from the color image forming apparatus (i.e., a color printing speed) tends to be reduced. In light of the above, there is a tandem-type color image forming apparatus in which a plurality of photoconductors are placed in a line and provided with a corresponding plurality of development devices in their vicinity. Thus configured, the tandem-type color image forming apparatus forms a plurality of single-color toner images on the respective plurality of photoconductors and sequentially transfers the plurality of single-color toner images onto a recording medium. 
     The tandem-type color image forming apparatus generally consumes a relatively large amount of toner. In view of a user&#39;s working efficiency, it is preferable to separately provide a development device from a developer supplying unit which supplies toner to the development device, rather than integrating the development device with the developer supplying unit within a cartridge. Further, in some of the tandem-type color image forming apparatuses, recording mediums on which color images have been formed are discharged to and stacked on an upper portion of such color tandem-type image forming apparatuses to save space. 
     The tandem-type color image forming apparatuses are, however, still open to further improvements in terms of usability thereof. 
     For example, the tandem-type color image forming apparatuses need to have a plurality of developer-storing containers (i.e., toner bottles) for a corresponding plurality of toner colors. 
     If these toner bottles can be checked by visual examination, the user&#39;s working efficiency is expected to increase. In a background color image forming apparatus, for example, a plurality of toner bottles are placed in a line such that a lateral direction of the plurality of toner bottles is perpendicular to a direction of discharging recording mediums, i.e., the respective toner bottles of four colors are sequentially placed along the direction of discharging the recording mediums. 
     However, placement of the toner bottles and display on an operation panel of background color image forming apparatuses seem not to be sufficiently based on usability for users who are unfamiliar to structures of the background image forming apparatuses, replacement works of components included in the background image forming apparatuses, and so forth. Under such circumstances, some users find it complicated and thus are reluctant to personally check the toner bottles and perform the replacement for such components. 
     SUMMARY OF THE INVENTION 
     This patent specification describes an image forming apparatus. In one example, an image forming apparatus includes an image forming mechanism for forming an image, at least one developer container, a housing, and an operation device. The at least one developer container is replaceably provided in the image forming apparatus and is configured to contain developer. The housing is configured to house the image forming mechanism and the at least one developer container. The housing includes at least one openable portion configured to be opened for replacement of the at least one developer container. The operation device is provided on the housing and includes an instruction display part and at least one developer-end display part. The instruction display part is configured to indicate a message prompting opening of the at least one openable portion. The at least one developer-end display part is configured to indicate depletion or near-depletion of the developer contained in any one of the at least one developer container. The at least one developer-end display part and the instruction display part are placed adjacent each other and are viewable from a front side of the image forming apparatus. 
     This patent specification further describes another image forming apparatus. In one example, another image forming apparatus includes an image forming mechanism for forming an image, a plurality of developer containers, a housing, and an operation device. The plurality of developer containers are arranged in parallel along a sheet-discharging direction, and each of the plurality of developer containers is configured to contain developer. The housing is configured to house the image forming mechanism and the plurality of developer containers. The housing includes at least one openable portion configured to be opened for replacement of any one of the plurality of developer containers. The at least one openable portion includes an upper openable portion configured to be opened to reveal the plurality of developer containers to be externally viewable. The operation device is provided on the housing and includes an instruction display part and a plurality of developer-end display parts. The instruction display part is configured to indicate a message prompting opening of the at least one openable portion. Each of the plurality of developer-end display parts is configured to indicate either depletion or near-depletion of the developer contained in any one of the plurality of the developer containers. The plurality of developer-end display parts and the instruction display part are placed adjacent each other and are viewable from a front side of the image forming apparatus. 
     This patent specification further describes another image forming apparatus. In one example, another image forming apparatus includes image forming means for forming an image, at least one developer containing means, housing means, and operation means. The at least one developer containing means is replaceably provided in the image forming apparatus for containing developer. The housing means houses the image forming means and the at least one developer containing means. The housing means includes at least one openable means for being opened for replacement of the at least one developer containing means. The operation means is provided on the housing means and includes instruction display means and at least one developer-end display means. The instruction display means indicates a message prompting opening of the at least one openable means. The at least one developer-end display means indicates either depletion or near-depletion of the developer contained in any one of the at least one developer containing means. The at least one developer-end display means and the instruction display means are placed adjacent each other and are viewable from a front side of the image forming apparatus. 
     This patent specification further describes another image forming apparatus. In one example, another image forming apparatus includes an image forming means for forming an image, a plurality of developer containing means, housing means, and operation means. The plurality of developer containing means contain developer and is arranged in parallel along a sheet-discharging direction. The housing means houses the image forming means and the plurality of developer containing means. The housing means includes at least one openable means for being opened for replacement of any one of the plurality of developer containing means. The at least one openable means includes an upper openable means opened for revealing the plurality of developer containing means so as to be externally viewable. The operation means is provided on the housing means and includes instruction display means and a plurality of developer-end display means. The instruction display means indicates a message prompting opening of the at least one openable means. The plurality of developer-end display means indicates any one of depletion and near-depletion of the developers contained in any one of the plurality of the developer containing means. The plurality of developer-end display means and the instruction display means are placed adjacent to each other and are viewable from a front side of the image forming apparatus. 
     This patent specification further describes an image forming method. In one example, an image forming method of includes the steps of placing, in a housing, an image forming mechanism and at least one developer container containing developer, the at least one developer container being replaceably provided; providing the housing with at least one openable portion opened for replacing the at least one developer container, using an operation device including an instruction display part and at least one developer-end display part, the instruction display part and the at least one developer-end display part being placed adjacent to each other and being viewable from a front side of the image forming apparatus; forming an image by the image forming mechanism; indicating, through the at least one developer-end display part, either depletion or near-depletion of the developer contained in any one of the at least one developer container; and indicating, through the instruction display part, a message prompting opening of the at least one openable portion. 
     This patent specification further describes another image forming method. In one example, another image forming method includes: providing, in a housing, an image forming mechanism and a plurality of developer containers each containing developer, the plurality of developer containers being arranged in parallel along a sheet-discharging direction; providing the housing with at least one openable portion opened for replacing any one of the plurality of developer containers, the at least one openable portion including an upper openable portion opened to reveal the plurality of developer containers to be externally viewable; providing the housing with an operation device including an instruction display part and a plurality of developer-end display parts, the instruction display part and the plurality of developer-end display parts being placed adjacent each other and being viewable from a front side of the image forming apparatus; forming an image by the image forming mechanism; indicating, through the plurality of developer-end display parts, either depletion or near-depletion of the developer contained in any one of the plurality of developer containers; and indicating, through the instruction display part, a message prompting opening of the at least one openable portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG. 1  is a sectional view of an image forming apparatus according to an embodiment of the present invention; 
         FIG. 2  is a perspective view of the image forming apparatus illustrated in  FIG. 1 ; 
         FIG. 3  is a perspective view of the image forming apparatus illustrated in  FIG. 1 , with an upper portion thereof lifted open; 
         FIG. 4  is a perspective view of the image forming apparatus illustrated in  FIG. 1 , as viewed in another angle; 
         FIG. 5A  is a plan view of an operation panel of the image forming apparatus illustrated in  FIG. 4 ; 
         FIG. 5B  is an enlarged plan view of a part of the operation panel illustrated in  FIG. 5A ; and 
         FIG. 5C  is a sectional view of the operation panel illustrated in  FIG. 5A  cut along a line  5 C- 5 C. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In describing the embodiments illustrated in the drawings, specific terminology is employed for the purpose of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so used, and it is to be understood that substitutions for each specific element can include any technical equivalents that operate in a similar manner. 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, particularly to  FIGS. 1 to 3 , a configuration and functions of an image forming apparatus  1  according to an exemplary embodiment of the present invention are described. 
       FIG. 1  illustrates a sectional view of the image forming apparatus  1 . The image forming apparatus  1  in the present example is a tandem-type color printer capable of forming a full-color image. The image forming apparatus  1  is not, however, limited to the printer illustrated in the present drawing but may also be another type of image forming apparatus, such as a copier, a facsimile machine, and a complex machine thereof. 
     The image forming apparatus  1  illustrated in  FIG. 1  includes a sheet-feeding unit  2 , a plurality of rollers  4 ,  5 , and  6 , an intermediate transfer belt  7 , image forming units  8 Y,  8 C,  8 M, and  8 K, first transfer rollers  14 Y,  14 C,  14 M, and  14 K, an optical writing unit  15 , a second transfer roller  20 , an intermediate transfer belt cleaning unit  21 , a fixing unit  22 , a sheet-discharging unit  23 , a resisting roller pair  24 , a sheet-stacking area  36 , toner bottles  37 ,  38 ,  39 , and  40 , a fulcrum portion  41 , a shaft  42 , a shaft-bearing  43 , a sheet-feeding cassette  45 , a tray  46 , a divider plate  50 , a toner bottle housing space  51 , a holder  52 , and an operation panel  60 . 
     In the image forming apparatus  1  illustrated in  FIG. 1 , the sheet-feeding unit  2  including the sheet-feeding cassette  45  is located in a lower part of the image forming apparatus  1  to store a recording medium P. The-feeding cassette  45  is opened in a direction H and closed in a direction G. The image forming units  8 Y,  8 C,  8 M, and  8 K are placed above the sheet-feeding unit  2  to respectively form toner images of yellow (Y), cyan (cyan), magenta (M), and black (K) colors. Each of the image forming units  8 Y,  8 C,  8 M, and  8 K (i.e., image forming unit  8 ) includes an image carrying member  10  (i.e., a photoconductor drum in the present example), a charging unit  11 , a developing unit  12 , and an image carrying member cleaning unit  13  of a corresponding color.  FIG. 1  illustrates, as an example, an image carrying member  10 Y, a charging unit  11 Y, a developing unit  12 Y, and an image carrying member cleaning unit  13 Y included in the image forming unit  8 Y. Similarly,  10 C,  10 M, and  10 K, charging units  11 C,  11 M, and  11 K, developing units  12 C,  12 M, and  12 K, and image carrying member cleaning units  13 C,  13 M, and  13 K are included in the corresponding image carrying members  8 C,  8 M, and  8 K, respectively, although their reference numbers are omitted for simplification in  FIG. 1 . 
     In the image forming unit  8 , the image carrying member  10  contacts the intermediate transfer belt  7  and is surrounded by the charging unit  11 , the developing unit  12 , and the image carrying member cleaning unit  13 . Further, the first transfer roller  14  for performing a first transferring operation is placed on an inner surface of the intermediate transfer belt  7  at a position where the image carrying member  10  contacts the intermediate transfer belt  7 . The image forming units  8 Y,  8 C,  8 M, and  8 K are basically similar in structure. The differences among the image forming units  8 Y,  8 C,  8 M, and  8 K lies in the colors of the toners stored in the respective developing units  12 Y,  12 C,  12 M, and  12 K. 
     The intermediate transfer belt  7  is a flexible endless belt passing over the plurality of rollers  4 ,  5 , and  6 . The optical writing unit  15  performs an optical writing operation to each of the image carrying members  10 Y,  10 C,  10 M, and  10 K. The fixing unit  22  fixes a toner image on the recording medium P. In  FIG. 1 , a dotted-and-dashed line R extending from the sheet-feeding unit  2  to the fixing unit  22  indicates a sheet path along which the recording medium P is conveyed. The roller  6  is positioned along the sheet path R. 
     A portion of the intermediate transfer belt  7  flanked by the rollers  4  and  5  forms a lower side of the intermediate transfer belt  7 . The roller  6  faces the second transfer roller  20  via the intermediate transfer belt  7  at a position on the sheet path R. Meanwhile, the roller  4  faces, via the intermediate transfer belt  7 , the intermediate transfer belt cleaning unit  21  which cleans an outer surface of the intermediate transfer belt  7 . 
     The image forming units  8 Y,  8 C,  8 M, and  8 K are placed below the intermediate transfer belt  7  to face the lower side of the intermediate transfer belt  7 . 
     The optical writing unit  15 , which is located below the image forming units  8 Y,  8 C,  8 M, and  8 K in the present example, applies optically-modulated laser beams to surfaces of the respective image carrying members  10 Y,  10 C,  10 M, and  10 K to form thereon latent images of the respective colors. 
     Upon start of an image forming operation, a driving device (not illustrated) drives to rotate the respective image carrying members  10 Y,  10 C,  10 M, and  10 K in a clockwise direction. Then, the charging units  11 Y,  11 C,  11 M, and  11 K uniformly charge the surfaces of the respective image carrying members  10 Y,  10 C,  10 M, and  10 K to a predetermined polarity. The surfaces of the image carrying members  10 Y,  10 C,  10 M, and  10 K thus charged are applied with the optically-modulated laser beams by the optical writing unit  15 . As a result, the latent images of the respective colors are formed on the surfaces of the image carrying members  10 Y,  10 C,  10 M, and  10 K. In this exposure process, data of a desired full-color image is divided into single-color data sets of the respective colors, i.e., yellow, cyan, magenta, and black. Based on the thus formed single-color data sets, the surfaces of the respective image carrying members  10 Y,  10 C,  10 M, and  10 K are exposed. When the image carrying members  10 Y,  10 C,  10 M, and  10 K contact the corresponding developing units  12 Y,  12 C,  12 M, and  12 K, the latent images formed on the surfaces of the image carrying members  10 Y,  10 C,  10 M, and  10 K are developed into visible toner images by the toners stored in the developing units  12 Y,  12 C,  12 M, and  12 K. 
     One of the plurality of rollers  4 ,  5 , and  6  passing over the intermediate transfer belt  7  is driven to rotate in a counterclockwise direction by a driving device (not illustrated). Accordingly, the intermediate transfer belt  7  is driven to rotate in a counterclockwise direction A in  FIG. 1 , and the other two of the plurality of rollers  4 ,  5 , and  6  are also driven to rotate. As the intermediate transfer belt  7  rotates, a yellow toner image formed by the image forming unit  8 Y is first transferred to the outer surface of the intermediate transfer belt  7  by the first transfer roller  14 Y. Then, a cyan toner image formed by the image forming unit  8 C, a magenta toner image formed by the image forming unit  8 M, and a black toner image formed by the image forming unit  8 K are sequentially superimposed on the yellow toner image. Thus, a full-color toner image is formed on the outer surface of the intermediate transfer belt  7 . 
     After the respective toner images are transferred from the image carrying members  10 Y,  10 C,  10 M, and  10 K to the intermediate transfer belt  7 , toner remaining on the surfaces of the respective image carrying members  10 Y,  10 C,  10 M, and  10 K are removed by the image carrying member cleaning units  13 Y,  13 C,  13 M, and  13 K, respectively. Then, electricity on the surfaces of the respective image carrying members  10 Y,  10 C,  10 M, and  10 K is removed by neutralization devices (not illustrated). Accordingly, potentials of the surfaces of the respective image carrying members  10 Y,  10 C,  10 M, and  10 K are initialized in preparation for a subsequent image forming operation. 
     Meanwhile, the recording medium P is sent out from the sheet-feeding unit  2  and conveyed along the sheet path R. The recording medium P is then fed by the resisting roller pair  24  into a nip formed by the roller  6  and the second transfer roller  20  at an appropriate sheet-feeding timing. The resisting roller pair  24  is located at an upstream position of the second transfer roller  20  in a sheet-conveying direction. In this process, the second transfer roller  20  is applied with a transfer voltage of a polarity opposite the polarity of the toner included in the toner image carried on the intermediate transfer belt  7 . As a result, the toner image carried on the intermediate transfer belt  7  (i.e., the full-color toner image formed by the four single-color toner images) is transferred from the outer surface of the intermediate transfer belt  7  onto the recording medium P. The recording medium P to which the toner image has been transferred is then conveyed to the fixing unit  22  and has heat and pressure applied thereto, so that the toner image is fused and fixed on the recording medium P. Thereafter, the recording medium P on which the toner image has been fixed is conveyed to the sheet-discharging unit  23  which is located at an end of the sheet path R in an upper part of the image forming apparatus  1 . Then, the recording medium P is discharged to the sheet-stacking area  36  which forms an upper portion of the image forming apparatus  1 . After the toner image is transferred from the outer surface of the intermediate transfer belt  7  to the recording medium P, toner remaining on the outer surface of the intermediate transfer belt  7  is removed by the intermediate transfer belt cleaning unit  21 . 
     In the thus configured image forming apparatus  1 , the four image forming units  8 Y,  8 C,  8 M, and  8 K face the intermediate transfer belt  7  so that the toner images of the respective colors formed by the image forming units  8 Y,  8 C,  8 M, and  8 K are transferred to the intermediate transfer belt  7 , with the toner images of the respective colors sequentially superimposed. According to the image forming apparatus  1 , therefore, the time required for performing the image transferring operation is substantially reduced, compared with an image forming apparatus which uses a single image forming unit having four developing units for performing the image transferring operation of transferring toner images from the image forming unit to the intermediate transfer belt and then to the recording medium P. 
     Further, forming the upper portion of the image forming apparatus  1 , the sheet-stacking area  36  does not outwardly protrude from the image forming apparatus  1 . As a result, the size of the image forming apparatus  1  is reduced. 
     The image forming apparatus  1  forms a full-color image on the recording medium P, as described above. The image forming apparatus  1  can also form a single-color image by using one of the image forming units  8 Y,  8 C,  8 M, and  8 K. Similarly, the image forming apparatus  1  can form a two-color image or a three-color image by using two or three of the image forming units  8 Y,  8 C,  8 M, and  8 K. Further, the image forming apparatus  1  can form a monochrome (i.e., black-and-white) image by forming a latent image on the image carrying member  10 K included in the image forming unit  8 K, developing the latent image into a black toner image by the image forming unit  8 K, transforming the black toner image to the recording medium P, and fixing the black toner image on the recording medium P by the fixing unit  22 . 
     As described above, the sheet-discharging unit  23  is provided in the upper part of the image forming apparatus  1  on a right side in  FIG. 1 . The sheet-discharging unit  23  is covered by an outer cover  1 A which is also in the upper part of the image forming apparatus  1  on the right side in  FIG. 1 . As illustrated in  FIG. 2 , the operation panel  60  and the tray  46  are provided on the outer cover  1 A such that a user of the image forming apparatus  1  can operate the operation panel  60  and the tray  46  from a front side of the image forming apparatus  1  (i.e., the right side in  FIG. 1 ). The tray  46  can be opened in the direction F and closed in the direction E illustrated in  FIG. 1 . 
     Operations of the image forming apparatus  1  are performed through the operation panel  60 . The tray  46  stores thereon the recording medium P. In the present example, the operation panel  60  is located at the right side of the image forming apparatus  1  where the sheet-discharging unit  23  is provided. Alternatively, the operation panel  60  may be provided at another side of the image forming apparatus  1 . 
     As illustrated in  FIG. 1 , the divider plate  50  is provided below the sheet-stacking area  36  in the image forming apparatus  1 . The divider plate  50  is located between the sheet-stacking area  36  and an upper side of the intermediate transfer belt  7  such that the toner bottle housing space  51  is formed in the image forming apparatus  1 . In the toner bottle housing space  51 , the toner bottles  37 ,  38 ,  39 , and  40  are provided below the sheet-stacking area  36  such that the direction perpendicular to a sheet-discharging direction C (i.e., direction of discharging the recording medium P) corresponds to the longitudinal direction of each of the toner bottles  37 ,  38 ,  39 , and  40 , as illustrated in  FIGS. 1 and 3 . The toner bottles  37 ,  38 ,  39 , and  40  contain the yellow toner, the cyan toner, the magenta toner, and the black toner, respectively. The toner bottles  37 ,  38 ,  39 , and  40  are connected to the developing units  12 Y,  12 C,  12 M, and  12 K of the image forming units  8 Y,  8 C,  8 M, and  8 K, respectively, via toner supply paths (not illustrated). Therefore, as the toner in any one of the developing units  12 Y,  12 C,  12 M, and  12 K decreases in amount, toner is supplied from a corresponding one of the toner bottles  37 ,  38 ,  39 , and  40 . 
     Further, the toner bottles  37 ,  38 ,  39 , and  40  are arranged in the toner bottle housing space  51  in an ascending order from the toner bottle  40  (i.e., the toner bottle closest to the sheet-discharging unit  23 ) to the toner bottle  37  (i.e., the toner bottle farthest from the sheet-discharging unit  23 ) such that the toner bottle  40  is at the lowest level and the toner bottle  37  is at the highest level among the four toner bottles  37 ,  38 ,  39 , and  40 . The sheet-discharging unit  23  is at a higher level than the toner bottle  40  and at an approximately equal level to the toner bottle  37 . 
     Furthermore, the toner bottles  37 ,  38 ,  39 , and  40  are detachably held by the holder  52  in the toner bottle housing space  51 . The holder  52  holds up the toner bottles  37 ,  38 ,  39 , and  40  so that the toner bottles  37 ,  38 ,  39 , and  40  can be attached to and detached from the image forming apparatus  1  in a space above the image forming apparatus  1  within a width D indicated in  FIGS. 2 and 3 . The direction of the width D is perpendicular to the sheet-discharging direction C within a single plane. Being held by the holder  52 , the toner bottles  37 ,  38 ,  39 , and  40  are appropriately positioned in the image forming apparatus  1 . 
     The sheet-stacking area  36  is formed on the image forming apparatus  1  to extend from a position below the sheet-discharging unit  23  toward the sheet-discharging direction C. The sheet-stacking area  36  includes an outer cover  1 D to cover the toner bottles  37 ,  38 ,  39 , and  40  housed in the toner bottle housing space  51 . Further, the sheet-stacking area  36  is shaft-supported on the image forming apparatus  1  so as to be opened and closed with respect to the image forming apparatus  1  in up-and-down directions, respectively. The fulcrum portion  41  is provided on an outer cover  1 E, which is at a left side of the toner bottle  37  in  FIG. 1 . The fulcrum portion  41  is positioned at a lower level than a top portion  37 A of the toner bottle  37 . As illustrated in  FIGS. 1 and 3 , the fulcrum portion  41  includes the shaft  42  and the shaft bearing  43 . The shaft  42  is provided on the image forming apparatus  1  in parallel with the width D perpendicular to the sheet-discharging direction C. The shaft bearing  43  is provided on a side of an end portion  36 B of the sheet-stacking area  36  to support the shaft  42 . Thus configured, the sheet-stacking area  36  formed by the outer cover  1 D is lifted up to depart from the sheet-discharging unit  23 , i.e., from a position at which a user operates the image forming apparatus  1 , and is lifted down to approach the sheet-discharging unit  23 . The sheet-stacking area  36  can be lifted up to a higher position than a position of the outer cover  1 A provided with the operation panel  60 . 
     The sheet-stacking area  36  is formed to be somewhat larger in size than the recording medium P sent out from the sheet-feeding unit  2 . Further, the sheet-stacking area  36  is formed in a slope such that an end portion  36 A close to the sheet-discharge unit  23  is at a lower level than the other end portion  36 B distant from the sheet-discharge unit  23 . The end portion  36 A (i.e., a lowest portion of the sheet-stacking area  36 ) is lower in level than a part of the sheet-discharge unit  23  from which the recording medium P is discharged. Meanwhile, the end portion  36 B (i.e., a highest portion of the sheet-stacking area  36 ) is at an approximately equal level to a highest portion  1 C of the outer cover  1 A. 
     With the configuration described above, the toner bottles  37 ,  38 ,  39 , and  40  are detachably provided in the image forming apparatus  1  so as to be attached to and detached from the image forming apparatus  1  in the space above the image forming apparatus  1  within the width D. Therefore, replacement work for replacing the toner bottles  37 ,  38 ,  39 , and  40  can be performed in the space above the image forming apparatus  1  within the width D. Accordingly, the usability of the image forming apparatus  1  is improved, and replacement of components of the image forming apparatus  1  can be conveniently performed. 
     As described above, the toner bottles  37 ,  38 ,  39 , and  40  are placed in parallel and in the ascending order from the toner bottle  40  to the toner bottle  37 . Therefore, when viewed from the position at which a user operates the image forming apparatus  1  (i.e., from a side of the sheet-discharging unit  23 ), the toner bottles  37 ,  38 ,  39 , and  40  are well viewable, not hidden by the sheet-discharging unit  23 . Accordingly, the usability of the image forming apparatus  1  is improved, and replacement of a component of the image forming apparatus  1  can be conveniently performed. 
     With the fulcrum portion  41  being provided on the outer cover  1 E at the left side of the toner bottle  37  distant from the sheet-discharging unit  23 , the sheet-stacking area  36  is opened and closed with respect to the image forming apparatus  1  around the fulcrum portion  41 . When the sheet-stacking area  36  is lifted open, therefore, the area of the toner bottle  37  (i.e., the toner bottle located close to the fulcrum portion  41 ) hidden by the sheet-stacking area  36  is reduced. Further, the sheet-stacking area  36  is opened and closed in the directions of departing from and approaching the position at which a user operates the image forming apparatus  1 . Therefore, the sheet-stacking area  36  can be opened and closed in a convenient manner. Further, the toner bottles  37 ,  38 ,  39 , and  40  are easily viewable from the position at which a user operates the image forming apparatus  1 . As a result, the usability of the image forming apparatus  1  is improved, and replacement of a component of the image forming apparatus  1  can be conveniently performed. Furthermore, the fulcrum portion  41  is provided at a lower level than the top portion  37 A of the toner bottle  37 . Therefore, the height of the sheet-stacking area  36 , when it is lifted up, is reduced. Thus, the toner bottles  37 ,  38 ,  39 , and  40  are easily viewable from the position at which a user operates the image forming apparatus  1 , with the size of the image forming apparatus  1  not increased. Accordingly, the usability of the image forming apparatus  1  is improved, and replacement of a component of the image forming apparatus  1  can be conveniently performed, 
     Further, the sheet-stacking area  36  can be lifted up to a position higher than the outer cover  1 A on which the operation panel  60  is provided. Therefore, the toner bottles  37 ,  38 ,  39 , and  40  are easily viewable from the position at which a user operates the image forming apparatus  1 . Accordingly, the usability of the image forming apparatus  1  is improved, and replacement of a component of the image forming apparatus  1  can be conveniently performed. 
     With reference to  FIGS. 4 and 5A  to  5 C, the operation panel  60  is described.  FIG. 4  illustrates the image forming apparatus  1 , as viewed from the front side thereof.  FIG. 5A  is a plane view of the operation panel  60 .  FIG. 5B  is an enlarged view of a part of the operation panel  60 .  FIG. 5C  is a sectional view cut across a line  5 C- 5 C in  FIG. 5A . 
     In  FIG. 4 , the sheet-stacking area  36  which forms a top cover of the image forming apparatus  1  is lifted open, and the toner bottles  37 ,  38 , and  39  excluding the front-most toner bottle  40  are viewable. As described above, the four toner bottles  37 ,  38 ,  39 , and  40  are placed in a line such that the longitudinal direction of each of the toner bottles  37 ,  38 ,  39 , and  40  is perpendicular to the direction of discharging of a recording medium P on which an image has been formed. That is, the toner bottles  37 ,  38 ,  39 , and  40  are placed in a line along the direction of discharging the recording medium P. 
     As illustrated in  FIG. 5A , the operation panel  60  comprises an information display part which includes a liquid crystal screen  61 , operation buttons  62 , LED (light-emitting diode) lenses  63 , LEDs  64 Y,  64 C,  64 M, and  64 K, labels  65 Y,  65 C,  65 M, and  65 K, and an illustration  66 . General functions and operations of components of the operation panel  60 , such as the liquid crystal screen  61  and the operation buttons  62 , are well known. Therefore, the functions and operations of the above components of the operation panel  60  are briefly described below. 
     The liquid crystal screen  61  displays a message indicating an operation performed, for example. The operation buttons  62  are pressed for performing a variety of operations. The LED lenses  63  indicate whether the image forming apparatus  1  is turned on or off, for example. The LEDs  64 Y,  64 C,  64 M, and  64 K indicate “toner-end” (i.e., a condition in which toner has run out) and “toner-near-end” (i.e., a condition in which toner has nearly run out), for example. The labels  65 Y,  65 C,  65 M, and  65 K are provided adjacent to the corresponding LEDs  64 Y,  64 C,  64 M, and  64 K. In the present example, the labels  65 Y,  65 C,  65 M, and  65 K are elongated rectangles extending in a direction parallel to the longitudinal direction of each of the toner bottles  37 ,  38 ,  39 , and  40 . The illustration  66  is provided on the left side of the labels  65 Y,  65 C,  65 M, and  65 K for indicating which part of the image forming apparatus  1  needs to be opened for performing a necessary operation. 
     As illustrated in  FIG. 4 , according to the image forming apparatus  1 , a user can properly see both the operation panel  60  and the toner bottles  37 ,  38 ,  39 , and  40  from the user&#39;s position which is usually at the front side of the image forming apparatus  1 . As illustrated in  FIGS. 4 and 5A , the LEDs  64 Y,  64 C,  64 M, and  64 K and the corresponding labels  65 Y,  65 C,  65 M, and  65 K are arranged in an order corresponding to an order of the toner bottles  37 ,  38 ,  39 , and  40  provided in the image forming apparatus  1 , which respectively contain the yellow toner, the cyan toner, the magenta toner, and the black toner. Therefore, when one of the LEDs  64 Y,  64 C,  64 M, and  64 K is turned on to indicate the toner-end or the toner-near-end, a user can easily see which one of the toner bottles  37 ,  38 ,  39 , and  40  is in a state of the toner-end or the toner-near-end. Further, the user can be prevented from replacing a wrong toner bottle. 
     The illustration  66  includes marks  67  (e.g., circled letters “A” and “Z” illustrated in  FIG. 5B ). Using an light emitter (not illustrated) such as an LED provided on an inside of the operation panel  60 , each of the marks  67  indicates a specific part of the image forming apparatus  1  which needs to be opened for a necessary operation. Therefore, when the sheet-stocking area  36  which forms the top cover of the image forming apparatus  1  needs to be opened for solving a paper jam problem, for example, a user can refer to the illustration  66  to find a part of the image forming apparatus  1  which needs to be opened (i.e., the sheet-stocking area  36 ). Also, if there are a plurality of parts to be opened, the user can see the order of opening the plurality of parts by checking the illustration  66 . Accordingly, an operator of the image forming apparatus  1 , such as an individual user and a service personnel, can smoothly perform any necessary operation such as a paper jam solving operation, without referring to much other information. 
     The above-described embodiments are illustrative, and numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative and exemplary embodiments herein may be combined with each other and/or substituted for each other within the scope of this disclosure and appended claims. It is therefore to be understood that within the scope of the appended claims, the disclosure of this patent specification may be practiced otherwise than as specifically described herein.