Abstract:
An image forming apparatus, having a sheet ejection section, provided in an upper portion of the image forming apparatus, for ejecting a recording sheet onto an upper surface portion of the image forming apparatus; a sheet post-processing apparatus for receiving the recording sheet, ejected from the sheet ejection section, so as to perform a post-processing operation upon the recording sheet; and a coupler for coupling the sheet post-processing apparatus with the image forming apparatus so that at least a part of the post-processing apparatus is located on the upper surface portion of the image forming apparatus.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an image forming apparatus capable of being mounted with a sheet post-processing apparatus which conducts post-processing such as staple processing, or shift sorting processing, on a sheet ejected out of an image forming apparatus such as an electrophotographic copying machine, a printer and a facsimile machine. 
     There is used a sheet post-processing apparatus called a finisher as an apparatus which conducts collating and stapling with a stapler for the number of sets of copies for plural recording sheets which have thereon recorded images and are ejected out of an image forming apparatus. Further, some of the sheet post-processing apparatuses have functions of shift sorting processing, collating processing, punching processing and bookbinding processing, in addition to the aforesaid staple processing. 
     This finisher is connected to an image forming apparatus such as a copying machine and a printer in terms of function, and it is driven in accordance with sequence operations of copy process or print process. 
     There is an image forming apparatus wherein a sheet ejection section is provided on the upper portion of the image forming apparatus, and a sheet having thereon formed images is ejected out of the sheet ejection section onto the top face of the apparatus to be stacked thereon, in the case of ordinary sheet ejection. 
     In TOKKAIHEI No. 9-309655, there is disclosed image forming apparatus 1 wherein image forming section 62 is arranged under sheet ejection section 61 and sheet-feeding section 63 is arranged under the image forming section 62, and a sheet is conveyed vertically. 
     Sheet S fed from sheet-feeding tray 631 of the sheet-feeding section 63 is fed to paired registration rollers 65 on sheet conveyance path 64. On the other hand, in synchronization with a toner image formed by writing unit 66 on photoreceptor drum 621 of the image forming section 62, the sheet S is conveyed from the paired registration rollers 65 to transfer section 622 where the toner image is transferred onto the sheet S. The sheet S carrying thereon the toner image is conveyed to fixing section 67 where the toner image is fixed, and then is conveyed to the sheet ejection section 61. Then, the sheet S is conveyed through horizontal conveyance path 681 of relay conveyance unit 68 provided on the upper portion of the image forming apparatus 1, to be fed into sheet post-processing apparatus FS. 
     The sheet post-processing apparatus FS conducts sheet post-processing such as staple processing, shift sorting and collating for the sheet S accepted by the sheet post-processing apparatus FS, and then, ejects the sheet S on a sheet ejection tray. 
     FIG.  7 ( b ) shows an another example of a conventional image forming apparatus wherein sheet conveyance in an image forming section is made to be in the vertical direction. On the upper portion of image forming apparatus 1, there is mounted sorter (mail box) ST having a sheet ejection tray with four bins. 
     Incidentally, sheet post-processing apparatuses are already disclosed in TOKKAISHO Nos. 60-142359, 60-158463, 62-239169, 62-288002, 63-267667, TOKKAIHEI Nos. 2-276691, 8-319054 and TOKKOHEI No. 5-41991. 
     In image forming apparatus 1 shown in FIG.  7 ( a ), sheet post-processing apparatus FS is connected to the side of image forming apparatus 1. Therefore, horizontal conveyance path 681 of relay conveyance unit 68 is made to be long and large and conveyance processing after sheet ejection is made to take a long time accordingly, which is a disadvantage, and sheet conveyance efficiency is lowered. Further, a housing which houses therein a staple processing section, a shift sorting processing section and a sheet intermediate stacking section (intermediate stacker section) is protruded bulkily from the side of image forming apparatus 1, which causes a disadvantage of increase in a floor space. 
     In image forming apparatus 1 shown in FIG.  7 ( b ), the total height as a system is increased, because sorter (mail box) ST as a sheet post-processing apparatus is connected to the top surface of image forming apparatus 1. In particular, if an image reading device (scanner) is provided on the upper portion of image forming apparatus 1, the scanning plane of the scanner is heightened to make an operation difficult. In addition to that, the number of bins in the sorter and the number of sheets to be stacked are restricted. 
     An object of the invention is to correct the aforesaid disadvantage in an image forming apparatus equipped with a conventional sheet post-processing apparatus and to attain the following objects. 
     (1) To improve copying productivity by shortening a sheet conveyance path in the image forming apparatus and in the sheet post-processing apparatus and thereby by reducing sheet conveyance time, and to improve sheet conveyance efficiency and lower the cost by simplifying the sheet conveyance mechanism. 
     (2) To offer a compact system by reducing the floor space of the image forming apparatus equipped with a sheet post-processing apparatus. 
     (3) To offer a sheet post-processing apparatus capable of being provided with multi-deck sheet ejection tray (for example, sheet ejection tray with 10-20 bins) or with a movable sheet ejection tray having a long distance to go up and down on which a large number of sheets (for example, 2000 sheets) can be stacked. 
     SUMMARY OF THE INVENTION 
     The object stated above can be attained by an image forming apparatus having on the upper portion thereof a sheet ejection section which ejects a sheet having thereon formed images onto the top face of the image forming apparatus, wherein a sheet post-processing apparatus having a sheet conveyance section capable of being connected to the sheet ejection section is installed removably on the top face of the image forming apparatus. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagram of the total structure of an image forming apparatus equipped with a sheet post-processing apparatus and an automatic document feeder. 
     FIG. 2 is a sectional view showing the structure of the upper portion of the image forming apparatus from which the sheet post-processing apparatus has been removed. 
     FIG. 3 is a sectional view of the sheet post-processing apparatus. 
     Each of FIGS.  4 ( a )- 4 ( c ) is an illustrative diagram showing how a sheet is conveyed by the sheet post-processing apparatus. 
     FIG. 5 is a sectional view of an image forming apparatus showing how a sheet ejection tray is mounted. 
     FIG. 6 is a side view of the left side of an image forming apparatus from which a sheet post-processing apparatus and a sheet ejection tray have been removed. 
     FIGS.  7 ( a ) and  7 ( b ) represent a structure diagram of an image forming apparatus equipped with a conventional sheet post-processing apparatus. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Next, an embodiment of the image forming apparatus equipped with a sheet post-processing apparatus will be explained based on the diagrams attached hereto. 
     FIG. 1 is a diagram of the total structure of image forming apparatus  1  equipped with sheet post-processing apparatus (finisher) FS, automatic document feeder DF and image reading device (scanner) Y. 
     The illustrated image forming apparatus  1  is equipped with image processing section  2 , image writing section  3 , image forming section  4 , high voltage power supply sections  5 A and  5 B, cassette sheet-feeding section  6 , fixing unit  7 , sheet ejection section  8  and automatic duplex copy sheet-feeding section (ADU)  9 . 
     On the upper portion of the image forming apparatus  1 , there are mounted image reading device Y and automatic document feeder DF. On the part of sheet ejection section  8  on the illustrated left side of the image forming apparatus  1 , there is connected sheet post-processing apparatus (finisher) FS. 
     Document d placed on a platen of automatic document feeder DF is conveyed in the arrayed direction, and images on one side or on both sides are read by an optical system of image reading device Y, and then are read into CCD image sensor Y 1 . 
     Analog signals obtained through photoelectric transfer by CCD image sensor Y 1  are subjected to analog processing, A/D transfer, shading correction, and image compression processing at the image processing section, and then, signals are sent to image writing section  3 . 
     In the image writing section  3 , light outputted from a semiconductor laser is irradiated on a photoreceptor drum of image forming section  4 , and a latent image is formed. In the image forming section  4 , processing operations such as charging, exposure, developing, transfer, separation and cleaning are conducted, and images are transferred onto sheet S conveyed from cassette sheet-feeding section  6 . The sheet S carrying images is subjected to fixing by fixing unit  7 , and is fed into sheet post-processing apparatus FS from sheet ejection section  8 . Or, sheet S on which image processing has been finished on one side thereof fed into automatic duplex copy sheet-feeding section  9  by conveyance path switching plate  8 A is subjected again to duplex image forming at image forming section  4 , and then is fed into sheet post-processing apparatus FS from sheet ejection section  8 . 
     The sheet post-processing apparatus FS is removably installed on the upper portion of the main body of image forming apparatus  1 . In the sheet post-processing apparatus FS, sheet conveyance section  10 , sheet stacking section  20 , sheet post-processing section  30  and movable sheet ejection tray section  40  are arranged to be almost in the horizontal direction. 
     FIG. 2 is a sectional view showing the structure of the upper portion of image forming apparatus  1  from which sheet post-processing apparatus FS is removed. 
     In FIG.  1  and FIG. 2, on the right side in the image forming apparatus main body, image forming section  4  is provided at the center, cassette sheet-feeding section  6  is provided under the image forming section  4  in the direction of the height of the apparatus main body, and fixing unit  7  and sheet ejection section  8  are provided above the image forming section  4 . Due to this vertical arrangement, sheet conveyance path (1) which is almost in the vertical direction is formed. Sheet S fed out of cassette sheet-feeding section  6  is conveyed along this vertical upper sheet conveyance path (1) to be ejected out of the apparatus main body. 
     Sheet conveyance path (2) formed by automatic duplex copy sheet-feeding section  9  is formed to be almost in parallel with this vertical sheet conveyance path (1). 
     Owing to these vertical sheet conveyance paths (1) and (2) thus formed, there is structured a shortest sheet conveyance path from cassette sheet-feeding section  6  to sheet ejection section  8 . By opening one side of the apparatus main body, it is possible to make the sheet conveyance paths (1) and (2) to be exposed easily. 
     In the vertical conveyance system like this, main structural means can be concentrated on one side of the apparatus main body. Therefore, it is possible to form concave space section  1 A on the top surface section of the apparatus main body and to form concave space section  1 B at the central section of the apparatus main body. These concave space sections  1 A and  1 B are formed to be lower in terms of position than a sheet ejection outlet of sheet ejection section  8 . 
     When sheet post-processing apparatus FS is mounted on image forming apparatus  1 , sheet conveyance section  10  of the sheet post-processing apparatus FS is housed in the aforesaid concave space section  1 A. In this case, sheet inlet section  10 A of the-sheet conveyance section  10  is connected with sheet ejection outlet  8 B of sheet ejection section  8  in image forming apparatus  1 . Further, under this state of mounting, sheet stacking section  20  and sheet post-processing section  30  of sheet post-processing apparatus FS are housed in the aforesaid concave space section  1 B. Movable sheet ejection tray section  40  composed of plural sheet ejection trays and means to move up and down is positioned on the side of the apparatus main body. 
     FIG. 3 is a sectional view of sheet post-processing apparatus FS. 
     In FIG. 3, sheet post-processing apparatus FS is composed of sheet conveyance section  10 , sheet stacking section  20 , sheet post-processing section  30  and movable sheet ejection tray  40  to be unitized as a unit which can be mounted on and dismounted from the apparatus main body, and it can be drawn out along a guide rail toward this side of the drawing. 
     The positioning of the post-processing apparatus, in relation to the apparatus main body, is carried out by, for example, inserting a roller, provided in the post-processing apparatus, to the dent portion provided in the apparatus main body. Therefore, a coupling member is configured with such guide rail, roller or the like. 
     The sheet conveyance section  10  is composed of sheet conveyance guide plate  11  which is connected with inlet section  10 A facing sheet ejection outlet  8 B of sheet ejection section  8  and guides ejected sheet S to sheet stacking section  20  and of sheet conveyance paired rollers  12  which nip sheet S to convey it. The sheet conveyance guide plate  11  forms a conveyance path which is mostly horizontal. 
     The sheet stacking section  20  is composed of conveyance belt  21 , driven rollers  22 A and  22 B which come in pressure contact with the conveyance belt  21  to be driven to rotate, guide plate  22 C located on the upper side of the conveyance belt  21 , driving roller  23 A which is arranged at the downstream side of the conveyance of the conveyance belt  21  and is connected with a driving source to rotate regularly and reversely, driving roller  23 B which is swung to be capable of coming in contact with or parting from the driving roller  23 A, stacking stand  24  on which the sheet S ejected from the conveyance belt  21  is stacked, width adjusting means  25  which regulates a width of sheet S stacked on the stacking stand  24  to true up the sheet edge, stopping means (stopper)  26  which is hit by the leading edge in the advancement direction of sheet S stacked on the stacking stand  24  to determine the position in the conveyance direction, and ring-shaped auxiliary conveyance member  27  which feeds sheet S stacked on the stacking stand  24  into the stopper  26 . 
     The sheet post-processing section  30  is composed of stapling means (stapler)  31  which forces staple SP into a bundle of sheets and moving means  32  which moves the stapler  31  to the prescribed position to rotate it. 
     The movable sheet ejection tray  40  is composed of plural bins  41  which are arranged obliquely, and elevator means  42  which moves the bins  41  up and down in the vertical direction. 
     Incidentally, though the illustrated sheet post-processing apparatus FS is equipped with bins  41  of four steps, there are margin spaces at the lower portion and the upper portion of the movable sheet ejection tray  40 . Therefore, it is possible to install sheet post-processing apparatus FS having the greater number of bins (for example, the sheet post-processing apparatus with 10-20 bins). Further, this sheet post-processing apparatus FS can also have a function for sorting such as a mail box. 
     Each of FIGS.  4 ( a )- 4 ( c ) is an illustration showing how sheet S is conveyed in sheet post-processing apparatus FS. 
     (1) First conveyance path (3) (see FIG.  4 ( a )) 
     Sheet S having thereon formed images ejected from sheet ejection outlet  8 B of sheet ejection section  8  in image forming apparatus  1  is led to inlet section  10 A of sheet conveyance section  10  in sheet post-processing apparatus FS, then, it passes through a conveyance path in sheet conveyance guide plate  11 , and is nipped by rotating sheet conveyance paired rollers  12  and is conveyed to be fed into sheet stacking section  20 . 
     The sheet S fed into the sheet stacking section  20  is conveyed by rotating conveyance belt  21  and by driven rollers  22 A and  22 B which are in pressure contact with the conveyance belt  21 . The leading edge section of the sheet S is nipped between driving roller  23 A which is located at the downstream side in conveyance and rotates in the regular direction and driving roller  23 B to pass, and goes up along the inclined face of bin  41  of the movable sheet ejection tray  40 . When the trailing edge section of the sheet S passes through the nipping position between the conveyance belt  21  and driven roller  22 B, the trailing edge section of the sheet S is lowered by gravity and it touches the inclined face of the stacking stand  24 . 
     (2) Second conveyance path (4) (see FIG.  4 ( b )) 
     After the passage of the trailing edge of sheet S is detected by sensor PS 1  provided in the vicinity of conveyance belt  21 , the prescribed time is measured by the timer, and driving roller  23 B is driven to rotate reversely, and thereby, rotation of driving roller  23 A driven by the same driving source is stopped through a one-way clutch. Incidentally, driving roller  23 B is made of soft foamed material such as a sponge roller, and it comes in slight pressure contact with sheet S on driving roller  23 A. 
     Due to switching to the reverse rotation of driving roller  23 B, sheet S which is in slight pressure contact with driving roller  23 B rotating reversely and driving roller  23 A which stops at the nipping position is conveyed downward obliquely on stacking stand  24 , and then is stopped when the trailing edge of the sheet S hits stopper  26 . When the sheet is conveyed downward obliquely, auxiliary conveyance member  27  conveys the sheet while preventing that the sheet is lifted. 
     Paired width adjusting means  25  provided rotatably on both sides of the stacking stand  24  can move in the direction perpendicular to the sheet conveyance direction, and they are opened to be broader than the sheet width when they accept the sheet conveyed on the stacking stand  24 , and they tap the side of sheet S in its lateral direction and conduct truing up of a bundle of sheets (width adjustment) when the sheet is conveyed on the stacking stand  24  and is stopped by stopper  26 . 
     Succeeding sheet S also passes through the first conveyance path (3) and the second conveyance path (4) in the same way, and is stacked successively on the preceding sheet S on the stacking stand  24 , and it is adjusted in terms of width each time it is stacked and comes in contact with the stopper to be stopped. 
     After trailing edges of all sheets S equivalent to one copy come in contact with stopper  26 , staple SP is forced into a bundle of sheets by stapler  31 , thus, a booklet is formed. 
     (3) Third conveyance path (5) (see FIG.  4 ( c )) 
     After completion of the staple processing, the suspended driving roller  23 A is switched to the regular rotation, and a bundle of sheets nipped between the driving roller  23 A and the driving roller  23 B which has been switched to strong pressure contact by a cam and others is conveyed upward obliquely to be housed in bin  41 . 
     FIG. 5 is a sectional view of image forming apparatus  1  showing how sheet ejection tray (fixed sheet ejection tray)  50  is mounted. 
     Positioning of unitized sheet post-processing apparatus FS is released, and it is drawn out of image forming apparatus  1  through a guide rail by pulling toward this side in FIG.  1 . 
     Next, sheet ejection tray  50  is inserted into concave space sections  1 A and  1 B on the upper portion of the image forming apparatus by pushing it from this side to the back side on the page, and the sheet ejection tray  50  is fixed. The sheet S requiring no post-processing can be ejected from sheet ejection section  8  to be stacked on the sheet ejection tray  50 . 
     FIG. 6 is a side view of the left side of image forming apparatus  1  from which sheet post-processing apparatus FS and sheet ejection tray  50  have been removed. 
     It is possible to get an unbroken view of sheet ejection outlet  8 B of sheet ejection section  8  and an sheet ejection roller from the left side of image forming apparatus  1 . Below the sheet ejection outlet  8 B, the concave space section  1 A on the upper step and the concave space section  1 B on the lower step are arranged to be opened. In the convex section on the illustrated left side of the concave space sections  1 A and  1 B, there are housed driving mechanism, a power supply section and control sections. 
     In the image forming apparatus  1  of the present embodiment, a sheet feeding means of cassette sheet feeding section  6 , image forming section  4 , fixing unit  7  and sheet ejection section  8  are provided upward in this order vertically in the main body of the image forming apparatus  1  as stated above. Therefore, it is possible to minimize the number of reversing sections in the conveyance path for sheet S, and thereby to restrain occurrence of problems such as conveyance troubles (occurrence of jam). 
     Incidentally, automatic duplex copy sheet feeding section (ADU)  9  is arranged on the side (right side in FIG. 1) which is opposite to that where a sheet-feeding cassette of cassette sheet feeding section  6 , high voltage power supply sections  5 A and  5 B and image writing section  3  are provided. 
     Further, since the image forming apparatus  1  is structured as stated above, concave space sections  1 A and  1 B are formed on the other side of the fixing unit  7  and sheet ejection section  8 . In the present embodiment, in particular, a useless space is formed between the image forming apparatus  1  and image reading device Y, because the image reading device Y is provided on the top surface of the main body of the image forming apparatus  1 . 
     In the present embodiment, therefore, sheet post-processing apparatus FS is provided removably in that space. In the structure in this case, a part of the sheet post-processing apparatus FS (including sheet conveyance section  10 , sheet stacking section  20  and sheet post-processing section  30 ) is arranged on the upper portion (above the sheet-feeding cassette of cassette sheet feeding section  6  and image writing section  3 ) of the image forming apparatus  1 , and movable sheet ejection tray section  40  wherein a large number of bins are arranged vertically is arranged to be protruded from the side of the main body of the image forming apparatus  1 . 
     Therefore, it is possible to shorten the conveyance path for sheet S ejected from sheet ejection section  8  of the image forming apparatus  1  and thereby to reduce the sheet conveyance time to improve copying productivity, and it is also possible to simplify the sheet conveyance structure for improvement of sheet conveyance and reduction of manufacturing cost. 
     It is further possible to reduce a floor space for the image forming apparatus  1  equipped with sheet post-processing apparatus FS, and thereby to attain a compact system. Further, the movable sheet ejection tray section  40  can be made to be one with multiple steps (having the steps in quantity not less than four steps in the present embodiment illustrated), or to be one on which a large number of sheets can be stacked. 
     In the present embodiment, it is further possible to install sheet ejection tray  50  or sheet post-processing apparatus FS in concave space sections  1 A and  1 B. Namely, sheet ejection tray  50  and sheet post-processing apparatus FS are made to be replaceable each other so that either one of them may be installed. It is therefore possible to establish a necessary system simply without increasing a floor space, in compliance with user&#39;s demands. 
     Though the sheet post-processing apparatus connected to a copying machine is shown in the present embodiment, the invention can also be applied to a sheet post-processing apparatus used through connection to an image forming apparatus such as a printer and a facsimile machine or to a printing machine of a popular type. For example, it is also possible to apply to one which is made to be of printer specifications by removing the image reading device Y installed removably on the image forming apparatus  1 . 
     In the image forming apparatus of the invention, owing to the structure wherein a concave space section is formed on the upper surface section of the apparatus, and a sheet post-processing apparatus equipped with a sheet conveyance section having a horizontal conveyance path, a sheet stacking section and with a sheet post-processing section is unitized to be capable of being installed on the concave space section, it is possible to minimize a floor space of an image forming apparatus equipped with a sheet post-processing apparatus. 
     In addition, by making a sheet conveyance path from a sheet ejection section to a post-processing section to be shortened, an improvement of efficiency of sheet conveyance is attained. 
     Further, due to the fixed sheet ejection tray which can be mounted on the concave space section stated above, it is possible to minimize a floor space to attain compactness by eliminating the protruded portion on the main body of the image forming apparatus, even when a sheet post-processing apparatus is not mounted, and to improve sheet handling efficiency.