Patent Publication Number: US-6983931-B2

Title: Sheet folding and binding apparatus and method

Description:
This is a divisional of application Ser. No. 09/896,737, filed Jun. 29, 2001, now U.S. Pat. No. 6,755,410. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a binding apparatus, and in particular relates to a binding apparatus that is connected with a sheet discharging part of an image forming apparatus, such as a printer and a copier, and that folds a sheet received from the image forming apparatus and binds stacked folded sheets at the folded side parts of the folded sheets. 
   2. Discussion of the Background 
   A binding technology used in producing weekly magazines is well known. After printed sheets are stacked and jogged, the stacked printed sheets are stapled at their center portions by a stapling device. The stapled sheets are then folded at their stapled portions. Because the stapled sheets are folded at their stapled portions, the side edges of the folded sheets, opposite the stapled and folded side of the folded sheets, are not uniform. Therefore, the side edges of the folded sheets, opposite the stapled and folded side, are cut off by a cutting apparatus so as to be uniform. 
   A binding apparatus is known to be connected with a copying machine, downstream of a sheet discharging part of the copying machine in the sheet discharging direction. The binding apparatus sorts or collates sheets carrying an image on one or both sides of the sheets, which have been discharged from the copying machine, and then jogs and binds the sheets into a stack of sheets. 
   In the binding technology used in producing a weekly magazine, as described above, the side edges of the folded sheets, opposite the stapled and folded side of the folded sheets, must be cut off by a cutting apparatus so as to be uniform. Noise is produced when the side edges of the folded sheets are cut off by the cutting apparatus. The cutting apparatus is relatively large, heavy and expensive. The life of a knife used in the cutting apparatus is relatively short. Further, the consumption of electric power is relatively large. When the number of printed sheets, which must be folded, is large, the folding apparatus may not sufficiently fold the sheets. 
   A binding apparatus used in conjunction with a copying machine generally stacks sheets, which have been received from the copying machine, without folding each of the sheets, into a stack of sheets, and then staples the stacked sheets. The stacked sheets are stapled at edge portions of the sheets at one side. Therefore, when a sheet of the stack of stapled sheets is pulled, the stapled part of the pulled sheet is easily torn, so that the pulled sheet is taken apart from the stack of stapled sheets. For avoiding this problem, the stapling position for a stack of sheets must be located well inside of the stack of sheets toward the center portion thereof. This may result in stapling the sheets at a part of the image area of each sheet, so that the inconvenience may be caused such that a part of the image at the stapled part of each sheet cannot be seen. For avoiding the inconvenience, the image must be formed on each sheet with a relatively large margin for stapling, which then reduces the area in each sheet where an image can be formed. 
   SUMMARY OF THE INVENTION 
   The present invention has been made in view of the above-discussed and other problems and addresses the above-discussed and other problems. 
   Preferred embodiments of the present invention provide a novel binding apparatus of a relatively small size, that folds a sheet, and binds stacked folded sheets so that side edges of the bound folded sheets are uniform. The preferred embodiments of the present invention further provide a novel binding apparatus and method that folds a sheet, carrying images of two pages on one side of the sheet and another images of another two pages on the other side of the sheet, at a center portion of the sheet, and that binds folded sheets, which are stacked, at the folded side parts of the folded sheets. The preferred embodiments of the present invention further provide a novel binding apparatus that reliably binds stacked folded sheets without loosening the stack. The preferred embodiments of the present invention further provide a novel binding apparatus that binds folded sheets into a stack of folded sheets so that each of the bound folded sheets is hard to be torn so as not to be easily pulled out of the stack of folded sheets. The preferred embodiments of the present invention further provide a novel binding apparatus and method that binds sheets with a relatively small binding margin so that a relatively large area of each sheet can be used for forming an image thereupon. The preferred embodiments of the present invention further provide a novel sheet folding apparatus that reliably folds a sheet. The preferred embodiments of the present invention further provide a novel jogging apparatus that reliably jog sheets which have been folded at their center portions. The preferred embodiments of the present invention further provide a novel image forming and binding system that allows to form images of image or document data of two pages on one side of a sheet and another images of another two pages on the other side of the sheet, fold the sheet at a center portion thereof, and bind the folded sheets, which are stacked, at the folded side parts of the folded sheets. 
   According to a preferred embodiment of the present invention, a binding apparatus includes a receiving device configured to receive a sheet from outside and convey the sheet, and a sheet folding device configured to fold the sheet, conveyed by the receiving device, in two at a center portion thereof in a direction the sheet is conveyed, so as to be a folded sheet, and convey the folded sheet with the folded portion thereof being a leading edge of the folded sheet. A jogging device includes a jogging table and is configured to receive and jog the folded sheet, conveyed by the sheet folding device, one after another, so as to be stacked into a stack of folded sheets on the jogging table. A binding device is configured to bind the stack of folded sheets stacked on the jogging table at an edge portion of the stack of folded sheets at the side where the folded portion of each folded sheet of the stack of folded sheets is located. A discharging device is configured to discharge the bound stack of folded sheets. 
   The binding apparatus may further include a controller to control an operation of the apparatus. The controller receives information on a size of the sheet conveyed from outside. Further, the sheet folding device includes a guiding device configured to guide the sheet conveyed by the receiving device, and a sheet folding/pressing device configured to fold the sheet conveyed by the receiving device and press the folded sheet. The guiding device includes a stopping device configured to stop the sheet being conveyed by the receiving device to be conveyed, and a position the stopping device stops the sheet to be conveyed is set by the controller according to the information on the size of the sheet so that the sheet is folded at the center portion of the sheet by the sheet folding/pressing device. The sheet being conveyed by the receiving device is stopped to be conveyed by the stopping device, so that the center portion of the sheet is downwardly slackened, the slackened centered portion of the sheet is pinched into the sheet folding/pressing device, and thereby the sheet is folded in two at the center portion thereof by the sheet folding/pressing device. 
   The sheet folding device may further include a detect device configured to detect a leading edge of the sheet guided by the guiding device, a pushing device configured to push the slackened center portion of the sheet toward the sheet folding/pressing device, and a pushing device moving device configured to move the pushing device downwardly toward the sheet folding/pressing device so as to push the slackened center portion of the sheet toward the folding/pressing device and upwardly so as to separate from the sheet folding/pressing device. The pushing device moving device moves the pushing device downwardly to push the slackened center portion of the sheet toward the sheet folding/pressing device at a predetermined timing after detection of the leading edge of the sheet with he detect device, so that the slackened center portion of the sheet is pushed by the pushing device so as to be pinched into and thereby the sheet is folded in two at the center portion thereof by the sheet folding/pressing device. 
   The pushing device may include a saw-toothed knife to push the center portion of the sheet, so that the sheet is perforated at the pushed center portion of the sheet when the saw-toothed knife pushes the center portion of the sheet. 
   The sheet folding device may include a sheet folding/pressing device having a pair of sheet folding rollers and a pair of supplementary pressing rollers. The pair of supplementary pressing rollers is arranged downstream of the pair of sheet folding rollers in the direction the folded sheet is conveyed and is angled relative to the pair of sheet folding rollers, and a distance between a nip portion of the pair of supplementary rollers and a nip portion of the pair of the sheet folding rollers at a position corresponding to a widthwise edge of the folded sheet, at a side of a widthwise direction where the pair of the supplementary rollers and the pair of sheet folding rollers are farther separated from each other, is shorter than a length of the folded sheet in the direction the folded sheet is conveyed. 
   The jogging device may include a leading edge stopping device configured to stop the folded sheet to be conveyed at the leading edge thereof, and a left side jogging device configured to jog the folded sheet with respect to a left side of the folded sheet in a direction the folded sheet is conveyed, a right side jogging device configured to jog the folded sheet with respect to a right side of the folded sheet, and a rear side jogging device configured to jog the folded sheet with respect to a rear side of the folded sheet, each including an upper guide member to guide the folded sheet being conveyed by the sheet folding device toward the jogging table and a jogging member to jog the folded sheets on the jogging table, The upper guide member of each of the left side, right side and rear side jogging devices is configured to swing between a horizontal position where the upper guide member is substantially horizontal so as to hold down a previously conveyed folded sheet on the jogging table and so that the folded sheet being conveyed by the sheet folding device slides over an upper surface of the upper guide member to be stopped by the leading edge stopping device and a slanted position where the upper guide member is upwardly slanted. Each of the left side, right side and rear side jogging devices is configured to move to a first position where the upper guide member thereof in the horizontal position separates from the folded sheet carried on the upper surfaces of the upper guide members of the left side, right side and rear side jogging devices and to a second position where the jogging member thereof is in a position corresponding to a size of the folded sheet being conveyed by the folding device, which is determined by the controller according to the information on the size of the sheet. When the folded sheet is conveyed to the jogging device by the sheet folding device, each of the left side, right side and rear side jogging devices is in the second position and the upper guide member of each of the left side, right side and rear side jogging devices is in the horizontal position. 
   After the folded sheet has been conveyed by the folding device to the jogging device so as to slide over the upper surfaces of the upper guide members of the left side, right side and rear side jogging devices, each of the left side, right side and rear side jogging devices moves, with the upper guide member thereof kept in the horizontal position, to the first position, where the upper guide member of each of the left, right and rear side jogging devices is swung to the slanted position, and each of the left, right and rear sides jogging devices is then moved to the second position, where the upper guide member of each of the left side, right side and rear side jogging devices is returned to the horizontal position. 
   The leading edge stopping device may include a leading edge binding position adjusting device configured to change a position the leading edge stopping device stops the folded sheet to be conveyed so that a position in the folded sheet relative to the leading edge thereof where the binding device binds the folded sheet is changed. 
   The folding device may include a detect device configured to detect that the folded sheet is discharged toward the jogging device, and the jogging device may include a sheet center thrusting device configured to swing between a horizontal position to downwardly thrust the folded sheet carried on the upper surfaces of the upper guide members of the left side, right side and rear side jogging devices and a slanted position where the sheet center thrusting device is upwardly slanted, and a sheet center thrusting device driving device configured to drive the sheet center thrusting device so as to swing between the horizontal position and the slanted position. 
   The sheet center thrusting device driving device drives the sheet center thrusting device downwardly to move to the horizontal position so as to downwardly thrust the folded sheet carried on the upper surfaces of the upper guide members of the left side, right side and rear side jogging devices, after the detect device detects that the folded sheet has been discharged toward the jogging device, and to swing back to the slanted position, after each of the left side, right side and rear side jogging devices in the second position moves toward outside to the first position, moves again toward inside to the second position after the upper guide member of each of the left side, right side and rear side jogging devices is swung to the slanted position, stops at the second position, and the upper guide member of each of the left side, right side and rear side jogging devices is swung to the horizontal position. 
   When the binding device binds the stack of folded sheets stacked on the jogging table, the jogging member of each of the left side, right side and rear side jogging devices is in the second position, the upper guide member of each of the left side, right side and rear side jogging devices is in horizontal position, and the sheet center thrusting device is in the horizontal position. 
   According to another preferred embodiment of the present invention, a sheet folding apparatus includes a pair of sheet folding rollers and a pair of supplementary pressing rollers. The pair of supplementary pressing rollers is arranged downstream of the pair of sheet folding rollers in a sheet conveyance direction and is angled relative to the pair of sheet folding rollers, and a distance between a nip portion of the pair of supplementary rollers and a nip portion of the pair of the sheet folding rollers at a position corresponding to a widthwise edge of the sheet, at a side of a widthwise direction where the pair of the supplementary rollers and the pair of sheet folding rollers are farther separated from each other, is shorter than a length of the folded sheet in the sheet feeding direction. A portion of a sheet is pinched into the pair of sheet folding rollers so that the sheet is folded in two by the pair of sheet folding rollers, and then the folded sheet is pressed by the pair of supplementary pressing rollers, so that the folded portion of the folded sheet is firmly folded. 
   According to another preferred embodiment of the present invention, a jogging apparatus includes a jogging table on which a sheet may be stacked one after another, and a leading edge stopping device configured to stop a sheet conveyed from outside at a leading edge thereof, a left side jogging device configured to jog the sheet with respect to a left side of the sheet in a direction the sheet is conveyed, a right side jogging device configured to jog the sheet with respect to a right side of the sheet, and a rear side jogging device configured to jog the sheet with respect to a rear side of the sheet. Each of the left side, right side, and rear side jogging devices includes an upper guide member to guide the sheet conveyed from outside onto the jogging table one after another so as to be stacked into a stack of sheets on the jogging table and a jogging member to jog the stack of sheets on the jogging table. The upper guide member of each of the left side, right side and rear side jogging devices is configured to swing between a horizontal position where the upper guide member is substantially horizontal so as to hold down a previously conveyed sheet on the jogging table and so that the sheet being conveyed from outside slides over an upper surface of the upper guide member to be stopped by the leading edge stopping device and a slanted position where the upper guide member is upwardly slanted. Each of the left side, right side and rear side jogging devices is configured to move to a first position where the upper guide member thereof in the horizontal position separates from the sheet carried on the upper surfaces of the upper guide members of the left side, right side and rear side jogging device and to a second position where the jogging member thereof is in a position corresponding to a size of the sheet being conveyed from outside. When the sheet is conveyed, each of the left side, right side and rear side jogging devices is in the second position and the upper guide member of each of the left side, right side and rear side jogging devices is in the horizontal. 
   According to another preferred embodiment of the present invention, an image forming and binding system includes an image formation controller configured to generate and transmit image or document data with page and sheet size information and printing and binding instructions thereof, and an image forming apparatus configured to form images of the image or document data received from the image formation controller on both sides of a sheet according to the page and sheet size information and the printing and binding instructions and discharge the sheet, and a binding apparatus configured to bind sheets received from the image forming apparatus. The image forming apparatus forms a second page image and a third page image of images of four pages of the image or document data on a first side of the sheet, which upwardly faces when the sheet is exited from the image forming apparatus, with the second page image at a leading edge side of the sheet in a direction the sheet is conveyed, and a first page image and a fourth page image of the images of four pages on a second side of the sheet, which downwardly faces when the sheet is exited from the image forming apparatus, with the first page image at the leading edge side of the sheet in the direction the sheet is conveyed, and the image formation controller controls the image forming apparatus to form the images of the image or document data starting from last four pages of the image or document data. The binding apparatus includes a controller to control an operation of the binding apparatus. The controller receives the sheet size information and the binding instruction from the image formation controller. A receiving device of the binding apparatus is configured to receive the sheet discharged by the image forming apparatus and convey the sheet. A sheet folding device is configured to fold the sheet, conveyed by the receiving device, in two at a center portion thereof in the direction the sheet is conveyed according to the sheet size information, and convey the folded sheet. A jogging device includes a jogging table and is configured to receive and jog the folded sheet, conveyed by the sheet folding device, one after another, so as to be stacked into a stack of folded sheets on the jogging table according to the sheet size information. A binding device is configured to bind the stack of folded sheets stacked on the jogging table at an edge portion of the stack of folded sheets at the side where the folded portion of each folded sheet of the stack of folded sheets is located according to the binding instruction, and a discharging device configured to discharge the bound stack of folded sheets. 
   According to another preferred embodiment of the present invention, a method of binding sheets includes receiving a sheet from outside and conveying the sheet; folding the conveyed sheet in two at a center portion thereof in a direction the sheet is conveyed so as to be a folded sheet and conveying the folded sheet with the folded portion of the fold sheet being a leading edge of the folded sheet with a sheet folding device; receiving and jogging the conveyed folded sheet one after another so as to be stacked into a stack of folded sheets with a receiving/jogging device; binding the stack of stacked folded sheets at an edge portion of the stack of folded sheets at the side where the folded portion of each folded sheet of the stack of folded sheets is located with a binding device; and discharging the bound stack of folded sheets. 
   The binding method may further include receiving information on a size of the sheet, and the folding/conveying may include receiving and guiding the conveyed sheet, setting a position where the conveyed sheet is stopped to be conveyed according to the size of the sheet so that the sheet is folded by the sheet folding device at the center portion of the sheet, and stopping the sheet to be conveyed at the position, so that the center portion of the sheet is downwardly slackened, the slackened center portion of the sheet is pinched into the sheet folding device, and thereby the sheet is folded in two at the center portioned of the sheet by the sheet folding device. 
   The folding/conveying may further include detecting a leading edge of the sheet, and pushing the slackened center portion of the sheet toward the sheet folding device with a pushing device at a predetermined timing after the detection of the leading edge of the sheet, so that the slackened center portion of the sheet is pinched into the sheet folding device. 
   In the above-described method, the pushing device may include a saw-toothed knife to push the slackened center portion of the sheet. In this case, the pushing includes perforating the sheet at the pushed center portion of the sheet with the saw-toothed knife. 
   In the above-described method, the sheet folding device may include a pair of sheet folding rollers and a pair of supplementary pressing rollers. The pair of supplementary pressing rollers is arranged downstream of the pair of sheet folding rollers in the direction the folded sheet is conveyed and is angled relative to the pair of sheet folding rollers, and a distance between a nip portion of the pair of supplementary rollers and a nip portion of the pair of the sheet folding rollers at a position corresponding to a widthwise edge of the folded sheet, at a side of a widthwise direction where the pair of the supplementary rollers and the pair of sheet folding rollers are farther separated from each other, is shorter than a length of the folded sheet in the direction the folded sheet is conveyed. In this case, the folding/pressing includes folding the sheet with the pair of sheet folding rollers and pressing the folded sheet with the pair of supplementary pressing rollers. 
   The binding method may further include receiving information on a size of the sheet and determining a size of the folded sheet folded at the center of the sheet, and the jogging device may include a leading edge stopping device to stop the folded sheet, an upper guide member to guide the folded sheet conveyed by the sheet folding device and a jogging member to jog the folded sheet. In this case, the receiving/jogging includes, sliding the conveyed folded sheet over an upper surface of the upper guide member of the jogging device, which is in a substantially horizontal position, to be stopped by the leading edge stopping device and to be carried on the upper surface of the upper guide member, moving the jogging device to a first position where the folded sheet carried on the upper surface of the upper guide member separates from the upper guide member to fall onto the jogging table, swinging the upper guide member from the horizontal position to a slanted position where the upper guide member is upwardly slanted, and moving the jogging device to a second position where the jogging member of the jogging device is in a position corresponding to the size of the folded sheet being received. 
   In the above-described method, the folding device may include a detect device to detect that the folded sheet is discharged toward the jogging device and a sheet center thrusting device to downwardly thrust the folded sheet carried on the upper surface of the upper guide member of the jogging device. In this case, the receiving/jogging further includes detecting that the folded sheet is discharged toward the jogging device with the detect device, and swinging the sheet center thrusting device between a substantially horizontal position where the sheet center thrusting device downwardly thrusts the folded sheet carried on the upper surface of the upper guide member of the jogging device and a slanted position where the sheet center thrusting device is upwardly slanted. 
   In the above-described method, in the binding, the jogging member of the jogging device is in the second position, the upper guide member is in the horizontal position, and the sheet center thrusting device is in the horizontal position. 
   The receiving/jogging may further include stopping the folded sheet to be conveyed at a leading edge of the folded sheet so that the folded sheet is jogged relative to the binding device, and adjusting a position to stop the folded sheet so that that a position in the folded sheet relative to the leading edge thereof where the binding device binds the stack of folded sheet is changed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the present 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 conjunction with accompanying drawings, wherein: 
       FIG. 1  is a schematic drawing illustrating an image forming and binding system according to a preferred embodiment of the present invention; 
       FIG. 2  is a schematic drawing illustrating a state of a sheet; 
       FIG. 3  is a cross section of a binding apparatus according to a preferred embodiment of the present invention; 
       FIG. 4  is a cross section illustrating a sheet receiving device, a sheet guiding part, a sheet folding part, and a supplementary pressing part of the binding apparatus; 
       FIG. 5  is cross section illustrating a driving mechanism of the sheet folding part, the supplementary pressing part and a knife unit of the sheet folding part of the binding apparatus; 
       FIG. 6  is a cross section illustrating a sheet stopping position adjusting mechanism of the binding apparatus; 
       FIG. 7  is cross section illustrating a mechanism of a jogging part of the binding apparatus; 
       FIG. 8  is a schematic drawing for explaining a positional relationship of a sheet folding roller pair of the sheet folding part and a supplementary pressing roller pair of the supplementary pressing part; 
       FIG. 9  is cross section illustrating mechanisms of a binding part and a stack discharging part of the binding apparatus; 
       FIG. 10  is a cross section for explaining the operations of a stapling position determining mechanism, a jogging table upwardly/downwardly moving mechanism and a sheet stack discharging part driving mechanism of the binding apparatus; 
       FIG. 11  is a plan view of a jogging table part of the binding apparatus; 
       FIG. 12  is a plan view of a part of the jogging table part for explaining an operation of jogging a sheet; 
       FIG. 13  is a cross section of the part of the jogging table part of  FIG. 10  for explaining the operation of jogging a sheet; 
       FIG. 14  is a schematic drawing of a part of the jogging table part for explaining the operation of jogging a sheet in conjunction with  FIG. 12 ; and 
       FIG. 15  is a cross section for explaining the operation of the sheet stack discharging part driving mechanism in conjunction with  FIG. 10 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, preferred embodiments of the present invention are described. 
     FIG. 1  is a schematic drawing illustrating an image forming and binding system according to a preferred embodiment of the present invention. Numeral  1  denotes an image formation controller, numeral  2  denotes a printer as an example of an image forming apparatus, and numeral  3  denotes a binding apparatus. 
   The image formation controller  1  is for example a personal computer including a display, a keyboard, a scanner, etc. The image formation controller  1  generates image or document data by inputting, or reading an image or a document with the scanner, and editing the data. The image formation controller  1  sets the page for the image or document data, sets various printing and binding instructions for printing the data and binding the printed sheets, e.g., the number of printed sets, the size of a sheet for printing, the stapling position, etc. Further, the image formation controller  1  displays a selected operational mode, the status of the system, the printer  2 , the binding apparatus  3  etc., with the display. 
   The image formation controller  1  stores the image or document data, read by the scanner, sent from a separate inputting apparatus or via a network, or generated by the image formation controller  1 . The image formation controller  1  edits the stored image or document data, for example, changes the pages of the stored image or document data. 
   The printer  2  forms an image of the data, sent from the image formation controller  1 , on a sheet conveyed from a sheet feeding part of the printer  2 . The printer  2  may use such image formation methods as an ink jet system and electrophotography. 
   The printer  2  reverses the sheet, after formation of an image on one side of the sheet, and then conveys the sheet to the image formation part of the printer  1  for forming another image on the other side of the sheet. The sheet carrying the images on both sides thereof is discharged from the discharging part of the printer  2 . 
   Referring to  FIG. 2  illustrating a state of a sheet, the binding apparatus  3  folds a sheet  4 , received from the printer  2 , in two at a center portion of the sheet  4  in a direction the sheet  4  is conveyed, so as to be a folded sheet  5 . The binding apparatus  3  stacks and jogs the folded sheet  5  into a stack of folded sheets  6 , and binds the stack of folded sheets  6  at binding positions  7  near the folded portion of the stack of folded sheets  6 . 
   The image formation controller  1  controls the printer  2  to form images of image or document data such that, when two images for two pages of the data are formed on one side of the sheet  4  and another two images for another two pages of the data are formed on the other side of the sheet  4 , as illustrated in the left portion of  FIG. 2 , a second page image and a third page image of the images of four pages are formed on an upper side of the sheet  4  (i.e., the side of the sheet  4 , which upwardly faces when the sheet  4  is exited from the printer  2 ) with the second page image at a leading edge side of the sheet  4  in the direction the sheet  4  is conveyed, and a first page image and a fourth page image of the images of four pages are formed on a back side of the sheet  4  (i.e., the side of the sheet  4 , which downwardly faces when the sheet  4  is exited from the image forming apparatus  2 ) with the first page image at the leading edge side of the sheet  4  in the direction the sheet  4  is conveyed. Accordingly, when the sheet  4  carrying the four images of four pages on both sides thereof as above is folded by the binding apparatus  3  at the center portion thereof in the direction the sheet  4  is conveyed and is discharged, the images of four pages are in a right order of pages with the first page image on the top surface of the folded sheet  5  and the fourth page image is on the back surface of the folded sheet  5 , as illustrated in the center portion of  FIG. 2 . 
   The binding apparatus  3  stacks the folded sheet  5  with the first page image of four images of four pages on the top surface of the folded sheet  5  as described. Accordingly, by controlling the printer  2  to print image or document data starting from the last four pages of the data, when the image or document data is printed on a sheet  4  by the printer  2 , and the sheet  4  is folded into a folded sheet  5 , the fold sheet  5  is stacked one after another into a stack of folded sheets  6  and the stack of folded sheets  6  is bound and discharged by the binding apparatus  3 , the images of the data are in right order of pages, i.e., the first page image is on the top surface of the stack of folded sheets  6 . For example, when the image or document data is the one of 12 pages, the image formation controller controls the printer  2  to first form the tenth page image and the eleventh page image on the upper surface of a first sheet, and the ninth page image and the twelfth page image on the back surface of the first sheet, and then to form the sixth page image and the seventh page image on the upper surface of a second sheet and the fifth page image and the eighth page on the back surface of the second sheet, and so on. A computer program for the image formation controller to control the printer  2  as described above can be practiced by an ordinary skilled programmer. 
   The binding apparatus  3  includes, as illustrated in  FIG. 3 , a sheet receiving part  11 , a sheet guiding part  12 , a sheet folding part  13 , a supplemental pressing part  14 , a jogging part  15 , a binding part  16 , a stack discharging part  17 , an exit part  18 , and a controller  19 . The sheet guiding part  12 , the sheet folding part  13 , and the supplementary pressing part  14  constitute a sheet folding device of the present invention. 
   The sheet receiving part  11  includes, as illustrated in  FIG. 4 , a sheet receiving table  31 , a side guide pair  32 , a sheet sensor  46 , an entrance roller  33 , and a driving mechanism including an entrance motor  21  illustrated in  FIG. 5 , which is a view of a part of the binding apparatus  3 , where the sheet receiving part  11  is provided, from the rear side thereof. The sheet receiving table  31  is fixed to the main body of the binding apparatus  3 . The side guide pair  32  is provided to the sheet receiving table  31  so as to guide the sheet  4 , conveyed from the printer  2 , with respect to right and left side positions of the sheet  4  in the sheet feeding direction. The sheet sensor  46  detects conveyance of the sheet  4 , jamming of the sheet  4  at the sheet receiving part  11 , and counts the number of the sheets  4  received by the sheet receiving part  11 . The entrance roller  33  is arranged above a sheet folding roller pair  42  of the sheet folding part  13  (described later) with a predetermined pressure given thereto. 
   As illustrated in  FIG. 5 , the entrance roller  33  includes a gear  25 , which is provided on the same axis as that of the entrance roller  33  and outside of a side plate of the binding apparatus  3 . The gear  25  engages with a pulley  23 , fixed to the sheet folding roller pair  42  of the sheet folding part  13  (described later), so that the entrance roller  33  rotates at the same circumferential speed as that of the sheet folding roller pair  42 . The pulley  23  engages with a gear  26 , and via an idle gear  27 , engages with a gear  28  and a gear  29 , to which a supplementary pressing roller pair  45  of the supplementary pressing part  14  (described later) are fixed. 
   A pulley  22  fixed to the entrance motor  21  and the pulley  23  are connected with each other via a belt  24 . When the entrance motor  21  starts to rotate upon detection of the sheet  4  with the sheet sensor  46 , the entrance roller  33 , the sheet folding roller pair  42 , and the supplementary pressing roller pair  45  start to rotate at the same time. 
   Thus, the entrance roller  33  and the sheet folding roller pair  42  rotate at the same circumferential speed to convey the sheet  4 , conveyed from outside, to the sheet guiding part  12 . 
   Referring back to  FIG. 4 , the sheet guiding part  12  includes, an upper guide plate  36 , a lower guide plate  37 , a sheet stopper  40 , and a sheet leading edge sensor  39 . 
   The upper guide plate  36  and the lower guide plate  37  may be substantially on a plane extending from the upper surface of the sheet receiving table  31 . However, as illustrated in  FIG. 4 , the upper guide plate  36  and the lower guide plate  37  may be upwardly angled relative to the upper surface of the sheet receiving table  31  so that the sheet  4  can be easily folded. In the embodiment, the upper guide plate  36  and the lower guide plate  37  are angled about 30°, but can be angled up to about 45°. 
   Further, the upper guide plate  36  and the lower guide plate  37  are spaced from each other so that the sheet  4  conveyed by the entrance roller  33  slides into between the upper guide plate  36  and the lower guide plate  37 . A window is provided in the upper guide plate  36  and the lower guide plate  37 , and a sheet stopper  40  is arranged so as to slidably engage with the window to stop the sheet  4  from sliding between the upper guide plate  36  and the lower guide plate  37 . The sheet leading edge sensor  39  is arranged in front of the sheet stopper  40  in the sheet conveying direction. 
   An adjusting rack  157  is fixed to the sheet stopper  40 . An adjusting pinion  156 , fixed to an adjusting axis  38 , engages with the adjusting rack  157 . With rotation of the adjusting axis  38 , the adjusting rack  157  moves, so that the sheet stopper  40  slidably moves along the window of the upper guide plate  36  and the lower guide plate  37 . 
   As illustrated in  FIG. 6 , the adjusting axis  38  is rotatably mounted to the both side plates of the main body of the binding apparatus  3 . An adjusting worm gear  154  is fixed to the outside surface of the side plate of the main body and engages with an adjusting worm  153 . 
   The adjusting worm  153  is fixed to the adjusting axis  155 , and is rotatably supported by a motor mounting plate table  158  via a bearing. An adjusting gear  152  is fixed at one end of the adjusting gear  155 , and the adjusting gear  152  engages with an adjusting gear  151  fixed to an axis of an adjusting motor  150 , which is fixed to the motor mounting table  158 . With rotation of the adjusting motor  150 , the adjusting axis  38  rotates, so that the sheet stopper  40  moves. 
   Referring back to  FIG. 4  again, when the sheet  4  (not shown), which has slid into between the upper guide plate  36  and the lower guide plate  37 , is stopped by the sheet stopper  40 , the sheet  4  slackens downwardly toward the sheet folding roller pair  42  at a portion thereof, which is out of the upper guide plate  36  and the lower guide plate  37 . The slackened portion of the sheet  4  is pinched into the sheet folding roller pair  42 , so that the sheet  4  is folded by the sheet folding roller pair  42 . 
   The position of the sheet stopper  40  is determined by the controller  19  according to the information as to the size of the sheet  4 , sent from the image formation controller  1 , so that the sheet  4  slackens at the center portion thereof, and the slackened center portion is pinched into the sheet folding roller pair  42 . Thereby, the sheet  4  is folded at the center portion thereof. 
   The sheet folding part  13  includes, as illustrated in  FIG. 5 , the sheet folding roller pair  42 , which is driven by the entrance motor  21 . The sheet folding roller pair  42  rotates at the same time when the supplementary pressing roller pair  45  rotates, and rotates at the same circumferential speed as the supplementary pressing roller pair  45 , as described above. 
   The sheet folding part  13  further includes, as illustrated in  FIG. 4 , a knife unit  35  in which a knife  34  is integrally mounted. The knife unit  35  is mounted to an axis  41 , which is rotatable relative to the side plate of the main body of the binding apparatus  3 . The sheet folding part  13  further includes a solenoid  47 , which is mounted to the outside surface of the side plate of the main body, and an arm  48 , which is connected with the solenoid  47  and which rotates the axis  41  on which the knife unit  35  is mounted by operation of the solenoid  47 . The solenoid  47  and the arm  48  constitute a knife unit upwardly/downwardly moving device. 
   When operating the knife unit  35 , after the sheet leading edge sensor  39  detects a leading edge of the sheet  4 , at a predetermined timing the solenoid  47  operates so as rotate the knife unit  35  around the axis  41  in the clockwise direction. Thereby, the sheet  4  is pushed by the knife unit  35  at the slackened center portion thereof toward the sheet folding roller pair  42 , so that the pushed slackened center portion of the sheet  4  is pinched into the sheet folding roller pair  42 . 
   The edge of the knife  34  is formed, for example in a saw-toothed shape. When the knife  34  is saw-toothed, the sheet  4  is perforated at the pushed portion of the sheet  4 , so that the sheet  4  is easily folded at the perforated portion of the sheet  4 . 
   Once the slackened and pushed center portion of the sheet  4  is pinched into the sheet folding roller pair  42 , the solenoid  47  is turned off, and at the same time the knife unit  35  is released to return to the position illustrated in  FIG. 4 . 
   The sheet  4  may be folded at the center portion thereof, without using the knife unit  35  having the knife  34 . However, by use of the above-described knife unit  35 , the sheet  4  can be more reliably folded at the center portion thereof with the sheet folding roller pair  42 . 
   The supplementary pressing part  14  includes, as illustrated in  FIG. 7 , the supplementary pressing roller pair  45 , an intermediate guide plate  43 , a sheet sensor  44 , and a supporting axis  49  around which the intermediate guide plate  43  rotates in the clockwise direction. The intermediate guide plate  43  can be rotated around the axis  49  in the clockwise direction when removing a sheet jammed in the supplementary pressing part  14 . The supplementary pressing roller pair  45  presses the folded portion of a folded sheet  5 , which has been conveyed by the sheet holding roller pair  42  with the folded portion of the folded sheet  5  as the leading edge, so as to be further firmly folded, and conveys the folded sheet  5  to a subsequent process. 
   The supplementary pressing roller pair  45  is arranged so as to be angled relative to the sheet folding roller pair  42 , as illustrated in  FIG. 8 . By arranging the supplementary pressing roller pair  45  so as not to be in parallel to the sheet folding roller pair  42 , the folded portion of the folded sheet  5  is successively pressed by the supplementary pressing roller pair  45  at a portiori of the folded portion, starting with the portion thereof at one side of the folded sheet  5  to the other portion thereof at the other side of the folded sheet  5 . Because the folding portion of the folded sheet  5  is protuberant relative to the other portions of the folded sheet  5 , when the folded sheet  5  passes through the supplementary roller pair  45 , the folded portion of the folded sheet  5  receives pressure higher than the one given to the other portions of the folded sheet  5  by the supplementary pressing roller pair  45 , thereby the folded portion of the folded sheet  5  is effectively pressed by the supplementary pressing roller pair  45 . Thereby, the sheet  4  is reliably folded. In this case, when the pressure between the supplementary pressing roller pair  45  is constant, as the angle of the supplementary pressing roller pair  45  relative to the sheet folding roller pair  42  increases, the pressure given to the folding portion of the folded sheet  5  increases, so that the sheet  4  is more reliably folded. 
   For conveying a folded sheet  5  without curving the conveying direction while applying a pressure to the folded portion of the folded sheet  5  by the supplementary pressing roller pair  45 , the supplementary pressing roller pair  45  must complete applying of the pressure to the folded portion of the folded sheet  5 , before the rear end of the folded sheet  5  passes through the sheet folding roller pair  42 , i.e., while the sheet folding roller pair  42  is pinching the folded sheet  5 . Once the supplemental pressing roller pair  45  completes applying the pressure to the folded portion of the folded sheet  5 , then the force of the supplementary pressing roller  45  to curve the conveyance direction of the folded sheet  5  decreases, because the pressure being applied to the folded sheet  5  by the supplementary roller pair  45  is uniform in the widthwise direction of the folded sheet  5 , so that the folded sheet  5  is correctly discharged toward a jogging table  57  ( FIG. 7 ). 
   Practically, the supplementary pressing roller pair  45  can be arranged so as to be angled relative to the sheet folding roller pair  42  between about 1° and about 20°. If the supplementary pressing roller pair  45  is excessively angled relative to the sheet folding roller pair  42 , e.g., more than about 20°, supporting of the supplementary pressing roller pair  45  at the side plate of the main body of the apparatus is hard. 
   When the distance between a nip portion of the sheet folding roller pair  42  and a nip portion of the supplementary pressing roller pair  45  at a position corresponding to a widthwise edge of the sheet  5  at a side, in the widthwise direction, where the supplementary pressing roller  45  and the sheet folding roller pair  42  are farther separated from each other, is shorter than the length of the folded sheet  5  in the sheet conveying direction, then pressing of the folded portion of the sheet  4  with the supplementary pressing roller pair  45  is completed while the sheet folding roller pair  42  is pinching the folded sheet  5 , so that the folded sheet  5  is correctly discharged. 
   Referring back to  FIG. 7 , the jogging part  15  includes, as illustrated in figure, a sheet center thrusting mechanism  200 , which thrusts a folded sheet  5  on the jogging table  7  from above, a stapling position determining mechanism  201  which makes uniform the leading edges the folded sheets  5  on the jogging table  57 , i.e., the folded portions of the folded sheets  5 , a jogging table part  202 , and a jogging table upward/downward moving mechanism  203 . 
   The sheet center thrusting mechanism  200  includes, as illustrated in  FIG. 7 , a sheet center thrusting plate  50 , an axis  56  for the sheet center thrusting plate  50  to swing, an upper guide  59  which guides, from above, both sides of the leading edge of the folded sheet  5 , an axis  51  which is integrally mounted to the sheet center thrusting plate  50 , an arm  52  which transmits a swinging force to swing the sheet center thrusting plate  50  to the sheet center thrusting plate  50 , an axis  53  which is rotatably mounted to the side plate of the main body and around which the arm  52  rotates, a solenoid  55  which performs the swinging operation of the sheet center thrusting plate  50 , and an arm  54  which transmits a force of the solenoid  55  to the arm  52  as a rotation movement. The arm  52 , the axis  53 , and the arm  54  are integrated with each other. 
   Referring now to  FIG. 9  and  FIG. 10 , the stapling position determining mechanism  201  determines the position where a position determining plate  60  stops in order to determine the position for the stapler  121  to staple the stack of folded sheets  6  with respect to the leading edge of the stack of folded sheets  5 . Further, the stapling position determining mechanism  201  pushes back the stapled stack of folded sheets  6  from the position where the stack of folded sheets  6  has been stapled. 
   In  FIG. 10 , the position determining plate  60  stops a folded sheet  5  (not shown) being conveyed over the jogging table  57  at a leading edge of the folded sheet  5 . An axis  61 , to which the position determining plate  60  is fixed, is rotatably mounted to the side plate of the main body, and an arm  107  is fixed to the outside surface of the side plate of the main body. A spring  108  is mounted to the tip end of the arm  107 . The spring  108  always pulls the arm  107  in the clockwise direction, so that a roller  104 , mounted to the arm  107 , is pressed against a cam plate  106 , which is fixed to a stapling position adjusting knob  105 . The stapling position adjusting knob  105  is mounted to the side plate of the main body, and the operation thereof is regulated by a spring (not shown) so as to be rotatable only by a manual operation thereof. By manipulating the stapling position adjusting knob  105 , the stapling position relative to the leading edge of a stack of folded sheets  6  can be adjusted. 
   The cam plate  106  fixed to the stapling position adjusting knob  105  engages with the roller  104  of the arm  107 . The position of the position determining plate  60  is adjusted according to the position of the stapling position adjusting knob  105  to stop rotating. 
   The arm  107  rotatably supports a link  103  at one end of the link  103 , and the other end of the link  103  is connected with a solenoid  101 . With the operation of the solenoid  101 , the arm  107  connected with the link  103  rotates in the counterclockwise direction. Thereby, the position determining plate  60  fixed to an axis  61  of the arm  107  swings in the counterclockwise direction, so that, in  FIG. 9 , the stack of folded sheets  6  on the jogging table  57 , which has been stapled, is pushed back toward right in  FIG. 9 . 
   The jogging table part  202  includes, as illustrated in  FIG. 7 , a sensor  58 , which is mounted to the jogging table  57  to detect existence of a sheet on the jogging table  57 . The jogging table part  202  further includes, as illustrated in  FIG. 11  and  FIG. 12 , a left side jogging plate  74 , which jogs the sheet at the left side of the sheet in the sheet advancing direction, and a left side upper guide  76 , which guides the sheet at the left side of the sheet and which is attached to the left side jogging late  74 . A jogging plate pin  80 , integrated with the left side jogging plate  74 , slides in a left side jogging plate guiding groove  71  of the jogging table  57 , so that the left side jogging plate  74  and the left side upper guide  76  move over the jogging table  57 . The left side upper guide  76  is supported by the left side jogging plate  74  via a jogging plate axis  77  so as to swing around the jogging plate axis  77 . 
   Further, referring to  FIG. 12 ,  FIG. 13  and  FIG. 14 , a lower plate  99  of the left side upper guide  76 , which is downwardly bent ( FIG. 13 ), extends, through the left side jogging plate guiding groove  71  of the jogging table  57  ( FIG. 12 ), to a hole  119  of a left side jogging plate rack  82  ( FIG. 14 ) (described later). 
   The jogging plate part  202  further includes, as illustrated in  FIG. 12 , the left side jogging plate rack  82  and a right side jogging plate rack  160 . Referring also to  FIG. 13 , a motor  88  is mounted to a back plate  90  of the jogging table  57 . A pulley  87  directly connected with the motor  88  and a pulley  86  connected with the pulley  87  via a belt  89  are rotated by the motor  88 , and thereby, the jogging plate rack  82  and the right side jogging plate rack  160  are rotated by a pinion integrated with the pulley  86 . 
   The jogging plate rack  82  includes, as illustrated in  FIG. 14 , the hole  119  for driving the lower plate  99  of the left side upper guide  76  ( FIG. 13 ), an elongated hole  118  for the jogging plate pin  80  to slidably move in the left side jogging plate guiding groove  71  to move the left side jogging plate  74  ( FIG. 12 ), and a rack groove  84  for the jogging plate pin  80  to slide along a rack guide  85 , which is integrated with the jogging table  57  ( FIG. 12 ). 
   The hole  119  of the jogging plate rack  82  is provided for moving the lower plate  99  of the left side upper guide  76 , so that the left side upper guide  76  is in a substantially horizontal position (x position) or in an upwardly slanted position (y position), illustrated  FIG. 13 . When the jogging plate rack  82  is moved so that the left side upper guide  76  is in the substantially horizontal position (x position) or in the upwardly slanted position (y position), the elongated hole  118  regulates the movement of the jogging plate pin  80  so that the left side upper guide  76  is in the substantially horizontal position (x position) or the upwardly slanted position (y position). When the jogging plate rack  82  moves inwardly in the direction indicated by “In” in  FIG. 12 , the lower plate  99  is moved by the first movement of the left side jogging plate rack  82 , and thereby the left side upper guide  76  is turned into the upwardly slanted position (y position). Thereafter, the elongated hole  118  allows the jogging plate pin  80  to move, so that the left side jogging plate  74  starts to move inwardly. 
   In  FIG. 12 , when the left side jogging plate  74  is positioned inside of the jogging table  57 , and when the jogging plate rack  82  starts to move outwardly in the direction indicated by “Ou”, first the lower plate  99  of the left side upper guide  76  ( FIG. 13 ) is moved so that the left side upper guide  76  is turned into the horizontal position (x position), and thereafter, the left side jogging plate rack  82  moves the jogging plate pin  80 , so that the left side jogging plate  74  is moved outwardly in the direction “Ou”. A left side position sensor  83  is arranged at a reference position for movement and driving of the left side jogging plate  74  and the right side jogging plate  73 . 
   As illustrated in  FIG. 11 , a right side jogging plate  73  and a right side upper guide  75 , respectively having substantially the same construction as those of the left side jogging plate  74  and the left side upper guide  76 , are arranged in symmetrical positions relative to the left side jogging plate  74  and the left side upper guide  76  with respect to the sheet conveying direction. The right side jogging plate  73  and the right side upper guide  75  are symmetrically operated, relative to the left side jogging plate  74  and the left side upper guide  76 , respectively, by the right side jogging plate rack  160 , which is engaged with the pinion integrated with the pulley  86 , which is driven by the motor  88  (see  FIG. 12 ). 
   An end plate part that jogs the folded sheet  5 , which have been discharged toward the jogging table  57 , with respect to front and rear sides of the folded sheet  5  in the direction the folded sheet  5  is conveyed, in cooperation with the position determining plate  60  of the binding position determining mechanism  201 , includes, as illustrated in  FIG. 12 , a pulley  92  including a motor  91  fixed to the back side of the jogging table  57 , a belt  93 , a pinion  94 , a rear end jogging plate rack  96 , an end plate position sensor  97 , an end plate  95 , a rear end jogging plate  78 , and an end plate axis  79 . The end plate part operates substantially in the same manner as the left side jogging plate  74  and the left side upper guide  76 , except that the end plate part operates with respect to the forward and backward directions of the folded sheets  5 . 
   Referring to  FIG. 15 , the jogging table upward/downward moving mechanism  203  includes a supporting axis  62  which mounts the jogging table  57  to the both side plates of the main body so as to swing, and a groove plate  63  which is integrally mounted to each of the side surfaces of the jogging table  57 . Further, an arm  64  having a protrusion  66 , which is integral with the arm  64  and which engages with a groove hole of the groove plate  63  to move in the groove hole, and an arm  111 , which is rotatable relative to the side plate of the main body and which is arranged outside of the arm  64  and the side plate, are fixed to an axis  65 . 
   The jogging table upward/downward moving mechanism  203  further includes an arm  115  and an interrupting plate  114 , which are fixed to and which rotate together with an axis fixed to an axis of a motor  116 , which is fixed to the side plate of the main body, and a link  117  connecting the arm  115  and the arm  111  with each other. 
   A sensor  113  and a sensor  112  are arranged so as to oppose each other via the axis of the motor  116 . When the interrupting plate  114  rotates together with the axis of the motor  116 , the interrupting plate  114  interrupts the sensor  113  and the sensor  112 . 
   When the arm  115 , which is integrated with the axis of the motor  116 , rotates, the link  117  is reciprocally moved to swing the arm  111 . When the arm  111  is in the left side end position (p) in  FIG. 15 , the interrupting plate  114  interrupts the sensor  112 , and when the arm  111  is in the right side end position (q) in  FIG. 10 , the interrupting plate  114  interrupts the sensor  113 . 
   Referring back to  FIG. 11  (see also  FIG. 9 ), the stapling part  16  includes a stapler  121  which is integrated with a rack  123  and an interrupting plate  120 , a guide  125  and a guide  126  which guide the stapler  121  to the (u) position and to the (v) position on the stapling table  128 , a rack  123  which engages with a pinion  127  fixed to an axis of a motor  122 , a rack guide  124  which guides the pinion  127  and the rack  123 , and a sensor  140  and a sensor  141  which detect the position of the stapler  121  so as to stop the stapler  121  at the predetermined positions (u) and (v). 
   The stack discharging part  17  includes, as illustrated in  FIG. 10 , a gear  130 , which is fixed to an axis of a motor  129  fixed to the side plate of the main body, a gear  131 , which engages with the gear  130  and which is integrated with an axis  132  of a roller  136 , an axis  133  which is rotatably supported by the side plate of the main body, and a roller  138  which is rotatably supported by a discharging plate  137  fixed to the axis  133 . An arm  134  integrated with the axis  133  is arranged outside of the side plate. The arm  134  is always pulled by a spring  109  in the counterclockwise direction, so as to be stopped by a stopper  135  at its home position. A spring  110  is attached to the arm  134 , at the side opposite the side the spring  109  is attached to, to be connected with a solenoid  102 . When a stack of folded sheets  6 , which has been stapled, is pushed by the end plate  95  (not shown) toward the stack discharging part  17  by a predetermined distance according to the size of the sheet into between the roller  138  and the roller  136 , the solenoid  102  operates so that the roller  138  presses the stapled stack of folded sheets  6  against the roller  136 . Thereby, the stapled stack of folded sheets  6  is discharged onto the discharging table  171 . 
   The exit part  18  includes, as illustrated in  FIG. 3 , an opening part  171  opened toward the rear side of the binding apparatus  3  and an exit table  170 . 
   Now, the operation of the binding apparatus  3  is described. 
   When the power of the binding apparatus  3  is turned on, each part of the binding apparatus  3  operates so as to be ready for receiving a sheet. As illustrated in  FIG. 7 , the knife unit  35  is in the (a) position, which is the home position of the knife unit  35 , separated from the sheet folding roller pair  42 . The sheet center thrusting plate  50  is in the (e) position, so as to be upwardly slanted. The position determining plate  60  is in the (k) position, which is the home position, and the roller  138  is in the (r) position, which is the home position. Further, the jogging table  57  is in the horizontal (m) position, with the interrupting plate  114  interrupting the sensor  112  ( FIG. 13 ) and the arm  64  being in the (p) position. 
   When a binding instruction including the information on the size of the sheet  4  is received by the controller  19 , the sheet stopper  40  of the sheet guiding part  12  is moved to the position corresponding to the size of the sheet  4  according to the information on the size of the sheet  4  so that the sheet  4  is folded at the center portion thereof by the sheet folding part  13 . Further, with respect to the left side jogging plate  74  and the right side jogging plate  73  on the jogging table  57 , illustrated in  FIG. 11 , when the motor  88  ( FIG. 12 ) rotates in the clockwise direction to move the left side jogging plate rack  82  and the right side jogging plate rack  160  toward the center of the jogging table  57 , first the left side upper guide  76  and the right side upper guide  75  are moved from the horizontal position (x) to the upwardly slanted position (y) ( FIG. 13 ). Thereafter, the jogging plate pin  80 , which is integrated with the left side jogging plate  74  and the right side jogging plate  73 , is moved, so that the left side jogging plate  74  and the right side jogging plate  73  are moved from the position to interrupt the left side position sensor  83  ( FIG. 12  and  FIG. 13 ), toward the center of the jogging table  57 , to the position where the folded sheet  5  is conveyed into and jogged, which is determined by the controller  19  according to the information on the size of the sheet  4  being conveyed from the printer  2 . The left side jogging plate rack  82  and the right side jogging plate rack  160  ( FIG. 12 ) return an allowance distance L of the elongated hole  118  ( FIG. 14 ), which engages with the jogging plate pin  80  integrated with the left side jogging plate  74  and the right side jogging plate  73 . Thereby, the left side upper guide  76  and the right side upper guide  75  in the upwardly slanted positions (y) are turned into the horizontal positions (x), respectively. 
   Further, referring to  FIG. 11 , the end plate  95  moves to the position where the folded sheet  5  is jogged, and the rear end thrusting plate  78  is placed in the horizontal position like the left side upper guide  76  and the right side upper guide  75 . The stapler  121  is in the (u) position, where the interrupting plate  120  interrupts the sensor  140 , to wait the folded sheet  5  to be conveyed thereto. 
   In  FIG. 4 , a sheet  4  (not shown) is conveyed from the printer  2  (not shown) into between the side guide pair  32  of the sheet receiving table  31  of the binding apparatus  3 . When the sheet sensor  46  detects the sheet  4  being conveyed, the entrance motor  21  ( FIG. 5 ) starts to rotate, so that the entrance roller  33  and the sheet folding roller pair  42  arranged on the entrance roller  33  start to rotate together, so as to convey the sheet  4  into between the lower guide plate  37  and the upper guide plate  36  of the sheet guide part  12 . 
   The sheet  4  is conveyed between the lower guide plate  37  and the upper guide plate  36 , and when the sheet leading edge detect sensor  39  detects the leading edge of the sheet  4 , the controller  19  adjusts the position of the sheet stopper  40 , which has been set according to the size of the sheet  4  as described above, again, according to the detection so that the sheet  4  is folded precisely at the center portion thereof. This adjustment is made because the actual size of the sheet  4  sometime differs from the standard size, for example, by about ±2 mm in an A3 size sheet. Further, the solenoid  47  is operated a predetermined period of time after the detection. 
   The sheet  4  is stopped by the sheet stopper  40  after the leading edge of the sheet  4  passes the sheet leading edge detect sensor  39 . At that time, because the entrance roller  33  and the sheet folding roller pair  42  are rotating, a part of the sheet  4  which is out of the lower guide plate  37  and the upper guide plate  37  is downwardly slackened. Further, the predetermined time after the sheet leading edge detect sensor  39  detects the leading edge of the sheet  4 , the solenoid  47  is operated to move the knife unit  35  in the clockwise direction to push the slackened portion of the sheet  4  with the knife  34  of the knife unit  35  toward the sheet folding roller pair  42 , so that the slackened pushed portion of the sheet  4  is pinched into between the sheet folding roller pair  42 , and thereby the sheet  4  is folded by the sheet folding roller pair  42 . The sheet  4  can be folded by the sheet folding roller pair  42  without using a knife unit mechanism, however, the precision of folding the sheet  4  at the center portion of the sheet  4  can be increased by using the knife unit mechanism, and thereby inferior folding of the sheet  4  can be decreased. 
   The sheet  4 , which has been folded into a folded sheet  5 , is pressed and is conveyed by the sheet folding roller pair  42  to pass the sheet sensor  44  and to be conveyed into between the supplementary pressing roller pair  45 . The folded sheet  5  is further pressed and is conveyed by the supplementary pressing roller pair  45  to be discharged toward the jogging table  57 . 
   Before the folded sheet  5  is discharged toward the discharging table  57 , the left side jogging plate  74 , the right side jogging plate  73 , and the end plate  95  have been placed in the position to jog the folded sheet  5  on the jogging table  57 , and the right side upper guide  76 , the right side upper guide  75 , and the rear end thrusting plate  78  are respectively in the horizontal positions, as described above. The folded sheet  5  discharged toward the jogging table  57  slides over the rear end thrusting plate  78  of the end plate  95 , the left side upper guide  76  of the left side jogging plate  74 , and the right side upper guide  75  of the right side jogging plate  73 , to be stopped by the position determining plate  60 . 
   Referring to  FIG. 7 , a predetermined period of time after the sheet detect sensor  44  detects the rear edge of the folded sheet  5 , the solenoid  55  operates to rotate the arm  54 , the axis  53 , and the arm  52 , which are integrated with each other, around the axis  53  in the clockwise direction, so that the sheet center thrusting plate  50  rotates around the axis  56  to the (f) position so as to thrust the folded sheet  5  substantially to the horizontal position. 
   Thereafter, referring to  FIG. 10 , the left side jogging plate  74 , the right side jogging plate  73  (not shown), and the end plate  95  are moved to the positions to interrupt the left side position sensor  83  and the end plate position sensor  97 , respectively. This position is where the left side upper guide  76 , the right side upper guide  75 , and the rear edge thrusting plate  78  separate from the folded sheet  5  carried thereupon, so that the folded sheet  5  is fallen onto the jogging table  57 . When the left side jogging plate  74 , the right side jogging plate  73 , and the end plate  95  are moved to the above-described positions, the left side upper guide  76 , the right side upper guide  75 , and the rear edge thrusting plate  78  are kept in the horizontal positions, respectively. 
   Immediately after the left side position sensor  83  and the end plate position sensor  97  have been interrupted, the motor  88  and the motor  91  start to rotate in the reverse direction, so that the left side jogging plate  74 , the right side jogging plate  73  (not shown in  FIG. 12 ), and the end plate  95  return to the jogging position for the folded sheet  5 . At this time, first, the left side upper guide  76 , the right side upper guide  75  (not shown in  FIG. 10 ), and the rear end thrusting plate  7  are turned into the upwardly slanted positions, respectively. 
   After the left side jogging plate  74 , the right side jogging plate  73 , and the end plate  95  return to the jogging position for the folded sheet  5 , the motor  88  and the motor  91  rotate in the reverse direction for the allowance distance L ( FIG. 14 ) of the elongated hole  118  relative to the jogging pin  80  for the left side jogging plate rack  82 , the right side jogging plate rack  160 , and the rear edge jogging plate rack  96 , so as to move the left side jogging plate rack  82 , the right side jogging plate rack  160 , and the rear end jogging plate rack  96 . Thereby, without moving the left side jogging plate  74 , the right side jogging plate  73 , and the end plate  95 , the left side upper guide  76 , the right side upper guide  75 , and the rear edge thrusting plate  78  are put into the horizontal positions, respectively, and stopped in the positions. 
   After the left side jogging plate  74 , the right side jogging plate  73 , and the end plate  95  moves to the jogging position for the folded sheet  5  so as to jog the folded sheet  5  to the position and the left side upper guide  75 , the right side upper guide  76 , and the rear edge thrusting plate  78  move to the horizontal positions (x) to be stopped in the positions, the solenoid  55  is released so that the sheet center thrusting plate  50  returns to the upwardly slanted position (e) ( FIG. 7 ). 
   The binding apparatus  3  then receives a subsequent sheet  4 , and the sheet  4  is folded at the center portion thereof, to be a folded sheet  5 . The folded sheet  5  is then conveyed by the supplementary pressing roller pair  45 , so as to be discharged toward the previously conveyed folded sheet  5  on the jogging plate  57 . 
   The sheet sensor  44  detects the rear edge of the discharged folded sheet  5 , and after a predetermined period of time, the sheet center thrusting plate  50  rotates to the horizontal position (f) (Fi.  7 ) so as to thrust the folded sheet  5  carried on the left side upper guide  75 , the right side upper guide  76 , and the rear edge thrusting plate  78 , and thereafter the left side jogging plate  74 , the right side jogging plate  73 , and the end plate  75  start to move toward outside in  FIG. 11 . After the left side jogging plate  74 , the right side jogging plate  73 , and the end plate  95  move to the positions to interrupt the left side position sensor  83  and the end plate position sensor  97  ( FIG. 12 ), where the left side upper guide  76 , the right side upper guide  75 , and the rear edge thrusting plate  78  separates from the folded sheet  5  carried thereupon, the left side upper guide  76 , the right side upper guide  75 , and the rear edge thrusting plate  78  are put into the upwardly directed positions (y), and then the left side jogging plate  74 , the right side jogging plate  73 , and the end plate  95  return to the jogging positions for the folded sheet  5 , where the left side upper guide  76 , the right side upper guide  75  and the rear edge thrusting plate  78  return to the horizontal positions (x), respectively, so as to thrust the subsequently conveyed folded sheet  5 . 
   Thus, the sheet center thrusting plate  50  thrusts each of the folded sheets  5 , received one by one on the jogging table  47 , from above, and the left side jogging plate  74 , the right side jogging plate  73 , and the end plate  95  jog the folded sheets  5 , respectively. Further, the left side upper guide  76 , the right side upper guide  75 , and the rear edge thrusting plate  78  suppress bulges of the folded sheets  5 . Furthermore, the sheet center thrusting plate  50  upwardly rotates, so that the upper surfaces of the left side upper guide  76 , the right side upper guide  75  and the rear edge thrusting plate  78  function as the guides for the folded sheet  5  which is subsequently conveyed thereto. 
   After a last sheet  4  of a predetermined number of sheets  4  according to the binding instruction is folded into a last folded sheet  5  and the last folded sheet  5  is stacked on the jogging table  57 , the sheet center thrusting plate  50  thrusts the last folded sheet  5  from above, and the left side jogging plate  74 , the right side jogging plate  73 , and the end plate  95  jog the last folded sheet  5  to the jogging position, with the left side upper guide  76 , the right side upper guide  75 , and the rear edge thrusting plate  78  kept in the horizontal positions (x) so as to hold a stack of folded sheets  6 , the stapler  121  staples the stack of folded sheets  6  in the (u) position of  FIG. 11 . Thereafter, the motor  122  rotates in the clockwise direction to move the rack  123  to thereby move the stapler  121  from the (u) position toward the (v) position. The stapler  12  staples again in the (v) position, where the interrupting plate  120  of the stapler  121  interrupts the sensor  141  and the motor  122  stops. The stapler  121  then returns to the (u) position. 
   When the stapling is completed at the (v) position, the sheet center thrusting plate  50  returns to the (e) position, and the end plate  95  on the jogging table  57  starts to move toward outside, to be stopped after moving a predetermined distance. At the same time, the solenoid  101  is turned on, so that the position determining plate  60  moves from the (k) position to the (l) position ( FIG. 7 ). Thereby, the stapled stack of sheets  6  is thrust to be discharged to the opening of the stapler  121 . 
   In  FIG. 10 , the motor  116  rotates in the clockwise direction, so that the interrupting plate  114  rotates to interrupt the sensor  113  and the jogging table  57  rotates from the (m) position to the (n) position ( FIG. 7 ) around the supporting axis  62 . The motor  129  rotates to rotate the roller  136 , and at the same time the end plate  95  on the jogging table  57  ( FIG. 11 ) moves toward the center of the base plate  57 . Thereby, the stack of folded sheets  6  is pushed toward the stack discharging part. When the stack of folded sheets  6  has been pushed toward the stack discharging part  17  the predetermined distance, which has been determined by the controller  19  according to the size of the sheet  4 , the solenoid  102  operates so that the roller  138  presses the stack of folded sheets  6  against the roller  136 , and the stack of folded sheets  6  is discharged onto the discharging table  171  with the roller  138  and the roller  136 . 
   The sensor  58  detects that stack of folded sheets  6  is discharged from the jogging table  57 , so that the stapling operation is completed. The binding apparatus  3  then prepares for receiving a next sheet  4  conveyed from the printer  4 . 
   Numerous additional modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein. 
   The present application claims priority and contains subject matter related to Japanese Patent Application No. 2000-213730 filed in the Japanese Patent Office