Abstract:
Sheets after having been sequentially folding-processed are stowed neatly without becoming dog-eared, wrinkled, etc. in the course of being transported to a stacker. A folding process unit folds sequentially fed copy paper or other sheets, and a sheet stacking unit loads/stows sheets from the folding unit. A conveyance device conveying one folding-processed sheet at a time is furnished between the folding unit and the sheet stacking unit. The conveyance device includes a first, upstream conveyance unit conveying sheets from the folding process unit in a direction approximately orthogonal to the sheets&#39; crease(s), and a second, downstream conveyance unit conveying sheets in the orientation of the crease(s). The second conveyance unit is configured with a tray member where sheets are supported one at a time, and is configured so as to sequentially deliver each sheet to the sheet stacking unit along the tray member in the orientation of the crease(s).

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     2. Description of the Related Art 
     The present invention—involving sheet-folding apparatuses and sheet-folding-apparatus-equipped imaging systems that fold sheets sequentially delivered from an image-forming or like apparatus—relates to improvements in mechanisms that automatically fold sheets in half or in thirds, and that securely stow the sheets in a stacker. 
     Commonly known among this kind of sheet-folding apparatus are in general machines that fold in half or in thirds sheets delivered from an imaging or like apparatus, and deliver the folded sheets to and stow them in a stacker. Therein, for the folding style various techniques, such as Z-folding or gate-folding, are adopted depending on the application, such as mailing or filing. For example, Japanese Unexamined Pat. App. Pub. No. 2004-352419 discloses an apparatus in which provided within a conveyance path is a plurality of folding roller mechanisms that fold sheets by nipping them between the rollers in a process that takes over the conveyance of sheets from an imaging apparatus, and that stows the gate-, Z-, or otherwise-folded sheets in a stacker, or that binds the sheets together in a binding apparatus disposed downstream of the folding mechanisms. 
     In Japanese Unexamined Pat. App. Pub. No. 2004-189413 as well, a similar apparatus is proposed. Either of these machines folds sheets in half or thirds, in creases that are orthogonal to the direction of sheet conveyance. Also, Japanese Unexamined Pat. App. Pub. No. H06-016317 discloses an apparatus in which after sheets from an imaging apparatus are folded by folding rollers, a predetermined number of copies of the sheets drop into a stack on a tray, and after being stapled, the sheets are conveyed out in the orthogonal direction (creasing direction). 
     In folding with folding rollers sheets sequentially delivered from an imaging apparatus and loading/stowing them onto a downstream stacker, as described above conventionally adopted have been either a method whereby the folded sheets are conveyed in a direction orthogonal to the crease orientation and stowed, as with the above-cited Pat. App. Pub. Nos. 2004-352419 and 2004-189413, or a method whereby after having been bound together the folded sheets are conveyed in the orientation of the crease and stowed in the stacker, as with Pat. App. Pub. No. H06-016317. Consequently, delivering in an orientation orthogonal to the crease orientation in loading/stowing on the stacker, as disclosed in Pat. App. Pubs. Nos. 2004-352419 and 2004-189413, can cause a folded sheet to advance into the fold of a sheet that has already been stacked, giving rise to a sheet jam.  FIG. 10  illustrates this, wherein in discharging a sheet from folding rollers into a stacking tray, the sheet S″ enters, as the arrow indicates, into the fold of already stacked sheet S′. 
     Therefore, conventionally a structure has been adopted that establishes the discharge outlet and stacking tray at different levels so that from the discharge outlet the sheet S″ falls on top of the uppermost sheet S′already stacked in the tray. This has meant that in the stacking tray sheets can get stowed in disarray, leading to the trouble of sheets scattering inside the apparatus, which compels the user to realign the sheets (bundles) stowed in the stacking tray after having taken them out of the tray. In the same way, with the structure in earlier cited Pat. App. Pub. No. H06-016317, folded sheets are dropped from the folding rollers directly into and stacked on a processing tray, and after sheets collated into a bundle on the processing tray are stapled, the sheet bundle is from an intermediary tray transported in the orientation of the crease and stowed in the stacking tray. Inasmuch as an intermediary tray is therefore disposed directly beneath the folding rollers, the apparatus layout is made complex; moreover, this intermediary tray carries with it the earlier described problem explained with  FIG. 10 . 
     BRIEF SUMMARY OF THE INVENTION 
     An issue for the present invention is to make available a sheet-folding apparatus that, after folding with a folding roller mechanism sequentially supplied sheets, enables neat stowage of the sheets into a stacker. 
     A further issue for the present invention is to make available a sheet-folding apparatus of a simple structure that in delivering folded sheets to the stacker, without dog-earing, wrinkling, or otherwise impairing the sheets, enables stacking the sheets neatly. 
     The present invention employs the following configuration to solve the aforementioned problems. A folding unit that folds sequentially fed sheets and other sheets, and a sheet stacking unit that stores sheets fed from the folding unit are provided. A conveyance means that conveys one folded sheet at a time is disposed between the folding unit and the sheet stacking unit. The conveyance means is composed of a first conveyance means disposed upstream to convey a sheet from the folding unit in a direction perpendicular to the fold in the sheet, and a second conveyance means disposed downstream that conveys the sheet in the direction of the fold. 
     The second conveyance means is composed of a tray member that stacks sheets from the first conveyance means, and a shift member that moves sheets on the tray member in the direction of the fold in the sheet. Because the sheet is fed from the folding unit by folding rollers along its folded seam, the crease in the sheet is securely pressed therebetween the rollers. The second conveyance means moves the folded sheet along the tray member in the direction of the fold in the sheet into the sheet stacker unit so the sheet does not slip into the fold of previously stacked sheets, and is neatly stacked. 
     Also, the first conveyance means is composed of a pair of rollers that nippingly convey sheets. The shift member is configured to touch a trailing edge of the sheet to shift the sheet into the sheet stacking unit. The folding roller mechanism securely folds the folded sheet along its fold using the pair of rollers. The sheet, now securely folded, is shifted securely into the stacker by the shift member without boxing its ears or wrinkling the sheet, and enabling the sheet to be securely stored. 
     Furthermore, the length of the tray member in the conveyance direction is shorter than the length of at least the maximum sized sheet in the conveyance direction. Therefore, when the leading edge of the sheet is moved over the stacker, there is no problem of it pushing on the trailing edge of previously stacked sheets which causes paper jams. This also makes it possible for a compact apparatus. 
     The sheet stacking unit is composed of a stacker that stacks sheets fed from the conveyance means. It has a first level-split formed between the first conveyance means and the tray member where sheets drop, and a second level-split formed between the tray member and stacker where sheets fall into the stacker for storage. In addition to enabling a configuration where the tray length is shorter than the sheet size, the leading edge of the sheet at the first level-split falls onto the top of the trailing edge of the an uppermost sheet stacked in the stacker. Because the sheet is pushed along the tray member into the stacker, it is neatly stacked without jamming. 
     A discharge path that conveys the sheet from the folding unit further downstream is linked downstream of the first conveyance means. A path switching member that selectively guides the sheet from the first conveyance means into the discharge path or the tray member is disposed in the discharge path. A guide member is provided above the tray member to guide a sheet from the path switching member to the tray member. The guide member is configured to move between a retracted position where it does not hinder the conveyance of the sheet in the discharge path and a guiding position to guide the sheet to the tray member. 
     A slit is formed in the tray member along the direction of the fold in the sheets. The shift member is mated to the slit. The guide member guides the sheet into the top of the tray member without the leading edge of the sheet getting caught in the slit when it advances into the tray member. 
     The shift member is equipped on an endless belt, for example, to circulate around the front and back sides of the tray member along the slit formed in the tray member in the direction of the folds in the sheets. The shift member is configured to pivot when it comes into contact with sheets on the stacker in the process to circulate around the front and back sides of the tray member. 
     The image forming system of the present invention is provided an image-forming apparatus that forms an image on the sheet, a folding apparatus that folds the sheet conveyed from the image-forming apparatus, and a finisher that stacks sheets conveyed from the folding apparatus, and binds the sheets together to form a sheet bundle. A discharge path that conveys sheets from the image-forming apparatus to the finisher, and a folding process path that folds sheets from the image-forming apparatus are provided in the sheet folding apparatus. The finisher configuration is described above. An inserter is provided in the image-forming system. The inserter is equipped with a tray that holds sheets, and separating means that separates sheets on the tray into single sheets. The system is configured to selectively feed a sheet on the tray or a sheet from the image-forming apparatus to the folding process path. 
     Sheets from the folding unit are conveyed in a direction perpendicular to the fold in the sheet by the first conveyance means, and are supported on the tray means. The sheets on the tray are conveyed by the second conveyance means in a direction along the fold in the sheets and then stored in the stacker. Therefore, the sheet fed from the folding unit by the folding rollers or the like are securely folded by the first conveyance means, and are shifted into the stacker along the fold in the sheet by the second conveyance means. In the process to convey the folded sheets, they are neither wrinkled nor do the experience boxed ears. When conveyed into the stacker, they do not slip into the fold of previously stacked sheets, so the problem of paper jams is alleviated. The sheets fed along the tray member are securely conveyed into the stacker, and are neatly stacked at the same time. 
     Furthermore, because the sheet falls into the tray member, and the tray member is configured to be shorter than the length of at least the maximum sheet size, there is no problem of the sheets previously stacked in the stacker being pushed out by the sheet advancing into the stacker. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  shows the overall configuration of an image-forming system that incorporates a sheet-folding apparatus B of the present invention; 
         FIG. 2  is an explanatory drawing of an upper unit (inserter) of the sheet-folding apparatus B that configures a portion of the system shown in  FIG. 1 ; 
         FIG. 3  is an explanatory drawing of a lower unit of the sheet-folding apparatus B shown in  FIG. 1 ; 
         FIGS. 4A to 4C  are explanatory drawings of examples of folding specifications in the apparatus shown in  FIG. 3 , wherein  FIG. 4A  shows a gate fold,  4 B shows a Z fold, and  4 C shows ¼ Z fold; 
         FIG. 5  is a perspective view of the overall configuration of the folded sheet stacking unit of the apparatus of  FIG. 3 ; 
         FIG. 6  is an explanatory drawing showing a sectional configuration of the stacking unit of  FIG. 5 ; 
         FIG. 7  is a perspective view of the configuration of a path switching member in the apparatus of  FIG. 3 ; 
         FIGS. 8A to 8D  are explanatory drawings of the operation of the essential portion of the apparatus shown in  FIG. 3 , wherein  FIG. 8A  shows a finger member in an upright state,  8 B shows the finger member in an inclined state,  8 C and  8 D show the operating states of the path switching member; 
         FIG. 9  is an explanatory diagram of the configuration of a control unit in the apparatus of  FIG. 3 ; and 
         FIG. 10  is an explanatory drawing of a problem to be solved by the present invention, showing a sheet S″ discharged from folding rollers entering a fold of a sheet S′ on the stacking tray. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Preferred embodiments of the present invention will now be explained with reference to the drawings provided.  FIG. 1  shows the overall configuration of an image-forming system that incorporates a sheet-folding apparatus B of the present invention;  FIGS. 2 and 3  are explanatory drawings of the overall folding apparatus that composes a portion of the image-forming system;  FIG. 2  shows the upper unit; and  FIG. 3  shows the lower unit.  FIG. 4  is an explanatory view showing examples of the folding specifications;  FIG. 5  is a perspective view of the structure of the sheet stacking unit; and  FIG. 6  is a sectional, explanatory view of the sheet stacking unit. 
     The following will explain the image-forming system with reference to  FIG. 1 . The system shown in  FIG. 1  is furnished with an image-forming apparatus A that forms images on sheets; a sheet-folding apparatus B that folds printed sheets into a predetermined shape; and a finisher C that applies a finishing process to sheets fed from that apparatus. Sheets can be conveyed sequentially downstream from the image-forming apparatus A, to the sheet-folding apparatus B and next to the finisher C. 
     Image-forming apparatus A conveys the sheet from a feeder unit  1  to a printing unit  2 . After images are printed on the sheet at the printing unit  2 , the sheet is conveyed out from a discharge outlet  3 . The feeder unit  1  stores a plurality sheet sizes in feeder cassettes  1   a  and  1   b , separates into a single sheet the specified sheet size and conveys that to the printing unit  2 . The printing unit  2  is equipped with an electrostatic drum  4 ; a print head (such as a laser)  5  disposed in the vicinity thereof; a developer  6 ; a transfer charger  7 ; and a fixer  8 . An electrostatic latent image is formed on the electrostatic drum by the laser  5 , and the developer causes toner ink to adhere to that latent image. After the toner image is transferred to the sheet by the transfer charger  7 , it is heat-fused to the sheet at the fixer. Sheets thus printed with images are sequentially conveyed out from the discharge outlet  3 . The cycling path  9  is a duplex printing path for turning over (from front to back) a sheet printed on one side, received from the fixer, and re-feeding that sheet to the printing unit  2  so that the other side of the sheet can be printed. Duplex-printed sheets are then conveyed to the discharge outlet  3  after being turned over from back to front again at a switchback path  10 . 
     An image-reading apparatus  11  uses photoelectric conversion elements to electrically read an original sheet set on a platen  12  by scanning with a scanning unit  13 . The read image data is digitally processed, for example, at an image-processing unit, then transferred to a data-storage unit  14 , and sent to the laser  5  as image signals. Also, a document feeder  15  feeds original sheets stored in a stacker  16  to the platen  12 . An electrostatic printing mechanism is shown as an example of the image-forming apparatus A described above. However, other methods such as an ink jet mechanism and a screen printing mechanism and the like are known. Any of these can be adopted for use with the present invention. 
     The sheet-folding apparatus B is composed of a folding unit B 1 , a folded sheet stacker B 2 , and an inserter B 3 . A conveyance-in inlet  20  connected to the discharge outlet  3  of the image-forming apparatus A is furnished in the sheet-folding apparatus B; a sheet conveyance path P 1  that conveys the sheet from the conveyance in inlet  20  to the finisher C, described below, intersects the sheet-folding apparatus B. A folding process path P 2 , and a paper feed path P 3  that branches from the inserter B 3  are linked to the sheet conveyance path P 1 . 
     The folding specifications executed by the folding unit B 1  will now be explained with reference to  FIG. 4 . A single-fold, a Z fold or gate fold, and a ¼Z fold are often-used paper folding formats (folding styles) in image-forming systems. The following will now explain each type of fold. 
     Single Fold 
     A sheet conveyed from the image-forming apparatus A is folded at a ½ way position in the length of the sheet in the conveyance direction. Although not shown, the sheet is folded in half, at a central position. The folded ends of sheets can then be bound by stapling or gluing and the like to form a closed-end document. Furthermore, if holes are punched into the folded sheets, they can be used in a variety of document organizing methods, such as filing. In such cases, the sheet must be folded by folding rollers so that the printed surface (possible only for simplex printing) faces outward. Therefore, at least a pair of folding rollers, and registration means that calculates the folding position based on the leading edge or the trailing edge of the sheet are necessary in the folding process path P 2 . 
     Gate Fold 
     In this folding method, the sheet is folded at ⅓ positions of the leading edge and the trailing edge of the sheet in the length direction. The two end panels, specifically, the leading and trailing ends of the sheet, are mutually folded inward over a middle third panel. As shown in  FIG. 4A , the leading end side of the sheet (in direction of sheet conveyance) is folded at a ⅓ position of the sheet, then the trailing end is folded over that panel at a ⅓ position of the sheet. A gate-folded sheet can be inserted into an envelope as a letter. In such cases, it is necessary for the printed side of the sheet (the front side when duplex printing has been applied) to be folded inward by the folding rollers. It is necessary to dispose a first pair of folding rollers that execute a first folding process, and a second pair of folding rollers positioned downstream of the first roller pair, in the folding process path P 2 . At the folding roller mechanism  21 , described below, a sheet fed in the folding process path P 2  in the manner (specifically, the front side of the sheet facing the left side of the drawing) indicated by arrow a in  FIG. 3  is folded at the ⅓ position of the trailing edge by the first and second rollers  21   a ,  21   b . The sheet is then folded at the ⅓ position of the leading edge by the second and third rollers  21   b ,  21   c.    
     Z Fold 
     In this folding method, the sheet is folded at the ⅓ positions of the leading and trailing edges in the length direction of sheet conveyance. Specifically, the leading and trailing ends of the sheet are folded in opposite directions. As shown in  FIG. 4B , the leading and the trailing ends of the sheet are folded in opposite directions at the ⅓ positions in the direction of sheet conveyance. Sheets folded in the Z-fold style can be inserted into an envelope as a direct mail. In such case, it is necessary that the printed side of the sheet (the front surface when duplex printing has been applied to the sheet) is folded so that the letter head portion of the sheet is facing outward so as to be visible. Therefore, a first pair of folding rollers must be disposed upstream, and a second pair of folding rollers must be disposed downstream of the first roller pair in the folding process path P 2 . At the folding roller mechanism  21 , described below, a sheet fed in the folding process path P 2  in the manner (the front surface of the sheet facing the right side of the drawing) indicated by arrow b in  FIG. 3 , is folded at the ⅓ position of the leading edge by the first and second rollers  21   a ,  21   b ; and the trailing edge of the sheet is folded at the ⅓ position by the second and third rollers  21   b ,  21   c.    
     ¼-Z Fold 
     As shown in  FIG. 4C , the sheet is folded at a one-quarter position of the sheet in the conveyance direction, then the sheet is folded at the ½ position of the original length of the sheet. Sheets folded in this way are then stacked as a series of documents. They can also be stapled, or holes can be punched therein for their filing. This makes it possible to bind large-sized documents, such as A3-size documents together with A4-sized documents. In such cases, the printed side of the sheet (the front surface when duplex printing has been applied to the sheet) must be at a ¼ position from the leading edge of the sheet, then the sheet is folded again at the ½ position of the original length of the sheet. Therefore, a first pair of folding rollers must be furnished at an upstream side and a second pair of folding rollers must be disposed downstream of the first roller pair in the folding process path P 2 . At the folding roller mechanism  21 , described below, a sheet fed in the folding process path P 2  in the manner (the front surface of the sheet facing the right side of the drawing) indicated by arrow b in  FIG. 3 , is folded at the ¼ position of the leading edge by the first and second rollers  21   a ,  21   b ; and then the sheet is folded at the ½ position by the second and third rollers  21   b ,  21   c.    
     The structure of the folding unit B 1  will now be explained with reference to  FIG. 3 . The folding process path P 2  is linked to the sheet conveyance path P 1  interposed by a path switching flapper  24 ; the folding roller mechanism  21  is disposed in the folding process path P 2 . A folded sheet path  23  branched in a T-shape is furnished adjacent to the folding process path P 2 , and a switchback path  22  is furnished downstream at a leading end of the folding process path P 2 . The folding roller mechanism  21  is furnished at the path branching point. The folding roller mechanism  21  shown in the drawing is composed of a first roller  21   a , a second roller  21   b , and a third roller  21   c . The first and second rollers  21   a  and  21   b  are in mutual contact to nip the sheet; the second and third rollers  21   b , and  21   c  are also in mutual contact to nip the sheet. Therefore, a first folding process is executed at the nipping point (the first folding unit) between the first and second rollers  21   a , and  21   b , and a second folding process is executed at the nipping point (the second folding unit) between the second and third rollers  21   b , and  21   c.    
     A conveyance roller  25  that conveys the sheet is disposed in the folding process path P 2 ; the folding roller mechanism  21  is positioned downstream of the conveyance roller. A switchback roller  26  that is capable of both forward and reverse rotations and a sheet sensor S 1  are disposed in the switchback path  22  downstream of the folding process path P 2 . The sensor S 1  detects the leading edge of the sheet fed downstream ( FIG. 3 ) by the switchback roller  26 . After detecting the leading edge of the sheet, the switchback roller  26  further conveys the sheet a predetermined amount and then stops. Then, the ¼ position of the sheet is bowed by the conveyance roller  25  continuing to rotate, thereby causing the bowed ¼ position of the sheet to enter the nipping point of the first folding unit. Next, the switchback roller  26  is driven in reverse thereby backing up the leading edge of the sheet. At the same time as that reverse drive, the conveyance roller  25  continues to feed the trailing edge of the sheet. These two actions cause the sheet to enter nipping point between the first and the second rollers  21   a  and  21   b . These rollers pull the sheet downstream into the folded sheet path  23 . This is the mechanism used to calculate the sheet folding position based on the leading edge of the sheet to apply a folding process. 
     On the other hand, a trailing edge registration stopper  38  is provided downstream of the conveyance roller  25  to calculate the folding position based on the trailing edge of the sheet. After the trailing edge of the sheet is fed past the registration stopper  38  by the switchback roller  26 , the switchback roller  26  rotates in reverse thereby abutting the trailing edge of the sheet against the registration stopper  38 . This causes the sheet to form a bow based on the sheet&#39;s trailing edge position. The bowed portion advances into the nipping point of the first and second rollers  21   a , and  21   b  (the first folding unit). Thus, the first folding process is executed based on the trailing edge of the sheet. Note that the sheet stopper mechanism is composed of a flapper-shaped stopper  38 . This stopper  38  is configured to retract from the path when the sheet advances downstream in the folding process path P 2 , and to advance back into the path when the sheet is being conveyed upstream to stop the trailing edge of the sheet. This stopper  38  that registers the trailing edge of the sheet can also be composed of the conveyance roller  25  as a switchback roller capable of forward and reverse rotations. Switchback rollers at the leading end of the path can also be configured for position registration. 
     Sheets whose folding positions are calculated by either their leading edge or their trailing edge when supplied to the first folding unit are folded by the first and second folding rollers  21   a , and  21   b , and then conveyed into the folded sheet path  23 . A sheet detection sensor S 2  and movable stopper  27  are disposed in the folded sheet path  23 . The movable stopper  27  is configured to move into the folded sheet path  23  to register the leading edge position of the sheet according to the sheet size and folding specifications. The leading edge of the folded sheet fed by the first and second rollers  21   a , and  21   b  abuts the movable stopper  27  and is registered. This also forms a bow in the trailing edge side. This bow causes the sheet to advance into the nipping point between the second  21   b  and third roller  21   c  so the trailing edge side of the sheet is folded. A first discharge path P 4  is disposed downstream of the nipping point (the second folding unit) of the second and third rollers  21   b  and  21   c . Sheets folded at the first and second folding units are conveyed out to the first discharge path P 4 . Note that in the event that the sheet does not require a second folding, for example if only a single fold is applied to the sheet, the movable stopper  27  retracts to a non-operational, standby position so that the sheet can be conveyed out to the first discharge path P 4  without being folded at the nipping position of the second and third rollers  21   b  and  21   c.    
     The first discharge path P 4  is composed of path guides  28   a  and  28   b  (see  FIG. 8C ) that guide folded sheets, and conveyance out rollers  29   a  and  29   b . Each of the pair of rollers is configured to nip the folded sheet and convey it downstream at the same time as securely folding it. A path switching member  30  and first discharge outlet  31  are furnished at the outlet end of the first discharge path P 4 . A second discharge path P 5  is linked downstream to the first discharge path P 4  interposed by the path switching member  30 ; the second discharge path P 5  conveys folded sheets to a finisher C described below. Conveyance means (the first conveyance means) that conveys one sheet at a time downstream of the folding roller mechanism  21  is composed of discharge rollers  29   a , and  29   b . This pair of rollers conveys the folded sheet in a direction perpendicular to the direction of the paper fold. Conveying the folded sheet with the discharge rollers  29   a  and  29   b  securely creases the fold in the sheet. A folded sheet stacker B 2  that stores sheets is provided below the first discharge outlet  31 . 
     As shown in  FIG. 5 , the folded sheet stacker B 2  is composed of a tray member  32  that temporarily stacks folded sheets conveyed from the first discharge outlet  31 , and a stacker  33  linked to the tray member  32 , that stores the folded sheets. Of particular note, the folded sheet is conveyed from the tray member  32  into the stacker  33  in the direction of the folded seam. The stacker  33  is disposed so that an access port is positioned at the front side of the apparatus (the front side of  FIG. 1 ). The tray member  32  is composed of a tray member that has a support surface  32   a  formed at a level-split L 1  (see  FIG. 6 ) below the first discharge outlet  31 . The sheet conveyance direction length L 3  (see  FIG. 6 ) of the support surface  32   a  is formed to be shorter than length of the folding direction of at least the maximum size of sheet L 4 . These lengths have a relationship of L 3 &lt;L 4 . The length L 3  of the support surface  32   a  is set to correspond to the apparatus specifications with the relationship of the maximum size length and the minimum size width. 
     A paper sensor Sp that detects a sheet that has fallen from the first discharge outlet  31 , and a shift means  34  that moves the sheet on the support surface  32   a  to the stacker  33  are disposed in the tray member  32 . This shift means  34  is composed of a finger member  35  that projects through the top of the support surface  32   a , a belt member  36 , and a shift motor MS that drives the belt member  36  to move the finger member  35  from one end (the left side of  FIG. 6 ) of the support surface  32   a  to another end (the right side of that drawing). Therefore, the finger member  35  mounted to the belt member  36  circulates around the back and front sides of the tray member  32 , as shown in  FIG. 6 . Also, the finger member  35  is supported by a spring  35   a  to pivot on the belt member  36 . As shown in  FIG. 8B , the spring  35   a  urges the finger member  35  to lay over when it comes into contact with sheets on the stacker  33 . The tray member  32  is formed with a slot  32   b  for being fit out with the finger member  35 . 
     The stacker  33  is disposed downstream of the tray member  32  configured as described above. As shown in the drawing, the stacker  33  is composed of a box shape to store folded sheets on the bottom wall  33   a . The number  37  (see  FIG. 7 ) in the drawing represents an opening door on the front side of the apparatus shown in  FIG. 1 . The bottom wall  33   a  is set to a depth forming a level-split (second level-split) L 2  between the maximum number of storable sheets (the tolerable maximum number of sheets) and the support surface  32   a  of the tray member  32 .  FIG. 6  shows a full detection sensor Sf. 
     Folded sheets from the first discharge outlet  31  are stored in the tray member  32 , but the guide member  39  is interlocked with the path switching member  30  so that the leading edge of the folded sheet does not get caught in the slot  32   b  formed in the support surface  32   a . The path switching member  30  of the first discharge outlet  31  is formed to open the first discharge path P 4 . A lever  40  interlocked to the path switching member  30  moves the guide member  39  from a standby position shown in  FIG. 8C  to a guiding position shown in  FIG. 8D . At the guiding position, the guide member  39  guides the folded sheet to fall from the first discharge outlet  31  into the tray member  32 . This prevents the leading edge of the sheet from getting caught in the slot  32   b . A solenoid SL opens and closes the path switching member  30  and the guide member  39 ; S 3  is a sheet sensor. 
     One end of the second discharge path P 5  is linked to the first discharge path P 4  and the other downstream end is linked to the sheet conveyance path P 1  to guide the sheet to the finisher C disposed downstream. Conveyance rollers  41  are provided at appropriate intervals in the second discharge path P 5 . The folded sheet guided to the sheet conveyance path P 1  is conveyed out of the sheet-folding apparatus B by the discharge roller  42  provided in the sheet conveyance path P 1 . 
     As described above, a printed sheet is conveyed in from the image-forming apparatus A to the folding unit B 1  but in addition to this, a sheet can be selectively conveyed from the inserter B 3  for the folding process. As shown in  FIG. 1 , the folding unit B 1  is disposed in the bottom portion of the apparatus and the inserter is disposed in the top portion of the apparatus. These units sandwich the sheet conveyance path P 1 . The inserter B 3  is composed of a feeder tray  44  where sheets such as cover sheets or a divider sheet can be set; a separating means  45  that separates and feeds one sheet on the tray at a time; and the paper feed path P 3  that guides the separated sheet to the sheet conveyance path P 1 . The separating means  45  is ordinarily composed of a friction roller (paper feed roller) and separating roller; a registration roller  46  is disposed downstream thereof. Of particular note, the drawing shows a turn-over path  47  provided in the paper feed path P 3  that turns a sheet from the registration roller  46  over from front to back. Therefore, it is possible to guide a sheet from a different printing process, not supplied from the image forming apparatus A, or to set a cover sheet in the feeder tray  44  to insert in front and behind sheets. It is also possible to set divider sheets in feeder tray  44  to insert the dividers into the sheet conveyance path P 1  for insertion between the pages at appropriate times. 
     The following will now explain the finisher C. A sheet from the discharge roller  42  of the sheet conveyance path P 1  is conveyed into the finishing process path P 6  shown in  FIG. 1 . A stapler  50  that staples sheets is disposed in the finishing process path P 6 . The system aligns sheets from the image-forming apparatus A or the inserter B 3 , or folded sheets fed directly from the sheet conveyance path P 1  or from the second discharge path P 5  via the folding unit B 1  in a processing tray  51 . Then, aligned sheets are stapled together by the stapler  50 . Sheets bound at the processing tray  51  are then stored in the storage tray  52 . Of course, sheets or folded sheets that do not require finishing at the processing tray  51  pass through the processing tray  51  to be stacked in the storage tray  52 . 
     A gluing apparatus can also be furnished in the finisher instead of the stapler  50 . In that case a back edge of a sheet bundle aligned in the processing tray is applied with glue, then a cover sheet is creased over that glued edge. A configuration that applies adhesive tape is also possible. It is also possible to adopt systems for hole-punching or applying marks, such as a seal and the like, by incorporating a hole-punching unit or stamping unit in the finishing process path P 6  along with the stapler  50 . 
     The following will now explain the actions of the sheet-folding apparatus B configured as describe above. When a sheet does not require finishing, such as when the sheet is folded in a gate fold (letter specification), the sheet is conveyed from the first discharge outlet  31  of the first discharge path P 4  and stored in the stacker  33 . When using other folding specifications, the system conveys the sheet via the second discharge path P 5  and stores it in the storage tray  52  of the finisher C. A control panel  56  is provided on the control unit  55  of the image-forming apparatus A; the control unit  55  sets the sheet folding mode. An operator uses an input means  57  connected to the control panel  56  to set a folding process mode that executes a folding process on the sheet, a finishing process mode that executes a finishing process such as stapling, hole-punching and marking sheets without applying the folding process, or a discharge mode that stacks sheets in the storage tray  52  without the folding or finishing processes being executed on the sheets according to the mode setting means  58 . 
     The folding process mode setting sets the type of folding process (the folding specification mentioned above) and the folded sheet finishing process, such as whether to finish the folded sheet at the finisher, or discharge the sheet unfinished. This also sets whether to supply a cover sheet or divider sheet from the inserter B 3  along with these processes. At the same time as setting the mode as describe above, the control unit  55  transmits the sheets size information and job end signal to the downstream sheet-folding apparatus. 
     The control unit  59  of the sheet-folding apparatus B is composed of a control CPU. The control unit  59  can be integrated to the control unit  55  of the image-forming apparatus A or the control unit of the finisher C, or it can be furnished separately to the sheet-folding apparatus. A ROM  60  that stores folding execution programs and a RAM  61  that stores control data are provided in the control unit (control CPU)  59 . The folding execution program executes folding processes with the folding specifications described above by controlling the conveyance roller  25  of the folding process path P 2 , the conveyance out rollers  29   a , and  29   b , the folding roller mechanism  21  and the movable stopper  27 . This program selects whether to move the folded sheet fed into the first discharge path P 4  from the first discharge outlet  31  to the stacker  33  or to move the folded sheet from the second discharge path P 5  to the finisher C according to the folding specifications, at the same time as executing a folding process described above. The drawings show sheet sizes of A4 or letter size. The sheet is conveyed from the first discharge path P 4  and is stored in the stacker  33  for gate fold folding specifications. For other folding specifications, the sheet is conveyed out from the second discharge path P 5  to the finisher C. 
     When the sheet size is A4 or letter size and a gate fold is applied thereto, the control unit  59  discharges the sheet from the discharge outlet  3  of the image-forming apparatus A facing upward. The sheet is handed over and conveyed into the folding process path P 2  in the manner indicated by arrow a in  FIG. 3 . Next, the sheet passes through the folding roller mechanism  21  and advances into the switchback path  22  downstream. At the point where the trailing edge of the sheet passes the stopper member  38  of the folding process path P 2 , the control CPU  59  rotates the switchback roller  26  in reverse. At that point, the trailing edge of the sheet is registered at the stopper member  38 , and the center of the sheet is bowed in the direction of the nipping point between the first and second rollers  21   a  and  21   b . The sheet is nipped between the two rollers, and the first folding process is executed therebetween. The length of the distance between the stopper member  38  and the nipping point is set to ⅓ the length of the sheet. Therefore, the printed surface of the sheet is folded inward at the ⅓ position from the trailing edge of the sheet, and the leading edge of the fold advances into the folded sheet path  23 . 
     The control CPU  59  moves the movable stopper  27  to a position in the path  23  that corresponds to the length of the sheet after the folding process. This movement is achieved by the use of a motor (not shown) connected to the movable stopper  27 . The crease of the sheet folded at the ⅓ position from the trailing edge touches the movable stopper  27  and is registered. Then, the leading edge (at the trailing end of the folded sheet path  23 ) of the sheet fed by the first and second rollers  21   a  and  21   b  is bowed and nipped by the second and third rollers  21   b  and  21   c . The printed surface of the sheet is folded inward between the second and third rollers  21   b  and  21   c . The distance between this nipping point and the movable stopper  27  is set to a ⅓ length of the sheet. Therefore, the sheet is folded at the ⅓ position from the leading edge by the second and third rollers  21   b  and  21   c  after the ⅓ position from the trailing edge of the sheet is folded by the first and the second rollers  21   a  and  21   b  to fold the sheet into a gate fold. 
     The folded sheet is fed from the second and third rollers  21   b  and  21   c  to the first discharge path P 4 . The control CPU  59  rotatingly drives the conveyance rollers  29   a , and  29   b  disposed in the first discharge path P 4  to convey the sheet from the folding rollers further downstream. The sheet fed in a direction perpendicular to the fold by the rollers  29   a , and  29   b  is securely folded at the fold by being pressed at the same time between the rollers. When the sheet is conveyed out, the solenoid SL activates to move the path switching member  30  from the state shown in  FIG. 8C  and open the first discharge outlet  31 . When the sheet reaches the first discharge outlet  31  from the first discharge path P 4 , the sheet falls from the opened first discharge outlet  31 . The guide member  39  connected to the path switching member  30  by the lever  40  is moved from the standby position shown in  FIG. 8C  to the actuating position of  FIG. 8D . 
     In the actuating position, the guide member  39  guides the sheet from the first discharge path P 4  to the support surface  32   a  of the tray member  32 , having the level-split L 1 , disposed below. The guide member  39  at this time guides the sheet so that it does get caught in the slot  32   b  formed in the tray member  32 . The standby position (the state shown in  FIG. 8C ) of the guide member  39  is set to a position (inclination) where the sheet conveyed from the first discharge path P 4  to the downstream second discharge path P 5  does not enter that path. 
     At this time, the control CPU  59  controls the shift motor MS of the finger member  35  disposed in the support tray  32   a  to idle at a home position (left side of  FIG. 6 ) so that it does not hinder the advancement of the sheet on the support tray  32   a  of the tray member  32 . The sheet falls onto the support surface  32   a  and activates the paper sensor Sp. The control CPU  59  starts the shift motor MS at the signal from the paper sensor Sp to move the finger member  35  from the left side of  FIG. 6 , to the right side. When this occurs, the sheet on the support surface  32   a  is pressed on its trailing edge and moved along the surface by the finger member  35 . The leading edge of the sheet at this time is gradually pushed to the right so that it is stacked upon the sheets stored in the downstream stacker  33  when the sheet falls and is stored on the support surface  32   a . The sheet is conveyed in the direction of its fold and moved to the top surface of the stacker  33 . 
     The finger member  35  is configured to pivot by the spring  35   a  as described above so after the sheet is shifted to the top of the stacker  33 , it is pushes the sheet on the stacker  33  and lays down along with the movement of the belt member  36  and recovers to the backside of the tray member  32 . The finger member  35  is configured to be at its home position so as not to interfere with the movement of the sheet. 
     Folding specifications such as a single fold, Z fold and ¼-Z fold that differ from the folding specifications described above will now be explained. When applying a Z fold to the sheet, the control unit  59  discharges the sheet from the discharge outlet  3  of the image-forming apparatus A facing downward and the sheet conveyed to the folding process path P 2  in the manner indicated by arrow b in  FIG. 3 . Next, the sheet passes by the folding roller mechanism  21  and advances into the switchback path  22  downstream. At the point where the leading edge of the sheet is conveyed a predetermined amount downstream, the switchback roller  26  is driven in reverse while the conveyance roller  25  is stopped. At that point, the trailing edge of the sheet is restrained by the conveyance roller  25 , and the center of the sheet is bowed in the direction of the nipping point between the first and second rollers  21   a  and  21   b . The sheet is nipped between the both rollers, and the first folding process is executed therebetween. The length of the distance between amount of feeding of the switchback rollers  26  and the nipping point is set to ⅓ the length of the sheet. Therefore, the printed surface of the sheet is folded outward at the ⅓ position from the leading edge of the sheet, and the leading edge of the fold is advanced into the folded sheet path  23 . 
     The control CPU  59  moves the movable stopper  27  to a position in the folded sheet path  23  that corresponds to the length of the sheet after the folding process. This movement is achieved by the use of a motor (not shown) connected to the movable stopper  27 . The sheet folded at the ⅓ position from the leading edge abuts the movable stopper  27  with its folded edge and is registered. Then, the trailing edge of the sheet fed by the first and second rollers  21   a  and  21   b  is bowed. This bowed portion is nipped between the second and third rollers  21   b  and  21   c . The printed surface of the sheet is folded inward between the second and third rollers  21   b  and  21   c . The distance between this nipping point and the movable stopper  27  is set to a ⅓ length of the sheet. Therefore, the sheet is folded to the inside at the ⅓ position from the trailing edge by the second and third rollers  21   b  and  21   c  after the ⅓ position from the leading edge of the sheet is folded by the first and the second rollers  21   a  and  21   b  to fold the sheet into a Z fold. 
     Note that when applying a ¼-Z fold, the sheet is folded at the ¼ position of the sheet size for a first folding process, using the same procedures as the Z fold described above. Then, the sheet is folded at its ½ position. Also, for the ½ fold, it is acceptable to fold the sheet using the first and second rollers  21   a , and  21   b  using the leading or the trailing edge of the sheet as a reference. 
     The sheet folded in a ¼-Z fold or a ½ fold is fed from the second and third rollers  21   b  and  21   c  to the first discharge path P 4 . The control CPU  59  rotatingly drives the conveyance rollers  29   a , and  29   b  disposed in the first discharge path P 4  to convey the sheet from the folding rollers further downstream. The crease in the sheet fed in a direction perpendicular to the fold by the rollers  29   a , and  29   b  is further pressed between those rollers. When the sheet is conveyed out, the control CPU moves the path switching member  30  to the state shown in  FIG. 8C  to guide the sheet from the first discharge path P 4  into the second discharge path P 5 . The sheet is conveyed to the finishing process path P 6  of the finisher C via the sheet conveyance path P 1 ; the sheet is finished at the finishing process path P 6  and then stored in the storage tray  52  thereafter. Also, when an operating mode that does not apply a finishing process to sheets is used, the sheet is conveyed out to the storage tray via the finishing process path P 6 . 
     When applying the folding processes described above, and the sheet is being fed from the inserter B 3 , the sheet is fed from the feeder tray  44  to the sheet conveyance path P 1  via the paper feed path P 3 . In such case, if it is necessary to turn the sheet over from top to bottom because of the printed surface, the sheet is conveyed from the paper feed path P 3  and is turned over at the turn-over path  47 , then fed to the folding process path P 2 . 
     This application claims priority rights from Japanese Pat. App. No. 2006-152680, which is herein incorporated by reference.