Abstract:
In a sheet finisher which receives a sheet from an image forming apparatus, conducts a sheet finishing onto the sheet and feeds out the sheet, the sheet finisher includes: a stacking section which stores temporarily one or more sheets; and a sheet finishing section which conducts the sheet finishing onto the sheet stored in the stacking section. The stacking section having a first guide member which forms a stacking surface to guide the sheet, and a second guide member which faces the first guide member and is spaced apart from the first guide member by a predetermined distance, and is provided obliquely from a horizontal direction, and the stacking surface formed by at least a part of the first guide member, is formed to be curved in a direction perpendicular to a sheet conveyance direction.

Description:
This application is based on Japanese Patent Application No. 2009-001425 filed on Jan. 7, 2009, which is incorporated hereinto by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a sheet finisher that receives a sheet coming from an image forming apparatus, then, conducts sheet finishing on the sheet and feeds out the sheet and to an image forming system characterized to have the sheet finisher and an image forming apparatus that feeds a sheet into the sheet finisher, and in particular, to a sheet finisher having a stacking section that is arranged obliquely from the horizontal direction and stores one or more sheets temporarily and an image forming system. 
     With respect to the aforesaid stacking section that is arranged obliquely from the horizontal direction, it is aslant so that an empty weight of the sheet causes the sheet to slip down along a stacking surface to stop at a prescribed position, when a sheet is fed into it. In a circumference of the stacking section, there are arranged sheet finishing sections that conduct sheet finishing for the sheets stored in the stacking section. 
     The sheet finishing section includes a stapling section that staples a sheet bundle, a folding section that conducts center-folding for a sheet bundle or folds each sheet in three, an aligning section that aligns sheet bundles in a width direction or in a conveyance direction, or a punching section that punches a hole for a sheet bundle. 
     Further, on the stacking section, there is also arranged a positioning regulating member that moves a sheet vertically to position for conducting processing for a sheet at a determined position in the aforesaid sheet finishing section. 
     Since the stacking section of this kind is arranged obliquely, there is sometimes an occasion of buckling that sheets stored in the stacking section buckle, namely, the sheets are bent and do not line up straight on the stacking surface. If the sheets do not line up due to the buckling, it is impossible to conduct sheet finishing on the lined up sheet bundle because of slippage of sheets, in the case of processing carried out by a sheet finishing device arranged on the stacking section. The bucking of this kind takes place frequently on the lower side portion of sheets where each of the sheets receives its own weight, in particular. 
     In the past, there has been a construction having the structure wherein an elastic sheet such as PET is arranged on an inside of the stacking section, to press the sheet that has been fed into against the stacking surface, to prevent the buckling of this kind. However, when the number of sheets stored grows greater, elastic sheets that press the sheet become resistance against sheet conveyance, and there have been troubles that the sheet is not conveyed to the prescribed position to cause slippage. 
     In the technology disclosed in Unexamined Japanese Patent Application Publication No. 2004-83261, there are provided a tapping roller that aligns sheets by applying a pendulum motion on the stacking surface and a pressing roller that presses a sheet bundle by swinging from a standing by position to an operation position, for preventing the buckling of the sheet. In the constitution of this technology, the tapping roller aligns sheets in the conveyance direction by applying a pendulum motion for each sheet carried in, and after that, the pressing roller presses a bundle of sheets in the direction of the sheet. 
     The technology disclosed in the aforesaid Unexamined Japanese Patent Application Publication No. 2004-83261 is complicated in terms of the construction, to cause cost increase, which is a defect. In addition, the construction needs to be provided in the vicinity of the position for sheet carry-in for aligning sheets by a pendulum motion, which further requires more space, resulting in a restriction of a position of installation for acquiring a space. 
     SUMMARY OF THE INVENTION 
     An embodiment of the invention is as follows. 
     A sheet finisher that receives a sheet from an image forming apparatus and feeds the sheet out after conducting sheet finishing on the sheet, wherein the sheet finisher is characterized in that a stacking section that stores one or more sheets temporarily and a sheet finishing section that conducts sheet finishing on the sheet stored in the stacking section are provided, and the stacking section has a guide member (also referred to as a first guide member) that forms a stacking surface and a guide member (also referred to as a second guide member) that faces the aforesaid first guide member through a prescribed space, and is provided obliquely from the horizontal direction and the stacking surface formed by at least a part of the first guide member is formed to be curved in the direction perpendicular to the conveyance direction for sheets. 
     An image forming system characterized to have the sheet finisher described in the above and an image forming apparatus that feeds the sheet in the sheet finisher. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic sectional view of an image forming apparatus main body and a sheet finisher to which the invention is applied. 
         FIG. 2  is a principal part enlarged sectional view of the stacking section of the sheet finisher. 
         FIG. 3  is a sectional view taken on line IIIA-IIIA in  FIG. 2 . 
         FIG. 4  is a sectional view taken on line IV-IV in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An embodiment of the invention will be explained as follows, referring to  FIG. 1-FIG .  4 . 
     (Image Forming System) 
       FIG. 1  is a general view of an image forming system relating to an embodiment of the invention composed of image forming apparatus A and sheet finisher FS. 
     &lt;Image Forming Apparatus A&gt; 
     The illustrated image forming apparatus A is equipped with image reading section  1 , image processing section  2 , image writing section  3 , image forming section  4 , sheet feeding cassette  5 , sheet feeding roller  6 , fixing device  7 , sheet ejection roller  8  and with automatic double-sided copy sheet feeding section  9 . 
     On the upper portion of the image forming apparatus A, there is installed automatic document feeder DF. Further, on the left side of the image forming apparatus A in the illustration where sheet ejection roller  8  is positioned, there is connected sheet finisher FS. 
     Images on one side or both sides of a document placed on a document platen of automatic document feeder DF are scanned by an optical system of image reading section  1  that is conveyed along a conveyance path, to be read into CCD image sensor  1 A. 
     Analog signals obtained through photoelectric conversion conducted by CCD image sensor  1 A undergo various processes including analog processing, A/D conversion, shading correction and image compression processing, in image processing section  2 , and then, are sent to image writing section  3 . 
     A semiconductor laser is driven to emit light based on the image data sent to the image writing section  3 , thus, photoreceptor drum  4 A of image forming section  4  is illuminated and a latent image is formed thereon. In the image forming section  4 , processes such as electrification, light exposure, development, transfer, separation and cleaning are carried out and a toner image is formed on the photoreceptor drum  4 A. 
     Recording sheet S 1  that is fed by sheet-feeding roller device  6  from sheet-feeding cassette  5  arrives at photoreceptor drum  4 A where the toner image is transferred onto the recording sheet S 1  by transfer section  4 B. The recording sheet S 1  carrying the toner image thereon undergoes fixing processing conducted by fixing device  7 , and is fed into the sheet finisher FS from sheet ejection roller  8 . 
     In the case of duplexing copying, the recording sheet S 1  on which the image processing has been finished on its one side is fed into automatic double-sided copy sheet feeding section  9  by conveyance path switching plate  8 A, and in image forming section  4 , a toner image is transferred onto the reverse side to be fixed, and is fed into the sheet finisher FS from sheet ejection roller  8 . 
     (Sheet Finisher FS) 
     Sheet finisher FS has therein sheet carry-in section  20 , insertion sheet feeding sections  30   a  and  30   b  and a plurality of sheet finishing sections. The sheet finishing sections include punching section  40 , folding section  50 , superimposing section  60 , corner stapling section  71 , center stapling section  72  and ejection section  80 . 
     Insertion sheet S 2  is loaded in insertion sheet feeding section  30   a  and another insertion sheet S 3  is loaded in insertion sheet feeding section  30   b . Insertion sheets S 2  and S 3  are those such as book cover sheets and sheets for insert which are inserted in plural recording sheets S 1  ejected from image forming apparatus A, and they can undergo punching processing and folding processing, in the same way as in the recording sheet S 1 . Incidentally, in the following explanation, recording sheet S 1 , insertion sheets S 2  and S 3  are called sheet S as a general name. 
     Insertion sheets S 2  and S 3  which are fed out of insertion sheet feeding sections  30   a  and  30   b  respectively are conveyed to sheet carry-in section  20  through a conveyance path that goes downward. 
     The punching section  40  is arranged at the downstream side of the sheet carry-in section  20  on the left side, to make a punched hole on sheet S. 
     Conveyance path H 1  branched downward from the downstream side of the punching section  40  is connected to sheet stacking section  100  relating to the invention through conveyance rollers  23 . On the sheet stacking section  100 , there are arranged center stapling section  72  and folding section  50 , which will be described in detail later. 
     The superimposing section  60  is arranged at the downstream side of conveyance path H 2  branched upward from the downstream side of the punching section  40 , and it is equipped with conveyance paths H 3 , H 4  and H 5 . 
     The superimposing section  60  causes succeeding sheets S including sheets for the second set and thereafter to stand by on conveyance paths H 3 , H 4  and H 5 , to secure a period of time for conducting stapling processing for preceding sheet S. 
     A conveyance path positioned at the downstream side of the conveyance path H 2  is branched into conveyance paths curved doubly, and they are divided into inside conveyance path H 4  and outside conveyance paths H 3  and H 5 . 
     On an exit of the inside conveyance path H 4  that is branched from the conveyance path H 2  and is curved, there are provided conveyance rollers  21 , and when stapling processing is conducted, sheet S for the first set is fed into stacking section  70  successively through the conveyance paths H 2  and H 4  and through the conveyance rollers  21  to be stapled at corner stapling section  71 . 
     When the first sheet of sheets S for the second set and thereafter has been conveyed, a leading edge of the sheet is stopped under the condition where the rotation of the conveyance rollers  21  is stopped, and the conveyance rollers  21  cause the leading edge of the sheet to stand by while touching a nip portion of the conveyance rollers  21 . 
     Though the sheet S which has been conveyed through conveyance path H 4  stands by while its leading edge is touching the conveyance rollers  21 , sheet S following the aforesaid sheet S enters conveyance path H 3  from conveyance path H 2 , and arrives at the conveyance rollers  21  through conveyance path H 5 . When the preceding sheet S and the following sheet S are superimposed on each other while their leading edges are touching the conveyance rollers  21 , the conveyance rollers  21  rotate to feed the two sheets into stacking section  70  by conveying them together. As stated above, sheets S for the second set and thereafter are caused to stand by at superimposing section  60  until the moment when the stapling processing for the preceding bundle of sheets is terminated, thus, the stapling processing is carried out without lowering productivity of image forming apparatus A. 
     Conveyance path H 3  located at the downstream side of conveyance path H 2  is further branched into conveyance path H 5  and conveyance path H 6 . The conveyance path H 6  is one to eject sheet S to fixed sheet ejection tray  81  that constitutes a part of ejection section  80 , and the fixed sheet ejection tray  81  is arranged at a position to project out of the sheet finisher FS at the downstream side of conveyance path H 6 , and it is used when sheets S in a small amount is stacked. 
     The ejection section  80  further has elevating sheet ejection tray  82  and lower sheet ejection tray  83  which will be described later, and sheet ejection rollers  22 , stacking section  70 , corner stapling section  71  and an unillustrated aligning mechanism are arranged between the conveyance rollers  21  and elevating sheet ejection tray  82 . 
     The sheet ejection rollers  22  are composed of a pair of rollers, and when sheets are not ejected, the paired rollers are apart from each other, while when sheets are ejected, the paired rollers come in contact with each other to eject sheet S onto the elevating sheet ejection tray  82 . 
     Sheet S to be conveyed by the conveyance rollers  21  travels in the direction to the left in the diagram between the sheet ejection rollers  22  which are separated from each other, and when a trailing edge of the sheet S leaves the conveyance rollers  21 , the sheet S falls on the stacking section  70  to slide down along the inclined stacking section  70 , and the sheet S hits a stopper (not shown) to be stopped on the stacking section  70 . Sheets S are ejected successively, and when sheets S in a quantity of established number are stacked on the stacking section  70 , the corner stapling section  71  operates to conduct stapling on an edge surface of the sheets s that is closer to the stopper. 
     The sheets S thus stapled are pushed up by the aforesaid stopper, to move to the left on the stacking section  70 . In this case, the paired rollers constituting the sheet ejection rollers  22  come in contact with each other to nip the sheet S to convey it and to eject it to the elevating sheet ejection tray  82 . 
     When large quantities of images are formed without sheet finishing, sheets S are ejected from the sheet carry-in section  20  to the elevating sheet ejection tray  82  through the conveyance paths H 2  and H 4 , and the elevating sheet ejection tray  82  moves downward as shown with chain lines in the drawing so that a topmost surface of the ejected sheets S may keep the fixed height constantly. Therefore, thousands of sheets can be stacked on the elevating sheet ejection tray  82 . 
     Sheet stacking section  100  is arranged obliquely from a horizontal direction at the downstream side of the conveyance rollers  23 , and it has therein a plurality of guide members to guide sheets S and regulating members, center stapling section  72  and folding section  50 , to conduct processing sheets in various modes including a center-folding mode, a center-folding and center stapling mode and three-folding mode for one or more sheets S, and to eject sheets to lower sheet ejection tray  83 . 
       FIG. 2  is a schematic sectional view of sheet stacking section  100 . 
     A two-dot chain line in  FIG. 2  represents a virtual plane, and it is drawn for the explanation which will be given later, and sheet S is mostly carried in from an obliquely upper portion downward obliquely along the virtual plane. Further, as is shown on the lower portion on the right in the drawing, it is assumed that X direction is a direction toward the lower portion obliquely along the virtual plane, Y direction is a direction that is perpendicular to the X direction on a page surface and Z direction is a direction that is perpendicular upward to the page surface, in the following explanation. 
     Guide members constituting the sheet stacking section  100  includes upstream side guide members  101  and  102  and downstream side guide members  103  and  104 , and in the middle of the upstream side guide members  101  and  102 , there is positioned center stapling section  72 , and between the upstream side guide members and the downstream side guide members, there is positioned folding section  50 . Incidentally, an unillustrated sheet width aligning member is arranged at a proper location of the upstream side guide members  101  and  102 , to conduct alignment in the width directions (Z direction and its opposite direction) of sheet S, and an explanation for the foregoing will be omitted here. 
     On the downstream side of the folding section  50 , there is provided regulating member  105  that can travel along the downstream side guide members  103  and  104 . The regulating member  105  is one to regulate a lower end of sheet S to be at the prescribed position, and it is moved in accordance with a sheet size. 
     The upstream side guide member  101  and the downstream side guide member  103  are positioned to be on the bottom side of the sheet stacking section  100  (opposite Y direction side), and they constitute a stacking surface along which sheets S slide down to be stacked. Further, the upstream side guide member  102  is arranged to face the upstream side guide member  101  with a fixed space in-between, and the downstream side guide member  104  is arranged to face the downstream side guide member  103  with a fixed space in-between. 
     The center stapling section  72  is composed of staple-receiving mechanism  72   a  and staple-nailing mechanism  72   b , and when a central portion of a bundle of sheets S in the conveyance direction is positioned by regulating member  105 , the center stapling section  72  operates to conduct center-stapling for sheets S. 
     The folding section  50  is equipped with folding plate  51 , folding upper roller  52 , folding lower roller  53 , second folding roller  54 , conveyance path switching member  55 , guide member  56  that constitutes folding introduction device and with leading edge stop member  57 , and it conducts two-fold processing or three-fold processing for sheet S. 
     In the two-fold processing, the regulating member  105  is moved first so that a central portion of sheet S may be positioned at a location of the folding plate  51 . Then, the folding plate  51  inserts the sheet S between the folding upper roller  52  and the folding lower roller  53 , while the folding upper roller  52  and the folding lower roller  53  are rotating. Since the folding upper roller  52  and the folding lower roller  53  are urged by an unillustrated spring member so that they may be pressed each other, the sheet S is folded at its central portion to form a crease, and it is ejected to lower sheet ejection tray  83  through a lower portion of the conveyance path switching member  55  that is located at a position shown by broken lines. 
     In the case of the three-fold processing, the conveyance path switching member  55  is set to the position shown with solid lines. Then, sheet S undergoes folding processing in the same way as in the two-fold processing at the position corresponding to a length equivalent to one-third of a length of the sheet S, and then, the sheet S is moved to be guided to the guide member  56  along the upper surface of the conveyance path switching member  55 , with a crease on the sheet S that serves as the forefront. In this case, the leading edge stop member  57  is located at a prescribed position corresponding to a sheet size, and the leading edge stop member  57  stops the crease on the leading edge of the sheet S. 
     Under the condition that the leading edge of the sheet S is stopped, when the folding upper roller  52 , the folding lower roller  53  and the second folding roller  54  are further rotated, the sheet S is bent and curved to be inserted between the folding lower roller  53  and the second folding roller  54 , thus, the second folding processing is carried out. Then, the sheet S is ejected to lower sheet ejection tray  83  through the lower part of the second folding roller  54 . 
     On the sheet stacking section  100 , sheets S are stacked for the aforesaid stapling processing and for the folding processing. However, in the conventional construction of the sheet stacking section, the empty weight of the sheet S causes the sheet S to buckle, resulting in an occasion wherein sheets S have not been aligned satisfactorily, and sheet bundles after sheet finishing processing have become uneven. 
     The invention is one wherein a guide member that constitutes sheet stacking section  100 , in particular, stacking surface a formed by downstream side guide members  103  and  104  is constituted so that sheet S may be curved downward on both sides of the sheet in the directions (Z direction and its opposite directions) that is perpendicular to the conveyance direction for sheet S, in order to solve the problem of this kind for buckling of sheet S. 
     Each of  FIGS. 3A-3B  is a sectional view of downstream side guide member section taken on line IIIA-IIIA in  FIG. 2 , and  FIG. 3B  is an abridged sectional view wherein principal parts only in  FIG. 3A  are displayed. 
     In  FIGS. 3A-3B , downstream side guide member  103  that forms a stacking surface among downstream side guide members is composed of downstream side guide member  103   a  at the center, and of downstream side guide members  103   b  and  103   c  respectively on the left and the right in the Z direction. Each of these downstream side guide members  103   b  and  103   c  is tilted by angle α from a virtual plane shown with a two-dot chain line as shown on the left side in  FIG. 3B , and the angle α is set to 4° in the embodiment of the invention. 
     On the other hand, downstream side guide member  104  has on its inside portion central rib  104   a , left side ribs  104   b  and right side ribs  104   c . A height of each of the left side ribs and the right side ribs grows greater toward an outer side. A height of the rib is one that forms a space that is almost the same as the tilted surface of the downstream side guide member  103 , as shown on the right side in  FIG. 3B . These ribs  104   a ,  104   b  and  104   c  form a guide surface that is curved in the same direction as that for the stacking surface. 
     In  FIG. 3A , the regulating members  105  are positioned on the left side and the right side of the rib  104   a , and they move in the X direction and its opposite direction to regulate leading edges of sheets S stacked between downstream side guide members  103  and  104  to the prescribed position. 
       FIG. 4  is a sectional view of an upstream side guide member taken on line IV-IV in  FIG. 2 . In the drawing, upstream side guide member  101  is constituted to be in parallel with a virtual plane, and in the same way, upstream side guide member  102  also has ribs at the center and in the left and right sides, and heights of the ribs are the same. 
     In  FIG. 4 , although the center stapling section  72  is illustrated to be at the center in the drawing, it moves to the left and to the right in the case of stapling processing to conduct stapling processing at two locations. In the drawing, guide rod  73  for this movement is illustrated only on staple-nailing mechanism  72   b  side. 
     Sheet S fed into sheet stacking section  100  by the conveyance rollers  23  advances downward while being guided by a flat stacking surface of the upstream side guide member  101 , and then, it slides down along the stacking surface when a trailing edge of the sheet S leaves the conveyance rollers  23 . Then, when a leading edge side of the sheet S enters a space between the downstream side guide members  103  and  104 , both sides of the sheet S are curved by the empty weight of the sheet S, following the stacking surfaces which are both sides hanging down of the downstream side guide member  103 . In addition, ribs on the downstream side guide member  104  accelerate curving of the sheet S. 
     The sheet S advances to the position of the regulating member  105  while being guided by the guide member, and the sheet S is stacked at that position to be in the state where the sheet S is curved along the stacking surface. The sheet S is curved along a shape of curvature of the guide member, resulting in an improvement of stiffness in the conveyance direction of the sheet S, thus, occurrence of buckling can be prevented. 
     It is preferable that angle α for downstream side guide members  103   b  and  103   c  to be tilted is 4° or more. This angle is one confirmed through experiments by the inventors of the present invention, and when the angle was less than 4°, there was an occasion where the sheet S was not curved sufficiently and buckling occurred. The upper limit of the angle is about 4° plus several degrees, though this value varies slightly depending on dimensions of a sheet stacking section and on types of sheets. 
     Further, the reason why the guide member that curves sheet S is only the downstream side guide member is to secure accuracy of sheet finishing by aligning sheets S flatly in the case of sheet finishing. However, it is also possible to employ the structure wherein the upstream side member is also tilted similarly to curve the sheet S, depending on the structure of the sheet finishing section. 
     Though the guide member  103  is made to be of the split construction in the embodiment described above, it is also possible to employ the construction wherein a guide member in a body is cut off by an amount equivalent to a portion of a range of movement of regulating member  105 , depending on a range of movement of the regulating member  105 . 
     Though the aforesaid sheet finisher FS has been explained in the form of connection with image forming apparatus A, the aforesaid sheet finisher FS can naturally be applied on the sheet finishing section, when a sheet finishing section is provided in the image forming apparatus main body. 
     As stated above, in the sheet finisher of the invention, buckling of sheet can be prevented by the simple construction that does not take a space and is low cost, because stiffness of the sheet is increased by curving the sheet, namely, by curling the sheet.