Patent Publication Number: US-2011062645-A1

Title: Sheet finishing apparatus and sheet finishing method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from: U.S. provisional applications 61/242,715 filed on Sep. 15, 2009, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to a sheet finishing apparatus and sheet finishing method. 
     BACKGROUND 
     In the related art, as a sheet finishing apparatus installed on the downstream side of an image forming apparatus such as a copying machine, a printer, or a MFP (Multi-Functional Peripheral) and configured to bind booklets by performing a finishing process such as folding or stapling on printed sheets is known. 
     Many of the sheet finishing apparatuses of these type include a sheet placing unit (loading tray) for loading a plurality of the bound booklets. 
     The booklets themselves are bound in a finishing apparatus body, and the booklets discharged from a discharging port of the finishing apparatus body one after another are loaded on the sheet placing unit in sequence. 
     A bundle of the booklets to be loaded on the sheet placing unit does not necessarily have a uniform thickness, and a leading end portion (a portion where a fold line is formed) is thicker, and thus a center portion is depressed in many cases. Consequently, a leading end of the booklet discharged subsequently may hit against the depression or the depression of the booklet pushes back the leading end of the booklet, so that smooth discharge may be hindered. Accordingly, improvement of a mechanism is required to achieve smooth discharge of the subsequent booklets even if the thickness of the bundle of booklets loaded on the sheet placing unit is not uniform. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing an example of an appearance of an image forming apparatus provided with a sheet finishing apparatus in an embodiment; 
         FIG. 2  is a cross-sectional view showing an example of a configuration of the image forming apparatus; 
         FIG. 3  is a cross-sectional view showing an example of a configuration of the sheet finishing apparatus; 
         FIG. 4  is a perspective appearance view showing an example of a configuration of a sheet placing unit; 
         FIG. 5  is a perspective outline view of the sheet placing unit with an upper arm and a fore arm removed; 
         FIG. 6  is a diagrammatic drawing of the sheet placing unit and part of the sheet finishing apparatus body viewed from the front of the image forming apparatus; 
         FIGS. 7A and 7B  are drawings showing discharging and loading situations of booklets in a sheet finishing apparatus in the related art as comparative examples; 
         FIGS. 8A and 8B  are first drawings showing discharging and loading situations of booklets in the sheet finishing apparatus according to the embodiment; 
         FIGS. 9A and 9B  are second drawings showing discharging and loading situations of booklets in the sheet finishing apparatus according to the embodiment; and 
         FIG. 10  is a drawing showing another example of a projecting member. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the attached drawings, an embodiment of a sheet finishing apparatus and a sheet finishing method will be described. 
     The sheet finishing apparatus according to the embodiment includes a main body configured to fold a bundle of sheets to form a booklet, a base plate extending obliquely downward from a side wall of the main body to allow loading of a plurality of the booklets discharged in sequence from a discharging port provided in the side wall, a discharging roller pair configured to push the booklet out from the discharging port to discharge the booklet on the base plate, and a projecting member configured to project from the side wall substantially horizontally and support the lower portion of the booklet between the discharging port and the base plate when the discharging roller pair pushes the booklet out. 
     (1) Configuration 
       FIG. 1  is a perspective view showing an appearance of an example of a basic configuration of an image forming apparatus  10  having a sheet finishing apparatus  20  according to a first embodiment. The image forming apparatus  10  includes a scanning unit  11  configured to scan documents, an image forming unit  12  configured to print image data of the scanned documents on a sheet on the basis of an electrophotographic system, and the sheet finishing apparatus  20  configured to perform a finishing process such as sorting, punching, folding, and saddle-stitching for the printed sheets. The image forming unit  12  also includes an operating unit  9  through which users perform various operations. 
       FIG. 2  is a cross-sectional view showing an example of a detailed configuration of the image forming apparatus  10 . 
     The image forming unit  12  of the image forming apparatus  10  includes a photoconductive drum  1  at a center thereof, and also includes a charging unit  2 , an exposure unit  3 , a developing unit  4 , a transfer unit  5 A, a charge removing unit  5 B, a separating claw  5 C, and a cleaning unit  6  disposed respectively around the photoconductive drum  1 . A fixing unit  8  is provided on the downstream side of the charge removing unit  5 B. Image formation is performed by these members in a sequence schematically shown below. 
     First, the charging unit  2  charges the surface of the photoconductive drum  1  uniformly. In the meantime, the document scanned by the scanning unit  11  is converted into image data, which is input to the exposure unit  3 . The exposure unit  3  irradiates the photoconductive drum  1  with laser beams according to the level of the image data to form an electrostatic latent image on the photosensitive drum  1 . The electrostatic latent image is developed by toner supplied from the developing unit  4 , whereby a toner image is formed on the photoconductive drum  1 . 
     A sheet stored in a sheet storage unit  7  ( 7 A,  7 B,  7 C) passes through a sheet thickness detector  90  via several carrying rollers and is carried to a transfer position (a clearance between the photoconductive drum  1  and the transfer unit  5 A). At the transfer position, the transfer unit  5 A transfers the toner image from the photoconductive drum  1  to the sheet. The charge removing unit  5 B removes a charge on the surface of the sheet having the toner image transferred thereto. The separating claw  5 C separates the sheet from the photoconductive drum  1 . An intermediate carrying unit  5 D carries the sheet, the fixing unit  8  heats and pressurizes, whereby the toner image is fixed to the sheet. The sheet after the fixation is discharged from the discharging unit  5 E and output to the sheet finishing apparatus  20 . 
     The cleaning unit  6  arranged on the downstream of the separating claw  5 C removes developer remaining on the surface of the photoconductive drum  1  for being ready for the next image formation. 
     The sheet finishing apparatus  20  includes a paper folding device  30  and a sheet placing unit  40  in addition to a sorter unit that sorts the sheets. 
     The paper folding device  30  staples the center portions of the plurality of printed sheets discharged from the image forming unit  12 , then folds and bookbinds the same (saddle-stitching) at the centers thereof to form a booklet. The saddle-stitching with a staple may be omitted. In this case, the sheets are simply folded in the middle and the folded bundles of sheets are loaded on the sheet placing unit  40 . 
     The booklets saddle-stitched and center-folded (or simply center-folded) by the paper folding device  30  are output to the sheet placing unit  40 , where the booklets (bundles of sheets) are finally placed on. 
       FIG. 3  is a cross-sectional view showing an example of a detailed configuration of the paper folding device  30 . 
     The paper folding device  30  receives a sheet discharged from the discharging unit  5 E of the image forming unit  12  by an inlet port roller pair  31 , and feeds the same to an intermediate roller pair  32 . The intermediate roller pair  32  in turn feeds the sheet to an outlet port roller pair  33 . The outlet port roller pair  33  delivers the sheet to a standing tray  34  having an inclined placing surface. A leading edge of the sheet is directed upward of the inclination of the standing tray  34 . 
     A stacker  35  waits below the standing tray  34  for receiving a lower end of the sheet being switched back and falling from upward of the inclination of the standing tray  34 . 
     A stapler (saddle-stitching unit)  36  is disposed in a midsection of the standing tray  34 . When saddle-stitching (stapling) the bundle of sheets, the position of the stacker  35  is adjusted so that a position of the bundle of sheets to be stapled (the center portion of the bundle of sheets in the vertical direction) opposes the stapler  36 . 
     When the saddle-stitching of the bundle of sheets is finished by the stapler  36 , the stacker  35  moves downward until the position of the bundle of sheets to be folded (stapled position at the center of the bundle of sheets in the vertical direction) comes to the front of a sheet-folding blade  37 . 
     When the position to be folded comes to the front of the sheet-folding blade  37 , a front end  37   a  of the sheet-folding blade  37  pushes the surface of the bundle of sheets, which is to be an inner surface when it is folded, inward. 
     A folding roller pair  38  is provided in front of the sheet-folding blade  37  in the direction of travel. The bundle of sheets pushed inward by the sheet-folding blade  37  is drawn into a nip of the folding roller pair  38 , so that a fold line is formed at the center portion of the bundle of sheets. The sheet-folding blade  37  and the folding roller pair  38  constitute a sheet-folding unit. 
     The bundle of sheets on which the fold line is formed by the folding roller pair  38  is carried to a fold reinforcing unit  50  provided on the further downstream side thereof. The bundle of sheets carried to the fold reinforcing unit  50  stops temporarily on a placing bed  52 . 
     The fold reinforcing unit  50  includes fold reinforcing rollers  51  (a pair of rollers including an upper roller  51   a  and a lower roller  51   b ). The fold reinforcing rollers  51  move while pressurizing the fold line in the direction orthogonal to the carrying direction of the bundle of sheets (the direction along the fold line) and reinforce the fold line. 
     The bundle of the sheets whose fold line is reinforced by the fold reinforcing unit  50  starts being carried again, is drawn into the nip of a discharging roller pair  39   a  and  39   b , and is output to the sheet placing unit  40 , where the saddled-stitched bundles of sheets, that is, booklets are placed on the sheet placing unit  40 . 
     Note that a projecting member  80 , which will be described later, is provided below the discharging roller pair  39   a  and  39   b.    
       FIG. 4  is a drawing showing the sheet placing unit  40  of the sheet finishing apparatus  20  in an enlarged scale. 
     The sheet placing unit  40  includes a bed  903 , a base plate  915 , an upper arm  907 , and a fore arm  908 . A demountable guard  905  is provided at a front end of the base plate  915 . 
     The base plate  915  is connected to an side wall  902  of the main body of the sheet finishing apparatus  20  via a spring  906 , and extends obliquely downward from the side wall  902  of the main body together with the bed  903 . The base plate  915  is a member for allowing the plurality of booklets discharged in sequence from the discharging port  901  provided in the side wall  902  to be loaded thereon. 
     A base end of the upper arm  907  is supported so as to be rotatable about a shaft  909  provided on a support  910 , which is fixed to the side wall  902 . 
     A shaft  914  is provided at a distal end of the upper arm  907 , and an upper end of the fore arm  908  is rotatably supported by the shaft  914 . 
     The base plate  915  forms a gentle hill at the center portion in the direction along the inclination, and includes a flapper  950  in the vicinity of the top of the hill. A depression is formed above the flapper  950  along the inclination. A lower end of the fore arm  908  engages the depression, and the fore arm  908  extends in the directions substantially orthogonal to the loading plane of the base plate  915 . 
     The booklets to be loaded on the base plate  915  slide down along the bed  903  and the loading plane of the base plate  915  by their own weights, and the fore arm  908  receives the leading ends of the booklets. 
     The side wall  902  on the lower side of the discharging port  901  includes a slot  81  formed therein. When the discharging roller pair  39   a  and  39   b  pushes the booklet and discharges the same from the discharging port  901 , the projecting member  80  projects substantially horizontally from the slot  81 . 
       FIG. 5  is a drawing showing the sheet placing unit  40  with the upper arm  907  and the fore arm  908  removed. The bed  903  accommodates a sheet sensor (not shown) that detects the booklet in the interior thereof, and the sheet sensor includes a detection lever  980 . If the booklet is not placed on the base plate  915 , the detection lever  980  projects and is exposed from the depression on the base plate  915 , as shown in  FIG. 5 . The detection lever  980  is retracted by the weight of the booklet placed on the base plate  915  even with a single booklet. With the movement of the detection lever  980 , the sheet sensor is capable of differentiating a state having no booklet placed on the base plate  915  (non-loaded state) and a state having at least one booklet loaded thereon (loaded state). 
       FIG. 6  is a diagrammatic drawing of the sheet placing unit  40  and part of the sheet finishing apparatus body (hereinafter, referred to simply as “main body”) viewed from the front (the direction where the operating unit  9  is located in  FIG. 1 ). As described before, the sheet placing unit  40  includes the bed  903 , the base plate  915 , the upper arm  907 , and the fore arm  908 . The bed  903  and the base plate  915  extend obliquely downward from the side wall  902  of the main body to allow loading of the plurality of booklets discharged in sequence from the discharging port  901  provided in the side wall. The guard  905  is provided at a lower end of the base plate  915 . 
     The discharging port  901  is provided in the side wall  902  of the main body, and the discharging roller pair  39   a  and  39   b  is provided inside thereof. The placing bed  52  is provided at the back of the discharging roller pair  39   a  and  39   b . The booklet whose fold line is reinforced on the placing bed  52  is pushed by the discharging roller pair  39   a  and  39   b  and proceeds toward the sheet placing unit  40 . 
     The sheet finishing apparatus  20  in this embodiment includes the plate-shaped or the rod-shaped projecting member  80  that projects from the side wall  902  substantially horizontally and supports the lower portion of the booklet between the discharging port  901  and the base plate  915  when the discharging roller pair  39   a  and  39   b  pushes the booklet out. 
       FIG. 6  shows a situation in which the projecting member  80  is at a home position. The home position of the projecting member  80  is a position in which the front end of the projecting member  80  aligns with, or comes inside the position of the side wall  902  in the direction of movement of the projecting member  80 . 
     When the leading end of the booklet starts to be discharged from the discharging port  901 , the projecting member  80  also starts to project horizontally from the slot  81 , and proceeds toward the bed  903  while supporting the lower portion of the booklet. 
     The projecting member  80  moves in the direction opposite from the projecting direction toward the side wall  902  when the front end reaches a predetermined extending distance from the side wall  902 . In contrast, the discharging roller pair  39   a  and  39   b  continues to push the booklet even after the projecting member  80  starts moving toward the side wall  902 , drops the booklet from the projecting member  80 , and loads the same on the bed  903  or the base plate  915 . If focusing only on the function to load the booklets, the bed  903  and the base plate  915  have almost the same functions. Therefore, the description is given below on condition that the bed  903  is included in the base plate  915 . 
     In the sheet finishing apparatus  20  in this embodiment, with the provision of the projecting member  80 , smooth discharge of the booklets to the sheet placing unit  40  as well as stable and well-conditioned loading are achieved. 
     (2) Operation of Projecting Member 
       FIGS. 7A and 7B  are diagrammatic drawings showing a situation in which the booklets are discharged and loaded by the sheet finishing apparatus in the related art, which does not have the projecting member  80 , as a comparative example with respect to the sheet finishing apparatus  20  in this embodiment. 
     As mentioned above, booklets B 0  loaded on the base plate  915  do not necessarily have a uniform thickness. Although it depends on the type or the number of sheets which constitute each booklet, they tend to be thicker at the leading end portions (portions in the vicinity of the fold lines) of the booklet. Therefore, when the number of the booklets B 0  to be loaded is increased, a depression D may be formed in the vicinity of the center of the booklets B 0 . In  FIG. 7A  (also drawings from  FIG. 7B  onward), the illustration of the depression D is exaggerated for easy understanding of this phenomenon. 
     On the other hand, in general, while the booklet is hard to bend in the direction of the fold line, it is relatively easy to bend in the direction orthogonal to the fold line. Therefore, the booklet B 1  discharged from the discharging port  901  tends to bend downward as shown in  FIG. 7B . The leading end of the bent booklet B 1  comes into abutment with the surface of the previously loaded booklet B 0 . 
     In particular, if the leading end of the booklet B 1  comes into abutment with the previously loaded booklets B 0  substantially at a right angle as shown in  FIG. 7B , the surface of the previously loaded booklet B 0  pushes back strongly the leading end of the booklet B 1 . Particularly, if the leading end of the booklet B 1  comes into abutment with the depression D of the booklets B 0 , the pushing-back force of the surface of the booklets B 0  further increases. 
     Therefore, even if the rear portion of the booklet B 1  is pushed by the discharging roller pair  39   a  and  39   b , the leading end of the booklet B 1  cannot move further forward, and then the booklet B 1  is placed on the base plate  915  in a bent state or in a displaced state. In addition, since the leading end of the booklet B 1  is strongly pushed back, the discharging roller pair  39   a  and  39   b  may stop in the course of discharge of the booklet B 1 . If the discharging roller pair  39   a  and  39   b  stops, the subsequent booklet cannot be discharged to the sheet placing unit  40 , so that a paper jamming occurs in the interior of the main body of the sheet finishing apparatus  20 . 
     By contrast, in the sheet finishing apparatus  20  in this embodiment, such event is avoided by adding a relatively simple configuration such as the projecting member  80 . 
     A method may be conceivable, which enhances the drive force of the discharging roller pair  39   a  and  39   b  and pushes the leading end of the booklet B 1  forcedly toward the front against the depression D. However, since the discharging roller pair  39   a  and  39   b  is provided in the proximity of the inside of the discharging port  901 , if the drive force of the discharging roller pair  39   a  and  39   b  is increased too much, it might cause a serious damage to a human body or the like when the human body such as a finger or a clothe is accidentally drawn therein. Therefore, the method of enhancing the drive force of the discharging roller pair  39   a  and  39   b  is not necessarily a preferable solving method. 
       FIGS. 8A and 8B  and  FIGS. 9A and 9B  are explanatory drawings showing effects of the projecting member  80 . 
       FIG. 8A  shows a situation in which the projecting member  80  is at the above-described home position. When the leading end of the booklet B 1  which is about to be discharged is still inside the discharging port  901 , the projecting member  80  is located at the home position. At this time, several booklets B 0  are assumed to be placed already on the base plate  915 . 
       FIG. 8B  is a drawing showing a situation in which the leading end of the booklet B 1  starts to be discharged from the discharging port  901 . When the leading end of the booklet B 1  starts to be discharged from the discharging port  901 , the projecting member  80  starts moving forward (the direction toward the fore arm  908  indicated by an arrow A in  FIG. 8B ) substantially simultaneously thereto. The projecting member  80  moves substantially horizontally. 
       FIG. 9A  is a drawing showing a situation in which the booklet B 1  is pushed further forward. At this time, the projecting member  80  still continues to move forward. With this movement of the projecting member  80 , even though the leading end portion of the booklet B 1  hangs over by its own weight, the projecting member  80  is capable of letting the booklet B 1  move forward while supporting the lower portion of the booklet B 1 . 
     By setting the discharging velocity of the booklet B 1  and the moving velocity of the projecting member  80  toward the front to be substantially the same, the booklet B 1  can be moved forward further stably without causing slippage between the lower portion of the booklet B 1  and the projecting member  80 . 
     When the projecting member  80  reaches a predetermined extending distance Dmax, the projecting member  80  changes the direction of movement and starts moving toward the home position. When the projecting member  80  starts moving toward the home position, the booklet B 1  falls down from the leading end thereof toward the booklets B 0  which are already loaded. 
     The extending distance Dmax is preferably a distance at which the position of the leading end of the booklet B 1  gets beyond a position of half the length of the loaded booklets B 0  in the discharging direction. In addition, the extending distance Dmax is preferably a distance at which the position of the leading end of the booklet B 1  extends beyond the position of the front end of the depression D of the loaded booklets B 0 . It is because if the extending distance Dmax is a distance getting beyond a position of half the length of the booklets B 0 , or a distance getting beyond the position of the front end of the depression D, the position of the leading end of the booklet B 1  which is falling down due to the backward movement of the projecting member  80  comes to a position beyond the deepest position of the depression D, and hence the pushing-back force that the leading end of the booklet B 1  receives from the booklets B 0  is alleviated. 
       FIG. 9B  is a drawing showing a situation in which the projecting member  80  returns to the home position. When the trailing end of the booklet B 1  is discharged from the discharging port  901 , the projecting member  80  is preferably back to the home position. As described above, the front end of the projecting member  80  at the home position aligns with, or comes inside the position of the side wall  902 . Therefore, the trailing end of the booklet B 1  discharged from the discharging port  901  falls down without being hindered by the projecting member  80  and is loaded without displacement. 
     The projecting member  80  is a plate-shaped member, that is, a blade. The blade is formed so that the longitudinal direction thereof is horizontal along the side wall  902  and the short side direction is a moving direction of the blade, as shown in  FIG. 4 . However, the invention is not limited to this shape. 
     For example, the projecting member  80   a  may be formed of a rod-shaped member moving in the longitudinal direction thereof as shown in  FIG. 10 . The rod-shaped projecting member  80   a  may be of a rectangular column shape as shown in  FIG. 10  or a circular column shape, and the cross-sectional shape is not specifically limited. Also, the number of the rod-shaped projecting members  80   a  is not limited specifically, as long as it can support the booklet B 1  stably. As shown in  FIG. 10 , two or more of the rod-shaped projecting members  80   a  may be employed. Since the booklet B 1  is generally hard to bend in the direction of the fold line, a configuration to support the center of the booklet B 1  using a single rod-shaped member may also be applicable. 
     A drive mechanism for the projecting member  80 ,  80   a  is not described in detail. Known drive mechanisms can be used. 
     As described thus far, with the sheet finishing apparatus  20  and a sheet finishing method (booklet discharging method) according to the embodiment, even though the thickness of the bundle of booklets to be loaded on the sheet placing unit is not uniform, the smooth discharge of the subsequent booklet is achieved only by adding the simple projecting member  80 ,  80   a  to the configuration in the related art. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. Indeed, the novel apparatuses and units described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the apparatuses and units described herein may be made without departing from the spirit of the invention. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.