Abstract:
Provided is a post-processing device including a stacking section that aligns and stacks recording materials which are sequentially transported, a saddle stitching section that binds plural sheets of recording materials in central portions of the recording materials, a center folding section that folds the plural sheets of recording materials into two in the central portions, a pressing section that presses a booklet in a thickness direction of the booklet, and a discharge section that discharges the booklet, which is pressed by the pressing section, with a folded portion of the booklet being a leading portion, wherein the booklet is held and stopped in a state of being nipped by the discharge section, and transport is initiated after the lapse of a predetermined stop time so that the booklet is discharged.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2014-059394 filed Mar. 24, 2014. 
     BACKGROUND 
     Technical Field 
     The present invention relates to a post-processing device. 
     SUMMARY 
     According to an aspect of the invention, there is provided a post-processing device including: 
     a stacking section that aligns and stacks recording materials which are sequentially transported; 
     a saddle stitching section that binds plural sheets of recording materials, which are stacked on the stacking section, in central portions of the recording materials; 
     a center folding section that folds the plural sheets of recording materials, which are bound in the central portions by the saddle stitching section, into two in the central portions; 
     a pressing section that presses a booklet, which is formed of the plural sheets of recording materials center-folded by the center folding section, in a thickness direction of the booklet; and 
     a discharge section that discharges the booklet, which is pressed by the pressing section, with a folded portion of the booklet being a leading portion, 
     wherein the booklet is held and stopped in a state of being nipped by the discharge section, and transport is initiated after the lapse of a predetermined stop time so that the booklet is discharged. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1  is a schematic cross-sectional view showing the internal configuration of an image forming system; 
         FIGS. 2A to 2F  are flowcharts for describing the flow of operation of a saddle stitching and folding processing mechanism in a post-processing device; 
         FIG. 3  is a schematic view for describing the flow of center folding processing in the saddle stitching and folding processing mechanism; and 
         FIGS. 4A to 4C  are schematic cross-sectional views for describing a state where a booklet is held in the saddle stitching and folding processing mechanism. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, exemplary embodiments and specific examples of the invention will be described in further detail with reference to the accompanying drawings. However, the invention is not limited to the exemplary embodiments and specific examples. 
     In addition, it should be noted that the drawings that are used for the following description are schematic, the ratios of dimensions and the like are different from actual ones, and only the members that are required for the description are shown for ease of understanding. 
     Hereinafter, the front-back direction is referred to as an X-axis direction, the left-to-right direction is referred to as a Y-axis direction, and the up-and-down direction is referred to as a Z-axis direction in the drawings for ease of understanding of the following description. 
     First Exemplary Embodiment 
     (1) Overall Configuration and Operation of Image Forming System 
       FIG. 1  is a schematic configurational view showing an image forming system  1  to which a post-processing device according to this exemplary embodiment is applied. The image forming system  1  that is shown in  FIG. 1  includes an image forming apparatus  2  such as a printer and a copying machine that forms an image by an electrophotography method, and a sheet processing device  3  that performs post-processing on a sheet P as a recording material where a toner image is formed by the image forming apparatus  2 . Hereinafter, the overall configuration and operation of the image forming system  1  will be described with reference to the drawing. 
     (1.1) Overall Configuration and Operation of Image Forming Apparatus 
     The image forming apparatus  2  is configured to have a control device  10 , a sheet feeding device  20 , photoconductor units  30 , developing devices  40 , a transfer device  50 , and a fixing device  60 . A transport device  100  is arranged on an upper surface (Z direction) of the image forming apparatus  2 , and the sheet P on which an image is recorded is guided to a post-processing device  200 . 
     The control device  10  has an image forming apparatus control unit  11  that controls the operation of the image forming apparatus  2 , a controller unit  12  that prepares image data in response to a print processing request, an exposure control unit  13  that controls the lighting of an exposure device LH, a power supply device  14 , and the like. The power supply device  14  applies a voltage to charging rollers  32 , developing rollers  42 , primary image transfer rollers  52 , a secondary image transfer roller  53 , and the like (described later), and supplies power to the exposure device LH. 
     The controller unit  12  converts printing information that is input from an external information transmission device (for example, a personal computer, and the like) to image information for forming a latent image, and outputs a driving signal to the exposure device LH at a timing set in advance. An LED head where light emitting diodes (LED) are linearly arranged constitutes the exposure device LH according to this exemplary embodiment. 
     The sheet feeding device  20  is disposed in a bottom portion of the image forming apparatus  2 . The sheet feeding device  20  has a sheet stacking plate  21 , and the multiple sheets P as a recording medium are stacked on an upper surface of the sheet stacking plate  21 . The sheets P that are stacked on the sheet stacking plate  21  with width-direction positions determined by a regulating plate (not shown) are drawn out forward (−X direction), sheet by sheet from an upper side, by a sheet drawing unit  22 , and then are transported to a nip portion of an resist roller pair  23 . 
     The photoconductor units  30  are disposed in parallel above the sheet feeding device  20  (Z direction), and have photosensitive drums  31  that are image holding members which are rotationally driven. The charging rollers  32 , the exposure device LH, the developing devices  40 , the primary image transfer rollers  52 , and cleaning blades  34  are arranged in the direction of rotation of the photosensitive drums  31 . Cleaning rollers  33  that clean surfaces of the charging rollers  32  are arranged to face and be in contact with the charging rollers  32 . 
     The developing devices  40  have developing housings  41  in which developers are accommodated. The developing roller  42  that is arranged to face the photosensitive drum  31  is arranged in the developing housing  41  with a pair of augers  44  and  45 , which agitate and transport the developer to the developing roller  42  side, obliquely downward on a back surface side of the developing roller  42 . Layer regulating members  46  that regulate the layer thicknesses of the developers are arranged close to the developing rollers  42 . 
     The respective developing devices  40  have substantially similar configurations with the exception of the developers that are accommodated in the developing housings  41 , and form yellow (Y), magenta (M), cyan (C), and black (K) toner images. 
     Surfaces of the rotating photosensitive drums  31  are charged by the charging rollers  32 , and electrostatic latent images are formed by latent image forming light which is emitted from the exposure device LH. The electrostatic latent images that are formed on the photosensitive drums  31  are developed as toner images by the developing rollers  42 . 
     The transfer device  50  has an intermediate image transfer belt  51  where the toner images of the respective colors that are formed with the photosensitive drums  31  of the respective photoconductor units  30  are subjected to multi layer transfer, and the primary image transfer rollers  52  that sequentially transfer (primary image transfer) the toner images of the respective colors which are formed with the respective photoconductor units  30  to the intermediate image transfer belt  51 . Further, the secondary image transfer roller  53  that collectively transfers (secondary image transfer) the toner images of the respective colors which are superposed on the intermediate image transfer belt  51  and transferred to the sheet P as the recording medium also constitutes the transfer device  50 . 
     The toner images of the respective colors which are formed with the photosensitive drums  31  of the respective photoconductor units  30  are sequentially and electrostatically transferred (primary image transfer) onto the intermediate image transfer belt  51  by the primary image transfer rollers  52  to which a predetermined transfer voltage is applied from, for example, the power supply device  14  controlled by the image forming apparatus control unit  11 , and a superposed toner image is formed with the toner of the respective colors superposed. 
     The superposed toner image on the intermediate image transfer belt  51  is transported to an area where the secondary image transfer roller  53  is arranged (secondary image transfer section T) in response to the movement of the intermediate image transfer belt  51 . At the timing when the superposed toner image is transported to the secondary image transfer section T, the sheet P is supplied to the secondary image transfer section T from the sheet feeding device  20 . A predetermined transfer voltage is applied to the secondary image transfer roller  53  from the power supply device  14  controlled by the image forming apparatus control unit  11 , and the multiple toner images on the intermediate image transfer belt  51  are collectively transferred onto the sheet P sent out from the resist roller pair  23  and guided by a transport guide. 
     The residual toner on the surfaces of the photosensitive drums  31  is removed by the cleaning blades  34  and is recovered into a waste developer accommodating portion. The surfaces of the photosensitive drums  31  are charged again by the charging rollers  32 . The residue that is not removed by the cleaning blades  34  and is attached to the charging rollers  32  is captured and accumulated on surfaces of the cleaning rollers  33  which rotate in contact with the charging rollers  32 . 
     The fixing device  60  has a heating module  61  and a pressure module  62 , and a fixing nip portion N (fixing area) is formed by an urge area of the heating module  61  and the pressure module  62 . 
     The sheet P where the toner image is transferred in the transfer device  50  is transported to the fixing device  60  through the transport guide in a state where the toner image is not fixed. The toner image is fixed onto the sheet P, which is transported to the fixing device  60 , through crimping and heating effects by the pair of the heating module  61  and the pressure module  62 . 
     The sheet P on which the fixed toner image is formed is guided by transport guides  65   a  and  65   b , and is discharged from a discharge roller pair  69  to the transport device  100  that is arranged on the upper surface of the image forming apparatus  2 . 
     (1.2) Configuration and Operation of Sheet Processing Device 
     The sheet processing device  3  has the transport device  100  that transports the sheets P which are output from the image forming apparatus  2  to the further downstream side, and the post-processing device  200  that has a saddle stitching and folding processing mechanism  210  which performs saddle stitching and folding processing on the sheets P brought in from the transport device  100  to manufacture a booklet, a compile tray  220  which collects and bundles the sheets P, an edge-binding mechanism (binding unit)  230  which binds end portions of the sheets P, and the like. 
     The transport device  100  has an inlet roller  110  that receives the sheet P which is output via the discharge roller pair  69  of the image forming apparatus  2 , a first transport roller  120  that transports the sheet P which is received by the inlet roller  110  to the downstream side, and a second transport roller  130  that transports the sheet P toward the post-processing device  200 . 
     The post-processing device  200  has a first post-processing transport path S 1 , a second post-processing transport path S 2 , and a third post-processing transport path S 3  on the downstream side of a receiving roller  201  that receives the sheets P via the transport device  100 , and the first post-processing transport path S 1 , the second post-processing transport path S 2 , and the third post-processing transport path S 3  are selected by a switching gate G 1 . In addition, the first post-processing transport path S 1  and the second post-processing transport path S 2  are selected by a switching gate G 2 . 
     The first post-processing transport path S 1  is connected to a top tray TR 1 , and the sheet P that is not subjected to post-processing is discharged from the first post-processing transport path S 1 . 
     The second post-processing transport path S 2  is connected to the compile tray  220  that is disposed on the downstream side, and a sheet bundle PB that is produced by the edge-binding mechanism (binding unit)  230  is discharged to a stacker tray TR 2 . 
     The third post-processing transport path S 3  is connected to the saddle stitching and folding processing mechanism  210 , and the booklet that is produced with the saddle stitching and folding processing mechanism  210  is nipped by a pair of folding rollers  217  and is discharged from a discharge roller  218  to a booklet tray TR 3 . 
     (2) Configuration and Operation of Saddle Stitching and Folding Processing Mechanism 
     As shown in  FIG. 1 , the saddle stitching and folding processing mechanism  210  has a saddle stitching compile tray  212  that stacks a required number of the sheets P where the images are formed by the image forming apparatus  2  during the production of the booklet, a positioning stopper  213  that is moved along the saddle stitching compile tray  212  so as to determine a saddle stitching position and a folding position, a paddle  214  that aligns the sheets P which are stacked on the saddle stitching compile tray  212  toward the positioning stopper  213 , and a saddle stitching stapler  215  that performs saddle stitching on the sheets P which are stacked on the saddle stitching compile tray  212 . 
     The saddle stitching and folding processing mechanism  210  further has a folding knife  216  that performs center folding on the sheet bundle PB, which is subjected to saddle stitching by the saddle stitching stapler  215 , from the saddle stitching position, a folding roller  217  as a pressing section that nips the sheet bundle PB where the folding by the folding knife  216  is initiated into the booklet, and the discharge roller  218  that discharges the booklet which is transported from the folding roller  217  to the booklet tray TR 3 . 
     In a case where the saddle-stitched booklet is produced, the third post-processing transport path S 3  is selected by the switching gate G 1 , the sheet P is extruded downward from the receiving roller  201 , and the sheet P is stacked on the saddle stitching compile tray  212  through a transport roller  211 . 
     For example, the sheets P are stacked on the saddle stitching compile tray  212  by the number of sheets, for example, 5, 10, 15, and the like, set by the image forming apparatus control unit  11  of the image forming apparatus  2 . 
     In this case, the positioning stopper  213  moves and stops so that, for example, the central parts of the sheets P are at a position of stapling by the saddle stitching stapler  215 . In addition, the paddle  214  rotates toward the positioning stopper  213 , presses the stacked sheets P against the positioning stopper  213 , and assists in the sheet alignment. 
     Saddle stitching is performed on a predetermined part (for example, the central part) of the sheet bundle PB by the saddle stitching stapler  215  after a predetermined number of the sheets P are accumulated on the saddle stitching compile tray  212 . 
     Then, the positioning stopper  213  moves upward along the saddle stitching compile tray  212 , and the sheet bundle PB where the saddle stitching is completed is transported so that a folding part (for example, the central part of the sheet) is at a tip end position of the folding knife  216 . The folding knife  216  is configured so that the tip of the folding knife  216  retracts downward from the saddle stitching compile tray  212  and does not protrude from a surface of the saddle stitching compile tray  212  during the stage when the sheet is stacked onto the saddle stitching compile tray  212 , the stage of saddle stitching by the saddle stitching stapler  215 , and the sheet transport stage after the saddle stitching. 
     After the sheet bundle PB is transported so that the folding position of the sheet bundle PB is changed to the tip end position of the folding knife  216 , the folding knife  216  is extruded from below the saddle stitching compile tray  212  in a direction orthogonal to an accommodating surface of the saddle stitching compile tray  212  so that the tip end abuts against the sheet bundle PB. 
     The tip end is further extruded in an upward direction, and the sheet bundle PB is lifted and is nipped by the folding roller  217 . Furthermore, the folding knife  216  is moved to a position where the sheet bundle PB is sufficiently into the folding roller  217 . 
     In this manner, the sheet bundle PB that is folded by the folding roller  217  is transported to the discharge roller  218  as the booklet, the folded portion first, and is discharged onto the booklet tray TR 3 . 
     The booklet that is produced in this manner may swell toward both sides about the folded portion at a point of time when the booklet is discharged onto the booklet tray TR 3  from the discharge roller  218 . In particular, the degree of the swelling may be higher in a case where the sheet size of the sheet P which is used is small than in a case where the size is large. 
     In addition, it is appreciated that the swelling decreases in a case where the center folded booklet is left in a state of slight shifting and overlapping. In the post-processing device  200  according to this exemplary embodiment, the swelling of the booklet is suppressed as the booklet is nipped by the discharge roller  218  in a state where the fiber of the sheet P is kept warm and soft and is left for a certain period of time, a pressing force is applied in the direction opposite to the force in a direction to open the booklet, and the fiber of the sheet P is corrected. 
     (3) Operation and Effect of Saddle Stitching and Folding Processing Mechanism 
       FIGS. 2A to 2F  are flowcharts for describing the flow of operation of the saddle stitching and folding processing mechanism  210  in the post-processing device  200  according to this exemplary embodiment,  FIG. 3  is a schematic view for describing the flow of center folding processing in the saddle stitching and folding processing mechanism  210 , and  FIGS. 4A to 4C  are schematic cross-sectional views for describing a state where the booklet is held in the saddle stitching and folding processing mechanism  210 . 
     Hereinafter, the flow and effect of the center folding processing in the saddle stitching and folding processing mechanism  210  will be described with reference to the accompanying drawings. 
     (3.1) Flow of Processing by Saddle Stitching and Folding Processing Mechanism 
     Firstly, the sheet P where the image is formed with the image forming apparatus  2  is brought into the saddle stitching compile tray  212  from the receiving roller  201  through the transport roller  211  (S 101 ). 
     Then, it is determined, on the saddle stitching compile tray  212 , whether the sheet P that is subjected to sheet alignment (S 102 , refer to  FIG. 2A ) and is brought in from the transport roller  211  is the final sheet (S 103 ). 
     The determination of whether the sheet P that is brought in is the final sheet or not is performed with the number of sheets set by the image forming apparatus control unit  11  of the image forming apparatus  2 . 
     Next, in a case where the sheet P that is brought into the saddle stitching compile tray  212  is determined to be the final sheet (S 103 : Yes), saddle stitching is performed by the saddle stitching stapler  215  on a predetermined part (for example, the central part) of the sheet bundle PB where the sheet alignment is performed (S 104 ). 
     Then, the sheet bundle PB where the saddle stitching is completed is moved (S 105 , refer to  FIG. 2B ) so that the folding part (for example, the central part of the sheet) is at the tip end position of the folding knife  216 , the tip end of the folding knife  216  is extruded to abut from a rear surface side of the sheet bundle PB, and the sheet bundle PB is lifted and is nipped by the folding roller  217  (S 106 , refer to  FIG. 2C ). 
     Furthermore, the folding knife  216  is moved to a position where the sheet bundle PB is sufficiently into the folding roller  217 , and a successful completion of booklet folding is detected at a point of time when a leading portion of the sheet bundle PB passes beyond a sensor SR (S 107 ). 
     Then, the sheet bundle PB is transported, the folded portion first, to the discharge roller  218  as the booklet and the leading portion of the booklet passes through the discharge roller  218  (S 108 ). 
     Then, it is determined whether the trailing edge of the booklet is transported to a position where the subsequent center folding processing is not interfered with (S 109 ). The determination in step S 109  is performed based on the time when the leading portion of the booklet passes beyond the sensor SR and the time predicted with the sheet size information of the sheet P which is notified of by the image forming apparatus control unit  11  of the image forming apparatus  2 . 
     In a case where the trailing edge of the booklet is transported to the position where the subsequent center folding processing is not interfered with as a result of the determination in step S 109  (S 109 : Yes), the rotational driving of the folding roller  217  and the discharge roller  218  is stopped, the transport of the booklet is stopped, and the booklet is held in a nipped state (S 110 , refer to  FIG. 2D ). 
     Then, it is determined whether saddle stitching processing is completed or not with respect to the subsequent sheet bundle PB that is brought into and stacked on the saddle stitching compile tray  212  (S 111 ). In a case where the saddle stitching processing is completed with respect to the subsequent sheet bundle PB as a result of the determination (S 111 : Yes), the transport of the previous booklet that is nipped and held by the folding roller  217  and the discharge roller  218  is resumed (S 112 , refer to  FIG. 2E ), and the booklet is discharged onto the booklet tray TR 3  (S 113 , refer to  FIG. 2F ). 
     (3.2) Effect of Saddle Stitching and Folding Processing Mechanism 
     In the saddle stitching and folding processing mechanism  210  of the post-processing device  200  according to this exemplary embodiment, it is determined whether the trailing edge of the booklet is transported to the position where the subsequent center folding processing is not interfered with after the sheet bundle PB is transported as the booklet, the folded portion first, to the discharge roller  218  and the leading portion of the booklet passes through the discharge roller  218 . 
     The determination of whether the trailing edge of the booklet is transported to the position where the subsequent center folding processing is not interfered with is performed based on the time when the leading portion of the booklet passes beyond the sensor SR and the time predicted with the sheet size information of the sheet P which is notified of by the image forming apparatus control unit  11  of the image forming apparatus  2 . 
     Then, in a case where the trailing edge of the booklet is transported to the position where the subsequent center folding processing is not interfered with, the rotational driving of the folding roller  217  and the discharge roller  218  is stopped, the transport of the booklet is stopped, and the booklet is held in a nipped state. 
     As a result, the booklet is nipped by the discharge roller  218  and is left for a certain period of time, the pressing force is applied in the direction opposite to the force in the direction to open the booklet, the fiber of the sheet P is corrected, and the swelling of the booklet is suppressed. 
     In addition, as shown in  FIGS. 4A to 4C , the protrusion length from the discharge roller  218  to the leading portion by sheet size is L 3 &lt;L 2 &lt;L 1  so that the leading portion side of the booklet is nipped and held by the discharge roller  218  in a state where the trailing edge of the booklet is nipped by the folding roller  217 . 
     In other words, the nipping position of the discharge roller  218  with respect to the booklet is closer to the leading portion in a case where the sheet size of the sheet P constituting the booklet is small, and the correction effect increases in the booklet of small size where the degree of swelling is higher than in a large size, and thus the swelling of the booklet may be suppressed. 
     In a case where it is determined whether the saddle stitching processing is completed or not with respect to the subsequent sheet bundle PB that is brought into and stacked on the saddle stitching compile tray  212  and the saddle stitching processing is completed with respect to the subsequent sheet bundle PB, the transport of the previous booklet that is nipped and held by the folding roller  217  and the discharge roller  218  is resumed, and the booklet is discharged onto the booklet tray TR 3 . 
     As such, the center folding processing is not discontinued, and the swelling of the booklet may be suppressed while the productivity of the post-processing is maintained. 
     The length of time during which the rotationally driving of the folding roller  217  and the discharge roller  218  is stopped, the transport of the booklet is stopped, and the booklet is held in a nipped state may also be determined based on the number of sheets per booklet. 
     The degree of swelling increases in a case where the number of sheets per booklet is large, and thus the swelling may be suppressed by lengthening the holding time. 
     The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.