Patent Publication Number: US-10766729-B1

Title: Sheet binding device and image forming system

Description:
FIELD 
     Embodiments described herein relate generally to a sheet binding device, an image forming system, and related methods. 
     BACKGROUND 
     In the related art, a sheet binding device that binds an edge part of a sheet bundle by using an adhesive tape is known. The sheet binding device is provided with a bundle forming part and a tape mounting part. The bundle forming part forms a sheet bundle by stacking a plurality of sheets. The bundle forming part forms a side part of the sheet bundle in a stepwise shape in order to secure a surface area when the tape is mounted thereon. The tape mounting part binds the sheet bundle by mounting the adhesive tape on the edge part of the sheet bundle. The tape mounting part is provided with a tape holding part that holds the adhesive tape. The tape mounting part is provided with a first roller and a second roller that are opposite to each other in a sheet bundle thickness direction. The adhesive tape is peeled from the tape holding part by inserting the sheet bundle shifted in the stepwise shape toward the adhesive tape held by the tape holding part. Thereafter, the sheet bundle enters between the first roller and the second roller together with the adhesive tape, and the adhesive tape adheres to the edge part of the sheet bundle. 
     However, the following problem may occur depending on a relationship between a thickness of the sheet bundle and a roller gap between the first roller and the second roller. For example, when the roller gap therebetween is too narrow with respect to the thickness of the sheet bundle, the sheet bundle cannot enter between the first roller and the second roller. On the other hand, for example, when the roller gap is too wide with respect to the thickness of the sheet bundle, the adhesive tape cannot sufficiently adhere to the edge part of the sheet bundle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view illustrating an image forming system of a first embodiment; 
         FIG. 2  is a front view illustrating an internal configuration of a sheet binding device according to the first embodiment; 
         FIGS. 3A and 3B  are side views illustrating an operation in which a shift amount between sheets is changed, wherein  FIG. 3A  is a diagram illustrating a case in which the shift amount between the sheets is relatively small, and  FIG. 3B  is a diagram illustrating a case in which the shift amount between the sheets is relatively large; 
         FIG. 4  is a front view illustrating an operation of the sheet binding device according to the first embodiment; 
         FIG. 5  is a front view illustrating the operation of the sheet binding device, following  FIG. 4 ; 
         FIG. 6  is a front view illustrating the operation of the sheet binding device, following  FIG. 5 ; 
         FIG. 7  is a front view illustrating the operation of the sheet binding device, following  FIG. 6 ; 
         FIG. 8  is a front view illustrating the operation of the sheet binding device, following  FIG. 7 ; 
         FIG. 9  is a front view illustrating the operation of the sheet binding device, following  FIG. 8 ; 
         FIG. 10  is a front view illustrating the operation of the sheet binding device, following  FIG. 9 ; 
         FIG. 11  is a front view illustrating an operation of a sheet binding device according to a comparative example; 
         FIG. 12  is a front view illustrating an internal configuration of a sheet binding device according to a first modification of the first embodiment; 
         FIG. 13  is a front view illustrating an internal configuration of a sheet binding device according to a second modification of the first embodiment; 
         FIG. 14  is a front view illustrating an internal configuration of a sheet binding device according to a second embodiment; 
         FIG. 15  is a front view illustrating an internal configuration of a sheet binding device according to a third embodiment; and 
         FIG. 16  is a front view illustrating an internal configuration of a sheet binding device according to a first modification of the third embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, a sheet binding device includes a first mounting part, a second mounting part, and a mounting adjustment part. The first mounting part mounts a tape on an edge part of a sheet bundle. The second mounting part is opposite to the first mounting part in a sheet bundle thickness direction. The mounting adjustment part can adjust a mounting gap between the first mounting part and the second mounting part based upon a thickness of the sheet bundle. The mounting gap is equal to or smaller than the thickness of the sheet bundle before the sheet bundle is inserted between the first mounting part and the second mounting part. 
     Hereinafter, the sheet binding device and an image forming system of the embodiment will be described with reference to the accompanying drawings. Further, in each drawing, the same configuration will be denoted by the same reference sign. Accordingly, redundant descriptions of those configurations may be omitted. Further, in the present application, various sheet-shaped media including paper and the like are referred to as a “sheet”. 
     First, one embodiment will be described with reference to  FIGS. 1 to 10 . 
       FIG. 1  is a front view illustrating an image forming system  1  according to the embodiment. The image forming system  1  of the embodiment is provided with a sheet binding device  3  that binds an edge part  5   a  of a sheet bundle  5  (refer to  FIG. 9 ) with a tape. For example, the sheet binding device  3  is a post-processing device that is disposed adjacent to an image forming device  2  and performs post-processing on a sheet S conveyed from the image forming device  2 . 
     Here, first the image forming device  2  will be briefly described. 
     As illustrated in  FIG. 1 , the image forming device  2  is provided with a control panel  11 , a scanner part  12 , a printer part  13 , a paper feed part  14 , a paper discharge part  15 , and a control part  16 . 
     The control panel  11  is provided with various keys and the like. The control panel  11  receives a user&#39;s operation. 
     The scanner part  12  reads image information of a copy object. 
     The printer part  13  forms an image on the sheet S based upon the image information received from the scanner part  12  or an external device. 
     The paper feed part  14  supplies the sheet S to the printer part  13 . 
     The paper discharge part  15  conveys the sheet S discharged from the printer part  13  to the sheet binding device  3 . 
     The control part  16  controls various operations of the control panel  11 , the scanner part  12 , the printer part  13 , the paper feed part  14 , and the paper discharge part  15 . 
     Next, the sheet binding device  3  will be described. 
     The sheet binding device  3  is provided with a bundle forming part  22 , a sheet shifting part  23 , a tape processing part  24 , an inter-guide adjustment part  80 , a mounting adjustment part  81 , an interlocking mechanism  82 , an operation part  83 , a storage part  25 , and a control part  26 . 
     Next, the bundle forming part  22  will be described. 
       FIG. 2  is a front view illustrating an internal configuration of the sheet binding device  3 . 
     As illustrated in  FIG. 2 , the bundle forming part  22  forms the sheet bundle  5  by stacking a plurality of the sheets S. The bundle forming part  22  is provided with a main guide  31  (a first guide), a sub guide  32  (a second guide), a stopper  33 , a switching member  34 . 
     The main guide  31  guides the sheet S along a sheet conveying direction X 1 . A plurality of the sheets S are sequentially stacked on the main guide  31 , thereby forming the sheet bundle  5 . The main guide  31  guides the sheet bundle  5  toward a space between a first roller  91  and a second roller  92 . The main guide  31  guides the sheet bundle  5  so that an edge tip of the sheet bundle  5  faces an inside of a width D 1  between a center of the first roller  91  and a center of the second roller  92 . A downstream side end part of the main guide  31  in the sheet conveying direction X 1  is formed in a comb-teeth shape so as to avoid the first roller  41  of the sheet shifting part  23 . 
     The sub guide  32  is opposite to the main guide  31  in a thickness direction Z of the sheet bundle  5  (hereinafter referred to as a “sheet bundle thickness direction Z”). A space for loading the sheet S is provided between the main guide  31  and the sub guide  32 . A downstream side end part of the sub guide  32  in the sheet conveying direction X 1  is formed in a comb-teeth shape so as to avoid the second roller  42  of the sheet shifting part  23 . 
     The stopper  33  is provided at the downstream side end part of the main guide  31  in the sheet conveying direction X 1 . The stopper  33  is movable between a regulating position (indicated by a solid line in  FIG. 2 ) and a releasing position (indicated by a two-dot chain line in  FIG. 2 ) by a moving mechanism which is not illustrated. At the regulating position, the stopper  33  protrudes upward further than an upper surface of the main guide  31 . At the regulating position, the stopper  33  stops the sheet S in such a manner that an end part of the sheet S abuts on the stopper  33 . Therefore, the sheet S is accumulated on the main guide  31 , thereby forming the sheet bundle  5 . On the other hand, at the releasing position, the stopper  33  is retracted downward further than the upper surface of the main guide  31 . At the releasing position, the stopper  33  allows the sheet bundle  5  on the main guide  31  to pass through toward the switching member  34 . 
     The switching member  34  switches a conveying path of the sheet bundle  5 . Hereinafter, a direction in which the sheet bundle  5  is conveyed toward the tape processing part  24  (specifically, a tape mounting part  59 ) is referred to as a “first conveying direction (an inserting direction)”. On the other hand, a direction in which the sheet bundle  5  is conveyed toward a position (for example, a position below the bundle forming part  22 ) different from the tape mounting part  59  is referred to as a “second conveying direction”. The switching member  34  switches the conveying path of the sheet bundle  5  between the first conveying direction and the second conveying direction. 
     Next, the sheet shifting part  23  will be described. 
     The sheet shifting part  23  forms a state in which the plurality of sheets S forming the sheet bundle  5  are shifted from each other at the edge part  5   a  of the sheet bundle  5  by sequentially shifting the plurality of sheets S in the sheet conveying direction X 1  little by little. For example, the sheet shifting part  23  forms a state in which the plurality of sheets S are shifted in a stepwise shape at the edge part  5   a  of the sheet bundle  5 . 
     The sheet shifting part  23  is provided with the first roller  41  and the second roller  42 . The first roller  41  and the second roller  42  form an example of a “bundle conveying part  40 ” in cooperation with each other. The bundle conveying part  40  conveys the sheet bundle  5  sandwiched between the main guide  31  and the sub guide  32  toward the space between the first roller  91  (a first mounting part  90 A) and the second roller  92  (a second mounting part  90 B). 
     The first roller  41  is mounted on a first shaft  43 . For example, the first roller  41  is a driven roller that rotates according to rotation of the second roller  42 . The first roller  41  is fixed at a fixed position. 
     The second roller  42  is mounted on a second shaft  44 . The second roller  42  is a drive roller driven by a motor (not illustrated) through the second shaft  44 . The second roller  42  is movable in a direction approaching the first roller  41  and a direction away from the first roller  41  by a moving mechanism which is not illustrated. As the second roller  42  is moved toward the first roller  41 , the second roller  42  contacts the sheet bundle  5  from a side opposite to the first roller  41 . A material of the second roller  42  is not particularly limited. For example, the second roller  42  is formed of ethylene propylene diene rubber (EPDM). 
     Here, an outer peripheral surface  41   s  of the first roller  41  is softer than an outer peripheral surface  42   s  of the second roller  42 , and is deformable along the surface of the sheet bundle  5 . For example, the first roller  41  is formed of a sponge or rubber and the like having a cavity therein. When the second roller  42  approaches the first roller  41 , the outer peripheral surface  41   s  of the first roller  41  is deformed into a circular arc shape along the outer peripheral surface  42   s  of the second roller  42  together with the sheet bundle  5  (refer to  FIGS. 3A and 3B ). 
       FIGS. 3A and 3B  are side views illustrating an operation in which a shift amount d between the sheets S is changed by the sheet shifting part  23 .  FIG. 3A  is a diagram illustrating a case in which the shift amount d between the sheets S is relatively small. On the other hand,  FIG. 3B  is a diagram illustrating a case in which the shift amount d between the sheets S is relatively large. 
     As illustrated in  FIGS. 3A and 3B , the sheet shifting part  23  can reduce the shift amount d between the sheets S by setting a rotating angle of the second roller  42  to be smaller than a preset reference amount. On the other hand, the sheet shifting part  23  can increase the shift amount d between the sheets S by setting the rotating angle of the second roller  42  to be greater than the reference amount. 
     Next, the tape processing part  24  will be described. 
     As illustrated in  FIG. 2 , the tape processing part  24  is provided with an unwinding part  51 , a tape conveying part  52 , a separating member  53 , a winding part  54 , a guide table  55 , a cutter  56 , a cutting length changing part  57 , a tape holding part  58 , and the tape mounting part  59 . 
     The unwinding part  51  is an example of a “tape supplying part”. For example, the unwinding part  51  holds a raw web roll around which a belt-shaped tape T (hereinafter simply referred to as a “tape T”) is wound. The unwinding part  51  supplies the tape T along a length direction of the tape T. Further, the tape T includes an adhesive layer  61 , a protective film (a first film)  62 , and a release film (a second film)  63  in a state of being held in the unwinding part  51 . The protective film  62  covers the adhesive layer  61  from one side. The protective film  62  is integrated with the adhesive layer  61  when the tape T is used. On the other hand, the release film  63  covers the adhesive layer  61  from the side opposite to the protective film  62 . The release film  63  is released from the adhesive layer  61  before the tape T is used. The release film  63  is wound up by the separating member  53  and the winding part  54 . 
     The tape conveying part  52  conveys the tape T supplied from the unwinding part  51  along the length direction of the tape T. For example, the length direction of the tape T is a direction approximately parallel to the sheet bundle thickness direction Z. For example, the tape conveying part  52  is a pair of conveying rollers for conveying the tape T. 
     The guide table  55  is an example of a tape conveying guide forming a conveying path of the tape T. The guide table  55  guides the tape T from which the release film  63  is separated. The guide table  55  supports the tape T when the tape T is held and cut. A conveying direction of the tape T (the length direction of the tape T) intersects with a vertical surface. 
     The cutter  56  cuts the belt-shaped tape T supplied from the unwinding part  51 , thereby forming a sheet-like tape T. For example, the cutter  56  is a rotor cutter. The cutter  56  includes a cutting blade  56   a  and a supporting shaft  56   b . The cutting blade  56   a  is rotationally driven in such a manner that the supporting shaft  56   b  is rotated by a motor which is not illustrated. Further, a configuration of the cutter  56  is not limited to the above-mentioned example. The configuration of the cutter  56  may be any configuration as long as the tape T supplied from the unwinding part  51  can be cut. The cutter  56  is movable in a direction approaching the tape T and a direction away from the tape T by a moving mechanism which is not illustrated. 
     The cutting length changing part  57  changes a length L (refer to  FIG. 7 ) of the tape T cut by the cutter  56 . Further, “the length L of the tape” in the present application is a length (a width) of the tape T in the sheet bundle thickness direction Z. In other words, the “tape length L” is a length in a direction of wrapping the edge part  5   a  of the sheet bundle  5  from the first surface  7   a  of the sheet bundle  5  toward the second surface  7   b  thereof. 
     The cutting length changing part  57  includes a moving mechanism  71  that changes a relative position of the cutter  56  with respect to a tip Te of the tape T supplied from the unwinding part  51 . For example, the moving mechanism  71  changes the relative position of the cutter  56  with respect to the tip Te of the tape T by moving the cutter  56 . For example, the moving mechanism  71  moves the cutter  56  along the sheet bundle thickness direction Z. Further, “the relative position of the cutter  56  with respect to the tip Te of the tape T” is, for example, the relative position of the cutter  56  with respect to the tip Te of the tape T when the tape T is cut by the cutter  56 . 
     In the embodiment, the moving mechanism  71  is provided with a supporting member  72  supporting the cutter  56 , and a drive source  73  moving the cutter  56  via the supporting member  72 . For example, the supporting member  72  is a ball screw connected to the cutter  56 . The drive source  73  is a motor for moving the cutter  56  by driving the ball screw. Further, configurations of the supporting member  72  and the drive source  73  are not limited to the above-mentioned example. For example, the supporting member  72  may be a cam and the like abutting on the cutter  56 . The drive source  73  may be a solenoid and the like for moving the cutter  56  via the supporting member  72 . In this case, the supporting member  72  is a connecting member that connects the cutter  56  and the solenoid. 
     Further, a configuration of the moving mechanism  71  is not limited to the above-mentioned example. For example, the moving mechanism  71  may change the relative position of the cutter  56  with respect to the tip Te of the tape T by changing a feed length of the tape T with respect to the cutter  56  fixed at a fixed position. 
     In the embodiment, the cutting length changing part  57  is controlled by the control part  26  (refer to  FIG. 1 ). For example, the control part  26  moves the cutter  56  by controlling the drive source  73  of the cutting length changing part  57 , thereby changing the length L of the tape T cut by the cutter  56 . For example, an operation of the cutting length changing part  57  described hereinbelow is performed in such a manner that the cutting length changing part  57  is controlled by the control part  26 . 
     In the embodiment, the cutting length changing part  57  changes the length of the tape T cut by the cutter  56  based upon the shift amount d between the sheets S changed by the control part  26 . For example, when the shift amount d between the sheets S is increased by the control part  26 , the cutting length changing part  57  lengthens the length L of the tape T cut by the cutter  56 . On the other hand, when the shift amount d between the sheets S is reduced by the control part  26 , the cutting length changing part  57  shortens the length L of the tape T cut by the cutter  56 . 
     The tape holding part  58  supports the tape T in a state of holding an attitude of the tape T approximately flat. The tape holding part  58  is movable along the length direction of the tape T by a moving mechanism which is not illustrated. Further, the tape holding part  58  is movable in a direction approaching the tape T and a direction separating from the tape T by the moving mechanism which is not illustrated. 
     The tape holding part  58  is provided with a first tape supporting part  58   a  and a second tape supporting part  58   b  for supporting the tape T. Each of the first tape supporting part  58   a  and the second tape supporting part  58   b  extends along an inserting direction of the sheet bundle  5  (the sheet conveying direction X 1 ). The first tape supporting part  58   a  and the second tape supporting part  58   b  are disposed with a space therebetween in the conveying direction of the tape T (the sheet bundle thickness direction Z). Each of the first tape supporting part  58   a  and the second tape supporting part  58   b  has a sharply tapered shape toward an adhesive surface of the tape T (an adhesive surface of the adhesive layer  61 ). 
     The tape mounting part  59  (a tape wrapping part) is provided with the first roller  91 , the second roller  92 , a first spring  93  (a first urging member), and a second spring  94  (a second urging member). The first roller  91  and the second roller  92  are arranged in the conveying direction of the tape T (the sheet bundle thickness direction Z). The first spring  93  urges the first roller  91  toward the second roller  92 . The second spring  94  urges the second roller  92  toward the first roller  91 . The first roller  91  and the first spring  93  form an example of “a first urging part (the first mounting part  90 A)” in cooperation with each other. The second roller  92  and the second spring  94  form an example of “a second urging part (the second mounting part  90 B)” in cooperation with each other. The edge part  5   a  of the sheet bundle  5  is inserted between the first roller  91  and the second roller  92  together with the tape T when the tape T is mounted. Accordingly, the tape T is bent by the tape mounting part  59  so as to wrap the edge part  5   a  of the sheet bundle  5 , and the tape T is mounted on the edge part  5   a  of the sheet bundle  5 . 
     Next, the inter-guide adjustment part  80  will be described. 
     The inter-guide adjustment part  80  can adjust a guide gap between the main guide  31  and the sub guide  32 . The guide gap therebetween is set based upon the thickness of the sheet bundle  5 . The inter-guide adjustment part  80  is provided with an eccentric cam  80   a  (hereinafter referred to as a “guide side cam  80   a ”) capable of adjusting the guide gap. The guide side cam  80   a  allows the sub guide  32  to be close to or to be away from the main guide  31 . A rotating shaft  80   b  of the guide side cam  80   a  is shifted from a center position of the guide side cam  80   a . The guide side cam  80   a  has a perfect circular outer shape. Further, the outer shape of the guide side cam  80   a  is not limited to the above-mentioned example. For example, the outer shape of the guide side cam  80   a  may be an elliptical shape. 
     The guide side cam  80   a  abuts on the sub guide  32 . The guide side cam  80   a  adjusts the guide gap by rotating around the rotating shaft  80   b . The guide side cam  80   a  can move the sub guide  32  between a close position (indicated by a solid line in  FIG. 2 ) and a separate position (indicated by a two-dot chain line in  FIG. 2 ) in such a manner that the guide side cam  80   a  rotates around the rotating shaft  80   b.    
     Next, the mounting adjustment part  81  will be described. 
     The mounting adjustment part  81  can adjust a roller gap (hereinafter referred to as a “mounting gap”) between the first roller  91  and the second roller  92  based upon the thickness of the sheet bundle  5 . In  FIG. 4 , a reference sign W 1  indicates the thickness of the sheet bundle  5  and a reference sign W 2  indicates the mounting gap. The mounting gap W 2  is equal to or smaller than the thickness W 1  of the sheet bundle  5  (W 2  W 1 ) before the sheet bundle  5  is inserted between the first roller  91  and the second roller  92 . In the embodiment, the mounting gap W 2  is greater than zero and smaller than the thickness W 1  of the sheet bundle  5  (0&lt;W 2 &lt;W 1 ) before the sheet bundle  5  is inserted between the first roller  91  and the second roller  92 . 
     As illustrated in  FIG. 2 , the mounting adjustment part  81  is provided with an eccentric cam  81   a  (hereinafter referred to as a “mounting side cam  81   a ”) capable of adjusting the mounting gap W 2 . The mounting side cam  81   a  allows the second roller  92  to be close to or to be away from the first roller  91 . A rotating shaft  81   b  of the mounting side cam  81   a  is shifted from a center position of the mounting side cam  81   a . The mounting side cam  81   a  has a perfect circular outer shape. Further, the outer shape of the mounting side cam  81   a  is not limited to the above-mentioned example. For example, the outer shape of the mounting side cam  81   a  may be an elliptical shape. 
     A reference sign  85  in the drawing indicates a supporting plate that supports a base end of the second spring  94 . The mounting side cam  81   a  abuts on the supporting plate  85 . The mounting side cam  81   a  adjusts the mounting gap by rotating around the rotating shaft  81   b . The mounting side cam  81   a  can move the second roller  92  between a close position (indicated by a two-dot chain line in  FIG. 2 ) and a separate position (indicated by a solid line in  FIG. 2 ) in such a manner that the mounting side cam  81   a  rotates around the rotating shaft  81   b.    
     In the embodiment, the mounting side cam  81   a  has substantially the same outer shape as that of the guide side cam  80   a . An adjustment amount of the mounting adjustment part  81  (an adjustment amount of the mounting gap) is substantially the same as an adjustment amount of the inter-guide adjustment part  80  (an adjustment amount of the guide gap). 
     Each of the guide side cam  80   a  and the mounting side cam  81   a  is positioned in one side of two regions partitioned by the sheet bundle  5  in the sheet bundle thickness direction Z. In the drawing, a reference sign A 1  indicates a first region partitioned by the sheet bundle  5  in the sheet bundle thickness direction Z, and a reference sign A 2  indicates a second region partitioned by the sheet bundle  5  in the sheet bundle thickness direction Z. In the embodiment, the guide side cam  80   a  and the mounting side cam  81   a  are positioned in the second region A 2 . 
     Next, the interlocking mechanism  82  will be described. 
     The interlocking mechanism  82  allows the inter-guide adjustment part  80  and the mounting adjustment part  81  to be interlocked with each other. In the embodiment, the interlocking mechanism  82  allows the inter-guide adjustment part  80  and the mounting adjustment part  81  to be interlocked with each other so that the mounting gap becomes gradually narrower as the guide gap becomes narrower. Additionally, the interlocking mechanism  82  allows the inter-guide adjustment part  80  and the mounting adjustment part  81  to be interlocked with each other so that the mounting gap gradually becomes wider as the guide gap becomes wider. 
     A pressing force (an urging force of the urging member) with respect to the sheet bundle  5  between the first roller  91  and the second roller  92  becomes greater as the guide gap becomes narrower. On the other hand, the pressing force becomes smaller as the guide gap becomes wider. Further, the pressing force may be increased after the sheet bundle  5  is inserted between the first roller  91  and the second roller  92 . 
     The interlocking mechanism  82  is provided with a power transmission mechanism  82   a  that transmits a rotational force of the guide side cam  80   a  to the mounting side cam  81   a . For example, the power transmission mechanism  82   a  is provided with a belt and a pulley which are not illustrated. Further, a configuration of the power transmission mechanism  82   a  is not limited to the above-mentioned example. For example, the power transmission mechanism  82   a  may be provided with a plurality of gears. 
     The operation part  83  is a member for rotating the guide side cam  80   a  around the rotating shaft  80   b  of the guide side cam  80   a . For example, the operation part  83  is a knob provided outside the sheet binding device  3 . For example, by operating the knob, the guide side cam  80   a  rotates around the rotating shaft  80   b  of the guide side cam  80   a . Accordingly, the mounting side cam  81   a  rotates around the rotating shaft  81   b  of the mounting side cam  81   a  according to the rotation of the guide side cam  80   a . As a result, the guide gap and the mounting gap are interlocked with each other, thereby being adjusted. 
     The control part  26  (refer to  FIG. 1 ) is formed by a control circuit including a CPU, a ROM, and a RAM provided in the sheet binding device  3 . The control part  26  controls the operation of the sheet binding device  3 , for example, in such a manner that a processor such as a CPU executes a program. For example, the control part  26  controls various operations of the bundle forming part  22 , the sheet shifting part  23 , and the tape processing part  24 . 
     Next, an operation example of the sheet binding device  3  will be described.  FIGS. 4 to 10  are front views illustrating the operation example of the sheet binding device  3 . 
     First, as illustrated in  FIG. 2 , the sheet binding device  3  stops the sheet S conveyed to the main guide  31  by moving the stopper  33  to the regulating position. Accordingly, the plurality of sheets S are sequentially stacked on each other, thereby forming the sheet bundle  5 . Next, the sheet binding device  3  moves the stopper  33  to the releasing position. Further, the sheet binding device  3  switches the switching member  34  toward the second conveying direction. 
     Next, as illustrated in  FIGS. 3A and 3B , the sheet binding device  3  moves the second roller  42  toward the first roller  41 . Thus, the sheet bundle  5  and the outer peripheral surface  41   s  of the first roller  41  are deformed into circular arc shapes along the outer peripheral surface  42   s  of the second roller  42 . The sheet binding device  3  normally rotates the second roller  42  in a state where the sheet bundle  5  is sandwiched between the first roller  41  and the second roller  42 . 
     Thus, the first roller  41  rotates according to the rotation of the second roller  42  while maintaining a state in which the first roller  41  is recessed so as to follow the outer peripheral surface  42   s  of the second roller  42 . As a result, a state in which the plurality of sheets S are shifted in the stepwise shape in the sheet conveying direction X 1  at the edge part  5   a  of the sheet bundle  5  is formed. Further, the “edge part  5   a  of the sheet bundle  5 ” in the following description means the edge part  5   a  of the sheet bundle  5  in which the plurality of sheets S are shifted in the stepwise shape. 
     Next, the sheet binding device  3  moves the second roller  42  in a direction away from the first roller  41 . Accordingly, the recess of the outer peripheral surface  41   s  of the first roller  41  is eliminated. Next, the sheet binding device  3  moves the sheet bundle  5  toward a reverse direction X 2  opposite to the sheet conveying direction X 1  by reversely rotating the first roller  41  and the second roller  42 . Next, the sheet binding device  3  switches the conveying path from the second conveying direction to the first conveying direction by switching the switching member  34 . Then, the sheet binding device  3  moves the sheet bundle  5  toward the tape mounting part  59  by normally rotating the first roller  41  and the second roller  42 . 
     The sheet binding device  3  according to the embodiment sets the mounting gap W 2  to be equal to or smaller than the thickness W 1  of the sheet bundle  5  (W 2  W 1 , refer to  FIG. 4 ) before the sheet bundle  5  is inserted between the first roller  91  and the second roller  92 . The sheet binding device  3  sets the guide gap based upon the thickness W 1  of the sheet bundle  5 . For example, when the number of sheets S forming the sheet bundle  5  is ten, the guide gap is set based upon the thickness of ten sheets. 
     For example, the guide side cam  80   a  rotates around the rotating shaft  80   b  of the guide side cam  80   a  by operating the knob (the operation part  83 ). Accordingly, the mounting side cam  81   a  rotates around the rotating shaft  81   b  of the mounting side cam  81   a  according to the rotation of the guide side cam  80   a . Thus, the guide gap and the mounting gap are interlocked with each other, thereby being adjusted. For example, when the number of sheets S forming the sheet bundle  5  is ten, the guide gap and the mounting gap are set based upon the thickness of ten sheets. 
     As illustrated in  FIG. 4 , the sheet binding device  3  according to the embodiment changes the length L of the tape T to be cut by the cutter  56  based upon the shift amount d between the sheets S changed by the control part  26  (refer to  FIG. 1 ). For example, in the embodiment, the position of the cutter  56  is changed in such a manner that the control part  26  controls the drive source  73  (refer to  FIG. 2 ) of the cutting length changing part  57 . 
     Next, as illustrated in  FIG. 5 , the sheet binding device  3  supports the tape T in a state where the attitude of the tape T is maintained by allowing the tape holding part  58  to abut on the tape T. In the embodiment, the tape holding part  58  abuts on opposite ends of the guide table  55  (an upstream end and a downstream end in the conveying direction of the tape T), thereby supporting the tape T having an approximately flat shape (a linear shape). 
     Next, as illustrated in  FIG. 6 , the sheet binding device  3  moves the tape holding part  58  between the sheet bundle  5  and the tape mounting part  59 . For example, the tape holding part  58  disposes the tape T so as to straddle the first roller  91  and the second roller  92 . For example, the tape holding part  58  disposes the tape T so that a center part of the linear tape T faces a center between the rollers of the first roller  91  and the second roller  92 . In other words, the tape holding part  58  allows the center part between the first tape supporting part  58   a  and the second tape supporting part  58   b  that hold the tape T to face the center between the rollers of the first roller  91  and the second roller  92 . 
     Next, as illustrated in  FIG. 7 , the sheet binding device  3  cuts a band-shaped tape T by the cutter  56 , thereby forming a sheet-like tape T. Accordingly, the tape T is cut in a required length. 
     Next, as illustrated in  FIG. 8 , the sheet binding device  3  moves the sheet bundle  5  toward the tape mounting part  59  by the sheet shifting part  23  (refer to  FIG. 2 ). For example, the sheet binding device  3  moves (inserts) the sheet bundle  5  toward the tape mounting part  59  by normally rotating the first roller  41  and the second roller  42  (refer to  FIG. 2 ). The sheet binding device  3  conveys the sheet bundle  5  that is in a state of being sandwiched between the main guide  31  and the sub guide  32  toward a space between the first roller  91  and the second roller  92 . The sheet binding device  3  allows the edge tip of the sheet bundle  5  to face the inside of the width D 1  between the center of the first roller  91  and the center of the second roller  92 . The sheet binding device  3  peels the tape T from the tape holding part  58  by inserting the sheet bundle  5  into the tape T held by the tape holding part  58 . The sheet binding device  3  inserts the edge part  5   a  of the sheet bundle  5  between the first roller  91  and the second roller  92  together with the tape T. 
     As illustrated in  FIG. 9 , when the edge part  5   a  of the sheet bundle  5  is inserted between the first roller  91  and the second roller  92  together with the tape T, the first roller  91  and the second roller  92  move along an outer shape of the edge part  5   a  of the sheet bundle  5 . Accordingly, the first roller  91  and the second roller  92  press the tape T against the edge part  5   a  of the sheet bundle  5 . As a result, the tape T sequentially follows and adheres to a stepwise-shaped portion of the sheet bundle  5 . Here, the edge part  5   a  of the sheet bundle  5  includes a first surface  7   a , a second surface  7   b , and an end surface  7   c . The first surface  7   a  and the second surface  7   b  are surfaces disposed along the sheet conveying direction X 1 . The second surface  7   b  is positioned on a side opposite to the first surface  7   a . The end surface  7   c  is positioned between the first surface  7   a  and the second surface  7   b , and the plurality of sheets S are shifted in the stepwise shape. The sheets S are mounted over the first surface  7   a , the end surface  7   c , and the second surface  7   b  at the edge part  5   a  of the sheet bundle  5 . As a result, all the sheets S including the intermediate page of the sheet bundle  5  are integrated by the tape T. Accordingly, a process of mounting the tape T on the edge part  5   a  of the sheet bundle  5  is completed. 
     Next, as illustrated in  FIG. 10 , the sheet binding device  3  reversely rotates the first roller  41  and the second roller  42  (refer to  FIG. 2 ), thereby taking out the sheet bundle  5  from between the first roller  91  and the second roller  92 . Then, the sheet binding device  3  further reversely rotates the first roller  41  and the second roller  42  (refer to  FIG. 2 ), thereby discharging the sheet bundle  5  to the discharge part of the sheet binding device  3 . 
     As described above, a series of operations by the sheet binding device  3  is completed. 
     Next, an operation of a sheet binding device according to a comparative example will be described. 
       FIG. 11  is a front view illustrating the operation of the sheet binding device according to the comparative example. 
     As illustrated in  FIG. 11 , the sheet binding device according to the comparative example does not include the mounting adjustment part  81  (refer to  FIG. 4 ). 
     In the comparative example, the mounting gap is constant (zero in the example of the drawing) regardless of the thickness of the sheet bundle  5  before the sheet bundle  5  is inserted between the first roller  91  and the second roller  92 . Therefore, there is a high possibility that the mounting gap is too narrow with respect to the thickness of the sheet bundle  5  such that the sheet bundle  5  cannot enter between the first roller  91  and the second roller  92 . 
     Meanwhile, as illustrated in  FIG. 4 , in the embodiment, the mounting adjustment part  81  capable of adjusting the mounting gap based upon the thickness of the sheet bundle  5  is provided. Therefore, there is a low possibility that the mounting gap is too narrow with respect to the thickness of the sheet bundle  5  such that the sheet bundle  5  cannot enter between the first roller  91  and the second roller  92 . 
     According to the embodiment, the sheet binding device  3  includes the first mounting part  90 A, the second mounting part  90 B, and the mounting adjustment part  81 . The first mounting part  90 A mounts the tape T on the edge part  5   a  of the sheet bundle  5 . The second mounting part  90 B is opposite to the first mounting part  90 A in the sheet bundle thickness direction Z. The mounting adjustment part  81  can adjust the mounting gap between the first mounting part  90 A and the second mounting part  90 B based upon the thickness of the sheet bundle  5 . The mounting gap W 2  is equal to or smaller than the thickness W 1  of the sheet bundle  5  before the sheet bundle  5  is inserted between the first mounting part  90 A and the second mounting part  90 B. An effect described hereinbelow is achieved by the above-mentioned configuration. 
     The mounting gap can be adjusted based upon the thickness of the sheet bundle  5  by the mounting adjustment part  81 . In comparison with a case in which the mounting gap is constant regardless of the thickness of the sheet bundle  5 , there is the low possibility that the mounting gap is too narrow with respect to the thickness of the sheet bundle  5  such that the sheet bundle  5  cannot enter between the first roller  91  and the second roller  92 . Additionally, there is a low possibility that the mounting gap is too wide with respect to the thickness of the sheet bundle  5  such that the tape T cannot sufficiently adhere to the edge part  5   a  of the sheet bundle  5 . Accordingly, it is possible to bind the sheet bundle  5  regardless of the thickness of the sheet bundle  5 . Further, before the sheet bundle  5  is inserted between the first mounting part  90 A and the second mounting part  90 B, the tape T easily follows the edge part  5   a  of the sheet bundle  5  in comparison with a case in which the mounting gap is greater than the thickness of the sheet bundle  5 . Therefore, it is possible to more surely bind the sheet bundle  5 . 
     The sheet binding device  3  is further provided with the main guide  31  that guides the sheet bundle  5  toward a space between the first mounting part  90 A and the second mounting part  90 B, the sub guide  32  opposite to the main guide  31  in the sheet bundle thickness direction Z, the inter-guide adjustment part  80  capable of adjusting the guide gap between the main guide  31  and the sub guide  32 , and the interlocking mechanism  82  that allows the inter-guide adjustment part  80  and the mounting adjustment part  81  to be interlocked with each other. An effect described hereinbelow is achieved by the above-mentioned configuration. 
     Since the sheet bundle  5  can be sandwiched by the main guide  31  and the sub guide  32 , curling of the sheet bundle  5  can be suppressed. Accordingly, the sheet bundle  5  is stably and easily guided in comparison with a case in which only one guide is provided. Further, the guide gap and the mounting gap can be adjusted by being interlocked with each other. The device configuration is simplified, thereby contributing to cost reduction in comparison with a case in which the guide gap and the mounting gap are respectively adjusted by using two motors. Additionally, complicated control is not required in this configuration, thereby contributing to energy saving. 
     The guide gap is set based upon the thickness of the sheet bundle  5 . An effect described hereinbelow is achieved by the above-mentioned configuration. 
     It is possible to hold the attitude of the sheet bundle  5  regardless of the thickness of the sheet bundle  5 . 
     The mounting adjustment part  81  can adjust the mounting gap. The interlocking mechanism  82  allows the inter-guide adjustment part  80  and the mounting adjustment part  81  to be interlocked with each other so that the mounting gap becomes gradually narrower as the guide gap becomes narrower. The interlocking mechanism  82  allows the inter-guide adjustment part  80  and the mounting adjustment part  81  to be interlocked with each other so that the mounting gap becomes gradually wider as the guide gap becomes wider. An effect described hereinbelow is achieved by the above-mentioned configuration. 
     The guide gap and the mounting gap can be adjusted in the stepwise shape by being interlocked with each other. Accordingly, the tape T easily follows the edge part  5   a  of the sheet bundle  5  in comparison with a case in which the guide gap and the mounting gap are adjusted with only one stage. 
     The sheet binding device  3  is further provided with the bundle conveying part  40  that conveys the sheet bundle  5  in a state of being sandwiched between the main guide  31  and the sub guide  32  toward the space between the first mounting part  90 A and the second mounting part  90 B. An effect described hereinbelow is achieved by the above-mentioned configuration. 
     It is possible to convey the sheet bundle  5  toward the space between the first mounting part  90 A and the second mounting part  90 B in a state where the attitude of the sheet bundle  5  is held. Accordingly, the tape T can be mounted on the edge part of the sheet bundle  5  while suppressing the curling of the sheet bundle  5 . 
     The mounting adjustment part  81  is provided with the eccentric cam  81   a  capable of adjusting the mounting gap. An effect described hereinbelow is achieved by the above-mentioned configuration. 
     The mounting gap can be adjusted with a simple configuration provided with the eccentric cam  81   a . Further, complicated control is not required in comparison with a case in which a motor is provided, thereby contributing to energy saving. 
     The inter-guide adjustment part  80  is provided with the guide side cam  80   a  that allows the sub guide  32  to be close to or to be away from the main guide  31 . The mounting adjustment part  81  is provided with the mounting side cam  81   a  that allows the second mounting part  90 B to be close to or to be away from the first mounting part  90 A. The interlocking mechanism  82  is provided with the power transmission mechanism  82   a  that transmits the rotational force of the guide side cam  80   a  to the mounting side cam  81   a . An effect described hereinbelow is achieved by the above-mentioned configuration. 
     The guide gap and the mounting gap can be adjusted by being interlocked with each other with a simple configuration provided with the guide side cam  80   a , the mounting side cam  81   a , and the power transmission mechanism  82   a . This device configuration is simplified, thereby contributing to cost reduction in comparison with a case in which the guide gap and the mounting gap are respectively adjusted by using two motors. Additionally, complicated control is not required, thereby contributing to energy saving. 
     Each of the guide side cam  80   a  and the mounting side cam  81   a  is positioned in one side (the second region A 2 ) of the two regions A 1  and A 2  that are partitioned by the sheet bundle  5  in the sheet bundle thickness direction Z. An effect described hereinbelow is achieved by the above-mentioned configuration. 
     A power transmission path between the guide side cam  80   a  and the mounting side cam  81   a  can be shortened in comparison with a case in which the guide side cam  80   a  and the mounting side cam  81   a  are positioned in mutually different regions in the sheet bundle thickness direction Z, resulting in contributing to miniaturization of the power transmission mechanism  82   a.    
     The sheet binding device  3  is further provided with the operation part  83  for rotating the guide side cam  80   a  around the rotating shaft  80   b  of the guide side cam  80   a . An effect described hereinbelow is achieved by the above-mentioned configuration. 
     The guide side cam  80   a  rotates around the rotating shaft  80   b  of the guide side cam  80   a  by the operation of the operation part  83 . Accordingly, the mounting side cam  81   a  rotates around the rotating shaft  81   b  of the mounting side cam  81   a  according to the rotation of the guide side cam  80   a . Accordingly, the guide gap and the mounting gap are adjusted by being interlocked with each other. As a result, the guide gap and the mounting gap can be adjusted by being interlocked with each other with a simple configuration provided with the operation part  83 . 
     The first mounting part  90 A is provided with the first roller  91  and the first spring  93  for urging the first roller  91  toward the second mounting part  90 B. The second mounting part  90 B is provided with the second roller  92  opposite to the first roller  91  in the sheet bundle thickness direction Z, and the second spring  94  for urging the second roller  92  toward the first roller  91 . The main guide  31  guides the sheet bundle  5  so that the edge tip of the sheet bundle  5  faces the inside of the width D 1  between the center of the first roller  91  and the center of the second roller  92 . An effect described hereinbelow is achieved by the above-mentioned configuration. 
     Since the tape T can follow the edge part  5   a  of the sheet bundle  5 , it is possible to more surely bind the sheet bundle  5 . Further, in comparison with a case in which the sheet bundle  5  is guided so that the edge tip of the sheet bundle  5  faces the outside of the width D 1  between the center of the first roller  91  and the center of the second roller  92 , the sheet bundle  5  easily enters between the first roller  91  and the second roller  92 . 
     Next, a first modification of the first embodiment will be described. 
     The mounting side cam  81   a  is not limited to having substantially the same outer shape as that of the guide side cam  80   a . The adjustment amount of the mounting adjustment part  81  (the adjustment amount of the mounting gap) is not limited to being substantially the same as the adjustment amount of the inter-guide adjustment part  80  (the adjustment amount of the guide gap). 
       FIG. 12  is a front view illustrating a sheet binding device according to the first modification of the first embodiment. As illustrated in  FIG. 12 , a mounting side cam  181   a  may have an outer shape smaller than that of the guide side cam  80   a . In the modification, an adjustment amount of a mounting adjustment part  181  (an adjustment amount of a mounting gap) is smaller than the adjustment amount of the inter-guide adjustment part  80  (the adjustment amount of the guide gap). For example, when the adjustment amount of the inter-guide adjustment part  80  is set to 1, the adjustment amount of the mounting adjustment part  181  is set to 0.5. For example, when the guide gap is opened by 1 mm, the mounting gap is opened by 0.5 mm. 
     According to the first modification of the first embodiment, the adjustment amount of the mounting adjustment part  181  is smaller than the adjustment amount of the inter-guide adjustment part  80 . An effect described hereinbelow is achieved by the above-mentioned configuration. 
     A pressing force (an urging force of an urging member) is easily applied to the sheet bundle  5  in comparison with a case in which the adjustment amount of the mounting adjustment part  181  is the same as the adjustment amount of the inter-guide adjustment part  80 . Therefore, the tape T easily follows the edge part  5   a  of the sheet bundle  5 . 
     Next, a second modification of the first embodiment will be described. 
     The mounting gap is not limited to being greater than zero and smaller than the thickness of the sheet bundle  5  before the sheet bundle  5  is inserted between the first roller  91  and the second roller  92 . 
       FIG. 13  is a front view illustrating a sheet binding device according to the second modification of the first embodiment. As illustrated in  FIG. 13 , the mounting gap may be zero before the sheet bundle  5  is inserted between the first roller  91  and the second roller  92 . In the example illustrated in the drawing, the number of sheets S forming the sheet bundle  5  is two. For example, when the number of sheets S forming the sheet bundle  5  is two, the guide gap is set based upon the thickness of two sheets. For example, the mounting gap is held at zero (constant) before the sheet bundle  5  is inserted between the first roller  91  and the second roller  92 . 
     According to the second modification of the first embodiment, the mounting gap is zero before the sheet bundle  5  is inserted between the first roller  91  and the second roller  92 . An effect described hereinbelow is achieved by the above-mentioned configuration. 
     When the number of sheets S forming the sheet bundle  5  is two, the tape T can follow the edge part  5   a  of the sheet bundle  5 . Accordingly, it is possible to more surely bind the sheet bundle  5  (two sheets). 
     Next, a second embodiment will be described. In the second embodiment, a description of the same configuration as that of the first embodiment will be omitted. 
     The first mounting part  90 A is not limited to being provided with the first spring  93  (the first urging member) that urges the first roller  91  toward the second mounting part  90 B. The second embodiment is different from the first embodiment in that the first mounting part  90 A does not include the first spring  93 . In other words, in the second embodiment, the second mounting part  90 B of the first mounting part  90 A and the second mounting part  90 B includes the urging member. 
       FIG. 14  is a front view illustrating a sheet binding device  203  according to the second embodiment. 
     As illustrated in  FIG. 14 , the first mounting part  90 A is provided with a supporting member  95  for rotatably supporting the first roller  91 . The supporting member  95  supports the first roller  91  at a fixed position. 
     The main guide  31  guides the sheet bundle  5  so that the edge tip of the sheet bundle  5  faces a nip forming end of the first roller  91 . Here, the nip forming end of the first roller  91  means a portion of the outer peripheral surface of the first roller  91  that forms a nip by cooperating with the second roller  92 . The nip forming end of the first roller  91  corresponds to an end edge of the first roller  91  closest to the second roller  92  in the sheet bundle thickness direction Z. A reference sign K 1  in the drawing indicates a virtual straight line that goes along the main guide  31 , and passes through the edge tip of the sheet bundle  5  and the nip forming end of the first roller  91 . 
     According to the second embodiment, the first mounting part  90 A is provided with the first roller  91 , and the supporting member  95  that rotatably supports the first roller  91 . The second mounting part  90 B is provided with the second roller  92  opposite to the first roller  91  in the sheet bundle thickness direction Z, and the second spring  94  that urges the second roller  92  toward the first roller  91 . The main guide  31  guides the sheet bundle  5  so that the edge tip of the sheet bundle  5  faces the nip forming end of the first roller  91 . An effect described hereinbelow is achieved by the above-mentioned configuration. 
     Since the tape T can follow the edge part  5   a  of the sheet bundle  5  by the urging member (the second spring  94 ) of the second mounting part  90 B, it is possible to more surely bind the sheet bundle  5 . Further, the sheet bundle  5  easily enters between the first roller  91  and the second roller  92  in comparison with a case in which the sheet bundle  5  is guided to a position where the edge tip of the sheet bundle  5  is shifted from the nip forming end of the first roller  91 . 
     Next, a third embodiment will be described. In the third embodiment, a description of the same configuration as that of the first embodiment will be omitted. 
     The sheet binding device is not limited to being provided with the interlocking mechanism  82  that allows the inter-guide adjustment part  80  and the mounting adjustment part  81  to be interlocked with each other. The third embodiment is different from the first embodiment in that the sheet binding device does not include the interlocking mechanism  82 . 
       FIG. 15  is a front view illustrating a sheet binding device  303  according to the third embodiment. 
     As illustrated in  FIG. 15 , the sheet binding device  303  is provided with a mounting adjustment part  381  capable of adjusting the mounting gap. The mounting adjustment part  381  may be provided with a sensor  310  that detects the thickness of the sheet bundle  5 , and a control part  320  (hereinafter referred to as a “mounting control part  320 ”) that controls the mounting gap based upon a detection result of the sensor  310 . 
     For example, the sensor  310  is a non-contact type displacement sensor such as a laser type displacement sensor. The sensor  310  is positioned between the main guide  31  and the first roller  91  in the inserting direction of the sheet bundle  5 . The sensor  310  is positioned between the tape holding part  58  and the tape mounting part  59  in a state where the tape T is disposed so that the tape holding part  58  straddles the first roller  91  and the second roller  92 . 
     A reference sign  321  in the drawing is a cam drive source for rotating the mounting side cam  81   a . For example, the cam drive source  321  is a motor. 
     The mounting control part  320  controls the cam drive source  321  based upon the detection result of the sensor  310 . The mounting control part  320  adjusts the mounting gap based upon the thickness of the sheet bundle  5  by controlling the cam drive source  321 . 
     According to the third embodiment, the mounting adjustment part  381  is provided with the sensor  310  that detects the thickness of the sheet bundle  5 , and the mounting control part  320  that controls the mounting gap based upon the detection result of the sensor  310 . An effect described hereinbelow is achieved by the above-mentioned configuration. 
     The mounting gap can be adjusted based upon the thickness of the sheet bundle  5  by the mounting control part  320 . In comparison with a case in which the mounting gap is constant regardless of the thickness of the sheet bundle  5 , there is the low possibility that the mounting gap is too narrow with respect to the thickness of the sheet bundle  5  such that the sheet bundle  5  cannot enter between the first roller  91  and the second roller  92 . Further, there is the low possibility that the mounting gap is too wide with respect to the thickness of the sheet bundle  5  such that the tape T cannot sufficiently adhere to the edge part  5   a  of the sheet bundle  5 . Accordingly, it is possible to automatically bind the sheet bundle  5  regardless of the thickness of the sheet bundle  5 . 
     Next, a first modification of the third embodiment will be described. 
     The mounting adjustment part is not limited to being provided with the mounting side cam  81   a  that allows the second mounting part  90 B to be close to or to be away from the first mounting part  90 A. 
       FIG. 16  is a front view illustrating a sheet binding device according to the first modification of the third embodiment. As illustrated in  FIG. 16 , a mounting adjustment part  381 A may not be provided with the mounting side cam  81   a . In the drawing, a reference sign  395  indicates a first supporting member that rotatably supports the first roller  91 ; a reference sign  396  indicates a second supporting member that rotatably supports the second roller  92 ; and a reference sign  397  indicates a roller drive source that allows the second roller  92  to be close to or to be away from the first roller  91 . For example, the roller drive source  397  is provided with a piston crank mechanism. The mounting control part  320  adjusts the mounting gap based upon the thickness of the sheet bundle  5  by controlling the roller drive source  397 . 
     According to the first modification of the third embodiment, the mounting adjustment part  381 A does not include the mounting side cam  81   a . An effect described hereinbelow is achieved by the above-mentioned configuration. 
     In comparison with a case in which the mounting adjustment part includes the mounting side cam  81   a , the number of parts is reduced, thereby contributing to cost reduction. 
     Hereinafter, another modification of the embodiment will be described. 
     The mounting gap W 2  is not limited to being greater than zero and smaller than the thickness W 1  of the sheet bundle  5  before the sheet bundle  5  is inserted between the first roller  91  and the second roller  92 . For example, the mounting gap W 2  may be the same as the thickness W 1  of the sheet bundle  5  (W 2 =W 1 ) before the sheet bundle  5  is inserted between the first roller  91  and the second roller  92 . That is, the mounting gap W 2  may be equal to or smaller than the thickness W 1  of the sheet bundle  5  (W 2 ≤W 1 ) before the sheet bundle  5  is inserted between the first roller  91  and the second roller  92 . 
     The interlocking mechanism  82  is not limited to allowing the inter-guide adjustment part  80  and the mounting adjustment part  81  to be interlocked with each other so that the mounting gap becomes gradually narrower as the guide gap becomes narrower. For example, the interlocking mechanism  82  may allow the inter-guide adjustment part  80  and the mounting adjustment part  81  to be interlocked with each other so that the mounting gap becomes narrower than an inter-mounting threshold value when the guide gap becomes smaller than an inter-guide threshold value. 
     The interlocking mechanism  82  is not limited to allowing the inter-guide adjustment part  80  and the mounting adjustment part  81  to be interlocked with each other so that the mounting gap becomes gradually wider as the guide gap becomes wider. For example, the interlocking mechanism  82  may allow the inter-guide adjustment part  80  and the mounting adjustment part  81  to be interlocked with each other so that the mounting gap becomes wider than the inter-mounting threshold value when the guide gap becomes wider than the inter-guide threshold value. 
     The sheet binding device is not limited to being provided with the main guide  31  that is provided between the first mounting part  90 A and the second mounting part  90 B, and guides the sheet bundle  5 , and the sub guide  32  that is opposite to the main guide  31  in the sheet bundle thickness direction Z. For example, the sheet binding device may not include the sub guide  32 . For example, the sheet binding device may be provided with the main guide  31 . 
     According to at least one embodiment described hereinabove, the sheet binding device  3  includes the first mounting part  90 A, the second mounting part  90 B, and the mounting adjustment part  81 . The first mounting part  90 A mounts the tape T on the edge part  5   a  of the sheet bundle  5 . The second mounting part  90 B is opposite to the first mounting part  90 A in the sheet bundle thickness direction Z. The mounting adjustment part  81  is capable of adjusting the mounting gap W 2  between the first mounting part  90 A and the second mounting part  90 B based upon the thickness of the sheet bundle  5 . The mounting gap W 2  is equal to or smaller than the thickness W 1  of the sheet bundle  5  before the sheet bundle  5  is inserted between the first mounting part  90 A and the second mounting part  90 B. The effects described hereinbelow are achieved by the above-mentioned configuration. 
     The mounting gap can be adjusted based upon the thickness of the sheet bundle  5  by the mounting adjustment part  81 . In comparison with a case in which the mounting gap is constant regardless of the thickness of the sheet bundle  5 , there is the low possibility that the mounting gap is too narrow with respect to the thickness of the sheet bundle  5  such that the sheet bundle  5  cannot enter between the first roller  91  and the second roller  92 . Additionally, there is the low possibility that the mounting gap is too wide with respect to the thickness of the sheet bundle  5  such that the tape T cannot sufficiently adhere to the edge part  5   a  of the sheet bundle  5 . Accordingly, it is possible to bind the sheet bundle  5  regardless of the thickness of the sheet bundle  5 . Further, before the sheet bundle  5  is inserted between the first mounting part  90 A and the second mounting part  90 B, the tape T easily follows the edge part  5   a  of the sheet bundle  5  in comparison with a case in which the mounting gap is greater than the thickness of the sheet bundle  5 . Therefore, it is possible to more surely bind the sheet bundle  5 . 
     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 inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.