Patent Publication Number: US-11021340-B2

Title: Sheet stacking device including turnable anti-slip stopper and post-processing device

Description:
INCORPORATION BY REFERENCE 
     This application is based on and claims the benefit of priority from Japanese Patent application No. 2019-028480 filed on Feb. 20, 2019, which is incorporated by reference in its entirety. 
     BACKGROUND 
     The present disclosure relates to a sheet stacking device which conveys the sheet stacks and stacks them and a post-processing device including the sheet stacking device. 
     In an operation for bookbinding booklets, a post-processing device for binding the sheet stack and then folding it is sometimes used. Such a post-processing device is provided with a sheet stacking device which conveys the folded sheet stacks (a booklet) and then stacks them. The sheet stacking device includes a tray on which the sheet stacks are stacked, a conveyance belt provided in the tray to convey the sheet stacks in the conveyance direction, and a stopper provided at the downstream end of the tray in the conveyance direction. 
     The stopper is provided so as to be movable in a position where the sheet stacks are inhibited from being conveyed and in another position where the sheet stacks are not inhibited from being conveyed. When the number of the sheet stacks is small, the stopper is moved to the sheet conveyance inhibiting position and allows the sheet stacks to be stacked. In this case, if the conveyance force of the conveyance belt is excessive, the sheet stacks inhibited from being conveyed may collapse. 
     Therefore, a conveyance force decreasing part may be provided, which decreases the conveyance force of the conveyance belt when the stopper is moved to the sheet conveyance inhibiting position. 
     However, if the stopper is moved to the sheet conveyance inhibiting position, in a case where the sheet stacks are continuously conveyed, there is a possibility that the sheet stack discharged earlier is pushed by the sheet stack discharged later and falls from the stopper. 
     SUMMARY 
     In accordance with an aspect of the present disclosure, a sheet stacking device includes a conveyance part and a stopper. The conveyance part includes a tray and a conveyance member. On the tray, sheet stacks discharged from a discharge part at predetermined time intervals are stacked. The conveyance member conveys the sheet stack on the tray along a predetermined conveyance direction. The stopper is located on a downstream side of the tray in the conveyance direction and prevents the sheet stack from falling from the tray. The stopper has a main plate and at least one anti-slip member. The main plate is inclined upward toward the downstream side with respect to the tray. The main plate has a contact face coming into contact with the sheet stack and a bent face bent downward from a tip end on the downstream side of the contact face so as to retract from the contact face. The at least one anti-slip member is provided from a downstream side end portion of the contact face to the bent face. A frictional coefficient between the anti-slip member and the sheet stack is larger than a frictional coefficient between the sheet stack and the contact face. 
     In accordance with an aspect of the present disclosure, a post-processing device includes a binding part binding a sheet stack, a folding part folding the sheet stack bound by the binding part and the sheet stacking device on which the sheet stack folded by the folding part is stacked. 
     The above and other objects, features, and advantages of the present disclosure will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present disclosure is shown by way of illustrative example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view schematically showing a post-processing device according to one embodiment of the present disclosure. 
         FIG. 2  is a front view schematically showing a folding device according to the embodiment of the present disclosure. 
         FIG. 3  is a perspective view showing a processing tray of the folding device, in the post-processing device according to the embodiment of the present disclosure. 
         FIG. 4  is a front view schematically showing a sheet stacking device, in the post-processing device according to the embodiment of the present disclosure. 
         FIG. 5  is a plan view swing a stopper, in the post-processing device according to the embodiment of the present disclosure. 
         FIG. 6  is a front view showing the downstream side end portion of the stopper, in the post-processing device according to the embodiment of the present disclosure. 
         FIG. 7  is a front view showing the sheet stacking device during the conveyance of the booklets, in the post-processing device according to the embodiment of the present disclosure. 
         FIG. 8  is a front view showing the sheet stacking device during the conveyance of the booklets, in the post-processing device according to the embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, with reference to the attached drawings, a post-processing device according to one embodiment of the present disclosure will be described. 
     Firstly, with reference to  FIG. 1 , an entire structure of the post-processing device will be described.  FIG. 1  is a front view schematically showing the entire structure of the post-processing device. In the following description, a near side of a paper surface of  FIG. 1  is defined to be a front side of the post-processing device. Fr, Rr, L and R shown in each figure respectively indicate a front side, a rear side, a left side and a right side of the post-processing device. 
     The post-processing device  1  has a main body  3 . On an upper portion of one side face (a right side face) of the main body  3 , a sheet receiving port  5  is formed. On the other face (a left side face) of the main body  3 , a first discharge port  7 , a second discharge port  9  and a third discharge port  11  are formed in the order from the upper side. Below the first discharge port  7 , a first discharge tray  13  is provided, below the second discharge port  9 , a second discharge tray  15  is provided and below the third discharge port  11 , a sheet stacking device  17  (described later in detail) is provided. 
     Inside the main body  3 , a conveyance path  21  for the sheet is provided such that the sheet is conveyed in a conveyance direction from the sheet receiving port  5  toward the inside of the main body  3 . On the conveyance path  21 , a punching device  23  is provided. The punching device  23  opens a punch hole on the sheet. 
     The conveyance path  21  is branched at a first branch point R 1  downstream the punching device  23  into a first branch path  25  and a second branch path  27 . The first branch path  25  extends from the first branch point R 1  toward the first discharge port  7 . The second branch path  27  extends from the first branch point R 1  toward the second discharge port  9 . On the second branch path  27 , a staple device  29  is provided. The staple device  29  binds a sheet stack using a staple. 
     The second branch path  27  is branched at a second branch point R 2  downstream the first branch point R 1  into a third branch path  35  via a waiting path  33 . The waiting path  33  is formed around a waiting drum  31  which holds the sheet temporarily. The third branch path  35  extends downward. Below the third branch path  35 , a folding device  41  which folds the sheet stack is provided. 
     Next, the folding device  41  will be described with reference to  FIG. 2  and  FIG. 3 .  FIG. 2  is a front view schematically showing the folding device and  FIG. 3  is a perspective view showing a processing tray of the folding device. 
     The folding device  41  includes a carrying path  45  along the upper-and-lower direction, a processing tray  47  disposed below the carrying path  45 , a binding part  49  and a folding part  51  supported by the processing tray  47  and a discharge part  53  formed between the folding part  51  and the third discharge port  11 . 
     The carrying path  45  is formed so as to extend downward from the exit of the third branch path  35 . The lower end portion  45   a  of the carrying path  45  is inclined in an oblique left lower direction. A carrying rollers pair  61  is disposed at the exit of the lower end portion  45   a . The carrying rollers pair  61  includes a drive roller driven by a drive source (not shown) to be rotated and a driven roller driven by the drive roller to be rotated. The carrying rollers pair  61  feeds the sheet carried in the carrying path  45  from the carrying path  45  obliquely downward along the oblique direction of the lower end portion  45   a . In the following description, the direction in which the sheet is fed out by the carrying rollers pair  61  is referred to a conveyance direction Y 1 . 
     The processing tray  47  includes an upstream side tray  63  disposed upstream in the conveyance direction Y 1  and a downstream side tray  65  disposed downstream of the upstream side tray  63  at a predetermined interval D. The upstream side tray  63  and the downstream side tray  65  are disposed so as to be inclined downward along the conveyance direction Y 1 . As shown in  FIG. 3 , the upstream side tray  63  and the downstream side dray  65  respectively have slits  63   a  and  65   a  formed along the conveyance direction Y 1  in the center portions in a width direction perpendicular to the conveyance direction Y 1 . 
     On the upstream side tray  63 , an upstream side cursor  67  is supported in a slidable manner along the conveyance direction Y 1  and the counter direction. Below the upstream side end and the downstream side end of the upstream side tray  63  in the conveyance direction Y 1 , pulleys  69 A and  69 B are respectively supported in a rotatable manner. Around the pullers  69 A and  69 B, an endless belt  71  is wound. The upstream side cursor  67  is mounted to the endless belt  71 , and protrudes upward from the upstream side tray  63  through the slit  63   a . When the pullies  69 A and  69 B are rotated to circulate the endless belt  71 , the upstream side cursor  67  is moved along the slit  63   a.    
     On the downstream side tray  65 , a downstream side cursor  75  is supported in a slidable manner along the conveyance direction Y 1  and the counter direction. Below the upstream side end and the downstream side end of the downstream side tray  65  in the conveyance direction Y, pulleys  77 A and  77 B are respectively supported in a rotatable manner. Around the pullers  77 A and  77 B, an endless belt  79  is wound. The downstream side cursor  75  is mounted to the endless belt  79 , and protrudes upward from the downstream side tray  65  through the slit  65   a . When the pullies  77 A and  77 B are rotated to circulate the endless belt  79 , the downstream side cursor  75  is moved along the slit  65   a.    
     Additionally, on the upstream side tray  63  and the downstream side tray  65 , two pairs of width alignment members  81 U and  81 D are respectively supported in a movable manner along the with direction. Furthermore, above the upstream side tray  63  and the downstream side tray  65 , two conveyance members  83 U and  83 D are respectively supported in a rotatable manner. 
     The biding part  49  is a stapler which binds the center portion of the sheet stack, and is disposed above the upstream side tray  63 . 
     The folding part  51  includes a pair of folding rollers  91  and a folding blade  93  capable of advancing and retracting into and from a nip N between the folding rollers  91 . The pair of folding rollers  91  is disposed along the width direction above the interval D between the upstream side tray  63  and the downstream side tray  65 . The upstream side folding roller  91  is driven by a drive source (not shown) to be rotated in the clockwise direction in  FIG. 2 . The downstream side folding roller  91  is biased by a biasing member (not shown) to press against the upstream side folding roller  91 . The folding blade  93  is driven by a drive mechanism (not shown) to advance and retract through the interval D into and from the nip N between the folding rollers  91 . 
     The discharge part  53  includes a discharge path  97  and a discharge roller  99 . The discharge path  97  extends from the exit of the nip N between the folding rollers of the folding part  51  toward the third discharge port  11 . The discharge roller  99  is supported at the exit of the discharge path  97  in a rotatable manner. 
     Next, the sheet stacking device  17  will be described with reference to  FIG. 4 . The sheet stacking device  17  is formed protruding leftward from the left side face of the main body  3  below the third discharge port  11 . The sheet stacking device  17  includes a conveyance part  101  and a stopper  103 . The conveyance part  101  conveys the sheet stack discharged through the third discharge port  11 , that is, the booklet produced by the folding device  41 , leftward. In this example, the conveyance direction Y 2  of the booklet by the conveyance part  101  is the left direction along an approximately horizontal direction. 
     The conveyance part  101  includes an upstream side conveyance mechanism  107  and a downstream side conveyance mechanism  109  which are disposed in the order along the conveyance direction Y 2 . Each of the conveyance mechanisms  107  and  109  includes a tray  111 , a drive roller  113 , a driven roller  115 , and two endless belts  117  as a conveyance member. 
     The tray  111  has two grooves formed along the conveyance direction Y 2  at an interval in the width direction. The drive roller  113  and the driven roller  115  are respectively disposed below the upstream side end portion and the downstream side end portion of the tray  111  in a rotating manner. The two endless belts  117  are disposed in the two grooves of the tray  111 , and wound around the drive roller  113  and the driven roller  115 . The upper traveling faces of the endless belts  117  wound around the rollers  113  and  115  are set to be almost the same height as the upper face of the tray  111 . 
     When the drive roller  113  is rotated to circulate the endless belts  117 , the booklet is conveyed on the upper face of the tray  111  in the conveyance direction Y 2 . Then, the booklet discharged through the third discharge port  11  and fallen on the upstream side conveyance mechanism  107  is conveyed from the upstream side conveyance mechanism  107  to the downstream side conveyance mechanism  109  along the conveyance direction Y 2 . 
     The tray  111  of the downstream side conveyance mechanism  109  is provided with an actuator  119  as a detection part. The actuator  119  is disposed in the downstream side end of the tray  111 , and turnable between a protruding position where the actuator  119  protrudes from the upper face of the tray  111  and a retracting position where the actuator  119  is retracted from the upper face of the tray  111 . When the actuator  119  is pushed down by the sheet stack conveyed along the tray  111 , it is turned from the protruding position to the retracting position. When the actuator  119  is turned, it is detected that the sheet stack is conveyed to a predetermined position. 
     Next, the stopper  103  will be described with reference to  FIG. 5  and  FIG. 6 .  FIG. 5  is a plan view showing the stopper  103  and  FIG. 6  is a front view showing the downstream side end portion of the stopper  103 . 
     The stopper  103  has a main plate  121  and two anti-slip members  123  adhered to the main plate  121 . 
     The main plate  121  has a rectangular plan shape long in the width direction W, and has a contact face  121   a  and a bent face  121   b  (a left side face) bent downward (in a direction retracting from the contact face  121   a ) from the downstream side end of the contact face  121   a  in the conveyance direction Y 2 . On the contact face  121   a , a plurality of ribs  131  is protruded along the conveyance direction Y 2 . The downstream side ends of the ribs  131  do not reach the downstream side end (the upper end) of the contact face  121   a.    
     As shown in  FIG. 4 , on the downstream side end portion of the lower face of the main plate  121 , a hook  133  is protruded downward in almost the center portion in the width direction W. Furthermore, on the bent face  121   b  of the main plate  121 , two cover parts  135  are formed at a predetermined interval in the width direction W. As shown in  FIG. 6 , each cover part  135  has a base portion  135   a  and a tip portion  135   b . The base portion  135   a  is stood almost perpendicularly to the bent face  121   b . The tip portion  135   b  is bent upward from the tip end of the base portion  135   a  at almost right angles to the base portion  135   a.    
     As shown in  FIG. 4 , the main plate  121  is supported by the downstream side end portion of the tray  111  of the downstream side conveyance mechanism  109  in a turnable manner between a restricting position and a retracting position. In the restricting position shown by a solid line in  FIG. 2 , the main plate  121  is inclined upward toward the downstream side in the discharge direction Y 2  such that the conveyance of the booklet by the conveyance part  101  is restricted to prevent the booklet from falling from the tray  111 . In the restricting position, the contact face  121   a  of the main plate  121  is smoothly continued from the upper face of the tray  111  of the downstream side conveyance mechanism  109 . In the retracting position shown by a two-dotted chain line in  FIG. 2 , the main plate  121  is retracted from the upper face of the tray  111  of the downstream side conveyance mechanism  109 , turned downward below the conveyance part  101 , and the hook  133  is inserted into an opening  139  of the main body  3 . The main plate  121  is held in the restricting position and the retracting position by the respective engagement means (not shown). 
     The anti-slip member  123  is a rectangular sheet like member long in the conveyance direction Y 2 . The anti-slip members  123  are disposed outside the ribs  131  at a predetermined interval in the width direction W, and adhered on the upper corner portion of the main plate  121 . In detail, the anti-slip member  123  is adhered to cover the contact face  121   a  except the ribs  131 , the bent face  121   b  and a corner  121   c  between the contact face  121   a  and the bent face  121   b . The upstream side end portions  123   u  of the anti-slip members  123  are disposed upstream the downstream side end portions of the ribs  131 . The downstream side end portions  123   d  of the anti-slip members  123  are stored in the cover parts  135 . In detail, the end face and the outer face of the downstream side end portion  123   d  is respectively covered with the base portion  135   a  and the tip portion  135   b  of the cover part  135 . The number of the anti-slip member  123  is not limited to two, and may be one, or three or more. 
     The anti-slip member  123  is made of felt, for example, and adhered on the main plate  121  with an adhesive or a double-side adhesive tape. Alternatively, the anti-slip member  123  may be made of anti-slip sheet with an adhesive face. The anti-slip member  123  has a thickness thinner than a height of the ribs  131 . That is, the upper faces of the anti-slip members  123  are lower than the upper faces of the ribs  131 . Additionally, a frictional force (a frictional coefficient) between the anti-slip member  123  and the booklet is larger than a frictional force between the main plate  121  (the contact face  121   a ) and the booklet. Furthermore, a frictional force between the anti-slip member  123  and the booklet is larger than a frictional force between the booklets. 
     Next, an operation for producing a booklet by using the folding device  41  having the above configuration will be described with reference to  FIG. 2  mainly. In an initial state, the downstream side cursor  75  is moved to the receiving position downstream the conveying member  83 D. The upstream side cursor  67  is moved upstream the carrying rollers pair  61 . The width alignment members  81 U and  81 D are moved to a waiting position outside both the side edges of the sheet in the width direction. 
     When the sheet is conveyed into the carrying path  45  from the third branch path  35 , the carrying rollers pair  61  is rotated to feed the first sheet from the lower end portion  45   a  of the carrying path  45  to the processing tray  47 . The fed first sheet is slid on the processing tray  47  toward the downstream side cursor  75 . At this time, the conveying members  83 U and  83 D are rotated to assists the conveyance of the first sheet on the processing tray  47 . The first sheet is conveyed until the leading edge of the first sheet comes into contact with the downstream side cursor  75 . Then, the downstream side cursor  75  is moved upstream until the trailing edge of the sheet comes into contact with the upstream side cursor  67 . Thereby, the first sheet is aligned by the upstream side cursor  67  and the downstream side cursor  75  in the conveyance direction Y 1 . 
     Next, the width alignment members  81 U and  81 D are moved along the width direction so as to come into contact with both the side edges of the first sheet. Thereby, the first sheet is aligned in the width direction. After the alignment of the sheet, the downstream side cursor  75  is returned to the receiving position and the width alignment members  81 U and  81 D are returned to the waiting position. 
     After that, the second is fed from the carrying path  45  by the carrying rollers pair  61 . The second sheet is conveyed on the first sheet by the two conveying members  83 U and  83 D toward the downstream side cursor  75 . Then, the downstream side cursor  75  is moved upstream to transport the first and second sheets until the trailing edges of the two sheets come into contact with the upstream side cursor  67 . Next, the width alignment members  81 U and  81 D are moved along the width direction so as to come into contact with both the side edges of the two sheets. The alignment in the conveyance direction Y by the downstream side cursor  75  and the upstream side cursor  67  and the alignment in the width direction by the width alignment members  81 U and  81 D are performed every one sheet. 
     Then, after a predetermined number of the sheets (for example, 20 sheets) are fed through the carrying path  45 , the sheet stack is formed on the processing tray  47 . 
     The sheet stack is transported to the binding part  49  by the upstream side cursor  67  and the downstream side cursor  75 , and the center portion of the sheet stack is bound by the binding part  49 . Then, the sheet stack whose center portion is bound is transported along the processing tray  47  to a folding position by the upstream side cursor  67  and the downstream side cursor  75 . That is, the upstream side cursor  67  and the downstream side cursor  75  are moved downstream together until the center portion of the sheet stack in the conveyance direction Y 1  is positioned at the folding position of the folding part (a position corresponding to the nip N between the folding rollers  91 ). 
     At the folding position, the folding blade  93  is driven by the drive mechanism to advance through the interval D into the nip N between the folding rollers  91 . Thereby, the center portion of the sheet stack is pushed up into the nip N by the folding blade  93 , and the sheet stack is pressed from both the sides by the upstream side roller and the downstream side roller to be folded. As a result, a booklet is produced. The downstream side roller is displaced against the biasing force by the thickness of the folded sheet stack. 
     The folding blade  93  retracts at a suitable timing, and the upstream and downstream side rollers of the folding roller  101  are further rotated. Then, the booklet is discharged from the nip N to the discharge path  97  of the discharge part  53  with the folded center portion forward. 
     The booklet discharged to the discharge path  97  is discharged through the third discharge port  11  by the discharge roller  99 . The discharged booklet is fallen on the conveyance part  101  of the sheet stacking device  17 . 
     An operation for conveying and stacking of the booklet by the sheet stacking device  17  will be described with reference to  FIG. 4 ,  FIG. 7  and  FIG. 8 .  FIG. 7  and  FIG. 8  are front views showing the sheet stacking device. 
     The first booklet B 1  discharged from the folding device is stacked on the tray  111  of the upstream side conveyance mechanism  107  of the conveyance part  101  of the sheet stacking device  17 . Then, the endless belts  117  of the upstream side conveyance mechanism  107  and the downstream side conveyance mechanism  109  are driven to convey the first booklet B 1  on the tray  111  along the discharge direction Y 2  with the folded center portion forward. The endless belts  117  of each conveyance mechanism is stopped after being driven for a predetermined period. Thus, the first booklet B 1  is conveyed for a predetermined distance. 
     Next, the endless belts  117  of each conveyance mechanism are driven at a timing where the second booklet B 2  is stacked on the tray  11  of the upstream side conveyance mechanism  107 , and then stopped after being driven for the predetermined period. Thus, the second booklet B 2  is stacked on a position displaced from the first booklet B 1  for the predetermined distance and then conveyed for the predetermined distance. When the above operation is repeated, the booklets are stacked on the tray  111  of each conveyance mechanism at the predetermined intervals. 
     When the first booklet B 1  reaches the downstream side end portion of the tray  111  of the downstream side conveyance mechanism  109 , the actuator  119  is pushed down by the first booklet B 1  to be turned from the protruding position to the retracting position. Then, it is detected that the first booklet is conveyed to the predetermined position. 
     When the first booklet reaches the downstream side end of the conveyance part  101 , the leading end portion (the downstream side end portion) of the booklet B 1  runs on the stopper  103 . During this time, the conveyance part  101  is driven so that the booklet B 1  runs on the contact face  121   a  of the main plate  121  completely and is held on the contact face  121   a . In other words, when the booklet B 1  runs on the stopper  103 , the conveyance of the booklet B 1  by the conveyance part  101  is inhibited. The booklet B 1  runs on the stopper  103  while guided along the ribs  131 , and therefore smoothly runs on the contact face  121   a.    
     The second booklet B 2  discharged next is conveyed in the same manner as the first booklet B 1 . When the second booklet B 2  reaches the downstream side end of the conveyance part  101 , the leading end portion (the downstream side end portion) of the second booklet B 2  runs on the first booklet B 1  held on the stopper  103 . Because the conveyance part  101  is driven during this time, as shown in  FIG. 7 , the second booklet B 2  runs on the first booklet B 1  so as to be stacked on the first booklet B 1 . 
     When the booklets are continuously conveyed in the above manner, the booklets B are aligned so as to gradually stand in a vertical posture and to be stacked on the tray  111  of each conveyance mechanism. Then, after the first booklet is conveyed to the predetermined position (after the actuator  119  is turned and then it is detected that the first booklet B 1  is conveyed to the predetermined position), at a timing when a predetermined number of booklets are stacked, it is determined that the tray  111  of each conveyance mechanism is full of the booklets. When the full state is determined, the driving of the endless belt  117  of each conveyance mechanism is stopped. Thus, the booklets are prevented from falling from the conveyance part  101 . The timing when the full state is determined depends on a size of the sheet and the number of sheets contained the sheet stack. 
     However, in a case where the full state is determined by the number of booklets as described above, depending on the sheet property (for example, a thickness or a stiffness of the sheet) and the folding state, there is a case where even if the number of booklets is less than the number of booklet determined to be the full state, the conveyance part  101  becomes full of the booklets. In such a case, the first booklet B 1  is pushed out downstream from the stopper  103  by the booklet discharged later. Then, the first booklet B 1  slides along the ribs  131  of the main plate  121 , and then reaches the anti-slip members  123 . Because a frictional force between the anti-slip member  123  and the booklet is larger than a frictional force between the main plate  121  (the contact face  121   a ) and the booklet, as shown in  FIG. 8 , the first booklet B 1  is prevented from being pushed out by the anti-slip members  123 . That is, the first booklet B 1  does not fall from the main plate  121 . As shown in a two-dotted chain line in  FIG. 8 , even if the leading end portion of the booklet B 1  is pushed out along the upper corner  121 C of the main plate  121 , the anti-slip members  123  adhered on the corner  121   c  and the bent face  121   b  of the main plate  121  prevent the booklet B 1  from falling. 
     Alternatively, in some cases, the second booklet B 2  may be pushed up along the first booklet B 1 . In this case, even if the second booklet B 2  is pushed out from the stopper  103 , the anti-slip members  123  is brought into contact with the second booklet B 2  so that the falling of the booklet B 2  is prevented. 
     In a case where the number of the booklets is relatively small, the booklets are blocked by the stopper  103  as described above, and then stacked on the conveyance part  101 . However, in a case where the number of the booklets is relatively large, the stopper  103  is turned from the restricting position to the retracting position (refer to the two-dotted chain line in  FIG. 4 ). Then, a collection box  141  (a collection part) is placed below the downstream side conveyance mechanism  109 . Thus, the booklet conveyed by the conveyance part  101  is fallen from the downstream side conveyance mechanism  109  and collected into the collection box  141 . 
     As described above, according to the sheet stacking device  17  of the present disclosure, in a case where the booklet discharged earlier is pushed out by the booklet discharged later, the anti-slip members  123  prevent the booklet from falling. Because the anti-slip member  123  is adhered on the upper corner of the main plate  121 , in detail, the contact face  121   a  except the ribs  131 , the bent face  121   b  and the corner  121   c  between the contact face  121   a  and the bent face  121   b , it becomes possible to increase an area where the anti-slip member  123  comes into contact with the booklet. Accordingly, it becomes possible to stack the booklets on the conveyance part  10  stably. The anti-slip member  123  is made of inexpensive material such as felt. Additionally, the anti-slip member  123  can be attached easily by an easy working, such as a work for adhering the anti-slip member  123  to the contact face  121   a  and the bent face  121   b  of the main plate  121 . Therefore, the means for decreasing the conveyance force of the conveyance part, as described in the above techniques, is not required. 
     Additionally, because the upper faces of the anti-slip members  123  are lower than the upper faces of the ribs  131 , the leading edge of the booklet is not caught by the anti-slip members  123 . Furthermore, the upstream side end portion  123   u  of the anti-slip member  123  is disposed upstream the downstream side end portion of the ribs  31  so that the leading edge of the booklet is not caught by the anti-slip members  123 . Accordingly, it becomes possible to guide the booklet smoothly along the ribs  131 . 
     Additionally, the downstream side end portion  123   d  of the anti-slip member  123  is covered with the base portion  135   a  and the tip portion  135   b  of the cover part  135  so that the downstream side end portion  123   d  is prevented from being peeled. 
     Additionally, the stopper  103  is supported in a turnable manner in the restricting position and the retracting position. When the number of the booklets is relatively small and the stopper  103  is turned to the restricting position, it becomes possible to stack the booklets on the conveyance part  101  without using a collection box. On the other hand, when the number of the booklet is relatively large and the stopper  103  is turned to the retracting position, it becomes possible to collect the booklets directly in the collection box  141  from the conveyance part  101  without interfering with the stopper  103 . 
     Furthermore, it becomes possible to couple the post-processing device  1  of the present embodiment to an electrophotographic type or an inkjet type image forming apparats and to produce a booklet using the sheet on which an image is formed by the image forming apparatus. Alternatively, it becomes possible to receive the sheet on which the image is formed by means other than the image forming apparatus. The sheet stacking device  17  of the present disclosure may be applied to a sheet stacking device of the conventional printer. 
     While the above description has been described with reference to the particular illustrative embodiments, the present disclosure is not limited to the above embodiments. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present disclosure.