Patent Publication Number: US-10308470-B2

Title: Blade and post-processing apparatus

Description:
FIELD 
     Embodiments described herein relate generally to a blade, a post-processing apparatus, and methods associated therewith. 
     BACKGROUND 
     A post-processing apparatus for post-processing a sheet carried from an image forming device (for example, an MFP) is known. The post-processing apparatus includes a processing unit for stapling or sorting the carried sheet. In addition, the post-processing apparatus includes a saddle folding unit that performs so-called saddle-folding, in which a plurality of sheets are bundled and folded in half. The saddle folding unit includes a blade capable of reciprocating so as to insert and remove a leading edge with respect to a nip portion of a pair of folding rollers. The blade enters a nip portion while pushing a central portion of a sheet into the nip portion between a pair of folding rollers. 
     However, in a case where the blade pushes the sheet into the nip portion, there is a possibility of slippage between the blade and the sheet. When undesired slippage occurs between the blade and the sheet, there is a possibility that the central portion of the sheet cannot be accurately pushed into the nip portion. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view showing an example of an image forming system of an embodiment. 
         FIG. 2  is a perspective view showing an example of a saddle folding unit of a post-processing apparatus of the embodiment. 
         FIG. 3  is a perspective view showing an example of a blade of the embodiment. 
         FIG. 4  is a perspective view showing an example of a leading edge of the blade of the embodiment. 
         FIG. 5  is a perspective view showing an example of a protrusion portion of the blade of the embodiment. 
         FIG. 6  is a side view showing an example of the protrusion portion of the blade of the embodiment. 
         FIG. 7  is a side view showing an example of a protrusion of a protrusion plate of the embodiment. 
         FIG. 8  is a diagram showing an example of a method of manufacturing the blade of the embodiment. 
         FIG. 9  is an explanatory view of an action of the blade in the embodiment. 
         FIG. 10  is an explanatory view of an action of the blade in the embodiment, following  FIG. 9 . 
         FIG. 11  is a side view showing an example of a protrusion portion of a blade of a first modification example of the embodiment. 
         FIG. 12  is a side view showing an example of a protrusion portion of a blade of a second modification example of the embodiment. 
         FIG. 13  is a side view showing an example of a protrusion portion of a blade of a third modification example of the embodiment. 
         FIG. 14  is a side view showing an example of a protrusion of a protrusion plate of the third modification example of the embodiment. 
         FIG. 15  is a diagram showing an example of a manufacturing method of the blade of the third modification example of the embodiment. 
         FIG. 16  is a side view showing an example of a protrusion portion of a blade of a fourth modification example of the embodiment. 
         FIG. 17  is a side view showing an example of a protrusion of a protrusion plate of a fifth modification example of the embodiment. 
         FIG. 18  is a side view showing an example of a protrusion of a protrusion plate of a sixth modification example of the embodiment. 
         FIG. 19  is a perspective view showing an example of a protrusion portion of a blade of a seventh modification example of the embodiment. 
         FIG. 20  is a perspective view showing an example of a protrusion portion of a blade of an eighth modification example of the embodiment. 
         FIG. 21  is a perspective view showing an example of a protrusion portion of a blade of a ninth modification example of the embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     According to the embodiment, there is provided a blade for a saddle folding unit capable of saddle-folding a sheet. At the edge of a folding side of the sheet in the blade, a protrusion portion protruding in a pushing direction of the blade is provided. 
     Hereinafter, the post-processing apparatus of the embodiment will be described with reference to the drawings. In each drawing, the same reference numerals are assigned to the same components. 
       FIG. 1  is a view showing an example of an image forming system  1  of the embodiment. 
     As shown in  FIG. 1 , the image forming system  1  includes an image forming device  2  and a post-processing apparatus  3 . The image forming device  2  forms an image on a sheet-like recording medium (hereinafter, referred to as a “sheet S”) such as paper. For example, the image forming device  2  is a multifunction peripheral (MFP), a printer, a copying machine, or the like. The post-processing apparatus  3  performs post-processing on the sheet S carried from the image forming device  2 . The sheet S is not limited to paper, but includes a plastic sheet such as an overhead projector (OHP) sheet. The sheet S is not limited to being sent from the image forming device  2  to the post-processing apparatus  3 , but can also be sent by being fed manually to the post-processing apparatus  3 . The image forming device  2  includes a control panel  11 , a scanner unit  12 , a printer unit  13 , a paper feed unit  14 , a paper discharge unit  15 , and an image formation control unit  16 . 
     The control panel  11  includes various keys or a touch panel for accepting an operation of a user. For example, the control panel  11  receives an input regarding a type of post-processing of the sheet S. The image forming device  2  sends information on the type of post-processing input by the control panel  11  to the post-processing apparatus  3 . 
     The scanner unit  12  includes a reading unit that reads image information of an object to be copied. The scanner unit  12  sends the read image information to the printer unit  13 . 
     The printer unit  13  forms an output image (hereinafter, referred to as a “toner image”) with a developer such as a toner based on image information transmitted from the scanner unit  12  or an external device. The printer unit  13  transfers the toner image onto the surface of the sheet S. The printer unit  13  applies heat and pressure to the toner image transferred to the sheet S to fix the toner image on the sheet S. 
     The paper feed unit  14  supplies the sheets S one by one to the printer unit  13  in accordance with a timing at which the printer unit  13  forms a toner image. 
     The paper discharge unit  15  carries the sheet S discharged from the printer unit  13  to the post-processing apparatus  3 . 
     The image formation control unit  16  controls the overall operation of the image forming device  2 . That is, the image formation control unit  16  controls the control panel  11 , the scanner unit  12 , the printer unit  13 , the paper feed unit  14 , and the paper discharge unit  15 . The image formation control unit  16  is formed of a control circuit including a Central Processing Unit (CPU), a Read Only Memory (ROM), and a Random Access Memory (RAM). 
     Next, the post-processing apparatus  3  will be described. 
     For example, the post-processing apparatus  3  is disposed adjacent to the image forming device  2 . The sheet S is carried from the image forming device  2  to the post-processing apparatus  3 . The post-processing apparatus  3  executes post-processing specified on the carried sheet S through the control panel  11 . For example, the post-processing apparatus  3  performs stapling processing and sort processing. For example, the post-processing apparatus  3  performs sheet folding processing in which the sheet S is folded into two and carried out. 
     The post-processing apparatus  3  includes a loading unit  20 , a standby unit  21 , a processing unit  22 , a carry-out unit  23 , a post-processing control unit  24 , and a saddle folding unit  40 . 
     The loading unit  20  is connected to the downstream side of the paper discharge unit  15  in a carrying direction. The loading unit  20  receives the sheet S carried from the image forming device  2 . A manual feed tray (not shown) is connected to the paper discharge unit  15 . 
     The standby unit  21  temporarily retains (buffers) the sheet S carried from the image forming device  2 . The standby unit  21  is provided above the processing unit  22 . When the processing unit  22  is empty, the standby unit  21  causes the retained sheet S to fall toward the processing unit  22 . 
     The processing unit  22  performs post-processing on the carried sheet S. For example, the processing unit  22  performs sorting processing in which a plurality of sheets S are sorted and aligned. For example, the processing unit  22  performs sheet binding processing on a sheet bundle in which a plurality of sheets S are sorted with staples or adhesive tapes. A reference numeral  25  in the drawing indicates a sheet binding apparatus which performs binding processing by stapling or the like on the sheet bundle in the processing unit  22 . The processing unit  22  carries out the post-processed sheet S to the carry-out unit  23 . 
     The carry-out unit  23  includes a fixed tray  23   a  and a movable tray  23   b . The fixed tray  23   a  is provided on an upper portion of the post-processing apparatus  3 . The movable tray  23   b  is provided on a side portion of the post-processing apparatus  3 . The sheet S is discharged from the standby unit  21  and the processing unit  22  to the fixed tray  23   a  and the movable tray  23   b.    
     The post-processing control unit  24  controls the overall operation of the post-processing apparatus  3 . That is, the post-processing control unit  24  controls operations of the loading unit  20 , the standby unit  21 , the processing unit  22 , the carry-out unit  23 , and the saddle folding unit  40 . Similarly, to the image formation control unit  16 , the post-processing control unit  24  is formed of a control circuit including a CPU, a ROM, and a RAM. 
     Next, the saddle folding unit  40  of the post-processing apparatus  3  will be described. 
     The post-processing apparatus  3  includes the saddle folding unit  40  for folding (saddle-folding) one or a plurality of sheets S in half. 
     The post-processing apparatus  3  is shown along a path along a paper surface of  FIG. 1 . The front and back surfaces of the sheet S are arranged in parallel with a direction orthogonal to the paper surface in  FIG. 1 . Hereinafter, a direction along a carrying path of the sheet S in the saddle folding unit  40  is referred to as a sheet carrying direction D (or simply, a carrying direction). Hereinafter, the direction orthogonal to the paper surface in  FIG. 1  is referred to as a sheet width direction W (see  FIG. 2 ). The sheet S is in a rectangular shape having two sides along the sheet carrying direction D and two sides along the sheet width direction W. 
     The sheet S is carried from the image forming device  2  via a sheet path  54  to the saddle folding unit  40 . The sheet S carried to the saddle folding unit  40  is received by a stacker  55 . 
     For example, the stacker  55  receives the sent sheet S in an upright manner. The stacker  55  tilts the sheet S such that the upper side of the received sheet S is located on the downstream side in the carrying direction (a folding roller  41  side). In the case of folding the plurality of sheets S in half, the plurality of sheets S are sequentially stacked and received by the stacker  55  to become a bundle. 
     The sheet S (or the sheet bundle) received by the stacker  55  is supported by a guide member  58  from the downstream side in the carrying direction and arranged in a flat shape. At this time, a central portion SC (the center in the sheet carrying direction) of the sheet S in the upright direction faces a nip portion  42  of the folding roller  41  in a thickness direction of the sheet S (see  FIG. 2 ). A folding blade  43  (hereinafter, simply referred to as a “blade  43 ”) is disposed at a portion facing the nip portion  42  across the sheet S in the thickness direction of the sheet S. 
     As shown in  FIG. 2 , the blade  43  pushes out the central portion SC in the upright direction of the sheet S toward the nip portion  42  of the folding roller  41  and pushes the central portion SC of the sheet S into the nip portion  42 . The folding roller  41  rotates while pinching the central portion SC of the sheet S and folds the sheet S in half. As shown in  FIG. 1 , the folded sheet S (hereinafter, referred to as a “folded body”) is carried by a discharge roller  44  located on the downstream side in the carrying direction of the nip portion  42  and discharged to a paper discharge tray  46 . The folding roller and the discharge roller  44  are rotationally driven independently of each other or synchronously by a driving motor (not shown). 
     As shown in  FIG. 1 , a gate  20   a  is provided in the loading unit  20  of the post-processing apparatus  3  in order to switch whether to carry the sheet S carried from the image forming device  2  to the processing unit  22  side or the saddle folding unit  40  side. When the sheet folding processing is not performed, the gate  20   a  carries the sheet S carried from the image forming device  2  to the processing unit  22  side. The gate  20   a  carries the sheet S to the saddle folding unit  40  side when performing the sheet folding processing. 
       FIG. 2  is a perspective view showing an example of the saddle folding unit  40  of the post-processing apparatus  3  of the embodiment. 
     As shown in  FIG. 2 , the saddle folding unit  40  includes the folding roller  41  and the blade  43 . 
     The folding roller  41  is composed of a pair of rollers forming the nip portion  42 . One of the pair of rollers of the folding roller  41  is a driving roller  41   a . The other of the pair of rollers of the folding roller  41  is a driven roller  41   b.    
     The driving roller  41   a  is rotationally driven at a fixed position without moving. The driving roller  41   a  is driven by a driving source (not shown). For example, a DC motor is used as the driving source of the driving roller  41   a . The driving source transmits a driving force to the driving roller  41   a . For example, the driving source of the driving roller  41   a  also transmits the driving force to the blade  43 . 
     The driven roller  41   b  is detachable with respect to the driving roller  41   a . The driven roller  41   b  is energized towards the driving roller  41   a  by an energizing mechanism (not shown). The driven roller  41   b  rotates following the rotation of the driving roller  41   a.    
     In the nip portion  42  of the folding roller  41 , the central portion SC of the sheet S is pinched by the blade  43 . The folding roller  41  folds the sheet S inserted into the nip portion  42  in half and carries the folded sheet S to the downstream side in the carrying direction. 
     The blade  43  is a plate-like member having a thickness in a direction in which the pair of rollers of the folding roller  41  faces to each other. The blade  43  can reciprocate so as to insert and remove the leading edge with respect to the nip portion  42 . For example, the blade  43  reciprocates via a slider-crank mechanism. The blade  43  enters the nip portion  42  while pushing the central portion SC of the sheet S into the nip portion  42 . The blade  43  retracts from the nip portion  42  while leaving the central portion SC of the sheet S in the nip portion  42 . 
     As shown in  FIG. 1 , the guide member  58  is disposed between the folding roller  41  and the sheet S in the sheet carrying direction D. The guide member  58  is a plate member orthogonal to an advancing and retracting direction of the blade  43 . The guide member  58  guides the sheet S carried from the sheet path  54  to an upright state and places the sheet S on the stacker  55 . The guide member  58  is divided into a first guide member  58   a  and a second guide member  58   b  with a gap allowing the blade  43  to advance and retract. The blade  43  can advance through the gap between the first guide member  58   a  and the second guide member  58   b  and push the central portion SC (see  FIG. 2 ) of the sheet S into the nip portion  42 . When the central portion SC (see  FIG. 2 ) of the sheet S is pushed into the nip portion  42 , folding sides are formed on the sheet S. After forming the folding side on the sheet S, the blade  43  can retract and escape from the nip portion  42 . 
     The stacker  55  includes a support claw  56  and a mobile device  57 . The support claw  56  supports the lower end of the sheet S in the upright state. The mobile device  57  can move the support claw  56  up and down. 
     A stapling unit  59  is disposed above the stacker  55 . According to the type of post-processing, the stapling unit  59  applies stapling processing to the central portion SC of the sheet S in advance. The sheet S placed on the stacker  55  can move up and down by the movement of the support claw  56 . For example, even when the blade  43  pushes the sheet S into the nip portion  42 , the support claw  56  also rises as the lower end of the sheet S is displaced. The sheet S placed on the stacker  55  is located (aligned) in the sheet carrying direction D by supporting the lower end of the sheet S on the support claw  56 . As shown in  FIG. 2 , a pair of alignment members  55   a  for positioning the sheets S in the sheet width direction W are disposed on both sides of the stacker  55  in the sheet width direction. 
     As shown in  FIG. 1 , the discharge roller  44  that discharges the folded body toward the downstream side in the carrying direction is disposed at a portion that is separated downstream from the folding roller  41  in the carrying direction. 
     The discharge roller  44  is composed of a pair of rollers forming a nip portion  45 . One of the pair of rollers of the discharge roller  44  is a driving roller. The other of the pair of rollers of the discharge roller  44  is a driven roller. The driving roller is rotationally driven at a fixed position without moving. The driven roller is detachable with respect to the driving roller. The driven roller is energized towards the driving roller by an energizing mechanism (not shown). In the nip portion  45  of the discharge roller  44 , the folded body carried by the folding roller  41  is pinched. The discharge roller  44  carries the folded body inserted into the nip portion  45  to the downstream side in the carrying direction. The nip portion  45  of the discharge roller  44  faces the nip portion  42  of the folding roller  41  in the sheet carrying direction D. 
     Hereinafter, the blade  43  will be described in detail. 
       FIG. 3  is a perspective view showing an example of the blade  43  of the embodiment. 
     As shown in  FIG. 3 , the blade  43  is a blade for the saddle folding unit  40  (see  FIG. 2 ) capable of saddle-folding the sheet S. A plurality of concave portions  43   a  recessed so as to avoid the folding roller  41  are provided at the edge of a folding side (hereinafter, also referred to as a “leading edge”) of the sheet S in the blade  43 . The plurality of concave portions  43   a  are recessed on the side opposite to a pushing direction V 1  of the blade  43 . Here, the pushing direction V 1  is a direction in which the blade  43  is directed toward the nip portion  42  (see  FIG. 2 ) of the folding roller  41 . 
     In other words, a plurality of pushing pieces  43   b  protruding in the pushing direction V 1  of the blade  43  are provided at the leading edge of the blade  43 . In the embodiment, a direction orthogonal to the pushing direction V 1  and a thickness direction V 2  of the blade  43  (hereinafter, also referred to as a “blade width direction V 3 ”) is parallel to the sheet width direction W. The plurality of pushing pieces  43   b  are arranged at intervals in the blade width direction V 3 . Reference numerals  43   h ,  43   i , and  43   j  in the drawing indicates positioning holes or mounting holes of the blade  43  or the like. 
       FIG. 4  is a perspective view showing an example of the leading edge of the blade  43  of the embodiment. 
     As shown in  FIG. 4 , the pushing piece  43   b  is in a trapezoidal shape protruding in the pushing direction V 1  of the blade  43 . The length of the pushing piece  43   b  in the sheet width direction is shorter toward the nip portion  42  side (see  FIG. 2 ) in the pushing direction V 1  of the blade  43 . A protrusion portion  30  protruding in the pushing direction V 1  of the blade  43  is provided at the leading edge of the blade  43 . The protrusion portion  30  is located at the end portion of the folding side of the sheet S of the pushing piece  43   b . In the embodiment, the edge (the leading edge) of the folding side of the sheet S in the protrusion portion  30  has a linear shape continuous in the blade width direction V 3  (the sheet width direction W). 
       FIG. 5  is a perspective view showing an example of the protrusion portion  30  of the blade  43  of the embodiment. 
     As shown in  FIG. 5 , the protrusion portion  30  includes a plurality of protrusions  31  aligned in the thickness direction V 2  of the blade  43 . In the embodiment, the protrusion portion  30  includes five protrusions  31  aligned in the thickness direction V 2  of the blade  43 . The blade  43  is a laminate in which a plurality of protrusion plates  29  having protrusions  31  are stacked in the thickness direction V 2  of the blade  43 . In the embodiment, the blade  43  is a laminate in which five protrusion plates  29  are stacked in the thickness direction V 2  of the blade  43 . 
       FIG. 6  is a side view showing an example of the protrusion portion  30  of the blade  43  of the embodiment. In other words,  FIG. 6  is a view of the protrusion portion  30  of the blade  43  as viewed from a direction (the blade width direction V 3 ) orthogonal to the pushing direction V 1  of the blade  43  and the thickness direction V 2  of the blade  43 . 
     As shown in  FIG. 6 , when viewed from the blade width direction V 3 , the protrusion ends  31   a  of the plurality of protrusions  31  are sorted over the entire thickness direction V 2  of the blade  43 . In other words, when viewed from the blade width direction V 3 , the protrusions  31  have the same amount of protrusion to the pushing direction V 1 . In the embodiment, the thickness of the five protrusion plates  29  is the same as each other. 
     In  FIG. 6 , a reference numeral t 1  indicates the thickness of the blade  43 , and a reference numeral t 2  indicates the thickness of the protrusion plate  29 . For example, the thickness t 1  of the blade  43  is set within a range of 0.25 mm or more and 0.5 mm or less. For example, the thickness t 2  of the protrusion plate  29  is set within a range of 0.05 mm or more and 0.1 mm or less. In the embodiment, the thickness t 1  of the blade  43  is about 0.25 mm and the thickness t 2  of the protrusion plate  29  is about 0.05 mm. 
       FIG. 7  is a side view showing an example of the protrusion  31  of the protrusion plate  29  of the embodiment. In other words,  FIG. 7  is a view of the protrusion  31  of the protrusion plate  29  as viewed from the blade width direction V 3 . 
     As shown in  FIG. 7 , when viewed from the blade width direction V 3 , the protrusion  31  protrudes to the pushing direction V 1  toward a center side of the thickness direction V 2 . 
     In  FIG. 7 , a reference numeral  3   b   1  indicates a first base end of the protrusion  31 , and a reference numeral  31   b   2  indicates a second base end of the protrusion  31 , respectively. Here, the second base end  31   b   2  of the protrusion  31  is a base end of the protrusion  31  located on the side opposite to the first base end  3   b   1  of the protrusion  31  in the thickness direction V 2 . In the embodiment, the protrusion end  31   a  of the protrusion  31  is located at the center position in the thickness direction V 2  of the blade  43 . The protrusion  31  has a sharp shape protruding most in the pushing direction V 1  at the center position in the thickness direction V 2  of the blade  43 . 
     In  FIG. 7 , a reference numeral  3   c   1  indicates a first surface located between the protrusion end  31   a  of the protrusion  31  and the first base end  3   b   1 , and a reference numeral  31   c   2  indicates a second surface located between the protrusion end  31   a  of the protrusion  31  and the second base end  31   b   2 , respectively. When viewed from the blade width direction V 3 , a first surface  3   c   1  and a second surface  31   c   2  have a circular arc-shaped convex toward the inside in the thickness direction V 2  of the blade  43 . 
     In  FIG. 7 , a reference numeral h 1  indicates a protrusion amount of the protrusion  31 . Here, the protrusion amount h 1  of the protrusion  31  is equal to or greater than the distance between the protrusion end  31   a  of the protrusion  31  and the first base end  3   b   1  in the pushing direction V 1 . For example, there is a relationship of h 1 ≥0.2×t 2  between the protrusion amount h 1  of the protrusion  31  and the thickness t 1  of the protrusion plate  29 . 
     In  FIG. 7 , a reference numeral CL indicates a center axis of the protrusion plate  29  in the thickness direction V 2 . When viewed from the blade width direction V 3 , the protrusion plate  29  is axisymmetric with respect to the center axis CL of the protrusion plate  29  as an axis of symmetry. That is, when viewed from the blade width direction V 3 , the first surface  3   c   1  and the second surface  31   c   2  are axisymmetric with respect to the center axis CL of the protrusion plate  29  as an axis of symmetry. 
     Next, an example of a method of manufacturing the blade  43  of the embodiment will be described. 
       FIG. 8  is a view showing an example of a method of manufacturing the blade  43  of the embodiment. As shown in  FIG. 8 , first, a base plate  28  which is a plate member having a thickness of 0.05 mm or more and 0.1 mm or less is prepared. 
     Next, a pair of masks  35  with opening portions  35   a  on both sides of the base plate  28  are disposed. At this time, the opening portions  35   a  of the pair of masks  35  face to each other via the base plate  28 . 
     Next, the base plate  28  is wet-etched via the opening portions  35   a  of the pair of masks  35 . By performing wet-etching for a predetermined time, a pair of circular arc-shaped concave portions  28   a  are formed in the base plate  28 . The pair of circular arc-shaped concave portions  28   a  are formed in a portion of the base plate  28  facing the opening portions  35   a  of the pair of masks  35 . 
     When the pair of circular arc-shaped concave portions  28   a  are formed to have a predetermined depth, the base plate  28  is divided into right and left sides of the paper surface. A reference numeral DL in the drawing indicates a dividing line of the base plate  28  passing through the center of a pair of arc-shaped concave portions  28   a . By dividing the base plate  28  having the pair of circular arc-shaped concave portions  28   a  formed to have the predetermined depth along a dividing line DL, the protrusion plate  29  (see  FIG. 7 ) having the protrusions  31  is obtained. 
     Next, five protrusion plates  29  having protrusions  31  are stacked in the thickness direction V 2 . At this time, when viewed from the blade width direction V 3 , the protrusion ends  31   a  of the plurality of protrusions  31  are sorted over the entire thickness direction V 2  of the blade  43 . 
     Next, the five protrusion plates  29  are joined. For example, the five protrusion plates  29  are placed in a vacuum furnace and joined by applying pressure and heat. That is, the five protrusion plates  29  are integrated under vacuum thermo-compression. Through the above steps, the blade  43  (see  FIG. 6 ) of the embodiment may be manufactured. 
     Next, an action of the blade  43  of the embodiment will be described. 
       FIGS. 9 and 10  are explanatory views of actions of the blade  43  (see  FIG. 6 ) of the embodiment and the blade  43 X of the comparative example. For convenience, in  FIGS. 9 and 10 , the illustration of the blade  43  of the embodiment will be omitted. 
     First, an action of the blade  43 X of the comparative example will be described. 
     The blade  43 X of the comparative example does not include the protrusion portion  30  in the embodiment. For example, when viewed from the blade width direction V 3 , the leading edge of the blade  43 X of the comparative example has a flat surface parallel to one side of the sheet S. 
     As shown in  FIG. 9 , the blade  43 X enters the nip portion  42  while pushing the central portion of the sheet S into the nip portion  42 . However, in a case where the blade  43 X pushes the sheet S into the nip portion  42 , there is a possibility of slippage between the blade  43 X and the sheet S. For example, factors causing slippage between the blade  43 X and the sheet S include the self weight of the sheet S or the stiffness of the sheet S. 
     As shown in  FIG. 10 , when slippage occurs between the blade  43 X and the sheet S, there is a possibility that the central portion of the sheet S cannot be accurately pushed into the nip portion  42 . For example, when slippage occurs between the blade  43 X and the sheet S due to the weight of the sheet S or the like, the central portion of the sheet S is displaced downwards from the blade  43 X. In  FIGS. 9 and 10 , a reference numeral PX indicates the central portion of the sheet S which is displaced downwards from the blade  43 X (the comparative example). 
     On the other hand, according to the embodiment, the blade  43  is a blade for the saddle folding unit  40  capable of saddle-folding the sheet S. The protrusion portion  30  protruding in the pushing direction V 1  of the blade  43  is provided at the edge (the leading edge) of the folding side of the sheet S in the blade  43 . With the above configuration, the following effects are achieved. In the blade  43  of the embodiment, a contact surface pressure of the blade  43  with respect to the sheet S is larger than that of the blade  43 X having a flat surface at the leading edge. That is, the contact resistance between the sheet S and the blade  43  may be increased as compared with the blade  43 X having a flat surface at the leading edge. According to the embodiment, in a case where the blade  43  pushes the sheet S into the nip portion  42 , it is possible to prevent a push-in position of the blade  43  and the central portion of the sheet S from slipping in a vertical direction (gravity direction). Accordingly, it is possible to push the central portion of the sheet S accurately into the nip portion  42 . In addition, it is possible to prevent a stapling position and a folding position from slipping from the sheet S. In  FIGS. 9 and 10 , a reference numeral SC indicates the central portion of the sheet S in the embodiment. 
     The protrusion portion  30  includes a plurality of protrusions  31  aligned in the thickness direction V 2  of the blade  43 , thereby achieving the following effects. Since the sheet S can be hooked by the plurality of protrusions  31 , it is possible to more effectively prevent the push-in position of the blade  43  and the central portion of the sheet S from slipping in the vertical direction. 
     When viewed from the blade width direction V 3 , the protrusion  31  protrudes in the pushing direction V 1  toward the center of the thickness direction V 2 , thereby achieving the following effects. By so-called double-side etching in which wet-etching is performed on both surfaces of the base plate  28 , it is possible to easily manufacture the blade  43 . In addition, in a case where the blade  43  is a laminate in which a plurality of the protrusion plates  29  are stacked in the thickness direction V 2 , the blade  43  can be stacked regardless of the vertical direction of the protrusion plate  29 , which is preferable. That is, since the order of stacking of the protrusion plates  29  is irrelevant, it is possible to easily manufacture the blade  43 . 
     The blade  43  is a laminate in which a plurality of protrusion plates  29  having protrusions  31  are stacked in the thickness direction V 2 , thereby achieving the following effects. Since the rigidity of the blade  43  can be increased as compared with the case where the blade  43  is formed of only one protrusion plate  29 , it is possible to stably push the central portion of the sheet S into the nip portion  42 . 
     The concave portion  43   a  recessed on the side opposite to the pushing direction V 1  of the blade  43  is provided at the leading edge of the blade  43  so as to avoid the folding roller  41 , thereby achieving the following effects. It is possible to increase the contact surface pressure of the blade  43  with respect to the sheet S as compared with the case where the leading edge of the blade  43  is formed in a linear shape continuous in the blade width direction V 3 . Accordingly, in a case where the blade  43  pushes the sheet S into the nip portion  42 , it is possible to prevent a push-in position of the blade  43  and the central portion of the sheet S from slipping in the sheet width direction. 
     The post-processing apparatus  3  includes the blade  43  according to the embodiment, thereby achieving the following effects. It is possible to provide the post-processing apparatus  3  capable of accurately pushing the central portion of the sheet S into the nip portion  42 . 
     Hereinafter, modification examples will be described. 
     First, the first modification example of the embodiment will be described. 
     When viewed the blade width direction V 3 , it is not limited that the protrusions  31  have the same amount of protrusion to the pushing direction V 1 . 
       FIG. 11  is a side view showing an example of a protrusion portion  130  of a blade  143  of the first modification example of the embodiment.  FIG. 11  is the same as  FIG. 6 , respectively. 
     As shown in  FIG. 11 , when viewed from the blade width direction V 3 , the plurality of protrusions  31  may be disposed so that the protrusion amount in the pushing direction V 1  becomes larger toward the center side in the thickness direction V 2 . In other words, the protrusion portion  130  may have a stepped shape in which the protrusion amount in the pushing direction V 1  is larger toward the center side in the thickness direction V 2 . 
     According to the first modification example, since the sheet S can be positioned by the protrusions  31  located at the center of the thickness direction V 2 , it is possible to more effectively prevent the push-in position of the blade  143  and the central portion of the sheet S from slipping in the vertical direction. 
     Next, the second modification example of the embodiment will be described. 
       FIG. 12  is a side view showing an example of a protrusion portion  230  of a blade  243  of the second modification example of the embodiment.  FIG. 12  is the same as  FIG. 6 , respectively. 
     As shown in  FIG. 12 , when viewed from the blade width direction V 3 , the plurality of protrusions  31  may be disposed so that the protrusion amount in the pushing direction V 1  becomes larger toward one side in the thickness direction V 2 . Specifically, when viewed from the blade width direction V 3 , the plurality of protrusions  31  may be disposed so that the protrusion amount in the pushing direction V 1  becomes larger toward the lower side in the vertical direction. 
     According to the second modification example, it is possible to prevent the sheet S from slipping downwards in the vertical direction by the protrusions  31  located on the lower side in the vertical direction, thereby more effectively preventing the push-in position of the blade  243  and the central portion of the sheet S from slipping in the vertical direction. 
     Next, the third modification example of the embodiment will be described. 
     When viewed from the blade width direction V 3 , it is not limited that the protrusion  31  protrudes to the pushing direction V 1  toward the center side of the thickness direction V 2 . 
       FIG. 13  is a side view showing an example of a protrusion portion  330  of a blade  343  of the third modification example of the embodiment.  FIG. 13  is the same as  FIG. 6 , respectively. 
     As shown in  FIG. 13 , when viewed from the blade width direction V 3 , a protrusion  331  may protrude to the pushing direction V 1  toward one side of the thickness direction V 2 . When viewed from the blade width direction V 3 , the protrusion ends  331   a  of the plurality of protrusions  331  are sorted over the entire thickness direction V 2  of the blade  343 . In other words, when viewed from the blade width direction V 3 , the protrusions  331  have the same amount of protrusion to the pushing direction V 1 . In the present modification example, when viewed from the blade width direction V 3 , the protrusion end  331   a  of each protrusion  331  is located on one side in the thickness direction V 2 . The protrusion  331  has a sharp shape protruding most in the pushing direction V 1  at one end position in the thickness direction V 2  of the blade  343 . A reference numeral  329  in the drawing indicates a protrusion plate having the protrusion  331 . 
       FIG. 14  is a side view showing an example of the protrusion  331  of a protrusion plate  329  of the third modification example of the embodiment.  FIG. 14  is the same as  FIG. 7 , respectively. 
     In  FIG. 14 , a reference numeral  331   b  indicates a base end of the protrusion  331 . In the present modification example, the protrusion end  331   a  of the protrusion  331  is located at one end in the thickness direction V 2  of the blade  343  (see  FIG. 13 ). 
     In  FIG. 14 , a reference numeral  331   c  indicates a continuous surface located between the protrusion end  331   a  and the base end  331   b  of the protrusion  331 . When viewed from the blade width direction V 3 , a continuous surface  331   c  has a circular arc-shaped convex toward the inside in the thickness direction V 2  of the blade  343 . 
     In  FIG. 14 , a reference numeral h 2  indicates a protrusion amount of the protrusion  331 . Here, the protrusion amount h 2  of the protrusion  331  is the distance between the protrusion end  331   a  of the protrusion  331  and the base end  331   b  in the pushing direction V 1 . For example, there is a relationship of h 2 =0.4×t 2  between the protrusion amount h 2  of the protrusion  331  and the thickness t 1  of the protrusion plate  329 . 
     Next, an example of a method of manufacturing the blade  343  of the present modification example will be described. 
       FIG. 15  is a view showing an example of a method of manufacturing the blade  343  of the third modification example of the embodiment. 
     As shown in  FIG. 15 , first, a base plate  328  which is a plate member having a thickness of 0.05 mm or more and 0.1 mm or less is prepared. 
     Next, the mask  35  with opening portion  35   a  on one side of the base plate  328  is disposed. On the other hand, a mask  335  having no opening portion is disposed on the other side of the base plate  28 . 
     Next, the base plate  328  is wet-etched via the opening portion  35   a  of the mask  35 . By performing wet-etching for a predetermined time, a circular arc-shaped concave portion  328   a  is formed in a portion facing the opening portion  35   a  of the mask  35  in the base plate  328 . 
     When circular arc-shaped concave portions  328   a  are formed to have a predetermined depth, the base plate  328  is divided into right and left sides of the paper surface. The reference numeral DL in the drawing indicates a dividing line of the base plate  328  passing through the center of arc-shaped concave portion  328   a . By dividing the base plate  328  having the circular arc-shaped concave portions  328   a  formed to have a predetermined depth along the dividing line DL, the protrusion plate  329  (see  FIG. 14 ) having the protrusions  331  is obtained. 
     Next, five protrusion plates  329  having protrusions  331  are stacked in the thickness direction V 2 . At this time, when viewed from the blade width direction V 3 , the protrusion ends  331   a  of the plurality of protrusions  331  are sorted over the entire thickness direction V 2  of the blade  343 . 
     Next, the five protrusion plates  329  are joined. For example, the five protrusion plates  329  are placed in a vacuum furnace and joined by applying pressure and heat. That is, the five protrusion plates  329  are integrated under vacuum thermo-compression. Through the above steps, the blade  343  (see  FIG. 13 ) of the present modification example may be manufactured. 
     According to the third modification example, by so-called single-side etching in which wet-etching is performed on a single surface of the base plate  328 , it is possible to easily manufacture the blade  343 . 
     Next, the fourth modification example of the embodiment will be described. 
     When viewed from the blade width direction V 3 , it is not limited that the protrusion end  331   a  of each protrusion  331  is located on one side in the thickness direction V 2 . 
       FIG. 16  is a side view showing an example of a protrusion portion  430  of a blade  443  of the fourth modification example of the embodiment.  FIG. 16  is the same as  FIG. 6 , respectively. 
     As shown in  FIG. 16 , the protrusion end  331   a  of each protrusion  331  may be alternately disposed on one side and the other side in the thickness direction V 2  of the blade  443 . In other words, in the blade  443 , protrusion ends  331   a  of two protrusions  331  adjacent to each other in the thickness direction V 2  may be connected to each other. 
     According to the fourth modification example, it is possible to increase the rigidity of the two protrusions  331  adjacent to each other in the thickness direction V 2  compared with the case where the protrusion ends  331   a  of the plurality of protrusions  331  are separated in the thickness direction V 2 . 
     Next, the fifth modification example of the embodiment will be described. 
     When viewed from the blade width direction V 3 , it is not limited that the first surface  3   c   1  and the second surface  31   c   2  of the protrusion  31  have a circular arc-shaped convex toward the inside in the thickness direction V 2  of the blade  43 . 
       FIG. 17  is a side view showing an example of a protrusion  531  of a protrusion plate  529  of the fifth modification example of the embodiment.  FIG. 17  is the same as  FIG. 7 , respectively. 
     As shown in  FIG. 17 , when viewed from the blade width direction V 3 , a first surface  53   c   1  of the protrusion  531  may have a linear shape inclined from the protrusion end  531   a  toward a first base end  53   b   1 . When viewed from the blade width direction V 3 , a second surface  531   c   2  of the protrusion  531  may have a linear shape inclined from the protrusion end  531   a  toward a second base end  531   b   2 . That is, when viewed from the blade width direction V 3 , the protrusion  531  may have an isosceles triangle shape convex in the pushing direction V 1 . 
     Next, the sixth modification example of the embodiment will be described. 
     When viewed from the blade width direction V 3 , it is not limited that the continuous surface  331   c  of the protrusion  331  has a circular arc-shaped convex toward the inside in the thickness direction V 2  of the blade  343 . 
       FIG. 18  is a side view showing an example of a protrusion  631  of a protrusion plate  629  of the sixth modification example of the embodiment.  FIG. 18  is the same as  FIG. 7 , respectively. 
     As shown in  FIG. 18 , when viewed from the blade width direction V 3 , a continuous surface  631   c  of the protrusion  631  may have a linear shape inclined from the protrusion end  631   a  toward a base end  631   b . That is, when viewed from the blade width direction V 3 , the protrusion  631  may have a right triangle shape convex in the pushing direction V 1 . 
     Next, the seventh modification example of the embodiment will be described. 
     It is not limited that the leading edge of the protrusion portion  30  has a linear shape continuous in the blade width direction V 3 . 
       FIG. 19  is a perspective view showing an example of a protrusion portion  730  of a blade  743  of the seventh modification example of the embodiment.  FIG. 19  is the same as  FIG. 4 , respectively. 
     As shown in  FIG. 19 , the leading edge of the protrusion portion  730  may have a concave-convex (zigzag shape) in the blade width direction V 3 . Specifically, a plurality of convex portions  732  protruding in the pushing direction V 1 , and aligned in the blade width direction V 3  may be provided at the leading edge of the protrusion portion  730 . 
     According to the seventh modification example, it is possible to increase the contact surface pressure of the blade  743  with respect to the sheet S as compared with the case where the leading edge of the protrusion portion  30  is formed in a linear shape continuous in the blade width direction V 3 . Accordingly, in a case where the blade  743  pushes the sheet S into the nip portion  42 , it is possible to prevent a push-in position of the blade  743  and the central portion of the sheet S from slipping in the sheet width direction. 
     Next, the eighth modification example of the embodiment will be described. 
       FIG. 20  is a perspective view showing an example of a protrusion portion  830  of a blade  843  of the eighth modification example of the embodiment. 
     As shown in  FIG. 20 , the leading edge of the protrusion portion  830  may have a lattice shape. Specifically, the leading edge of the protrusion portion  830  may have a mesh shape having a plurality of first line portions  833  forming a linear shape parallel to the blade width direction V 3  and a plurality of second line portions  834  forming a linear shape orthogonal to the first line portions  833 . 
     According to the eighth modification example, it is possible to increase the contact surface pressure of the blade  843  with respect to the sheet S as compared with the case where the leading edge of the protrusion portion  30  is formed in a linear shape continuous in the blade width direction V 3 . Accordingly, in a case where the blade  843  pushes the sheet S into the nip portion  42 , it is possible to prevent a push-in position of the blade  843  and the central portion of the sheet S from slipping in the sheet width direction. 
     Next, the ninth example of the embodiment will be described. 
       FIG. 21  is a perspective view showing an example of a protrusion portion  930  of a blade  943  of the ninth modification example of the embodiment. 
     As shown in  FIG. 21 , the leading edge of the protrusion portion  930  may have a mesh shape having a plurality of first line portions  933  forming a linear shape intersecting the blade width direction V 3  and a plurality of second line portions  934  forming a linear shape orthogonal to the first line portions  933 . 
     According to the ninth modification example, it is possible to increase the contact surface pressure of the blade  943  with respect to the sheet S as compared with the case where the leading edge of the protrusion portion  30  is formed in a linear shape continuous in the blade width direction V 3 . Accordingly, in a case where the blade  943  pushes the sheet S into the nip portion  42 , it is possible to prevent a push-in position of the blade  943  and the central portion of the sheet S from slipping in the sheet width direction. 
     Next, another modification example of the embodiment will be described. 
     It is not limited that the protrusion portion  30  includes five protrusions  31  aligned in the thickness direction V 2  of the blade  43 . For example, the protrusion portion  30  may have only one protrusion  31 . Alternately, the protrusion portion  30  may include a plurality of protrusions  31  that are two or more and four or less that are aligned in the thickness direction V 2  of the blade  43 . In addition, the protrusion portion  30  may include a plurality of protrusions  31  that are six or more that are aligned in the thickness direction V 2  of the blade  43 . 
     It is not limited that the blade  43  is a laminate in which five protrusion plates  29  are stacked in the thickness direction V 2  of the blade  43 . For example, the blade  43  may have only one protrusion plate  29 . Alternatively, the blade  43  may be a laminate in which two to four or six or more of the protrusion plates  29  are stacked in the thickness direction V 2  of the blade  43 . 
     It is not limited that the protrusion portion  30  is formed by wet etching the base plate  28 . For example, the protrusion portion  30  may be formed by cutting the base plate  28 . 
     It is not limited that the protrusion portion  30  is provided only at the leading edge of the blade  43 . For example, the protrusion portion  30  may be provided over the entire outer peripheral edge of the blade  43 . 
     According to at least one embodiment described above, the blade  43  is a blade for the saddle folding unit  40  capable of saddle-folding the sheet S. The protrusion portion  30  protruding in the pushing direction V 1  of the blade  43  is provided at the edge (the leading edge) of the folding side of the sheet S in the blade  43 . With the above configuration, the following effects are achieved. In the blade  43  of the embodiment, a contact surface pressure of the blade  43  with respect to the sheet S is larger than that of the blade  43 X having a flat surface at the leading edge. That is, the contact resistance between the sheet S and the blade  43  may be increased as compared with the blade  43 X having a flat surface at the leading edge. According to the embodiment, in a case where the blade  43  pushes the sheet S into the nip portion  42 , it is possible to prevent a push-in position of the blade  43  and the central portion of the sheet S from slipping in a vertical direction (gravity direction). Accordingly, it is possible to push the central portion of the sheet S accurately into the nip portion  42 . 
     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 there equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.