JP2010163235A - Paper stacking device, paper postprocessing device and image forming system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that paper is not orderly stacked in a paper stacking device since the paper buckles when the paper ejected to a carrier belt drops. <P>SOLUTION: A sliding member 107 having a paper receiving surface having friction resistance lower than that of the carrier belt 101 and higher than a carrying surface of the carrier belt is arranged in a position for landing the ejected paper S, and the tip of the ejecting paper slides on the sliding member, and moves in the carrying direction of the carrier belt, and thereby, is orderly stacked by preventing the buckling of the paper tip. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sheet stacking apparatus that stacks sheets discharged from a sheet post-processing apparatus, a sheet post-processing apparatus having the sheet stacking apparatus, and an image forming system having the sheet post-processing apparatus.

  As a paper post-processing device used as an accessory device of an image forming apparatus, there is a paper post-processing device that performs folding processing such as half-folding (two-folding) and three-folding on a paper.

  Since the sheet discharged from such a sheet post-processing apparatus is not a flat sheet but is folded, a specific sheet stacking apparatus is used for stacking the discharged sheets.

  In Patent Documents 1 and 2, it is possible to stack a large number of sheets by conveying the discharged sheets with a conveying belt. In Patent Document 2, various sheets can be collected in an orderly manner.

Japanese Patent Laid-Open No. 11-193162 JP 2008-184111 A

  In a paper stacking apparatus that transports paper discharged from a main body such as a paper post-processing apparatus by a transport belt, the transport belt needs to have a certain amount of frictional resistance against the paper. If the frictional resistance is low, slippage may occur on the conveyor belt, and the sheets may not be collected in an orderly manner.

  However, it has been found that there is a problem that the leading edge of the paper buckles due to the frictional resistance of the conveyor belt. This problem is presumed to occur when the sheet is discharged from the discharge port of the main body and the leading edge of the sheet comes into contact with the conveyance belt at a considerable speed. That is, when the sheet comes into contact with the conveying belt at high speed, it is assumed that the leading end of the sheet is stopped by the conveying belt having high frictional resistance, the leading end of the sheet is reversed, and buckles.

  Such a sheet buckling phenomenon is particularly likely to occur when the conveying belt is inclined so that the downstream side in the sheet conveying direction is higher than the upstream side.

  As a result, the sheets may not be neatly stacked on the sheet stacking apparatus.

  The present invention solves such a problem, a sheet stacking apparatus that neatly stacks sheets, particularly folded sheets, a sheet post-processing apparatus including such a sheet stacking apparatus, and an image forming system including such a sheet post-processing apparatus. The purpose is to provide.

  The object is achieved by the following invention.

  1. In a paper stacking apparatus having a transport belt for loading and transporting discharged paper, a sliding member is provided at a position where the discharged paper lands, and the sliding member is higher than the transport surface of the transport belt, and the transport A paper stacking device having a paper receiving surface having a frictional resistance smaller than a frictional resistance of a belt.

  2. 2. The sheet accumulating apparatus according to 1, wherein a plurality of the sliding members are provided in a width direction perpendicular to the conveying direction of the conveying belt.

  3. 3. The paper stacking apparatus according to 1 or 2, wherein the transport belt is inclined so that a downstream side in the transport direction is higher than an upstream side.

  4). 4. The paper stacking apparatus according to any one of claims 1 to 3, further comprising a paper stop member that is provided on a downstream side of the transport belt in a transport direction and stops the paper.

  5. 5. A sheet post-processing apparatus, comprising: a folding unit that folds a sheet; and the sheet stacking device according to any one of the above items 1 to 4 that receives a sheet folded and processed by the folding unit.

  6). 6. The paper post-processing apparatus according to 5 above, wherein the transport belt transports the paper at a transport speed slower than a transport speed at a paper discharge port of the paper post-processing apparatus.

  7). An image forming system comprising the image forming apparatus and the sheet post-processing apparatus described in 6 above.

  In the present invention, a sliding member is provided at the landing position of the discharged paper in the paper stacking apparatus. The leading edge of the discharged paper slides on the sliding member sliding member and moves in the conveying direction by the conveying belt. Thereby, buckling of the leading edge of the paper is prevented, and the paper is neatly stacked on the paper stacking device.

1 is an overall view of an image forming system including an image forming apparatus A and a sheet post-processing apparatus FS according to an embodiment of the present invention. It is a front view of the upstream part of the folding part 50 and the lower paper discharge part 100 as a paper stacking apparatus which concerns on embodiment of this invention. 3 is a perspective view of a lower paper discharge unit 100. FIG. FIG. 6 is a diagram illustrating a state of paper accumulation in the lower paper discharge unit 100. It is a figure which shows the shape and arrangement | positioning of an example of a sliding member. It is a figure which shows the other example of a sliding member.

  Although the present invention will be described based on the illustrated embodiment, the present invention is not limited to the embodiment.

  FIG. 1 is an overall view of an image forming system including an image forming apparatus A and a sheet post-processing apparatus FS according to an embodiment of the present invention.

[Image forming apparatus A]
The illustrated image forming apparatus A includes an image reading unit 1, an image processing unit 2, an image writing unit 3, an image forming unit 4, a paper feed cassette 5, a paper feed unit 6, a fixing device 7, a paper discharge unit 8, and automatic duplexing. A copy feeding unit (ADU) 9 is provided.

  An automatic document feeder DF is mounted on the upper part of the image forming apparatus A. A sheet post-processing device FS is connected to the left side of the image forming apparatus A in the drawing on the paper discharge unit 8 side.

  The document placed on the document table of the automatic document feeder DF is conveyed in the direction of the arrow, and an image on one or both sides of the document is read by the optical system of the image reading unit 1 and read by the CCD image sensor 1A.

  The analog signal photoelectrically converted by the CCD image sensor 1A is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in the image processing unit 2, and then sent to the image writing unit 3.

  At the time of image formation, output light is emitted from the semiconductor laser of the image writing unit 3, and the photosensitive drum 4A of the image forming unit 4 is irradiated to form a latent image. In the image forming unit 4, processes such as charging, exposure, development, transfer, separation, and cleaning are performed, and a toner image is formed on the photosensitive drum 4A. The recording paper S1 fed from the paper feeding cassette 5 by the paper feeding means 6 contacts the photosensitive drum 4A, and the toner image is transferred to the recording paper S1 by the transfer means 4B. The recording paper S1 carrying the toner image is fixed by the fixing device 7 and sent from the paper discharge unit 8 to the paper post-processing device FS. In the case of double-sided copying, the recording paper S1 that has undergone single-sided image processing is sent to the automatic double-sided copy paper feeding unit 9 by the conveyance path switching plate 8A, and after the toner image is transferred and fixed on the back side in the image forming unit 4 The paper is discharged from the paper discharge unit 8.

[Paper post-processing device FS]
The paper post-processing device FS includes a paper carry-in unit 20, insertion paper feeding units 30a and 30b, and a plurality of post-processing units. The post-processing unit includes a punching processing unit 40, a folding unit 50, an overlay processing unit 60, a binding processing unit 71 and 72, a paper discharge unit 80, and a lower paper discharge as a paper stacking apparatus according to an embodiment of the present invention. Part 100.

  The insertion sheet feeding unit 30a is loaded with the insertion sheet S2, and the insertion sheet feeding unit 30b is loaded with another insertion sheet S3.

  The insertion sheets S2 and S3 are insertion sheets such as a cover sheet and an insert sheet inserted between the plurality of recording sheets S1 discharged from the image forming apparatus A. Like the recording sheet S1, the insertion sheets S2 and S3 are punched and folded. Processing can be performed.

  The insertion sheets S2 and S3 sent out from the insertion sheet feeding sections 30a and 30b are conveyed to the sheet carry-in section 20 through a downward conveyance path (without reference numerals).

  The punching processing unit 40 is disposed in the paper carry-in unit 20.

  In the following description, the recording sheet S1 and the insertion sheets S2 and S3 are collectively referred to as a sheet S.

  The folding unit 50 is disposed on a conveyance path H1 branched downward from the paper carry-in unit 20.

  The superposition processing unit 60 is disposed on the downstream side of the transport path H2 branched upward from the paper carry-in section 20, and includes transport paths H3, H4, and H5.

  In the binding processing unit 71 located on the downstream side, the superposition processing unit 60 transfers the succeeding paper S to the transport path H3 and the transport paths H4 and H5 in order to secure time for binding the preceding paper S. Wait.

  The conveyance path located on the downstream side of the conveyance path H2 is branched into a doubly curved conveyance path, and is divided into an inner conveyance path H4 and outer conveyance paths H3 and H5.

  A conveyance roller 21 is provided at the discharge port of the conveyance path H4 that forms an inner conveyance path that is branched and curved from the conveyance path H2, and rotates when the first sheet S of sheets S to be bound is conveyed. In a state in which the paper is stopped, the front end of the paper is received and kept in contact with the conveying roller 21.

  As described above, the sheet S conveyed on the conveyance path H2 waits in a state where the leading end abuts against the conveyance roller 21, but the subsequent sheet S enters the conveyance path H3 from the conveyance path H2 and is conveyed to the conveyance roller. 21 is reached.

  From the transport roller 21, the preceding sheet S and the succeeding sheet S are transported together and transported to the stacking unit 70 in a state where they overlap each other.

  The conveyance path H3 is continuous with the conveyance path H2 downstream of the conveyance path H2, and the conveyance path H5 is continuous with the conveyance path H3.

  The conveyance path H3 is branched into a conveyance path H5 and a conveyance path H6.

  The transport path H6 forms a paper discharge path for discharging the paper S to the fixed paper discharge tray 81.

  The fixed paper discharge tray 81 is disposed at a position protruding from the sheet post-processing device FS outside the conveyance path H6 on the conveyance roller 24 on the conveyance path H3, on the downstream side of the conveyance path H6 branched from the stacking processing unit 60. .

  As described above, the fixed paper discharge tray 81 is conveyed through the conveyance paths H2, H3, and H6 and accumulates the discharged paper S.

  The paper discharge unit 80 includes a paper discharge roller 22 and an alignment mechanism, and discharges the paper S to the lift paper discharge tray 82. Although not shown, the alignment mechanism is constituted by a known mechanism that reciprocates in the horizontal direction perpendicular to the transport discharge direction to align the sheets.

  The paper discharge roller 22 is composed of a pair of rollers. When the paper is not discharged, the pair of rollers are separated from each other.

  The sheet S transported by the transport roller 21 constitutes a paper discharge roller 22, travels leftward between a pair of spaced rollers, and reaches the stacking unit 70 when the rear end is separated from the transport roller 21. The accumulated portion 70 that has fallen and slanted is slid down, received by a stopper (not shown), and stopped on the accumulated portion 70.

  When the set number of sheets S are stacked on the stacking unit 70, the binding processing unit 71 operates to bind the sheets S.

  The bound sheet S is pushed up by the stopper and moves to the upper left on the stacking unit 70.

  At this time, a pair of rollers constituting the paper discharge roller 22 come into contact with each other to nip the paper S, convey it, and discharge it to the lift paper discharge tray 82.

  In the folding mode, the sheet S is conveyed downward along the conveyance path H <b> 1 from the sheet carry-in unit 20, is subjected to middle folding or tri-fold processing in the folding unit 50, and is discharged to the lower sheet discharging unit 100.

  In the saddle stitching mode, the paper S is transported from the paper carry-in unit 20 through the transport path H1, is subjected to saddle stitching processing in the binding processing unit 72, and is subjected to center folding processing in the folding unit 50, and then is sent to the lower paper discharge unit 100. Discharged.

As described above, there are the following four paths as the sheet S discharge path.
1) Paper carry-in section 20 → conveyance path H2 → conveyance path H3 → conveyance path H6 → fixed discharge tray 81
2) Paper carry-in section 20 → conveyance path H2 → conveyance paths H3, H4, H5 → stacking section 70 → discharge section 80 → lifting / discharging tray 82
3) Paper carry-in section 20 → conveyance path H2 → H4 → paper discharge section 80 → lifting / discharging tray 82
4) Paper carry-in section 20 → conveying path H1 → folding section 50 → lower sheet discharge section 100
The routes 1), 2) and 4) are as described above.

  The path 3) is selected when a large amount of image is formed without performing a binding process or a folding process.

  The paper S is discharged to the lifting / lowering tray 82 without post-processing, and the lifting / lowering tray 82 is indicated by a chain line in the figure so that the top surface of the discharged paper S is always at a constant height. Move down to.

  Therefore, it is possible to stack thousands of sheets on the lifting / discharging tray 82.

<Folding part>
FIG. 2 is a front view of the upstream portion of the folding unit 50 and the lower sheet discharge unit 100 as the paper stacking apparatus according to the embodiment of the present invention.

  The folding unit 50 includes a folding plate 52, a folding upper roller (hereinafter referred to as an upper roller) 53, a folding lower roller (hereinafter referred to as a lower roller) 54, a folding roller 55, a conveyance path switching member 57 as a switching guide means, A guide member 58 and a leading end stop member 581 are provided, and the sheet S is folded in half or folded in three.

  The upper roller 53 and the lower roller 54 constituting the folding means for forming the fold in the two-fold process or the first fold in the three-fold process bend the sheet S by conveyance in the three-fold process and fold with the lower roller 54. Conveying means to be inserted between the rollers 55 is configured.

  The lower roller 54 and the folding roller 55 constitute folding means for forming a second fold on the sheet S by conveying the sheet S while nipping it.

  The lower roller 54 is shared by the conveying unit and the folding unit. However, the conveying unit and the folding unit may be configured by a pair of rollers, and a sheet folding device may be configured by four rollers. .

  The conveyance path switching member 57 is driven by a solenoid (not shown) and can be swung. At the time of tri-folding, the conveyance path switching member 57 is set at a position indicated by a dotted line and guides the paper S to the conveyance path formed by the guide member 58. .

  The conveyance path switching member 57 is set to the position of the solid line at the time of bi-folding, that is, half-folding, saddle stitching and half-folding, and discharges the paper S through the conveyance path formed by the pair of paper discharge guide members 61. .

  Reference numeral 58 denotes a guide member that guides the sheet S conveyed by the upper roller 53 and the lower roller 54. With respect to the conveyance direction formed by the upper roller 53 and the lower roller 54, the paper guide direction of the guide member 58 is formed to bend the paper S so as to protrude downward in the drawing.

  Reference numeral 581 denotes a leading end stopping member for stopping the leading end of the sheet S.

  By configuring the upper roller 53, the lower roller 54, the guide member 58, and the leading end stopping member 581 in this way, the sheet S is conveyed by the rotation of the upper roller 53 and the lower roller 54, and the leading end is stopped by the leading end stopping member 581. The sheet S is bent downward in the figure between the upper roller 53 and the lower roller 54 and the guide member 58.

  Reference numerals 61 and 62 denote discharge guide members for guiding the sheet that is folded and discharged.

  The folding operation of the folding unit 50 having the above configuration will be described.

  The half-folding process is a mode in which the folding process is performed at the center with respect to the conveyance direction of the sheet S. Sometimes it is folded.

  In the folding process, the folding plate 52 pushes the central portion of the sheet S conveyed on the conveyance path H1 (see FIG. 1), and the sheet S is inserted between the upper roller 53 and the lower roller 54. The sheet S conveyed and folded by the upper roller 53 and the lower roller 54 is guided by the conveyance path switching member 57 at the solid line position, passes between the pair of sheet discharge guide members 61, and lower from the sheet discharge outlet E1. The paper is discharged to the paper discharge unit 100.

  In the three-fold process, the conveyance path switching member 57 is set at a position indicated by a dotted line.

  The sheet S is conveyed through the conveyance path H1 (see FIG. 1), and the folding plate 52 is driven by a driving unit (not shown) to insert the fold of the sheet S between the upper roller 53 and the lower roller 54.

  Simultaneously with the operation of the folding plate 52, the upper roller 53, the lower roller 54, and the folding roller 55 rotate as indicated by arrows, and the sheet S is conveyed while being folded.

  When the sheet S is nipped between the upper roller 53 and the lower roller 54, the folding plate 52 moves and retracts in the direction opposite to the transport direction of the sheet S.

  The sheet S folded by the upper roller 53 and the lower roller 54 is guided by the transport path switching member 57 at the position of the dotted line and proceeds to the transport path formed by the guide member 58 with the crease leading. The crease of the sheet S hits the leading end stop member 581 and stops.

  The upper roller 53, the lower roller 54, and the folding roller 55 continue to rotate even after the fold line of the sheet S hits the leading end stop member 581.

  As the upper roller 53 and the lower roller 54 continue to rotate, the sheet S bends and curves between the nip between the upper roller 53 and the lower roller 54 and the leading end stop member 581.

  The fold of the sheet S formed by this bending enters a nip formed by the lower roller 54 and the folding roller 55, a fold is formed, a second fold is formed on the sheet S, and the sheet S is folded in three. The

  The folded sheet S is guided by the paper discharge guide member 62 and discharged from the paper discharge port E2 to the lower paper discharge unit 100.

<Lower output section>
The lower paper discharge unit 100 will be described with reference to FIGS. FIG. 3 is a perspective view of the lower paper discharge unit 100. FIG. 3 shows the lower paper discharge unit 100 removed from the paper post-processing apparatus FS. FIG. 4 shows a state in which the sheets S are stacked on the lower sheet discharge unit 100.

  The lower sheet discharge unit 100 stacks the sheets S that have been folded and discharged. The lower paper discharge unit 100 includes a conveyance belt 101, a paper pressing member 103, and a paper stopping member 104. The conveyor belt 101 is stretched around a pair of pulleys 102.

  The conveyor belt 101, the paper stopping member 104, and the like are supported by the frame body 106 of the lower paper discharge unit 100. As shown in FIG. 3, the frame body 106 forms a surface for supporting and accumulating sheets. As shown in FIGS. 2 and 3, the conveyance surface of the conveyance belt 101 and the sheet support surface of the frame body 106 are inclined so that the downstream side in the paper discharge conveyance direction W is higher than the upstream side.

  The transport belt 101 transports the paper placed thereon in the paper discharge transport direction W indicated by the arrow and brings it to the paper stop member 104, and transports the paper S with frictional force. Therefore, the conveyance belt 101 is made of a highly frictional material such as a rubber material such as EPDM (ethylene-propylene-diene rubber).

  As shown in FIGS. 1, 3, and 4, the sheet stopping member 104 is arranged so that its upper surface is inclined so as to form an obtuse angle with the sheet supporting surface of the frame body 106 and the conveying belt 101, and is conveyed by the conveying belt 101. The leading edge of the sheet is stopped and the sheet S is accumulated on the conveyor belt 101 in a scale shape as shown in FIG.

  As shown in FIG. 3, two conveyor belts 101 are provided in parallel in the width direction orthogonal to the paper sheet discharge direction W.

  Reference numeral 103 denotes a paper pressing member rotatably supported on the paper discharge side wall of the paper post-processing device FS. When the paper S does not pass as shown in FIG. When the paper S passes, it is pushed by the paper and rotates clockwise. The sheet pressing member 103 presses the sheet S downward by its own weight, and suppresses the lifting of the sheet S.

  Reference numeral 105 denotes a paper discharge guide member attached to the paper post-processing apparatus FS.

  Reference numeral 107 denotes a sliding member that slides the paper S that has fallen on the conveyance belt 101 in the paper discharge conveyance direction W. Provided. The installation position of the sliding member 107 in the width direction is in the vicinity of the conveyance belt 101. The landing position of the paper S varies depending on the positional relationship between the paper discharge ports E1 and E2 and the lower paper discharge unit 100, the discharge speed of the paper from the paper post-processing device FS, the size and the number of the paper S to be discharged. However, the range of landing positions is limited to a certain area for all of the various variable factors. Therefore, the arrangement position of the sliding member 107 is obtained by a paper discharge experiment. The height of the sliding member 107 is set to be slightly higher than the conveying surface of the conveying belt 101.

  The folded sheet S discharged from the folding unit 50 is landed at the front end and then at the rear end, and is further conveyed by the conveyance belt 101 in the sheet discharge conveyance direction W indicated by the arrow. Since the leading sheet S is stopped by the sheet stopping member 104, a large number of discharged sheets S are accumulated on the conveying belt 101 in a scale-like manner as shown in FIG.

  The transport belt 101 transports the paper S at a speed lower than the transport speed at the paper discharge ports E1 and E2 of the paper post-processing device FS, that is, the transport speed at the folding unit 50. This is to ensure overlap with the front part in order to correctly stack the sheets. Further, the conveyor belt 101 arranged in an inclined manner is activated when the sheet S is discharged and the leading edge of the conveyor belt comes into contact with the conveyor belt. When the paper S comes into contact with the moving conveyor belt 101, buckling of the front end of the paper is suppressed.

  When the conveyance speed of the conveyance belt 101 is slower than the conveyance speed at the paper discharge port of the sheet post-processing device FS as described above, the leading edge of the sheet S buckles when the leading edge of the sheet S lands on the conveyance belt 101. There is a case. That is, when the paper S comes into contact with the transport belt 101, a portion behind the leading edge of the paper S may move forward beyond the leading edge, and the paper leading edge may be reversed and bent.

  By providing the sliding member 107, the leading edge of the paper S discharged from the paper discharge outlets E1 and E2 first comes into contact with the sliding member 107 and slides on the sliding member 107 in the paper discharge conveyance direction W. As a result, the above-described bending of the paper, that is, buckling is prevented.

  Reference numeral 108 denotes a rib formed on the frame body 106. The ribs 108 are for improving the transportability of the paper S, and the ribs 108 have no conditions regarding the height relationship with the transport surface of the transport belt 101 like the sliding member 107.

  The installation position and shape of the sliding member 107 will be described with reference to FIG. FIG. 5 shows an example of the sliding member 107, FIG. 5 (a) is a cross-sectional view of the sliding member 107 along the width direction perpendicular to the conveying direction, and FIG. 5 (b) is an illustration of the sliding member 107 along the conveying direction. It is sectional drawing.

  The sliding member 107 is formed as a rib protruding from the frame body 106 by processing a sheet metal constituting the frame body 106. As described above, the sliding member 107 has a sheet receiving surface abutting against the discharged sheet S having a smaller frictional resistance than the conveying belt 101. However, in order to reduce the frictional resistance, the sliding member 107 A fluorine resin layer may be provided on the paper receiving surface 107. The difference D between the conveyance surface 101S of the conveyance belt 101 and the height of the paper surface of the sliding member 107 is, for example, about 1 mm.

  The distance G between the width direction end of the conveyor belt 101 and the width direction end of the sheet receiving surface of the sliding member 107 is preferably about 5 mm to 20 mm. If the gap G is smaller than 5 mm, the conveyance belt 101 may come into contact with the sliding member 107, which may hinder travel of the conveyance belt 101.

  On the other hand, if the gap G is larger than 20 mm, the leading edge of the paper S comes into contact with the transport belt 101 and buckling is likely to occur. In the example of FIG. 5, the center portion in the width direction of the sliding member 107 forms a sheet receiving surface, and the interval G is the interval between the center of the sliding member 107 and the belt 101.

  It is not necessary to provide the sliding member 107 in a region outside the landing position. Therefore, the length L of the sliding member 107 in the paper discharge conveyance direction W is, for example, about 70 mm.

  FIG. 6 shows another example of the sliding member 107 and is a cross-sectional view of the sliding member 107 along the width direction. In this example, the sheet receiving surface of the sliding member 107 is formed as a flat surface having a length in the width direction.

  The interval G in this example is the interval between the end of the belt 101 and the end of the sheet receiving surface of the sliding member 107.

A Image forming apparatus FS Paper post-processing apparatus 50 Folding part 100 Lower paper discharge part 101 Conveying belt 103 Paper pressing member 104 Paper stopping member 107 Sliding member

Claims (7)

  In a paper stacking apparatus having a transport belt for loading and transporting discharged paper, a sliding member is provided at a position where the discharged paper lands, and the sliding member is higher than the transport surface of the transport belt, and the transport A paper stacking device having a paper receiving surface having a frictional resistance smaller than a frictional resistance of a belt.   The sheet accumulating apparatus according to claim 1, wherein a plurality of the sliding members are provided in a width direction perpendicular to a conveying direction of the conveying belt.   3. The paper stacking apparatus according to claim 1, wherein the transport belt is inclined so that a downstream side in the transport direction is higher than an upstream side.   The paper stacking apparatus according to claim 1, further comprising a paper stopping member that is provided on a downstream side of the transport belt in a transport direction and stops the paper.   5. A sheet post-processing apparatus comprising: a folding unit configured to fold a sheet, and a sheet stacking device according to claim 1 that receives a sheet folded and discharged by the folding unit.   The paper post-processing apparatus according to claim 5, wherein the transport belt transports the paper at a transport speed that is slower than a transport speed at a paper discharge port of the paper post-processing apparatus.   An image forming system comprising the image forming apparatus and the sheet post-processing apparatus according to claim 6.

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