Sheet processing apparatus and image formation system

Abstract

To provide a configuration capable of suppressing reduction in productivity caused by square back processing.SOLUTION: The length of a conveyance path from a folding roller pair 113 to a lower clamp unit 120 and an upper clamp unit 121 is longer than a half of the length of the long side of a sheet in the maximum size on which center-folding processing can be executed by a center-folding processing unit 112. In a state in which conveyance by a saddle third roller pair 118 is stopped for a first sheet bundle to which square back processing is applied, at least one sheet included in a second sheet bundle following the first sheet bundle is conveyed toward a saddle stack tray 150 by a conveyance unit 410.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a sheet processing apparatus that performs square spine processing on a sheet, and an image forming system that includes the sheet processing apparatus. [Background technology]

[0002] A sheet processing device has been proposed that clamps a folded sheet stack with a pair of clamps and uses a roller to press the spine of the sheet stack that protrudes beyond the clamps, thereby creating a corner in the spine of the sheet stack (hereinafter referred to as "corner spine processing") (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-112445 A Summary of the Invention [Problem to be solved by the invention]

[0004] Here, when performing the square spine treatment on multiple sheet bundles in succession, it is necessary to stop the conveyance of the sheet bundle while performing the square spine treatment on the sheet bundle. Therefore, while performing the square spine treatment on the preceding sheet bundle, if the fore-edge side of the preceding sheet bundle is located upstream of the folding roller pair, the conveyance of the sheets included in the succeeding sheet bundle must be stopped. In this case, after the square spine treatment of the preceding sheet bundle is completed, the sheets included in the succeeding sheet bundle are accumulated and the square spine treatment is performed, which reduces the productivity of the entire device.

[0005] The present invention aims to provide a configuration capable of suppressing a decrease in productivity due to square back processing. [Means for solving the problem]

[0006] One aspect of the present invention includes a first transport path that receives sheets discharged from an image forming apparatus and transports the sheets, a first stacking unit that stacks the sheets transported to the first transport path, a first binding processing unit that performs a binding process on an end of a sheet stack consisting of a plurality of sheets stacked in the first stacking unit, a stacking unit that is movable up and down with respect to the first stacking unit and that stacks the sheet stack that has been bound by the first binding processing unit, a second transport path that branches off from the first transport path and transports the sheets in a direction vertically downward with respect to the first transport path, and a stacking unit that is connected to the second transport path. a second stacking section which stacks the transported sheets, a transport means which transports the sheets from the first transport path to the second stacking section, a second binding processing section which performs a saddle-stitching process on a sheet bundle consisting of a plurality of sheets stacked in the second stacking section, a pair of folding rollers which sandwich and transport the sheet bundle so that the spine of the sheet bundle is located downstream of an end portion on the fore-edge side, thereby center-folding the sheet bundle, and a pressing section which presses the sheet bundle center-stitched by the second binding processing section toward a nip portion of the pair of folding rollers, a pair of conveying rollers that clamp and convey a sheet bundle that has been center-folded by a folding processing section; a pair of clamp sections that clamp and release the clamp of the sheet bundle by moving relatively along the thickness direction of the sheet bundle conveyed by the conveying roller pair; and a pressure roller that moves along the width direction of the sheet bundle when the spine of the sheet bundle conveyed by the conveying roller pair protrudes downstream in the conveying direction of the conveying roller pair from the pair of clamp sections to press the spine of the sheet bundle clamped by the pair of clamp sections; and a square spine processing section that performs square spine processing to add a corner to the spine of the sheet bundle that has been center-folded by the center-folding processing section, wherein the length of the conveying path from the folding roller pair to the pair of clamp sections is longer than half the length of the long side of a sheet of a maximum size that can be center-folded by the center-folding processing section, and when conveying by the conveying roller pair for a first sheet bundle to be center-folded is stopped, the conveying means conveys at least one sheet included in a second sheet bundle following the first sheet bundle toward the second stacking section. Effect of the Invention

[0007] According to the present invention, it is possible to suppress a decrease in productivity caused by performing back square processing. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of an image forming system according to an embodiment. [Diagram 2] FIG. 1 is a cross-sectional view showing a schematic configuration of a sheet processing apparatus according to an embodiment. [Diagram 3] FIG. 2 is a control block diagram of the image forming system according to the embodiment. [Figure 4] FIG. 4 is an enlarged cross-sectional view of a saddle portion according to the embodiment. [Diagram 5] FIG. [Figure 6] FIG. 2A is a perspective view and FIG. 2B is a cross-sectional view of a square spine processing unit according to an embodiment. [Figure 7] 1A is a perspective view of the square spine processing portion according to the embodiment, and FIG. 1B is a perspective view of the square spine processing portion according to the embodiment, as seen from the front side. [Figure 8] FIG. 4 is a perspective view showing a part of the square spine processing unit and the drive unit according to the embodiment. [Figure 9] FIG. 4 is a perspective view of the square spine processing unit and the clamp unit according to the embodiment. [Figure 10] FIG. 4 is a cross-sectional view of a square spine processing unit and a clamp unit according to the embodiment. [Figure 11] Schematic diagrams showing, during the operation of square spine processing in an embodiment, (a) the state in which the sheet stack is stopped from being transported by the clamp section, (b) the state in which the sheet stack is clamped, (c) the state in which square spine processing is being performed on the sheet stack, and (d) the state in which the clamp on the sheet stack is released. [Figure 12] 5 is a flowchart of a sheet stack receiving control according to the embodiment. [Figure 13]1A and 1B are diagrams showing sheet movement in the receiving control of a sheet stack according to an embodiment, in which (a) shows the state in which the sheets of the first stack are transported to the straight path, (b) shows the state in which the sheets are transported to the stack path, (c) shows the state in which the sheets are transported from the stack path to the saddle path, and (d) shows the state in which the sheets are transported from the saddle path to the saddle stack tray. [Figure 14] 1A and 1B are diagrams showing sheet movement in the receiving control of a sheet stack according to an embodiment, in which (a) shows the second sheet of the first stack being transported to the straight path, (b) shows the sheet being transported to the stack path, (c) shows the sheet being transported from the stack path to the saddle path, and (d) shows the sheet being transported from the saddle path to the saddle stack tray. [Figure 15] 1A and 1B are diagrams showing sheet movement in the receiving control of a sheet stack according to an embodiment, in which (a) shows a state in which the sheets of the second stack are transported to the straight path, (b) shows a state in which the sheets are transported to the stack path, (c) shows a state in which the second sheet of the second stack is transported to the straight path and the first stack of sheets is center-folded, and (d) shows a state in which the second sheet of the second stack is transported to the stack path and transport of the first stack of sheets has stopped. [Figure 16] 1A and 1B are diagrams showing sheet movement in the receiving control of a sheet bundle according to an embodiment, in which (a) a part of the second sheet bundle is transported from the stack path to the saddle path and square spine processing has been started on the first sheet bundle; (b) a part of the second sheet bundle is transported from the saddle path to the saddle stack tray and square spine processing has been performed on the first sheet bundle; (c) a diagram showing a state in which the discharge of the first sheet bundle has started and the third sheet of the second sheet bundle has been transported to the straight path; and (d) a diagram showing a state in which the discharge of the first sheet bundle has been completed and the third sheet of the second sheet bundle has been transported to the stack path. [Figure 17]1A and 1B are diagrams showing sheet movement in the receiving control of a sheet stack according to an embodiment, in which (a) shows the third sheet of the second sheet stack being transported from the stack path to the saddle path, (b) shows the sheet being transported from the saddle path to the saddle stack tray, (c) shows the second sheet stack being center-folded, and (d) shows the second sheet stack being square-back processed. [Figure 18] 13A and 13B are diagrams illustrating the movement of sheets during reception control of a sheet bundle according to the embodiment, and illustrate a state in which a second sheet bundle is being discharged. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The embodiment will be described with reference to Figures 1 to 18. First, the schematic configuration of an image forming system according to the present embodiment will be described with reference to Figure 1.

[0010] [Image formation system] In this embodiment, a copying machine is used as the image forming apparatus, and a sheet processing device is connected to the sheet discharge port of the copying machine, and a saddle unit for saddle stitching and center folding is further provided inside the sheet processing device. The image forming system 1000 includes an image forming apparatus A and a sheet processing device B. The downstream sheet processing device B receives the sheet S on which an image is formed by the image forming apparatus A, and performs saddle stitching, center folding, back square processing, etc. as necessary, and discharges the sheet to the downstream discharge unit. The image forming apparatus A includes various structures such as copying machines, printers, printing machines, facsimiles, and multifunction machines having multiple functions. The image forming apparatus A and the sheet processing device B will be described in detail below. In the following description, the side of the image forming apparatus A and the sheet processing device B where an operator such as a user operates the apparatus (for example, the side where an operation panel, operation buttons, etc. are located) will be referred to as the front side (the front side of the paper in FIGS. 1 and 2, etc.), and the opposite side to the front side will be referred to as the rear side (the rear side of the paper in FIGS. 1 and 2, etc.).

[0011] [Image forming device] 1, the image forming apparatus A includes an image forming unit A1, an image reading unit A2, and a document feeding unit A3. The image forming unit A1 includes a feeding section 2, an image forming section 3, a discharge section 4, and a data processing section 5 within a housing 1.

[0012] The feeding section 2 includes a plurality of cassettes 2a, 2b, and 2c, and each of the cassettes 2a, 2b, and 2c can store sheets S of different standard sizes selected in advance in a plurality of stages. The sheets S are, for example, paper or plastic sheets. Each of the cassettes 2a, 2b, and 2c is provided with a separation mechanism for separating the sheets S inside one by one, and a feeding mechanism for feeding the sheets S. The sheets S stored in the feeding section 2 configured as described above are fed out in the form of sheets S of a size designated by the control unit 310 (FIG. 3) of the image forming apparatus A. The sheets S supplied from the plurality of cassettes 2a, 2b, and 2c are further conveyed downstream by the conveying rollers 7. The leading edge of the sheet conveyed by the conveying rollers 7 is aligned by the pair of registration rollers 8, and skew is corrected. Then, the sheet S whose leading edge has been aligned by the pair of registration rollers 8 is fed to the downstream image forming section 3 at a predetermined timing.

[0013] A large-capacity cassette 2d and a manual feed tray 2e are connected to the image forming apparatus A. The large-capacity cassette 2d is an optional unit that stores sheets of a size that are consumed in large quantities. The manual feed tray 2e is configured to be able to feed special sheets such as thick paper sheets, coated sheets, and film sheets that are difficult to separate and feed.

[0014] The image forming unit 3 may be configured to form an image on the sheet S fed from the feeding unit 2, and various image forming mechanisms may be employed. In the illustrated embodiment, an electrostatic image forming mechanism is shown as the image forming unit 3. However, the image forming unit 3 is not limited to the illustrated electrostatic image forming mechanism, and it is also possible to employ an inkjet image forming mechanism, an offset image forming mechanism, or the like.

[0015] The image forming section 3 shown in FIG. 1 includes a photoconductor 9 formed in a drum or belt shape, an exposure device 10 for exposing the photoconductor 9, a development device 11 for developing the photoconductor 9 with toner, a charging device (not shown) for charging the photoconductor 9, and a cleaner (not shown) for cleaning the photoconductor 9. FIG. 1 shows a monochrome printing mechanism as an example. The photoconductor 9 is exposed by the exposure device 10 to form an electrostatic latent image, and the electrostatic latent image is developed by the development device 11 to form a toner image on the photoconductor 9. The toner image formed on the photoconductor 9 is transferred by the transfer device 12 to a sheet S conveyed from the registration roller pair 8. The sheet S with the transferred toner image is fixed by the fixing device 13. The image forming device A is also provided with a reversing conveying path, and the sheet S with the toner image fixed by the fixing device 13 is reversed and then sent to the registration roller pair 8 again, where an image is formed on the back side of the sheet S. Discharge rollers 15 are provided downstream of the fixing device 13 and downstream of the branch to the reverse transport path, and the discharge rollers 15 transport the sheet S from a discharge port 16 of the image forming apparatus A to a sheet processing apparatus B described later.

[0016] An image reading unit A2 that optically reads an original image is provided above the image forming unit A1 configured in this manner, and an original feeding unit A3 is mounted further above the image reading unit A2.

[0017] The image reading unit A2 includes a first platen glass 17, a second platen glass 21, a reading carriage 18 having a light source, a photoelectric conversion element 19, and a reduction optical system 20 formed by combining mirrors and lenses. The reading carriage 18 is scanned along the first platen glass 17 to irradiate light from the light source onto an image of an original placed on the first platen glass 17, and the light reflected from the image of the original is guided by the reduction optical system 20 to the photoelectric conversion element 19 to read the image. The photoelectric conversion element 19 converts image data into an electrical signal and transfers it to the image forming section 3, so that the image read by the image reading unit A2 can be formed on a sheet by the image forming unit A1.

[0018] The document feeding unit A3 includes a feed tray 22 and a discharge tray 24, and transports documents placed on the feed tray 22 one by one, passes them over the second platen glass 21, and discharges them onto the discharge tray 24. When reading a document fed from the document feeding unit A3 and passing over the second platen glass 21, the reading carriage 18 is stopped below the second platen glass 21 in advance, and image data is read from the image passing over the second platen glass 21.

[0019] [Overall configuration of sheet processing device] Next, the overall configuration of sheet processing device B that performs processing such as stapling and folding on sheets conveyed from image forming device A will be described with reference to Fig. 2. Fig. 2 shows the detailed configuration of sheet processing device B. Sheet processing device B processes sheets received from receiving section 26, which is the entrance of straight path 28 connected to discharge port 16 of image forming device A, and can then load the sheets onto a first tray (first stacking tray) 49, a saddle discharge unit 131, and a second tray (second stacking tray) 71, which will be described later.

[0020] In the illustrated device, a sheet sent to the straight path 28 as the transport path and the first transport path is discharged to the first tray 49 after being processed by a processing section B1 described later, or a sheet transported on the straight path 28 is discharged to the second tray 71, or is discharged to a saddle discharge unit 131 after being processed by a saddle section B2 described later. Each device has a control section, a communication section, etc., as shown in the block diagram of the control configuration of the entire device in Fig. 3, and controls the device by using these sections.

[0021] The processing section B1 as an end binding processing section is disposed below the path exit (transfer section 35) of the straight path 28, collates and accumulates a plurality of sheets sequentially delivered from the straight path 28 via the transfer section 35 to form a sheet bundle, and can perform a binding process, which is an example of a predetermined process, on the end of this sheet bundle. The bound sheet bundle is stacked on a first tray 49 as a stacking section. The rear end (upstream end) of the sheet or sheet bundle stacked on the first tray 49 abuts against a stacking wall 50 on the upstream side of the first tray 49 in the sheet discharge direction, and is stacked along the stacking wall 50.

[0022] The first tray 49 can be raised and lowered relative to the processing tray 37 described later, and stacks a sheet bundle that has been stapled by a staple processing mechanism 47 described later. In this embodiment, the first tray 49 and the second tray 71 can be raised and lowered by a lifting mechanism (not shown). That is, in this embodiment, when sheets are sent to the first tray 49 or the second tray 71 serving as a stacking tray, the first tray 49 or the second tray 71 is raised and lowered to keep the position of the top sheet on the stacking surface of the tray constant relative to the pair of discharge rollers 42 or the second discharge roller 207 so that the alignment of the stacked sheets does not deteriorate.

[0023] The saddle section B2 is disposed below the transfer section of the saddle path 32 as a second transport path branching vertically downward from the straight path 28, and collates and accumulates a plurality of sheets sequentially delivered from the straight path 28 via the saddle path 32 and the transfer section to form a sheet bundle, and discharges the bundle to the saddle discharge unit 131 after saddle-stitching or folding without saddle-stitching. Each component will be described in detail below.

[0024] [housing] As shown in FIG. 2, the sheet processing apparatus B includes a housing 27, a straight path 28, a processing section B1, a saddle section B2, a first tray 49, a saddle discharge unit 131, a second tray 71, and the like. The straight path 28, the processing section B1, and the saddle section B2 are disposed inside the housing 27. The straight path 28 also includes a sheet receiving section 26 and a sheet delivery section 35. The processing section B1 and the saddle section B2 process the sheet delivered from the delivery section 35 of the straight path 28. The first tray 49, the saddle discharge unit 131, and the second tray 71 stack the sheets sent from each processing section. The illustrated housing 27 is connected to the housing 1 of the image forming apparatus A located upstream of the straight path 28 in the sheet conveying direction. The housing 27 and the housing 1 are arranged so that the heights of the discharge outlet 16 of the image forming device A and the receiving section 26 of the sheet processing device B from the installation surface are approximately the same, and the discharge outlet 16 and the receiving section 26 are connected.

[0025] [Sheet delivery route] The straight path 28, which is a sheet carry-in path, is configured as a substantially straight path that crosses the housing 27 in a substantially horizontal direction, and includes a receiving section 26 that is connected to the discharge port (main body discharge port) 16 of the image forming apparatus A, and a delivery section 35 that is located on the opposite side across the apparatus from the receiving section 26. In the straight path 28, an entrance roller 29, a first conveying roller 201, a second conveying roller 202, and a third conveying roller 203 are arranged as conveying rollers that can convey a sheet in a first direction from the receiving section 26 to the first discharge path 31, and can convey a sheet in a second direction from the first discharge path 31 to the receiving section 26. That is, the entrance roller 29, the first conveying roller 201, the second conveying roller 202, and the third conveying roller 203 can convey a sheet in a first direction and a second direction opposite to the first direction in the conveying path, and are arranged in order from the receiving section 26 side with respect to the first direction.

[0026] The first discharge path 31 is connected to a transfer section 35 of the straight path 28, and a first conveying roller 36 is disposed at this connection section. A sheet that is transferred from the straight path 28 to the first discharge path 31 and discharged from the first discharge path 31 is stacked on a first tray 49 or guided to processing section B1. Note that each of the above-mentioned conveying rollers may be other members capable of conveying a sheet, such as a conveying belt.

[0027] [Sheet delivery route layout] As shown in FIG. 2, the straight path 28 is connected to a saddle path 32 and an upper conveying path 30, which are branch paths. The saddle path 32 and the upper conveying path 30 are arranged in this order in the first direction from the receiving section 26 toward the first discharge path 31. The saddle path 32 branches from the straight path 28 toward the vertically downward direction, and the upper conveying path 30 branches from the straight path 28 toward the vertically upward direction. At the branching points of the straight path 28, the saddle path 32, and the upper conveying path 30, a saddle path switching member 33 and an upper conveying path switching member 34 are arranged as switching members for switching the conveying direction of the conveyed sheet. The conveying path from the saddle path switching member 33 to the upper conveying path 30 is a stack path 400 as a third stacking section capable of stacking a sheet stack, as described later. That is, the stack path 400 is composed of the section of the straight path 28 from the saddle path switching member 33 to the upper conveying path switching member 34 , and the upper conveying path 30 .

[0028] [Path branching method] The upper conveying path switching member 34 is composed of a switching guide that is movable to change the conveying path so that the sheet conveyed from the receiving unit 26 is conveyed to either the first discharge path 31 or the upper conveying path 30, and is moved by a driving unit (not shown) such as an electromagnetic solenoid or a mini motor. That is, the upper conveying path switching member 34 that functions as a conveying path switching member can switch the path along which the sheet is conveyed between the straight path 28 and the upper conveying path 30. Specifically, the upper conveying path switching member 34 can be moved between a straight guide position where the sheet conveyed from the upstream side of the upper conveying path 30 in the first direction in the straight path 28 is guided along the straight path 28 toward the first discharge path 31, and an upper conveying guide position where the sheet conveyed from the upstream side of the upper conveying path 30 in the first direction in the straight path 28 is guided to the upper conveying path 30.

[0029] [Upper transport path] An upper conveying path 30 (printout discharge path) that conveys sheets other than those discharged to the first discharge path 31 branches off from the straight path 28, and the path branching portion is provided with an upper conveying path switching member 34 for guiding a sheet to the upper conveying path 30. The upper conveying path 30 is also provided with a fourth conveying roller 204, a fifth conveying roller 205, a sixth conveying roller 206, and a second discharge roller 207 as conveying rollers that guide the sheet to the second tray 71. As a result, the sheet guided to the upper conveying path 30 is discharged from the upper conveying path discharge port 40 to the second tray 71 (overflow tray).

[0030] The processing section B1 is composed of a processing tray 37 as a loading section and a first stacking section on which sheets conveyed through the first discharge path 31 downstream of the straight path 28 are loaded and which collates and stacks the loaded sheets, and a binding processing mechanism (end binding staple unit) 47 as a first binding processing section which binds the stacked sheet bundle. The processing section B1 performs binding processing on the sheet bundle loaded on the processing tray 37. The binding processing mechanism 47 is disposed vertically below the straight path 28. As shown in FIG. 2, the first discharge path 31 has a step formed thereon and the processing tray 37 is disposed below the step. Between the first discharge path 31 and the processing tray 37, a first switchback path is provided which changes the conveying direction to the opposite direction in a state where a part of the sheet is discharged from the discharge port 31a of the first discharge path 31 to the first tray 49, and guides the sheet onto the processing tray 37.

[0031] Specifically, the first discharge path 31 is provided with an upper conveying roller 41 and a lower conveying roller 48 that sandwich and convey a sheet. The upper conveying roller 41 and the lower conveying roller 48 form a discharge roller pair 42 as a discharge section. The upper conveying roller 41 can come into contact with and separate from the lower conveying roller 48, and can convey a sheet in a direction toward the first tray 49 with the upper conveying roller 41 and the lower conveying roller 48 sandwiching the sheet, and in a direction opposite to this direction. The upper conveying roller 41 and the lower conveying roller 48 can convey the sheet toward the processing tray 37 via the first switchback path.

[0032] Furthermore, the upper conveying roller 41 and the lower conveying roller 48 (i.e., the discharge roller pair 42) discharge the sheet or sheet stack on the processing tray 37 from the discharge opening 31a to a first tray 49 serving as a stacking tray (stacking section). The discharge opening 31a is a portion of the housing 27 that opens above the lower conveying roller 48. Furthermore, the discharge roller pair 42 discharges the sheet, which has been conveyed to the first discharge path 31 without passing through the processing tray 37, from the discharge opening 31a to the first tray 49.

[0033] The binding mechanism 47 has a trailing end regulating section 47a that abuts against an end (trailing end) of a sheet to position the sheet. On the processing tray 37, a pick-up section 38 is disposed that conveys the sheet conveyed to the processing tray 37 by the upper conveying roller 41 and the lower conveying roller 48 toward the trailing end regulating section 47a. The binding mechanism 47 performs binding processing on the end of a sheet bundle made up of multiple sheets that is placed on the processing tray 37 and whose end position is regulated by the trailing end regulating section 47a. The binding mechanism 47 also has a sheet bundle conveying mechanism that conveys the sheet bundle to the first tray 49 after performing binding processing on the end of the sheet bundle.

[0034] 2 supports the sheet fed from the first discharge path 31 between the processing tray 37 and the first tray 49 on the downstream side thereof so that the sheet straddles between them. In other words, the sheet fed from the first discharge path 31 is supported with its leading end on the uppermost sheet of the first tray 49 on the downstream side and its trailing end on the processing tray 37.

[0035] [Saddle Pass] The straight path 28 is connected to a saddle path 32 for conveying a sheet to the saddle portion B2, and the path branching portion is provided with a saddle path switching member 33 for guiding a sheet to the saddle path 32. That is, the saddle path switching member 33 as a switching member can switch the path along which the sheet is conveyed between the straight path 28 and the saddle path 32. Specifically, the saddle path switching member 33 can move between a first guide position where a sheet conveyed from the upstream side of the saddle path 32 in the first direction in the straight path 28 is guided along the straight path 28 in the first direction, and a second guide position where a sheet conveyed from the downstream side of the saddle path 32 in the first direction in the second direction is guided to the saddle path 32. The stack path 400 as the third stacking portion described above is located downstream of the saddle path switching member 33 in the first direction, and a saddle stack tray 150 as the second stacking portion described later is located vertically below the saddle path switching member 33.

[0036] The sheets guided to the saddle section B2 by the saddle path 32 are accumulated on the saddle stack tray 150, and after being subjected to center folding and folding processes, are discharged to the saddle discharge unit 131 via the substantially horizontal post-fold path guide 114, the second roller post-path guide 116, the clamp pre-guide 119, and the saddle discharge guide 124. In this embodiment, the saddle discharge guide 124 as a discharge guide section is used as an auxiliary guide for appropriately stacking the sheets in the saddle discharge unit 131.

[0037] In this embodiment, the above-mentioned second conveying roller 202, third conveying roller 203, fourth conveying roller 204, fifth conveying roller 205, sixth conveying roller 206, and saddle path roller 100 constitute a conveying unit 410 as a conveying means for conveying a sheet from the stack path 400 and the straight path 28 to the saddle stack tray 150. The conveying unit 410 is divided into a conveying roller group 411 as a first conveying section and a saddle path roller 100 as a second conveying section. The conveying roller group 411 has the second conveying roller 202, the third conveying roller 203, the fourth conveying roller 204, the fifth conveying roller 205, and the sixth conveying roller 206, and further conveys the sheet conveyed to the straight path 28 toward the stack path 400. The saddle path roller 100 further conveys the sheet conveyed to the saddle path 32 toward the saddle stack tray 150.

[0038] Further, when the saddle path switching member 33 is located at the first guide position, the conveying roller group 411 conveys the sheet received in the straight path 28 in a first direction toward the stack path 400, and when the saddle path switching member 33 is located at the second guide position, the conveying roller group 411 conveys the sheet or sheet stack from the stack path 400 in a second direction toward the saddle path 32. The sheet or sheet stack conveyed to the saddle path 32 is conveyed by the saddle path rollers 100 toward the saddle stack tray 150.

[0039] [Control configuration] An outline of the control configuration of the image forming system 1000 will be described with reference to Fig. 3. First, the image forming apparatus A has a control unit 310, an operation unit 302, a conveyance control unit 303, an image processing unit 304, a drive unit 305, and a communication unit 306. The control unit 310 has a CPU (Central Processing Unit) 311, a ROM (Read Only Memory) 312, and a RAM (Random Access Memory) 313. The CPU 311 controls each unit while reading a program corresponding to a control procedure stored in the ROM 312. In addition, working data and input data are stored in the RAM 313, and the CPU 311 performs control by referring to the data stored in the RAM 313 based on the above-mentioned programs and the like.

[0040] The operation unit 302 is, for example, an operation panel provided in the image forming apparatus A and connected to the control unit 310, and an operator operates the apparatus and performs various settings. The transport control unit 303 controls various transport rollers that transport sheets in the image forming apparatus A and a switching member that switches the transport path. The image processing unit 304 controls the image forming unit 3. The drive unit 305 controls various motors and power sources. The communication unit 306 connects the control unit 310 to an external device 301 such as a personal computer and a communication unit 321 of the sheet processing apparatus B so that the control unit 310 can communicate with each other.

[0041] The sheet processing device B includes a stacker control unit 330, a conveyance control unit 322, an end binding control unit 323, a discharge processing control unit 324, and a communication unit 321. The stacker control unit 330 includes a CPU 331, a ROM 332, and a RAM 333, similar to the control unit 310. The conveyance control unit 322 controls various conveyance rollers that convey the sheet and a switching member that switches the conveyance path other than the saddle unit B2 of the sheet processing device B. The end binding control unit 323 controls the processing unit B1. The discharge processing control unit 324 controls the discharge of the sheet and various stacking trays on which the discharged sheets are stacked. The communication unit 321 connects the communication unit 306 of the image forming device A and the communication unit 341 of the saddle unit B2 to the stacker control unit 330 so that they can communicate with each other. The communication between the communication unit 306 and the communication unit 321 may be performed by wired communication or wireless communication.

[0042] The saddle unit B2 has a saddle control unit 350, a conveyance control unit 342, a saddle stitching control unit 343, a center folding control unit 344, a square spine processing control unit 345, and a communication unit 341. The saddle control unit 350 has a CPU 351, a ROM 352, and a RAM 353, similar to the control unit 310. The conveyance control unit 342 controls various conveyance rollers that convey the sheet in the saddle unit B2 and a switching member that switches the conveyance path. The saddle stitching control unit 343 controls the saddle stitching processing unit 104. The center folding control unit 344 controls the center folding processing mechanism C1. The square spine processing control unit 345 controls the square spine processing unit C2. The communication unit 341 connects the communication unit 321 of the sheet processing device B and the saddle control unit 350 so that they can communicate with each other.

[0043] [Saddle] The saddle section B2 will be described with reference to Figs. 2 and 4. The saddle section B2 has a folding mechanism C1 and a square spine processing section C2. The folding mechanism C1 collates and stacks the sheets sent from the straight path 28 to form a sheet bundle, binds the sheet bundle in the center of the sheet bundle in the conveying direction (a middle part in the second conveying direction, which is the conveying direction of the saddle path roller 100 as the second conveying section, which will be described later), and performs a folding process to fold the sheet bundle at the position where the binding process is performed (hereinafter also referred to as "magazine finishing"). The square spine processing section C2 is disposed on the downstream side of the sheet bundle conveying direction of the folding mechanism C1 (the downstream side in the first conveying direction, which is the conveying direction of the saddle third roller pair 118, which will be described later), and performs a square spine processing to crease the spine of the sheet bundle that has been subjected to the folding process. A saddle discharge unit 131 is disposed on the downstream side of the square spine processing section C2 in the first conveying direction, and the bound sheet bundle is stacked thereon. It is also possible to collate one or more sheets and stack them, and then perform only center folding, in which the central portion in the conveying direction is folded, without performing saddle stitching or square spine processing.

[0044] [Folding mechanism] The center-folding mechanism C1 has a leading edge regulating stopper 109, a center-stitching processing section (center-stitching staple unit) 104, and a center-folding processing section 112, and accumulates sheets in a bundle and performs center-folding and center-stitching processes. That is, the sheets conveyed from the straight path 28 to the saddle path 32 are conveyed to the accumulating section and the saddle stack tray 150 as the second accumulating section by the saddle path rollers 100 as the second conveying section. The saddle stack tray 150 accumulates a plurality of sheets conveyed in the second conveying direction by the saddle path rollers 100 via the saddle path 32 to form a sheet bundle. The sheet bundle accumulated on the saddle stack tray 150 is positioned at a predetermined position on the saddle stack tray 150 by the leading edge regulating stopper 109.

[0045] The saddle stack tray 150 is provided with a saddle stack sensor 106 as a sheet detection unit that detects the presence or absence of a sheet. The saddle stack sensor 106 may be located anywhere as long as it can detect the presence or absence of a sheet in the saddle stack tray 150. In this embodiment, the saddle stack sensor 106 is located in a position that does not interfere with the operation of the abutting plate 112a and in the vicinity of the folding roller pair 113. For example, the saddle stack sensor 106 is preferably located between the saddle stitching processing unit 104 and the abutting plate 112a, and more preferably located between the pull-in separation roller 105 and the abutting plate 112a.

[0046] The saddle stitching processing section 104 as the second binding processing section performs binding processing (saddle stitching processing) on ​​the center in the conveying direction (middle in the second conveying direction) of the sheet bundle positioned by the leading end regulating stopper 109. The center folding processing section 112 has a pushing plate 112a and a pair of folding rollers 113, and folds the sheet bundle by conveying the sheet bundle with the pair of folding rollers 113 while pushing the vicinity of the position where the sheet bundle has been bound by the saddle stitching processing section 104 (the center in the conveying direction of the sheet bundle bound) with the pushing plate 112a, and conveys the sheet bundle so that the spine of the sheet bundle is on the downstream side in the conveying direction.

[0047] The saddle stitching processing unit 104 is a mechanism that performs stitching processing by moving the sheet stack along the center (line) of the sheets while sandwiching the sheet stack between a head unit and an anvil unit. Also, the center folding processing unit 112 employs a configuration in which the sheet stack is inserted into the nip of a pair of folding rollers 113 pressed against each other by abutment plate 112a, and the sheet stack is folded and conveyed by the rotation of the pair of folding rollers 113, as shown in Figs. 2 and 4.

[0048] [Square back processing section] The square spine processing section C2, which serves as a square spine processing means, performs square spine processing to make the sheet bundle into a square spine shape along the crease (line) of the folded sheet bundle. The square spine processing section C2 includes a lower clamp unit 120 and an upper clamp unit 121 as a pair of clamp units, and a square spine processing unit 134 having a pressing roller 123. The lower clamp unit 120 and the upper clamp unit 121 relatively move along the thickness direction of the sheet bundle conveyed by a saddle third roller pair 118 described later, thereby clamping and releasing the clamping of the sheet bundle. The pressing roller 123 presses the spine of the sheet bundle by moving along the width direction of the sheet bundle (the direction perpendicular to the conveying direction of the sheet bundle, the front-back direction in Figs. 2 and 4). The square spine processing section C2 performs square spine processing to form a corner on the spine of the sheet bundle by pressing the spine of the sheet bundle clamped between the lower clamp unit 120 and the upper clamp unit 121 with the pressing roller 123 while the spine of the sheet bundle protrudes downstream relative to the lower clamp unit 120 and the upper clamp unit 121 in the first conveying direction. Note that the above-mentioned "corner" includes a curved surface and refers to the boundary between the front cover and the spine cover, and the boundary between the spine cover and the back cover of the sheet bundle.

[0049] Specifically, the square spine processing unit C2 clamps a part of the sheet bundle from both sides in the vertical direction (thickness direction of the sheet bundle) while the spine of the sheet bundle folded in the middle by the folding mechanism C1 is projected downstream in the first conveying direction. The pressing roller 123 presses the spine of the sheet bundle clamped by the lower clamp unit 120 and the upper clamp unit 121 along the width direction of the sheet bundle perpendicular to the conveying direction and thickness direction of the sheet bundle. In this way, the square spine processing unit C2 performs square spine processing to give a corner to the spine of the sheet bundle. The square spine processing is a process in which the spine of the sheet bundle shown in Figs. 11(a) and (b) described later is crushed by the pressing roller 123 to form two creases on the spine of the sheet bundle as shown in Figs. 11(c) and (d), thereby forming two corners on the spine of the sheet bundle. The two corners of the spine of the sheet bundle are formed at positions in the thickness direction of the sheet bundle that sandwich the staples driven in during the binding process by the saddle stitching processing unit 104. The two corners of the spine of the sheet bundle are also formed at positions that sandwich the creases formed during the center folding process by the center folding processing unit 112.

[0050] Between the folding mechanism C1 and the square spine processing section C2, a folding transport mechanism is disposed which transports the sheet stack folded in the folding mechanism C1 to the square spine processing section C2 downstream and stops the sheet stack there.

[0051] As described above, the processing section B1 and the straight path 28 are disposed in a substantially horizontal direction, the saddle path 32 that guides the sheets to the saddle section B2 is disposed in a substantially vertical direction, and the saddle stack tray 150 that collates and stacks the sheets is disposed so as to follow the substantially vertical direction. By disposing the straight path 28 in a direction that crosses the housing 27 in this way, and disposing the saddle path 32 and the saddle section B2 in a substantially vertical direction, it is possible to slim down the horizontal width of the device.

[0052] A saddle discharge unit 131 is disposed downstream of the saddle portion B2 in the sheet stack transport direction, and stores the folded sheet stack in a magazine shape. The illustrated saddle discharge unit 131 is disposed vertically below the first tray 49. This is because the device specifications assume that the first tray 49 is used more frequently than the saddle discharge unit 131, and the first tray 49 is set at a height position that makes it easy to remove the sheets on the tray.

[0053] [Saddle section configuration] Next, the center-folding mechanism C1, center-folding conveying mechanism C3, and back square processing section C2 that constitute the saddle section B2 will be described in more detail.

[0054] [Details of the center-folding mechanism] 2, the saddle path switching member 33 is switched to convey the sheet to the saddle path 32, thereby guiding the sheet to the center-folding mechanism C1. In terms of the height direction of the center-folding mechanism C1, there are arranged, in order from the vertically upper side (upstream side) which is the entrance side, a saddle entrance roller 101, a sorting beater 102, a trailing end press guide 103, a center-stitching processing section 104, a pull-in separation roller 105, a center-folding processing section 112, a first alignment roller 107, a second alignment roller 108, a leading end regulating stopper 109, and a leading end gripper 110.

[0055] The saddle inlet roller 101 further conveys the sheet delivered by the saddle path roller 100 from the saddle path 32 downward. The sorting beater 102 shifts the sheet conveyed downward from the saddle inlet roller 101 to the right side of FIG. 2 and accumulates the sheet on the saddle stack tray 150. The rear end pressing guide 103 presses the rear end of the sheet stacked on the saddle stack tray 150. The saddle stitching processing unit 104 performs a stitching process on the center of the sheet stack accumulated on the saddle stack tray 150 in the conveying direction. The pull-in separation roller 105 assists the conveyance of the sheet conveyed to the saddle stack tray 150, and is a roller that pulls the sheet toward the leading end regulation stopper 109. The pull-in separation roller 105 is arranged so as to be able to abut against and separate from the opposing roller 105a.

[0056] The center-folding processing section 112 has a pair of folding rollers 113, a pushing plate 112a as a pressing section, and a roller guide 111. The pair of folding rollers 113 form creases in the center-folding process. The pushing plate 112a pushes the sheet into the nip portion of the pair of folding rollers 113. That is, the pair of folding rollers 113 sandwiches and conveys the sheet bundle so that the spine of the sheet bundle is located downstream of the end portion on the fore-edge side, thereby center-folding the sheet bundle. The pushing plate 112a presses the sheet bundle that has been saddle-stitched by the saddle-stitching processing section 104 toward the nip portion of the pair of folding rollers 113. The roller guide 111 covers the pair of folding rollers 113. The first alignment roller 107 and the second alignment roller 108 convey the sheet conveyed to the saddle stack tray 150, and also align the sheet in the height direction. The leading edge regulating stopper 109 abuts against the leading edge (lower edge) of the conveyed sheet, thereby determining the height position of the leading edge of the sheet. The leading edge gripper 110 holds down the leading edge (lower edge) of the sheet stacked on the leading edge regulating stopper 109.

[0057] The saddle inlet roller 101 and the pull-in separation roller 105 are driven by the same motor. The rear end pressing guide 103 is positioned opposite the sorting beater 102 across the saddle stack tray 150. The saddle stitching processing section 104 is disposed downstream of the sorting beater 102 and the rear end pressing guide 103 and upstream of the pull-in separation roller 105.

[0058] The sheet conveyed from the saddle path 32 to the saddle section B2 is conveyed by the saddle inlet roller 101 to the leading edge regulating stopper 109 that has moved to a position according to the size of the sheet. The pull-in separation roller 105 has an auxiliary conveying function for accurately conveying the sheet being conveyed to the leading edge regulating stopper 109 in the saddle stack tray 150. At this time, the folding roller pair 113 is covered by a roller guide 111 to prevent the leading edge of the sheet from getting caught on the folding roller pair 113 and to convey the sheet efficiently.

[0059] The first alignment roller 107 and the second alignment roller 108 accurately abut the conveyed sheet against a leading edge regulation stopper 109, and align the sheet in the height direction.

[0060] The sorting beater 102 prepares to receive the next sheet by moving the sheet conveyed to the leading edge regulating stopper 109 to the trailing edge pressing guide 103 and pressing the trailing edge (upper edge) of the sheet by the trailing edge pressing guide 103. At this time, the trailing edge pressing guide 103 moves to a position according to the size and waits.

[0061] The leading end (lower end) of the sheet bundle formed by stacking a predetermined number of sheets on the saddle stack tray 150 is fixed by being gripped by the leading end gripper 110. In this state, the saddle stitching processing unit 104 performs a stitching process on the center of the sheet bundle in the second conveying direction. After the stitching process, the leading end regulating stopper 109 is lowered while the leading end (lower end) of the sheet bundle is gripped by the leading end gripper 110. At this time, the leading end regulating stopper 109 is lowered so that the position where the abutting plate 112a pushes into the pair of folding rollers 113 is a position that is half the sheet size, thereby lowering the sheet bundle from the stitching position.

[0062] When performing center folding, the roller guide 111 is retracted, the leading edge gripper 110 is released, and then the pusher plate 112a pushes the center of the sheet stack into the nip portion of the pair of folding rollers 113. This causes the sheet stack to be center folded.

[0063] The saddle inlet roller 101, the pull-in separation roller 105, the sorting beater 102, and the rear end pressing guide 103 are controlled by a conveyance control unit 342 (FIG. 3). In addition, the leading end regulating stopper 109, the leading end gripper 110, the saddle stitching processing unit 104, the first alignment roller 107, and the second alignment roller 108 are controlled by a saddle stitching control unit 343 (FIG. 3). In addition, the folding roller pair 113 and the abutment plate 112a are controlled by a center folding control unit 344 (FIG. 3).

[0064] [Folding transport mechanism] The configuration of the folding conveying mechanism C3 will be described with reference to Figs. 2 and 4. The folding conveying mechanism C3 is a mechanism that transfers the sheet bundle that has been folded in the folding mechanism C1 to the spine processing section C2. Specifically, the folding conveying mechanism C3 first transfers the sheet bundle that has been folded in the folding process by the folding roller pair 113 so that the spine of the sheet bundle is located downstream in the conveying direction from the edge on the fore-edge side, and transfers the sheet bundle to the post-folding path guide 114. The post-folding path guide 114 is disposed along a direction (here, substantially horizontal) that bends downward in the vertical direction with respect to the folding roller conveying direction 113c (Fig. 2), which is a direction along a perpendicular line (first virtual line α2 described next, Fig. 4) that passes through the rotation center of each roller of the folding roller pair 113 as the first conveying roller pair, and is disposed downstream in the conveying direction of the folding roller pair 113.

[0065] Here, as shown in FIG. 4, a first line α1 passing through the rotation centers of the pair of folding rollers 113 and a straight line perpendicular to the width direction (the direction perpendicular to the conveying direction of the sheet bundle, the front-back direction in FIGS. 2 and 4) and passing through the nip of the pair of folding rollers 113 in a state where the sheet bundle is not being nipped are defined as a first virtual line α2. In this case, the pair of folding rollers 113 are disposed so that the first virtual line α2 is parallel to the horizontal direction or inclined vertically upward with respect to the horizontal direction toward the downstream of the conveying direction. In this embodiment, the first virtual line α2 is inclined vertically upward with respect to the horizontal direction toward the downstream of the conveying direction. On the other hand, the post-folding path guide 114 is extended in a direction inclined with respect to the first virtual line α2, and in this embodiment, is extended in a substantially horizontal direction.

[0066] The post-fold path guide 114 guides the conveyance of the sheet bundle, and leads the sheet bundle to the saddle second roller pair 115 located downstream in the conveyance direction. The saddle second roller conveyance direction 115c, which is a direction along a perpendicular line to a straight line passing through the rotation centers of the rollers of the saddle second roller pair 115, is disposed along a direction that descends vertically downward toward the downstream in the conveyance direction. The saddle second roller pair 115 is driven by the center folding control unit 344 to convey the sheet bundle.

[0067] The sheet bundle conveyed by the saddle second roller pair 115 is delivered to the second roller post-path guide 116 arranged on the downstream side of the conveying direction and parallel to the saddle second roller conveying direction 115c (FIG. 2), and is guided by the second roller post-path guide 116. The second roller post-path guide 116 also has a second roller post-path upper guide 116a that guides the upper surface of the sheet bundle, and a second roller post-path lower guide 116b that guides the lower surface of the sheet bundle. A saddle conveying sensor 117 is arranged vertically above the guide surface of the second roller post-path upper guide 116a, and between the sheet bundle receiving port and the sheet bundle discharge port. The saddle conveying sensor 117 detects the position of the leading edge of the sheet bundle.

[0068] The second roller rear path guide 116 guides the conveyance of the sheet, and leads it to a saddle third roller pair 118 located downstream in the conveyance direction. A saddle third roller conveyance direction 118c (FIG. 2), which is a direction along a perpendicular line (a second virtual line β2 described next, FIG. 4) to a straight line passing through the rotation centers of the respective rollers of the saddle third roller pair 118, is disposed along a direction that descends vertically downward toward the downstream in the conveyance direction.

[0069] The saddle third roller pair 118 as a conveying roller pair is driven by the center folding control unit 344, and conveys the sheet bundle that has been subjected to the center stitching and center folding processing while sandwiching it so that the spine of the sheet bundle is located downstream of the end of the fore-edge side in the conveying direction. In other words, the saddle third roller pair 118 conveys the sheet bundle so that the spine of the sheet bundle is the leading end. When the direction in which the sheet bundle is conveyed by the saddle third roller pair 118, which is also the first conveying means, is the first conveying direction (saddle third roller conveying direction 118c), the saddle path roller 100 as a second conveying means that conveys the sheet to the center folding mechanism C1 is located upstream of the saddle third roller pair 118 in the first conveying direction. Then, the saddle path roller 100 conveys the sheet in a second conveying direction different from the first conveying direction, upstream of the saddle third roller pair 118 in the first conveying direction. Hereinafter, the upstream side and downstream side of the first conveying direction (saddle third roller conveying direction 118c) in which the sheet stack is conveyed by the saddle third roller pair 118 may be simply referred to as the "upstream side" and the "downstream side".

[0070] The folding roller pair 113, the saddle second roller pair 115, and the saddle third roller pair 118 are driven by the same motor, and the center folding control unit 344 controls the driving of each roller pair by controlling this motor. The saddle third roller pair 118 holds the sheet bundle center-folded by the center folding unit 112 and transports it toward the square spine processing unit C2, and is located immediately upstream of the square spine processing unit C2.

[0071] 4, a second line β1 passing through the rotation centers of the saddle third roller pair 118 and a straight line perpendicular to the width direction and passing through the nip of the saddle third roller pair 118 when the sheet stack is not being sandwiched are defined as a second imaginary line β2. In this case, the saddle third roller pair 118 is provided such that the second imaginary line β2 intersects with the first imaginary line α2 and is inclined vertically downward as it moves toward the downstream of the folding roller pair 113 in the conveying direction.

[0072] In other words, the saddle third roller pair 118 is disposed such that the second virtual line β2 is inclined downward in the vertical direction as it approaches the horizontal direction and downstream in the conveying direction. That is, in this embodiment, the second virtual line β2 is inclined with respect to the first virtual line α2. The folding roller pair 113 conveys the sheet bundle in a horizontal direction or in a direction (folding roller conveying direction 113c) that is inclined upward in the vertical direction as it approaches the horizontal direction and downstream in the conveying direction. In contrast, the saddle third roller pair 118 conveys the sheet bundle in a direction (saddle third roller conveying direction 118c) that is inclined downward in the vertical direction as it approaches the horizontal direction and downstream in the conveying direction.

[0073] Therefore, in the present embodiment, the center-folding conveying path C4 as a third conveying path that conveys the sheet bundle between the folding roller pair 113 and the saddle third roller pair 118 is bent so that the sheet bundle conveyed by the folding roller pair 113 is handed over to the saddle third roller pair 118. That is, the center-folding conveying path C4 has a post-folding path guide 114 and a second-roller post-path guide 116, and the conveying path is bent between the post-folding path guide 114 and the second-roller post-path guide 116. In other words, the direction in which the sheet bundle is guided by the second-roller post-path guide 116 is inclined with respect to the direction in which the sheet bundle is guided by the post-folding path guide 114.

[0074] In this way, by making the conveying direction of the sheet bundle of the folding roller pair 113 and the conveying direction of the sheet bundle of the saddle third roller pair 118 different and bending the conveying path between the post-fold path guide 114 and the second roller post-path guide 116, the width of the sheet processing device B (the length in the second conveying direction, the length in the left-right direction in FIG. 2) can be reduced, and the device can be made more compact. Also, by discharging the sheet bundle downward by the saddle third roller pair 118, obliquely downward in the folding roller conveying direction 113c, which is the sheet conveying direction of the saddle third roller pair 118, the sheet bundle processed by the saddle section B2 can be discharged to a lower position in the device.

[0075] As described above, the first tray 49 can be raised and lowered in the vertical direction. In this embodiment, as shown in Fig. 2, when the lifting area H of the first tray 49 is viewed in a direction perpendicular to the vertical direction and from the downstream side to the upstream side of the sheet conveying direction by the saddle third roller pair 118 (from the left side to the right side in Fig. 2), this lifting area H overlaps with the folding roller pair 113.

[0076] This allows the saddle discharge unit 131, to which the sheet stack processed in the saddle section B2 is discharged, to be disposed below the device, and increases the amount that the first tray 49 located above the saddle discharge unit 131 can descend. As a result, it is possible to increase the sheet stacking capacity of the first tray 49 while reducing the size of the sheet processing device B. Note that when the arrangement of the transport path guides for the above-mentioned sheets or sheet stacks and the transport direction of the sheets or sheet stacks are horizontal, vertical, or parallel, this also includes cases where an angle is made with respect to the horizontal, vertical, or parallel due to tolerances, etc.

[0077] [Details of back corner processing section] The square spine processing section C2 will be described with reference to Figs. 2 and 4, and with reference to Figs. 5 to 10. As described above, the square spine processing section C2 includes a pair of clamp sections, namely, a lower clamp unit 120 and an upper clamp unit 121, and a square spine processing unit 134 having a pressing roller 123. The clamp mechanism C5 including the lower clamp unit 120 and the upper clamp unit 121 includes a clamp pre-guide 119 as shown in Fig. 5. The clamp pre-guide 119 is disposed downstream of the saddle third roller pair 118 in the conveying direction and along a direction that bends downward in the vertical direction with respect to the saddle third roller conveying direction 118c, and guides the conveyance of the sheet stack.

[0078] The clamp front guide 119 has a clamp front upper guide portion 119a as a first guide portion that guides the upper surface of the sheet bundle, and a clamp front lower guide portion 119b as a second guide portion that guides the lower surface of the sheet bundle. The clamp front upper guide portion 119a and the clamp front lower guide portion 119b are disposed at a position in the thickness direction away from a line centered on the saddle third roller conveying direction 118c by more than 1 / 2 the thickness of the sheet bundle that can pass through the device (the thickness of the sheet bundle when the center folding process is performed on the sheet bundle with the maximum thickness that can be conveyed in the device). In other words, the distance between the clamp front upper guide portion 119a and the clamp front lower guide portion 119b is greater than the maximum thickness of the sheet bundle that can be processed by the sheet processing device B (the maximum thickness of the sheet bundle that can be center folded by the center folding process mechanism C1). At least one of the clamp front upper guide portion 119a and the clamp front lower guide portion 119b may be omitted.

[0079] The lower clamp unit 120 and the upper clamp unit 121 are relatively movable between a first position where the sheet bundle conveyed from the saddle third roller pair 118 can be received, and a second position where the sheet bundle is sandwiched between them. The lower clamp unit 120 and the upper clamp unit 121 sandwich a part of the sheet bundle from both sides in the thickness direction of the sheet bundle by moving from the first position to the second position.

[0080] In this embodiment, the upper clamp unit 121 as the first clamp unit is movable, and the lower clamp unit 120 as the second clamp unit is fixed. That is, the upper clamp unit 121 moves in a direction approaching the lower clamp unit 120 to clamp the sheet bundle. However, the upper clamp unit 121 may be fixed and the lower clamp unit 120 may be movable, or both may be movable. In either case, the sheet bundle is clamped between an upper clamp surface (upper clamp pressing portion) 142, which is a surface of the upper clamp unit 121 facing the lower clamp unit 120, and a lower clamp surface (lower clamp pressing portion) 143, which is a surface of the lower clamp unit 120 facing the upper clamp unit 121 (see FIG. 5 and FIG. 11(a) to (d)).

[0081] The lower clamp surface 143 of the lower clamp unit 120 and the upper clamp surface 142 of the upper clamp unit 121 are parallel to the clamp pre-upper guide portion 119a and the clamp pre-lower guide portion 119b, respectively, and are disposed downstream of the clamp pre-guide 119 in the sheet bundle conveying direction. The sheet bundle conveyed while being guided by the clamp pre-guide 119 is further guided by the upper clamp surface 142 and the lower clamp surface 143 to be conveyed a predetermined amount. The clamp pre-lower guide portion 119b is fixed to the lower clamp unit 120, and the clamp pre-upper guide portion 119a is fixed to the upper clamp unit 121. In this embodiment, the clamp pre-upper guide portion 119a moves together with the upper clamp unit 121 in a substantially vertical direction (thickness direction of the sheet bundle). The upper clamp unit 121 and the lower clamp unit 120, like the pre-clamp upper guide portion 119a and the pre-clamp lower guide portion 119b, are positioned in the first position at a thickness direction away from a line centered on the saddle third roller conveying direction 118c by more than half the thickness of the sheet stack that can pass through the device (the thickness of the sheet stack when a center folding process is performed on a sheet stack of the maximum thickness that can be conveyed in the device).

[0082] [Square back processing unit] Next, the internal configuration of the square spine processing unit 134 will be described with reference to Figures 5 to 10. The square spine processing unit 134 has a pressing roller (square spine processing roller) 123, a unit frame 147, roller pressure units 138a and 138b, pressure springs 145a and 145b, an upper movement regulating unit 139, and a lower movement regulating unit 140. As shown in Figures 5 and 10, the pressing roller 123 is arranged so that its outer circumferential surface contacts the downstream end surfaces of the lower clamp unit 120 and the upper clamp unit 121. In addition, as shown in Figure 6(b), the pressing roller 123 has a roller shaft 141 arranged on its inner diameter side, and is rotatable with respect to the roller shaft 141.

[0083] 6(a) and (b), the unit frame 147 has a pair of side plates 147a arranged on both sides of the pressing roller 123, a rear plate 147b arranged on the left side of the pressing roller 123 on the downstream side in the first transport direction (FIG. 6(b)), and an upper plate 147c and a lower plate 147d arranged on both sides in the rotation axis direction of the pressing roller 123 and bent from both ends of the rear plate 147b. The unit frame 147 is configured in this way to house the pressing roller 123 inside the side plates and expose the pressing roller 123 to the upstream side in the first transport direction.

[0084] In this embodiment, the rear plate 147b, the upper plate 147c, and the lower plate 147d are integrally formed, and as shown in FIG. 6(b), the cross section is substantially U-shaped. These may be separate bodies, or may be integrally formed with the pair of side plates 147a. Both ends of the roller shaft 141 of the pressure roller 123 are rotatably supported by the upper plate 147c and the lower plate 147d, respectively. The upper plate 147c and the lower plate 147d are extended upstream in the first conveying direction from the pressure roller 123, and the upper movement restricting portion 139 and the lower movement restricting portion 140 are supported at the tip portions, respectively.

[0085] That is, the upper movement restricting portion 139 is provided at the tip of the support shaft 139a fixed to the upper plate 147c and extending downward from the upper plate 147c. The lower movement restricting portion 140 is provided at the tip of the support shaft 140a fixed to the upper plate 147c and extending downward from the lower plate 147d. The upper movement restricting portion 139 is a roller rotatably supported at the tip of the support shaft 139a, and the lower movement restricting portion 140 is a roller rotatably supported at the tip of the support shaft 140a. In this embodiment, two lower movement restricting portions 140 are arranged side by side, but one may be used. The upper movement restricting portion 139 may also be two. The upper movement restricting portion 139 and the lower movement restricting portion 140 are located on both sides of the pressing roller 123 with respect to the rotation axis direction of the roller shaft 141.

[0086] Roller pressure members 138a and 138b are connected to the roller shaft 141 on the outer side of the pressure roller 123 in the roller thickness direction and downstream in the conveying direction. Pressure springs 145a and 145b are arranged between the roller pressure members 138a and 138b and a rear plate 147b of the unit frame 147, and the roller shaft 141 is urged by the pressure springs 145a and 145b. Since the roller shaft 141 is configured to be movable in the conveying direction, the pressure with which the pressure roller 123 presses the spine of the sheet stack by the urging forces of the pressure springs 145a and 145b changes with the change in the amount of protrusion of the spine of the sheet stack from the lower clamp unit 120 and the upper clamp unit 121, which will be described later.

[0087] Further, the pressure roller 123 is biased by pressure springs 145a and 145b via the roller shaft 141, and is therefore pressed against the lower clamp unit 120 and the upper clamp unit 121. On the other hand, an upper movement restricting portion 139 and a lower movement restricting portion 140 are disposed on the opposite side of the pressure roller 123 and the lower clamp unit 120 and the upper clamp unit 121 so as to face the lower clamp unit 120 and the upper clamp unit 121, respectively (FIG. 5). That is, in terms of the conveying direction (first conveying direction) of the sheet bundle, on the upstream side of the lower clamp unit 120 and the upper clamp unit 121, the upper movement restricting portion 139 is disposed with respect to the upper clamp unit 121, and the lower movement restricting portion 140 is disposed with respect to the lower clamp unit 120.

[0088] 9 and 10, an upstream end surface 120a of the lower clamp unit 120 abuts against the lower movement restricting portion 140. An upstream end surface 121a of the upper clamp unit 121 abuts against the upper movement restricting portion 139. In this embodiment, the lower movement restricting portion 140 and the upper movement restricting portion 139 are rollers having rotation axes in a direction perpendicular to the width direction of the sheet bundle and the conveying direction of the sheet bundle (up and down direction in FIG. 10, approximately vertical direction in this embodiment), and rotate while abutting against the end surfaces 120a and 121a. As a result, the pressure applied from the pressure roller 123 to the lower clamp unit 120 and the upper clamp unit 121 restricts the lower clamp unit 120 and the upper clamp unit 121 from moving upstream.

[0089] When the leading edge of the sheet bundle conveyed by the saddle third roller pair 118 is detected by the above-mentioned saddle conveyance sensor 117, the conveyance amount of the sheet bundle is counted by the square spine processing control unit 345, and the sheet bundle is stopped after being conveyed a predetermined conveyance amount. Specifically, as shown in FIG. 11(a) described later, the center-folded sheet bundle is stopped in a state where the spine of the sheet bundle protrudes downstream in the conveyance direction from the upper clamp unit 121 and the lower clamp unit 120. In this embodiment, in the square spine processing, the conveyance amount of the sheet bundle by the saddle third roller pair 118 is controlled to adjust the protruding amount of the spine of the sheet bundle from the upper clamp unit 121 and the lower clamp unit 120.

[0090] [Upper clamp unit and lower clamp unit] The upper clamp unit 121 moves from a receiving position (first position) where the sheet bundle is received to a clamp holding position (second position) where the sheet bundle is held, thereby pressurizing the sheet bundle between the lower clamp unit 120 and holding the sheet bundle with the upper clamp surface 142 and the lower clamp surface 143. At this time, as shown in Fig. 11(b) described later, the leading end of the sheet bundle protrudes by a predetermined protrusion amount P1 from end surfaces 120c and 121b on the downstream side in the conveying direction of the lower clamp unit 120 and the upper clamp unit 121 after clamp holding.

[0091] The upper clamp unit 121 is operated by driving the clamp drive motor 132 (FIGS. 7(a) and 7(b)) by the square spine processing control unit 345. As shown in FIG. 7(a) and 7(b), the square spine processing unit C2 further transmits the drive transmitted by the clamp drive train 133, which is composed of a pulley, a belt, and further a gear train, to the clamp drive link 122, thereby moving the upper clamp unit 121 connected to the clamp drive link 122 in the sheet bundle thickness direction. A plurality of clamp springs 144 for pressing the sheet bundle are built in between the clamp drive link 122 and the upper clamp unit 121, and the amount of movement of the clamp drive link 122 remains constant, and the amount of compression of the clamp spring 144 changes depending on the thickness of the sheet bundle, so that the pressing force also changes. The clamp holding position described above also changes depending on the thickness of the sheet bundle.

[0092] [Square back processing section] 11(c) described later, the square spine processing section C performs square spine processing by pressing the spine of the sheet bundle held between the lower clamp unit 120 and the upper clamp unit 121 in a state where the sheet bundle is protruding from the end faces 120c, 121b by a predetermined protrusion amount P1 while scanning in the width direction of the sheet bundle with the pressing roller 123 arranged downstream in the conveying direction. That is, in the square spine processing, the pressing roller 123 moves in the width direction to press the spine of the sheet bundle sandwiched by the lower clamp unit 120 and the upper clamp unit 121 located at the second position in a state where the spine of the sheet bundle conveyed by the saddle third roller pair 118 protrudes downstream in the conveying direction from the lower clamp unit 120 and the upper clamp unit 121.

[0093] When processing the square spine, the square spine processing control unit 345 operates the drive motor 135 (FIG. 7(b)) to move the square spine processing unit 134. As shown in FIG. 8, the square spine processing unit 134 is connected to a drive belt 137 arranged in the width direction of the sheet bundle, and can move in the width direction of the sheet bundle along a guide rail 120b shown in FIG. 9 described later. The drive belt 137 rotates by transmitting power from the drive motor 135 through a drive train 136 (FIG. 7(b)) composed of a gear train. This allows the square spine processing unit 134 to scan the sheet bundle in the width direction. The home positions of the square spine processing unit 134 are provided on the front side and rear side of the sheet processing device B. In other words, the square spine processing unit 134 can be moved from the rear side to the front side for the first sheet bundle to perform the square spine processing, and then the square spine processing unit 134 can be moved from the front side to the rear side for the second sheet bundle to perform the square spine processing. Each home position of the square spine processing unit 134 is provided with a sensor (not shown), which makes it possible to detect the position of the square spine processing unit 134. However, the home position may be provided on either the front side or the rear side, and the square spine processing unit 134 may scan in the width direction from the front side to the rear side or from the rear side to the front side. In this way, when the home position is provided on either side, for example, the square spine processing unit 134 may be moved from the rear side to the front side for the first sheet bundle to perform the square spine processing, and then the square spine processing unit 134 may be returned from the front side to the rear side, and the square spine processing unit 134 may be moved from the rear side to the front side for the second sheet bundle to perform the square spine processing, etc.

[0094] In addition, in one square spine processing, the pressing roller 123 is moved in one direction from the front side to the rear side or from the rear side to the front side, but the pressing roller 123 may be moved back and forth in one square spine processing. For example, in one square spine processing, whether the pressing roller 123 is moved in one direction or moved back and forth may be set according to the number of sheets and the type of sheets included in the sheet bundle. This setting may be performed automatically on the control unit side, or may be set by an operator such as a user or a serviceman. Furthermore, in one square spine processing, whether the pressing roller 123 is moved in one direction or moved back and forth may be arbitrarily set by the operator.

[0095] The lower clamp unit 120 has a guide rail 120b formed along the width direction of the sheet bundle, as shown in Figs. 9 and 10. When the square spine processing unit 134 moves in the width direction of the sheet bundle, the lower movement restricting portion 140 moves along the guide rail 120b while engaging with the guide rail 120b. The guide rail 120b is formed by combining a plurality of members, as shown in Fig. 10, into a substantially U-shaped cross section, and is formed so that a part of the roller-shaped lower movement restricting portion 140 can enter into it. The lower surface of the outer diameter side of the lower movement restricting portion 140 engages with the lower surface of the guide rail 120b, and the outer peripheral surface of the lower movement restricting portion 140 abuts against the end surface 120a. This restricts the movement of the square spine processing unit 134 in the thickness direction of the sheet bundle when it moves. The guide rail 120b may be a groove formed in a part of the material on the upstream side of the lower clamp unit 120 in the conveying direction.

[0096] After the square spine processing is completed, the drive motor 135 (FIG. 7(b)) is operated to move the square spine processing unit 134 in the width direction to move it out of the conveying path of the sheet bundle, and the clamp drive motor 132 (FIGS. 7(a) and (b)) is further operated to move the upper clamp unit 121 in a direction away from the sheet bundle (FIG. 11(d) described later). This makes it possible to convey the sheet bundle further downstream. It is also possible to discharge the sheet bundle without performing the above-mentioned square spine processing.

[0097] [Discharge section] As shown in FIG. 2, the sheet bundle that has passed through the saddle portion B2 is conveyed by the saddle third roller pair 118 toward the saddle discharge guide 124 disposed further downstream in the first conveying direction than the square spine processing unit 134. The saddle discharge guide 124 as a discharge guide portion is supported so as to be swingable about a first fulcrum 124b having a rotation axis parallel to the rotation axis of each roller of the saddle third roller pair 118. The first fulcrum 124b is located above a line extending downstream in the conveying direction of the sheet bundle by the saddle third roller pair 118 (first conveying direction, saddle third roller conveying direction 118c). The saddle discharge guide 124 is disposed so as to hang down vertically downward from the first fulcrum 124b.

[0098] The saddle discharge guide 124 has a first transport direction upstream side inclined toward the upstream side in the first transport direction from the first fulcrum 124b toward the middle part 124a in the vertical direction. The saddle discharge guide 124 has a first transport direction upstream side inclined toward the downstream side in the first transport direction from the middle part 124a toward the lower end in the vertical direction. That is, the saddle discharge guide 124 has a first transport direction upstream side side inclined toward the downstream side in the first transport direction from the middle part 124a toward the lower end in the vertical direction. In addition .... In other words, the saddle discharge guide 124 has a first transport direction upstream side side inclined toward the downstream side in the first transport direction. In addition, the saddle discharge guide 124 has a first transport direction upstream side side inclined toward the downstream side in the first transport direction from the middle part 124a toward the lower end.

[0099] The guide surface 124d is located below a line extending downstream in the above-mentioned saddle third roller conveying direction 118c, and comes into contact with the sheet bundle conveyed by the saddle third roller pair 118 to guide the sheet bundle downward. The saddle discharge guide 124 is rotatable about the first fulcrum 124b when the sheet bundle comes into contact with the guide surface 124d. Depending on the rigidity of the sheet bundle, the saddle discharge guide 124 may not come into contact with the guide surface 124d of the saddle discharge guide 124, and even if the sheet bundle does come into contact, the amount of rotation varies depending on the rigidity, so the saddle discharge guide 124 does not necessarily rotate.

[0100] A second fulcrum 124c is provided at the lower end of the saddle ejection guide 124, and a saddle ejection roller 125 described later is connected to the second fulcrum 124c so as to be rotatable about the second fulcrum 124c. The second fulcrum 124c is located below the guide surface 124d, and has a rotation axis parallel to the rotation axis of the first fulcrum 124b.

[0101] As the sheet stack continues to be transported by the saddle third roller pair 118, it is delivered to a saddle discharge unit 131 disposed downstream of the square spine processing unit 134 in the first transport direction and vertically below the saddle discharge guide 124. The saddle discharge unit 131 has a saddle discharge upstream belt 127, a saddle discharge upstream sensor 128, a saddle discharge downstream belt 129, and a saddle discharge downstream sensor 130.

[0102] The saddle discharge upstream belt 127 is located below the guide surface 124d of the saddle discharge guide 124, and conveys the sheet bundle guided downward by the guide surface 124d while guiding it further downstream. The saddle discharge upstream belt 127 is inclined so as to face vertically downward as it approaches the downstream side in the conveying direction. The saddle discharge downstream belt 129 as a sheet bundle discharge section receives the sheet bundle conveyed from the saddle discharge upstream belt 127 and conveys it while guiding it further downstream. The saddle discharge downstream belt 129 is inclined so as to face vertically upward as it approaches the downstream side in the conveying direction. Therefore, the sheet bundle guided to the saddle discharge upstream belt 127 by the guide surface 124d is conveyed in a direction inclined vertically downward by the saddle discharge upstream belt 127, and then conveyed in a direction inclined vertically upward by the saddle discharge downstream belt 129.

[0103] In addition, a saddle discharge upstream sensor 128 that detects the sheet stack on the upstream side is arranged on the upstream side within the transportable area of ​​the saddle discharge upstream belt 127, and a saddle discharge downstream sensor 130 that detects the sheet stack on the downstream side is arranged on the upstream side within the transportable area of ​​the saddle discharge downstream belt 129.

[0104] The sheet bundle delivered to the saddle discharge unit 131 is guided and transported by the saddle discharge upstream belt 127 and the saddle discharge downstream belt 129, and then the sheet bundle is stacked. The saddle discharge upstream belt 127 holds the sheet bundle at a nip point between the saddle discharge roller 125 described above on the downstream side in the transport direction. The sheet bundle present on the saddle discharge upstream belt 127 is configured to suppress the opening side (small edge side) from opening at this nip point. The position of this nip point can be changed around the second fulcrum 124c depending on the thickness of the sheet bundle.

[0105] When the succeeding sheet bundle is being processed, the preceding sheet bundle is transported upstream in the transport direction by the saddle discharge upstream belt 127, and is stopped at a predetermined transport distance after being detected by the saddle discharge upstream sensor 128 or the saddle discharge downstream sensor 130. This transport distance is a position where the opening side of the preceding sheet bundle can be suppressed from opening at the nip point with the saddle discharge roller 125, and the succeeding sheet bundle is in a positional relationship where it comes into contact with the upper surface of the preceding sheet bundle when it is discharged. That is, in this embodiment, the succeeding sheet bundle is stacked on top of the preceding sheet bundle in the saddle discharge unit 131 (so-called tile stacking).

[0106] In this way, the saddle discharge unit 131 discharges the succeeding sheet bundle onto the top surface of the preceding sheet bundle without entering the opening of the preceding sheet bundle, so that the succeeding sheet bundle is stably stacked in a shingle-like manner without causing problems such as getting caught, curling, or being pushed out of the preceding sheet bundle. In other words, by appropriately changing the above-mentioned conveyance amount according to the size of the sheet bundle, the succeeding sheet bundle can be stably stacked on top of the preceding sheet bundle.

[0107] The saddle discharge port 126 is disposed downstream of the saddle discharge guide 124 in the first conveying direction and between the saddle discharge upstream belt 127 and the saddle discharge downstream belt 129. The sheet bundle conveyed to the saddle discharge unit 131 passes through the saddle discharge port 126 and is discharged to the outside of the sheet processing device B, making it easier for the user to access the discharged sheet bundle.

[0108] If another device exists downstream of the saddle discharge unit 131, it is possible to transfer the sheet bundle to the downstream device by continuing the conveyance without stacking. In this embodiment, a discharge cover 151 is provided as a cover member on the outside of the saddle discharge port 126. The discharge cover 151 is arranged so as not to prevent the sheet bundle from being discharged from the saddle discharge port 126, and is arranged so as not to allow an operator such as a user to access the inside of the device through the saddle discharge port 126.

[0109] [Control of back corner processing] Next, the control of the square spine processing of this embodiment will be described with reference to Figs. 11(a) to 11(d). As described above, the square spine processing unit C2 performs square spine processing to make a corner on the spine of the sheet bundle that has been saddle-stitched and center-folded. The center-folding control unit 344 shown in Fig. 3 controls each of the conveying roller pairs, namely, the folding roller pair 113, the saddle second roller pair 115, and the saddle third roller pair 118, with the same drive. Such square spine processing will be described with reference to Figs. 11(a) to 11(d).

[0110] In the square spine processing, the center folding control unit 344 is triggered by detecting the leading end of the sheet bundle Sb by the saddle conveyance sensor 117, and conveys the center folded sheet bundle Sb between the upper clamp unit 121 and the lower clamp unit 120 which are in a separated state. Then, as shown in FIG. 11(a), the center folding control unit 344 stops conveying the sheet bundle Sb in a state where the spine Ssp of the sheet bundle Sb protrudes further downstream in the first conveying direction than the end faces 121b and 120c on the downstream side in the first conveying direction of the upper clamp unit 121 and the lower clamp unit 120.

[0111] In this state, the square spine processing control unit 345 drives the clamp drive motor 132 (FIGS. 7(a) and (b)) to move the upper clamp unit 121 toward the lower clamp unit 120, and as shown in FIG. 11(b), the sheet stack Sb is clamped by the upper clamp unit 121 and the lower clamp unit 120. At this time, the spine Ssp of the sheet stack Sb protrudes downstream by P1 beyond the end faces 121b and 120c on the downstream side in the first conveying direction of the upper clamp unit 121 and the lower clamp unit 120.

[0112] Next, the square spine processing control unit 345 operates the drive motor 135 (FIG. 7(b)) to move the square spine processing unit 134 in the width direction of the sheet bundle Sb. At this time, as shown in FIG. 11(c), the pressing roller 123 of the square spine processing unit 134 moves in the width direction while pressing the spine Ssp of the sheet bundle Sb, so that the square spine processing is performed on the spine Ssp of the sheet bundle Sb. After that, as shown in FIG. 11(d), the square spine processing control unit 345 drives the clamp drive motor 132 (FIGS. 7(a) and (b)) to separate the upper clamp unit 121 from the lower clamp unit 120, and releases the clamping of the sheet bundle Sb. Then, the above-mentioned discharge operation of the sheet bundle Sb is performed.

[0113] [Sheet stack acceptance control] Next, the sheet bundle receiving control during the square back processing in this embodiment will be described with reference to Figures 12 to 18. As described above, when performing the square back processing on multiple sheet bundles in succession, if the sheets included in the following sheet bundle are accumulated after the square back processing of the preceding sheet bundle is completed, and the square back processing is performed, the productivity of the entire device will decrease. Therefore, in this embodiment, the sheet bundle receiving control is performed as follows.

[0114] Here, the folding conveying path C4 along which the folded sheet stack is conveyed will be described with reference to Fig. 4. As described above, the folding conveying path C4 conveys the sheet stack between the folding roller pair 113 and the saddle third roller pair 118, and further conveys the sheet stack from the saddle third roller pair 118 to the square spine processing section C2. In this embodiment, the length L of the conveying path from the folding roller pair 113 to the lower clamp unit 120 and the upper clamp unit 121 of the square spine processing section C2 is set to be longer than half the length of the long side of the maximum size sheet that can be folded by the folding section 112.

[0115] As described above, the center-folding conveying path C4 is bent so that the sheet stack conveyed by the folding roller pair 113 is delivered to the saddle third roller pair 118. Therefore, the length L of the conveying path is the length along this bent path. For example, the maximum size of a sheet that can be center-folded by the center-folding processing unit 112 is 13 inches by 19 inches (330.2 mm by 482.6 mm). In this embodiment, the length L of the conveying path from the folding roller pair 113 to the lower clamp unit 120 and the upper clamp unit 121 is 254 mm. Therefore, the length L of the conveying path is longer than 241.3 mm, which is half the length of the long side of the maximum size sheet.

[0116] For this reason, as described below, while the preceding sheet bundle (first sheet bundle) is in the center-folding transport path C4, a sheet or sheet bundle included in the succeeding sheet bundle (second sheet bundle) can be accumulated on the saddle stack tray 150. That is, in the sheet bundle receiving control of this embodiment, in a state where the transport of the first sheet bundle to be squared by the saddle third roller pair 118 is stopped, at least one sheet included in the second sheet bundle following the first sheet bundle is transported by the transport unit 410 toward the saddle stack tray 150.

[0117] Hereinafter, a control flow for performing square spine processing continuously on a plurality of sheet bundles using the sheet bundle receiving control of this embodiment will be described with reference to the flowchart in Fig. 12 and Figs. 13(a) to 18. In the following description, it is assumed that the number of sheets contained in the preceding first sheet bundle (first sheet bundle) Sb1 is two, and the number of sheets contained in the following second sheet bundle (second sheet bundle) Sb2 is three.

[0118] First, in S101 of FIG. 12, the first sheet bundle Sb1 is stacked on the saddle stack tray 150. That is, as shown in FIG. 13(a), the first sheet S11 of the first sheet bundle is received in the straight path 28. At this time, the saddle path switching member 33 is located at the first guide position, and the upper conveying path switching member 34 is located at the upper conveying guide position. Then, as shown in FIG. 13(b), the first sheet S11 is conveyed toward the stack path 400 by the conveying roller group 411. Next, the saddle path switching member 33 is switched from the first guide position to the second guide position, and the first sheet S11 is conveyed toward the saddle path 32 by the conveying roller group 411, as shown in FIG. 13(c).

[0119] Furthermore, as shown in FIG. 13(d), the first sheet S11 is conveyed toward the saddle stack tray 150 by the saddle path roller 100, and the first sheet S11 is accumulated on the saddle stack tray 150. In FIG. 13(d), the position of the upper conveying path switching member 34 is switched to the straight guide position, but the position of the upper conveying path switching member 34 may remain at the upper conveying position when performing sheet stack reception control when performing square spine processing on multiple sheet stacks in succession. In other words, the upper conveying path switching member 34 only needs to be located at the upper conveying guide position while sheets are being accumulated on the stack path 400 and while sheets are being conveyed from the stack path 400 to the saddle path 32, and may be located at either the upper conveying guide position or the straight guide position at other times.

[0120] Next, the saddle path switching member 33 is switched from the second guide position to the first guide position, and the second sheet S12 of the first sheet bundle Sb1 is received in the straight path 28, as shown in Fig. 14(a). Then, like the first sheet S11, the second sheet S12 is transported to the stack path 400 (Fig. 14(b)), and then transported to the saddle path 32 (Fig. 14(c)), and stacked on the saddle stack tray 150 (Fig. 14(d)). As a result, the first sheet bundle Sb1 is stacked on the saddle stack tray 150.

[0121] Next, in S102 of Fig. 12, the saddle stitching processing unit 104 performs saddle stitching processing on the first sheet bundle Sb1. In parallel with this, in S103 of Fig. 12, the second sheet bundle Sb2 is stacked in the stack path 400. That is, as shown in Fig. 15(a), the saddle path switching member 33 is switched from the second guide position to the first guide position, and the first sheet S21 of the second sheet bundle is received in the straight path 28.

[0122] 15B, the first sheet S21 is conveyed toward the stack path 400 by the conveying roller group 411. That is, after the last sheet S12 of the first sheet bundle Sb1 is accumulated on the saddle stack tray 150, the conveying roller group 411 conveys the first sheet S21 of the second sheet bundle Sb2 toward the stack path 400. Specifically, the conveying roller group 411 conveys the last sheet S12 of the first sheet bundle Sb1 in the second direction toward the saddle path 32, and after the upstream end (rear end) of the last sheet S12 in the second direction passes through the saddle path switching member 33 and the saddle path switching member 33 switches from the second guide position to the first guide position, the conveying roller group 411 conveys the first sheet S21 of the second sheet bundle Sb2 in the first direction toward the stack path 400.

[0123] At this time, as shown in FIG. 15(a), the saddle stitching processing unit 104 performs saddle stitching on the first sheet bundle Sb1. Next, as shown in FIG. 15(b), the leading edge regulating stopper 109 is lowered to lower the first sheet bundle Sb1 that has been saddle stitched from the stitching position. Furthermore, as shown in FIG. 15(c), the abutting plate 112a pushes the center of the sheet bundle Sb1 into the nip of the pair of folding rollers 113, and the center folding process is started (S104 in FIG. 12). At this time, as shown in FIG. 15(c), the second sheet S22 of the second sheet bundle Sb2 is received in the straight path 28.

[0124] 15(d), the folded sheet bundle Sb1 is conveyed by the folding roller pair 113 as it is, and in the folding conveying path C4, the sheet bundle Sb1 is further conveyed by the second saddle roller pair 115 and reaches the third saddle roller pair 118. At this time, as shown in FIG. 15(d), the second sheet S21 of the second sheet bundle Sb2 is conveyed to the stack path 400. In this state, of the sheets included in the sheet bundle Sb2, two sheets S21 and S22 are accumulated in the stack path 400.

[0125] 16(a), the first sheet bundle Sb1 is further conveyed and conveyance of the sheet bundle Sb1 is stopped at a position (clamp position) where the sheet bundle Sb1 is clamped by the lower clamp unit 120 and the upper clamp unit 121 (S105 in FIG. 12). That is, at this position, conveyance of the sheet bundle Sb1 by the saddle third roller pair 118 and the saddle second roller pair 115 is stopped. Then, as shown in FIG. 16(b), the pressure roller 123 is pressed against the first sheet bundle Sb1 to perform a square spine process on the sheet bundle Sb1 (S106 in FIG. 12).

[0126] When the sheet bundle Sb1 is conveyed to a position where it is clamped by the lower clamp unit 120 and the upper clamp unit 121, as shown in FIG. 16(a), the saddle stack sensor 106 in the saddle stack tray 150 no longer detects the sheets (S107 in FIG. 12). Then, the conveying roller group 411 conveys the two sheets S21 and S22 of the second sheet bundle Sb2 that have been accumulated in the stack path 400 to the saddle path 32. Furthermore, as shown in FIG. 16(b), the saddle path roller 100 conveys the two sheets S21 and S22 to the saddle stack tray 150, so that the two sheets S21 and S22 are accumulated on the saddle stack tray 150 (S108 in FIG. 12).

[0127] That is, in a state where the conveyance of the sheet bundle Sb1 by the saddle third roller pair 118 is stopped, the conveyance unit 410 conveys at least one sheet included in the sheet bundle Sb2 accumulated in the stack path 400 toward the saddle stack tray 150. In this embodiment, two sheets S21 and S22 are conveyed to the saddle stack tray 150.

[0128] The relationship between the timing of detection of the absence of sheets by the saddle stack sensor 106 and the timing of start of conveying the sheets of the sheet bundle Sb2 is set based on the position of the saddle stack sensor 106 and the conveying speed of the sheet bundle in the center-folding conveying path C4. That is, the timing of start of conveying the sheets of the sheet bundle Sb2 is set in consideration of the time from when the saddle stack sensor 106 detects the absence of sheets until the rear end of the sheet bundle Sb1 exits from the saddle stack tray 150 into the center-folding conveying path C4.

[0129] At least one sheet included in the second sheet bundle Sb2 may be conveyed to the saddle stack tray 150 when the conveyance of the sheet bundle Sb1 by the saddle third roller pair 118 stops, regardless of the detection of the presence or absence of a sheet by the saddle stack sensor 106. This is because, when the saddle third roller pair 118 stops, the sheet bundle Sb1 has been conveyed to a position where it is clamped by the lower clamp unit 120 and the upper clamp unit 121, and the rear end of the sheet bundle Sb1 is not on the saddle stack tray 150.

[0130] Therefore, the timing for starting conveyance of at least one sheet included in the second sheet bundle Sb2 to the saddle stack tray 150 may be, for example, before the saddle third roller pair 118 stops. This timing may be, for example, the timing when the center folding process is started for the first sheet bundle Sb1, or after this timing. However, it is preferable that conveyance of at least one sheet included in the second sheet bundle Sb2 to the saddle stack tray 150 is completed by the time the square spine process for the sheet bundle Sb1 is completed.

[0131] That is, while the saddle third roller pair 118 is stopping the conveyance of the preceding sheet bundle to perform the square spine processing, the sheets (at least one sheet) constituting the succeeding sheet bundle may be accumulated on the saddle stack tray 150. The period from when the saddle third roller pair 118 stops conveying the sheet bundle to when it resumes conveying is the period during which the square spine processing is being performed, and the sheets of the succeeding sheet bundle are conveyed to the saddle stack tray 150 during this period.

[0132] Furthermore, if the time required for the first sheet bundle Sb1 accumulated on the saddle stack tray 150 to be conveyed to a position where it is clamped by the lower clamp unit 120 and the upper clamp unit 121 after being center-folded is known in advance, the timing for starting conveyance of at least one sheet included in the sheet bundle Sb2 may be set based on this time. Alternatively, the timing for starting conveyance of at least one sheet included in the sheet bundle Sb2 may be set based on the time from when the leading edge of the sheet bundle Sb1 reaches the saddle conveyance sensor 117 until it is conveyed to a position where it is clamped by the lower clamp unit 120 and the upper clamp unit 121. In short, it is sufficient that the timing does not cause interference between the first sheet bundle Sb1 and the sheets included in the second sheet bundle Sb2 on the saddle stack tray 150.

[0133] Next, as shown in FIG. 16(c), the first sheet bundle Sb1 for which the square spine processing has been completed is discharged toward the saddle discharge guide 124 (S109 in FIG. 12). At this time, the third sheet S23, which is the final sheet of the second sheet bundle Sb2, is received in the straight path 28. Then, as shown in FIG. 16(d), the sheet S23 is conveyed to the stack path 400. At this time, the first sheet bundle Sb1 has been discharged to the saddle discharge downstream belt 129.

[0134] Thus, in this embodiment, while the saddle third roller pair 118 stops transporting the first sheet bundle Sb1, transport of at least one sheet included in the second sheet bundle Sb2 is started from the stack path 400. In this embodiment, transport of two sheets S21 and S22 included in the sheet bundle Sb2 is started, but the number of sheets transported at this timing differs depending on the timing of receiving the sheets of the second sheet bundle Sb, the processing time at the saddle section B2, etc.

[0135] For example, one sheet included in the sheet bundle Sb2 may be conveyed, or three or more sheets may be conveyed. Furthermore, when the number of sheets in the sheet bundle Sb2 is small, all of the sheets included in the sheet bundle Sb2 may be conveyed. That is, the number of sheets accumulated in the stack path 400 that temporarily accumulates the second and subsequent sheet bundles may be one, two or more, or even the total number of sheets in the sheet bundle. For example, when the productivity of the image forming apparatus A side is high and the processing time in the saddle section B2 becomes long for reasons such as quality improvement, the number of sheets accumulated in the stack path 400 may be increased according to the processing performance of the apparatus (the productivity of the upstream apparatus).

[0136] Next, as shown in Fig. 17(a), the third sheet S23 of the second sheet bundle Sb2 is conveyed to the saddle path 32. Then, as shown in Fig. 17(b), the sheets are stacked on the saddle stack tray 150 (S110 in Fig. 12), and the second sheet bundle Sb2 is subjected to saddle stitching processing in the same manner as the first sheet bundle Sb1 (S111 in Fig. 12). Furthermore, as shown in Fig. 17(c), the abutting plate 112a pushes the center of the sheet bundle Sb2 into the nip portion of the pair of folding rollers 113, and the center folding processing is started (S112 in Fig. 12).

[0137] Next, as shown in FIG. 17(d), the folded sheet bundle Sb2 is conveyed by the folding roller pair 113 as it is, and further conveyed by the saddle second roller pair 115 and the saddle third roller pair 118 in the folding conveying path C4. Then, conveyance of the sheet bundle Sb2 is stopped at a position (clamp position) where the sheet bundle Sb2 is clamped by the lower clamp unit 120 and the upper clamp unit 121 (S113 in FIG. 12). In this state, the pressing roller 123 is pressed against the second sheet bundle Sb2, as in the first sheet bundle Sb1, to perform the square spine processing on the sheet bundle Sb2 (S114 in FIG. 12). Furthermore, as shown in FIG. 18, the second sheet bundle Sb2, which has been subjected to the square spine processing, is discharged toward the saddle discharge guide 124 (S115 in FIG. 12).

[0138] In this manner, in the present embodiment, in a state where the conveyance of the sheet bundle Sb1 to be subjected to the square spine processing by the saddle third roller pair 118 is stopped, at least one sheet included in the sheet bundle Sb2 following the sheet bundle Sb1 is conveyed by the conveyance unit 410 toward the saddle stack tray 150. Therefore, it is possible to suppress a decrease in productivity due to the square spine processing, compared to a case where the sheets included in the succeeding sheet bundle Sb2 are accumulated after the square spine processing of the sheet bundle Sb1 is completed, and the square spine processing is performed.

[0139] Furthermore, in the present embodiment, after the last sheet of the sheet bundle Sb1 is accumulated on the saddle stack tray 150, the first sheet of the sheet bundle Sb2 is transported toward the stack path 400, and while the sheet bundle Sb1 is being subjected to saddle stitching, folding, and the like, multiple sheets included in the sheet bundle Sb2 can be accumulated on the stack path 400. Therefore, when the sheets included in the sheet bundle Sb2 are transported to the saddle stack tray 150 in a state in which the transport of the sheet bundle Sb1 by the third saddle roller pair 118 is stopped, more sheets can be transported, thereby further suppressing a decrease in productivity.

[0140] <Other embodiments> In the above embodiment, in the control for performing the square spine processing continuously on a plurality of sheet bundles, the third stacking section for temporarily stacking the sheet bundle following the preceding sheet bundle is the stack path 400, but the third stacking section may be provided at a location other than the stack path 400. For example, a buffer path capable of temporarily stacking the sheets conveyed to the straight path 28 may be provided separately.

[0141] Moreover, without providing the third stacking section, a sheet included in the succeeding sheet bundle may be directly transported from the straight path 28 to the saddle path 32 and the saddle stack tray 150. Even in this case, at least one sheet included in the second sheet bundle following the first sheet bundle is transported to the saddle stack tray 150 in a state in which the transport of the preceding first sheet bundle by the saddle third roller pair 118 is stopped.

[0142] In the above embodiment, the square spine processing is performed downstream inside the saddle unit B2 in the sheet processing device B, but the same square spine processing may be performed in another housing connected to the outside. For example, it may be a single unit that performs only the square spine processing without performing saddle stitching or center folding. In this case, this unit has the above-mentioned square spine processing unit C2 and a conveying unit such as a conveying roller pair that conveys the sheet bundle that has been saddle stitched and center folded to the square spine processing unit C2.

[0143] In addition, in the above-described embodiment, the sheet processing device B has a control unit that controls each internal configuration of the sheet processing device B, but each internal configuration of the sheet processing device B may be configured to be controlled by a control unit provided in the image forming device.

[0144] In the above embodiment, the image forming system 1000 in which the sheet processing apparatus B is directly connected to the image forming apparatus A has been described, but other system configurations may be used. For example, a configuration in which other processing apparatuses, conveying apparatuses, etc. are connected between the image forming apparatus A and the sheet processing apparatus B may be used. In the above embodiment, the image forming apparatus A that forms a monochrome image using toner has been described as an example, but the image forming apparatus may be an image forming apparatus that forms a color image using toner, or an image forming apparatus that forms an image on a sheet using ink.

[0145] Furthermore, in the above embodiment, a pair of rollers is used as an example of a conveying means for conveying a sheet inside the sheet processing device B, but a belt may be used to convey the sheet. Specifically, the conveying means may be any of a pair of rollers that sandwiches the belt to convey the sheet, a pair of belts that sandwiches the sheet to convey the sheet, and a belt and rollers that sandwich the sheet. The conveying structure may be changed depending on the position or route to convey the sheet. For example, the sheet may be conveyed by a pair of rollers at one position and by a pair of belts at another position.

[0146] The disclosure of this embodiment also includes the following configuration. (Configuration 1) a first transport path that receives a sheet discharged from the image forming apparatus and transports the sheet; a first stacking unit that stacks the sheets transported to the first transport path; a first binding processing unit that performs a binding process on an end of a sheet bundle made up of a plurality of sheets accumulated in the first accumulation unit; a stacking section that is movable up and down with respect to the first stacking section and that stacks the sheet bundle that has been bound by the first binding processing section; a second transport path that branches off from the first transport path and transports a sheet in a vertically downward direction relative to the first transport path; a second stacking unit that stacks the sheets transported to the second transport path; a conveying means for conveying a sheet from the first conveying path to the second stacking section; a second binding processing section that performs saddle stitching processing on a sheet bundle consisting of a plurality of sheets accumulated in the second accumulation section; a folding roller pair that sandwiches and conveys the sheet bundle so that the spine of the sheet bundle is located downstream of the end of the fore-edge side, thereby folding the sheet bundle in the middle; and a pressing section that presses the sheet bundle that has been saddle-stitched by the second binding section toward a nip section of the folding roller pair, and a center-folding processing section that performs center-folding on the sheet bundle; a pair of conveying rollers for sandwiching and conveying the sheet bundle that has been center-folded by the center-folding processing unit; a pair of clamping sections that relatively move along a thickness direction of the sheet bundle conveyed by the conveying roller pair to clamp and release the clamping of the sheet bundle; and a pressing roller that moves along a width direction of the sheet bundle in a state in which the spine of the sheet bundle conveyed by the conveying roller pair protrudes downstream in the conveying direction of the conveying roller pair from the pair of clamping sections to press the spine of the sheet bundle clamped by the pair of clamping sections, and a square spine processing section that performs square spine processing to form a corner on the spine of the sheet bundle center-folded by the center-folding processing section, a length of a conveying path from the pair of folding rollers to the pair of clamping units is longer than half the length of a long side of a maximum size sheet that can be folded by the folding unit; A sheet processing device characterized in that, when the conveying roller pair is stopped from conveying the first sheet stack to be subjected to the square spine processing, the conveying means conveys at least one sheet included in a second sheet stack following the first sheet stack toward the second stacking section. (Configuration 2) a third stacking unit that stacks the sheets transported to the first transport path, the third stacking unit is capable of stacking at least one sheet included in the second sheet stack, The sheet processing device described in configuration 1 is characterized in that, when transport by the pair of transport rollers for the first sheet stack is stopped, the transport means transports at least one sheet included in the second sheet stack accumulated in the third stacking section toward the second stacking section. (Configuration 3) the conveying means includes a first conveying section that further conveys the sheet conveyed to the first conveying path toward the third stacking section, and a second conveying section that further conveys the sheet conveyed to the second conveying path toward the second stacking section, The sheet processing device described in configuration 2, characterized in that the first transport section transports the first sheet of the second stack of sheets toward the third stacking section after the last sheet of the first stack of sheets is stacked in the second stacking section. (Configuration 4) a switching member capable of switching a path along which a sheet is transported between the first transport path and the second transport path; the conveying means includes a first conveying section that further conveys the sheet conveyed to the first conveying path toward the third stacking section, and a second conveying section that further conveys the sheet conveyed to the second conveying path toward the second stacking section, the first transport section is capable of transporting a sheet in a first direction and a second direction opposite to the first direction on the first transport path; the switching member is movable between a first guide position at which the sheet transported in the first transport path from an upstream side in the first direction of the second transport path is guided along the first transport path in the first direction, and a second guide position at which the sheet transported in the second direction from a downstream side in the first direction of the second transport path is guided to the second transport path, The third accumulation portion is located downstream of the switching member in the first direction, The sheet processing device described in configuration 2 is characterized in that, when the switching member is located at the first guide position, the first transport section transports a sheet received on the first transport path in the first direction toward the third stacking section, and, when the switching member is located at the second guide position, transports a sheet or a stack of sheets from the third stacking section in the second direction toward the second transport path. (Configuration 5) The sheet processing device described in configuration 4, characterized in that the first transport section transports the last sheet of the first stack of sheets in the second direction toward the second transport path, and after the upstream end of the last sheet in the second direction passes through the switching member and the switching member switches from the second guiding position to the first guiding position, transports the first sheet of the second stack of sheets in the first direction toward the third stacking section. (Configuration 6) a sheet detection unit that detects the presence or absence of a sheet in the second stacking unit, The sheet processing device of any one of configurations 1 to 5, characterized in that the conveying means starts conveying at least one sheet included in the second sheet stack toward the second stacking section based on the timing when the center folding process is started for the first sheet stack stacked in the second stacking section and the sheet detection section detects that there are no sheets in the second stacking section. (Configuration 7) A first virtual line is a line passing through the rotation centers of the pair of folding rollers and a line perpendicular to the width direction that passes through the nip of the pair of folding rollers when the sheet stack is not being sandwiched, and a second virtual line is a line passing through the rotation centers of the pair of conveying rollers and a line perpendicular to the width direction that passes through the nip of the pair of conveying rollers when the sheet stack is not being sandwiched, the conveying roller pair is provided such that the second imaginary line intersects with the first imaginary line and the second imaginary line is inclined downward in a vertical direction toward a downstream of the folding roller pair in a conveying direction, The sheet processing device according to any one of configurations 1 to 6, characterized in that a conveying path for conveying the sheet stack between the folding roller pair and the conveying roller pair is curved so that the sheet stack conveyed by the folding roller pair is handed over to the conveying roller pair. (Configuration 8) The loading section is capable of ascending and descending in a vertical direction, The sheet conveying device described in configuration 7, characterized in that when the lifting area of ​​the stacking section is viewed in a direction perpendicular to the vertical direction and from the downstream side to the upstream side of the sheet conveying direction by the conveying roller pair, the lifting area overlaps with the folding roller pair. (Configuration 9) an image forming unit having an image forming section for forming an image on a sheet; The sheet processing device according to any one of configurations 1 to 8, The image forming system is characterized in that the sheet processing device performs square spine processing on a sheet stack obtained by bundling sheets on which images have been formed by the image forming unit. [Explanation of symbols]

[0147] 3. Image forming section 28 Straight path (first transfer path) 32 Saddle path (second transfer path) 33 Saddle path switching member (switching member) 37 Processing tray 47 Binding processing mechanism (first binding processing section) 49 First tray (loading area) 100···Saddle path roller (second conveying section) 104: Saddle stitch processing section (second stitch processing section) 106···Saddle stack sensor (seat detection part) 112 Center-folding processing section 112a... Veneer (pressing part) 113... Folding roller pair 118....Saddle third roller pair (transport roller pair) 120···Lower clamp unit (clamp section) 121···Upper clamp unit (clamp section) 123 Pressure roller 150···Saddle stack tray (second stacking section) 400··· Stack path (third stacking section) 410....Transport unit (transport means) 411: Conveying roller group (first conveying section) 1000···Image forming system A. Image forming device B Sheet processing device C2: Corner back processing section Sb: Sheet bundle Sb1...1st page Sb2...2nd side

Claims

1. A first transport path receives the sheet discharged from the image forming apparatus and transports the sheet, A first accumulation unit for accumulating sheets transported along the first transport path, A first binding processing unit that performs a binding process on the ends of a sheet bundle consisting of multiple sheets accumulated in the first accumulation unit, A stacking section that is vertically movable relative to the first stacking section and stacks sheet bundles that have been bound in the first binding processing section, A second transport path branches off from the first transport path and transports the sheet in a direction perpendicularly downward relative to the first transport path, A second accumulation unit for accumulating sheets transported along the second transport path, A conveying means for conveying sheets from the first conveying path to the second accumulation section, A second binding processing unit performs a saddle-stitching process on a sheet bundle consisting of multiple sheets accumulated in the second accumulation unit, A folding processing unit that performs a folding process on a sheet bundle includes a pair of folding rollers that grip and transport the sheet bundle so that the spine of the sheet bundle is located downstream of the end on the fore-edge side, and a pressing unit that presses the sheet bundle that has been saddle-stitched in the second saddle-stitching processing unit toward the nip portion of the folding roller pair, A pair of conveying rollers that grip and transport the sheet bundle that has been folded by the aforementioned folding processing unit, A pair of clamping parts that grip and release the sheet bundle by moving relative to each other along the thickness direction of the sheet bundle conveyed by the pair of conveying rollers, and a pressing roller that presses the back of the sheet bundle gripped by the pair of clamping parts by moving along the width direction of the sheet bundle when the back of the sheet bundle conveyed by the pair of conveying rollers protrudes downstream of the pair of clamping parts in the conveying direction of the pair of conveying rollers, and a corner back processing part that gives corners to the back of the sheet bundle that has been folded in the middle processing part, The second accumulation unit includes a sheet detection unit that detects the presence or absence of a sheet, The length of the transport path from the pair of folding rollers to the pair of clamping sections is longer than half the length of the long side of the largest sheet size on which the folding process can be performed by the folding section. A sheet processing apparatus characterized in that, when the sheet detection unit detects that there are no sheets in the second accumulation unit while the first sheet bundle is being held by the pair of clamping units, the conveying means conveys at least one sheet included in the second sheet bundle that follows the first sheet bundle toward the second accumulation unit.

2. The system includes a third accumulation unit for accumulating the sheets that have been transported along the first transport path, The third stacking unit is capable of stacking at least one sheet included in the second sheet bundle, The sheet processing apparatus according to claim 1, characterized in that the conveying means conveys at least one sheet included in the second sheet bundle accumulated in the third accumulation section toward the second accumulation section when the conveying by the conveying roller pair with respect to the first sheet bundle has been stopped.

3. The transport means includes a first transport unit that further transports the sheets transported along the first transport path toward the third accumulation unit, and a second transport unit that further transports the sheets transported along the second transport path toward the second accumulation unit. The sheet processing apparatus according to claim 2, characterized in that the first conveying unit conveys the first sheet of the second sheet bundle toward the third stacking unit after the last sheet of the first sheet bundle has been stacked toward the second stacking unit.

4. The system includes a switching member that can switch the path through which the sheet is transported between the first transport path and the second transport path. The transport means includes a first transport unit that further transports the sheets transported along the first transport path toward the third accumulation unit, and a second transport unit that further transports the sheets transported along the second transport path toward the second accumulation unit. The first transport unit is capable of transporting the sheet in a first direction and a second direction opposite to the first direction along the first transport path. The switching member is movable between a first guide position that guides sheets transported from upstream of the second transport path in the first direction along the first transport path in the first transport path in the first direction, and a second guide position that guides sheets transported from downstream of the second transport path in the first direction in the second transport path to the second transport path. The third accumulation unit is located downstream of the switching member in the first direction, The sheet processing apparatus according to claim 2, characterized in that the first conveying unit conveys the sheets received in the first conveying path toward the third accumulation unit in the first direction while the switching member is positioned in the first guide position, and conveys the sheets or sheet bundles from the third accumulation unit toward the second conveying path in the second direction while the switching member is positioned in the second guide position.

5. The sheet processing apparatus according to claim 4, characterized in that the first conveying unit conveys the last sheet of the first sheet bundle toward the second conveying path in the second direction, the upstream end of the last sheet in the second direction passes the switching member, the switching member switches from the second guide position to the first guide position, and then conveys the first sheet of the second sheet bundle toward the third accumulation unit in the first direction.

6. When a first imaginary line is defined as a line passing through the rotation centers of the folding roller pair and a line perpendicular to the width direction that passes through the nip of the folding roller pair when it is not gripping a sheet bundle, and a second imaginary line is defined as a line passing through the rotation centers of the conveying roller pair and a line perpendicular to the width direction that passes through the nip of the conveying roller pair when it is not gripping a sheet bundle, The transport roller pair is provided such that the second virtual line intersects the first virtual line, and the second virtual line inclins vertically downward as it moves downstream in the transport direction of the transport roller pair. The sheet processing apparatus according to claim 1, characterized in that the conveying path for conveying the sheet bundle between the folding roller pair and the conveying roller pair is bent so that the sheet bundle conveyed by the folding roller pair is handed over to the conveying roller pair.

7. The aforementioned loading section is capable of moving up and down in the vertical direction. The sheet processing apparatus according to claim 6, characterized in that when the lifting and lowering area of ​​the loading section is viewed in a direction perpendicular to the vertical direction and in a direction from the downstream side to the upstream side in the direction of sheet transport by the transport roller pair, the lifting and lowering area overlaps with the folding roller pair.

8. An image forming unit having an image forming section that forms an image on a sheet, A sheet processing apparatus according to any one of claims 1 to 7, comprising: The sheet processing apparatus is an image forming system characterized by performing a corner-back processing on a sheet bundle, which is a bundle of sheets on which images have been formed by the image forming unit.

Images