Sheet processing device and image forming system

Abstract

This configuration provides a way to more effectively correct the skew of the sheet bundle before performing the corner-edge treatment. [Solution] Before performing the corner backing treatment, the contact member 501 corrects the skewness of the sheet bundle by pushing the back of the sheet bundle that protrudes downstream in the conveying direction toward the upper clamp unit 121 and the lower clamp unit 120 toward the upstream in the conveying direction. The skew correction operation is performed multiple times if both of the following conditions are met: first, the number of sheets included in the sheet bundle to be performed the corner backing treatment is equal to or greater than a predetermined number; and second, the difference between the image ratio on one side of the center and the image ratio on the other side of the center in the width direction of the outer surface of the outermost sheet included in the sheet bundle is equal to or greater than a predetermined value. If at least one of the first and second conditions is not met, the skew correction operation is performed once.

Description

Technical Field

[0001] The present invention relates to a sheet processing apparatus that performs a corner backing process on a sheet, and an image forming system including the sheet processing apparatus.

Background Art

[0002] As a sheet processing apparatus, a configuration has been proposed in which, in a state where a folded sheet bundle is clamped by a pair of clamp parts, the back portion of the sheet bundle protruding from the clamp parts is pressed by a roller to form a corner on the back of the sheet bundle (hereinafter, corner backing process) (Patent Document 1). Further, Patent Document 1 describes that by conveying the sheet bundle by a conveyance belt in a state where the back of the sheet bundle is abutted against a reference member, skew correction of the sheet bundle is performed before the corner backing process.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the case of the configuration described in Patent Document 1, there are cases where sufficient skew correction cannot be performed depending on the number of sheets in the sheet bundle or the state of the image on the sheet bundle.

[0005] An object of the present invention is to provide a configuration capable of more sufficiently performing skew correction of a sheet bundle before performing a corner backing process.

Means for Solving the Problems

[0006] One aspect of the present invention includes a pair of conveying rotating bodies for conveying sheet bundles that have been saddle-stitched and folded so that the spine of the sheet bundle is located downstream in the conveying direction from the fore-edge; 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 rotating bodies; and a pressing roller that presses the spine of the sheet bundle by moving along the width direction of the sheet bundle, wherein the back of the sheet bundle is pressed by the pressing roller with respect to the pair of clamping parts when the back of the sheet bundle is protruding downstream relative to the pair of clamping parts in the conveying direction, thereby performing a corner back treatment on the back of the sheet bundle; a skew correction member located downstream of the pair of clamping parts in the conveying direction, which corrects the skew of the sheet bundle by pushing the back of the sheet bundle that protrudes downstream in the conveying direction relative to the pair of clamping parts toward the upstream direction in the conveying direction before performing the corner back treatment; and during the operation of correcting the skew of the sheet bundle The sheet processing apparatus further comprises a moving mechanism for moving the skew correction member toward the upstream side in the transport direction, wherein the skew correction operation includes a series of operations: an operation to grip and transport the sheet bundle with the pair of transport rotating bodies, an operation to stop the transport of the sheet bundle by the pair of transport rotating bodies, an operation to release the grip of the sheet bundle by the pair of transport rotating bodies, and an operation to push the back of the sheet bundle with the skew correction member, and is characterized in that the skew correction operation is performed multiple times if both of the following conditions are met: a first condition that the number of sheets included in the sheet bundle to be subjected to the corner back processing is a predetermined number or more, and a second condition that the difference between the image ratio on one side of the center and the image ratio on the other side of the center with respect to the width direction intersecting the transport direction in the outer surface of the outermost sheet included in the sheet bundle is a predetermined value or more, and the skew correction operation is performed once if at least one of the first and second conditions is not met. [Effects of the Invention]

[0007] According to the present invention, the skew correction of the sheet bundle can be performed more effectively before the corner-back processing is carried out. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic cross-sectional view of the image forming system according to the embodiment. [Figure 2] A schematic cross-sectional view of the sheet processing apparatus according to the embodiment. [Figure 3] A control block diagram of the image forming system according to the embodiment. [Figure 4] Enlarged cross-sectional view of the saddle portion according to the embodiment. [Figure 5] Front view of the corner back section according to the embodiment. [Figure 6] (a) Perspective view and (b) Cross-sectional view of the corner back processing unit according to the embodiment. [Figure 7] (a) A perspective view of the corner back section according to the embodiment, viewed from the front, and (b) A perspective view of the rear. [Figure 8] A perspective view showing a part of the corner back processing unit and drive unit according to an embodiment. [Figure 9] A perspective view of the corner back processing unit and the vicinity of the clamping portion according to the embodiment. [Figure 10] Cross-sectional view of the corner back processing unit and clamp section according to the embodiment. [Figure 11] A perspective view of the oblique correction unit and clamp section according to an embodiment. [Figure 12] (a) A perspective view of the oblique correction unit, (b) A plan view of the oblique correction unit and the corner back processing unit, and (c) A cross-sectional view of the oblique correction unit and the corner back processing unit, showing the contact member according to the embodiment in a standby position. [Figure 13] (a) A perspective view of the oblique correction unit, (b) A plan view of the oblique correction unit and the angled back section, and (c) A cross-sectional view of the oblique correction unit and the angled back section, showing the contact member according to the embodiment in a contact position. [Figure 14] (a) A perspective view of the oblique correction unit, and (b) A cross-sectional view of the oblique correction unit and the corner back processing unit, showing the state in which the contact member according to the embodiment has moved to the upstream side in the transport direction at the contact position. [Figure 15]In the operation of the skew correction process according to the embodiment, cross-sectional views around the intermediate conveyance path schematically showing (a) the state where the conveyance of the sheet bundle is stopped and (b) the state where the contact member pushes back the sheet bundle, respectively. [Figure 16] In the operation of the corner folding process in the embodiment, schematic views showing (a) the state where the conveyance of the sheet bundle is stopped by the clamp part, (b) the state where the sheet bundle is clamped, (c) the state where the corner folding process is being performed on the sheet bundle, and (d) the state where the clamping of the sheet bundle is released, respectively. [Figure 17] A flowchart showing an example of the control of the skew correction process and the corner folding process according to the embodiment. [Embodiments for Carrying out the Invention]

[0009] The embodiment will be described with reference to FIGS. 1 to 17. First, the schematic configuration of the image forming system of the present embodiment will be described with reference to FIG. 1.

[0010] [Image Forming System] In the present embodiment, a copying machine is used as the image forming apparatus, a sheet processing apparatus is connected to the sheet discharge port of this copying machine, and a saddle part for performing intermediate binding and intermediate folding is further provided inside the sheet processing apparatus. The image forming system 1000 includes an image forming apparatus A and a sheet processing apparatus B, receives the sheet S on which an image is formed by the image forming apparatus A by the downstream sheet processing apparatus B, performs intermediate binding processing, intermediate folding processing, corner folding processing, etc. as necessary, and discharges it to the downstream discharge part. The image forming apparatus A includes various structures such as, for example, a copying machine, a printer, a printing machine, a facsimile machine, and a multifunction machine having a plurality of these functions. Hereinafter, the image forming apparatus A and the sheet processing apparatus B will be described in detail. In the following description, for the image forming apparatus A and the sheet processing apparatus B, the side where an operator such as a user operates the apparatus (for example, the side where there is an operation panel or operation buttons) is referred to as the front side (the front side of the paper surface in FIGS. 1, 2, etc.), and the side opposite to the front side is referred to as the rear side (the back side of the paper surface in FIGS. 1, 2, etc.).

[0011] [Image Forming Apparatus] As shown in FIG. 1, the image forming apparatus A includes an image forming unit A1, an image reading unit A2, and an original document feeding unit A3. The image forming unit A1 includes a feeding unit 2, an image forming unit 3, a discharging unit 4, and a data processing unit 5 in a housing 1.

[0012] The feeding unit 2 includes a plurality of cassettes 2a, 2b, and 2c. Each of the cassettes 2a, 2b, and 2c can store a plurality of sheets S of different standard sizes selected in advance in multiple stages. The sheet S is, for example, paper, a plastic sheet, or the like. Each of the cassettes 2a, 2b, and 2c is provided with a separating mechanism for separating the internal sheets S one by one and a feeding mechanism for feeding out the sheets S. The sheet S stored in the feeding unit 2 configured as described above feeds out a sheet 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 a conveying roller 7. The sheet conveyed by the conveying roller 7 has its leading edge aligned by a registration roller pair 8, and skew is corrected. Then, the sheet S with its leading edge aligned by the registration roller pair 8 is fed to the downstream image forming unit 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 composed of an optional unit for storing sheets of a size that is consumed in large quantities. The manual feed tray 2e is configured to be able to supply special sheets such as thick paper sheets, coated sheets, and film sheets for which separation feeding is difficult.

[0014] The image forming unit 3 only needs to be configured to form an image on the sheet S sent from the feeding unit 2, and various image forming mechanisms can be adopted. 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 an inkjet image forming mechanism, an offset image forming mechanism, or the like can also be adopted.

[0015] The image forming unit 3 shown in Figure 1 includes a photoreceptor 9 formed in the shape of a drum or belt, an exposure device 10 for exposing the photoreceptor 9, a developing device 11 for developing the photoreceptor 9 using toner, a charging device (not shown) for charging the photoreceptor 9, and a cleaner (not shown) for cleaning the photoreceptor 9. Figure 1 shows a monochrome printing mechanism as an example. The photoreceptor 9 is exposed by the exposure device 10 to form an electrostatic latent image, and the electrostatic latent image is developed by the developing device 11 to form a toner image on the photoreceptor 9. The toner image formed on the photoreceptor 9 is transferred by the transfer device 12 to a sheet S transported from the registration roller pair 8. The sheet S on which the toner image has been transferred is fixed by the fixing device 13. The image forming unit A is also provided with an inversion transport path, which inverts the sheet S on which the toner image has been fixed by the fixing device 13, and then sends it back to the registration roller pair 8 to form an image on the back side of the sheet S. Downstream of the fixing device 13 and downstream of the branch to the reversal transport path, a discharge roller 15 is provided, and the sheet S is transported from the discharge port 16 of the image forming apparatus A to the sheet processing apparatus B, which will be described later, by the discharge roller 15.

[0016] An image reading unit A2, which optically reads the original image, is provided at the top of the image forming unit A1 configured in this way, and a document feeding unit A3 is mounted even higher up on the image reading unit A2.

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

[0018] The document feeding unit A3 comprises a feeding tray 22 and an output tray 24. It transports documents placed on the feeding tray 22 one by one, passes them over the second platen glass 21, and outputs them to the output tray 24. When scanning documents fed from the document feeding unit A3 and passing over the second platen glass 21, the scanning carriage 18 is stopped in advance below the second platen glass 21, and image data is read from the image passing over the second platen glass 21.

[0019] [Overall configuration of the sheet processing device] Next, the overall configuration of the sheet processing device B, which performs processing such as stapling and folding on sheets transported from the image forming apparatus A, will be explained using Figure 2. Figure 2 shows the detailed configuration of the sheet processing device B. After processing the sheets received by the sheet processing device B from the receiving section 26, which is the entrance to the transport path 28 connected to the discharge port 16 of the image forming apparatus A, the sheets can be loaded onto the first tray (first loading tray) 49, the saddle discharge unit 131, and the second tray (second loading tray) 71, which will be described later. In this embodiment, the term "path" refers to the entire route through which the sheets are transported by transport guides, transport rollers, etc.

[0020] In the illustrated apparatus, sheets sent to the transport path and the transport path 28, which is the first transport path, are discharged to the first tray 49 after processing by the processing unit B1 described later, or sheets transported along the transport path 28 are discharged to the second tray 71, or sheets are discharged to the saddle discharge unit 131 after processing by the saddle unit B2 described later. Each device has a control unit, a communication unit, etc., as shown in the block illustrating the control configuration of the entire apparatus in Figure 3, and controls the apparatus.

[0021] The processing unit B1, which functions as an end-binding processing unit, is located below the exit (transfer section 35) of the transport path 28. It aligns and stacks multiple sheets sequentially transferred from the transport path 28 via the transfer section 35 to form a sheet bundle, and can perform binding on the ends of this sheet bundle, which is an example of a predetermined process. The bound sheet bundle is loaded onto the first tray 49, which functions as a loading section. The sheets or sheet bundles loaded onto the first tray 49 have their rear ends (upstream ends) abut against the loading wall 50 on the upstream side in the sheet discharge direction of the first tray 49, and are loaded along the loading wall 50.

[0022] The first tray 49 is movable up and down relative to the processing tray 37, which will be described later, and loads sheet bundles that have been bound by the binding mechanism 47, which will be described later. In this embodiment, the first tray 49 and the second tray 71 are movable up and down by a lifting mechanism (not shown). That is, in this embodiment, when sheets are fed to the first tray 49 and the second tray 71 as loading trays, the first tray 49 and the second tray 71 are moved up and down in order to keep the position of the uppermost sheet on the loading surface of the tray constant relative to the discharge roller pair 42 and the second discharge roller 207 so as not to reduce the alignment of the loaded sheets.

[0023] The saddle section B2 is located below the transfer section of the saddle path 32, which is a second transport path branching vertically downward from the transport path 28. Multiple sheets that are sequentially transferred from the transport path 28 via the saddle path 32 and the transfer section are aligned and stacked to form a sheet bundle, which is then saddle-stitched or folded without saddle-stitching before being discharged to the saddle discharge unit 131. The details of each component will be described below.

[0024] [housing] As shown in Figure 2, the sheet processing apparatus B comprises a housing 27, a transport path 28, a processing unit B1, a saddle unit B2, a first tray 49, a saddle discharge unit 131, a second tray 71, and the like. The transport path 28, processing unit B1, and saddle unit B2 are located inside the housing 27. The transport path 28 also has a sheet receiving section 26 and a sheet transfer section 35. The processing unit B1 and saddle unit B2 process the sheets transferred from the transfer section 35 of the transport path 28. The first tray 49, saddle discharge unit 131, and second tray 71 load the sheets sent from each processing unit. The illustrated housing 27 is connected to the housing 1 of the image forming apparatus A, which is located upstream of the sheet transport direction in the transport path 28. The housing 27 and housing 1 are positioned such that their heights from the installation surface of the discharge port 16 of the image forming apparatus A and the receiving section 26 of the sheet processing apparatus B are approximately the same, and the discharge port 16 and the receiving section 26 are connected.

[0025] [Sheet delivery route] The transport path 28, which is the sheet loading route, is a substantially straight path that crosses the housing 27 in a substantially horizontal direction and includes a receiving section 26 connected to the discharge port (main body discharge port) 16 of the image forming apparatus A, and a transfer section 35 located on the opposite side across the apparatus from the receiving section 26. The transport path 28 is equipped with an inlet roller 29, a first transport roller 201, a second transport roller 202, and a third transport roller 203, which are transport rollers capable of transporting sheets in a first direction from the receiving section 26 toward the first discharge path 31, and in a second direction from the first discharge path 31 toward the receiving section 26. In other words, the inlet roller 29, the first transport roller 201, the second transport roller 202, and the third transport roller 203 are capable of transporting sheets in a first direction and a second direction opposite to the first direction along the transport path, and are arranged in order from the receiving section 26 side toward the first direction.

[0026] The first discharge path 31 is connected to the transfer section 35 of the transport path 28, and a first transport roller 36 is positioned at this connection section. Sheets are transferred from the transport path 28 to the first discharge path 31, and the sheets discharged from the first discharge path 31 are either loaded onto the first tray 49 or guided to the processing unit B1. Note that the above-mentioned transport rollers may be other components capable of transporting sheets, such as transport belts.

[0027] [Layout of the sheet delivery route] As shown in Figure 2, the transport path 28 is connected to branch paths, the saddle path 32 and the upper transport path 30. The saddle path 32 and the upper transport path 30 are arranged sequentially from the receiving section 26 toward the first discharge path 31 in the first direction. The saddle path 32 branches off vertically downward from the transport path 28, and the upper transport path 30 branches off vertically upward from the transport path 28. At the branching points of the transport path 28 and the saddle path 32 and upper transport path 30, respectively, a saddle path switching member 33 and an upper transport path switching member 34 are provided to switch the transport direction of the transported sheets.

[0028] [Methods for branching paths] The upper transport path switching member 34 is composed of a switching guide that moves to change the transport path so that the sheet brought in from the receiving section 26 is transported to either the first discharge path 31 or the upper transport path 30, and is moved by a drive unit (not shown) such as an electromagnetic solenoid or a mini motor.

[0029] [Upper transport path] The upper transport path 30 (printout transport path), which transports sheets other than those to be transported to the first transport path 31, branches off from the transport path 28, and the branching point is equipped with an upper transport path switching member 34 for guiding the sheets to the upper transport path 30. The upper transport path 30 is also equipped with a fourth transport roller 204, a fifth transport roller 205, a sixth transport roller 206, and a second transport roller 207 as transport rollers for guiding the sheets to the second tray 71. As a result, the sheets guided to the upper transport path 30 are transported from the upper transport path discharge port 40 to the second tray 71 (overflow tray).

[0030] The processing unit B1 consists of a processing tray 37, which serves as a loading unit for placing sheets transported along the first discharge path 31 downstream of the transport path 28 and for aligning and accumulating multiple sheets, and a binding mechanism 47 for binding the accumulated sheet bundles. The processing unit B1 then performs binding on the sheet bundles placed on the processing tray 37. The binding mechanism 47 is positioned vertically below the transport path 28. As shown in Figure 2, the processing tray 37 is positioned below the first discharge path 31, forming a step. Between the first discharge path 31 and the processing tray 37, there is a first switchback path that guides the sheets onto the processing tray 37 by changing the transport direction in the reverse direction while a portion of the sheets are discharged from the discharge port 31a of the first discharge path 31 to the first tray 49.

[0031] Specifically, the first discharge path 31 is equipped with an upper conveyor roller 41 and a lower conveyor roller 48 that grip and transport the sheet. The upper conveyor roller 41 and the lower conveyor roller 48 constitute a discharge roller pair 42 as a discharge section. The upper conveyor roller 41 can come into contact with and separate from the lower conveyor roller 48, and the upper conveyor roller 41 and the lower conveyor roller 48 can transport the sheet toward the first tray 49 and in the opposite direction while gripping the sheet. The upper conveyor roller 41 and the lower conveyor roller 48 can then transport 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 sheets or bundles of sheets on the processing tray 37 from the discharge port 31a to the first tray 49, which serves as a loading tray (loading section). The discharge port 31a is a portion of the housing 27 that opens above the lower conveying roller 48. In addition, the discharge roller pair 42 discharges the sheets that have been transported to the first discharge path 31 without passing through the processing tray 37 to the first tray 49 from the discharge port 31a.

[0033] The binding mechanism 47 has a rear end regulating section 47a that contacts the end (rear end) of the sheet to position the sheet. A scraping section 38 is arranged on the processing tray 37 that conveys the sheets conveyed to the processing tray 37 by the upper conveying roller 41 and the lower conveying roller 48 toward the rear end regulating section 47a. The binding mechanism 47 then performs binding on the end of a sheet bundle consisting of multiple sheets placed on the processing tray 37, the position of which is regulated by the rear end regulating section 47a. The binding mechanism 47 also has a sheet bundle discharge mechanism that discharges the sheet bundle to the first tray 49 after performing binding on the end of the sheet bundle.

[0034] Furthermore, the binding mechanism 47 shown in Figure 2 supports the sheet sent from the first discharge path 31 so that it straddles the processing tray 37 and the first tray 49 downstream of it. In other words, the leading edge of the sheet sent from the first discharge path 31 is supported on the uppermost sheet of the first tray 49 downstream, and the rear end is supported on the processing tray 37.

[0035] [Saddle Pass] The transport path 28 is connected to a saddle path 32 for transporting sheets to the saddle section B2 described above, and the path branching section is equipped with a saddle path switching member 33 for guiding sheets to the saddle path 32. Sheets guided to the saddle section B2 by the saddle path 32 undergo a folding process, and after the folding process, are discharged to the saddle discharge unit 131 via a post-folding path guide 114, a post-second roller path guide 116, a pre-clamp guide 119, and a saddle discharge guide 124. In this embodiment, the saddle discharge guide 124, which serves as a discharge guide, is used as an auxiliary guide to ensure that sheets are properly loaded into the saddle discharge unit 131.

[0036] [Control Configuration] Using Figure 3, the control configuration of the image forming system 1000 will be outlined. First, the image forming apparatus A has a control unit 310, an operation unit 302, a transport 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 part while reading programs corresponding to control procedures stored in the ROM 312. In addition, the RAM 313 stores work data and input data, and the CPU 311 controls by referring to the data stored in the RAM 313 based on the aforementioned programs, etc.

[0037] The operation unit 302 is connected to the control unit 310 and is, for example, an operation panel provided in the image forming apparatus A, where the operator performs the operation of the apparatus and various settings. The transport control unit 303 controls the various transport rollers and switching members that switch transport paths for transporting sheets in the image forming apparatus A. The image processing unit 304 controls the image forming unit 3. The drive unit 305 controls various motors and power supplies. The communication unit 306 connects the control unit 310 to external devices 301 such as a personal computer and the communication unit 321 of the sheet processing apparatus B so that they can communicate with each other.

[0038] The sheet processing apparatus B includes a stacker control unit 330, a transport control unit 322, an edge binding control unit 323, an discharge processing control unit 324, and a communication unit 321. The stacker control unit 330, like the control unit 310, includes a CPU 331, a ROM 332, and a RAM 333. The transport control unit 322 controls various transport rollers and switching members that switch transport paths for transporting sheets in areas other than the saddle section B2 of the sheet processing apparatus B. The edge binding control unit 323 controls the processing unit B1. The discharge processing control unit 324 controls the discharge of sheets and various loading trays on which the discharged sheets are stacked. The communication unit 321 connects the stacker control unit 330 to the communication unit 306 of the image forming apparatus A and the communication unit 341 of the saddle section B2 so that they can communicate with each other. Communication between the communication unit 306 and the communication unit 321 may be performed by wired communication or wireless communication.

[0039] The saddle unit B2 includes a saddle control unit 350, a transport control unit 342, a saddle stitching control unit 343, a center folding control unit 344, a corner spine processing control unit 345, and a communication unit 341. The saddle control unit 350, like the control unit 310, includes a CPU 351, a ROM 352, and a RAM 353. The transport control unit 342 controls the various transport rollers and switching members that switch transport paths for transporting sheets in the saddle unit B2. 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 corner spine processing control unit 345 controls the corner 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 to enable communication.

[0040] In this embodiment, the saddle control unit 350 communicates with the stacker control unit 330 via the communication unit 341 and the communication unit 321, but a configuration in which each unit is controlled by a common control unit is also possible. Furthermore, in this embodiment, the configuration for controlling the sheet processing device B includes a transport control unit 322, an edge binding control unit 323, an discharge processing control unit 324, a stacker control unit 330, and a saddle control unit 350, but a configuration in which each unit is controlled by a single control unit is also possible. In this embodiment, the saddle control unit 350 is given as an example of a control means, but as described above, if control is performed using a common control unit with other control units, that common control unit becomes an example of a control means.

[0041] [Saddle section] The saddle section B2 will be explained using Figures 2 and 4. The saddle section B2 has a center-folding mechanism C1 and a corner-back processing section C2. The center-folding mechanism C1 aligns and stacks the sheets sent from the transport path 28 to form a sheet bundle, performs a binding process at the center of the sheet bundle in the transport direction (the middle part in the second transport direction, which is the transport direction of the saddle path roller 100 as the second transport section, as described later), and performs a center-folding process to fold the sheet bundle at the bound position. The corner-back processing section C2 is located downstream of the center-folding mechanism C1 in the transport direction of the sheet bundle (downstream of the first transport direction, which is the transport direction of the saddle third roller pair 118 as the first transport section, as described later), and performs a corner-back processing to create a crease on the spine of the center-folded sheet bundle. A saddle discharge unit 131 is located downstream of the corner-back processing section C2 in the first transport direction, and loads the bound sheet bundles. Furthermore, it is also possible to assemble one or more sheets and perform only a center-folding process, which involves folding the center of the sheet in the direction of transport, without saddle stitching or corner-spine finishing.

[0042] [Folding mechanism] The center folding mechanism C1 includes a front-end regulating stopper 109, a saddle-stitching processing unit (saddle-stitching staple unit) 104, and a center folding processing unit 112, and stacks sheets into bundles, performs center folding, and saddle-stitching. Specifically, sheets transported from the transport path 28 to the saddle path 32 are transported by the saddle path roller 100 to the stacking section and the saddle stack tray 150, which serves as a second stacking section. The saddle stack tray 150 stacks multiple sheets transported in the second transport direction by the saddle path roller 100 via the saddle path 32 to form a sheet bundle. The sheet bundles stacked in the saddle stack tray 150 are positioned at a predetermined position on the saddle stack tray 150 by the front-end regulating stopper 109. The saddle-stitching processing unit 104 performs stapling on the center of the sheet bundle in the transport direction (intermediate part in the second transport direction) positioned by the front-end regulating stopper 109. The center folding processing unit 112 has a veneer plate 112a and a pair of folding rollers 113. The veneer plate 112a is used to press the sheet bundle near the position where the sheet bundle was bound by the saddle stitching processing unit 104 (the center of the sheet bundle in the transport direction), while the sheet bundle is transported by the pair of folding rollers 113, thereby folding the sheet bundle so that the back of the sheet bundle is on the downstream side in the transport direction.

[0043] The saddle stitching unit 104 is a mechanism that performs saddle stitching by moving the sheet bundle along the center (line) of the sheet while it is sandwiched between the head unit and the anvil unit. The center folding unit 112, as shown in Figures 2 and 4, employs a configuration in which the sheet bundle is inserted into the nip of a pair of folding rollers 113 that are pressed against each other by a veneer plate 112a, and the sheet bundle is conveyed while being folded by the rotation of the pair of folding rollers 113.

[0044] [Back and corner treatment area] The corner-back processing unit C2 performs a corner-back processing on the sheet bundle to create a corner-back shape along the fold (line) of the folded sheet bundle. The corner-back processing unit C2 comprises a lower clamp unit 120 and an upper clamp unit 121 as a pair of clamping units, and a corner-back processing unit 134 having a pressing roller 123. The lower clamp unit 120 and the upper clamp unit 121 clamp and release the sheet bundle by moving relative to each other along the thickness direction of the sheet bundle conveyed by the saddle third roller pair 118, which will be described later. The pressing roller 123 presses the back of the sheet bundle by moving along the width direction of the sheet bundle (a direction perpendicular to the conveying direction of the sheet bundle, in the direction of the rotation axis of the saddle third roller pair 118, the front and back direction in Figures 2 and 4). The corner-shaping section C2 then performs a corner-shaping process on the back of the sheet bundle by pressing the back of the sheet bundle, which is held between the lower clamp unit 120 and the upper clamp unit 121, with the pressing roller 123 in the first transport direction, with the back of the sheet bundle protruding downstream from the lower clamp unit 120 and the upper clamp unit 121. The above-mentioned "corner" includes curved surfaces and refers to the boundary between the front cover and the spine of the sheet bundle, and the boundary between the spine and the back cover.

[0045] Specifically, the corner back processing unit C2 clamps a portion of the sheet bundle from both sides in the vertical direction (thickness direction of the sheet bundle) with respect to the back of the sheet bundle that has been folded in the middle by the middle folding processing mechanism C1, with the back of the sheet bundle protruding downstream in the first conveying direction. The pressing roller 123 presses the back of the sheet bundle, which is clamped by the lower clamp unit 120 and the upper clamp unit 121, while moving along the width direction of the sheet bundle, which is perpendicular to the conveying direction and the thickness direction of the sheet bundle, toward the lower clamp unit 120 and the upper clamp unit 121. In this way, the corner back processing unit C2 performs corner back processing to create corners on the back of the sheet bundle. Corner back processing is a process in which the back of the sheet bundle, as shown in Figures 16(a) and (b) described later, is crushed by the pressing roller 123 to form two grooves on the back of the sheet bundle, as shown in Figures 16(c) and (d), thereby forming two corners on the back of the sheet bundle. Two corners are formed on the spine of the sheet bundle at positions that hold the staples driven in during the saddle stitching process by the saddle stitching processing unit 104, in the thickness direction of the sheet bundle. Additionally, the two corners formed on the spine of the sheet bundle are formed at positions that hold the fold created during the saddle folding process by the saddle folding processing unit 112.

[0046] Furthermore, a folding and conveying mechanism is positioned between the folding mechanism C1 and the corner back processing mechanism C2 to transport and stop the sheet bundle that has been folded in the folding mechanism C1 to the downstream corner back processing mechanism C2.

[0047] As described above, the processing unit B1 and the transport path 28 are arranged in a substantially horizontal direction, the saddle path 32 that guides the sheet to the saddle section B2 is arranged in a substantially vertical direction, and the saddle stack tray 150 that aligns and stacks the sheets is arranged to follow a substantially vertical direction. By arranging the transport path 28 along a direction that crosses the housing 27 in this way, and arranging the saddle path 32 and the saddle section B2 along a substantially vertical direction, it is possible to reduce the horizontal width (size) of the device.

[0048] A saddle discharge unit 131 is positioned downstream of the saddle section B2 in the direction of conveying the sheet bundles, and stores the sheet bundles processed by the saddle section B2. The saddle discharge unit 131 shown in the figure is positioned vertically below the first tray 49.

[0049] [Saddle section configuration] Next, we will explain in more detail the components of the saddle section B2: the folding mechanism C1, the folding and transporting mechanism C3, and the corner back processing section C2.

[0050] [Details of the folding mechanism] As shown in Figure 2, the saddle path switching member 33 guides the sheet to the center folding mechanism C1 by switching to transport the sheet to the saddle path 32. With respect to the height direction of the center folding mechanism C1, the following are arranged in order from the upper vertical side (upstream side), which is the entrance side: saddle entrance roller 101, sorting tap 102, rear end pressing guide 103, saddle stitching processing section 104, pull-in separation roller 105, center folding processing section 112, first alignment roller 107, second alignment roller 108, front end regulating stopper 109, and front end gripper 110.

[0051] The saddle inlet roller 101 further transports the sheets received from the saddle path 32 by the saddle path roller 100 downwards. Upstream of the saddle inlet roller 101, an inlet sensor 190 is provided to detect when a sheet has reached the saddle path 32. The sorting beater 102 moves the sheets transported downwards from the saddle inlet roller 101 to the right side in Figure 2 and stacks the sheets in the saddle stack tray 150. The rear end pressing guide 103 holds down the rear end of the sheets stacked in the saddle stack tray 150. The saddle stitching processing unit 104 performs stitching on the center of the sheet bundle in the transport direction in the saddle stack tray 150. The pull-in separation roller 105 assists in the transport of the sheets transported to the saddle stack tray 150 and is a roller that pulls the sheets toward the front end restricting stopper 109. The retraction and separation roller 105 is positioned to be able to contact and separate from the opposing roller 105a.

[0052] The center folding section 112 includes a folding roller pair 113, a veneer plate 112a as a pressing part, and a roller guide 111. The folding roller pair 113 forms a fold in the center folding process. The veneer plate 112a pushes the sheet into the nip portion of the folding roller pair 113. The roller guide 111 covers the folding roller pair 113. The first alignment roller 107 and the second alignment roller 108 transport the sheets that have been conveyed to the saddle stack tray 150 and also perform alignment processing in the height direction of the sheets. The tip regulating stopper 109 determines the height position of the tip of the sheet by abutting against the tip (lower end) of the sheet that has been conveyed. The tip gripper 110 holds down the tip (lower end) of the sheet that has been loaded onto the tip regulating stopper 109.

[0053] The saddle inlet roller 101 and the retraction / separation roller 105 are driven by the same motor. The rear end press guide 103 is positioned opposite the sorting tap 102, with the saddle stack tray 150 in between. The saddle stitching unit 104 is located downstream of the sorting tap 102 and the rear end press guide 103, and upstream of the retraction / separation roller 105.

[0054] The sheets transported from the saddle path 32 to the saddle section B2 are carried by the saddle entrance roller 101 to the tip regulating stopper 109, which has been moved to a position appropriate to the sheet size. The pull-in / separation roller 105 has an auxiliary transport function to accurately transport the sheets in transit to the tip regulating stopper 109 located in the saddle stack tray 150. At this time, the folding roller pair 113 is covered by the roller guide 111 to prevent the leading edge of the sheet from getting caught on the folding roller pair 113 and to transport it efficiently.

[0055] The first alignment roller 107 and the second alignment roller 108 accurately abut the conveyed sheet against the front-end regulating stopper 109, performing alignment processing in the sheet height direction.

[0056] The sorting and beating machine 102 moves the sheet that has been transported to the front regulating stopper 109 towards the rear end holding guide 103, and holds down the rear end (upper end) of the sheet that has been moved with the rear end holding guide 103, thereby preparing to receive the next sheet. At this time, the rear end holding guide 103 moves to a position according to the size and waits.

[0057] The leading edge (lower end) of the sheet bundle formed by stacking a predetermined number of sheets on the saddle stack tray 150 is secured by the leading edge gripper 110. In this state, the saddle stitching section 104 performs a stitching process on the center of the sheet bundle in the second transport direction. After the stitching process, the leading edge regulating stopper 109 is lowered while the leading edge (lower end) of the sheet bundle is still held by the leading edge gripper 110. At this time, the leading edge regulating stopper 109 is lowered so that the position where the veneer 112a is pressed against the folding roller pair 113 is at half the size of the sheet, thereby lowering the sheet bundle from the stitching position.

[0058] When performing the center-folding process, the roller guide 111 is retracted, the tip gripper 110 is released, and then the center of the sheet bundle is folded with the veneer 112a and pushed into the nip portion of the roller pair 113. This completes the center-folding process of the sheet bundle.

[0059] The saddle inlet roller 101, the pull-in / separation roller 105, the sorting tapper 102, and the rear end pressing guide 103 are controlled by the transport control unit 342 (Figure 3). The front end restricting stopper 109, the front end gripper 110, the saddle stitching processing unit 104, the first alignment roller 107, and the second alignment roller 108 are controlled by the saddle stitching control unit 343 (Figure 3). Furthermore, the folding roller pair 113 and the veneer 112a are controlled by the saddle folding control unit 344 (Figure 3).

[0060] [Folding and transport mechanism] The configuration of the center-fold conveying mechanism C3 will be explained using Figures 2 and 4. The center-fold conveying mechanism C3 is a mechanism that transfers the sheet bundle that has been folded in the center-folding processing mechanism C1 to the corner-back processing processing mechanism C2. Specifically, the center-fold conveying mechanism C3 first transports the center-folded sheet bundle using the folding roller pair 113 so that the back of the sheet bundle is located downstream of the end in the conveying direction, and then transfers the sheet bundle to the post-folding path guide 114. The post-folding path guide 114 is positioned along a direction (here, approximately horizontal) that bends vertically downward with respect to the folding roller conveying direction 113c (Figure 2), which is in the direction of a perpendicular line (the first imaginary line α2 described below, Figure 4) passing through the rotation centers of each roller of the folding roller pair 113 as the first conveying roller pair, and is positioned downstream of the folding roller pair 113 in the conveying direction.

[0061] Here, as shown in Figure 4, the first imaginary line α2 is defined as a straight line passing through the nip of the folding roller pair 113 when it is not gripping a sheet bundle, and is perpendicular to the width direction (the direction perpendicular to the conveying direction of the sheet bundle, the front and back direction in Figures 2 and 4), and passing through the nip of the folding roller pair 113 when it is not gripping a sheet bundle. In this case, the folding roller pair 113 is arranged such that the first imaginary line α2 is parallel to the horizontal direction or inclined vertically upward as it moves downstream in the conveying direction relative to the horizontal direction. In this embodiment, the first imaginary line α2 is inclined vertically upward as it moves downstream in the conveying direction relative to the horizontal direction. On the other hand, the post-folding path guide 114 extends in a direction inclined with respect to the first imaginary line α2, and in this embodiment, it extends in a substantially horizontal direction.

[0062] The folded path guide 114 guides the conveyance of the sheet bundle and leads it to the saddle second roller pair 115 located downstream in the conveyance direction. The saddle second roller conveyance direction 115c, which is along the perpendicular line to the line passing through the rotation center of each roller of the saddle second roller pair 115, is arranged to descend vertically as it moves downstream in the conveyance direction. The saddle second roller pair 115, as a pair of conveying rotating bodies (a pair of conveying rollers), is driven by the mid-fold control unit 344 to convey the sheet bundle.

[0063] The sheet bundles conveyed by the saddle second roller pair 115 are passed to the second roller post-path guide 116, which is located downstream in the conveying direction and parallel to the saddle second roller conveying direction 115c (Figure 2), and are guided by the second roller post-path guide 116. The second roller post-path guide 116 also has a second roller post-path lower guide (lower guide portion) 116a having a lower guide surface 116a1 that guides the lower surface of the sheet bundle, and a second roller post-path upper guide (upper guide portion) 116b having an upper guide surface 116b1 that guides the upper surface of the sheet bundle.

[0064] The second roller post-path guide 116 guides the sheet's transport and leads it to the saddle third roller pair 118 located downstream in the transport direction. The saddle third roller transport direction 118c (Figure 2), which is along the perpendicular line (second imaginary line β2, described below, Figure 4) to the line passing through the rotation centers of each roller of the saddle third roller pair 118, is arranged in a direction that slopes downward vertically as it moves downstream in the transport direction. A saddle transport sensor 117 is located downstream of the saddle third roller pair 118 in the transport direction and between the sheet bundle receiving port and the sheet bundle discharge port. This saddle transport sensor 117 detects the position of the leading edge of the sheet bundle. In this embodiment, the saddle transport sensor 117 is located downstream of the saddle third roller pair 118 with respect to the transport direction and upstream of the lower clamp unit 120 and the upper clamp unit 121.

[0065] The saddle third roller pair 118, acting as a pair of conveying rotating bodies (a pair of conveying rollers), is driven by the center-folding control unit 344 and grips and conveys sheet bundles that have undergone saddle stitching and center-folding processing so that the spine of the sheet bundle is positioned downstream of the end 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 leads. If the direction in which the sheet bundle is conveyed by the saddle third roller pair 118 is defined as the first conveying direction (saddle third roller conveying direction 118c), the saddle pass roller 100 that conveys the sheet to the center-folding processing mechanism C1 is positioned upstream of the saddle third roller pair 118 in the first conveying direction. The saddle pass roller 100 then conveys the sheet in a second conveying direction, which is different from the first conveying direction, upstream of the saddle third roller pair 118 in the first conveying direction. In the following, the upstream and downstream sides of the first conveying direction (saddle third roller conveying direction 118c), which is the direction in which the sheet bundle is conveyed by the saddle third roller pair 118, may simply be referred to as the "upstream side" and the "downstream side."

[0066] The folding roller pair 113, the second saddle roller pair 115, and the third saddle roller pair 118 are each driven by different motors, and the mid-fold control unit 344 controls the driving of each of these roller pairs by controlling these motors. The third saddle roller pair 118 grips the sheet bundle folded by the mid-fold processing unit 112 and conveys it toward the corner back processing unit C2, and is located directly upstream of the corner back processing unit C2.

[0067] Here, as shown in Figure 4, the second imaginary line β2 is defined as a straight line perpendicular to the width direction and passing through the nip of the saddle third roller pair 118 when it is not gripping a sheet bundle, with the second imaginary line β1 passing through the rotation centers of the saddle third roller pair 118. In this case, the saddle third roller pair 118 is positioned such that the second imaginary line β2 intersects the first imaginary line α2, and the second imaginary line β2 is inclined vertically downward as it moves downstream in the conveying direction of the folding roller pair 113.

[0068] In other words, the saddle third roller pair 118 is positioned such that the second virtual line β2 is inclined vertically downward as it moves downstream in the transport direction relative to the horizontal. 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 transports the sheet bundle in the horizontal direction or in a direction that is inclined vertically upward as it moves downstream in the transport direction relative to the horizontal (folding roller transport direction 113c). In contrast, the saddle third roller pair 118 transports the sheet bundle in a direction that is inclined vertically downward as it moves downstream in the transport direction relative to the horizontal (saddle third roller transport direction 118c).

[0069] Therefore, in this embodiment, the middle-fold transport path C4, which serves as a third transport path for transporting the sheet bundle between the folding roller pair 113 and the saddle third roller pair 118, is bent so that the sheet bundle transported by the folding roller pair 113 is handed over to the saddle third roller pair 118. That is, the middle-fold transport path C4 has a post-fold path guide 114 and a second roller post-path guide 116, and the transport path is bent between the post-fold 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-fold path guide 114.

[0070] In this way, by making the conveying direction of the sheet bundles of the folding roller pair 113 different from the conveying direction of the sheet bundles of the saddle third roller pair 118, and by bending the conveying path between the post-folding path guide 114 and the post-second roller path guide 116, the width of the sheet processing device B (length in the second conveying direction, length in the left-right direction in Figure 2) can be reduced, and the device can be made smaller. In addition, by making the folding roller conveying direction 113c, which is the sheet conveying direction of the saddle third roller pair 118, diagonally downward, and by discharging the sheet bundles downward by the saddle third roller pair 118, the sheet bundles processed in the saddle section B2 can be discharged to a lower position in the device. As a result, the saddle discharge unit 131, which discharges the sheet bundles processed in the saddle section B2, can be placed lower in the device, and the amount that the first tray 49, located above the saddle discharge unit 131, can descend can be increased. As a result, the sheet loading capacity of the first tray 49 can be increased. Furthermore, the arrangement of the sheet or sheet bundle transport path guides and the transport direction of the sheets or sheet bundles described above include cases where angles are introduced relative to horizontal, vertical, or parallel directions due to tolerances and other factors.

[0071] [Details of the back treatment area] The corner back processing unit C2 will be described with reference to Figures 2 and 4, and with reference to Figures 5 to 10. As described above, it comprises a lower clamp unit 120 and an upper clamp unit 121 as a pair of clamping parts, and a corner back processing unit 134 having a pressing roller 123. The clamping mechanism C5 having the lower clamp unit 120 and the upper clamp unit 121 has a pre-clamping guide 119, as shown in Figure 5. The pre-clamping guide 119 is located downstream of the saddle third roller pair 118 in the conveying direction, and is positioned along a direction that bends vertically downward with respect to the saddle third roller conveying direction 118c, and guides the conveying of the sheet bundle.

[0072] The clamping guide 119 has a clamping lower guide section (lower guide section) 119a having a lower guide surface 119a1 that guides the lower surface of the sheet bundle, and a clamping upper guide section (upper guide section) 119b having an upper guide surface 119b1 that guides the upper surface of the sheet bundle. The clamping lower guide section 119a and the clamping upper guide section 119b are positioned at a distance in the thickness direction from a line centered on the saddle third roller transport direction 118c that is greater than half 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 of the maximum thickness that can be transported in the device). In other words, the distance between the clamping lower guide section 119a and the clamping upper guide section 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 folded by the center-folding mechanism C1). Note that at least one of the guide sections, the lower front guide section 119a and the upper front guide section 119b, may be omitted.

[0073] The lower clamping unit 120 and the upper clamping unit 121 are relatively movable between a first position capable of receiving the sheet bundle conveyed from the saddle third roller pair 118 and a second position for clamping the sheet bundle. By moving from the first position to the second position, the lower clamping unit 120 and the upper clamping unit 121 clamp a portion of the sheet bundle from both sides in the thickness direction of the sheet bundle.

[0074] In this embodiment, the upper clamp unit 121, which serves as the first clamping section, is movable, and the lower clamp unit 120, which serves as the second clamping section, is fixed. That is, the sheet bundle is clamped by the upper clamp unit 121 moving toward the lower clamp unit 120. However, the upper clamp unit 121 may be fixed and the lower clamp unit 120 movable, or both may be movable. In any case, the sheet bundle is clamped by the upper clamp surface (upper clamp pressing section) 142 of the upper clamp unit 121, which is the surface facing the lower clamp unit 120, and the lower clamp surface (lower clamp pressing section) 143 of the lower clamp unit 120, which is the surface facing the upper clamp unit 121 (see Figures 5 and 16(a) to (d)).

[0075] The lower clamping surface 143 of the lower clamping unit 120 and the upper clamping surface 142 of the upper clamping unit 121 are parallel to the lower front guide portion 119a and the upper front guide portion 119b, respectively, and are positioned downstream of the front guide 119 in the direction of conveying the sheet bundle. The sheet bundle, which is conveyed while being guided by the front guide 119, is further guided by the upper clamping surface 142 and the lower clamping surface 143 to convey a predetermined amount. The lower front guide portion 119a is fixed to the lower clamping unit 120, and the upper front guide portion 119b is fixed to the upper clamping unit 121. In this embodiment, the upper front guide portion 119b moves together with the upper clamping unit 121 in a substantially vertical direction (in the thickness direction of the sheet bundle).

[0076] [Square back processing unit] Next, the internal structure of the corner back processing unit 134 will be described using Figures 5 to 10. The corner back processing unit 134 has a unit frame 147, roller pressurizing sections 138a and 138b, pressurizing springs 145a and 145b, an upper movement restricting section 139, and a lower movement restricting section 140 as a structure for supporting and moving the pressing roller (corner back processing roller) 123. As shown in Figures 5 and 10, the pressing roller 123 is positioned so that its outer circumferential surface is in contact with the downstream end faces of the lower clamping unit 120 and the upper clamping unit 121, respectively. Also, as shown in Figure 6(b), the pressing roller 123 has a roller shaft 141 positioned on its inner diameter side and is rotatable relative to the roller shaft 141.

[0077] As shown in Figures 6(a) and (b), the unit frame 147 has a pair of side plates 147a positioned on both sides of the pressing roller 123, a rear side plate 147b positioned on the left side of the pressing roller 123 downstream in the first conveying direction (Figure 6(b)), and upper side plates 147c and lower side plates 147d positioned on both sides in the direction of the rotation axis of the pressing roller 123 and provided to bend from both ends of the rear side plate 147b. With this configuration, the unit frame 147 houses the pressing roller 123 inside each side plate while exposing the pressing roller 123 to the upstream side in the first conveying direction.

[0078] In this embodiment, the rear plate 147b, the upper plate 147c, and the lower plate 147d are integrally formed, and as shown in Figure 6(b), the cross-section is approximately U-shaped. These may be separate parts, or they may be integrally formed with a pair of side plates 147a. Both ends of the roller shaft 141 of the pressing roller 123 are rotatably supported by the upper plate 147c and the lower plate 147d, respectively. Furthermore, the upper plate 147c and the lower plate 147d extend upstream of the pressing roller 123 in the first conveying direction, and the upper movement restricting part 139 and the lower movement restricting part 140 are supported at their tip ends, respectively.

[0079] Specifically, the upper movement restricting part 139 is provided at the tip of a support shaft 139a that is fixed to the upper plate 147c and extends downward from the upper plate 147c. The lower movement restricting part 140 is provided at the tip of a support shaft 140a that is fixed to the upper plate 147c and extends downward from the lower plate 147d. The upper movement restricting part 139 is a roller rotatably supported at the tip of the support shaft 139a, and the lower movement restricting part 140 is a roller rotatably supported at the tip of the support shaft 140a. In this embodiment, two lower movement restricting parts 140 are arranged side by side, but one may be used. Similarly, two upper movement restricting parts 139 may also be used. The upper movement restricting part 139 and the lower movement restricting part 140 are located on both sides of the pressing roller 123 with respect to the rotation axis direction of the roller shaft 141.

[0080] Roller pressurizing sections 138a and 138b are connected to the roller shaft 141, respectively, on the outer side in the roller thickness direction of the pressing roller 123 and downstream in the conveying direction. Pressurizing springs 145a and 145b are positioned between the roller pressurizing sections 138a and 138b and the rear side plate 147b of the unit frame 147, and the roller shaft 141 is biased by the pressurizing springs 145a and 145b. Since the roller shaft 141 is configured to be movable in the conveying direction, the pressing force applied by the pressing roller 123 to the back of the sheet bundle due to the biasing force of the pressurizing springs 145a and 145b changes in accordance with the change in the amount of protrusion from the lower clamping unit 120 and upper clamping unit 121 of the back of the sheet bundle, which will be described later.

[0081] Furthermore, the pressure roller 123 is biased by pressure springs 145a and 145b via the roller shaft 141, thereby applying pressure to the lower clamp unit 120 and the upper clamp unit 121. On the opposite side of the pressure roller 123 from the lower clamp unit 120 and the upper clamp unit 121, the upper movement restricting section 139 and the lower movement restricting section 140 are positioned facing the lower clamp unit 120 and the upper clamp unit 121, respectively (Figure 5). That is, with respect to the conveying direction of the sheet bundle (first conveying direction), the upper movement restricting section 139 is positioned upstream of the lower clamp unit 120 and the upper clamp unit 121, and the lower movement restricting section 140 is positioned upstream of the lower clamp unit 120.

[0082] As shown in Figures 9 and 10, the upstream end face 120a of the lower clamp unit 120 is in contact with the lower movement restricting section 140. Similarly, the upstream end face 121a of the upper clamp unit 121 is in contact with the upper movement restricting section 139. In this embodiment, the lower movement restricting section 140 and the upper movement restricting section 139 are rollers having rotation axes in directions perpendicular to the width direction and the conveying direction of the sheet bundle (the vertical direction in Figure 10, and approximately vertical in this embodiment), respectively, and rotate while in contact with the end faces 120a and 121a. As a result, the pressure applied to the lower clamp unit 120 and the upper clamp unit 121 from the pressing roller 123 restricts their movement to the upstream side.

[0083] When the leading edge of the sheet bundle conveyed by the saddle third roller pair 118 is detected by the aforementioned saddle conveying sensor 117, the corner back processing control unit 345 counts the amount of conveyed and stops after conveying a predetermined amount. Specifically, as shown in Figure 16(a) described later, the sheet bundle is stopped with the back of the folded sheet bundle protruding downstream in the conveying direction from the upper clamp unit 121 and the lower clamp unit 120. In this embodiment, in corner back processing, the amount of the sheet bundle's back protruding from the upper clamp unit 121 and the lower clamp unit 120 is adjusted by controlling the amount of the sheet bundle conveyed by the saddle third roller pair 118.

[0084] [Upper clamp unit and lower clamp unit] The upper clamp unit 121 moves from a receiving position (first position) for receiving the sheet bundle to a clamp holding position (second position) for holding the sheet bundle, thereby pressurizing the sheet bundle between itself and 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 Figure 16(b) described later, the leading edge of the sheet bundle protrudes by a predetermined amount P1 from the downstream end faces 120c and 121b of the lower clamp unit 120 and upper clamp unit 121, respectively, in the transport direction after clamping.

[0085] The upper clamp unit 121 operates by the corner back processing control unit 345 driving the clamp drive motor 132 (Figures 7(a) and (b)). As shown in Figures 7(a) and (b), the corner back processing unit C2 transmits the drive transmitted by the clamp drive train 133, which is composed of pulleys, belts, and a gear train, to the clamp drive link 122, thereby moving the upper clamp unit 121, which is connected to the clamp drive link 122, in the sheet bundle thickness direction. Multiple clamp springs 144 that pressurize the sheet bundle are built into the clamp drive link 122 and the upper clamp unit 121. The amount of movement of the clamp drive link 122 remains constant, and the amount of compression of the clamp springs 144 changes according to the thickness of the sheet bundle, thereby changing the applied pressure. The clamp holding position also changes in the same way according to the thickness of the sheet bundle. Note that the skew correction unit, which will be described later, is not shown in Figure 7.

[0086] [Back and corner treatment area] As shown in Figure 16(c) described later, the corner back processing unit C2 performs corner back processing on a sheet bundle that is held between the lower clamp unit 120 and the upper clamp unit 121 with a predetermined protrusion amount P1 from the end faces 120c and 121b, by applying pressure to the back of the sheet bundle while scanning it in the width direction with a pressure roller 123 located downstream in the conveying direction.

[0087] During corner back processing, the corner back processing control unit 345 operates the drive motor 135 (Figure 7(b)) to move the pressure roller 123. As shown in Figure 8, the pressure roller 123 is connected to a drive belt 137 arranged in the width direction of the sheet bundle and is movable in the width direction of the sheet bundle along the guide rail 120b shown in Figure 9, which will be described later. The drive belt 137 rotates when power is transmitted from the drive motor 135 via a drive train 136 (Figure 7(b)) which is composed of a gear train. This enables the pressure roller 123 to scan in the width direction of the sheet bundle. The home position of the pressure roller 123 is provided on the front and rear sides of the sheet processing device B. In other words, corner back processing can be performed on the first sheet bundle by moving the pressure roller 123 from the rear side to the front side, and then on the second sheet bundle by moving the pressure roller 123 from the front side to the rear side. Each home position of the pressure roller 123 is equipped with a sensor (not shown), which makes it possible to detect the position of the pressure roller 123. However, a home position may be set on either the front or rear side, and the scanning of the pressure roller 123 in the width direction may be performed from the front to the rear side, or from the rear to the front side. If a home position is set on either side in this way, for example, the pressure roller 123 may be moved from the rear to the front side for the first sheet bundle to perform corner back processing, and then the pressure roller 123 may be moved from the front to the rear side for the second sheet bundle to perform corner back processing.

[0088] Furthermore, in a single corner-back processing cycle, the pressure roller 123 is moved in one direction, either from the front to the rear or from the rear to the front. However, the pressure roller 123 may also be moved back and forth in a single corner-back processing cycle. For example, in a single corner-back processing cycle, the setting for whether the pressure roller 123 moves in one direction or back and forth may be configured depending on the number and type of sheets included in the sheet bundle. This setting may be performed automatically by the control unit, or it may be set by an operator such as a user or service technician. Moreover, the operator may be able to arbitrarily set whether the pressure roller 123 moves in one direction or back and forth in a single corner-back processing cycle.

[0089] As shown in Figures 9 and 10, the lower clamp unit 120 has a guide rail 120b formed along the width direction of the sheet bundle. The lower movement restricting portion 140 moves along the guide rail 120b while engaging with it as the pressing roller 123 moves in the width direction of the sheet bundle. The guide rail 120b is formed by combining multiple members, as shown in Figure 10, with a substantially U-shaped cross-section, and is formed so that a part of the roller-shaped lower movement restricting portion 140 can enter it. The lower surface on the outer diameter side of the lower movement restricting portion 140 engages with the lower surface of the guide rail 120b, and the outer circumferential surface of the lower movement restricting portion 140 abuts against the end face 120a. This restricts the movement of the pressing roller 123 in the thickness direction of the sheet bundle when it moves. The guide rail 120b may also be a groove formed in a part of the lower clamp unit 120 on the upstream side in the conveying direction.

[0090] After the corner-back processing is complete, the drive motor 135 (Figure 7(b)) is operated to move the pressure roller 123 in the width direction, thereby moving it out of the sheet bundle's transport path. Furthermore, the clamp drive motor 132 (Figures 7(a), (b)) is operated to move the upper clamp unit 121 away from the sheet bundle (Figure 16(d), described later). This makes it possible to transport the sheet bundle further downstream. It is also possible to discharge the sheet bundle without performing the corner-back processing described above.

[0091] [Discharge section] As shown in Figure 2, the sheet bundle that has passed through the saddle section B2 is transported by the saddle third roller pair 118 toward the saddle discharge guide 124, which is located further downstream in the first transport direction than the pressure roller 123. The saddle discharge guide 124 is pivotably supported around a first pivot point 124b, which has a rotation axis parallel to the rotation axis of each roller of the saddle third roller pair 118. The first pivot point 124b is located above the line extending downstream from the transport direction of the sheet bundle by the saddle third roller pair 118 (first transport direction, saddle third roller transport direction 118c). The saddle discharge guide 124 is positioned to hang vertically downward from the first pivot point 124b.

[0092] Furthermore, the saddle discharge guide 124 has a side surface on the upstream side in the first conveying direction that slopes towards the upstream side in the first conveying direction as it moves from the first support point 124b towards the intermediate portion 124a in the vertical direction. Also, the side surface on the upstream side in the first conveying direction of the saddle discharge guide 124 slopes towards the downstream side in the first conveying direction as it moves from the intermediate portion 124a towards the lower end in the vertical direction. In other words, the side surface on the upstream side in the first conveying direction of the saddle discharge guide 124 is formed to bend so that the intermediate portion 124a in the vertical direction protrudes more towards the upstream side in the first conveying direction than the other parts. And, a guide surface 124d is provided between the intermediate portion 124a and the lower end of the side surface on the upstream side in the first conveying direction of the saddle discharge guide 124.

[0093] The guide surface 124d is located below the line extending downstream from the saddle third roller conveying direction 118c described above, and contacts the sheet bundle conveyed by the saddle third roller pair 118, guiding the sheet bundle downward. The saddle discharge guide 124 is rotatable around the first pivot point 124b when the sheet bundle contacts the guide surface 124d. However, depending on the rigidity of the sheet bundle, the saddle discharge guide 124 may not contact the guide surface 124d, and even if contact occurs, the amount of rotation will vary depending on the rigidity, so the saddle discharge guide 124 does not necessarily rotate.

[0094] Furthermore, a second pivot point 124c is provided at the lower end of the saddle discharge guide 124, and the saddle discharge roller 125, described later, is rotatably connected to the second pivot point 124c. The second pivot point 124c is located below the guide surface 124d and has a pivot axis parallel to the pivot axis of the first pivot point 124b.

[0095] As the sheet bundle continues to be transported by the saddle third roller pair 118, it is passed to the saddle discharge unit 131, which is located downstream of the corner back 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.

[0096] The saddle discharge upstream belt 127 is located below the guide surface 124d of the saddle discharge guide 124, and conveys the sheet bundles guided downward by the guide surface 124d while further guiding them downstream. The saddle discharge upstream belt 127 is inclined so that it is vertically downward as it moves downstream in the conveying direction. The saddle discharge downstream belt 129, which serves as the sheet bundle discharge section, receives the sheet bundles conveyed from the saddle discharge upstream belt 127 and conveys them while further guiding them downstream. The saddle discharge downstream belt 129 is inclined so that it is vertically upward as it moves downstream in the conveying direction. Therefore, the sheet bundles guided by the guide surface 124d to the saddle discharge upstream belt 127 are 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.

[0097] Furthermore, a saddle discharge upstream sensor 128 is positioned on the upstream side of the conveyable area of ​​the saddle discharge upstream belt 127 to detect sheet bundles on the upstream side, and a saddle discharge downstream sensor 130 is positioned on the upstream side of the conveyable area of ​​the saddle discharge downstream belt 129 to detect sheet bundles on the downstream side.

[0098] The sheet bundles, once handed over to the saddle discharge unit 131, are guided and transported by the saddle discharge upstream belt 127 and the saddle discharge downstream belt 129, after which the sheet bundles are loaded. The saddle discharge upstream belt 127 grips the sheet bundles at a nip point between itself and the aforementioned saddle discharge rollers 125 on the downstream side in the transport direction. The sheet bundles on the saddle discharge upstream belt 127 are configured to suppress opening on the opening side (short end side) at this nip point. The position of this nip point can be changed using the second support point 124c as the support point depending on the thickness of the sheet bundle.

[0099] While processing subsequent sheet bundles, the preceding sheet bundle is transported upstream in the transport direction by the saddle discharge upstream belt 127, and stops at a predetermined transport amount after detection by the saddle discharge upstream sensor 128 and the saddle discharge downstream sensor 130. This transport amount is positioned so that the opening of the preceding sheet bundle is suppressed at the nip point between it and the saddle discharge roller 125, and so that the subsequent sheet bundle comes into contact with the upper surface of the preceding sheet bundle when it is discharged. In other words, in this embodiment, the saddle discharge unit 131 stacks subsequent sheet bundles on top of the preceding sheet bundles (in a so-called tile-like manner).

[0100] In this way, the saddle discharge unit 131 discharges the subsequent sheet bundle onto the upper surface of the preceding sheet bundle without entering the opening of the preceding sheet bundle, so that the subsequent sheet bundle is stably stacked in a tile-like manner without any problems such as getting caught, curling, or being pushed out relative to the preceding sheet bundle. In other words, by appropriately changing the amount of conveyance described above according to the size of the sheet bundle, the subsequent sheet bundle can be stably stacked on top of the preceding sheet bundle.

[0101] The saddle discharge port 126 is located 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 bundles conveyed to the saddle discharge unit 131 are discharged to the outside of the sheet processing device B by passing through the saddle discharge port 126, making it easier for the user to access the discharged sheet bundles.

[0102] Furthermore, 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 to transport it without loading. In addition, in this embodiment, a discharge cover 151 is provided on the outside of the saddle discharge port 126 as a cover member. The discharge cover 151 is positioned so as not to obstruct the discharge of the sheet bundle from the saddle discharge port 126, and is also positioned so that operators such as users cannot access the inside of the device through the saddle discharge port 126.

[0103] [Correction of sheet stack skew] Next, in this embodiment, the correction of the skew of the sheet bundle performed before the corner-spine processing will be explained using Figures 11 to 15(b). Sheet bundles that have undergone saddle stitching and center folding may be transported in a skewed state due to the influence of component tolerances in each component. If corner-spine processing is performed by the corner-spine processing unit C2 while the sheet bundle is skewed, the finish of the corner-spine processing may become uneven in the width direction of the sheet bundle, and the desired output may not be provided to the user.

[0104] Therefore, in this embodiment, the skewness of the sheet bundle is corrected before performing the corner back processing on the sheet bundle. Figure 11 is a diagram illustrating the skew correction unit 500 for correcting the skewness of the sheet bundle, and is a perspective view of the corner back processing unit 134 and the skew correction unit 500 from the upstream side in the transport direction of the saddle third roller pair 118. In the following description, the transport direction of the saddle third roller pair 118 (first transport direction) will simply be referred to as the "transport direction". The skew correction unit 500 has a contact member (skew correction member) 501 that contacts the back of the sheet bundle, a moving mechanism (second moving mechanism) 510 that moves the contact member 501 from a standby position (second position) to a contact position (first position), and a moving mechanism (first moving mechanism) 520 that moves the contact member 501 in the transport direction.

[0105] Figures 12(a) to 12(c) show the contact member 501 in the standby position. Figures 13(a) to 13(c) show the contact member 501 in the lifted position, i.e., the contact member 501 in the contact position (receiving position). Figures 12(a) and 13(a) are perspective views of the skew correction unit 500. Figures 12(b) and 13(b) show the skew correction unit 500 and the corner back processing unit C2 as viewed from the downstream side in the conveying direction of the sheet bundle. Figures 12(c) and 13(c) are schematic cross-sectional views of the skew correction unit 500 and the corner back processing unit C2. As shown in Figures 11 to 13(c), the moving mechanism 510 is provided vertically below the lower clamp unit 120 and the upper clamp unit 121.

[0106] The contact member 501, acting as a diagonal correction member, is located downstream of the lower clamp unit 120 and the upper clamp unit 121 in the conveying direction. As will be described in more detail later, before the corner backing is applied, it corrects the diagonal orientation of the sheet bundle by pushing the back of the sheet bundle that protrudes downstream in the conveying direction relative to the lower clamp unit 120 and the upper clamp unit 121 toward the upstream in the conveying direction. The moving mechanism 510 is capable of moving the contact member 501 between a first contact position, which is downstream of the lower clamp unit 120 and the upper clamp unit 121 in the conveying direction and faces the back of the sheet bundle that has passed the lower clamp unit 120 and the upper clamp unit 121, and a second standby position, which is retracted from the contact position.

[0107] In other words, the contact member 501 is located below the lower clamp unit 120 in the standby position shown in Figures 12(b) and 12(c). Furthermore, the contact member 501 in the standby position is located below the pressing roller 123 so as not to obstruct the movement of the pressing roller 123. The pressing roller 123 is movable in the width direction of the sheet bundle when the contact member 501 is in the standby position (retracted position). In other words, when the contact member 501 is in the standby position, the corner back processing by the corner back processing unit 134 can be performed.

[0108] Furthermore, the contact member 501 is located downstream in the transport direction from the lower clamp unit 120 and the upper clamp unit 121 at the contact positions shown in Figures 13(b) and 13(c), and is capable of contacting the back of the sheet bundle after it has passed the lower clamp unit 120 and the upper clamp unit 121.

[0109] The contact member 501 can be raised from the standby position to the contact position and lowered from the contact position to the standby position by the moving mechanism 510. The moving mechanism 510, which is a second moving mechanism, includes a link mechanism 502, a motor 511, a gear train 512, a rotating gear 513, etc. The link mechanism 502 includes links 502a, 502b, a sliding sheet metal 515, and pivot shafts 502aa, 502ab, 502ba, and 502bb. These members are combined with the contact member 501 to form a parallel link mechanism. The two links 502a and 502b are pivotably connected to the sliding sheet metal 515 via pivot shafts 502aa and 502ba, respectively, and are pivotably connected to the contact member 501 via pivot shafts 502ab and 502bb. The sliding sheet metal 515 is supported so as to be slidable along the transport direction with respect to shafts 513a and 514, which will be described later. Shaft 513a is connected to the oscillating shaft 502aa, and shaft 514 is connected to the oscillating shaft 502ba, and is rotatably supported with respect to the frame of the oblique correction unit 500.

[0110] When the moving mechanism 510 moves the contact member 501 from the standby position to the contact position, the motor 511 is driven. Drive is then transmitted from the drive shaft of the motor 511 to the drive gear 511a via the drive pulley, causing the drive gear 511a to rotate in the direction of the arrow in Figure 12(a). Drive is then transmitted from the drive gear 511a to the rotating gear 513 via the drive transmission unit (gear train in the illustrated example) 512, causing the rotating gear 513 to rotate in the direction of the arrow in Figure 12(a). The rotating gear 513 is connected to the link 502a via the shaft 513a. Therefore, when the rotating gear 513 rotates, the link 502a rotates in the same direction as the rotating gear 513, and the link 502b, which is connected to the link 502a via the contact member 501, also rotates together with the link 502a. This lifts the contact member 501 from the standby position to the contact position.

[0111] Furthermore, after the contact member 501 moves to the contact position by the moving mechanism 510, it is also capable of moving further in a direction toward the lower clamp unit 120 and the upper clamp unit 121, that is, toward the upstream side in the conveying direction. Then, as will be described in detail later, the contact member 501 pushes the back of the sheet bundle to correct the skewness of the sheet bundle. Figures 14(a) and (b) show the state in which the contact member 501 has moved toward the lower clamp unit 120 and the upper clamp unit 121. Figure 14(a) is a perspective view of the skew correction unit 500, and Figure 14(b) is a schematic cross-sectional view of the skew correction unit 500 and the corner back processing unit C2.

[0112] The first moving mechanism, the moving mechanism 520, is able to slide the contact member 501 along the transport direction together with the link mechanism 502 when the contact member 501 is positioned in contact with the moving mechanism 510. As a result, the contact member 501 moves in a direction toward the lower clamp unit 120 and the upper clamp unit 121 (upstream in the transport direction), and in a direction toward the lower clamp unit 120 and the upper clamp unit 121 (downstream in the transport direction).

[0113] The moving mechanism 520 includes a motor 521, a gear train 522, a slide gear 523, a slide rack 524, and the like. When the moving mechanism 520 moves the contact member 501, which is located in the contact position, to the upstream side in the conveying direction, the motor 521 is driven. As a result, the drive pulley 521a connected to the drive shaft of the motor 521 rotates in the direction of the arrow in Figure 12(a), and the drive is transmitted to the slide gear 523 via the drive transmission unit (pulley and belt, etc., in the illustrated example) 522, causing the slide gear 523 to rotate in the direction of the arrow in Figure 12(a). The slide gear 523 meshes with the rack gear of the slide rack 524, and as the slide gear 523 rotates, the slide rack 524 moves toward the upstream side in the conveying direction.

[0114] The slide rack 524 is connected to the slide sheet metal 515. As described above, the slide sheet metal 515 is supported so as to be slidable along the transport direction relative to the shafts 513a and 514. Therefore, when the slide rack 524 moves along the transport direction, the slide sheet metal 515 moves along with the slide rack 524 in the transport direction. Then, when the slide rack 524 and the slide sheet metal 515 move upstream in the transport direction, the contact member 501, which is connected to the slide sheet metal 515 via links 502a and 502b, also moves upstream in the transport direction.

[0115] In this manner, the moving mechanism 510 and the moving mechanism 520 move the contact member 501 from the standby position to the contact position, and further move the contact member 501 from the contact position toward the lower clamp unit 120 and the upper clamp unit 121. This allows the back of the sheet bundle that protrudes downstream in the conveying direction relative to the lower clamp unit 120 and the upper clamp unit 121 to be pushed back toward the upstream direction in the conveying direction. At this time, the back of the sheet bundle comes into contact with the contact member 501, and is further pushed back by the contact member 501, so that the back of the sheet bundle conforms to the contact surface 501a of the contact member 501. Since the contact surface 501a is a surface parallel to the width direction, the slanting of the sheet bundle is corrected when the back of the sheet bundle conforms to the contact surface 501a.

[0116] Next, the operation during sheet bundle skew correction will be explained using Figures 15(a) and (b). Figures 15(a) and (b) are schematic cross-sectional views for explaining sheet bundle skew correction. Figure 15(a) shows the state in which the contact member 501 has moved to the contact position, and Figure 15(b) shows the state in which the contact member 501 has moved from the contact position toward the lower clamp unit 120 and the upper clamp unit 121.

[0117] The sheet bundles, which have undergone saddle stitching and folding, are conveyed in the direction of the arrows in Figure 15(a) by the saddle second roller pair 115 and the saddle third roller pair 118. Then, in response to the detection of the leading edge (spine) of the sheet bundle by the saddle conveying sensor 117, the saddle second roller pair 115 and the saddle third roller pair 118 convey the sheet bundle by a predetermined amount and then stop conveying. At this time, the spine of the sheet bundle is stopped at a position where it does not come into contact with the contact member 501 located at the contact position. Note that since this stage is before the corner spine processing, the lower clamping unit 120 and the upper clamping unit 121 are not in a state of clamping the sheet bundle, that is, they are at a position further apart from each other than the position where the sheet bundle is clamped.

[0118] Subsequently, the second saddle roller pair 115 and the third saddle roller pair 118 are separated, releasing the grip on the sheet bundle. Here, the second saddle roller pair 115 consists of a second lower roller (conveying rotating body) 115a located on the lower side in the direction of gravity and a second upper roller (conveying rotating body) 115b located on the upper side in the direction of gravity. At least the second lower roller 115a of these rollers is movable between a gripping position in which it grips the sheet bundle between itself and the second upper roller 115b, and a separated position in which it moves downward from the gripping position and separates from the second upper roller 115b. The separated position is the position in which the grip on the sheet bundle is released. Furthermore, when the second lower roller 115a is in a separated position, the second lower roller 115a is located below in the direction of gravity from the lower guide surface 116a1 of the second roller rear path lower guide 116a that guides the lower surface of the sheet bundle and the lower guide surface 119a1 of the clamp front lower guide portion 119a.

[0119] In this embodiment, when clamping and releasing the sheet bundle, the second upper roller 115b also moves vertically. Specifically, from the separated position, the second lower roller 115a moves upward and the second upper roller 115b moves downward, creating a clamping position for clamping the sheet bundle. From the clamping position, the second lower roller 115a moves downward and the second upper roller 115b moves upward, creating a separated position for releasing the sheet bundle. Furthermore, when the second upper roller 115b is in the separated position, the second upper roller 115b is positioned above the upper guide surface 116b1 of the second roller rear path upper guide 116b and the upper guide surface 119b1 of the clamp front upper guide portion 119b in the direction of gravity.

[0120] Similarly, the saddle third roller pair 118 consists of a third lower roller (conveying rotating body) 118a located on the lower side in the direction of gravity and a third upper roller (conveying rotating body) 118b located on the upper side in the direction of gravity. At least the third lower roller 118a of these rollers is movable between a clamping position in which it clamps the sheet bundle between itself and the third upper roller 118b, and a separated position in which it moves downward from the clamping position and separates itself from the third upper roller 118b. The separated position is the position in which the clamping of the sheet bundle is released. Furthermore, when the third lower roller 118a is in the separated position, the third lower roller 118a is located below the lower guide surface 116a1 of the second roller rear path lower guide 116a and the lower guide surface 119a1 of the clamp front lower guide portion 119a, which guide the lower surface of the sheet bundle.

[0121] In this embodiment, when clamping and releasing the sheet bundle, the third upper roller 118b also moves vertically. Specifically, from the separated position, the third lower roller 118a moves upward and the third upper roller 118b moves downward, respectively, to reach the clamping position for clamping the sheet bundle. From the clamping position, the third lower roller 118a moves downward and the third upper roller 118b moves upward, respectively, to reach the separated position for releasing the sheet bundle. Furthermore, when the third upper roller 118b is in the separated position, the third upper roller 118b is positioned above the upper guide surface 116b1 of the second roller rear path upper guide 116b and the upper guide surface 119b1 of the clamp front upper guide portion 119b in the direction of gravity.

[0122] With the saddle second roller pair 115 and the saddle third roller pair 118 in a separated position, the moving mechanism 520 moves the contact member 501 in the direction of the arrow shown in Figure 15(b). That is, the contact member 501 is moved upstream in the conveying direction. As the contact member 501 moves at this time, the contact member 501 comes into contact with the back of the sheet bundle. Then, as the contact member 501 moves further in the direction of the arrow in Figure 15(b) while in contact with the back of the sheet bundle, it pushes the sheet bundle back upstream in the conveying direction.

[0123] As the sheet bundle is pushed back while in contact with the contact member 501, the back of the sheet bundle conforms to the contact surface 501a of the contact member 501, and the slanting of the sheet bundle is corrected. At this time, as described above, in the state shown in Figure 15(b), that is, when the back of the sheet bundle is pushed by the contact member 501, the second lower roller 115a and the third lower roller 118a, which are located vertically downward, are spaced apart to the point where they are both below the lower guide surface 116a1 of the second roller rear pass lower guide 116a and the lower guide surface 119a1 of the clamp front lower guide portion 119a. Therefore, when the sheet bundle is pushed back by the contact member 501, the sheet bundle does not come into contact with the second lower roller 115a and the third lower roller 118a.

[0124] If the sheet bundle pushed upstream in the conveying direction by the contact member 501 were to come into contact with the second lower roller 115a and the third lower roller 118a, which have conveying force, there is a risk that the cover of the sheet bundle may be damaged due to friction between the second lower roller 115a and the third lower roller 118a and the sheet bundle. For this reason, in this embodiment, when the sheet bundle is pushed back by the contact member 501 (when the contact member 501 pushes the back of the sheet bundle), the second lower roller 115a and the third lower roller 118a are positioned below the lower guide surface 116a1 of the second roller rear pass lower guide 116a and the lower guide surface 119a1 of the clamp front lower guide portion 119a. As a result, the sheet bundle pushed upstream in the conveying direction by the contact member 501 does not come into contact with the second lower roller 115a and the third lower roller 118a, and the load on the sheet bundle's movement upstream in the conveying direction can be reduced. Furthermore, the surface frictional force of the lower guide surface 116a1 of the second roller rear pass lower guide 116a and the lower guide surface 119a1 of the clamp front lower guide portion 119a when the sheet bundle is moving is about one-tenth of that of the second lower roller 115a and the third lower roller 118a, which have the transporting force. Also, the coefficient of friction of the second lower roller 115a and the third lower roller 118a is 1.0 or higher. Therefore, even if the sheet bundle pushed upstream in the transporting direction by the contact member 501 comes into contact with the lower guide surface 116a1 of the second roller rear pass lower guide 116a and the lower guide surface 119a1 of the clamp front lower guide portion 119a, damage to the cover of the sheet bundle can be suppressed.

[0125] Furthermore, the more sheets that make up the sheet bundle, the higher the likelihood that the sheet bundle will come into contact with the upper guide 116b behind the second roller and the upper guide portion 119b in front of the clamp compared to when there are fewer sheets. Therefore, when the sheet bundle is pushed back by the contact member 501, the second upper roller 115b and the third upper roller 118b are positioned above the upper guide surface 116b1 of the upper guide 116b behind the second roller and the upper guide surface 119b1 of the upper guide portion 119b in front of the clamp. However, the upper rollers of the sheet bundle are not subject to gravity, so the surface friction force acting on them during the movement of the sheet bundle is smaller than that on the lower rollers. Therefore, when the sheet bundle is pushed back by the contact member 501, the second upper roller 115b and the third upper roller 118b do not need to be positioned above the upper guide surface 116b1 of the upper guide 116b behind the second roller and the upper guide surface 119b1 of the upper guide portion 119b in front of the clamp. Also, the surface friction force of the guide surface 116b1 of the upper guide 116b behind the second roller and the guide surface 119b1 of the upper guide portion 119b in front of the clamp when the sheet bundle moves is about one-tenth that of the second upper roller 115b and the third upper roller 118b. The coefficient of friction of the second upper roller 115b and the third upper roller 118b is 1.0 or higher. Therefore, even if the sheet bundle pushed upstream in the transport direction by the contact member 501 comes into contact with the upper guide surface 116b1 of the upper guide 116b behind the second roller and the upper guide surface 119b1 of the upper guide portion 119b in front of the clamp, damage to the cover of the sheet bundle can be suppressed.

[0126] Thus, in this embodiment, when diagonal correction is performed by pushing the sheet bundle back with the contact member 501, the sheet bundle does not come into contact with at least the second lower roller 115a and the third lower roller 118a, thus preventing damage to the cover of the sheet bundle.

[0127] In the state shown in Figure 15(b), the contact member 501 stops at a position where the amount of protrusion of the back of the sheet bundle downstream in the conveying direction from the lower clamp unit 120 and the upper clamp unit 121 is a predetermined amount. In this state, the sheet bundle is clamped by the lower clamp unit 120 and the upper clamp unit 121. At this time, the saddle second roller pair 115 and the saddle third roller pair 118 also return to the clamping position (releasing the separated state), and the sheet bundle is clamped by the saddle second roller pair 115 and the saddle third roller pair 118. After that, the moving mechanism 510 retracts the contact member 501 to the standby position shown in Figures 12(a) to 12(c), and the pressing roller 123 is moved in the width direction of the sheet bundle to perform corner back processing on the sheet bundle after diagonal correction.

[0128] [Arch back processing control] Next, the control of the corner back processing in this embodiment will be explained using Figures 16(a) to 16(d). As described above, the corner back processing unit C2 performs corner back processing on the back of the sheet bundle whose skewing has been corrected by the skewing correction unit 500. The middle folding control unit 344, triggered by the detection of the leading edge of the sheet bundle Sb by the saddle transport sensor 117, executes the skewing correction operation by the skewing correction unit 500 described above. Then, as shown in Figure 16(a), the middle folding control unit 344 stops the return operation of the sheet bundle Sb by the contact member 501 when the back Ssp of the sheet bundle Sb protrudes further downstream in the transport direction than the end faces 121b and 120c on the downstream side in the transport direction of the upper clamp unit 121 and the lower clamp unit 120.

[0129] In this state, the corner back processing control unit 345 drives the clamp drive motor 132 (Figures 7(a), (b)) to move the upper clamp unit 121 toward the lower clamp unit 120, and the sheet bundle Sb is clamped by the upper clamp unit 121 and the lower clamp unit 120 as shown in Figure 16(b). At this time, the back Ssp of the sheet bundle Sb protrudes by P1 downstream from the end faces 121b and 120c on the downstream side in the transport direction of the upper clamp unit 121 and the lower clamp unit 120.

[0130] Next, the corner back processing control unit 345 operates the drive motor 135 (Figure 7(b)) to move the press roller 123 in the width direction of the sheet bundle Sb. At this time, as shown in Figure 16(c), the press roller 123 moves in the width direction while applying pressure to the back Ssp of the sheet bundle Sb, thereby performing corner back processing on the back Ssp of the sheet bundle Sb. After that, as shown in Figure 16(d), the corner back processing control unit 345 drives the clamp drive motor 132 (Figures 7(a), (b)) to separate the upper clamp unit 121 from the lower clamp unit 120, releasing the clamping of the sheet bundle Sb. With the corner back processing now complete, the sheet bundle Sb discharge operation described above is performed.

[0131] In this embodiment, since the corner-edge processing is performed on the sheet bundle after correcting the skew of the sheet bundle, it is possible to perform the corner-edge processing uniformly in the width direction of the sheet bundle. Furthermore, as described above, it is possible to suppress damage to the cover of the sheet bundle during the skew correction process.

[0132] [Number of diagonal correction operations] Here, depending on the number of sheets included in the sheet bundle and the state of the image on the sheet bundle's cover, a single skew correction may not be sufficient to correct the skew of the sheet bundle. For example, if the sheet bundle contains 20 or more sheets, and the image ratio (printing density) of the outer surface (cover) of the outermost sheet in the sheet bundle is such that one side (one of the front and rear sides) is a solid image in the width direction (front-to-back direction) intersecting the transport direction, and the image ratio on the other side (the other of the front and rear sides) is 50% or less, then the inventors' investigations have shown that a single skew correction operation may not be sufficient to correct the skew of the sheet bundle.

[0133] In other words, regarding the image ratio, if the difference between the image ratio on one side of the center and the image ratio on the other side of the center in the width direction intersecting the transport direction is 50% or more, a single diagonal correction operation may not be sufficient to correct the diagonal of the sheet bundle. This is because if the image ratio of the cover of the sheet bundle differs significantly in the front-to-back direction, a difference in frictional force occurs between the lower guide 116a after the second roller pass and the lower guide portion 119a in front of the clamp and the cover of the sheet bundle, causing the amount of return of the sheet bundle to differ significantly in the front-to-back direction. If the correction of the sheet bundle's diagonal is insufficient, the quality of the sheet bundle will deteriorate, such as when the corner shape formed on the spine of the sheet bundle after corner processing is not the desired shape.

[0134] Therefore, in this embodiment, the number of skew correction operations is changed according to the conditions of the sheet bundle. A solid image refers to a toner image formed on the entire surface of the image-forming area of ​​the photosensitive drum, where the image ratio (printing rate) is 100%. The skew correction operation includes a series of operations: gripping the sheet bundle with the saddle second roller pair 115 and the saddle third roller pair 118; transporting the sheet bundle with the saddle second roller pair 115 and the saddle third roller pair 118; stopping the transport of the sheet bundle by the saddle second roller pair 115 and the saddle third roller pair 118; releasing the grip of the sheet bundle with the saddle second roller pair 115 and the saddle third roller pair 118; and pushing the back of the sheet bundle with the contact member 501.

[0135] The number of skew correction operations performed according to the conditions of the sheet bundle will be explained in detail. In this embodiment, if the following first and second conditions are met, the skew correction operation is performed multiple times, and if neither the first nor the second condition is met, the skew correction operation is performed once. First, the first condition is that the number of sheets included in the sheet bundle to be subjected to corner back processing is equal to or greater than a predetermined number. In this embodiment, the predetermined number is 20 sheets. Next, the second condition is that, in the image ratio of the outer surface of the outermost sheet among the sheets included in the sheet bundle, the difference between the image ratio on one side of the center and the image ratio on the other side of the center in the width direction is equal to or greater than a predetermined value. In this embodiment, the predetermined value is 50%. Then, if both the first and second conditions are met, the skew correction operation is performed twice, and if at least one of the first or second conditions is not met, the skew correction operation is performed once.

[0136] The number of skew correction operations performed when the first and second conditions are met can be multiple, but in this embodiment, it is set to two. However, it may be three or more times. Since increasing the number of skew correction operations reduces the productivity of the device, the number of skew correction operations may be changed depending on the conditions. For example, it may be two times when the above-mentioned first and second conditions are met, and three times when the conditions are stricter, such as when the number of sheets is greater than in the first condition (e.g., 30 sheets) or when the difference in image aspect ratio is greater than in the second condition (e.g., 70%).

[0137] Furthermore, while the predetermined number of sheets in the first condition was set to 20 in the example above, the predetermined number can be set as appropriate. For example, it can be set to 10, 15, 25, or 30 sheets, depending on the frictional force between the surface of the sheet bundle and the guide in the device, and the conveying force of the sheet bundle by the contact member 501. Similarly, while the predetermined value in the second condition was set to 50% in the example above, the predetermined value can be set as appropriate. For example, the predetermined value may be set to 30% or 40%.

[0138] [Control flow for skew correction operation and horn processing] Next, an example of the control flow for the skew correction operation and corner back processing described above will be explained using Figure 17. First, in response to the inlet sensor 190 detecting that a sheet has been transported to the saddle section B2 (Yes in S1), the saddle control unit 350 moves the contact member 501 from the standby position (retracted position, Figures 12(a) to 12(c)) to the contact position (receiving position, Figures 13(a) to 13(c)) using the moving mechanism 510 (S2). Then, in response to the saddle transport sensor 117 detecting the sheet bundle (Yes in S3), the saddle control unit 350 transports the sheet bundle, which has undergone saddle stitching and saddle folding, by a predetermined amount using the saddle second roller pair 115 and the saddle third roller pair 118. Here, it is determined that the predetermined amount has been transported when a predetermined time has elapsed from the timing when the sheet bundle was detected by the saddle transport sensor 117.

[0139] After a predetermined amount of sheet bundles have been conveyed (Yes in S4), the saddle control unit 350 stops the conveyance of the sheet bundles by the saddle second roller pair 115 and the saddle third roller pair 118 (S5). At this time, the conveyance of the sheet bundles is stopped when the back of the sheet bundles protrudes beyond the downstream end faces 121b and 120c (hereinafter referred to as the clamp ends) of the upper clamp unit 121 and the lower clamp unit 120, respectively, in the conveyance direction. In this embodiment, after the sheet bundles are detected by the saddle conveyance sensor 117, the conveyance of the sheet bundles is continued at 175 mm / s so that the back of the sheet bundles protrude 12 mm from the clamp ends, and then the conveyance is stopped.

[0140] In this state, the saddle control unit 350 separates the second saddle roller pair 115 and the third saddle roller pair 118 (indicated as conveying rollers in Figure 17) (S6). Subsequently, the saddle control unit 350 moves the contact member 501 in the opposite direction to the conveying direction, as shown in Figure 15(b) (S7). In this embodiment, the contact member 501 pushes the sheet bundle back upstream in the conveying direction by the contact member 501 to a position where the back of the sheet bundle protrudes 4 mm from the clamp end. This position is, for example, when the sheet bundle has a basis weight of 80 g / m². 2This is an example where the bundle consists of 30 sheets. The amount of protrusion from the clamp end after the sheet bundle is pushed back by the contact member 501 may be variable depending on the number of sheets in the bundle and the basis weight.

[0141] Next, the saddle control unit 350 determines whether the sheet bundle satisfies the first and second conditions described above (S8). The first condition is whether the number of sheets in the sheet bundle (bundle size) is 20 or more (a predetermined number or more), and the second condition is whether the difference in the image ratio between the front and back of the cover of the sheet bundle is 50% or more (a predetermined value or more). The bundle size is counted by the entrance sensor 190. That is, the saddle control unit 350 counts the number of sheets detected by the entrance sensor 190. Note that the bundle size information may also be obtained by the saddle control unit 350 from the control unit 310 on the image forming apparatus A side. The saddle control unit 350 then determines that the first condition is satisfied if the bundle size counted by the entrance sensor 190 is 20 or more, and that the first condition is not satisfied if it is less than 20.

[0142] In S8, the saddle control unit 350 determines whether the difference in the front-to-back image ratio of the cover of the sheet bundle is 50% or more. The saddle control unit 350 obtains information on the front-to-back image ratio of the cover of the sheet bundle from the control unit 310 on the image forming apparatus A side, for example. The saddle control unit 350 then determines that the second condition is met if the difference in the front-to-back image ratio is 50% or more, and that the second condition is not met if it is less than 50%. If at least one of the first and second conditions is not met (No. in S8), the saddle control unit 350 proceeds to S9. That is, if neither the first nor the second condition is met, if the first condition is met but the second condition is not, or if the second condition is met but the first condition is not, the skew correction operation is performed once, and then the sheet bundle is clamped by the upper clamp unit 121 and the lower clamp unit 120 (S9).

[0143] Subsequently, the saddle control unit 350 clamps the sheet bundle with the saddle second roller pair 115 and the saddle third roller pair 118 (S10). In this embodiment, a configuration was described in which the sheet bundle is clamped by the upper clamp unit 121 and the lower clamp unit 120 in S9, and then clamped by the saddle second roller pair 115 and the saddle third roller pair 118 in S10, but the clamping order may be reversed.

[0144] Next, the saddle control unit 350 moves the contact member 501 to the standby position while the sheet bundle is clamped by the clamp and the respective pairs of transport rollers (S11). After that, the saddle control unit 350 performs the corner backing process. That is, the pressing roller 123 moves in the width direction of the sheet bundle while pressing the back of the sheet bundle toward the upper clamp unit 121 and the lower clamp unit 120, thereby performing corner backing on the back of the sheet bundle (S12).

[0145] The saddle control unit 350 then releases the clamping of the sheet bundle by the upper clamp unit 121 and the lower clamp unit 120 (S13), and discharges the sheet bundle that has undergone the corner-back treatment (S14).

[0146] In S8, if both the first and second conditions are met (Yes in S8), the process proceeds to S15. That is, the second diagonal correction operation is performed. Specifically, the sheet bundle is clamped by the saddle second roller pair 115 and the saddle third roller pair 118 (S15). After that, the saddle control unit 350 uses the moving mechanism 520 to return the contact member 501, which had moved to the upstream side in the conveying direction to correct the diagonal of the sheet bundle as described above, to the downstream side in the conveying direction. That is, the contact member 501 is moved away from the upper clamp unit 121 and the lower clamp unit 120, from a position close to the upper clamp unit 121 and the lower clamp unit 120 (Figure 14) to the contact position (Figure 13) (S16). Then, the saddle control unit 350 again transports the sheet bundle downstream in the transport direction by the saddle second roller pair 115 and the saddle third roller pair 118 (S17), and after a predetermined time has elapsed (Yes in S18), it stops the transport of the sheet bundle by the saddle second roller pair 115 and the saddle third roller pair 118 (S19).

[0147] In this state, the saddle control unit 350 separates the saddle second roller pair 115 and the saddle third roller pair 118 (S20). Then, as shown in Figure 15(b), the saddle control unit 350 moves the contact member 501 in the opposite direction to the conveying direction (S21). In this embodiment, the contact member 501 pushes the sheet bundle back to the upstream side in the conveying direction until the back of the sheet bundle protrudes 4 mm from the clamp end. That is, it performs the same operation as the first diagonal correction operation. After the second diagonal correction operation is completed, proceed to S9 described above.

[0148] The predetermined number of sheets in the first condition described above is, for example, based on a sheet with a basis weight of 80 g / m². 2 This is an example of a configuration consisting of the above. However, the predetermined number of sheets in the first condition may be variable depending on the basis weight of the sheets. For example, if the basis weight of the sheets is high, the number of skew correction operations will be increased even if the number of sheets is the same. In addition, the number of skew correction operations may be set arbitrarily by the user. For example, the user may be able to input information regarding the number of skew correction operations from the control panel, and the number of skew correction operations before corner back processing may be performed based on the input information.

[0149] Thus, in this embodiment, if the conditions of the sheet bundle are such that the skew correction of the sheet bundle cannot be sufficiently corrected with a single skew correction operation, the skew correction operation is performed multiple times (twice in the above example) to ensure that the skew of the sheet bundle is sufficiently corrected. As a result, regardless of the conditions of the sheet bundle, the shape of the corners formed on the back of the sheet bundle during the corner back processing performed after skew correction can be made into a desired shape, thereby suppressing a deterioration in the quality of the sheet bundle.

[0150] <Other Embodiments> In the above-described embodiment, a pair of conveying rollers are used as a pair of conveying rotating bodies for conveying the sheet bundle that has undergone saddle stitching and folding, but a configuration in which a pair of conveying belts is used for conveying may also be used. That is, the conveying rotating body may be a conveying belt. Alternatively, the pair of conveying rotating bodies may be configured to form a conveying nip with the conveying belt and the conveying rollers. Even with such a configuration, by retracting the rollers or belts that have conveying force below (or above) the conveying guide and pushing the sheet bundle back with the contact member 501, the conveying load can be reduced and damage to the sheet bundle cover during skew correction can be suppressed.

[0151] In the above-described embodiment, the corner back processing is performed downstream inside the saddle section B2 within the sheet processing device B, but the same corner back processing may be performed in a separate housing connected to the outside. For example, it may be a standalone unit that performs only corner back processing without performing saddle stitching or folding. In this case, this unit has the corner back processing unit C2 described above, and conveying means such as a pair of conveying rollers for conveying the sheet bundle that has been saddle-stitched and folded in the corner back processing unit C2.

[0152] Furthermore, in the above-described embodiment, the sheet processing apparatus B has a control unit that controls each internal component of the sheet processing apparatus B. However, the internal components of the sheet processing apparatus B may also be controlled by a control unit provided in the image forming apparatus.

[0153] Furthermore, although the above embodiment described a pair of rollers as the conveying unit for transporting sheets within the sheet processing device B, a configuration in which sheets are transported by a belt is also possible. Specifically, it may be a configuration in which sheets are transported by a belt gripped by a pair of rollers, a configuration in which sheets are transported by a pair of belts, or a configuration in which sheets are gripped by a belt and rollers, and the transport configuration may be changed depending on the position and path in which the sheets are transported. For example, sheets may be transported by a pair of rollers at one position and by a pair of belts at another position.

[0154] Furthermore, although the above-described embodiment described an image forming system 1000 in which the sheet processing apparatus B is directly connected to the image forming apparatus A, other system configurations are also possible. For example, a configuration in which other processing apparatuses or transport devices are connected between the image forming apparatus A and the sheet processing apparatus B is also possible. In addition, although the above-described embodiment described an image forming apparatus A that forms monochrome images using toner as an example, it may also be an image forming apparatus that forms color images using toner, or an image forming apparatus that forms images on a sheet using ink.

[0155] Furthermore, the disclosure of this embodiment includes the following configuration. (Composition 1) A pair of conveying rotating bodies that convey sheet bundles that have undergone saddle stitching and saddle folding so that the spine of the sheet bundle is located downstream in the conveying direction from the fore-edge, A pair of clamping parts that clamp and release the sheet bundle by moving relative to each other along the thickness direction of the sheet bundle being conveyed by the pair of conveying rotating bodies, and a pressing roller that presses the back of the sheet bundle by moving along the width direction of the sheet bundle, wherein in the conveying direction the back of the sheet bundle protrudes downstream from the pair of clamping parts, the back of the sheet bundle clamped by the pair of clamping parts is pressed by the pressing roller to give the back of the sheet bundle a squared back. A skew correction member is located downstream of the pair of clamping portions with respect to the transport direction, and corrects the skewness of the sheet bundle by pushing the back of the sheet bundle that protrudes downstream in the transport direction relative to the pair of clamping portions toward the upstream in the transport direction before the corner back processing is performed. The system includes a moving mechanism that moves the skew correction member toward the upstream side in the conveying direction when correcting the skew of the sheet bundle, The aforementioned skew correction operation includes a series of operations: an operation in which the sheet bundle is gripped and conveyed by the pair of conveying rotating bodies; an operation in which the conveying of the sheet bundle by the pair of conveying rotating bodies is stopped; an operation in which the gripping of the sheet bundle by the pair of conveying rotating bodies is released; and an operation in which the back of the sheet bundle is pushed by the skew correction member. The skew correction operation is performed multiple times if both of the following conditions are met: first, the number of sheets included in the sheet bundle to be subjected to the slanted back processing is equal to or greater than a predetermined number; and second, the difference between the image ratio on one side of the center and the image ratio on the other side of the center in the width direction intersecting the transport direction of the outermost sheet included in the sheet bundle is equal to or greater than a predetermined value. If at least one of the first and second conditions is not met, the skew correction operation is performed once. A sheet processing apparatus characterized by the following: (Configuration 2) With respect to the conveying direction, the lower guide portion is further provided, having a lower guide surface that is positioned between the pair of conveying rotating bodies and the pair of clamps and guides the lower surface of the sheet bundle conveyed by the pair of conveying rotating bodies in the direction of gravity, Of the pair of conveying rotating bodies, the lower conveying rotating body in the direction of gravity is positioned below the lower guide surface in the direction of gravity when the diagonal correction member pushes the back of the sheet bundle. A sheet processing apparatus according to configuration 1, characterized by the above. (Composition 3) With respect to the conveying direction, the upper guide portion is further provided, which is positioned between the pair of conveying rotating bodies and the pair of clamps and has an upper guide surface that guides the upper surface of the sheet bundle conveyed by the pair of conveying rotating bodies in the direction of gravity, Of the pair of conveying rotating bodies, the upper conveying rotating body in the direction of gravity is positioned above the upper guide surface in the direction of gravity when the diagonal correction member pushes the back of the sheet bundle. The sheet processing apparatus according to configuration 2, characterized by the features described above. (Composition 4) The aforementioned moving mechanism is a first moving mechanism, The oblique correction member is further provided with a second movement mechanism that allows it to move between a first position downstream of the pair of clamps with respect to the transport direction and facing the back of the sheet bundle that has passed through the pair of clamps, and a second position retracted from the first position. The second moving mechanism moves the diagonal correction member to the first position before the diagonal correction member pushes the back of the sheet bundle, and moves the diagonal correction member to the second position after the diagonal correction member pushes the back of the sheet bundle and before the corner back processing is performed. A sheet processing apparatus according to any one of configurations 1 to 3, characterized by the above. (Composition 5) An image forming unit having an image forming section that forms an image on a sheet, A sheet processing device according to any one of configurations 1 to 4, comprising The sheet processing apparatus is a sheet bundle comprising sheets on which images have been formed by the image forming unit, and is characterized by performing the corner spine processing on a sheet bundle that has undergone saddle stitching and saddle folding. [Explanation of symbols]

[0156] 3. Image forming unit 115...Saddle second roller pair (a pair of conveying rotating bodies) 115a...Second lower roller (lower conveying rotating body) 115b...Second upper roller (upper conveying rotating body) 116a...Second roller rear path lower guide (lower guide section) 116a1...Lower guide surface 116b...Second roller rear path upper guide (upper guide section) 116b1...Upper guide surface 118...Saddle third roller pair (a pair of conveying rotating bodies) 118a...Third lower roller (lower conveying rotating body) 118b...Third upper roller (upper conveying rotating body) 119a...Clamp front lower guide section (lower guide section) 119a1···Lower guide surface 119b... Upper guide section in front of the clamp (upper guide section) 119b1...Upper guide surface 120...Lower clamp unit (clamping part) 121... Upper clamp unit (clamping part) 123...Pressure roller 500... Skew correction unit 501... Contact member (diagonal correction member) 510...Movement mechanism (second movement mechanism) 520...Movement mechanism (first movement mechanism) 1000...Image forming system A...Image forming apparatus B... Sheet processing device C2... Square back processing area

Claims

1. A pair of conveying rotating bodies that convey sheet bundles that have undergone saddle stitching and saddle folding so that the spine of the sheet bundle is located downstream in the conveying direction from the fore-edge, A pair of clamping parts that clamp and release the sheet bundle by moving relative to each other along the thickness direction of the sheet bundle being conveyed by the pair of conveying rotating bodies, and a pressing roller that presses the back of the sheet bundle by moving along the width direction of the sheet bundle, wherein in the conveying direction the back of the sheet bundle protrudes downstream from the pair of clamping parts, the back of the sheet bundle clamped by the pair of clamping parts is pressed by the pressing roller to give the back of the sheet bundle a squared back. A skew correction member is located downstream of the pair of clamping portions with respect to the transport direction, and corrects the skewness of the sheet bundle by pushing the back of the sheet bundle that protrudes downstream in the transport direction relative to the pair of clamping portions toward the upstream in the transport direction before the corner back processing is performed. The system includes a moving mechanism that moves the skew correction member toward the upstream side in the conveying direction when correcting the skew of the sheet bundle, The aforementioned skew correction operation includes a series of operations: an operation in which the sheet bundle is gripped and conveyed by the pair of conveying rotating bodies; an operation in which the conveying of the sheet bundle by the pair of conveying rotating bodies is stopped; an operation in which the gripping of the sheet bundle by the pair of conveying rotating bodies is released; and an operation in which the back of the sheet bundle is pushed by the skew correction member. The skew correction operation is performed multiple times if both of the following conditions are met: first, the number of sheets included in the sheet bundle to be subjected to the slanted back processing is equal to or greater than a predetermined number; and second, the difference between the image ratio on one side of the center and the image ratio on the other side of the center in the width direction intersecting the transport direction of the outermost sheet included in the sheet bundle is equal to or greater than a predetermined value. If at least one of the first and second conditions is not met, the skew correction operation is performed once. A sheet processing apparatus characterized by the following:

2. With respect to the conveying direction, the lower guide portion is further provided, having a lower guide surface that is positioned between the pair of conveying rotating bodies and the pair of clamps and guides the lower surface of the sheet bundle conveyed by the pair of conveying rotating bodies in the direction of gravity, Of the pair of conveying rotating bodies, the lower conveying rotating body in the direction of gravity is positioned below the lower guide surface in the direction of gravity when the diagonal correction member pushes the back of the sheet bundle. The sheet processing apparatus according to feature 1.

3. With respect to the conveying direction, the upper guide portion is further provided, which is positioned between the pair of conveying rotating bodies and the pair of clamps and has an upper guide surface that guides the upper surface of the sheet bundle conveyed by the pair of conveying rotating bodies in the direction of gravity, Of the pair of conveying rotating bodies, the upper conveying rotating body in the direction of gravity is positioned above the upper guide surface in the direction of gravity when the diagonal correction member pushes the back of the sheet bundle. The sheet processing apparatus according to feature 2.

4. The aforementioned moving mechanism is a first moving mechanism, The oblique correction member is further provided with a second movement mechanism that allows it to move between a first position downstream of the pair of clamps with respect to the transport direction and facing the back of the sheet bundle that has passed through the pair of clamps, and a second position retracted from the first position. The second moving mechanism moves the diagonal correction member to the first position before the diagonal correction member pushes the back of the sheet bundle, and moves the diagonal correction member to the second position after the diagonal correction member pushes the back of the sheet bundle and before the corner back processing is performed. The sheet processing apparatus according to feature 1.

5. 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 4, comprising: The sheet processing apparatus is a sheet bundle comprising sheets on which images have been formed by the image forming unit, and is characterized by performing the corner spine processing on a sheet bundle that has undergone saddle stitching and saddle folding.

Images