Sheet post-processing device

Abstract

To make it possible to perform high-efficient post-processing without giving influence on an image forming device on an upstream side and a device on a downstream side while reducing a product size in a sheet conveyance direction, according to a sheet post-processing device for performing various post-processing of forming images.SOLUTION: According to a sheet post-processing device comprising a plurality of pieces of post-processing means for subjecting sheets each on which an image is formed, to a plurality of pieces of post-processing, there is provided the post-processing device comprising: a first conveyance passage for conveying the sheets without passing through the plurality of pieces of post-processing means, by connecting a carry-in port with an exhaust port; a second conveyance passage for conveying the sheets received at the carry-in port by passing through the plurality of pieces of post-processing means; a branch part for branching the sheets into any of the first conveyance passage and the second conveyance passage, that is provided near the carry-in port in the first conveyance passage; and a merging part for merging the second conveyance passage into the first conveyance passage, that is provided near the branch part in the first conveyance passage.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a sheet post-processing device that post-processes a sheet sent from an image forming apparatus, and more particularly to a sheet post-processing device including a plurality of post-processing units that perform post-processing such as cutting, severing, perforating, punching, and scoring on the sheet.

Background Art

[0002] Conventionally, there is known a sheet post-processing device that can perform a plurality of post-processings on a sheet on which an image has been formed by an image forming apparatus main body.

[0003] In such a sheet post-processing device, an image forming apparatus that discharges sheets sequentially after forming an image on the sheet is disposed upstream of the sheet post-processing device, and the above-described sheet post-processing device is disposed downstream thereof.

[0004] It is known that a sheet stacking device for stacking the post-processed sheets is disposed downstream of the above-described sheet post-processing device (see FIG. 1).

[0005] Since such a sheet post-processing device performs a plurality of post-processings on the sheets sequentially carried in from the image forming apparatus, complicated control such as timing adjustment of the sheet carry-in from the upstream image forming apparatus and the discharge of the post-processed sheets to the downstream sheet stacking device, deceleration of the sheets, and temporary stop is required. In particular, it has a great influence on so-called long sheets having a conveyance direction length of 1300 mm or the like.

[0006] If the sheet post-processing device waits to receive the sheet sent from the image forming apparatus, the efficiency of sheet processing as an image forming system deteriorates.

[0007] As a technique for solving this problem, a space path capable of accommodating a sheet is arranged upstream or downstream of the processing means in the sheet post-processing apparatus. For example, when the sheet to be post-processed straddles an image forming apparatus and sheet post-processing, the image-formed sheet is accommodated or retained in a path provided in the space within the sheet post-processing apparatus, so that the sheet during the post-processing operation does not straddle the upstream image forming apparatus or the downstream sheet stacking apparatus, and thus a device has been proposed that performs post-processing without adversely affecting the above-mentioned apparatuses on the upstream and downstream sides. (For example, refer to "Patent Document 1").

[0008] Since such a post-processing apparatus adopts an in-line method connected to an image forming apparatus, the installation area of the entire system, particularly the length in the conveyance direction, often becomes long, and miniaturization is desired for small and medium-sized printing businesses.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] However, in the configuration of the apparatus described in Patent Document 1, it is necessary to provide space paths 213, 214, 215 corresponding to various lengths of the sheets to be handled in the image forming apparatus main body 100 on the upstream side and the finisher FS on the downstream side of the processing means in the post-processing apparatus 200. Therefore, the housing of the post-processing apparatus becomes large in the sheet conveyance direction, and it has been difficult to save space.

[0011] Also, although a relay unit RU for sheet transfer is provided between the image restriction device main body 100 and the post-processing device 200 disclosed in this Patent Document 1, while the post-processing is being performed on the preceding sheet in the post-processing device 200, since the lengths of the space paths (retreat paths) 213 and 214 are short, the post-processing device 200 cannot accept the subsequent sheet, and it is necessary to widen the acceptance interval of the sheet from the image forming apparatus 100, so the processing efficiency of sheet post-processing as a whole decreases.

[0012] The present invention has been made in view of the above circumstances, and with respect to the sheet conveyance direction in the image forming system from upstream to downstream, while minimizing the size of the sheet post-processing device as much as possible, it does not adversely affect the sheet processing in the upstream and downstream devices and aims to provide a sheet post-processing device that enhances the productivity of sheet processing from image formation to post-processing.

Means for Solving the Problems

[0013] In order to achieve the above object, the present invention provides a sheet post-processing apparatus including a plurality of post-processing means for sequentially performing a plurality of post-processing operations such as cutting, trimming, perforating, punching, and scoring on an image-formed sheet that is sequentially discharged. The sheet post-processing apparatus includes a loading port for sequentially receiving the image-formed sheet, an outlet for discharging the received sheet downstream as it is without post-processing or after post-processing, a first conveyance path connecting the loading port and the outlet and conveying the sheet without passing through the plurality of post-processing means, a second conveyance path for conveying the sheet received at the loading port through the plurality of post-processing means, a branching portion provided near the loading port in the first conveyance path for branching the sheet to either the first conveyance path or the second conveyance path, and a merging portion provided near the branching portion in the first conveyance path for merging the second conveyance path into the first conveyance path. The plurality of post-processing means are arranged below the first conveyance path, and the second conveyance path is arranged such that the sheet branched at the branching portion passes below the plurality of post-processing means, then advances in a direction opposite to that of the first conveyance path within the plurality of post-processing means, and merges into the first conveyance path through the merging portion.

[0014] Thus, in the sheet post-processing apparatus according to the present invention, since the plurality of post-processing means are arranged below the first conveyance path, and the second conveyance path is arranged such that the sheet branched at the branching portion passes below the plurality of post-processing means, then advances in a direction opposite to that of the first conveyance path within the plurality of post-processing means, and merges into the first conveyance path through the merging portion, a sufficiently long sheet conveyance path can be ensured within the sheet post-processing apparatus without increasing the size of the housing with respect to the sheet conveyance direction in the image forming system.

[0015] Here, a cutting piece storage portion for storing the cut pieces of the sheet generated by the post-processing is arranged below the plurality of post-processing means, and the second conveyance path passes below the cutting piece storage portion. This prevents the cut pieces of the sheet from falling onto the second conveyance path and causing an obstruction to the sheet conveyance.

[0016] Furthermore, below the plurality of post-processing means, there is further arranged a post-processing sheet storage section for storing the post-processed sheet. The post-processing apparatus storage section is movable between the storage position of the post-processed sheet and the take-out position for taking out the post-processed sheet. The second conveyance path passes below the movement path of the post-processing sheet storage section. This is the gist of the invention.

[0017] And the lengths of the first conveyance path and the second conveyance path are set such that when the processing means located at the most upstream of the plurality of processing means is performing post-processing on the sheet, the upstream end of the sheet does not straddle the loading port or the discharge port, and when the processing means located at the most downstream of the plurality of processing means is performing post-processing on the sheet, the downstream end of the sheet does not straddle the loading port or the discharge port.

Advantages of the Invention

[0018] According to the present invention, when post-processing an image-formed sheet, by effectively using the space inside the apparatus for the sheets sequentially conveyed from the upstream image-forming apparatus side, and providing a path for retractably and circuitously conveying the sheets in the apparatus until they are post-processed as long as possible, miniaturization of the apparatus is achieved, and it becomes possible to provide a sheet post-processing apparatus configured not to affect the processing speeds of the upstream and downstream apparatuses.

Brief Description of the Drawings

[0019]

Figure 1

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Figure 8

[0020] Hereinafter, a sheet post-processing apparatus according to a preferred embodiment of the present invention and an image forming system including the same will be described with reference to the drawings. FIG. 1 is an explanatory view of the overall configuration of the image forming system according to the present embodiment. As shown in FIG. 1, the image forming system 100 includes an image forming apparatus A, a sheet post-processing apparatus B attached thereto, and a sheet stacking apparatus C.

[0021] <Overall Configuration of Image Forming Apparatus> The image forming apparatus A includes an image forming unit A1, a scanner unit (image reading device) A2, and a feeder unit (automatic paper feeding device) 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 inside the apparatus housing 1.

[0022] The feeding unit 2 in the image forming unit A1 is composed of a plurality of cassette mechanisms 2a, 2b, 2c that store image forming sheets (papers) of different sizes, and feeds out the sheets of the size specified by a control unit (not shown) in the present image forming unit A1 to the feeding path 2f. Each cassette mechanism 2a, 2b, 2c is detachably installed from the feeding unit 2, and includes a separating mechanism that separates the sheets inside one by one and a feeding mechanism that feeds out the sheets. In the feeding path 2f, there are provided conveying rollers that feed the sheets supplied from each cassette mechanism 2a, 2b, 2c to the downstream side, and a registration roller pair that aligns the leading ends of the sheets at the end of the path.

[0023] The supply path 2f is connected to a large-capacity cassette 2d and a manual feed tray 2e. 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.

[0024] In this embodiment, the image forming unit 3 is configured using an electrophotographic method, and includes a rotating photosensitive drum 3a, a light emitter 3b that emits an optical beam disposed around it, a developing device 3c, and a cleaner (not shown). What is shown in the figure is a monochrome printing mechanism. The photosensitive drum 3a with a uniformly charged peripheral surface is irradiated with light corresponding to the image signal by the light emitter 3b to optically form a latent image, and a toner image is formed by attaching toner to this latent image with the developing device 3c.

[0025] In accordance with the timing of forming an image on the photosensitive drum 3a, a sheet is sent from the supply path 2f to the image forming unit 3, and the toner image formed on the photosensitive drum 3a is transferred onto the sheet by applying a transfer bias from the transfer charger 3d. The sheet onto which the toner image has been transferred is heated and pressurized when passing through the fuser 6, the toner image is fixed, and it is discharged from the discharge port 4b by the discharge roller 4a and conveyed to a sheet post-processing device B described later.

[0026] The scanner unit A2 includes a platen 7a on which an image original is placed, a carriage 7b that reciprocates along this platen 7a, a photoelectric conversion means 7c, and a reduction optical system 7d that guides the reflected light from the original on the platen 7a by the carriage 7b to the photoelectric conversion means 7c. The photoelectric conversion means 7c photoelectrically converts the optical output from the reduction optical system 7d into image data and outputs it as an electrical signal to the image forming unit 3.

[0027] Further, the scanner unit A2 includes a traveling platen 7e for reading the sheet sent from the feeder unit A3. The feeder unit A3 includes a feeding tray 8a for stacking the original sheets, a feeding path 8b for guiding the original sheets sent out from the feeding tray 8a to the traveling platen 7e, and a discharge tray 8c for storing the original sheets that have passed through the traveling platen 7e. The original sheets from the feeding tray 8a are read by the carriage 7b and the reduction optical system 7d when passing through the traveling platen 7e.

[0028] <Overall Configuration of Sheet Post-processing Device> Next, the overall configuration of the sheet post-processing device B that processes the sheets sent from the image forming device A will be described.

[0029] FIG. 2 is an explanatory diagram of the configuration of the sheet post-processing device B. The sheet post-processing device B is a device that performs processing on the sheets conveyed from the image forming device A as necessary. Examples of the processing include cutting processing in the conveyance direction, cutting processing in the direction perpendicular to the conveyance, slitter processing, crease processing, sewing processing, etc. The processing unit of the sheet post-processing device B is composed of processing means M1 to M5. The processing means M1 to M5 are recombinable and are configured to be able to change the processing order and processing content of each.

[0030] When cutting processing is performed within the processing means M1 to M5, unnecessary cut pieces are generated. In order to store the cut pieces, a cut piece storage unit 91 is provided below the processing means M1 to M5. The cut piece storage unit 91 is configured to be movable between a position for storing the cut pieces and a take-out position for taking out the cut pieces to the outside.

[0031] Immediately downstream in the second conveyance direction of the processing means M1 to M5, there is a post-processing sheet storage unit 92 for storing the post-processing sheets generated by the processing means M1 to M5. The post-processing sheet storage unit 92 is a storage unit for storing post-processing sheets of small sizes such as business cards and cards, and has a role of storing post-processing sheets of sizes that are difficult to convey at the roller pitch of the second conveyance means 70. The post-processing sheet storage unit 92 is configured to be movable between a position for storing the post-processing sheets and a take-out position for taking out the post-processing sheets to the outside.

[0032] FIG. 3 is a control block diagram of the sheet post-processing apparatus, FIG. 4 is a flowchart during sheet conveyance of the sheet post-processing apparatus, and FIGS. 5 to 7 are cross-sectional explanatory views during sheet conveyance of the sheet post-processing apparatus. The sheet post-processing apparatus B includes a carry-in port 51 for introducing a sheet from the image forming apparatus A, and is arranged so that the carry-in port 51 is aligned with the discharge port 4b of the image forming apparatus A. The sheet conveyed from the carry-in port 51 is conveyed in the conveyance direction from the carry-in port 51 toward the discharge port 52 along the first conveyance path 53 by the first conveyance means 60 constituted by the conveyance rollers 60a to 60k.

[0033] The first conveyance path 53 is provided with a branch portion 58 constituted by a flapper guide and a merging portion 59. The branch portion 58 is switched and controlled by the control unit 200 between a position for guiding the sheet to the first conveyance path 53 and a position for guiding the sheet to the second conveyance path 54. When the branch portion 58 is switched to the position for guiding the sheet to the second conveyance path 54, the sheet conveyed on the first conveyance path 53 is guided to the second conveyance path 54 with the downstream end of the sheet in the conveyance direction as the leading end (S1 to S4, FIG. 5). The sheet guided to the second conveyance path 54 is conveyed in the second conveyance direction from the branch portion 58 toward the merging portion 59 along the second conveyance path 54 by the second conveyance means 70 constituted by the second conveyance rollers 70a to 70u.

[0034] The second conveyance path 54 is configured by a path connecting second conveyance rollers 70a to 70m that guide the sheet so as to bypass the processing means M1 to M5, the cut piece storage unit 91, and the post-processing sheet storage unit 92, second conveyance rollers 70n to 70s that convey the sheet in a direction opposite to the conveyance direction toward the discharge port 52, and second conveyance rollers 70t to 70u that convey the sheet toward the confluence unit 59. Note that the sheet that enters the second conveyance path 54 and the sheet that passes through the confluence unit 59 are accelerated and moved at a higher speed than when the image forming apparatus A receives the sheet. As a result, it is possible to receive the sheet without delaying the image forming apparatus A while widening the interval between the preceding sheet and the subsequent sheet to secure time for post-processing.

[0035] A curved path 55 is provided in the second conveyance path 54, and the curved path 55 is provided with skew correction means 80 composed of a pair of rollers that can be switched between drive stop and drive start by control. By abutting the downstream end of the sheet in the second conveyance direction of the sheet conveyed through the curved path 55 against the skew correction means 80 during drive stop, skew correction of the downstream end of the sheet is performed while forming a loop shape in the sheet. After skew correction, the drive of the skew correction means 80 is started to re-convey the sheet, and the sheet is guided in the second conveyance direction while eliminating the loop. In this embodiment, the skew correction means 80 is provided in the curved path 55 to facilitate formation of a loop in the sheet, but it may be provided in another path (not shown).

[0036] The sheet conveyed in the second conveyance direction through the second conveyance path 54 is guided again to the first conveyance path 53 with the downstream end of the sheet in the second conveyance direction at the head by the confluence unit 59, and is conveyed toward the discharge port 52 by the first conveyance means 60 (S5, S7, FIG. 7).

[0037] The branch unit 58 recognizes whether or not the subsequent sheet sent from the image forming apparatus A is to be processed by the process recognition means 81, and switches again to a position where it guides the sheet to the first conveyance path 53 or the second conveyance path 54 (S7, S2).

[0038] Here, the conveyance path lengths of the first conveyance path 53 and the second conveyance path 54 will be described. For the processing means M1 to M5 that perform processing on the sheet, there are appropriate sheet conveyance conditions for performing each process. For example, in the case of CD cutting processing, it is necessary to perform stop control on the conveyed sheet so that the position of the cutting blade and the cutting designated position of the sheet are aligned. In the case of slitter processing, it is necessary to perform speed control on the conveyed sheet so that the sheet conveyance speed at which cutting defects do not occur is achieved. Thus, it is necessary to perform conveyance control of the conveyed sheet according to the content of each process. Further, when the sheet to be processed straddles the upstream and downstream devices, it is necessary to synchronize the stop control and speed control between the sheet post-processing device B and the upstream and downstream devices, so the control response becomes enormous and difficult.

[0039] Therefore, the sheet post-processing device B is configured such that when the processing means located most upstream in the second conveyance direction among the processing means M1 to M5 performs processing on the sheet, the upstream end of the sheet in the second conveyance direction does not straddle the conveyance inlet 51. Also, when the processing means located most downstream in the second conveyance direction among the processing means M1 to M5 performs processing on the sheet, the downstream end of the sheet in the second conveyance direction does not straddle the discharge port 52. As a result, the sheet being processed by the processing means M1 to M5 does not straddle the upstream and downstream devices, and processing can be performed without affecting the upstream and downstream devices.

[0040] Also, the sheet post-processing device B is provided with a process recognition means 81 for recognizing whether or not processing is performed on the sheet by the processing means M1 to M5. When the process recognition means 81 recognizes that processing is not performed on the sheet, the branch portion 58 does not switch to a position for guiding to the second conveyance path 54 so that the sheet conveyed along the first conveyance path 53 from the conveyance inlet 51 can reach the discharge port 52 without passing through the second conveyance path 54, and maintains the position for guiding to the first conveyance path 53. As a result, the sheet on which processing is not performed by the processing means M1 to M5 is conveyed to the discharge port 52 by the shortest distance without passing through the second conveyance path 54, so productivity can be improved.

[0041] Furthermore, the sheet post-processing device B includes basis weight (stiffness) recognition means 82 for recognizing the basis weight and stiffness of the sheet. When the basis weight (stiffness) recognition means 82 recognizes that the basis weight of the conveyed sheet exceeds a predetermined basis weight (stiffness), the branch portion 58 does not switch to a position guiding the sheet to the second conveyance path 54 so that the sheet conveyed along the first conveyance path 53 from the conveyance inlet 51 can reach the discharge port 52 without passing through the second conveyance path 54, and maintains the position guiding the sheet to the first conveyance path 53. As a result, sheets with a large basis weight and stiffness are conveyed to the discharge port 52 without passing through the second conveyance path 54 including the curved portion, so that conveyance failures in the second conveyance path 54 can be reduced.

[0042] <Overall Configuration of Sheet Stacking Device> Next, the overall configuration of the sheet stacking device C that processes the sheets sent from the sheet post-processing device B will be described.

[0043] FIG. 8 is an explanatory diagram of the configuration of the sheet stacking device C according to the present embodiment. The sheet stacking device C includes a conveyance inlet 10 for introducing the sheets from the sheet post-processing device B, and is arranged so that the conveyance inlet 10 communicates with the discharge port 52 of the sheet post-processing device B.

[0044] The sheet stacking device C includes a sheet introduction path 12 for conveying the sheets introduced from the conveyance inlet 10, a first discharge path 13a, a second discharge path 13b, and a third discharge path 13c branched from the sheet introduction path 12, a first path switching means 14a, and a second path switching means 14b. The first path switching means 14a and the second path switching means 14b are each constituted by a flapper guide for changing the conveyance direction of the sheets conveyed along the sheet introduction path 12.

[0045] The first path switching means 14a switches between a mode of guiding a sheet from the loading port 10 directly in the lateral direction to the first discharge path 13a and in the direction of the second discharge path 13b for downward conveyance, and a mode of guiding the sheet to the third discharge path 13c for upward conveyance. The first discharge path 13a and the second discharge path 13b communicate with each other such that a sheet once introduced into the first discharge path 13a can be switchback conveyed to the second discharge path 13b by reversing the conveyance direction.

[0046] The second path switching means 14b is arranged on the downstream side of the first path switching means 14a with respect to the conveyance direction of the sheet conveyed along the sheet loading path 12. The second path switching means 14b also switches, by means of a driving means (not shown), between a mode of introducing the sheet that has passed through the first path switching means 14a into the first discharge path 13a, and a mode of switchback conveying a sheet once introduced into the first discharge path 13a to the second discharge path 13b.

[0047] The sheet stacking device C includes a first processing unit C1, a second processing unit C2, and a third processing unit C3 that each perform a plurality of processes. Further, a punching unit 15 for punching punch holes in the loaded sheet is arranged on the sheet loading path 12.

[0048] The first processing unit C1 accumulates, collates, and binds a plurality of sheets discharged from the discharge port 16a at the downstream end of the first discharge path 13a with respect to the conveyance direction of the sheet conveyed along the sheet loading path 12, and is a binding processing unit that discharges the sheets to a loading tray 16b provided outside the apparatus housing 11. The first processing unit C1 also includes a sheet conveyance device 16c for conveying the sheet or the bundle of sheets, and a binding processing unit 16d for binding the bundle of sheets. At the downstream end of the first discharge path 13a, a pair of discharge rollers 16e is provided for discharging the sheet from the discharge port 16a and for switchback conveying the sheet from the first discharge path 13a to the second discharge path 13b.

[0049] The second processing unit C2 is a folding processing unit that forms a sheet bundle from the sheet or sheets switchback-conveyed from the second discharge path 13b and performs a folding process, or performs a folding process after binding the sheet bundle. The second processing unit C2 includes a folding processing device F that folds the loaded sheet or sheet bundle, and a binding processing unit 17a that is disposed immediately upstream of the folding processing device F along the sheet conveyance direction of the sheet conveyed to the second discharge path 13b and binds the sheet bundle. The folded sheet or sheet bundle is discharged by the discharge roller pair 17b to a stacking tray 17c provided outside the apparatus housing 11.

[0050] The third processing unit C3 performs jog sorting to divide the sheets sent from the third discharge path 13c into a group that accumulates the sheets by offsetting a predetermined amount in the sheet width direction orthogonal to the conveyance direction and a group that accumulates the sheets without offsetting. The jog-sorted sheets are discharged to a stacking tray 18 provided outside the apparatus housing 11, and the offset sheet bundle and the non-offset sheet bundle are stacked.

Explanation of Reference Numerals

[0051] A: Image forming apparatus B: Sheet post-processing apparatus C: Sheet stacking apparatus M1, M2, M3, M4, M5: Each processing means constituting the sheet post-processing apparatus 51: Loading port 52: Discharge port 53: First conveyance path 54: Second conveyance path 58: Branching portion 59: Confluence portion 60: First conveyance means 70: Second conveyance means 80: Skew correction means 91: Cutting piece storage portion 92: Post-processed sheet storage portion

Claims

1. A sheet post-processing apparatus including a plurality of post-processing means for performing a plurality of processes on sequentially discharged image-formed sheets, comprising: a carry-in port for sequentially receiving the image-formed sheets; a discharge port for discharging the received sheets downstream as they are without post-processing or after post-processing; a first conveyance path connecting the carry-in port and the discharge port and configured to convey sheets without passing through the plurality of post-processing means; a second conveyance path for conveying the sheets received at the carry-in port through the plurality of post-processing means; a branch portion provided near the carry-in port in the first conveyance path and configured to branch the sheets to either the first conveyance path or the second conveyance path; a merging portion provided near the branch portion in the first conveyance path and configured to merge the second conveyance path into the first conveyance path, wherein the plurality of post-processing means are arranged below the first conveyance path, and the second conveyance path is arranged such that the sheets branched at the branch portion pass below the plurality of post-processing means, then proceed in a direction opposite to that of the first conveyance path within the plurality of post-processing means, and merge into the first conveyance path through the merging portion.

2. A cutting piece storage portion for storing cutting pieces of the sheets generated by post-processing is arranged below the plurality of post-processing means, and the second conveyance path passes below the cutting piece storage portion. The sheet post-processing apparatus according to claim 1, characterized in that.

3. A post-processed sheet storage portion for storing the post-processed sheets is further arranged below the plurality of post-processing means, the post-processed sheet storage portion is movable between a storage position for storing the post-processed sheets and a take-out position for taking out the post-processed sheets, and the second conveyance path passes below the movement path of the post-processed sheet storage portion. The sheet post-processing apparatus according to claim 2, characterized in that.

4. The lengths of the first conveyance path and the second conveyance path are set such that when the processing means located at the most upstream of the plurality of processing means is performing post-processing on the sheet, the upstream end of the sheet does not straddle the carry-in port or the discharge port, and when the processing means located at the most downstream of the plurality of processing means is performing post-processing on the sheet, the downstream end of the sheet does not straddle the carry-in port or the discharge port. The sheet post-processing apparatus according to claim 3, characterized in that.

5. A processing recognition means for recognizing whether the sheet carried in from the carry-in port is post-processed by any of the plurality of processing means is provided. When recognized by the processing recognition means as a sheet to be post-processed, the branch section guides the sheet to the second conveyance path. When recognized by the processing recognition means as a sheet not to be post-processed, the branch section branches the sheet to the discharge port. The sheet post-processing apparatus according to claim 4.

6. Further provided with a basis weight and stiffness recognition means for recognizing the basis weight or stiffness of the sheet. Even when the sheet recognized by the basis weight and stiffness recognition means as exceeding the predetermined basis weight or stiffness is recognized by the processing recognition means as a sheet to be post-processed, the branch section branches the sheet to the first conveyance path without branching it to the second conveyance path. The sheet post-processing apparatus according to claim 5.

7. A curved section is formed in the second conveyance path leading to the plurality of post-processing means. The sheet post-processing apparatus according to claim 1, wherein skew correction means for performing skew correction of the sheet carried into the plurality of post-processing means is arranged in the curved section.

8. An image forming apparatus for forming an image on a sheet. The sheet post-processing apparatus according to any one of claims 1 to 7. A sheet stacking apparatus for stacking the sheets discharged from the sheet post-processing apparatus. An image forming system comprising:

Images