JP4925978B2 - Paper post-processing apparatus and image forming system - Google Patents

Description

  The present invention relates to a sheet post-processing apparatus provided in an image forming apparatus such as a copying machine, a printer, or a printing machine, and particularly includes a shift unit for shifting a stacking position of sheets discharged on a sheet stacking tray in the width direction. The present invention relates to an improvement of a paper post-processing apparatus.

2. Description of the Related Art A sheet post-processing apparatus that performs various post-processing such as stapling and punching on a sheet that has undergone image formation by an image forming apparatus such as a copying machine, a printer, or a printing machine has been known.
For example, Japanese Patent Application Laid-Open No. 2002-179330 discloses a sheet post-processing apparatus that performs fine adjustment of the punch hole position in the width direction orthogonal to the transport direction by using a shift mechanism for sorting discharged sheet bundles. Is disclosed. This post-processing apparatus for paper processing shifts the paper by moving the transport roller in the width direction. However, since the shift means in the shift direction is independent, when shifting, the preceding paper is shifted, and the preceding paper is shifted by the shifting means. There is a problem that the productivity is lowered because the succeeding sheet cannot be received unless the shift means returns to the sheet receiving position after exiting.
JP 2002-179330 A

The present invention has been made in view of the above, and discharges paper continuously conveyed toward the paper stacking tray onto the paper stacking tray while shifting the position in the width direction without reducing the transport speed. It is an object of the present invention to provide a sheet post-processing apparatus and an image forming system that can perform the above processing.
In the paper post-processing apparatus according to the present invention, a plurality of branch transport paths are provided in the transport path for discharging the paper to the paper stacking tray, and a shift unit is provided in each branch transport path. Since one shift means performs the shift operation of the preceding paper and does not wait for the shift means to return to the receiving position, the subsequent paper is received by the other shift means, thereby improving productivity. Can do.

In order to achieve the above object, a first aspect of the present invention is directed to a transport path for receiving a sheet discharged from an image forming apparatus and transporting the sheet to a sheet stacking tray, a transport mechanism for transporting a sheet in the transport path, and the sheet stacking A plurality of branch conveyance paths provided in the conveyance path upstream of the tray, and a switching unit that is arranged in an upstream branch portion of the plurality of branch conveyance paths and switches the paper conveyance direction to one of the branch conveyance paths A shift unit that shifts and moves a sheet that is arranged in each branch conveyance path in a width direction perpendicular to the conveyance direction, a detection unit that detects the passage of the sheet, and the detection unit and characterized in that and a control means for controlling the conveying mechanism to change the conveying speed of the shift means at an arbitrary timing after it is detected that the sheet has reached the shift means That.
According to a second aspect of the present invention, in the first aspect, the plurality of shift means are configured to shift and move independently of each other.
The invention of claim 3 is characterized in that in claim 1 or 2, a common drive source for driving the plurality of shift means is provided.
The invention of claim 4 is characterized in that, in claim 1 or 2, the plurality of shift means are driven by separate drive sources.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the branch conveyance path to be used is switched by the switching unit for each sheet.
A sixth aspect of the invention is characterized in that, in any one of the first to fifth aspects, the shift means to be used is switched by switching the branch conveyance path by the switching means.
A seventh aspect of the invention is characterized in that in any one of the first to sixth aspects, the shift operation is performed by switching the plurality of shift means alternately for each sheet of paper or alternately for any number of sheets. To do.

The invention of claim 8 is characterized in that, in claim 7 , the control means determines whether or not to switch the shift means according to the size and transport speed of the paper.
A ninth aspect of the present invention is that in the first aspect , the control unit controls the transport mechanism to stop the transport of the paper by the shift unit at an arbitrary timing after the paper reaches the shift unit. Features.
The invention of claim 10 is characterized in that, in claim 9 , the transport of the stopped paper is transported in synchronism with the transport timing of the succeeding paper in another branch transport path, and a plurality of papers are stacked and transported. To do.
An eleventh aspect of the invention is characterized in that, in the first aspect, the plurality of shift means are arranged while being shifted in the paper transport direction.
An invention of claim 12 is an image forming system comprising the sheet post-processing apparatus according to any one of claims 1 to 11 and the image forming apparatus.

As a shift mechanism equipped in a conventional paper post-processing apparatus, there is a mechanism that shifts a sheet by moving a shift unit such as a conveyance roller in a direction orthogonal to the sheet conveyance direction, but the shift unit in the shift direction is independent. It is. For this reason, when shifting the paper, after the preceding paper is shifted, the paper leaves the shift means, and the shift means cannot return the paper to the paper receiving position before the subsequent paper can be received. There's a problem.
According to the first aspect of the present invention, a plurality of branch transport paths are provided in parallel in the transport path, and shift means for shifting the paper in the width direction and switching means for switching the branch transport paths are provided in each branch transport path. Further, during the shifting operation of the preceding sheet, the succeeding sheet can be prepared and operated by another shifting unit, and the productivity can be improved. Further, after the paper reaches the shift means, the stacking property is improved because the alignment time after the paper is discharged can be gained by increasing the transport speed of the shift means. Further, since the time until the sheet is removed from the shift roller can be shortened, the preparation time for receiving the succeeding sheet is shortened, and the productivity can be improved.
According to the second aspect of the present invention, the shift driving of the plurality of shift means is made independent, and it is possible to drive independently without waiting for one shift process to be completed for the continuously conveyed sheets. Productivity can be improved because the next paper shift preparation and operation can be performed.

According to the invention of claim 3, by making the driving for conveying the paper of each shift means a common drive, the error of the conveying speed can be reduced, the drive unit can be reduced, energy can be reduced, and the machine cost is reduced. be able to.
The invention according to claim 4 makes it possible to change the transport speed of each shift means at an arbitrary timing by making the plurality of drive means for transporting the paper independent of each other, so that the transport speed of the preceding paper or the following paper can be changed. Therefore, it is possible to convey the sheet at an independent optimum conveyance speed without being influenced by the above, so that it is possible to further increase the sheet interval during conveyance and to improve the corresponding productivity.

According to the fifth aspect of the present invention, the shift means to be used can be switched for each sheet, and the operation of the shift means for the preceding sheet and the return to the sheet receiving position are not in time before the succeeding sheet arrives. Since the sheet is guided to another shift means and the shift operation is controlled so as to be processed in parallel, productivity can be improved.
According to the sixth aspect of the present invention, the paper can be guided to another shift means by switching the branch conveyance path of the preceding paper and the subsequent paper, and the control of claim 5 is realized by making the paper branch conveyance path different. So productivity can be improved.
According to the seventh aspect of the present invention, when shifting the sheet being conveyed, if the shift sheet cannot be received in time by one shift means, the shift means can be switched alternately to improve productivity. Yes. When the shift direction is switched, the last sheet is accelerated if it is necessary to increase the distance between the last sheet before switching the shift direction and the first sheet after switching the shift direction by retracting the alignment device that aligns the sheets in the sheet stacking tray. By switching the leading sheet to the conveyance path of another shift means while conveying, the sheet interval can be earned. Thus, productivity can be improved by switching the shift means at any necessary timing.
It is only necessary to switch the shifting means when productivity is not in time.

In the invention of claim 8 , judgment is made based on information including paper size, speed, etc., and the shift means is switched as in the control of claim 7 only when necessary, so that useless operations can be eliminated and energy is reduced. be able to.
According to the ninth aspect of the present invention, after the paper reaches the shift means, the control of stopping the transfer of the shift means is performed so that the paper is conveyed along the transport path of another shift means at the same timing as the production. Can be improved.
In the invention of claim 10 , the sheet passing through the shift means is conveyed at an arbitrary timing before or after the shift, overlapping with the sheet conveyed on the other path at the same timing. By superposing and conveying, it is possible to reduce the number of alignment operations when aligning sheets on the stacking tray, and to improve productivity.
According to the eleventh aspect of the present invention, by disposing a plurality of shift means, a useless space can be eliminated and the machine can be downsized.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.
FIG. 1 is an explanatory diagram of a schematic configuration of a sheet post-processing apparatus according to the present invention.
The paper post-processing apparatus 200 is connected to the image forming apparatus in a state where the paper inlet is connected to the paper discharge port of the image forming apparatus 100 such as a copying machine, a printer, or a printing apparatus, and forms an image in the image forming apparatus. Accept the received paper one by one.
The paper post-processing apparatus 200 can perform post-processing such as binding, punching, shifting, and alignment for the paper received from the image forming apparatus 100, or can convey and discharge the paper to a paper stacking tray without performing post-processing. . In this embodiment, the paper transport path in the paper post-processing apparatus includes a transport path H that goes straight from the paper inlet to the paper stacking tray 229, and a post-processing section (in this example, a stapling section) from the branch section (branching claw 211b) I. And a post-processing conveyance path K extending to J. The conveyance path is switched depending on whether or not post-processing is performed in the post-processing mechanism J. Further, on the upstream side of the branching portion I, a paper discharge path M (conveying roller 212, paper discharge roller 213) and a branching portion L for guiding the paper to the paper discharge tray 214 are provided, and the paper is discharged by the branching claw 211a. The sheet is switched and conveyed to the path M.

The paper discharged from the paper discharge roller 101 provided at the paper discharge port of the image forming apparatus 100 passes through the inlet guide 201 provided at the introduction port of the paper post-processing apparatus 200 and is introduced into the introduction path G (upstream of the conveyance path H). To be introduced. On the introduction path G, conveying rollers 204 and 205, a punch 251, and branch claws 211a and 211b are arranged.
The conveyance path H on the downstream side of the branching section I branches into a plurality of branch conveyance paths 220 and 230, and the branch conveyance paths merge before the paper discharge roller 225. Shift rollers (pairs) 202 and 203 as shift means are arranged in the branch conveyance paths 220 and 230 while shifting the positions in the conveyance direction. A branch claw (switching means) 222 for switching the transport direction to any one of the branch transport paths 220 and 230 is arranged at a branch portion of the branch transport path.
The sheet post-processing apparatus 200 includes a control unit (CPU) and controls each control target based on a control signal from the image forming apparatus 100 side.
The sheet post-processing device 200 and the image forming apparatus constitute an image forming system.

The operation of the shift control method according to the present invention will be described below with reference to the drawings, taking as an example the case of discharging in straight mode.
The paper discharged from the image forming apparatus 100 passes through the inlet guide plate 201 of the paper post-processing apparatus 200 and is carried into the transport path H (introduction path G) by the transport roller 204. The sheet conveyance drive is performed by a step motor (conveyance mechanism), and the conveyance distance per pulse is known for control, so that the sheet conveyance position can be managed accurately. In the course of traveling along the transport path H, the paper passes through the transport roller 205, the shift roller 202 or 203, and is discharged onto the external paper stacking tray 229 by the paper discharge roller 225. Along the sheet stacking tray 229, and the aligning device 300 disposed above the sheet stacking tray 229 can align the ends in the B direction (width direction) perpendicular to the paper discharge direction A. Yes. If necessary, the sheets can be stacked in a sorting state in which the positions are shifted by a predetermined number in the shift direction B (width direction) orthogonal to the paper discharge direction A (FIGS. 2 and 3).

FIG. 4 is a structural view of the alignment device 300 as viewed from below. The driving force of the aligning member driving motors 301 and 302 arranged close to the center in the width direction is transmitted to the moving members 307 and 308 fixed to the timing belt by the timing belts 303 and 304 and the pulleys 305 and 306, respectively. The The drive motors 301 and 302 of the present embodiment use step motors, and the movement distance per pulse can be understood for control, so that the aligning members 310 and 311 can be accurately stopped at the target positions. it can. The aligning members 310 and 311 are incorporated in the moving members 307 and 308, and can be moved independently in the left and right directions in a direction orthogonal to the sheet discharge direction, and are aligned with the both end surfaces in the width direction of the sheet (bundle) being sandwiched. It has become. The transmission sensors 312 and 313 are reference position sensors for confirming the reference positions of the alignment members 310 and 311, and depend on whether the sensor detection plates 307 a and 308 a of the moving members 307 and 308 shield the sensors 312 and 313. Sensor output changes. From the output signals of the sensors 312, 313 and the number of drive pulse signals sent to the motor, it is possible to recognize how far the alignment members 310, 311 have moved from this reference position.
Further, the alignment members 310 and 311 are assembled so as to be movable in the axial direction (width direction B) by a shaft 309 penetrating the alignment device 300 in the width direction B, and the alignment members disposed at the ends of the shaft 309. The rotation of the vertical retraction motor 315 is transmitted to the gear 314, and the shaft 309 is rotated to rotate in the vertical direction shown in FIG. 1, and the alignment in the direction B perpendicular to the paper discharge direction as shown in FIG. In combination with the operation, the end face can be aligned with the sheets stacked in the sorting state shifted by the post-processing device.

Next, a case will be described in which when the sheet alignment mode is selected, the sheets themselves are shifted and sorted to perform sheet alignment.
In the present embodiment, an example in which two shift rollers as shift means are provided as shown in FIG. 1 will be described. The shift rollers (shift means) 202 and 203 of this embodiment are respectively provided in the branch conveyance paths 220 and 230 provided in parallel, and each shift roller is arranged at a position shifted in the paper conveyance direction. By displacing a plurality of shift rollers, the space for arranging the shift rollers 202 and 203 in parallel can be reduced, and the machine can be reduced in size and space.
Next, a case will be described in which when the sheet alignment mode is selected, the sheets themselves are shifted and sorted to perform sheet alignment. The control system of the sheet post-processing apparatus is as shown in FIG. 12, and various control objects are controlled by a CPU as a control means.

FIG. 6 shows a shift roller that is a part of the structure of a shift mechanism that shifts a sheet in a width direction B orthogonal to the transport direction A. Although the present invention has a plurality of shift mechanisms, an embodiment provided with two shift mechanisms will be described. Since the two shift mechanisms have the same configuration, only one shift mechanism will be described.
A pair of driven rollers 601 that are slidable in the width direction perpendicular to the sheet conveyance direction are pressed against the outer peripheral surface of each shift roller (shift means) 202 in an elastic manner. The driven rollers 601 rotatably supported by the support shaft 602 are elastically biased toward the central portion of the support shaft 602 (direction in which the driven rollers 601 approach each other) by the spring 630, and each shift roller 202 is shifted in the shift direction. It is configured to self-return to the original position after moving to.

Each shift roller 202 has its axis fixed by a shaft 612, and the shaft 612 obtains a conveying force by a rotational force transmitted from a driving unit (not shown) via a gear 613. Reference numeral 620 denotes a shift motor, which is connected to the shaft 610 via a gear portion 610 and a link portion 611. When the shift motor 620 rotates by a certain amount, the shift roller 202 is moved to a central position in a direction perpendicular to the paper transport direction. For example, 10 mm to one side and 20 mm on both sides. This shift movement amount can be varied to an arbitrary shift amount by using the shift motor 620 as a motor capable of controlling the movement amount such as a step motor. This amount of movement needs to be set to an amount that allows discrimination between the discharged bundles when the sheets are discharged and stacked on the sheet stacking tray 229. The shift means 202 and 203 are configured to shift the sheets one by one in the left-right direction perpendicular to the transport direction while transporting the received paper at the center when viewed from the top of the paper transport path H (FIG. 5).
The shift roller 202 is connected to a conveyance drive source via a gear 613. The drive source of the plurality of shift rollers 202 and 203 is a common drive source, and the conveyance speed and acceleration / deceleration of the plurality of shift rollers are always conveyed at the same speed. If controlled to do so, it is possible to reduce the transport drive section of the shift means, to reduce the machine, and to reduce the cost.
Contrary to the above, each of the transport rollers (drive sources) of the plurality of shift rollers 202 and 203 is separately and independently increased so as to be combined with the transport shift operation regardless of the transport speed of another shift means. By conveying, the space between the subsequent sheets can be increased and the productivity can be improved.

When the paper sorting alignment mode is selected on the image forming apparatus 100 side, the paper discharged from the image forming apparatus 100 is transported through transport rollers 204 and 205. The conveyance path H is guided to the shift roller 202 or the shift roller 203 by switching the branch claw 222. When the sheet is shifted by the shift roller 202, the leading end of the branching claw 222 is switched upward and the sheet is conveyed in the direction of the shift unit 202 (first branch conveyance path 220). After the trailing edge of the sheet passes through the conveyance roller 205, the sheet is shifted by the shift roller 202 in a direction perpendicular to the sheet conveyance direction. Further, by increasing the shift roller 202 from the conveying speed at an arbitrary timing different from the shift operation, it is possible to secure a wide interval from the succeeding sheet, and to improve the productivity by increasing the shift operation time and the return time. . When the shift direction is performed in the reverse direction, only the control that reverses the drive direction of the shift roller is different, and the other control is the same.
As described above, in the present invention, after the paper reaches the shift roller, control is performed so as to change the transfer speed of the shift roller at an arbitrary timing (see the flowchart of FIG. 13).

When the trailing edge of the sheet passes through the shift roller 202 after the shift operation is completed, the shift roller 202 is returned to the sheet receiving position to prepare for receiving the subsequent sheet. When shifting by another shift roller 203, the leading end of the branching claw 222 is switched to the lower side and the sheet is conveyed in the direction of the shift means 203 (second branch conveyance path 230).
If the shift operation by the shift roller is sufficiently in time with respect to the interval time of the continuously conveyed paper, it is sufficient to perform the shift operation using only one of the shift roller 202 or the shift roller 203. Good.

Next, the control when the shift operation and the return of the shift rollers 202 and 203 to the receiving position are not in time for the interval time of continuously conveyed sheets will be described with reference to FIGS. FIG. 7 is a view immediately after the preceding sheet 501 is shifted in the width direction B by the shift roller 202 and the shift movement is completed. The shift roller 202 holds the shifted position until the rear end of the paper 501 passes through the shift roller 202. After the rear end of the paper 501 passes through the shift roller 202, the shift roller 202 is in a direction orthogonal to the paper transport direction A. The returning operation to B is started, but when the interval between the preceding sheet 501 and the succeeding sheet 502 is short, the time for returning the shift roller 202 to the receiving position of the sheet 502 is not in time. In such a case, after the trailing edge of the sheet 501 passes through the branching claw 222, the branching claw 222 is switched to the lower side to open the second branch conveyance path 230 and convey the subsequent sheet 502 in the direction of the shift roller 203. The shift roller 203 has already been returned to the paper receiving position, and the succeeding paper 502 can be received and shifted. If there is a succeeding sheet of the sheet 502 and the sheet interval is not in time for the shift operation by the shift roller 203, the branch claw 222 is switched upward again to open the first branch conveyance path 220 as shown in FIG. The sheet is conveyed in the 202 direction and the shift operation is performed in the same manner as described above.
When the shift operation is in time for the conveyance interval between the preceding sheet and the succeeding sheet, or when the sheet interval becomes large on the way, the shift roller need not be switched. In this embodiment, whether or not to switch the shift roller can be determined by the control means (CPU) shown in FIG. 12 based on size information, speed information, etc. sent from the image forming apparatus ( (See the flowchart in FIG. 14).

Next, control when the alignment time of the sheet alignment apparatus 300 is not in time for the sheet conveyance interval will be described by taking as an example a case where the preceding sheet 501 is shifted by the shift roller 202 and the subsequent sheet 502 is shifted by the shift roller 203.
The preceding paper 501 is conveyed to the shift roller 202 in the same manner as described above, the paper 501 is shifted, and the conveyance drive of the shift roller 202 is temporarily stopped at the position where the leading edge of the paper 501 reaches an arbitrary position to stop the paper 501. (See the flowchart in FIG. 16).
The succeeding sheet 502 continuously conveyed is switched in the direction of the shift roller 203 by switching the branch claw 222, and the shift roller 203 continues to be conveyed by performing the same shift operation as described above. The transport distance of the paper is managed by the number of transport pulses from the sensor 250. When the leading edge of the succeeding paper 502 coincides with the leading edge position of the preceding paper 501, the shift roller is moved so that the paper 501 and the paper 502 are transported at the same speed. The conveyance of the sheet 202 is resumed, and the sheet 501 and the sheet 502 are stacked and conveyed and discharged. Thus, by stacking and discharging a plurality of sheets, the alignment apparatus 300 can be operated once for a plurality of sheets, and the productivity that can be handled can be improved.

FIG. 1 is an explanatory diagram of a schematic configuration of a sheet post-processing apparatus according to the present invention. FIG. 6 is a diagram illustrating a shift state on a paper stacking tray. FIG. 6 is a diagram illustrating a shift state on a paper stacking tray. It is a figure which shows the bottom part structure of a paper aligning apparatus. It is a top view which shows operation | movement of a shift roller and a paper aligning apparatus. FIG. 6 is a diagram illustrating a shift mechanism that shifts a sheet in a width direction orthogonal to a conveyance direction. FIG. 6 is a diagram showing a state immediately after the preceding paper is shifted in the width direction with a shift roller and the shift movement is completed. FIG. 6 is a diagram illustrating a state in which a first branch conveyance path is opened and a subsequent sheet is conveyed in a shift roller direction to perform a shift operation. It is a figure which shows the shift procedure in the case of passing a paper continuously. It is a figure which shows the shift procedure in the case of passing a paper continuously. It is a figure which shows the shift procedure in the case of passing a paper continuously. It is explanatory drawing of a control system. It is a flowchart which shows one of the control procedures of this invention. It is a flowchart which shows one of the control procedures of this invention. It is a flowchart which shows one of the control procedures of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Image forming apparatus, 101 ... Discharge roller, 200 ... Paper post-processing apparatus, 201 ... Entrance guide, 202, 203 ... Shift roller (shift means), 204 ... Conveyance roller, 204, 205, ... Conveyance roller, 205 ... Conveyance Roll, 203 ... Shift roller, 211a ... Branch claw, 211b ... Branch claw, 212 ... Conveying roller, 213 ... Discharge roller, 214 ... Discharge tray, 220, 230 ... Branch conveyance path, 222 ... Branch claw, 225 ... Discharge Roller, 228 ... Roller, 229 ... Paper stacking tray, 230 ... Branch conveyance path, 250 ... Sensor, 251 ... Punch, 300 ... Paper alignment device, 301, 302 ... Drive motor, 303 ... Timing belt, 305 ... Pulley, 307 ... Moving member, 307a, 308a ... sensor detection plate, 309 ... shaft, 312 ... sensor, 312 ... transmission type sensor, 314 ... gear, DESCRIPTION OF SYMBOLS 15 ... Member vertical retraction motor, 501 ... Preceding paper, 502 ... Subsequent paper, 601 ... Driven roller, 602 ... Support shaft, 610 ... Gear part, 610 ... Shaft, 611 ... Link part, 612 ... Shaft, 613 ... Gear, 620 ... shift motor, 630 ... spring.

Claims (12)

A transport path for receiving the paper discharged from the image forming apparatus and transporting it to the paper stacking tray, a transport mechanism for transporting the paper in the transport path, and a plurality of transport paths provided in the transport path upstream of the paper stacking tray. A branch transport path, switching means disposed at an upstream branch portion of the plurality of branch transport paths to switch the paper transport direction to one of the branch transport paths, and a path disposed in each branch transport path. Shift means for shifting the paper to be shifted in the width direction orthogonal to the transport direction, detection means for detecting passage of the paper, and after the detection means detects that the paper has reached any of the shift means And a control means for controlling the transport mechanism so as to change the transport speed of the shift means at an arbitrary timing .   2. The sheet post-processing apparatus according to claim 1, wherein the plurality of shift means are configured to shift and move independently of each other.   3. A sheet post-processing apparatus according to claim 1, further comprising a common drive source for driving the plurality of shift means.   3. The sheet post-processing apparatus according to claim 1, wherein each of the plurality of shift means is driven by a separate drive source. 5. The sheet post-processing apparatus according to claim 1, wherein a branch conveyance path used by the switching unit is switched for each sheet. 6. The sheet post-processing apparatus according to claim 1, wherein the shift unit to be used is switched by switching the branch conveyance path by the switching unit. 7. The sheet post-processing apparatus according to claim 1, wherein the shift unit performs a shift operation by alternately switching the plurality of shift units for each sheet or alternately for each arbitrary number of sheets. 8. The sheet post-processing apparatus according to claim 7, wherein the control unit determines and controls whether or not to switch the shift unit according to a size and a conveyance speed of the sheet. 2. The sheet post-processing apparatus according to claim 1, wherein the control unit controls the transport mechanism to stop the transport of the sheet by the shift unit at an arbitrary timing after the sheet reaches the shift unit. . 10. The sheet post-processing apparatus according to claim 9, wherein the stopped sheet transport is transported in synchronization with the transport timing of the succeeding sheet in another branch transport path, and the plurality of sheets are stacked and transported. 2. The sheet post-processing apparatus according to claim 1, wherein the plurality of shift units are arranged so as to be shifted in the sheet conveyance direction. 12. An image forming system comprising: the sheet post-processing apparatus according to claim 1; and the image forming apparatus.

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