Sheet processing device and image forming system

Abstract

The present invention provides a sheet processing device that allows the retaining member to be rotated even when the loading tray is raised due to the removal of a sheet bundle while the sheet bundle is being continuously discharged. [Solution] When a subsequent sheet bundle is continuously discharged onto the loading tray following the previous sheet bundle, the retaining member rotates to a retaining position to press down on the upper surface of the sheet bundle that has been discharged onto the loading section. If a sheet bundle loaded onto the loading tray is removed during the continuous discharge of sheet bundles, and the retaining member in the retaining position separates from the loading tray, the loading tray is repeatedly raised by a predetermined amount in response to a command to rotate the retaining member, so that the retaining member does not get caught between the loading tray and the abutment surface when the loading tray is raised.

Description

Technical Field

[0001] The present invention relates to a sheet processing device that performs a predetermined process on a sheet and discharges it, and more particularly to a sheet processing device capable of accurately operating a sheet pressing unit that presses a sheet discharged to a stacking unit, and an image forming system including the same.

Background Art

[0002] In recent years, not only is a sheet on which an image has been formed by an image forming device simply discharged as it is, but a sheet processing device that performs a stapling process on the image-formed sheet is integrally assembled with the image forming device and used.

[0003] In such a sheet processing device, a pressing member is provided to press the upper surface of the already stacked sheet bundle so that the discharged sheet bundle does not push out the sheet bundle already discharged onto the stacking tray. (Patent Document 1). For example, as shown in FIG. 15, a pressing member 500 made of an elastically deformable member such as a rubber plate is rotatably provided, and each time a sheet bundle 502 is discharged onto the stacking tray 501, the pressing member 500 is rotated to press the upper surface of the discharged sheet bundle, thereby preventing the already stacked sheet bundle from being pushed out.

[0004] Further, the stacking tray 501 is configured to be movable up and down. When the sheet bundle stacked on the stacking tray 501 is removed, the stacking tray 501 is raised so that the height of the uppermost sheet of the sheet bundle on the stacking tray 501 falls within a predetermined range (sheet receiving position).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the configuration described above for raising and lowering the loading tray, as shown in Figure 16(a), when a sheet bundle is removed from the loading tray 501 after a sheet has been discharged, the loading tray 501 is raised. At this time, if the discharge of sheet bundles continues, the retaining member 500 is positioned at a retaining angle (tip facing downward) in order to discharge the next sheet bundle, and the contact portion of the retaining member 500 that contacts the sheet is separated from the loading surface, which is the area on the loading tray 501 where the sheet bundles are loaded.

[0007] The contact portion of the retaining member 500 is made of a rubber plate or the like with a thickness of several millimeters, and a gap 505 is formed between the loading tray 501 and the abutment surface 503 to allow the loading tray 501 to move up and down smoothly. Therefore, if the loading tray 501 is raised all at once to the sheet receiving position, as shown in Figure 16(b), the elastically deformable contact portion of the retaining member 500 may get caught in the gap between the loading tray 501 and the abutment surface 503. If the retaining member 500 gets caught in the gap 505, the retaining member 500 will not be able to rotate, which may cause a malfunction in the discharge operation.

[0008] The present invention has been made in view of the above problems, and its object is to provide a sheet processing apparatus and an image forming system that can rotate the pressing member even when raising the loading tray when, while a predetermined stack of sheets is being continuously discharged, the stack of sheets loaded on the loading surface of the loading tray is removed, causing the contact portion of the pressing member in the pressing position to separate from the loading surface. [Means for solving the problem]

[0009] A typical configuration according to the present invention for achieving the above objective is a sheet processing apparatus comprising: a binding unit for binding a sheet bundle; a discharge unit for discharging the sheet bundle bound by the binding unit; a loading tray having a loading surface for loading the sheet bundle discharged by the discharge unit; abutment surface against which one end of the sheet bundle discharged to the loading surface abuts; a sensor for detecting the height of the uppermost sheet of the sheet bundle loaded on the loading surface; a lifting mechanism for raising and lowering the loading tray so that the height of the uppermost sheet of the sheet bundle on the loading surface is within a predetermined range according to the output of the sensor; and a contact unit that elastically deforms and abuts against the upper surface of the sheet bundle abutted against the abutment surface to press down on the upper surface of the sheet bundle. The device comprises a pressing member that can be rotated to a position, a rotation mechanism for rotating the pressing member, and a control unit that controls the lifting mechanism and the rotation mechanism, wherein the control unit is capable of repeatedly raising the loading tray by a predetermined amount in response to a command to rotate the pressing member, so that the pressing member does not get caught between the loading tray and the abutment surface when, while a plurality of sheet bundles consisting of predetermined sheets are being continuously discharged, the sheet bundles loaded on the loading surface are removed and the contact portion of the pressing member in the pressing position is separated from the loading surface, and the loading tray is raised so that the height of the top sheet of the sheet bundle on the loading surface is within the predetermined range. [Effects of the Invention]

[0010] In the present invention, even if the sheet is removed from the loading section while discharge is continuing, the loading section rises to a degree that does not hinder the rotation of the sheet retaining member, so the sheet retaining member does not become unable to rotate. [Brief explanation of the drawing]

[0011] [Figure 1] Schematic diagram of the overall configuration of an image forming system equipped with a sheet processing device. [Figure 2] Perspective view of the sheet processing device [Figure 3]Configuration explanatory diagram of the sheet processing apparatus [Figure 4] Explanatory diagram of sheet alignment and binding operations [Figure 5] Explanatory diagram of the lifting mechanism of the loading tray [Figure 6] Explanatory diagram of the drive mechanism of the sheet pressing paddle [Figure 7] Control configuration block diagram of the image forming system [Figure 8] Flowchart of sheet discharge processing [Figure 9] Explanatory diagram of the sheet discharge operation to the loading tray [Figure 10] Explanatory diagram of the sheet discharge operation to the loading tray [Figure 11] Explanatory diagram of the sheet discharge operation to the loading tray [Figure 12] Explanatory diagram of the sheet discharge operation to the loading tray [Figure 13] Explanatory diagram of the sheet discharge operation to the loading tray [Figure 14] Explanatory diagram of the sheet discharge operation to the loading tray [Figure 15] Explanatory diagram of the prior art [Figure 16] Explanatory diagram of the prior art

Modes for Carrying Out the Invention

[0014] The feeding unit 2 is composed of a plurality of cassette mechanisms 2a, 2b, and 2c that store image forming sheets of different sizes, and feeds out the sheet of the specified size from the main body control unit to the feeding path 2f. Each cassette mechanism 2a, 2b, and 2c is detachably installed from the feeding unit 2, and incorporates 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, and 2c to the downstream side, and a registration roller pair that aligns the leading edges of the sheets at the end of the path.

[0015] In this embodiment, the image forming unit 3 is configured using an electrophotographic method, and includes a rotating photosensitive drum 3a, and a charging roller 3b, an exposure device 3c, a developing device 3d, and a cleaner (not shown) arranged around it. The illustrated one is a color printing mechanism, and the image forming mechanism is provided according to each color of yellow Y, magenta M, cyan C, and black K.

[0016] During image formation, the circumferential surface of the rotating photosensitive drum 3a is uniformly charged by the charging roller 3b, irradiated with light according to the image signal by the exposure device 3c to form an electrostatic latent image, and the latent image is developed by the developing device 3d to form a toner image. The toner images of each color thus formed are primary-transferred to the rotating intermediate transfer belt 3e to form a color image. In accordance with the timing of this image formation, the sheet is sent from the feeding path 2f to the secondary transfer unit, and the toner image formed on the intermediate transfer belt 3d is transferred onto the sheet by applying a transfer bias from the secondary transfer roller 3f. The sheet onto which the toner image has been transferred is heated and pressurized when passing through the fixing device 5, the toner image is fixed, and is discharged from the discharge port 4b by the discharge roller 4a and conveyed to the sheet processing device B described later.

[0017] Scanner unit A2 comprises a platen 6a on which an image document is placed, a carriage 6b that reciprocates along the platen 6a, a photoelectric conversion element 6c, and a reduction optical system 6d that guides the reflected light from the document on the platen 6a by the carriage 6b to the photoelectric conversion element 6c. The photoelectric conversion element 6c converts the optical output from the reduction optical system 6d into image data using photoelectric conversion and outputs it as an electrical signal to the image forming unit 3. Scanner unit A2 is also capable of reading document sheets that are fed in from feeder unit A3.

[0018] <Sheet processing device> Next, we will explain the overall configuration of the sheet processing device B, which processes the sheets sent from the image forming apparatus A.

[0019] Figure 2 is a perspective view of the sheet processing apparatus according to this embodiment, and Figure 3 is an explanatory diagram of the configuration of the sheet processing apparatus B. The sheet processing apparatus B includes an apparatus housing 11 provided with an inlet 10 for introducing sheets from the image forming apparatus A. The apparatus housing 11 is positioned in alignment with the housing 1 of the image forming apparatus A so that the inlet 10 communicates with the outlet 4b of the image forming apparatus A.

[0020] In this embodiment, the discharge section 4 of the image forming apparatus A is formed in a space (internal space) 4c formed between the image forming unit A1 and the scanner unit A2, and the sheet processing apparatus B is located in the space 4c.

[0021] The sheet processing device B consists of a device frame 11, a sheet transport path 12 arranged on the device frame 11, a processing tray 14 located downstream of the transport path exit 13, and a loading tray 15 located further downstream. As shown in Figure 2, the front side of the device frame 11 is equipped with a staple needle cartridge mounting opening 16, a manual feed setting section 17, and manual operation buttons 18.

[0022] Furthermore, the processing tray 14 is equipped with a scraping paddle 19 made of a rubber plate that scrapes the sheets into the rear end stopper 21, and a knurled rubber belt 20 with knurling on its outer surface. In addition, a sheet rear end stopper 21 and alignment plate 22 are arranged to stack the sheets in bundles. The processing tray 14 is also equipped with a stapling unit 23 for stapling the sheet bundles and a stapleless stapling unit 24 for stapling the sheet bundles without staples.

[0023] (Sheet binding mechanism) The sheet on which the image has been formed by the image forming apparatus A is fed from the discharge port 4b of the image forming apparatus to the receiving port 10 of the sheet processing apparatus B, where predetermined sheet processing is performed in the sheet processing apparatus. In the sheet processing apparatus of this embodiment, the sheet P fed in from the receiving port 10 is transported by a transport roller 30a, which is a sheet transport member provided in the sheet transport path 12, as shown in Figure 4(a), and is transported to the processing tray 14 by a transport roller 30b, which is a sheet transport member provided near the transport path exit 13.

[0024] The sheet P, which is transported from the transport path exit 13 to the processing tray 14, is scraped off by the counterclockwise rotating scraping paddle 19 shown in Figure 4(b), and is transported by the counterclockwise rotating knurled belt 20 so that the rear end of the sheet abuts against the sheet rear end stopper 21, and the alignment plate 22 is slid in the sheet width direction to align both sides of the sheet in the width direction.

[0025] After transporting a predetermined number of sheets to the processing tray 14 as described above, the stapling unit 23, which is a processing unit, is operated to perform stapling on the sheet bundle on the processing tray 14. Once the sheets have been stapled, the upper discharge roller 31a of the separated discharge roller pair 31a, 31b moves and nips the sheets on the processing tray 14. Then, as shown in Figure 4(c), the driving force of the discharge motor is transmitted to the lower discharge roller 31b, and the sheets are discharged by the rotating discharge roller pair 31a, 31b and loaded into the loading tray 15, which serves as the sheet loading section. This loading tray 15 is equipped with a tray lifting mechanism that lowers it sequentially according to the amount of sheets loaded. The loading tray 15 also has a loading surface 15a, which is the area on which the sheets are loaded.

[0026] (Loading tray lifting mechanism) Figure 5 shows the lifting mechanism (lifting section) for raising and lowering the loading tray 15. As shown in Figure 5, the base 40 of the loading tray 15 is mounted so as to be slidable vertically along a rail (not shown) formed in the device housing 11. A rack section 41 is formed on the tray base 40, and this rack section 41 meshes with a pinion gear 42 provided on the device housing 11. The pinion gear 42 receives driving force from the tray lifting motor M1 via a transmission gear 43 and rotates, causing the rack section 41 to move up and down, thereby raising and lowering the loading tray 15. An encoder 44 that rotates integrally with the pinion gear 42 is attached to it, and the amount of lifting and lowering of the loading tray 15 can be controlled by detecting the amount of rotation of this encoder 44.

[0027] Furthermore, a loading tray HP sensor Sn1 is provided at a predetermined position on the device housing 11, and this sensor Sn1 detects a sensor flag 45 provided on the tray base 40, thereby enabling the loading tray 15 to be positioned in the home position.

[0028] The loading tray 15 is controlled to move up and down in accordance with the discharge of the sheets, as will be described later. The sheet holding paddle 50 is also controlled to rotate in accordance with the discharge of the sheets and the raising and lowering of the loading tray 15.

[0029] (Seat holding paddle) The sheet-holding paddle 50 acts as a sheet-holding member that prevents previously loaded sheets from being pushed out by sheets subsequently discharged onto the loading tray 15 by pressing down on the upper surface of the sheets that have been discharged onto the loading tray 15. This sheet-holding paddle 50 is rotatable coaxially with the lower discharge roller 31b and is also rotatable independently of the lower discharge roller 31b.

[0030] Figure 6(a) is a perspective view showing the drive configuration (rotation mechanism) of the lower discharge roller 31b and the sheet-holding paddle 50.

[0031] The lower discharge roller 31b is driven by the discharge motor M2 via a drive transmission mechanism 32. In the illustrated example, the drive transmission mechanism 32 consists of a pulley and a belt, and transmits the rotational drive of the drive shaft of the discharge motor M2 to the rotation shaft 31b1 of the lower discharge roller 31b. On the other hand, the sheet pressing paddle 50 is driven by the sheet pressing paddle motor M3, which acts as the drive unit, via a drive transmission mechanism 51. In the illustrated example, the drive transmission mechanism 51 consists of a pulley and a belt, and transmits the rotational drive of the drive shaft of the sheet pressing paddle motor M3 to the rotation shaft 52 of the sheet pressing paddle 50.

[0032] The rotating shaft 31b1 of the lower discharge roller 31b is designed so that the rotating shaft 52 of the sheet-holding paddle 50 can pass through its interior, allowing the two sheet-holding paddles 50 located on either side of the lower discharge roller 31b's rotation axis to be mounted on a single rotating shaft 52. The rotating shaft 31b1 of the lower discharge roller 31b is rotatably supported on the rotating shaft 52 of the sheet-holding paddle 50, for example, via a bearing. This allows the lower discharge roller 31b and the sheet-holding paddle 50 to be driven independently by separate motors. In addition to the pulley and belt configuration, the drive transmission mechanisms 32 and 51 may also be configured using other drive transmission members, such as multiple gears.

[0033] As shown in Figure 6(b), the sheet-holding paddle 50 has a fixed portion 50a fixed to the rotating shaft 52 and a plate-shaped paddle portion 50b that serves as an elastic contact portion provided on the fixed portion 50a. The paddle portion 50b extends from the fixed portion 50a fixed to the rotating shaft 52 in a direction perpendicular to the rotating shaft 52. The paddle portion 50b is made of an elastic material such as rubber (for example, ethylene propylene rubber (EPDM) with a hardness of 30±5HS(A) ((old JIS K6301, spring type A))). The sheet-holding paddle 50 configured in this way rotates with the rotation of the rotating shaft 52, and when the paddle portion 50b comes into contact with the sheet on the loading tray 15, it elastically deforms to hold down the rear end of the sheet.

[0034] Furthermore, a sensor flag 53 is provided on the rotation axis 52 of the sheet-holding paddle 50 so as to rotate integrally with the rotation axis 52, and a paddle HP sensor Sn2 capable of detecting the sensor flag 53 is provided in the device housing 11. The position where the paddle HP sensor Sn2 detects the sensor flag 53 becomes the home position of the sheet-holding paddle 50.

[0035] <Department Head> Next, the control configuration of the image forming system described above will be explained with reference to the block diagram in Figure 7.

[0036] The image forming system of this embodiment includes an image forming control unit 200 of the image forming apparatus A and a sheet processing device control unit (CPU: also called MPU; that is, a chip that integrates the calculation functions of a CPU, not just the calculation part) 100 of the sheet processing device B. The image forming control unit 200 includes a sheet feeding control unit 201 and an input unit 202. The "print mode" and "sheet processing mode" are set from a control panel 203 provided on the input unit 202.

[0037] The sheet processing control unit 100 operates the sheet processing device B according to the sheet processing mode. This sheet processing control unit 100 is equipped with a ROM that stores the operation program shown in the flowchart of Figure 8, and a RAM that stores control data. The sheet processing control unit 100 also receives signals from various sensors from the various sensor input unit 101, such as the loading tray HP sensor Sn1 that detects the home position of the loading tray 15, the paddle HP sensor Sn2 that detects the home position of the sheet holding paddle 50, and the sheet surface detection sensor Sn3 that detects the top surface of the sheet loaded on the loading tray 15. The sheet surface detection sensor Sn3 detects the sheet loading surface of the loading tray 15, and the position of the top surface of the loaded sheet when a sheet is loaded on the loading tray 15, and is provided at a predetermined position in the movement area of ​​the loading tray 15. The sheet surface detection sensor Sn3 turns on when it detects a sheet loaded on the loading tray 15, and turns off when it does not detect a sheet.

[0038] Furthermore, the sheet processing apparatus control unit 100 includes a sheet transport control unit 104 that controls the discharge motor M2 which provides driving force to the discharge roller 31b, the transport motor M4 which provides driving force to the transport rollers 30a and 30b, and the like.

[0039] Furthermore, the sheet processing device control unit 100 includes a processing tray control unit 105 that controls the driving of a matching motor that moves the matching plate 22 which performs sheet stacking operations on the processing tray 14, and a motor that rotates the scraping paddle 19 and the knurling belt 20. In addition, the sheet processing device control unit 100 has a stapling control unit 106 that performs stapling operations on the sheet bundles on the processing tray 14.

[0040] Furthermore, the sheet processing control unit 100 also includes a sheet loading control unit 107 that controls the loading tray lifting motor M1 for raising and lowering the loading tray 15, the sheet pressing paddle motor M3 for operating the sheet pressing paddle 50, and the like.

[0041] The control unit described above controls the execution of sheet processing, such as image formation processing and sheet discharge and loading processing as shown in the flowchart of Figure 8.

[0042] <Sheet discharge and loading processing control> In the sheet processing device B of this embodiment, when discharging sheets stapled by the staple binding unit 23 to the loading tray 15, the lifting and lowering operation of the loading tray 15 and the rotational operation of the sheet pressing paddle 50 are controlled by drive control as shown in the flowchart of Figure 8, thereby ensuring that the sheet pressing paddle 50 operates accurately. Next, the drive control for this purpose will be explained with reference to the flowchart of Figure 8 and the operation diagrams of Figures 9 to 13.

[0043] The sheet discharge to the loading tray 15 can be performed in two modes: a single-sheet discharge mode in which each sheet is discharged individually without stapling, and a bundled sheet discharge mode in which a predetermined number of sheets are transported and aligned to the processing tray 14, stapling is performed by the stapling unit 23, and the bundled sheets are discharged to the loading tray 15. Here, the lifting and lowering control of the loading tray 15 and the rotation control of the sheet holding paddle 50 when discharging sheets to the loading tray 15 will be explained using the bundled sheet discharge mode as an example, but the principle is the same for the single-sheet discharge mode. Below, the case in which multiple bundles of sheets, each consisting of a predetermined number of sheets, are discharged consecutively in the bundled sheet discharge mode will be explained. The predetermined sheet is A4 size with a basis weight of 80 g / m², and the predetermined number of sheets is 10, as used in the explanation, but other sizes, basis weights, and numbers of sheets are also applicable.

[0044] First, when a bundle discharge mode job is received, an discharge start initial processing is performed before sheet discharge occurs (S1). This may be performed when the device is powered on. This discharge start initial processing lowers the loading tray 15, moves the loading tray 15 to the home position upon detection by the loading tray HP sensor Sn1, resets the encoder 44 to position the loading tray 15, and then raises the loading tray 15 until the sheet surface detection sensor Sn3 turns on. After that, the loading tray 15 is lowered to the position where the sheet surface detection sensor Sn3 turns off and stops. As a result, the sheet loading surface of the loading tray 15 moves to a sheet receiving position that is slightly lower than the position directly opposite the sheet surface detection sensor Sn3. Also, the sheet holding paddle 50 is stopped at the sheet holding position (shown in Figures 3 and 15) from the home position (shown in Figure 13). Note that the above-mentioned sheet receiving position is synonymous with a position where the height of the sheet loading surface 15a or the top sheet of the sheet bundle loaded on the sheet loading surface 15a is within a predetermined range. Alternatively, the receiving position may be defined as a position that has risen or fallen a predetermined distance from the position where the sheet surface detection sensor Sn3 is turned on.

[0045] In the state described above, a predetermined number of sheets are transported and aligned to the processing tray 14, and the stapling process is performed by the stapling unit 23. The stapled sheet bundle is then discharged by the discharge roller pair 31a, 31b (S2). If the discharged sheet bundle is not the last sheet bundle in a continuous series of discharged sheet bundles, that is, as shown in Figure 9(a), if sheet bundle P2 is discharged immediately after sheet bundle P1 discharged to the loading tray 15 (YES in S3), the sheet pressing paddle 50 is rotated so that the paddle portion 50b presses against the upper surface of the sheets on the loading tray 15 (S4). As a result, the paddle portion 50b elastically deforms and presses against sheet bundle P1 on the loading tray 15 from above (see Figure 9(a)). In addition, one end of sheet bundle P1 abuts against the upright surface 11a (butt surface) of the device housing 11, restricting its movement in the direction opposite to the sheet discharge direction.

[0046] Next, it is determined whether or not the sheet bundle has been removed from the loading tray 15. In this embodiment, this determination is made by checking whether or not the sheet surface detection sensor Sn3 is turned on after the sheet bundle has been discharged (S5).

[0047] If the sheet surface detection sensor Sn3 turns on as a result of the previous sheet bundle P1 being discharged onto the loading tray 15 (YES in S5), it is determined that the discharged sheet bundle remains stacked on the loading tray 15, and it is discharged in normal discharge mode (first discharge mode). In this normal discharge mode, the loading tray 15 is lowered until the sheet surface detection sensor Sn3 turns off in order to receive the next sheet bundle P2, that is, until the top surface of the discharged sheet bundle P1 is below the position of the sheet surface detection sensor Sn3 (S6).

[0048] Next, the process returns to step S2 to discharge the next sheet bundle P2 onto the loading tray 15 (see Figure 9(b)). The later sheet bundle P2 is discharged onto the previous sheet bundle P1 which has already been discharged onto the loading tray 15, but because the previous sheet bundle P1 is held down by the sheet holding paddle 50, it is not pushed out of the loading tray 15 by the discharged sheet bundle P2.

[0049] By performing the above discharge process on sheet bundles P1, P2, ... that are continuously discharged onto the loading tray 15, the sheet bundles are sequentially stacked and discharged onto the loading tray 15.

[0050] Next, as shown in Figure 10(a), the case in which a previously loaded sheet bundle P1 is removed from the loading tray 15 while the sheet bundle is being continuously discharged to the loading tray 15 will be described. In this embodiment, if the number of sheets in the removed sheet bundle P1 exceeds 200, as shown in Figure 10(b), the sheet pressing paddle 50 (paddle portion 50b) will be separated from the loading surface 15a of the loading tray 15 at the pressing position, and the tip of the sheet pressing paddle 50 will be facing downwards. Also, when a previously loaded sheet bundle P1 is removed from the loading tray 15, the sheet surface detection sensor Sn3 turns off because the sheet bundle is gone (NO in S5). That is, when the sheet surface detection sensor Sn3 turns off despite the sheet bundle P1 being discharged, it is determined that the sheet bundle has been removed from the loading tray 15, and if there is a sheet bundle P2 to be discharged next in that state, it is discharged in the post-removal discharge mode (second discharge mode).

[0051] In the post-removal discharge mode, the process proceeds to step S7, where the loading tray 15 is raised by a preset amount (S7). Here, the "preset amount" for raising the loading tray 15 is the amount that can be raised even when the sheet-holding paddle 50 is rotated while the loading tray 15 is raised.

[0052] Here, the set amount, which is the amount the tray rises after sheet removal, will be explained in detail. As shown in Figure 11, a gap 11b is formed between the end of the loading tray 15 and the upright surface 11a of the device housing 11 so that the loading tray 15 can move up and down smoothly along the upright surface 11a. This gap 11b is such that even if a large amount of sheets are loaded onto the loading tray 15 and the loading tray 15 bends slightly, the tray will not come into contact with the upright surface 11a. In this embodiment, a gap 11b of about 5 mm is formed. Therefore, when the sheet-holding paddle 50 is in the sheet-holding position and the tip of the paddle portion 50b is in contact with the loading tray 15, if the loading tray 15 is raised rapidly until the sheet surface detection sensor Sn3 turns on, the elastically deformable paddle portion 50b may bend and fold, potentially entering the gap 11b (see Figure 16(b)). When the paddle portion 50b enters the gap 11b, the sheet-pressing paddle 50 becomes unable to rotate even when the sheet-pressing paddle motor M3 is driven.

[0053] The aforementioned setting amount is the amount of upward movement at which the sheet-pressing paddle 50 can rotate when the sheet-pressing paddle motor M3 is driven, even if the paddle portion 50b, which elastically deforms when the loading tray 15 is raised from a state in which the tip of the paddle portion 50b is in contact with the loading tray 15, does not deform to the point where it enters the gap 11b, or even if the deformed paddle portion 50b enters the gap 11b slightly. This setting amount varies depending on the material, length, thickness, and other paddle shape of the paddle portion 50b, as well as the spacing of the gap 11b. As a method for determining the setting amount, the sheet-pressing paddle 50 is rotated by raising the loading tray 15 a small amount from a state in which the tip of the sheet-pressing paddle 50 is in contact with the loading tray 15. This is repeated until the sheet-pressing paddle 50 bends and enters the gap 11b and stops rotating, thereby determining the maximum upward movement at which rotation is possible, and this value is determined as the setting amount.

[0054] The sheet-holding paddle 50 in this embodiment is an elastically deformable rubber member with a paddle portion 50b that is 31 mm long, 9.5 mm wide, and 2.5 mm thick, and the gap 11b between the loading tray 15 and the upright surface 11a is 5 mm. When the set amount was determined using this sheet-holding paddle 50 as described above, it was found that the paddle portion 50b could rotate up to 6 mm above the position where its tip was in contact with the loading tray 15. Therefore, in the device of this embodiment, the "set amount" is set to 6 mm. This tray rise by the set amount is controlled by counting the number of pulses of the rotating encoder 44.

[0055] As described above, if the previously loaded sheets on the loading tray 15 are removed during discharge and the sheet surface detection sensor Sn3 turns off, the loading tray 15 is raised by the set amount as shown in Figure 12(a). Then, it is determined whether or not the sheet surface detection sensor Sn3 turns on (S8). If the sheet surface detection sensor Sn3 remains off even after raising the loading tray 15 as described above (NO in S8), the process returns to step S2 to discharge the next sheet bundle P2 and rotates the sheet holding paddle 50 to the sheet holding position. On the other hand, if the sheet surface detection sensor Sn3 turns on as a result of raising the loading tray 15 by the set amount (YES in S8), the process proceeds to step S6, where the loading tray 15 is lowered until the sheet surface detection sensor Sn3 turns off, and then the process returns to step S2 to discharge the next sheet bundle P2.

[0056] As described above, if the sheet surface detection sensor Sn3 remains off even after the sheet bundle is discharged, the discharge mode is continued as shown in Figures 12(b) and 12(c), raising the loading tray 15 by the set amount and rotating the sheet pressing paddle 50 to the sheet pressing position to sequentially press down on the upper surfaces of the discharged sheet bundles P3 and P4.

[0057] In other words, as shown in the flowchart of Figure 8, the operation of raising the loading tray 15 by a set amount is performed after the rotation of the sheet-holding paddle 50 (S4 → S5 → S7). For subsequent sheet bundles, after the sheet bundle is discharged (S2), the sheet-holding paddle 50 is rotated (S4), and then, if the sheet surface detection sensor Sn3 is off (S5), the loading tray 15 is raised by a set amount (S7). In this way, the operation of raising the loading tray 15 by a set amount after rotating the sheet-holding paddle 50 is repeated until the sheet surface detection sensor Sn3 turns on (until the output state of the sheet surface detection sensor Sn3 changes). In other words, after the sheet bundle P1 is removed, in order to raise the loading tray 15 so that the height of the top sheet of the sheet bundle on the loading surface 15a is within a predetermined range, the operation of raising the loading tray 15 by a set amount is repeated in accordance with the rotation command of the sheet-holding paddle 50. As a result, even if the raised loading tray 15 comes into contact with the paddle portion 50b of the downward-facing sheet-holding paddle 50, the sheet-holding paddle 50 rotates before the loading tray 15 rises again. Therefore, the angle at which the tip of the paddle portion 50b of the sheet-holding paddle 50 contacts the loading tray 15 when the loading tray 15 rises afterward is different (see Figures 11 and 12(a)). Thus, it is possible to prevent the paddle portion 50b of the sheet-holding paddle 50 from getting stuck in the gap 11b and becoming unable to rotate. To put it another way, after the loading tray 15 rises by a set amount once, it waits for the next sheet bundle to be discharged and the sheet-holding paddle 50 to rotate, and then rises by the next set amount if the sheet surface detection sensor Sn3 is off. This is equivalent to repeatedly raising the loading tray 15 by a predetermined amount in response to a command to rotate the sheet-holding paddle 50, although there is a condition that "the sheet surface detection sensor Sn3 is off".

[0058] Then, when the sheets discharged onto the loading tray 15 are stacked and the sheet surface detection sensor Sn3 turns on (YES in S5), the loading tray 15 is lowered to return to normal discharge mode and discharge the next sheet until the sheet surface detection sensor Sn3 turns off.

[0059] After discharging the sheet bundles as described above and discharging the final sheet bundle (NO in S3), the sheet holding paddle 50 is returned to the home position (Figure 13) (S9), and the loading tray 15 is lowered until the sheet surface detection sensor Sn3 turns off (S10, S11), after which the discharge completion initial processing is performed (S12).

[0060] The discharge completion initial process involves raising the loading tray 15 and stopping it until the sheet surface detection sensor Sn3 turns on. In this state, as shown in Figure 14(a), once the sheet is removed from the loading tray 15 and the sheet surface detection sensor turns off, the loading tray 15 is raised again after a predetermined time has elapsed (3 seconds in this embodiment) until the sheet surface detection sensor Sn3 turns on (see Figure 14(b)). At this time, the sheet holding paddle 50 is not facing downwards, so even if the loading tray 15 is raised, it will not get caught in the gap 11b as described above. Therefore, the loading tray 15 is raised all at once.

[0061] As described above, if a bundle of sheets being continuously discharged onto the loading tray 15 is removed midway, and the paddle portion 50b of the sheet-holding paddle 50, which is in the holding position, separates from the loading surface 15a of the loading tray 15, the loading tray 15 is not raised all at once, but is raised in stages by a predetermined amount in response to a command to rotate the sheet-holding paddle 50. This staged raising operation prevents the sheet-holding paddle 50 from getting stuck in the gap 11b and becoming unable to rotate, and ensures that the sheet discharge operation is performed accurately.

[0062] In the embodiment described above, it was determined whether the sheet surface detection sensor Sn3 was on or off each time a sheet bundle was discharged (S5), that is, whether a sheet bundle had been removed from the loading tray 15. However, in the case of sheet bundles that have been bound with a small number of sheets, for example, the determination may be made each time multiple sheet bundles are discharged, rather than each bundle.

[0063] Furthermore, although the above-described embodiment showed an example of discharging a stack of stapled sheets, the same method can be applied when discharging unstapled sheets one by one into the loading tray 15. In this case, similar to the case of a small number of sheets in a stack, the sheet removal determination in step S5 of Figure 8 may be performed each time multiple sheets (for example, 15 sheets) are discharged.

[0064] Furthermore, in the embodiment described above, the removal of a sheet was determined by turning the sheet surface detection sensor Sn3 on or off, but other methods may also be used to determine if a sheet has been removed. For example, a sensor capable of detecting the sheet surface could be provided at a predetermined position in addition to the sheet surface detection sensor Sn3, and when this removal detection sensor is turned off, it could be determined that a sheet has been removed from the loading tray 15.

[0065] Furthermore, in the embodiment described above, the condition for the paddle portion 50b to become trapped in the gap 11b is that the tip portion of the paddle portion 50b wears down and becomes more prone to bending when the sheet-holding paddle 50 is rotated more than a predetermined number of times, which may result in it becoming trapped in the gap 11b. Therefore, the "removal and discharge mode" described above, which involves repeatedly rotating the sheet-holding paddle 50 and increasing the set amount of the loading tray 15, may be executed after the sheet-holding paddle 50 has been rotated more than a predetermined number of times (for example, 100,000 times).

[0066] In the embodiments described above, the sheet processing apparatus B is configured to be placed within the internal space 4c of the image forming apparatus A. However, the sheet processing apparatus of the present invention may be configured, for example, to be mounted on the side of the image forming apparatus. Furthermore, the sheet processing apparatus may be controlled by an image forming control unit 200 provided in the image forming apparatus A. That is, the control unit may be located within the sheet processing apparatus or within the image forming apparatus, as long as it is possible to control the sheet processing apparatus within the image forming system. [Explanation of Symbols]

[0067] A...Image forming apparatus B...Sheet processing device M1 ... Tray lifting motor M2 ... Discharge roller motor M3... Seat-holding paddle motor M4 ... Conveyor motor S...Seat Sn1 ... Loading tray HP sensor Sn2 ... Paddle HP Sensor Sn3 ... Sheet surface detection sensor 11a...erecting surface 11b ... gap 14… Processing tray 15…Loading tray 23… Staple binding unit 31a ... Upper discharge roller 31b ... Lower discharge roller 50...Seat retaining paddle 100 ... Sheet processing device control unit

Claims

1. A binding section for binding the sheet bundle, A discharge unit for discharging the sheet bundles that have been bound by the binding unit, A loading tray having a loading surface for loading the sheet bundles discharged by the aforementioned discharge section, The loading surface includes a contact surface against which one end of the sheet bundle discharged is abutted, A sensor for detecting the height of the top sheet in the sheet bundle stacked on the aforementioned loading surface, A lifting mechanism that raises or lowers the loading tray so that the height of the top sheet of the sheet bundle on the loading surface is within a predetermined range, in accordance with the output of the sensor, A pressing member having a contact portion that elastically deforms and contacts the upper surface of a sheet bundle abutted against the aforementioned abutting surface to press down, and which is rotatable to a pressing position to press down on the upper surface of a sheet bundle, A rotating mechanism for rotating the aforementioned retaining member, A control unit that controls the lifting mechanism and the rotating mechanism, Equipped with, The control unit, If, while multiple sheet bundles consisting of predetermined sheets are being discharged in succession, a sheet bundle loaded on the loading surface is removed, causing the contact portion of the pressing member in the pressing position to be separated from the loading surface, A sheet processing device capable of raising the loading tray by a predetermined amount in response to a command to rotate the pressing member, so that the pressing member does not get caught between the loading tray and the abutment surface, when raising the loading tray so that the height of the top sheet of the sheet bundle on the loading surface is within the predetermined range.

2. An image forming unit that forms an image on a sheet, A binding unit that performs a binding process on a sheet bundle consisting of sheets on which images have been formed by the image forming unit, A discharge unit for discharging the sheet bundles that have been bound by the binding unit, A loading tray having a loading surface for loading the sheet bundles discharged by the aforementioned discharge section, The loading surface includes a contact surface against which one end of the sheet bundle discharged is abutted, A sensor for detecting the height of the top sheet in the sheet bundle stacked on the aforementioned loading surface, A lifting mechanism that raises or lowers the loading tray so that the height of the top sheet of the sheet bundle on the loading surface is within a predetermined range, in accordance with the output of the sensor, A pressing member having a contact portion that elastically deforms and contacts the upper surface of a sheet bundle abutted against the aforementioned abutting surface to press down, and which is rotatable to a pressing position to press down on the upper surface of a sheet bundle, A rotating mechanism for rotating the aforementioned retaining member, A control unit that controls the lifting mechanism and the rotating mechanism, Equipped with, The control unit, If, while multiple sheet bundles consisting of predetermined sheets are being discharged in succession, a sheet bundle loaded on the loading surface is removed, causing the contact portion of the pressing member in the pressing position to be separated from the loading surface, An image forming system capable of raising the loading tray by a predetermined amount in response to a command to rotate the pressing member, so that the pressing member does not get caught between the loading tray and the abutment surface, when raising the loading tray so that the height of the top sheet of the sheet bundle on the loading surface is within the predetermined range.

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