Sheet folding device

Abstract

A sheet folding device for folding a sheet comprises conveyance means (FR1, Fr1a) that convey a sheet, a conveyance roller pair (SR1) that forms a bend in the sheet between the conveyance means, folding means (FR1, FR2) that fold the sheet by nipping a folding position of the sheet bent between the conveyance means and the conveyance roller pair, a drive motor (MT9) that rotates the conveyance roller pair forward in order to rotate the conveyance roller pair in the same direction as the sheet conveyance direction of the conveyance means when folding the sheet, and a drive transmission means (360) that allows rotation of the conveyance roller pair in the direction opposite to the direction in which the sheet is conveyed by forward rotation of the drive motor in a state in which the drive motor is rotated forward or stopped when both the folding means and the conveyance roller pair nip the sheet.

Description

Sheet folding device

[0001] The present invention relates to a sheet folding device including a folding unit that folds a sheet and a conveying path that supplies and discharges a sheet to and from the folding unit.

[0002] 2. Description of the Related Art A known sheet folding device folds a sheet by bending the sheet and nipping the bent sheet at a predetermined position with a pair of rollers (see Patent Document 1).

[0003] Such a sheet folding device includes an upstream conveying roller pair and a downstream conveying roller pair for forming a flexure in the sheet, and a folding roller pair that nip and fold the flexed sheet at a predetermined position. The upstream conveying roller pair and the downstream conveying roller pair rotate forward to convey the sheet in one direction, and the downstream conveying roller pair nip the sheet conveyed by the upstream conveying roller pair, then conveys the sheet a predetermined amount and stops. By continuing to drive the upstream conveying roller pair while the downstream conveying roller pair is stopped, a flexure is formed in the sheet between the upstream conveying roller pair and the downstream conveying roller pair. When the flexure formed by the upstream conveying roller pair and the downstream conveying roller pair reaches a certain size, the predetermined position of the flexed sheet is pulled into the nip portion of the driven folding roller pair, where it is nipped and folded. At this time, the upstream conveying roller pair rotates forward to convey the sheet in one direction toward the folding roller pair. Meanwhile, the downstream conveying roller pair rotates backward from its stopped state at the timing when the predetermined position of the sheet is nipped by the folding roller pair, and conveys the sheet in the other direction toward the folding roller pair.

[0004] While the folding roller pair nips and transports the sheet, the upstream transport roller pair rotates forward to transport the sheet at a speed equal to the sheet transport speed of the folding roller pair, and the downstream transport roller pair rotates backward to transport the sheet, thereby preventing the sheet from pulling against each other between the folding roller pair and the upstream transport roller pair, and between the folding roller pair and the downstream transport roller pair.

[0005] Japanese Patent Application Laid-Open No. 2020-1931

[0006] In a conventional sheet folding device, the downstream conveying roller pair is stopped to bend the sheet between the upstream conveying roller pair, and when the folding roller pair nip a predetermined position on the bent sheet, the downstream conveying roller pair is rotated in the reverse direction. After that, when the edge of the sheet passes the downstream conveying roller pair, the downstream conveying roller pair stops from a state in which they are rotating in the reverse direction at the sheet conveying speed of the folding roller pair, then rotates forward from the stopped state, accelerating up to the sheet conveying speed of the upstream conveying roller pair. The downstream conveying roller pair then receives the next sheet at the same sheet conveying speed as the upstream conveying roller pair.

[0007] Therefore, when the folding roller pair nips the bent sheet at a predetermined position, the downstream conveying roller pair is reversed, making it impossible to shorten the interval between the conveyed sheets, which results in a problem of reduced productivity.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a sheet folding device that can shorten the interval between successively conveyed sheets and improve productivity.

[0009] A sheet folding device according to one embodiment of the present invention includes a conveying means for conveying a sheet, a pair of conveying rollers that form a bend in the sheet between the conveying means, a folding means that folds the sheet by nipping the folding position of the bent sheet between the conveying means and the pair of conveying rollers, a drive motor that rotates forward to rotate the pair of conveying rollers in the same direction as the sheet conveying direction of the conveying means when folding the sheet, and a drive transmission means that, when both the folding means and the pair of conveying rollers are nipping the sheet, allows the pair of conveying rollers to rotate in the opposite direction to the direction in which the sheet is conveyed by the forward rotation of the drive motor when the drive motor is rotating forward or stopped.

[0010] According to the sheet folding device according to an embodiment of the present invention, it is possible to shorten the interval between successively conveyed sheets and improve productivity.

[0011] 1 is a cross-sectional view showing a schematic configuration of an image forming system; FIG. 2 is a block diagram of control centered on a sheet folding device; FIG. 3 is a cross-sectional view showing a drive system of the sheet folding device; FIG. 4 is a cross-sectional view showing a drive system of the folding unit; FIG. 5 is a cross-sectional view showing a conveying path of the sheet folding device; FIG. 6 is a schematic flowchart showing a series of processes in the sheet folding device; FIG. 7 is an explanatory diagram showing sheet supply operations (a), (b), and (c) toward the folding unit; FIG. 8 is an explanatory diagram showing sheet supply operations (d) and (e) toward the folding unit; FIG. 9 is a detailed flowchart of overlapping processing; FIG. 10 is an explanatory diagram showing pre-registration operations (a), (b), and (c); FIG. 11 is an explanatory diagram showing pre-registration operations (d), (e), and (f); FIG. 12 is an explanatory diagram showing pre-registration operations (g) and (h); FIG. 13 is a detailed flowchart of registration processing; FIG. 14 is an explanatory diagram showing sheet conveying operations in the folding unit; FIG. 15 is an explanatory diagram showing sheet discharge operations discharged from the folding unit; FIG. 16 is a perspective view showing a drive mechanism for a speed-change roller pair; FIG. 17 is an explanatory diagram showing a first folding process; FIG. 18 is a timing chart of the first folding process; FIG. 19 is a timing chart of a second embodiment of the first folding process; and FIG. 20 is a timing chart of a third embodiment of the first folding process.

[0012] An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing the configuration of an image forming system 100 equipped with a sheet folding device (hereinafter referred to as a folding device) 300. The image forming system 100 shown in FIG. 1 is configured to include an image forming device 200, a folding device 300, and a sheet post-processing device (post-processing device) 400. The folding device 300 is connected downstream of the image forming device 200, and the post-processing device 400 can be connected downstream of the folding device 300. The post-processing device 400 performs a binding process using staples or the like on multiple sheets on which images have been formed by the image forming device 200. In the following description, a description of the configuration of the post-processing device 400 will be omitted.

[0013] The image forming apparatus 200 includes cassettes 201a, 201b, and 201c, a sheet feeding unit 201d that supplies sheets stored in the cassettes 201a, 201b, and 201c, and an image forming unit 202 that forms images on the supplied sheets. The sheets stored in the cassettes 201a, 201b, and 201c are supplied to the image forming unit 202 at a predetermined timing by the sheet feeding unit 201d.

[0014] The image forming unit 202 has photosensitive drums 202a to 202d of yellow, magenta, cyan, and black as image forming means, respectively. The image forming unit 202 transfers the toner images of each color formed on the photosensitive drums 202a to 202d onto a sheet. As a result, an unfixed toner image is formed on the sheet. Thereafter, the unfixed toner image is fixed onto the sheet by a fuser 203. The sheet is then discharged to the folding device 300 by a pair of discharge rollers 205.

[0015] Image forming apparatus 200 is equipped with an operation panel PA for selecting whether or not to perform folding processing. When performing folding processing is selected on operation panel PA, the type of folding can then be selected, such as half-fold, Z-fold, C-fold, etc. Folding device 300 performs folding processing, such as half-fold, Z-fold, C-fold, etc., based on the folding information selected on operation panel PA of image forming apparatus 200.

[0016] Fig. 2 is a block diagram of the drive control of the image forming system 100, focusing on the folding device 300. Fig. 3 is a cross-sectional view showing the drive configuration of the entire folding device 300. Fig. 4 is a cross-sectional view showing the drive configuration of the folding means (hereinafter referred to as the folding unit) 351 in the folding device 300. As shown in Fig. 2, the folding device 300 has a control unit 350. Based on information from the image forming apparatus 200 and the detection results of the two conveying sensors SE1 to SE2, the seven supplying sensors SE3 to SE9, the four folding sensors SE10 to SE13, the five paper discharge sensors SE14 to SE18, and the tray sensor SE30, the control unit 350 controls the driving of the three conveying motors MT1 to MT3, the four supplying motors MT4 to MT7, the stacking motors MT20 and MT21, the paddle motor MT22, the movement motor MT23, the four sheet guide motors MT30 to MT33, the five folding motors MT8 to MT12, the three paper discharge motors MT13 to MT15, and the three solenoids SOL1 to SOL3, and performs various sheet conveying operations and various sheet folding operations.

[0017] 1, sheets on which images are formed by the image forming apparatus 200 are discharged toward the folding device 300. In the folding device 300, it is selected whether to perform various folding processes such as Z-folding or C-folding on the discharged sheets, or to discharge the sheets directly to a folding tray 315 or to a post-processing device 400 without folding them. When the sheets are discharged to the post-processing device 400, post-processing such as binding is performed on the sheets.

[0018] As shown in Figure 5, the folding device 300 is equipped with a vertically elongated housing 300a that is approximately the same height as the image forming device 200 and has a narrow width in the sheet transport direction, a sheet storage section (folding tray) 315 provided above the housing 300a, a folding section 351 located approximately in the middle of the height of the housing 300a, a supply path 340 that supplies sheets discharged from the image forming device 200 to the folding section 351, and a discharge path 344 that discharges sheets from the folding section 351 to the folding tray 315.

[0019] The folding unit 351 has a receiving unit 351a that receives a sheet from below and a discharge unit 351b that discharges a sheet that has been folded upward. The supply path 340 is composed of a first supply path 341 that is provided on the discharge unit 351b side of the folding unit 351 and that extends downward from the top of the housing 300a, and a second supply path 342 that is provided continuous with the first supply path 341 and that reaches the receiving unit 351a via a detour unit 343 that detours in a U-shape below the folding unit 351.

[0020] The downstream portions of the first supply path 341 and the second supply path 342, and the discharge path 344 all extend substantially vertically and are parallel to one another. This minimizes the width of the housing 300a in the sheet conveyance direction, thereby saving space. In addition, a folding tray 315 is located at the top of the housing 300a, making it easy to remove folded sheets.

[0021] Next, the sheet conveying operation in the folding device 300 will be described with reference to FIGS. 6 to 12. FIG. 6 shows the overall process flow in the folding device 300. The overall process flow in the folding device 300 is executed by the control unit 350 in accordance with a program stored in the control unit 350. When a sheet is conveyed to the folding device 300, a shift process is first performed to align the sheet widthwise (ST10). Then, it is confirmed whether or not multiple sheets will be folded in an overlapping manner (ST20). If multiple sheets will be folded in an overlapping manner (YES in ST20), the overlapping process is performed (ST30) and the process proceeds to the registration process (ST40). On the other hand, if multiple sheets will not be folded in an overlapping manner (NO in ST20), the process proceeds directly to the registration process (ST40). In the registration process, the leading edges of the sheets in the conveyance direction are aligned (ST40). Then, the folding unit 351 folds the sheet (ST50). The folded sheets are discharged and stored in the folding tray 315 (ST60). In this embodiment, the number of sheets that can be folded in a stack is limited to three.

[0022] The sheet conveying operation will be described in detail below. As shown in FIG. 7A (a), when a sheet discharged from the image forming apparatus 200 is detected by the first conveyance sensor SE1, the pair of inlet rollers 301 rotates and the sheet is conveyed into the folding apparatus 300. At this time, when a user operates the operation panel PA to receive information about the folding process, the solenoid SOL1 switches the first flapper F1 upward, and the sheet is conveyed to the supply path 340. The edge of the sheet guided by the pair of inlet rollers 301 passes through the supply sensor SE3. This supply sensor SE3 detects whether the position of the sheet in the sheet width direction, which is perpendicular to the sheet conveyance direction, is deviated from a predetermined position.

[0023] When the supply sensor SE3 detects a misalignment in the sheet width direction, the first shift roller pair 302a and the second shift roller pair 302b are moved in the front-rear direction, and a shift process (ST10) is executed to move the sheet to a predetermined position.

[0024] Here, a pair of flappers F2a and F2b are arranged along the conveyance direction on the upstream side of the supply path 340. The flappers F2a and F2b are used depending on the length of the sheet in the conveyance direction. If the sheet is longer than a predetermined length, the flapper F2a is activated, and if the sheet is shorter than the predetermined length, the flapper F2b is activated.

[0025] As shown in FIG. 7A (b), the sheet after the shift process is conveyed from the first shift roller pair 302a and the second shift roller pair 302b to a pair of conveying rollers for pre-registration (pre-registration roller pair) 303. At this time, when the sheet is not folded in layers, i.e., when a single sheet is folded, the pre-registration roller pair 303 receives the sheet from the first shift roller pair 302a and the second shift roller pair 302b and conveys it downstream. On the other hand, when the sheet is folded in layers, the sheet is scraped downward by the rotation of the paddles 304a and 304b, and its leading edge abuts against the pre-registration roller pair 303. Thereafter, the sheet is nipped by the pre-registration roller pair 303 and conveyed. As shown in FIG. 3, the pre-registration roller pair 303 is provided so as to be movable up and down in accordance with the length of the sheet by a moving means including a moving motor MT23 and a rack and pinion 305. In addition, when the sheet is not folded in layers, i.e., when a single sheet is folded, the pre-registration roller pair 303 moves to an appropriate position where the sheet of the minimum length to be handled can be transported, receives the sheet from the first shift roller pair 302a and the second shift roller pair 302b, and transports it downstream.

[0026] When the operation panel PA is operated to perform folding processing for each sheet, the pre-registration roller pair 303 rotates to convey the sheet toward the supply roller pair 306 of the first supply path 341 .

[0027] When folding multiple sheets in an overlapping state, an overlapping process (ST30) is performed by the pre-registration roller pair 303. In this overlapping process, the leading edge of the first sheet S1 abuts against the pre-registration roller pair 303 (see FIG. 7A (c)). Then, the subsequent second sheet S2 is conveyed to the supply path 340. The sheet S2 is conveyed by the inlet roller pair 301 and the first shift roller pair 302a to the right side of the preceding sheet S1, which has been retracted by the flapper F2b (see FIG. 7A (c)). Then, the leading edge of the second sheet S2 abuts against the pre-registration roller pair 303, and the first sheet S1 and the second sheet S2 are overlapped. Note that up to three sheets can be overlapped, as described below.

[0028] The overlapping process (ST30) will be described in more detail. FIG. 8 shows the process flow of the overlapping process (ST30). The overlapping process is executed by the control unit 350 according to a program stored in the control unit 350. First, a sheet is supplied by the supply motor MT4 rotating the first shift roller pair 302a and the second shift roller pair 302b (ST301). It is determined whether the supplied sheet is the first sheet S1 (ST302). If it is the first sheet S1 (YES in ST302), the paddle motor MT22 is driven to rotate the pair of paddles 304a, 304b after a predetermined time has elapsed since the first shift roller pair 302a and the second shift roller pair 302b began to be rotated (ST306-ST307). As a result, the pair of paddles 304a and 304b contact the surface of the first sheet S1 and guide it downstream in the conveying direction, ensuring that the sheet abuts against the pair of pre-registration rollers 303 (see FIG. 7A (b)). When the pair of paddles 304a and 304b bring the leading edge of the first sheet S1 into contact with the pair of pre-registration rollers 303, it is determined whether the second sheet S2 and the third sheet are present (ST308). If the second sheet S2 and the third sheet are not present (NO in ST308), the process ends. On the other hand, if the second sheet S2 and the third sheet are present, it is determined whether the length of the first sheet S1 is longer than a predetermined length (ST309). If the length of the first sheet S1 is equal to or shorter than the predetermined length (NO in ST309), the stacking motor MT21 is driven to rotate the flapper F2b 180 degrees (ST311). 7A(b), the trailing edge of the first sheet S1 is moved by the flapper F2b toward the inside (left side in the drawing) of the supply path 340. Then, the trailing edge of the first sheet S1 is restricted to the inside (left side in the drawing) of the supply path 340 by one surface of the flapper F2b.

[0029] On the other hand, if the length of the first sheet S1 is longer than the predetermined length (YES in ST309), the stacking motor MT20 is driven to rotate the flapper F2a 180 degrees (ST310). As a result, the trailing edge of the sheet is pulled by the flapper F2a to the inside of the supply path 340 (left side in the drawing). Then, the trailing edge of the first sheet S1 is restricted to the inside of the supply path 340 (left side in the drawing) by one surface of the flapper F2a.

[0030] 7A(c), the other surface of the flapper F2b guides the second sheet S2 to a position where it overlaps with the first sheet S1. In other words, by operating the flappers F2a and F2b, the leading edge of the second sheet S2 can be conveyed to a position where it overlaps with the first sheet S1 without contacting the trailing edge of the first sheet S1. Furthermore, if there is a third sheet, by operating the flappers F2a and F2b, the leading edge of the third sheet can be conveyed to a position where it overlaps with the first and second sheets without contacting the trailing edges of the first and second sheets.

[0031] On the other hand, if the sheet being conveyed by the first shift roller pair 302a and the second shift roller pair 302b in step ST302 is the second sheet S2 or the third sheet (NO in ST302), the supply motor MT5 starts rotating the pre-registration roller pair 303 (ST303). After a predetermined time has elapsed (YES in ST304), the pre-registration roller pair 303 is stopped (ST305). As a result, the leading edge of the first sheet S1 protrudes downward by a predetermined distance L (5 to 7 mm) from the nip point of the pre-registration roller pair 303 (see FIGS. 7A(c) and 7B(d)). Note that the first sheet S1 is conveyed the predetermined distance L (5 to 7 mm) from the nip point of the pre-registration roller pair 303 and stops before the leading edge of the second sheet S2 contacts the pre-registration roller pair 303. Then, after determining whether a predetermined time has elapsed (ST306), the pair of paddles 304a, 304b are rotated by driving the paddle motor MT22 (ST306-ST307). As a result, the pair of paddles 304a, 304b contact one side of the second sheet S2 and guide it downstream in the conveying direction, causing the leading edge of the second sheet S2 to abut against the pair of pre-registration rollers 303. Next, it is confirmed whether a third sheet is present (ST308). If there is no third sheet (NO in ST308), the overlapping process ends. On the other hand, if there is a third sheet (YES in ST308), step 309 (ST309) and step 311 (ST311) or step 309 (ST309) and step 310 (ST310) are executed, similar to the case of the second sheet S2. As will be described later, when the second and third sheets are stacked, the leading edge of the second sheet is shifted upstream in the sheet transport direction by a predetermined distance L relative to the leading edge of the first sheet, and the leading edge of the third sheet is shifted upstream in the sheet transport direction by a predetermined distance L relative to the leading edge of the second sheet and then stacked.

[0032] The first sheet S1 and the second sheet S2 conveyed by the pre-registration roller pair 303 are detected by the supply sensor SE9. The first sheet S1 and the second sheet S2 are conveyed a predetermined distance from the time they are detected by the supply sensor SE9. At this time, the leading edges of the first sheet S1 and the second sheet S2 reach the registration roller pair 310, and a flexure (loop) is formed in the two sheets S1 and S2 between the supply roller pair 309 and the registration roller pair 310, as shown in FIG. 7B(e). This allows the leading edges of the first sheet S1 and the second sheet S2 to be aligned.

[0033] In this embodiment, the pre-registration roller pair 303 has a pre-registration function. This pre-registration function ensures that multiple sheets are registered by the downstream registration roller pair 310. The pre-registration function will be described below with reference to FIGS. 9A, 9B, and 9C, as well as with reference to FIGS. 7B(d) and (e).

[0034] 9A to 9C illustrate the operation of the pre-registration roller pair 303. The leading edge of the first sheet S1 reaches the nip point of the pre-registration roller pair 303 (FIG. 9A(a)). The pre-registration roller pair 303 then rotates, advancing the leading edge of the sheet S1 a predetermined distance L from the nip point and stopping (FIG. 9A(b)). Next, the following second sheet S2 reaches the nip point of the pre-registration roller pair 303 (FIG. 9A(c)). The pre-registration roller pair 303 then rotates, advancing the second sheet S2 together with the first sheet S1 a predetermined distance L from the nip point and stopping (FIG. 9B(d)). Next, the following third sheet S3 reaches the nip point of the pre-registration roller pair 303 (FIG. 9B(e)). The pre-registration roller pair 303 then rotates, and the third sheet S3 is fed out in an overlapping state with the first, second, and second sheets S1 and S2 (FIG. 9B(f)). In this manner, the sheet stack, with the leading edges of sheets S1, S2, and S3 shifted slightly and regularly, is conveyed from the first supply path 341 toward the pair of supply rollers 309 of the second supply path 342 ( FIG. 9C (g)). The first sheet S1 of the sheet stack sent from the pair of supply rollers 309 first reaches the nip point of the pair of registration rollers 310 and forms a large loop in the direction opposite to the side where the second and subsequent sheets overlap (toward the right in FIG. 9C (g)). Thereafter, the second and third sheets S2 and S3 arrive at the nip point of the pair of registration rollers 310, forming loops in the bending directions of the first and second sheets, respectively ( FIG. 9C (h)). As shown in FIGS. 9C (g) and (h), one conveying guide 346a of the pair of conveying guides 346a and 346b that form the second supply path 342 is provided with a loop space LP for the sheet to form a loop. The other conveying guide 346b is provided with a protruding member 347 elastically supported by a spring that protrudes into the second supply path 342. As a result, as shown in Fig. 9C(h), a loop is always formed in a fixed direction, and in this embodiment, a loop is always formed on the side of the third sheet S3 among the stacked sheets.

[0035] In this way, the three overlapping sheets reach the registration roller pair 310 while being regularly shifted by a predetermined amount. While the first sheet S1 is forming a loop, the leading edge of the second sheet S2 reaches the nip point of the registration roller pair 310, and then the leading edge of the third sheet S3 reaches the nip point of the registration roller pair 310. This allows the three sheets S1, S2, and S3 to be conveyed toward the folding section 351 by the registration roller pair 310 with their leading edges aligned. In other words, the direction of the loop formed by the leading edges of the sheets contacting the registration roller pair 310 is set to the side of the sheet whose leading edge is located furthest downstream among the multiple sheets shifted in the overlapping order, thereby aligning the leading edges of the multiple overlapping sheets. The means for overlapping the sheets is not limited to the above-described means, and any means may be used to overlap the sheets such that the leading edge of the uppermost sheet in the direction of the loop formed by the leading edges of the sheets contacting the registration roller pair 310 is located downstream of the leading edge of the lowermost sheet in the sheet conveyance direction.

[0036] FIG. 10 shows a detailed flow of the registration process. In the registration process (ST40), the supply motor MT5 is driven to start rotation of the pre-registration roller pair 303 (ST401). At the same time, the supply motor MT6 is driven to rotate the supply roller pairs 306, 307, and 308 (ST402). The sheet is conveyed toward the registration roller pair 310 by the rotation of the pre-registration roller pair 303 and the supply roller pairs 306-308. Then, when a predetermined time has elapsed (YES in ST404) since the supply sensor SE9 turned ON (YES in ST403), the registration process is considered complete, and the registration roller pair 310 begins conveying the sheet. Note that this predetermined time corresponds to the distance from the supply sensor SE9 to the registration roller pair 310 plus the loop amount. Although the loop amount is the same when registering a single sheet and when registering multiple stacked sheets, it may be different.

[0037] When the registration process is completed, the pair of registration rollers 310 starts conveying the sheet and supplies the sheet to the folding unit 351. As shown in Figures 11(a) and 11(b), the sheet supplied to the folding unit 351 is folded in various ways by a plurality of folding rollers. The folding unit 351 will be described in detail later.

[0038] 12A, the sheet that has been folded in the predetermined manner by the folding unit 351 is discharged from the discharge unit 351b toward the discharge path 344. As shown in FIG. 12B, in the discharge path 344, discharge roller pairs 321, 322, 323, 324, and 325 are arranged at an arrangement interval P2 that is shorter than the arrangement interval P1 of the plurality of supply roller pairs 306, 307, 308, and 309 that are arranged in the first supply path 341, the detour unit 343, and the second supply path 342. The arrangement interval P2 of the discharge roller pairs 321 to 325 is set to match the size of the sheet conveyance width that matches the maximum number of folds by the folding unit 351. In this way, when the arrangement interval P2 of the discharge roller pairs 321 to 325 becomes shorter, the number of discharge roller pairs increases accordingly. However, in the folding device 300 of this embodiment, the total length of the discharge path 344 is shorter than the first supply path 341, the detour section 343, and the second supply path 342, so the number of discharge roller pairs 321 to 325 can be kept small.

[0039] Although the image forming system 100 of this embodiment is configured to include a folding device 300, there are cases where folding is not necessary or where the sheet is not suitable for folding, such as tab paper or coated board paper. In such cases, the folding device 300 of this embodiment is provided with a through-conveyance path 345 for discharging the sheet without passing through the folding section 351, as shown in FIG.

[0040] The through conveyance path 345 is formed by switching between flappers F1 and F4. The sheet conveyed into the folding device 300 by the inlet roller pair 301 is delivered to the relay conveyance roller pair 316 and guided to the through discharge roller pair 317 via the flapper F4. The sheet discharged by the through discharge roller pair 317 is then delivered to the inlet roller pair 401 of the post-processing device 400, as shown in FIG. 1, and can be discharged to a predetermined discharge tray.

[0041] Next, the configuration and operation of the folding unit 351 will be described with reference to Figures 4, 13, 14, and 15. The folding unit 351 configured as shown in Figure 4 has four folding sections with five folding rollers FR1 to FR5 so that a sheet can be folded in a maximum of four places. The first folding section consists of a first folding roller FR1 and a second folding roller FR2. The second folding section consists of a second folding roller FR2 and a third folding roller FR3. The third folding section consists of a third folding roller FR3 and a fourth folding roller FR4. The fourth folding section consists of a fourth folding roller FR4 and a fifth folding roller FR5.

[0042] Furthermore, the roller pair consisting of the first folding roller FR1 and the first folding sub-roller FR1a and the first variable speed roller pair SR1 form a flexure for folding in the first folding portion. The roller pair consisting of the first folding roller FR1 and the second folding roller FR2 and the second variable speed roller pair SR2 form a flexure for folding in the second folding portion. The roller pair consisting of the second folding roller FR2 and the third folding roller FR3 and the third variable speed roller pair SR3 form a flexure for folding in the third folding portion. The roller pair consisting of the third folding roller FR3 and the fourth folding roller FR4 and the fourth variable speed roller pair SR4 form a flexure for folding in the fourth folding portion. In other words, the first to fourth folding rollers FR1 to FR4 also function as conveying rollers that convey the sheet toward the first to fourth variable speed roller pairs SR1 to SR4, respectively.

[0043] The first to fourth sheet guides SG1, SG2, SG3, and SG4 are driven by sheet guide motors MT30, MT31, MT32, and MT33, respectively. When folding a sheet in the first folding section, the first sheet guide SG1 moves to a position where it guides the sheet from a roller pair (conveying means) consisting of a first folding roller FR1 and a first folding sub-roller FR1a (feed roller) to the first variable speed roller pair SR1. On the other hand, when not folding a sheet, the first sheet guide SG1 moves to a position where it guides the sheet from the roller pair consisting of the first folding roller FR1 and the first folding sub-roller FR1a to the roller pair consisting of the first folding roller FR1 and the second folding roller FR2. Similar to the first sheet guide SG1, the second to fourth sheet guides SG2 to SG4 are configured to move to positions where folding is performed in the folding sections corresponding to the sheet guides SG2 to SG4 and positions where folding is not performed.

[0044] The first to fifth folding rollers FR1, FR2, FR3, FR4, and FR5 are rotated by an eighth folding motor MT8 at a constant speed in a direction that transports the sheet downstream. The first to fourth variable speed roller pairs SR1 to SR4 are capable of forward and reverse rotation. They are rotated forward by the unidirectional rotation of the ninth to twelfth folding motors MT9, MT10, MT11, and MT12 to transport the sheet downstream, and are rotated reversely by the sheet transported by each folding roller FR1 to FR5. The first to fourth variable speed roller pairs SR1 to SR4 rotate at the same speed as the first to fifth folding rollers FR1 to FR5. The first to fourth variable speed roller pairs SR1 to SR4 receive the sheet from each folding roller FR1 to FR4 located upstream of each variable speed roller pair SR1 to SR4 and transport it downstream. Then, the first to fourth variable speed roller pairs SR1 to SR4 convey the sheet a predetermined distance from the point at which the sheet is detected by each of the folding sensors SE10, SE11, SE12, and SE13 located upstream of each variable speed roller pair SR1 to SR4, and then the ninth to twelfth folding motors MT9 to MT12 are decelerated and rotate at a speed slower than the eighth folding motor MT8.

[0045] The sheet that has been registered by the registration roller pair 310 is conveyed by the rotation of the first folding roller FR1 and the first folding sub-roller FR1a until the leading edge thereof reaches the first folding path FP1.

[0046] The first folding path FP1 is disposed at a certain angle to the sheet conveying direction by the first folding roller FR1 and the first folding sub-roller FR1a. When the leading edge of the sheet reaches the first folding path FP1, the sheet is nipped by the first variable speed roller pair SR1 while curving along the first folding path FP1, and after being conveyed a predetermined distance, the ninth to twelfth folding motors MT9 to MT12 are decelerated to form a predetermined flexure.

[0047] FIG. 13 shows a drive transmission mechanism 360 (drive transmission means) that transmits drive to the first variable speed roller pair SR1. The first variable speed roller pair SR1 is connected to a ninth folding motor MT9 (drive motor) via a torque limiter TQL. The drive of the ninth folding motor MT9 is transmitted from a gear G to the torque limiter TQL, and then from the torque limiter TQL to the shaft of the first variable speed roller pair SR1. The torque limiter TQL is configured to slip when torque (rotational torque) greater than or equal to a set torque is generated in the first variable speed roller pair SR1. A one-way clutch OW is built into the gear G. The one-way clutch OW is configured to disconnect the gear G from the shaft of the first variable speed roller pair SR1 when the rotation direction input from the ninth folding motor MT9 is one direction, and to connect the gear G to the shaft of the first variable speed roller pair SR1 when the rotation direction is the other direction. In other words, the one-way clutch OW is configured to connect the gear G and the shaft of the first variable speed roller pair SR1 when the rotation direction input from the first variable speed roller pair SR1 is forward rotation, and to disconnect the gear G and the shaft of the first variable speed roller pair SR1 when the rotation direction is reverse rotation. Note that the drive transmission mechanism 360 has the same configuration for the second to fourth variable speed roller pairs SR2 to SR4, so a description thereof will be omitted.

[0048] 14A and 14B illustrate the process from the formation of the first flexure to the first folding operation. The sheet S is conveyed downstream by the first folding roller FR1 and the first folding sub-roller FR1a. As the sheet S is guided to the first folding path FP1, it is nipped by the first variable speed roller pair SR1, which rotates in the same direction and at the same speed as the first conveying roller pair (the first folding roller FR1 and the first folding sub-roller FR1a) ( FIG. 14A ). As the sheet S is guided to the first folding path FP1, the leading edge of the sheet S is detected by the folding sensor SE10. After a certain time (T1), the first variable speed roller pair SR1 begins to decelerate from the same speed as the first folding roller FR1 and the first folding sub-roller FR1a to a slower speed ( FIG. 14B ). As a result, the forward rotation speed of the first variable speed roller pair SR1 gradually slows down, and the amount of sagging of the sheet gradually increases due to the speed difference with the first folding roller FR1 and the first folding sub-roller FR1a, which rotate (forward) at a constant speed.

[0049] 14C, after a predetermined time (T2) for determining the folding position has elapsed, the predetermined position of the flexed sheet is pulled into the nip point between the first folding roller FR1 and the second folding roller FR2. At this time, the sheet conveying direction of the first variable speed roller pair SR1 is opposite to the sheet conveying direction of the first folding roller FR1 and the second folding roller FR2. However, when the pulling force of the first folding roller FR1 and the second folding roller FR2 exceeds the conveying force of the first variable speed roller pair SR1, the pulling force of the first folding roller FR1 and the second folding roller FR2 causes the torque limiter TQL, which transmits driving force from the ninth folding motor MT9 to the first variable speed roller pair SR1, to slip, causing the first variable speed roller pair SR1 to rotate in the reverse direction. At this time, the one-way clutch OW disconnects the shaft of the first variable speed roller pair SR1 from the gear G in response to the input of reverse rotation of the first variable speed roller pair SR1, so there is no hindrance to the reverse rotation of the first variable speed roller pair SR1. Note that the same applies to the second to fourth variable speed roller pairs SR2 to SR4, so a description thereof will be omitted.

[0050] FIG. 15 is a timing chart of the first folding operation. After a predetermined time has elapsed since the supply sensor SE9 detected the sheet, the eighth folding motor MT8 starts to rotate. The eighth folding motor MT8 accelerates from the start of rotation to a constant conveying speed. The eighth folding motor MT8 is then driven at a first speed V1. Meanwhile, after a predetermined time has elapsed since the supply sensor SE9 detected the sheet, the ninth folding motor MT9 starts to rotate in the forward direction when it reaches time A in FIG. 15 and accelerates to the first speed V1. This first speed V1 is a speed at which the sheet conveying speed of the first folding roller FR1 and first folding sub-roller FR1a rotated by the eighth folding motor MT8 is equal to the sheet conveying speed of the first variable speed roller pair SR1.

[0051] Then, after a predetermined time (T1) has elapsed since the sheet was detected by the folding sensor SE10, the ninth folding motor MT9 decelerates from the first speed V1 at time B in FIG. 15 (see FIG. 14A). As a result, the slack in the sheet gradually increases due to the speed difference between the sheet conveyance speed of the first folding roller FR1 and the first folding sub-roller FR1a by the eighth folding motor MT8 and the sheet conveyance speed of the first variable speed roller pair SR1 by the ninth folding motor MT9. Then, after a predetermined time (T2) has elapsed since the ninth folding motor MT9 began to decelerate, the ninth folding motor MT9 reaches the second speed V2. When the ninth folding motor MT9 reaches time C in FIG. 15, the folding position at the slack formed between the first and second folding rollers FR1 and FR2 and the first variable speed roller pair SR1 is nipped between the first and second folding rollers FR1 and FR2, and the sheet is folded. The folded sheet is then conveyed by the first folding roller FR1 and the second folding roller FR2. At this time, the first variable speed roller pair SR1 rotates in the sheet conveying direction of the first and second folding rollers FR1 and FR2 due to the action of the torque limiter TQL described above.

[0052] After a certain time (T3) has elapsed since the ninth folding motor MT9 started to decelerate, at time point D in Fig. 15, the ninth folding motor MT9 accelerates from the second speed V2 to return to the first speed V1. At this time, the ninth folding motor MT9 is driven to rotate in the forward direction, but the first variable speed roller pair SR1 rotates in the direction of the first and second folding rollers FR1 and FR2 due to the action of the torque limiter TQL, following the sheet being conveyed by the first and second folding rollers FR1 and FR2.

[0053] 14(d), when the sheet passes through the first variable speed roller pair SR1, the slippage of the torque limiter TQL caused by the pulling force of the first folding roller FR1 and the second folding roller FR2 is eliminated, and the forward rotation drive of the ninth folding motor MT9 is transmitted to the first variable speed roller pair SR1, causing the first variable speed roller pair SR1 to rotate. Note that E in FIG. 15 indicates the timing when the sheet passes through the first variable speed roller pair SR1.

[0054] When a sheet passes the first speed-change roller pair SR1, the leading edge of the next sheet is detected by SE10. Then, after the leading edge of the next sheet is detected by SE10, the first speed-change roller pair SR1 nips and conveys the next sheet at time F in FIG. 15 . At this time, the ninth folding motor MT9 is already rotating forward at the first speed V1, so the first speed-change roller pair SR1 can smoothly nip and convey the next sheet. Thus, when the sheet passes the first speed-change roller pair SR1, the sheet conveying speed of the first speed-change roller pair SR1 is the same as the sheet conveying speed of the first folding roller FR1 and the first folding sub-roller FR1a. Therefore, once the previous sheet has passed the first speed-change roller pair SR1, the next sheet can be conveyed. This allows the intervals between successively conveyed sheets to be narrowed, improving productivity.

[0055] In the above embodiment, the ninth folding motor MT9 is decelerated from the first speed V1 to the second speed V2 to form a flexure in the sheet by the speed difference between the sheet conveyance speed by the first folding roller FR1 and the first folding sub-roller FR1a and the sheet conveyance speed by the first variable speed roller pair SR1, but as shown in Fig. 16, the ninth folding motor MT9 may be stopped from the first speed V1 to form a flexure in the sheet by the speed difference between the sheet conveyance speed by the first folding roller FR1 and the first folding sub-roller FR1a and the speed difference due to the deceleration and stop of the first variable speed roller pair SR1. Reference symbol T4 in Fig. 16 represents the time during which a certain flexure is formed when the sheet is nipped by the first and second folding rollers FR1 and FR2.

[0056] Furthermore, as shown in FIG. 17, if a flexure is formed that is nipped between the first and second folding rollers FR1 and FR2 while the ninth folding motor MT9 is decelerating, the motor may be accelerated to the first speed V1 at the point when the folding position of the flexure is nipped between the first and second folding rollers FR1 and FR2.

[0057] In the above embodiment, when the first speed-change roller pair SR1 decelerates, a pushing force caused by the sheet being fed by the upstream first folding roller FR1 and first folding sub-roller FR1a is applied to the first speed-change roller pair SR1. If this pushing force exceeds the set value of the torque limiter TQL, the torque limiter TQL slips. As a result, the first speed-change roller pair SR1 attempts to rotate at a speed faster than the speed at which it is driven by the ninth folding motor MT9 due to the pushing force of the sheet. However, the one-way clutch OW receives a forward rotation input from the first speed-change roller pair SR1 and connects the shaft of the first speed-change roller pair SR1 to gear G. Due to the action of this one-way clutch OW, even if a pushing force is applied to the first speed-change roller pair SR1 by the sheet, the first speed-change roller pair SR1 does not rotate at a speed faster than the deceleration speed, thereby preventing misalignment of the folding position. The one-way clutch OW acts as a braking mechanism that prevents the first variable speed roller pair SR1 from accelerating due to a pushing force of the sheet fed by the first folding roller FR1 and the first folding sub-roller FR1a.

[0058] Next, because the pulling force of the first folding roller FR1 and the second folding roller FR2, which form the fold, is greater than the set value of the torque limiter TQL, the drive of the ninth folding motor MT9 is not transmitted to the first variable speed roller pair SR1 and the ninth folding motor MT9 rotates idly when the sheet is pulled out. This causes the first variable speed roller pair SR1 to rotate in the opposite direction (reverse rotation) from the normal rotation direction, allowing the sheet to be smoothly transported in the pull-out direction. Furthermore, due to the action of the torque limiter TQL, once the sheet passes through the first variable speed roller pair SR1, the sheet transport speed of the first variable speed roller pair SR1 becomes the same as the sheet transport speed of the first folding roller FR1 and the first folding sub-roller FR1a. This allows the next sheet to be transported immediately, shortening the interval between successively transported sheets and improving productivity.

[0059] In this way, the sheet can be bent by the difference in conveying speed caused by decelerating the downstream first to fourth speed-change roller pairs SR1 to SR4, so the predetermined folding process can be continuously performed while the conveying direction and conveying speed by the first to fifth folding rollers FR1 to FR5 remain constant. This improves the productivity of the folding process. Furthermore, by providing the torque limiter TQL and one-way clutch OW to each of the first to fourth speed-change roller pairs SR1 to SR4, the sheet can be bent by decelerating the first to fourth speed-change roller pairs SR1 to SR4, and the sheet can be pulled out following the folding conveyance by the first to fifth folding rollers FR1 to FR5. This allows the sheet to be smoothly conveyed without placing an excessive load on the folding motor.

[0060] The folding device 300 determines the type of folding form and the size of the folded sheet in the conveying direction by operating the operation panel PA, or conveys the sheet to the folding tray 315 or the post-processing device 400 based on information selected by the user.

[0061] When the folding tray 315 is selected as the discharge destination, as shown in FIG. 5, the folding device 300 switches the flappers F3 and F4 to face the folding tray 315, and discharges the sheet onto the folding tray 315 using the discharge roller pairs 321 to 330.

[0062] The sheets conveyed to the folding tray 315 are propped up against a stopper 320. The stopper 320 predicts the amount of sheets to be stacked based on information from a counter, and moves as the number of sheets increases to ensure an appropriate sheet stacking space.

[0063] On the other hand, when the post-processing device 400 is selected as the discharge destination, the folding device 300 switches the flapper F3 in the direction opposite to the folding tray 315, and transports the sheet that has passed through the discharge path 344 toward the through discharge roller pair 317.

[0064] 1, the sheet discharged by the through discharge roller pair 317 is delivered to the inlet roller pair 401 of the post-processing device 400, where it is subjected to binding processing etc. The description of the post-processing device 400 will be omitted.

[0065] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0066] This application claims priority based on Japanese Patent Application No. 2023-197670, filed November 21, 2023, the entire contents of which are incorporated herein by reference.

[0067] 100 Image forming system 200 Image forming device 205 Discharge roller pair 300 Folding device 300a Housing 301 Inlet roller pair 302a First shift roller pair 302b Second shift roller pair 303 Pre-registration roller pair 304a, 304b Paddle 305 Rack and pinion 306 to 309 Supply roller pair 310 Registration roller pair 315 Folding tray (storage section) 316 Intermediate conveyance roller pair 317 Through discharge roller pair 320 Stopper 321 to 330 Discharge roller pair 340 Supply path 341 First supply path 342 Second supply path 343 Diversion section 344 Discharge path 345 Through conveyance path 346a, 346b Conveyance guide 347 Protruding member 351 Folding section 351a Receiving section 351b Discharge section 360 Drive transmission mechanism F1 to F4 Flapper FR1 First folding roller FR1a First folding sub-roller FR2 Second folding roller FR3 Third folding roller FR4 Fourth folding roller FR5 Fifth folding roller FP1 First folding path FP2 Second folding path FP3 Third folding path FP4 Fourth folding path SR1 First variable speed roller pair SR2 Second variable speed roller pair SR3 Third variable speed roller pair SR4 Fourth variable speed roller pair SG1 First sheet guide SG2 Second sheet guide SG3 Third sheet guide SG4 Fourth sheet guide 400 Post-processing device

Claims

1. A sheet folding device comprising: a conveying means for conveying a sheet; a pair of conveying rollers for forming a bend in the sheet between the conveying means; folding means for nipping the folding position of the bent sheet between the conveying means and the pair of conveying rollers to fold the sheet; a drive motor that rotates forward to rotate the pair of conveying rollers in the same direction as the sheet conveying direction of the conveying means when folding the sheet; and drive transmission means that, when both the folding means and the pair of conveying rollers are nipping the sheet, allows the pair of conveying rollers to rotate in the opposite direction to the direction in which the sheet is conveyed by the forward rotation of the drive motor when the drive motor is rotating forward or stopped.

2. A sheet folding device according to claim 1, wherein said drive motor decelerates or stops said pair of conveying rollers from a sheet conveying speed equal to the sheet conveying speed of said conveying means, thereby bending the sheet conveyed by said conveying means and said pair of conveying rollers.

3. A sheet folding device as described in claim 2, wherein the drive motor accelerates until the pair of conveying rollers reaches a sheet conveying speed equal to the sheet conveying speed of the conveying means between the time when both the folding means and the pair of conveying rollers nip the sheet and the time when the end of the sheet being nipped and conveyed by the folding means leaves the pair of conveying rollers.

4. A sheet folding device according to claim 2 or 3, wherein the drive transmission means includes a torque limiter which slips when the rotational torque of the pair of conveying rollers reaches or exceeds a predetermined torque.

5. A sheet folding device as described in claim 4, wherein the drive transmission means is provided with a braking mechanism that prevents the pair of conveying rollers from accelerating due to a pushing force of the sheet conveyed by the conveying means when the pair of conveying rollers is decelerated or stopped from a sheet conveying speed equal to the sheet conveying speed of the conveying means to bend the sheet conveyed by the conveying means and the pair of conveying rollers.

6. The sheet folding device according to claim 5, wherein the braking mechanism comprises a one-way clutch.

7. A sheet folding device as described in claim 1, wherein said folding means has a first folding roller and a second folding roller pressed against said first folding roller, and said transport means comprises said first folding roller of said folding means and a feed roller pressed against said first folding roller.

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