Sheet folding device

Abstract

To provide a sheet folding device capable of reliably aligning a plurality of overlapping sheets and preventing defective folding of a sheet.SOLUTION: A sheet folding device includes: a folding part for folding a plurality of stacked sheets; a supply path 340 for conveying the sheets to the folding part; a pre-registration roller pair 303 that shifts a leading ends in a conveyance direction of the next sheets S2 and S3 upstream in a sheet conveyance direction relative to the leading end in a conveyance direction of a previous sheet S1 conveyed in the supply path 340, and stacks the plurality of sheets; and a registration roller pair against which the leading edges of the plurality of sheets S1, S2, and S3 conveyed in the supply path 340 in a stacked state by the pre-registration roller pair 303 come into contact, that bends the stacked sheets toward a leading sheet side, and that aligns the leading edges of the sheets.SELECTED DRAWING: Figure 9B

Description

Technical Field

[0001] The present invention relates to a sheet folding device for folding a sheet, and more particularly to a configuration for aligning the leading ends of a plurality of sheets that are folded one on top of the other.

Background Art

[0002] Conventionally, a sheet folding device that performs a folding process on a sheet on which an image has been formed by an image forming device such as a copier or a printer at a predetermined position is widely known. The folding processes include double folding at the center position of the sheet, triple folding by folding the sheet inward at two locations, and so-called Z-folding in which the sheet is alternately folded inward and outward to form a triple fold. In recent years, there has been a demand for a sheet folding device that can perform various folds such as concertina folding and accordion folding with four or more folds in addition to double folding and triple folding.

[0003] Conventional sheet folding devices include those with a structure in which the conveyed sheet is bent, and a folding roller pair nips at the folding position of the bent portion to form various folds, and those with a structure in which the folding position of the sheet is pushed by a push plate and guided to the nip portion of the folding roller pair, and the folding roller pair nips to form various folds.

[0004] In the case of the above-described device that bends the sheet and folds it with a folding roller pair, with the downstream conveyance roller pair in the conveyance path portion (the portion where bending is formed) that guides the sheet to the nip portion of the folding roller pair stopped, the upstream conveyance roller pair is rotated to bend the sheet. Then, the defined folding position of the bent sheet is nipped by the folding roller pair to fold the sheet.

[0005] Patent Document 1 discloses a structure in which, before performing a predetermined folding process on a sheet conveyed toward a folding portion, the leading end of the sheet is abutted against a registration roller pair, and the leading ends of the sheets are aligned (matched) by forming a loop due to the bending of the sheet.

Prior Art Documents

Patent Documents

[0006] Patent Document 1 Japanese Patent Application Laid-Open No. 2005-8333 Summary of the Invention Problems to be Solved by the Invention

[0007] As disclosed in the above Patent Document 1, in a configuration in which the leading edge of a sheet is abutted against a pair of resist rollers to align the leading edge of the sheet, when resist is performed with a plurality of sheets stacked, the lower sheet in the direction in which the sheet bends may protrude in the conveyance direction with respect to the upper sheet. In such a case, there has been a problem that if the upper sheet does not abut against the pair of resist rollers and is not aligned and the folding process is performed, the folded sheet with the ends of the stacked sheets displaced is formed, which has been a cause of folding defects.

[0008] Therefore, an object of the present invention is to provide a sheet folding device capable of surely aligning a plurality of stacked sheets and preventing folding defects of the sheets. Means for Solving the Problems

[0009] In order to solve the above problems, the present invention is a sheet folding device for folding a sheet, comprising folding means for folding a plurality of stacked sheets, conveying means for conveying the sheet to the folding means, superposing means for shifting the leading edge in the conveyance direction of the next sheet upstream in the sheet conveyance direction with respect to the leading edge in the conveyance direction of the leading sheet conveyed by the conveying means to stack a plurality of sheets, and aligning means for abutting the leading edges of the plurality of sheets conveyed by the conveying means in a state stacked by the superposing means and bending the plurality of sheets in the direction of the leading sheet side among the plurality of stacked sheets to align the leading edges of the plurality of sheets. Effects of the Invention

[0010] According to the sheet folding device of the present invention, since the pair of conveying rollers that conveys a plurality of sheets stacked toward the resist roller pair has a function of regularly shifting the leading ends of the plurality of sheets in advance, it is possible to surely form the bending of the sheet when it reaches the resist roller pair. As a result, the folding process of the plurality of sheets can be performed accurately and surely.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7A

Figure 7B

Figure 8

Figure 9A

Figure 9B

Figure 9C

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a cross-sectional configuration of an image forming system 100 including a sheet folding device (folding device) 300 of the present invention. The image forming system 100 shown in FIG. 1 has a configuration including, as an example, an image forming apparatus 200, a folding device 300, and a sheet post-processing device (post-processing device) 400. The folding device 300 is connected to the downstream side of the image forming apparatus 200, and the post-processing device 400 can be connected to the downstream side thereof. The post-processing device 400 performs binding processing such as stapling on a plurality of sheets on which images are formed by the image forming apparatus 200. In the following description, the description of the internal configuration and the like will be omitted.

[0013] The image forming apparatus 200 includes cassettes 201a, 201b, 201c, a sheet feeding unit 201d that feeds sheets stored in the cassettes 201a, 201b, 201c, and an image forming unit 202 that forms an image on the fed sheets. The sheets stored in the cassettes 201a, 201b, 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 yellow, magenta, cyan, and black photosensitive drums 202a to 202d as image forming means, respectively, and transfers the toner images of respective colors formed on the photosensitive drums 202a to 202d to the sheet. Thereby, an unfixed toner image is formed on the sheet. Thereafter, the unfixed toner image is fixed by the fixing device 203, and the sheet is discharged to the folding device 300 by the discharge roller pair 205.

[0015] The folding device 300 determines whether to perform a folding process based on the operation of the operation panel PA by the user, and performs a predetermined folding operation based on the given information.

[0016] FIG. 2 is a block diagram of the drive control of the image forming system 100 centered on the folding device 300, FIG. 3 is a cross-sectional view showing the drive configuration of the entire folding device 300, and FIG. 4 is a cross-sectional view showing the drive configuration of the folding means (folding section) 351 in the folding device 300. As shown in FIG. 3, the folding device 300 has a control unit CONT, and based on an instruction from the image forming device 200, it performs a sheet conveyance operation and various folding operations. The loading of the sheet from the image forming device 200 and the unloading of the sheet to the post-processing device 400 are performed by the conveyance sensors SE1, SE2, and the conveyance motors MT1 to MT3. The sheet loaded into the folding device 300 is supplied toward the folding section 351 by the supply motors MT4 to MT7 while being detected by the supply sensors SE3 to SE9. When supplying the sheet, the stacking motors MT20, MT21, the paddle motor MT22, and the moving motor MT23 are driven. In the folding section 351, it is detected by the folding sensors SE10 to SE13, and the folding process operation by the folding motors MT8 to MT12 is performed by switching between folding and non-folding by the guide motors MT30 to MT33. The sheet that has passed through the folding section 351 is detected by the paper discharge sensors SE14 to SE18, conveyed toward the folding tray 315 by the paper discharge motors MT13 to MT15, and stored in the folding tray 315 when detected by the tray sensor SE30. Also, the solenoids SOL1 to SOL3 perform the operation of switching the conveyance of the sheet to the folding tray 315 or the post-processing device 400.

[0017] As shown in FIG. 1, the sheet on which the image is formed by the image forming device 200 is 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 sheet, or to discharge it directly to the folding tray 315 or the post-processing device 400 without performing the folding process. When discharging to the post-processing device 400, post-processing such as binding is performed.

[0018] As shown in FIG. 5, the folding device 300 has a vertically long casing 300a that is approximately the same height as the image forming device 200 and has a narrow width in the sheet conveyance direction, a sheet storage section (folding tray) 315 provided above the casing 300a, a folding section 351 disposed at approximately the middle in the height direction of the casing 300a, a supply path 340 as conveyance means for supplying the sheet discharged from the image forming device 200 to the folding section 351, and a discharge path 344 for discharging the sheet from the folding section 351 to the folding tray 315.

[0019] The folding section 351 has a receiving section 351a for receiving the sheet from below and a discharging section 351b for discharging the folded sheet upward. The supply path 340 is composed of a first supply path 341 that extends downward from above the casing 300a on the discharging section 351b side of the folding section 351, and a second supply path 342 that is continuously provided to the first supply path 341 and reaches the receiving section 351a via a detouring section 343 that detours in a U shape below the folding section 351 from the discharging section 351b side of the folding section 351.

[0020] The first supply path 341, the second supply path 342, and the discharge path 344 all extend in a substantially vertical direction and are parallel to each other. As a result, the width size of the casing 300a in the sheet conveyance direction can be minimized, achieving space saving. Further, since the folding tray 315 is disposed at the upper part of the casing 300a, it is easy to take out the folded sheet.

[0021] Next, the sheet conveyance operation in the folding device 300 will be described with reference to FIGS. 6 to 12. FIG. 6 shows the overall processing flow in the folding device 300. When a sheet is conveyed to the folding device 300, first, a shift process (ST10) for aligning the width direction of the sheet is executed. Then, it is determined whether there are a plurality of sheets (sheet stack) that have been subjected to the shift process (ST20). If there is a sheet stack, a stacking process is executed and the process proceeds to the registration process (ST40). On the other hand, if there is no sheet stack, the process proceeds directly to the registration process (ST40). In the registration process (ST40), an alignment means (process) for aligning the leading end in the conveyance direction of the sheet is executed, and various folding processes (ST50) are executed at the folding portion 351. The folded sheet is stored in the folding tray 315 by the paper discharge process (ST60). In this embodiment, the assumed number of stacked sheets is about three sheets.

[0022] As shown in FIG. 7A(a), when the sheet discharged from the image forming apparatus 200 is detected by the first conveyance sensor SE1, the entrance roller pair 301 rotates and the sheet is carried into the folding device 300. At this time, when a folding process command is received by operating the operation panel PA by the user, the first flapper F1 is switched downward by the solenoid SOL1, and the sheet is conveyed to the supply path 340. The end of the sheet guided by the entrance roller pair 301 passes through the supply sensor SE3. This supply sensor SE3 detects a sheet width direction error as to whether the end position in the direction orthogonal to the conveyance direction of the sheet deviates from a predetermined position.

[0023] When the sheet width direction error is detected by the supply sensor SE3, a shift process (ST10) is performed in which the first shift roller pair 302a and the second shift roller pair 302b move a predetermined amount in the near and far direction.

[0024] On the upstream side of the supply path 340, a pair of flaps F2a and F2b are arranged along the conveyance direction. These flaps F2a and F2b are selectively used according to the conveyance direction size of the sheet to be folded. When the size of the sheet exceeds a predetermined value, the flap F2a acts, and when it is below the predetermined value, the flap F2b acts.

[0025] The sheet for which the shift process has been completed is conveyed from the first shift roller pair 302a and the second shift roller pair 302b to a conveyance roller pair for pre-resist (pre-resist roller pair) 303 as shown in FIG. 7A(b). At this time, when the sheet is not double-folded, that is, when folding a single sheet, the pre-resist 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 double-folded, the sheet is scraped downward by the rotation of the paddles 304a and 304b, and after the tip thereof abuts against the pre-resist roller pair 303, it is nipped by the pre-resist roller pair 303 and conveyed. As shown in FIG. 3, the pre-resist roller pair 303 is arranged so as to be vertically movable according to the length of the sheet by a moving means including a moving motor MT23 and a rack & pinion 305. Note that when the sheet is not double-folded, that is, when folding a single sheet, the pre-resist roller pair 303 moves to an appropriate position where the smallest size sheet that can be handled can be conveyed, receives the sheet from the first shift roller pair 302a and the second shift roller pair 302b, and conveys it downstream.

[0026] When the folding process is performed for each single sheet by operating the operation panel PA, the sheet is directly conveyed toward the supply roller pair 306 of the first supply path 341 by the rotation of the pre-resist roller pair 303.

[0027] When folding multiple sheets by overlapping, as shown in Fig. 7A(c), an overlapping process (ST30) is executed by the preregister roller pair 303. In this overlapping process, the leading edge of the first sheet S1 is abutted against the preregister roller pair 303. Then, when 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 (as shown in the figure) of the preceding sheet that has been retracted by the flapper F2a. Fig. 7B(d) shows a state where two sheets overlap, but as will be described later, it is possible to overlap up to about three sheets at most.

[0028] FIG. 8 shows the detailed flow of the stacking process (ST30). In the stacking process (ST30), when the sheet is fed by the rotational drive (ST301) of the first shift roller pair 302a and the second shift roller pair 302b by the supply motor MT4, it is determined whether it is the first sheet (ST302). Here, if it is determined that it is the first sheet, after a predetermined time from when the first shift roller pair 302a and the second shift roller pair 302b are rotationally driven, the paddle motor MT22 is driven to rotate the pair of paddles 304a, 304b (ST306, ST307). As a result, the pair of paddles 304a, 304b come into contact with the surface of the first sheet and guide it downstream in the conveyance direction, ensuring that the sheet abuts against the pre-registration roller pair 303 (see FIG. 7A(b)). When the tips of the pair of paddles 304a, 304b abut against the pre-registration roller pair 303, it is checked whether there is a subsequent next sheet (ST308). If there is no next sheet, the stacking process ends. On the other hand, if there is a next sheet (the second sheet), it is determined whether the sheet is a large size. If it is a large size, the stacking motor MT20, which is a regulating means, is driven to rotate the flapper F2a by 180 degrees to regulate the rear end of the large-size sheet inside the supply path 340 (ST310). If it is not a large size, the stacking motor MT21 is driven to rotate the flapper F2b by 180 degrees to regulate the rear end of the sheet below the large size inside the supply path 340 (ST311). In this way, by regulating the rear ends of the large-size and large-size-or-smaller sheets by the flappers F2a, F2b, the next sheet can be conveyed to a position where it overlaps the first sheet without any trouble (see FIG. 7A(c)).

[0029] If it is determined that the sheet is the second or third sheet instead of the first sheet, after the first shift roller pair 302a and the second shift roller pair 302b are rotationally driven, the rotation of the pre-resist roller pair 303 is started by driving the supply motor MT5 and stops after a predetermined time has elapsed (ST303 to ST305). As a result, the second sheet is conveyed toward the pre-resist roller pair 303, and the leading end of the first sheet protrudes downward by a predetermined distance L (about 5 to 7 mm) from the nip point of the pre-resist roller pair 303 (see FIGS. 7A(c) and 7B(d)). Note that the first sheet is conveyed by a predetermined distance L (about 5 to 7 mm) from the nip point of the pre-resist roller pair 303 and stops before the leading end of the second sheet abuts against the pre-resist roller pair 303. Then, after confirming whether a predetermined time has elapsed (ST306), the pair of paddles 304a and 304b are rotated by driving the paddle motor MT22 (ST306 to ST307). As a result, the pair of paddles 304a and 304b come into contact with one surface of the next sheet and guide it downstream in the conveyance direction, and the leading end of the next sheet is made to abut against the pre-resist roller pair 303. Next, it is detected whether there is a subsequent next sheet (ST308), and if there is no next sheet, the stacking process ends. On the other hand, if there is a next sheet (the third sheet), the stacking means (process) is executed in the same manner as for the second sheet. Note that as will be described later, when stacking the second and third sheets, the leading end of the second sheet is displaced upstream in the sheet conveyance direction by a predetermined distance L with respect to the leading end of the first sheet, and the leading end of the third sheet is displaced upstream in the sheet conveyance direction by a predetermined distance L with respect to the leading end of the second sheet and they are stacked together.

[0030] When the sheet conveyed by the pre-resist roller pair 303 is detected by the supply sensor SE9, the sheet is conveyed by a predetermined distance, and the leading end of the sheet reaches the resist roller pair 310. At this time, as shown in FIG. 7B(e), a deflection (loop) is formed in the sheet between the supply roller pair 309 and the resist roller pair 310, and a resist process for aligning the leading ends of the sheets is performed.

[0031] In this embodiment, a preregist function corresponding to the folding of up to three sheets is provided. This preregist function is provided in the preregist roller pair 303, and a plurality of sheets can be reliably subjected to resist processing in the downstream resist roller pair 310. Hereinafter, the preregist function will be described with reference to FIGS. 7B(d) and (e) based on FIGS. 9A to 9C.

[0032] Figs. 9A to 9C show the operation of the pre-resist roller pair 303. When the leading edge of the first sheet S1 reaches the nip point of the pre-resist roller pair 303 (Fig. 9A(a)), the pre-resist roller pair 303 is rotated to advance the leading edge of the sheet by a distance L from the nip point and then stopped (Fig. 9A(b)). Next, when the subsequent second sheet S2 reaches the nip point of the pre-resist roller pair 303 (Fig. 9A(c)), the pre-resist roller pair 303 is rotated to advance the second sheet S2 together with the first sheet S1 by a distance L from the nip point and then stopped (Fig. 9B(d)). Subsequently, when the subsequent third sheet S3 reaches the nip point of the pre-resist roller pair 303 (Fig. 9B(e)), the pre-resist roller pair 303 is rotated to feed out the third sheet S3 in a state where it overlaps with the first and second sheets S1 and S2 (Fig. 9B(f)). In this way, a sheet bundle in a state where the leading edges of the sheets S1 to S3 are regularly shifted little by little is conveyed from the first supply path 341 toward the supply roller pair 309 of the second supply path 342 (Fig. 9C(g)). The first sheet S1 of the sheet bundle fed out from the supply roller pair 309 first reaches the nip point of the resist roller pair 310, and a large loop is formed in the direction opposite to the side where it overlaps with the second and subsequent sheets (the right direction in the figure). Thereafter, the delayed second and third sheets S2 and S3 reach the nip point of the resist roller pair 310 while forming loops in the directions of deflection of the first and second sheets, respectively (Fig. 9C(h)). As shown in Figs. 9C(g) and (h), one of the pair of conveyance guides 346a and 346b forming the second supply path 342, i.e., the conveyance guide 346a, is provided with a loop space portion LP for the sheet to form a loop, and the other conveyance guide 346b is provided with a protruding member 347 elastically supported by a spring protruding into the second supply path 342. As a result, as shown in Fig. 9C(h), the loop is always formed in a constant direction, and in this embodiment, a loop is always formed on the side of the third sheet S3 among the overlapped sheets.

[0033] In this way, when the resist roller pair 310 reaches the three sheets in an overlapping state that are regularly displaced by a preset predetermined amount, while the first sheet S1 forms a loop, the leading end of the second sheet S2 reaches the nip point of the resist roller pair 310, and then the leading end of the third sheet S3 reaches the nip point of the resist roller pair 310. As a result, the resist by the resist roller pair 310 is performed with the leading ends of the three sheets S1 to S3 aligned without leakage, and the sheets can be conveyed toward the folding portion 351. That is, the direction of the loop formed by the contact of the leading end of the sheet with the resist roller pair 310 is set to the side of the sheet whose leading end is located on the most downstream side among the plurality of sheets shifted in the stacking order, so that the leading ends of the stacked plurality of sheets can be aligned. Note that the means for stacking the sheets is not limited to the above-described means, and any means can be used as long as the leading end of the upper sheet on the loop direction side where the leading end of the sheet contacts the resist roller pair 310 is located downstream in the sheet conveyance direction from the leading end of the lower sheet.

[0034] FIG. 10 shows a detailed flow of the resist process. In the resist process (ST40), the rotation of the pre-resist roller pair 303 is started by driving the supply motor MT5 (ST401), and subsequently, the supply roller pairs 306 to 308 are rotated by driving the supply motor MT6 (ST402). Next, detection of the sheet by the supply sensor SE9 (ST403) is performed, and it is monitored whether a predetermined time has elapsed since the supply sensor SE9 became ON (ST404). Here, if the predetermined time has elapsed, the resist process by the resist roller pair 310 is executed. Note that the predetermined time here is set to the time for conveying the sheet by a distance obtained by adding the loop amount to the distance from the leading end of the first sheet to the leading end of the third sheet.

[0035] When the resist process is completed, the resist roller pair 310 starts conveying and supplies the sheet to the folding portion 351. The sheet supplied to the folding portion 351 is subjected to various folds by a plurality of folding rollers as shown in FIGS. 11(a) and 11(b). The details of the folding portion 351 will be described later.

[0036] The sheet for which a predetermined folding has been completed by the folding section 351 is discharged from the discharge section 351b toward the discharge path 344 as shown in FIG. 12(a). As shown in FIG. 12(b), in the discharge path 344, the discharge roller pairs 321 to 325 are arranged at an arrangement interval P2 that is shorter than the arrangement interval P1 of the plurality of supply roller pairs 306 to 309 arranged in the supply path 340. The arrangement interval P2 of the discharge roller pairs 321 to 325 is adjusted according to the size of the sheet conveyance width corresponding to the maximum number of folds by the folding section 351. In this way, when the arrangement interval P2 of the discharge roller pairs 321 to 325 becomes shorter, the number of arranged discharge roller pairs increases accordingly. However, in the folding device 300 of the present invention, since the total length of the discharge path 344 is shorter than that of the supply path 340, the number of the discharge roller pairs 321 to 325 can be suppressed to be small.

[0037] The image forming system 100 of the present embodiment is configured to include the folding device 300. However, there are cases where folding is not required or sheets such as tab paper and coated board paper that are not suitable for folding. In such cases, the folding device 300 of the present embodiment is provided with a through conveyance path 345 for discharging the sheet while avoiding the folding section 351 as shown in FIG. 5.

[0038] The through conveyance path 345 is formed by switching the 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. Then, the sheet discharged by the through discharge roller pair 317 is 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.

[0039] Next, the configuration and operation of the folding portion 351 will be described based on FIGS. 4, 13 to 15. The folding portion 351 having the configuration shown in FIG. 4 has five folding rollers FR1 to FR5 arranged such that up to four folds can be made on the sheet. The first bending fold is between the roller pair consisting of the first folding roller FR1 and the first folding sub-roller FR1a and the first speed change roller pair SR1, the second bending fold is between the roller pair consisting of the first folding roller FR1 and the second folding roller FR2 and the second speed change roller pair SR2, the third bending fold is between the roller pair consisting of the second folding roller FR2 and the third folding roller FR3 and the third speed change roller pair SR3, and the fourth bending fold is between the roller pair consisting of the third folding roller FR3 and the fourth folding roller FR4 and the fourth speed change roller pair SR4. The first to fourth folding rollers FR1 to FR4 also serve as conveying rollers for conveying the sheet toward the first to fourth speed change roller pairs SR1 to SR4, respectively.

[0040] The first to fourth sheet guides SG1 to SG4 are each driven by sheet guide motors MT30 to MT33, and serve to guide the bending direction of the sheet and to regulate the number of sheet folds. In the state shown in FIG. 4, since the first to fourth sheet guides SG1 to SG4 are in positions where they are not fold-regulated, four folding processes by valleys are performed.

[0041] The first sheet guide SG1 moves on the conveyance path from the first folding roller FR1 to the first folding path FP1 by the guide motor M30, thereby closing the conveyance path to the first folding path FP1. As a result, the sheet is guided to the nip point with the second folding roller FR2 on the downstream side in the conveyance direction adjacent thereto without performing a fold. The same applies to the second to fourth sheet guides SG2 to SG4.

[0042] The first to fifth folding rollers FR1 to FR5 rotate in the direction of conveying the sheet downstream at a constant speed by the folding motor MT8. The first to fourth speed-changing roller pairs SR1 to SR4 can rotate forward and backward, rotate forward by the one-way rotational drive of the respective folding motors MT9 to MT12 to convey the sheet downstream, and rotate backward by the sheet conveyed by the respective folding rollers FR1 to FR5. Further, the first to fourth speed-changing roller pairs SR1 to SR4 rotate at the same speed as the first to fifth folding rollers FR1 to FR5, receive the sheet from the first to fifth folding rollers FR1 to FR5, and convey it downstream. Then, when the sheet is detected by the folding sensors SE10 to SE13, the first to fourth speed-changing roller pairs SR1 to SR4 convey the sheet a predetermined distance and then the folding motors MT9 to MT12 are decelerated and rotate at a speed slower than the folding motor MT8.

[0043] The sheet on which the resist process has been completed by the resist roller pair 310 is conveyed by the rotation of the first folding roller FR1 and the first folding sub-roller FR1a until the leading end reaches the first folding path FP1.

[0044] The first folding path FP1 is arranged at a certain angle with respect to the sheet conveying direction by the first folding roller FR1 and the first folding sub-roller FR1a. The sheet whose leading end has reached the first folding path FP1 is nipped by the first speed-changing roller pair SR1 while curving along the first folding path FP1, conveyed a predetermined distance, and then the folding motors MT9 to MT12 are decelerated to form a predetermined deflection.

[0045] After the leading end side of the sheet with the deflection formed passes through the first folding sensor SE10 that detects the first folding position, it is conveyed a predetermined distance downstream by the first speed-changing roller pair SR1.

[0046] In this embodiment, various folding processes are performed by forming a deflection at a predetermined folding position of the sheet between the folding rollers FR1 to FR5, which are the first pair of conveying rollers on the upstream side for conveying the sheet, and the variable speed roller pair SR1 to SR4, which is the second pair of conveying rollers arranged on the downstream side thereof. As the means for forming the deflection, the drive control is performed so that the rotational speed of the first variable speed roller pair SR1 is decelerated to a predetermined speed with respect to the conveying speed of the folding roller FR1. The first variable speed roller pair SR1 rotates forward by the rotational drive in one direction of the folding motor MT9 and conveys the sheet to the downstream side. The same applies to the second to fourth variable speed roller pairs SR2 to SR4.

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

[0048] FIG. 14 shows the process from the formation of the first bend to the first folding operation. When the sheet S is conveyed downstream by the first pair of conveying rollers (the first folding roller FR1 and the first folding sub-roller FR1a), it is nipped by the second pair of conveying rollers (the first speed-changing roller pair SR1) while being guided by the first folding path FP1, and the second pair of conveying rollers rotates in the same direction as the rotation direction (forward rotation direction) of the first pair of conveying rollers (FIG. 14(a)). The leading edge of the sheet S is detected by the folding sensor SE10 during the process of being guided by the first folding path FP1, and after a predetermined time (T2) has elapsed, the first speed-changing roller pair SR1 starts to decelerate from the same speed as the first folding roller FR1 and the first folding sub-roller FR1a to a slower speed (FIG. 14(b)). As a result, the forward rotation of the first speed-changing roller pair SR1 gradually decelerates, and due to the speed difference with the first folding roller FR1 and the first folding sub-roller FR1a that rotate at a constant speed (forward rotation), the amount of bending of the sheet gradually increases.

[0049] Then, as shown in FIG. 14(c), when a predetermined time (T3) for determining the folding position has elapsed, a predetermined position of the bent sheet is drawn into the nip point between the first folding roller FR1 and the second folding roller FR2. At this time, the conveyance direction of the sheet by the first speed-changing roller pair SR1 is opposite to the conveyance direction of the sheet by the first folding roller FR1 and the second folding roller FR2, but when the pulling force by the first folding roller FR1 and the second folding roller FR2 exceeds the conveyance force by the first speed-changing roller pair SR1, the torque limiter TQL that transmits the drive from the folding motor MT9 to the first speed-changing roller pair SR1 slips due to the pulling force by the first folding roller FR1 and the second folding roller FR2, and the first speed-changing roller pair SR1 rotates reversely. At this time, the one-way clutch OW disconnects the connection between the shaft of the first speed-changing roller pair SR1 and the gear G in response to the reverse rotation input of the first speed-changing roller pair SR1, so there is no obstacle to the reverse rotation of the first speed-changing roller pair SR1. Note that the same applies to the second to fourth speed-changing roller pairs SR2 to SR4, so the description is omitted.

[0050] FIG. 15 shows the above-described first folding operation in a timing chart. When a sheet is detected by the supply sensor SE9, the folding motors MT8 and MT9 start driving (c), (d), and reach a constant conveyance speed after a predetermined time has elapsed since the start of driving. The folding motor MT8 is then driven at a constant speed. On the other hand, when the sheet is detected by the folding sensor SE10, the folding motor MT9 decelerates after a predetermined time (T2) has elapsed. When the deceleration starts, the deflection of the sheet gradually increases due to the speed difference from the folding motor MT8, and when a predetermined time (T3) has elapsed since the start of deceleration, the folding position is nipped between the first folding roller FR1 and the second folding roller FR2, and the sheet is folded. Then, the folded sheet is conveyed by the first folding roller FR1 and the second folding roller FR2. At this time, the first speed-changing roller pair SR1 rotates in the sheet conveyance direction of the first and second folding rollers FR1 and FR2 due to the action of the torque limiter TQL described above. According to the present embodiment, since the first speed-changing roller pair SR1 is decelerated compared to the first folding roller FR1 and the first folding sub-roller FR1a to form a deflection, the folding time of the sheet can be shortened compared to a configuration in which the first speed-changing roller pair SR1 is stopped to form a loop. Therefore, the above-described "deceleration" does not include "stop".

[0051] When the first speed-changing roller pair SR1 decelerates, a pushing force due to the feeding of the sheet by the upstream first folding roller FR1 and the first folding sub-roller FR1a is applied to the first speed-changing roller pair SR1. When the pushing force at this time exceeds the set value of the torque limiter TQL, the torque limiter TQL slips. As a result, the first speed-changing roller pair SR1 tries to rotate at a speed higher than the speed at which it is driven by the folding motor MT9 due to the pushing force of the sheet, but the one-way clutch OW receives a positive rotation input from the first speed-changing roller pair SR1 and connects the shaft and gear G of the first speed-changing roller pair SR1. Due to the action of this one-way clutch OW, even when a pushing force by the sheet is applied to the first speed-changing roller pair SR1, the first speed-changing roller pair SR1 does not rotate at a speed higher than the deceleration speed, and the deviation of the folding position can be prevented.

[0052] Next, since the pulling force by the first folding roller FR1 and the second folding roller FR2 that form the fold is greater than the set value of the torque limiter TQL, when pulling out the sheet, the drive of the folding motor MT9 is not transmitted to the first speed change roller pair SR1 and idles. As a result, the rotation of the first speed change roller pair SR1 rotates in the direction opposite to the normal rotation direction (reverse rotation), and the conveyance of the sheet in the pulling direction can be performed smoothly.

[0053] In this way, since the sheet can be bent by the conveyance speed difference caused by decelerating the first to fourth speed change roller pairs SR1 to SR4 on the downstream side, the conveyance direction and conveyance speed by the first to fifth folding rollers FR1 to FR5 remain constant, and a predetermined folding process can be continuously performed. As a result, the productivity of the folding process is improved. In addition, by providing torque limiters TQL and one-way clutches OW to the first to fourth speed change roller pairs SR1 to SR4 respectively, the first to fourth speed change roller pairs SR1 to SR4 can be decelerated to bend the sheet and the sheet can be pulled out following the folding conveyance by the first to fifth folding rollers FR1 to FR5. Therefore, the conveyance of the sheet can be performed smoothly without applying an excessive load to the folding motor.

[0054] The folding device 300 discriminates the type of folding form and the conveyance direction size of the sheet subjected to the folding process by operating the operation panel PA, or conveys the discharge destination to the folding tray 315 or the post-processing device 400 based on information of an arbitrary selection by the user.

[0055] 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 in the direction toward the folding tray 315, and discharges the sheet to the folding tray 315 by the discharge roller pair 321 to 330.

[0056] The sheet conveyed to the folding tray 315 is leaned against the stopper 320. The stopper 320 predicts the sheet loading amount based on information from the counter, and moves as the sheet increases to secure an appropriate sheet loading space.

[0057] 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 conveys the sheet that has passed through the discharge path 344 toward the through-discharge roller pair 317.

[0058] The sheet discharged by the through-discharge roller pair 317 is delivered to the inlet roller pair 401 of the post-processing device 400 as shown in FIG. 1, and binding processing and the like are performed. Note that the description of the post-processing device 400 is omitted.

Explanation of Signs

[0059] 100 Image forming system 200 Image forming apparatus 205 Discharge roller pair 300 Folding device 300a Housing 301 Inlet roller pair 302a First shift roller pair 302b Second shift roller pair 303 Preregister roller pair 304a, 304b Paddles 305 Rack & pinion 306~309 Supply roller pair 310 Registration roller pair 315 Folding tray (storage section) 316 Relay conveyance roller pair 317 Through-discharge roller pair 320 Stopper 321~330 Discharge roller pair 340 Supply path 341 First supply path 342 Second supply path 343 Detour section 344 Discharge path 345 Through-conveyance path 346a, 346b Conveyance guides 347 Protruding member 351 Folding section 351a Receiving section 351b Discharge section 360 Drive Transmission Mechanism F1 - 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 Speed - Changing Roller Pair SR2 Second Speed - Changing Roller Pair SR3 Third Speed - Changing Roller Pair SR4 Fourth Speed - Changing Roller Pair SG1 First Sheet Guide SG2 Second Sheet Guide SG3 Third Sheet Guide SG4 Fourth Sheet Guide 400 Post - treatment Device

Claims

1. A sheet folding device for folding a sheet, comprising: folding means for folding a plurality of stacked sheets; conveying means for conveying the sheet to the folding means; superposing means for superposing a plurality of sheets by shifting the leading end in the sheet conveying direction of the next sheet upstream in the sheet conveying direction with respect to the leading end in the sheet conveying direction of the leading sheet conveyed by the conveying means; an aligning means for aligning the leading ends of the plurality of sheets by causing the leading ends of the plurality of sheets conveyed by the conveying means in a superposed state by the superposing means to abut and deflecting the plurality of sheets in the direction of the leading sheet side. A sheet folding device comprising the above.

2. The superposing means has a pair of conveying rollers for conveying the sheet, The sheet folding device according to claim 1, wherein the pair of conveying rollers stops driving after conveying the leading sheet by a predetermined amount, and starts driving after the next sheet reaches the pair of conveying rollers, so as to superpose the leading end of the leading sheet at a position downstream of the leading end of the next sheet.

3. The aligning means according to claim 1, comprising: a pair of resist rollers for causing the leading ends of the sheets to abut and deflecting the plurality of sheets; and a protruding member protruding into the conveying path for guiding the sheet to the pair of resist rollers and deflecting the plurality of sheets in the direction of the leading sheet side.

4. Moving means for moving the pair of conveying rollers along a conveying path composed of a pair of guide members for guiding the sheet to the folding means of the sheet; and restricting means for restricting the upstream end in the conveying direction of the leading sheet in contact with the pair of conveying rollers moved to a predetermined position by the moving means to one side of the guide member and guiding the next sheet to a position overlapping the leading sheet. The sheet folding device according to claim 1.

5. Folding means for folding a sheet, comprising: conveying means for conveying the sheet; superposing means for superposing a plurality of sheets conveyed by the conveying means; folding means for folding the sheets superposed by the superposing means; aligning means for aligning the leading ends of the sheets by causing the leading ends of the plurality of sheets conveyed by the conveying means in a superposed state by the superposing means to abut and deflecting the sheets in a certain direction; The superposing means superposes the sheets such that the leading end of the upper sheet in the direction of deflection of the plurality of sheets when aligning the leading ends of the plurality of sheets by the aligning means is at a position downstream in the sheet conveying direction from the leading end of the lower sheet. A sheet folding device.

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