Sheet Processing Device

Abstract

To provide a sheet processing device that enables smooth discharge of a sheet by separating the sheet discharge roller pair when the sheet is discharged straight from the transport roller pair to the stack tray.SOLUTION: The sheet processing device includes: a sheet discharge roller pair 27 that is provided on the carry-out port of a sheet S and can press-contact and separate from each other; and a stack tray 21b that stacks the sheet S discharged by the sheet discharge roller pair 27 from the carry-out port. The sheet discharge roller pair 27 in the separated condition causes the leading end Sa of the sheet S to pass through and press-contacts the sheet S before the leading end Sa of the sheet S reaches the stack tray 21b.SELECTED DRAWING: Figure 4B

Description

[Technical field]

[0001] The present invention relates to a sheet processing apparatus capable of selecting an optimum paper discharge mode according to the type of sheet. [Background technology]

[0002] Conventionally, there is known a sheet processing apparatus that has a function of stacking and discharging sheets on which images have been formed by an image forming device such as a printer or scanner directly onto a stack tray, or discharging a stack of sheets stacked on the stack tray after performing post-processing such as stapling (Patent Documents 1 and 2). This type of sheet processing apparatus is provided with a pair of conveying rollers that conveys sheets onto a processing tray, and a pair of forward and reverse rotating discharge rollers that discharge the sheets onto the stack tray at the sheet discharge outlet. The apparatus also has a non-staple mode in which the sheets from the pair of conveying rollers are discharged directly onto the stack tray while the pair of discharge rollers are pressed against each other, and a staple mode in which multiple sheets (sheet stack) discharged onto the processing tray are switched back, and after post-processing such as stapling, the sheets are stored in the stack tray. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-263027 A [Patent Document 2] JP 2009-126658 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the sheet processing devices disclosed in Patent Documents 1 and 2, the pair of conveying rollers drops the sheet onto a processing tray. However, since there is no lower guide to guide the sheet to the pressure contact portion of the pair of discharge rollers, depending on the conveying state of the sheet and the type of sheet, there is a problem that the leading edge of the sheet collides with the peripheral surface of the pair of discharge rollers, making it difficult to discharge the sheet smoothly.

[0005] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a sheet processing apparatus that, when a sheet is discharged directly from a pair of conveying rollers onto a stack tray, enables smooth discharge of the sheet by separating the pair of discharge rollers. [Means for solving the problem]

[0006] In order to solve the above problems, the sheet processing apparatus of the present invention is composed of a processing tray for post-processing sheets, a binding unit for binding sheets on the processing tray, a pair of transport rollers for transporting sheets onto the processing tray, a stack tray for stacking sheets, a first roller, and a second roller movable to a pressing position for pressing against the first roller and to a retracted position spaced from the first roller, and is equipped with a pair of discharge rollers for discharging sheets that have been stapled in the processing tray and sheets from the pair of transport rollers onto the stack tray, and a control means for executing a staple mode in which sheets transported from the pair of transport rollers to the processing tray are stapled and then discharged onto the stack tray, and a non-staple mode in which sheets are not stapled and are discharged from the pair of transport rollers onto the stack tray by the pair of discharge rollers, When the sheet to be discharged is a first type sheet in the non-staple mode, the control unit causes a leading edge of the sheet to pass through the pair of conveying rollers in a state in which the second roller is separated from the first roller, and causes the leading edge of the sheet to pass through the pair of conveying rollers before the leading edge of the sheet reaches the stack tray. Noro The pair of conveying rollers is moved from a retracted position to a pressing position, and when the sheet to be discharged is a second type of sheet, the leading edge of the sheet passes through the pair of conveying rollers while the second roller is separated from the first roller, and after the leading edge of the sheet reaches the stack tray, the second roller is moved from the retracted position to the pressing position. Effect of the Invention

[0007] According to the sheet processing device of the present invention, the leading edge of a sheet discharged toward a stack tray is pressed against the pair of discharge rollers before it reaches the stack tray, so that the leading edge of the sheet can be guided while being discharged onto the stack tray, thereby enabling the sheet to be discharged smoothly.

[0008] In particular, when the sheet is a specific sheet such as an envelope having a flap portion, the sheet can be discharged smoothly without disturbing the alignment of the envelope, such as the leading edge of the following envelope hitting the flap portion of the previously loaded envelope. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of an image forming system including a sheet processing apparatus according to the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing a main configuration inside the sheet processing apparatus. [Figure 3A] FIG. 13 is an explanatory diagram showing the discharge operation (1) of plain paper in the non-staple mode. [Figure 3B] FIG. 13 is an explanatory diagram showing the discharge operation (2) of plain paper in the non-staple mode. [Figure 3C] FIG. 11 is an explanatory diagram showing the discharge operation (3) of plain paper in the non-staple mode. [Figure 4A] FIG. 13 is an explanatory diagram showing the envelope discharge operation (1) in the non-staple mode. [Figure 4B] FIG. 13 is an explanatory diagram showing the envelope discharge operation (2) in the non-staple mode. [Figure 4C] FIG. 13 is an explanatory diagram showing the envelope discharge operation (3) in the non-staple mode. [Figure 5A] FIG. 13 is an explanatory diagram showing a paper discharge operation (1) in the staple mode. [Figure 5B] FIG. 13 is an explanatory diagram showing the paper discharge operation (2) in the staple mode. [Figure 5C] FIG. 13 is an explanatory diagram showing a paper discharge operation (3) in the staple mode. [Figure 5D]FIG. 13 is an explanatory diagram showing a paper discharge operation (4) in the staple mode. [Figure 6] FIG. 11 is a flow chart showing the discharge operation of plain paper and envelopes in the non-staple mode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiment of the present invention will be described in detail with reference to the attached drawings. First, an overview of an image forming system A including a sheet processing device C of the present invention will be described with reference to FIG. 1. The image forming system A is composed of an image forming device B and a sheet processing device C. The image forming device B and the sheet processing device C are connected via an outlet 3 of the image forming device B and an inlet 22 of the sheet processing device C. A sheet on which an image is formed by the image forming device B is discharged to one of stack trays 21a and 21b via the sheet processing device C. In the sheet processing device C, various post-processing such as stapling is performed as specified. The sheets handled in the image forming system A include flat plain paper as well as specific sheets such as envelopes having a flap portion. The flap portion includes an opening of the envelope as well as a bonding portion. In the sheet processing device of the present invention, a paper discharge operation is performed at an optimal timing according to the type of sheet such as the plain paper or the envelope. In the following, plain paper (other than the specific sheet) and envelopes (specific sheets) are both referred to as sheets, but when describing operations particularly suited to plain paper and envelopes, they will be referred to as plain paper or envelopes. In addition, the leading edge of a sheet refers to the edge in the sheet's conveyance (discharge) direction, and the trailing edge of a sheet refers to the edge on the opposite side to the sheet's conveyance (discharge) direction.

[0011] The image forming apparatus B is configured to send a sheet from a paper feed section 1 to an image forming section 2, print an image on the sheet in the image forming section 2, and then discharge the sheet from a discharge port 3. The paper feed section 1 stores sheets of a plurality of sizes in paper feed cassettes 1a and 1b, and separates and feeds designated sheets one by one to the image forming section 2. The image forming section 2 includes, for example, an electrostatic drum 4, a print head (not shown) arranged around the electrostatic drum 4, a developing device 6, a transfer charger 7, a fixing device 8, and the like. An image is formed on a sheet by forming an electrostatic latent image on the electrostatic drum 4, attaching toner to the electrostatic latent image by the developing device 6, transferring the image onto the sheet by the transfer charger 7, and fixing the image by heat by the fixing device 8. The sheets on which the image is formed in this way are sequentially discharged from the discharge port 3 toward the sheet processing device C. In the circulation path 9, the sheet printed on the front side from the fixing device 8 is inverted through a switchback path 10, and then fed again to the image forming section 2. This allows printing on both the front and back sides of the sheet. The sheet thus double-sided printed is inverted in the switchback path 10 and then discharged from the discharge port 3 toward the sheet processing apparatus C.

[0012] In the image reading device 11, an original sheet set on a platen 12 is scanned by a scan unit 13 and electrically read via a photoelectric conversion element 14. The read image data is digitally processed by an image processing unit (not shown). In the original feeding device 15, an original sheet set on a stack tray 16 is fed to the platen 12.

[0013] The image forming apparatus B having the above configuration is provided with a control unit (not shown) in which image forming conditions, such as sheet size specification, color / monochrome printing specification, number of copies to be printed, single-sided / double-sided printing specification, enlarged / reduced printing specification, and other printing conditions are set.

[0014] The sheet processing device C of the present invention includes a normal sheet discharge means for directly discharging sheets carried in from the carry-in entrance 22 via the carry-in roller pair 23, a post-processing means arranged at one end of the processing tray 28 for stapling sheets at the staple position on the processing tray 28, and a control means for controlling the post-processing and discharge of the sheets. The normal sheet discharge means discharges sheets on which images have been formed by the image forming device B to either the stack tray 21a or 21b. The post-processing means of this embodiment includes a staple unit 30, which bundles together a plurality of sheets on which images have been formed by the image forming device B, performs processing such as stapling, and then discharges the sheets to the stack tray 21b.

[0015] A transport path R extends from the entrance 22 toward the downstream side in the sheet transport direction, and this transport path R branches into a first discharge path R1 toward the upper stack tray 21a and a second discharge path R2 toward the lower stack tray 21b via a flapper Ra. The first discharge path R1 has a first transport roller pair 24 on the upstream side and a first discharge roller pair 25 on the downstream side. The second discharge path R2 has a second transport roller pair 26 on the upstream side and a second discharge roller pair 27 on the downstream side toward the exit 29. The second transport roller pair 26 is disposed above the processing tray 28 and transports a sheet onto the processing tray 28. The second discharge roller pair 27 is disposed on the other end side of the processing tray 28 and discharges the sheet post-processed in the processing tray 28 and the sheet from the second transport roller pair 26.

[0016] The first conveying roller pair 24 and the first discharge roller pair 25 each consist of a drive roller, one of which is rotated by a drive motor not shown, and a driven roller, the other of which is rotated following the drive roller, and discharge the sheet toward the stack tray 21a while pressing the sheet against the drive roller.

[0017] 2, the second conveying roller pair 26 is composed of a driving roller 26a rotated by a conveying motor MT1 and a driven roller 26b rotated by the driving roller 26a. The second paper discharge roller pair 27 is composed of an upper driving roller 27a rotated by a paper discharge motor MT2 and a lower driving roller 27b rotated by a switchback motor MT4.

[0018] The upper driving roller 27a of the second discharge roller pair 27 is attached to one end of a first arm 32 that can swing about a rotation shaft 26a1 of the driving roller 26a of the second conveying roller pair 26. The first arm 32 is connected to a pressing motor MT3 via a link member 33 and a rack and pinion 34, and by driving the pressing motor MT3, the upper driving roller 27a can be moved up and down between a pressing position where it is pressed against the lower driving roller 27b and a standby position where it is separated from the upper driving roller 27a.

[0019] In addition, as a mechanism related to the staple unit 30, a take-in roller 35 is provided which presses the sheets conveyed to the processing tray 28 and guides them to the staple unit 30. The processing tray 28 is formed of a synthetic resin plate or the like, and its upper surface is a sheet support surface 28a for supporting and stacking sheets. The sheet support surface 28a is disposed downstream of the second conveying roller pair 26 with a step formed therein, and stacks and accommodates the sheets from the second conveying roller pair 26. As shown in FIG. 2, the sheet support surface 28a is formed to have a length dimension shorter than the length of the sheet in the sheet discharge direction, supports the rear end of the sheet from the discharge port 29, and supports the leading end of the sheet on the top sheet of the stack tray 21b. The take-in roller 35 is attached to one end of a second arm 37 which swings about a rotation shaft 36 which is rotated by a lifting motor MT5 as a fulcrum. Usually, the pick-up roller 35 waits at a position separated from the processing tray 28, and when a sheet is carried into the processing tray 28 by the reverse rotation of the second discharge roller pair 27 by the switchback, the pick-up roller 35 descends and abuts against the sheet surface. Then, the rear end of the sheet is aligned with an alignment plate 38 in the staple unit 30. The aligned sheet stack is stapled by the staple unit 30, and is then gripped by the gripper 31 and discharged to the stack tray 21b, as shown in FIG. 5D. The conveyor belt 40 is stretched over a pair of pulleys 39, and the gripper 31 is moved by the drive of a belt motor MT6. Details of the staple process are omitted.

[0020] Further, a sheet sensor SE is provided on the second discharge path R2 near the upstream side of the second conveying roller pair 26. This sheet sensor SE detects the leading edge of the sheet conveyed into the second discharge path R2.

[0021] The sheet processing device C of the present invention has a staple mode in which the sheet from the second conveying roller pair 26 is subjected to post-processing (stapling) on ​​the processing tray 28 and the stapled sheet is discharged to the stack tray 21b by the gripper 31, and a non-staple mode in which the sheet from the second conveying roller pair 26 is directly discharged to the stack tray 21b by the second discharge roller pair 27. In this embodiment, when discharging the sheet to the second stack tray 21b in the non-staple mode, the second discharge roller pair 27 is switched from a separated state to a pressure contact state, and further, the pressure contact timing of the second discharge roller pair 27 is changed depending on the type of sheet (plain paper and envelope). In the case of an envelope, the second discharge roller pair 27 is pressed when the leading edge of the envelope reaches a predetermined position between the pressure contact position P2 of the second discharge roller pair 27 and the second stack tray 21b. On the other hand, in the case of a sheet other than an envelope, the second discharge roller pair 27 is pressed against the sheet after the leading edge of the sheet reaches the second stack tray 21b.

[0022] In the case of the envelope, the envelope is discharged with its front side facing down onto the stack tray 21b, but if the sheet is discharged onto the second stack tray 21b with the second discharge roller pair 27 separated, there is a problem that the leading edge Sa of the envelope S to be discharged next hits the flap portion Sf of the envelope S previously stacked on the stack tray 21b. In contrast, in the present invention, the sheet is discharged by being pressed by the second discharge roller pair 27 before being discharged onto the second stack tray 21b, so that it can be discharged while avoiding the flap portion Sf of the previous envelope S.

[0023] 3A to 3C show the discharge operation of a sheet (plain paper) other than a specific sheet in the non-staple mode. In this operation, as shown in FIG. 3A, the second discharge roller pair 27 is in a standby position separated from the sheet S, and in this state, the leading edge Sa of the sheet S is sent to the vicinity of the pressing position P2 of the second discharge roller pair 27. Next, as shown in FIG. 3B, the pressing motor MT3 starts driving, and the upper drive roller 27a descends toward the lower drive roller 27b. During this time, the leading edge Sa of the sheet S is sent to a position P3 where it reaches the stack tray 21b. Then, as shown in FIG. 3C, after the leading edge Sa of the sheet S reaches the second stack tray 21b, when the leading edge Sa side portion of the sheet S is placed on the second stack tray 21b, the second discharge roller pair 27 presses the sheet S. That is, in the case of a sheet S other than an envelope, the second discharge roller pair 27 presses the sheet S after the leading edge Sa of the sheet S reaches the second stack tray 21b.

[0024] 4A to 4C show the discharge operation of a specific sheet (envelope) in the non-staple mode. In this operation, as shown in FIG. 4A, the second discharge roller pair 27 is in a standby position separated from the sheet (envelope), and in this state, the leading edge Sa of the sheet (envelope) S is sent to a position P4 where the leading edge Sa does not reach the second conveyance roller pair 26. Next, as shown in FIG. 4B, the pressing motor MT3 starts to drive, and the upper drive roller 27a descends toward the lower drive roller 27b. During this time, the leading edge Sa of the envelope S reaches the second discharge roller pair 27, and the upper drive roller 27a and the lower drive roller 27b press against each other at a position P5 slightly past the pressing position P2 by the second discharge roller pair 27. That is, in the envelope, the leading edge Sa of the envelope S presses against the second discharge roller pair 27 before it reaches the stack tray 21b. Thereafter, as shown in FIG. 4C, the succeeding envelope S is smoothly discharged without hitting or being caught by the flap portion Sf of the previously stacked envelope S.

[0025] 5A to 5D show the sheet pick-up and discharge operations in the staple mode. In this staple mode, as shown in FIG. 5A, the second discharge roller pair 27 is separated, and the second conveying roller pair 26 conveys the leading edge Sa of the sheet S until it reaches the stack tray 21b. Then, as shown in FIG. 5B, the trailing edge Sb of the sheet S passes through the second conveying roller pair 26 and falls onto the processing tray 28, and then presses the second discharge roller pair 27, and the upper drive roller 27a and the lower drive roller 27b rotate in the opposite direction to the discharge direction. At this time, the pick-up roller 35 is lowered by the drive of the lift motor MT5, and the sheet S on the processing tray 28 is guided to the alignment plate 38 of the staple unit 30 as shown in FIG. 5C. Then, when the alignment of a predetermined number of sheets S is completed, the staple unit 30 performs the staple process. Thereafter, as shown in FIG. 5D, the belt motor MT6 is driven to move the gripper 31 toward the stack tray 21b, and the stapled stack of sheets S is discharged onto the stack tray 21b.

[0026] Hereinafter, the sheet (plain paper, envelope) discharge operation in the non-staple mode will be described in detail based on the operation flowchart shown in FIG. 6 with reference to FIGS. 3A to 3C and 4A to 4C. A sheet (plain paper or envelope) is transported from image forming apparatus B to sheet processing apparatus C, and image forming apparatus B executes a paper discharge operation (ST01). At this point, a non-staple mode command has already been received from image forming apparatus B. When the sheet received from image forming apparatus B is detected by sheet sensor SE, conveying motor MT1, paper discharge motor MT2, and switchback motor MT4 are driven (ST02-ST03). Then, a pressing operation of second paper discharge roller pair 27 is executed (ST04). In the pressing operation of second paper discharge roller pair 27, it is first determined whether the discharged sheet is plain paper or an envelope (ST04-1).

[0027] If the type of sheet is plain paper, the pressing motor MT3 starts to rotate in the forward direction when the sheet is conveyed by the first conveyance amount L1 from the time when the sheet sensor SE detects the leading edge of the sheet (ST04-2, ST04-4) (see FIG. 3A). Then, the pressing motor MT3 is stopped when the pressing motor MT3 is driven by the predetermined amount (ST04-5, ST04-6). As a result, the upper driving roller 27a moves from the standby position to the pressing position, and the upper driving roller 27a and the lower driving roller 27b are pressed against each other. In the process of the upper driving roller 27a moving, the leading edge of the sheet reaches the stacking surface of the stack tray 21b (see FIG. 3B) before the upper driving roller 27a reaches the pressing position, and the leading edge Sa of the sheet S is placed on the stacking surface of the stack tray 21b (see FIG. 3C). The first transport amount L1 is a transport amount corresponding to a distance set from a detection position P1 of the sheet sensor SE to the vicinity of the downstream side of the pressure contact position P2 of the second discharge roller pair 27 as shown in FIG. 3A.

[0028] On the other hand, in the pressing operation of the second discharge roller pair 27, if the type of sheet is an envelope, the pressing motor MT3 starts to rotate forward when the sheet S is conveyed by the second conveyance amount L2 from the time when the sheet sensor SE detects the leading edge Sa of the sheet S (ST04-3, ST04-4) (see FIG. 4A). Then, when the pressing motor MT3 has driven by the predetermined amount, the pressing motor MT3 is stopped (ST04-5, ST04-6). As a result, the upper drive roller 27a moves from the standby position to the pressing position, and the upper drive roller 27a and the lower drive roller 27b are pressed against each other. At this time, the leading edge Sa of the sheet S is in a position slightly protruding downstream from the pressing position P2 of the second discharge roller pair 27 pressed against each other, and has not yet reached the placement surface of the second stack tray 21b (see FIG. 4B). Therefore, when the type of the sheet is an envelope, the leading edge of the sheet is pressed by the second discharge roller pair 27 and then sent onto the second stack tray 21b (see FIG. 4C).

[0029] The second discharge roller pair 27 is usually in a standby position, and is already in a separated state when the leading edge Sa of the sheet S is detected by the sheet sensor SE. Then, after the pressing operation of the second discharge roller pair 27 is completed, when the trailing edge Sb of the sheet S is detected by the sheet sensor SE, the sheet S is fed by a third conveyance amount L3 from that point, and the conveyance motor MT1, the discharge motor MT2, and the switchback motor MT4 are stopped (ST05-ST07). As a result, the sheet S is discharged onto the second stack tray 21b. The third conveyance amount L3 is a conveyance amount equivalent to the distance by which the trailing edge Sb of the sheet S reaches the second stack tray 21b, plus a predetermined amount. The first, second, and third conveyance amounts are the drive amounts (drive times) of the second conveyance roller pair 26 and the second discharge roller pair 27 for conveying the sheet. In this embodiment, the number of pulses corresponding to the first, second, and third transport amounts are preset, and the number of drive pulses of the transport motor MT1, the discharge motor MT2, and the switchback motor MT4 are counted. When the count value reaches each of the set pulses, it is detected that each transport amount has been transported.

[0030] After the sheet S is discharged onto the second stack tray 21b and the conveying motor MT1, the discharge motor MT2, and the switchback motor MT4 are stopped, the pressing motor MT3 is driven in the reverse direction by a predetermined amount and then stopped (ST08-ST10). As a result, the upper driving roller 27a moves from the pressing position to the standby position, and the upper driving roller 27a and the lower driving roller 27b are separated from each other.

[0031] As described above, the sheet processing apparatus of the present invention is configured such that, in the sheet discharge operation to the second stack tray 21b in the non-staple mode, the leading edge of the sheet passes through the second discharge roller pair 27 in a separated state, and the second discharge roller pair 27 is switched to a pressure contact state after the leading edge of the sheet passes through the second discharge roller pair 27. This allows smooth discharge. Furthermore, the timing of pressing the sheet by the second discharge roller pair 27 can be changed according to the type of sheet to be discharged. Here, in the case where the sheet material is an envelope having a flap portion, the second discharge roller pair 27 is pressed before the leading edge of the envelope reaches the second stack tray 21b. This allows good alignment on the stack tray 21b to be maintained even if the type of sheet is an envelope. [Explanation of symbols]

[0032] A Image forming system B Image forming device C Sheet Processing Device R Transport route Ra Flapper R1 First ejection path R2 Second ejection path S sheet (envelope) Sa tip Sb rear end Sf Flap section SE seat sensor MT1 Transport motor MT2 paper ejection motor MT3 Pressure Motor MT4 Switchback Motor MT5 Lifting Motor MT6 belt motor 1 Paper feed section 2 Image forming section 3 Exit 11 Image reading device 15 Document feeder 21a, 21b Stack Tray 22 Loading entrance 23 Loading roller pair 24 First conveyor roller pair 25 First discharge roller pair 26 Second conveying roller pair 26a Drive roller 26a1 Rotating shaft 26b Driven roller 27 Second discharge roller pair 27a Upper drive roller 27b Lower drive roller 28 Processing Tray 29 Exit 30 Staple unit 31 Gripper 32 First Arm 33 Link member 34 Rack and pinion 35 Scraping roller 36 Rotation Axis 37 Second Arm 38 Matching plate 39 Pulley 40 Conveyor belt

Claims

1. a processing tray for post-processing the sheets; a binding unit that performs a binding process on the sheets on the processing tray; a pair of conveying rollers for conveying a sheet onto the processing tray; A stack tray for stacking sheets; a pair of discharge rollers including a first roller and a second roller movable to a pressing position where the second roller is pressed against the first roller and to a retracted position where the second roller is separated from the first roller, the pair of discharge rollers discharging the sheets that have been stapled in the processing tray and the sheets from the pair of conveying rollers to the stack tray; A sheet processing apparatus including a control means for executing a staple mode in which sheets conveyed from the conveying roller pair to the processing tray are stapled and then discharged onto the stack tray, and a non-staple mode in which the sheets are not stapled but discharged from the conveying roller pair onto the stack tray by the discharge roller pair, The control means, in the non-staple mode, When the sheet to be discharged is a first type of sheet, the leading edge of the sheet passes through the pair of conveying rollers in a state in which the second roller is separated from the first roller, and the second roller is moved from a retracted position to a pressing position before the leading edge of the sheet reaches the stack tray; When the sheet to be discharged is a second type of sheet, the leading edge of the sheet passes through the pair of conveying rollers while the second roller is separated from the first roller, and after the leading edge of the sheet reaches the stack tray, the second roller is moved from a retracted position to a pressing position.

2. A sheet processing device as described in claim 1, wherein the first type of sheet is an envelope having a flap portion, and the pair of discharge rollers consisting of the first and second rollers discharges the tip of the envelope downstream in the sheet discharge direction from the tip of the flap portion of a preceding envelope on the stack tray.

3. a driving means for rotating the first roller in a forward direction for discharging the sheet onto the stack tray and in a reverse direction different from the forward direction; The control means In the non-staple mode, the second roller is moved to a pressing position while being rotated in a forward direction by the driving means, and the sheet is discharged from the pair of conveying rollers onto the stack tray.

2. The sheet processing apparatus according to claim 1, wherein in a staple mode, after a sheet is transported to the processing tray, the second roller is rotated in a reverse direction by the driving means, and the sheet is moved to a staple position on the processing tray where the sheet is stapled.

4. A pair of conveying rollers for conveying a sheet; A stack tray for stacking sheets; a pair of discharge rollers including a first roller and a second roller movable between a pressure contact position where the second roller is in pressure contact with the first roller and a retracted position where the second roller is spaced from the first roller, the pair of discharge rollers discharging the sheet from the pair of conveying rollers onto the stack tray; a moving means for moving the second roller from a retracted position to a pressing position; In a sheet processing apparatus comprising: The moving means is When the sheet to be discharged is a first type of sheet, the second roller passes a leading edge of the sheet conveyed by the pair of conveying rollers in a state separated from the first roller, and the second roller reaches a pressing position before the leading edge of the sheet reaches the stack tray and before the trailing edge of the sheet passes the pair of conveying rollers; When the sheet to be discharged is a second type of sheet, the sheet processing device causes the leading edge of the sheet transported by the pair of transport rollers to pass through the second roller while being spaced apart from the first roller, and causes the second roller to reach a pressure contact position after the leading edge of the sheet reaches the stack tray and before the trailing edge of the sheet passes through the pair of transport rollers.

5. A sheet sensor is provided upstream of the pair of conveying rollers to detect a leading edge of the sheet, The moving means is 5. The sheet processing device according to claim 4, wherein, in the case of the first type of sheet, the second roller starts moving from the retracted position to the pressing position when the sheet has been transported a first distance from the time when the sheet sensor detects the leading edge of the sheet, and, in the case of the second type of sheet, the second roller starts moving from the retracted position to the pressing position when the sheet has been transported a second distance from the time when the sheet sensor detects the leading edge of the sheet.

6. 5. The sheet processing device according to claim 4, wherein the first type of sheet is an envelope having a flap portion, and the pair of discharge rollers consisting of the first and second rollers discharges the leading end of the envelope downstream in the sheet discharge direction from the leading end of the flap portion of a preceding envelope on the stack tray.

7. a processing tray for post-processing the sheets; a post-processing unit disposed on one end side of the processing tray and performing post-processing on the sheets at the staple position on the processing tray; a pair of conveying rollers disposed above the processing tray and configured to convey a sheet onto the processing tray; a pair of discharge rollers disposed on the other end side of the processing tray and configured to discharge the sheet that has been post-processed in the processing tray and the sheet from the pair of conveying rollers; a stack tray for stacking sheets discharged by the pair of discharge rollers; A sheet processing apparatus including a control unit for executing a staple mode in which a sheet is subjected to post-processing and then discharged onto the stack tray, and a non-staple mode in which a sheet is discharged onto the stack tray without being subjected to post-processing, The pair of discharge rollers is configured to be capable of rotating forward and reverse and to be brought into pressure contact with and separated from each other, The pair of discharge rollers in the non-staple mode allows the leading edge of the sheet to pass while separated from each other, presses the sheet before the leading edge of the sheet reaches the stack tray, and rotates forward to discharge the sheet toward the stack tray. In the staple mode, the pair of discharge rollers allow the leading edge of the sheet to pass while spaced apart, press the sheet after it is transported to the processing tray, and rotate in reverse to transport the sheet transported to the processing tray to the staple position.

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