Sheet processing apparatus, image forming apparatus, and image forming system

Abstract

To suppress two-ply sheets fixed by heating and compressing from curving.SOLUTION: A sheet processing device 100, formed by overlapping two sheets and sandwiching a sheet-like medium P between two-ply sheets S a part of which is joined, includes a fixing part 120 for heating and compressing the two-ply sheets S and loading means 104 for loading the two-ply sheets S on the downstream side in the conveyance direction of the fixing part 120. The two-ply sheets S are conveyed perpendicularly downward toward the loading means after passing of the fixing part 120.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sheet processing apparatus, an image forming apparatus, and an image forming system. [Background technology]

[0002] A technique known as lamination is known in which two sheets are stacked on top of each other and joined (connected) at one side to form a double-layered sheet (laminate sheet or laminate film), and then an interlayer (paper, photograph, etc.) is inserted between them, and heat and pressure are applied to bond the two layers together.

[0003] For example, in a conventional laminating machine such as that described in Patent Document 1, two stacked sheets are transported horizontally in order to be heated and pressed in the fixing unit, which means that there is insufficient space in the paper output tray, making it impossible to stack two stacked sheets on the paper output tray. Also, some laminating machines allow stacking by positioning the paper output tray at an angle to save space, but this causes the leading edge of the pressed two stacked sheets to droop in the paper output tray, resulting in a problem of the two stacked sheets becoming curved.

[0004] Here, we will explain the curvature of two-ply sheets in detail. First, during lamination, two-ply sheets are heated in the fixing section. Therefore, when the two-ply sheets deform while hot and cool in that state, the curved shape becomes fixed. When two-ply sheets are discharged onto an upwardly angled output tray, such as the output tray of the laminating machine shown in Patent Document 1, the leading edge of the discharged two-ply sheets is lifted upward along the output tray. When two-ply sheets come into contact with an inclined portion during discharge, an external force is applied, causing deformation of the hot two-ply sheets. Because heat is gradually removed during discharge in this state, the curvature formed during discharge remains, resulting in a curved two-ply sheet being output. In other words, if the two-ply sheets are not discharged while maintaining their parallelism with the fixing nip, the output two-ply sheets will be curved. In a horizontally conveying laminating device, the two-ply sheets must be kept aligned with the fixing nip until they pass through the fixing nip. Therefore, not only in an output tray facing diagonally upward, but also in a drop-type output tray facing diagonally downward, the leading edge of the double-ply sheets will sag downward due to gravity, causing the double-ply sheets to curve. Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, an object of the present invention is to prevent two overlapping sheets that have been fixed by applying heat and pressure from being curved. [Means for solving the problem]

[0006] This problem is solved by a sheet processing apparatus that sandwiches a sheet-like medium between two sheets that are overlapped and partially joined together. Transport vertically downward,This problem is solved by a sheet processing device comprising a fixing section that applies heat and pressure, a stacking means downstream of the fixing section in the conveying direction for stacking the two-ply sheets, and a discharge roller arranged downstream of the fixing section for discharging the two-ply sheets toward the stacking means, wherein the two-ply sheets are conveyed vertically downward toward the stacking means after passing through the fixing section, and the discharge roller stops conveying the two-ply sheets after the rear end of the two-ply sheets has passed through the fixing section, holds the two-ply sheets, and then resumes the discharge operation of the two-ply sheets after a preset time has elapsed. [Effects of the Invention]

[0007] The two-ply sheet fixed by heating and pressure can be prevented from curving. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating the overall configuration of a sheet processing apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a partially enlarged view showing the portion from the heat and pressure roller 120 to the paper discharge tray 104. [Figure 3] 10 is another enlarged partial view showing the portion from the heat and pressure roller 120 to the paper discharge tray 104. FIG. [Figure 4] 10 is a flowchart illustrating an embodiment of a sheet discharging operation of a sheet processing apparatus. [Figure 5] 10 is a flowchart showing another embodiment of the sheet discharging operation of the sheet processing apparatus. [Figure 6] 1 is a diagram illustrating an overall configuration of an example of an image forming apparatus including a sheet processing apparatus according to an embodiment of the present invention. [Figure 7] 1 is a diagram illustrating an overall configuration of an example of an image forming system including a sheet processing apparatus according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] 1 is a diagram showing the overall configuration of a sheet processing apparatus according to an embodiment of the present invention. The sheet processing apparatus 100 of this embodiment separates two stacked sheets (hereinafter referred to as sheets S) from each other, and inserts and holds a sheet-like medium (hereinafter referred to as an inner sheet P) between the separated sheets S.

[0010] Here, the sheet S is a two-ply sheet in which two sheets are stacked and a part (or one side) of the two sheets is joined together. For example, a two-ply sheet may have a transparent sheet such as a transparent polyester sheet on one side and a transparent or opaque sheet on the other side, joined together at one side. The two-ply sheet also includes a laminate film.

[0011] The inner paper P is an example of a sheet medium that is inserted between these two sheets. In addition to plain paper, sheet media includes cardboard, postcards, envelopes, thin paper, coated paper (such as coated paper and art paper), tracing paper, and transparencies.

[0012] 1, the sheet processing apparatus 100 includes a paper feed tray 102, which is a first stacking unit for stacking sheets S, a pickup roller 105 for feeding the sheets S from the paper feed tray 102, and a first conveying roller 107. In addition, the paper feed tray 102 of the sheet processing apparatus 100 is provided with a plurality of sensors C11 for detecting the size of the sheets S.

[0013] After the inner sheet insertion is completed, the sheet S is discharged and stacked on the discharge tray 104 by the third conveyance roller 113 or rollers arranged thereafter. The discharge tray 104 is arranged inside the housing of the sheet processing apparatus 100. This facilitates vertical conveyance of the sheet S toward the discharge tray 104.

[0014] A transport sensor C1 that detects the transport position of the sheet S is provided downstream of the first transport roller 107 in the transport direction, and a transport sensor C2 that detects the transport position of the inner sheet P is provided downstream of the entrance roller 146 in the transport direction.

[0015] The sheet processing apparatus 100 also includes, downstream in the conveying direction of the first conveying roller 107, a second conveying roller 108, a winding roller 109 as a rotating member, a third conveying roller 113, a fourth conveying roller 144, a fifth conveying roller 145, a discharge roller 121, and a paper discharge tray 104. Between the winding roller 109 and the third conveying roller 113, a peeling claw 116 is provided so as to be movable in the width direction of the sheet S. The peeling claw 116 is an example of a peeling means for peeling the sheet S.

[0016] A conveyance sensor C3 that detects the conveyance positions of the sheet S and the inner paper P is provided downstream of the second conveyance roller 108 in the conveyance direction, and an abnormality detection sensor C4 that detects the state of the sheet S is provided downstream of the winding roller 109 in the conveyance direction. And a conveyance sensor C5 that detects the conveyance position of the sheet S is provided downstream of the third conveyance roller 113 in the conveyance direction.

[0017] The pickup roller 105, the first conveying roller 107, the second conveying roller 108, and the winding roller 109 are an example of a first feeding means.

[0018] 1, the second conveying roller 108 and the third conveying roller 113 are, for example, a pair of rollers, each of which is rotationally driven by a driving means (such as a motor). The second conveying roller 108 is rotationally driven in one direction, and the third conveying roller 113 is rotationally driven in forward and reverse directions, thereby sandwiching and conveying the sheet S and the inner paper P.

[0019] The second conveying rollers 108 convey the sheet S and the inner paper P vertically downward toward the third conveying rollers 113.

[0020] On the other hand, the rotation direction of the third conveying roller 113 can be switched between forward and reverse. The third conveying roller 113 can convey the sandwiched sheet S vertically downward toward the discharge tray 104, and can also convey the sheet S vertically upward toward the winding roller 109 in the opposite direction (pull-back direction).

[0021] The sheet processing apparatus 100 also includes a winding roller 109 and a peeling claw 116, which are rotating members, between the second conveying roller 108 and the third conveying roller 113. The winding roller 109 is driven to rotate in forward and reverse directions by a driving means (such as a motor), and its rotation can be switched between two directions (clockwise and counterclockwise).

[0022] The winding roller 109 has a roller member 111 and a movable gripping means 110 that is provided on the roller member 111 and grips the sheet S. The movable gripping means 110 is characterized by gripping the leading edge of the sheet S together with the roller member 111. The gripping means 110 may be molded integrally with the outer periphery of the roller member 111, or may be configured as a separate part.

[0023] Next, a series of operations of the sheet processing apparatus 100, that is, operations from peeling off the sheet S to inserting the inner sheet P, will be described with reference to FIG.

[0024] 1, the sheets S on the paper feed tray 102 are stacked so that a portion where two sheets are joined together is located downstream in the feeding direction (conveying direction) of the pickup roller 105. Then, the sheet processing apparatus 100 picks up the sheet S on the paper feed tray 102 with the pickup roller 105 and conveys it toward the first conveying roller 107.

[0025] Next, the sheet S is conveyed toward the winding roller 109 by a second conveying roller 108 disposed downstream in the conveying direction of the first conveying roller 107. Here, the sheet processing apparatus 100 conveys the sheet S with the side where the end portion, which is one of the four sides of the sheet S, joined being the downstream side in the vertical direction (vertically downward).

[0026] Subsequently, when the trailing edge of the sheet S in the vertical direction (vertically downward) passes the winding roller 109, the sheet processing apparatus 100 temporarily stops the conveyance of the sheet S.

[0027] Next, the sheet processing apparatus 100 opens the gripping means 110, reverses the rotation direction of the third conveying roller 113, and conveys the sheet S vertically upward toward the opening of the gripping means 110.

[0028] Next, the sheet processing apparatus 100 stops conveying the sheet S when the edge of the sheet S is inserted into the open gripping means 110, and closes the gripping means 110 to grip the edge of the sheet S. These operations are performed by conveying the sheet S by a specified amount.

[0029] Next, the sheet processing apparatus 100 rotates the winding roller 109 clockwise to wind the sheet S around the winding roller 109. Here, the sheet S is wound around the winding roller 109 from the side of the two sheets that is not joined together.

[0030] When the sheet S is wound around the winding roller 109, the difference in the winding circumference of the two overlapping sheets (difference in the amount of winding) causes excess sheet on the inner periphery, resulting in slack toward the joined edge of the sheet S. As a result, a space is created between the two sheets. By inserting the peeling claws 116 into this space from both sides of the sheet S, it is possible to reliably maintain the space between the two sheets. Note that these operations are triggered by the detection of the leading edge of the sheet S by the transport sensor C5, and are performed by transporting the sheet S by a specified amount from the transport sensor C5.

[0031] With the peeling claw 116 inserted into the space created in the sheet S, the sheet processing apparatus 100 rotates the winding roller 109 counterclockwise to move the space created by the peeling of the sheet S vertically (vertically downward) to the rear end of the sheet S. Then, when the space has been moved a specified distance, the gripping means 110 is released, separating the rear end of the sheet S into upper and lower parts.

[0032] In this state, the sheet processing apparatus 100 temporarily stops conveying the sheet S, and then moves the peeling claw 116 further in the sheet width direction to peel off the entire rear end of the sheet S. These operations are triggered by the detection of the leading edge of the sheet S by the conveying sensor C5, and are performed by conveying the sheet S by a specified amount from the conveying sensor C5.

[0033] Next, the sheet processing apparatus 100 rotates the third conveying roller 113 counterclockwise to convey the sheet S in the reverse conveying direction. When the leading edge of the sheet passes the conveying sensor C5, the branching claw 118 can be switched. When the sheet S is conveyed to the non-fixing path, the branching claw 118 remains in the position shown in the figure, but when the sheet S is conveyed to the fixing path 128, the branching claw 118 is switched to the fixing path side.

[0034] The two peeled sheets of the sheet S are guided in the left-right direction by the peeling claws 116, and the two entire sheets are peeled off from each other. Then, the sheet processing apparatus 100 temporarily stops conveying the sheet S, and the joint portion of the sheet S is gripped (nipped) by the third conveying roller 113. Therefore, the sheet S is opened widely, with the joined side as the end.

[0035] These operations are triggered by the detection of the leading edge of the sheet S by the conveyance sensor C5, and are carried out by conveying the sheet S by a specified amount from the conveyance sensor C5.

[0036] Next, the sheet processing apparatus 100 rotates the second conveying roller 108 to convey the inner sheet P conveyed from the image forming apparatus side vertically downward toward the third conveying roller 113. The image forming apparatus will be described later with reference to FIG.

[0037] Next, the sheet processing apparatus 100 rotates the third conveying roller 113 to merge the sheet S and the inner sheet P, and inserts the inner sheet P into the sheet S that has been opened. The above is the operation from peeling off the sheet S to inserting the inner paper P. The state of the opened sheet S is shown in FIG.

[0038] Next, the sheet processing apparatus 100 conveys the sheet S with the inserted interleaf P vertically downward by the third conveying roller 113, thereby overlapping the two sheets of the sheet S again and closing the opening. Then, the sheet S with the interleaf P sandwiched therebetween is conveyed to a fixing unit having a heat and pressure roller 120 by the third conveying roller 113 or a roller arranged thereafter.

[0039] The sheet S is heated and pressurized and fixed as it passes under the heat and pressure roller 120. After passing under the heat and pressure roller 120, the sheet S continues to be transported vertically downward toward the discharge tray 104 and is stacked on the discharge tray 104. Because the pressed sheet S is discharged vertically downward after passing under the heat and pressure roller 120, the heated sheet S can be stacked on the discharge tray 104 while preventing the sheet S from bending due to external forces.

[0040] More specifically, with the vertical conveyance according to the embodiment of the present invention, the sheet S is discharged vertically downward, so that gravity acting on the sheet S is parallel to the tangent of the fixing nip of the heat and pressure roller 120, and no external force that could deform the sheet S is applied to the sheet S. Therefore, as long as the sheet S continues to be discharged vertically, deformation of the sheet S is suppressed. Furthermore, the discharge tray 104 is located after the trailing edge of the sheet S has passed through the heat and pressure roller 120 and the discharge roller 121, and the sheet S is cooled by the time it reaches the discharge tray 104. Therefore, the inclination of the stacking surface of the discharge tray 104 does not apply an external force to the sheet S that could deform the sheet S.

[0041] Furthermore, as the sheet S is conveyed vertically downward, the leading edge of the sheet S reaches the heat and pressure roller 120, and the sheet S continues to be conveyed vertically downward until the trailing edge of the sheet S completely passes through the heat and pressure roller 120. This ensures that the sheet S is conveyed vertically, and prevents the sheet S from being curved by an external force after heat and pressure application.

[0042] This sheet processing device 100 is configured to be able to perform a series of operations, from feeding the sheet S, peeling it, inserting the inner paper P, and laminating it by heat and pressure, all in one device. This series of operations can be performed automatically without the need for human intervention, making it more convenient than conventional technology. Since the sheet processing device 100 is equipped with a fixing unit having a heat and pressure roller 120 and can perform laminating, it can also be said that the sheet processing device 100 is a laminating device in the narrow sense.

[0043] FIG. 2 is a partially enlarged view showing the area from the heat and pressure roller 120 to the paper discharge tray 104. As shown in FIG. In this example, a plurality of sheets (laminated sheets SG) are stacked on the discharge tray 104. As shown in the figure, the distance L from the fixing nip of the heat and pressure roller 120 to the stacking surface of the discharge tray 104 on the extension of the conveyance path or to the top surface of the sheets SG stacked on the discharge tray 104 is longer than the length of the sheets S in the conveyance direction. This prevents the leading edge of the sheets S from touching the stacking surface of the discharge tray 104 or the stacked sheets SG until the trailing edge of the sheets S has completely passed through the heat and pressure roller 120, thereby preventing the heated sheets S from bending due to external forces.

[0044] The discharge tray 104 can hold sheets S up to a thickness of, for example, 50 mm. To detect when the tray is full of sheets SG, an optical sensor 160 (for example, a laser displacement meter) that detects the top surface of the stacked sheets SG is disposed on the discharge tray 104. In this case, the distance L is longer than the length of the sheets S in the conveying direction, at least up to a thickness of 50 mm for the sheets SG.

[0045] FIG. 3 is another enlarged view showing the area from the heat and pressure roller 120 to the paper discharge tray 104. As shown in FIG. In this example, more sheets (laminated sheets SG) are stacked on the discharge tray 104 than in the example shown in Fig. 2. As shown in the figure, when the leading edge of the sheet S being discharged from the discharge roller 121 comes into contact with the top surface of the fixed sheet SG in the discharge tray 104, the sheet S curves.

[0046] Here, the sheet processing apparatus 100 is configured so that the distance D between the contact point between the leading edge of the sheet S being discharged and the top surface of the sheet SG and the vertical line passing through the nip of the discharge roller 121 is 30 mm or less. For example, by installing an optical sensor 160 (for example, a laser displacement meter) on the discharge tray 104 that detects the distance to the stacked sheets S at a position where the distance D is 30 mm, it is possible to determine whether the distance D is 30 mm or less.

[0047] By setting the distance D to 30 mm or less, even if the leading edge of the sheet S contacts the top surface of the sheet SG during discharge, the curvature of the sheet S can be kept small and stacking performance is improved. Furthermore, if the optical sensor 160 detects that the distance D exceeds 30 mm, the sheet discharge tray 104 is determined to be full, and the sheet processing apparatus 100 stops fixing and conveying the sheet S. In this way, by preventing the distance D from exceeding 30 mm, it is possible to prevent the sheet S from curving significantly when the leading edge of the sheet S contacts the top surface of the sheet SG during discharge. However, the value of 30 mm is merely an example, and is a value determined in advance by evaluation based on the thickness of the sheet S and the inner paper P used, which depends on the specifications of the sheet processing apparatus.

[0048] 1 to 3, a discharge roller 121 that discharges the sheet S toward the discharge tray 104 is disposed downstream of the heat and pressure roller 120. Discharging the sheet S with the discharge roller 121 can prevent wrinkles from forming in the sheet S after heat and pressure application. Discharging the sheet S in the vertical direction with the discharge roller 121 can prevent the sheet S from curving after heat and pressure application.

[0049] FIG. 4 is a flowchart showing an embodiment of the sheet discharging operation of the sheet processing apparatus. After the start of the heat and pressure operation in the fixing unit having the heat and pressure roller 120, the sheet processing apparatus 100 determines in step S1 whether the trailing edge of the sheet S has completely passed through the heat and pressure roller 120. For this purpose, the sheet processing apparatus 100 has a detection means for detecting the sheet S, and the detection means is, for example, a sensor C12 (FIG. 3) arranged downstream of the heat and pressure roller 120 in the conveying direction.

[0050] When the rear end of the sheet S has completely passed through the heat and pressure roller 120 (S1, Yes), the sheet processing apparatus 100 stops the discharge operation of the sheet S (S2) and holds the sheet S with the discharge roller 121. Next, in step S3, a timer provided in the sheet processing apparatus 100 sets a waiting time T according to the size of the sheet S detected by the sensor C11, and in step S4, it is determined whether the waiting time T has elapsed. Next, when the waiting time T has elapsed (S4, Yes), the sheet processing apparatus 100 resumes the discharge operation of the sheet S in step S5 and discharges the sheet.

[0051] As described above, the discharge rollers 121 are stopped, the sheet S is held by the discharge rollers 121, and the discharge operation is resumed after the waiting time T (required time) has elapsed. As a result, the sheet S is discharged after waiting for the temperature of the heat-pressurized sheet S to drop, and therefore, the sheet S can be prevented from curving.

[0052] FIG. 5 is a flowchart showing another embodiment of the sheet discharging operation of the sheet processing apparatus. After the start of the heat and pressure operation in the fixing unit having the heat and pressure roller 120, the sheet processing apparatus 100 determines in step S11 whether the trailing edge of the sheet S has completely passed through the heat and pressure roller 120. For this purpose, the sheet processing apparatus 100 has a detection means for detecting the sheet S, and the detection means is, for example, a sensor C12 (FIG. 3) arranged downstream of the heat and pressure roller 120 in the conveying direction.

[0053] When the rear end of the sheet S has completely passed through the heat and pressure roller 120 (S11, Yes), the sheet processing apparatus 100 increases the rotation speed of the discharge roller 121 in step S12 to increase the conveying speed of the sheet S. This shortens the time that the leading end of the heat and pressure applied sheet S contacts the stacking surface of the discharge tray 104 or the top surface of the stacked sheets SG, thereby suppressing the curvature of the sheet S.

[0054] 6 is an overall configuration diagram showing an example of an image forming apparatus equipped with a sheet processing apparatus according to an embodiment of the present invention. This image forming apparatus 300 includes an image forming unit that forms images on inner sheets P and the like, and an external sheet processing apparatus 100 as a sheet processing unit. The sheet processing apparatus 100 includes a paper feed tray 102 for loading sheets S, and is configured to be able to feed inner sheets P from the image forming apparatus 300 via a relay device 310. Therefore, the image forming apparatus 300 (e.g., a printer, a copier, etc.) can insert images inline onto the inner sheets P that are inserted into the sheets S. Therefore, the image forming apparatus 300 can perform a series of operations, from feeding the sheets S to peeling, inserting the inner sheets, and laminating them using heat and pressure, without the need for human intervention.

[0055] An operation panel 10, which is a display and operation means for displaying information on the image forming apparatus 300 and receiving operation inputs, is installed on the exterior of the image forming apparatus 300. The operation panel 10 also serves as a notification means for issuing a sensory signal to the user. Alternatively, a notification means other than the operation panel 10 may be provided separately in the image forming apparatus 300.

[0056] 7 is a diagram showing an overall configuration of an example of an image forming system including a sheet processing apparatus according to an embodiment of the present invention. The image forming system includes an image forming apparatus 300, a relay apparatus 310, a sheet processing apparatus 100, and a post-processing apparatus 400. This image forming system is configured so that the inner paper P can be fed from the image forming device 300 via the relay device 310, and by installing another post-processing device 400 downstream of the image forming device 300, the user can use it without reducing the efficiency of print jobs that do not require lamination processing.

[0057] In the case of a print job that does not involve lamination, the inner sheets P fed from the image forming apparatus 300 are received by the inlet rollers 146 of the sheet processing apparatus 100, and are transported to the post-processing apparatus 400 located downstream of the sheet processing apparatus 100 by the paper discharge rollers 147 located downstream in the transport direction of the inlet rollers 146. The post-processing apparatus 400 can perform post-processing such as stapling on the sheets S that have not been subjected to lamination processing. The inner sheets P are stacked on the paper discharge tray 150 of the post-processing apparatus 400.

[0058] In the case of a print job that requires lamination, the sheet processing apparatus 100 feeds the sheet S from a paper feed tray 102 in which the sheets S are stacked by a pickup roller 105 and a first conveyance roller 107. The peeled sheet SR is held by a third conveyance roller 113, and the inner sheet P fed from the image forming apparatus 300 is received by an entrance roller 146 of the sheet processing apparatus 100 and merged with the sheet S by a second conveyance roller 108. The sheet S is then laminated by pressure and heat applied by a heat and pressure roller 120. The laminated sheet SG is then ejected by an ejection roller 121 and placed on an ejection tray 104. [Explanation of symbols]

[0059] 100 Sheet processing device 104 Paper output tray (loading means) 120 Heat and pressure roller (fuser unit) P Inner paper (sheet media) S sheet (two-ply sheet) [Prior art documents] [Patent documents]

[0060] [Patent Document 1] Japanese Patent Publication No. 2020-121868

Claims

1. In a sheet processing apparatus in which a sheet medium is sandwiched between two overlapping sheets that are partially joined together, a fixing section that conveys the two-ply sheet vertically downward and applies heat and pressure to the two-ply sheet; a stacking unit for stacking the two-ply sheets downstream of the fixing unit in the conveying direction; a discharge roller disposed downstream of the fixing unit and configured to discharge the two-ply sheet toward the stacking means; the two-ply sheet is conveyed vertically downward toward the stacking means after passing through the fixing section, The sheet processing apparatus is characterized in that the discharge roller stops conveying the two-ply sheet after the rear end of the two-ply sheet passes through the fixing section, holds the two-ply sheet, and then resumes the discharge operation of the two-ply sheet after a predetermined time has elapsed.

2. A sheet processing device in which a sheet-like medium is sandwiched between two sheets that are stacked and partially joined together, a fixing unit that heats and presses the two-ply sheet; a stacking unit for stacking the two-ply sheets downstream of the fixing unit in the conveying direction; a discharge roller disposed downstream of the fixing unit and configured to discharge the two-ply sheet toward the stacking means; The two-ply sheet is conveyed vertically downward toward the fixing unit and the stacking means, The sheet processing apparatus is characterized in that the discharge roller stops conveying the two-ply sheet after the rear end of the two-ply sheet passes through the fixing section, holds the two-ply sheet, and then resumes the discharge operation of the two-ply sheet after a predetermined time has elapsed.

3. 3. The sheet processing apparatus according to claim 1, wherein the predetermined time is set in accordance with the size of the two-ply sheets.

4. 3. The sheet processing apparatus according to claim 1, wherein the two-ply sheet is transported vertically downward until the leading edge of the two-ply sheet reaches the fixing section and the trailing edge of the two-ply sheet completely passes through the fixing section.

5. A sheet processing apparatus according to any one of claims 1 to 3, characterized in that the distance from the fixing unit to the loading surface of the loading means on the extension line of the conveying path or to the top surface of the two-ply sheet loaded on the loading means is longer than the length of the two-ply sheet.

6. 6. The sheet processing apparatus according to claim 1, wherein the rotation speed of the discharge roller is increased after the trailing edge of the two-ply sheet has passed through the fixing unit.

7. a sheet processing apparatus according to any one of claims 1 to 6; and an image forming unit that forms an image.

8. 7. An image forming system comprising the sheet processing apparatus according to claim 1.

Images