Sheet processing device and image forming system

Abstract

To provide a structure capable of improving the alignment of sheets to be bonded together.SOLUTION: A sheet processing device comprises: a stacking processing part for stacking a plurality of sheets which are conveyed one by one in a state of having an adhesive applied; aligning means having a placement part on which the sheets are stacked and aligning positions of the sheets stacked on the placement part; and bonding means for bonding the sheets stacked on the placement part to each other. After a second sheet bundle stacked in advance by the stacking processing part is stacked on a first sheet bundle stacked on the placement part and aligned by the aligning means, the aligning means aligns a position of the second sheet bundle with a position of the first sheet bundle. The bonding means heats and pressurizes the second sheet bundle aligned by the aligning means, thereby bonding the sheets of the second sheet bundle to each other by an adhesive, and bonding the first sheet bundle and the second sheet bundle to each other.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present invention relates to a sheet processing apparatus for processing sheets and an image forming system for forming an image on a sheet.

Background Art

[0002] Conventionally, there has been proposed an image forming apparatus that forms a toner image on a sheet, applies an adhesive toner, and then overlaps the sheets and heats and presses them with a heating and pressing member to produce a product in which the sheets are adhered to each other (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the configuration of the above document, alignment of the sheets is performed each time a sheet coated with the adhesive toner is discharged one by one onto the stacking tray. Therefore, due to the adhesive strength of the adhesive toner of the already stacked sheets or the adhesive toner of the newly stacked sheets, the alignment of the newly stacked sheets may be hindered and the alignment accuracy may decrease.

[0005] Therefore, an object of the present invention is to provide a configuration capable of improving the alignment accuracy of the sheets to be adhered.

Means for Solving the Problems

[0006] One aspect of the present invention stacks a plurality of sheets that are conveyed one by one in a state where an adhesive is applied An adhesive layer is formed Form a sheet bundle ​The assembly comprises a stacking section, a loading section on which sheets are stacked, an alignment means for aligning the positions of sheets stacked in the loading section, and an adhesive means for bonding the sheets stacked in the loading section together, wherein the alignment means is configured to align the position of the second sheet bundle with the first sheet bundle after a second sheet bundle, which has been stacked in the stacking section and aligned by the alignment means, is stacked on top of the first sheet bundle, which has been stacked in the stacking section, and the adhesive means is configured to align the position of the second sheet bundle with the first sheet bundle, After bonding the first sheet bundle with the adhesive layer, The second sheet bundle, aligned by the alignment means By performing a single thermocompression operation By heating and pressurizing, the adhesive Through layers Each sheet of the second sheet bundle is bonded to each other. 、 and via the adhesive layer formed on the upper surface of the top sheet of the first sheet bundle and the adhesive layer formed on the lower surface of the bottom sheet of the second sheet bundle The sheet processing apparatus is characterized by bonding the first sheet bundle and the second sheet bundle together. [Effects of the Invention]

[0007] According to the present invention, the consistency of the sheets to be bonded can be improved. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic diagram of the image forming system according to the embodiment. [Figure 2] A diagram showing an example of the coating area of ​​the adhesive toner according to the embodiment. [Figure 3] A schematic diagram of the buffer section according to the embodiment. [Figure 4] Figures (a-h) illustrating the buffer operation according to the embodiment. [Figure 5] Cross-sectional view of the alignment section according to the embodiment. [Figure 6] Exploded view of the movable unit of the alignment section according to the embodiment. [Figure 7] Figures (a-d) illustrating the alignment operation of the alignment unit according to the embodiment. [Figure 8] A perspective view of the heat-sealed portion according to the embodiment. [Figure 9] Cross-sectional views (a-f) of the heat-sealed portion for illustrating the bonding operation according to the embodiment. [Figure 10] Cross-sectional view of the thermocompression bonding part according to the embodiment. [Figure 11] Time chart showing the time series during booklet production according to the embodiment. [Figure 12] Time chart showing the time series during booklet production according to the modified example. [Figure 13] Cross-sectional view of the thermocompression bonding part according to the comparative example.

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings.

[0010] FIG. 1 is a schematic diagram of an image forming system 1S according to an embodiment. The image forming system 1S is composed of an image forming apparatus 1 and a post-processing apparatus 6. The image forming system 1S forms an image on a sheet S which is a recording material by the image forming apparatus 1, and outputs, as a product, what has been processed by the post-processing apparatus 6 as a sheet processing apparatus as necessary. As the sheet S, various sheet materials with different sizes and materials can be used, such as paper such as plain paper and cardboard, plastic film, cloth, sheet materials with surface treatment such as coated paper, and special-shaped sheet materials such as envelopes and index paper.

[0011] (Image Forming Apparatus) The image forming apparatus 1 is an electrophotographic apparatus provided with an electrophotographic image forming unit 1B inside the apparatus main body 1A. The image forming unit 1B includes an intermediate transfer belt 8 as an intermediate transfer body, and process cartridges 95s, 95k arranged along the intermediate transfer belt 8. Each of the process cartridges 95s, 95k includes a photosensitive drum 2s, 2k as an image carrier (electrophotographic photosensitive member), charging devices 3s, 3k, and developing units 5s, 5k, and is detachable from the apparatus main body 1A. The developing units 5s, 5k have containers 5s2, 5k2 for storing toner as a developer, and developing rollers 5s, 5k1 as developer carriers that are rotatably held in the containers and carry and rotate the toner.

[0012] The process cartridge 95k is a first process unit that creates a toner image using the first toner. The process cartridge 95s is a second process unit that creates a toner image using the second toner. Note that the "apparatus main body 1A" of the image forming apparatus 1 refers to the part of the image forming apparatus 1 excluding the process cartridges 95s, 95k and the toner cartridge 96.

[0013] The process cartridge 95k creates a toner image for recording an image on the sheet S using black toner. The process cartridge 95s creates a toner image of the adhesive toner for applying a transparent toner (hereinafter referred to as the adhesive toner), which is a powder adhesive, to the sheet S. That is, in the present embodiment, black toner is used as the first toner, and the adhesive toner is used as the second toner. The image forming unit 1B including the process cartridge 95s is an application means for applying a powder adhesive to the sheet S. Further, the image forming unit 1B including the process cartridge 95k is also an image forming means for forming an image on the sheet S using a colored toner.

[0014] In the present embodiment, the adhesive toner accommodated in the process cartridge 95s uses a transparent toner, but for example, a colored toner may be used as the powder adhesive. Further, since the toner image of the adhesive toner is transparent, it is different from the normal toner image for recording an image on the sheet S. However, unless otherwise specified, the "toner image" in the following description includes the toner image of the adhesive toner.

[0015] A toner cartridge 96 containing black toner for replenishing the process cartridge 95k is detachably mounted on the apparatus main body 1A and is connected to the process cartridge 95k via a toner conveyance pipe 97.

[0016] Within the main body 1A of the apparatus, a scanner unit 4, which serves as an exposure means, is positioned below the process cartridges 95s and 95k. Below the scanner unit 4, a cassette 13 (also called a sheet tray or storage compartment) on which sheets S used for image formation are loaded is retractably inserted into the main body 1A of the apparatus. Furthermore, an optional sheet feeding device 30, including the cassette 13, can be connected to the bottom of the main body 1A of the apparatus.

[0017] The intermediate transfer belt 8 is a movable (rotatable) endless belt stretched over a drive roller 9a, a tension roller 9b, and a tension roller 10 that rotate around mutually parallel axes, and moves (rotates, conveys) counterclockwise in the figure as the drive roller 9a rotates. On the inner circumference side of the intermediate transfer belt 8, primary transfer rollers 7k and 7s, which serve as primary transfer members, are positioned facing the photosensitive drums 2k and 2s via the intermediate transfer belt 8. On the outer circumference side of the intermediate transfer belt 8, a secondary transfer roller 11, which serves as a transfer member (secondary transfer member), is provided at a position facing the drive roller 9 via the intermediate transfer belt 8. A secondary transfer section is formed as a nip between the intermediate transfer belt 8 and the secondary transfer roller 11. The intermediate transfer belt 8, primary transfer rollers 7k and 7s, and secondary transfer roller 11 constitute a transfer unit for transferring the toner image formed on the photosensitive drums 2k and 2s, which are image carriers, to the sheet S.

[0018] A belt cleaner 12 is provided at a position opposite the tension roller 10 via the intermediate transfer belt 8, serving as a cleaning means for cleaning the intermediate transfer belt 8. The belt cleaner 12 includes a cleaning member 12a, such as a blade or brush, which is positioned in contact with the intermediate transfer belt 8 to remove deposits such as residual toner from the intermediate transfer belt 8, and a waste toner container 98, which serves as a collection container for collecting the deposits removed by the cleaning member 12a.

[0019] A fixing device 18 is positioned above the secondary transfer section within the main body 1A of the device, serving as a fixing means. The fixing device 18 has a thermal fixing method configuration that fixes the toner image by heating, and includes, for example, a fixing roller and a pressure roller that grip and transport the sheet S, and a heat source (e.g., a halogen lamp) that heats the toner image on the sheet S via the fixing roller.

[0020] (Image formation process) When the image forming apparatus 1 performs an image forming operation, sheets S are fed from the cassette 13 at the bottom of the apparatus body 1A or from the cassette 13 of the sheet feeding device 30 by the feeding roller 14, which acts as a feeding means, and are separated one by one by the separation roller pair 15 and transported. These sheets S are transported toward the registration roller pair 17 by the pull-out roller 16, and the skew of the sheet S is corrected when the leading edge of the sheet S abuts against the nip of the registration roller pair 17 when it is stopped. The registration roller pair 17 feeds the sheet S to the secondary transfer unit at a timing synchronized with the progress of the toner image creation process by the image forming unit 1B.

[0021] Meanwhile, in the image forming unit 1B, the photosensitive drums 2s and 2k rotate, and the charging devices 3s and 3k uniformly charge the surfaces of the photosensitive drums 2s and 2k. The scanner unit 4 irradiates the photosensitive drum 2k with laser light to write an electrostatic latent image based on image information representing the image to be recorded on the sheet S. This electrostatic latent image is visualized as a black toner image when the developing unit 5k develops it using black toner. Furthermore, when the post-processing device 6 performs the adhesion process described later, the scanner unit 4 irradiates the photosensitive drum 2s with laser light to write an electrostatic latent image based on information indicating the adhesion position on the sheet S. This electrostatic latent image is developed by the developing unit 5s using adhesive toner, forming a toner image of the adhesive toner in the area on the photosensitive drum 2s corresponding to the adhesion position on the sheet S.

[0022] The toner image formed on the photosensitive drums 2s and 2k is transferred (primary transfer) to the intermediate transfer belt 8 by the primary transfer rollers 7s and 7k, and is transported toward the secondary transfer section by the rotation of the intermediate transfer belt 8. In the secondary transfer section, a voltage is applied to the secondary transfer roller 11, transferring (secondary transfer) the toner image to the sheet S fed from the registration roller pair 17. The sheet S that has passed through the secondary transfer section is sent to the fixing device 18, where the toner image is heated and pressurized as it passes through the nip portions of the fixing roller and pressure roller, fixing the toner image to the sheet S.

[0023] After passing through the fixing device 18, the sheet S has its transport path switched by the switching unit 19. In the case of single-sided printing, the sheet S is guided to the discharge path 90 by the switching unit 19 and discharged from the device body 1A by the discharge roller pair 91. In this embodiment, the image forming apparatus 1 is connected to the post-processing device 6 via the relay transport unit 92, and the sheet S discharged from the discharge roller pair 91 is passed to the post-processing device 6 via the transport roller pair 93, 94 of the relay transport unit 92. If the relay transport unit 92 and the post-processing device 6 are not connected, the discharge roller pair 91 discharges the sheet S as the output product onto the loading tray 126 provided on the top of the device body 1A.

[0024] In the case of double-sided printing, the sheet S, on which an image has been formed on the first side, is guided by the switching unit 19 to the reversing roller pair r1, and after being reversed and transported (switchback transported) by the reversing roller pair r1, it is transported towards the registration roller pair 17 via the double-sided transport path r2. Then, after passing through the secondary transfer unit and the fixing device 18, an image is formed on the second side opposite to the first side, and then it is discharged from the device body 1A by the discharge roller pair 91. Therefore, in this embodiment, adhesive toner can be applied to both the first and second sides of the sheet S.

[0025] Figure 2 shows an example of the application area of ​​adhesive toner on a sheet (adhesion area during the bonding process). On the sheet S, the process cartridge 95 The toner image (the letter "A") of the black toner created by k, and the process cartridge95 A layer 39 of adhesive toner, created by s, is formed.

[0026] In the case of a single-sided printed booklet, the adhesive toner layer 39 is formed only on one side of the sheet S. In the case of a double-sided printed booklet, the adhesive toner layer 39 may be formed on only one side of the sheet S, or on both sides of the sheet S. Furthermore, although the coating area shown here is for creating a booklet bound along the long edge of the sheet S, corner binding can also be performed by applying the adhesive toner to the corners of the sheet S, for example.

[0027] (Post-processing device) As shown in Figure 1, the post-processing device 6 has a buffer unit 20 as a stacking processing unit for stacking multiple sheets S, an alignment unit 56 as an alignment means for aligning multiple sheets S, and a heat-sealing unit 67 as an adhesive means for applying an adhesive treatment to the sheets S. The post-processing device 6 is a sheet processing device capable of creating a sheet bundle (booklet) by applying an adhesive treatment to multiple sheets S on which images have been formed by the image forming device 1. The post-processing device 6 can also discharge the sheets S on which images have been formed by the image forming device 1 to the upper discharge tray 25 or the lower discharge tray 37 without applying an adhesive treatment. The upper discharge tray 25 and the lower discharge tray 37 are controlled to move up and down according to the amount of sheets loaded. The buffer unit 20, the alignment unit 56, and the heat-sealing unit 67 will be described in detail later.

[0028] The post-processing device 6 includes an inlet roller 21, a buffer-pre-roller 22, a reversing roller 24, an internal discharge roller 26, an intermediate transport roller 28, a kick-out roller 29, and a bundle discharge roller 36 as transport members for transporting the sheet S. The inlet roller 21, buffer-pre-roller 22, and reversing roller 24 are arranged in a transport path from the receiving inlet that receives the sheet S from the image forming apparatus 1 to the discharge upper tray 25. The internal discharge roller 26, intermediate transport roller 28, and kick-out roller 29 are arranged in a transport path that branches off between the buffer-pre-roller 22 and the reversing roller 24 and extends toward the alignment section 56. The bundle discharge roller 36 is arranged in a transport path from the alignment section 56 toward the discharge lower tray 37.

[0029] Inside the post-processing device 6, the sheet S received from the image forming apparatus 1 can be transported at a faster transport speed than the transport speed of the sheet S in the image forming apparatus 1 (and the relay transport unit 92) (process speed during image formation). Specifically, for example, the sheet S is transported at the same speed as the image forming apparatus 1 until the rear end of the sheet S passes the entrance roller 21, and then the buffer pre-roller 22 is accelerated. Each roller after the buffer pre-roller 22 also transports the sheet at substantially the same speed as the accelerated buffer pre-roller 22. Furthermore, the passage of the rear end of the sheet S can be detected by the entrance sensor 27, which will be described later. As a result, the sheet S can be processed in the post-processing device 6 without reducing the productivity of the image forming apparatus 1, and the productivity of the image forming system 1S is improved.

[0030] (Buffer section) Next, we will provide a detailed explanation of the buffer unit 20 using Figures 3 and 4 (a-h). Figure 3 is a schematic diagram of the buffer unit 20. Figures 4 (a-h) show the operation of the buffer unit 20 stacking multiple sheets (hereinafter referred to as buffer operation).

[0031] As shown in Figure 3, the post-processing device 6 includes an upper entrance guide 40 and a lower entrance guide 41 that guide the sheet between the entrance roller 21 and the pre-buffer roller 22, and an entrance sensor 27 that detects the sheet S between the entrance roller 21 and the pre-buffer roller 22. The entrance sensor 27 is positioned on the upper entrance guide 40. The entrance sensor 27 is a reflective photosensor that, for example, irradiates infrared light into the space within the transport path and outputs a signal according to the presence or absence of reflected light from the sheet passing through the transport path. The lower entrance guide 41, which faces the entrance sensor 27, is provided with a hole, for example, larger than the spot diameter of the entrance sensor 27, so that infrared light is not reflected when the sheet is not passing through the transport path.

[0032] The buffer section 20 of this embodiment includes a buffer front roller 22 as a first roller pair, a reversing roller 24 as a second roller pair, and an inner discharge roller 26 as a third roller pair.

[0033] The internal discharge roller 26 is positioned on a transport path that branches off from the transport path leading from the buffer-front roller 22 to the reversing roller 24 and leads to the binding processing unit 6A (alignment unit 56) (see Figure 1). The reversing roller 24 and the internal discharge roller 26 are each driven by motors capable of reversing their rotation direction. In other words, the reversing roller 24 and the internal discharge roller 26 can transport sheets in the direction from the reversing roller 24 to the alignment unit 56 and in the opposite direction. The buffer unit 20 forms a sheet bundle by reciprocating the preceding sheet (bundle) with the reversing roller 24 and the internal discharge roller 26, while overlapping the subsequent sheet transported via the buffer-front roller 22 with the preceding sheet (bundle) at the reversing roller 24. The detailed operation of the buffer unit will be explained below.

[0034] The post-processing device 6 includes an inverting upper guide 42 that guides the sheet between the buffer pre-roller 22 and the inverting roller 24, and an inverted guide 43 that guides the sheet between the inverting roller 24 and the internal discharge roller 26. The post-processing device 6 also includes an internal discharge upper guide 46 and an internal discharge lower guide 47 that guide the sheet downstream of the internal discharge roller 26.

[0035] A backflow prevention valve 23 is positioned downstream of the buffer front roller 22. The backflow prevention valve 23 is rotatably supported by an internal discharge upper guide 46, and is movable between a position that opens the conveying path connecting the buffer front roller 22 and the reversing roller 24 and a position that closes the conveying path. The backflow prevention valve 23 is constantly biased in the C2 direction, which is toward the position that closes the conveying path, by a spring (not shown). The tip of the backflow prevention valve 23 is formed in a comb-like shape so that it overlaps with the reversing upper guide 42 when viewed in the direction of the rotation axis of the buffer front roller 22 (sheet width direction).

[0036] The backflow prevention valve 23 rotates in the C1 direction when the sheet S is fed out from the buffer front roller 22, allowing the sheet S to pass. Furthermore, when the rear end of the sheet S has passed, the backflow prevention valve 23 rotates in the C2 direction to return to its original position, restricting the backflow of the sheet S towards the buffer front roller 22. Note that the backflow prevention valve 23 may be configured to be biased by its own weight, for example, instead of being biased by a spring.

[0037] The reversing roller 24 is a roller pair composed of an upper reversing roller 24a and a lower reversing roller 24b. In this embodiment, driving force is supplied to both the upper reversing roller 24a and the lower reversing roller 24b. Furthermore, the rotation of the upper reversing roller 24a and the lower reversing roller 24b is always synchronized. A separation lever 44 is connected to the upper reversing roller 24a. The separation lever 44 is rotatably supported at its lever pivot shaft 44a by the upper reversing guide 42, and is rotatably connected to a plunger solenoid 45 at its solenoid connection shaft 44b.

[0038] When current flows through the plunger solenoid 45, the core moves in the direction D1 in the figure, and the separation lever 44 rotates in the direction E1 in the figure. As a result, the reversing roller 24 enters a separated state where the upper reversing roller 24a and the lower reversing roller 24b are separated (the nip of the roller pair is released). When the current to the plunger solenoid 45 is stopped, the biasing force of the pressure spring 48 causes the upper reversing roller 24a to move in the direction E2 in the figure, and the plunger solenoid 45 moves in the direction D2 in the figure. As a result, the reversing roller 24 enters a contact state where the upper reversing roller 24a and the lower reversing roller 24b are in contact (the nip of the roller pair can grip the sheet).

[0039] (Buffer operation) Next, we will explain in detail the buffer operation of the buffer unit 20 using Figure 4(a-h). The sheets S being transported to the post-processing device 6 will be described as S1, S2, and S3 in that order. Here, we will explain using the operation of stacking two sheets S1 and S2 as an example. The transport speed of the inlet roller 21 will be V1. The transport speed of the buffer pre-roller 22, the reversing roller 24, and the internal discharge roller 26 (the transport speed after acceleration in the post-processing device 6) will be V2.

[0040] Unless otherwise specified, the "leading end" of a sheet refers to the leading end of the sheet in the current transport direction (downstream end in the transport direction), and the "rear end" of a sheet refers to the rear end of the sheet in the current transport direction (upstream end in the transport direction).

[0041] As shown in Figure 4(a), the trailing edge of the first sheet S1 (leading sheet) passes the entrance sensor 27. At this timing, the buffer front roller 22 and the reversing roller 24 accelerate sheet S1 from speed V1 to speed V2. This ensures that there is enough space between sheet S1 and the second sheet S2 (following sheet) which is transported from the image forming apparatus 1 following sheet S1, for the switchback described below.

[0042] As shown in Figure 4(b), the reversing roller 24 temporarily stops the sheet S1 at the position where it has passed the backflow prevention valve 23.

[0043] As shown in Figure 4(c), the reversing roller 24 reverses its direction of rotation after a brief pause and conveys the sheet S1 toward the internal discharge roller 26.

[0044] As shown in Figure 4(d), the conveyance of the sheet S1 is stopped when the leading edge of the sheet S1 has been conveyed by a predetermined amount from the internal discharge roller 26 by the reversing roller 24 and the internal discharge roller 26. After the sheet S1 is held between the internal discharge roller 26, the reversing upper roller 24a moves in the E1 direction, and the reversing roller 24 moves apart.

[0045] The second sheet S2 is transported towards the reversing roller 24, passing the first sheet S1. Sheet S2 is then transported by passing through the space between the reversing upper roller 24a and the reversing lower roller 24b of the reversing roller 24, which is in a separated state. The subsequent sheet S2 is also accelerated after its rear end passes the inlet sensor 27.

[0046] As shown in Figure 4(e), based on the transport timing of the second sheet S2, the internal discharge roller 26 transports the first sheet S1 toward the reversing roller 24. The transport timing is determined based on the elapsed time since the rear end of sheet S2 passed the inlet sensor 27. Then, when the transport speeds of the first sheet S1 and the second sheet S2 become equal (relative speed is substantially 0), the reversing upper roller 24a is moved in the E2 direction. As a result, the sheet bundle consisting of the two sheets S1 and S2 is gripped by the reversing roller 24, which is now in contact with the sheet bundle. The reversing roller 24 is driven and controlled to reach a speed V2 equal to the transport speed of sheets S1 and S2 by the time it reaches contact.

[0047] As shown in Figure 4(f), after the rear end of sheet S2 passes the backflow prevention valve 23, the reversing roller 24 pauses again. Here, the transport timing is set so that the rear end of sheet S1 (the leading edge when the transport direction is toward the alignment section 56) protrudes by a predetermined amount k toward the internal discharge roller 26 than the rear end of sheet S2. In other words, the buffer section 20 stacks the sheets by shifting them so that, when the sheets are stacked in the alignment section 56, the lower sheets protrude further toward the vertical reference plate 54 (described later) than the upper sheets. The meaning of shifting the sheets and the magnitude of the predetermined amount k will be described later.

[0048] As shown in Figure 4(g), the reversing roller 24 reverses its direction of rotation after a brief pause and conveys the sheets S1 and S2 toward the internal discharge roller 26. In the illustrated example, the two sheets S1 and S2 are conveyed downstream from the internal discharge roller 26. After the sheets S1 and S2 are held between the internal discharge roller 26, the reversing upper roller 24a moves in the E1 direction, and the reversing roller 24 separates. This allows the reversing roller 24 to receive the subsequent sheet S3.

[0049] As shown in Figure 4(h), after the rear ends of sheets S1 and S2 have passed the reversing roller 24, the reversing upper roller 24a moves in the E2 direction, causing the reversing roller 24 to come into contact with the sheet. As a result, the reversing roller 24 grips sheet S3 (the first sheet in the next buffer processing after sheets S1 and S2). Then, as in Figure 4(c), the reversing roller 24 pauses briefly, reverses its direction of rotation, and transports sheet S3 toward the inner discharge roller 26.

[0050] By repeatedly executing the operations shown in Figure 4(c~h), the buffer unit 20 can perform a buffering operation to pre-stack the two sheets.

[0051] When stacking three or more sheets using the buffer operation, the reversing roller 24 transports sheets S1 and S2 toward the internal discharge roller 26 from the state shown in Figure 4(f) (corresponding to Figure 4(c)). When the leading edge of sheet S2 has been transported a predetermined amount from the internal discharge roller 26, the transport of sheets S1 and S2 (the preceding sheet bundle) is stopped (corresponding to Figure 4(d)). Based on the transport timing of the subsequent sheet, the internal discharge roller 26 transports the preceding sheet bundle toward the reversing roller 24 (corresponding to Figure 4(e)). After the trailing edge of the subsequent sheet has passed the backflow prevention valve 23, the reversing roller 24 pauses again (corresponding to Figure 4(f)). In other words, in Figures 4(c~f), sheet S1 should be read as "the already stacked sheet bundle" and sheet S2 as "the subsequent sheet".

[0052] In this way, by repeatedly performing the operations shown in Figure 4(c~f), the sheet bundle can be moved back and forth between the reversing roller 24 and the internal discharge roller 26, and subsequent sheets can be added to the sheet bundle one by one. This allows the buffer unit 20 to perform a stacking process (buffer operation) where three or more sheets are stacked on top of each other. In addition, among the three or more sheets, it is possible to make it so that the lower sheet protrudes by a predetermined amount k relative to the upper sheet between two adjacent sheets.

[0053] In this embodiment, the configuration example allows for stacking (buffering) of up to five sheets. Furthermore, according to this embodiment, since the sheets are stacked based on their edge positions, the sheets can be stacked with substantially the same operation even if the length of the sheets in the transport direction changes.

[0054] Multiple sheets that have been stacked in advance in the buffer section 20 are conveyed via the internal discharge roller 26, intermediate conveying roller 28, and kick-out roller 29, and loaded onto the alignment section 56 (Figure 1).

[0055] (matching part) Next, the configuration of the alignment section 56 will be explained using Figures 5 and 6. Figure 5 is a cross-sectional view of the alignment section 56 taken by a plane perpendicular to the X direction shown below. Figure 6 is an exploded view showing the components of the movable unit 59 of the alignment section 56.

[0056] In the following description, the direction parallel to the sheet loading surface in the alignment section 56 and along the conveying direction of the sheet being transported from the kick-off roller 29 to the alignment section 56 is referred to as the Y direction or vertical direction. The direction parallel to the sheet loading surface in the alignment section 56 and perpendicular to the Y direction is referred to as the X direction or horizontal direction. The "vertical direction" is the direction along the sheet conveying direction, and the "horizontal direction" is the sheet width direction perpendicular to the sheet conveying direction. The direction perpendicular to both the X and Y directions (normal direction of the loading surface, thickness direction of the loaded sheet) is referred to as the Z direction or height direction. Where necessary, the directions opposite to the directions of the illustrated arrows representing the X, Y, and Z directions are referred to as the -X direction, -Y direction, and -Z direction.

[0057] As shown in Figure 5, the alignment section 56 includes an upper loading guide 51, a lower loading guide 52, a vertical reference plate 54, a vertical alignment roller 53, horizontal reference plates 72a, 72b (see Figure 7(a)), and a horizontal alignment member 55. The alignment section 56 is also provided with a bundle retaining flag 50 (Figure 1) that suppresses the lifting of the rear end of a sheet bundle so that the leading edge of a subsequent sheet does not interfere with the rear end of a sheet bundle already loaded on the lower loading guide 52.

[0058] The upper loading guide 51 and the lower loading guide 52 are positioned opposite each other in the Z direction and extend in the X and Y directions, respectively. A space is formed between the upper loading guide 51 and the lower loading guide 52 on which the sheet bundles are loaded. In other words, the upper loading guide 51 and the lower loading guide 52 constitute an intermediate loading section 57, which is a loading section on which the sheet bundles to be bonded are loaded. The upper surface of the lower loading guide 52 constitutes a loading surface on which the sheet bundles are loaded (a support surface that supports the lower surface of the lowest sheet).

[0059] The vertical reference plate 54 and the vertical alignment roller 53 function as the first alignment unit of this embodiment for aligning the sheet in the first direction (Y direction).

[0060] The vertical reference plate 54 is positioned at the downstream end of the intermediate loading section 57 in the Y direction. The vertical reference plate 54 is a reference member (first reference member) that serves as the reference for the sheet position in the Y direction (first direction). The vertical alignment roller 53 is a conveying member that transports the sheet in the Y direction in order to abut the sheet against the vertical reference plate 54 and align it. The vertical reference plate 54 includes a plurality of contact portions 54a to 54c that are spaced apart in the X direction (Figure 6).

[0061] As shown in Figure 6, the vertical reference plate 54 and the vertical alignment roller 53 are integrally configured as a movable unit 59 that can move in the Y direction. The movable unit 59 is movable in the Y direction relative to the intermediate loading section 57 by a driving means (not shown). In other words, the vertical reference plate 54 and the vertical alignment roller 53 are configured to be position-adjustable in the Y direction according to the size of the sheet.

[0062] The longitudinal alignment roller 53 is rotatably supported by a roller holder 60. The roller holder 60 is attached to the frame of the movable unit 59 in a state that it can swing about a pivot point (not shown). Furthermore, the movable unit 59 is provided with a solenoid 63. By energizing the solenoid 63, the roller holder 60 swings via a link mechanism (not shown). The swinging of the roller holder 60 changes the position of the longitudinal alignment roller 53 in the Z direction. As a result, the longitudinal alignment roller 53 can move between a position that abuts the upper surface of the sheet bundle loaded on the intermediate loading section 57 and a position that is retracted upward from the sheet bundle. A motor 61 is also attached to the movable unit 59. The motor 61 rotates the longitudinal alignment roller 53 via a drive gear 62.

[0063] The lateral reference plates 72a, 72b and the lateral alignment member 55 function as the second alignment unit of this embodiment, which aligns the sheet in a second direction (X direction) perpendicular to the first direction.

[0064] As shown in Figure 5, the transverse alignment member 55 is connected to a motor 58 via a drive train (not shown) and is configured to be movable in the X direction. The transverse alignment member 55 has a plurality of pressing portions 55a, 55b, and 55c arranged at intervals in the Y direction. The pressing portions 55a to 55c are pressing surfaces that press the side edges (ends in the X direction) of the sheets loaded on the intermediate loading section 57. The transverse reference plates 72a and 72b (see Figure 7(a)) serve as reference members (second reference members) that serve as a reference for the sheet position (lateral position, width direction position) in the X direction (second direction), and are arranged to face the pressing portions 55a to 55c of the transverse alignment member 55 in the X direction. In this embodiment, the transverse reference plates 72a and 72b are composed of a plurality of contact portions arranged at intervals in the Y direction.

[0065] (matching operation) The matching operation in the matching unit 56 will be explained using Figures 7(a-d). Each of the figures in Figures 7(a-d) shows the necessary components of the matching unit 56 when viewed from the Z-direction side (above side). Figures 7(a-d) show the matching operation when five sheets S1-S5, which have been stacked in the buffer unit 20, are transported to the matching unit 56.

[0066] Figure 7(a) shows how sheets S1 to S5 are being transported toward the kick-off roller 29. Sheets S1 to S5 are transported to the alignment section 56 with the lower sheet protruding further in the Y direction than the upper sheet. Before the sheets are loaded into the alignment section 56, the movable unit 59 is pre-adjusted to a predetermined standby position according to the size of the sheets to be aligned. The standby position is set so that the -Y direction end position of the sheet remains constant regardless of the sheet size. In other words, the standby position is a position where the distance in the Y direction from the nip position of the kick-off roller 29 to the contact portions 54a to 54c of the vertical reference plate 54 is slightly longer than the Y direction length of the sheet. The lateral alignment member 55 also waits at a position away from the sheet being transported in the X direction so as not to obstruct the transport of the sheet S.

[0067] Figure 7(b) shows the state when the rear end of the first sheet S1 has passed through the nip of the kick roller 29 and the front end of the sheet S1 has reached the longitudinal alignment roller 53. The longitudinal alignment roller 53 is lowered to a contact position beforehand by energizing the solenoid 63 and is rotated by the motor 61 (Figure 6). As a result, the sheet S1 abuts against the longitudinal reference plate 54 and is aligned with the position of the longitudinal reference plate 54 as a reference.

[0068] As the vertical alignment roller 53 continues to rotate, the second and subsequent sheets S2 to S5, which reach the vertical alignment roller 53 after sheet S1, are sequentially brought into contact with the vertical reference plate 54. As a result, the five sheets S1 to S5 are aligned in the Y direction (vertical direction) with respect to the position of the vertical reference plate 54.

[0069] Figure 7(c) shows the state after the alignment of sheets S1 to S5 in the Y direction (vertical direction) is completed and the alignment in the X direction (lateral direction) begins. The motor 58 (Figure 5) drives the lateral alignment member 55 in the X direction, which is the alignment direction, and the pressing parts 55a to 55c come into contact with the side edges of sheets S1 to S5, pressing sheets S1 to S5 toward the lateral reference plates 72a and 72b. Then, the other side edge of each sheet comes into contact with the contact surface of the lateral reference plates 72a and 72b, and sheets S1 to S5 are aligned in the X direction (lateral direction) with respect to the position of the lateral reference plates 72a and 72b.

[0070] Figure 7(d) shows the state after alignment of the five sheets S1 to S5 in the X and Y directions has been completed. The target position (alignment position) in the alignment operation is the position of the sheet bundle when the bonding process (thermocompression bonding) is performed by the thermocompression bonding unit 67. Therefore, in the image forming apparatus 1, adhesive toner is applied to each sheet such that the side on which the aforementioned adhesive toner layer 39 (Figure 2) is formed faces the side facing the thermocompression bonding unit 67.

[0071] As shown in Figure 7(d), the aligned sheets S1 to S5 are bonded together by the heat-sealing section 67. During this process, the transverse alignment member 55 retracts in the -X direction. This allows the alignment section 56 to be ready to receive the next set of sheets.

[0072] Subsequently, the next set of sheets, which have been pre-stacked in the buffer section 20, are placed on top of the sheets S1 to S5 stacked in the intermediate stacking section 57. Then, through the same operation as described using Figures 7(a to d), the next set of sheets are aligned in the Y direction (vertical direction) and the X direction (horizontal direction), and after alignment is complete, they are bonded together by the heat-sealing section 67.

[0073] In this example, the buffer unit 20 pre-stacks five sheets, but the number of sheets stacked in the buffer unit 20 is not limited to five; for example, it could be two or three sheets. Also, the number of sheets stacked in the buffer unit 20 does not have to be constant within a set of sheets. For example, five sheets could be stacked in the first stacking process (buffer operation), and then four sheets could be stacked in subsequent stacking processes (buffer operations).

[0074] (Heat-sealed area) The configuration of the heat-sealing section 67 (heat-sealing unit) as an adhesive means will be explained with reference to Figure 8. Figure 8 is a perspective view showing the heat-sealing section 67 of this embodiment. The heat-sealing section 67 comprises a heater unit 71, a pressurizing mechanism 67D that pressurizes the heater unit 71, and a pressurizing plate 80 that receives the pressurizing force of the heater unit 71.

[0075] The heater unit 71 includes a heating plate 69, a heater 68, and a metal stay 70. The heating plate 69, an example of a heating element, is made of a material with high thermal conductivity, such as aluminum. The heating plate 69 has a contact portion that contacts the top sheet in order to heat and pressurize the sheet bundle loaded in the intermediate loading section 57. The heater 68 is made of, for example, a ceramic substrate with a pattern of heating resistors formed on it. The heater 68 is positioned on the opposite side of the heating plate 69 from the pressurizing plate 80. The heating plate 69 is supported by the heater 68. The metal stay 70 supports the heater 68 and also increases the rigidity of the heater unit 71. The heating plate 69, heater 68, and metal stay 70 are all elongated members that extend in the Y direction.

[0076] A thermistor, for example, is attached to the heater unit 71 as a temperature sensing means. The control unit of the post-processing device 6 monitors the temperature of the heater 68 based on the signal from the thermistor and controls the power supply to the heater 68 so that the surface temperature of the heating plate 69 reaches a predetermined target temperature.

[0077] The pressurizing mechanism 67D includes a motor 77 as a drive source, a gear train 78, a pinion gear 79, a rack gear 75, and a lift plate 72. The gear train 78 functions as a reducer that increases torque by reducing and transmitting the rotation output by the motor 77. The pinion gear 79 meshes with the rack gear 75. The pinion gear 79 and the rack gear 75 convert the rotation received by the pinion gear 79 via the gear train 78 into linear motion in the Z direction. The rack gear 75 is fixed to the lift plate 72, and the metal stay 70 of the heater unit 71 is fixed to the lift plate 72.

[0078] Thus, the heater unit 71 is configured to move (raise and lower) in the Z direction and the -Z direction in accordance with the forward and reverse rotation of the motor 77. During the bonding process, the -Z force transmitted from the motor 77 to the lift plate 72 is transmitted to the heating plate 69 via the metal stay 70 and the heater 68, and the heating plate 69 is pressed against the sheet bundle.

[0079] The pressure plate 80 is positioned opposite the heating plate 69 of the heater unit 71 in the Z direction. The pressure plate 80 is, for example, a plate-shaped member made of silicone rubber. The pressure plate 80 is fixed to the frame of the post-processing device 6, for example, by being fitted into the loading guide 52. As a result, the pressure plate 80 can stably receive the pressure force applied by the heater unit 71 to the sheet bundle, and maintain a stable pressurized state for the sheet bundle sandwiched between the heating plate 69 and the pressure plate 80.

[0080] In this embodiment, the aforementioned horizontal reference plates 72a and 72b are integrally formed with the lift plate 72. This reduces the number of parts and improves the alignment accuracy of the sheet bundle with respect to the heater unit 71. The horizontal reference plates 72a and 72b can also be separate components from the lift plate 72. For example, the horizontal reference plates 72a and 72b may be components fixed to the frame of the post-processing device 6.

[0081] (Adhesive action) The bonding operation (thermocompression bonding process) of the sheet bundle by the heat-sealing section 67 will be explained using Figures 9(a-f) and 10. Figures 9(a-f) and 10 show the heat-sealing section 67 as viewed in the Y direction.

[0082] Figure 9(a) shows the heat-sealed section 67 at the same point in time as Figure 7(c). In other words, it shows the state after the alignment of sheets S1 to S5 in the Y direction has been completed, and while the alignment in the X direction is in progress. Before the alignment of sheets S1 to S5 is completed, the heater unit 71 waits at a position separated from sheets S1 to S5 in the Z direction.

[0083] Figure 9(b) shows the heat-sealing section 67 at the same point in time as Figure 7(d). That is, it shows the state in which the sheets S1 to S5 come into contact with the horizontal reference plates 72a and 72b, completing the alignment of the sheets S1 to S5 in the X direction. Once the alignment of the sheets S1 to S5 is complete, the heater unit 71 begins to move (descend) in the -Z direction due to the forward rotation drive of the motor 77.

[0084] Figure 9(c) shows the state when the heating plate 69 comes into contact with the uppermost sheet S5 as the heater unit 71 descends. The heater unit 71 is controlled so that the heating plate 69 pressurizes the sheet bundle with a predetermined pressure. When the heating plate 69 comes into contact with the sheet S5, heat is transferred from the heater 68 to the sheets S1-S5 via the heating plate 69, and the temperature of the adhesive toner applied to the sheets S1-S5 begins to rise.

[0085] The adhesive toner melts when heated and pressurized by the heating plate 69 for a predetermined time. As a result, sheets S1 to S5 are bonded together using the adhesive toner as the bonding medium.

[0086] Figure 9(d) shows the state when the next set of sheets S6 to S10, which have been stacked in the buffer section 20, are transported so as to overlap sheets S1 to S5. In this embodiment, the next set of sheets S6 to S10 can be transported to the alignment section 56 while the first set of sheets S1 to S5 stacked in the buffer section are being heat-pressed together (while the heating plate 69 is in contact with sheet S5).

[0087] Figure 10 shows the state after the heat-pressing of sheets S1 to S5 is complete, when the heater unit 71 moves (rises) in the Z direction by the reverse drive of the motor 77, and the heating plate 69 separates from sheet S5. Figure 10 also shows the state after the heating plate 69 has risen to a predetermined standby position, and the alignment of sheets S6 to S10 in the X direction is in progress. The advantages of aligning the multiple sheets S6 to S10 that have been stacked in advance in the buffer section 20 with the alignment section 56 will be described later.

[0088] Figure 9(e) shows the state in which sheets S6 to S10 are in contact with the horizontal reference plates 72a and 72b, and the alignment of sheets S6 to S10 is completed.

[0089] Figure 9(f) shows the state when the heater unit 71 moves (descends) again in the -Z direction due to the forward rotation drive of the motor 77, and the heating plate 69 comes into contact with the uppermost sheet S10. Sheets S6 to S10 are bonded together by the adhesive toner through heating and pressurization via the heating plate 69. In addition, the multiple sheets S1 to S5 (first sheet bundle) that were first fed into the matching unit 56 and the multiple sheets S6 to S10 (second sheet bundle) that were later fed into the matching unit 56 are bonded together by the adhesive toner. This is because the adhesive toner is applied to the upper surface of sheet S5 and the lower surface of sheet S6. As a result, a sheet bundle SB is created with a number of sheets greater than the maximum number that the buffer unit 20 can stack.

[0090] Once the bonding process is complete on all the sheets constituting one booklet, the sheet bundle SB is discharged from the alignment unit 56 as a finished product. Specifically, the movable unit 59 (Figure 5) moves in the -Y direction, causing the sheet bundle SB to be pushed toward the bundle discharge roller 36 by the vertical reference plate 54. In addition to the movable unit 59, a transport mechanism may be provided to transport the bonded sheet bundle SB toward the bundle discharge roller 36.

[0091] The bundle discharge roller 36 (Figure 1) is configured such that the upper roller 36a is movable relative to the lower roller 36b, and it switches between a nip state in which it can grip the sheet bundle SB and an open state in which the upper roller 36a is separated upward from the lower roller 36b. When the sheet bundle SB is discharged from the alignment unit 56, the bundle discharge roller 36 is initially set to the open state and is in standby mode. When the leading edge of the sheet bundle SB reaches a position slightly beyond the bundle discharge roller 36, the movable unit 59 stops and the bundle discharge roller 36 switches to the nip state. Then, the bundle discharge roller 36 is rotated, and the sheet bundle SB is discharged into the lower discharge tray 37. Meanwhile, the movable unit 59 moves in the Y direction after the sheet bundle SB is gripped by the bundle discharge roller 36 and returns to the standby position.

[0092] (Advantages over the comparative example) The advantages of this embodiment will now be explained in comparison with the comparative example shown in Figure 13. Unlike this embodiment, in which multiple sheets that have been pre-stacked in the buffer unit 20 are loaded into the alignment unit 56, this comparative example loads and aligns sheets one by one into the alignment unit 56. The other configurations and operations are the same as those of this embodiment.

[0093] Figure 13 shows the comparative example, where the bonding process for sheets S1 to S5 has been completed and the alignment of the sixth sheet S6 in the X direction is in progress. The adhesive layer S5b is a layer of adhesive toner applied to the upper surface of the fifth sheet S5 (the upper surface when it is stacked in the intermediate stacking section 57). The adhesive layer S6a is a layer of adhesive toner applied to the lower surface of the sixth sheet S6 (the lower surface when it is stacked in the intermediate stacking section 57).

[0094] At the point shown in Figure 13, sheets S1 to S5 have just undergone bonding treatment by the heat-sealing section 67, and the temperature and viscosity of the adhesive layer S5b are high. Therefore, when the sixth sheet S6 is moved in the X direction toward the transverse reference plate 72a, the movement of sheet S6 may be hindered by the adhesive force of the adhesive layer S5b exposed on the surface of the already bonded sheet bundle. For example, when the leading edge S6c or adhesive layer S6a of sheet S6 in the direction of movement (X direction) comes into contact with the adhesive layer S5b, the movement of sheet S6 may be hindered. As a result, the leading edge S6c of sheet S6 may not be able to reach the transverse reference plate 72a, potentially causing misalignment (mismatch) between sheet S6 and sheets S1 to S5. Furthermore, if the misalignment of sheet S6 is severe, it may lead to poor adhesion.

[0095] On the other hand, in this embodiment, as shown in Figure 10, multiple sheets S6 to S10 (second sheet bundle) that have been pre-stacked in the buffer section 20 are aligned together in the X direction. The multiple sheets S6 to S10 have a substantially higher rigidity than a single sheet S6 because they overlap each other. Therefore, even if the tip S6c or adhesive layer S6a comes into contact with the adhesive layer S5b exposed on the surface of the sheet bundle (first sheet bundle) already stacked in the intermediate loading section 57, the movement of sheet S6 is not easily hindered. Consequently, sheets S6 to S10 can be brought into contact with the transverse reference plate 72a more reliably, and the possibility of misalignment of sheets S1 to S10 can be reduced.

[0096] Furthermore, after the sheets S6 to S10 are aligned in the Y direction (vertical alignment) using the vertical alignment roller 53 and vertical reference plate 54 (first alignment unit), the sheets are aligned in the X direction (lateral alignment) using the horizontal alignment member 55 and horizontal reference plates 72a, 72b (second alignment unit). This reduces the possibility that the alignment of sheet S6, which protrudes only once in the Y direction, may be hindered by the viscosity of the adhesive layers S5b and S6a.

[0097] Thus, the alignment means of this embodiment aligns the position of the second sheet bundle with the first sheet bundle after the second sheet bundle, which has been stacked in the stacking section and aligned by the alignment means, is stacked on top of the first sheet bundle, which has been stacked in the stacking section and aligned by the alignment means. Furthermore, the bonding means of this embodiment heats and pressurizes the second sheet bundle, which has been aligned by the alignment means, thereby bonding each sheet of the second sheet bundle to each other with the adhesive and bonding the first sheet bundle to the second sheet bundle.

[0098] This configuration improves the alignment when aligning the next sheet on top of a sheet already loaded in the loading section.

[0099] Furthermore, after bonding the first and second sheet bundles, the bonded sheet bundles become a new first sheet bundle, and the previously stacked sheet bundles in the overlapping processing section become a new second sheet bundle. By repeating the same operation, it becomes possible to produce a product with multiple sheets bonded together.

[0100] (Variation 1) Figures 10 and 13 illustrate a configuration in which adhesive toner is applied to both sides of each sheet, excluding the two sheets S1 and S10 located on the front and back (front and back covers) of a particular deliverable (booklet) (a configuration in which adhesive toner is applied to both sides of the sheet to be bonded). Alternatively, a configuration in which adhesive toner is applied to only one side of the sheet to be bonded is also possible. For example, in the example in Figure 10, adhesive toner is applied to the bottom surface of sheets S2 to S10, excluding the bottommost sheet S1.

[0101] Thus, even in a configuration where adhesive is applied to one side of the sheet, misalignment may occur during alignment in the X direction due to resistance caused by the adhesive force of the adhesive layer S6a. This is because the toner in the adhesive layer S6a is heated by the fixing process in the image forming apparatus 1, and is also heated by the heat generated by the heat-sealing section 67 and sheets S1 to S5 in the binding section 6A, so its viscosity may be higher than at room temperature. Therefore, the configuration of this embodiment, in which multiple sheets that have been stacked in advance in the buffer section 20 are aligned together, rather than aligning each sheet one by one as shown in Figure 13, can reduce the possibility of misalignment.

[0102] Furthermore, the configuration of this embodiment, in which adhesive toner is applied to both surfaces of the sheet to be bonded, has the advantage of making it easier to ensure adhesive strength regardless of the roughness of the sheet surface, as the adhesive layer becomes thicker. On the other hand, when using an adhesive that can ensure sufficient adhesive strength even with single-sided application, or when the required adhesive strength is low (for example, when producing semi-bonded products), this modified version can be applied. An advantage of this modified version is that the image forming apparatus 1 can perform image formation and adhesive toner application in a single-sided printing operation, which may improve productivity.

[0103] (Comparison of productivity) Another advantage of this embodiment is the productivity during booklet production. Figure 11 is a time chart illustrating the movement of sheet S in chronological order. Here, we will explain the process when producing two booklets, each consisting of 10 sheets S1 to S10 and T1 to T10.

[0104] The upper part of Figure 11 shows the period during which the discharge roller pair 91 (Figure 1), which discharges image-formed sheets from the main body 1A of the image forming apparatus 1, discharges each sheet S1 to S10 and T1 to T10. The middle part shows the period during which the intermediate transport roller 28 (Figure 1), which transports sheets between the buffer section 20 and the alignment section 56, transports sheets S1 to S10 and T1 to T10. The lower part shows the period during which sheets S1 to S10 and T1 to T10 are aligned, bonded, and discharged in the binding section 6A.

[0105] As shown in Figure 11, the image forming apparatus 1 discharges image-formed sheets S1-S10 and T1-T10 at substantially constant intervals (top). The buffer unit 20 sends out multiple sheets stacked on top of each other. Therefore, the intermediate transport roller 28 transports four sets of sheet bundles SB1, SB2, TB1, and TB2, each consisting of five unbonded sheets S1-S5, S6-S10, T1-T5, and T6-T10, to the binding processing unit 6A (middle). In the binding processing unit 6A, each sheet bundle SB1, ST2, TB1, and TB2 is sequentially subjected to alignment in the vertical direction (Y direction), alignment in the horizontal direction (X direction), and bonding by the heat-sealing unit 67 (bottom). When the creation of sheet bundles with 10 sheets S1-S10 and T1-T10 bonded to each other is complete, the sheet bundles are discharged from the binding processing unit 6A.

[0106] Here, the period during which the binding processing unit 6A aligns, adheres, or ejects the previous sheet bundles SB1, SB2, and TB1 overlaps with the period during which the buffer unit 20 stacks the next sheet bundles SB2, TB1, and TB2 (buffer operation). In other words, by inserting a stacking process (buffer operation) in the buffer unit 20, in which multiple sheets are stacked in advance, between the image forming process and the binding processing unit 6A process, an interval t1 can be secured for the sheets to be fed into the alignment unit 56. This interval t1 can be used to perform operations (alignment, adhesion, and ejection) in the binding processing unit 6A.

[0107] As a comparative example, consider a case where, without buffering in the buffer unit 20, sheets S1 to S10 are discharged one by one into the alignment unit 56, and the heat-sealing unit 67 performs bonding treatment each time five sheets are loaded. In this case, the timing of the fifth sheet S5 being fed into the alignment unit 56 and the timing of the completion of the first bonding treatment can be approximately the same as in this embodiment. However, because buffering in the buffer unit 20 is not performed, if it becomes necessary to reduce the productivity of the image forming apparatus 1 so that the next sheet is not fed into the alignment unit 56 while the bonding treatment is in progress, the productivity of the image forming system 1S will decrease.

[0108] In contrast, the image forming apparatus 1 can secure the processing time of the binding processing unit 6A without widening the discharge interval (image forming interval) of sheets S1 to S10 and T1 to T10. In other words, by stacking sheets that are transported one by one to the sheet processing apparatus into a predetermined number of sheets by the stacking processing unit and transporting them to the stacking unit, sheets can be accepted at a constant interval even while alignment by the alignment means and bonding by the adhesive means are being performed. As a result, the productivity of the image forming system 1S (number of booklets that can be produced per unit time) can be increased.

[0109] (Modification 2) Figure 11 assumes that the image forming apparatus 1 forms images at regular intervals. However, the productivity of the image forming apparatus 1 may be adjusted to match the processing speed of the post-processing device 6. For example, if an image forming apparatus 1 with even higher productivity during image formation (number of images formed per unit time) is used, as shown in Figure 12, a time interval t2 may be added during image formation for every number of sheets stacked in the buffer unit 20 (in this case, every 5 sheets). This ensures sufficient processing time for alignment, bonding, and ejection in the binding processing unit 6A. Furthermore, even in this modified example, stacking multiple sheets in the buffer unit 20 beforehand and then transporting them to the alignment unit 56 increases the productivity of the image forming system 1S compared to transporting them one sheet at a time to the alignment unit 56.

[0110] In the embodiments and modifications described above, an example was shown in which, when producing a booklet consisting of 10 sheets S1 to S10, the sheets are stacked in groups of 5 and the bonding process is performed twice. The number of sheets stacked in the buffer section 20 (buffer size) and the number of bonding processes are not limited to these. For example, when producing a booklet consisting of 3 sheets, the booklet may be produced by stacking 3 sheets in the buffer section 20 and performing the bonding process once. Also, when producing a booklet consisting of 100 sheets, the sheets may be stacked in groups of 5 in the buffer section 20 and transported to the alignment section 56, and the bonding process may be performed 20 times in the heat-sealing section 67. Furthermore, when producing a booklet consisting of 80 sheets, the sheets may be stacked in groups of 4 in the buffer section 20 and transported to the alignment section 56, and the bonding process may be performed 10 times every 8 sheets in the heat-sealing section 67.

[0111] (Variation 3) In the embodiment described above, as shown in Figure 9(d), the next sheet bundle SB2 is fed into the alignment unit 56 while the bonding process of the previous sheet bundle SB1 is being carried out. Figure 11 shows an example in which the Y-direction alignment (vertical alignment) of the next sheet bundle SB2 begins after the bonding process of the previous sheet bundle SB1, but the bonding process of the previous sheet bundle SB1 and the Y-direction alignment (vertical alignment) of the next sheet bundle SB2 may be carried out in parallel. In other words, the vertical alignment roller 53 may start moving the first sheet S6 of the next sheet bundle SB2 in the Y direction while the heating plate 69 of the heat-sealing unit 67 is in contact with the top sheet (sheet S5) of the previous sheet bundle SB1. In this embodiment, since the feeding of the sheet bundle SB2 and the Y-direction alignment (vertical alignment) are carried out at a position that does not interfere with the heat-sealing unit 67 in the X direction, the bonding process of the previous sheet bundle SB1 and the Y-direction alignment (vertical alignment) of the next sheet bundle SB2 can be carried out in parallel.

[0112] This allows the period during which the bonding process is performed on the previous sheet bundle SB1 to overlap with the period during which the alignment operation is performed on the next sheet bundle SB2, thereby improving the productivity of the post-processing device 6. Specifically, if the interval t1 for transporting the sheet bundles from the buffer unit 20 to the alignment unit 56 can be shortened compared to the embodiment in Figure 11, one booklet can be completed faster than in the embodiment. Alternatively, if the time required for the bonding process is set to be longer than in the embodiment, the booklet can be produced in the post-processing device 6 without significantly reducing the productivity of the image forming apparatus 1.

[0113] In the embodiment described above, since the Y-direction alignment (longitudinal alignment) of the next sheet bundle SB2 is started after the bonding process for the previous sheet bundle SB1 (Figure 11), the time from the end of the bonding process to the start of the X-direction alignment (lateral alignment) of the next sheet bundle SB2 becomes longer. This has the advantage of ensuring sufficient cooling time for the adhesive layer S5b (Figure 10) until the next sheet bundle SB2 reaches the adhesive layer S5b exposed on the upper surface of the previous sheet bundle SB1. Therefore, for example, when using an adhesive toner with high viscosity at high temperatures, it may be advantageous in terms of alignment to start the Y-direction alignment (longitudinal alignment) of the next sheet bundle SB2 after the bonding process for the previous sheet bundle SB1 is completed.

[0114] (Other embodiments) In the above-described embodiment, an image forming system 1S was illustrated in which the post-processing device 6 is positioned on the same mounting surface as the image forming apparatus 1 (floor-standing type). The configuration of the image forming system is not limited to this, and for example, the post-processing device 6 may be installed on top of the image forming apparatus 1. Furthermore, the image forming system 1S may include units other than the image forming apparatus 1 and the post-processing device 6. In addition, the image forming system 1S may have a configuration in which the image forming means, the buffer unit 20 and the binding processing unit 6A of this embodiment are arranged in the same housing.

[0115] Furthermore, the term "adhesive" in this disclosure is not limited to adhesive toner applied to a sheet by an electrophotographic process, as long as it can bond sheets together by heating. For example, the image forming apparatus 1 may be configured to include an inkjet-type image forming means and apply the adhesive to the sheet together with ink for recording an image.

[0116] (Summary of this disclosure) This disclosure includes at least the following components:

[0117] (Composition 1) A stacking processing unit that stacks multiple sheets that are transported one by one with adhesive applied to them, It has a loading section on which sheets are stacked, and an alignment means for aligning the positions of the sheets stacked in the loading section, Adhesive means for bonding sheets stacked on the aforementioned loading section together, Equipped with, The alignment means is configured to align the position of the second sheet bundle with the first sheet bundle after the second sheet bundle, which has been stacked in the stacking section, is stacked on top of the first sheet bundle, which has been stacked in the stacking section and aligned by the alignment means. The bonding means heats and pressurizes the second sheet bundle aligned by the alignment means, thereby bonding each sheet of the second sheet bundle to each other with the adhesive, and bonding the first sheet bundle to the second sheet bundle. A sheet processing apparatus characterized by the following:

[0118] (Configuration 2) Of the sheets constituting a portion of the deliverable bonded by the adhesive means, the adhesive is applied to both sides of each sheet, excluding two sheets located on the front and back surfaces of the deliverable. After the first sheet bundle has been bonded by the adhesive means and before the first sheet bundle is bonded to the second sheet bundle, the adhesive is exposed on the upper surface of the first sheet bundle. A sheet processing apparatus according to configuration 1, characterized by the above.

[0119] (Composition 3) The matching means includes a first matching unit that matches the second sheet bundle in a first direction, and a second matching unit that matches the second sheet bundle in a second direction perpendicular to the first direction. A sheet processing apparatus according to configuration 1 or 2, characterized by the above.

[0120] (Composition 4) The adhesive means is arranged to adhere the end of the sheet in the second direction, The second alignment unit, after alignment by the first alignment unit, moves the second sheet bundle in the second direction to perform alignment. A sheet processing apparatus according to configuration 3, characterized by the above.

[0121] (Composition 5) The first alignment unit is configured to align the second sheet bundle at a position different from the bonding position by the adhesive means in the second direction, and The first alignment unit starts aligning the second sheet bundle while the first sheet bundle is being bonded by the adhesive means. A sheet processing apparatus according to configuration 3 or 4, characterized by the above.

[0122] (Composition 6) The first alignment unit has a transport member that transports sheets toward a first reference member which serves as a reference for the sheet position in the first direction, and aligns each sheet of the second sheet bundle by abutting it against the first reference member using the transport member. A sheet processing apparatus according to any one of configurations 3 to 5, characterized by the above.

[0123] (Composition 7) The overlapping processing unit overlaps the sheets by shifting them so that, after the second sheet bundle has been loaded onto the loading section and before it has been aligned with the first alignment unit, the lower sheets in the second sheet bundle protrude further toward the first reference member in the first direction than the upper sheets. A sheet processing apparatus according to configuration 6, characterized by the above.

[0124] (Composition 8) The second alignment unit has an alignment member that faces a second reference member which serves as a reference for the sheet position in the second direction and is movable in the second direction, and aligns by pressing the second sheet bundle with the alignment member and bringing it into contact with the second reference member. A sheet processing apparatus according to any one of configurations 3 to 7, characterized by the above.

[0125] (Composition 9) The second sheet bundle is transported to the loading section during the period in which the first sheet bundle is being bonded by the adhesive means. A sheet processing apparatus according to any one of configurations 1 to 8.

[0126] (Composition 10) The sheets being transported one by one to the sheet processing device are stacked in predetermined quantities by the stacking processing unit and then transported to the stacking unit, so that sheets can be received at regular intervals even while the alignment by the alignment means and bonding by the bonding means are being performed. A sheet processing apparatus according to any one of configurations 1 to 9, characterized by the above.

[0127] (Composition 11) The period during which alignment by the alignment means or adhesion by the adhesive means is performed on the first sheet bundle overlaps with the period during which the overlapping processing unit overlaps multiple sheets to form the second sheet bundle. A sheet processing apparatus according to configuration 10, characterized by the above.

[0128] (Composition 12) The stacking section includes a first roller pair, a second roller pair, and a third roller pair, each for conveying the sheets. The third roller pair is arranged in a transport path that branches off from the transport path leading from the first roller pair to the second roller pair and leads to the loading section. Each of the second roller pair and the third roller pair is capable of conveying the sheet in the direction toward the loading section from the second roller pair and in the opposite direction. The stacking section forms a sheet bundle by reciprocating a preceding sheet with the second and third roller pairs, and stacking subsequent sheets conveyed via the first roller pair with the preceding sheet using the second roller pair. A sheet processing apparatus according to any one of configurations 1 to 11, characterized by the above.

[0129] (Composition 13) The aforementioned stacking section forms a sheet bundle consisting of three or more sheets. A sheet processing apparatus according to any one of configurations 1 to 12, characterized by the above.

[0130] (Composition 14) The bonding means comprises a pressure plate that supports the edge of the sheet to be loaded in the loading section, a heating member facing the pressure plate in the thickness direction of the sheet loaded in the loading section, a heater positioned on the opposite side of the heating member from the pressure plate in the thickness direction and generating heat when energized, and a pressure mechanism that moves the heater and the heating member relative to the pressure plate in the thickness direction. A sheet processing apparatus according to any one of configurations 1 to 13, characterized by the above.

[0131] (Composition 15) An image forming means for forming an image on a sheet and applying a powder adhesive to the sheet, A sheet processing device according to any one of configurations 1 to 14, Equipped with, An image forming system characterized by the following:

[0132] (Composition 16) The device further includes a fixing device that heats the image and powder adhesive formed on the sheet to fix them to the sheet. The image forming system according to configuration 15, characterized by the features described herein.

[0133] (Composition 17) The image forming means is capable of double-sided printing, and when producing a single product bonded by the adhesive means, the powder adhesive is applied to both sides of each sheet constituting the product, excluding the two sheets located on the front and back surfaces of the product. The image forming system according to configuration 15 or 16, characterized by the above. [Explanation of symbols]

[0134] 6…Sheet processing device (post-processing device) / 20…Stacking processing device (buffer section) / 53…First alignment unit (vertical alignment roller) / 55…Second alignment unit (horizontal alignment member) / 56…Alignment means (alignment section) / 57…Loading section (intermediate loading section) / 67…Adhesion means (thermocompression bonding section)

Claims

1. A stacking section that stacks multiple sheets, which are transported one by one with adhesive applied and an adhesive layer formed, to form a sheet bundle, It has a loading section on which sheets are stacked, and an alignment means for aligning the positions of the sheets stacked in the loading section, Adhesive means for bonding sheets stacked on the aforementioned loading section together, Equipped with, The alignment means is configured to align the position of the second sheet bundle with the first sheet bundle after the second sheet bundle, which has been stacked in the stacking section, is stacked on top of the first sheet bundle, which has been stacked in the stacking section and aligned by the alignment means. The bonding means, after bonding the first sheet bundle with the adhesive layer, heats and pressurizes the second sheet bundle, which has been aligned by the alignment means, in a single thermocompression operation, thereby bonding each sheet of the second sheet bundle to each other via the adhesive layer, and bonding the first sheet bundle and the second sheet bundle via the adhesive layer formed on the upper surface of the uppermost sheet of the first sheet bundle and the adhesive layer formed on the lower surface of the lowest sheet of the second sheet bundle. A sheet processing apparatus characterized by the following:

2. Of the sheets constituting a portion of the deliverable bonded by the adhesive means, the adhesive is applied to both sides of each sheet, excluding two sheets located on the front and back surfaces of the deliverable. After the first sheet bundle has been bonded by the adhesive means and before the first sheet bundle is bonded to the second sheet bundle, the adhesive layer is exposed on the upper surface of the topmost sheet of the first sheet bundle. The sheet processing apparatus according to feature 1.

3. The matching means includes a first matching unit that aligns the second sheet bundle in a first direction, and a second matching unit that aligns the second sheet bundle in a second direction perpendicular to the first direction. The sheet processing apparatus according to feature 1.

4. The adhesive means is arranged to adhere the end of the sheet in the second direction, The second alignment unit, after alignment by the first alignment unit, moves the second sheet bundle in the second direction to perform alignment. The sheet processing apparatus according to claim 3.

5. The first alignment unit is configured to align the second sheet bundle at a position different from the bonding position by the adhesive means in the second direction, and The first alignment unit starts aligning the second sheet bundle while the first sheet bundle is being bonded by the adhesive means. The sheet processing apparatus according to claim 3.

6. The first alignment unit has a transport member that transports sheets toward a first reference member which serves as a reference for the sheet position in the first direction, and aligns each sheet of the second sheet bundle by abutting it against the first reference member using the transport member. The sheet processing apparatus according to claim 3.

7. The overlapping processing unit overlaps the sheets by shifting them so that, after the second sheet bundle has been loaded onto the loading section and before it has been aligned with the first alignment unit, the lower sheets in the second sheet bundle protrude more in the first direction toward the first reference member than the upper sheets. The sheet processing apparatus according to claim 6.

8. The second alignment unit has an alignment member that faces a second reference member which serves as a reference for the sheet position in the second direction and is movable in the second direction, and aligns by pressing the second sheet bundle with the alignment member and bringing it into contact with the second reference member. The sheet processing apparatus according to claim 3.

9. The second sheet bundle is transported to the loading section during the period in which the first sheet bundle is being bonded by the adhesive means. The sheet processing apparatus according to feature 1.

10. The sheets being transported one by one to the sheet processing device are stacked in predetermined quantities by the stacking processing unit and then transported to the stacking unit, so that sheets can be received at regular intervals even while the alignment by the alignment means and bonding by the bonding means are being performed. The sheet processing apparatus according to feature 1.

11. The period during which alignment by the alignment means or adhesion by the adhesive means is performed on the first sheet bundle overlaps with the period during which the overlapping processing unit overlaps multiple sheets to form the second sheet bundle. The sheet processing apparatus according to feature 10.

12. The stacking section includes a first roller pair, a second roller pair, and a third roller pair, each for conveying the sheets. The third roller pair is arranged in a transport path that branches off from the transport path leading from the first roller pair to the second roller pair and leads to the loading section. Each of the second roller pair and the third roller pair is capable of conveying the sheet in the direction toward the loading section from the second roller pair and in the opposite direction. The stacking section forms a sheet bundle by reciprocating a preceding sheet with the second and third roller pairs, and stacking subsequent sheets conveyed via the first roller pair with the preceding sheet using the second roller pair. The sheet processing apparatus according to feature 1.

13. The aforementioned stacking section forms a sheet bundle consisting of three or more sheets. The sheet processing apparatus according to feature 1.

14. The bonding means comprises a pressure plate that supports the edge of the sheet to be loaded in the loading section, a heating member facing the pressure plate in the thickness direction of the sheet loaded in the loading section, a heater positioned on the opposite side of the heating member from the pressure plate in the thickness direction and generating heat when energized, and a pressure mechanism that moves the heater and the heating member relative to the pressure plate in the thickness direction. The sheet processing apparatus according to feature 1.

15. An image forming means for forming an image on a sheet and applying a powder adhesive to the sheet, A sheet processing apparatus according to any one of claims 1 to 14, Equipped with, An image forming system characterized by the following:

16. The device further includes a fixing device that heats the image and powder adhesive formed on the sheet to fix them to the sheet. The image forming system according to claim 15, characterized in that it is the same as described above.

17. The image forming means is capable of double-sided printing, and when producing a single product bonded by the adhesive means, the powder adhesive is applied to both sides of each sheet constituting the product, excluding the two sheets located on the front and back surfaces of the product. The image forming system according to claim 15, characterized in that it is the same as described above.

Images