Sheet processing device

Abstract

In the present invention, a printing device (1) comprises a printing cylinder (16) that holds and conveys a sheet (4), inkjet heads (22‒25) that deposit ink on the sheet (4), an ink drying device (27) that dries the ink, and pressing cylinders (41, 48) that press a processing surface of the sheet (4). As a result, the thickness of the ink adhering to the sheet can be reduced.

Description

Sheet Processing Device

[0001] The present invention relates to a sheet processing apparatus including a pressing device that presses a sheet.

[0002] Examples of sheet processing devices that apply a substance to a sheet include printing devices such as inkjet printing devices and offset printing devices, coating devices that apply varnish, etc. An example of an inkjet printing device is disclosed in Patent Document 1.

[0003] The inkjet printing device disclosed in Patent Document 1 includes first to fourth inkjet heads that eject ink onto a sheet, and a drying device that is located downstream of the first to fourth inkjet heads in the sheet transport direction. The drying device is composed of ink drying lamps. The ink is dried (cured) by being irradiated with infrared or ultraviolet rays from the ink drying lamps.

[0004] In the inkjet printing device disclosed in Patent Document 1, infrared or ultraviolet rays are irradiated from an ink drying lamp immediately after the ink is ejected onto a sheet. This causes the ink to harden before it soaks into the sheet, resulting in a thicker ink film compared to typical offset printing. This problem becomes more pronounced when UV-curable ink is used for printing. There are two reasons for this. The first reason is that UV-curable ink has a higher viscosity than other inks, such as oil-based inks, and therefore does not soak into a sheet of paper easily. The second reason is that UV-curable ink cures much faster than oil-based inks and the like.

[0005] If the ink film thickness is too thick, it will hinder subsequent processing of the sheet. This will result in poor workability in the subsequent processing. Furthermore, if the image is concentrated in one area, this area will be raised, making it impossible to stack the sheets flat. This same problem occurs in offset printing machines and coating machines, which share the same process as inkjet printing machines in that they also apply a substance to the treated surface of the sheet.

[0006] JP 2017-210337 A JP 5-16330 A

[0007] An object of the present invention is to provide a sheet processing apparatus capable of reducing the thickness of deposits adhering to a sheet.

[0008] A first aspect of the present invention is a sheet processing apparatus comprising a conveying device configured to hold and convey a sheet, a processing device configured to process the sheet held by the conveying device, and a pressing device arranged downstream of the processing device in the sheet conveying direction and configured to press the processing surface of the sheet processed by the processing device.

[0009] Here, "processing" includes printing such as inkjet printing and offset printing, and coating such as varnishing. Therefore, the sheet processing apparatus includes aspects of a printing apparatus and a coating apparatus. The printing apparatus further includes aspects of an inkjet printing apparatus and an offset printing apparatus.

[0010] One embodiment of the transport apparatus includes a processing cylinder configured to hold and transport the sheet.

[0011] One embodiment of the processing device includes a printing device configured to apply ink to the sheet held by the conveying device, and an ink drying device arranged downstream of the printing device in the sheet conveying direction and configured to dry the ink applied to the sheet.

[0012] One embodiment of the printing device includes a plurality of print heads configured to eject the ink onto the sheet. Another embodiment of the printing device includes an offset printing section configured to transfer the ink supplied from a plate cylinder to a blanket cylinder onto the sheet.

[0013] Another embodiment of the processing device includes a coating device configured to coat the sheet held by the conveying device with varnish, and an ink drying device arranged downstream of the coating device in the sheet conveying direction and configured to dry the varnish coating the sheet.

[0014] The sheet processing apparatus according to the above aspect may further include a transport drum disposed downstream of the processing device in the sheet transport direction and configured to transport the sheet processed by the processing device with the processing surface facing radially outward. In this case, the pressing device may include a pressing drum disposed opposite the transport drum.

[0015] The sheet processing apparatus may be configured to selectively perform double-sided processing, which processes both sides of the sheet, and single-sided processing, which processes only one side of the sheet. In this case, the pressing device may include a first pressing device configured to press a first processed side of the processed sides of the sheet when performing the double-sided processing, and a second pressing device configured to press a second processed side of the processed sides of the sheet when performing the double-sided processing, and to press the second processed side of the processed sides of the sheet when performing the single-sided processing.

[0016] The above-mentioned aspect of the sheet processing device may further include an inversion mechanism configured to invert the sheet processed by the processing device and return it to the conveying device, an ejection mechanism configured to eject the sheet processed by the processing device, a conveying path switching device arranged between the conveying device and the inversion mechanism and the ejection mechanism, and configured to receive the sheet processed by the processing device from the conveying device and convey the sheet to the inversion mechanism or the ejection mechanism, and a controller connected to the conveying path switching device and configured to control the conveying path switching device to switch the destination of the sheet.

[0017] The controller is configured to, when the single-sided processing is selected, transport the sheet whose one side has been processed to the discharge mechanism, and, when the double-sided processing is selected, transport the sheet whose one side has been processed to the reversing mechanism and transport the sheet whose both sides have been processed to the discharge mechanism.

[0018] In this case, the first pressing device may be arranged in the reversing mechanism, and the second pressing device may be arranged in the discharge mechanism. The reversing mechanism and the discharge mechanism may include a first transport cylinder and a second transport cylinder, respectively. The first transport cylinder of the reversing mechanism is configured to transport the sheet so that the processed surface, which has been previously processed by the processing device, faces radially outward. The first pressing device may include a first pressing cylinder arranged opposite the first transport cylinder. The second transport cylinder of the discharge mechanism is configured to transport the sheet so that the processed surface, which has been subsequently processed by the processing device, faces radially outward. The second pressing device may include a second pressing cylinder arranged opposite the second transport cylinder.

[0019] Alternatively, the first pressing device and the second pressing device may be disposed in the discharge mechanism. The discharge mechanism may include a first transport cylinder and a second transport cylinder. The first transport cylinder is configured to transport the sheet with the processed surface, which has been previously processed by the processing device, facing radially outward. The first pressing device may include a first pressing cylinder disposed opposite the first transport cylinder. The second transport cylinder is configured to transport the sheet with the processed surface, which has been subsequently processed by the processing device, facing radially outward. The second pressing device may include a second pressing cylinder disposed opposite the second transport cylinder.

[0020] One embodiment of the reversing mechanism includes a reversing side transfer drum configured to receive the sheet from the conveying path switching device, a front reversing drum configured to receive the sheet from the reversing side transfer drum, and a reversing device configured to grab the upstream end of the sheet being conveyed to the front reversing drum in the sheet conveying direction and return it to the conveying device.

[0021] One embodiment of the discharge mechanism includes a first discharge side transfer drum configured to receive the sheet from the transport path switching device, a second discharge side transfer drum configured to receive the sheet from the first discharge side transfer drum, and a discharge device that receives the sheet from the second discharge side transfer drum and discharges the sheet.

[0022] In one embodiment, the pressure cylinders (the first pressure cylinder, the second pressure cylinder) have smooth outer peripheral surfaces.

[0023] Another embodiment of the pressure cylinder (the first pressure cylinder, the second pressure cylinder) has a rough outer peripheral surface. This outer peripheral surface may have an arithmetic mean roughness comparable to the arithmetic mean roughness of the surface of the sheet. When the sheet is a water-absorbent medium that absorbs the ink, the arithmetic mean roughness of this outer peripheral surface may be within ±30% of the arithmetic mean roughness of the sheet.

[0024] Another embodiment of the processing device is configured to apply a deposit to the sheet and to dry the deposit.

[0025] The pressing device may be configured to press the treatment surface of the sheet with a pressing force such that the height of the deposit exposed from the treatment surface of the sheet is ⅕ or less.

[0026] The sheet processing apparatus according to the above aspect may further include an actuator for changing the distance (axis distance) between the axis of the transport drum that transports the sheet and the axis of the pressure drum. The controller may previously store data (a table or a function) indicating the relationship between the axis distance and a parameter including at least one of the thickness of the sheet and the thickness of the deposit (e.g., thickness of the pattern, thickness of the ink, thickness of the varnish). The controller may be configured to refer to the data to determine the axis distance corresponding to the parameter input before starting processing, and to control the actuator so that the axis distance is determined.

[0027] According to the above aspect of the present invention, the protruding deposits on the treatment surface of the sheet are pressed into the sheet by the pressing device, so that the thickness of the deposits can be reduced.

[0028] FIG. 1 is a side view of a printing apparatus according to a first embodiment. FIG. 2 is a side view of a reversing mechanism. FIG. 3 is a side view of a discharge mechanism. FIG. 4 is a block diagram showing the configuration of a control system. FIG. 5 is a side view of a printing apparatus according to a second embodiment. FIG. 6 is a side view of a discharge mechanism. FIG. 7 is a side view showing a part of a printing apparatus according to a third embodiment. FIG. 8 is a side view of a printing apparatus according to a fourth embodiment. FIG. 9 is a side view of a printing apparatus according to a fifth embodiment. FIG. 10 is a side view of a coating apparatus according to a sixth embodiment. FIG. 11 is a side view of a printing apparatus according to a seventh embodiment.

[0029] (First embodiment) A first embodiment of a sheet processing apparatus according to the present invention will be described in detail with reference to Figures 1 to 4. Here, an embodiment in which the present invention is applied to an inkjet printing apparatus will be described.

[0030] The printing apparatus 1 shown in Figure 1 transports sheets 4 from a feeder section 2 located at the far right in Figure 1 to a printing unit 3, where printing is performed on one or both sides of the sheets 4. In this embodiment, the printed side when printing on one side of the sheet 4 and the side printed first when printing on both sides of the sheet 4 are referred to as the "front side" of the sheet 4, and the side opposite the front side is referred to as the "back side." After printing by the printing unit 3, i.e., a sheet 4 to be printed on only the front side or a sheet 4 printed on both sides, is sent from the printing unit 3 to a delivery section 6 via a discharge drum 5 (described later) and accumulated in a delivery pile 7.

[0031] The feeder section 2 is configured to transfer sheets 4 from the feeder pile 11 to the upper end of the feeder board 12 using a sucker (not shown). The sucker operates in either a continuous or intermittent manner. When printing is performed only on the front side of the sheet 4, i.e., single-sided printing, the sucker continuously feeds the sheet 4 to the feeder board 12. On the other hand, when printing is performed on both the front and back sides of the sheet 4, i.e., double-sided printing, the sucker intermittently feeds the sheet 4 to the feeder board 12. The operation of the sucker is controlled by a controller 13 (see FIG. 4), which will be described later. When the sheet 4 reaches the lower end of the feeder board 12, it is transferred to a supply cylinder 15 by a swing device 14.

[0032] (Printing unit) The printing unit 3 includes a supply cylinder 15 that receives the sheet 4 supplied from the feeder section 2 via a swing device 14, a printing cylinder 16 to which the sheet 4 is fed from the supply cylinder 15, and a discharge cylinder 5 that serves as a transport path switching device that distributes the printed sheet 4 to either an inversion mechanism 17 or a discharge mechanism 18, which will be described later.

[0033] The supply cylinder 15 has a first gripper device 21 that holds the sheet 4. The first gripper device 21 grips and holds the leading end 4a of the sheet 4, which is the end on the downstream side in the conveying direction, and supplies the sheet 4 received from the swing device 14 to the printing cylinder 16 at a supply position P1.

[0034] The printing cylinder 16 constitutes a transport device (processing cylinder) that holds and transports the sheet 4, adsorbing the sheet 4 and transporting it to a position where printing is performed by first to fourth inkjet heads 22 to 25, which will be described later. The printing cylinder 16 in this embodiment is a so-called triple cylinder, and is equipped with second gripper devices 26 at three locations in the rotational direction. The second gripper devices 26 are equivalent to the first gripper device 21 provided on the supply cylinder 15.

[0035] Near the periphery of the printing cylinder 16 and downstream of the supply cylinder 15 in the conveying direction of the sheet 4, first to fourth inkjet heads 22 to 25 and an ink drying device 27 are arranged in this order. The first to fourth inkjet heads 22 to 25 and the ink drying device 27 constitute a processing device that processes the sheet 4 held by the conveying device. The first to fourth inkjet heads 22 to 25 constitute a plurality of print heads.

[0036] The first to fourth inkjet heads 22 to 25 print by ejecting ink onto the printing surface of the sheet 4 held on the printing cylinder 16. The first to fourth inkjet heads 22 to 25 constitute a printing device that deposits ink onto the sheet 4 held on a conveying device. The printing surface of the sheet 4 refers to the treated surface opposite the conveying surface that contacts the printing cylinder 16. The operation of the first to fourth inkjet heads 22 to 25 is controlled by the controller 13, which will be described later.

[0037] The ink drying device 27 is disposed downstream of the fourth inkjet head 25 in the conveyance direction of the sheet 4, and dries the ink adhering to the sheet 4. The ink drying device 27 can be configured, for example, by an ink drying lamp. The ink drying lamp irradiates the sheet 4 with infrared or ultraviolet rays. The ink dries or hardens when irradiated with infrared or ultraviolet rays. In the printing device 1 according to this embodiment, the ink is completely dried or hardened when the sheet 4 passes near the ink drying lamp.

[0038] The discharge cylinder 5 is disposed between the printing cylinder 16 and the reversing mechanism 17 and discharge mechanism 18, which will be described later. The discharge cylinder 5 receives the printed sheet 4 from the printing cylinder 16 at a receiving position P2, which is located downstream of the ink drying device 27 in the conveyance direction of the sheet 4, and distributes and conveys the sheet 4 to either the reversing mechanism 17 or the discharge mechanism 18 depending on the printing state of the sheet 4. The printed state refers to a state in which one side of the sheet 4 is printed, or a state in which both sides of the sheet 4 are printed.

[0039] The discharge cylinder 5 receives the sheet 4 from the printing cylinder 16 and transfers the sheet 4 to the reversing mechanism 17 and the discharge mechanism 18 using a third gripper device 31 provided on the discharge cylinder 5. After holding the leading end 4a of the sheet 4 at the receiving position P2, the third gripper device 31 operates under the control of the controller 13 to transfer the sheet 4 to either the reversing mechanism 17 or the discharge mechanism 18. The configuration for the discharge cylinder 5 to switch the destination of the sheet 4 can be realized using a switching mechanism such as that disclosed in Patent Document 1, for example. The operation of the discharge cylinder 5 when switching the destination is controlled by the controller 13, which will be described later.

[0040] (Reversal mechanism) As shown in FIG. 2 , the reversal mechanism 17 includes a reversal side transfer cylinder 33 that receives the sheet 4 from the discharge cylinder 5 using a fourth gripper device 32, a pre-reversal double cylinder 35 that receives the sheet 4 from the reversal side transfer cylinder 33 using a fifth gripper device 34, and a reversal swing device 37 that serves as a reversal device that grips the rear end (tail end) 4b, which is the end on the upstream side in the conveying direction of the sheet 4 conveyed by the pre-reversal double cylinder 35, using a sixth gripper device 36 and returns the sheet to the printing cylinder 16.

[0041] The reversing swing device 37 is configured to swing about an axis parallel to the axes of the printing cylinder 16 and the pre-reversing doubler cylinder 35, and a sixth gripper device 36 provided at the swinging end swings back and forth between a position close to the pre-reversing doubler cylinder 35 and a sheet return position P3 close to the printing cylinder 16. When the reversing swing device 37 swings toward the printing cylinder 16 with the sixth gripper device 36 of the reversing swing device 37 gripping the rear end 4b of the sheet 4 on the pre-reversing doubler cylinder 35 side, the sheet 4 is turned over and delivered to the printing cylinder 16 at the sheet return position P3.

[0042] The reverse-side transfer drum 33 constitutes a first transfer drum that transfers the sheet 4 with the processed surface (front surface) that has been previously processed by the processing device facing radially outward. The reverse-side transfer drum 33 has an outer peripheral surface 33a to which the entire printing area of ​​the sheet 4 is in close contact. The outer peripheral surface 33a is formed of a metal material or other highly rigid material. The surface of the outer peripheral surface 33a is also formed smoothly. The sheet 4 to be printed on both sides is transferred to the reverse-side transfer drum 33 with printing only on the front surface. The sheet 4 is held by the reverse-side transfer drum 33 with the printed surface (front surface) exposed.

[0043] A first pressing cylinder 41 constituting a first pressing device that presses the processed surface of the sheet 4 processed by the processing device is disposed at a position opposite the reversing-side transfer cylinder 33. The first pressing cylinder 41 presses the sheet 4 being transported by the reversing-side transfer cylinder 33 with a predetermined pressing force. This pressing force is set to a value equal to the printing pressure (5 to 20 kgf / cm) in offset printing. ２ ) is 4 to 12 times the pressure.

[0044] The first pressing cylinder 41 is a rotary cylinder having an outer peripheral surface 41a formed to be smooth over its entire area. The outer peripheral surface 41a has an arithmetic mean roughness Ra (surface roughness) that is smaller than the arithmetic mean roughness Ra (surface roughness) of the surface of the sheet 4. The arithmetic mean roughness Ra (surface roughness) of the outer peripheral surface 41a is preferably 2 μm or less.

[0045] The first pressure cylinder 41 is rotatably supported on a printing apparatus frame (not shown) via a bearing structure 42, with its axis parallel to the axis of the reverse-side transfer cylinder 33 and its outer peripheral surface 41a in contact with the outer peripheral surface 33a of the reverse-side transfer cylinder 33. The bearing structure 42 is configured to adjust the axial distance between the first pressure cylinder 41 and the reverse-side transfer cylinder 33. An eccentric bearing, for example, can be used as a structure for adjusting the axial distance. By adjusting the axial distance, the pressing force with which the first pressure cylinder 41 presses the sheet 4 can be adjusted. The outer diameter of the first pressure cylinder 41 in this embodiment is approximately the same as that of the single-cylinder reverse-side transfer cylinder 33.

[0046] The first pressing cylinder 41 rotates as the sheet 4 is conveyed while pressing the sheet 4. Note that the first pressing cylinder 41 is not limited to a configuration in which it rotates by being co-rotated as described above. There are no limitations on the method of driving the first pressing cylinder 41, and it is possible to adopt a configuration in which the first pressing cylinder 41 is driven independently to rotate, or to transmit the power that drives the reversing-side transfer cylinder 33 to rotate the first pressing cylinder 41.

[0047] The outer peripheral surface 41 a of the first pressing cylinder 41 is formed of an elastic material. Examples of the elastic material include rubber materials such as silicone rubber and synthetic rubber, elastomers, and elastic plastic materials. The outer peripheral surface 41 a can also be formed of a metal material to press the sheet 4 more firmly.

[0048] 3 , the discharge mechanism 18 includes a first discharge-side transfer cylinder 44 that receives the sheet 4 from the discharge cylinder 5 with a seventh gripper device 43, a second discharge-side transfer cylinder 46 that receives the sheet 4 from the first discharge-side transfer cylinder 44 with an eighth gripper device 45, and a discharge belt 47 that transports the sheet 4 discharged from the second discharge-side transfer cylinder 46 to the delivery section 6. The discharge belt 47 constitutes a discharge device that discharges the sheet 4.

[0049] The first discharge-side transfer cylinder 44 constitutes a second transfer cylinder that transfers the sheet 4 with the processed surface (back surface) that has been processed later by the processing device facing radially outward. The first discharge-side transfer cylinder 44 has an outer peripheral surface 44a to which the entire printing area of ​​the sheet 4 is in close contact. This outer peripheral surface 44a is formed of a metal material or other highly rigid material. The surface of the outer peripheral surface 44a is formed smoothly. In the case of single-sided printing, the first discharge-side transfer cylinder 44 holds the sheet 4 that has been printed on only one side with the printed surface (front surface) exposed. In the case of double-sided printing, the first discharge-side transfer cylinder 44 holds the sheet 4 that has been printed on both sides with the second printed surface (back surface) exposed.

[0050] A second pressing cylinder 48 constituting a second pressing device that presses the processed surface of the sheet 4 that has been processed by the processing device is disposed in a position opposite the first discharge-side transfer cylinder 44. The second pressing cylinder 48 in this embodiment is disposed directly above the first discharge-side transfer cylinder 44. The second pressing cylinder 48 has the same configuration as the above-described first pressing cylinder 41, and presses the sheet 4 being transported by the first discharge-side transfer cylinder 44 with a predetermined pressing force. This pressing force is 4 to 12 times the printing pressure in offset printing.

[0051] The second pressure cylinder 48 has a smooth outer peripheral surface 48a, similar to the first pressure cylinder 41. The second pressure cylinder 48 is rotatably supported on a printing apparatus frame (not shown) via a bearing structure 49, with its axis parallel to the axis of the first discharge-side transfer cylinder 44 and its outer peripheral surface 48a in contact with the outer peripheral surface 44a of the first discharge-side transfer cylinder 44. The bearing structure 49 is configured to adjust the axial distance between the second pressure cylinder 48 and the first discharge-side transfer cylinder 44. An eccentric bearing, for example, is one example of a configuration for adjusting the axial distance. Adjusting the axial distance allows adjustment of the pressing force when the second pressure cylinder 48 presses the sheet 4. The outer diameter of the second pressure cylinder 48 in this embodiment is approximately the same as that of the single-cylinder first discharge-side transfer cylinder 44.

[0052] The second pressing cylinder 48 rotates as the sheet 4 is conveyed while pressing the sheet 4. Note that the second pressing cylinder 48 is not limited to a configuration in which it rotates by being co-rotated as described above. There are no limitations on the method of driving the second pressing cylinder 48, and it is possible to adopt a configuration in which the second pressing cylinder 48 is driven independently to rotate, or the second pressing cylinder 48 is rotated by transmitting the power that drives the first discharge-side transfer cylinder 44.

[0053] The outer peripheral surface 48a of the second pressing cylinder 48 is formed of an elastic material. Examples of the elastic material include rubber materials such as silicone rubber and synthetic rubber, elastomers, and elastic plastic materials. The outer peripheral surface 48a may be formed of a metal material to apply even stronger pressure to the sheet 4.

[0054] The discharge belt 47 is an endless belt that is stretched over an upstream sprocket 47a located near the bottom of the second discharge-side transfer cylinder 46 and a downstream sprocket 47b located above the delivery pile 7, and extends substantially horizontally from near the bottom of the second discharge-side transfer cylinder 46 to the opposite side from the printing cylinder 16. The discharge belt 47 rotates when the upstream sprocket 47a and downstream sprocket 47b, along with the printing cylinder 16 and other cylinders, are driven by a drive unit (not shown). The sheet 4 is placed on the discharge belt 47 and is transported to the delivery section 6 as the discharge belt 47 moves (rotates) and travels.

[0055] (Controller) The controller 13 is configured by a CPU (Central Processing Unit) or a computer. As shown in Fig. 4, the controller 13 is connected to a print mode selection switch 51 and a rotary encoder 52 serving as a phase detection device. The controller 13 is also connected to the first to fourth inkjet heads 22 to 25, a sucker operation switching actuator 53 of the feeder unit 2, and a transport path switching actuator 54 of the discharge drum 5.

[0056] The print mode selection switch 51 is used to switch between a single-sided print mode in which single-sided printing is performed and a double-sided print mode in which double-sided printing is performed in the printing device 1. When the single-sided print mode is selected by the print mode selection switch 51, the controller 13 controls the operation of the feeder unit 2 (sucker operation switching actuator 53), the first to fourth inkjet heads 22 to 25, the discharge drum 5 (transport path switching actuator 54), etc. so that single-sided printing is performed. On the other hand, when the double-sided print mode is selected by the print mode selection switch 51, the controller 13 controls the operation of the feeder unit 2 (sucker operation switching actuator 53), the first to fourth inkjet heads 22 to 25, the discharge drum 5 (transport path switching actuator 54), etc. so that double-sided printing is performed.

[0057] The controller 13 particularly controls the discharge drum 5 (conveyance path switching actuator 54) to switch the destination of the sheet 4. When the single-sided processing mode is selected, the controller 13 causes the sheet 4 printed on only one side to be conveyed to the discharge mechanism 18. When the double-sided processing mode is selected, the controller 13 causes the sheet 4 printed on only one side to be conveyed to the reversing mechanism 17, and causes the sheet 4 printed on both sides to be conveyed to the discharge mechanism 18.

[0058] (Operation During Single-Sided Printing) Next, the operation of the printing apparatus 1 according to this embodiment will be described. When an operator (not shown) operates the printing mode selection switch 51 to select single-sided printing mode, the controller 13 switches to single-sided printing mode and controls the operation of various devices. In single-sided printing mode, the sheet 4 is continuously supplied from the feeder section 2 to the printing unit 3. The sheet 4 transported to the printing cylinder 16 of the printing unit 3 is printed as it passes near the first to fourth inkjet heads 22 to 25. Printing is performed by the controller 13 identifying the position of the sheet 4 based on the phase signal of the rotary encoder 52. The ink printed on the sheet 4 is cured as the sheet 4 passes near the ink drying device 27.

[0059] Thereafter, the sheet 4 is fed from the printing cylinder 16 to the discharge cylinder 5. In the simplex printing mode, the sheet 4 held on the discharge cylinder 5 is fed to the first discharge-side transfer cylinder 44 of the discharge mechanism 18 without being fed to the reversing mechanism 17. The sheet 4 is pressed by the second pressure cylinder 48 during its transport by the first discharge-side transfer cylinder 44.

[0060] At this time, the second pressure cylinder 48 presses the printing surface (front surface) of the sheet 4. Hardened ink is attached to the printing surface of the sheet 4 in a state where it protrudes from the surface of the sheet 4. This ink is forced into the interior of the sheet 4 by the outer circumferential surface 48a of the second pressure cylinder 48 being pressed against it. This makes it possible to reduce the thickness of the ink film exposed on the surface of the sheet 4. The thickness of the ink film exposed on the surface of the sheet 4 is 5 μm to 10 μm before pressing, but becomes approximately 1 μm after pressing. In other words, by being pressed against the second pressure cylinder 48, the thickness of the ink film exposed on the surface of the sheet 4 becomes 1 / 5 or less.

[0061] When ink film thickness increases with inkjet printing, the ink surface becomes less smooth, resulting in diffused reflection of light. As a result, the glossiness of the printed portion produced by inkjet printing is weaker than that of offset printing. In particular, halftone areas, where ink is scattered compared to solid areas, tend to cause diffused reflection of light, further weakening the glossiness. However, with this embodiment, the ink is pressed by the second pressure cylinder 48, smoothing the ink surface and imparting a glossiness to the printed portion on the surface of the sheet 4.

[0062] The sheet 4 that has passed between the first discharge side transfer cylinder 44 and the second pressure cylinder 48 is handed over to the second discharge side transfer cylinder 46, discharged from the second discharge side transfer cylinder 46 onto the discharge belt 47, discharged above the delivery pile 7 by the discharge belt 47, and stacked on the delivery pile 7.

[0063] (Operation during double-sided printing) When the operator operates the printing mode selection switch 51 to select double-sided printing mode, the controller 13 controls the operation of various devices in double-sided printing mode. In double-sided printing mode, sheets 4 are intermittently supplied from the feeder section 2 to the printing unit 3. That is, a sheet 4 is transported to the printing cylinder 16 every two rotations of the supply cylinder 15. A new sheet 4 transported to the printing cylinder 16 in this way is printed on its front side by being transported by the printing cylinder 16, just as in single-sided printing, and is then sent to the discharge cylinder 5.

[0064] In the double-sided printing mode, a new sheet 4 printed on its front side is transferred from the discharge cylinder 5 to the reverse-side transfer cylinder 33. The sheet 4, which has been printed only on its front side, is pressed by the first pressure cylinder 41 while being transported by the reverse-side transfer cylinder 33. At this time, the first pressure cylinder 41 presses the printed side of the sheet 4. Hardened ink is adhering to the printed side of the sheet 4 in a state where it protrudes from the surface of the sheet 4. This ink is pressed into the interior of the sheet 4 by the outer peripheral surface of the first pressure cylinder 41 being pressed against it. Therefore, similar to when the sheet 4 is pressed by the second pressure cylinder 48 during single-sided printing, the thickness of the ink film exposed on the surface of the sheet 4 can be reduced, the ink surface becomes smooth, and a glossy appearance is imparted to the printed portion of the surface of the sheet 4.

[0065] The sheet 4 that has passed between the reversing-side transfer cylinder 33 and the first pressure cylinder 41 is transferred from the reversing-side transfer cylinder 33 to the pre-reversing double cylinder 35, and is then inverted by the reversing swing device 37 so that it is transferred to the printing cylinder 16 with its back side exposed. The sheet 4 held on the printing cylinder 16 with its back side exposed is printed on its back side as it passes near the first to fourth inkjet heads 22 to 25. At this time, the controller 13 distinguishes between a new sheet 4 and a sheet 4 with its back side exposed based on the phase signal of the rotary encoder 52, and performs printing according to the respective sheet 4.

[0066] The sheet 4 with the back side printed passes near the ink drying device 27 and is sent to the discharge drum 5 in a state where the ink has hardened. The discharge drum 5 delivers the sheet 4 with double-sided printing in double-sided printing mode to the first discharge-side transfer drum 44. The destination of the sheet 4 by the discharge drum 5 varies depending on the printing state of the sheet 4. That is, if the printing mode of the controller 13 is a double-sided printing mode and printing has been completed on only one side of the sheet 4, the destination is the reversing mechanism 17, and in other cases the destination is the discharge mechanism 18. The other cases include when the printing mode of the controller 13 is a single-sided printing mode or when printing has been completed on both sides of the sheet 4 in double-sided printing mode.

[0067] The sheet 4 sent from the discharge cylinder 5 to the first discharge-side transfer cylinder 44 is pressed by the second pressure cylinder 48 while being transported by the first discharge-side transfer cylinder 44. That is, the ink adhering to the back surface of the sheet 4 is pressed by the second pressure cylinder 48 and pushed into the inside of the sheet 4, just as in single-sided printing. This makes it possible to reduce the thickness of the ink film exposed on the back surface of the sheet 4, and also makes the ink surface smooth, imparting a glossy appearance to the printed portion on the back surface of the sheet 4.

[0068] The sheet 4 that has passed between the first discharge side transfer cylinder 44 and the second pressure cylinder 48 is discharged onto the delivery pile 7 by the second discharge side transfer cylinder 46 and the discharge belt 47, in the same way as in single-sided printing.

[0069] (Effects of the embodiment) The printing apparatus 1 according to this embodiment comprises a printing cylinder 16 (transport device) configured to hold and transport the sheet 4, a printing device (first to fourth inkjet heads 22 to 25) configured to apply ink to the sheet 4 held on the printing cylinder 16, an ink drying device 27 arranged downstream of the printing device in the transport direction of the sheet 4 and configured to dry the ink adhered to the sheet 4, and first and second pressure cylinders 41, 48 (pressing devices) arranged downstream of the ink drying device 27 in the transport direction of the sheet 4 and configured to press the printed surface of the sheet 4.

[0070] The ink thickness can be reduced because the ink (adhered matter) raised on the printing surface of the sheet 4 is pressed into the sheet 4 by the first and second pressure cylinders 41, 48. In addition, the ink surface becomes smooth, making it possible to impart a glossy appearance to the printing portion (treated portion) of the sheet 4.

[0071] The printing device according to this embodiment is composed of first to fourth inkjet heads 22 to 25 that eject ink onto a sheet 4 held on a printing cylinder 16. Inkjet printing tends to result in a thicker ink film and a weaker glossiness in the printed portion compared to general offset printing. However, according to this embodiment, despite using inkjet printing, it is possible to reduce the ink film thickness and impart a glossiness to the printed portion of the sheet 4.

[0072] The printing device 1 according to this embodiment is configured to selectively perform double-sided printing, in which both the front and back sides of the sheet 4 are printed, and single-sided printing, in which only one side of the sheet is printed. The printing device 1 also includes a first pressure cylinder 41 (first pressure device) configured to press the previously printed surface (front side) of the sheet 4 during double-sided printing, and a second pressure cylinder 48 (second pressure device) configured to press the subsequently printed surface (back side) of the sheet 4 during double-sided printing and to press the printed surface (front side) of the sheet 4 during single-sided printing.

[0073] Therefore, the raised ink is pressed by the first and second pressure cylinders 41, 48 into the sheet 4, thereby reducing the ink film thickness in both single-sided and double-sided printing. In addition, the ink surface becomes smooth, making it possible to impart a glossy appearance to the printed portion in both single-sided and double-sided printing.

[0074] The printing device 1 according to this embodiment includes a controller 13 configured to switch between single-sided printing and double-sided printing, and a discharge drum 5 (transport path switching device) configured to switch the destination of the sheet 4 according to the printing mode of the controller 13. The destinations of the sheet 4 transported by the discharge drum 5 are a reversing mechanism 17 configured to turn over the sheet 4, which has been printed on only one side, and return it to the printing drum 16 when the printing mode of the controller 13 is a double-sided printing mode, and a discharge mechanism 18 configured to discharge the sheet 4 when the printing mode is single-sided printing or when printing has been completed on both sides of the sheet 4 in a double-sided printing mode.

[0075] When double-sided printing is performed, the sheet 4 is inverted and returned to the printing cylinder 16, so that printing for single-sided printing and double-sided printing can be performed using the same first to fourth inkjet heads 22 to 25. Therefore, in both single-sided printing and double-sided printing, a compact printing device can be realized in which the ink film thickness is thin and the ink surface is flat, giving the printed area a glossy appearance.

[0076] In this embodiment, the first pressure cylinder 41 is disposed in the reversing mechanism 17, and the second pressure cylinder 48 is disposed in the discharge mechanism 18. Therefore, before printing is performed on the back side of the sheet 4, the thickness of the ink film adhering to the front side of the sheet 4 is thinned and the ink is flattened, so that printing on the back side can be performed without being affected by the ink on the front side. Therefore, a printing device that improves the print quality on the back side can be provided.

[0077] Second Embodiment Next, a second embodiment of a sheet processing apparatus of the present invention will be described with reference to Figures 5 and 6. In Figures 5 and 6, components that are the same as or equivalent to those described with reference to Figures 1 to 4 are designated by the same reference numerals, and detailed description thereof will be omitted where appropriate. A printing apparatus 61 shown in Figure 5 differs from the printing apparatus 1 of the first embodiment in the configuration of the reversing mechanism 17 and the discharge mechanism 18, but the other configurations are the same as those of the printing apparatus 1 shown in the first embodiment.

[0078] 5 does not include the first pressure cylinder 41. This reversing mechanism 17 does not include the first pressure cylinder 41, and the other configurations are the same as those of the reversing mechanism 17 in the first embodiment.

[0079] Instead, a first pressure cylinder 41 is disposed in the discharge mechanism 18 of a printing apparatus 61 shown in Fig. 5. More specifically, as shown in Fig. 6, the first pressure cylinder 41 is disposed in a position facing the second discharge-side transfer cylinder 46. In this embodiment, the first pressure cylinder 41 is disposed directly below the second discharge-side transfer cylinder 46. The first pressure cylinder 41 is rotatably supported by a bearing structure 42 on a printing press frame (not shown) with its axis parallel to the second discharge-side transfer cylinder 46 and its outer peripheral surface 41a in contact with the second discharge-side transfer cylinder 46. The bearing structure 42 is equivalent to the one that supports the first pressure cylinder 41 in the first embodiment.

[0080] In this manner, in the printing device 61 in which the first pressure cylinder 41 is disposed in the discharge mechanism 18, the ink on the front surface of the sheet 4 is pressed by the second pressure cylinder 48 during single-sided printing. The sheet 4 that passes between the second pressure cylinder 48 and the first discharge-side transfer cylinder 44 is handed over to the second discharge-side transfer cylinder 46 and conveyed, and passes between the second discharge-side transfer cylinder 46 and the first pressure cylinder 41. At this time, since no ink adheres to the back surface of the sheet 4, the sheet 4 is hardly pressed. Note that the bearing structure 42 that supports the first pressure cylinder 41 can be provided with a movement mechanism that retracts the first pressure cylinder 41 in a direction away from the sheet 4 during single-sided printing. By adopting this configuration, it is possible to avoid unnecessary contact between the first pressure cylinder 41 and the sheet 4 during single-sided printing.

[0081] On the other hand, during double-sided printing, the second pressure cylinder 48 presses the ink on the back side of the sheet 4, and the first pressure cylinder 41 presses the ink on the front side of the sheet 4. Therefore, in this embodiment, as in the first embodiment, in both single-sided printing and double-sided printing, the ink film thickness is reduced and the ink surface is flattened, making it possible to impart a glossy appearance to the printed portion.

[0082] In the printing device 61 according to this embodiment, the first pressure cylinder 41 and the second pressure cylinder 48 are disposed in the discharge mechanism 18. Therefore, a strong support structure for supporting the first pressure cylinder 41 and the second pressure cylinder 48 can be concentrated in the discharge mechanism 18. As a result, the manufacturing of the printing device is easier than when highly rigid parts are distributed in multiple locations.

[0083] In this embodiment, the second discharge-side transfer drum 46 serves as a first transfer drum that transfers the sheet 4 with the surface (front side) that has been previously processed by the processing device facing radially outward, and the first discharge-side transfer drum 44 serves as a second transfer drum that transfers the sheet 4 with the surface (back side) that has been subsequently processed by the processing device facing radially outward.

[0084] The printing apparatuses 1 and 61 shown in the first and second embodiments described above are both equipped with a reversing mechanism 17 that uses a reversing swing device 37 (reversing device). This allows for a compact reversing mechanism 17. As a result, it is possible to provide a printing apparatus that is compact and capable of double-sided printing, despite being equipped with first and second pressure cylinders 41 and 48.

[0085] The printing apparatuses 1, 61 shown in the first and second embodiments described above both include first and second discharge-side transfer cylinders 44, 46, and a discharge belt 47 (discharge device) that receives and discharges the sheet 4 from the second discharge-side transfer cylinder 46. This makes it possible to use the first and second discharge-side transfer cylinders 44, 46 as cylinders that receive the pressing forces of the first pressing cylinder 41 and the second pressing cylinder 48, thereby increasing the degree of freedom in determining the locations where the first and second pressing cylinders 41, 48 are disposed.

[0086] (Third embodiment) The reversing mechanism 17 can be configured as shown in Fig. 7. In Fig. 7, the same or equivalent members as those described with reference to Figs. 1 to 4 are designated by the same reference numerals, and detailed description thereof will be omitted where appropriate.

[0087] 7 includes a reversing cylinder 71 between the pre-reversing double cylinder 35 and the supply cylinder 15, and does not include the above-described reversing swing device 37. Note that the configuration of this embodiment other than the reversing mechanism 17 is the same as that of the first embodiment, although some of the configuration is shown in the figure.

[0088] The reversing cylinder 71 rotates in synchronization with the cylinders that transport the sheet 4, receives the sheet 4 from the pre-reversing double cylinder 35, turns the sheet 4 over, and supplies the turned-over sheet 4 to the supply cylinder 15. The supply cylinder 15 shown in FIG. 7 is configured as a double cylinder.

[0089] This reversing drum 71 is equivalent to the turning drum disclosed in, for example, Patent Document 2, and has a gripping member 72 that grips the rear end 4b, which is the end upstream in the conveying direction of the sheet 4 being conveyed by the pre-reversing double drum 35.

[0090] As the reversing cylinder 71 rotates with the gripping members 72 gripping the rear end of the sheet 4, the sheet 4 is conveyed toward the supply cylinder 15 with the rear end 4b of the sheet 4 positioned downstream in the conveyance direction. The sheet 4 conveyed in this manner is handed over from the gripping members 72 to the gripper device 21 of the supply cylinder 15. As the sheet 4 is conveyed by the supply cylinder 15, the front side of the sheet 4 is exposed to the outside of the supply cylinder 15. Therefore, the sheet 4 conveyed through the reversing mechanism 17 is conveyed from the supply cylinder 15 to the printing cylinder 16 in an inverted state.

[0091] Even if the reversing mechanism 17 is configured as shown in Figure 7, as in the first embodiment, in both single-sided printing and double-sided printing, the ink film thickness becomes smaller and the ink surface becomes flat, making it possible to impart a glossy appearance to the printed area.

[0092] In the first to third embodiments described above, an example was shown in which the pressing device was configured with the first pressing cylinder 41 and the second pressing cylinder 48. However, the pressing device is not limited to this and can be configured with one or more rollers.

[0093] (Fourth embodiment) In the above-described embodiments, examples have been shown in which the present invention is applied to a printing device capable of printing on both the front and back sides of a sheet, but the present invention can also be applied to a printing device that prints on only one side of a sheet. An example of a printing device having this configuration is shown in Figure 8. In Figure 8, components that are the same as or equivalent to those described in Figures 1 to 4 are designated by the same reference numerals, and detailed descriptions thereof will be omitted where appropriate.

[0094] 8 has a configuration in which the reversing mechanism 17 is removed from the printing apparatus 1 shown in the first embodiment. Therefore, the discharge drum 5 provided in this printing apparatus 81 does not have a switching mechanism for switching the destination of the sheet 4.

[0095] In the printing device 81 according to this embodiment, printing is performed on only one side of the sheet 4, and the entire printed sheet 4 is sent from the discharge cylinder 5 to the first discharge-side transfer cylinder 44. The sheet 4 is then pressed by the second pressure cylinder 48 while being transported by the first discharge-side transfer cylinder 44. Therefore, in the printing device 81 configured to perform only single-sided printing, the ink film thickness after printing can be reduced, and a glossy appearance can be imparted to the printed portion on the surface of the sheet 4.

[0096] Fifth Embodiment The sheet processing apparatus of the present invention can be applied to an offset printing apparatus as shown in Fig. 9. In Fig. 9, the same or equivalent members as those described in Figs. 1 to 4 and 8 are designated by the same reference numerals, and detailed description thereof will be omitted where appropriate.

[0097] An offset printing apparatus 91 shown in FIG. 9 is the printing apparatus 81 shown in the fourth embodiment, except that an offset printing unit 92 is provided as a printing device in place of the first to fourth inkjet heads 22 to 25.

[0098] The offset printing unit 92 includes an ink supply unit 94, a plate cylinder 93, and a blanket cylinder 95. The ink supply unit 94 supplies ink to the plate cylinder 93. The plate cylinder 93 supplies the ink from the ink supply unit 94 to the blanket cylinder 95. The blanket cylinder 95 sandwiches the sheet 4 between itself and the printing cylinder 16, and transfers the ink from the plate cylinder 93 to the sheet 4.

[0099] In the printing device 91 according to this embodiment, printing is performed by offset printing on only one side of the sheet 4, and the printed sheet 4 passes near the ink drying device 27 and is sent from the discharge cylinder 5 to the first discharge-side transfer cylinder 44 in a state where the ink is dried. Then, this sheet 4 is pressed by the second pressure cylinder 48 while being transported by the first discharge-side transfer cylinder 44. Therefore, in the printing device 91 configured to perform single-sided printing by offset printing, the ink film thickness after printing can be reduced, and a glossy appearance can be imparted to the printed portion on the surface of the sheet 4.

[0100] In addition, in the printing apparatuses according to the first to third embodiments, the offset printing unit 92 can be used in place of the first to fourth inkjet heads 22 to 25.

[0101] (Sixth embodiment) The sheet processing apparatus of the present invention can be applied to a coating apparatus that coats a sheet held by a conveying device with varnish, as shown in Fig. 10. In Fig. 10, the same or equivalent members as those described in Figs. 1 to 4 and 8 are designated by the same reference numerals, and detailed descriptions thereof will be omitted where appropriate.

[0102] 10 is the printing apparatus 81 shown in the fourth embodiment, except that a coating unit 102 is provided in place of the first to fourth inkjet heads 22 to 25. The coating unit 102 includes a coater cylinder 103 that abuts against the printing cylinder 16, and a varnish supply cylinder 104 that supplies varnish to the coater cylinder 103.

[0103] In this coating apparatus 101, as the sheet 4 being transported by the printing cylinder 16 passes between the coater cylinder 103 and the printing cylinder 16, the varnish is transferred from the coater cylinder 103 to the surface of the sheet 4, and the surface of the sheet 4 is coated with varnish. After this coating, the sheet 4 passes near the ink drying device 27, and the varnish is dried before it is sent from the discharge cylinder 5 to the first discharge-side transfer cylinder 44. Then, while being transported by the first discharge-side transfer cylinder 44, the sheet 4 is pressed by the second pressure cylinder 48. Therefore, in the coating apparatus 101 that performs varnish coating, the thickness of the varnish film after coating can be reduced, and a gloss is imparted to the coated portion of the surface of the sheet 4.

[0104] It is also possible to configure a coating device by providing a coating unit 102 in place of the first to fourth inkjet heads 22 to 25 of the printing device in the first to third embodiments.

[0105] Seventh Embodiment In the first to sixth embodiments described above, the thickness of the deposits such as ink and varnish is reduced and a glossy finish is imparted by pressing the deposits with the first and second pressing cylinders 41 and 48. However, it is also possible to reduce the thickness of the deposits while suppressing the appearance of a glossy finish.

[0106] Fig. 11 shows the configuration of a printing apparatus according to this embodiment. In Fig. 11, components that are the same as or equivalent to those described with reference to Figs. 1 to 4 are given the same reference numerals, and detailed descriptions thereof will be omitted where appropriate.

[0107] The printing apparatus 111 shown in FIG. 11 differs from the printing apparatus 1 shown in FIG. 1 in the configuration of the first and second pressure cylinders. In the printing apparatus 1, the outer peripheral surfaces 41 a, 48 a of the first and second pressure cylinders 41, 48 are formed smoothly throughout. In contrast, in the printing apparatus 111 according to this embodiment, the outer peripheral surfaces 141 a, 148 a of the first and second pressure cylinders 141, 148 are formed rough throughout. For example, the outer peripheral surfaces 141 a, 148 a can have an arithmetic mean roughness Ra (surface roughness) similar to the arithmetic mean roughness Ra (surface roughness) of the surface of the sheet 4. When the sheet 4 is an absorbent medium that absorbs ink, such as plain paper, it is desirable for the arithmetic mean roughness of the outer peripheral surfaces 141 a, 148 a of the first and second pressure cylinders 141, 148 to be within ±30% of the arithmetic mean roughness of the sheet 4. In terms of abrasive paper standards, it is desirable that the outer peripheral surfaces 141 a, 148 a of the first and second pressing cylinders 141, 148 have an abrasive grain size of 20 μm or less, particularly 15 μm to 10 μm (in the case of JIS (Japanese Industrial Standards), #800 or more, particularly #1000 to #2000; in the case of FEPA (Federation of European Producers of Abrasives) standards, P1000 or more, particularly P1200 to P2400).

[0108] The first pressure cylinder 141 presses the printed surface (front side) of the sheet 4 being transported by the reversing-side transfer cylinder 33. The second pressure cylinder 148 presses the printed surface (back side) of the sheet 4 being transported by the first discharging-side transfer cylinder 44. Hardened ink is adhered to the printed surfaces (front and back sides) of the sheet 4 in a state where it protrudes from the surface of the sheet 4. This ink is forced into the interior of the sheet 4 by the outer circumferential surfaces 141 a, 148 a of the pressure cylinders 141, 148 being pressed against them. This makes it possible to reduce the thickness of the ink film exposed on the surface of the sheet 4.

[0109] Furthermore, when the ink is pressed by the pressure cylinders 141, 148, the shape of the outer peripheral surfaces 141 a, 148 a of the pressure cylinders 141, 148 is transferred to the surface (upper surface) of the ink. This roughens the ink surface to a predetermined roughness, imparting a matte finish to the printed portion on the surface of the sheet 4. Therefore, according to this embodiment, even if the ink film thickness is reduced, it is possible to suppress the appearance of a glossy finish and achieve a desirable matte finish.

[0110] Here, an example has been described in which the first and second pressure cylinders 141, 148 having rough surfaces are applied to the printing apparatus 1 according to the first embodiment. However, it is also possible to apply the second pressure cylinder 148 (and the first pressure cylinder 141) having a rough surface to the printing apparatus according to the second to fifth embodiments or the coating apparatus according to the sixth embodiment.

[0111] (Another Example of Adjusting Pressing Force) In the above-described embodiments, the pressing force applied by the first and second pressing cylinders 41, 48 to press the sheet 4 is adjusted by changing the centerline distance between the first and second pressing cylinders 41, 48 and the reverse-side transfer cylinder 33, the first discharge-side transfer cylinder 44, the second discharge-side transfer cylinder 46, etc. This pressing force can be automatically adjusted by changing the centerline distance using an actuator (not shown). In this case, the operation of the actuator is controlled according to the thickness of the printing substrate (e.g., paper) constituting the sheet 4 and the density of the printed image. The operation of the actuator is controlled by the controller 13. The controller 13 previously stores data (tables, functions) indicating the relationship between the centerline distance and parameters such as the printing substrate and image density. The controller 13 references this data to determine the centerline distance corresponding to the thickness of the printing substrate and the density of the image input during print settings, and controls the actuator to achieve this centerline distance. For example, if the printing substrate is thick, or if the image is dark and the ink film is thick, the pressing force can be increased by operating the actuator so that the above-mentioned axis distance is shortened.

[0112] 1, 61, 81, 111...printing device, 4...sheet, 5...discharge cylinder (transport path switching device), 13...controller, 16...printing cylinder (transport device), 17...inverting mechanism, 18...discharge mechanism, 22-25...first to fourth inkjet heads (print heads), 27...ink drying device, 33...reversing side transfer cylinder, 35...pre-reversing double cylinder (pre-reversing cylinder), 37...reversing swing device (reversing device), 41, 141...first pressure cylinder (first pressure device), 44...first discharge side transfer cylinder, 46...second discharge side transfer cylinder, 47...discharge belt (discharge device), 48, 148...second pressure cylinder (second pressure device), 71...reversing cylinder (inverting device), 91...offset printing device, 101...coating device.

Claims

1. A sheet processing apparatus comprising: a conveying device configured to hold and convey a sheet; a processing device configured to process the sheet held by the conveying device; and a pressing device arranged downstream of the processing device in the sheet conveying direction and configured to press the processing surface of the sheet processed by the processing device.

2. A sheet processing apparatus as described in claim 1, wherein the processing device includes a printing device configured to apply ink to the sheet held by the conveying device, and an ink drying device arranged downstream of the printing device in the sheet conveying direction and configured to dry the ink applied to the sheet.

3. The sheet processing apparatus of claim 2, wherein the printing device includes a plurality of printheads configured to eject the ink onto the sheet.

4. A sheet processing apparatus as described in claim 1, wherein the processing device includes a coating device configured to coat the sheet held by the conveying device with varnish, and an ink drying device arranged downstream of the coating device in the sheet conveying direction and configured to dry the varnish coating the sheet.

5. The sheet processing device according to any one of claims 1 to 4, wherein the sheet processing device is configured to be able to selectively perform double-sided processing, which processes both sides of the sheet, and single-sided processing, which processes only one side of the sheet, and the pressing device includes a first pressing device configured to press a first processed side of the processed sides of the sheet that has been processed first when performing the double-sided processing, and a second pressing device configured to press a second processed side of the processed sides of the sheet that has been processed last when performing the double-sided processing, and to press the processed side of the sheet when performing the single-sided processing.

6. A sheet processing apparatus according to claim 5, further comprising: a reversing mechanism configured to reverse the sheet processed by the processing device and return it to the conveying apparatus; a discharge mechanism configured to discharge the sheet processed by the processing device; a transport path switching device disposed between the conveying apparatus, the reversing mechanism, and the discharge mechanism, and configured to receive the sheet processed by the processing device from the conveying apparatus and transport the sheet to the reversing mechanism or the discharge mechanism; and a controller connected to the transport path switching device and configured to control the transport path switching device to switch the destination of the sheet, wherein the controller is configured to: when the single-sided processing is selected, transport the sheet processed on only one side to the discharge mechanism; and when the double-sided processing is selected, transport the sheet processed on only one side to the reversing mechanism and transport the sheet processed on both sides to the discharge mechanism.

7. The sheet processing apparatus according to claim 6, wherein the first pressing device is disposed in the reversing mechanism, and the second pressing device is disposed in the discharging mechanism.

8. The sheet processing apparatus according to claim 6, wherein the first pressing device and the second pressing device are disposed in the discharge mechanism.

9. A sheet processing device as described in claim 6, wherein the reversing mechanism includes a reversing side transfer drum configured to receive the sheet from the transport path switching device, a front reversing drum configured to receive the sheet from the reversing side transfer drum, and a reversing device configured to grab the upstream end of the sheet transported to the front reversing drum in the sheet transport direction and return it to the transport device.

10. A sheet processing device as described in claim 6, wherein the discharge mechanism includes: a first discharge side transfer cylinder configured to receive the sheet from the transport path switching device; a second discharge side transfer cylinder configured to receive the sheet from the first discharge side transfer cylinder; and a discharge device that receives the sheet from the second discharge side transfer cylinder and discharges the sheet.

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