Sheet processing device

Abstract

This sheet processing device (1) is provided with: a printing cylinder (33) which conveys a sheet (S1) having a front end held by a gripping claw device (33A-33C); a processing device (34) which faces the peripheral surface of the printing cylinder (33) and processes a surface of the sheet (S1) being conveyed by the printing cylinder (33); a standby unit (52) which holds the processed sheet (S1) in standby; and a return cylinder (40) which delivers the trailing end of the sheet (S1) held in standby in the standby unit (52) to the gripping claw device (33A-33C) of the printing cylinder (33) so that the processed surface of the sheet (S1) is in contact with the peripheral surface of the printing cylinder (33). As a result, it is possible to achieve a sheet processing device (1) having a simpler and smaller configuration than before.

Description

Sheet Processing Device

[0001] The present invention relates to a sheet processing apparatus having a reversing mechanism for reversing the front and back sides of a sheet.

[0002] There is a sheet-fed rotary printing press that has a sheet reversing mechanism for printing the back side of a sheet after printing the front side of the sheet. This sheet-fed rotary printing press is equipped with a reversing mechanism that reverses the sheet between adjacent printing units, and is capable of single-sided printing and double-sided printing.

[0003] In the sheet-fed rotary printing press disclosed in Patent Document 1, the reversing mechanism comprises a transfer cylinder (reference numeral 17 in Figure 4 of Patent Document 1) and an impression cylinder (reference numeral 16 in Figure 4 of Patent Document 1), and when performing double-sided printing, the transfer cylinder grasps the leading edge of the sheet while it is being transported, and the impression cylinder grasps the trailing edge of the sheet, changing the transport direction of the sheet for transport.

[0004] Special Publication No. 03-080108

[0005] However, the sheet-fed rotary printing press disclosed in Patent Document 1 has separate configurations for printing the front and back sides, and has the problem of being large in size because the entire device is long in a straight line.

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet processing apparatus having a simpler and smaller structure than conventional ones.

[0007] One aspect of the present invention is a sheet conveying device including a first gripper device configured to grip a top-bottom edge of a sheet, the first gripper device configured to transport the sheet with the edge gripped by the first gripper device; a processing device disposed outside the first gripper device so as to face the circumferential surface of the first gripper device and configured to process the surface of the sheet being conveyed by the first gripper device; a discharge device configured to discharge the processed sheet; and a waiting device configured to receive the processed sheet from the first edge, which is the edge gripped by the first gripper device. The sheet processing apparatus includes a standby section configured to hold the sheet in a standby position; a distribution mechanism configured to selectively distribute the sheet from the first cylinder to the discharge device or the standby section; and an inverting device including a second gripper device configured to grip a second end of the sheet waiting in the standby section, the second end being the end in the vertical direction that was not gripped by the first gripper device, and configured to deliver the second end of the sheet to the first gripper device of the first cylinder so that the surface processed by the processing device contacts the circumferential surface of the first cylinder. This configuration allows for a reduction in the number of cylinders used by using a standby section for holding the sheet and a conveying section for conveying the sheet from the first cylinder to the standby section. Furthermore, the first cylinder can be reused to process inverted sheets. This simplifies the configuration, allowing for a sheet processing apparatus with a simpler and more compact configuration than conventional ones.

[0008] The sheet processing apparatus may further include a first adjustment device configured to adjust the position of the second end of the sheet in the standby section. By adjusting the position of the sheet in the standby section with the first adjustment device, even if the sheet size changes, the sheet can be reliably inverted to match the sheet size.

[0009] The waiting section may include a belt configured to transport the sheet. One embodiment of the first adjustment device includes a stopper disposed on the belt to abut against the first end of the sheet. This allows the sheet to be transported using the belt, and the position of the sheet in the waiting section to be adjusted by the stopper.

[0010] The stopper may be movable in the sheet conveying direction.

[0011] The belt may be inclined downward as it approaches the position of the stopper.

[0012] The standby section may further include a guide cover disposed opposite to a surface of the belt on which the sheet is placed.

[0013] Another embodiment of the first adjustment device includes a pair of rollers configured to sandwich both sides of the sheet and having a rotation axis extending in a direction perpendicular to the sheet conveyance direction, a motor configured to rotate at least one of the pair of rollers, and a controller configured to control the motor based on the size of the sheet. By controlling the motor that rotates the pair of rollers that sandwich the sheet to adjust the position of the sheet in the waiting section, it is possible to reliably flip the sheet to match the sheet size even if the sheet size changes.

[0014] This embodiment may further include a first sensor configured to detect the length of the sheet in the transport direction and output the detected length to the controller.

[0015] The sheet processing device may further include a second adjustment device configured to adjust the position of a side edge in the width direction of the sheet before the sheet is gripped by the second gripper device in the waiting section, thereby enabling widthwise registration adjustment when processing the other side of the inverted sheet.

[0016] One embodiment of the second adjustment device includes a pair of rollers configured to be able to move toward and away from each other and having a rotation axis extending in a direction parallel to the conveying direction of the sheet; a motor configured to rotate the pair of rollers while the pair of rollers sandwich both sides of the sheet; and a side contact positioned to abut against the side edge of the sheet that moves in a direction perpendicular to the conveying direction due to the rotation of the pair of rollers.

[0017] Another embodiment of the second adjustment device includes a pair of rollers configured to pinch both sides of the sheet and having a rotation axis extending in a direction perpendicular to the conveying direction of the sheet; an adjustment mechanism configured to adjust the axial position of the pair of rollers; and a controller configured to control the adjustment mechanism based on the position of the side edge of the sheet.

[0018] This embodiment may further include a second sensor configured to sense the position of the side edge of the sheet.

[0019] The sheet processing device may further include a second cylinder that faces the first cylinder and includes a third gripper device configured to receive the processed sheet from the first cylinder and is configured to transport the sheet gripped by the third gripper device; and a front reversing cylinder that faces the second cylinder and includes a fourth gripper device configured to receive the sheet from the second cylinder and is configured to transport the sheet gripped by the fourth gripper device. The sorting mechanism may be formed by the second cylinder. The belt may be configured to receive the sheet being transported by the front reversing cylinder. With this configuration, the sheet is transported from the second cylinder to a waiting section by the front reversing cylinder and the belt, and the belt also serves as the waiting section, thereby simplifying the configuration of the sheet processing device.

[0020] The reversing device may include a guide member configured to lift the second end of the sheet waiting in the waiting section and deliver the sheet to the second gripper device. By lifting the second end of the sheet in the waiting section, the sheet can be reliably delivered to the second gripper device of the reversing device.

[0021] The waiting section may include a belt configured to transport the sheet. The inverting device may include an upper roller arranged above the belt, and a lower roller arranged below the belt, movable vertically, configured to lift the sheet together with the belt, and to sandwich the sheet together with the upper roller. The upper roller and the lower roller are configured to rotate in a direction in which the sheet moves toward the second gripper device.

[0022] The upper roller and the lower roller may be disposed at positions corresponding to the second end of the sheet waiting in the waiting section.

[0023] The reversing device may further include a return cylinder that includes the second gripper device and is in contact with the first cylinder.

[0024] The inverting device may further include a guide disposed above the belt and configured to guide the sheet, the second end of which has been lifted by the lower roller, to the second gripper device.

[0025] The guide may include an upper guide and a lower guide each made up of two plate-like members facing each other.

[0026] The belt may be inclined downward with increasing distance from the positions of the upper roller and the lower roller.

[0027] The sheet processing device may further include a second cylinder configured to transport the sheet gripped by the third gripper device, a first guide extending from the second cylinder to the discharge device, and a second guide branching from the first guide to the belt. The belt may be configured to receive the sheet being transported by the second guide.

[0028] The first guide may include an upper guide and a lower guide each made of two opposing plate-like members. The second guide may include an upper guide and a lower guide each made of two opposing plate-like members. The second guide may include a semicircular portion.

[0029] The first guide may include a first roller configured to transport the sheet from the second cylinder to the discharge device, and the second guide may include a second roller configured to transport the sheet from the second cylinder to the belt.

[0030] One example of the sorting mechanism is the second cylinder. In this case, the sheet can be sorted to the first guide or the second guide depending on the timing when the third gripper device of the second cylinder releases the sheet. If the second guide branches downward from the first guide, the third gripper device can release the sheet at the latest before the second end of the sheet gripped by the third gripper device passes the branch point between the first and second guides, thereby sorting the sheet to the second guide. On the other hand, the third gripper device can release the sheet after the second end of the sheet gripped by the third gripper device passes the branch point between the first and second guides, thereby sorting the sheet to the first guide.

[0031] Another example of the sorting mechanism is a plate provided at the branch point between the first guide and the second guide and configured to selectively block the first guide and the second guide.

[0032] According to one aspect of the present invention, by using a standby section for waiting sheets and a transport section for transporting sheets from the first cylinder to the standby section, the number of cylinders used can be reduced. Also, the first cylinder can be used again to process inverted sheets. This simplifies the configuration and realizes a sheet processing apparatus with a simpler and smaller configuration than conventional ones.

[0033] FIG. 1 is a side view showing the overall configuration of a digital printing apparatus according to a first embodiment of the sheet processing apparatus of the present invention. FIG. 2 is a side view showing an enlarged view of the return cylinder and the vicinity of the guide roller. FIG. 3 is a side view showing a sheet transport process (1). FIG. 4 is a side view showing a sheet transport process (2). FIG. 5 is a side view showing a sheet transport process (3). FIG. 6 is a side view showing a sheet transport process (4). FIG. 7 is a side view showing a sheet transport process (5). FIG. 8 is a side view showing a sheet transport process (6). FIG. 9 is a side view showing a sheet transport process (7). FIG. 10 is a side view showing the overall configuration of a digital printing apparatus according to a second embodiment of the sheet processing apparatus of the present invention. FIG. 11 is a side view showing the configuration of an upper guide and a lower guide. FIG. 12 is a side view showing a sheet transport process (1). FIG. 13 is a side view showing a sheet transport process (2). FIG. 14 is a side view showing a sheet transport process (3). FIG. 15 is a side view showing a sheet transport process (4). Fig. 16 is a side view showing a sheet conveying step (5). Fig. 17 is a side view showing a sheet conveying step (6). Fig. 18 is a side view showing a sheet conveying step (7). Fig. 19 is a side view showing a pair of nip rollers constituting a part of the first adjusting device and the second adjusting device. Fig. 20 is a block diagram showing another part of the configuration of the first adjusting device and the second adjusting device. Fig. 21A is a side view showing another mechanism of the upper guide and the lower guide. Fig. 21B is a side view showing another mechanism of the upper guide and the lower guide.

[0034] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0035] 1 shows the configuration of a digital printing apparatus 1, which is a first embodiment of the sheet processing apparatus of the present invention. The digital printing apparatus 1 includes a sheet feeder 2, a digital printing unit 3, and a sheet delivery 4 as a discharge device.

[0036] The sheet feeder 2 of the digital printing device 1 uses a sheet sucker 23 as a sheet supply device to suck up a single sheet S1 at the top of a sheet stack 22 stacked on a stacking plate 21, and the sheet sucker 23 then moves the sheet S1 to the feeder board FB and places it there, thereby sequentially supplying the sheets S1 one by one to the digital printing unit 3. The sheet sucker 23 is connected to a negative pressure source (not shown), and moves horizontally while sucking up the sheet S1 of the sheet stack 22 via a first suction 23A and a second suction 23B, and then releases the suction, thereby transporting the sheet S1 to the feeder board FB.

[0037] When a single-sided printing mode, in which only the front side of sheet S1 is printed, is selected, the sheet feeder 2 performs continuous feeding by continuously adsorbing sheet S1 using the sheet sucker 23 at predetermined time intervals and transporting it to the feeder board FB in accordance with commands from a controller consisting of a CPU (Central Processing Unit) (not shown). On the other hand, when a double-sided printing mode, in which both the front and back sides of sheet S1 are printed, is selected, the sheet feeder 2 performs intermittent feeding by adsorbing sheet S1 intermittently using the sheet sucker 23 at intervals of every other sheet, compared to the continuous feeding mode, and transporting it to the feeder board FB in accordance with commands from the controller (not shown). In this way, the digital printing device 1 can continuously feed sheets S1 one sheet at a time from the sheet feeder 2 to the digital printing unit 3, or can intermittently feed sheets S1.

[0038] The sheet S1 conveyed to the feeder board FB has its conveying position aligned in the top, bottom, left and right directions by a register device (not shown) at the leading edge FB1 of the feeder board.

[0039] The digital printing unit 3 of the digital printing device 1 includes a swing device 31 that receives the sheet S1 supplied from the feeder board FB with a claw portion (not shown), a supply cylinder 32 that grips a first end portion of the sheet S1 in the vertical direction (length direction) supplied by the swing device 31 with a gripper device 32A and then transfers the sheet to a printing cylinder 33 serving as a first cylinder, the printing cylinder 33 that grips the first end portion of the sheet S1 supplied from the supply cylinder 32 with one of three first gripper devices 33A, 33B, and 33C and rotates to transport the sheet S1 while adhering to its circumferential surface, a four-color inkjet nozzle unit 34 serving as a processing device that is located downstream of the supply cylinder 32 in the transport direction and opposite the circumferential surface of the printing cylinder 33, and a transfer cylinder 36 that is located downstream of the inkjet nozzle unit 34 in the transport direction and in contact with the printing cylinder 33.

[0040] Here, the supply cylinder 32 has one gripper device 32A and is large enough to transport one sheet S1 on its peripheral surface, while the printing cylinder 33 is a triple cylinder having three first gripper devices 33A, 33B, and 33C arranged at regular angular intervals and having a circumferential length equivalent to that of three of the largest sheets S1 expected to be connected together.

[0041] In addition, the printing cylinder 33 has a plurality of suction holes (not shown) formed at predetermined intervals across its entire circumferential surface, and is structured to transport the sheet S1 while holding it by suction from the inside through these plurality of suction holes.

[0042] The printing cylinder 33 sequentially grips the sheets S1 supplied one by one by the gripper device 32A of the supply cylinder 32 with the first gripper devices 33A, 33B, and 33C of the printing cylinder 33, and by rotating in the direction of the arrow (counterclockwise), sequentially transports the sheets S1 to the inkjet nozzle section 34.

[0043] The inkjet nozzle section 34 comprises a black inkjet nozzle head 34A, a cyan inkjet nozzle head 34B, a magenta inkjet nozzle head 34C, and a yellow inkjet nozzle head 34D, which are arranged in that order downstream in the conveying direction, and performs a digital printing process on the sheet S1 by ejecting and spraying minute droplets of ink onto the outer surface of the sheet S1 which is conveyed while being fully adsorbed to the circumferential surface of the printing cylinder 33.

[0044] In order to maintain a predetermined level of print quality, the gap between the inkjet nozzle heads 34A to 34D corresponding to each color of the inkjet nozzle section 34 and the sheet S1 that is fully attracted to the circumferential surface of the printing cylinder 33 must be set to a very small minimum gap. Therefore, the printing cylinder 33 attracts the entire sheet S1 to its circumferential surface, thereby maintaining the gap between the inkjet nozzle heads 34A to 34D and the sheet S1 that is attracted to the printing cylinder 33 at a very small minimum gap.

[0045] In the digital printing unit 3, a transfer cylinder 36 serving as a sorting mechanism is arranged downstream of the printing cylinder 33 in the conveying direction, facing the printing cylinder 33, a conveyor-like delivery belt DB for transporting the sheet S1 to the sheet delivery 4 is arranged downstream of the transfer cylinder 36 in the conveying direction, and a front reversal cylinder 39 is arranged downstream of the transfer cylinder 36 in the conveying direction, facing the transfer cylinder 36.

[0046] Therefore, when single-sided printing mode is selected, the transfer cylinder 36 in the digital printing unit 3 shifts the grip of the sheet S1, which is gripped by one of the first gripper devices 33A to 33C of the printing cylinder 33 and is entirely adsorbed on the circumferential surface of the printing cylinder 33, to the third gripper device 36A of the transfer cylinder 36, and then places the sheet S1 on the delivery belt DB, thereby sequentially discharging the sheet S1 via the delivery belt DB to the subsequent sheet delivery 4.

[0047] The sheet delivery 4 stacks the sheet S1 conveyed via the delivery belt DB onto a stacking plate 41, and discharges the sheet S1 after digital printing.

[0048] When a double-sided printing mode in which the back side of sheet S1 is to be printed is selected, the digital printing unit 3 digitally prints the front side of sheet S1 using the printing cylinder 33 and inkjet nozzle section 34, and then, instead of transferring sheet S1 to the delivery belt DB using the third gripper device 36A of the transfer cylinder 36, transfers the first end of sheet S1 from the third gripper device 36A of the transfer cylinder 36 to the fourth gripper device 39A of the front reversal cylinder 39.

[0049] The front reversing cylinder 39 grips the first end of the sheet S1 from the transfer cylinder 36 with the fourth gripper device 39A, and then passes the sheet S1 to a belt 64 located downstream in the conveyance direction of the front reversing cylinder 39. In the digital printing unit 3, a return cylinder 40 is located downstream in the conveyance direction of the transfer cylinder 36, in contact with the printing cylinder 33.

[0050] Next, we will explain the configuration of belt 64. One end of belt 64 is in contact with front reversing cylinder 39, and the other end forms standby section 52. Belt 64 is wound around drive rollers 62 and 68 disposed at both ends and driven roller 63 disposed near drive roller 62, and is configured to place sheet S1 conveyed from front reversing cylinder 39 on it.

[0051] A thin guide cover 61 is provided on the belt 64 so as to face the placement surface on which the sheet S1 is to be placed, and is spaced a small distance from the belt 64 and substantially parallel to the belt 64. This allows the belt 64 to convey the sheet S1 while suppressing flapping of the sheet S1 conveyed on the belt 64 via the drive rollers 62 and 68 by the guide cover 61.

[0052] A stopper 67 that stops the sheet S1 being conveyed by the belt 64 by contacting the first edge of the sheet S1 is attached near the drive roller 68. Therefore, the sheet S1 being conveyed by the belt 64 will eventually contact the stopper 67 and wait in the waiting section 52. At this time, because the drive rollers 62 and 68 continue to rotate, the sheet S1 continues to press the first edge (leading edge) of the sheet S1 against the stopper 67 while sliding on the belt 64. As a result, the top-bottom register of the sheet S1 is adjusted.

[0053] The stopper 67 is attached so as to be movable along the belt 64 in accordance with the length of the sheet S1 in the sheet conveying direction. That is, the longer the sheet S1, the closer the stopper 67 is attached to the drive roller 68, while the shorter the sheet S1, the closer the stopper 67 is attached to the return cylinder 40. Therefore, the standby position of the sheet S1 can be adjusted by changing the attachment position of the stopper 67.

[0054] At this time, the left-right (widthwise) register of the sheet S1 is adjusted by a side gauge device 67A serving as a second adjustment device provided between the stopper 67 and the upper guide 66A (described later). Although not shown in detail, the side gauge device 67A includes a pair of rollers that selectively pinch one of the left-right side edges of the sheet S1 and a side stopper located on the side of the sheet S1. The pair of rollers rotate around a rotation axis extending in a direction parallel to the conveyance direction of the sheet S1 and are configured to move toward and away from each other. More specifically, the pair of rollers separate from each other just before the sheet S1 arrives, pinch the sheet S1 when it enters between the rollers, and rotate by a motor to advance the sheet S1 toward the side stopper. The side stopper determines the position of the side edge of the sheet S1. The side edge of the sheet S1, driven by the pair of rollers and moved laterally, abuts against the side stopper, thereby adjusting the left-right register of the sheet S1.

[0055] In the belt 64, a guide roller 65 is disposed at a position corresponding to the rear end, which serves as the second end, of the sheet S1 when the conveyance of the sheet S1 remains inhibited by the stopper 67. The guide roller 65 has an upper drive roller 65A disposed above the belt 64 and a lower driven roller 65B disposed below the belt 64. When the conveyance of the sheet S1 described above remains inhibited, the second end of the sheet S1 is located between the upper drive roller 65A and the lower driven roller 65B.

[0056] Through holes are formed in the guide cover 61 at portions corresponding to the upper drive roller 65A and the lower driven roller 65B, so that the sheet S1 can be conveyed while being sandwiched between the upper drive roller 65A and the lower driven roller 65B and the belt 61.

[0057] The lower driven roller 65B is configured to be able to freely move upward with the second end of the sheet S1 positioned between the upper drive roller 65A and the lower driven roller 65B of the guide roller 65. As a result, with the second end of the sheet S1 sandwiched between the upper drive roller 65A and the lower driven roller 65B, the entire guide roller 65 is lifted above the placement surface of the belt 64, so that the second end of the sheet S1 is separated above the placement surface of the belt 64.

[0058] In practice, the upper drive roller 65A is configured to rotate so that, in synchronization with the gripping change timing in which the second end of sheet S1 is gripped by the second gripper device 40A of the return cylinder 40, the lower driven roller 65B of the guide roller 65 moves upward to lift the trailing end of sheet S1, thereby sandwiching the trailing end of sheet S1 between itself and the upper drive roller 65A, and transporting sheet S1 toward the second gripper device 40A of the return cylinder 40. At this time, the upper drive roller 65A may start rotating from a stopped state when it sandwiches sheet S1 between itself and the lower driven roller 65B, or it may be configured to rotate constantly. At this time, the drive rollers 62, 68 may continue to rotate or may stop rotating.

[0059] As a result, as shown in Figure 2, the belt 64 guides the rear end of the sheet S1, which is sandwiched between the upper drive roller 65A and the lower driven roller 65B, to the return drum 40.By inserting the rear end of the sheet S1 between the upper guide 66A and the lower guide 66B, the rear end of the sheet S1 is guided to the second gripper device 40A of the return drum 40 and is gripped by the second gripper device 40A.

[0060] The return cylinder 40 rotates clockwise in the direction of the arrow while holding the sheet S1 whose trailing edge is gripped by the second gripper device 40A, thereby transferring the sheet S1 in an inverted state from the front side to the back side to the printing cylinder 33. By using this transfer cylinder 40, the inverted sheet S1 gripped by the second gripper device 40A can be transferred again from the rear end to the printing cylinder 33 so that the front side that has been digitally printed by the printing cylinder 33 comes into contact with the circumferential surface of the printing cylinder 33.

[0061] In practice, in the digital printing unit 3, when the second gripper device 40A of the return cylinder 40 faces one of the first gripper devices 33A to 33C of the printing cylinder 33, the sheet S1 can be transferred from the return cylinder 40 to the printing cylinder 33, thereby transporting the inverted sheet S1 from the return cylinder 40 to the printing cylinder 33.

[0062] Thus, the digital printing unit 3 transports the sheet S1, which has been gripped by one of the first gripper devices 33A to 33C of the printing cylinder 33, back to the inkjet nozzle section 34 while adsorbing the entire surface of the sheet S1, performs digital printing processing on the back side of the sheet S1, and then passes it on to the delivery belt DB via the transfer cylinder 36, completing the double-sided printing process.

[0063] The belt device 60 is made up of the drive rollers 62 and 68, the driven roller 63, and the belt 64. Of the entire range of the belt 64 from the drive roller 62 to the drive roller 68, the conveying belt portion from the drive roller 62 to just before the guide roller 65 and the front reversal cylinder 39 make up the conveying unit 51. Of the entire range of the belt 64 from the drive roller 62 to the drive roller 68, the conveying belt portion from the guide roller 65 to the drive roller 68 makes up the waiting unit 52 for temporarily waiting the sheet S1 to be transferred from the return cylinder 40 to the printing cylinder 33. The conveying unit 51 and the waiting unit 52 are defined here for convenience's sake and are not necessarily limited thereto. For example, the conveying unit 51 can be defined so as not to include the front reversal cylinder 39.

[0064] As described above, the digital printing press 1 of this embodiment includes a printing cylinder 33 as a first cylinder configured to grip the top-bottom edges of a sheet S1 and transport the sheet S1 whose edges are gripped by the first gripper devices 33A to 33C; an inkjet nozzle unit 34 as a processing device disposed on the outside of the printing cylinder 33 so as to face the circumferential surface of the printing cylinder 33 and configured to process the surface of the sheet S1 being transported by the printing cylinder 33; a sheet delivery 4 as a discharge device configured to discharge the processed sheet S1; and a sheet delivery unit 4 as a discharge device configured to discharge the processed sheet S1. The apparatus includes a standby section (52) configured to receive the sheet S1 from the printing cylinder (33) starting from the first end, which is the end that has been gripped, and to hold the sheet S1 on standby; a distribution mechanism configured to selectively distribute the sheet S1 from the printing cylinder (33) to the sheet delivery (4) or the standby section (52); a second gripper device (40A) configured to grip the second end, which is the end in the top-bottom direction that has not been gripped by the first gripper devices (33A-33C) of the sheet S1 on standby in the standby section (52); and an inverting device configured to transfer the second end of the sheet S1 to the first gripper devices (33A-33C) of the printing cylinder (33) so that the surface that has been processed by the inkjet nozzle section (34) contacts the circumferential surface of the printing cylinder (33).

[0065] The digital printing machine 1 further includes a first adjustment device configured to adjust the position of the second end of the sheet S1 in the waiting section 52. The waiting section 52 includes a belt 64 configured to transport the sheet S1, and the first adjustment device includes a stopper 67 arranged to be contacted by the first end of the sheet S1 on the belt 64.

[0066] The digital printing press 1 further includes a side gripper device 67 as a second adjustment device configured to adjust the position of the side edge in the width direction of the sheet S1 before it is gripped by the second gripper device 40A in the standby section 52. The side gripper device 67 includes a pair of rollers configured to be able to move toward and away from each other and having rotation axes extending in a direction parallel to the sheet conveyance direction, a motor configured to rotate the pair of rollers while the pair of rollers sandwich both sides of the sheet, and a side stop arranged to come into contact with the side edge of the sheet S1 that moves in a direction perpendicular to the conveyance direction due to the rotation of the pair of rollers.

[0067] The digital printing press 1 further includes a transfer cylinder 36 as a second cylinder configured to convey the sheet S1 gripped by the third gripper device 36A, which is in contact with the printing cylinder 33 and configured to receive the processed sheet S1 from the printing cylinder 33; and a front reversing cylinder 39 configured to convey the sheet S1 gripped by the fourth gripper device 39A, which is in contact with the transfer cylinder 36 and configured to receive the sheet S1 from the transfer cylinder 36. The above-mentioned sorting mechanism is formed by the transfer cylinder 36. The above-mentioned belt 64 is configured to receive the sheet S1 being conveyed by the front reversing cylinder 39.

[0068] The above-described reversing device includes a guide member configured to lift the second end of sheet S1 waiting in waiting section 52 and deliver sheet S1 to second gripper device 40A. The guide member includes lower driven roller 65B, upper guide 66A, and lower guide 66B.

[0069] The above-mentioned reversing device includes an upper drive roller 65A as an upper roller arranged above the belt 64; a lower driven roller 65B as a lower roller arranged below the belt 64, movable vertically, and configured to lift the sheet S1 together with the belt 64 and sandwich the sheet S1 together with the upper drive roller 65A; a return cylinder 40 that includes the above-mentioned second gripper device 40A and faces the printing cylinder 33; and a guide arranged above the belt 64 and configured to guide the sheet S1, whose second end has been lifted by the lower driven roller 65B, to the second gripper device 40A. The guide includes an upper guide 66A and a lower guide 66B made of two opposing plate-shaped members. The upper drive roller 65A and the lower driven roller 65B are configured to rotate in a direction in which the sheet S1 moves toward the second gripper device 40A (return cylinder 40). The upper drive roller 65A and the lower driven roller 65B are disposed at positions corresponding to the second end of the sheet S1 waiting in the waiting section 52. The belt 64 is inclined downward as it moves away from the positions of the upper drive roller 65A and the lower driven roller 65B.

[0070] Next, we will explain the operation of the digital printing unit 3. When the double-sided printing mode is selected, as shown in Figure 3, the leading edge of the sheet S1 gripped by the gripper device 32A of the supply cylinder 32 is re-gripped by, for example, the first gripper device 33A of the printing cylinder 33.

[0071] As shown in FIG. 4, the printing cylinder 33 rotates counterclockwise, and the sheet S1 held by the first gripper device 33A is transferred to the third gripper device 36A of the transfer cylinder 36.

[0072] 5, when the third gripper device 36A of the transfer cylinder 36 and the fourth gripper device 39A of the front reversing cylinder 39 face each other, the sheet S1 is transferred from the transfer cylinder 36 to the front reversing cylinder 39. At the same time, a new sheet S1 next intermittently fed by the supply cylinder 32 is held by the first gripper device 33C of the printing cylinder 33.

[0073] 6, the sheet S1 held by the fourth gripper device 39A of the front reversing cylinder 39 is placed on the belt 64. At this time, the printing cylinder 33 conveys the next sheet S1, which was previously held by the first gripper device 33C, while adsorbing it to its peripheral surface.

[0074] As shown in FIG. 7, the sheet S1 placed on the belt 64 is conveyed by the belt 64 to the waiting section 52 through the lower guide 66B, and the leading end of the sheet S1 is brought into contact with the stopper 67, and the horizontal needle device 67A is operated to perform register adjustment.

[0075] 8, in synchronization with the arrival of the second gripper device 40A of the return cylinder 40 for gripping change, the lower driven roller 65B rises and lifts the rear end of the sheet S1, which has been held by the stopper 67 of the standby section 52, above the conveyor belt 64 and sandwiches it between the upper drive roller 65A, which then rotates to transport the sheet S1 toward the second gripper device 40A of the return cylinder 40. The sheet S1 is passed between the upper guide 66A and the lower guide 66B, and the rear end of the sheet S1 is gripped by the second gripper device 40A of the return cylinder 40. The sheet S1 is then gripped from the second gripper device 40A of the return cylinder 40 to the first gripper device 33C of the printing cylinder 33.

[0076] 9, the sheet S1 is already inverted to its back side when it is transferred from the return cylinder 40 to the printing cylinder 33, and is then conveyed by the printing cylinder 33. Therefore, the back side of the sheet S1 conveyed again by the printing cylinder 33, which has printed on its front side, can be digitally printed by the inkjet nozzle unit 34.

[0077] As described above, in the digital printing unit 3 of the digital printing device 1, the surface of the sheet being transported by the printing cylinder 33 is digitally printed by the inkjet nozzle section 34, and then the sheet S1 is transferred to the belt 64 via the transfer cylinder 36 and the front reversal cylinder 39. The sheet S1 is transported via the belt 64 to the conveying section 51 and the waiting section 52, where the end (front end) of the sheet S1 is abutted against the stopper 67 of the waiting section 52, and the horizontal needle device 67A is operated to adjust the waiting position of the sheet S1, i.e., to perform a register adjustment.

[0078] Then, in accordance with the gripping change timing when the second gripper device 40A of the return drum 40 approaches the rear end of the sheet S1, the lower driven roller 65B rises and lifts the rear end of the sheet S1 above the conveying belt 64, sandwiching it between the upper drive roller, and the upper drive roller 65A of the guide roller 65 rotates to transport the sheet S1 toward the second gripper device 40A of the return drum 40.

[0079] As a result, the digital printing unit 3 can reliably guide the sheet S1 from the guide roller 65 to the second gripper device 40A of the return cylinder 40 via the upper guide 66A and the lower guide 66B, have the second gripper device 40A grip the trailing edge of the sheet S1, and transfer the grip of the sheet S1 from the second gripper device 40A of the return cylinder 40 to the first gripper devices 33A to 33C of the printing cylinder 33. Therefore, the sheet S1 can be transported again to the printing cylinder 33 while maintaining its register-adjusted state.

[0080] Thus, the digital printing unit 3 can perform digital printing processing on the back side of the sheet S1 after register adjustment has been performed via the printing cylinder 33 and the inkjet nozzle unit 34. This can prevent misalignment between the print results on the front side and the back side, improving the print quality on both the front and back sides of the sheet S1.

[0081] Furthermore, the digital printing unit 3 can reuse the printing cylinder 33 and inkjet nozzle unit 34 that have been used to perform digital printing on the front side of the sheet S1 to also perform digital printing on the back side of the sheet S1. Therefore, since the printing cylinder 33 and inkjet nozzle unit 34 can be used for digital printing on both the front and back sides, double-sided printing on the sheet S1 can be performed with high precision without increasing the size of the entire device.

[0082] [Second embodiment] Fig. 10 shows the configuration of a digital printing apparatus 100, which is a second embodiment of the sheet processing apparatus of the present invention. In Fig. 10, parts that are the same as or correspond to those in Fig. 1 are given the same reference numerals, and their description will be omitted as appropriate.

[0083] The digital printing apparatus 100 includes a sheet feeder 2, a digital printing unit 3, and a sheet delivery 4 as a discharge device. The digital printing apparatus 100 differs from the digital printing apparatus 100 shown in Figure 1 mainly in the configuration from the transfer cylinder 36 to the return cylinder 40, i.e., the configuration of the conveying section, standby section, and reversing device.

[0084] In the digital printing unit 3, a transfer cylinder 36 serving as a distribution mechanism in contact with the printing cylinder 33 is arranged downstream in the conveying direction from the printing cylinder 33, and an auxiliary cylinder 36B in contact with the transfer cylinder 36 is arranged downstream in the conveying direction from the transfer cylinder 36.

[0085] Between the transfer cylinder 36 and the auxiliary cylinder 36B, there are provided upper and lower guides 71 and 72, which are made of thin plates formed in a horizontally linear shape in a side view, for guiding and transporting the sheet S1 transported by the transfer cylinder 36 to the sheet delivery 4. In the digital printing unit 3, a return cylinder 40 is disposed downstream of the transfer cylinder 36 in the transport direction, in contact with the printing cylinder 33.

[0086] 11 , an upper guide 84 and a lower guide 85, which are curved in a semicircular shape in a side view, branch off from the middle of the upper guide 71 and the lower guide 72 provided between the transfer cylinder 36 and the auxiliary cylinder 36B. The sheet S1 is discharged to the sheet delivery 4 via the upper guide 71 and the lower guide 72, and is conveyed from the upper guide 71 and the lower guide 72 to the conveying section 151 via the upper guide 84 and the lower guide 85.

[0087] Nip rollers 73A and 73B and nip rollers 74A and 74B are provided between the upper guide 71 and the lower guide 72, with the sheet S1 sandwiched therebetween, for transporting the sheet S1 from the transfer cylinder 36 to the sheet delivery 4. The nip rollers 73B and 74B provided on the lower side are driven to rotate counterclockwise by a motor (not shown), and the nip rollers 73A and 74A in contact with the nip rollers 73B and 74B are rotated accordingly.

[0088] Through holes are formed in the upper guide 71 and the lower guide 72 at locations corresponding to the two pairs of nip rollers 73A and 73B, and 74A and 74B. Therefore, the two pairs of nip rollers 73A and 73B, 74A and 74B do not interfere with the upper guide 71 and the lower guide 72, and the sheet S1 can be conveyed while being sandwiched between the nip rollers 73A and 73B, and 74A and 74B.

[0089] The upper guide 84 and the lower guide 85 are made of thin plates that are curved in a semicircular shape and then extend in a substantially linear shape in a side view. The upper guide 84 and the lower guide 85 are provided with nip rollers 75A and 75B, nip rollers 76A and 76B, nip rollers 77A and 77B, nip rollers 78A and 78B, and guide rollers 65 (upper drive roller 65A and lower driven roller 65B) for conveying the sheet S1 from the transfer cylinder 36 with the sheet S1 sandwiched therebetween.

[0090] Here, the nip rollers 75B, 76B, 77B, and 78B provided on the lower side and the upper drive roller 65A are driven to rotate clockwise by a motor (not shown), while the nip rollers 75B, 76B, 77B, and 78B, the nip rollers 75A, 76A, 77A, and 78A in contact with the upper drive roller 65A, and the lower driven roller 65B are driven to rotate.

[0091] Similar to the upper guide 71 and the lower guide 72, the upper guide 84 and the lower guide 85 also have through holes formed at locations corresponding to the pairs of nip rollers 75A and 75B, 76A and 76B, 77A and 77B, 78A and 78B, and the guide roller 65 (upper drive roller 65A and lower driven roller 65B). This allows the sheet S1 to be conveyed while being sandwiched between the nip rollers 75A and 75B, 76A and 76B, 77A and 77B, 78A and 78B, and the guide roller 65 (upper drive roller 65A and lower driven roller 65B) without interference between the nip rollers 75A and 75B, 76A and 76B, 77A and 77B, 78A and 78B, and the upper guide 84 and the lower guide 85.

[0092] The upper guide 84 and the lower guide 85 extend to the vicinity of the drive roller 80 of the belt 87. The upper guide 84 and the lower guide 85 are inclined slightly downward from the nip rollers 78A, 78B toward the belt 87.

[0093] The belt 87 is wound around drive rollers 80 and 81 arranged along the extension lines of the upper guide 84 and the lower guide 85, and a driven roller 82 arranged near the drive roller 80, and the sheet S1 transported via the upper guide 84 and the lower guide 85 is placed on top of the belt 87.

[0094] A thin guide cover 86 is provided on the belt 87 so as to face the placement surface on which the sheet S1 is to be placed, and is substantially parallel to the belt 87 at a small distance from the belt 87. This allows the guide cover 86 to suppress flapping of the sheet S1 transported on the belt 87 via the drive rollers 80 and 81.

[0095] A stopper 67 is provided for stopping the sheet S1 in place by contacting the first end of the sheet S1 being conveyed by the belt 87. As a result, the sheet S1 being conveyed by the rotation of the belt 87 via the drive rollers 80 and 81 contacts the stopper 67 and waits in a waiting section 152 on the belt 87. At this time, because the drive rollers 80 and 81 continue to rotate, the first end (leading edge) of the sheet S1 continues to be pressed against the stopper 67 while the sheet S1 slides on the belt 87. As a result, the top-bottom register of the sheet S1 is adjusted.

[0096] The stopper 67 is attached so as to be movable along the belt 87 in accordance with the length of the sheet S1 in the sheet conveying direction. That is, the longer the sheet S1, the closer the stopper 67 is attached to the drive roller 81, whereas the shorter the sheet S1, the closer the stopper 67 is attached to the drive roller 80. Therefore, the standby position of the sheet S1 can be adjusted by changing the attachment position of the stopper 67.

[0097] At this time, the left-right register of the sheet S1 is adjusted by a horizontal needle device 67A provided between the stopper 67 and the upper drive roller 65A.

[0098] In the belt 87, a guide roller 65 is disposed at a position corresponding to the rear end of the sheet S1 when the conveyance of the sheet S1 is restricted by the stopper 67. The guide roller 65 has an upper drive roller 65A disposed above the belt 64 and a lower driven roller 65B disposed below the belt 64. When the conveyance of the sheet S1 is restricted as described above, the rear end of the sheet S1 is positioned between the upper drive roller 65A and the lower driven roller 65B.

[0099] In this embodiment, the upper guide 84 and the lower guide 85 extend to the vicinity of the drive roller 80. The upper guide 84 and the lower guide 85 are separate from the belt 87, but the gap between them is extremely small. Therefore, when the front end as the first end of the sheet S1 abuts against the stopper 67, the rear end as the second end of the sheet S1 is located between the upper drive roller 65A and the lower driven roller 65B.

[0100] The lower driven roller 65B is configured to be able to freely move upward in a state in which the second end of the sheet S1 is positioned between the upper drive roller 65A and the lower driven roller 65B of the guide roller 65. As a result, with the second end of the sheet S1 sandwiched between the upper drive roller 65A and the lower driven roller 65B, the lower driven roller 65B is lifted above the placement surface of the belt 64, and the second end of the sheet S1 is separated above the placement surface of the belt 87.

[0101] In practice, the upper drive roller 65A is configured to rotate so that, in synchronization with the gripping change timing when the second end of sheet S1 is gripped by the second gripper device 40A of the return cylinder 40, the lower driven roller 65B of the guide roller 65 moves upward to lift the trailing end of sheet S1, thereby sandwiching the trailing end of sheet S1 between itself and the upper drive roller 65A, and transporting sheet S1 toward the second gripper device 40A of the return cylinder 40. At this time, the upper drive roller 65A may start rotating from a stopped state when it sandwiches sheet S1 between itself and the lower driven roller 65B, or it may be configured to rotate constantly. At this time, the drive rollers 80, 81 may continue to rotate or may stop rotating.

[0102] As a result, the belt 87 transports the rear end of the sheet S1 sandwiched between the upper drive roller 65A and the lower driven roller 65B toward the return cylinder 40, and the rear end of the sheet S1 is gripped by the second gripper device 40A of the return cylinder 40.

[0103] The return cylinder 40 rotates clockwise in the direction of the arrow while holding the sheet S1 whose trailing edge is gripped by the second gripper device 40A, thereby transferring the sheet S1 in an inverted state from the front side to the back side to the printing cylinder 33. By using this transfer cylinder 40, the inverted sheet S1 gripped by the second gripper device 40A can be transferred again from the rear end to the printing cylinder 33 so that the front side that has been digitally printed by the printing cylinder 33 comes into contact with the circumferential surface of the printing cylinder 33.

[0104] A guide cover 40B is provided on the return cylinder 40 in the section between the guide roller 65 and the printing cylinder 33. The guide cover 40B has an arc shape that follows the circumferential surface of the guide cover 40B and is positioned slightly away from that circumferential surface. The guide cover 40B prevents the sheet S1 being transported from the return cylinder 40 to the printing cylinder 33 from separating from the circumferential surface of the return cylinder 40 and flapping.

[0105] In the digital printing unit 3, when the second gripper device 40A of the return cylinder 40 faces one of the first gripper devices 33A to 33C of the printing cylinder 33, the sheet S1 can be transferred from the return cylinder 40 to the printing cylinder 33, thereby transporting the inverted sheet S1 from the return cylinder 40 to the printing cylinder 33.

[0106] Thus, the digital printing unit 3 transports the sheet S1, which has been gripped by one of the first gripper devices 33A to 33C of the printing cylinder 33, back to the inkjet nozzle section 34 while adsorbing the entire surface of the sheet S1, performs digital printing processing on the back side of the sheet S1, and then passes it on to the delivery belt DB via the transfer cylinder 36, completing the double-sided printing process.

[0107] The range of the upper guide 84 and the lower guide 85 is defined as a conveying section 151 for conveying the sheet S1, and the range of the belt 87 is defined as a waiting section 152 for temporarily waiting the sheet S1 to be transferred from the return cylinder 40 to the printing cylinder 33. These are definitions for convenience and are not necessarily limited to these. In the present embodiment, the "reversing device" is composed of the guide roller 65 and the return cylinder 40.

[0108] Next, in this embodiment, we will explain how the destination of sheet S1 is allocated when sheet S1 is transported from transfer drum 36 to sheet delivery 4 via upper guide 71 and lower guide 72, and when sheet S1 is transported from transfer drum 36 to conveying section 151 via upper guide 84 and lower guide 85.

[0109] 11 , when sheet S1 gripped by gripper device 36A of transfer cylinder 36 is conveyed to conveying section 151 via upper guide 84 and lower guide 85, the timing at which gripper device 36A releases sheet S1 is advanced. At the latest, gripper device 36A releases sheet S1 before the leading edge of sheet S1 gripped by gripper device 36A passes the branch point between guides 71, 72 and guides 84, 85. As a result, the leading edge of sheet S1 is naturally guided to upper guide 84 and lower guide 85 by its own weight, and sheet S1 is conveyed to conveying section 151.

[0110] On the other hand, when the sheet S1 gripped by the gripper device 36A of the transfer cylinder 36 is transported to the sheet delivery 4 via the upper guide 71 and the lower guide 72, the timing at which the gripper device 36A releases the sheet S1 is delayed as much as possible. Preferably, the gripper device 36A releases the sheet S1 after the leading end of the sheet S1 gripped by the gripper device 36A passes the branch point between the guides 71, 72 and the guides 84, 85. As a result, the leading end of the sheet S1 does not sag due to its own weight and is not guided to the upper guide 84 and the lower guide 85, but is guided to the upper guide 71 and the lower guide 72, so that the sheet S1 is transported to the sheet delivery 4.

[0111] As described above, digital printing press 100 of this embodiment includes third gripper device 36A that contacts printing cylinder 33 and is configured to receive processed sheet S1 from printing cylinder 33, and is equipped with transfer cylinder 36 as a second cylinder configured to transport sheet S1 gripped by gripper device 36A, a first guide that leads from transfer cylinder 36 to sheet delivery 4, and a second guide that branches off from the first guide and leads to belt 87 in standby section 152. Belt 87 is configured to receive sheet S1 being transported by the second guide.

[0112] The first guide includes an upper guide 71 and a lower guide 72, which are two opposing plate-like members. The first guide includes a first roller configured to transport the sheet S1 from the printing cylinder 33 to the sheet delivery 4. The first roller includes two pairs of nip rollers, 73A and 73B, and 74A and 74B.

[0113] The second guide includes an upper guide 84 and a lower guide 85, which are made up of two plate-like members facing each other. The second guide includes a semicircular portion. The second guide includes a second roller configured to transport sheet S1 from printing cylinder 36 to belt 87. The second rollers include four pairs of nip rollers: 75A and 75B, 76A and 76B, 77A and 77B, and 78A and 78B, and a pair of guide rollers 65A and 65B.

[0114] An example of the distribution mechanism is the transfer drum 36. Another example of the distribution mechanism is a plate 101 that is provided at the branch point between the first guide and the second guide and is configured to selectively close the first guide and the second guide.

[0115] Next, we will explain the operation of the digital printing unit 3. When the double-sided printing mode is selected, as shown in Figure 12, the leading edge of the sheet S1 gripped by the gripper device 32A of the supply cylinder 32 is re-gripped by, for example, the first gripper device 33A of the printing cylinder 33.

[0116] As shown in FIG. 13, the rotation of the printing cylinder 33 causes the sheet S1 held by the first gripper device 33A to be transferred to the third gripper device 36A of the transfer cylinder 36.

[0117] 14, the third gripper device 36A of the transfer cylinder 36 releases the sheet S1 at a predetermined timing. As a result, as shown in FIG. 15, the sheet S1 passes through an upper guide 84 and a lower guide 85, and is conveyed by nip rollers 75A and 75B, 76A and 76B, 77A and 77B, 78A and 78B, and guide roller 65 in the conveying section 151.

[0118] As shown in FIG. 16, the sheet S1 is conveyed from the conveying section 151 to the standby section 152 by nip rollers 77A and 77B, 78A and 78B, and guide roller 65.

[0119] As shown in FIG. 17, the sheet S1 placed on the belt 87 in the waiting section 152 is transported by the belt 87, and the leading edge of the sheet S1 is brought into contact with the stopper 67, and the horizontal needle device 67A is operated to perform register adjustment.

[0120] 18 , in synchronization with the arrival of the second gripper device 40A of the return cylinder 40 for gripping change, the lower driven roller 65B rises and lifts the rear end of the sheet S1, which has been locked via the stopper 67 of the standby section 152, above the belt 87 and sandwiches it between the lower driven roller 65B and the upper drive roller 65A, and the upper drive roller 65A of the guide roller 65 rotates to transport the sheet S1 toward the second gripper device 40A of the return cylinder 40. The guide roller 65 grips the rear end of the sheet S1 into the second gripper device 40A of the return cylinder 40, and then the sheet S1 is gripped from the second gripper device 40A of the return cylinder 40 to the first gripper device 33C of the printing cylinder 33.

[0121] In this case, the printing cylinder 33 conveys the sheet S1, which has already been turned over to its back side when it is handed over from the return cylinder 40 to the printing cylinder 33. Therefore, the back side of the sheet S1 conveyed again by the printing cylinder 33, which has printed on its front side, can be digitally printed by the inkjet nozzle unit 34.

[0122] As described above, in the digital printing unit 3 of the digital printing device 1, the surface of the sheet S1 being transported by the printing cylinder 33 is digitally printed by the inkjet nozzle section 34, and then the sheet S1 is transferred to the transport section 151 via the transfer cylinder 36, and the end (front end) of the sheet S1 is abutted against the stopper 67 of the standby section 152, and the horizontal needle device 67A is activated to adjust the standby position of the sheet S1, i.e., to perform register adjustment.

[0123] Then, in accordance with the gripping change timing when the second gripper device 40A of the return drum 40 approaches the rear end of the sheet S1, the lower driven roller 65B rises and lifts the rear end of the sheet S1 above the conveying belt 64, clamping it between the upper drive roller 65A, and the upper drive roller 65A of the guide roller 65 rotates to transport the sheet S1 toward the second gripper device 40A of the return drum 40.

[0124] This allows the digital printing unit 3 to reliably grip the rear end of the sheet S1 with the second gripper device 40A of the return cylinder 40, and transfer the grip of the sheet S1 from the second gripper device 40A of the return cylinder 40 to the first gripper devices 33A to 33C of the printing cylinder 33. Therefore, the sheet S1 can be transported again to the printing cylinder 33 while maintaining its register-adjusted state.

[0125] Thus, the digital printing unit 3 can perform digital printing processing on the back side of the sheet S1 after register adjustment has been performed via the printing cylinder 33 and the inkjet nozzle unit 34. This can prevent misalignment between the print results on the front side and the back side, improving the print quality on both the front and back sides of the sheet S1.

[0126] Furthermore, the digital printing unit 3 can reuse the printing cylinder 33 and inkjet nozzle unit 34 that have been used to perform digital printing on the front side of the sheet S1 to also perform digital printing on the back side of the sheet S1. Therefore, since the printing cylinder 33 and inkjet nozzle unit 34 can be used for digital printing on both the front and back sides, double-sided printing on the sheet S1 can be performed with high precision without increasing the size of the entire device.

[0127] In the digital printing unit 3, the upper guide 84 and lower guide 85 of the conveying section 151 are mounted at a slight incline so that they are slightly downward from the nip rollers 78A, 78B toward the belt 87, and the surface on which the sheet is placed is also mounted at a similar incline to the belt 87. As a result, even if the sheet S1 placed on the belt 87 slips against the rotation of the belt 87 and is no longer conveyed, the sheet S1 will naturally be conveyed toward the stopper 67 due to its own weight, preventing the sheet S1 from being out of register in the top-bottom direction.

[0128] [Other Embodiments] In the first and second embodiments described above, a triple-sized printing cylinder 33 is used as the first cylinder. However, the present invention is not limited to this, and a double-sized, quadruple-sized, or sextuple-sized printing cylinder may also be used.

[0129] In the first embodiment, the conveying unit 51 is integrated with the standby unit 52. However, the present invention is not limited to this, and a conveying unit separate from the standby unit 52 may be used.

[0130] In the first and second embodiments, the transfer cylinder 36 having a single cylinder size is used as the second cylinder. However, the present invention is not limited to this, and a transfer cylinder having a double or triple cylinder size may be used.

[0131] In the first and second embodiments, the return cylinder 40, which is a single-size cylinder, is used as the reversing device. However, the present invention is not limited to this, and a reversing swing device having a configuration similar to the swing device 31 and swinging from the standby section 52, 152 toward the printing cylinder 33 may also be used.

[0132] In the first and second embodiments, the first adjustment device is a movably attached stopper 67. However, the present invention is not limited to this, and if the size of the seat S1 is fixed, a stopper 67 fixed in a predetermined position may be used.

[0133] Furthermore, in the first and second embodiments, the movably attached stopper 67 is used as the first adjustment device. However, the present invention is not limited to this, and the conveyance of the sheet S1 may be stopped and the standby position may be adjusted by the following configuration.

[0134] Instead of using belts 64, 87 and stopper 67, a pair of nip rollers 79A and 79B that sandwich and transport sheet S1 as shown in Fig. 19 is provided at the position of guide roller 65 in the first and second embodiments. Nip rollers 79A and 79B have rotation axes that extend in a direction perpendicular to the transport direction of sheet S1, and are rotatable and movable in the axial direction.

[0135] As shown in FIG. 20 , the digital printing apparatus 1 (sheet processing apparatus) in this case includes a sheet size detection sensor 91, a sheet side edge position detection sensor 92, an encoder 93, a nip roller rotation motor 94, a nip roller shaft adjustment mechanism 95, and a controller 96. The sheet size detection sensor 91 is a sensor for detecting the length of the sheet S1 in the conveying direction (top-bottom direction) and is configured using a photoelectric sensor or the like. The sheet side edge position detection sensor 92 is a sensor for detecting the position of one side edge of the sheet S1 and is configured using a photoelectric sensor or the like. The encoder 93 can detect the phase of the drive unit of the digital printing apparatus 1. A motor 94 rotates the nip rollers 79A and 79B. Alternatively, the motor 94 may be configured to rotate only the nip roller 79A located above the belts 64 and 87, while the nip roller 79B located below the belts 64 and 87 is driven to rotate. The adjustment mechanism 95 adjusts the axial positions of the nip rollers 79A and 79B. The controller 96 controls the motor 94 and the adjustment mechanism 95 based on the outputs of the sheet size detection sensor 91 , the sheet side edge position detection sensor 92 , and the encoder 93 .

[0136] The following describes the position adjustment of sheet S1 in standby section 52, 152 that is performed using these configurations. Sheet S1 that has been transported to nip rollers 79A and 79B is transported to standby section 52, 152 by the rotation of nip rollers 79A and 79B. At this time, in accordance with information about the length of sheet S1 from sheet size detection sensor 91, controller 96 rotates motor 94 until the transport amount to standby section 52, 152 is appropriate for sheet S1, and then stops motor 94, thereby adjusting the top-bottom register.

[0137] Next, the controller 96 operates the adjustment mechanism 95 in accordance with information on the widthwise position of the sheet S1 from the sheet side edge position detection sensor 92 so that the sheet S1 is positioned at the correct widthwise register position.

[0138] Next, based on the signal from the encoder 93, the controller 96 causes the motor 94 to rotate in reverse at the timing when the second end of the sheet S1, which has been registered in the top-to-bottom and width directions, is gripped by the second gripper device 40A of the return cylinder 40. This causes the nip rollers 79A and 79B to rotate in reverse, and the second end of the sheet S1 is gripped by the second gripper device 40A.

[0139] In this embodiment, the first adjustment device includes nip rollers 79A and 79B as a pair of rollers configured to sandwich both sides of the sheet S1 and having a rotation axis extending in a direction perpendicular to the conveyance direction of the sheet S1, a motor 94 configured to rotate at least one of the nip rollers 79A and 79B, and a controller 96 configured to control the motor 94 based on the size of the sheet S1. The first adjustment device may further include a sheet size detection sensor 91 as a first sensor configured to detect the length of the sheet S1 in the conveyance direction and output the detected length to the controller 96.

[0140] The second adjustment device includes nip rollers 79A and 79B as a pair of rollers configured to sandwich both sides of the sheet S1 and having a rotation axis extending in a direction perpendicular to the conveyance direction of the sheet S1, an adjustment mechanism 95 configured to adjust the axial position of at least one of the nip rollers 79A and 79B, and a controller 96 configured to control the adjustment mechanism 95 based on the position of the side edge of the sheet S1. The second adjustment device may further include a sheet side edge position detection sensor 92 as a second sensor configured to detect the position of the side edge of the sheet S1.

[0141] Furthermore, in the second embodiment, the conveyance of the sheet S1 from the transfer cylinder 36 to the sheet delivery 4 via the upper guide 71 and the lower guide 72 and the conveyance of the sheet S1 from the transfer cylinder 36 to the belt conveyance unit 150 via the upper guide 84 and the lower guide 85 are switched by adjusting the timing at which the gripper device 36A of the transfer cylinder 36 releases the sheet S1. However, the present invention is not limited to this. As shown in FIGS. 21A and 21B , a switching unit 101 serving as a plate-shaped sorting mechanism may be provided at the branch point between the upper guide 71 and the lower guide 72 and the upper guide 84 and the lower guide 85, and this switching unit 101 may be switched to the upper guide 71 and the lower guide 72 side or the upper guide 84 and the lower guide 85 side. Furthermore, the control of the release timing of the sheet S1 by the gripper device 36A and the switching of the plate-shaped switching unit 101 may be used in combination to increase reliability.

[0142] Furthermore, in the first and second embodiments, the sheet processing apparatus is described as being applied to a digital printing apparatus. However, the present invention is not limited to this, and may be applied to an offset printing apparatus, an inspection apparatus, a foil transfer apparatus, an embossing apparatus, etc. As a processing apparatus that processes the surface of a sheet, a blanket cylinder for offset printing, a printing cylinder for foil transfer or embossing, etc. can be used instead of the inkjet nozzle unit, depending on the application of the sheet processing apparatus.

[0143] Furthermore, in the first and second embodiments, the sheet is conveyed by a belt in the conveying unit 51 and the waiting unit 52, 152, and a guide cover provided along the belt prevents the sheet S1 from flapping or lifting off the belt. However, the present invention is not limited to this, and a configuration may be provided in which suction holes are formed in the belt and negative pressure is generated on the surface of the belt that does not come into contact with the sheet. By suctioning the sheet S1 instead of using a guide cover, it is possible to convey the sheet S1 while preventing it from flapping or lifting off the belt.

[0144] 1, 100...digital printing device, 2...sheet feeder, 3...digital printing unit, 4...sheet delivery, 21...loading plate, 22, 42...loaded sheets, 23...sheet sucker, 31...swing device, 32...supply cylinder, 33...printing cylinder, 36...transfer cylinder, 39...front reversal cylinder, 40...return cylinder, FB...feeder board, DB...delivery belt, S1...sheet, 51, 151...conveying section, 52, 152...waiting section, 65...guide roller, 67...stopper, 62, 68, 80, 81...drive roller, 63, 82...driven roller, 64, 87...belt, 61...guide cover, 71, 84...upper guide, 72, 85...lower guide, 73-78...nip roller.

Claims

1. A sheet processing apparatus comprising: a first gripping claw device configured to grip an end portion in the vertical direction of a sheet; a first cylinder configured to convey the sheet gripped by the first gripping claw device; a processing device disposed outside the first cylinder so as to face the circumferential surface of the first cylinder and configured to perform a process on the surface of the sheet being conveyed by the first cylinder; a discharging device configured to discharge the processed sheet; a standby unit configured to receive and hold the processed sheet from a first end portion, which is the end portion gripped by the first gripping claw device; a sorting mechanism configured to selectively distribute the sheet from the first cylinder to the discharging device or the standby unit; and a reversing device including a second gripping claw device configured to grip a second end portion, which is an end portion in the vertical direction of the sheet not gripped by the first gripping claw device while the sheet is on standby in the standby unit, and configured to transfer the second end portion of the sheet to the first gripping claw device of the first cylinder so that the surface on which the process has been performed by the processing device contacts the circumferential surface of the first cylinder.

2. The sheet processing apparatus according to claim 1, further comprising a first adjusting device configured to adjust a position of the second end portion of the sheet in the standby unit.

3. The sheet processing apparatus according to claim 2, wherein the standby unit includes a belt configured to convey the sheet, and the first adjusting device includes a stopper disposed so that a first end portion of the sheet on the belt abuts thereon.

4. The sheet processing apparatus according to claim 2, wherein the first adjusting device includes: a pair of rollers configured to sandwich both surfaces of the sheet and having a rotation axis extending in a direction orthogonal to a conveyance direction of the sheet; a motor configured to rotate at least one of the pair of rollers; and a controller configured to control the motor based on a size of the sheet.

5. The sheet processing apparatus according to claim 2, further comprising a second adjusting device configured to adjust a position of a side end portion in a width direction of the sheet before the sheet is gripped by the second gripping claw device in the standby unit.

6. The second adjusting device includes a pair of rollers having a rotation axis extending in a direction parallel to the conveyance direction of the sheet, which are configured to be capable of approaching and separating from each other, a motor configured to rotate the pair of rollers with the pair of rollers sandwiching both surfaces of the sheet, and a lateral stopper disposed so that a side edge of the sheet moving in a direction orthogonal to the conveyance direction abuts against the pair of rollers when the pair of rollers rotate. The sheet processing apparatus according to claim 5.

7. The second adjusting device includes a pair of rollers having a rotation axis extending in a direction orthogonal to the conveyance direction of the sheet, which are configured to sandwich both surfaces of the sheet, an adjusting mechanism configured to adjust an axial position of the pair of rollers, and a controller configured to control the adjusting mechanism based on a position of a side edge of the sheet. The sheet processing apparatus according to claim 5.

8. The sheet processing apparatus further includes a third gripper device configured to face the first cylinder and receive the processed sheet from the first cylinder, and a second cylinder configured to convey the sheet gripped by the third gripper device, and a fourth gripper device configured to face the second cylinder and receive the sheet from the second cylinder, and a pre-inversion cylinder configured to convey the sheet gripped by the fourth gripper device. The sorting mechanism is constituted by the second cylinder, and the belt is configured to receive the sheet conveyed by the pre-inversion cylinder. The sheet processing apparatus according to claim 3.

9. The inverting device includes a guide member configured to lift a second end of the sheet waiting in the standby unit and transfer the sheet to the second gripper device. The sheet processing apparatus according to claims 1 to 8.

10. The standby unit includes a belt configured to convey the sheet, and the reversing device includes an upper roller disposed above the belt and a lower roller disposed below the belt and movable in the vertical direction. The lower roller is configured to lift the sheet together with the belt and sandwich the sheet together with the upper roller. The upper roller and the lower roller are configured to rotate in a direction in which the sheet moves toward the second gripper device. The sheet processing apparatus according to claim 1.

11. The sheet processing apparatus according to claim 3, further comprising a third gripper device configured to be in contact with the first cylinder and receive the processed sheet from the first cylinder, a second cylinder configured to convey the sheet gripped by the third gripper device, a first guide extending from the second cylinder to the discharging device, and a second guide branching from the first guide and leading to the belt. The belt is configured to receive the sheet conveyed by the second guide.

Images