JP2013241264A - Printing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized digital printing apparatus capable of performing duplex printing on a sheet with a high degree of front-side and back-side registration accuracy.SOLUTION: A printing apparatus includes: a sheet feeding device 2 which feeds sheets one by one; a printing cylinder 33 which includes printing cylinder gripping pawl devices 33a-33c for holding the sheet by gripping one end of the sheet fed from the sheet feeding device 2, and which conveys the sheet; an inkjet nozzle part 34 which performs printing by discharging an ink droplet onto the sheet conveyed by the printing cylinder 33; and a reversal mechanism which has a reversal gripping pawl device 31bt for gripping the other end of the sheet, which transfers the other end of the sheet to the printing cylinder gripping pawl devices 33a-33c, and which feeds the sheet to the printing cylinder 33 by reversing the front and back sides of the sheet. The reversal mechanism, which has a plurality of gripping claw devices 31b, 36a, 37a and 39a including the reversal gripping pawl device 31bt, conveys the sheet by re-gripping only the plurality of gripping claw devices 31b, 36a, 37a and 39a, until transferring the sheet to the printing cylinder 33 after receiving the sheet from the printing cylinder 33.

Description

  The present invention relates to a digital printing apparatus that performs printing on a sheet by an inkjet method.

  Conventionally, as a digital printing apparatus that prints on a sheet by an inkjet method, a sheet-like recording medium is transported with a nail mounted on the surface of a table moving in one direction, and ink is ejected from four-color inkjet nozzles. In some cases, image recording is performed (see, for example, Patent Document 1).

JP 2009-262537 A

  However, in the digital printing apparatus of Patent Document 1, a recording medium is conveyed in a horizontal direction through a table, and an image is recorded by a head of inkjet nozzles arranged in series along the moving direction of the table. There is a problem that double-sided printing cannot be performed on a recording medium.

  The present invention has been made to solve such a problem, and an object of the present invention is to propose a small digital printing apparatus capable of duplex printing on a sheet with high front and back registration accuracy.

  In order to solve such a problem, the present invention includes a sheet feeding device that feeds sheets one by one, and a printing cylinder gripping nail device that holds and holds one end of the sheet fed from the sheet feeding device. A printing cylinder that conveys the sheet; an inkjet nozzle that performs printing by discharging ink droplets onto the sheet conveyed by the printing cylinder; and a reversing gripper device that holds the other end of the sheet. A reversing mechanism that delivers the end of the sheet to the printing cylinder holding nail device, reverses the front and back of the sheet and supplies it to the printing cylinder, and the reversing mechanism includes a plurality of holding nail devices including the reversing holding nail device. And having the sheet transferred from the printing cylinder until the sheet is transferred to the printing cylinder by only changing the plurality of holding nail devices.

  In the present invention, the reversing mechanism includes the conveyance cylinder before reversing which conveys the one end of the sheet with the gripping claw device, and the other end of the sheet with the reversing gripping claw device. A reversing device for receiving and transporting the sheet from the transport cylinder before reversing is provided.

  In the present invention, the reversing mechanism includes a first discharge side transfer cylinder that is in contact with the printing cylinder and includes the gripping nail device, and conveys the sheet while holding one end of the sheet, and the first discharge side. A second discharge-side transfer cylinder that comes in contact with the transfer cylinder and includes the gripping claw device and conveys one end of the sheet, and the transfer cylinder before reversing is opposed to the second discharge-side transfer cylinder. In contact, the reversing device delivers the sheet to the printing cylinder.

  Furthermore, in the present invention, a sheet discharge device that discharges a sheet, a conveyance path switching device that switches a sheet conveyance destination to the discharge device or the reversing device, and a single-sided printing mode that performs printing by the inkjet nozzle unit only on one side of the sheet Or a double-sided printing mode for selecting both sides of the sheet, and a control unit for controlling the conveyance path cutting device based on the printing mode selection unit.

  Furthermore, in the present invention, a sheet supply device that supplies a sheet to the printing cylinder is provided, and the control device is configured to continuously supply the sheet at a first cycle when single-sided printing is selected by the print mode selection unit. The sheet supply device is controlled, and the sheet supply device is controlled to intermittently supply a sheet at a second cycle that is twice as long as the first cycle when double-sided printing is selected by the print mode selection unit. To do.

  According to the present invention, it is possible to perform double-sided printing with high front and back registration accuracy by transferring and reversing a sheet while changing it with a gripper device, and performing front side printing and back side printing using the same printing cylinder. Therefore, it is possible to print on both sides of a sheet without increasing the size of the entire apparatus, and thus to realize a small digital printing apparatus capable of performing high-quality double-sided printing on a sheet. it can.

It is a side view which shows the whole structure of a digital printing apparatus. It is a side view which shows the structure of an inversion swing apparatus. It is a block diagram which shows the structure of the control system of a digital printing apparatus. It is a basic diagram with which it uses for description of the continuous paper feed in a digital printing apparatus. It is a side view which shows the printing process (1) in a digital printing apparatus. It is a side view which shows the printing process (2) in a digital printing apparatus. It is a basic diagram with which it uses for description of the intermittent paper feeding in a digital printing apparatus. It is a side view which shows the printing process (3) in a digital printing apparatus. It is a side view which shows the printing process (4) in a digital printing apparatus. It is a side view which shows the printing process (5) in a digital printing apparatus.

  Next, an embodiment of the present invention will be described with reference to the drawings.

<Configuration of digital printing device>
As shown in FIG. 1, a digital printing apparatus 1 as a printing apparatus includes a paper feeding device 2 as a sheet supply device, a digital printing unit 3 as a processing unit, and a paper discharge device 4 as a sheet discharge device.

  The paper feeding device 2 is provided with a stacking table 21 on which a plurality of sheets S1 are stacked, and a soccer device 23 that conveys the uppermost sheet S1 of the stacking table 21 to the feeder board FB. The soccer device 23 includes a first suction 23 a and a second suction 23 b, and the first suction 23 a and the second suction 23 b are connected to the negative pressure source 25 through a continuous supply valve 26 and an intermittent supply valve 27.

  The continuous supply valve 26 and the intermittent supply valve 27 both connect and disconnect the suction from the negative pressure source 25 of the first suction 23a and the second suction 23b, but the timings for connecting and disconnecting the suction are different as will be described later. Yes.

  On the front end side in the sheet conveying direction of the feeder board FB, it is supported by the frame 3a of the digital printing unit 3 so as to be swingable, and holds the front end (the end on the holding side) as one end of the sheet S1. A swing device 31f provided with a gripper device is provided. A paper feed side transfer drum 32 is disposed opposite to the swing device 31f, and the paper feed side transfer drum 32 is rotatably supported by the frame 3a.

  The feeding side transfer cylinder 32 is provided with a gripping claw device 32a that holds the leading end of the sheet S1 delivered by the gripping claw device of the swing device 31f. In the digital printing unit 3, the swing device 31f and the sheet feeding side transfer cylinder 32 constitute an upstream sheet conveying device.

  A printing cylinder 33 is disposed in contact with the sheet feeding side transfer cylinder 32 on the downstream side in the sheet conveying direction from the swing device 31f, and the printing cylinder 33 is rotatably supported by the frame 3a. The printing cylinder 33 includes a printing cylinder holding claw device 33a, 33b, 33c that receives and holds the leading end of the sheet S1 from the holding claw device 32a of the paper feeding side transfer cylinder 32, and the printing cylinder holding claw device 33a, 33b, 33c. Correspondingly provided support surfaces 33d, 33e, 33f for supporting the sheet S1, and in the present embodiment, a triple cylinder is provided in which three sets of the printing cylinder holding nail device and the support surface are provided. The diameter of the paper feeding side transfer cylinder 32 is three times as large. Here, the printing cylinder holding claw devices 33a, 33b, and 33c that hold the sheet S1 are provided in a state in which the phases are shifted from each other by 120 degrees in the circumferential direction.

  A plurality of suction holes are formed in the support surfaces 33d, 33e, and 33f of the printing cylinder 33, and the plurality of suction holes are connected to a negative pressure source. An ink jet nozzle portion 34 is disposed on the downstream side of the printing cylinder 33 with respect to the sheet feeding side transfer cylinder 32 in the sheet conveying direction so as to face the peripheral surface of the printing cylinder 33.

  A plurality of inkjet nozzle heads 34 a to 34 d in which inks of different colors are set are arranged in the inkjet nozzle portion 34 side by side along the circumferential surface of the printing cylinder 33, and each of them is a circumferential surface of the printing cylinder 33. Is oriented. The inkjet nozzle heads 34a to 34d are arranged close to the printing cylinder 33 so that the gap between the printing nozzle 33 and the sheet S1 adsorbed on the entire surface of the supporting surface 33d, 33e, 33f is slightly spaced. The printing cylinder 33 and the inkjet nozzle unit 34 constitute a sheet printing apparatus.

  An ink printed on the sheet S1 by irradiating the sheet S1 with light such as infrared rays or ultraviolet rays is disposed on the downstream side of the printing cylinder 33 in the sheet conveyance direction with respect to the inkjet nozzle portion 34, and is irradiated with light such as infrared rays or ultraviolet rays. An ink drying lamp 35 is provided as a drying device for drying. Here, the term “drying” includes evaporation of moisture of the ink by applying thermal energy and curing of the ink, which can be called solidification.

  A first discharge side transfer cylinder 36 as a first discharge side transfer cylinder is disposed in contact with the printing cylinder 33 downstream of the ink jet nozzle portion 34 in the sheet conveyance direction, and the first discharge side of the first discharge side transfer cylinder 36 is disposed. A transfer drum 36 is rotatably supported by the frame 3a. The first paper discharge side transfer cylinder 36 is provided with a gripping claw device 36a that receives and holds the leading end of the sheet S1 conveyed by the printing cylinder 33 from the printing cylinder gripping claw devices 33a, 33b, and 33c.

  A second discharge-side transfer cylinder 37 as a second discharge-side transfer cylinder is located on the downstream side in the sheet conveyance direction from the contact portion of the first discharge-side transfer cylinder 36 with the printing cylinder 33. The second paper discharge side transfer drum 37 is disposed in contact with the paper discharge side transfer drum 36, and is rotatably supported by the frame 3a. The second paper discharge side transfer drum 37 is provided with a gripping claw device 37a for receiving and holding the leading edge of the sheet S1 conveyed by the first paper discharge side transfer drum 36.

  A paper take-up cylinder 38 is disposed in contact with the first paper discharge-side transfer cylinder 37 on the downstream side of the second paper discharge-side transfer cylinder 37 with respect to the first paper discharge-side transfer cylinder 36. 3a is rotatably supported. The paper take-up cylinder 38 is provided with a gripping claw device 38a that receives and holds the leading end of the sheet S1 conveyed by the second paper discharge side transfer cylinder 37.

  Below the paper drum 38, a belt-conveyor-like delivery belt 40 that conveys the sheet S1 is disposed. On the leading end side of the delivery belt 40 in the sheet conveyance direction, a stacking base 41 on which the sheet S1 subjected to digital printing processing by the digital printing unit 3 is stacked is provided. The paper take-up cylinder 38, the delivery belt 40, and the stacking base 41 constitute the paper discharge device 4, and the path of the sheet S1 conveyed by the paper take-up cylinder 38 and the delivery belt 40 constitutes the sheet discharge path.

  A pre-reversal double cylinder 39 as a pre-reversal conveyance cylinder is disposed in contact with the downstream side of the second paper discharge side transfer cylinder 37 and the paper drum 38 in the sheet conveyance direction. A barrel 39 is rotatably supported by the frame 3a. The pre-inversion double cylinder 39 is a double cylinder having a diameter twice that of the second paper discharge side transfer cylinder 37, and receives and holds the leading end of the sheet S1 conveyed by the second paper discharge side transfer cylinder 37. A holding claw device 39a is provided.

  As shown in FIG. 2, as shown in FIG. 2, the rear end (the other end portion of the sheet S <b> 1) is located downstream of the contact portion of the pre-reverse double cylinder 39 with the second discharge-side transfer cylinder 37. A reversing swing device 31b having a gripping claw device 31bt as a reversing gripping claw device that receives and holds the (butt end side) is disposed to face. The reversing swing device 31b constitutes a reversing device that reverses the front and back of the sheet S1.

  The reversing swing device 31b is located downstream of the printing cylinder 33 in the rotational direction of the printing cylinder 33 with respect to the first discharge-side transfer cylinder 36 and more than the printing cylinder with respect to the feeding cylinder 32. It is disposed opposite to the printing cylinder 33 on the upstream side in the rotational direction of 33. The reversing swing device 31b includes a receiving position (FIG. 1) indicated by a broken line that receives the rear end of the sheet S1 conveyed by the pre-reversing double cylinder 39, and printing cylinder holding claw devices 33a and 33b of the printing cylinder 33. , 33c is supported by the frame 33a so as to be swingable with respect to a delivery position (FIG. 1) indicated by a solid line that delivers the rear end of the sheet S1. The first paper discharge side transfer drum 36, the second paper discharge side transfer drum 37, the pre-reverse double drum 39, and the reverse swing device 31b constitute a reversing mechanism, and the first paper discharge side transfer drum 36, The path of the sheet S1 conveyed by the sheet discharge side transfer cylinder 37, the pre-reverse double cylinder 39, and the reverse swing device 31b constitutes a sheet reverse path.

The gripping claw device 37a of the second paper discharge side transfer drum 37 can selectively deliver the sheet S1 to the gripping claw device 38a of the paper take-up drum 38 and the gripping claw device 39a of the pre-reverse double cylinder 39. Driven. Further, the gripping claw device 38a of the paper take-up cylinder 38 is driven so as to be able to selectively receive the leading end of the sheet S1 conveyed by the second paper discharge side transfer cylinder 37. The gripping claw devices 37a, 38a A conveyance path switching unit 82 is configured as a conveyance path switching device that switches the conveyance destination of the sheet S1 to the paper discharge apparatus 4 or the reverse swing apparatus 31b, that is, switches the conveyance path of the sheet S1 to the sheet discharge path or the sheet reverse path.

<Configuration of control system of digital printing device>
As shown in FIG. 3, the digital printing apparatus 1 includes a control device 81 having a central processing unit (CPU) configuration for overall control. The control device 81 allows the operator to select either a single-sided printing mode in which digital printing processing is performed on only one side of the sheet S1, or a double-sided printing mode in which digital printing processing is performed on both the front and back surfaces of the sheet S1. The printing mode selection switch 80 as means, the continuous supply valve 26 and the intermittent supply valve 27 of the paper feed unit 2, the inkjet nozzle heads 34a to 34d of the inkjet nozzle unit 34, and the transport path switching unit 82 are connected.

<Printing operation of digital printing device>
The printing operation of the digital printing apparatus 1 configured as described above will be described separately when the single-sided printing mode is selected and when the double-sided printing mode is selected.

  As shown in FIG. 1, when the single-sided printing mode is selected by the operator's operation of the printing mode selection switch 80, the control device 81 activates the continuous supply valve 26, whereby the first suction 23a and the second suction are performed. 23b adsorbs the sheet S1 on the loading table 21 and conveys it to the feeder board FB.

  As shown in FIG. 4, the continuous supply valve 26 supplies the same number of sheets S <b> 1 as the number of the printing cylinder holding nail devices 33 a, 33 b, 33 c provided in the printing cylinder 33 during one rotation of the printing cylinder 33. The valve is “opened” at each timing (cycle) at which the printing cylinder holding claw devices 33a to 33c in the printing cylinder 33 and the holding claw device 32a of the paper feeding side transfer cylinder 32 face each other. Control is performed so that suction from the negative pressure source 25 of 23a and second suction 23b is performed. In this way, supplying the sheet S1 so that all the printing cylinder holding claw devices 33a, 33b, and 33c of the printing cylinder 33 hold the sheet S1 is called continuous feeding, and the continuous supply valve 26 in continuous feeding is used. The opening / closing cycle is referred to as a first cycle. With the operation of the continuous supply valve 26, the soccer device 23 supplies the sheet S1 to the feeder board FB in the first cycle.

  The sheet S1 conveyed by the feeder board FB is held by the gripping claw device of the swing device 31f and then oscillated toward the sheet feeding side transfer cylinder 32. The sheet S1 is held by the sheet feeding side transfer cylinder 32. The leading end of the sheet S1 is replaced by the nail device 32a.

  The sheet S1 conveyed along with the rotation of the sheet feeding side transfer cylinder 32 is transferred from the gripping claw device 32a of the sheet feeding side transfer cylinder 32 to the printing cylinder holding claw device 33a to 33a of the printing cylinder 33 at the contact portion with the printing cylinder 33. After the tip is replaced by any of 33c, it is conveyed along with the rotation of the printing cylinder 33. At this time, the entire surface of the sheet S1 is adsorbed to the support surfaces 33d to 33f of the printing cylinder 33 through the plurality of suction holes in the printing cylinder 33 and closely contacts the support surfaces 33d to 33f.

  Digital printing processing is performed on the surface of the sheet S <b> 1 conveyed by the printing cylinder 33 by ejecting fine droplets of ink from the inkjet nozzle heads 34 a to 34 d of the inkjet nozzle portion 34. Since the sheet S <b> 1 is in close contact with the support surfaces 33 d to 33 f of the printing cylinder 33, the sheet S <b> 1 is conveyed in a state where a minute gap between the ink jet nozzle heads 34 a to 34 d is maintained. By maintaining this minute interval, the ejected ink can land on the sheet S1 with high accuracy, and high-quality printing can be performed.

  The sheet S1 that has been printed by the inkjet nozzle unit 34 passes between the printing cylinder 33 and the ink drying lamp 35, and is irradiated with light from the ink drying lamp 35, whereby the ink on the sheet S1 is dried. . Thereafter, the sheet S1 is conveyed to the first paper discharge side transfer cylinder 36.

  As shown in FIG. 5, in the contact portion between the printing cylinder 33 and the first paper discharge side transfer cylinder 36, the print cylinder holding claw devices 33 a to 33 c of the printing cylinder 33 hold the first paper discharge side transfer cylinder 36. The leading end of the sheet S1 is replaced with the nail device 36a. Thereafter, as shown in FIG. 6, the sheet S <b> 1 held by the gripping claw device 36 a of the first paper discharge side transfer drum 36 is transferred to the first paper discharge side transfer drum 36 and the second paper discharge side transfer drum 37. At the contact portion, the gripper claw device 36a of the first paper discharge side transfer drum 36 is replaced with the gripper claw device 37a of the second paper discharge side transfer drum 37.

  In the single-sided printing mode, the holding claw device 37a of the second discharge side transfer cylinder 37 releases the holding of the leading edge of the sheet S1 at the contact portion between the second discharge side transfer cylinder 37 and the paper take-up cylinder 38. At the same time, the holding claw device 38a of the paper take-up cylinder 38 holds the leading end of the sheet S1, and the holding is changed. As a result, the sheet S1 is transferred from the second delivery side transfer cylinder 37 to the paper take-up cylinder 38 and conveyed.

  The sheet S1 that has been replaced by the paper take-up cylinder 38 is released from being held by the holding claw device 38a at the timing when the holding claw device 38a of the paper take-up cylinder 38 is positioned above the delivery belt 40 and placed on the delivery belt 40. It is done.

  The sheet S1 placed on the delivery belt 40 is conveyed along with the travel of the delivery belt 40, and the sheet S1 whose surface is subjected to digital printing processing is discharged onto the stacking table 41.

  On the other hand, when the duplex printing mode is selected by the operator's operation of the printing mode selection switch 80, the control device 81 operates the intermittent supply valve 27, and the sheet S1 of the stack 21 by the first suction 23a and the second suction 23b. Is sucked and conveyed to the feeder board FB.

  As shown in FIG. 7, the intermittent supply valve 27 supplies the sheet S <b> 1 at every other sheet timing with respect to the continuous sheet feeding timing, in other words, the printing cylinder holding claw devices 33 a to 33 c in the printing cylinder 33. The valve is controlled to be “open”, “closed”, “open”, “closed”,... At the timing (cycle) at which the gripping claw device 32a of the sheet feeding side transfer cylinder 32 faces. This is twice the period of continuous supply. In this way, feeding the sheet S1 so that the printing cylinder holding claw devices 33a, 33b, 33c of the printing cylinder 33 hold the sheet S1 every other time is called intermittent feeding, and the intermittent supply valve in intermittent feeding The open / close cycle of 27 is referred to as a second cycle. By the operation of the intermittent supply valve 27, the soccer device 23 intermittently sucks every other sheet S1 in the second period and conveys it to the feeder board FB.

The sheet S1 sent to the feeder board FB by the soccer device 23 is delivered to the printing cylinder 33 via the swing device 31f and the sheet feeding side transfer cylinder 32 as in the single-sided printing mode, but the sheet S1 is intermittently fed. Since the paper is fed at the paper timing, the printing cylinder holding claw devices 33a to 33c of the printing cylinder 33 receive every other new sheet S1 conveyed from the sheet feeding side transfer cylinder 32.

  Thereafter, the sheet S1 is conveyed to the inkjet nozzle portion 34, and printing for the surface is performed on one surface (front surface) thereof. Here, the control device 81 performs printing on a new sheet S1 held every other one of the printing cylinder holding nail devices 33a to 33c of the printing cylinder 33, and the printing cylinder holding nail that does not hold the sheet S1. The inkjet nozzle heads 34a to 34d of the inkjet nozzle portion 34 are controlled so that printing is not performed on the support surfaces 33d to 33f corresponding to the devices 33a to 33c.

In the double-sided printing mode, the sheet S1 printed on the surface by the ink jet nozzle unit 34 is not delivered from the second paper discharge side transfer cylinder 37 to the paper take-up cylinder 38, but before-inversion double cylinder 39. Is passed on.

  Thus, in the case of the duplex printing mode, when printing is performed on the front side but printing is not performed on the other side (back side), the transport path switching means 82 is controlled by the control device 81. The nail of the gripping device 37a of the second paper discharge side transfer cylinder 37 remains closed without opening at the contact portion between the second paper discharge side transfer cylinder 37 and the paper take-up cylinder 38, that is, the sheet. The state in which the tip of S1 is held is maintained, and the claw of the gripping claw device 38a of the paper drum 38 is maintained in an open state without closing.

  As a result, the sheet S1 is conveyed from the second discharge side transfer drum 37 to the paper take-up drum 38 without being replaced by the pre-inversion double drum 39. The claw of the gripping claw device 39a of the pre-reverse double cylinder 39 is closed at the contact portion between the second paper discharge side transfer cylinder 37 and the pre-reverse double cylinder 39 to hold the leading edge of the sheet S1, and the second paper discharge The nail of the gripping claw device 37a of the side transfer cylinder 37 is opened to release the holding of the leading edge of the sheet S1, and as shown in FIG. The leading end of the sheet S1 is replaced by 39 holding claw devices 39a.

  As shown in FIG. 9, the sheet S1 conveyed along with the rotation of the pre-reverse double cylinder 39 swings the reverse swing device 31b from the delivery position indicated by the solid line to the reception position indicated by the broken line, and the rear end of the sheet S1. Is held by the holding claw device 31bt of the reversing swing device 31b, and at the same time, the holding of the double cylinder 39 before reversing to the leading end of the sheet S1 by the holding claw device 39a is released.

  As shown in FIG. 10, the sheet S1 is conveyed toward the printing cylinder 33 with the trailing edge at the top by the swing of the reverse swing device 31b from the receiving position indicated by the broken line to the delivery position indicated by the solid line, and the reverse swing device 31b. The rear end of the sheet S1 in the reversed state is switched from the gripper nail device 31bt to any of the print cylinder gripper nail devices 33a to 33c of the printing cylinder 33.

Here, the printing cylinder holding claw devices 33a to 33c of the printing cylinder 33 hold every other new sheet S1 conveyed from the sheet feeding side transfer cylinder 32, but the reverse swing device 31b is a new one. Positioned at the delivery position at a timing facing the printing cylinder holding claw devices 33a to 33c not holding the sheet S1, and the rear end of the sheet S1 from the holding claw device 31bt of the reverse swing device 31b is printed to the printing cylinder holding claw devices 33a to 33c. Hand over to. As a result, the front and back of the new sheet S1 delivered from the paper feeding side transfer cylinder 32 and the front and back reversal device 31bt of the reversing swing device 31b are transferred to the print cylinder holding claw devices 33a to 33c of the printing cylinder 33. The sheet S1 in the state is held alternately and conveyed to the ink jet nozzle unit 34.

  At this time, the sheet S1 in the reverse state, which has been transferred from the gripper device 31bt of the reversing swing device 31b, has a surface that has already been subjected to digital printing processing by the inkjet nozzle unit 34 (surface that has been subjected to digital printing processing). In contact with the support surfaces 33d, 33e, and 33f of the sheet S1, and the rear surface of the sheet S1 is exposed (surface not yet processed by digital printing), and the rear end of the sheet S1 is held by the printing cylinder holding nail devices 33a to 33c of the printing cylinder 33 In other words, the sheet S1 is conveyed in an inverted state, and a digital printing process is performed on the back surface of the sheet S1 by the inkjet nozzle unit 34.

Here, the control device 81 performs printing for the back side of the sheet S1 in the front and back inverted state transferred from the gripping claw device 31bt of the reversing swing device 31b, and the gripping claw devices 33a to 33c of the printing cylinder 33. The ink jet nozzle heads 34a to 34d of the ink jet nozzle unit 34 are controlled so as to perform printing for the front surface for every other new sheet S1 held. As a result, the inkjet nozzle heads 34a to 34d alternately perform printing for the front surface and printing for the back surface corresponding to the new sheet S1 held alternately on the printing cylinder 33 and the sheet S1 in the reverse state. Become.

  Thereafter, the sheet S1 printed on the back side is printed on the first discharge side transfer drum 36, the second discharge side transfer drum 37, and the paper drum 38 in the same manner as in the single-sided printing mode. Then, the paper is discharged from the delivery belt 40 to the loading table 41 of the paper discharge device 4.

  As described above, the digital printing apparatus 1 can perform the digital printing process on the front surface and the back surface of the sheet S1 by the same printing cylinder 33 and the same inkjet nozzle unit 34. Therefore, the printing cylinder and the inkjet nozzle unit for the back surface printing process are separately provided. Compared with the case of providing, the sheet S1 can be efficiently printed on both sides while saving space.

  In addition, the digital printing apparatus 1 sequentially feeds the paper feeding side transfer cylinder 32, the printing cylinder 33, the first paper discharge side transfer cylinder 36, the second paper discharge side transfer cylinder 37, the pre-reverse double cylinder 39, and the reverse swing apparatus 31b. Since the sheet S1 is delivered by the gripper device, it is possible to obtain a high registration accuracy in the conveying direction and the width direction of the sheet S1 with respect to the front and back surfaces of the sheet S1, and to obtain a high front and back registration accuracy. Print quality can be improved.

  Further, in the digital printing unit 3, the triple cylinder is used as the printing cylinder 33, so that the size of the printing apparatus is suppressed, and the paper supply side transfer cylinder 32, the inkjet nozzle unit 34, and the ink drying lamp 35 are provided around the printing cylinder 33. The first paper discharge side transfer cylinder 36, the second paper discharge side transfer cylinder 37, the paper take-up cylinder 38, the pre-reverse double cylinder 39, and the reverse swing device 31b can be arranged.

  In particular, the digital printing unit 3 can use the first paper discharge side transfer cylinder 36 and the second paper discharge side transfer cylinder 37 in both the front surface printing process and the back surface printing process. The printing apparatus 1 can be reduced in size.

<Other embodiments>
In the above-described embodiment, the case where the four-color ink jet nozzle portion 34 is used has been described. However, the present invention is not limited to this, and an ink jet nozzle portion having a number of colors equal to or greater than that is used. You may do it.

  In the above-described embodiment, the first discharge side transfer cylinder 36, the second discharge side transfer cylinder 37, and the paper take-up cylinder 38 constituting the sheet discharge unit are used as a plurality of cylinders. The first discharge-side transfer cylinder 36, the second discharge-side transfer cylinder 37, and the pre-reverse double cylinder 39 as a reverse cylinder are used. Although the case where it is used as the reversing mechanism has been described, the present invention is not limited to this, and a plurality of cylinders and reversing mechanisms having various sizes and numbers may be used.

  Furthermore, in the above-described embodiment, the case where the printing cylinder 33 having a triple cylinder is used as the printing cylinder has been described. However, the present invention is not limited to this, and the four-color ink jet nozzle portions 34 are, for example, 6 When the ink jet nozzle portion is changed to a color, a printing cylinder having a quadruple cylinder may be used.

  Further, in the above-described embodiment, the continuous supply valve 26 and the intermittent supply valve 27 of the paper feeding device 2 are used corresponding to the single-sided printing mode and the double-sided printing mode. However, the present invention is not limited to this and is the same. The valve may be controlled so as to vary the timing of opening and closing the valve by a control device.

  DESCRIPTION OF SYMBOLS 1 ... Digital printing apparatus (printing apparatus), 2 ... Paper feed apparatus, 3 ... Digital printing unit, 4 ... Paper discharge apparatus (sheet discharge apparatus), 21, 41 ... Loading platform, 23 ... Soccer apparatus, 25 ... Negative pressure source , 26 ... Continuous supply valve, 27 ... Intermittent supply valve, 31b ... Reversing swing device (reversing device), 31f ... Swing device, 32 ... Feeding side transfer cylinder, 33 ... Printing cylinder, 33a-33c ... Printing cylinder holding nail device , 33d to 33f ... support surface, 34 ... inkjet nozzle section, 35 ... ink drying lamp, 36 ... first discharge side transfer cylinder (first discharge side transfer cylinder), 37 ... second discharge side transfer cylinder (Second discharge side transfer cylinder), 38 ... paper take-up cylinder, 39 ... pre-reversal double cylinder (conveyance cylinder before reversal), 40 ... delivery belt, 80 ... print mode selection switch (print mode selection means), 81 ... control Device, 82 ... Transfer route switching Stage (conveying path switching device), FB ... feeder board, S1 ... sheet.

Claims (5)

A sheet supply device for supplying sheets one by one;
A printing cylinder having a printing cylinder holding claw device for holding and holding one end of the sheet supplied from the sheet supply apparatus;
An inkjet nozzle portion that performs printing by discharging ink droplets onto a sheet conveyed by the printing cylinder;
A reversing gripper device that grips the other end of the sheet, a reversing mechanism that delivers the other end of the sheet to the printing cylinder gripping device, and reverses the front and back of the sheet to supply to the printing cylinder. ,
The reversing mechanism has a plurality of gripping nail devices including the reversing gripping nail device, and only the plurality of gripping nail devices are replaced until the sheet is transferred from the printing cylinder to the printing cylinder. A printing apparatus, characterized by being conveyed by The reversing mechanism includes a conveying cylinder before reversing that includes the gripping claw device and conveys one end of the sheet, and a reversing conveying cylinder that includes the reversing gripping claw device and adds the other end of the sheet. The printing apparatus according to claim 1, further comprising a reversing device that receives and conveys the sheet. The reversing mechanism is
A first discharge side transfer cylinder that is in contact with the printing cylinder, includes the gripper device, and conveys by holding one end of the sheet;
A second discharge-side transfer cylinder that contacts the first discharge-side transfer cylinder and includes the gripping claw device and conveys one end of the sheet;
The conveyance cylinder before reversing is in contact with the second discharge side transfer cylinder,
The printing apparatus according to claim 2, wherein the reversing device delivers a sheet to the printing cylinder. A sheet discharge device for discharging the sheet;
A transport path switching device that switches the sheet transport destination to the discharge device or the reversing device;
A printing mode selection unit that selects a single-sided printing mode in which printing by the inkjet nozzle unit is performed only on one side of the sheet or a double-sided printing mode in which both sides of the sheet are performed;
The printing apparatus according to claim 2, further comprising: a control device that controls the transport path cutting device based on the print mode selection unit. A sheet supply device for supplying a sheet to the printing cylinder;
The control device includes:
Controlling the sheet feeding device to continuously feed sheets in a first cycle when single-sided printing is selected by the printing mode selection means;
The sheet feeding device is controlled to intermittently feed a sheet at a second cycle that is twice as long as the first cycle when double-sided printing is selected by the printing mode selection unit. Item 5. The printing apparatus according to Item 4.

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