JP2013248879A - Digital sheet printing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To propose a digital sheet printing apparatus capable of preventing damage of a nozzle head even if a failure in conveying a sheet occurs.SOLUTION: A digital sheet printing apparatus includes: a conveyance unit 33 for conveying a sheet S1; nozzle heads 34a-34d for discharging ink onto the sheet S1 conveyed by the conveyance unit 33; a conveyance state detecting unit 99 provided on an upstream side in the conveying direction of the sheet S1 from the nozzle heads 34a-34d to detect a conveyance state of the sheet S1; nozzle mounting/removing devices 276 and 278 for moving the nozzle heads 34a-34d between a printing position for printing on the sheet S1 and a retreat position separate from a surface of the sheet S1; and a control unit 100 for controlling the nozzle mounting/removing devices 276 and 278 to move the nozzle heads 34a-34d to the retreat position when the conveyance state detecting unit 99 detects a failure in conveying the sheet S1 conveyed by the conveyance unit 33.

Description

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

  Conventionally, a printing machine capable of digital printing on a sheet has been proposed (see, for example, Patent Document 1). In the invention of Patent Document 1, it is disclosed that an image is recorded by an ink jet method while a recording medium is accurately conveyed by a nail.

JP 2009-262537 A

  Here, in general, in a sheet digital printing machine that performs printing on a sheet by an ink jet method, an image is printed on the sheet by ejecting ink onto the sheet, but ink droplets are ejected during printing. It is desirable to make the ink nozzle head to be as close as possible to the sheet. Thereby, the accuracy of the landing position of the ink droplet on the sheet is increased, and high-quality printing can be performed.

  However, the sheet may be conveyed in a state where wrinkles or creases occur, and when the sheet is conveyed to the ink nozzle head in such a poor conveyance state, the ink nozzle head approaches the sheet. For this reason, there is a problem in that the ink nozzle head interferes with the raised portion due to wrinkling or folding of the sheet, and the ink nozzle head is damaged.

  The present invention has been made to solve such a problem, and an object of the present invention is to propose a sheet digital printing machine capable of preventing the nozzle head from being damaged even when a sheet conveyance failure occurs.

  In order to solve this problem, in the first aspect of the present invention, a transport unit that transports a sheet, a nozzle head that ejects ink onto the sheet transported by the transport unit, and an upstream side of the nozzle head in the transport direction of the sheet A conveyance state detection unit that detects a conveyance state of the sheet, a nozzle attachment / detachment device that moves the nozzle head between a printing position for printing on the sheet and a retreat position away from the surface of the sheet, and the conveyance state And a control unit that controls the nozzle attaching / detaching device to move the nozzle head to the retracted position when the detection unit detects a conveyance failure state of the sheet conveyed by the conveyance unit.

  In the invention of claim 2, when the conveyance state detection unit detects a conveyance failure state of the sheet, the control unit stops the conveyance unit and then moves the nozzle head to a retracted position. Can do.

  According to a third aspect of the present invention, the control unit drives the transport unit while moving the nozzle head to the retracted position based on an operation of the discharge instruction switch.

  Furthermore, in the invention of claim 4, the conveyance failure detection unit can be a sensor for detecting a distance from the sheet.

  According to the first aspect of the present invention, when the sheet conveyance failure is detected, the nozzle head is moved to the retracted position, so that the sheet conveyance failure and the nozzle head are prevented from colliding in advance. Even if it occurs, it is possible to prevent the nozzle head from being damaged.

It is a side view which shows the whole structure of a digital printing apparatus. It is a side view which shows the sheet thickness adjustment mechanism in a printing position. It is a side view showing a sheet thickness adjustment mechanism in the retracted position. It is a side view which shows the sheet thickness adjustment mechanism in a maintenance position. It is sectional drawing which shows the structure of a 1st clamp member. 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 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 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 sheet digital printing machine includes a paper feeding device 2 as a supply unit, a digital printing unit 3 as a processing unit, and a paper discharge device 4 as a discharge unit.

  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 as a conveyance unit is disposed in contact with the sheet feeding-side transfer cylinder 32 on the downstream side in the sheet conveyance direction from the swing device 31f, and the printing cylinder 33 is rotatably supported by the frame 3a. The printing cylinder 33 has a diameter three times that of the sheet feeding side transfer cylinder 32, and the printing cylinder holding nail apparatus 33a that receives and holds the leading end of the sheet S1 from the holding nail apparatus 32a of the sheet feeding side transfer cylinder 32. , 33b, 33c, and support surfaces 33d, 33e, 33f that are provided corresponding to the printing cylinder gripper devices 33a, 33b, 33c and support the sheet S1, and are a set of the printing cylinder gripping device and the support surface It is configured as a triple cylinder provided with three sets. 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.

  As shown in FIG. 2, a plurality of suction holes 33g are formed in the support surfaces 33d, 33e, and 33f of the printing cylinder 33, and the plurality of suction holes 33g are connected to a negative pressure source (not shown). Yes. A gear 270 is fixed to one of the shafts 33p of the printing cylinder 33, and is connected to a drive motor (not shown).

  As shown in FIG. 1, the suction operation range of the sheet S <b> 1 by the suction hole 33 g of the printing cylinder 33 starts the suction in the vicinity of the downstream side in the sheet conveying direction from the contact portion of the printing cylinder 33 with the sheet feeding side transfer cylinder 32. From the position 33 i to the suction end position 33 j near the upstream side in the sheet conveying direction from the contact portion with the first delivery side transfer cylinder 36, the entire surface of the sheet S 1 is in the suction cylinder 33 in this suction operation range. It is adsorbed on the support surfaces 33d, 33e, 33f.

  An inkjet nozzle portion 34 is disposed opposite to the peripheral surface of the printing cylinder 33 on the downstream side in the sheet conveyance direction from the portion where the printing cylinder 33 is in contact with the sheet feeding side transfer cylinder 32.

  In the inkjet nozzle section 34, a plurality of inkjet nozzle heads 34a to 34d in which inks of different colors are set are arranged side by side along the circumferential surface of the printing cylinder 33 in the sheet conveying direction. Oriented. The inkjet nozzle heads 34a to 34d as the nozzle heads have a printing cylinder 33 so that the gaps between the sheet S1 adsorbed on the entire supporting surfaces 33d, 33e and 33f by the plurality of suction holes 33g of the printing cylinder 33 are slightly spaced. It is arrange | positioned adjacent to. The printing cylinder 33 and the inkjet nozzle unit 34 constitute a sheet printing apparatus, and the peripheral surface portion of the printing cylinder 33 facing the inkjet nozzle heads 34a to 34d forms a printing region 33k for printing on the sheet S1. doing.

  Next, the support structure of the inkjet nozzle part 34 is demonstrated using FIG. 2 thru | or FIG. Here, the support configuration of the inkjet nozzle head 34d will be described in particular, but the support configuration of the inkjet nozzle heads 34a to 34c is the same as that of the inkjet nozzle head 34d.

  Guide rails 281 that are provided above the printing cylinder 33 and extend in the axial direction of the printing cylinder 33 and extend at both ends thereof to the outside of the frames 3a and 3a are fixed to the frames 3a and 3a via support members (not shown). Has been. Sliders 282 and 284 are slidably supported on the guide rail 281, and holders 283 and 285 are fixed to the sliders 282 and 284, respectively.

  To the holders 283 and 285, stays ST1 and ST2 on which cylinder bodies 276a and 278a of air cylinders 276 and 278 as ink jet nozzle attaching / detaching devices are supported are fixed to one end. Both end portions of the support plate 34dp are fixed to the piston rods 276b and 278b of the air cylinders 276 and 278, and the inkjet nozzle head 34d is supported on the support plate 34dp.

  The ink jet nozzle head 34d is detachable by air cylinders 276 and 278, and from a printing position close to the printing cylinder 33 shown by a solid line in FIGS. 2 and 1 and a printing position shown by a broken line in FIGS. The printing cylinder 33 is supported so as to be movable between a retreat position and a retreat position away from the print cylinder 33 in the radial direction. Further, the inkjet nozzle head 34d is supported so as to be movable between a retracted position shown in FIG. 3 and a maintenance position outside the frame 3a shown in FIG. 4 by moving along the guide rail 281. .

  Reference numerals 275 and 277 in FIG. 2 denote inkjet nozzle adjusting devices serving as inkjet nozzle adjusting means that are provided at both ends of the support plate 34dp and adjust the position of the inkjet nozzle head 34d with respect to the printing cylinder 33. FIG. A detailed configuration is shown. The detailed configuration of the inkjet nozzle adjustment devices 275 and 277 will be described with reference to FIG. 5, but since both have the same structure, only the inkjet nozzle adjustment device 275 will be described here.

  An outer peripheral wall 291b of a housing 291 in the inkjet nozzle adjusting devices 275 and 277 is fixed to the support plate 34dp, and a female screw portion 297 having a female screw on the inner periphery is fixed inside the outer peripheral wall 291b. A holding plate 291a is fixed inside the housing 291 and a motor 294 is fixed to the holding plate 291a. A male screw member 296 is supported at one end of the motor shaft 294a of the motor 294 so as to rotate integrally with the motor shaft 294a and to be movable in the axial direction of the motor shaft 294a. The male screw member 296 is screwed into the female screw portion 297, and a first engagement member 298 having an engagement hole 298b formed at the tip thereof is fixed.

  A potentiometer 292 is provided at the upper end of the housing 291, and the potentiometer 292 and the motor 294 are connected to each other via a motor shaft 294 a and a coupling 293.

  On the other hand, as shown in FIG. 3, second engaging members 271 and 272 are provided at upper ends of the left and right frames 3 a and 3 a, respectively. The second engagement members 271 and 272 protrude from the main bodies 271a and 272a fixed to the frame 3a by a predetermined amount from the upper end surfaces of the main bodies 271a and 272a and are inserted into the engagement holes 298b and 298b of the inkjet nozzle adjustment devices 275 and 277. Guide pins 271b and 272b. Further, the upper end surfaces of the main bodies 271a and 272a and the outer peripheral surface of the printing cylinder 33 are aligned at substantially the same height. The slider heads 282 and 284, the holders 283 and 285, the stays ST1 and ST2, and the air cylinders 276 and 278 are movable in the direction in which the nozzle heads 34a to 34d of the ink jet nozzle section 34 are moved toward and away from the printing surface of the sheet S1. The head holding unit that holds the head is configured.

  The printing cylinder 33 is disposed on the downstream side in the sheet conveyance direction from the printing region 33k by the ink jet nozzle portion 34, and is arranged in contact with the printing cylinder 33. The sheet S1 is irradiated with light such as infrared rays or ultraviolet rays to be printed on the sheet S1. An ink drying lamp 35 is provided as a drying device for drying the ink. Here, the drying includes applying heat energy to evaporate the moisture of the ink or curing the ink, and can be called solidification.

  A first paper discharge side transfer cylinder 36 is disposed in contact with the printing cylinder 33 on the downstream side in the sheet conveying direction from the ink jet nozzle portion 34, and the first paper discharge side transfer cylinder 36 is rotatable to the frame 3a. It is supported by. 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 paper discharge side transfer cylinder 37 is in contact with the first paper discharge side transfer cylinder 36 on the downstream side of the first paper discharge side transfer cylinder 36 in contact with the printing cylinder 33 in the sheet conveying direction. The second paper discharge side transfer cylinder 37 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-reverse double cylinder 39 is disposed in contact with the paper discharge cylinder 38 on the downstream side of the second paper discharge side transfer cylinder 37 and the paper take-up cylinder 38. The pre-reverse double cylinder 39 is disposed on the frame 3a. It is supported rotatably. 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 set of gripper claw devices 39a is provided.

  As shown in FIG. 6, as shown in FIG. 6, the rear end (the other end of the sheet S <b> 1) is located downstream of the portion of the pre-reverse doubler 39 that is in contact with the second discharge-side transfer cylinder 37. A reversing swing device 31b provided with a gripper device 31bt for receiving and holding the (butt side end) is disposed oppositely. The reversing swing device 31b constitutes a reversing unit 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 3a so as to be swingable between 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 (FIG. 7) is configured to switch the conveyance destination of the sheet S1 to the paper discharge device 4 or the reverse swing device 31b, that is, to switch the conveyance path of the sheet S1 to the sheet discharge route or the sheet reverse route.

  Further, the printing cylinder 33 is conveyed by the printing cylinder 33 at the downstream side in the sheet conveying direction from the contact portion of the printing cylinder 33 with the feeding side transfer cylinder 32 and at the upstream side in the sheet conveying direction from the printing area 33K by the ink jet nozzle unit 34. A sheet conveyance defect detection device 99 is provided as a conveyance state detection unit that detects conveyance defects such as floating or folding of the sheet S1 from the printing cylinder 33.

  The sheet conveyance defect detection device 99 is a sensor such as a photoelectric sensor that detects the distance from the sheet S1 conveyed by the printing cylinder 33, and outputs the detection result to the control device 100 (FIG. 7) described later. When the distance detected by the sheet conveyance defect detection device 99 is shorter than a preset threshold value, the control device 100 determines that a conveyance defect due to the folding or wrinkling of the sheet S1 occurs.

<Configuration of control system of digital printing device>
As shown in FIG. 7, the digital printing apparatus 1 includes a control device 100 as a control unit having a CPU (Central processing Unit) configuration for overall control. The control device 100 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. A switch 101, a drive motor 302 that rotationally drives the printing cylinder 33, a rotary encoder 304 as a phase detection device that detects the phase of the printing cylinder 33, and the sheet S <b> 1 supplied from the sheet feeding device 2 are loaded on the loading table 41 of the sheet ejection device 4 A discharge instruction switch 98 for outputting a discharge instruction, a sheet thickness input means 301 for inputting the thickness of the sheet S1 by an input by an operator or detection by a detector, a sheet conveyance defect detection device as a conveyance defect state detection unit 99, continuous supply valve 26, intermittent supply valve 27, transport path switching means 82, inkjet nozzle part 34 inkjet nozzle heads 34a to 34d, nozzle attachment / detachment devices 3401a to 3401d for the inkjet nozzle heads 34a to 34d, nozzle adjustment devices 3402a to 3402d for the inkjet nozzle heads 34a to 34d, and inkjet nozzle heads 34a to 34d Potentiometers 292a to 292d, head position adjusting switches 303a to 303d for the respective ink jet nozzle heads 34a to 34d, and an ink drying lamp 35 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 101, the control device 100 operates 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.

  The continuous supply valve 26 feeds the same number of sheets S1 as the number of the printing cylinder holding nail devices 33a, 33b, 33c provided in the printing cylinder 33 during one rotation of the printing cylinder 33, in other words, the printing cylinder. The continuous supply valve 26 is "opened" at each timing (cycle) at which each gripper claw device 33a, 33b, 33c and the gripping claw device 32a of the paper feed side transfer cylinder 32 face each other at 33, and the first suction 23a and second The suction 23b is operated so as to be sucked from the negative pressure source 25. 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. Thereby, the soccer device 23 conveys the sheet S1 to the feeder board FB in the first cycle.

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

  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. Since the printing cylinder 33 has a suction force acting on the suction hole 33g on the downstream side in the rotation direction from the suction start position 33i, when the sheet S1 passes the suction start position 33i, the entire surface of the sheet S1 is applied to the support surfaces 33d, 33e, and 33f. Adsorbed and adhered.

  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 be landed on the sheet with high accuracy, and high-quality printing can be performed. The sheet S1 printed by the ink jet 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.

  Since the sheet S1 is in close contact with the support surfaces 33d, 33e, and 33f of the printing cylinder 33 in the suction operation range from the suction start position 33i to the suction end position 33j, the sheet S1 is applied to the entire surface of the sheet S1 from the ink drying lamp 35. Light is uniformly irradiated, and ink drying without unevenness is performed.

  As shown in FIG. 8, in the contact portion between the printing cylinder 33 and the first discharge-side transfer cylinder 36, the first discharge-side transfer cylinder 36 is held from the printing cylinder holding claw devices 33 a to 33 c of the printing cylinder 33. The leading end of the sheet S1 is replaced with the nail device 36a. At that time, since the leading end side of the sheet S1 passes through the suction end position 33j, the suction force from the suction hole 33g is lost, and the sheet S1 is easily peeled off from the support surfaces 33d, 33e, and 33f, so It can be changed.

  After that, as shown in FIG. 9, the sheet S <b> 1 held by the gripper 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 case of the single-sided printing mode, the controller 100 switches the conveyance path switching unit so that all the sheets S1 are transferred from the second paper discharge side transfer cylinder 37 to the paper take-up cylinder 38 based on the detection signal from the rotary encoder 304. 82 is controlled. That is, in a phase where the leading end of the sheet S1 is positioned at the contact portion between the second discharge side transfer cylinder 37 and the paper take-up cylinder 38, the gripping claw device 37a of the second discharge side transfer cylinder 37 moves the sheet S1. The holding of the leading edge is released, and the gripping claw device 38a of the paper drum 38 holds and holds the leading edge of the sheet S1. As a result, all the sheets S1 printed on one side are transferred from the second discharge 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 subjected to digital printing processing on the surface is discharged onto the stacking table 41 of the paper discharge device 4.

  On the other hand, when the double-sided printing mode is selected by the operator's operation of the printing mode selection switch 101, the control device 100 operates the intermittent supply valve 27, whereby the stack 21 is moved by the first suction 23a and the second suction 23b. The sheet S1 is adsorbed and conveyed to the feeder board FB.

  The intermittent supply valve 27 supplies the sheet S1 at every other timing with respect to the continuous supply timing, in other words, the gripping device 33a, 33b, 33c in the printing cylinder 33 and the feeding cylinder 32. The valve is controlled to be “open”, “closed”, “open”, “closed”,... At the timing (cycle) at which the gripper device 32a 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. Thereby, the soccer device 23 conveys the sheet S1 to the feeder board FB in the second cycle.

  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, based on the detection signal from the rotary encoder 304, the control device 100 performs printing on the new sheets S1 held every other one of the printing cylinder holding nail devices 33a to 33c of the printing cylinder 33, 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 printing cylinder holding nail devices 33a to 33c not holding the sheet S1.

  In the double-sided printing mode, the control device 100 does not transfer the sheet S1 printed on the surface by the inkjet nozzle unit 34 from the second paper discharge side transfer cylinder 37 to the paper take-up cylinder 38. The conveyance path switching means 82 is controlled so as to be delivered to the pre-reverse double cylinder 39.

  That is, in the case of the duplex printing mode, the sheet S1 that has been printed on the front surface but not digitally printed on the other surface (back surface) is the second discharge side transfer drum 37 and the paper drum 38. In the phase positioned at the contact portion, the claw of the gripping claw device 37a of the second paper discharge side transfer cylinder 37 is kept open, that is, the state in which the leading edge of the sheet S1 is held is maintained. At the same time, the claw of the gripping claw device 38a of the paper drum 38 is kept open without being closed.

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

  As shown in FIG. 11, the sheet S1 conveyed along with the rotation of the pre-inversion double cylinder 39 is conveyed along with the rotation of the pre-inversion double cylinder 39, and the reverse swing device 31b receives from the delivery position indicated by the solid line as indicated by a broken line. Swinging to the position, the rear end of the sheet S1 is held by the reversing gripping claw device 31bt of the reversing swing device 31b, and at the same time, the holding of the front claw device 39a of the double cylinder 39 before reversing is released from the front end of the sheet S1. Thereby, the sheet S1 is replaced by the reverse swing device 31b from the pre-inversion double cylinder 39.

  Then, as shown in FIG. 12, the sheet S <b> 1 is placed on the printing cylinder 33 with the trailing edge (end of the paper bottom side) as the leading edge by swinging from the receiving position indicated by the broken line to the delivery position indicated by the solid line of the reverse swing device 31 b. The rear end of the sheet S1, which is conveyed toward and reversed from the reverse gripping device 31bt of the reverse swing device 31b to the printing cylinder gripping device 33a to 33c of the printing cylinder 33, is replaced.

  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. It is positioned at the delivery position at a timing facing the printing cylinder holding nail devices 33a to 33c not holding the sheet S1, and the rear end of the sheet S1 is transferred from the reverse holding nail device 31bt to the printing cylinder holding nail devices 33a to 33c. As a result, a new sheet S1 delivered from the feed-side transfer cylinder 32 and a sheet S1 in an inverted state received from the reversing gripper nail apparatus 31bt are supplied to the printing cylinder holding claw apparatuses 33a to 33c of the printing cylinder 33. Are alternately held and conveyed to the inkjet nozzle section 34.

  At this time, the sheet S1 in the front and back reversed state transferred from the reversing 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 section 34 (surface that has been subjected to digital printing processing). With the support surfaces 33d, 33e, and 33f of the sheet 33 in contact with each other and the back surface of the sheet S1 (the surface that has not been digitally printed) exposed, the rear end of the sheet S1 is formed by the printing cylinder holding nail devices 33a to 33c of the printing cylinder 33. The sheet S <b> 1 is conveyed while being held, that is, the sheet S <b> 1 is conveyed in an inverted state, and digital printing processing is performed on the back surface of the sheet S <b> 1 by the inkjet nozzle unit 34.

  Here, the control device 100 performs printing for the back side of the sheet S1 in the reverse state, which is transferred from the reverse gripping device 31bt of the reverse swing device 31b based on the detection signal from the rotary encoder 304, The inkjet nozzle heads 34a to 34d of the inkjet nozzle section 34 are controlled so that printing is performed on the surface of the new sheet S1 held every other one of the printing cylinder holding nail devices 33a to 33c of the printing cylinder 33. To do. Accordingly, the inkjet nozzle heads 34a to 34d alternately perform front surface printing and back surface printing corresponding to the new sheet S1 held alternately by the printing cylinder 33 and the front and back reversed sheet S1. 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. Through the delivery belt 40 to the loading table 41.

  The above is the printing operation in the single-sided printing mode and the double-sided printing mode in the digital printing apparatus 1. Next, head position adjustment with respect to the sheet S1 of the inkjet nozzle heads 34a to 34d will be described.

  When the head position adjustment switches 303a to 303d for the respective ink jet nozzle heads 34a to 34d are operated by the operator and the thickness of the sheet S1 is input to the sheet thickness input unit 301 by the operator or the detector, the control is performed. The apparatus 100 calculates the operation amount of a motor 294 (FIG. 5) as a head position adjustment device based on the potentiometers 292a to 292d of the ink jet nozzle heads 34a to 34d, and operates the motor 294 according to the operation amount.

  When the motor 294 is operated, the motor shaft 294a rotates with the male screw member 296 as shown in FIG. Due to the rotation of the male screw member 296, the male screw member 296 moves in the axial direction of the motor shaft 294a by the screw action with the female screw portion 297, and the protruding amount L from the support plate 34dp is adjusted. The adjustment work of the ink jet nozzle heads 34a to 34d is performed in a state where the ink jet nozzle heads 34a to 34d are at the retracted positions (FIG. 3) prior to the printing work.

  Thus, after the protrusion amount L of the male screw member 296 from the support plate 34dp is adjusted, when the air cylinders 276 and 278 are operated from the state where the inkjet nozzle heads 34a to 34d are in the retracted position, the support plate 34dp The ink jet nozzle heads 34 a to 34 d and the ink jet nozzle adjusting devices 275 and 277 are moved in the direction approaching the printing cylinder 33.

  During this movement, the engagement hole 298b of the first engagement member 298 engages with the guide pins 271b, 272b of the second engagement members 271, 272, and then the lower end surface of the first engagement member 298 is the second engagement. The combined members 271 and 272 are pressed against the upper end surfaces of the main bodies 271a and 272a. Due to the engagement between the engagement hole 298b and the guide pins 271b and 272b and the pressing of the lower end surface of the first engagement member 298 to the upper end surfaces of the main bodies 271a and 272a by the air cylinders 276 and 278, the support plate 34dp, that is, the inkjet The nozzle heads 34a to 34d are integrally fixed to the frames 3a and 3b.

  By adjusting the protrusion amount L in this way, the head positions of the inkjet nozzle heads 34a to 34d with respect to the upper end surfaces of the main bodies 271a and 272a are adjusted, that is, the head positions of the inkjet nozzle heads 34a to 34d with respect to the printing cylinder 33 are adjusted. The In this manner, the distance between the ink jet nozzle heads 34a to 34d and the sheet S1 is adjusted to be a predetermined distance.

  Thereby, even if the thickness of the sheet S1 is changed, a predetermined minute gap is maintained between the inkjet nozzle heads 34a to 34d and the sheet S1, and the ink discharged from the inkjet nozzle heads 34a to 34d is applied to the sheet S1 with high accuracy. Landing can be achieved, and high-quality printing can be performed.

  Next, the operation of the sheet conveyance defect detection device 99 will be described. Before the sheet S1 conveyed by the printing cylinder 33 is conveyed to the ink jet nozzle section 34, the sheet conveyance defect detecting device 99 detects conveyance defects such as lifting and folding from the printing cylinder 33. When the sheet S1 is normally conveyed, the entire surface of the sheet S1 is in close contact with the support surfaces 33d, 33e, and 33f of the printing cylinder 33, and the distance from the sheet S1 measured by the sheet conveyance defect detection device 99 is If the sheet S1 is wrinkled, floated, bent, or the like for some reason, the distance from the sheet S1 measured by the sheet conveyance defect detection device 99 becomes smaller than the threshold. The control device 100 controls the drive motor 302 to stop and stops the printing cylinder 33 when a conveyance failure such as wrinkles, floats, corner breaks, or the like occurs in the sheet S1 based on the detection result by the sheet conveyance failure detection device 99. At the same time, the air cylinders 276 and 278 as the ink jet nozzle attaching / detaching device are operated.

  By the operation of the air cylinders 276 and 278, the support plate 34dp moves in a direction away from the printing cylinder 33 along with the ink jet nozzle heads 34a to 34d and the ink jet nozzle adjusting devices 275 and 277. Thereby, the inkjet nozzle heads 34a to 34d of the inkjet nozzle portion 34 move from the printing position to the retracted position.

  By stopping the rotation of the printing cylinder 33, the sheet S1 having a conveyance failure conveyed by the printing cylinder 33 is prevented from reaching the inkjet nozzle section 34, and the inkjet nozzle heads 34a to 34d are positioned at the retracted positions. By separating from the printing cylinder 33, it is possible to reliably avoid the interference between the sheet S1 having poor conveyance and the ink jet nozzle heads 34a to 34d, and to prevent the ink jet nozzle heads 34a to 34d from being damaged. The control device 100 controls the inkjet nozzle heads 34a to 34d so as not to eject ink based on the detection result by the sheet conveyance defect detection device 99.

  Then, the control device 100 rotates the printing cylinder 33 via the drive motor 302 while moving the inkjet nozzle heads 34a to 34d to the retracted position based on the operation of the discharge instruction switch 98 from the operator.

  Further, the control device 100 conveys the sheet S1 supplied from the paper feeding device 2 by the printing cylinder 33 regardless of the printing mode selection result by the printing mode selection switch 101, and the first discharge side transfer cylinder 36, The transport device including the transport path switching means 82 is controlled so that the paper is discharged to the stacking base 41 via the paper discharge side transfer drum 37, the paper take-up drum 38, and the delivery belt 40. As a result, all the sheets S1 supplied from the sheet feeding device 2 when the sheet conveyance failure is detected are discharged to the stacking table 41, and the discharge operation of the sheet S1 including the sheet S1 causing the conveyance failure is easily performed. be able to. Of course, since the sheet S1 does not interfere with the ink jet nozzle heads 34a to 34d during the discharging operation, the ink jet nozzle heads 34a to 34d are prevented from being damaged.

  Finally, when printing by the digital printing apparatus 1 is completed and maintenance work is performed on the ink jet nozzle heads 34a to 34d, the ink jet nozzle heads 34a to 34d positioned at the retracted position shown in FIG. And move to the maintenance position shown in FIG. Since the inkjet nozzle heads 34a to 34d are positioned outside the frame 3a at the maintenance position, the maintenance work can be easily performed, and the burden on the operator is greatly reduced.

<Other embodiments>
In the above-described embodiment, the case where the sheet thickness adjustment process is performed in the retracted position (FIG. 3) has been described. However, the present invention is not limited to this, and the maintenance position (FIG. 4) is used. In some cases, or a printing position in which the inkjet nozzle adjustment devices 275 and 277 on the inkjet nozzle head 34d (34a to 34d) side and the second engaging members 271 and 272 on the printing cylinder 33 side are coupled to each other ( It may be performed in FIG.

  Further, in the above-described embodiment, the sheet reversing mechanism is configured by the first discharge side transfer drum 36, the second discharge side transfer drum 37, the pre-reverse double drum 39, and the reverse swing device 31b. However, the size and the number of the cylinders are not limited to those of the present embodiment as long as the cylinders and the swings having the gripping claw device are used. In short, what is necessary is just to comprise so that the sheet | seat S1 can be conveyed by the holding change only of these holding nail apparatuses.

  In the above-described embodiment, the case where the printing cylinder 33 having a triple cylinder is used has been described. A printing cylinder may be used.

  Furthermore, in the above-described embodiment, the motor 294, the male screw member 296, and the female screw part 297 are provided as actuators for finely adjusting the position of the ink jet nozzle head 34d (34a to 34c) with respect to the ink jet nozzle adjusting devices 275 and 277 in the vertical direction. However, the present invention is not limited to this, and the motor 294 pushes the male screw member 296 downward, or biases the male screw member 296 upward via a spring (not shown). The position of the inkjet nozzle head 34d (34a to 34c) with respect to the inkjet nozzle adjustment devices 275 and 277 may be finely adjusted in the vertical direction.

  Furthermore, in the above-described embodiment, the case where the printing cylinder 33 is used has been described. However, the present invention is not limited to this, and digital printing is performed by the inkjet nozzle unit 34 while the sheet S1 is conveyed horizontally. A simple transport table (not shown) 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.

  In the above-described embodiment, the continuous supply valve 26 and the intermittent supply valve 27 of the paper feeder 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 by the control device 100 so that the valve opening / closing timing (cycle) is different.

  DESCRIPTION OF SYMBOLS 1 ... Digital printing apparatus (sheet digital printing machine), 2 ... Sheet feeder, 3 ... Digital printing unit, 4 ... Discharge device, 21 and 41 ... Loading platform, 23 ... Soccer device, 25 ... Negative pressure source, 26 ... Continuous Supply valve, 27 ... intermittent supply valve, 31b ... reverse swing device, 31f ... swing device, 32 ... paper feed side transfer cylinder, 33 ... printing cylinder, 34 ... inkjet nozzle section, 34a-34d ... inkjet nozzle head (nozzle head) 35 ... Ink drying lamp, 36 ... First paper discharge side transfer cylinder, 37 ... Second paper discharge side transfer cylinder, 38 ... Paper cylinder, 39 ... Double cylinder before reversing, 40 ... Delivery belt, FB ... Feeder Board, S1 ... sheet, 82 ... conveyance path switching means, 98 ... discharge instruction switch, 99 ... sheet conveyance defect detection device (conveyance state detection unit), 100 ... control device (control unit) 270 ... Gear, 271, 272 ... Second engaging member, 275, 277 ... Inkjet nozzle adjusting device, 276, 278 ... Air cylinder, 281 ... Guide rail, 282, 284 ... Slider, 292 ... Potentiometer, 293 ... Cup Ring, 294 ... motor, 296 ... male screw member, 297 ... female screw part, 298 ... first engaging member, 301 ... sheet thickness input means, 302 ... drive motor, 303 ... position adjustment switch, 304 ... rotary encoder, 3401a- 3401d ... Nozzle attaching / detaching device, 3402a-3402d ... Nozzle adjusting device.

Claims (4)

A conveyance unit for conveying a sheet;
A nozzle head that ejects ink onto a sheet conveyed by the conveyance unit;
A conveyance state detection unit that is provided upstream of the nozzle head in the sheet conveyance direction and detects the conveyance state of the sheet;
A nozzle attaching / detaching device for moving the nozzle head between a printing position for printing on a sheet and a retracted position away from the surface of the sheet;
A controller that controls the nozzle attaching / detaching device to move the nozzle head to the retracted position when the conveyance state detection unit detects a conveyance failure state of the sheet conveyed by the conveyance unit. Sheet digital printing machine. 2. The sheet according to claim 1, wherein when the conveyance state detection unit detects a conveyance failure state of the sheet, the control unit stops the conveyance unit and then moves the nozzle head to a retracted position. 3. Digital printing machine. The sheet digital printing machine according to claim 2, wherein the control unit drives the conveyance unit while moving the nozzle head to the retracted position based on an operation of a discharge instruction switch. The sheet digital printing machine according to claim 3, wherein the conveyance state detection unit is a sensor that detects a distance from the sheet.

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