Printing device and maintenance method for printing device

Abstract

To provide a printing device and a maintenance method for a printing device that are capable of reducing loosening and wrinkles in a sheet member due to elongation over time.SOLUTION: A printing device comprises a printing drum. The printing drum includes: a main body configured to rotate around a first rotation axis and provided with a cutout, which is formed in an outer surface of the main body and which extends in a direction of the first rotation axis; a sheet member, which is wrapped, under tension, around the outer surface of the main body, and partially located within the cutout; and a pressing member that presses the sheet member within the cutout in a pressing direction different from a direction of the tension applied to the sheet member.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a printing device and a maintenance method for the printing device. [Background technology]

[0002] Conventionally, printing devices such as inkjet printing devices use a technique in which a printing sheet is adsorbed to the outer peripheral surface of a printing drum and transported (see, for example, Patent Documents 1 to 4). In printing devices configured in this way, a coloring material such as ink is applied to the printing sheet that is adsorbed to the printing drum and transported, and an image is printed on it. A sheet member made of resin or the like, which has a large number of through-holes for suctioning air, is wrapped around the outer peripheral surface of the printing drum under tension. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-1198 [Patent Document 2] Japanese Patent Application Publication No. 10-175338 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-279795 [Patent Document 4] Japanese Patent Application Laid-Open No. 2011-178547 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above-mentioned conventional technology has a problem in that the sheet member stretches over time, causing it to loosen and wrinkle. When the sheet member loosens or wrinkles, the printing sheet floats on the sheet member or is not properly adsorbed, resulting in a decrease in print quality.

[0005] An object of the present invention is to provide a printing device and a maintenance method for a printing device that can reduce loosening and wrinkles caused by elongation of a sheet member over time. [Means for solving the problem]

[0006] In order to achieve the above object, the invention of the printing device described in claim 1 is as follows: A printing device having a printing drum, The printing drum is a main body portion that rotates around a first rotation axis and has a notch portion on its outer circumferential surface that extends in the direction of the first rotation axis; a sheet member that is wrapped around the outer peripheral surface of the main body portion in a tensioned state, and a portion of the sheet member is located within the cutout portion; a pressing member that presses the sheet member in a pressing direction different from the direction of the tension applied to the sheet member within the cutout portion; It has.

[0007] The invention described in claim 2 is the printing device described in claim 1, The pressing member is a rod-shaped or plate-shaped member extending in the direction of the first rotation axis.

[0008] The invention described in claim 3 is the printing device described in claim 1, The pressing member has a curved surface at a portion that comes into contact with the sheet member.

[0009] The invention described in claim 4 is the printing device described in claim 1, The sheet member is pressed by the pressing member by moving the pressing member in the pressing direction.

[0010] The invention described in claim 5 is the printing device described in claim 1, The device further includes a rotation mechanism that rotates the pressing member around a second rotation axis that is parallel to the first rotation axis, thereby causing the pressing member to press the sheet member.

[0011] The invention described in claim 6 is the printing device described in claim 1, a holding member for holding the pressing member in a state fixed to the printing drum, The pressing member presses the sheet member by moving or rotating relative to the holding member.

[0012] The invention described in claim 7 is the printing device described in claim 6, a tension member provided in the cutout portion and applying the tension to the sheet member; The retaining member is provided independently of the tension member.

[0013] The invention described in claim 8 is the printing device described in claim 6, a tension member provided in the cutout portion and applying the tension to the sheet member; The retaining member is fixed to the tension member.

[0014] The invention described in claim 9 is the printing device described in claim 1, The pressing member has a crown shape in which the amount of protrusion toward the seat member is greatest at the center in the direction of the first rotation axis.

[0015] The invention described in claim 10 is the printing device described in claim 1, The pressing force with which the pressing member presses the sheet member is determined by the elastic force exerted by a specified elastic member on the pressing member, the fastening force of a specified screw that exerts force directly or indirectly on the pressing member, or the force exerted by a specified actuator on the pressing member.

[0016] The invention described in claim 11 is the printing device described in claim 1, The pressing force with which the pressing member presses the sheet member is determined by the position of a predetermined elastic member that exerts an elastic force on the pressing member, the fastening position of a predetermined screw that exerts a force directly or indirectly on the pressing member, or the position of a predetermined actuator that exerts a force on the pressing member.

[0017] The invention described in claim 12 is the printing device described in claim 10 or 11, an adjustment member for adjusting the pressing force; The adjustment member includes the elastic member, the screw, or the actuator.

[0018] The invention described in claim 13 is the printing device described in claim 1, the sheet member is heat-shrinkable, The pressing member includes a built-in heater that transfers heat to the sheet member when the pressing member is in contact with the sheet member.

[0019] The invention described in claim 14 is the printing device described in claim 13, A control unit is provided to control the heat generation operation of the heater.

[0020] The invention described in claim 15 is the printing device described in claim 13, The heater is capable of adjusting the temperature distribution in the direction of the first rotation axis.

[0021] The invention described in claim 16 is the printing device described in claim 15, The heater is a carbon heater, a sheathed heater, or a halogen heater.

[0022] The invention described in claim 17 is the printing device described in claim 1, The pressing direction is perpendicular to the direction in which the tension is applied.

[0023] In order to achieve the above object, the invention of a maintenance method for a printing device as set forth in claim 18 comprises: A maintenance method for a printing device equipped with a printing drum, comprising: The printing drum is a main body portion that rotates around a first rotation axis and has a notch portion on its outer circumferential surface that extends in the direction of the first rotation axis; a sheet member that is wrapped around the outer peripheral surface of the main body portion in a tensioned state, and a portion of the sheet member is located within the cutout portion; and The maintenance method includes a step of pressing the sheet member in the cutout portion with a pressing member in a pressing direction different from a direction of the tension applied to the sheet member. [Effects of the Invention]

[0024] According to the present invention, loosening and wrinkling of the sheet member due to elongation over time can be reduced. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a side view schematically illustrating a configuration of a printing device. [Figure 2] FIG. 2 is a block diagram illustrating the main functional configuration of the printing apparatus. [Figure 3] FIG. 2 is a side view schematically showing the inside of the main body of the printing apparatus. [Figure 4] FIG. 4 is an enlarged view of an area A in FIG. 3. [Figure 5] FIG. [Figure 6] 10A and 10B are diagrams illustrating a state in which a pressing member presses a resin sheet. [Figure 7] FIG. 10 is a diagram showing a resin sheet in which wrinkles have occurred. [Figure 8] 10A and 10B are diagrams showing a resin sheet in which wrinkles have been reduced by a pressing member; [Figure 9] 10 is a flowchart showing a control procedure for maintenance processing. [Figure 10] 10A and 10B are diagrams illustrating the configuration and operation of a pressing mechanism according to a modified example. [Figure 11] 10A and 10B are diagrams illustrating the configuration and operation of a pressing mechanism according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the scope of the invention is not limited to the illustrated examples.

[0027] (Printing device) FIG. 1 is a side view schematically illustrating the configuration of a printing device 1. As shown in FIG. FIG. 2 is a block diagram showing the main functional configuration of the printing device 1. As shown in FIG. The printing device 1 is a sheet-fed on-demand printer. The printing method of the printing device 1 is an inkjet method in which an image is formed by ejecting ink from the nozzles of an inkjet head onto a printing sheet 99. As shown in FIG. 1, the printing device 1 includes a paper feed unit 10, a printing device main body 30, a paper discharge unit 20, and a control unit 90. The printing device main body 30 includes a print head 31, a transport device 40, a temperature sensor 71, a paper lift detector 72, an ultraviolet irradiator 73, an imaging unit 74, a first heater 75, a transport drive unit 76, a rotary actuator 77, and a pressing mechanism 80.

[0028] A plurality of printing sheets 99 are stored in a stacked state in the paper feed unit 10. The paper feed unit 10 feeds the stacked printing sheets 99 one by one to the printing device main body 30. The printing sheets 99 are also referred to as recording media or media.

[0029] The paper supply unit 10 has a paper supply tray 11, a separator 12, and a feeder board 13. The paper supply tray 11 supports a plurality of stacked print sheets 99 from below. The separator 12 removes the print sheets 99 from the paper supply tray 11 one by one from the top to the feeder board 13. The feeder board 13 has, for example, an endless belt conveyor. The feeder board 13 transports the print sheets 99 removed by the separator 12 to an intake port of the printing device main body 30.

[0030] The printing device main body 30 prints an image on a printing sheet 99 supplied by the paper feed section 10, and discharges the printed printing sheet 99 to the paper discharge section 20. Details of the printing device main body 30 will be described later.

[0031] The paper discharge section 20 stacks and stores the printable sheets 99 printed by the printing device main body 30. The paper discharge section 20 has a discharger 21 and a paper discharge tray 22. The discharger 21 is arranged from the discharge opening of the printing device main body 30 to the paper discharge tray 22. The discharger 21 has, for example, an endless belt conveyor or the like. The discharger 21 transports the printable sheets 99 printed by the printing device main body 30 to the paper discharge tray 22. The printable sheets 99 transported by the discharger 21 are placed in a stack on the paper discharge tray 22.

[0032] (printing device body) The transport device 40 of the printing apparatus main body 30 transports the printable sheet 99 supplied from the feeder board 13 of the paper supply unit 10 to the discharge device 21 of the paper discharge unit 20. The transport device 40 inverts the printable sheet 99 as needed while it is being transported. The transport device 40 includes a swing arm 41, transport drums 42, 44, 46, a printing drum 60, a selection drum 45, a reversing drum 47, a swing arm 48, and a transport drive unit 76. The drum is also called a body, cylinder, or roller.

[0033] The rotation axes of the transport drums 42, 44, 46, print drum 60, selection drum 45, and reversing drum 47 are parallel to one another. Outside the outer circumferential surface of the print drum 60, the transport drum 42, temperature sensor 71, paper lift detector 72, print head 31, ultraviolet irradiator 73, imaging unit 74, transport drum 44, first heater 75, reversing drum 47, and swing arm 48 are arranged in this order with respect to the forward rotation direction of the print drum 60. The forward rotation direction of the print drum 60 is indicated by arrow 96 in the figure. Hereinafter, the direction parallel to the rotation axis of the print drum 60 will be referred to as the axial direction. The direction of forward rotation around the rotation axis of the print drum 60 will be referred to as the circumferential direction. The direction perpendicular to the rotation axis of the print drum 60 will be referred to as the radial direction.

[0034] The transport drive unit 76 drives and rotates the swing arm 41, transport drums 42, 44, and 46, printing drum 60, selection drum 45, reversing drum 47, and swing arm 48 under the control of the control unit 90. The transport drive unit 76 has one or more motors and a transmission mechanism. The transmission mechanism transmits the motor's power to the swing arm 41, transport drums 42, 44, and 46, printing drum 60, selection drum 45, reversing drum 47, and swing arm 48. The transmission mechanism is, for example, a gear transmission mechanism or a wrap transmission mechanism. The rotation directions of the transport drums 42, 44, and 46 and the reversing drum 47 are opposite to the rotation directions of the printing drum 60 and the selection drum 45. In FIG. 1 , the transport drums 42, 44, and 46 and the reversing drum 47 rotate clockwise, while the printing drum 60 and the selection drum 45 rotate counterclockwise.

[0035] The swing arm 41 is disposed near the end of the feeder board 13. The swing arm 41 scoops up the printing sheet 99 conveyed by the feeder board 13 from the feeder board 13 onto the conveying drum 42. As a result, the printing sheet 99 is wound around the outer peripheral surface of the conveying drum 42.

[0036] The transport drum 42 is disposed between the swing arm 41 and the printing drum 60. The transport drum 42 is located close to the outer circumferential surface of the printing drum 60. The transport drum 42 has a gripper 42a on its outer periphery. The rotational movement of the transport drum 42 is converted into the movement of the gripper 42a by, for example, a cam. The movement of the gripper 42a refers to the action of holding and releasing the printing sheet 99. The same applies to the movement of grippers 61, 44a, 45a, 46a, and 47a, which will be described later. The transport drum 42 holds the leading end of the printing sheet 99 picked up by the swing arm 41 with the gripper 42a, and sends the printing sheet 99 to the printing drum 60 while winding it up from the feeder board 13. The gripper is also referred to as a claw mechanism, claw device, gripping mechanism, gripping device, or fastener.

[0037] The transport drum 42 preheats the sheet to be printed 99. That is, the transport drum 42 has a preheater 42b, and the preheater 42b heats the sheet to be printed 99. Since the outer circumferential surface of the transport drum 42 is close to the outer circumferential surface of the printing drum 60, the printing drum 60 is heated by the heat of the preheater 42b.

[0038] The printing drum 60 is disposed between the transport drum 42 and the transport drum 44. The first rotation axis 60a of the printing drum 60 is positioned above the rotation axes of the transport drums 42 and 44. The printing drum 60 has three axially extending notches 62 on its outer circumferential surface. A gripper 61 is provided inside each notch 62. The three notches 62 and the three grippers 61 are disposed at equal intervals in the circumferential direction. The arrangement interval of the notches 62 and the grippers 61 is equal to the circumferential lengths of the transport drums 42, 44, 46 and the selection drum 45. The circumferential length of the printing drum 60 is set to a length that allows three printing sheets 99 to be held simultaneously on the outer periphery of the printing drum 60 without overlapping.

[0039] The number of grippers 61 is not limited to three, and may be one, two, or four or more. Even if the number of grippers 61 changes, the pitch of the grippers 61 does not change, and the diameter of the print drum 60 increases as the number of grippers 61 increases. If the number of grippers 61 on the print drum 60 is n, one cycle is defined as the period in which the print drum 60 makes one-nth rotation. In this embodiment, the print drum 60 has three grippers 61, and therefore one cycle is the period in which the print drum 60 makes one-third rotation. n is also the number of box-shaped members 65 (described below) that the print drum 60 has on its outer periphery. n is also the number of cutout portions 62 (described below) that the print drum 60 has on its outer periphery.

[0040] The rotational movement of the printing drum 60 is converted into the movement of the grippers 61 by, for example, a cam. Each time the transport drum 42 makes one rotation, one of the grippers 61 of the printing drum 60 approaches the gripper 42a of the transport drum 42. Therefore, when the sheet to be printed 99 is transferred from the transport drum 42 to the printing drum 60, the gripper 42a of the transport drum 42 releases the leading end of the sheet to be printed 99, and the gripper 61 that is adjacent to it holds the leading end of the sheet to be printed 99. The printing drum 60 holds the leading end of the sheet to be printed 99 transported by the transport drum 42 with the gripper 61, and sends the sheet to be printed 99 to the transport drum 44 while winding it up from the transport drum 42.

[0041] As shown by the dashed arrow, a region 97 extending from the transport drum 42 to the transport drum 44 along the outer circumferential surface of the print drum 60 in the forward rotation direction of the print drum 60 is a path along which the print sheet 99 is fed by the print drum 60. In this region 97, the print sheet 99 is adsorbed to the outer circumferential surface of the print drum 60 by the suction function of the print drum 60. As shown by the dashed arrow, in a region 98 extending from the transport drum 44 to the transport drum 42 along the outer circumferential surface of the print drum 60 in the forward rotation direction of the print drum 60, the print drum 60 does not exert its suction function. The forward rotation direction of the print drum 60 is also the direction in which the print sheet 99 is transported by the print drum 60.

[0042] The print head 31 prints on the print sheet 99 transported in the circumferential direction by the print drum 60. The print sheet 99 is then exposed to ultraviolet light by the ultraviolet irradiator 73. The print sheet 99 is then transferred from the print drum 60 to the transport drum 44.

[0043] The print head 31 is disposed in a position facing the outer peripheral surface of the print drum 60 in the circumferential direction between the transport drum 42 and the ultraviolet irradiator 73. When the print sheet 99 passes between the print head 31 and the print drum 60 in the circumferential direction, the print head 31 forms an image on the print sheet 99.

[0044] The print head 31 has multiple head units 32-35 arranged at intervals in the circumferential direction. Each of the head units 32-35 includes multiple inkjet heads (not shown). Each inkjet head has multiple nozzles for ejecting ink, ink chambers connected to the nozzles, and a piezoelectric element for deforming the walls of the ink chambers. The control unit 90 applies a drive signal to the piezoelectric element to deform the walls of the ink chambers, thereby varying the ink pressure in the ink chambers and ejecting ink from the nozzles. In each head unit, the multiple inkjet heads are arranged in a staggered pattern so that the nozzle arrangement ranges are continuous in the axial direction. Under the control of the control unit 90, the head units 32-35 eject ink from the nozzles of the inkjet heads toward a print sheet 99 held by suction on the outer circumferential surface of the print drum 60, thereby forming an image on the print sheet 99. The head units 32-35 eject ink of different colors. The head units 32, 33, 34, and 35 eject yellow, magenta, cyan, and black ink from their nozzles, respectively. The distance between the outer peripheral surface of the print drum 60 and the nozzle surface of the inkjet head where the nozzles are provided is adjusted to a predetermined value, for example, a few millimeters. In addition to the head units 32 to 35, the print head 31 may also have head units that eject ink of other colors, such as light cyan and light magenta. Inside the head units 32 to 35, there is provided an ink heater that heats the ink. The ink heater heats the ink to a temperature of, for example, about 80°C.

[0045] The ink used in this embodiment contains a gelling agent in addition to coloring materials such as pigments, and changes phase between a sol state and a gel state depending on the temperature. This ink is in a gel state at room temperature and becomes a sol state when heated to a temperature above the phase transition temperature. The ink used in this embodiment is also an ultraviolet-curable ink that hardens when exposed to ultraviolet light. The head units 32 to 35 eject ink that has been heated by an ink heater and turned into a sol state. When this sol-state ink is ejected and lands on the print sheet 99, it quickly becomes a gel state due to natural cooling and solidifies on the print sheet 99.

[0046] The transport drum 44 is disposed on the opposite side of the transport drum 42 with respect to the printing drum 60. The transport drum 44 is close to the outer circumferential surface of the printing drum 60. The transport drum 44 has a gripper 44a on the inside near its outer circumferential surface. As in the case of the transport drum 42, each time the transport drum 44 makes one rotation, the gripper 44a of the transport drum 44 approaches one of the grippers 61 of the printing drum 60. The transport drum 44 holds the leading end of the printed sheet 99 transported by the printing drum 60 with the gripper 44a, and sends the printed sheet 99 from the printing drum 60 to the selection drum 45 while winding it up.

[0047] The selection drum 45 is disposed below and in close proximity to the transport drum 44. The selection drum 45 has a gripper 45a on the inside near its outer circumferential surface. Every time the selection drum 45 rotates once, the gripper 45a of the selection drum 45 approaches the gripper 44a of the transport drum 44. The selection drum 45 holds the leading end of the printed sheet 99 transported by the transport drum 44 with the gripper 45a, and sends the printed sheet 99 to the transport drum 46 or the reversing drum 47 while winding it up from the transport drum 44.

[0048] The transport drum 46 is disposed adjacent to the selection drum 45 and the discharger 21. The transport drum 46 is disposed on the opposite side of the print drum 60 with respect to the selection drum 45 and the transport drum 44. The transport drum 46 has a gripper 46a on the inside near its outer circumferential surface.

[0049] The reversing drum 47 is disposed below the printing drum 60, adjacent to the selection drum 45. The reversing drum 47 is disposed on the opposite side of the selection drum 45 from the transport drum 46 and the discharger 21. The circumferential length of the reversing drum 47 is twice the circumferential length of the transport drums 42, 44, 46 and the selection drum 45. The swing arm 48 is disposed between the reversing drum 47 and the transport drum 42, adjacent to the printing drum 60.

[0050] Every time the selection drum 45 makes one rotation, the gripper 45 a of the selection drum 45 approaches the gripper 46 a of the transport drum 46 , and then the gripper 45 a of the selection drum 45 approaches the gripper 47 a of the reversing drum 47 .

[0051] When the printable sheet 99 is to be discharged, it is delivered from the selection drum 45 to the transport drum 46. The printable sheet 99 is sent from the transport drum 46 to the discharger 21 and discharged by the discharger 21. When the printable sheet 99 is to be turned over, it is delivered from the selection drum 45 to the reversing drum 47. When the printable sheet 99 is delivered from the printable sheet 99 to the reversing drum 47, the printable sheet 99 is turned over. The printable sheet 99 is delivered to the gripper 61 of the printing drum 60 via the swing arm 48. When the printable sheet 99 passes between the head units 32 to 35 and the printing drum 60, the head units 32 to 35 eject ink onto the printable sheet 99, thereby printing the back side of the printable sheet 99.

[0052] The temperature sensor 71 is disposed circumferentially between the transport drum 42 and the print head 31 at a position facing the outer peripheral surface of the print drum 60. The temperature sensor 71 detects the temperature of the print sheet 99 attracted to the outer peripheral surface of the print drum 60, and outputs a signal indicating the detected temperature of the print sheet 99 to the control unit 90. The temperature sensor 71 may be a contact-type temperature sensor that contacts the outer peripheral surface of the print drum 60 or the print sheet 99, or a non-contact-type temperature sensor that is separated from the outer peripheral surface of the print drum 60 or the print sheet 99.

[0053] The paper lift detector 72 is disposed circumferentially between the temperature sensor 71 and the print head 31, at a position facing the outer circumferential surface of the print drum 60. When the paper lift detector 72 detects that the printing sheet 99 passing the position of the paper lift detector 72 is lifted from the outer circumferential surface of the print drum 60, the paper lift detector 72 outputs, for example, a high-level detection signal to the control unit 90. When the paper lift detector 72 does not detect lifting of the printing sheet 99, the paper lift detector 72 outputs, for example, a low-level non-detection signal to the control unit 90. The paper lift detector 72 is composed of, for example, an optical sensor, an image sensor, a proximity sensor, a contact switch, a contact sensor, or a magnetic sensor.

[0054] The ultraviolet irradiator 73 is disposed in a position facing the outer peripheral surface of the printing drum 60 in the circumferential direction between the print head 31 and the transport drum 44. The ultraviolet irradiator 73 has a light-emitting unit disposed across the axial width of the printing drum 60. The ultraviolet irradiator 73 irradiates ultraviolet light from the light-emitting unit onto the printing sheet 99 attracted to the printing drum 60, and hardens and fixes the ink ejected onto the printing sheet 99.

[0055] The imaging unit 74 is disposed circumferentially between the ultraviolet irradiator 73 and the conveying drum 44, facing the outer circumferential surface of the printing drum 60. The imaging unit 74 has a linear image sensor such as a CIS (Contact Image Sensor). The CIS has an integrated LED illuminator, a 1:1 imaging optical system, and a linear imaging element. When a printing sheet 99 is present on the outer circumferential surface of the printing drum 60, the imaging unit 74 reads the surface of the printing sheet 99 and generates imaging data under the control of the control unit 90. When a printing sheet 99 is not present on the outer circumferential surface of the printing drum 60, the imaging unit 74 reads the surface of the outer circumferential surface of the printing drum 60 (i.e., the surface of the resin sheet 603 described below) and generates imaging data under the control of the control unit 90. The imaging unit 74 outputs the generated imaging data to the control unit 90. The control unit 90 analyzes the imaging data to detect the printing quality of the printing sheet 99 and wrinkles in the resin sheet 603.

[0056] The first heater 75 is disposed in a space surrounded by the print drum 60, the transport drum 44, the selection drum 45, and the reversing drum 47. The first heater 75 is, for example, a convection heater, a radiation heater, or a contact heater, and heats the outer circumferential surface of the print drum 60. The heating operation of the first heater 75 is controlled by the control unit 90.

[0057] The control unit 90 is a hardware processor having a CPU 91 (Central Processing Unit), RAM 92 (Random Access Memory), and storage unit 93. The CPU 91 reads a program 931 and setting data stored in the storage unit 93, stores them in the RAM 92, and executes the program 931 to perform various arithmetic operations. This allows the control unit 90 to comprehensively control the overall operation of the printing device 1. The RAM 92 provides the CPU 91 with working memory space and stores temporary data. The storage unit 93 stores the program 931 executed by the CPU 91, setting data, and the like. The storage unit 93 may be, for example, a hard disk drive (HDD), flash memory, or read-only memory (ROM). The storage unit 93 stores print jobs (image recording commands) input from an external device via a communication unit (not shown), image data related to the print jobs, and image data generated by the imaging unit 74.

[0058] (printing drum) Next, the configuration of the print drum 60 will be described in detail. FIG. 3 is a side view schematically illustrating the interior of the printing apparatus main body 30. The print drum 60 includes a substantially cylindrical main body 601 and a metal sheet 602 and a resin sheet 603 (sheet members) wrapped around the outer circumferential surface of the main body 601. In FIG. 3, the metal sheet 602 and the resin sheet 603 are collectively represented by a single dashed line. The main body 601 rotates around a first rotation shaft 60a. The outer circumferential surface of the main body 601 is provided with three cutouts 62 extending in the axial direction. The cutouts 62 may be recesses provided in the outer circumferential surface, or may communicate with the space inside the main body 601. The metal sheet 602 and the resin sheet 603 are wrapped around the outer circumferential surface of the main body 601, overlapping in this order, in the area between adjacent cutouts 62. In other words, the portion of the printing drum 60 excluding the metal sheet 602 and the resin sheet 603 is the main body 601. The surface of the resin sheet 603 forms the outer peripheral surface of the printing drum 60.

[0059] The main body 601 includes a shaft 63, flanges 64 that form both axial end surfaces of the main body 601, and three box-shaped members 65 that are provided on the outer periphery of the main body 601. The shaft 63 extends in the axial direction. The shaft 63 is connected to a conveying drive unit 76 and is driven to rotate by the conveying drive unit 76. The flanges 64 are attached to the shaft 63 parallel to each other and spaced apart in the axial direction. The flanges 64 are provided in a disk shape that extends radially and circumferentially from the shaft 63. The flanges 64 are made of, for example, metal.

[0060] The box-shaped members 65 are provided between adjacent cutout portions 62. These box-shaped members 65 span between the outer periphery of one flange 64 and the outer periphery of the other flange 64, and are attached to these flanges 64. The box-shaped members 65 open toward the outside in the radial direction of the printing drum 60. The openings of these box-shaped members 65 are covered by a metal sheet 602 and a resin sheet 603. The metal sheet 602 and the resin sheet 603 are, for example, rectangular in shape. The box-shaped members 65, the metal sheet 602, and the resin sheet 603 form a mounting table on which the print-receiving sheet 99 is placed. A space 65a is formed inside this mounting table.

[0061] The metal sheet 602 and the resin sheet 603 are provided with a plurality of air intake holes 65b that penetrate these members. The space 65a of the mounting base is connected to a suction unit (not shown). The suction unit sucks air from the space 65a, causing the printable sheet 99 placed on the surface of the resin sheet 603 to be adsorbed to the resin sheet 603, i.e., the outer peripheral surface of the printing drum 60. Note that no air intake holes 65b are provided in the part of the metal sheet 602 that corresponds to the outside of the printable sheet 99 that is placed on it. As a result, when the printable sheet 99 is adsorbed, the space 65a and the space outside the printing drum 60 are no longer in communication, making it possible to efficiently generate negative pressure in the space 65a.

[0062] The resin sheet 603 is made of a heat-shrinkable resin such as fluorinated ethylene propylene (FEP) or perfluoroalkoxy alkane (PFA). Specifically, the resin sheet 603 is made of tetrafluoroethylene-hexafluoropropylene copolymer resin or tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin. The resin sheet 603 made of such a material hardly shrinks in a temperature range of approximately 40° C. or less, and the shrinkage rate increases as the temperature rises above 40° C. However, the material of the resin sheet 603 is not limited to the above.

[0063] Fig. 4 is an enlarged view of region A in Fig. 3. Fig. 4 shows the configuration inside a cutout 62 located between a front end 651 of a certain box-shaped member 65 and a rear end 652 of an adjacent box-shaped member 65. A gripper 61, a first tensioning member 67, a second tensioning member 68 (tensioning member), a front end holding portion 69, and a pressing mechanism 80 are arranged in the cutout 62. The gripper 61, the first tensioning member 67, the second tensioning member 68, the front end holding portion 69, and the pressing mechanism 80 are attached directly or indirectly to the flange 64, for example.

[0064] The front end holding portion 69 is adjacent to a front end portion 651 of the box-shaped member 65. The front ends of the metal sheet 602 and the resin sheet 603 are clamped and held by the front end holding portion 69 and the front end portion 651. The metal sheet 602 and the resin sheet 603, whose front ends are held in this manner, cover the opening of the box-shaped member 65 and extend to another cutout portion 62 that sandwiches the box-shaped member 65. Figure 4 shows the front ends of a certain metal sheet 602 and resin sheet 603 and the rear ends of another metal sheet 602 and resin sheet 603.

[0065] The first tension member 67 holds and fixes the rear end of the metal sheet 602 that is routed from the rear end 652 of the box-shaped member 65 into the inside of the cutout portion 62 .

[0066] The second tensioning member 68 holds and fixes the rear end of the resin sheet 603, which is routed from the rear end 652 of the box-shaped member 65 into the cutout portion 62. The second tensioning member 68 includes a holder 681, an adjustment bolt 682, and a guide member 683. The holder 681 clamps and holds a nozzle 603a (see FIGS. 7 and 8) provided at the rear end of the resin sheet 603. The holder 681 is movable left and right along the guide member 683 in the figure. The adjustment bolt 682 is connected to the holder 681. The guide member 683 is fixed to, for example, the flange 64. By rotating the adjustment bolt 682 in one direction, the holder 681 can be moved rightward in the figure, i.e., in the direction in which the resin sheet 603 is pulled. By moving the holder 681 rightward in the figure, tension is applied to the resin sheet 603. The direction d1 shown in FIG. 4 is the direction of tension. By rotating the adjustment bolt 682 in the other direction, the holder 681 can be moved to the left in the figure, i.e., in the direction that loosens the tension on the resin sheet 603. The guide member 683 is connected to the rotary actuator 77. The control unit 90 rotates the adjustment bolt 682 in one or the other of the above directions by operating the rotary actuator 77. However, the adjustment bolt 682 may also be rotated manually.

[0067] The pressing mechanism 80 presses the resin sheet 603 to reduce or remove looseness or wrinkles that may occur in the resin sheet 603. The pressing mechanism 80 includes a pressing member 81, a holding / driving mechanism 82 (moving mechanism, holding member), and a second heater 83 (heater). The pressing member 81 is disposed parallel to the portion of the resin sheet 603 that is located within the cutout portion 62. As shown in FIG. 5 , the pressing member 81 is a rod-shaped member extending in the axial direction. The pressing member 81 may also be a plate-shaped member. The pressing member 81 has a crown-like shape in which the amount of protrusion toward the resin sheet 603 is greatest at the center in the axial direction. However, the shape of the pressing member 81 is not limited thereto and can be appropriately changed depending on the distribution of wrinkles that are likely to occur in the resin sheet 603, etc. For example, the shape of the holding / driving mechanism 82 may be a concave crown-like shape with both axial ends protruding, or a non-crown-like shape, i.e., a linear shape. 4, when viewed from the axial direction, pressing member 81 has a curved portion in contact with resin sheet 603. The curved portion in contact with resin sheet 603 means that the portion in contact with resin sheet 603 does not have any corners.

[0068] The holding and driving mechanism 82 moves the pressing member 81 in a predetermined pressing direction d2 (see FIG. 6 ) under the control of the control unit 90. The holding and driving mechanism 82 has, for example, attachment portions to which both axial ends of the pressing member 81 are attached, and moves the pressing member 81 by moving the attachment portions. As a result, the pressing member 81 presses the resin sheet 603 in the pressing direction d2 within the cutout portion 62. That is, the pressing member 81 presses the resin sheet 603 by moving relative to the holding and driving mechanism 82. Here, the pressing direction d2 is different from the direction d1 of tension applied to the resin sheet 603 by the second tension member 68 within the cutout portion 62. In this embodiment, the pressing direction d2 is perpendicular to the tension application direction d1. In this way, the holding and driving mechanism 82 functions as both a moving mechanism that moves the pressing member 81 in the pressing direction d2 to cause the pressing member 81 to press the resin sheet 603, and a holding member that holds the pressing member 81 in a state fixed to the print drum 60. In this embodiment, the holding and driving mechanism 82 as a holding member is provided separately and independently from the second tensioning member 68. In other words, the holding and driving mechanism 82 and the second tensioning member 68 are separate entities.

[0069] The holding and driving mechanism 82 includes an adjustment member 821 (see FIG. 2 ) for adjusting the pressing force with which the pressing member 81 presses the resin sheet 603. The adjustment member 821 includes, for example, an elastic member that applies an elastic force to the pressing member 81, a predetermined screw that applies a force directly or indirectly to the pressing member 81, or an actuator that applies a force to the pressing member 81. The pressing force may be determined and managed by the force that the adjustment member 821 applies to the holding and driving mechanism 82. That is, the pressing force may be determined by the elastic force that the elastic member applies to the pressing member 81, the fastening force of the screw, or the force that the actuator applies to the pressing member 81. Alternatively, the pressing force may be determined by the position of the elastic member, the fastening position of the screw, or the position of the actuator.

[0070] As shown in FIG. 4, the second heater 83 is built into the pressing member 81 and transfers heat to the resin sheet 603 when the pressing member 81 is in contact with the resin sheet 603. The second heater 83 is rod-shaped and has a length in the axial direction substantially equal to that of the pressing member 81. The heat generation operation of the second heater 83 is controlled by the control unit 90. The second heater 83 is, for example, a carbon heater that generates heat by passing electricity through carbon fiber, a sheathed heater in which a nichrome wire serving as a heating element is covered with a metal pipe, or a halogen heater that uses a halogen lamp as a heating element. The temperature distribution of the second heater 83 in the axial direction can be adjusted. For example, the second heater 83 can generate heat with a temperature distribution in which the temperature is highest in the center in the axial direction and decreases toward both ends.

[0071] (Printing device operation) The printing device 1 operates as follows under the control of the control unit 90. When the printing device 1 performs a printing operation according to a print job, the control unit 90 activates the preheater 42b and the first heater 75 to heat the outer circumferential surfaces of the transport drum 42 and the print drum 60. Once heating is complete, the control unit 90 sends a control signal to the transport drive unit 76 to rotate each drum of the transport device 40 and activates the head units 32-35, the ultraviolet irradiator 73, and other components to form an image on the print sheet 99. Specifically, the control unit 90 transfers the print sheet 99 from the paper feed unit 10 to the print drum 60, and ejects ink from each nozzle when the print sheet 99 faces the nozzles of the head units 32-35. As a result of the heating, the print sheet 99 on the outer circumferential surface of the print drum 60 reaches a temperature of approximately 40°C. This allows the ink that has landed on it to wet and spread over the desired area. The ink is then cured by the ultraviolet irradiator 73. The printing sheet 99 on which the image has been formed is discharged to the paper discharge section 20.

[0072] In the initial state, the resin sheet 603 of the printing drum 60 is tensioned by the second tensioning member 68, forming a smooth cylindrical curved surface. However, over time, the resin sheet 603 stretches over time, causing it to loosen and wrinkle (hereinafter collectively referred to as wrinkles). As shown in FIG. 7, the resin sheet 603 develops, for example, multiple wrinkles W extending in the circumferential direction. When wrinkles develop in the resin sheet 603, the printing sheet 99 may float on the resin sheet 603 or may not be properly adsorbed, resulting in a decrease in print quality.

[0073] Therefore, the control unit 90 causes the imaging unit 74 to capture an image of the surface of the resin sheet 603 at a predetermined timing, and detects the presence or absence of wrinkles in the resin sheet 603 based on the captured image data. The presence or absence of wrinkles is detected based on, for example, the brightness distribution of pixels in the captured image data. If wrinkles are detected, the control unit 90 controls the pressing mechanism 80 to cause the pressing member 81 to press the resin sheet 603, thereby reducing or removing the wrinkles in the resin sheet 603.

[0074] FIG. 6 is a diagram showing a state in which the pressing member 81 is pressing the resin sheet 603. The holding and driving mechanism 82, under the control of the control unit 90, moves the pressing member 81 in the pressing direction d2 from a state in which the pressing member 81 is not in contact with the resin sheet 603 as shown in FIG. 4 to a state in which the pressing member 81 abuts against the resin sheet 603 as shown in FIG. 6. The holding and driving mechanism 82 moves the pressing member 81 in the pressing direction d2 further from the point where the pressing member 81 abuts against the resin sheet 603, thereby pressing the resin sheet 603. This extends the extension distance of the resin sheet 603 to the position held by the holder 681. As a result, as shown in FIG. 8, slack in the resin sheet 603 is eliminated, and wrinkles are reduced or eliminated. At this time, because the pressing member 81 has a crown shape as shown in FIG. 5, wrinkles can be reduced by pushing them out toward both ends in the width direction of the resin sheet 603. In the initial state without any wrinkles, the pressing member 81 may be separated from the resin sheet 603 as shown in FIG. 4, or may be in contact with the resin sheet 603 with a predetermined weak pressure.

[0075] The control unit 90 may identify the degree of wrinkles based on the image data of the resin sheet 603, and may cause the pressing member 81 to press the resin sheet 603 so that the pressing force of the pressing member 81 increases as the degree of wrinkles increases. The pressing force required depending on the degree of wrinkles may be determined in advance and stored in the storage unit 93. Alternatively, the relationship between the position of the pressing member 81 in the pressing direction d2 and the pressing force may be identified in advance and stored in the storage unit 93, and the pressing member 81 may be moved to a position where the desired pressing force can be obtained. Alternatively, a measuring unit may be provided that measures the pressing force of the pressing member 81, i.e., the force that the pressing member 81 receives from the resin sheet 603, and the pressing member 81 may be moved in the pressing direction d2 until the pressing force measured by the measuring unit reaches the desired value.

[0076] Additionally, the resin sheet 603 may be heated by the second heater 83 to heat and shrink the resin sheet 603, thereby reducing wrinkles. In this case, it is preferable to release the tension on the resin sheet 603 applied by the second tensioning member 68 before contacting the pressing member 81 with the resin sheet 603, i.e., before heating the resin sheet 603 with the second heater 83. This is because the thermal shrinkage effect of the resin sheet 603 is less likely to occur when tension is applied. In this case, the pressing member 81 is first contacted with the resin sheet 603 with the tension on the resin sheet 603 released, and the resin sheet 603 is heated by the second heater 83 to thermally shrink the resin sheet 603. Next, tension is applied to the resin sheet 603 again by the second tensioning member 68, and then the resin sheet 603 is pressed by the pressing member 81. Furthermore, by setting the temperature distribution of the second heater 83 so that the temperature is highest in the axial center and decreases toward both ends, thermal shrinkage can be effectively achieved near the axial center, where wrinkles are likely to occur. If heat shrinkage is not used, the second heater 83 may be omitted.

[0077] Next, a description will be given of the maintenance process executed by the control unit 90 to realize the above-described operation of reducing wrinkles in the resin sheet 603. Fig. 9 is a flowchart showing the control procedure of the maintenance process.

[0078] When the maintenance process starts, the control unit 90 repeatedly determines whether it is a predetermined maintenance timing (step S101). The maintenance timing can be, for example, when the operating time of the printing device 1 reaches a predetermined time or when the cumulative number of printed sheets reaches a predetermined number. The control unit 90 may also determine that it is the maintenance timing when a user issues an instruction to perform maintenance. If it is determined that it is the maintenance timing ("YES" in step S101), the control unit 90 causes the imaging unit 74 to capture an image of the resin sheet 603 and acquires the captured image data (step S102). The control unit 90 analyzes the captured image data and determines whether wrinkles have occurred in the resin sheet 603 based on the pixel brightness distribution, etc. (step S103).

[0079] If it is determined that wrinkles have occurred ("YES" in step S103), the control unit 90 determines the degree of wrinkles (step S104). Here, the degree of wrinkles is determined based on, for example, the length and depth of the wrinkles. The depth of the wrinkles may be estimated, for example, from the difference between the upper and lower limit values ​​of the brightness of pixels in the imaging data. The control unit 90 determines the pressing force of the pressing member 81 according to the determined degree of wrinkles (step S105). Here, the control unit 90 determines the pressing force so that the greater the degree of wrinkles, the greater the pressing force.

[0080] The control unit 90 operates the rotary actuator 77 to loosen the adjustment bolt 682 of the second tensioning member 68 and move the holder 681 leftward in FIG. 4 to loosen the tension on the resin sheet 603 (step S106). Here, the tension may be loosened until it becomes equal to or less than a predetermined value, or until it becomes zero. The control unit 90 operates the holding and driving mechanism 82 to move the pressing member 81 in the pressing direction d2 and bring it into contact with the resin sheet 603, thereby heating the resin sheet 603 with the second heater 83 (step S107). This causes the resin sheet 603 to thermally shrink. Next, the control unit 90 operates the rotary actuator 77 to tighten the adjustment bolt 682 of the second tensioning member 68 and move the holder 681 rightward in FIG. 4 to apply a predetermined tension to the resin sheet 603 (step S108). Thereafter, the control unit 90 operates the holding and driving mechanism 82 to move the pressing member 81 in the pressing direction d2 to a position where the pressing force determined in step S105 is applied. That is, the control unit 90 causes the pressing member 81 to press the resin sheet 603 with the determined pressing force (step S109). This reduces or eliminates wrinkles in the resin sheet 603. Note that if heating by the second heater 83 is omitted, steps S106 to S108 may be omitted.

[0081] When step S109 is completed, or when it is determined in step S103 that no wrinkles have occurred ("NO" in step S103), the control unit 90 determines whether or not to terminate the operation of the printing device 1 (step S110). If the control unit 90 determines that the operation of the printing device 1 is to continue ("NO" in step S110), it transitions the process to step S101. If the control unit 90 determines that the operation of the printing device 1 is to terminate ("YES" in step S110), it terminates the maintenance process.

[0082] (Variation) Next, a modified example of the above embodiment will be described. This modified example differs from the above embodiment in the configuration of the pressing mechanism 80, but is otherwise similar to the above embodiment. The differences from the above embodiment will be described below.

[0083] 10 and 11 are diagrams illustrating the configuration and operation of a pressing mechanism 80 (rotating mechanism, holding member) according to a modified example. FIG. 10 illustrates the pressing mechanism 80 in a state in which the pressing member 81 is not in contact with the resin sheet 603. FIG. 11 illustrates the pressing mechanism 80 in a state in which the pressing member 81 is in contact with and pressing the resin sheet 603. In this modified example, a holding / driving mechanism 82, which functions as a holding member, is fixed to a holder 681 of the second tensioning member 68. The holding / driving mechanism 82 causes the pressing member 81 to press the resin sheet 603 by rotating (turning) the pressing member 81 around a second rotation shaft 80a parallel to the axial direction. The holding / driving mechanism 82 has, for example, mounting portions to which both axial ends of the pressing member 81 are attached, and rotates the mounting portions around the second rotation shaft 80a to rotate the pressing member 81. As a result, the pressing member 81 presses the resin sheet 603 in the pressing direction d2 within the cutout portion 62. That is, the pressing member 81 presses the resin sheet 603 by rotating relative to the holding and driving mechanism 82. In this way, the holding and driving mechanism 82 of the modified example combines the function of a moving mechanism that rotates the pressing member 81 around the second rotation shaft 80a to cause the pressing member 81 to press the resin sheet 603, and the function of a holding member that holds the pressing member 81 in a state fixed to the print drum 60. In this modified example as well, the pressing force of the pressing member 81 is adjusted by an adjustment member 821 that is an elastic member, a screw, or an actuator.

[0084] 10 and 11, in which the holding and driving mechanism 82 is fixed to the second tensioning member 68, the driving method of the pressing member 81 may be translation instead of rotation. Also, in the configuration in which the second tensioning member 68 and the holding and driving mechanism 82 are provided separately and independently as in FIGS. 4 and 6, the driving method of the pressing member 81 may be rotation.

[0085] (effect) As described above, the printing apparatus 1 according to this embodiment includes a printing drum 60. The printing drum 60 includes a main body 601, a resin sheet 603, and a pressing member 81. The main body 601 rotates around a first rotation shaft 60a, and a notch 62 extending in the direction of the first rotation shaft 60a is provided on its outer circumferential surface. The resin sheet 603 is wrapped around the outer circumferential surface of the main body 601 under tension, with a portion of the resin sheet 603 positioned within the notch 62. The pressing member 81 presses the resin sheet 603 within the notch 62 in a pressing direction d2, which is different from the direction d1 of tension applied to the resin sheet 603. In this manner, if the resin sheet 603 becomes loose or wrinkled due to elongation over time, the pressing member 81 can press the resin sheet 603 to extend the extension distance of the resin sheet 603, thereby reducing the looseness and wrinkles. This makes it possible to prevent problems such as the print-receiving sheet 99 floating or not being properly adsorbed on the resin sheet 603. As a result, it is possible to prevent a decrease in print quality.

[0086] The pressing member 81 is a rod-shaped or plate-shaped member extending in the direction of the first rotation shaft 60a, thereby reducing looseness and wrinkles across the entire width of the resin sheet 603 in the axial direction.

[0087] Furthermore, the pressing member 81 has a curved surface at the portion that comes into contact with the resin sheet 603. This makes it possible to make the resin sheet 603 less susceptible to damage caused by pressing.

[0088] The printing device 1 also includes a holding and driving mechanism 82 as a moving mechanism that moves the pressing member 81 in the pressing direction d2 to cause the pressing member 81 to press the resin sheet 603. This makes it possible to press the resin sheet 603 with a simple configuration that moves the pressing member 81 in the pressing direction d2.

[0089] Furthermore, the printing device 1 of the modified example includes a holding and driving mechanism 82 as a rotation mechanism that rotates the pressing member 81 around a second rotation shaft 80a parallel to the first rotation shaft 60a, causing the pressing member 81 to press the resin sheet 603. This makes it possible to press the resin sheet 603 with a simple configuration that rotates the pressing member 81.

[0090] The printing device 1 also includes a holding and driving mechanism 82 as a holding member that holds the pressing member 81 while being fixed to the printing drum 60, and the pressing member 81 presses the resin sheet 603 by moving or rotating relative to the holding and driving mechanism 82. This allows the pressing member 81 to press the resin sheet 603 while being supported by the holding and driving mechanism 82.

[0091] The printing device 1 also includes a second tensioning member 68 that is provided within the cutout portion 62 and applies tension to the resin sheet 603, and the holding and driving mechanism 82 as a holding member is provided independently of the second tensioning member 68. This allows for greater freedom in designing the pressing mechanism 80, the second tensioning member 68, and the like within the cutout portion 62.

[0092] Furthermore, in a modified example, the printing device 1 includes a second tensioning member 68 that is provided in the cutout portion 62 and applies tension to the resin sheet 603, and the holding and driving mechanism 82 as a holding member is fixed to the second tensioning member 68. This allows the pressing mechanism 80 and the second tensioning member 68 to have a compact configuration.

[0093] Furthermore, the pressing member 81 has a crown shape in which the amount of protrusion toward the resin sheet 603 is greatest at the center in the direction of the first rotation shaft 60a. This makes it possible to reduce wrinkles while pushing them out toward both ends of the resin sheet 603 in the width direction.

[0094] Furthermore, the pressing force with which pressing member 81 presses resin sheet 603 is determined by the elastic force that a predetermined elastic member exerts on pressing member 81, the fastening force of a predetermined screw that directly or indirectly exerts force on pressing member 81, or the force that a predetermined actuator exerts on pressing member 81. This makes it possible to manage the pressing force by the force exerted by adjustment member 821 with a simple configuration that uses adjustment member 821 having an elastic member, a screw, or an actuator.

[0095] Furthermore, the pressing force with which pressing member 81 presses resin sheet 603 is determined by the position of a predetermined elastic member that exerts an elastic force on pressing member 81, the fastening position of a predetermined screw that directly or indirectly exerts force on pressing member 81, or the position of a predetermined actuator that exerts force on pressing member 81. This makes it possible to manage the pressing force by the position of adjustment member 821 with a simple configuration that uses adjustment member 821 that has an elastic member, a screw, or an actuator.

[0096] The printing device 1 also includes an adjustment member 821 for adjusting the pressing force of the pressing member 81, and the adjustment member 821 has the above-mentioned elastic member, screw, or actuator. This makes it possible to adjust the pressing force depending on the degree of wrinkles, etc.

[0097] Furthermore, the resin sheet 603 has heat shrinkability, and the pressing member 81 has a built-in second heater 83 that transfers heat to the resin sheet 603 when the pressing member 81 is in contact with the resin sheet 603. This allows the resin sheet 603 to thermally shrink due to the heat from the second heater 83. This thermal shrinkage can further reduce loosening and wrinkles.

[0098] The printing apparatus 1 also includes a control unit 90 that controls the heat generation operation of the second heater 83. This allows the resin sheet 603 to be heated by the second heater 83 at an appropriate timing and temperature.

[0099] The second heater 83 can also adjust the temperature distribution in the direction of the first rotating shaft 60a. This makes it possible to more effectively reduce loosening and wrinkles. For example, by creating a temperature distribution in which the temperature is highest in the center of the axial direction and decreases toward both ends, it is possible to effectively achieve thermal shrinkage near the center of the axial direction, where wrinkles are likely to occur.

[0100] The second heater 83 is a carbon heater, a sheath heater, or a halogen heater, which allows the second heater 83 to be realized with a simple configuration.

[0101] The pressing direction d2 is perpendicular to the direction in which the tension is applied, which effectively increases the extension distance of the resin sheet 603 and reduces loosening and wrinkles.

[0102] Furthermore, the maintenance method for the printing device 1 equipped with the printing drum 60 of this embodiment includes a step of pressing the resin sheet 603 in the cutout portion 62 by the pressing member 81 in a pressing direction d2 different from the direction d1 of the tension applied to the resin sheet 603. As a result, when the resin sheet 603 becomes loose or wrinkled due to elongation over time, pressing the resin sheet 603 by the pressing member 81 can increase the extension distance of the resin sheet 603 and reduce the looseness or wrinkles.

[0103] The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, in the above embodiment, the resin sheet 603 is exemplified as the sheet member, but the material of the sheet member is not limited to resin. For example, a paper sheet member may be used instead of a resin sheet member.

[0104] Furthermore, in the above embodiment, a rectangular resin sheet 603 sized to cover the opening of the box-shaped member 65 was exemplified, but instead, a tubular (endless) sheet member that covers the entire outer peripheral surface of the main body 601 of the printing drum 60 may be used. In this case, an adjustment mechanism that adjusts the position of the box-shaped member 65 in the radial direction is provided on the printing drum 60. When the position of the box-shaped member 65 is adjusted radially inward by the adjustment mechanism, the tension of the resin sheet is relaxed. When the position of the box-shaped member 65 is adjusted radially outward by the adjustment mechanism, the resin sheet is tensioned. Furthermore, the resin sheet has an opening at a position that overlaps with the cutout portion 62.

[0105] 4, 6, 10, and 11 illustrate an example in which the holding and driving mechanism 82 is located inside the cutout portion 62, but this is not limiting. For example, a configuration may be adopted in which only the pressing member 81 and the second heater 83 of the pressing mechanism 80 are located inside the cutout portion 62, and the holding and driving mechanism 82 is located outside the cutout portion 62 in the axial direction. In this case, the holding and driving mechanism 82 may be configured to hold and drive the pressing member 81, which extends to the flange 64, at the position of the flange 64 or at a position outside the flange 64.

[0106] Furthermore, although the method of using image data captured by the imaging unit 74 has been exemplified as a wrinkle detection method, the present invention is not limited to this. For example, wrinkles may be detected by a method of detecting unevenness on the surface of the resin sheet 603 using an optical sensor, a contact sensor, or the like. Alternatively, the user may visually determine whether or not wrinkles exist.

[0107] Furthermore, when a sheet member is provided on the outer peripheral surface of a drum other than the printing drum 60, such as the conveying drums 42, 44, 46, the selection drum 45, or the reversing drum 47, the sheet member may be pressed in a manner similar to that of the above embodiment to reduce looseness and wrinkles.

[0108] Furthermore, in the above embodiment, a piezoelectric inkjet printing device using a piezoelectric element has been described as an example of the printing device, but the present invention is not limited to this. For example, the present invention can be applied to various types of printing devices, such as a thermal inkjet printing device that uses heat to generate bubbles in the ink and eject the ink, or a dry electrophotographic printing device that forms an image using toner particles on a photosensitive drum and transfers it to a recording medium.

[0109] Although several embodiments of the present invention have been described, the scope of the present invention is not limited to the above-described embodiments, but includes the scope of the invention described in the claims and its equivalents. [Explanation of symbols]

[0110] 1 Printing device 30 Printing device body 32~35 head unit 40 Conveyor 60 printing drums 60a First rotation axis 601 Main body 602 Metal Sheet 603 Resin sheet 61 Gripper 62 Notch 63 Shaft 64 flange 65 Box-shaped member 65a Space 651 Front end 652 Rear end 67 First tension member 68 Second tension member (tension member) 681 Holder 682 Adjustment bolt 683 Guide member 69 Front end holding part 80 Pressing mechanism 80a Second rotation axis 81 Pressing member 82 Holding and driving mechanism (moving mechanism, rotating mechanism, holding member) 821 Adjustment parts 83 Second heater (heater) 90 Control Unit 99 Printed Sheets d1 Tension direction d2 Pressing direction

Claims

1. A printing device having a printing drum, The printing drum is a main body portion that rotates around a first rotation axis and has a notch portion on its outer circumferential surface that extends in the direction of the first rotation axis; a sheet member that is wrapped around the outer peripheral surface of the main body portion in a tensioned state, and a portion of the sheet member is located within the cutout portion; a pressing member that presses the sheet member in a pressing direction different from the direction of the tension applied to the sheet member within the cutout portion; A printing device comprising:

2. The pressing member is a rod-shaped or plate-shaped member extending in the direction of the first rotation axis. The printing device of claim 1 .

3. The pressing member has a curved surface at a portion where it comes into contact with the sheet member. The printing device of claim 1 .

4. a moving mechanism for moving the pressing member in the pressing direction to cause the pressing member to press the sheet member; The printing device of claim 1 .

5. a rotation mechanism that rotates the pressing member around a second rotation axis parallel to the first rotation axis, thereby causing the pressing member to press the sheet member; The printing device of claim 1 .

6. a holding member for holding the pressing member in a state fixed to the printing drum, The pressing member presses the sheet member by moving or rotating relative to the holding member. The printing device of claim 1 .

7. a tension member provided in the cutout portion and applying the tension to the sheet member; The retaining member is provided independently of the tensioning member. The printing device according to claim 6.

8. a tension member provided in the cutout portion and applying the tension to the sheet member; The retaining member is fixed to the tension member. The printing device according to claim 6.

9. the pressing member has a crown shape in which the amount of protrusion toward the seat member is greatest at a central portion in the direction of the first rotation axis; The printing device of claim 1 .

10. The pressing force with which the pressing member presses the sheet member is determined by an elastic force exerted by a predetermined elastic member on the pressing member, a fastening force of a predetermined screw that directly or indirectly exerts force on the pressing member, or a force exerted by a predetermined actuator on the pressing member. The printing device of claim 1 .

11. The pressing force with which the pressing member presses the sheet member is determined by the position of a predetermined elastic member that applies an elastic force to the pressing member, the fastening position of a predetermined screw that directly or indirectly applies a force to the pressing member, or the position of a predetermined actuator that applies a force to the pressing member. The printing device of claim 1 .

12. an adjustment member for adjusting the pressing force; the adjustment member includes the elastic member, the screw, or the actuator; 12. The printing device according to claim 10 or 11.

13. the sheet member is heat-shrinkable, The pressing member has a built-in heater that transfers heat to the sheet member when the pressing member is in contact with the sheet member. The printing device of claim 1 .

14. a control unit for controlling the heat generation operation of the heater; The printing device of claim 13.

15. the heater is capable of adjusting a temperature distribution in the direction of the first rotation axis. The printing device of claim 13.

16. The heater is a carbon heater, a sheathed heater, or a halogen heater. The printing device of claim 15.

17. The pressing direction is perpendicular to the direction in which the tension is applied. The printing device of claim 1 .

18. A maintenance method for a printing device equipped with a printing drum, comprising: The printing drum is a main body portion that rotates around a first rotation axis and has a notch portion on an outer circumferential surface that extends in a direction of the first rotation axis; a sheet member that is wrapped around the outer peripheral surface of the main body portion in a tensioned state, and a portion of the sheet member is located within the cutout portion; and The maintenance method includes a step of pressing the sheet member in the cutout portion with a pressing member in a pressing direction different from a direction of the tension applied to the sheet member. A method for maintaining a printing device.

Images