Printing apparatus

Abstract

To suppress local overheating of an outer periphery of a printing drum.SOLUTION: Printing equipment 1 comprises: a printing drum 60; a drive device 85 which rotationally drives the printing drum 60; a heater 81 which is arranged outside the printing drum 60 and heats the outer periphery of the printing drum 60; and a control portion 79. The printing drum 60 has at least one loading base 65 that has an outer periphery to which a sheet 99 sticks, and at least one heat releasing portion that more easily releases heat than the loading base 65. The control portion 79 stops the drive device 85 in such a state that any one of the heat releasing portions is located at a position opposed to the heater 81.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a printing apparatus.

Background Art

[0002] Patent Documents 1 to 3 disclose a printing apparatus that causes a sheet to be adsorbed onto the outer circumferential surface of a printing drum by the printing drum, feeds the sheet in the circumferential direction through rotation of the printing drum, and forms an image on the sheet by a print head disposed outside the printing drum. In the printing apparatus of Patent Document 1, a heater is disposed outside the printing drum to face the outer circumference of the printing drum, and the outer circumference of the printing drum is heated by the heater. In the printing apparatus of Patent Document 2, the sheet is heated by a heater before the sheet is supplied to the printing drum.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problem to be Solved by the Invention

[0004] In the printing apparatus of Patent Document 1, when the rotation of the printing drum stops after printing is completed, a portion of the outer circumferential surface of the printing drum that faces the heater is locally overheated. Even if the heater is stopped after printing is completed, since the heater retains heat, the portion facing the heater is locally overheated. When the outer circumferential surface of the printing drum becomes locally high in temperature, the quality of an image formed in the next printing is degraded. Accordingly, an object of one or more embodiments of the present invention is to suppress local overheating of the outer circumferential surface of the printing drum. Furthermore, Patent Document 1 does not disclose that the heater is stopped after printing is completed. [Means for solving the problem]

[0005] To solve the above problems, according to one aspect of the present invention, the printing apparatus is Printing drum and A drive device for rotating the printing drum, A heater is positioned outside the printing drum and heats the outer circumference of the printing drum, It comprises a control unit and, The aforementioned printing drum A mounting platform having an outer surface to which the sheet adheres, The internal space enclosed by the aforementioned mounting platform, At least one slot extending from the internal space to the outside of the printing drum, It has, After the control unit stops the heater from generating heat, it stops the drive unit while at least one of the slots is positioned facing the heater. [Effects of the Invention]

[0006] According to one aspect of the present invention, localized overheating of the outer surface of the printing drum after the printing drum has stopped is prevented. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 shows the printing apparatus. [Figure 2] Figure 2 shows the inside of the printing device. [Modes for carrying out the invention]

[0008] Several embodiments of the present invention will be described below with reference to the drawings. The features and technical effects of the embodiments will be understood from the following detailed description and drawings. However, the scope of the present invention is not limited to the embodiments disclosed below. The scope of the present invention is not limited to the examples shown in the drawings, as the drawings are provided for illustrative purposes only.

[0009] <<Printing device>> Printing device 1 is a sheet-fed on-demand printer. Printing device 1 comprises a feeder 10, a printing device body 30, a delivery unit 20, and a control unit 79.

[0010] The feeder 10 stores multiple sheets 99 stacked on top of each other. The feeder 10 feeds the stacked sheets 99 one by one to the printing device body 30. The sheets 99 fed by the feeder 10 are positioned with their front ends facing forward in the direction of travel. The sheets 99 are also referred to as recording media or media.

[0011] The feeder 10 includes a paper feed tray 11, a separator 12, and a feeder board 13. The paper feed tray 11 supports multiple stacked sheets 99 from below. The paper feed tray 11 is provided to be vertically movable. The vertical position of the paper feed tray 11 is determined by the number of sheets 99 placed on the paper feed tray 11, and the paper feed tray 11 rises as the number of sheets 99 on the paper feed tray 11 decreases. The separator 12 is located above the paper feed tray 11. The separator 12 removes the sheets 99 from the top of the paper feed tray 11 one by one and places them on the feeder board 13. The feeder board 13 is provided between the separator 12 and the intake port of the printing device body 30. The feeder board 13 has, for example, an endless belt conveyor. The feeder board 13 transports the sheets 99 removed by the separator 12 to the intake port of the printing device body 30.

[0012] The printing device 30 prints images onto sheets supplied by the feeder 10 and discharges the printed sheets 99 to the delivery 20. Details of the printing device 30 will be described later.

[0013] The delivery 20 stacks and stores sheets 99 printed by the printing apparatus main body 30. The delivery 20 includes a discharger 21 and a paper discharge tray 22. The discharger 21 is arranged from a discharge outlet of the printing apparatus main body 30 to the paper discharge tray 22. The discharger 21 includes, for example, an endless belt conveyor or the like. The discharger 21 conveys sheets 99 printed by the printing apparatus main body 30 to the paper discharge tray 22. The sheets 99 conveyed by the discharger 21 are stacked and placed on the paper discharge tray 22.

[0014] The control unit 79 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like. The control unit 79 governs control of the entire printing apparatus 1.

[0015] <<Printing Apparatus Main Body>> The printing apparatus main body 30 includes a print head 31, a conveying device 40, and an ultraviolet irradiator 50. The conveying device 40 conveys a sheet 99 supplied from the feeder board 13 of the feeder 10 to the discharger 21 of the delivery 20. The conveying device reverses the front and back sides of the sheet 99 during conveyance of the sheet 99 as necessary. Details of the conveying device 40 will be described later.

[0016] <<Print Head>> The print head 31 forms an image on a sheet 99 transported by a transport device 40. The print head 31 has a plurality of inkjet heads 32 to 35. The inkjet heads 32 to 35 are located outside the print drum 60 (described later) of the transport device 40, facing the outer surface of the print drum 60, and are spaced apart and arranged in the circumferential direction of the print drum 60. The inkjet heads 32 to 35 form an image on the sheet 99 by ejecting ink toward the sheet 99 attached to the outer surface 62 of the print drum 60. The ink colors ejected by the inkjet heads 32 to 35 are different from each other, with inkjet heads 32, 33, 34, and 35 ejecting yellow, magenta, cyan, and black ink, respectively. In addition to the inkjet heads 32 to 35, the print head 31 may also have inkjet heads that eject light cyan and light magenta ink, respectively.

[0017] The print head 31 may have a laser printer type head that forms yellow, magenta, cyan, and black images on the sheet 99, instead of the inkjet heads 32 to 35. The laser printer type head includes a photosensitive drum, a scanning laser beam irradiator that forms a latent image on the outer surface of the photosensitive drum, and a toner drum that adheres toner to the photosensitive drum to make the latent image visible. Alternatively, the print head 31 may have a thermal transfer type thermal head that forms yellow, magenta, cyan, and black images on the sheet 99, instead of the inkjet heads 32-35.

[0018] <<UV irradiator>> The ultraviolet irradiator 50 is positioned away from the print head 31 in the direction of the forward rotation of the print drum 60, and is located on the outside of the print drum 60, facing the outer surface of the print drum 60. The ultraviolet irradiator 50 emits ultraviolet light radially inward from the print drum 60. The ultraviolet irradiator 50 irradiates the sheet 99 with ultraviolet light to cure the ink adhering to the sheet 99 and fix the ink to the sheet 99. The direction of forward rotation of the print drum 60 is indicated by arrow 96 in the figure.

[0019] <<Conveyor System>> The conveying device 40 includes a swing arm 41, a conveying drum 42, a printing drum 60, a conveying drum 44, a selection drum 45, a conveying drum 46, a reversing drum 47, a swing arm 48, a rotary encoder 71, a phase reference sensor 72, a phase detection sensor 73, a heater 81, a fan 82, and a drive device 85. Note that "drum" is also called "body," "cylinder," or "roller."

[0020] The rotation axes of the transport drum 42, printing drum 60, transport drum 44, selection drum 45, transport drum 46, and reversing drum 47 are arranged parallel to each other. The transport drum 42, printing drum, transport drum 44, selection drum 45, transport drum 46, and reversing drum 47 are connected to a drive unit 85. The drive unit 85 rotationally drives the swing arm 41, transport drum 42, printing drum 60, transport drum 44, selection drum 45, transport drum 46, reversing drum 47, and swing arm 48. The drive unit 85 has one or more motors and a transmission mechanism. The transmission mechanism transmits the power of the motor to the swing arm 41, transport drum 42, printing drum 60, transport drum 44, selection drum 45, transport drum 46, reversing drum 47, and swing arm 48. The transmission mechanism is, for example, a gear transmission mechanism or a winding transmission mechanism. The rotation direction of the transport drums 42, 44, 46, and reversing drum 47 is opposite to the rotation direction of the printing drum and selection drum 45. In Figure 1, the transport drums 42, 44, 46, and reversing drum 47 rotate clockwise, while the printing drum and selection drum 45 rotate counterclockwise.

[0021] The swing arm 41 is positioned near the end of the feeder board 13. The swing arm 41 scoops up the sheet 99, which has been transported by the feeder board 13, from the feeder board 13 to the transport drum 42. As a result, the sheet 99 is wrapped around the outer surface of the transport drum 42.

[0022] The transport drum 42 is positioned between the swing arm 41 and the printing drum 60. The transport drum 42 is in close proximity to the outer surface 62 of the printing drum 60. The transport drum 42 has a clip 42a on its outer circumference. The transport drum 42 uses the clip 42a to secure the front end of the sheet 99 picked up by the swing arm 41, and feeds the sheet 99 from the feeder board 13 to the printing drum 60 while winding it up. The “clip” is also called a “claw mechanism,” “claw device,” “gripping mechanism,” “gripping device,” or “fastener.”

[0023] The printing drum 60 is positioned between the transport drums 42 and 44. The axis of rotation of the printing drum 60 is located above the axes of rotation of the transport drums 42 and 44. The printing drum 60 has three clips 61 on the inside near its outer circumferential surface 62. These clips 61 are arranged circumferentially around the printing drum 60 at equal pitches. The pitch of these clips 61 is equal to the circumference of the transport drums 42, 44, selection drum 45, and transport drum 46. The circumference of the printing drum 60 is set to a length that allows three sheets 99 to be held simultaneously around the outer circumference of the printing drum 60 without overlapping. Note that the number of clips 61 is not limited to three; there may be one, two, or four or more. The pitch of the clips 61 remains the same even if the number of clips 61 changes, and the diameter of the printing drum 60 increases as the number of clips 61 increases.

[0024] Furthermore, if the number of clips 61 on the printing drum 60 is n, then one cycle is defined as the period in which the printing drum 60 rotates by 1 / n. In this embodiment, since the printing drum 60 has 3 clips 61, one cycle is defined as the period in which the printing drum 60 rotates by 1 / 3. n is also the number of mounting bases 65, described later, that the printing drum 60 has on its outer circumference. n is also the number of slots 67, described later, that the printing drum 60 has on its outer circumference.

[0025] Each time the transport drum 42 rotates, one of the clips 61 on the printing drum 60 moves closer to the clip 42a of the transport drum 42. Therefore, when the sheet 99 is transferred from the transport drum 42 to the printing drum 60, the clip 42a of the transport drum 42 releases the front end of the sheet 99, and the adjacent clip 61 secures the front end of the sheet 99. The printing drum 60 secures the front end of the sheet 99 being transported by the transport drum 42 with the clip 61 and sends the sheet 99 from the transport drum 42 to the transport drum 44 while winding it up. The printing drum 60 is heated by a heater 81, and the sheet 99 is heated by the heat from the printing drum 60. The heater 81 and the printing drum 60 will be described in detail later. In addition, when the sheet 99 is transferred from the transport drum 42 to the printing drum 60, it may be heated by a heater other than the heater 81.

[0026] As indicated by the dashed arrow, the region 97 along the outer surface 62 of the printing drum 60, from the transport drum 42 to the transport drum 44 in the direction of the printing drum 60's forward rotation, is the path through which the sheet 99 is fed by the printing drum 60. In this region 97, the sheet 99 is attracted to the outer surface of the printing drum 60 by its suction function. As indicated by the dashed arrow, in the region 98 along the outer surface 62 of the printing drum 60, from the transport drum 44 to the transport drum 42 in the direction of the printing drum 60's forward rotation, the printing drum 60 does not exhibit its suction function. The suction function of the printing drum 60 will be described in detail later.

[0027] The sheet 99, which is fed by the printing drum 60, is printed on by the printing head 31 and then exposed to ultraviolet light by the ultraviolet irradiator 50. The inkjet heads 32-35 of the printing head 31 are positioned in the path of the sheet 99 as it is transported by the printing drum 60 from the transport drum 42 to the transport drum 44. In other words, the inkjet heads 32-35 are positioned facing the outer circumferential surface 62 of the printing drum 60 in region 97. As the sheet 99 passes circumferentially between the inkjet heads 32-35 and the printing drum 60, the inkjet heads 32-35 eject ink onto the sheet 99.

[0028] The ultraviolet irradiator 50 is positioned in the path of the sheet 99 as it is transported from the print head 31 to the transport drum 44 by the print drum 60. In other words, the ultraviolet irradiator 50 is positioned radially outward from the print head 31 to the transport drum 44 in the forward rotation direction of the print drum 60, along the outer circumferential surface 62 of the print drum 60, and facing the outer circumferential surface 62 of the print drum 60. As the sheet 99 passes circumferentially between the ultraviolet irradiator 50 and the print drum 60, the ink adhering to the sheet 99 is exposed to ultraviolet light emitted from the ultraviolet irradiator 50, thereby fixing the image onto the sheet 99.

[0029] The transport drum 44 is positioned on the opposite side of the transport drum 42 with respect to the print drum 60. The transport drum 44 is in close proximity to the outer surface 62 of the print drum 60. The transport drum 44 has a clip 44a on its inner side near its outer surface. As with the transport drum 42, with each rotation of the transport drum 44, the clip 44a of the transport drum 44 moves closer to one of the clips 61 of the print drum 60. The transport drum 44 uses the clip 44a to hold the front end of the sheet 99 being transported by the print drum 60 and feeds the sheet 99 from the print drum 60 to the selection drum 45 while winding it up.

[0030] The selection drum 45 is positioned close to and beneath the conveying drum 44. The selection drum 45 has a clip 45a on its inner side near its outer circumferential surface. Each time the selection drum 45 rotates, the clip 45a of the selection drum 45 moves closer to the clip 44a of the conveying drum 44. The selection drum 45 uses the clip 45a to secure the front end of the sheet 99 being conveyed by the conveying drum 44, and then feeds the sheet 99 from the conveying drum 44 to the conveying drum 46 or the reversing drum 47 while winding it up.

[0031] The transport drum 46 is positioned close to the selection drum 45 and the discharger 21. The transport drum 46 is positioned 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 clip 46a on the inside near its outer circumferential surface. The reversing drum 47 is positioned close to the selection drum 45 and below the print drum 60. The reversing drum 47 is positioned on the opposite side of the transport drum 46 and the discharger 21 with respect to the selection drum 45. The circumference of the reversing drum 47 is twice the circumference of the transport drums 42, 44, 46 and the selection drum 45. The swing arm 48 is positioned close to the print drum 60 and between the reversing drum 47 and the transport drum 42.

[0032] Each time the selection drum 45 rotates, the clip 45a of the selection drum 45 moves closer to the clip 46a of the transport drum 46, and subsequently, the clip 45a of the selection drum 45 moves closer to the clip 49a of the reversing drum 49.

[0033] When the sheet 99 being transported by the selection drum 45 is being discharged, the clip 45a of the selection drum 45 releases the front end of the sheet 99, and the clip 46a of the adjacent transport drum 46 secures the front end of the sheet 99. As a result, the transport drum 46 secures the front end of the sheet 99 being transported by the selection drum 45 with the clip 46a and sends the sheet 99 to the discharge machine 21 while winding it up from the selection drum 45. The sheet 99 is then discharged by the discharge machine 21.

[0034] When the front and back sides of the sheet 99 being transported by the selection drum 45 are reversed, the clip 45a of the selection drum 45 releases the front end of the sheet 99, and the clip 47a of the reversal drum 47, which is adjacent to it, secures the front end of the sheet 99. Therefore, the reversal drum 47 secures the front end of the sheet 99 being transported by the selection drum 45 with the clip 47a and winds the sheet 99 from the selection drum 45. At this time, the front and back sides of the sheet 99 are reversed as the sheet 99 is wound onto the reversal drum 47. When the rear end of the sheet 99 approaches the swing arm 48, the swing arm 48 transfers the rear end of the sheet 99 from the reversal drum 47 to one of the clips 61 of the printing drum 60, and the clip 47a of the reversal drum 47 releases the front end of the sheet 99. Therefore, the printing drum 60 secures the rear end of the sheet 99 with the clip 61 and sends the sheet 99 to the transport drum 44 while winding it from the reversal drum 47. The sheet 99 is discharged by the discharger 21, passing through the transport drum 44, selection drum 45, and transport drum 46 in order from the print drum 60. As the sheet 99 passes circumferentially between the inkjet heads 32-35 and the print drum 60, the inkjet heads 32-35 eject ink onto the sheet 99, thereby printing on the back side of the sheet 99.

[0035] The selection drum 45 is positioned diagonally downward from the print drum 60, and a space 90 exists between the selection drum 45 and the print drum 60. This space 90 is surrounded not only by the selection drum 45 and the print drum 60, but also by the transport drum 44 and the reversing drum 47. This space 90 is located within the region 98, closer to the transport drum 44. This space 90 is located below the print drum 60. A heater 81 and a fan 82 are located in this space 90.

[0036] The heater 81 faces the outer surface 62 of the printing drum 60 in space 90. The heater 81 is composed of an infrared heater. The heater 81 irradiates infrared rays toward the outer surface 62 of the printing drum 60, thereby heating the outer surface 62 of the printing drum 60.

[0037] The fan 82 is positioned radially outward from the heater 81 in space 90. Here, radial direction refers to the direction perpendicular to the rotation axis of the printing drum 60. The fan 82 blows air toward the heater 81, and the air generated by the fan 82 strikes the outer surface of the printing drum 60. Alternatively, the fan 82 may be positioned radially inward from the heater 81 in space 90.

[0038] The heater 81 and the fan 82 are controlled to control the temperature of the outer surface 62 of the printing drum 60.

[0039] The printing drum 60 will be described in detail with reference to Figure 2. In the following description, the axial direction refers to the direction parallel to the rotation axis of the printing drum 60, the circumferential direction refers to the direction around the rotation axis of the printing drum 60, and the radial direction refers to the direction perpendicular to the rotation axis of the printing drum 60.

[0040] The printing drum 60 has three clips 61, as well as a shaft 63, two flanges 64, and three mounting bases 65. Note that in Figure 2, one flange 64 is shown, while the other flange 64 is not.

[0041] The shaft 63 extends in the axial direction. The shaft 63 is connected to a drive unit 85 and is rotationally driven by the drive unit 85. The flanges 64 are attached to the shaft 63, spaced apart in the axial direction and parallel to each other. The flanges 64 are provided in a disc shape, extending radially and circumferentially from the shaft 63. The flanges 64 are made of metal, for example. Because the flanges 64 are large, their heat capacity is large. In particular, the flanges 64 have a larger heat capacity than the mounting base 65. The mounting bases 65 are formed as arc-shaped hollow columns. These mounting bases 65 are arranged around the shaft 63 at circumferential intervals. These mounting bases 65 are spanned between the outer periphery of one flange 64 and the outer periphery of the other flange 64, and are attached to these flanges 64 via insulating material. The insulating material insulates the flanges 64 from the mounting bases 65, making it difficult for heat from the mounting bases 65 to be conducted to the flanges 64. The outer periphery of the mounting bases 65 forms the outer periphery 62 of the printing drum 60.

[0042] The mounting platform 65 has a hollow 65a inside and multiple suction ports 65b on its outer surface. These suction ports 65b are distributed across the entire outer surface of the mounting platform 65. The hollow 65a of the mounting platform 65 is connected to a vacuum. The vacuum sucks air from the hollow 65a, generating suction force at the suction ports 65b. As a result, the sheet 99 is attracted to the outer surface of the mounting platform 65. One sheet 99 is attracted to each mounting platform 65.

[0043] The mounting platform 65 has a box body 65c and a sheet 65d. The box body 65c is shaped like an arc-shaped hollow column, and its outer circumference is open. The sheet 65d is attached to the box body 63c so as to cover the opening on the outer circumference of the box body 65c. The sheet 65d is formed in the shape of an arc-shaped column. The sheet 65d has a plurality of suction ports 65b. The sheet 65d is made of resin or metal.

[0044] The printing drum 60 has an internal space 66 inside it. The internal space 66 is surrounded by a mounting base 65 and a flange 64. The printing drum 60 has slots 67 between adjacent mounting bases 65 in the circumferential direction. The internal space 66 is accessible from the outside of the printing drum 60 through the slots 67. Therefore, heat transfer between the outside and inside of the printing drum 60, particularly heat transfer by convection, is likely to occur through the slots 67. The slots 67 are an example of a heat release section.

[0045] Furthermore, for example, an insulating material may be provided on the inner surface of the mounting base 65, making it difficult for heat from the mounting base 65 to dissipate into the internal space 66 due to the insulating material. Alternatively, a heat transfer section with high thermal conductivity, such as metal, may be attached to the flange 64 in contact with it within the slot 67, so that the heat absorbed by the heat transfer section is conducted to the flange 64. Alternatively, a heat exchange section with high thermal conductivity and a large surface area, such as metal, may be provided in the slot 67, so that heat exchange between the outside and inside of the printing drum 60 is performed by the heat exchange section. The heat transfer section and the heat exchange section have a higher thermal conductivity than the mounting base 65, especially the box body 65c. The heat transfer section and the heat exchange section are examples of heat dissipation sections. Furthermore, the heat transfer section and the heat exchange section are examples of high thermal conductivity sections among heat dissipation sections.

[0046] The three clips 61 are each attached to the mounting base 65 or flange 64 within three slots 67. A thin-walled section, thinner than the mounting base 65, may be connected to the mounting base 65 between adjacent mounting bases 65, and the slots 67 may be blocked by the thin-walled section. In this case, a recess is formed on the outside of the thin-walled section, recessed from the outer surface of the mounting base 65, and the clips 61 are attached to the mounting base 65 or flange 64 within this recess. The thin-walled section may have a higher thermal conductivity than the mounting base 65, particularly the box body 65c. The thin-walled section and the recess are examples of heat dissipation sections, and the thin-walled section is an example of a high-thermal-conductivity section among heat dissipation sections.

[0047] As shown in Figure 1, the printing drum 60, and in particular the shaft 63 of the printing drum 60, is connected to a rotary encoder 71. The rotary encoder 71 may be directly connected to the shaft 63, or it may be connected to the shaft 63 via the transmission mechanism of the drive unit 85. The rotary encoder 71 outputs a pulse to the control unit 79 each time the printing drum 60 rotates by a predetermined angle. Therefore, the control unit 79 recognizes the rotation angle of the printing drum 60 (i.e., the phase during one rotation of the printing drum 60) by counting the number of output pulses from the rotary encoder 71. The pulse output period from the rotary encoder 71 is sufficiently shorter than the duration of one cycle, i.e., the duration of one-third of a rotation of the printing drum 60. Therefore, the rotary encoder 71 outputs pulses to the control unit 79 many times during one-third of a rotation of the printing drum 60.

[0048] The phase reference sensor 72 is located outside the print drum 60 in region 98. Specifically, the phase reference sensor 72 is located outside the print drum 60 at a position away from the heater 81 in the direction of the print drum 60's forward rotation.

[0049] The phase reference sensor 72 outputs a signal to the control unit 79. The phase reference sensor 72 is composed of, for example, an optical sensor or a magnetic sensor. The phase reference sensor 72 detects the phase reference during one cycle by detecting the edge of the mounting base 65. For example, when the edge of the mounting base 65 on the side of the printing drum 60 that is rotating in the forward direction passes the phase reference sensor 72, the output signal of the phase reference sensor 72 rises. Therefore, the rising edge of the output signal of the phase reference sensor 72 marks the start of one cycle, and its phase is zero° (=360°). Accordingly, the control unit 79 resets the count when the phase reference sensor 72 detects the edge of the mounting base 65, and recognizes the phase during one cycle by counting the number of output pulses of the rotary encoder 71 from that point onward.

[0050] The phase detection sensor 73 is positioned on the outside of the print drum 60, away from the phase reference sensor 72 in the direction of the print drum 60's forward rotation. The phase detection sensor 73 is composed of, for example, an optical sensor or a magnetic sensor. The phase detection sensor 73 detects the edge of the mounting base 65. The perimeter from the phase reference sensor 72 to the sensor 72 is set to a value other than an integer multiple of 1 / n of the perimeter of the print drum 60. Therefore, the phase at which the phase detection sensor 73 detects the edge of the mounting base 65 is different from the phase at which the phase reference sensor 72 detects the edge of the mounting base 65, and the phase reference sensor 72 detects a predetermined phase other than zero.

[0051] In addition to the output signal of the phase detection sensor 73, the output signals of the rotary encoder 71 and the phase reference sensor 72 are used to detect the forward and reverse rotation of the printing drum 60. This is because the number of pulses output by the rotary encoder 71 from the time the phase reference sensor 72 detects the edge of the mounting base 65 until the phase detection sensor 73 detects the edge of the mounting base 65 differs between the forward rotation and reverse rotation of the printing drum 60.

[0052] <<Printer Operation>> The printing device 1 configured as described above performs the following printing operations under the control of the control unit 79.

[0053] Before the printing device 1 performs a printing operation, the control unit 79 stops the heater 81 and the drive unit 85. Therefore, the heater 81 is not generating heat, and the swing arm 41, transport drum 42, printing drum 60, transport drum 44, selection drum 45, transport drum 46, reversing drum 47, and swing arm 48 are stopped. The stopping position of the printing drum 60 is such that the slot 67 of the printing drum 60 faces the heater 81.

[0054] When an external device such as a personal computer transfers print job data to the control unit 79, the control unit 79 activates the drive unit 85, vacuum, and delivery unit 20. The drive unit 85 then starts driving the swing arm 41, transport drum 42, print drum 60, transport drum 44, selection drum 45, transport drum 46, reversing drum 47, and swing arm 48. While the print drum 60 is rotating, the mounting platform 65 passing through region 97 generates suction force on its outer surface due to the vacuum, while the mounting platform 65 passing through region 98 is disconnected from the vacuum and does not generate suction force.

[0055] Next, the control unit 79 drives the heater 81 and the fan 82. As a result, the heater 81 generates heat, and the fan 82 blows air onto the heater 81. The air heated by the heater 81 then hits the outer surface of the printing drum 60, heating the outer surface of the printing drum 60. Because the printing drum 60 rotates, the outer surface of the printing drum 60 does not overheat locally, and the temperature distribution on the outer surface of the printing drum 60 becomes uniform.

[0056] Next, the control unit 79 controls the feeder 10 to perform a sheet feeding operation for the sheets 99, and the feeder 10 periodically feeds the sheets 99 to the printing device body 30. For example, if the print job data includes data indicating single-sided printing, the period during which the feeder 10 feeds one sheet 99 is equal to the duration of one cycle. If the print job data includes data indicating double-sided printing, the period during which the feeder 10 feeds one sheet 99 is equal to twice the duration of one cycle.

[0057] When the sheet 99 is sent to the main body of the printing device 30 by the feeder 10, the swing arm 41 scoops the sheet 99 from the feeder board 13 to the transport drum 42, and then the transport drum 42 secures the front end of the sheet 99 with a clip 42a and sends the sheet 99 to the printing drum 60 while winding it up. After that, the printing drum 60 secures the front end of the sheet 99 with one of the clips 61, and uses the adjacent mounting base 65 to attract the sheet to the outer surface of the mounting base 65 and sends it to the transport drum 44. As the sheet 99 passes circumferentially between the inkjet heads 32-35 and the printing drum 60, the control unit 79 controls the inkjet heads 32-35 according to the print job data, so that the inkjet heads 32-35 eject ink onto the front surface of the sheet 99 and form an image on the front surface of the sheet 99. Subsequently, the transport drum 44 secures the front end of the sheet 99 with the clip 44a and sends the sheet 99 to the selection drum 45 while winding it up.

[0058] If the print job data includes data indicating single-sided printing, the selection drum 45 uses a clip 45a to secure the front end of the sheet 99 being transported by the transport drum 44, and sends the sheet 99 to the transport drum 46 while winding it up. The transport drum 46 then uses a clip 46a to secure the front end of the sheet 99 and sends the sheet 99 to the discharger 21 while winding it up. The discharger 21 then transports the sheet 99 to the output tray 22.

[0059] If the print job data includes data indicating double-sided printing, the selection drum 45 uses a clip 45a to secure the front end of the sheet 99 being transported by the transport drum 44, and sends the sheet 99 to the reversing drum 47 while winding it up. The reversing drum 47 then uses a clip 47a to secure the front end of the sheet 99 and winds it up from the selection drum 45. At this time, the front and back sides of the sheet 99 are reversed. Subsequently, the swing arm 48 takes the rear end of the sheet 99 from the reversing drum 47 to one of the clips 61 on the print drum 60, and the print drum 60 uses the clip 61 to secure the rear end of the sheet 99, and sends the sheet 99 to the transport drum 44 while winding it up from the reversing drum 47. As the sheet 99 passes circumferentially between the inkjet heads 32-35 and the print drum 60, the control unit 79 controls the inkjet heads 32-35 according to the print job data, causing the inkjet heads 32-35 to eject ink onto the back side of the sheet 99, forming an image on the back side of the sheet 99. The sheet 99 is discharged by the discharger 21, passing through the transport drum 44, selection drum 45, and transport drum 46 in order from the printing drum 60.

[0060] The control unit 79 continuously operates the drive unit 85, vacuum, delivery unit 20, heater 81, and fan 82, and causes the feeder 10 to perform periodic feeding operations, thereby enabling single-sided or double-sided printing of multiple sheets 99.

[0061] During printing, that is, while the printing drum 60 is rotating, the control unit 79 recognizes the rotation angle of the printing drum 60 (i.e., the phase during one rotation of the printing drum 60) based on the output signal of the rotary encoder 71. Furthermore, the control unit 79 recognizes the phase during one cycle and the position of each slot 67 in the circumferential direction based on the output signals of the rotary encoder 71 and the phase reference sensor 72. In addition to the output signals of the rotary encoder 71 and the phase reference sensor 72, the control unit 79 may also recognize the phase during one cycle and the position of each slot 67 in the circumferential direction based on the output signal of the phase detection sensor 73.

[0062] When the feeder 10 has fed the number of sheets 99 corresponding to the number of sheets data included in the print job data, the control unit 79 stops the feeding operation of the feeder 10. Then, when single-sided or double-sided printing of the last sheet 99 is completed and the last sheet 99 is discharged by the discharger 21, the control unit 79 stops the heating of the heater 81 by cutting off the power supply to the heater 81 without stopping the fan 82. Even though the heating of the heater 81 has stopped, heat remains in the heater 81, so the temperature of the heater 81 and its surroundings does not immediately decrease. Nevertheless, as will be described later, the slot 67 dissipates the heat from the heater 81 and its surroundings into the internal space 66 of the print drum 60.

[0063] Furthermore, the control unit 79 decelerates the drive unit 85, reducing the speeds of the swing arm 41, transport drum 42, printing drum 60, transport drum 44, selection drum 45, transport drum 46, reversing drum 47, and swing arm 48. When any slot 67 reaches a position facing the heater 81, the control unit 79 recognizes this based on the output signals of the rotary encoder 71 and the phase reference sensor 72, and stops the drive unit 85. Because the speed of the printing drum 60 has been reduced, it stops precisely at a position where any slot 67 faces the heater 81. The control unit 79 may also gradually reduce the speed of the drive unit 85 between the start of deceleration and the stopping of the drive unit 85.

[0064] When the print drum 60 is stopped, the slot 67 faces the heater 81, so the heat from the heater 81 moves through the slot 67 into the internal space 66 of the print drum 60, and heat does not easily accumulate in the narrow space 90 around the heater 81. Because the slot 67 is located above the heater 81, the heat from the heater 81 moves easily into the internal space 66 of the print drum 60. In particular, because the fan 82 is operating, the heat from the heater 81 moves into the internal space 66 of the print drum 60 by the airflow from the fan 82. These factors contribute to preventing overheating of the mounting base 65 and to uniformizing the temperature distribution on the outer surface of the mounting base 65.

[0065] Furthermore, as mentioned above, even when the heat transfer unit is in contact with the flange 64 within the slot 67 and attached to the flange 64, the heat from the heater 81 is absorbed by the heat transfer unit and conducted to the flange 64. As a result, overheating of the mounting base 65 is prevented, and the temperature distribution on the outer surface of the mounting base 65 becomes uniform.

[0066] Furthermore, as mentioned above, even when the heat exchange unit is located in the slot 67, the heat from the heater 81 is dissipated by the heat exchange unit into the internal space 66 of the printing drum 60. As a result, overheating of the mounting base 65 is prevented, and the temperature distribution on the outer surface of the mounting base 65 becomes uniform.

[0067] Furthermore, even when a thin-walled section thinner than the mounting base 65 is connected to an adjacent mounting base 65, the heat from the heater 81 is trapped in the recess on the outside of the thin-walled section. This prevents overheating of the mounting base 65. In particular, if the thermal conductivity of the thin-walled section is higher than that of the mounting base 65, especially the box body 65c, the heat trapped in the recess is less likely to be absorbed by the mounting base 65 and more likely to be absorbed by the thin-walled section. The heat absorbed by the thin-walled section is dissipated by the printing drum 60. Therefore, not only is overheating of the mounting base 65 prevented, but the temperature distribution on the outer surface of the mounting base 65 becomes uniform.

[0068] While the drive unit 85 is stopped, the control unit 79 measures the time during which any of the slots 67 is stopped in a position facing the heater 81 (hereinafter referred to as the normal stop time). Even if multiple print jobs are executed sequentially and the print drum 60 is stopped multiple times, the control unit 79 does not reset the normal stop time and accumulates the normal stop time after each stop of the print drum 60.

[0069] If the control unit 79 makes an emergency stop of the drive unit 85 due to a jam in the sheet 99 during printing, there may be cases where no slot 67 is facing the heater 81. In such cases, the control unit 79 measures the stop time of the print drum 60 (hereinafter referred to as the abnormal stop time) separately from the normal stop time. Even if the print drum 60 is stopped multiple times in an emergency, the control unit 79 accumulates the abnormal stop time after each emergency stop of the print drum 60 without resetting the abnormal stop time.

[0070] In other words, while the drive unit 85 is operating, and while any slot 67 is not facing the heater 81 even when the drive unit 85 is stopped, the control unit 79 temporarily suspends the timing of the normal stop time. Also, while the drive unit 85 is operating, and while any slot 67 is facing the heater 81 even when the drive unit 85 is stopped, the control unit 79 temporarily suspends the timing of the abnormal stop time.

[0071] <<Summary>> When the print drum 60 stops, the slot 67 faces the heater 81, preventing localized overheating of the mounting tray 65, resulting in a uniform temperature distribution on the outer surface of the mounting tray 65. When the print drum 60 stops, the heater 81 is also stopped, effectively preventing localized overheating of the mounting tray 65. When the print drum 60 stops, the fan 82 is operating, further enhancing the prevention of localized overheating of the mounting tray 65. As the temperature distribution of the mounting tray 65 is uniform, the sheet 99 is heated uniformly throughout for the next print. Therefore, the quality of the next print is high. Furthermore, deterioration of the mounting base 65 due to overheating is prevented. In particular, if the sheet 65d of the mounting base 65 is a resin sheet, thermal deformation of the sheet 65d can be efficiently prevented.

[0072] Since the output signal from the rotary encoder 71 is input to the control unit 79, the position of the slot 67 when the print drum 60 stops is precisely controlled. In particular, since the print drum 60 is decelerated before it stops, the position of the slot 67 when the print drum 60 stops is precisely controlled. When the slot 67 stops precisely in a position facing the heater 81, localized overheating of the mounting base 65 is precisely prevented.

[0073] The control unit 79 can predict the lifespan of the printing drum 60, particularly the sheet 65d, by cumulatively measuring the normal stop time and the abnormal stop time.

[0074] <<Variation>> In the above embodiment, the number of clips 61, the number of mounting bases 65, and the number of slots 67 are 3. In contrast, the number of clips 61, the number of mounting bases 65, and the number of slots 67 may be 1 or 2, or 4 or more. Even if the number of clips 61 and mounting bases 65 changes, the pitch of the clips 61 and the circumferential length of the mounting bases 65 remain unchanged, and the diameter of the printing drum 60 increases as the number of clips 61 increases. [Explanation of Symbols]

[0075] 1 Printing device 60 Printing Drums 64 Flange 65 mounting units 65d seat 67 slots 71 Rotary Encoder 72 Phase Reference Sensor 73 Phase detection sensor 79 Control Unit 85 Drive unit 99 seats

Claims

1. Printing drum and A drive device for rotating the printing drum, A heater is positioned outside the printing drum and heats the outer circumference of the printing drum, It comprises a control unit and, The aforementioned printing drum A mounting platform having an outer surface to which the sheet adheres, The internal space enclosed by the aforementioned mounting platform, At least one slot extending from the internal space to the outside of the printing drum, It has, After the control unit stops the heater from generating heat, it stops the drive unit while at least one of the slots is positioned facing the heater. Printing device.

2. Multiple mounting platforms are arranged at intervals in the circumferential direction, and multiple slots are provided between adjacent mounting platforms. The printing apparatus according to claim 1.

3. A high thermal conductivity portion provided within the slot, having a higher thermal conductivity than the mounting base The printing apparatus according to claim 1 or 2.

4. The printing drum has a pair of flanges, The pair of flanges are arranged at intervals in the axial direction of the printing drum, and are provided in a disc shape that extends radially and circumferentially around the printing drum, and together with the mounting base, surround the internal space. The high heat conductivity portion is in contact with the flange. The printing apparatus according to claim 3.

5. The control unit decelerates the drive unit before stopping the drive unit. The printing apparatus according to claim 1 or 2.

6. The printing drum is equipped with a fan positioned outside the printing drum that generates an airflow from the heater toward the outer surface of the printing drum, The control unit continues to operate the fan even after stopping the heating of the heater. The printing apparatus according to claim 1 or 2.

7. The mounting base has a resin sheet on its outer surface. The printing apparatus according to claim 1 or 2.

8. The system includes an encoder that detects the phase during one rotation of the printing drum, The control unit recognizes the position of the slot in the circumferential direction based on the output signal of the encoder. The printing apparatus according to claim 1 or 2.

9. It is equipped with a sensor that detects the edge of the mounting platform in the circumferential direction, The control unit recognizes the position of the slot in the circumferential direction based on the output signals of the encoder and the sensor. The printing apparatus according to claim 8.

10. The control unit cumulatively measures the time during which any of the plurality of slots stops in a position facing the heater. The printing apparatus according to claim 2.

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