Printer

Abstract

To suppress deterioration in image quality that results from forming an image on a diameter reduced portion of a container for beverages by using an inkjet head.SOLUTION: An inkjet head 19S for small dot images is disposed on a side closer to an axial center 10G of a can 10 for beverages, than an inkjet head 19L for large dot images. A distance L1 between the inkjet head 19S for small dot images and the axial center 10G of the can 10 for beverages is smaller than a distance L2 between the inkjet head 19L for large dot images and the axial center 10G of the can 10 for beverages.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a printing device. [Background technology]

[0002] Patent Document 1 discloses a configuration in which a conical drinking cup is rotated by a mandrel that is pushed into the inside of the drinking cup during a printing process on the drinking cup. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2010-522651 Summary of the Invention [Problem to be solved by the invention]

[0004] 2. Description of the Related Art A cylindrical beverage container may be provided with a tapered portion in which the outer diameter decreases along the axial direction of the container. When an inkjet head is used to form an image on this tapered portion, a large gap may occur between the inkjet head and the portion of the tapered portion with a small outer diameter, which can lead to a decrease in the quality of the image formed. An object of the present invention is to suppress deterioration in image quality caused by forming an image on a reduced diameter portion of a beverage container using an inkjet head. [Means for solving the problem]

[0005] A printing device to which the present invention is applicable includes: a rotating means for rotating a cylindrical beverage container in a circumferential direction, the beverage container having a tapered portion whose outer diameter decreases as the container advances in the axial direction; a first inkjet head arranged opposite the outer peripheral surface of the container and ejecting ink into the tapered portion of the rotating container; and a second inkjet head arranged opposite the outer peripheral surface of the container, closer to the axis of the container than the first inkjet head, and ejecting ink into the tapered portion of the rotating container.

[0006] Here, when the first inkjet head ejects ink into the container, the container may be positioned with its axial direction aligned with the longitudinal direction of the first inkjet head, and when the second inkjet head ejects ink into the container, the container may be positioned with its axial direction aligned with the longitudinal direction of the second inkjet head. The first inkjet head and the second inkjet head may be arranged in a horizontal direction. In addition, the reduced diameter portion of the container may have a large outer diameter portion having a large outer diameter and a small outer diameter portion having a small outer diameter and a position in the axial direction of the container different from the position of the large outer diameter portion, and the second inkjet head may eject ink into a portion of the reduced diameter portion of the container that is located on the small outer diameter portion side of an adhesion point where ink ejected by the first inkjet head adheres. Furthermore, the first inkjet head may eject ink at a frequency greater than the second inkjet head. Furthermore, the size of the dot image formed in the reduced diameter portion by the first inkjet head may be larger than the size of the dot image formed in the reduced diameter portion by the second inkjet head. Furthermore, the rotation speed of the container when the first inkjet head ejects ink into the narrowed portion of the container may be smaller than the rotation speed of the container when the second inkjet head ejects ink into the narrowed portion of the container. In addition, the reduced diameter portion of the container may have a large outer diameter portion having a large outer diameter and a small outer diameter portion having a small outer diameter and a position in the axial direction of the container different from the position of the large outer diameter portion, and the second inkjet head may be provided closer to the small outer diameter portion than the first inkjet head. In addition, a container conveying means for conveying the container may be further provided, and multiple container stopping points may be provided that are located at different positions in the direction in which the container is conveyed by the container conveying means, and an inkjet head may be provided at each of the container stopping points, so that the container stopping point at which the first inkjet head is provided is different from the container stopping point at which the second inkjet head is provided. Furthermore, the length of the first inkjet head in the axial direction may be shorter than the length of the reduced diameter portion in the axial direction of the container, and the length of the second inkjet head in the axial direction may be shorter than the length of the reduced diameter portion in the axial direction. Furthermore, the reduced diameter portion of the container may have a large outer diameter portion having a large outer diameter, and a small outer diameter portion having a small outer diameter and a position in the axial direction of the container different from that of the large outer diameter portion, and when the container moves along the longitudinal direction of at least one of the first inkjet head and the second inkjet head and the container moves downward of the at least one inkjet head, the small outer diameter portion may be located downstream in the movement direction of the container, and the large outer diameter portion may be located upstream in the movement direction. [Effects of the Invention]

[0007] According to the present invention, it is possible to suppress deterioration in image quality caused by forming an image on a reduced diameter portion of a beverage container using an inkjet head. [Brief explanation of the drawings]

[0008] [Figure 1] 1A and 1B are diagrams illustrating a beverage can according to the present embodiment. [Figure 2] FIG. 1 is a diagram showing a printing device that prints on beverage cans. [Figure 3] FIG. 2 is a diagram illustrating an example of the hardware configuration of a control unit. [Figure 4] 4 is a view of the upstream printing unit and the downstream printing unit as viewed from the direction indicated by arrow IV in FIG. 2. [Figure 5] 10A and 10B are diagrams showing another example of an image formed on a reduced diameter portion of a beverage can. [Figure 6] FIG. 5 is a diagram of the large dot image inkjet head, the small dot image inkjet head, and the beverage can, viewed from the direction indicated by arrow VI in FIG. 4. [Figure 7] 10A and 10B are diagrams illustrating other configuration examples of the upstream printing unit and the downstream printing unit. [Figure 8] 10A and 10B are diagrams illustrating other configuration examples of the upstream printing unit and the downstream printing unit. [Figure 9] FIG. 10 is a diagram showing another example of the configuration of the printing device, in which the upstream printing unit and downstream printing unit are viewed from above. [Figure 10] 10A and 10B are diagrams showing other configuration examples of beverage cans. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Figures 1(A) and (B) are diagrams illustrating a beverage can 10 according to this embodiment. Figure 1(A) is a front view of the beverage can 10, and Figure 1(B) is a view of the beverage can 10 as viewed from the direction of arrow IB in Figure 1(A). Beverage can 10, which is an example of a container, is formed in a cylindrical shape. More specifically, beverage can 10 is formed in a cylindrical shape. Furthermore, beverage can 10 is provided with a reduced diameter portion 11 in which the outer diameter decreases in the axial direction, as shown in FIG. 1(A).

[0010] In this embodiment, a reduced diameter portion 11 is provided in the beverage can 10, and the beverage can 10 of this embodiment is a so-called tapered can. The beverage can 10 is provided with a can body 31, and in this embodiment, the entire can body 31 is tapered. As shown in FIG. 1(A), a beverage can 10 has one end 11A and another end 11B that are located at different axial positions. A circular opening 11E is provided at one end 11A of beverage can 10. A bottom 11F is provided at the other end 11B of beverage can 10. Can body 31 is located between opening 11E and bottom 11F.

[0011] In this embodiment, the outer diameter of one end 11A of the beverage can 10 is larger than the outer diameter of the other end 11B of the beverage can 10. The reduced diameter portion 11 is provided on the beverage can 10 from the one end 11A side to the other end 11B side. The reduced diameter portion 11 is provided so that the outer diameter gradually decreases as it progresses in the axial direction of the beverage can 10. More specifically, the reduced diameter portion 11 is provided so that the outer diameter gradually decreases as it progresses from one end 11A of the beverage can 10 to the other end 11B.

[0012] The reduced diameter portion 11 has a large outer diameter portion 11X, which is a portion with a large outer diameter, and a small outer diameter portion 11Y, which is a portion with a small outer diameter. In this embodiment, when comparing positions in the axial direction of the beverage can 10, the position of the large outer diameter portion 11X and the position of the small outer diameter portion 11Y are different. Furthermore, the reduced diameter portion 11 has an intermediate portion 11Z between the large outer diameter portion 11X and the small outer diameter portion 11Y. In this embodiment, when comparing the outer diameter of the large outer diameter portion 11X, the outer diameter of the intermediate portion 11Z, and the outer diameter of the small outer diameter portion 11Y, the relationship among the outer diameters is as follows. Relationship of outer diameter: outer diameter of large outer diameter part 11X > outer diameter of intermediate part 11Z > outer diameter of small outer diameter part 11Y

[0013] As shown in FIG. 1(A), an image 101 is formed on an outer peripheral surface 11M of a beverage can 10. This image 101 is made up of a plurality of dot images 102 formed by hardening ink ejected by an inkjet, which will be described later. The drawings indicated by reference numerals 1A, 1B, and 1C in FIG. 1 are enlarged views of a portion of an image 101 formed on an outer peripheral surface 11M of a beverage can 10. In this embodiment, as shown in the figures indicated by symbols 1A, 1B, and 1C, a dot image 102 is formed on the outer peripheral surface 11M of the reduced diameter portion 11, and an image 101 is formed by a plurality of these dot images 102.

[0014] The dot images 102 are arranged in the axial direction of the beverage can 10. The dot images 102 are also arranged in the circumferential direction of the beverage can 10. The figures indicated by symbols 1A, 1B, and 1C in Figure 1(A) show dot images 102 arranged in the axial direction of the beverage can 10, and show one row of dot images 102 along this axial direction. In this embodiment, as shown in the figures indicated by symbols 1A and 1C, the size of the dot image 102 formed in the large outer diameter portion 11X of the narrowing portion 11 is larger than the size of the dot image 102 formed in the small outer diameter portion 11Y of the narrowing portion 11. In other words, in this embodiment, the diameter of the dot image 102 formed on the large outer diameter portion 11X of the reduced diameter portion 11 is larger than the diameter of the dot image 102 formed on the small outer diameter portion 11Y of the reduced diameter portion 11.

[0015] In the printing device of this embodiment (described later), when forming a dot image 102 using an inkjet head, the dot image 102 is formed so that the size of the dot image 102 formed in the large outer diameter portion 11X is larger than the size of the dot image 102 formed in the small outer diameter portion 11Y. In this embodiment, two types of dot images 102, large dot images 102 and small dot images 102, are formed.

[0016] In this embodiment, as shown by the symbol 1B in Figure 1(A), the dot image 102 is formed so that a large dot image 102 is formed in the large outer diameter region 11J, which is the region located closer to the large outer diameter portion 11X than the intermediate portion 11Z, with the intermediate portion 11Z as the boundary. In this embodiment, the dot images 102 are formed so that small dot images 102 are formed in the small outer diameter region 11K, which is a region located closer to the small outer diameter portion 11Y than the intermediate portion 11Z.

[0017] In this embodiment, two types of dot images 102 are formed in this way: large dot images 102 and small dot images 102. However, the present invention is not limited to this, and the types of dot images 102 with different sizes may be three or more. When the dot images 102 are of a plurality of different sizes, the sizes of the dot images 102 are changed in order from the small outer diameter portion 11Y to the large outer diameter portion 11X, and the dot images 102 become larger each time the size changes. Alternatively, the dot images 102 may be formed so that they become gradually larger from the small outer diameter portion 11Y toward the large outer diameter portion 11X.

[0018] In this embodiment, the beverage content is filled into the beverage can 10 through an opening 11E located at one end 11A of the beverage can 10. A can lid (not shown) is then attached to the opening 11E to close the opening 11E. This completes the beverage can filled with the beverage. Examples of beverages that can be filled include alcoholic beverages such as beer, and non-alcoholic beverages such as soft drinks. In this embodiment, the beverage can 10 refers to an empty can body before being filled with a beverage. It should be noted that a can lid is not essential, and in some cases, after a beverage is poured into the beverage can 10, a can lid is not attached, and the beverage inside the beverage can 10 may be consumed by a user without the can lid.

[0019] The beverage can 10 of this embodiment is an example of a container. More specifically, the beverage can 10 of this embodiment is an example of a beverage container. The beverage can 10 of this embodiment is made of metal and is formed from a metal material. Specifically, the beverage can 10 is formed from, for example, aluminum, an aluminum alloy, or the like. The beverage can 10 is formed, for example, by subjecting a flat plate material (substrate) to draw and ironing (DI) forming or stretch draw forming. The material of the beverage can 10 is not particularly limited, and the beverage can 10 may be made of a resin material or paper. In other words, a container having a reduced diameter portion 11, such as the beverage can 10 of this embodiment, may be made of a resin material or paper. Furthermore, the method for forming the container is not limited, and the container may be formed by a method other than the above-mentioned draw and ironing (DI) forming or stretch draw forming.

[0020] FIG. 2 is a diagram showing a printing device 100 that prints on a beverage can 10. As shown in FIG. In this embodiment, the printing device 100 shown in Figure 2 forms an image 101 on the reduced diameter portion 11 (see Figure 1(A)). In other words, in this embodiment, the printing device 100 forms an image 101 on the can body 31 of the beverage can 10. In other words, in this embodiment, the printing device 100 forms an image 101 on the outer peripheral surface 11M of the beverage can 10. The printing device 100 is provided with a control unit 60 that controls each unit of the printing device 100 .

[0021] 3 is a diagram showing an example of the hardware configuration of the control unit 60. The control unit 60 is realized by a computer. The control unit 60 has an arithmetic processing unit 21 that executes digital arithmetic processing according to a program, and a secondary storage unit 212 that stores information. The secondary storage unit 212 is realized by an existing information storage device such as an HDD (Hard Disk Drive), semiconductor memory, or magnetic tape.

[0022] The arithmetic processing unit 21 includes a CPU 21a as an example of a processor. The arithmetic processing unit 21 is also provided with a RAM 21b used as a working memory for the CPU 21a, and a ROM 21c in which programs executed by the CPU 21a are stored. The arithmetic processing unit 21 is also provided with a nonvolatile memory 21d that is rewritable and can retain data even if the power supply is interrupted.

[0023] The nonvolatile memory 21d is configured, for example, with a battery-backed SRAM, a flash memory, etc. The secondary storage unit 212 stores files and the like, as well as programs executed by the arithmetic processing unit 21. In this embodiment, the CPU 21a of the arithmetic processing unit 21 reads programs stored in the ROM 21c or the secondary storage unit 212, and thereby various processes performed by the printing device 100 are executed.

[0024] The program executed by the CPU 21a may be provided to the printing device 100 in a state where it is stored in a computer-readable recording medium such as a magnetic recording medium (such as a magnetic tape or a magnetic disk), an optical recording medium (such as an optical disk), a magneto-optical recording medium, or a semiconductor memory. The program executed by the CPU 21a may also be provided to the printing device 100 using a communication means such as the Internet.

[0025] The printing device 100 will be further described with reference to FIG. The printing apparatus 100 is provided with a supply unit 510 to which beverage cans 10 are supplied. In the supply section 510, beverage cans 10 are attached to support members 20 designated by the reference symbol 2A. The support members 20 designated by the reference symbol 2A move to the supply section 510. In the supply section 510, beverage cans 10 are attached to the support members 20. In the printing device 100, the beverage can 10 is supported by the support member 20.

[0026] The outer peripheral surface of the support member 20 is tapered. The support member 20 is provided with its axis aligned horizontally. In this embodiment, the support member 20 is inserted into the beverage can 10, and thereby the beverage can 10 is supported by the support member 20. Furthermore, the printing device 100 of this embodiment is provided with a plurality of moving units 550 as an example of a moving body that moves while supporting the beverage can 10.

[0027] In this embodiment, the support member 20 that supports the beverage can 10 is attached to the moving unit 550. The support member 20 and the beverage can 10 supported by the support member 20 move together with the moving unit 550. As indicated by the reference symbol 2A, each of the moving units 550 is provided with a rotation mechanism 550E as an example of a rotation means for rotating the support member 20 in the circumferential direction. The rotation mechanism 550E is provided with a drive motor (not shown).

[0028] In this embodiment, the control unit 60 controls the rotation of the drive motor, thereby making it possible to change the rotation speed of the beverage can 10. In this embodiment, a control signal is sent from the control unit 60 to the drive motor, thereby changing the rotation speed of the beverage can 10. In this embodiment, the control signal is sent from the control unit 60 to the moving unit 550 by wireless communication.

[0029] An upstream printing unit 700 is provided downstream of the supply unit 510 . The upstream printing unit 700 is provided with a plurality of inkjet heads 19. Each of the inkjet heads 19 is provided to extend in a direction perpendicular to the plane of the paper in Fig. 2. Each of the inkjet heads 19 is provided to extend along the horizontal direction. The upstream printing unit 700 uses an inkjet printing method to form an image 101 (see FIG. 1(A)) on a beverage can 10 that has been moved from the upstream side.

[0030] Forming an image by inkjet printing refers to printing onto the beverage can 10 by ejecting ink from the inkjet head 19. When ink is ejected from inkjet head 19 and adhered to beverage can 10, a plurality of dot images 102 are formed on outer peripheral surface 11M of beverage can 10 (see FIG. 1(A)). In this embodiment, the image 101 shown in FIG. 1(A) is formed by the plurality of dot images 102.

[0031] A plurality of ejection ports (not shown) for ejecting ink are provided on the bottom surface of the inkjet head 19, and in this embodiment, an image 101 is formed by ejecting ink from the plurality of ejection ports. When forming an image by inkjet printing, known methods can be used, such as a piezo method, a thermal (bubble) method, or a continuous method.

[0032] Furthermore, in this embodiment, a downstream printing unit 800 is provided downstream of the upstream printing unit 700 . The downstream printing unit 800 has the same configuration as the upstream printing unit 700 . The downstream printing unit 800 is also provided with a plurality of inkjet heads 19. The inkjet heads 19 provided in the downstream printing unit 800 are also provided along the horizontal direction. The downstream printing unit 800 also uses an inkjet printing method to form an image 101 on a beverage can 10 that has been moved from the upstream side.

[0033] A light irradiation unit 751 as an example of a light irradiation means is provided downstream of the downstream printing unit 800. The light irradiating unit 751 has a light source and irradiates light onto the beverage cans 10 after image formation by the upstream printing unit 700 and image formation by the downstream printing unit 800 has been performed. This hardens the image 101 formed on the outer peripheral surface 11M of the beverage can 10. In other words, the dot image 102 formed on the outer peripheral surface 11M of the beverage can 10 hardens.

[0034] The upstream printing unit 700 and the downstream printing unit 800 form the image 101 using ultraviolet curable ink. In other words, the upstream printing unit 700 and the downstream printing unit 800 form the image 101 using actinic radiation curable ink. The light irradiating section 751 irradiates ultraviolet light onto the image 101 formed on the outer peripheral surface 11M of the beverage can 10. As a result, the image 101 is hardened.

[0035] The ink used to form the image 101 is not limited to ultraviolet curable ink, and other types of ink such as heat curable ink may also be used. Image 101 can be formed using any existing ink that has been conventionally used, and there are no particular limitations on the ink used to form image 101. In other words, image 101 can be formed using any known ink that has been conventionally used for printing on beverage cans 10, and there are no particular limitations on the ink used to form image 101.

[0036] Furthermore, in the printing apparatus 100 of this embodiment, a protective layer forming unit 770 is provided downstream of the light irradiating unit 751 . The protective layer forming unit 770 applies paint onto the image 101 formed by the upstream printing unit 700 and the downstream printing unit 800, forming a transparent layer that covers the image 101. As a result, in this embodiment, a transparent protective layer (not shown) is formed on the outermost layer of the beverage can 10.

[0037] Downstream of the protective layer forming section 770, a removing section 780 is provided where the beverage cans 10 are removed from the support member 20. In this embodiment, the beverage can 10 is removed from the support member 20 at the removal unit 780. Then, in this embodiment, the beverage can 10 is ejected to the outside of the printing device 100. The beverage can 10 discharged outside the printing apparatus 100 is heated by a heating device (not shown), which hardens the protective layer formed on the outermost layer of the beverage can 10.

[0038] The printing device 100 is provided with a plurality of moving units 550 as an example of a moving body. In this embodiment, the moving units 550 support the beverage cans 10, and the beverage cans 10 move together with the moving units 550. Furthermore, in this embodiment, there is provided a moving mechanism 560 that functions as a moving means for moving the moving unit 550. The moving mechanism 560 is provided with an annular guide member 561 that guides the moving unit 550.

[0039] Each of the moving units 550 is guided by a guide member 561 and moves circularly along a predetermined circular moving path 850 . In this embodiment, a conveying mechanism 600, which is an example of a container conveying means, is configured by the moving unit 550 and the moving mechanism 560. In this embodiment, the conveying mechanism 600 conveys the beverage cans 10.

[0040] An electromagnet (not shown) is provided inside guide member 561. Furthermore, a permanent magnet (not shown) is provided in moving unit 550. In this embodiment, a linear mechanism is used to move moving unit 550. The conveying mechanism 600 of this embodiment conveys beverage cans 10 using the linear mechanism. The moving unit 550 is not limited to a linear mechanism and may be moved by other mechanisms. For example, the moving unit 550 may be provided with a motor so that the moving unit 550 moves autonomously.

[0041] The moving unit 550 moves along a predetermined circular moving path 850 . The movement path 850 is disposed so that its axis 800C is aligned with the horizontal direction. In other words, the movement path 850 is disposed around the axis 800C aligned with the horizontal direction. The axis 800C extends in a direction perpendicular to the plane of the paper in FIG. 2 . In this case, in this embodiment, the moving unit 550 moves around this axis center 800C that extends in a direction perpendicular to the paper surface in the drawing.

[0042] In this embodiment, an example has been described in which the annular movement path 850 is arranged around an axial center 800C along the horizontal direction, but this is not limiting, and the annular movement path 850 may also be arranged around an axial center along the vertical direction. Even when the annular movement path 850 is arranged around an axis center that is aligned in the vertical direction, it is preferable that the support member 20 and the inkjet head 19 are aligned in the horizontal direction.

[0043] 2, if the annular movement path 850 is arranged around a vertical axis, the support member 20 and the inkjet head 19 will be aligned vertically. This can easily lead to a decrease in the quality of the image 101 formed on the beverage can 10. Therefore, when the annular movement path 850 is arranged around an axial center along the vertical direction, it is preferable not to maintain the configuration of each part shown in FIG. 2 as it is. When the circular movement path 850 is arranged around an axial center along the vertical direction, it is preferable to change the arrangement angle of at least the support member 20 and the inkjet head 19 so that they are arranged along the horizontal direction.

[0044] The upstream printing unit 700 and the downstream printing unit 800 will now be described in detail. Each of the upstream printing unit 700 and the downstream printing unit 800 is provided with a plurality of inkjet heads 19 arranged side by side in the left-right direction in the figure. Each of the inkjet heads 19 is provided along the horizontal direction. Each of the upstream printing unit 700 and the downstream printing unit 800 is provided with a first inkjet head 19C that ejects cyan ink, a second inkjet head 19M that ejects magenta ink, a third inkjet head 19Y that ejects yellow ink, and a fourth inkjet head 19K that ejects black ink.

[0045] In this embodiment, each of the upstream printing unit 700 and the downstream printing unit 800 is provided with an inkjet head 19 that ejects ink of the same color, and in this embodiment, two inkjet heads 19 that eject ink of the same color are provided. In this embodiment, a plurality of inkjet heads 19 are provided for each color. Specifically, two inkjet heads 19 are provided for each color.

[0046] Four inkjet heads 19, namely, first inkjet head 19C to fourth inkjet head 19K, provided in each of the upstream printing unit 700 and the downstream printing unit 800, form images on the outer peripheral surface 11M of the beverage can 10 using ultraviolet curable ink. In this embodiment, the beverage can 10 moves with its axial direction horizontal, and a part of the outer circumferential surface 11M of the beverage can 10 faces upward in the vertical direction. In this embodiment, ink is ejected downward from above this outer peripheral surface 11M to form an image 101 (see FIG. 1(A)) on the outer peripheral surface 11M of the beverage can 10.

[0047] Furthermore, in this embodiment, the four inkjet heads 19 provided in each of the upstream printing unit 700 and the downstream printing unit 800 are arranged side by side in the conveyance direction of the beverage cans 10. Moreover, each of the four inkjet heads 19 is arranged along a direction perpendicular to (intersecting with) the conveyance direction of the beverage cans 10. In this embodiment, ink is ejected from above onto the outer peripheral surface 11M of the beverage can 10 as the beverage can 10 passes below four inkjet heads 19 provided in each of the upstream printing unit 700 and the downstream printing unit 800. In this way, an image 101 is formed on the outer peripheral surface 11M of the beverage can 10.

[0048] Each of the moving units 550 stops at the installation location of one of the multiple inkjet heads 19. Then, at the installation location of each inkjet head 19, ink is ejected onto the outer peripheral surface 11M of the beverage can 10, and an image 101 is formed on the outer peripheral surface 11M of the beverage can 10. When the inkjet heads 19 form the image 101, the drive motor provided in the rotation mechanism 550E is driven, and the beverage can 10 rotates in the circumferential direction.

[0049] The beverage can 10 supported by the moving unit 550 stops at the installation locations of the multiple inkjet heads 19. In this embodiment, the installation locations of the inkjet heads 19 are beverage can stopping locations 91, where the beverage can 10 stops. At each of these beverage can stopping points 91, which are examples of container stopping points, ink is ejected from the inkjet head 19 onto the outer surface 11M of the beverage can 10, forming an image 101 on this outer surface 11M. When the image 101 is formed on the outer peripheral surface 11M of the beverage can 10, the beverage can 10 is rotating, and ink is ejected from each inkjet head 19 onto the rotating beverage can 10.

[0050] Each of the moving units 550 also stops at the supplying section 510, the light irradiating section 751, the protective layer forming section 770, and the removing section 780, respectively. In addition, in the light irradiation section 751 and the protective layer forming section 770, the beverage can 10 supported by the moving unit 550 is rotated in the circumferential direction.

[0051] FIG. 4 is a diagram of the upstream printing unit 700 and the downstream printing unit 800 as viewed from the direction indicated by arrow IV in FIG. In this embodiment, as described above, the upstream printing unit 700 and the downstream printing unit 800 are each provided with four inkjet heads 19, the first inkjet head 19C to the fourth inkjet head 19K. In this embodiment, when the inkjet heads 19 form an image 101 on the beverage can 10, each of the inkjet heads 19 is arranged along the axial direction of the beverage can 10 and positioned opposite the outer peripheral surface 11M of the beverage can 10.

[0052] In this embodiment, the inkjet head 19 is provided with a large dot image inkjet head 19L for forming a large dot image 102. In this embodiment, the inkjet head 19 includes a small-dot-image inkjet head 19S that forms dot images 102 that are smaller than the dot images 102 formed by the large-dot-image inkjet head 19L.

[0053] In this embodiment, each of the four inkjet heads 19 provided in the upstream printing section 700 is a large-dot image inkjet head 19L. In this embodiment, the large dot image inkjet head 19L, which is an example of a first inkjet head, is provided close to one end 11A of the beverage can. In this embodiment, the large dot image inkjet head 19L ejects ink onto the large outer diameter region 11J including the large outer diameter portion 11X. In this embodiment, when ink is ejected into the beverage can 10 by the large dot image inkjet head 19L, the beverage can 10 is positioned so that the axial direction of the beverage can 10 is aligned with the longitudinal direction of the large dot image inkjet head 19L.

[0054] In this embodiment, each of the four inkjet heads 19 provided in the downstream printing section 800 is an inkjet head 19S for small dot images. In this embodiment, the dot images 102 formed by the inkjet head 19S for small dot images are smaller than the dot images 102 formed by the inkjet head 19L for large dot images. In other words, in this embodiment, the amount of ink contained in the ink droplets ejected by the inkjet head 19S for small dot images is less than the amount of ink contained in the ink droplets ejected by the inkjet head 19L for large dot images. In other words, in this embodiment, the volume of ink ejected by the inkjet head 19S for small dot images, which is the volume per ink droplet, is smaller than the volume of ink ejected by the inkjet head 19L for large dot images, which is the volume per ink droplet.

[0055] In this embodiment, the small dot image inkjet head 19S, which is an example of a second inkjet head, is provided closer to the other end 11B of the beverage can . In this embodiment, when ink is ejected into the beverage can 10 by the inkjet head 19S for small dot images, the beverage can 10 is positioned so that the axial direction of the beverage can 10 is aligned with the longitudinal direction of the inkjet head 19S for small dot images. In this embodiment, the small dot image inkjet head 19S ejects ink onto the small outer diameter region 11K including the small outer diameter portion 11Y.

[0056] When ink is ejected from the inkjet head 19L for large dot images and the inkjet head 19S for small dot images, as shown in Figure 1(A), a large dot image 102 is formed in the large outer diameter region 11J including the large outer diameter portion 11X, and a small dot image 102 is formed in the small outer diameter region 11K including the small outer diameter portion 11Y. In this embodiment, as will be described later, each of the small dot image inkjet heads 19S is disposed closer to the axis of the beverage can 10 than the large dot image inkjet heads 19L.

[0057] In this embodiment, as described above, the reduced diameter portion 11 (see FIG. 1(A)) of the beverage can 10 has a large outer diameter portion 11X having a large outer diameter and a small outer diameter portion 11Y having a small outer diameter. In this embodiment, the position of the large outer diameter portion 11X in the axial direction of the beverage can 10 differs from the position of the small outer diameter portion 11Y in the axial direction. The large dot image inkjet head 19L ejects ink onto a large outer diameter region 11J, which is a portion of the reduced diameter portion 11 of the beverage can 10 that is located on the large outer diameter portion 11X side. In contrast, the small dot image inkjet head 19S ejects ink onto the small outer diameter region 11K, which is a portion of the reduced diameter portion 11 of the beverage can 10 that is located on the small outer diameter portion 11Y side.

[0058] The large outer diameter region 11J is a deposition area where ink ejected from the large dot image inkjet head 19L is deposited. The small dot image inkjet head 19S ejects ink to a location located on the small outer diameter portion 11Y side of the large outer diameter region 11J, which is the adhesion location of the ink ejected by the large dot image inkjet head 19L. Specifically, the small dot image inkjet head 19S ejects ink onto the small outer diameter region 11K, which is located closer to the small outer diameter portion 11Y than the large outer diameter region 11J.

[0059] As shown in FIG. 4, the inkjet head 19S for small dot images is provided closer to the small outer diameter portion 11Y than the inkjet head 19L for large dot images. Here, "the inkjet head 19S for small dot images is located closer to the smaller outer diameter portion 11Y than the inkjet head 19L for large dot images" does not mean that the entire inkjet head 19S for small dot images is located closer to the smaller outer diameter portion 11Y than the inkjet head 19L for large dot images.

[0060] The large dot image inkjet head 19L has an end portion 198 located at one end in the longitudinal direction of the large dot image inkjet head 19L and located on the large outer diameter portion 11X side. The inkjet head 19S for small dot images also has an end 199 located at one end in the longitudinal direction of the inkjet head 19S and on the side of the large outer diameter portion 11X. In this embodiment, when comparing end 198 of inkjet head 19L for large dot images with end 199 of inkjet head 19S for small dot images, end 199 of inkjet head 19S for small dot images is located closer to the small outer diameter portion 11Y of beverage can 10 than end 198 of inkjet head 19L for large dot images.

[0061] When comparing the axial positions of the beverage can 10, the end 199 of the inkjet head 19S for small dot images is located closer to the small outer diameter portion 11Y of the reduced diameter section 11 than the end 198 of the inkjet head 19L for large dot images. If end 199 of inkjet head 19S for small dot images is located closer to the small outer diameter portion 11Y of beverage can 10 than end 198 of inkjet head 19L for large dot images, then this corresponds to "inkjet head 19S for small dot images is located closer to the small outer diameter portion 11Y than inkjet head 19L for large dot images."

[0062] Note that the dot image 102 shown in FIG. 1(A) and the dot image 102 described below each represent a dot image 102 formed by one of four sets of inkjet heads 19 provided for each color. More specifically, the dot image 102 shown in FIG. 1(A) and the dot images 102 described below are both dot images 102 formed by a set of inkjet heads 19 corresponding to one color, such as an inkjet head 19L for large dot images corresponding to black and an inkjet head 19S for small dot images corresponding to black. Of the four sets of inkjet heads 19, the remaining three sets of inkjet heads 19 each form a dot image 102 in the same manner as the dot image 102 formed by the one set of inkjet heads 19 described above.

[0063] In the case where a reduced diameter section 11 is provided on the beverage can 10 as in this embodiment, if ink is ejected from the inkjet head 19 at regular time intervals, the formed image 101 may have variations in shade, which may result in a deterioration in the quality of the formed image 101. When a beverage can 10 is provided with a reduced diameter section 11, the spacing between the dot images 102 arranged in a circumferential direction of the part of the reduced diameter section 11 with a larger outer diameter differs from the spacing between the dot images 102 arranged in a circumferential direction of the part of the reduced diameter section 11 with a smaller outer diameter.

[0064] In this case, the formed image 101 may have uneven shading, which may result in a deterioration in the quality of the formed image 101. In contrast to this, in this embodiment, a large dot image 102 is formed on the side of the reduced diameter portion 11 where the large outer diameter portion 11X is located. Also, in this embodiment, a small dot image 102 is formed on the side of the reduced diameter portion 11 where the small outer diameter portion 11Y is located. In this case, the shading of the image 101 formed on the reduced diameter portion 11 becomes smaller.

[0065] In this embodiment, as shown in FIG. 4, a plurality of beverage can stopping points 91 are provided. The plurality of beverage can stopping points 91 are provided at mutually different positions in the direction in which the beverage cans 10 are conveyed by the conveying mechanism 600 (see FIG. 2). In this embodiment, an inkjet head 19 is provided at each of the beverage can stopping points 91 . Furthermore, in this embodiment, the beverage can stopping location 91 where the large dot image inkjet head 19L is provided is different from the beverage can stopping location 91 where the small dot image inkjet head 19S is provided.

[0066] FIG. 5 is a diagram showing another example of an image 101 formed on the reduced diameter portion 11 of a beverage can 10. In FIG. In this example shown in Figure 5, the number of dot images 102 located in the large outer diameter region 11J and arranged in the circumferential direction of the beverage can 10 is greater than the number of dot images 102 located in the small outer diameter region 11K and arranged in the circumferential direction of the beverage can 10. Specifically, for example, the number of large dot images 102 arranged in a line around the circumference of the beverage can 10 located in the area indicated by reference symbol 5A in Figure 5 is greater than the number of small dot images 102 arranged in a line around the circumference of the beverage can 10 located in the area indicated by reference symbol 5B in Figure 5.

[0067] In this embodiment, multiple dot image rows 193A in which large dot images 102 are arranged in the circumferential direction of the beverage can 10 are present within the large outer diameter region 11J. In this embodiment, a plurality of dot image rows 193B in which small dot images 102 are arranged in the circumferential direction of the beverage can 10 are present within the small outer diameter region 11K. In this embodiment, the number of large dot images 102 included in each of the multiple dot image arrays 193A is the same. In this embodiment, there are multiple dot image arrays 193A (only one dot image array 193A is shown in FIG. 5), but the number of large dot images 102 included in one of the multiple dot image arrays 193A is the same as the number of large dot images 102 included in another of the multiple dot image arrays 193A. Furthermore, in this embodiment, each of the multiple dot image arrays 193B contains the same number of small dot images 102. In this embodiment, there are multiple dot image arrays 193B (only one dot image array 193B is shown in FIG. 5), but the number of small dot images 102 contained in one of the multiple dot image arrays 193B is the same as the number of small dot images 102 contained in another of the multiple dot image arrays 193B.

[0068] In the example shown in Figure 5, the number of large dot images 102 contained in each dot image row 193A located in the large outer diameter region 11J and extending along the circumferential direction of the beverage can 10 is greater than the number of small dot images 102 contained in each dot image row 193B located in the small outer diameter region 11K and extending along the circumferential direction of the beverage can 10. In this way, by making the number of large dot images 102 contained in each dot image row 193A greater than the number of small dot images 102 contained in each dot image row 193B, it is possible to make the shading of the image 101 even less pronounced than when the numbers of dot images 102 are the same.

[0069] When forming a dot image 102 in the form shown in Figure 5, for example, the frequency of ink ejection onto the beverage can 10 at the beverage can stopping point 91 where the large dot image inkjet head 19L (see Figure 4) is provided is made higher than the frequency of ink ejection onto the beverage can 10 at the beverage can stopping point 91 where the small dot image inkjet head 19S is provided. In other words, the ink ejection frequency of the large dot image inkjet head 19L that ejects ink onto the large outer diameter region 11J is set higher than the ink ejection frequency of the small dot image inkjet head 19S that ejects ink onto the small outer diameter region 11K.

[0070] In other words, the number of times that the large dot image inkjet head 19L ejects ink per unit time is set to be greater than the number of times that the small dot image inkjet head 19S ejects ink per unit time. As a result, in this embodiment, the number of large dot images 102 aligned in the circumferential direction of the beverage can 10 is greater than the number of small dot images 102 aligned in the circumferential direction of the beverage can 10.

[0071] Additionally, when forming a dot image 102 in the form shown in FIG. 5, the rotational speed of the beverage can 10 at the beverage can stopping point 91 where the large dot image inkjet head 19L (see FIG. 4) is provided may be set lower than the rotational speed of the beverage can 10 at the beverage can stopping point 91 where the small dot image inkjet head 19S is provided. In this case as well, the number of large dot images 102 aligned in the circumferential direction of the beverage can 10 is greater than the number of small dot images 102 aligned in the circumferential direction of the beverage can 10.

[0072] Alternatively, when forming dot image 102 in the form shown in FIG. 5, the ink ejection frequency of large dot image inkjet head 19L may be set higher than the ink ejection frequency of small dot image inkjet head 19S, and the rotation speed of beverage can 10 at beverage can stopping point 91 where large dot image inkjet head 19L is provided may be set lower than the rotation speed of beverage can 10 at beverage can stopping point 91 where small dot image inkjet head 19S is provided. In other words, the ink ejection frequency of the inkjet head 19L for large dot images may be set to be higher than the ink ejection frequency of the inkjet head 19S for small dot images, and the rotation speed of the beverage can 10 when the large dot image 102 is formed may be set to be lower than the rotation speed of the beverage can 10 when the small dot image 102 is formed.

[0073] FIG. 6 is a diagram of large dot image inkjet head 19L, small dot image inkjet head 19S, and beverage can 10 as viewed from the direction indicated by arrow VI in FIG. In this embodiment, the inkjet head 19S for small dot images, which is an example of a second inkjet head, is positioned closer to the axis 10G of the beverage can 10 than the inkjet head 19L for large dot images, which is an example of a first inkjet head. In this embodiment, the distance L1 between the inkjet head 19S for small dot images and the axis 10G of the beverage can 10 is smaller than the distance L2 between the inkjet head 19L for large dot images and the axis 10G of the beverage can 10. As a result, in this embodiment, deterioration in the quality of the image 101 (see FIG. 1(A)) formed on the outer peripheral surface 11M of the beverage can 10 can be further suppressed.

[0074] In this embodiment, the deterioration in the quality of the image 101 formed on the outer surface 11M of the beverage can 10 can be suppressed compared to when the distance L1 between the inkjet head 19S for small dot images and the axis 10G of the beverage can 10 is the same as the distance L2 between the inkjet head 19L for large dot images and the axis 10G of the beverage can 10. Here, it is assumed that the distance L1 between the inkjet head 19S for small dot images and the axial center 10G of the beverage can 10 is the same as the distance L2 between the inkjet head 19L for large dot images and the axial center 10G of the beverage can 10, and that the inkjet head 19S for small dot images is farther away from the axial center 10G of the beverage can 10 than the state shown in Figure 6.

[0075] In this case, the position where the ink ejected from the inkjet head 19S for small dot images adheres to the beverage can 10 is more likely to deviate from the originally intended position than when the inkjet head 19S for small dot images is positioned closer to the axis 10G of the beverage can 10. In contrast, when the inkjet head 19S for small dot images is positioned near the axis 10G of the beverage can 10, as in this embodiment, this deviation is smaller than when it is not positioned near the axis 10G of the beverage can 10.

[0076] Furthermore, in this embodiment, as shown in FIG. 4, the beverage can stopping location 91 where the inkjet head 19L for large dot images is provided is different from the beverage can stopping location 91 where the inkjet head 19S for small dot images is provided. In this embodiment, a plurality of beverage can stopping points 91 are provided, each of which is positioned differently in the direction in which the beverage can 10 is conveyed by the conveying mechanism 600 (see Figure 2), and an inkjet head 19 is provided at each of these beverage can stopping points 91. In this embodiment, the beverage can stopping location 91 where the large dot image inkjet head 19L is provided is different from the beverage can stopping location 91 where the small dot image inkjet head 19S is provided.

[0077] Here, the beverage can stopping location 91 where the large dot image inkjet head 19L is provided and the beverage can stopping location 91 where the small dot image inkjet head 19S is provided may be the same, but it is more preferable that they are different. It is assumed that one beverage can stopping location 91 is provided with inkjet head 19L for large dot images and inkjet head 19S for small dot images.

[0078] In this case, in order to avoid interference between the inkjet heads 19, it may be necessary to position one or both of the inkjet head for large dot images 19L and the inkjet head for small dot images 19S at an angle, or it may be necessary to position one or both of them in a direction other than the vertical direction. In this case, the quality of the formed image 101 is more likely to deteriorate than when the height direction of the inkjet head 19 coincides with the vertical direction and the inkjet head 19 is arranged along the vertical direction.

[0079] In contrast to this, in this embodiment, the beverage can stopping location 91 where the large dot image inkjet head 19L is provided is different from the beverage can stopping location 91 where the small dot image inkjet head 19S is provided. In this case, the large dot image inkjet head 19L and the small dot image inkjet head 19S can be arranged vertically, which reduces the risk of problems such as a decrease in the quality of the formed image 101. As described above, the beverage can stopping location 91 where the large dot image inkjet head 19L is provided and the beverage can stopping location 91 where the small dot image inkjet head 19S is provided may be the same, and this does not exclude a situation where the beverage can stopping location 91 where the large dot image inkjet head 19L is provided and the beverage can stopping location 91 where the small dot image inkjet head 19S is provided are the same. In an embodiment where the beverage can stopping location 91 where the inkjet head 19L for large dot images is provided is the same as the beverage can stopping location 91 where the inkjet head 19S for small dot images is provided, the printing device 100 can be made smaller than in an embodiment where the beverage can stopping location 91 where the inkjet head 19L for large dot images is provided is different from the beverage can stopping location 91 where the inkjet head 19S for small dot images is provided.

[0080] 7 and 8 are diagrams showing other configuration examples of the upstream printing unit 700 and the downstream printing unit 800. In FIG. Fig. 7 shows the upstream printing unit 700 and the downstream printing unit 800 as viewed from above. Fig. 8 shows the large dot image inkjet head 19L, the small dot image inkjet head 19S, and the beverage can 10 as viewed from the direction indicated by arrow VIII in Fig. 7.

[0081] In the above, a configuration has been described in which the inkjet head 19S for small dot images is provided closer to the small outer diameter portion 11Y of the beverage can 10 than the inkjet head 19L for large dot images, but the arrangement of the inkjet head 19S for small dot images and the inkjet head 19L for large dot images is not limited to this. As shown in Figures 7 and 8, in the axial direction of beverage can 10, the position of inkjet head 19L for large dot images and the position of inkjet head 19S for small dot images may be aligned with the direction of axis 10G of beverage can 10. In this configuration example shown in Figures 7 and 8, as in the above, as shown in Figure 8, the inkjet head 19S for small dot images is positioned closer to the axis 10G of the beverage can 10 than the inkjet head 19L for large dot images.

[0082] In this configuration example, similarly to the above, ink is applied to the large outer diameter region 11J of the beverage can 10 from the large dot image inkjet head 19L. In this configuration example, similar to the above, ink is applied to the small outer diameter region 11K of the beverage can 10 from the small dot image inkjet head 19S arranged closer to the axis 10G of the beverage can 10. As a result, in this case as well, deterioration in the quality of the image 101 formed on the outer peripheral surface 11M of the beverage can 10 can be suppressed.

[0083] Although not explained above, in the configuration example shown in Figure 6, the length L4 of the large dot image inkjet head 19L in the axial direction is shorter than the length L3 of the reduced diameter portion 11 of the beverage can 10 in the axial direction of the beverage can 10. Similarly, in the configuration example shown in Figure 6, the length L5 of the inkjet head 19S for small dot images in the axial direction is shorter than the length L3 of the reduced diameter portion 11 of the beverage can 10 in the axial direction of the beverage can 10.

[0084] In this case, the volume occupied by the inkjet head 19 in the printing device 100 (see FIG. 2) is reduced, making it easier to make the printing device 100 smaller. More specifically, compared to when the length L5 of the inkjet head 19S for small dot images and the length L4 of the inkjet head 19L for large dot images are longer than the length L3 of the narrowed portion 11 of the beverage can 10, the volume occupied by the inkjet head 19 in the printing device 100 is reduced, making it easier to miniaturize the printing device 100.

[0085] FIG. 9 is a diagram showing another example of the configuration of the printing device 100, in which the upstream printing unit 700 and downstream printing unit 800 are viewed from above. In this configuration example, the upstream printing unit 700 and the downstream printing unit 800 are not located above the movement path 300R of the beverage can 10 when the beverage can 10 is moved by the conveying mechanism 600 (see Figure 2). In this configuration example, when the upstream printing unit 700 and the downstream printing unit 800 are viewed from above, the upstream printing unit 700 and the downstream printing unit 800 are located at a location outside the movement path 300R of the beverage can 10.

[0086] When the upstream printing unit 700, downstream printing unit 800, and movement path 300R are viewed from above, the upstream printing unit 700 and downstream printing unit 800 are provided on one side 300S of the movement path 300R. In this configuration example, an inkjet head 19L for large dot images and an inkjet head 19S for small dot images are provided on one side 300S. Furthermore, in this configuration example, each moving unit 550 is provided with a moving mechanism 556 that moves the beverage can 10 supported by this moving unit 550 toward the large dot image inkjet head 19L and the small dot image inkjet head 19S. As in the above, in this configuration example, the inkjet head 19S for small dot images, which forms an image on the small outer diameter portion 11Y side of the narrowed diameter portion 11, is positioned closer to the axis 10G of the beverage can 10 than the inkjet head 19L for large dot images, which forms an image on the large outer diameter portion 11X side of the narrowed diameter portion 11.

[0087] The movement mechanism 556 is realized by a known configuration used to move an object, and is not particularly limited. For example, a linear slider mechanism, a mechanism using an air cylinder, or a mechanism using a motor or solenoid may be used as the movement mechanism 556. The movement mechanism 556 moves the beverage can 10 supported by the movement unit 550 toward below the large dot image inkjet head 19L, as shown by arrow 9A. Additionally, this movement mechanism 556 moves the beverage can 10 supported by the movement unit 550 toward below the small-dot image inkjet head 19S, as shown by arrow 9B.

[0088] In this configuration example, when an image is formed by each of the large dot image inkjet head 19L and the small dot image inkjet head 19S, the moving unit 550 stops at each of the unit stopping positions 97 provided corresponding to each of the large dot image inkjet head 19L and the small dot image inkjet head 19S. Here, for example, when an image is formed by the large dot image inkjet head 19L indicated by reference numeral 9C, the moving unit 550 stops at a unit stopping point 97 indicated by reference numeral 9D.

[0089] Then, the movement mechanism 556 is actuated to move the beverage can 10 along the longitudinal direction of the large dot image inkjet head 19L in a direction approaching the large dot image inkjet head 19L. As a result, the beverage can 10 reaches below the large dot image inkjet head 19L. In this embodiment, when the beverage can 10 moves downwardly from the large dot image inkjet head 19L, the small outer diameter portion 11Y of the beverage can 10 is located downstream in the direction of movement of the beverage can 10, and the large outer diameter portion 11X of the beverage can 10 is located upstream in this direction of movement.

[0090] After the beverage can 10 reaches below the large dot image inkjet head 19L, ink is ejected from the large dot image inkjet head 19L to form an image on the large outer diameter region 11J of the rotating beverage can 10. Thereafter, the beverage can 10 returns to the movement path 300R. In this embodiment, the above operation is repeated at each of the four large-dot-image inkjet heads 19L. At each of the four large dot image inkjet heads 19L, the beverage can 10 is moved to the large dot image inkjet head 19L, an image is formed by the large dot image inkjet head 19L, and the beverage can 10 is moved to the movement path 300R in this order.

[0091] Next, in the configuration example shown in FIG. 9, an image is formed by the inkjet head 19S for small dot images. In forming an image using the inkjet head 19S for small dot images, first, an image is formed using the inkjet head 19S for small dot images designated by reference numeral 9F. When forming an image using the inkjet head 19S for small dot images, indicated by reference numeral 9F, the moving unit 550 stops at a unit stopping position 97, indicated by reference numeral 9G. Next, the beverage can 10 moves along the longitudinal direction of the inkjet head 19S for small dot images and in a direction approaching the inkjet head 19S for small dot images. At this time, similarly to the above, the small outer diameter portion 11Y of the beverage can 10 is located downstream in the movement direction of the beverage can 10, and the large outer diameter portion 11X of the beverage can 10 is located upstream in the movement direction.

[0092] When the beverage can 10 reaches below the inkjet head 19S for small dot images, ink is ejected from the inkjet head 19S for small dot images to form an image in the small outer diameter region 11K. Thereafter, the beverage can 10 returns to the movement path 300R. Here too, the beverage can 10 is moved to the inkjet head 19S for small dot images, an image is formed by the inkjet head 19S for small dot images, and the beverage can 10 is moved to the movement path 300R in that order, corresponding to each of the four inkjet heads 19S for small dot images.

[0093] In this configuration example shown in FIG. 9, when the beverage can 10 is moved below the inkjet head 19L for large dot images and below the inkjet head 19S for small dot images, the beverage can 10 is moved along the longitudinal direction of the inkjet head 19 and along the axial direction of the beverage can 10. In this embodiment, when the beverage can 10 moves in this manner, as described above, the small outer diameter portion 11Y is located downstream in the direction of movement of the beverage can 10, and the large outer diameter portion 11X is located upstream in the direction of movement of the beverage can 10.

[0094] Here, it is assumed that during this movement of beverage can 10, large outer diameter portion 11X is located downstream in the direction of movement of beverage can 10, and small outer diameter portion 11Y is located upstream in the direction of movement of beverage can 10. In this case, the large outer diameter portion 11X of the beverage can 10 and the inkjet head 19 interfere with each other, and it is likely that the beverage can 10 cannot be placed below the inkjet head 19. Alternatively, in this case, the quality of the image formed on the beverage can 10 may be reduced.

[0095] Here, the above-mentioned interference between the large outer diameter portion 11X and the inkjet head 19 can be avoided by increasing the vertical distance between the inkjet head 19 and the movement path 400R when the beverage can 10 moves downward toward the inkjet head 19. In this case, the gap between the inkjet head 19 and the beverage can 10 becomes larger, and the quality of the image 101 formed on the beverage can 10 tends to deteriorate.

[0096] In contrast, in this embodiment, when the beverage can 10 moves, the small outer diameter portion 11Y is located downstream in the direction of movement of the beverage can 10, and this small outer diameter portion 11Y is configured to be at the front, making it less likely that interference will occur between the beverage can 10 and the inkjet head 19. Furthermore, with this configuration, the beverage can 10 can be placed closer to the inkjet head 19. In this case, degradation in the quality of the image 101 formed on the beverage can 10 is less likely to occur.

[0097] In the above description, the small outer diameter portion 11Y is positioned downstream in the direction of movement of the beverage can 10, both when the beverage can 10 is moved below the inkjet head 19L for large dot images and when the beverage can 10 is moved below the inkjet head 19S for small dot images. However, the present invention is not limited to this configuration, and the small outer diameter portion 11Y may be located downstream in the direction of movement of the beverage can 10 only when the beverage can 10 is moved below the inkjet head 19L for large dot images or when the beverage can 10 is moved below the inkjet head 19S for small dot images. In both cases, the above-mentioned interference is less likely to occur and the quality of the image 101 is less likely to deteriorate compared to a configuration in which the large outer diameter portion 11X is located downstream in the direction of movement of the beverage can 10.

[0098] Another method for varying the number of dot images 102 will now be described. Other methods for making the number of large dot images 102 formed in the large outer diameter region 11J and arranged in the circumferential direction of the beverage can 10 greater than the number of small dot images 102 formed in the small outer diameter region 11K and arranged in the circumferential direction of the beverage can 10 will be further described. Another embodiment is one in which the rotation speed of the beverage can 10 is varied. Specifically, one example of this other aspect is one in which the number of rotations of beverage can 10 from the start of formation of large dot image 102 in large outer diameter region 11J until the end of formation of this large dot image 102 is made greater than the number of rotations of beverage can 10 from the start of formation of small dot image 102 in small outer diameter region 11K until the end of formation of this small dot image 102.

[0099] In this embodiment, too, the number of large dot images 102 formed in the large outer diameter region 11J and arranged in the circumferential direction of the beverage can 10 can be made greater than the number of small dot images 102 formed in the small outer diameter region 11K and arranged in the circumferential direction of the beverage can 10. More specifically, in this case, for example, when forming a large dot image 102 in the large outer diameter region 11J, the beverage can 10 is first rotated once, and while the beverage can 10 is rotating once, the large dot image 102 is formed in this large outer diameter region 11J.

[0100] Furthermore, during subsequent rotations of the beverage can 10, new large dot images 102 are formed between the large dot images 102 already formed in the large outer diameter region 11J. Furthermore, when forming the small dot image 102 in the small outer diameter region 11K, for example, the beverage can 10 is rotated once, and while the beverage can 10 is rotating once, the small dot image 102 is formed in this small outer diameter region 11K.

[0101] More specifically, when forming the large dot image 102 in the large outer diameter region 11J, for example, the beverage can 10 is first rotated once at the location where the large dot image inkjet head 19L (see FIG. 4) is installed. Then, while the beverage can 10 is rotating once, the large dot image 102 is formed in the large outer diameter region 11J. Furthermore, rotation continues at the location where large dot image inkjet head 19L is installed. Then, during rotation of beverage can 10 after this one rotation, new large dot images 102 are formed between the large dot images 102 already formed in large outer diameter region 11J.

[0102] Furthermore, when forming the dot image 102 in the small outer diameter region 11K, the beverage can 10 is rotated once at the location where the inkjet head 19S for small dot images (see FIG. 4) is installed. Then, while the beverage can 10 is rotating once, the small dot image 102 is formed in this small outer diameter region 11K. As a result, in this case, the number of large dot images 102 formed in the large outer diameter region 11J and arranged in the circumferential direction of the beverage can 10 is greater than the number of small dot images 102 formed in the small outer diameter region 11K and arranged in the circumferential direction of the beverage can 10.

[0103] When forming a large dot image 102 in the large outer diameter region 11J, if a new large dot image 102 is to be formed between large dot images 102 that have already been formed, as described above, an encoder or the like is used to identify the phase in the rotational direction of the beverage can 10. Specifically, for example, an encoder that identifies the phase of the support member 20 in the rotation direction is provided on the moving unit 550 (see FIG. 2). This encoder is then used to identify the phase of the beverage can 10 when the large dot image 102 is formed during the first rotation of the beverage can 10 supported by the support member 20.

[0104] Then, when a new large dot image 102 is formed during the second rotation of the beverage can 10, the timing of forming the new large dot image 102 during this second rotation is determined based on this identified phase and information about the phase newly acquired during the second rotation of the beverage can 10. Specifically, the timing for forming the large dot image 102 during the second rotation is determined so that the new large dot image 102 is positioned between the large dot images 102 formed by the formation of the large dot images 102 during the first rotation of the beverage can 10.

[0105] Note that, although the above describes processing that assumes that the sizes of the dot images 102 are made different, it is also possible to form the dot images 102 without making the sizes of the dot images 102 different, and instead making all the dot images 102 the same size. In this case, one common type of inkjet head 19 is provided at each of the locations where the large dot image inkjet head 19L and the small dot image inkjet head 19S are provided.

[0106] Furthermore, in the above, a process has been described in which the number of large dot images 102 arranged circumferentially in the large outer diameter region 11J is made greater than the number of small dot images 102 arranged circumferentially in the small outer diameter region 11K, but the dot images 102 may be formed without varying the number of dot images 102, with the number of dot images 102 all being the same. In this case, the number of dot images 102 formed by the large-dot-image inkjet head 19L is the same as the number of dot images 102 formed by the small-dot-image inkjet head 19S.

[0107] Alternatively, the dot images 102 may be formed by keeping the number of dot images 102 the same for all, without varying the number of dot images 102, and keeping the size of the dot images 102 the same for all, without varying the size of the dot images 102. Regardless of the manner in which the dot image 102 is formed, by positioning the inkjet head 19 that forms the image on the small outer diameter portion 11Y of the narrowed diameter section 11 closer to the axial center 10G of the beverage can 10, as in this embodiment, the deterioration in the quality of the formed image can be suppressed. In the above description, two inkjet heads 19, an inkjet head 19S for small dot images and an inkjet head 19L for large dot images, are provided as inkjet heads 19 at different distances from the central axis 10G. However, the inkjet heads 19 at different distances from the central axis 10G are not limited to this, and three or more inkjet heads 19 may be provided.

[0108] FIG. 10 is a diagram showing another example of the configuration of the beverage can 10. In this beverage can 10 shown in FIG. 10, as indicated by the reference numeral 8A, one end 11A of the beverage can 10 is provided with a tapered portion 11 whose outer diameter decreases toward the opening 11E. 10, there is no taper in the can body 31. In this configuration example, the outer diameter of one end 31A of the can body 31 is approximately equal to the outer diameter of the other end 31B.

[0109] The above describes the process of forming the dot image 102 on the reduced diameter portion 11 provided on the can body 31, but the above-described formation process may also be applied to a reduced diameter portion 11 provided other than on the can body 31 of the beverage can 10. Specifically, the above-described forming process may be applied to forming an image 101 on the reduced diameter portion 11 of a beverage can 10 shown in FIG.

[0110] In addition, the beverage can 10 shown in FIG. 10 is also provided at the other end 11B of the beverage can 10 with a tapered diameter portion 81, as indicated by reference numeral 8B, whose outer diameter decreases toward the bottom 11F. The formation process described above may be applied to the formation of the image 101 on the reduced diameter portion 81 located on the bottom portion 11F side. The configuration of moving the inkjet head 19 that forms an image on the small outer diameter portion 11Y side closer to the axis 10G is not limited to forming images on the reduced diameter portion 11 provided on the can body 31, but may also be applied to forming images on the reduced diameter portion 11 provided on the opening 11E side of the beverage can 10 or the reduced diameter portion 81 provided on the bottom 11F side.

[0111] Here, the "large outer diameter portion 11X" is not limited to the large outer diameter portion 11X located at one end 11A of the beverage can 10 shown in FIG. 1(A). The "large outer diameter portion 11X" refers to a portion having a relatively larger outer diameter than the "small outer diameter portion 11Y", and does not refer to a specific portion such as one end 11A of the beverage can 10 in the axial direction. If there are two portions with relatively different outer diameters, then a "large outer diameter portion 11X" and a "small outer diameter portion 11Y" are provided.

[0112] In addition, in the above, an example has been described in which the size of one dot image 102 is changed by changing the amount of ink contained in one drop of ink ejected from the inkjet head 19, but the size of one dot image 102 may also be changed in other ways. For example, the size of one dot image 102 may be changed by changing the number of times ink is ejected when forming one dot image 102.

[0113] For example, when forming one large dot image 102, the number of times ink is ejected from one ink ejection port corresponding to this one large dot image 102 may be increased to form this one large dot image 102. Furthermore, when forming one small dot image 102, the number of times ink is ejected from one ink ejection port corresponding to this one small dot image 102 may be reduced to form this one small dot image 102.

[0114] Furthermore, in the printing device 100 described above, the beverage can 10 is moved using a so-called linear mechanism, but the manner in which the beverage can 10 is moved is not limited to this. For example, a rotating disk-shaped member may be provided, and support member 20 may be attached to the outer periphery of this disk-shaped member, with beverage can 10 being supported by this support member 20. In this case, the beverage can 10 moves as the disk-shaped member rotates, and the beverage can 10 stops as the disk-shaped member stops rotating. An inkjet head 19 is provided at the stop position of the beverage can 10, and a dot image 102 is formed on the beverage can 10 at the stop position of the beverage can 10 in the same manner as described above. [Explanation of symbols]

[0115] 10... beverage can, 10G... shaft center, 11... reduced diameter portion, 11X... large outer diameter portion, 11Y... small outer diameter portion, 19... inkjet head, 19L... inkjet head for large dot images, 19S... inkjet head for small dot images, 91... beverage can stopping point, 100... printing device, 550E... rotation mechanism, 600... conveying mechanism

Claims

1. a rotating means for rotating a cylindrical beverage container in a circumferential direction, the beverage container having a tapered portion whose outer diameter decreases along the axial direction; a first inkjet head disposed at a position facing the outer circumferential surface of the container and configured to eject ink into the reduced diameter portion of the rotating container; a second inkjet head that is disposed at a position facing the outer circumferential surface of the container, that is disposed closer to an axis of the container than the first inkjet head, and that ejects ink into the reduced diameter portion of the rotating container; A printing device is provided.

2. when the first inkjet head ejects ink into the container, the container is disposed in a state where an axial direction of the container is aligned with a longitudinal direction of the first inkjet head; 2. The printing device according to claim 1, wherein when the second inkjet head ejects ink into the container, the container is positioned such that the axial direction of the container is aligned with the longitudinal direction of the second inkjet head.

3. The printing device according to claim 2 , wherein the first inkjet head and the second inkjet head are arranged in a horizontal direction.

4. the reduced diameter portion of the container has a large outer diameter portion that is a portion with a large outer diameter, and a small outer diameter portion that is a portion with a small outer diameter and whose position in the axial direction of the container is different from that of the large outer diameter portion, 2. The printing device according to claim 1, wherein the second inkjet head ejects ink to a location in the reduced diameter portion of the container that is located closer to the smaller outer diameter portion than a location where ink ejected by the first inkjet head adheres.

5. 5. The printing device according to claim 4, wherein the ink ejection frequency of the first inkjet head is greater than the ink ejection frequency of the second inkjet head.

6. 5. The printing device according to claim 4, wherein a size of a dot image formed in the reduced diameter portion by the first inkjet head is larger than a size of a dot image formed in the reduced diameter portion by the second inkjet head.

7. 5. The printing device according to claim 4, wherein a rotation speed of the container when the first inkjet head ejects ink into the narrowed portion of the container is lower than a rotation speed of the container when the second inkjet head ejects ink into the narrowed portion of the container.

8. the reduced diameter portion of the container has a large outer diameter portion that is a portion with a large outer diameter, and a small outer diameter portion that is a portion with a small outer diameter and whose position in the axial direction of the container is different from that of the large outer diameter portion, The printing device according to claim 1 , wherein the second ink-jet head is provided closer to the small outer diameter portion than the first ink-jet head.

9. a container conveying means for conveying the container is further provided, a plurality of container stopping points are provided, the positions of which are different from each other in the direction in which the container is transported by the container transport means; An inkjet head is provided at each of the container stop locations; The printing device according to claim 1 , wherein the container stop position where the first inkjet head is provided is different from the container stop position where the second inkjet head is provided.

10. a length of the first inkjet head in the axial direction is shorter than a length of the reduced diameter portion in the axial direction of the container, and a length of the second inkjet head in the axial direction is shorter than the length of the reduced diameter portion in the axial direction; The printing device of claim 1 .

11. the reduced diameter portion of the container has a large outer diameter portion that is a portion with a large outer diameter, and a small outer diameter portion that is a portion with a small outer diameter and whose position in the axial direction of the container is different from that of the large outer diameter portion, 2. The printing device according to claim 1, wherein when the container moves along a longitudinal direction of at least one of the first inkjet head and the second inkjet head and the container moves toward below the at least one inkjet head, the small outer diameter portion is located downstream in the movement direction of the container and the large outer diameter portion is located upstream in the movement direction.

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