Manufacturing method for beverage cans

Abstract

To form a wider variety of images on the outer peripheral surface of a beverage can. [Solution] As shown in (A), a can body is provided with a reduced diameter section 11 at one end of the can body, the outer diameter of which decreases toward the opening of the can body. Furthermore, a can body section 12 is provided, which is located closer to the bottom of the can body than the reduced diameter section 11. A first base-coated section 500A is provided on the outer peripheral surface 19A of the reduced diameter section 11. Furthermore, a second base-coated section 500B, which is a different color from the first base-coated section 500A, is provided on the outer peripheral surface 19A of the can body section 12.

Description

Technical Field

[0003]

[0001] The present invention relates to a method for manufacturing a beverage can.

Background Art

[0002] Patent Document 1 discloses a method for manufacturing a metal beverage can, which includes a step of applying a thermosetting paint containing thermally expandable microcapsules having a softening temperature lower than the baking temperature to the outer surface of the body of the metal can.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a beverage can, a base layer may be formed on the surface of the can body, and an image may be formed on this base layer. When forming the base layer, it is common to apply a paint over the entire outer peripheral surface of the can body. In this case, the base layer is uniformly formed on the outer peripheral surface of the can body. Also, in a beverage can, a reduced-diameter portion may be formed at the end on the opening side. However, when the reduced-diameter portion is formed after an image is formed on the can body, there is a risk that the image may be damaged during the formation of the reduced-diameter portion. Such damage can be suppressed, for example, by increasing the strength of the image, etc. However, in this case, restrictions are likely to occur on the types of images that can be formed. An object of the present invention is to enable the formation of a wider variety of images on the outer peripheral surface of a beverage can. <{

Means for Solving the Problems

[0005] A method for manufacturing a beverage can to which the present invention applies comprises: a diameter reduction step of reducing the diameter of one end of an empty can body formed in a cylindrical shape, having an opening at one end and a bottom at the other end, so that the empty can body has a diameter reduction portion provided at the one end that decreases in outer diameter towards the opening and a can body portion located closer to the bottom than the diameter reduction portion; a paint application step of applying a colored paint to the outer surface of the portion of the empty can body that will become the diameter reduction portion, and applying a transparent paint to the outer surface of the portion of the empty can body that will become the can body portion, before the diameter reduction step is performed; and an image forming step of forming an image on the outer surface of the empty can body having the diameter reduction portion after the diameter reduction step has been performed. In this case, the image forming step may be performed to form an image on the outer surface of the can body portion of the empty can, but not on the outer surface of the reduced diameter portion of the empty can. Furthermore, in the image forming step, an inkjet head extending along the axial direction of the empty can and positioned facing both the reduced-diameter portion and the can body of the empty can is used to create an image on the outer surface of the empty can. When forming the image on the outer surface, the outer surface of the can body may be formed, but the outer surface of the reduced-diameter portion may not be formed. Furthermore, in the paint application process, white paint may be applied to the outer surface of the portion that becomes the reduced diameter. Furthermore, in the paint application process, a colorless, transparent paint may be applied to the outer surface of the portion that will become the can body. Furthermore, in the paint application process, a colored paint may be applied to the outer surface of the portion that becomes the reduced diameter.

[0006] From another perspective, the method for manufacturing a beverage can to which the present invention applies comprises: a diameter reduction step of reducing the diameter of one end of an empty can body formed in a cylindrical shape, having an opening at one end and a bottom at the other end, so that the empty can body has a diameter reduction portion provided at the one end that decreases in outer diameter towards the opening and a can body portion located closer to the bottom than the diameter reduction portion; a paint application step of applying a colored paint to the outer surface of the portion of the empty can body that will become the diameter reduction portion, and applying a white paint to the outer surface of the portion of the empty can body that will become the can body portion, before the diameter reduction in the diameter reduction step is performed; and an image forming step of forming an image on the outer surface of the empty can body having the diameter reduction portion after the diameter reduction step has been performed.

[0007] From another perspective, the method for manufacturing a beverage can to which the present invention applies comprises: a diameter reduction step of reducing the diameter of one end of an empty can body formed in a cylindrical shape, having an opening at one end and a bottom at the other end, so that the empty can body has a diameter reduction portion provided at the one end that decreases in outer diameter towards the opening and a can body portion located closer to the bottom than the diameter reduction portion; a paint application step of applying a colored paint to the outer surface of the portion of the empty can body that will become the diameter reduction portion, while not applying paint to the outer surface of the portion of the empty can body that will become the can body portion; and an image forming step of forming an image on the outer surface of the empty can body having the diameter reduction portion after the diameter reduction step. [Effects of the Invention]

[0008] According to the present invention, it becomes possible to form a wider variety of images on the outer surface of a beverage can. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram illustrating the manufacturing process for beverage cans. [Figure 2] This shows the can body after neck treatment has been performed. [Figure 3] This is a diagram illustrating the flanging process. [Figure 4] It is a diagram for explaining the processing in a printer. [Figure 5] It is a diagram showing an example of a mandrel whose diameter is expanded. [Figure 6] It is a diagram showing another example of a mandrel whose diameter is expanded. [Figure 7] It is a diagram showing another example of a mandrel whose diameter is expanded. [Figure 8] It is a diagram showing another embodiment of the manufacturing process of a beverage can. [Figure 9] It is a diagram showing the manufacturing process of a conventional can body. [Figure 10] It is a diagram showing another example of supporting a can body by a mandrel. [Figure 11] It is a diagram showing another configuration example of a mechanism for supporting a can body. [Figure 12] It is a diagram showing another configuration example of a mechanism for supporting a can body. [Figure 13] (A) to (G) are diagrams schematically showing specific examples of the base layer. [Figure 14] (A) to (D) are diagrams schematically showing the state of the can body after the processing by the printer.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram showing the manufacturing process of a beverage can according to the present embodiment. The manufacturing process shown in FIG. 1 is a diagram showing the manufacturing process of a so-called two-piece can. In the manufacturing process of the two-piece can (can body) in the present embodiment, after forming aluminum or an aluminum alloy or the like by draw and ironing (DI) molding, the open end is trimmed so that the height of the can body becomes constant. Next, the can body is washed, and then inner surface coating (coating process) and the like are performed.

[0011] Next, a neck portion is formed by necking the opening 13 gradually to reduce its diameter, and a flange is formed on the opening 13 of the neck portion by flanging (diameter reduction process). Then, using a printing device, outer surface printing (image formation) is performed. As a result, a beverage can that is bottomed cylindrical and made of metal with an image formed on its outer peripheral surface is manufactured. In addition, in FIG. 1 and each subsequent figure, the symbols (symbols represented by alphabet letters) represent the names of the respective processes that make up the manufacturing process of the two-piece can. Each process is provided with a device corresponding to that process, and the processing in each process is performed by this device. Also, hereinafter, the "process name" and the "device name (equipment name)" in that process may be called by the same name.

[0012] Here, the beverage filled in the can body (beverage can) is not particularly limited, and the can body is filled with, for example, alcoholic beverages such as beer and chu-hi, or soft drinks (non-alcoholic beverages) (beverage filling process). After filling, a lid member is attached to the can body, and a beverage can filled with beverage is completed. In the following description, the can body before filling with beverage may be referred to as a beverage can, and the can body after filling with beverage may be referred to as a beverage-filled can.

[0013] As shown in FIGS. 1 and 2, in the manufacturing process of this embodiment, an uncoiler (UC), a lubricator (LU), a capping press (CP), a body maker (BM), a trimmer (TR), and a washer (WS) are provided in order from the upstream side in the conveyance direction of the can body. In the uncoiler (UC), the aluminum thin plate wound around the coil is unwound. In the lubricator (LU), lubricating oil is applied to this aluminum thin plate. In the capping press (CP), a circular blank material is punched out, and further drawing is performed to form a cup-shaped material.

[0014] In a body maker (BM) as an example of a molding process, the cup-shaped material is subjected to drawing and ironing processes to create a predetermined thickness for the peripheral wall. Furthermore, the bottom is formed into a dome shape. This results in the formation of a cylindrical can body having an opening 13 on one side and a bottom on the other (DI molding). Next, the trimmer (TR) trims the edges on the upper part of the can's perimeter wall. The washer (WS) cleans the can, removing lubricating oil and other contaminants, and applies a chemical conversion coating as needed.

[0015] Downstream of the washer (WS), an overburnish (OV) step is provided as a paint application process. In the overburnish (OV) step, a colorless, transparent paint is applied to the outer surface 19A of the can body. This forms a base layer on the outer surface 19A of the can body. Here, the base layer refers to the layer formed between the image formed by the printer (PR) later and the can body. Furthermore, a pin oven (PO) is provided downstream of the overburnish (OV). In the pin oven (PO), the can body is heated and the undercoat formed by the overburnish (OV) is baked onto the can body.

[0016] Here, baking in the pin oven (PO) is performed by known methods. Generally, hot air drying is used for curing. Alternatively, curing may be performed by irradiating the can body with infrared radiation. Furthermore, a combination of hot air drying and infrared radiation may be used. For example, the baking conditions could be a heating temperature of 200°C and a heating time of 30 seconds.

[0017] Downstream of the washer (WS), in addition to the overburnish (OV), a base coater (BC) is provided as another example of the paint application process. In the case of a can body in which a colored undercoat is formed, the paint is applied to the can body using this base coater (BC) instead of an overburnish (OV). As a result, in this case as well, an undercoat is formed on the outer surface 19A of the can body. In the base coater (BC), a colored paint is applied to the outer surface 19A of the can body. Specifically, for example, white paint is applied.

[0018] The base coat (BC) is typically white to enhance the vibrancy of the image produced by subsequent printing, but other colors are also acceptable. Furthermore, the base coat (BC) can be applied to the can body and is colorless and transparent; in this case, it will be indistinguishable from the overburn (OV). Downstream of the base coater (BC), a pin oven (PO) is installed, where the can body is heated and the base layer is baked onto the can body.

[0019] In this embodiment, the transport path for the can body branches downstream of the washer (WS), and the can body, after passing through the washer (WS), is transported to either the overburnish (OV) or the base coater (BC). Furthermore, in this embodiment, if a base layer is formed on the can body using a base coater (BC), the formation of the base layer is omitted in the next base coater (BC) (described later), which is located in a later step.

[0020] After passing through the washer (WS), the can body has a high coefficient of friction on its outer surface, which can easily lead to problems during transport. Furthermore, the can body surface is prone to scratches, resulting in a less-than-perfect appearance. By applying an overburnish (OV) or base coater (BC) to form a base layer on the surface of the can, the can is transported more smoothly and is less prone to damage.

[0021] Furthermore, supplying the can body, after passing through the washer (WS), directly to the Necker flanger (SDN) (described later) may cause malfunctions. Specifically, the high frictional force between the can body and the mold used in the Necker flanger could cause the can body to buckle and deform. It could also damage the mold.

[0022] Therefore, in this embodiment, at least the neck portion is coated with either an overburnish (OV) or a base coater (BC) to form a base layer (undercoat). This helps to suppress buckling deformation of the can body and damage to the mold. In addition, the can body can be transported more smoothly compared to when no base layer is formed at all.

[0023] [Painting Process] Downstream of the pin oven (PO), other examples of paint application processes include inside spray (INS) and bake oven (BO). In the inside spray (INS) method, paint is applied (sprayed) onto the inside of the can, resulting in internal coating. In the bake oven (BO) method, the can is heated, and the paint is baked onto it (painting process).

[0024] In this embodiment, we have described a case where the overburnish (OV), base coater (BC), and pin oven (PO) processes are performed first, and the inside spray (INS) and bake oven (BO) processes are performed later. However, this is not the only option; the inside spray (INS) and bake oven (BO) treatments may be performed first, followed by the overburnish (OV), base coater (BC), and pin oven (PO) treatments.

[0025] Furthermore, a more preferable treatment is to perform the overburnish (OV), base coater (BC), and pin oven (PO) treatments first, followed by the inside spray (INS) and bake oven (BO) treatments. Performing the inside spray (INS) and bake oven (BO) treatments later ensures that the inside of the can is covered with paint after the overburn (OV) and base coat (BC) are applied, resulting in a more hygienic interior for the can.

[0026] Specifically, in processes such as overburnishing (OV) and base coater (BC), a mandrel (support member) is inserted inside the can to support the can, and the mandrel comes into contact with the inner circumferential surface of the can. If inside spraying (INS) or baking in a bake oven (BO) is performed afterward, the portion of the inner surface of the can that the mandrel touches will be covered with paint, resulting in a more hygienic interior for the can.

[0027] [Diameter reduction process] Downstream of the bake oven (BO), a Necker flanger (SDN) is provided as an example of a forming process. The Necker flanger (SDN) reduces the diameter of the opening 13 of the can body and forms a flange for attaching the can lid. In the following, necking (a process to reduce the diameter of the opening 13 of the can body) and flanging (a process to form a flange for attaching the can lid) will be collectively referred to as "neck treatment."

[0028] Figure 2 shows the can body after neck treatment has been performed. In this embodiment, a can body 19 is provided. The can body 19 is formed in a cylindrical shape and has an outer circumferential surface 19A. Furthermore, the can body 19 has one end 19C and the other end 19B. Furthermore, the can body 19 has an opening 13 at one end 19C and a bottom 14 at the other end 19B. Furthermore, the can body 19 is provided with a reduced diameter portion (neck portion) 11 and a can body portion 12.

[0029] The reduced diameter section 11 is located on the side of the opening 13 of the can body 19. More specifically, the reduced diameter section 11 is provided at one end 19C of the can body 19. The reduced diameter section 11 is formed such that its outer diameter gradually decreases as it approaches the opening 13. The can body portion 12 is formed in a cylindrical shape and is located closer to the bottom 14 than the reduced diameter portion 11. Here, the can body portion 12 refers to the portion of the can body whose axial length is greater than that of the reduced diameter portion 11, and which is not reduced in diameter or whose reduction ratio is smaller than that of the reduced diameter portion 11. In this embodiment, the can body 12 is connected to the reduced diameter section 11 at a connection point 18. Furthermore, the can body 12 is formed such that the outer diameter at the point where it is connected to the reduced diameter section 11 (the outer diameter at the connection point 18) is approximately equal to the outer diameter at the bottom section 14. That is, in this embodiment, the outer diameter of the can body 12 is approximately constant in the axial direction of the can. Note that this does not eliminate the possibility of reducing the diameter of the can body 12; the can body 12 may be reduced in diameter by a smaller percentage than the reduction ratio of the reduced diameter section 11.

[0030] Necking can be performed using existing methods, and is generally carried out by methods such as the so-called "die-neck" method, which involves pushing the can body into the inside of a mold, or the so-called "spin-flow" method, which involves rotating a rotary mold 90. Furthermore, the flanging process can also be carried out using existing methods, for example, by the technology described in Japanese Patent Publication No. 2016-016419. In this technology described in Japanese Patent Publication No. 2016-016419, as shown in Figure 3 (a diagram illustrating the flanging process), the flanging process is performed using a rotating die 90 called a spinner.

[0031] By the way, with the Necker flanger (SDN), the mold is pressed against the can body, which may cause damage to the can body or the mold. In this embodiment, a base coater (BC) and overburnish (OV) are provided before the necker flanger (SDN), and furthermore, an inside spray (INS) is provided. As a result, in this embodiment, the neck treatment is performed after a base layer that acts as a protective layer is formed on the outer and inner surfaces of the can body (after the base coating is applied). In this case, scratches on the can body and mold are less likely to occur.

[0032] More specifically, in this embodiment, a plain metal can body (can body 19) is coated with, for example, a colorless transparent or colored (for example, white) paint, and then this paint is cured. As a result, a protective layer is formed on the outer surface 19A of the can body. Furthermore, in this embodiment, a protective layer is formed on the inner surface of the can by inside spraying (INS). This makes it less likely for scratches to occur on the inner and outer surfaces of the can. In this case, scratches to the mold are also less likely to occur.

[0033] As shown in Figure 1, a temporary storage process is provided downstream of the Necker flanger (SDN). In the temporary storage process, for example, a palletizer (PT) is used to stack and store the cans. Alternatively, for example, an accumulator (ACC) may be used to store the cans.

[0034] In the temporary storage process, multiple cans having a reduced diameter section 11 (see Figure 2) are stacked vertically in an axially aligned manner. More specifically, in the temporary storage process, after arranging multiple cans horizontally (arranging the cans two-dimensionally horizontally), a sheet or similar material is placed on top of these cans, and then multiple cans are arranged two-dimensionally on top of this sheet. This process is repeated thereafter. As a result, multiple cans are arranged both horizontally and vertically. In this case, if cans without the reduced diameter section 11 (cans that have not undergone diameter reduction treatment) are stacked, the cans will be prone to deformation. However, in this embodiment, the cans have the reduced diameter section 11, making them less susceptible to deformation.

[0035] Subsequently, in this embodiment, when predetermined conditions are met, such as when a shipment order for the cans is issued, the supply of cans from the temporary storage process begins (the discharge of cans from the temporary storage process begins). In other words, the stacks are broken down in a depalletizer (DPL), and the cans are reintroduced into the can manufacturing process. Although not shown in the diagram, other "metal can discharge processes" may be used in addition to the existing depalletizer (DPL).

[0036] Downstream of the depalletizer (DPL), there is a base coater (BC) and a pin oven (PO). In this specification, the base coater (BC) will be referred to as the downstream base coater (BC), and the base coater (BC) located upstream of the Necker flanger (SDN) will be referred to as the upstream base coater (BC).

[0037] If the supplied canisters have only undergone overburnishing (OV), a colored undercoat is formed on the outer surface 19A of the canister by a downstream base coater (BC) as needed. Furthermore, this undercoat is baked in a pin oven (PO).

[0038] Furthermore, when the downstream base coater (BC) forms the base layer on the can body, the can body already has a reduced diameter section 11, and the downstream base coater (BC) forms the base layer on the can body section 12 of the can body. Specifically, in the downstream base coater (BC), a cylindrical or cylindrical roll member aligned with the axial direction of the can body is pressed against the outer surface 19A of the can body, but this roll member does not come into contact with the reduced diameter portion 11. As a result, in the downstream base coater (BC), a base layer is formed on the can body portion 12 of the can body.

[0039] Furthermore, in this embodiment, even if the tank body has been treated with an upstream base coater (BC), a sub-layer is formed by a downstream base coater (BC) as needed. Specifically, for example, if the base layer is formed only on the reduced diameter section 11 by the upstream base coater (BC), the base layer is formed on the can body section 12 by the downstream base coater (BC).

[0040] Furthermore, if the upstream base coater (BC) forms a base layer not only on the reduced diameter section 11 but also on the can body section 12, the downstream base coater (BC) will not perform the treatment. In this case, processing by the downstream base coater (BC) and pin oven (PO) is not performed, and the can body is transported along the path shown in reference numeral 1A. Furthermore, even if only the overburnishing (OV) has been performed on the can body, if processing by the downstream base coater (BC) is not required, the can body is similarly transported along the path shown in reference numeral 1A.

[0041] In this embodiment, the base layer (the base layer formed by the overburnish (OV) and base coater (BC)) was hardened by baking, but this is just one example. If the base layer is made of a paint that hardens when exposed to ultraviolet light or similar radiation, the base layer is hardened by exposure to ultraviolet light or similar radiation.

[0042] [Image forming process] Subsequently, a printer (PR) process is disclosed as an example of the image formation process. Specifically, in this embodiment, as shown in Figure 4 (a diagram illustrating the process in the printer (PR)), the printer (PR) is equipped with an inkjet head 300. Ink is ejected from this inkjet head 300 toward the can located below. This forms an image on the outer surface 19A of the can. In other words, in this embodiment, a non-contact image forming method is used to form an image on the can.

[0043] In this embodiment, the can body is provided with a reduced diameter portion 11, and the portion of the outer peripheral surface 19A of the can body where the reduced diameter portion 11 is provided is separated from the lower surface 301 of the inkjet head 300 (the surface on which the ink ejection port is provided). In this case, the quality of the image formed may be reduced in the area where the reduced diameter portion 11 is provided on the outer surface 19A of the can body.

[0044] Therefore, in the image formation process using the printer (PR), for example, image formation may be performed only on the can body portion 12 without performing image formation on the reduced diameter portion 11. Thus, when image formation is performed only on the can body portion 12, a plain, single-color image or a colorless base layer is formed on the reduced-diameter portion 11, and an image composed of multiple colors is formed on the can body portion 12.

[0045] In addition, the reduced diameter section 11 will have only a colorless base layer formed by overburnishing (OV), or only a single-color base layer formed by base coater (BC), while the can body section 12 will have a multi-colored design. Furthermore, this does not exclude image formation on the reduced diameter portion 11; image formation may be performed on the outer surface of the reduced diameter portion 11 using the inkjet head 300.

[0046] The image formed on the reduced diameter section 11 using the inkjet head 300 is not particularly limited. For example, a color image may be formed using multiple inks, or a single-color image (solid image) may be formed using one ink. Alternatively, for example, a strip-shaped image along the circumferential direction of the can body may be formed. Furthermore, if the outer shape of the reduced diameter portion 11 is stepped, such as a four-stage neck (where the diameter gradually decreases towards the opening 13), the color of the image to be formed may be made different for each stage, for example, forming a strip-shaped image of four colors along the circumferential direction of the can body on the reduced diameter portion 11.

[0047] Furthermore, in the image formation process of the printer (PR), after image formation by the inkjet head 300, paint is applied to the outer surface 19A of the can body to form a protective layer (overcoat layer). In other words, in the printing process using a printer (PR), ink is ejected as droplets from a nozzle, and this ink adheres to the outer surface 19A of the can, forming an image on the outer surface 19A of the can. Next, paint is applied on top of this image to form a protective layer.

[0048] In a printer (PR), for example, four basic inks—cyan (C), magenta (M), yellow (Y), and black (K)—are used, and special colored inks (spot inks) prepared for each brand are also used as needed. In this case, an inkjet head 300 is prepared for each color, and multiple inkjet heads 300 are used to form an image on the can body. Furthermore, it is preferable to use an active radiation-curable ink. Here, active radiation-curable inks include, for example, ultraviolet (UV) curable inks.

[0049] Furthermore, in the printer (PR), a cylindrical mandrel (not shown in Figure 4), which is an example of a support member, is inserted into the inside of the ink can, and the mandrel supports the ink can from the inside. Furthermore, the ink can is positioned opposite the inkjet head 300. Furthermore, the ink can is positioned so that its axial direction is aligned with the longitudinal direction of the inkjet head 300. Then, ink is ejected and printing is performed while the ink can is rotated in the circumferential direction. Here, the printer (PR) performs what is known as digital printing, which is printing based on image data.

[0050] While a higher print resolution is preferable for a printer (PR), considering factors such as cost and productivity, a print resolution of around 600 dpi is preferable. Furthermore, from the viewpoint of improving the quality of the formed image, it is preferable to reduce the distance between the inkjet tank and the inkjet head 300, but if it is too small, there is a risk of interference between the inkjet tank and the inkjet head 300. The distance between the inkjet tank and the inkjet head 300 can be, for example, about 1 mm.

[0051] Furthermore, while a higher rotation speed of the ink can contributes to productivity, if it is too high, the ink may spread circumferentially around the can when it lands, potentially reducing resolution. Therefore, it is desirable to rotate the ink can at a speed that allows for high rotation while suppressing the circumferential spread of the ink. Furthermore, when using UV-curing ink, the ink may be cured by irradiating it with UV light each time a single color of ink is dispensed into the can, or multiple colors of ink may be dispensed and then irradiated with UV light to cure them all at once.

[0052] Furthermore, for printers (PRs), it is preferable to use a mandrel that expands in diameter in part when inserted into the can. In other words, it is preferable to use a mandrel that expands in part after insertion into the can, and this part comes into contact with the inner circumferential surface of the can. Furthermore, it is preferable to use a mandrel that has a portion that approaches and contacts the inner circumferential surface of the can body, starting from a portion spaced away from the inner circumferential surface.

[0053] In this embodiment, the opening 13 of the can body (see Figure 2) is reduced in diameter due to neck processing, and during image formation, the diameter of the opening 13 is smaller than the diameter of the can body portion 12 of the can body. Therefore, simply inserting a cylindrical mandrel into the can body results in a gap between the can body and the mandrel, making the support of the can body unstable. By using an expanding mandrel and ensuring that a portion of the mandrel contacts the inner surface of the can body, the can body can be supported more stably.

[0054] Figure 5 shows an example of an expanding mandrel. In this mandrel, when the mandrel is inserted into the can body (not shown in Figure 5), the disc-shaped contact member 40 comes into contact with the opening edge 13A of the can body (see Figure 2). Subsequently, the mandrel (shaft 41) is moved further toward the bottom 14 of the can body (see Figure 2). As a result, the tapered surface 42A of the mounting member 42 attached to the shaft 41 presses the movable member 43 toward the inner circumferential surface of the can body, causing the movable member 43 to be pressed against the inner circumferential surface of the can body.

[0055] Here, the mandrel is reversible, and when the mandrel is moved in the direction of being removed from the can body, the mounting member 42 moves towards the contact member 40 due to the spring member 44. As a result, the pressure on the moving member 43 by the mounting member 42 is released, and the moving member 43 can move in the direction away from the inner circumferential surface of the can body.

[0056] Figure 6 shows another example of an expanding mandrel, in which compressed air is used to move a movable body 51 in the axial direction of the mandrel body 52, and this movable body 51 compresses an annular elastic member 53 attached to the outer circumference of the mandrel body 52. ​​As a result, the elastic member 53 protrudes outward in the radial direction of the mandrel, and this elastic member 53 is pressed against the inner circumferential surface of the can body. When removing the mandrel, for example, the air inside the mandrel body 52 is sucked out. This causes the movable body 51 to move in the opposite direction, and the elastic member 53 returns to its original position. When the elastic member 53 returns to its original position, it separates from the inner circumferential surface of the can body.

[0057] Figure 7 shows another example of a mandrel with an expanding diameter. This mandrel is provided with a reciprocating member 81 that moves back and forth relative to the inner circumferential surface of the can body. Compressed air is supplied to this mandrel, and this compressed air presses against the reciprocating member 81, causing it to contact the inner circumferential surface of the can body. This mandrel is also reversible; when the supply of compressed air is stopped, the reciprocating member 81 moves away from the inner circumferential surface of the can body by a coil spring 82.

[0058] The manufacturing process will be further explained with reference to Figure 1. Downstream from the printer (PR), there are a bottom coater (BTC), pin oven (PO), defective can tester (DCT), light tester (LT), and palletizer (PT).

[0059] In the bottom coater (BTC), paint is applied to the contact area of ​​the bottom 14 of the can body. In the pin oven (PO), the can body is heated and the image on the outer surface of the can body and the paint on the bottom 14 are baked on. In this embodiment, two sets of bottom coaters (BTC) and pin ovens (PO) are provided, corresponding to each of the two types of printers (PR) (indicated by reference numerals 1B and 1C). However, the invention is not limited to this configuration; one set of bottom coaters (BTC) and pin ovens (PO) may be provided to facilitate equipment sharing.

[0060] A defective can tester (DCT) inspects the external appearance and printing quality of the cans, removing any defective products. The Light Tester (LT) inspects the can for holes and removes any defective products. In a palletizer (PT), cans that have passed inspection are stacked onto pallets. The cans are then shipped to, for example, a beverage can manufacturing plant (where the beverage is filled), where the beverage is filled into the cans and the lids are attached. This completes the beverage can.

[0061] The manufacturing process shown in Figure 1 is just one example, and each step may be rearranged without departing from the spirit of the present invention. Furthermore, while conveyors are primarily used for transporting the can bodies during the manufacturing process, other transport mechanisms besides conveyors may also be used to transport the can bodies. Furthermore, when conveyors are used to transport the cans, for example, mass conveyors or single conveyors are used. In Figure 1, the transport path shown by one line represents the transport path where the cans are transported by a single conveyor, and the transport path shown by two lines represents the transport path where the cans are transported by a mass conveyor.

[0062] Furthermore, each process may have one piece of equipment or multiple pieces of equipment. When multiple facilities are installed, the transport route for the cans is branched so that cans are supplied to each of these facilities. In this case, the transport routes are merged downstream of each facility.

[0063] [Second Embodiment] Figure 8 shows another embodiment of the beverage can manufacturing process. Steps having the same function as those shown in Figure 1 are denoted by the same reference numerals, and their explanation is omitted. The embodiment shown in Figure 1 illustrates the manufacturing process for beverage cans (manufacturing process at a can manufacturing plant). Figure 8 illustrates not only the manufacturing process for beverage cans (manufacturing process at a can manufacturing plant), but also the content filling process (manufacturing process at a beverage can manufacturing plant) in which beverages or other contents are filled into the inside of the beverage cans.

[0064] Figure 8 shows the manufacturing process in a can manufacturing plant in the upper section. In the manufacturing process at the can-making plant, the process up to the Necker flanger (SDN) is the same as the embodiment shown in Figure 1. Specifically, each step from the uncoiler (UC) to the Necker flanger (SDN) is included. On the other hand, in the manufacturing process in this embodiment (the manufacturing process in the can-making factory), a printer (PR) is not provided, and this manufacturing process is equipped with a defective can tester (DCT), a light tester (LT), and a palletizer (PT).

[0065] In the manufacturing process of this embodiment (manufacturing process at the can manufacturing plant), after neck processing is performed, the can body is inspected without image formation processing. Specifically, the appearance and printing condition of the can body are inspected, and the presence or absence of holes in the can body is also inspected. Next, the cans are stacked in a palletizer (PT), creating pallets containing multiple cans. These pallets are then shipped to beverage can manufacturing plants.

[0066] In this embodiment, the can manufacturing plant produces can bodies in which a base layer (base coating) is formed on at least the reduced diameter portion 11, as described above. In addition, the can manufacturing plant produces can bodies without image formation. Specifically, can bodies are produced in which internal coating, external coating (base layer formation), and neck treatment are performed, but image formation is not performed. These can bodies without image formation are then shipped to a beverage can manufacturing plant.

[0067] In this embodiment, we have shown an example where the goods are stacked using a palletizer (PT) before shipment, but the shipping method can be anything. Additionally, the Defective Can Tester (DCT) and Light Tester (LT) may be omitted if they are not necessary.

[0068] In beverage can manufacturing plants, the first step is depalletization (DPL), after which the cans are dispensed. Downstream of the depalletizer (DPL), a downstream base coater (BC) and a pin oven (PO) are provided. As described above, the base layer is formed and baked on cans that have only undergone overburnishing (OV) or on cans in which the base layer has been formed only on the reduced diameter section 11 by the upstream base coater (BC).

[0069] Furthermore, even for cans where the undercoat has been formed over the entire outer surface in the upstream base coater (BC), or for cans where only overburnishing (OV) has been performed, if undercoat formation is not required, the downstream base coater (BC) and pin oven (PO) are unnecessary, and the undercoat formation and baking in the downstream base coater (BC) are omitted. In this case, the can is transported along the transport path indicated by reference numeral 8A.

[0070] Subsequently, image formation is performed by the printer (PR) in the same manner as described above. Specifically, as described above, ink is ejected from the inkjet head 300 provided in the printer (PR) toward the can, and an image is formed on the outer surface of the can. Downstream of the printer (PR), a bottom coater (BTC) and a pin oven (PO) are provided. Paint is applied to the contact area of ​​the bottom 14 of the can body, and the can body is then heated. This process bakes the image on the outer surface of the can body and the paint on the bottom 14 of the can body onto the can body. Afterward, the can body is rinsed with water using a rinser (RN). The printer (PR) may be installed after the rinser (RN).

[0071] [Beverage filling process] Next, as an example of the beverage filling process, the cans are filled with beverage using a filler (FL), and then the can lids are attached to the cans using a seamer (SM). The can lids are attached to the cans using a method known as double seaming. Can lids are generally formed in a panel shape, with a score (drinking spout) in the center. Furthermore, an opening tab is fixed to the lid, and the lid has a countersink section, a chuck wall section, and a curled section. Can lids are typically made of aluminum or an aluminum alloy. Furthermore, the filler (FL) treatment can be carried out using existing techniques, for example, by the treatment described in Japanese Patent Publication No. 2009-026009.

[0072] Subsequently, various inspection machines (DT) are used to check the filling amount and for foreign objects. This inspection only needs to be performed before the boxes are packed using the case packer (CS), which will be described later. Furthermore, this inspection may be performed multiple times to improve quality. Afterward, the contents are returned to room temperature using a warmer (WM). However, for high-temperature filling methods such as hot packing, which are used for filling tea and coffee beverages, a warmer (WM) is not necessary. Furthermore, contents requiring sterilization are sterilized before being packed into boxes using the case packer (CS), as described later. Sterilization methods include low-temperature pasteurization (pasteurization) and high-temperature, high-pressure steam sterilization (retort).

[0073] Subsequently, a bottom printing machine (BIP) uses an inkjet head to print necessary information such as the manufacturing date, lot number, and expiration date onto the bottom 14 of the can (beverage can). The printed content is then inspected using an inspection machine (not shown). In this case, when printing with a bottom printing machine (BIP), it is preferable to blow away any water droplets from the bottom 14 of the can with high-pressure air before printing. After leaving the warmer (WM), water droplets adhere to the bottom 14 of the can, and blowing away these water droplets with high-pressure air before printing improves the print quality.

[0074] Furthermore, the bottom printing press (BIP) may be installed not only downstream of the warmer (WM), but also between the filler (FL) and the warmer (WM). However, in this case, the can body is at a low temperature, and condensation will quickly occur even if water droplets are blown away with high-pressure air. For this reason, it is more preferable to install the bottom printing press (BIP) downstream of the warmer (WM). Furthermore, printing using a bottom-of-can printing machine (BIP) can be done at any point before the cans are packed into boxes in the case packer (CS), for example, immediately after the depalletizer (DPL).

[0075] Afterward, the cans (beverage cans) are packed into boxes at the case packer (CS). Typically, 24 cans are packed into each box. However, if the cans are packed in 6-packs, then 4 packs' worth of cans will be packed into one box. Afterward, a palletizer (PT) loads the boxes containing the cans onto pallets.

[0076] In this embodiment, since the image is formed on the can body at the beverage can manufacturing plant, it becomes possible to prepare printed can bodies according to the amount (total amount) of contents prepared. In this case, the contents and container can be used without excess or deficiency (consumed), thus reducing the generation of wasted contents and containers.

[0077] Figure 9 shows a diagram illustrating a conventional can manufacturing process. Steps having the same function as those described in the embodiments above are denoted by the same reference numerals, and their explanations are omitted. In this conventional manufacturing process, the printing method used in the printer (PR) is plate printing. Furthermore, in this conventional manufacturing process, the printer (PR) is located upstream of the Necker flanger (SDN) in the direction of can transport.

[0078] Furthermore, in this conventional manufacturing process, a palletizer (PT) (temporary storage process) is provided downstream of the printer (PR) and necker flanger (SDN). Therefore, when the cans are in storage, the images are already formed on the cans and the neck treatment has been applied. Therefore, in this conventional manufacturing process, when the cans are shipped, they are shipped with the image already formed and the neck processed.

[0079] In this conventional manufacturing process, the printing method is plate printing. This plate printing method requires more time for preparation before printing, making it difficult to respond to urgent orders. Specifically, with plate printing, it takes a considerable amount of time before printing can begin, as it requires obtaining the design drawing, creating the printing plate, placing the plate on the printing press, and then performing further preparations such as color matching.

[0080] To reduce processing time, it is preferable to manufacture the cans in advance before receiving an order and to store the printed cans as inventory beforehand. By the way, in this case, there are problems such as the need to secure storage space for inventory, which incurs warehouse costs. Also, recently, the time until a design is changed or a brand is discontinued has become shorter, so if cans are manufactured in advance and kept in stock, it is likely that unnecessary cans will be generated. Furthermore, sometimes only a part of the design is changed, in which case unnecessary cans that will be discarded will also be generated. Thus, conventional manufacturing processes required the maintenance of inventory, and furthermore, this inventory was prone to being discarded.

[0081] In contrast, in this embodiment, the cans are not printed on and are kept as inventory. In this case, even if the design changes, printing can be done with the revised design, thus reducing the amount of wasted cans. Furthermore, in this embodiment, since digital printing is performed using the inkjet head 300, there is no need to prepare printing plates, and printing can be started in a shorter time. Furthermore, using an inkjet method allows for high-resolution printing and also enables contactless printing.

[0082] Even when using printing plates, printing can be done on pre-necked cans only after receiving an order, thereby reducing the waste of inventory described above. However, in plate printing, ink must be transferred onto the can, so a large amount of pressure is applied between the can and the printing press blanket (the contact element that contacts the can and transfers the ink to it) during printing.

[0083] In this case, the can deforms, becoming concave inward, making printing practically impossible. More specifically, as described above, in a can body that has undergone neck treatment, the diameter of the can body 12 is larger than the diameter of the opening 13 (see Figure 2), and if a typical mandrel is simply inserted into the can body, a gap will be created between the can body and the mandrel. In this state, if the printing press blanket is pressed against the can body, the can body will be indented inward.

[0084] In contrast, in the inkjet method employed in this embodiment, the inkjet head 300 and the can body are not in contact, and no pressure is applied to the can body during printing. In this case, printing can be performed on the can body even if there is a gap between the mandrel and the can body. Furthermore, more preferably, as shown in Figures 5-7, it is desirable to use a mandrel with an expanding diameter and to bring the mandrel into contact with the inner circumferential surface of the can body 12 of the can. This allows the can to be supported more stably.

[0085] In this case, expanding the diameter of the mandrel is not essential. For example, if the bottom 14 of the can (see Figure 2) is held in place by suction from the tip of the mandrel, the vibration of the can can be suppressed, and in this case, expanding the diameter of the mandrel becomes unnecessary. Figure 10 (a diagram showing another example of supporting a can body with a mandrel) illustrates a case where the bottom 14 of the can body is supported by suction using a mandrel. The mandrel is formed in a cylindrical shape and has an opening 71 at its tip in the direction of insertion when inserted into the can body. Furthermore, in this example configuration, air inside the mandrel is sucked out from the base 72 side of the mandrel by a suction mechanism (not shown).

[0086] In this configuration example, a mandrel is inserted through the opening 13 of the can body, and the bottom 14 located on the opposite side of the opening 13 is drawn in by the mandrel, so that the bottom 14 is supported by the mandrel. Furthermore, in this example, the opening 13 of the can body is also supported by the mandrel. This ensures that the can body is stably supported by the mandrel.

[0087] Furthermore, in this configuration example, the bottom portion 14 is convex toward the inside of the can body (it protrudes in a dome shape toward the inside of the can body), and this convex portion is embedded inside the mandrel. As a result, the axis of the mandrel and the center position of the bottom portion 14 of the can body (the center position in the radial direction) coincide.

[0088] Furthermore, the can body may be supported using other mechanisms. Specifically, as shown in Figure 11 (a diagram showing another example of the mechanism for supporting the can body), the can body may be supported by sandwiching the reduced diameter portion 11 of the can body from both the inside and outside of the can body. More specifically, in this example configuration, the can body is held in place by sandwiching the reduced diameter portion 11 of the can body between an inner member 95 positioned inside the can body and moving back and forth relative to the inner circumferential surface of the can body, and an outer member 96 positioned outside the can body.

[0089] Alternatively, the can body may be supported by suction from the outside of the can body using a pad member 400, as shown in Figure 12 (a diagram showing another example of the mechanism for supporting the can body). The pad member 400 has a protrusion 401 that fits into a recess 98 (a recess 98 that is recessed on the inside side of the can) provided in the bottom 14 of the can body. Furthermore, the pad member 400 holds the can body by suction through a hole 402 located in the center in the radial direction. In addition, the pad member 400 has a flat plate portion 403 that serves as a base for the protrusion 401. Furthermore, if an annular groove matching the shape of the contact portion of the can is provided on the surface of the flat plate portion 403 that is positioned on the can body side and located around the convex portion 401, the can body holding performance will be improved.

[0090] Next, we will explain in detail the underlying layers that are formed before the Necker flanger (SDN) (as shown in Figures 1 and 8). In this embodiment, as described above, before processing in the Necker flanger (SDN), either overburnish (OV)-pin oven (PO) or upstream base coater (BC)-pin oven (PO) processing is performed. As a result, a base layer is formed on the outer surface 19A of the can body (a base coat is provided). Specifically, the base layer is formed on at least the reduced diameter portion 11 of the outer surface 19A of the can body.

[0091] Here, various formation patterns are possible for the underlying layers. Specifically, one possible configuration is to form the base layer only in the reduced-diameter section (neck section) 11. Alternatively, one possible configuration is to form the base layer in both the reduced-diameter section 11 and the can body section 12. Furthermore, when the underlayer is formed on both the reduced-diameter section 11 and the can body section 12, it is conceivable that the color of the underlayer formed on the reduced-diameter section 11 and the color of the underlayer formed on the can body section 12 be the same. Alternatively, when the underlayer is formed on both the reduced-diameter section 11 and the can body section 12, it is conceivable that the color of the underlayer formed on the reduced-diameter section 11 and the color of the underlayer formed on the can body section 12 be different.

[0092] In this case, if the base layer formed on the can body 12 is colored, this base layer can be, for example, white. In this case, the color reproduction (saturation) of the image formed on this base layer (the image formed by the printer (PR)) will be improved. Furthermore, the base layer formed in the reduced diameter section 11 may be a chromatic color, such as a blue color. Using a blue color for the base layer can give the user a feeling of coolness. The base layer formed in the can body section 12 may also be a chromatic color.

[0093] Furthermore, if it is desired to retain a metallic luster (to impart gloss) to the reduced-diameter section 11 or the can body section 12, it is possible to make the base layer formed on the reduced-diameter section 11 or the base layer formed on the can body section 12 transparent. Specifically, in this case, for example, a transparent paint is applied to the reduced-diameter section 11 or to the entire outer surface 19A of the can body using an overburnish (OV) process. As a result, the base layer formed on the reduced diameter section 11 and the can body section 12 becomes transparent, and the image formed on top of the base layer can be given a gloss due to metallic luster.

[0094] Furthermore, the color of the base layer of the reduced diameter section 11 and the color of the base layer of the can body section 12 may be, for example, colored and the same color. In this case, the base layer is formed, for example, by applying colored paint over the entire outer surface 19A of the can body using an upstream base coater (BC). In this case, there is no need to apply different paints to the reduced diameter section 11 and the can body section 12, and the base layer can be formed more easily.

[0095] Figures 13(A) to (G) are schematic diagrams illustrating specific examples of underlying layers. Figures 13(A) to (G) show the state of the can body on the side with the opening 13 (see Figure 2). Also, Figures 13(A) to (G) show only one side of the parts located on both sides of the can body, straddling the axis of the can body. Furthermore, Figures 13(A) to (G) show the state before neck treatment. Additionally, Figures 13(A) to (G) depict the substrate layer as being thicker than it actually is.

[0096] As shown in Figures 13(A) to (G), there are seven possible formation modes for the underlying layer, such as the first to seventh formation modes. In the first to third formation modes, the underlying layer of the reduced diameter portion 11 is colored. Specifically, as shown in Figure 13(A), in the first forming configuration, a colored undercoat portion 500 is provided on the outer circumferential surface 19A of the reduced diameter portion 11. In the forming configuration shown in Figure 13(A), no undercoat portion is provided on the can body portion 12. Thus, by making the base coat portion 500 of the reduced diameter portion 11 colored, it is possible to provide a can body that is more appealing to users compared to when the base coat portion 500 of the reduced diameter portion 11 is colorless.

[0097] The color of the base coat portion 500 of the reduced diameter portion 11 is not particularly limited and can be, for example, white. In this case, an image may also be formed on the reduced diameter portion 11, and if the base coat portion 500 of the reduced diameter portion 11 is white, the color development of the image formed on the reduced diameter portion 11 will be improved. Furthermore, in this first forming embodiment, as described above, the can body 12 is not provided with a base coat 500. In this case, the can body 12 retains its metallic luster, which can give a glossy appearance to the image later formed by the printer (PR).

[0098] Next, with reference to Figure 13(B), the second formation method will be described. In the second forming embodiment, a colored undercoat portion 500 is provided on both the reduced diameter portion 11 and the can body portion 12. This undercoat portion 500 is formed, for example, by applying colored paint over the entire outer surface 19A of the can body using an upstream base coater (BC). Here, the color of this base coat 500 is not particularly limited, but for example, it may be white. In this case, the color development of the image formed on this base coat 500 (the image later formed by a printer (PR)) is improved.

[0099] In Figure 13(B), the thickness of the undercoat 500 provided on the outer surface 19A of the reduced diameter portion 11 is equal to the thickness of the undercoat 500 provided on the outer surface 19A of the can body portion 12. However, the thickness of the undercoat 500 of the reduced diameter portion 11 and the thickness of the undercoat 500 of the can body portion 12 may be different. More specifically, the thickness of the undercoat portion 500 of the can body portion 12 may be greater than the thickness of the undercoat portion 500 of the reduced diameter portion 11.

[0100] In this case, the metal portion of the can body 12 is more reliably shielded, and the color reproduction of the image subsequently formed by the printer (PR) is further improved. Furthermore, if the thickness of the undercoat 500 of the reduced diameter portion 11 and the thickness of the undercoat 500 of the can body portion 12 are made different, it becomes possible to make the color development of the image formed on the reduced diameter portion 11 and the color development of the image formed on the can body portion 12 different, thereby enabling the formation of a wider variety of images on the outer surface 19A of the can body.

[0101] Furthermore, in order to increase the thickness of the base coat portion 500 of the can body 12, for example, two roll members for paint application can be provided on the upstream base coater (BC). For example, first, the first roll member is used to apply paint to the entire outer surface 19A of the can body. Then, the second roll member is pressed only against the can body 12. As a result, the thickness of the undercoat 500 of the can body 12 becomes greater than the thickness of the undercoat 500 of the reduced diameter section 11.

[0102] Figure 13(C) shows a third configuration. In this third configuration, a colored first undercoat portion 500A is provided on the reduced diameter portion 11, and a transparent second undercoat portion 500B is provided on the can body portion 12. In this third forming embodiment, the color of the first undercoat section 500A and the color of the second undercoat section 500B are different.

[0103] Furthermore, in this third forming configuration, the thickness of the second undercoat portion 500B formed on the can body portion 12 is greater than the thickness of the first undercoat portion 500A formed on the reduced diameter portion 11. In this configuration, the colored first undercoat 500A formed on the reduced-diameter portion 11 can create an appealing effect. More specifically, compared to the case where the first undercoat 500A formed on the reduced-diameter portion 11 is colorless and transparent, users will pay more attention to the can. Furthermore, in this third forming method, a metallic luster remains on the can body 12, which can give a glossy appearance to the image later formed by the printer (PR).

[0104] Furthermore, the colors of the first undercoat section 500A and the second undercoat section 500B are not particularly limited and may be in various combinations. For example, one of the colors of the first undercoat section 500A and the second undercoat section 500B can be white, and the other can be a color other than white. Here, this other color includes colorless transparent and colored transparent.

[0105] Furthermore, one of the colors of the first undercoat section 500A and the second undercoat section 500B may be transparent, such as a colored transparent or colorless transparent, while the other color may be a color other than transparent. Furthermore, at least one of the colors of the first undercoat section 500A and the second undercoat section 500B may be a chromatic color, and the other color may be a different color from the other color. This other color may include other chromatic colors, achromatic colors, and transparent colors such as colored transparent and colorless transparent.

[0106] Next, we will explain the fourth to sixth forms of formation. In all of the fourth to sixth forming embodiments, the base coat portion 500 provided on the reduced diameter portion 11 is colorless and transparent. In the fourth forming configuration shown in Figure 13(D), a transparent first undercoat portion 500A is provided on the reduced diameter portion 11, while the undercoat portion 500 is not provided on the can body portion 12. In the fourth forming embodiment, the first undercoat portion 500A is transparent, and a metallic luster can be imparted to the reduced diameter portion 11. In addition, there are portions of the can body portion 12 that do not have an undercoat portion, and a metallic luster can also be imparted to the can body portion 12.

[0107] In the fifth forming configuration shown in Figure 13(E), a transparent first undercoat 500A is provided on the reduced diameter portion 11, and a colored second undercoat 500B is provided on the can body portion 12. In other words, in this forming configuration, the color of the first undercoat 500A and the color of the second undercoat 500B are different. In this configuration as well, the first undercoat portion 500A is transparent, and a metallic luster can be imparted to the reduced diameter portion 11. Furthermore, the second undercoat portion 500B provided on the can body 12 is colored, which can enhance the color development of the image formed later or give the can a design that attracts the user's attention. In other words, this configuration also provides a can that is appealing to the user.

[0108] Furthermore, the first undercoat section 500A and the second undercoat section 500B shown in Figure 13(E) are formed, for example, by an upstream base coater (BC), as described above. Specifically, for example, the upstream base coater (BC) is equipped with two roll members for paint application. Then, for example, the first roll member is used to form a first base coat section 500A on the reduced diameter section 11. The second roll member is then used to form a second base coat section 500B on the can body section 12.

[0109] In the sixth forming embodiment shown in Figure 13(F), a transparent undercoat 500 is provided on both the reduced-diameter portion 11 and the can body portion 12. In other words, in this sixth forming embodiment, the color of the first undercoat portion 500A and the color of the second undercoat portion 500B are the same. In this sixth forming embodiment, a metallic luster can be given to both the reduced-diameter portion 11 and the can body portion 12. Here, the undercoat 500 (first undercoat portion 500A, second undercoat portion 500B) shown in this sixth forming embodiment is formed, for example, by overburning (OV). More specifically, for example, by applying a transparent paint over the entire outer surface 19A of the can body using overburning (OV), a transparent undercoat portion 500 is formed on both the reduced diameter portion 11 and the can body portion 12.

[0110] Furthermore, in the seventh forming configuration shown in Figure 13(G), the color of the first undercoat 500A and the color of the second undercoat 500B are different, and both the first undercoat 500A and the second undercoat 500B are colored. In the seventh forming embodiment, the first undercoat section 500A and the second undercoat section 500B are formed, for example, by an upstream base coater (BC). Specifically, for example, the upstream base coater (BC) is equipped with two roll members for paint application. Then, for example, the first roll member is used to form the first base coat section 500A of the first color on the reduced diameter section 11. The second roll member is then used to form the second base coat section 500B of the second color on the can body section 12.

[0111] Here, the paint used to form the colored undercoat portion 500 described in each of the above formation embodiments is not particularly limited, and existing paints can be used. Colored paints contain colored pigments, and existing pigments can also be used. More specifically, for example, when forming a white base coat 500, titanium dioxide can be used.

[0112] Furthermore, there are no particular restrictions on the paint used to form the transparent undercoat portion 500; existing paints can be used. Specifically, for example, the same transparent paint used to form the overcoat (protective layer) described above can be used. More specifically, epoxy / acrylic, epoxy / phenol, and epoxy / urea-based paints can be used. Epoxy / acrylic paints are water-based, thus reducing environmental impact.

[0113] Furthermore, the transparent undercoat portion 500 may be formed using a different paint than the paint used for the overcoat. In this case, a paint specifically designed for the undercoat portion 500 can be used. Specifically, for example, it will become possible to use paints that are more suitable for treatment in Necker flangers (SDN). More specifically, for example, it will become possible to use paints with improved lubricity by increasing the amount of wax added to existing paints.

[0114] Furthermore, if the color of the undercoat portion 500 (first undercoat portion 500A) of the reduced diameter portion 11 and the color of the undercoat portion 500 (second undercoat portion 500B) of the can body portion 12 are to be the same, the undercoat portion 500 of the reduced diameter portion 11 and the undercoat portion 500 of the can body portion 12 may be formed at the same time. Specifically, for example, an upstream base coater (BC) may press a paint application roll member against the outer circumferential surface 19A of the can body over the entire area in the axial direction of the can body to form a common base coat portion 500 on both the reduced diameter portion 11 and the can body portion 12. Furthermore, the base coat portion 500 may be formed not only by a method using a roll member, but also by other methods such as an inkjet printing method.

[0115] Furthermore, if the color of the base coat portion 500 of the reduced diameter portion 11 and the color of the base coat portion 500 of the can body portion 12 are to be different, it is preferable to form the lighter-colored base coat portion 500 before the darker-colored base coat portion 500 so that the effect of color mixing is minimized. Specifically, for example, when forming a white base coat portion 500 and a transparent base coat portion 500, it is preferable to form the transparent base coat portion 500 first, and then form the white base coat portion 500.

[0116] To explain in more detail, when forming a colored undercoat portion 500 and a transparent undercoat portion 500, as shown in the formation configurations in Figures 13(C) and (E), it is preferable to form the transparent undercoat portion 500 first, and then form the colored undercoat portion 500. Furthermore, as shown in the formation configuration in Figure 13(G), when forming undercoat sections 500 of different colors, it is preferable to form the lighter-colored undercoat section 500 first and then the darker-colored undercoat section 500.

[0117] Furthermore, when forming the base coat portion 500 separately on the reduced diameter portion 11 and the can body portion 12, it is preferable to form the base coat portion 500 formed on the reduced diameter portion 11 and the base coat portion 500 formed on the can body portion 12 in a butt joint state (a state in which there is no overlap and no gaps). Furthermore, due to errors and other factors, it is often difficult to form the base coat portion 500 formed on the reduced diameter portion 11 and the base coat portion 500 formed on the can body portion 12 in a butt-joint state. For this reason, for example, the two base coat portions 500 may be formed such that they overlap.

[0118] Alternatively, the undercoat portion 500 of the reduced diameter portion 11 and the undercoat portion 500 of the can body portion 12 may be formed such that a gap is formed between them. In other words, the first undercoat portion 500A and the second undercoat portion 500B may be provided at a distance from each other, and the first undercoat portion 500A and the second undercoat portion 500B may not overlap. In this case, the protective layer (the overcoat layer formed on top of the image to protect the image) is placed in the gap between the first undercoat section 500A and the second undercoat section 500B. This suppresses corrosion of the can body caused by the exposure of the base material of the can body.

[0119] Furthermore, when the first undercoat section 500A and the second undercoat section 500B are overlapped, an overlapping section will be provided where the first undercoat section 500A and the second undercoat section 500B overlap. It is preferable that this overlapping portion be located closer to the bottom 14 than the connection point 18 (see Figure 2) between the reduced diameter portion 11 and the can body portion 12. In this case, the possibility of this overlapping portion entering the mold for neck processing (the mold used to form the reduced diameter portion 11 with a necker flanger (SDN)) is reduced, and the reduced diameter portion 11 can be formed more reliably.

[0120] If the overlapping portion is located at the planned location for forming the reduced-diameter portion 11, this overlapping portion may prevent the opening 13 side of the can body 19 (see Figure 2) from entering the mold (the mold used to form the reduced-diameter portion 11). In this case, forming the reduced-diameter portion 11 becomes difficult. When the overlapping portion is located closer to the bottom 14 than the connection point 18, the opening 13 side of the can body 19 is more easily inserted into the mold, and the reduced diameter portion 11 is formed more reliably. Furthermore, it is preferable that the first undercoat portion 500A formed on the reduced diameter portion 11 and the second undercoat portion 500B formed on the can body portion 12 have a thickness of 2 to 10 μm. Also, as described above, it is preferable that the thickness of the second undercoat portion 500B be greater than the thickness of the first undercoat portion 500A.

[0121] Figures 14(A) to (D) schematically show the state of the can body after processing by the printer (PR) shown in Figures 1 and 8. Figures 14(A) to (D) show the state of the can body on the side with the opening 13 (see Figure 2). Also, Figures 14(A) to (D) show only one side of the parts located on both sides of the can body, straddling the axis of the can body. Furthermore, in Figures 14(A) to (D), the thicknesses of the can body, base layer, and protective layer are shown with thicknesses that differ from their actual thicknesses.

[0122] In this embodiment, an image G is formed on the first base coat portion 500A of the reduced diameter portion 11 and the second base coat portion 500B of the can body portion 12 using a printer (PR). Furthermore, in the printer (PR), paint is applied on top of this image G (external coating is performed, and a transparent protective layer OL (overcoat layer) is formed).

[0123] In this embodiment, as shown in Figures 14(A) to (D), an image G is formed on at least the outer peripheral surface 19A of the can body 12, and a transparent protective layer OL is formed on at least the uppermost layer of the can body 12. In other words, a transparent protective layer OL is formed on top of the formed image G. More specifically, in this embodiment, an image G is formed on the outer surface 19A of the can body using an inkjet head 300 (see Figure 4). Next, a roll member that is aligned with the axial direction of the can body and holds paint on its outer surface is pressed against the outer surface 19A of the can body to form a transparent protective layer OL.

[0124] Figure 14(A) illustrates a case in which a colored image G is formed on the second undercoat portion 500B (on the can body portion 12) of a can body having a transparent first undercoat portion 500A and a colored second undercoat portion 500B. Furthermore, it illustrates a case in which a transparent protective layer OL is formed on top of this image G. Furthermore, Figure 14(B) illustrates a case in which a color image G is formed on the can body portion 12 of a can body having a single, colored undercoat portion 500, and a transparent protective layer OL is further formed.

[0125] Furthermore, Figure 14(C) illustrates a case in which a color image G is formed on the can body portion 12 of a can body having only the first undercoat portion 500A. It also illustrates a case in which a transparent protective layer OL is formed on top of this image G. Note that the first undercoat area 500A in Figures 14(A) and (C) may be transparent or colored. Furthermore, Figure 14(D) illustrates a case in which a color image G is formed on the reduced diameter portion 11 and the can body portion 12 of a can body having a single, colored undercoat portion 500, and a transparent protective layer OL is further formed.

[0126] Here, the images G shown in Figures 14(A) to (D) are all images G formed on the outer surface 19A of the can body after the reduced diameter portion 11 has been formed, and can be considered as images after the reduced diameter portion has been formed. In addition, the first undercoat portion 500A and the second undercoat portion 500B (the parts where the paint has hardened and become layers) can be considered as layers formed on the surface of the outer surface 19A before the reduced diameter portion 11 was formed, and are therefore considered as layers before the reduced diameter portion has been formed.

[0127] In this case, if the image G is formed after the reduced diameter portion 11 is formed, it is possible to diversify the image G to be formed. Here, if the image G is formed before the reduced-diameter portion 11 is formed, the mold for forming the reduced-diameter portion 11 may be pressed against the already formed image G, potentially damaging it. This damage can be suppressed, for example, by increasing the strength of the image G, but in this case, the types of images G that can be formed tend to become limited. In contrast, when the reduced-diameter portion 11 is formed first and then the image G is formed, as in this embodiment, such constraints are less likely to occur, and the variety of images G to be formed can be increased.

[0128] There are no particular restrictions on the color of the protective layer OL, but it is generally colorless and transparent (clear). If the protective layer OL is colored, it is preferable to make it colored and transparent, in which case the image G beneath the protective layer OL will be visible. Additionally, the protective layer OL may be made of a matte finish paint. When the protective layer OL is formed, image G is protected. In addition, the outer surface 19A of the can body becomes more slippery, allowing the can body to move more smoothly on the manufacturing line.

[0129] Furthermore, as shown in Figure 14(D), the protective layer OL can be formed not only on the can body 12 but also on the reduced diameter portion 11. It should be noted that there may be cases where it is difficult to press the roll member (a roll member for applying the paint that constitutes the protective layer OL) against the reduced diameter portion 11. For this reason, the protective layer OL may be formed on the reduced diameter portion 11 by applying the paint using, for example, an inkjet head.

[0130] Furthermore, image formation on the outer surface 19A of the can body may be performed not only on the can body portion 12, but also on the reduced diameter portion 11, as shown in Figure 14(D). Since the reduced diameter section 11 is positioned away from the inkjet head 300 (see Figure 4), it is more difficult to form an image G in it compared to the can body section 12. However, for example, a strip-shaped image along the circumferential direction of the can body can be formed.

[0131] Here, the protective layer OL (external coating) is not necessarily required for areas where image G is not formed. For example, as shown in Figures 14(A) to (C), if image G is not formed on the reduced diameter portion 11, the formation of the protective layer OL on the reduced diameter portion 11 may be omitted. Furthermore, the exterior coating is not limited to being uniformly applied over the entire outer surface 19A of the can body; the exterior coating applied to the reduced diameter portion 11 and the exterior coating applied to the can body portion 12 may be different.

[0132] Furthermore, when applying an exterior coating to areas where image G is not formed, this exterior coating may be opaque (colored) rather than transparent. Furthermore, as described above, exterior painting may be omitted for areas where image G is not formed. In addition, for areas where image G is not formed but the base coat portion 500 has already been formed, exterior painting can be omitted because a layer that substantially protects the base of the can body has been formed.

[0133] Furthermore, as explained above, if the first undercoat section 500A and the second undercoat section 500B are provided at a distance from each other and do not overlap, it is preferable to apply the exterior coating to the gap formed between them. This prevents the base material of the can from being exposed in the area located between the first undercoat section 500A and the second undercoat section 500B. [Explanation of symbols]

[0134] 11...Reduced diameter section, 12...Can body section, 13...Opening, 14...Bottom section, 19...Can body, 19A...Outer circumference, 19B...Other end, 19C...One end, 500...Primer coating section, 500A...First primer coating section, 500B...Second primer coating section, G...Image

Claims

1. A diameter reduction step is performed to reduce the diameter of one end of an empty can body that is formed in a cylindrical shape, has an opening at one end and a bottom at the other end, and the empty can body is made to have a diameter reduction section provided at the one end that decreases in outer diameter towards the opening and a can body section located closer to the bottom than the diameter reduction section. Prior to the diameter reduction process described above, a paint application process is performed in which a colored paint is applied to the outer surface of the portion of the empty can body that will become the diameter reduction portion, and a transparent paint is applied to the outer surface of the portion of the empty can body that will become the can body portion. An image forming step is performed on the outer surface of the empty can body having undergone the diameter reduction step and having the reduced diameter portion, wherein a chromatic paint is attached to the outer surface of the reduced diameter portion. A method for manufacturing beverage cans equipped with [a specific feature / feature].

2. In the image forming step, an inkjet head extending along the axial direction of the empty can and positioned facing both the reduced diameter portion and the can body portion of the empty can is used to form an image on the outer surface of the empty can, and in forming the image on the outer surface, an image is formed on the outer surface of the can body portion but not on the outer surface of the reduced diameter portion. A method for manufacturing a beverage can according to claim 1.

3. In the paint application process, a colorless, transparent paint is applied to the outer surface of the portion that will become the can body. A method for manufacturing a beverage can according to claim 1.

Images