JP7629979B2 - Manufacturing method for beverage cans - Google Patents

Description

The present invention relates to a method for manufacturing beverage cans.

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

JP 2005-14971 A

In the case of beverage cans, a base layer is formed on the surface of the can body, and an image is formed on this base layer. In forming the base layer, a paint is generally applied over the entire outer peripheral surface of the can body, and in this case, the base layer is formed uniformly on the outer peripheral surface of the can body.
In addition, beverage cans may have a tapered portion formed at the end on the opening side, but if this tapered 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 tapered portion. This damage can be suppressed, for example, by increasing the strength of the image, but in this case, restrictions are likely to be imposed on the types of images that can be formed.
An object of the present invention is to enable a greater variety of images to be formed on the outer peripheral surface of a beverage can.

The method for manufacturing beverage cans to which the present invention is applicable includes a diameter reduction step in which one end of an empty can body formed in a cylindrical shape and having an opening at one end and a bottom at the other end is reduced in diameter to form the empty can body into an empty can body having a reduced diameter portion at the one end whose outer diameter decreases toward the opening and a can body portion located on the bottom side of the reduced diameter portion; a paint application step in which, before the reduction in diameter is performed in the diameter reduction step, a chromatic paint is applied to the outer peripheral surface of the portion of the empty can body that will become the reduced diameter portion, and a white paint is applied to the outer peripheral surface of the portion of the empty can body that will become the can body; and an image formation step in which an image is formed on the outer peripheral surface of the empty can body that has been reduced in diameter in the diameter reduction step and has the reduced diameter portion.

From another perspective, the method for manufacturing beverage cans to which the present invention is applicable includes a diameter reduction step of reducing the diameter of one end of an empty can body that is formed in a cylindrical shape and has an opening at one end and a bottom at the other end, and converting the empty can body into an empty can body having a reduced diameter portion that is provided at the one end and whose outer diameter decreases toward the opening and a can body portion that is located on the bottom side of the reduced diameter portion; a paint application step of applying colored paint to the outer peripheral surface of the portion of the empty can body that will become the reduced diameter portion before the diameter reduction step, without applying paint to the outer peripheral surface of the portion of the empty can body that will become the can body; and an image formation step of forming an image on the outer peripheral surface of the empty can body that has been reduced in the diameter reduction step and has the reduced diameter portion.

Here, in the image forming process, an image is formed on the outer peripheral surface of the can barrel of the empty can body, and no image is formed on the outer peripheral surface of the reduced diameter portion of the empty can body, and after the image has been formed in the image forming process, a user may be able to visually recognize a chromatic image made of the chromatic paint on the empty can body.
In addition, in the image forming process, an image is formed on the outer peripheral surface of the can barrel of the empty can body, and no image is formed on the outer peripheral surface of the reduced diameter portion of the empty can body, and after the image has been formed in the image forming process, a user may be able to visually recognize a colored image made of the colored paint on the empty can body.
In addition, in the image forming process, an image is formed on the outer peripheral surface of the empty can body using an inkjet head extending along the axial direction of the empty can body and positioned opposite both the narrowed portion and the can body of the empty can body, and when forming an image on the outer peripheral surface, an image is formed on the outer peripheral surface of the can body and no image is formed on the outer peripheral surface of the narrowed portion.
In addition, in the paint application step, white paint may be applied to an outer circumferential surface of the portion that becomes the reduced diameter portion.
In addition, in the paint application step, a chromatic paint may be applied to an outer circumferential surface of the portion that becomes the reduced diameter portion.

The present invention makes it possible to form a wider variety of images on the outer surface of a beverage can.

FIG. 1 is a diagram showing a manufacturing process for beverage cans. 3 shows the can body after necking has been performed. FIG. 1 is a diagram illustrating a flanging process. FIG. 4 is a diagram illustrating a process in the printer. FIG. 13 is a diagram showing an example of a diameter-expanding mandrel. FIG. 13 is a diagram showing another example of a diameter-expanding mandrel. FIG. 13 is a diagram showing another example of a diameter-expanding mandrel. 11A-11D are diagrams illustrating another embodiment of a manufacturing process for beverage cans. 1 is a diagram showing a conventional manufacturing process for a can body. 13A and 13B are diagrams showing another example of supporting a can body by a mandrel. 13A and 13B are diagrams showing another example of the configuration of the mechanism for supporting the can body. 13A and 13B are diagrams showing another example of the configuration of the mechanism for supporting the can body. 1A to 1G are diagrams illustrating specific examples of the underlayer. 13A to 13D are diagrams showing the state of a can body after processing by a printer.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a diagram showing a manufacturing process for a beverage can according to the present embodiment.
The manufacturing process shown in FIG. 1 is a diagram showing a manufacturing process for a so-called two-piece can.
In the manufacturing process of a two-piece can (can body) in this embodiment, aluminum or an aluminum alloy is formed by draw and ironing (DI) forming, and then the open end is trimmed so that the height of the can body is uniform. Next, the can body is washed, and then the inside surface is painted (painting process) and the like.

Next, a neck is formed by gradually reducing the diameter of the opening 13, and a flange is formed at the opening 13 of the neck by flange processing (diameter reduction step). After that, a printing device is used to perform exterior printing (image formation). This results in the manufacture of a beverage can that is cylindrical with a bottom and made of metal, and has an image formed on its outer circumferential surface.
The symbols (represented by alphabetical letters) in Fig. 1 and the following figures indicate the names of the steps constituting the manufacturing process for two-piece cans. Each step is provided with a device corresponding to the step, and the processing in the step is carried out by this device.
In the following description, the "process name" and the "device name (facility name)" used in that process may be referred to by the same name.

Here, the beverage filled into the can body (beverage can) is not particularly limited, and the can body is filled with, for example, an alcoholic beverage such as beer or chuhai, or a soft drink (non-alcoholic beverage) (beverage filling process). After filling, a lid member is attached to the can body, and a beverage can filled with the beverage is completed.
In the following description, a can body before being filled with a beverage may be referred to as a beverage can, and a can body after being filled with a beverage may be referred to as a beverage can.

As shown in FIGS. 1 and 2 , in the manufacturing process of this embodiment, an uncoiler (UC), a lubricator (LU), a cupping press (CP), a body maker (BM), a trimmer (TR), and a washer (WS) are provided in this order from the upstream side in the conveying direction of the can body.
The uncoiler (UC) unwinds the coiled aluminum sheet. The lubricator (LU) applies lubricant to the aluminum sheet. The cupping press (CP) punches out a circular blank and then draws it to form a cup-shaped blank.

In the body maker (BM) process, which is an example of a forming process, a cup-shaped material is subjected to drawing and ironing processes to form the peripheral wall to a predetermined thickness. The bottom is then formed into a dome shape. This results in a cylindrical can body having an opening 13 on one side and a bottom on the other side (DI forming).
Then, in the trimmer (TR), the edges on the upper part of the peripheral wall of the can body are trimmed to evenness. In the washer (WS), the can body is washed to remove lubricating oil and other deposits, and a chemical coating is applied if necessary.

Downstream of the washer (WS), an overburnish (OV) is provided as a paint application process. In the overburnish (OV), a colorless and transparent paint is applied to the outer peripheral surface 19A of the can body. As a result, a base layer is formed on the outer peripheral surface 19A of the can body. Here, the base layer refers to a layer formed between the can body and an image formed later by the printer (PR).
Furthermore, a pin oven (PO) is provided downstream of the over burnish (OV) to heat the can body and bake the base layer formed by the over burnish (OV) onto the can body.

Here, baking in a pin oven (PO) is carried out by a known method.
The baking is generally performed by hot air drying. Alternatively, the baking may be performed by irradiating the can body with infrared rays. Alternatively, hot air drying and infrared irradiation may be used in combination.
The baking conditions are, for example, a heating temperature of 200° C. and a heating time of 30 seconds.

In addition to an over burnisher (OV), a base coater (BC) is provided downstream of the washer (WS) as another example of a paint application process.
In the case of a can body on which a colored undercoat layer is to be formed, the paint is applied to the can body by this base coater (BC) instead of the over burnisher (OV), so that a undercoat layer is also formed on the outer peripheral surface 19A of the can body.
The base coater (BC) applies a colored paint to the outer peripheral surface 19A of the can body. Specifically, for example, a white paint is applied.

The color of the base layer formed by the base coater (BC) is generally white in order to make the color of the image formed by the subsequent printing vivid, but it may be another color. Also, the color of the paint applied to the can body by the base coater (BC) may be colorless and transparent, in which case it is no different from over burnish (OV).
A pin oven (PO) is provided downstream of the base coater (BC), and the can body is heated in the pin oven (PO) to bake the base layer onto the can body.

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 an over burnisher (OV) or a base coater (BC).
In addition, in this embodiment, when a base layer is formed on a can body using a base coater (BC), the formation of a base layer is omitted in another base coater (BC) (described later) located in a subsequent process.

After passing through the washer (WS), the friction coefficient of the outer surface of the can body is large, and if this continues, the can body is likely to suffer from poor transport. In addition, the surface of the can body is likely to be scratched, leading to poor appearance.
By providing an over burnisher (OV) or base coater (BC) to form a base layer on the surface of the can body, the can body can be transported more smoothly and is less likely to be scratched.

Furthermore, if the can body after passing through the washer (WS) is directly fed to a necker flanger (SDN) (described later), problems may occur.
Specifically, the large friction between the can body and the die used in the Necker flanger may cause the can body to buckle and deform, and may also damage the die.

Therefore, in this embodiment, a base layer (base coating portion) is formed at least on the neck portion by using either an over burnish (OV) or a base coater (BC).
This suppresses buckling deformation of the can body, damage to the mold, etc. Also, compared to a case where no undercoat layer is formed at all, the can body can be transported more smoothly.

[Painting process]
An inside spray (INS) and a bake oven (BO) are provided downstream of the pin oven (PO) as another example of a paint application process.
In the inside spray (INS), paint is applied (sprayed) to the inside of the can body to paint the inside, and in the bake oven (BO), the can body is heated to bake the paint (painting process).

In this embodiment, a case has been described in which the over burnish (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 limiting, and the inside spray (INS) and bake oven (BO) treatments may be performed first, followed by over burnish (OV), base coater (BC) and pin oven (PO) treatments.

It is more preferable to carry out the over burnish (OV), base coater (BC) and pin oven (PO) treatments first, and then the inside spray (INS) and bake oven (BO) treatments.
If inside spray (INS) and bake oven (BO) treatments are performed later, the inside of the can body will be covered with paint after over burnish (OV) and base coater (BC), making the inside of the can body more hygienic.

Specifically, in processes such as over burnish (OV) and base coater (BC), a mandrel (support member) for supporting the can body is inserted inside the can body, and the mandrel comes into contact with the inner peripheral surface of the can body.
If inside spray (INS) and bake oven (BO) are performed later, the part of the inner surface of the can body that has been in contact with the mandrel will be covered with paint, making the inner surface of the can body more hygienic.

[Diameter reduction process]
A Necker flanger (SDN), which is an example of a forming process, is provided downstream of the bake oven (BO), in which the opening 13 of the can body is reduced in diameter and a flange for attaching a can lid is formed.
In the following description, the necking process (the process of reducing the diameter of the opening 13 of the can body) and the flanging process (the process of forming a flange for attaching a can lid) will collectively be referred to as "necking."

FIG. 2 shows the can body after necking has been performed.
The can body of this embodiment is provided with a can body 19. The can body 19 is formed in a cylindrical shape and has an outer circumferential surface 19A. The can body 19 further has one end 19C and the other end 19B. The can body 19 further has an opening 13 at the one end 19C and a bottom 14 at the other end 19B. The can body 19 further has a reduced diameter portion (neck portion) 11 and a can barrel portion 12.

The reduced diameter portion 11 is located on the opening 13 side of the can body 19. In addition, the reduced diameter portion 11 is provided at one end 19C of the can body 19. The reduced diameter portion 11 is formed such that the outer diameter gradually becomes smaller as it approaches the opening 13.
The can body 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 12 refers to a portion of the can body whose length in the axial direction is greater than that of the reduced diameter portion 11, and which is not reduced in diameter or whose reduced diameter rate is smaller than that of the reduced diameter portion 11.
The can body 12 of this embodiment is connected to the narrowed portion 11 at a connection point 18. The can body 12 is formed so that the outer diameter of the portion connected to the narrowed portion 11 (the outer diameter at the connection point 18) is approximately equal to the outer diameter on the bottom 14 side. That is, the can body 12 of this embodiment has an approximately constant outer diameter in the axial direction of the can body. Note that the can body 12 may be narrowed at a smaller rate than the narrowed portion 11.

The necking process may be carried out by any of the existing methods, and is generally carried out by the so-called "die neck" method in which the can body is pressed into the inside of a mold, or the so-called "spin flow" method in which a rotating mold 90 is rotated.
In addition, the flanging process may be performed by an existing method, for example, the technique described in JP 2016-016419 A.
In the technique described in JP 2016-016419 A, as shown in FIG. 3 (a diagram for explaining the flanging process), the flanging process is performed using a rotating die 90 called a spinner.

However, in the case of the Necker flanger (SDN), since the die is pressed against the can body, there is a risk of scratching the can body or the die.
In this embodiment, a base coater (BC) and an over burnisher (OV) are provided before the necker flanger (SDN), and further an inside sprayer (INS) is provided. As a result, in this embodiment, neck treatment is performed after a base layer that serves as a protective layer is formed on the outer and inner surfaces of the can body (after the base coating portion is provided). In this case, scratches are less likely to occur on the can body and the mold.

More specifically, in this embodiment, for example, a colorless transparent or colored (e.g., white) paint is applied to a plain metal can body (can body 19) and then the paint is cured, resulting in the formation of a protective layer on the outer circumferential surface 19A of the can body.
Furthermore, in this embodiment, a protective layer is formed on the inner surface of the can body by inside spray (INS). This makes it difficult for scratches to occur on the inner and outer surfaces of the can body. In this case, it also makes it difficult for scratches to occur on the mold.

As shown in FIG. 1, a temporary storage step is provided downstream of the Necker flanger (SDN).
In the temporary storage step, the can bodies are stacked and stored using, for example, a palletizer (PT). Alternatively, the can bodies may be stored using, for example, an accumulator (ACC).

In the temporary storage step, a plurality of can bodies each having a reduced diameter portion 11 (see FIG. 2) are stacked vertically in a state of being aligned in the axial direction.
More specifically, in the temporary storage process, after arranging multiple can bodies horizontally (after arranging the can bodies two-dimensionally in the horizontal direction), a sheet or the like is placed on the multiple can bodies, and the multiple can bodies are further arranged two-dimensionally on the sheet. This process is then repeated. As a result, the multiple can bodies are arranged horizontally and vertically.
Here, if can bodies without reduced diameter portions 11 (can bodies that have not been subjected to a reduction treatment) are stacked, the can bodies are likely to deform. However, in this embodiment, the can bodies have reduced diameter portions 11, making the can bodies less likely to deform.

In this embodiment, thereafter, when a predetermined condition is met, such as when a shipping instruction is received for the can bodies, the supply of the can bodies from the temporary storage process begins (the removal of the can bodies from the temporary storage process begins).
In other words, the stack is broken by the depalletizer (DPL), and the can bodies are re-introduced into the can body manufacturing process. Although not shown, it is not limited to the existing depalletizer (DPL), and other "metal can discharging processes" may be used.

A base coater (BC) and a pin oven (PO) are provided downstream of the depalletizer (DPL).
In the following, in this specification, this base coater (BC) may be referred to as the downstream base coater (BC), and the above-mentioned base coater (BC) located upstream of the Necker-Flanger (SDN) may be referred to as the upstream base coater (BC).

If the can body that has started to be fed has only been overburnished (OV), a colored base layer is formed on the outer circumferential surface 19A of the can body by the downstream base coater (BC) as necessary. This base layer is then baked in the pin oven (PO).

When the downstream base coater (BC) forms a base layer on the can body, the can body already has a reduced diameter portion 11, and the downstream base coater (BC) forms a base layer on the can body barrel portion 12 of the can body.
Specifically, in the downstream base coater (BC), a columnar or cylindrical roll member aligned along the axial direction of the can body is pressed against the outer peripheral surface 19A of the can body, but at this time, this roll member does not come into contact with the reduced diameter portion 11. Therefore, in the downstream base coater (BC), a base layer is formed on the can body portion 12 of the can body.

In this embodiment, even if a can body has been treated by an upstream base coater (BC), a base layer is formed by a downstream base coater (BC) as necessary.
Specifically, for example, when a base layer is formed only on the reduced diameter portion 11 by the upstream base coater (BC), a base layer is formed on the can body portion 12 by the downstream base coater (BC).

In addition, when the base coater (BC) on the upstream side forms a base layer not only on the reduced diameter portion 11 but also on the can body portion 12, processing by the base coater (BC) on the downstream side is not performed.
In this case, the processing by the downstream base coater (BC) and pin oven (PO) is not carried out, and the can body is transported along the path indicated by the symbol 1A.
Even if the can body has been subjected to only overburnishing (OV), if treatment by the downstream base coater (BC) is not required, the can body is similarly transported along the path indicated by the symbol 1A.

In this embodiment, the undercoat layer (the undercoat layer formed by the over burnish (OV) and base coater (BC)) is hardened by baking, but this is just one example.
When the undercoat layer is formed of a paint that is cured by irradiation with ultraviolet light or the like, the undercoat layer is cured by irradiating it with ultraviolet light or the like.

[Image forming process]
Then, processing in a printer (PR) is disclosed as an example of an image forming process.
Specifically, in this embodiment, as shown in Fig. 4 (a diagram explaining the processing in the printer (PR)), an inkjet head 300 is provided in the printer (PR). Ink is then ejected from this inkjet head 300 towards the can body located below. In this way, an image is formed on the outer circumferential surface 19A of the can body. In other words, in this embodiment, a non-contact image forming method is used to form an image on the can body.

Here, in this embodiment, a reduced diameter portion 11 is provided in the can body, and the portion of the outer peripheral surface 19A of the can body where the reduced diameter portion 11 is provided is spaced away from the lower surface 301 of the inkjet head 300 (the surface where the ink ejection ports are provided).
In this case, there is a risk that the quality of the formed image will be reduced at the portion of the outer circumferential surface 19A of the can body where the reduced diameter portion 11 is provided.

Therefore, in the image forming process by the printer (PR), for example, an image may be formed only on the can body portion 12 without forming an image on the reduced diameter portion 11 .
In this way, when an image is formed only on the can body portion 12, a plain, monochromatic image or a colorless base layer is formed on the narrowed diameter portion 11, and an image made up of multiple colors is formed on the can body portion 12.

In addition, the reduced diameter portion 11 is formed with only a colorless base layer formed by over burnishing (OV) or only a monochrome base layer formed by a base coater (BC), and the can body portion 12 is formed with a multicolored pattern.
Note that image formation on the reduced diameter portion 11 is not excluded, and an image may be formed on the outer circumferential surface of the reduced diameter portion 11 using the inkjet head 300 .

The image formed on the reduced diameter portion 11 using the inkjet head 300 is not particularly limited, and may be, for example, a color image formed using ink of multiple colors, or a monochromatic image (solid image) formed using ink of one color. Also, for example, a band-shaped image may be formed along the circumferential direction of the can body.
In addition, when the external shape of the reduced diameter portion 11 is stepped, such as a four-stage neck (when the diameter is reduced in stages toward the opening 13), the color of the image formed can be different for each stage, and for example, a four-color band-shaped image running circumferentially around the can body can be formed on the reduced diameter portion 11.

Furthermore, in the image forming process in the printer (PR), after the image is formed by the inkjet head 300, paint is applied to the outer circumferential surface 19A of the can body to form a protective layer (overcoat layer).
In other words, in the printing process by the printer (PR), ink is ejected from a nozzle as droplets, and the ink is deposited on the outer peripheral surface 19A of the can body to form an image on the outer peripheral surface 19A of the can body. Next, paint is applied on the image to form a protective layer.

Here, the printer (PR) uses, for example, four colors of ink, cyan (C), magenta (M), yellow (Y), and black (K), as basic inks, and further uses special color inks (special color inks) prepared for each brand as necessary.
In this case, an inkjet head 300 is prepared for each color, and the image is formed on the can body using the multiple inkjet heads 300.
The ink used is preferably an actinic radiation curable ink, and examples of the actinic radiation curable ink include ultraviolet (UV) curable ink.

Furthermore, in the printer (PR), a cylindrical mandrel (not shown in FIG. 4), which is an example of a support member, is inserted inside the can body, and the mandrel supports the can body from the inside. The can body is then placed in a position facing the inkjet head 300. The can body is then placed so that the axial direction of the can body is aligned with the longitudinal direction of the inkjet head 300. Then, while the can body is rotated in the circumferential direction, ink is ejected and printing is performed.
Here, the printer (PR) performs so-called digital printing, which is printing based on image data.

Although a higher printing resolution in a printer (PR) is more preferable, taking into consideration costs, productivity, and the like, it is preferable that the printing resolution is, for example, about 600 dpi.
From the viewpoint of improving the quality of the formed image, it is more preferable to reduce the distance between the can body and the inkjet head 300, but if the distance is too small, there is a risk of interference between the can body and the inkjet head 300. The distance between the can body and the inkjet head 300 may be, for example, about 1 mm.

In addition, while a higher rotation speed of the can body contributes to productivity, if the rotation speed is too high, when the ink lands on the can body, the ink may spread in the circumferential direction of the can body, resulting in a decrease in resolution. For this reason, it is desirable to rotate the can body at a high rotation speed that suppresses the ink from spreading in the circumferential direction of the can body.
Furthermore, when ultraviolet-curable ink is used, the ink may be cured by irradiating it with ultraviolet light each time one color of ink is ejected onto the can body, or multiple colors of ink may be ejected and then irradiated with ultraviolet light to cure the ink all at once.

In addition, in the printer (PR), it is preferable to use a mandrel whose diameter partially expands when it is inserted into the can body. In other words, it is preferable to use a mandrel whose diameter partially expands after insertion into the can body and whose part contacts the inner peripheral surface of the can body.
In addition, it is preferable to use a mandrel having a portion that approaches the inner peripheral surface of the can body from a portion spaced from the inner peripheral surface and contacts the inner peripheral surface.

In this embodiment, the opening 13 (see FIG. 2) of the can body is reduced in diameter by necking, and the diameter of the opening 13 is smaller than the diameter of the can body 12 of the can body during image formation.
For this reason, simply inserting a cylindrical mandrel into a can body creates a gap between the can body and the mandrel, making support of the can body unstable. By using a mandrel that expands in diameter and bringing part of the mandrel into contact with the inner circumferential surface of the can body, the can body can be supported more stably.

Fig. 5 shows an example of an expanding mandrel, in which when the mandrel is inserted into a can body (not shown in Fig. 5), the disk-shaped contact member 40 comes into contact with the opening edge 13A (see Fig. 2) of the can body. The mandrel (shaft 41) is then moved further toward the bottom 14 (see Fig. 2) of the can body.
As a result, the tapered surface 42A of the mounting member 42 attached to the shaft 41 presses the moving member 43 towards the inner circumferential surface of the can body, and the moving member 43 is pressed against the inner circumferential surface of the can body.

The mandrel is reversible, and when the mandrel is moved in the direction to remove it from the can body, the spring member 44 moves the mounting member 42 closer to the contact member 40. This releases the pressure on the moving member 43 from the mounting member 42, allowing the moving member 43 to move in the direction away from the inner circumferential surface of the can body.

6 is a diagram showing another example of a diameter-expanding mandrel, in which compressed air is used to move a moving body 51 in the axial direction of a mandrel body 52, and this moving body 51 compresses an annular elastic member 53 attached to the outer periphery of the mandrel body 52. As a result, 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, which causes the movable body 51 to move in the opposite direction and the elastic member 53 to return to its original state. When the elastic member 53 returns to its original state, the elastic member 53 separates from the inner peripheral surface of the can body.

FIG. 7 is a diagram showing another example of a diameter-expanding mandrel.
This mandrel is provided with an advancing/retreating member 81 that advances and retreats relative to the inner circumferential surface of the can body. Compressed air is supplied to this mandrel, and the advancing/retreating member 81 is pressed by this compressed air, causing the advancing/retreating member 81 to come into contact with the inner circumferential surface of the can body. This mandrel is also reversible, and when the supply of compressed air is stopped, the advancing/retreating member 81 moves in a direction away from the inner circumferential surface of the can body due to the coil spring 82.

With further reference to FIG. 1, the manufacturing process will be further explained.
A bottom coater (BTC), a pin oven (PO), a defective can tester (DCT), a light tester (LT), and a palletizer (PT) are provided downstream of the printer (PR).

In the bottom coater (BTC), coating is performed on the ground contact portion of the bottom 14 of the can body.
In the pin oven (PO), the can body is heated and the image on the outer periphery of the can body and the coating on the bottom 14 are baked.
In this embodiment, two sets of bottom coaters (BTC) and pin ovens (PO) are provided to correspond to the two types of printers (PR) (two types of printers (PR) indicated by reference characters 1B and 1C). However, this is not limiting, and only one set of bottom coaters (BTC) and pin ovens (PO) may be provided to allow the equipment to be shared.

The defective can tester (DCT) inspects the appearance and printing of the can body, and removes any defective products.
The light tester (LT) checks the can body for holes and removes any defective products.
At the palletizer (PT), can bodies that have passed inspection are loaded (stacked) onto pallets.
Thereafter, the can bodies are shipped to, for example, a beverage can manufacturing factory (where the beverage is filled), where the beverage is filled into the can bodies and a lid is attached, completing the beverage cans.

The manufacturing process shown in FIG. 1 is merely an example, and the steps may be interchanged without departing from the spirit of the present invention.
In the can body manufacturing process, a conveyor is mainly used to transport the can bodies, but the can bodies may be transported using a transport mechanism other than a conveyor.
In addition, when a conveyor is used to transport the can bodies, for example, a mass conveyor or a single conveyor is used. Here, in Fig. 1, the transport path indicated by one line indicates the transport path along which the can bodies are transported by the single conveyor, and the transport path indicated by two lines indicates the transport path along which the can bodies are transported by the mass conveyor.

In addition, in each process, one piece of equipment may be provided, or multiple pieces of equipment may be provided.
When a plurality of facilities are provided, the conveying path for the can bodies is branched so that the can bodies are supplied to each of the plurality of facilities, and in this case, the conveying paths are joined downstream of each facility.

Second Embodiment
Fig. 8 is a diagram showing another embodiment of the manufacturing process for beverage cans. Note that steps having the same functions as those in the embodiment shown in Fig. 1 are denoted by the same reference numerals and will not be described.
In the embodiment shown in Fig. 1, a manufacturing process for beverage cans (a manufacturing process in a can manufacturing factory) is shown. Fig. 8 illustrates not only the manufacturing process for beverage cans (a manufacturing process in a can manufacturing factory) but also a content filling process (a manufacturing process in a beverage can manufacturing factory) for filling the beverage can with contents such as a beverage.

In FIG. 8, the upper part shows the manufacturing process in a can manufacturing factory.
In the manufacturing process in the can manufacturing plant, the manufacturing process up to the necker flanger (SDN) is the same as that in the embodiment shown in Fig. 1. Specifically, each process starting from the uncoiler (UC) up to the necker flanger (SDN) is provided.
On the other hand, in the manufacturing process in this embodiment (the manufacturing process in a can manufacturing factory), a printer (PR) is not provided, and this manufacturing process is provided with a defective can tester (DCT), a light tester (LT), and a palletizer (PT).

In the manufacturing process in this embodiment (the manufacturing process at a can manufacturing factory), after neck processing, the can body is inspected without performing image formation processing. Specifically, the appearance and printing condition of the can body are inspected, and further, the presence or absence of holes in the can body is inspected.
The can bodies are then stacked in a palletizer (PT) to produce pallets containing multiple can bodies, and these pallets are then shipped to a beverage can manufacturing plant.

In this embodiment, the can manufacturing factory produces can bodies with a base layer (base coating portion) formed at least on the narrowed diameter portion 11, as described above. The can manufacturing factory also produces can bodies without image formation on the can bodies. Specifically, can bodies are produced that have been painted on the inside and outside (formed with a base layer) and necked, but have not been imaged. The can bodies without image formation are then shipped to a beverage can manufacturing factory.

In this embodiment, a case where the products are stacked in a palletizer (PT) and then shipped is shown as an example, but the shipping form may be any form.
Moreover, the defective can tester (DCT) and the light tester (LT) may be omitted if they are not necessary.

In a beverage can manufacturing factory, first, a depalletizer (DPL) is performed to start dispensing of can bodies.
Downstream of the depalletizer (DPL), a downstream base coater (BC) and a pin oven (PO) are provided, and as described above, a base layer is formed and baked on can bodies that have only been overburnished (OV) or on can bodies that have a base layer formed only on the reduced diameter portion 11 by the upstream base coater (BC).

For can bodies in which a base layer has been formed over the entire outer surface of the can body in the upstream base coater (BC), or can bodies that have only been overburnished (OV), but do not require the formation of a base layer, the downstream base coater (BC) and pin oven (PO) are not required, and the formation and baking of the base layer in the downstream base coater (BC) is omitted. In this case, the can body is transported along the transport path indicated by the symbol 8A.

Thereafter, image formation is performed by the printer (PR) in the same manner as described above. Specifically, ink is ejected from the inkjet head 300 provided in the printer (PR) toward the can body, and an image is formed on the outer peripheral surface of the can body in the same manner as described above.
A bottom coater (BTC) and a pin oven (PO) are provided downstream of the printer (PR), where coating is performed on the grounded portion of the bottom 14 of the can body, and the can body is heated. As a result, the image on the outer peripheral surface of the can body and the coating on the bottom 14 of the can body are baked onto the can body.
Thereafter, the can body is rinsed with water in a rinser (RN). The printer (PR) may be provided after the rinser (RN).

[Beverage filling process]
Next, the can bodies are filled with beverage in a filler (FL), which is an example of a beverage filling process, and then a can lid is attached to the can body in a seamer (SM). The can lid is attached to the can body by so-called double seaming.
A can lid is generally formed in a panel shape, and further has a score (a drinking opening) formed in the center. Further, an opening tab is fixed to the can lid, and the can lid also has a countersink portion, a chuck wall portion, and a curl portion. The can lid is formed of, for example, aluminum or an aluminum alloy.
The treatment with the filler (FL) may be carried out by an existing technique, for example, the treatment described in JP-A-2009-026009.

After that, various inspection machines (DT) are used to inspect the filling amount, foreign objects, etc. This inspection should be done before the product is packed in the caser (CS) described later. This inspection may be done any number of times to improve the quality.
The contents are then returned to room temperature in a warmer (WM). Here, in the case of high-temperature filling, known as hot packing, which is used for filling tea-based beverages, coffee beverages, etc., a warmer (WM) is not required.
In addition, the contents that require sterilization are sterilized before being packed in a caser (CS) described later. Sterilization methods include low-temperature sterilization (pasteurization) and high-temperature, high-pressure steam sterilization (retort), etc.

Thereafter, a can bottom printer (BIP) uses an inkjet head to print necessary information such as the manufacturing date, lot number, and expiration date on the bottom 14 of the can body (beverage can). The printed content is inspected by an inspection machine (not shown).
Here, when printing with a can bottom printer (BIP), it is preferable to blow off water droplets on the bottom 14 of the can body with high-pressure air before printing. After the can body leaves the warmer (WM), water droplets adhere to the bottom 14 of the can body, and by blowing off these water droplets with high-pressure air before printing, the printing quality is improved.

The can bottom printer (BIP) is not limited to being installed downstream of the warmer (WM), but may be installed between the filler (FL) and the warmer (WM). In this case, however, the can body is at a low temperature, and condensation will soon form even if the water droplets are blown off with high-pressure air. For this reason, it is more preferable to install the can bottom printer (BIP) downstream of the warmer (WM).
Furthermore, printing by the bottom printer (BIP) may be performed at any time up to the time of packing in the caser (CS), and may be performed, for example, immediately after the depalletizer (DPL).

The cans (beverage cans) are then packed in a caser (CS). Generally, 24 cans are packed in one box. When packing six cans in a six-pack, four packs of cans are packed in one box.
Thereafter, the boxes containing the can bodies are loaded onto pallets by a palletizer (PT).

In this embodiment, since images are formed on the can bodies at a beverage can manufacturing factory, it becomes possible to prepare printed can bodies according to the amount (total amount) of contents prepared.
In this case, the contents and the can body can be used (consumed) without excess or deficiency, and waste of the contents and the can body can be reduced.

9 is a diagram showing a conventional manufacturing process for a can body. Note that steps having the same functions as those in the embodiment described above are denoted by the same reference numerals and will not be described.
In this conventional manufacturing process, the printing method in the printer (PR) is a plate printing method. Furthermore, in this conventional manufacturing process, the printer (PR) is located upstream of the necker flanger (SDN) in the conveying direction of the can body.

Furthermore, in this conventional manufacturing process, a palletizer (PT) (temporary storage process) is provided downstream of the printer (PR) and necker flanger (SDN), so that when the can bodies are in storage, images have already been formed on the can bodies and neck processing has already been performed on them.
Therefore, in this conventional manufacturing process, the can bodies are shipped in a state in which the image has been formed and the necking has been completed.

In this conventional manufacturing process, the printing method is a plate printing method, which requires more time for printing preparation and makes it difficult to respond to urgent orders.
Specifically, with the plate printing method, a design drawing must be obtained, plates must be made, the printing plates must be placed on the printing press, and preparations such as color matching must be made, so it takes a lot of time before printing can begin.

In order to shorten the time, it is preferable to manufacture the cans in advance before receiving an order and to store the printed can bodies as inventory.
However, in this case, it is necessary to secure a place to store the inventory, which causes problems such as warehousing costs. Furthermore, the time until a design is changed or a brand is discontinued has become shorter recently, so if cans are made in advance and stocked, wasteful can bodies are likely to occur. Furthermore, there are cases where a part of the design is changed, and in this case, wasteful can bodies that are to be discarded are also generated.
Thus, in the conventional manufacturing process, it was necessary to secure inventory, and furthermore, this inventory was prone to being discarded.

In contrast, in this embodiment, the can bodies are not printed on and are kept in stock. In this case, even if the design is changed, printing can be done with the changed design, so can bodies are less likely to go to waste.
Furthermore, in this embodiment, since digital printing is performed using the inkjet head 300, there is no need to prepare a printing plate or the like, and printing can be started in a shorter time.
Furthermore, when the inkjet method is used, high-definition printing is possible, and non-contact printing can be performed.

Even when using printing plates, if printing is performed on a can body for which the neck has been treated after an order is received, the occurrence of the above-mentioned waste of inventory can be reduced.
However, in plate printing, the ink must be transferred onto the can body, so during printing, a large amount of pressure is applied between the can body and the printing press's blanket (a contact member that comes into contact with the can body and transfers the ink to the can body).

In this case, the can body is deformed so as to be concave inward, making printing substantially difficult.
More specifically, as described above, the diameter of the can body 12 of a can body that has undergone necking is larger than the diameter of the opening 13 (see FIG. 2), and simply inserting a general mandrel into the can body results in a gap between the can body and the mandrel. In this state, if a blanket from a printing machine is pressed against the can body, the can body will be dented inward.

In contrast, in the inkjet method employed in this embodiment, the inkjet head 300 and the can body are not in contact with each other, 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.
More preferably, as shown in Figures 5 to 7, it is desirable to use an expanding mandrel and bring the mandrel into contact with the inner peripheral surface of the can body 12 of the can body. This allows the can body to be supported more stably.

Here, it is not necessary to expand the diameter of the mandrel. For example, if the bottom 14 of the can body (see Figure 2) is sucked by the tip of the mandrel to hold the can body, the vibration of the can body can be suppressed, and in this case, it is not necessary to expand the diameter of the mandrel.
10 (a diagram showing another example of supporting a can body with a mandrel) illustrates the case where the bottom 14 of the can body is sucked by the mandrel. The mandrel is formed in a cylindrical shape and has an opening 71 at its tip in the insertion direction when it is inserted into the can body. Furthermore, in this configuration example, air is sucked from inside the mandrel from the base 72 side of the mandrel by a suction mechanism (not shown).

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 to the opening 13 is sucked 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, so that the can body is stably supported by the mandrel.

Furthermore, in this configuration example, the bottom 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 fits into the mandrel. This causes the axis of the mandrel to coincide with the center position of the bottom 14 of the can body (the center position in the radial direction).

The can body may also be supported by other mechanisms.
Specifically, for example, as shown in Fig. 11 (a diagram showing another configuration example of a mechanism for supporting a can body), the can body may be supported by sandwiching the reduced diameter portion 11 of the can body from the inside and outside of the can body. More specifically, in this configuration example, an inner member 95 that is disposed inside the can body and moves forward and backward relative to the inner circumferential surface of the can body, and an outer member 96 that is disposed outside the can body, sandwich the reduced diameter portion 11 of the can body and hold the can body.

In addition, the can body may be supported by sucking the bottom 14 of the can body from the outside of the can body with a pad member 400, as shown in Figure 12 (a diagram showing another example of the configuration of the mechanism for supporting the can body).
The pad member 400 has a protrusion 401 that fits into a recess 98 (recess 98 recessed toward the inside of the can body) provided in the bottom 14 of the can body. Furthermore, the pad member 400 sucks and holds the can body through a hole 402 located in the center in the radial direction. Furthermore, the pad member 400 has a flat plate portion 403 that serves as a base for the protrusion 401.
Furthermore, if a circular groove that matches the shape of the ground contact portion of the can body is provided on the surface of the flat portion 403 that faces the can body and is located around the convex portion 401, the holding performance of the can body is improved.

Next, the underlayer formed before the Necker flanger (SDN) (the underlayer formed before the Necker flanger (SDN) shown in FIG. 1 and FIG. 8) will be described in detail.
In this embodiment, as described above, before the treatment in the Necker-Flanger (SDN), either the over burnish (OV)-pin oven (PO) treatment or the upstream base coater (BC)-pin oven (PO) treatment is performed.
As a result, a base layer is formed on the outer peripheral surface 19A of the can body (a base coating portion is provided). Specifically, a base layer is formed on at least the portion of the reduced diameter portion 11 of the outer peripheral surface 19A of the can body.

Here, various modes of forming the underlayer are possible.
Specifically, a mode in which the base layer is formed only on the reduced diameter portion (neck portion) 11 is conceivable. Also, a mode in which the base layer is formed on both the reduced diameter portion 11 and the can body portion 12 is conceivable.
Furthermore, when the base layer is formed on both the reduced diameter portion 11 and the can body portion 12, a conceivable embodiment is that the color of the base layer formed on the reduced diameter portion 11 is the same as the color of the base layer formed on the can body portion 12. Furthermore, when the base layer is formed on both the reduced diameter portion 11 and the can body portion 12, a conceivable embodiment is that the color of the base layer formed on the reduced diameter portion 11 is different from the color of the base layer formed on the can body portion 12.

Here, when the base layer formed on the can body 12 is colored, the base layer may be, for example, white in color, which improves the color development (saturation) of the image formed on the base layer (the image formed by the printer (PR)).
The base layer formed on the reduced diameter portion 11 may be a chromatic color, such as a bluish color. If the base layer is a bluish color, the user can feel a sense of coolness. The base layer formed on the can body 12 may also be a chromatic color.

Furthermore, when it is desired to leave a metallic luster on the reduced diameter portion 11 or the can body 12 (when it is desired to impart luster), it is possible to make the base layer formed on the reduced diameter portion 11 or the base layer formed on the can body 12 transparent. Specifically, in this case, for example, a transparent paint is applied to the reduced diameter portion 11 or over the entire outer peripheral surface 19A of the can body by over burnishing (OV).
As a result, the base layer formed on the reduced diameter portion 11 and the can body portion 12 becomes transparent, and the image formed on the base layer can be imparted with a gloss due to metallic gloss.

Furthermore, the base layer of the reduced diameter portion 11 and the base layer of the can body portion 12 may be colored and may be the same color. In this case, the base layer is formed by applying a colored paint to the entire outer peripheral surface 19A of the can body, for example, by an upstream base coater (BC).
In this case, it is not necessary to apply different paints to the reduced diameter portion 11 and the can body portion 12, and the base layer can be formed more easily.

13A to 13G are diagrams showing typical examples of the underlayer.
13A to 13G show the state of the opening 13 (see FIG. 2) side of the can body. Also, 13A to 13G show only one side of the portions located on both sides of the can body with the axis of the can body in between.
13A to 13G show the state before neck treatment is performed, and furthermore, in Fig. 13A to 13G, the undercoat layer is shown in a thicker state than it actually is.

As shown in FIGS. 13A to 13G, seven formation modes, a first formation mode to a seventh formation mode, for example, are conceivable as the formation mode of the undercoat layer.
In the first to third forming modes, the base layer of the reduced diameter portion 11 is colored.
Specifically, as shown in Fig. 13(A) , in the first forming embodiment, a colored base coating portion 500 is provided on the outer circumferential surface 19A of the reduced diameter portion 11. Note that in the forming embodiment shown in Fig. 13(A) , no base coating portion is provided on the can body portion 12.
In this way, by making the base coating portion 500 of the narrowing portion 11 colored, a can body that is more appealing to users can be provided compared to a case in which the base coating portion 500 of the narrowing portion 11 is colorless.

The color of the base coating portion 500 of the narrowing portion 11 is not particularly limited and may be, for example, white. Here, an image may also be formed on the narrowing portion 11, and if the base coating portion 500 of the narrowing portion 11 is white, the color development of the image formed on the narrowing portion 11 is improved.
In addition, in this first forming embodiment, as described above, the can body 12 is not provided with the base coating portion 500. In this case, a metallic luster remains on the can body 12, and a glossy appearance can be imparted to the image formed later by the printer (PR).

Next, the second formation mode will be described with reference to FIG.
In the second forming embodiment, a colored base-coated portion 500 is provided on both the reduced diameter portion 11 and the can body portion 12. This base-coated portion 500 is formed, for example, by applying a colored paint to the entire outer peripheral surface 19A of the can body using an upstream base coater (BC).
Here, the color of the base coating portion 500 is not particularly limited, but may be, for example, white, which improves the color development of an image formed on the base coating portion 500 (an image formed later by a printer (PR)).

In FIG. 13(B), the thickness of the base coating portion 500 provided on the outer peripheral surface 19A of the reduced diameter portion 11 is equal to the thickness of the base coating portion 500 provided on the outer peripheral surface 19A of the can body portion 12; however, the thickness of the base coating portion 500 of the reduced diameter portion 11 may be made different from the thickness of the base coating portion 500 of the can body portion 12.
More specifically, the thickness of the base coating portion 500 in the can body portion 12 may be made greater than the thickness of the base coating portion 500 in the reduced diameter portion 11 .

In this case, the metal base portion of the can body 12 is more reliably shielded, and the color development of the image formed later by a printer (PR) is further improved.
Furthermore, if the thickness of the base coating portion 500 of the narrowed diameter portion 11 is made different from the thickness of the base coating portion 500 of the can body portion 12, it becomes possible to make the color development of the image formed in the narrowed diameter portion 11 different from the color development of the image formed in the can body portion 12, making it possible to form a greater variety of images on the outer surface 19A of the can body.

In order to increase the thickness of the base coat portion 500 of the can body 12, for example, two roll members for coating the paint are provided in the upstream base coater (BC).
For example, first, a first roll member is used to apply paint to the entire outer peripheral surface 19A of the can body. Then, a second roll member is pressed against only the can body portion 12. As a result, the thickness of the base-coated portion 500 of the can body portion 12 becomes greater than the thickness of the base-coated portion 500 of the reduced diameter portion 11.

FIG. 13C shows a third formation mode.
In the third forming embodiment, the reduced diameter portion 11 is provided with a colored first basecoat portion 500A, and the can body portion 12 is provided with a transparent second basecoat portion 500B.
In the third formation mode, the first base-coated portion 500A and the second base-coated portion 500B are different in color.

Also in this third forming mode, the thickness of the second base-coated portion 500B formed on the can body 12 is greater than the thickness of the first base-coated portion 500A formed on the reduced diameter portion 11.
In this embodiment, it is possible to generate appeal by the colored first base-coated portion 500A formed on the narrowing portion 11. More specifically, the user will be more likely to notice the can body than if the first base-coated portion 500A formed on the narrowing portion 11 was colorless and transparent.
Furthermore, in the third forming mode, a metallic luster remains on the can body 12, which gives a glossy appearance to the image formed later by a printer (PR).

The colors of the first base-coated portion 500A and the second base-coated portion 500B are not particularly limited, and may be variously combined.
For example, one of the first base-coated portion 500A and the second base-coated portion 500B may be white, and the other may be a color other than white, including colorless and transparent, colored and transparent, and the like.

Furthermore, one of the colors of the first base-coated portion 500A and the second base-coated portion 500B may be transparent, such as colored transparent or colorless transparent, and the other color may be a color other than transparent.
Furthermore, at least one of the colors of the first base-coated portion 500A and the second base-coated portion 500B may be a chromatic color, and the other color may be a color different from the one color. The other color may be another chromatic color, an achromatic color, or a transparent color such as a colored transparent or a colorless transparent.

Next, the fourth to sixth forming modes will be described.
In all of the fourth to sixth forming modes, the base coating portion 500 provided on the reduced diameter portion 11 is colorless and transparent.
In the fourth forming embodiment shown in FIG. 13(D), a transparent first base coating portion 500A is provided on the reduced diameter portion 11, and no base coating portion 500 is provided on the can body portion 12.
In the fourth formation mode, the first base-coated portion 500A is transparent, and can impart a metallic luster to the reduced diameter portion 11. Also, the can body 12 has a portion where no base-coated portion is provided, and can body 12 can also be imparted with a metallic luster.

13(E), a transparent first base-coated portion 500A is provided on the reduced diameter portion 11, and a colored second base-coated portion 500B is provided on the can body portion 12. In other words, in this formation mode, the first base-coated portion 500A and the second base-coated portion 500B are different in color.
Even in this formation mode, the first base-coated portion 500A is transparent, and can impart a metallic luster to the reduced diameter portion 11. Moreover, the second base-coated portion 500B provided on the can body 12 is colored, and in this case, it is possible to enhance the color development of an image to be formed later, or to impart a design to the can body that will attract the user's attention. In other words, even in this case, it is possible to provide a can body that is appealing to users.

The first base coating section 500A and the second base coating section 500B shown in FIG. 13(E) are formed by, for example, the upstream base coater (BC) in the same manner as described above.
Specifically, for example, two roll members for coating a paint are provided in an upstream base coater (BC). Then, for example, the first roll member is used to form a first base-coated portion 500A in the reduced diameter portion 11. The second roll member is used to form a second base-coated portion 500B in the can body portion 12.

13(F), a transparent base-coated portion 500 is provided on both the reduced diameter portion 11 and the can body portion 12. In other words, in this sixth embodiment, the first base-coated portion 500A and the second base-coated portion 500B have the same color. In this sixth embodiment, it is possible to impart a metallic luster to both the reduced diameter portion 11 and the can body portion 12.
Here, the base layer 500 (first base-coated portion 500A, second base-coated portion 500B) shown in this sixth formation mode is formed, for example, by overburnishing (OV). More specifically, for example, by applying a transparent paint to the entire outer peripheral surface 19A of the can body by overburnishing (OV), the transparent base-coated portion 500 is formed on both the reduced diameter portion 11 and the can body portion 12.

In addition, in the seventh formation mode shown in Figure 13 (G), the color of the first base-coated portion 500A and the color of the second base-coated portion 500B are different, and both the first base-coated portion 500A and the second base-coated portion 500B are colored.
In the seventh formation mode, the first base coating section 500A and the second base coating section 500B are formed, for example, by an upstream base coater (BC).
Specifically, for example, two roll members for coating paint are provided on the upstream base coater (BC). Then, for example, the first roll member is used to form a first base coat portion 500A of a first color on the reduced diameter portion 11. The second roll member is used to form a second base coat portion 500B of a second color on the can body portion 12.

Here, the paint for forming the colored undercoated portion 500 explained in each of the above forming embodiments is not particularly limited, and existing paints can be used.
The colored paint includes a colored pigment, and an existing pigment can be used for this pigment as well. More specifically, for example, when forming a white base coating portion 500, titanium oxide can be used.

Furthermore, the paint for forming the transparent base coating portion 500 is not particularly limited, and existing paints can be used.
Specifically, for example, the same transparent paint as that used to form the overcoat (protective layer) described above can be used.
More specifically, it is possible to use paints such as epoxy/acrylic paints, epoxy/phenol paints, epoxy/urea paints, etc. The epoxy/acrylic paints are water-based paints, and therefore can reduce the environmental impact.

The transparent undercoat portion 500 may be formed using a paint different from the paint for the overcoat. In this case, a paint specialized for the undercoat portion 500 can be used.
Specifically, for example, it becomes possible to use a paint that is more suitable for processing in a Necker-Flanger (SDN). More specifically, for example, it becomes possible to use a paint having improved lubricity by increasing the amount of wax added to an existing paint.

In addition, when the color of the base coating portion 500 (first base coating portion 500A) of the narrowed diameter portion 11 and the color of the base coating portion 500 (second base coating portion 500B) of the can body portion 12 are made the same, the base coating portion 500 of the narrowed diameter portion 11 and the base coating portion 500 of the can body portion 12 may be formed simultaneously.
Specifically, for example, an upstream base coater (BC) may press a paint application roll member against the outer peripheral surface 19A of the can body over the entire axial area of the can body, thereby forming a common base coating portion 500 on both the reduced diameter portion 11 and the can body portion 12.
Further, the method for forming the undercoated portion 500 is not limited to the method using a roll member, and it may be formed by other methods such as inkjet printing.

Furthermore, when the color of the base coat portion 500 of the reduced diameter portion 11 is to be different from the color of the base coat portion 500 of the can body portion 12, it is preferable to form the light-colored base coat portion 500 before the dark-colored base coat portion 500 so as to reduce the effect of color mixing.
Specifically, for example, when forming a white basecoat portion 500 and a transparent basecoat portion 500, it is preferable to form the transparent basecoat portion 500 first, and then form the white basecoat portion 500.

More specifically, when forming a colored basecoat portion 500 and a transparent basecoat portion 500, as in the formation modes shown in Figures 13 (C) and (E), it is preferable to form the transparent basecoat portion 500 first and then form the colored basecoat portion 500.
Also, when forming basecoat portions 500 of different colors, as in the formation mode of Figure 13 (G), it is preferable to form the light-colored basecoat portion 500 first and then the dark-colored basecoat portion 500.

In addition, when forming the base coating portion 500 separately for the reduced diameter portion 11 and the can body portion 12, it is preferable to form the base coating portion 500 formed in the reduced diameter portion 11 and the base coating portion 500 formed in the can body portion 12 in an abutting state (without overlap and without gaps).
Incidentally, due to errors and the like, it is often difficult to form the base-coated portion 500 formed in the reduced diameter portion 11 and the base-coated portion 500 formed in the can body portion 12 in an abutting state. For this reason, for example, the base-coated portion 500 formed in the reduced diameter portion 11 and the base-coated portion 500 formed in the can body portion 12 may be formed so that these two base-coated portions 500 overlap each other.

The base coating portion 500 of the reduced diameter portion 11 and the base coating portion 500 of the can body portion 12 may be formed so that a gap is formed between the base coating portion 500 of the reduced diameter portion 11 and the base coating portion 500 of the can body portion 12. In other words, the first base coating portion 500A and the second base coating portion 500B may be provided apart from each other, and the first base coating portion 500A and the second base coating portion 500B may not overlap each other.
In this case, the protective layer (the overcoat layer formed on the image to protect the image) is placed in the gap between the first base-coated portion 500A and the second base-coated portion 500B, thereby suppressing corrosion of the can body caused by the base of the can body being exposed.

Furthermore, when the first base-coated portion 500A and the second base-coated portion 500B are overlapped, an overlapping portion is provided where the first base-coated portion 500A and the second base-coated portion 500B overlap.
This overlapping portion is preferably located closer to the bottom 14 than a connection point 18 (see FIG. 2 ) between the reduced diameter portion 11 and the can body 12. In this case, the possibility that this overlapping portion will enter a die for neck processing (a die used to form the reduced diameter portion 11 by a necker flanger (SDN)) is reduced, and the reduced diameter portion 11 can be formed more reliably.

If an overlapping portion is provided at the location where the reduced diameter portion 11 is to be formed, there is a risk that the opening 13 side of the can body 19 (see FIG. 2 ) will not fit inside the mold (the mold used to form the reduced diameter portion 11) due to the overlapping portion. In this case, it will be difficult to form the reduced diameter portion 11.
When the overlapping portion is located closer to the bottom 14 side than the connection portion 18, the opening 13 side of the can body 19 can be easily inserted into the mold, and the reduced diameter portion 11 can be formed more reliably.
The first base-coated portion 500A formed on the reduced diameter portion 11 and the second base-coated portion 500B formed on the can body portion 12 preferably have a thickness of 2 to 10 μm. As described above, the second base-coated portion 500B is preferably thicker than the first base-coated portion 500A.

14A to 14D are diagrams that show the state of the can body after processing by the printer (PR) shown in FIGS. 1 and 8.
14(A) to 14(D) show the state of the opening 13 (see FIG. 2) side of the can body. Also, 14(A) to 14(D) show only one side of the parts located on both sides of the can body with the axis of the can body in between.
Furthermore, in Figures 14(A) to (D), the thicknesses of the can body, the base layer, and the protective layer are shown as thicknesses different from their actual thicknesses.

In this embodiment, an image G is formed on the first base-coated portion 500A of the reduced diameter portion 11 and the second base-coated portion 500B of the can body portion 12 by a printer (PR).
Furthermore, in the printer (PR), paint is applied onto this image G (exterior painting is performed to form a transparent protective layer OL (overcoat layer)).

14(A) to 14(D), an image G is formed at least on the outer peripheral surface 19A of the can body 12, and further, a transparent protective layer OL is formed at least on the uppermost layer of the can body 12. In other words, the transparent protective layer OL is formed on the formed image G.
More specifically, in this embodiment, an image G is formed on the outer peripheral surface 19A of the can body using an inkjet head 300 (see FIG. 4 ). Next, a roll member that runs along the axial direction of the can body and holds paint on the outer peripheral surface is pressed against the outer peripheral surface 19A of the can body to form a transparent protective layer OL.

14A illustrates an example of a can body having a transparent first basecoat portion 500A and a colored second basecoat portion 500B, in which a color image G is formed on the second basecoat portion 500B (on the can body portion 12). Furthermore, a transparent protective layer OL is formed on this image G.
FIG. 14(B) illustrates an example in which a color image G is formed on the can body 12 of a can body having a single colored base coating portion 500, and further a transparent protective layer OL is formed thereon.

14(C) illustrates an example in which a color image G is formed on the can body 12 of a can body having only the first base coating portion 500A. Furthermore, a transparent protective layer OL is formed on this image G.
The first basecoated portion 500A in FIGS. 14(A) and 14(C) may be transparent or colored.
FIG. 14(D) illustrates an example in which a color image G is formed in the reduced diameter portion 11 and the can body portion 12 of a can body having a single colored base coating portion 500, and further a transparent protective layer OL is formed.

Here, the images G shown in Figures 14 (A) to (D) are all images G formed on the outer peripheral surface 19A of the can body after the narrowed portion 11 is formed, and can be regarded as images after the narrowed portion is formed. Also, the first base-coated portion 500A and the second base-coated portion 500B (portions where the paint has hardened to form a layer) can be regarded as layers before the narrowed portion is formed, which are layers formed on the surface of the outer peripheral surface 19A before the narrowed portion 11 is formed.

Here, when the image G is formed after the reduced diameter portion 11 is formed, the image G to be formed can be diversified.
Here, when the image G is formed before the narrowed portion 11 is formed, the die for forming the narrowed portion 11 is pressed against the formed image G, which may cause damage to the image G. This damage can be suppressed, for example, by increasing the strength of the image G, but in this case, restrictions are likely to occur on the types of images G that can be formed.
In contrast, in the case of forming the image G after forming the reduced diameter portion 11 as in the present embodiment, such restrictions are unlikely to arise, and the images G to be formed can be diversified.

The color of the protective layer OL is not particularly limited, but is generally colorless and transparent (clear). When the protective layer OL is colored, it is preferable that the protective layer OL is colored and transparent, and in this case, the image G below the protective layer OL can be seen through the protective layer OL.
Moreover, the protective layer OL may be made of a matte paint.
Forming the protective layer OL protects the image G. Also, the outer peripheral surface 19A of the can body is given lubricity, allowing the can body to move more smoothly on the production line.

Further, the protective layer OL can be formed not only on the can body portion 12 but also on the reduced diameter portion 11 as shown in FIG.
It is assumed that it may be difficult to press a roll member (a roll member for applying the coating material constituting the protective layer OL) against the reduced diameter portion 11. For this reason, the protective layer OL may be formed by applying the coating material to the reduced diameter portion 11 using, for example, an inkjet head.

Furthermore, image formation on the outer peripheral surface 19A of the can body is not limited to the can body portion 12, and may also be performed on the reduced diameter portion 11 as shown in FIG. 14(D).
Since the reduced diameter portion 11 is positioned away from the inkjet head 300 (see Figure 4), it is more difficult to form an image G on the reduced diameter portion 11 than on the can body portion 12. However, it is possible to form, for example, a band-shaped image along the circumferential direction of the can body.

Here, the protective layer OL (external surface coating) is not necessarily required for the portion where the image G is not formed. For example, as shown in Figures 14 (A) to (C), when the image G is not formed in the narrowing portion 11, the formation of the protective layer OL on the narrowing portion 11 may be omitted.
In addition, the exterior coating is not limited to being formed uniformly over the entire outer peripheral surface 19A of the can body, and the exterior coating applied to the narrowed diameter portion 11 and the exterior coating applied to the can body portion 12 may be different.

Furthermore, when applying exterior coating to the portion on which the image G is not formed, the exterior coating is not limited to being transparent, but may be opaque (colored).
As described above, the outer surface painting may be omitted for the portion where the image G is not formed. In addition, for the portion where the image G is not formed and where the base coating portion 500 is already formed, a layer that protects the base portion of the can body is substantially formed, so that the outer surface painting can be omitted.

As explained above, when the first base coating section 500A and the second base coating section 500B are provided apart from each other and do not overlap, it is preferable to apply exterior coating to the gap formed between the two. This prevents the base of the can body from being exposed in the area located between the first base coating section 500A and the second base coating section 500B.

11...reduced diameter portion, 12...can body, 13...opening, 14...bottom, 19...can body, 19A...outer periphery, 19B...other end, 19C...one end, 500...undercoat portion, 500A...first undercoat portion, 500B...second undercoat portion, G...image

Claims (3)

a diameter reducing process for reducing the diameter of one end of an empty can body formed in a cylindrical shape and having an opening at one end and a bottom at the other end, to produce an empty can body having a reduced diameter portion provided at the one end and having an outer diameter that becomes smaller toward the opening, and a can body portion located on the bottom side of the reduced diameter portion;
a paint application process in which, before the diameter is reduced in the diameter reduction process, a chromatic paint is applied to an outer peripheral surface of a portion of the empty can body that will become the reduced diameter portion, and a white paint is applied to an outer peripheral surface of a portion of the empty can body that will become the can body portion;
an image forming step of forming an image on an outer peripheral surface of the empty can body having the reduced diameter portion that has been reduced in the diameter reducing step;
A method for manufacturing a beverage can , comprising:
In the paint application step,
a chromatic paint is applied to a portion of the outer peripheral surface of the empty can body that is located closer to the opening than a connection point between the portion that will become the reduced diameter portion and the portion that will become the can body, and a chromatic paint is not applied to a portion that is located closer to the bottom than the connection point.
A method for manufacturing beverage cans . a diameter reducing process for reducing the diameter of one end of an empty can body formed in a cylindrical shape and having an opening at one end and a bottom at the other end, to produce an empty can body having a reduced diameter portion provided at the one end and having an outer diameter that becomes smaller toward the opening, and a can body portion located on the bottom side of the reduced diameter portion;
a paint application process in which, before the diameter is reduced in the diameter reduction process, a chromatic paint is applied to an outer peripheral surface of a portion of the empty can body that will become the reduced diameter portion, and a white paint is applied to an outer peripheral surface of a portion of the empty can body that will become the can body portion;
an image forming step of forming an image on an outer peripheral surface of the empty can body having the reduced diameter portion that has been reduced in the diameter reducing step;
Equipped with
In the image forming step, an image is formed on an outer peripheral surface of the can body of the empty can body having the reduced diameter portion, and an image is not formed on an outer peripheral surface of the reduced diameter portion of the empty can body having the reduced diameter portion,
In the empty can body after the image is formed in the image forming process, a user can visually recognize a chromatic image made of the chromatic paint that is attached to the outer peripheral surface of the portion that will become the reduced diameter portion before the diameter reduction is performed in the diameter reduction process.
A method for manufacturing beverage cans. In the image forming step, an image is formed on an outer peripheral surface of the empty can body using an inkjet head that extends along the axial direction of the empty can body and is arranged so as to face both the reduced diameter portion and the can body portion of the empty can body, and when forming an image on the outer peripheral surface, an image is formed on the outer peripheral surface of the can body portion and an image is not formed on the outer peripheral surface of the reduced diameter portion.
A method for producing a beverage can according to claim 1 or 2 .

Images