JP7259892B2 - Can body manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a bottle-shaped can body.

As for the bottle-shaped can body, containers with a screw cap having a screw-formed opening are widely used. Such a bottle-shaped can body is produced by punching a raw plate made of a material such as an aluminum alloy into a circular shape, drawing it to obtain a cylindrical cup-shaped body with a bottom, and further drawing and ironing it. After processing (DI molding) to obtain a bottomed cylindrical can body, a tapered shoulder portion and a cylindrical mouth portion (or neck portion) are formed in a necking process. After that, the mouth portion is threaded, and if necessary, a further necking process is performed, and the tip portion is curled.

In the necking process described above, a plurality of dies (neck-in dies) are used, and diameter-reducing drawing (necking) is performed in stages. The mold consists of a core part (center ring) arranged inside the opening of the bottomed cylindrical can body, and a cylindrical mold into which the opening of the bottomed cylindrical can body is inserted. and an outer part (drawing die or insert) that Then, in the process of moving forward along the can axis with respect to the bottomed cylindrical can body, the drawn surface formed on the inner peripheral surface of the tip of the outer child part is moved to the outer peripheral surface of the bottomed cylindrical can body. The core portion is pressed radially inward while being in sliding contact, and the outer peripheral surface of the core portion supports the pressed inner peripheral surface of the opening portion, whereby the diameter reduction drawing of the opening portion is performed. Reference 1).

In addition, in order to provide a threaded metal can with improved strength at the top of the mouth and the shoulder, at least one or more threads are provided around the top of the tapered shoulder that gradually widens in the radial direction from the bottom of the threaded portion of the mouth. There has been proposed a threaded metal can having an inwardly curved smooth recess and at least one or more outwardly curved smooth protrusions (see Patent Document 2 below).

JP 2006-150426 A JP-A-2001-213416

Conventionally, a curved surface with a curvature radius of 8 to 10 mm is formed on the drawing surface of the inner peripheral surface of the tip of the outer child part in the die for performing diameter reduction drawing as exemplified in the above-mentioned Patent Document 1. It enables smooth diameter reduction drawing of the opening with suppressed wrinkles. When such a mold is used to form a tapered shoulder portion, the joint portion (neck) between the shoulder portion and the mouth portion formed in the final stage has a curvature in the cross section along the can axis. An R portion with a radius of 7 to 8 mm is formed.

In the capping process, a bottle-shaped can body that has undergone screw processing or curling processing on the mouth portion that has been diameter-reduced and drawn is used when roll-on forming a cap with a bridge on the screw of the mouth portion in the capping process. It has been confirmed that depending on the molding conditions, deformation of the mouth portion occurs due to insufficient deformation resistance, and bridge breakage is likely to occur.

On the other hand, the threaded metal can in which the strength of the upper end of the mouth portion and the shoulder portion of Patent Document 2 is improved is thought to be imparted with resistance to deformation of the mouth portion. Forming a concave portion that curves and a convex portion that curves outward increases the number of processes, the amount of pressing, and the molding load, which causes damage to the outer varnish and inner coating of the can body, dents, buckling, etc. There is fear.

The present invention has been proposed to address such problems. In other words, in a bottle-shaped can body with a threaded mouth that has undergone a diameter reduction drawing process in the necking process, when a cap with a bridge is roll-on molded to the mouth, deformation of the mouth due to insufficient deformation resistance may occur. The problem is to suppress the occurrence of bridge disconnection.

In addition, in order to roll-on a cap with a bridge to the mouth of a metal can, it prevents damage, dents, buckling, etc. to the outer varnish and inner paint of the can body when imparting deformation resistance to the mouth of the metal can. The task is to manufacture can bodies.

The method for manufacturing a can body according to the present invention solves the problem by providing the following configuration.
A method for manufacturing a bottle-shaped can body, comprising forming a shoulder portion and a mouth portion by a necking step, and then performing a mouth portion necking step for forming a diameter-reducing step in the mouth portion; A reforming step is performed in which a reforming molding surface is pressed against the R portion connecting the shoulder portion and the mouth portion to reduce the curvature radius of the R portion in a cross section along the can axial direction. A manufacturing method for a can body.
In addition, aside from reducing the number of steps, the method for manufacturing a can body according to the present invention solves the problem by providing the following configuration.
In a method for manufacturing a bottle-shaped can body, after molding a shoulder portion and a mouth portion by a necking process, a reform molding surface is pressed against an R portion connecting the shoulder portion and the mouth portion, thereby 1. A method for manufacturing a can body, characterized by performing a reforming step to reduce the radius of curvature in a cross section of the R portion along the can axis direction.

According to the can body of the present invention, it is possible to suppress the occurrence of bridge breakage when the cap with the bridge is roll-on-molded to the mouth portion.

In the present invention, in a bottle-shaped can body in which the neck portion is subjected to threading or the like after diameter reduction drawing in the necking process, various causes of bridge breakage that occur when a cap with a bridge is roll-on-molded to the mouth portion are investigated. As a result of investigation, the present inventors have found that the cause is the deformation of the opening due to the skirt roll load during roll-on molding of the cap, leading to the completion of the invention.

That is, conventionally, in the state of the connecting curved surface of the shoulder portion and the mouth portion of the can formed in the final stage of the necking process, the mouth portion is easily deformed into an elliptical shape by the skirt roll load during roll-on molding of the cap. It is thought that if the opening is elliptically deformed during roll-on molding of the cap, a tensile load in the circumferential direction is applied to the side surface of the cap on the long diameter side of the deformed state, and this tends to cause bridge breakage. Based on this hypothesis, reform molding was carried out so that the radius of curvature r1 of the R portion connecting the shoulder and mouth of the can body was within a predetermined range (2 to 6 mm, preferably 3 to 5 mm). It was confirmed that the deformation resistance was enhanced and the probability of occurrence of bridge breakage was significantly reduced.

The method for manufacturing a can body according to the present invention includes a neck necking step for forming a diameter-reducing step that defines the forming range of a bead portion, a skirt portion, a screw portion, and a curl portion, and at the same time, a can body that enhances the deformation resistance of the mouth portion. Reform molding is performed to reduce the curvature radius of the R portion connecting the shoulder portion and the mouth portion. As a result, the number of processes can be reduced, the amount of pressing and the forming load can be reduced, and damage, dents, buckling, etc. to the outer surface varnish and inner surface paint of the can body can be prevented.

The can body manufactured by the method for manufacturing a can body of the present invention can be the following can body.
(Can body 1)
A bottle-shaped can body comprising a shoulder portion tapered from a body portion and a mouth portion extending from the shoulder portion along the can axis direction, and a can shaft connecting the shoulder portion and the mouth portion. A can body characterized by having an R portion having a curvature radius r1 of 2 to 6 mm in a cross section along a direction.
(Can body 2)
A can body 1, characterized in that the radius of curvature r1 is 3 to 5 mm.
(Can body 3)
A can body 1 or 2 characterized in that a mouth portion above the R portion has a bead portion, a skirt portion, a screw portion, and a curl portion in this order.

It is a sectional view showing the important section of the can concerning the embodiment of the present invention. FIG. 4 is an explanatory view showing a necking process for forming a shoulder portion and a mouth portion ((a) to (d) show the procedure of one processing step); FIG. 4 is an explanatory diagram showing a molding state in a necking process for molding a shoulder portion and a mouth portion ((a) is an enlarged view of A portion in FIG. 2, and (b) is an enlarged view of B portion in FIG. 2). . FIG. 3 is an explanatory view showing the mouth necking process and the reforming process ((a) shows the mouth necking process and the reforming process in the first stage, and (b) shows the mouth necking process and the reforming process in the second stage); .). FIG. 5 is an enlarged view of a C portion in FIG. 4; FIG. 10 is an explanatory view showing another embodiment of the mouth necking process and the reforming process ((a) is the mouth necking process and the reforming process in the first stage; (b) is the mouth necking process and the reforming process in the second stage); ). 7 is an enlarged view of a D portion in FIG. 6. FIG.

Embodiments of the present invention will be described below with reference to the drawings. Hereinafter, the same reference numerals in different figures denote portions having the same function, and duplication of description in each figure will be omitted as appropriate.

As shown in FIG. 1, a can body 1 according to an embodiment of the present invention is a bottle-shaped metal can having a body portion 1A, a shoulder portion 1B, and a mouth portion 1C. The mouth portion 1C is formed by diameter reduction in a tapered shape by diameter drawing, and the mouth portion 1C extends along the can axis P, and includes a bead portion 2, a skirt portion 3, a screw portion 4, and a curl portion 5 in order from the bottom. is formed. The shoulder portion 1B is tapered without a recess and has a set taper angle (neck shoulder angle) θ.

An R portion 6 is formed at the connection (neck) between the shoulder portion 1B and the mouth portion 1C of the can body 1 . The R portion 6 connects the shoulder portion 1A and the mouth portion 1C with a curved surface having a set curvature radius r1. ).

A necking process for forming the shoulder portion 1B and the mouth portion 1C will be described with reference to FIG. In this necking process, the core portion 10 of the mold is inserted inside the open end 1D of the can body 1, and the outer core portion 11 is brought into sliding contact with the outer peripheral surface of the can body 1 from the outside thereof. , diameter reduction drawing is performed.

(a) to (d) of FIG. 2 show one working step of the diameter reduction drawing that is performed multiple times with different dies. As shown in (a), the mold comprising the core portion 10 and the outer child portion 11 is mounted on the can axis while the open end 1D of the can body 1 faces the drawing surface 11A of the outer child portion 11 of the mold. As shown in (b), the core portion 10 is moved to the inside of the can body 1 first, and the squeezed surface 11A of the outer child portion 11 is brought to the open end 1D of the can body 1. Then, as shown in (c) and (d), the outer element portion 11 is further moved in the can axis P direction, whereby the drawing surface 11A of the outer element portion 11 is subjected to diameter reduction drawing.

At this time, as shown in FIG. 3A, the squeezing surface 11A forms the opening 1C along the squeezing surface 11A. As shown in (b), an R portion 6 similar to the curved surface of the drawing surface 11A is formed at the joint (neck) between the shoulder portion 1B and the mouth portion 1C. At this time, if the curvature radius R0 of the diaphragm surface 11A is 8 to 10 mm, the curvature radius Rs of the R portion 6 connecting the shoulder portion 1B and the mouth portion 1C is 7 to 8 mm.

Then, after forming the shoulder portion 1B by a plurality of times (for example, 21 times) of diameter reduction drawing, as shown in FIG. According to B), the shoulder portion 1B is not formed, and the mouth portion 1C is subjected to a mouth portion necking step in which stepwise diameter reduction drawing is performed. 1C1 and 1C2 are formed. By forming the diameter-reducing steps 1C1 and 1C2 in the mouth portion 1C in this manner, the section modulus is improved by the steps, and the resistance to deformation against the compressive load from the side can be enhanced. This also prevents deformation of the opening 1C during roll-on molding of the cap.

In the case where two steps of diameter reduction steps 1C1 and 1C2 are formed in the mouth portion 1C, the skirt portion 3 and the bead portion 2 formed in subsequent processes are formed by the R portion after reforming described later and the lower diameter reduction steps. 1C1, and the screw portion 4 is formed between the steps of the two diameter-reducing steps 1C1 and 1C2, or between the skirt portion 3 and the diameter-reducing step 1C2. By forming the bead portion 2, the skirt portion 3 and the screw portion 4 separately for each step in this manner, the strength of the mouth portion after forming each portion can be increased.

Simultaneously with the neck necking step described above, the reform ring 12 is used to perform reform molding to reduce the radius of curvature Rs of the R portion 6 connecting the shoulder portion 1B and the mouth portion 1C. In the reform molding, the reform ring 12 is connected to the outer child part 11 , the reform ring 12 is moved together with the outer child part 11 , and the reform molding surface 12 A of the reform ring 12 is pressed against the R part 6 . As a result, as shown in FIG. 5, the curvature radius r1 of the R portion 6 connecting the shoulder portion 1B and the mouth portion 1C can be made small according to the curvature radius R01 of the reform molding surface 12A. Specifically, by setting the curvature radius R01 of the reform molding surface 12A to 0.5 to 1.0 mm, the curvature radius r1 of the R portion 6 can be molded to 2 to 6 mm. The final radius of curvature r1 of the R portion 6 can be appropriately adjusted by the pushing amount of the reform ring 12 .

In the example shown in FIG. 4, in the process shown in FIG. In the process shown in b), the reforming process of the second stage is performed by the reforming ring 12 connected to the second outer element part 11(B). In this way, by performing the reforming process step by step, smooth reforming molding becomes possible. Reform molding can also be performed.

6 and 7 show another embodiment of the mouth necking and reforming steps. In this example, the inner peripheral surfaces of the tips of the first outer element part 11 (C) and the second outer element part 11 (D) have a reform molding surface 12A, and the reform ring 12 described above is attached to the outer element part. 11 and integrated. The reform molding surface 12A has a gap with respect to the outer peripheral surface of the core portion 10. As shown in FIG. Also in this example, as shown in FIG. 7, the radius of curvature R01 of the reform molding surface 12A is formed to be about 0.5 to 1.0 mm.

As shown in FIGS. 6(a) and 6(b), when a two-stage reforming process is performed, the first outer element portion 11(C) has a diameter-reducing aperture of the mouth portion 1C on its inner peripheral surface. A drawing surface for processing is formed, and the second outer child part 11 (D) is separated from the reform molding surface 12A so as to release the stepped part 1C1 formed by the first stage diameter reduction drawing. A diaphragm surface is formed at the position Also in this example, one of the two steps of the reforming process can be omitted, and the reforming can be performed by one molding.
Either the first outer element part 11 (C) or the second outer element part 11 (D) shown in FIG. You may make it reform-molding by .

As described above, the can body 1 according to the embodiment of the present invention is reformed to reduce the curvature radius Rs of the R portion connecting the shoulder portion and the mouth portion at the same time as the mouth portion necking process, so that the number of processes is reduced. In addition, the pressing amount and the forming load are reduced, and damage to the outer surface varnish and inner surface paint of the can body 1, dents, buckling, and the like are prevented.

[Example]
<Production of bottle-shaped can body>
Using an aluminum metal plate, a can body is created by drawing and ironing, and the opening end of the can body is subjected to a diameter reduction drawing process, and the tapered shoulder portion extends along the can axis. formed a closed mouth. Next, the mouth portion is subjected to two-stage diameter reduction drawing (neck necking process) to form a two-stage diameter reduction step. was reform-molded into an R portion having a curvature radius r1 shown in Table 1. After that, the bead portion and the skirt portion were sequentially formed between the R portion and the lower diameter-reducing step, the screw portion was formed between the two-step diameter-reducing steps, and the curled portion was formed at the tip of the mouth portion.
The reform molding was performed for 100 cans each.

<Bottle-shaped can body>
Can body outer diameter: 62.20 mm, can body thickness: 0.135 mm, can body height: 132.60 mm, mouth outer diameter: 33.45 mm, screw thickness: 0.34 mm, shoulder upper end thickness Thickness: 0.33 mm, Thickness at lower end of shoulder: 0.21 mm, Taper angle of shoulder: 28 degrees, Curvature radius of connection between shoulder and mouth: Rs: 7 mm, r1: Table 1, n: 100 each can

<Evaluation>
These bottle-shaped can bodies were evaluated as follows. Table 1 shows the results.
[broken bridge]
An aluminum cap was roll-on-molded onto the screw portion of the mouth portion of the bottle-shaped can body described above by pressing the skirt portion with a skirt roll load of 111N. Occurrence of bridge breakage (the number of cans) per 100 cans at this time was visually confirmed.

As a result, by setting the curvature radius r1 of the R portion after reform molding to 2 to 6 mm, it is possible to obtain sufficient deformation resistance against roll-on molding of the cap, and the occurrence of bridge breakage is suppressed. It turns out that
When the radius of curvature r1 of the R portion after reforming is less than 2 mm, the radius of curvature R01 of the reforming surface of the reforming ring must be less than 0.5 mm. There is concern about scraping.
On the other hand, if the radius of curvature r1 of the R portion after reform molding exceeds 6 mm, the resistance to deformation decreases and bridge breakage occurs. Therefore, it is particularly preferable that the curvature radius r1 of the R portion after reform molding is 3 to 5 mm.

Although the embodiments of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments, and design modifications and the like are made within the scope of the present invention. is included in the present invention. In addition, each of the above-described embodiments can be combined by utilizing each other's techniques unless there is a particular contradiction or problem in the purpose, configuration, or the like.

1: can body, 1A: trunk, 1B: shoulder, 1C: mouth,
2: bead portion, 3: skirt portion 3, 4: screw portion, 5: curl portion, 6: R portion,
10: Core part, 11: Outer part,
12: Reform ring, 12A: Reform molding surface,
P: can axis

Claims (5)

A method for manufacturing a bottle-shaped can body, comprising:
After forming the shoulder and mouth by the necking process, a mouth necking process is performed to form a diameter-reducing step in the mouth. A method for manufacturing a can body, characterized by performing a reforming step of forming a smaller radius of curvature in a cross section along the can axis direction of the R portion by pressing a reforming molding surface against the R portion.
A method for manufacturing a bottle-shaped can body, comprising:
After forming the shoulder and the mouth by the necking process, the reform molding surface is pressed against the R section connecting the shoulder and the mouth. A method for manufacturing a can body, characterized by performing a reforming process to form a small radius of curvature.

3. The method for manufacturing a can body according to claim 1, wherein the radius of curvature R01 of the reform molding surface is 0.5 to 1.0 mm.
2. The method of manufacturing a can body according to claim 1, wherein, in said mouth portion necking step, two steps of diameter reduction are formed in said mouth portion.
A skirt portion and a bead portion are formed between the R portion and the lower diameter-reducing step of the two-step diameter-reducing step, and a screw portion is formed between the steps of the diameter-reducing step. The manufacturing method of the can body described in Claim 4 .

Images