JP2002240815A - Light-weight two-piece container and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a weight of a container itself wherein a bottom of a two- piece container represented by a DI can is thinned without losing pressure- resistant strength. SOLUTION: The two-piece can is characterized by a fact that a ratio t1/t2 of a thickness t1 at the center of a can bottom and a thickness t2 at a rim of the can bottom is 0.70 or more to 0.95 or less. The method of manufacturing uses a spherical head punch whose overhang radius is 1.15 times or more to four times or less in a first drawing process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a two-piece beverage container represented by a DI can and a method for producing the same.

[0002]

2. Description of the Related Art A two-piece can having a can body and a three-piece can with a lid attached to both sides of the can body and a two-piece can having a can body and a can bottom integrated together. There is something called. After squeezing and re-drawing 2-piece cans,
Ironing is performed while the side wall is being ironed or drawn, and forming is performed so that the can body thickness is reduced and the can height is secured. In the case of reducing the weight of a container manufactured by using this method, it is possible to increase the ironing rate, but if the wall of the can is too thin, the strength of the can becomes weak, and the container cannot be put to practical use. At present, the thickness of the can wall is about 0.08 mm, which is considered to have reached the limit thickness.

Therefore, in order to reduce the weight of the can, it is necessary to make the bottom of the can thin. To make the can bottom thinner, it is possible to cope with it by making the blank before molding thinner. However, if the can bottom is made too thin, the pressure resistance of the can bottom becomes insufficient, which is also unsuitable for practical use. To overcome this situation,
Japanese Patent Application Laid-Open No. 7-232230 discloses a method in which a portion corresponding to the can bottom is subjected to overhanging treatment and cured to ensure pressure resistance even when the can bottom is thinned.

[0004]

SUMMARY OF THE INVENTION The above-mentioned JP-A-7-23
When the technique disclosed in Japanese Patent No. 2230 was used, the thickness of the can bottom was excessively reduced, and although the material was work-hardened, the pressure resistance of the can bottom could not be sufficiently secured. In view of such circumstances, an object of the present invention is to provide a two-piece container that efficiently controls the thickness of the can bottom and achieves both a pressure resistance and a thinner thickness of the can bottom, and a method for manufacturing the same.

[0005]

Means for Solving the Problems The present inventors have conducted basic studies to solve the above problems. as a result,
It has been found that by making the punch shape appropriate, the thickness of the can bottom can be reduced without impairing the pressure resistance of the can bottom. That is, the gist of the present invention is as follows. (1) The ratio t ₁ / t ₂ of the thickness t _{1 at the} center of the can bottom to the thickness t ₂ at the end of the can bottom is 0.70 or more and 0.95 or less. Lightweight two-piece container. (2) In the production of two-piece containers, flared diameter in the first drawing step is used spherical head punch or less and 4 times 1.15 times the punch radius, can bottom center of the plate thickness t ₁ and the can A method for producing a lightweight two-piece container, characterized in that a ratio t ₁ / t ₂ of a plate thickness t ₂ of the bottom end portion is 0.70 or more and 0.95 or less.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The reason why the ratio of the plate thickness at the center of the can bottom to the plate thickness at the end of the can bottom, which is a feature of the present invention, will be described. One of the important characteristics of the two-piece container is that it is important that the container does not deform even when the inside of the container becomes high pressure. In this case, the bottom of the can is most easily deformed. When the pressure inside the container increases, the bottom of the can is deformed when the pressure reaches a certain value, and this critical pressure is usually called pressure resistance. The pressure resistance is affected by the thickness of the bottom of the can, particularly the thickness of the bottom of the can near the body.

Therefore, in order to reduce the weight of the container by reducing the thickness of the bottom of the can, it is important that only the portion near the center of the can bottom be thinned and the portion near the body is not too thin. Also, by suppressing the thickness reduction in the area near the can body, if only the center of the can bottom is thinned, if the center of the can bottom is extremely thinned, the strength of this part will be too low and the pressure resistance will also be secured. I'm falling into a situation where I can't. The standard of the pressure resistance differs depending on the contents.

As a result of a detailed study on this point, the inventors of the present invention have found that the thickness distribution of the can bottom portion is defined as t _{1 where the} thickness of the can bottom center portion 3 shown in FIG. the thickness is taken as t _2, the ratio t ₁ / t ₂ of the plate thickness was found that the strength of the can bottom center 3 becomes less than 0.70 too weak.
That is, FIG. 1 is a sectional view of a can shape showing the thickness distribution of the can bottom portion according to the present invention, FIG. 1 (a) is a sectional view after first-stage drawing, and FIG. 1 (b) is a final can shape. FIG.
As shown in this figure, in the present invention, this ratio needs to be 0.95 or less in order to obtain the effect of can weight reduction. That is, the plate thickness ratio t ₁ / t _{2 is set} to 0.70 or more and 0.95 or less. In order to further exert the above effects, it is desirable that t ₁ / t ₂ be 0.80 or more and 0.92 or less. The end of the can bottom is the can body wall 1 at the bottom of the can.
From the center to the center of the can bottom was defined as the average thickness of the portion of 0.5 to 1 mm.

Next, the molding method will be described. In order to produce a two-piece container by the DI molding method, cup molding is usually performed by two-stage drawing. In this cup molding, a flat-bottomed cylindrical punch is usually used, but the can bottom can be made thinner by using a ball head instead of a flat in the first step. Here, if the ball head is a hemisphere, the plate thickness at the bottom of the can becomes too thin. As a result of examination on this point, it is found that the shape of the present invention can be obtained by using a ball-head punch whose punch overhang diameter R1 is 1.15 times or more and 4 times or less the punch radius Rp as shown in FIG. Was. That is, FIG. 2 is a view showing a ball-head punch according to the present invention. Reference numeral 4 denotes a punch.

Further, the overhang diameter R1 does not need to be a fixed value, and there is no problem even if the diameter in the range of the present invention is continuous. Note that the shoulder R2 between the punch overhanging portion and the punch wall is not particularly defined in the present invention. The present invention is applicable not only to DI cans but also to containers manufactured by a manufacturing method in combination with a stretch draw.

In the present invention, a sufficient effect can be obtained by using a normal steel plate for cans. In this case, however, the surface treatment of the material or the application of the resin to the surface need not be particularly specified, and any material can be used. Can be applied, and sufficient effects can be obtained. The steel plate used is not particularly limited. A steel plate for a Sn plating can having a normal temper degree can be used. The sheet thickness is not particularly limited, but any steel sheet having a thickness of 0.19 mm or more that is commonly used can be used as a can after molding according to the present invention, and the light weight effect is sufficiently exhibited. .

[0012]

EXAMPLE A normal steel plate for a Sn plating can (sheet thickness 0.19 m)
m), cup first molding was performed with a punch having the shape shown in Table 1, and thereafter DI molding was performed in a usual process. The temper degree of the material is T4-CA. Table 1 also shows the thickness ratio of the bottom of the can and the pressure resistance at that time. As described above, the required pressure-resistant strength varies depending on the content, but here, 6.5 kgf / cm ² was used as a reference, and a value higher than 6.5 kgf / cm ² was accepted and a value less than that was rejected. Numbers 1 to 8 in Table 1
Is within the range of the conditions of the present invention, and satisfies the pressure resistance and can achieve weight reduction. On the other hand, although the pressure resistance of No. 9 is satisfactory, the thickness ratio of the center of the can bottom and the end of the can bottom is out of the range of the present invention, and the weight is hardly reduced.
In No. 10, the plate thickness ratio is within the range of the present invention, and although the weight is reduced, the pressure resistance is insufficient, and both are out of the range of the present invention.

[0013]

[Table 1]

[0014]

As described above, according to the present invention, a two-piece container can be efficiently obtained, which has an extremely large industrial effect.

[Brief description of the drawings]

FIG. 1 is a sectional view of a can shape showing a thickness distribution of a can bottom portion according to the present invention.

FIG. 2 is a view showing a ball head punch according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 can body wall 2 can bottom end 3 can bottom center 4 punch R1 punch overhang radius R2 shoulder diameter between punch overhang and can wall

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hirokazu Yokoya 1-1-1 Tobata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka New Nippon Steel Corporation Yawata Works F-term (reference) 3E033 AA07 BA08 CA20 DD05 FA01

Claims (2)

[Claims] 1. Plate thickness t _{1 at the} center of the can bottom and plate thickness at the end of the can bottom
The ratio t of the thickness of t _{2 1} / t ₂ is 0.70 or more and 0.95
A lightweight two-piece container characterized by the following: 2. In manufacturing a two-piece container, a ball-thickness punch having an overhang diameter of 1.15 times or more and 4 times or less the punch radius in the first drawing step is used, and a plate thickness t _{1 at the} center of the can bottom. And the ratio t ₁ / t _{2 of the} thickness of the can bottom end to the thickness t ₂ ,
A method for producing a lightweight two-piece container, which is not less than 0.70 and not more than 0.95.