JPH0472134A - Aluminum can - Google Patents

Abstract

PURPOSE:To increase buckling strength of an drawn portion by connecting a convex arc section adjacent to a cylindrical section of a can and a concave section adjacent to an earth contact section to a straight segment section extending tangentially to both the sections. CONSTITUTION:A drawn section 20 comprises a convex arc section 21 being a part of a circle C1 in tangential contact with a cylindrical section of a can 1, in a section including an axis O of the can, a concave arc section 22 being a part of a circle C2 in tangential contact with an earth contact section 5 of the can 1, and a straight segment section 23 having a specified length L tangent to the section 21,22 at points P2 and P3 respectively, extending in the direction of a common tangential line (l). When an angle of inclination theta between the section 23 and a plane S normal to the axis 0 is less than 29 deg., the thickness of section 23 becomes insufficient and hence buckling strength of a drawn section 9 is not sufficient against an axial load F exerted on a neck section 3. Consequently, even when width or height of the drawn section has been determined, by comparatively freely determining radius of curvature of each of the arc sections, the thickness of the drawn section in the axial direction of can is increased to increase the buckling strength of the drawn section, while preventing surface area of the cylindrical section or the inner volume of the can from decreasing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an aluminum can, and more particularly to an aluminum can having a structure that increases the buckling strength of a constricted portion formed on the outer periphery of the can bottom.

BACKGROUND ART In recent years, in the field of beverage cans, for example, as shown in FIG. An aluminum can having a so-called two-piece structure is used, in which a neck portion 3 whose diameter gradually decreases toward the outside in the axial direction of the aluminum can is formed, and a can lid 4 is fixed to the tip of the neck portion 3.

Here, the can bottom l includes a grounding part 5 annularly protruding from the can bottom 1, a counter part 6 connected to the inner circumferential side of the grounding part 5 and inclined toward the center of the can, and this counter part 6. The device is composed of a dome portion 7 that is continuous and recesses into the inside of the can in a substantially hemispherical shape. A constricted portion 9 is formed whose diameter gradually decreases as it goes outward. This aperture part 9
As shown in FIG. 5, in a cross-sectional view including the axis O of the can body 2, a convex arc part ■0 that curves while drawing a circular arc that contacts the can body 8 and contacts the grounding part 5 of the can bottom l. It is composed of a concave circular arc portion 11 that curves while drawing a circular arc, and the radius of curvature R3, R2 of each of these circular arc portions 10.11 and the can body 8.
Width W from to the center of the grounding part 5 (= (D-d)/2
, however, D (outer diameter of the can, d (diameter of the grounding part 5)) are carefully set in consideration of the performance required of the constricted part 9.

That is, the performance required of the drawing part 9 is that it has a strength that does not easily buckle against the axial load F that occurs when forming a can or when wrapping a can lid onto a can body. The can should not be easily deformed when dropped or when internal pressure is applied to the can, the formability should be good with no burrs etc. occurring during the forming of the can, and the can should be axially The shape of the can does not cause problems when insects inhabit the can, the surface area of the can body 8 is not unnecessarily reduced, and the shape does not result in insufficient printing area for trademarks, etc. printed on the can body 8, and the internal volume of the can. The optimum value is determined by integrating all of these required performances.

[Problems to be Solved by the Invention] Incidentally, in the above-mentioned aluminum cans, in recent years,
From the perspective of saving materials and reducing the weight of cans, improvements have been made in the direction of reducing the thickness of the aluminum plate used as the material. was used, but recently 0
．． Thinner than 32mm are now being used.

However, reducing the thickness of the material also poses the problem of reducing the pressure resistance of the can bottom. Therefore, in order to eliminate such drawbacks, the shape of the can bottom 1 was also improved, specifically, the diameter d of the ground contact portion 5 (hereinafter referred to as the ground contact diameter d
It is called. ), thereby improving the pressure resistance of the dome portion 7 and the counter portion 6, thereby improving the strength of the can bottom l.

However, when the ground contact diameter d is set small, the width W of the constricted portion 9 increases, and as a result, the buckling strength of the constricted portion 9 against the axial load F decreases, causing the constricted portion 9 to buckle. A new drawback has arisen: the frequency of bending increases.

That is, the above-mentioned axial load F is, when forming the neck portion 3,
Alternatively, the buckling strength of the can against the axial load F, which occurs when the can lid 4 is tightened around the can body 2, is related to the part where the wall thickness is the thinnest in the axial direction of the can. . However, in the aperture section 9, each arcuate section 1o
, 11, the wall thickness in the axial direction of the can is close to the thickness of the material, so the buckling strength is particularly low among all parts of the can body 2, and therefore buckling occurs at the constricted part 9. This makes it more likely to occur.

Here, in order to improve the strength against buckling of the constricted part 9, the thickness of the constricted part 9 in the can axis direction is increased;
In other words, the inclination angle 0 of the common tangent Q at the contact point P1 of each arcuate portion 1o, 11 with respect to the plane S perpendicular to the can axis O may be increased. For this purpose, it is effective to increase the radius of curvature R1 of the convex arc part 1o while keeping the radius of curvature R7 of the concave arc part 11 the same, as shown by the two-dot chain line in FIG. 5, for example. In the case of bending, the height H of the constricted part 9 in the can axial direction increases and at the same time the inner wall of the constricted part 9 recedes greatly into the can, resulting in a significant reduction in the surface area of the can body 8. This is not an effective solution because it causes a decrease in can volume.

The present invention was made against this background, and provides an aluminum can having a structure that can improve the buckling strength of the constricted portion while preventing an excessive reduction in the surface area and internal volume of the can body. The purpose is to provide.

[Means for Solving the Problems] In order to solve the above problems, the aluminum can of the present invention has a constriction part formed at the intersection of the grounding part of the can bottom and the can body of the can body, or In a cross-sectional view including the axis of the can body, a convex arc portion drawing a convex arc in contact with the can body, a concave arc portion drawing a concave arc in contact with the grounding portion, and a common tangent of these convex arc portions and the concave arc portion. It is made up of a straight section extending in the direction.

Here, in a cross-sectional view of the can bottom including the axis of the can body, the angle formed by the straight portion with respect to a plane perpendicular to the axis of the can body may be determined as appropriate depending on the outer diameter of the can body, etc. However, it is preferably 29° or more.

[Operation] According to the above configuration, the convex arc portion and the concave arc portion of the aperture portion do not touch each other and are connected via the straight line portion extending in the common tangential direction, so that the radius of curvature of each arc portion is It can be arbitrarily set within a wider range than in the conventional example described above. In other words, in the conventional example described above, once the radius of curvature of one arc part and the width and height of the aperture part are determined, the radius of curvature of the other arc part needs to draw an arc that is tangent to the other arc part. Either the radius of curvature of each arc can be determined almost uniquely, or the radius of curvature of each arc can be relatively freely determined even if the width, height, etc. of the aperture part are fixed, since the arc parts do not have to touch each other in the above configuration. I can do it.

Furthermore, the angle of inclination of the straight portion with respect to the plane orthogonal to the can axis can be varied by changing the radius of curvature of each of the arcuate portions, so that the angle of inclination of the straight portion can be made larger than before. By determining the radius of curvature of each arcuate part so that the height of the constricted part does not change, the wall thickness of the constricted part in the can axis direction is increased while preventing a decrease in the surface area of the can body and the internal volume of the can. As a result, the buckling strength of the constricted portion can be improved.

[Example] Hereinafter, an example of the present invention will be described with reference to FIGS. 1 and 2. Note that this embodiment is based on the above-mentioned FIGS. 4 and 5.
Since the shape of the constricted portion 9 of the can bottom 1 has been changed compared to the conventional aluminum can shown in the figure, the same components as in the conventional example are given the same reference numerals and their explanations will be omitted.

As shown in Fig. 1, in the aluminum can of this example,
A constricted portion 20 whose diameter gradually decreases as it goes outward in the axial direction of the can body 2 is formed at the intersection of the can bottom l and the can body 8 of the can body 2, and this constricted portion 20 includes the can axis O. a convex arc portion 21 that draws a circular arc C1 in contact with the can body 8 in a cross-sectional view;
A concave arc portion 22 that draws an arc C7 that touches the ground portion 5 of the can bottom l
and a straight line portion 23 of a predetermined length extending in the direction of the common tangent Q of each of these circular arc portions 21.22 and touching each circular arc portion 21.22 at intersections P, , P.

Here, the inclination angle θ of the straight portion 23 with respect to the plane S perpendicular to the can axis O is the width W of the constricted portion 20 in the can radial direction.
Although the radius of curvature R, R, of each arcuate portion 21, 22 may be changed as appropriate, it is preferable that the radius R is 29° or more.

If the inclination angle θ is less than 29°, the wall thickness of the straight portion 23 in the can axis direction will be insufficient, and the drawn portion will not be able to withstand the axial load F applied during molding of the bent portion 3 (see % in Figure 4). This is because there is a possibility that the buckling strength of No. 9 cannot be sufficiently improved.

Therefore, in this embodiment, the straight part 23 extending in the common tangential direction of each of the circular arc parts 21 and 22 is provided in the constricted part 20 formed on the outer peripheral edge of the can bottom 1. The radii of curvature R1 and R7 of the convex arc portion 21 and the concave arc portion 22 can be freely set without being restricted by the width W and height H of the aperture portion 20. Therefore, as shown in FIG.
The inclination angle θ1 of 3 is larger than the inclination angle θ of the common tangent Q of the conventional aperture part 9 (indicated by the chain line 2F!3 in the figure), and the height H of the aperture part 20 does not change. By setting the radii of curvature R, , R, of each arcuate portion 21, 22 as shown in FIG. Therefore, it is possible to improve the buckling strength of the constricted portion 20.

[Experimental Example] In order to confirm the effect of the present invention, a can bottom l having the shape shown in Fig. 3 was prepared.
The buckling strength of the constricted portion 9 of the aluminum can was investigated. In order to clarify the effects of the present invention, as comparative examples, an aluminum can with a conventional can bottom shape and an aluminum can in which only the radius of curvature R1 of the convex arc portion is set larger than that of the conventional aluminum can were prepared. were also prepared and their buckling strength was also investigated.

Here, the dimensions of each part of the can bottom are as shown in FIG. 3 and Attached Table 1. In addition, the buckling strength referred to here refers to the magnitude of the load F when the axial load F applied to the can body 2 is gradually increased and deformation occurs in the constricted portion 9, and its value is shown in the attached table 1. Displayed at the end of t2.

(The following is a blank space) Table 1 As is clear from these results, the aluminum can of the present invention has a buckling strength of the constricted portion that is 10% or more higher than that of Comparative Example 1, which is a conventional aluminum can, and The amount of decrease in the surface area of the can body and the internal volume of the can is also small and does not cause any practical problems.

[Effects of the Invention] As explained above, according to the present invention, the constriction portion formed on the can body is formed of a convex arc portion that draws an arc in contact with the can body;
Since it is composed of a concave circular arc part that draws a circular arc that touches the grounding part of the can bottom, and a straight part that extends in a common tangential direction of each of these circular arc parts, the wall thickness of the drawing part in the can axis direction is made larger than before. In addition, by determining the radius of curvature of each arcuate part and the angle of inclination of the straight part so that the width and height of the constricted part are almost the same as conventional ones, the constricted part can be improved while preventing a decrease in the surface area of the can body and the internal volume of the can. An excellent effect can be obtained in that the buckling strength of the material can be improved.

[Brief explanation of drawings]

Figures 1 and 2 show one embodiment of the present invention. Figure 1 is an enlarged cross-sectional view of the can bottom, and Figure 2 is a cross-sectional view of the can body showing the can bottom part, and Figure 2 shows the inclination of the straight part of the constriction part and each part. A sectional view of a can bottom for explaining the radius of curvature of an arcuate portion in comparison with a conventional example; FIG. 3 is a sectional view showing details of the shape of the can bottom in an experimental example of the present invention and a comparative example; FIGS. FIG. 5 is a diagram showing a conventional example, FIG. 4 is a diagram showing the overall structure of the can body, and FIG. 5 is a sectional view of the lower part of the can body. 1 - Can bottom, 2 - Can body, 5 - Grounding part, 8 - Can body, 20 - Squeezed part, 21 Convex arc part, 22 - Concave arc part, 23 - Straight line part.

Claims (2)

[Claims] (1) A can bottom is integrally molded on one end side of the can body which is approximately cylindrical, and a grounding part is formed on the can bottom to protrude annularly from the can bottom, and the outer peripheral side of this grounding part and the can body An aluminum can, in which a constricted portion is formed at the intersection with the can body, the diameter of which gradually decreases toward the outside in the axial direction of the can body, the constricted portion including the axis of the can body. In a cross-sectional view of the can bottom, a convex circular arc portion drawing a circular arc in contact with the can body, a concave circular arc portion drawing a circular arc in contact with the grounding portion, and extending in a common tangential direction of these convex circular arc portions and the concave circular arc portion. An aluminum can comprising a straight section. (2) In a cross-sectional view of the can bottom including the axis of the can body, the straight portion makes an angle of 29° or more with respect to a plane perpendicular to the axis of the can body. The aluminum can according to claim 1.