Can container

Abstract

Provided is a can container that obtains higher pressure resistance with a further improvement in the shape of a bottom part of the can container. The can container is provided with a can body and a can bottom. The can bottom is provided with a dome part that is recessed toward an inside of the can container along a direction of a can axis at a center thereof and a ring-shaped protruding part that protrudes toward an outside of the can container so as to form a ring-shaped support part on an outer periphery of the dome part. An inner peripheral surface that ranges from the support part of the ring-shaped protruding part to an outer peripheral edge part of the dome part has a recess part that is positioned in a direction in which an outer peripheral edge part of the dome part is separated from the can axis than an innermost part of an inner peripheral surface.

Description

Technical Field

[0001] The present invention relates to a can container.

Background Art

[0002] As can containers for filling and sealing contents such as beverages and foods, two-piece cans, bottle cans, etc. are known. These can containers include at least a can body and a can bottom.

[0003] In order to reduce the raw materials used, such can containers are being promoted to reduce the plate thickness and thus reduce the container weight. Even when the plate thickness is reduced, in order to obtain a predetermined pressure resistance as a container, the shape of the can bottom has been devised.

[0004] Generally, as a can bottom shape for increasing the pressure resistance, a dome portion is formed by recessing the central portion of the can bottom in a dome shape toward the inside of the can container along the can axis direction, and an annular convex portion serving as a support portion is formed on the outer peripheral edge of the dome portion.

[0005] Also, as a conventional technique, in order to increase the pressure resistance, the shapes of the above-described dome portion and annular convex portion are appropriately designed. For example, among the annular convex portions, on the inner peripheral wall continuous with the dome portion, in a longitudinal sectional view along the can axis direction, a first concave curved surface portion that curves concave toward the outer side in the radial direction orthogonal to the can axis is formed, and on the dome portion, a dome top located on the can axis and a second concave curved surface portion that is connected to the outer side in the radial direction of the dome top and has a smaller radius of curvature than the dome top are formed, and on the outer peripheral edge portion of the dome portion, a taper portion that connects the above-described first concave curved surface portion and second concave curved surface portion and forms a straight line that contacts the first curved surface portion and the second curved surface portion is proposed (see Patent Document 1 below).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] According to the above-described prior art, after forming the dome portion and the annular convex portion at the bottom, reforming is performed on the inner peripheral wall of the above-described annular convex portion to form the above-described first concave curved surface portion and the tapered portion. The first concave curved surface portion forms a curved surface on the forming surface of the forming tool by roll forming. In such reforming by a forming roll, the curved surface of the first concave curved surface portion has to have a certain large radius of curvature that allows roll forming, and there is a limit to making the amount of indentation that indents the inner peripheral surface of the annular convex portion outward in the radial direction perpendicular to the can axis deeper.

[0008] Also, in the above-described prior art, when roll forming the first concave curved surface portion, it is necessary to avoid the roll interfering with the dome portion, and there is a limit to increasing the distance (height h) in the can axis direction between the center of the radius of curvature (R1) of the first concave curved surface portion and the nose portion (the outer edge along the can axis direction in the annular convex portion).

[0009] For this reason, in the prior art, even if reforming is performed, the inner peripheral surface of the annular convex portion cannot be indented deeper outward in the radial direction perpendicular to the can axis, and the distance in the can axis direction between the center of the radius of curvature of the first concave curved surface portion and the nose portion cannot be increased, so there is a problem that effective improvement in pressure resistance cannot be obtained.

[0010] Furthermore, in the prior art, if an attempt is made to indent deeper by roll forming, the oxide film of the aluminum alloy, which is the material of the can, will be destroyed. When sterilization treatment is performed after filling the can with the contents, blackening occurs on the surface of the roll-formed portion, which also deteriorates the appearance of the product.

[0011] The present invention has been proposed to address such circumstances. That is, an object of the present invention is to provide a can container that can obtain higher pressure resistance by further improving the shape of the bottom of the can container and maintain the aesthetic appearance of the product, etc.

Means for Solving the Problems

[0012] In order to solve such problems, the can container according to the present invention has the following configuration. A can container comprising a can body and a can bottom, wherein the can bottom has a dome portion recessed toward the inside of the can container along the direction of the can axis at the center, and an annular convex portion protruding toward the outside of the can container so as to form an annular support portion around the outer periphery of the dome portion, and the inner peripheral surface from the support portion to the outer peripheral edge portion of the dome portion has a recess portion in which the outer peripheral edge portion of the dome portion is located in a direction away from the can axis from the innermost portion of the inner peripheral surface. O A can container characterized by this. O and the recess portion has a linear tapered surface in a longitudinal cross-sectional view on the can axis O, the inclination angle on the can axis O side between the tapered surface and the support surface in contact with the support portion is 115° to 125°, the height from the support surface to the outermost part of the inner peripheral surface is 2.6 to 4.0 mm, a virtual line parallel to the can axis O in contact with the innermost part of the inner peripheral surface is defined as L1, and a virtual line parallel to the can axis O in contact with the outermost part is defined as L2, the distance between the virtual line L1 and the virtual line L2 (depth of the recess portion) is 0.3 mm to 1.0 mm

Effects of the Invention

[0013] A can container having such characteristics can provide a can container with higher pressure resistance by improving the shape of the bottom of the can container.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Best Mode for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same reference numerals in different drawings indicate parts having the same function, and duplicate descriptions in each drawing are omitted as appropriate. Further, the cross-sectional views of FIGS. 1 and 2 show the cross-sectional shape as a diagram with the description of the plate thickness omitted.

[0016] As shown in FIG. 1, the can container 1 according to the embodiment of the present invention has a can body 1A and a can bottom 1B, and the can body 1A and the can bottom 1B have the same shape over the entire circumference around the can axis O. Here, the can bottom 1B includes a dome portion 10 and an annular convex portion 20, and in the illustrated example, an outer wall portion 30 is provided outside the annular convex portion 20.

[0017] The dome portion 10 is provided at the center of the can bottom 1B and has a curved surface that is recessed in a dome shape toward the inside of the can container 1 along the direction of the can axis O. In the illustrated example, the curved surface of the dome portion 10 has a first curved surface 11 with a radius of curvature R1 at the central portion and a second curved surface 12 with a radius of curvature R2 smaller than the radius of curvature R1 around it. However, the dome portion 10 may be a curved surface with a single radius of curvature.

[0018] The annular convex portion 20 is formed to project outward along the can axis direction of the can container 1 so as to form an annular support portion 21 around the outer circumference of the dome portion 10. The support portion 21 is a portion that supports the can container 1 on a plane and is formed on a support surface 21A orthogonal to the can axis O.

[0019] In the can bottom 1B, the inner peripheral surface 22 from the support portion 21 of the annular convex portion 20 to the outer peripheral edge portion 10A of the dome portion 10 has a recessed portion 22A in which the inner peripheral surface 22 is inclined in a direction away from the can axis O and is connected to the outer peripheral edge portion 10A of the dome portion 10.

[0020] As shown in Fig. 2, in the recessed portion 22A on the inner peripheral surface 22 of the annular convex portion 20, the outer peripheral edge portion 10A of the dome portion 10 is located in a direction away from the can axis O with respect to the innermost portion 22B of the inner peripheral surface 22 (the portion closest to the can axis O on the inner peripheral surface 22). As a result, a virtual line L1 that is in contact with the innermost portion 22B of the inner peripheral surface 22 and is parallel to the can axis O intersects the curved surface (for example, the second curved surface 12) of the dome portion 10.

[0021] Also, in a more specific example, the recessed portion 22A on the inner peripheral surface 22 has a linear tapered surface 22T in a longitudinal cross-sectional view on the can axis O. This tapered surface 22T forms an obtuse inclination angle θ with the support surface 21A that is in contact with the aforementioned support portion 21. This inclination angle θ is the angle on the can axis O side between the tapered surface 22T and the support surface 21A, and the angle is preferably set to 100° to 125° in order to obtain high pressure resistance at the can bottom 1B.

[0022] The recessed portion 22A on the inner peripheral surface 22 reaches the outer peripheral edge portion 10A of the dome portion 10 through the recess at the outermost portion 22C (the portion farthest from the can axis O on the inner peripheral surface 22) from the aforementioned tapered surface 22T. This outermost portion 22C is not formed by roll forming as in the aforementioned prior art, but is formed as a bent portion by compression deformation in the can axis direction, so that the radius of curvature of the curved surface of the outermost portion 22C is set smaller (for example, 0.7 mm or less) than the radius of curvature of the first concave curved surface portion in the prior art.

[0023] As a result, the outermost portion 22C on the inner peripheral surface 22 can be recessed deeper in a direction away from the can axis O with respect to the innermost portion 22B on the inner peripheral surface 22. Here, if a virtual line in contact with the outermost portion 22C and parallel to the can axis O is defined as L2, the distance d (the depth of the recessed portion 22A) between the aforementioned virtual line L1 and the virtual line L2 is preferably set to 0.3 mm to 1.0 mm in order to obtain high pressure resistance at the can bottom 1B.

[0024] When the outermost part 22C of the inner peripheral surface 22 is a compression deformation bending part, there are no roll forming marks that occur when forming a curved surface by roll forming as in the prior art on the inner peripheral surface 22. For this reason, the inner peripheral surface 22 having the outermost part 22C formed as a compression deformation bending part can avoid a decrease in appearance due to roll forming marks (blackening due to destruction of the aluminum oxide film). When the outermost part 22C is a compression deformation bending part, the height h from the support surface 21A to the outermost part 22C becomes the forming height. This height h is preferably set to 2.0 mm to 4.0 mm in order to obtain a high pressure resistance strength of the can bottom 1B.

[0025] The embodiment of the present invention having such a can bottom shape has a high can bottom pressure resistance strength compared with the prior art described above. The can bottom pressure resistance strength here refers to the buckling strength until the concave shape of the can bottom is completely reversed. Assuming the dome depth hs and the grounding diameter ds (see Fig. 1) of the can bottom are hs = 10.63 mm and ds = 45.5 mm, when comparing the can bottom pressure resistance strengths of the embodiment of the present invention (θ = 115°, h = 2.6 mm) and the prior art for each original plate thickness, as shown in Fig. 3, the strength of the embodiment of the present invention is about 1.2 to 1.5 times higher than that of the prior art.

[0026] The above-described recessed part 22A is formed by performing reforming that causes compression deformation after forming the dome part 10 and the annular convex part 20 on the can bottom 1B. Figs. 4 and 5 show the differences in the can bottom pressure resistance strengths when reforming is performed by changing the above-described inclination angle θ using two types of cans (capacity: 350 ml, grounding diameter φ49) with bottom shapes having dome depths of 13.45 mm and 13.95 mm before the reforming. The values in the parentheses in the figures indicate the values of the height h (forming height from the support surface 21A to the outermost part 22C) shown in Fig. 2 when the inclination angle θ is changed.

[0027] When the inclination angle θ is in the range of 100° to 125°, the desired bottom pressure resistance of the can can be obtained. The larger the dome depth hs of the can bottom, the higher the bottom pressure resistance of the can. However, when the dome depth hs is increased, it inevitably becomes difficult to secure the can internal volume necessary for filling the contents from a certain range. Also, within a certain range, the larger the inclination angle θ, the higher the bottom pressure resistance of the can. However, if it exceeds a certain range, the deformation mode changes and only the dome portion 10 will invert, and conversely, the bottom pressure resistance of the can will decrease.

[0028] The above-mentioned bottom pressure resistance of the can was measured as the minimum internal pressure of the can at which the concave shape of the can bottom is inverted by using a hydraulic buckling tester, sealing the inside of the can near the central portion in the axial direction of the can body of the can container in an inverted state without fixing the can bottom, and injecting water to increase the internal air pressure of the can container at a pressure increase speed of 30 kPa / s by water pressure.

[0029] The required values of the bottom pressure resistance of the can vary depending on the type of container, the type of liquid of the contents, the sterilization conditions, etc. For example, when filling some carbonated beverages, a high pressure resistance is required. However, even in such a case, it is judged that it is sufficient if it has a pressure resistance of 690 kPa.

[0030] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to these embodiments, and design changes and the like within the scope not departing from the gist of the present invention are also included in the present invention.

Explanation of Reference Numerals

[0031] 1: Can container, 1A: Can body, 1B: Can bottom, 10: Dome portion, 10A: Outer peripheral edge portion, 11: First curved surface, 12: Second curved surface, 20: Annular convex portion, 21: Support portion, 21A: Support surface, 22: Inner peripheral surface, 22A: Recess portion, 22B: Innermost part, 22C: Outermost part, 22T: Tapered surface, O: Can axis, θ: Inclination angle

Claims

1. A can container comprising: a can body and a can bottom, wherein the can bottom has a dome portion recessed inwardly of the can container along the direction of the can axis O at the center, and has an annular convex portion protruding outwardly of the can container so as to form an annular support portion around the outer periphery of the dome portion, wherein the inner peripheral surface from the support portion to the outer peripheral edge portion of the dome portion has a recess portion in which the outer peripheral edge portion of the dome portion is located in a direction away from the can axis O from the innermost part of the inner peripheral surface, the recess portion has a linear tapered surface in a longitudinal sectional view on the can axis O, the inclination angle on the can axis O side between the tapered surface and the support surface in contact with the support portion is 115° to 125°, the height from the support surface to the outermost part of the inner peripheral surface is 2.6 to 4.0 mm, and when a virtual line parallel to the can axis O in contact with the innermost part is defined as L1 and a virtual line parallel to the can axis O in contact with the outermost part is defined as L2, the distance between the virtual line L1 and the virtual line L2 (depth of the recess portion) is 0.3 mm to 1.0 mm. The can container is characterized by this.

2. The can container according to claim 1, wherein the virtual line parallel to the can axis O in contact with the innermost part intersects the curved surface of the dome portion.

3. The can container according to claim 1 or 2, wherein the outermost part of the inner peripheral surface is a compression deformation bending portion.

4. The can container according to any one of claims 1 to 3, wherein there are no roll forming marks on the inner peripheral surface.

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