Abstract
A threaded metal container capable of improving strength (neck portion transverse rigidity) in a direction perpendicular to a container axis at a neck portion composed of a mouth portion and a shoulder portion. The container includes a body portion, a shoulder portion, and a mouth portion. The mouth portion includes a base portion connected to an upper end of the shoulder portion, and a skirt valley portion, a skirt portion, and a threaded portion, which are above the base portion. The base portion 8 includes a protruding portion protruding radially outward and has a diameter gradually increasing downward from the skirt valley portion and a bead portion radially inwardly protruding and smoothly curving downward from the protruding portion. The bead portion circumferentially extends in a linear or dotted pattern. The bead height between the protruding portion and the bead portion in the direction perpendicular to the container axis is 0.1 to 0.6 mm.
Claims
1. A threaded metal container, comprising: a cylindrical body portion; a shoulder portion formed from an upper portion of the body portion so as to incline with respect to a container axis and reduce in diameter upward; and a tubular mouth portion extending upward from an upper portion of the shoulder portion, wherein the mouth portion includes a base portion smoothly connected to an upper end of the shoulder portion, a skirt valley portion connected to the base portion, a skirt portion connecting to the skirt valley portion, and a threaded portion connected to the skirt portion, wherein the base portion includes a protruding portion protruding radially outward and having a diameter gradually increasing downward from the skirt valley portion and a bead portion radially inwardly protruding and smoothly curving downward from the protruding portion, the bead portion circumferentially extending in a linear or dotted pattern, and wherein a bead height distance is a distance between a line parallel to a container axis and passing through an outer surface of the protruding portion furthest away from the container axis and a line parallel to the container axis and passing through an outer surface of the bead portion closest to the container axis, in a direction perpendicular to the container axis, is 0.1 to 0.6 mm.
2. A threaded metal container as recited in claim 1, wherein a radius of curvature of a curved line forming the bead portion is 0.5 to 2.5 mm.
3. The threaded metal container as recited in claim 2, wherein the protruding portion is smoothly connected to the bead portion in a curved manner, and wherein a radius of curvature of a curved line forming the protruding portion is 2.0 to 5.0 mm.
4. The threaded metal container as recited in claim 1, wherein a mouth diameter to body diameter ratio which is a ratio of an outer diameter of the mouth portion to an outer diameter of the body portion is 0.5 or more.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) FIG. 1 is a front view showing an entire threaded metal can according to an embodiment of the present invention.
(2) FIG. 2 is a longitudinal cross-sectional view enlarging the vicinity of the mouth portion of the metal can shown in FIG. 1.
(3) FIG. 3 is a partially enlarged view of FIG. 2 and shows a bead height.
(4) FIGS. 4A, 4B and 4C illustrate modified examples of a base portion having a bead portion.
(5) FIGS. 5A and 5B are schematic views showing a test method for evaluating strength of a metal can, where FIG. 5A shows a neck portion strength evaluation test and FIG. 5B shows an axial strength evaluation test.
(6) FIG. 6 is an enlarged view of the vicinity of a bead portion of a test can, where the solid line shows a can of this embodiment and the broken line shows a conventional can.
(7) FIG. 7 is a graph showing experimental results and analysis results between the axial strength/the neck portion transverse rigidity and the bead height.
(8) FIGS. 8A, 8B, and 8C show modified examples of a bead portion.
(9) FIG. 9 is a partial front view showing a conventional threaded metal can.
(10) FIG. 10 is a view showing a conventional load applied situation at the time of capping.
EMBODIMENT FOR CARRYING OUT THE INVENTION
(11) Hereinafter, an embodiment of the present invention will be described in detail with reference to the attached figures. FIG. 1 is a front view showing the entire threaded metal can according to an embodiment of the present invention, and FIG. 2 is a view showing the vicinity of the mouth portion. As shown in FIG. 1, in the case of the threaded metal can 1 of this embodiment, a bottomed cylindrical body is formed by a method in which, for example, an aluminum plate is subjected to a drawing process or a drawing and ironing process or an aluminum slag is subjected to an impact process. Then, an opening end side portion of the cylindrical body is subjected to a diameter reduction process to thereby form a shoulder portion 3 inwardly inclined with respect to the container axis, a cylindrical mouth portion 4 at the portion above the upper end 3a of the shoulder portion 3, and a cylindrical body portion 2 below the shoulder portion 3. Then, a threaded portion 5, a skirt portion 6, and a skirt valley portion 6a smaller in diameter than the skirt portion are formed on the mouth portion 4, and a curled portion 7 is formed at the upper end of the mouth portion 4 to thereby produce a threaded metal can. Such a can is called a two-piece can, but may be a three-piece can. In the case of a three-piece can (not shown), the bottom portion side of a cylindrical body is reduced in diameter to thereby form a shoulder portion 3, a bottomed mouth portion 4, and a cylindrical body portion 2 on the opening portion side of the cylindrical body. Then, the upper end of the bottomed mouth portion 4 is cut to open. A threaded portion 5, a skirt portion 6, and a skirt valley portion 6a smaller in diameter than the skirt portion are formed on the mouth portion 4. The upper end of the mouth portion 4 is formed into a curled portion 7. Further, a bottom cover (not shown) is joined to the lower end opening portion of the body portion 2. Thus, a threaded metal can is produced. Note that a base portion 8 larger in diameter than the skirt valley portion 6a is formed below the skirt valley portion 6a of these two-piece can and three-piece can. The region from the base portion 8 to the curled portion 7 of the upper end forms the mouth portion 4, and the base portion 8 is connected to the upper end 3a of the shoulder portion 3.
(12) After contents are filled in such a threaded metal can 1, the mouth portion 4 is sealed with a metal cap 60 by the similar capping process as shown in FIG. 9. That is, a cylindrical cap 60 is put on the mouth portion 4 and a load is applied to the can 1 in the axial direction with the pressure block 61. Then, in a state in which the contents are sealed with the cap 60 to which this axial load is being applied, from the side of the cap 60, a thread forming roller 62 is pressed along the threaded portion 5 of the can 1, and a hem bending roller 63 is pressed along the area from the skirt portion 6 to the skirt valley portion 6a of the can 1. With this, on the side wall of the cap 60, a female threaded portion 60a is formed, and at the lower end of the side wall, a fastened portion 60b is formed along the step 6b between the skirt portion 6 and the skirt valley portion 6a. This sealed state of the contents is maintained until the cap 60 is unscrewed and opened.
(13) In this embodiment, as shown in FIG. 2 and FIG. 3, between the skirt valley portion 6a and the upper end 3a of the shoulder portion 3, i.e., at the base portion 8 located at the lowest end of the mouth portion 4, a protruding portion 8a which radially outwardly protrudes and gradually expands in diameter downward from the skirt valley portion 6a and a bead portion 8b which radially inwardly protrudes and smoothly curves downward from the protruding portion 8a are formed over the entire circumference. The inventors of the present invention found the fact that when the bead height H of the bead portion 8b is set within the range of 0.1 to 0.6 mm, preferably within the range of 0.2 to 0.4 mm, the transverse rigidity of the neck portion composed of the mouth portion 4 and the shoulder portion 3 is improved. Here, as shown in FIG. 3, the bead height H denotes a distance between two lines La and Lb parallel to the container axis in a direction perpendicular to the container axis. The line La is a line parallel to the container axis and passing through the outer surface of the protruding portion 8a furthest away from the container axis, and the line Lb is a line parallel to the container axis and passing through the outer surface of the bead portion 8b closest to the container axis. The above-described distance is defined as the bead height H. In other words, assuming that the maximum outer diameter of the protruding portion 8a is Da and the minimum outer diameter of the bead portion 8b is Db, the bead height H is H=(DaDb)/2.
(14) As described above, the bead portion 8b formed at the base portion 8 of the mouth portion 4 may be formed such that the radius of curvature r1 of the curved line (line Lb) passing through the bottom portion of the bead portion 8b is set to 0.5 to 2.5 mm. Also, the protruding portion 8a located above the bead portion 8b may be smoothly bent adjacent to the bead portion 8b. In that case, the radius of curvature r2 of the curved line (line La) passing through the top of the protruding portion 8a may be formed to 2.0 to 5.0 mm. When the curved line of the bead portion 8b has the radius of curvature r1 falling with the above-described range, or when the curved line of the bead portion 8b has the radius of curvature r1 falling within the above-described range and the curved line of the protruding portion 8a has the radius of curvature r2 falling within the above-described range, it is possible to form the bead portion 8b and the protruding portion 8a in a limited height range. Therefore, it is possible to improve the transverse rigidity of the neck portion composed of the mouth portion 4 and the shoulder portion 3 without changing the dimensions of the can in the container axis direction (e.g., the total height, the mouth portion height, etc.).
(15) Furthermore, in cases where the outer diameter of the mouth portion 4 is 30 mm or more, especially 35 mm or more, and the (mouth diameter/body diameter) ratio of the outer diameter of the mouth portion 4 to the outer diameter of the body portion 2 is 0.5 or more, particularly 0.6 or more, in other words, in cases where the can has a wide mouth portion, local deformation is likely to occur in the neck portion composed of the mouth portion 4 and the shoulder portion 3. For this reason, the present invention is effective for such a can having a wide mouth portion. Note that in the present invention, the outer diameter of the mouth portion 4 refers to the outer diameter of the screw thread of the threaded portion 5. For example, in cases where the outer diameter of the body portion 2 is 53 mm and the screw thread outer diameter of the threaded portion 5, i.e., the outer diameter of the mouth portion 4, is 37 mm, the (mouth diameter/body diameter) ratio becomes 0.70. Further, the cap for sealing the mouth portion (reference numeral 60 in FIG. 10) is 38 mm in the outer diameter.
(16) Returning to FIG. 1 to FIG. 3, the base portion 8 is formed such that the protruding portion 8a and the bead portion 8b are formed in a shape in which they are adjacent to each other and smoothly connected, but may be formed in the shapes shown in FIGS. 4A, 4B, and 4C. That is, as shown in FIG. 4A, the protruding portion may be a protruding portion 8a having a linear portion 8c parallel to the container axis. Further, as shown in FIG. 4B, a linear portion 8d parallel to the container axis may be provided between the bead portion 8b and the upper end 3a of the shoulder portion 3. As shown in FIG. 4C, a protruding portion 8a and a linear portion 8d may be provided.
(17) Next, the functions and effects of the present embodiment will be described. In this embodiment, the height H of the bead portion 8b formed at the base portion 8 of the mouth portion 4 is 0.1 to 0.6 mm, preferably 0.2 to 0.4 mm Such a bead portion 8b is formed at the base portion 8 of the mouth portion 4 located at the upper end 3a of the shoulder portion 3. Therefore, in the capping process, even if a load is applied to the neck portion in a direction perpendicular to the container axis, it is possible to prevent occurrence of local deformation at the neck portion composed of the mouth portion 4 and the shoulder portion 3.
(18) Hereinafter, tests for confirming the effects of the present invention will be described.
(19) [Test 1]
(20) In order to verify the strength change of the can by the bead portion 8b, tests were carried out by the methods shown in FIGS. 5A and 5B. FIG. 5A is a schematic view showing a neck portion strength evaluation test. A load (see the arrow in the figure) toward the radial center of the can is applied to the skirt valley portion 6a of the mouth portion 4 by a compression jig indicated by a circle, and the transverse rigidity (stiffness in the radial direction) of the neck portion composed of the mouth portion 4 and the shoulder portion 3 is measured. FIG. 5B is a schematic diagram showing an axial strength evaluation test, and a load is applied in the container axis direction (the direction of the arrow) by a compression jig indicated by a square shape and the axial strength is measured.
(21) A test can was used in which the total height of the can 1 was 130 mm, the outer diameter of body portion 2 was 53 mm, the outer diameter of the mouth portion 4 (the outer diameter of the threaded portion 5) was 37 mm, the thickness of the body portion 2 was 0.20 mm, and the thickness of the threaded portion 5 was 0.33 mm FIG. 6 is an enlarged view of the vicinity of the bead portion of the test can. The solid line portion shows a can according to this embodiment. On the other hand, the broken line portion shows a conventional can, and its shape from the base portion 58 located at the lower end of the mouth portion to the upper end 53a of the shoulder portion 3 is different from that of the can according to this embodiment. Note that FIG. 6 shows that the bead height H of the conventional can is 0 mm and that the bead height H of the can according to this embodiment exceeds 0 mm Using the conventional can and the can of this embodiment as test cans, the neck portion transverse rigidity and the axial strength were measured by the methods shown in FIG. 5A and FIG. 5B. The results are shown in FIG. 7.
(22) In FIG. 7, the mark .square-solid. and the mark .diamond-solid. indicate the measurement results of the test cans formed to have the bead height of 0 mm, 0.2 mm, 0.3 mm, and 0.5 mm, and the measurement results of the neck portion transverse rigidity are indicated by the mark .square-solid. and the measurement results of the axial strength are indicated by the mark .diamond-solid.. Further note that the broken lines in FIG. 7 show the analysis results of the axial strength and the neck portion transverse rigidity under the above-described conditions. As shown by the broken lines, as the bead height increases, the neck portion transverse rigidity increases, while the axial strength is likely to decrease. By the way, it is considered that it is preferable that the axial strength be 1.6 kN or more and the neck portion transverse rigidity be 47 N/mm or more in order to secure the soundness at the time of capping. In FIG. 7, when the bead height is set to 0.6 mm, its axial strength decreases to a value close to 1.6 kN, which is considered to be preferable under the capping condition. Also, when the bead height exceeds 0.6 mm, the strength at the bead portion in the container axis direction decreases and buckling is likely to occur at the bead portion. For this reason, the bead height is preferably set so as to fall within the range of 0.1 to 0.6 mm. It is more preferred that the bead height be set so as to fall within the range of 0.2 to 0.4 mm. In this range, the neck portion transverse rigidity can be increased without remarkably lowering the axial strength.
(23) [Test 2]
(24) Then, tests were carried out on the thinning of the material (weight saving of the can). The results are shown in Table 1. Note that No. 3 (reference can) in Table 1 is a can using a non-thinned material (aluminum alloy plate with a thickness of 0.435 mm) and the bead height H shown by the broken line in FIG. 6 is set to 0 mm. As a thinned material obtained by thinning the material of the No. 3 (reference can), in a can having a bead height of 0 mm, a material (an aluminum alloy plate having a thickness of 0.385 mm) having an axial strength of about 1.6 kN was prepared. Using this thinned material, No. 1 (a conventional can in which a bead height is set to 0 mm) and No. 2 (a can of this embodiment in which a bead height is set to 0.2 mm) were produced. Note that in these No. 1 can to No. 3 can, the basic specifications on the overall height of the can 1, the outer diameter of the body portion 2, and the outer diameter of the threaded portion 5 were made to approximately the same size as the test can used in the above-described Test 1, that is, the total height of the can 1 was set to 130 mm, the outer diameter of the body portion 2 was set to 53 mm, and the outer diameter of mouth portion 4 (outer diameter of the threaded portion 5) was set to 37 mm. As for the wall thickness of the body portion 2, the No. 1 can and the No. 2 can were each set to 0.17 mm, the No. 3 can was set to 0.20 mm. As for the wall thickness of the threaded portion 5, the No. 1 can and the No. 2 can were each set to 0.32 mm, and the No. 3 can was set to 0.35 mm
(25) TABLE-US-00001 TABLE 1 Neck portion Material Can Bead Axis transverse thickness weight height strength rigidity Test can No. [mm] [g] [mm] [N] [N/mm] No. 1 0.385 15.2 0 1,576 39.2 (Conventional can) No. 2 0.385 15.2 0.2 1,541 49.8 (Embodiment can) No. 3 0.435 17.2 0 2,045 52.1 (Reference can)
(26) As shown in Table 1, it was verified that in the can (No. 2) of this embodiment in which the bead height was 0.2 mm, the neck portion transverse rigidity greatly was improved to 47 N/mm or more, which is said to be preferable, while maintaining the similar axial strength as that of the conventional can (No. 1) with a bead height of 0 mm. Further, the can (No. 2) according to the embodiment shows that strength close to the axial strength (1.6 kN or more) and the neck portion transverse rigidity (47 N/mm or more) which is considered to be preferable under capping conditions can be obtained while achieving about 12% weight reduction in the can weight. In summary, with this test, it was verified that the bead portion contributes to the material thinning (weight reduction of the can).
(27) Although some embodiments of the present invention have been described above, it is needless to say that the present invention is not limited to the above-described embodiments and various modifications can be adopted. For example, the bead portion 9b shown in FIG. 1 to FIG. 4C can be formed in various shapes as shown in FIGS. 8A, 8B, and 8C. FIG. 8A shows a plurality of linear bead portions 21. FIG. 8B shows a plurality of dotted bead portions 22. These bead portions 21 and 22 may be provided at equal intervals at the base portion 9 of the mouth portion 4 with a space in the circumferential direction. In FIG. 8C, two or more bead portions 23 and protruding portions 24 are formed at different height positions in the container axis direction. In both the cases, the same effects as those of FIG. 1 to FIG. 4C can be obtained.
DESCRIPTION OF REFERENCE SYMBOLS
(28) 1, 51: threaded metal can 2, 52: body portion 3, 53: shoulder portion 3a, 53a: shoulder portion upper end 4, 54: mouth portion 5, 55: threaded portion 6, 56: skirt portion 6a, 56a: skirt valley portion 6b, 56b: step 7, 57 curled portion 8, 58 base portion 8a, 8a, 24: protruding portion 8b, 21, 22, 23: bead portion 8c: linear portion 60: cap 60a: female threaded portion 60b: fastened portion 61: pressure block 62: thread forming roller 63: hem bending roller
