Metal container and method for manufacturing the same

Abstract

The present invention provides a metal container with a wide opening that is easy to mold, easy to remove cleaning solution from, and has a curled section that provides a pleasant mouthfeel. [Solution] The bottomed cylindrical body has a curled portion at its open end. In a longitudinal cross-section passing through the central axis of the body, the curled portion has an upper inner circumferential curved portion that extends radially outward from the upper end of the body, an upper outer circumferential curved portion that forms a folded top between it and the upper inner circumferential curved portion, and an outer cylindrical portion that is continuous with the outer edge of the upper outer circumferential curved portion and forms the part with the largest outer diameter. The curled end is formed radially inward from the outer cylindrical portion via an end bend with the smallest radius of curvature. The curled end extends toward the inner surface of the upper outer circumferential curved portion or the outer cylindrical portion. The distance perpendicular to the central axis in the gap between the tip of the curled end and the inner surface of the upper outer circumferential curved portion or the outer cylindrical portion is smaller than the distance perpendicular to the central axis in the gap between the end bend and the outer surface of the body.

Description

Technical Field

[0001] The present invention relates to a metal container made of an aluminum alloy or the like and a method for manufacturing the same.

Background Art

[0002] A metal cup made of an aluminum alloy or the like has attracted attention because it is superior in strength to a paper cup and is lighter than a pottery cup. In this metal cup, the opening where the lips touch when drinking is rounded to improve the mouthfeel.

[0003] The metal container disclosed in Patent Document 1 is a metal cup having a bottom portion and a body portion, with an open upper surface side. The body portion has a curled portion at the tip of the upper opening side. The curled portion has a curvature region from the body portion toward the tip, and at least the section from the body portion to the lowermost part of the curled portion in the curvature region is configured such that the radius of curvature gradually decreases stepwise or continuously. In this case, the tip of the curled portion is located above the lowermost part of the curled portion, and on the tip side relative to the lowermost part, there is a portion closer to the side wall of the body portion than the lowermost part.

[0004] On the other hand, in the formed container disclosed in Patent Document 2, a bent edge portion is formed by bending downward from the bent base end within a predetermined width from the end of the extended flange formed by expanding outward from the opening end of the body portion, and the bent edge portion is wound so as to be located within the curled portion to form a curled portion. Therefore, the tip of the bent edge portion is located inside the curled portion and faces outward from the body portion. This curled portion is formed by curling after forming the bent edge portion by precurling. The curled portion described in this Patent Document 2 is generally the same in overall outer shape as the curled portion described in Patent Document 1. However, because it has undergone a precurling process, the tip portion of the curled portion is disposed inside the curled portion in a state where it is bent at an acute angle.

[0005] Incidentally, a similar curled portion is formed on the mouth of a so-called bottle can, but the metal cup described above has a larger diameter opening than the mouth of a bottle can. Since this curled portion is formed by folding the open end, which is formed by drawing and ironing into a cylindrical shape, radially outward while widening it, a large diameter opening causes significant material elongation, making it prone to cracking and other damage. For this reason, as disclosed in Patent Document 2, it is considered advantageous to pre-bend only the tip portion with a pre-curl before curling, in order to improve the strength of the tip portion and reduce elongation. On the other hand, after the metal cups are formed, they are washed before shipment. In this washing process, the cups are transported in an inverted position with the opening facing downwards, and a cleaning solution is sprayed onto the inner and outer surfaces of the cups. After that, they are dried and shipped. At this time, if the cleaning solution penetrates into the curled part, it becomes difficult to remove. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2022 / 059441 [Patent Document 2] Japanese Patent Publication No. 2010-42869 [Overview of the project] [Problems that the invention aims to solve]

[0007] This invention has been made in view of these circumstances, and aims to provide a metal container such as a metal cup that is easy to mold even if it has a wide mouth, is easy to remove cleaning solution from, and has a curled portion that is pleasant to the mouth. [Means for solving the problem]

[0008] The metal container of the present invention has a bottomed cylindrical body with a curled portion at the open end, which is formed by folding the open end radially outward and rounding it. The curled portion, in a longitudinal cross-section passing through the central axis of the body, has an upper inner circumferential curved portion that extends radially outward from the upper end of the body, an upper outer circumferential curved portion that forms a folded top between it and the upper inner circumferential curved portion, and an outer cylindrical portion that is continuous with the outer edge of the upper outer circumferential curved portion and forms the part of the curled portion with the largest outer diameter, and a curled end is formed radially inward from the outer cylindrical portion via an end bend portion with the smallest radius of curvature in the curled portion, and the curled end extends toward the inner surface of the upper outer circumferential curved portion or the outer cylindrical portion. The distance in the direction perpendicular to the central axis in the gap between the tip of the curled end and the inner surface of the upper outer curved portion or the outer cylindrical portion is smaller than the distance in the direction perpendicular to the central axis in the gap between the end bend and the outer surface of the body portion.

[0009] Since the curled ends of this metal container are formed via a bent end section with a small radius of curvature, this bent end section should be formed first before curling. This prevents cracking at the curled ends. The resulting curled portion is formed by a small radius of curvature at the end of the curled section, extending toward the inner surface of the upper outer curved section or outer cylindrical section. In other words, the curled portion is rounded by tucking the end of the curled section into the curled section. Consequently, a very small space is formed inside the end curved section, and this small space opens to a larger space within the curled portion through a gap (a minute gap) between the tip (edge) of the curled end and the inner surface of the upper outer curved section or outer cylindrical section.

[0010] On the other hand, a large gap (referred to as an inlet gap) is formed between the bent end portion and the outer surface of the body portion, connecting the curled portion to the outside. Therefore, during cleaning, cleaning fluid can enter from the large space inside the curled portion through this inlet gap and clean the inner surface of the curled portion. During this cleaning process, the metal container is placed in an inverted position. This creates a tiny gap between the tip of the curled end and the inner surface of the upper outer curved section or outer cylindrical section, opening a small space downwards inside the bent end. As a result, when the cleaning solution level reaches the vicinity of this tiny gap, the pressure of the air trapped within the small space prevents the cleaning solution from entering it. Therefore, the cleaning solution is not trapped within the small space after cleaning. On the other hand, the larger space is open through a large inlet gap, so the cleaning solution is easily removed by drying. This prevents the cleaning solution from remaining inside the curled section. Furthermore, when drinking beverages, the curved end may come into contact with the lips, but the tip of the curled end does not, resulting in a pleasant mouthfeel.

[0011] In the metal container of the present invention, the end bend portion is preferably connected to the lower end of the outer cylindrical portion via a second bend portion, and the radius of curvature of the outer surface of the second bend portion is preferably greater than the radius of curvature of the outer surface of the end bend portion and smaller than the radius of curvature of the outer surface of the upper inner circumferential curved portion and the upper outer circumferential curved portion.

[0012] In the absence of a second bend, the curled end extends diagonally upward from below. However, because it has two bends—a second bend and an end bend—the angle of inclination of the curled end with respect to the central axis becomes even larger. As a result, the tip (edge) of the curled end becomes completely invisible from the outside, and the intrusion of cleaning fluid into the small space is more reliably prevented.

[0013] In the metal container of the present invention, the curled end can be made to be inclined downwards toward the tip with respect to a direction perpendicular to the central axis.

[0014] In the metal container of the present invention, the curled end may be inclined in a direction that gradually widens in diameter from bottom to top.

[0015] In the metal container of the present invention, the inclination angle of the curled end with respect to the central axis is preferably 10° or more and 135° or less.

[0016] The present invention provides a method for manufacturing a metal container, comprising a body forming step of press-forming an aluminum alloy sheet to form a bottomed cylindrical body, and a curling step of forming a curled portion at the open end of the body, The curl portion forming process includes a pre-curl step of forming a pre-curl portion with its tip facing radially outward by pressing the open end of the body along the central axis with a pre-curl roll that rotates around the central axis of the body, and folding the open end radially outward; an end bending step of bending the pre-curl portion to form an end bend that is convex upward; and a curl step of forming a curl portion by pressing the end bend along the central axis with a curl roll that rotates around the central axis, and folding back the portion of the end bend that is on the body side of the end bend while spreading the end bend radially outward.

[0017] In the method for manufacturing a metal container of the present invention, the bending step may be performed by placing an inner mold inside the body and bending the pre-curled portion while pressing it along the central axis direction with an outer mold.

[0018] In the method for manufacturing a metal container of the present invention, the curling step preferably includes a first curling step of pressing the end bent portion along the central axis to spread it radially outward while folding back the portion on the base end side from the end bent portion to form a second bent portion that is convex upward; and a second curling step of pressing the second bent portion along the central axis to spread it radially outward while folding back the portion on the base end side from the second bent portion to position the second bent portion in a downward convex shape to form a curled portion. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a metal container having a curled portion that is easy to mold even for a wide-mouthed cup, easy to remove cleaning liquid, and has a good mouthfeel.

Brief Description of the Drawings

[0020] [Figure 1] It is a front view showing a half longitudinal section around the central axis of a metal cup (metal container) according to an embodiment of the present invention. [Figure 2] It is an enlarged cross-sectional view of the curled portion of the metal cup of the first embodiment. [Figure 3] It is a front view showing a half longitudinal section around the central axis showing a part of the manufacturing process in the order from (a) to (c). [Figure 4] It is a longitudinal sectional view showing a precurl process. [Figure 5] It is a top view of FIG. 4. [Figure 6] It is a longitudinal sectional view of the main part showing the (a) precurl process and the (b) end buckling process, and changes from left to right as the processing progresses. [Figure 7] It is a longitudinal sectional view of the main part showing the (a) first curl process and the (b) second curl process, and changes from left to right as the processing progresses. [Figure 8] It is a longitudinal sectional view of the main part explaining the state of penetration of the cleaning liquid in the cleaning process. [Figure 9] It is an enlarged cross-sectional view showing the curled portion of the second embodiment. [Figure 10] It is a longitudinal sectional view showing a curl process for forming the curled portion of the second embodiment, and changes from e1 to e2 as the processing progresses.

Modes for Carrying Out the Invention

[0021] Hereinafter, embodiments of the metal container according to the present invention will be described with reference to the drawings. One embodiment of the metal container is a wide-mouthed metal cup 1, as shown in Figure 1. This metal cup 1 is formed from an aluminum alloy sheet into a bottomed cylindrical shape by press molding. The diameter of the opening 3 is larger than the diameter of the bottom 2, and the body 4 has a tapered shape that gradually widens from the bottom 2 to the opening 3. A curled portion 5 is formed at the opening 3, with the end portion including the edge E being rolled radially outward. The radial center of this metal cup 1 is defined as the central axis C1.

[0022] The bottom portion 2 has a shape consisting of a concave, curved dome portion 6, an inner tapered wall portion 7 that is continuous with its outer periphery and gradually widens in diameter as it extends downward along the central axis, a contact portion 8 that is continuous with the outer periphery of the inner tapered wall portion 7 and makes contact with the ground when the metal cup 1 is placed on a table or the like, and a tapered rising portion 9 that extends from the outer periphery of the contact portion 8 to the lowest end of the body portion 4. The dome portion 6 is concave at the position on the central axis C1 where it is furthest from the tip of the contact portion 8. The contact portion 8 is formed in a ring shape around the central axis C1 and is formed in a curved surface shape that is convex downward along the central axis C1, with its most protruding position being the contact point. The outermost periphery of the curved surface of the contact portion 8 is formed to have a smaller diameter than the lowest end of the body portion 4, and the outer periphery of this contact portion 8 and the lowest end of the body portion 4 are connected by the rising portion 9.

[0023] The body portion 4 has straight cylindrical portions 11 and 12 formed along the central axis C1 near the bottom portion 2 and near the opening portion 3. A small lower stepped portion 13 is formed at the upper end of the lower cylindrical portion 11 which is continuous with the bottom portion 2, and a small upper stepped portion 14 is also formed at the lower end of the upper cylindrical portion 12 which is continuous with the curled portion 5. The space between the upper end of the lower stepped portion 13 and the lower end of the upper stepped portion 14 is formed as a tapered cylindrical portion 15 in which the diameter gradually increases from bottom to top.

[0024] As shown in the figure, the curled portion 5 has a rounded, folded shape overall, but the curled end portion 20 that forms its tip is formed to be drawn inside the curled portion 5 via an end bend portion 21 with a small radius of curvature. Specifically, the curled portion 5 has, in a longitudinal cross-section passing through the central axis C1 of the metal cup 1 (central axis of the body portion 4), an enlarged diameter portion 22 that is continuous with the upper end of the upper cylindrical portion 12 of the body portion 4 and gradually widens in diameter in a tapered manner as it extends upward, an upper inner circumferential curved portion 23 that curves while widening radially outward from the upper end of the enlarged diameter portion 22, an upper outer circumferential curved portion 25 that forms a folded top portion 24 between it and the upper inner circumferential curved portion 23, and an outer circumferential cylindrical portion 26 that is continuous with the outer circumferential edge of the upper outer circumferential curved portion 25 and forms the part of the curled portion 5 with the largest outer diameter. In this embodiment, the outer circumferential cylindrical portion 26 is formed in a substantially straight cylindrical shape.

[0025] Furthermore, a downward-curving portion (the second curved portion of the present invention, and sometimes referred to as the second curved portion hereinafter) 27 is formed at the lower end of the outer cylindrical portion 26, and the curled end portion 20 is continuous with the inner circumference end of the downward-curving portion 27 via the aforementioned end curved portion 21 with a small radius of curvature. The radius of curvature R1 of the outer surface of this end curved portion 21 is smaller than the radius of curvature R2 of the outer surface of the downward-curving portion 27, and the radius of curvature R2 of the downward-curving portion 27 is smaller than the radius of curvature R3 of the outer surface of the upper inner curved portion 23 and the radius of curvature R4 of the outer surface of the upper outer curved portion 25. In other words, in the curled portion 5, the radius of curvature R1 of the end curved portion 21 is formed to be the smallest radius of curvature.

[0026] In this curled section 5, the midpoint (vertex) of the folded top 24 is located at the uppermost position (highest position) of the curled section 5, and the end bend 21 is located near directly below the vertex. The curled end 20 extends radially outward from the end bend 21 with a downward slope, and its tip (edge) is directed from near the maximum outer diameter of the outer cylindrical section 26 towards the inner surface near the connection point with the downward bend 27. Although this curled end 20 is slightly curved, its length is short, so it can be considered to extend almost in a straight line. On the other hand, in the curled portion 5, the midpoint of the downward bend portion 27 is formed at the lowest end position.

[0027] Furthermore, the small space S1 formed inside the end bend portion 21, that is, the small space S1 surrounded by the downward bend portion 27, the end bend portion 21, and the curled end portion 20, is in communication with the large space S2 within the curled portion 5 via a minute gap g2 between the edge of the curled end portion 20 and the inner circumferential surface of the curled portion. Furthermore, the end bend portion 21 is formed to be convex radially inward, and a relatively wide gap (referred to as the entrance gap) g1 is formed between this end bend portion 21 and the outer circumferential surface of the body portion 4 (in this case, the outer circumferential surface of the upper cylindrical portion 12) (for example, about half the thickness T of the curl portion 5), and the external space and the large space S2 inside the curl portion 5 are in communication through this entrance gap g1. The distance g2 between the tip of the curled end 20 and the inner surface of the outer cylindrical portion 26 is smaller than the distance g1 between the bent end portion 21 and the outer surface of the upper cylindrical portion 12.

[0028] For example, the curled portion 5 has a diameter (outer diameter of the outer cylindrical portion 26) D1 of 70 mm to 100 mm, a diameter (outer diameter) D4 of the upper cylindrical portion 12 of the body 4 of 65 mm to 95 mm, a radial thickness (thickness from the inner surface of the upper cylindrical portion of the body to the outer surface of the outer cylindrical portion) T of 2 mm to 5 mm, and a height W of the curled portion 5 along the central axis C1 of the metal cup 1 (distance from the highest point of the folded top portion 24 to the lowest point of the second bend portion 27) of 2 mm to 5 mm. Furthermore, the inclination angle θ1 of the enlarged diameter portion 22 with respect to the central axis C1 is 10° or more and 60° or less, the radius of curvature R3 of the outer surface of the upper inner circumferential curved portion 23 is 0.8 mm or more and 3.5 mm or less, and the radius of curvature R4 of the outer surface of the upper outer circumferential curved portion 25 is 1.0 mm or more and 4.0 mm or less. In this case, the upper inner circumferential curved portion 23 and the upper outer circumferential curved portion 25 may be formed as a substantially single arc surface.

[0029] Furthermore, the radius of curvature R2 of the outer surface of the downward-bent portion 27 is 0.5 mm or more and 2.0 mm or less, preferably 0.6 mm or more and 1.2 mm or less, and the radius of curvature R1 of the outer surface of the end-bent portion 21 is 0.1 mm or more and 2.0 mm or less, preferably 0.15 mm or more and 1.0 mm or less. And, the distance along the direction orthogonal to the central axis C1 in the inlet gap g1 between the end bending portion 21 and the outer peripheral surface of the upper cylindrical portion 12 of the body portion 4 is 1.0 mm or more and 3.0 mm or less, preferably 1.0 mm or more and 2.5 mm or less, and the distance along the direction orthogonal to the central axis C1 in the minute gap g2 between the tip (edge) of the curled end portion 20 and the inner surface of the outer peripheral cylindrical portion 26 is 0.5 mm or more and 1.5 mm or less, preferably 0.5 mm or more and 1.0 mm or less. However, g2 < g1. Further, the inclination angle θ2 of the curled end portion 20 with respect to the central axis C1 is formed to be 10° or more and 135° or less, preferably 60° or more and 125° or less. This inclination angle θ2 is the angle formed by the tangent line of the intermediate portion in the length direction of the curled end portion 20 with respect to the central axis C1.

[0030] Although other various dimensions are not necessarily limited, for example, the diameter D2 of the grounding point in the grounding portion 8 is 45 mm or more and 60 mm or less, the overall height H1 is 80 mm or more and 180 mm or less, the depth H2 of the dome portion 6 is 1 mm or more and 15 mm or less, the diameter D3 of the lower cylindrical portion 11 is 50 mm or more and 70 mm or less, the height H3 from the bottom surface to the lower end of the lower step portion 13 is 8 mm or more and 25 mm or less, the length H4 from the upper end of the curl portion 5 to the upper end of the upper step portion 14 is 8 mm or more and 20 mm or less, and the angle θ3 of the tapered cylindrical portion 15 with respect to the horizontal plane is formed to be 80° or more and 88° or less.

[0031] Next, a manufacturing method of this metal cup 1 will be described. This metal cup 1 includes a cylindrical body forming step of forming a bottomed cylindrical body 17 by drawing and ironing a plate material made of an aluminum alloy plate using a press, and after the cylindrical body forming step, while using a plurality of punches with different outer diameters in ascending order of the outer diameter, pushing the punches into the cylindrical body 17 from the opening portion 18 side to gradually expand the diameter of the body portion 19 of the cylindrical body 17 from the bottom portion 2 side toward the opening portion 18 side to form a tapered cylindrical body 50, and a curl portion forming step of forming a curl portion 5 at the opening end portion of the tapered cylindrical body 50 formed by this diameter expanding step, and is manufactured through a process having these steps. Hereinafter, it will be described in the order of the steps.

[0032] [Cylindrical body forming step] The cylindrical body forming process includes a cup forming process, as shown in Figure 3(a), in which a cup 16 larger in diameter and shallower than the cylindrical body 17 of the next process is formed by punching out and drawing a sheet of aluminum or aluminum alloy, and a drawing and ironing process, in which a bottomed cylindrical body 17 smaller in diameter than the cup 16 and of a predetermined height is formed as shown in Figure 3(b). In this drawing and ironing process, the bottom 2 of the cylindrical body 17 is finished to the final shape of the bottom 2 of the metal cup 1, and has a dome portion 6, an inner tapered wall portion 7, a contact portion 8, and a tapered rising portion 9.

[0033] [Diameter expansion process] The diameter expansion process consists of several steps: a step formation step in which a step portion is formed on the body portion 19 of the cylindrical body 17, where the diameter on the opening 18 side is larger than the diameter on the bottom 2 side; and a shaping step in which the step portion is expanded and shaped into a tapered surface. By repeating these steps, the diameter is gradually expanded from the bottom side to the opening side, thereby forming the tapered cylindrical body 50 shown in Figure 3(c). In this case, after the initial lower step formation step, the step formation step and the shaping step are performed alternately to form one step, smoothing the step and shaping it while forming the entire structure into a tapered shape. Finally, at the top of the cylindrical body 17, the upper step formation step is performed to form the upper step 14, thus completing the diameter expansion process. The tapered cylindrical body 50 formed by this diameter expansion process has the same shape as the metal cup 1 shown in Figure 1, except that the open end extends upward, as shown in Figure 3(c). Therefore, the same reference numerals are used to describe the corresponding parts. In this embodiment, the body forming process of the present invention consists of a cylindrical body forming process and a diameter enlargement process.

[0034] [Curl formation process] After the diameter expansion process, the end of the upper cylindrical portion 12 of the tapered cylindrical body 50 is folded back radially outward while being wound to form the curled portion 5. This curled portion formation process includes a pre-curling step in which the upper cylindrical portion 12 is pressed along the central axis C1 by a pre-curling roll 71 that rotates around the central axis C1 of the tapered cylindrical body 50, and the open end is folded radially outward to form a pre-curled portion 72 with the tip facing radially outward; an end bending step in which the base end of the pre-curled portion 72 is bent to form an end bent portion 21' that is convex upward; and a curling step in which the end bent portion 21' is pressed along the central axis C1 by a curling roll 74 that rotates around the central axis C1, and the end bent portion 21' is spread radially outward while the portion on the upper cylindrical portion 12 side of the end bent portion 21' is folded back to form a curled portion 5.

[0035] The following explains the process step by step. Figures 6(a), 6(b), 7(c), and 7(d) show the changes in each process, and in each figure, the processing is done from left to right (for example, from a1 to a2 in Figure 6(a), and from b1 to b2 in Figure 6(b)). Also, the shape of the open end of the tapered cylindrical body 50 changes sequentially in each process, but for convenience, the same reference numerals are used for explanation.

[0036] (Pre-curl process) In the pre-curling process, the pre-curling roll 71 shown in Figures 4, 5, and 6(a) is used. This pre-curling roll 71 has an inclined surface 75 that contacts the open end of the upper cylindrical portion 12 at an angle and presses in a direction along the central axis C1 of the tapered cylindrical body 50, and a forming recess 76 that is formed in the shape of a circular arc groove in cross-section and opens downwards. The inclined surface 75 is inclined in a direction that widens in diameter as it goes upwards with respect to the central axis C1, and the inner periphery of the forming recess 76 is smoothly connected to the upper end edge of the inclined surface 75.

[0037] The pre-curling roll 71 is rotatable around a roll centerline C2 that is aligned with the central axis C1 of the tapered cylindrical body 50, and can be rotated around the central axis C1 of the tapered cylindrical body 50. Then, as shown in a1 of Figure 6(a), when the inclined surface 75 is brought into contact with the upper end (edge) of the upper cylindrical portion 12' and pressed towards the bottom 2 of the tapered cylindrical body 50 along the central axis C1, as shown in a2 of the same figure, the tip (edge) of the upper cylindrical portion 12 moves along the inclined surface 75 of the pre-curling roll 71 and enters the molding recess 76, curling it by pushing out the base end side (tapered cylindrical portion 15 side) from the tip (edge). However, the pre-curling process ends when the edge reaches an intermediate position in the molding recess 76 (near where the edge has passed the top of the molding recess 76). As a result, a pre-curled portion 72 is formed at the open end, which curves into a predetermined arc and is radially outward in a flange-like shape.

[0038] (End bending process) In the pre-curling process, a pre-curling roll 71 that rotates around a central axis C1 is used, but in this end bending process, molds 81 and 82 that reciprocate along the central axis C1 are used. Specifically, as shown in Figure 6(b), there is an inner mold 81 that is inserted inside the opening having the pre-curling portion 72, and a cylindrical outer mold 82 that is positioned outside the inner mold 81. The inner mold 81 supports the pre-curling portion 72 from the inside by being inserted inside the upper cylindrical portion 12 of the tapered cylindrical body 50, and is formed in a substantially cylindrical shape. The outer mold 82 is provided so as to surround the inner mold 81 with a slight gap between it and the outer circumferential surface of the inner mold 81, and an inclined surface 83 is formed at the tip (lower end) that slopes away from the inner mold 81 as it goes downwards. The inclined surface 83 and the inner circumferential surface 84 are smoothly connected by an arcuate surface 85.

[0039] Then, as shown in b1 of Figure 6(b), with the inner mold 81 inserted inside the upper cylindrical portion 12, the outer mold 82 is moved along the central axis C1 towards the bottom 2, and as shown in b2 of Figure 6(b), the tip of the pre-curl portion 72 is pressed against it by the inclined surface 83 and bent, and the outer mold 82 is advanced to a position where the bent portion is sandwiched between the outer circumferential surface 84 of the outer mold 82 and the outer circumferential surface 81. When the outer mold 82 is returned to its initial position, some springback occurs, but the opening end is bent at a sharp angle. This bent portion is referred to as the end bend portion 21'.

[0040] (Curling process) In this embodiment, the curling process consists of two steps. Specifically, as shown in Figure 7(c), the first curling step involves spreading the aforementioned end bend portion 21' radially outward while folding back the portion on the base end side (tapered cylinder portion 15 side) from the end bend portion 21' to form a second bend portion 27' that is convex upward, and the second curling step involves pressing the second bend portion 27' along the central axis C1, spreading the second bend portion 27' radially outward while folding back the portion on the base end side (tapered cylinder portion 15 side) from the second bend portion 27' to form a downward-facing second bend portion 27 and form the curl portion 5.

[0041] The first curling process forms a second bend 27' with a radius of curvature slightly larger than the end bend 21' formed in the pre-curling process. The first curling roll 91 used in this process has the same shape as the pre-curling roll 71, although its dimensions are different. It is rotatable around a roll central axis C3 that is perpendicular to the direction along the central axis C1 of the tapered cylindrical body 50, and can also be rotated around the central axis C1 of the tapered cylindrical body 50. It comprises an inclined surface 92 that contacts the open end of the tapered cylindrical body 50 at an angle and presses in the direction along the central axis C1, and a forming recess 93 that is received downwards and opens in the shape of a circular arc groove in cross-section. The inclined surface 92 is inclined in a direction that expands in diameter as it goes upward with respect to the central axis C1, and the inner periphery of the forming recess 93 is smoothly connected to the upper end edge of the inclined surface 92. In addition, the side of the forming recess 93 opposite to the inclined surface 92 is formed as a cylindrical surface 94 that is almost along the central axis C1.

[0042] As shown in c1 of Figure 7(c), when the inclined surface 92 is brought into contact with the upper end of the upward-facing end bend portion 21' and pressed in the direction of the bottom 2 along the central axis C1, as shown in c2 of the same figure, the upper end of the end bend portion 21' moves along the inner surface of the first curling roll 91 and enters the molding recess 93, bending so that the base end side of the end bend portion 21' is folded back. The first curling process ends when the end bend portion 21' reaches near the outer peripheral edge of the molding recess 93 (near the connection between the molding recess 93 and the cylindrical surface 94). As a result, the second bent portion 27' is formed to be convex upwards, continuous with the end bent portion 21'. Note that the end bent portion 21' may widen slightly (its radius of curvature may increase) during this first curling process.

[0043] Next, in the second curling step, as shown in Figure 7(d), similar to the first curling step, a second curling roll 95, which is rotatable by a roll central axis C4 that is perpendicular to the central axis C1 of the tapered cylindrical body 50, is rotated around the central axis C1 of the tapered cylindrical body 50. The second curling step includes an inclined surface 96 that contacts the open end of the tapered cylindrical body 50 after the first curling step in an inclined state and presses in a direction along the central axis C1, and a forming recess 97 that is received downwards and opens up in the shape of a circular arc groove in cross-section. The inclined surface 96 is inclined in a direction that widens in diameter as it goes upwards with respect to the central axis C1, and the inner periphery of the forming recess 97 is smoothly connected to the upper end edge of the inclined surface 96. In addition, in this forming recess 97, the side opposite to the inclined surface 96 is formed as a cylindrical surface 98 that is almost parallel to the central axis C1. The forming recess 97 in this second curling step is formed to be wider than the forming recess 93 in the first curling step.

[0044] As shown in d1 of Figure 7(d), the inclined surface 96 is brought into contact with the upper end of the upward-facing second bend 27' and pressed in the direction of the bottom 2 along the central axis C1. In the pre-curling process in Figure 6(a) and the first curling process in Figure 7(c), the tips are brought into contact with the relatively inner part of the inclined surfaces 75 and 92, but in this second curling process, the inner circumference of the second bend 27' is brought into contact with the entrance of the inclined surface 96. When pressed by the second curling roll 95 along the central axis C1 from this state, as shown in d2 of the same figure, the upper end of the second bend 27' moves along the inner surface of the second curling roll 95 and enters the molding recess 97, bending so that the base end side (tapered cylindrical portion 15 side) of the second bend 27' folds back, and is pressed by the inclined surface 96 to deform it into a tapered shape. The curled portion 5 is formed when the second bend 27' reaches the lower end of the cylindrical surface 98 via the molding recess 97. As a result, an enlarged diameter portion 22 is formed at the base end of the curled portion 5, and the second bent portion 27 is formed to become convex downwards while the end bent portion 21 is rolled inward. In some cases, the second bent portion 27 may widen slightly (its radius of curvature may increase) during this second curling process.

[0045] In addition, during this series of curling processes, the tapered cylindrical portion 15 of the tapered cylindrical body 50 is also pressed in the axial direction. However, since the opening of the tapered cylindrical body 50 is formed by a straight upper cylindrical portion 12 along the central axis C1, and combined with the work hardening effect achieved through the previous diameter expansion process, buckling and deformation are unlikely to occur.

[0046] The metal cup 1 manufactured in this manner has straight cylindrical sections 11 and 12 of some length formed near the bottom 2 and the opening 3, and most of the body 4 between them is formed in a tapered shape that gradually widens in diameter from the bottom 2 to the opening 3, with a curled section 5 formed at the opening 3.

[0047] Following this curling process, a cleaning process is carried out. In the cleaning process, the metal cup 1 is transported downwards on a mesh conveyor G, with its opening facing downwards, and during this time, a cleaning solution is sprayed onto the inside of the metal cup 1 from below and onto the outside from the outside by a shower. At this time, in the curl section 5, as shown in Figure 8, the wide opening inlet gap g1 is directed upward, so the cleaning liquid sprayed from the outside, as indicated by the arrow, penetrates into the curl section 5 through this inlet gap g1.

[0048] As shown by the dashed line, once the cleaning liquid L has entered the large space S2 within the curled section 5, the liquid level exceeds the bent end section 21 and reaches the vicinity of the curled end 20. At this point, air accumulates in the small space S1, creating a seal, and the further intrusion of the cleaning liquid L is stopped at a position where it is in equilibrium with the pressure near this small space S1. After the cleaning process, the material is heated and dried, so the cleaning solution L that had penetrated the large space S2 within the curled section 5 also dries and disappears. Since the cleaning solution L did not penetrate the small space S1, no cleaning solution remains in this small space S1.

[0049] The curled portion 5 is rounded in the same way as a normal curled portion in terms of its overall appearance, and the second bent portion 27 that forms the lower surface of the curled portion 5 is formed to be convex downwards, resulting in a smooth feel in the mouth.

[0050] [Second Embodiment] Figure 9 shows the curled portion 101 of the second embodiment. In the first embodiment, the curled portion 5 had two bent portions, an end bent portion 21 and a second bent portion 27. However, the curled portion 101 of this second embodiment lacks the second bent portion and only has an end bent portion 102. The other configurations are almost the same as those of the curled portion of the first embodiment. In other words, the curled portion 101, in a longitudinal cross-section passing through the central axis C1 of the metal cup 1, has an enlarged diameter portion 22 that is continuous with the upper end of the upper cylindrical portion 12 of the body portion 4 and gradually widens in diameter in a tapered manner as it extends upward, an upper inner circumferential curved portion 23 that curves outward radially from the upper end of the enlarged diameter portion 22, an upper outer circumferential curved portion 25 that forms a folded top portion 24 between itself and the upper inner circumferential curved portion 23, and an outer circumferential cylindrical portion 103 that is continuous with the outer circumferential edge of the upper outer circumferential curved portion 25 and forms the part of the curled portion 101 with the largest outer diameter. In this embodiment, the outer circumferential cylindrical portion 103 is formed in a curved surface shape that is convex radially outward.

[0051] Furthermore, the curled end 104 is continuous with the lower end of the outer cylindrical portion 103 via the end bend portion 102. In this case, the curled end 104 is inclined outward diagonally upward, in other words, gradually expanding in diameter from bottom to top. Therefore, the tip (edge) of the curled end 104 extends toward the upper outer curved portion 25 or the inner surface of the outer cylindrical portion 103. The space between the tip of the curled end 104 and the inner surface of the outer cylindrical portion 103 becomes a minute gap g2 relative to the small space S1 formed within the end bend portion 102. Furthermore, the end bend portion 102 is located at the lowest end of the curl portion 101, and the distance from the lowest point of the end bend portion 102 to the highest point of the folded top portion 24 is the height W of the curl portion 101. The distance from the innermost part of the end bend portion 102 to the outer surface of the upper cylindrical portion 12 of the body portion 4 is the entrance gap g1 to the large space S2 within the curl portion 101.

[0052] In this second embodiment, the inclination angle θ1 of the diameter-expanded portion 22 with respect to the central axis C1 is formed to be 10° or more and 60° or less. Further, the radius of curvature R1 of the outer surface of the curled end portion 104 is formed to be 0.1 mm or more and 2.0 mm or less, preferably 0.15 mm or more and 1.0 mm or less. Also, the inlet gap g1 between the end bent portion 102 and the outer peripheral surface of the upper cylindrical portion 12 of the body portion 4 is 1.0 mm or more and 3.0 mm or less, preferably 1.0 mm or more and 2.5 mm or less, and the minute gap g2 between the tip (edge) of the curled end portion 104 and the inner surface of the outer peripheral cylindrical portion 103 is 0.5 mm or more and 1.5 mm or less, preferably 0.5 mm or more and 1.0 mm or less. However, g2 < g1. Further, the inclination angle θ2 of the curled end portion 104 with respect to the central axis C1 is formed to be 10° or more and 135° or less, preferably 10° or more and 90° or less. This inclination angle θ2 is the angle formed by the tangent line at the intermediate portion in the longitudinal direction of the curled end portion 104 with respect to the central axis C1. This inclination angle θ2 tends to be smaller than in the case of the first embodiment. Other dimensions are the same as in the case of the first embodiment.

[0053] When forming this curled portion 101, the precurl process and the end bending process of the first embodiment are the same in this second embodiment as well, and as shown in FIGS. 6(a) and 6(b), an end bent portion 21' is formed. Next, in the curling process, instead of processing in two steps as in the first embodiment, it is processed once using the curling roll shown in FIG. 10. The curling roll 111 is rotatable about a roll central axis C5 along a direction orthogonal to the central axis C1 of the tapered cylindrical body 50, and is rotated around the central axis C1 of the tapered cylindrical body 50. And it includes an inclined surface 112 that abuts against the open end of the tapered cylindrical body 50 in an inclined state and presses in the direction along the central axis C1, and a molding concave portion 113 formed in a cross-sectional arc groove shape that opens while receiving downward. The inclined surface 112 is inclined in a direction of increasing diameter as it goes upward with respect to the central axis C1, and the inner peripheral edge of the molding concave portion 113 is smoothly connected to the upper end edge of the inclined surface 112. Also, in this molding concave portion 113, the side opposite to the inclined surface 112 is formed on a cylindrical surface 114 substantially along the central axis C1.

[0054] Then, as shown in e1 of Figure 10, when the entrance area of ​​the inclined surface 112 is brought into contact with the upper end of the upward-facing end bend 21' and pressed in the direction of the bottom 2 along the central axis C1, as shown in e2 of the same figure, the upper end of the end bend 21' moves along the inner surface of the curling roll 111 and enters the molding recess 113, bending so that the base end side of the end bend 21' is folded back. The curled portion 101 is formed when the end bend 21' reaches the lower end of the cylindrical surface 114 via the molding recess 113. This creates a curled portion 101 having a downwardly convex bent end portion 102.

[0055] In the curled portion 101 formed in this way, the large space S2 within the curled portion 101 opens at the entrance gap g1, while the small space S1 inside the end bent portion 102 within the curled portion 101 opens upward through a minute gap g2. During the cleaning process, because the product is in an inverted position, the minute gap g2 of the small space S1 faces downward. Therefore, even if the cleaning liquid penetrates into the large space S2 of the curled portion 101, it is prevented from penetrating into the small space S1 through the minute gap g2. Consequently, the residue of the cleaning liquid inside the curled portion 101 is suppressed. Furthermore, since the curled end 104 is rounded so as to be tucked inside the curled portion 101, the tip (edge) of the curled end 104 does not touch the lips, resulting in a pleasant mouthfeel when drinking.

[0056] In the above embodiment, multiple curling rolls were used in the curling process, but the number is not limited to those shown in the illustration. Although six are shown in the illustration, at least three or more are sufficient. Furthermore, the above embodiments can be modified as appropriate without departing from the spirit of the present invention. [Explanation of Symbols]

[0057] C1 center axis E-edge 1. Metal cup (metal container) 2 bottom 3 Opening 4 Torso 5. Curl section 6 Dome section 11 Lower cylindrical section 12 Upper cylindrical section 13 Lower section 14 Upper step 15 Tapered cylinder section 20 Curl ends 21 End bend 22 Expanded diameter part 23 Upper inner circumference curved section 24 Folded top 25 Upper outer circumference curved section 26 Outer cylindrical part 27. Downward bending section (second bending section) 50 Tapered cylindrical body 71 Pre-curl Roll 72 Pre-curl section 74 curling rolls 81 Inner mold 82 Outside mold 91 Roll for the first curl 95 Roll for the second curl 101 Curl section 102 End bend 103 Outer cylindrical part 104 Curl end 111 Curl Roll S1 small space S2 large space g1 entrance gap g2 minute gap

Claims

1. The bottomed cylindrical body has a curled portion at its open end, which is formed by folding the open end radially outward and rounding it. The curled portion, in a longitudinal cross-section passing through the central axis of the body, has an upper inner circumferential curved portion that extends radially outward from the upper end of the body, an upper outer circumferential curved portion that forms a folded top between it and the upper inner circumferential curved portion, and an outer cylindrical portion that is continuous with the outer edge of the upper outer circumferential curved portion and forms the part of the curled portion with the largest outer diameter, and a curled end is formed radially inward from the outer cylindrical portion via an end bend portion with the smallest radius of curvature in the curled portion, and the curled end extends toward the inner surface of the upper outer circumferential curved portion or the outer cylindrical portion. A metal container characterized in that the distance in the direction perpendicular to the central axis in the gap between the tip of the curled end and the inner surface of the upper outer curved portion or the outer cylindrical portion is smaller than the distance in the direction perpendicular to the central axis in the gap between the end bend and the outer surface of the body.

2. The metal container according to claim 1, wherein the end bend is connected to the lower end of the outer cylindrical portion via a second bend, and the radius of curvature of the outer surface of the second bend is greater than the radius of curvature of the outer surface of the end bend and smaller than the radius of curvature of the outer surface of the upper inner curved portion and the upper outer curved portion.

3. The metal container according to claim 2, characterized in that the curled end is inclined downwards toward the tip with respect to a direction perpendicular to the central axis.

4. The metal container according to claim 1, characterized in that the curled end is inclined in a direction that gradually widens in diameter from bottom to top.

5. The metal container according to any one of claims 1 to 4, characterized in that the angle of inclination of the curled end with respect to the central axis is 10° or more and 135° or less.

6. The process includes a body forming step of press-forming an aluminum alloy sheet to form a bottomed cylindrical body, and a curling step of forming a curled portion at the open end of the body, A method for manufacturing a metal container, characterized in that the curl portion forming step comprises: a pre-curling step of forming a pre-curled portion with its tip facing radially outward by pressing the open end of the body along the central axis with a pre-curling roll that rotates around the central axis of the body; an end bending step of forming an end bend that is convex upward by bending the pre-curled portion; and a curling step of forming a curl portion by pressing the end bend along the central axis with a curling roll that rotates around the central axis, thereby spreading the end bend radially outward and folding back the portion on the body side of the end bend.

7. The method for manufacturing a metal container according to claim 6, characterized in that the bending step involves placing an inner mold inside the body and bending the pre-curled portion while pressing it along the central axis direction with an outer mold.

8. The method for manufacturing a metal container according to claim 6, characterized in that the curling step comprises: a first curling step of pressing the end bent portion along the central axis to spread it radially outward while folding back the portion on the base end side from the end bent portion to form a second bent portion that is convex upward; and a second curling step of pressing the second bent portion along the central axis to spread it radially outward while folding back the portion on the base end side from the second bent portion to position the second bent portion in a downward convex shape to form a curled portion.

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