Resin-coated aluminum alloy squeezing can

Abstract

To prevent crack in a can trunk while stripping.SOLUTION: A resin coated aluminum alloy drawn and ironed can includes a bottomed cylindrical can body 10 having a can bottom 11, and a cylindrical can trunk 12 around a can shaft extending along the can shaft from an outer periphery of the can bottom. In the can body, can height from a grounding part of the can bottom to an upper end of the can trunk is within a range of 151 mm or more and 160 mm or less. In the can trunk, an outer diameter is within a range of 45 mm or more and 59 mm or less, and at least at one part from 80 mm to 140 mm from the grounding part 112A of the can bottom toward an upper end side of the can trunk, a tapered part 122 is provided in which plate thickness of the can trunk becomes gradually thicker toward the inner side of the can trunk, and an angle of the tapered part with respect to the can shaft is 50 seconds or more and 1 minute and 30 seconds or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a drawn and ironed can made of a resin-coated aluminum alloy.

Background Art

[0002] As a container for filling contents such as beverages, a drawn and ironed can (two-piece can) made of a resin-coated aluminum alloy is known. The drawn and ironed can made of a resin-coated aluminum alloy can be obtained, for example, by integrally forming a can body and a can bottom by a DI (Drawing & Ironing) method.

[0003] In the DI method, first, in the capping press process, a metal plate is punched into a disk shape and subjected to drawing to form a shallow cup-shaped material. Next, in the body maker process, while pressing the can material against the lid loader die, the punch is moved to perform redrawing to form a deeper cup shape. Then, the punch is further moved and passed through the forming die to perform ironing, gradually thinning the side wall thickness of the cup to form a bottomed cylindrical can. Next, the can is stripped from the punch by fingers and removed (see, for example, Patent Document 1).

[0004] In the above-described forming process, for a drawn and ironed can made of an aluminum alloy without resin coating, lubricant is directly sprayed onto the can and the die during forming, whereas for a drawn and ironed can made of a resin-coated aluminum alloy, since the resin coating serves as a lubricant, forming is performed without using a lubricant (coolant) (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

[0006] As mentioned above, in resin-coated aluminum alloy pressed cans, no lubricant is used in the molding process, so depending on various conditions such as the punch temperature, a greater force may be required to remove the can from the punch.

[0007] Incidentally, in recent years, smaller, elongated two-piece cans (for example, 204mm diameter) are increasingly being adopted as a replacement for the common two-piece cans (211mm diameter) used for beer and other beverages, due to their stylish design. Furthermore, in response to the demand for resource conservation, the thickness of the can body is also being reduced.

[0008] In the case of small-diameter, elongated cans like these, the degree of elongation in the height direction of the can is large. Therefore, during the stripping process in the body maker, the length of the can that is attached to the punch is long relative to the unit length that the stripper fingers engage with the opening edge of the can. Consequently, if a fast forming speed (for example, 300 cans per minute) is maintained, the opening edge of the can may not withstand the force during stripping, potentially causing cracks in the can body. Such cracks in the can body become more likely as the thickness of the can body is reduced.

[0009] This invention has been made in view of the above circumstances, and one example of its objective is to solve the problems described above. Specifically, this invention aims to prevent cracking of the can body during stripping. [Means for solving the problem]

[0010] One aspect of the present invention provides a bottomed cylindrical can body having a can bottom and a cylindrical can body centered on a can axis that extends from the outer circumference of the can bottom along the can axis, wherein the can body has a can height of 151 mm or more and 160 mm or less from the ground contact portion of the can bottom to the upper end of the can body, and the can body has an outer diameter of 45 mm or more and 59 mm or less, and extends from the ground contact portion of the can bottom toward the upper end of the can body The can body has a tapered section in which the plate thickness changes continuously in the can axis direction from 90 mm, and the tapered section is The thickness of the can body is UpwardThe inside of the can body gradually becomes thicker Furthermore, as the plate thickness increases, the inner surface of the can body slopes inward. The angle of the tapered portion with respect to the can shaft is 50 seconds or more and 1 minute 30 seconds or less. The resin-coated aluminum alloy constituting the can body includes an outer surface coating resin that forms the outer surface of the can body, an inner surface coating resin that forms the inner surface, and an aluminum alloy provided between the outer surface coating resin and the inner surface coating resin. The can bottom has a concave curved dome portion in the center that is recessed toward the inside of the can body along the can axis, and in a predetermined region including a point on the can axis of the dome portion, the thickness of the outer surface coating resin is 0.008 to 0.015 mm, the thickness of the aluminum alloy is 0.18 to 0.24 mm, and the thickness of the inner surface coating resin is 0.010 to 0.020 mm. The present invention provides a resin-coated aluminum alloy squeezing and ironing can characterized by the above. [Effects of the Invention]

[0011] According to the present invention, it is possible to prevent the can body from cracking during stripping. [Brief explanation of the drawing]

[0012] [Figure 1] This is a longitudinal cross-sectional view along the can axis of a resin-coated aluminum alloy pressed and ironed can according to an embodiment of the present invention. [Figure 2] This is an enlarged cross-sectional view of portion A of a resin-coated aluminum alloy drawing can according to an embodiment of the present invention. [Figure 3] This is an enlarged cross-sectional view of portion B of a resin-coated aluminum alloy drawing can according to an embodiment of the present invention. [Figure 4] This graph shows the plate thickness distribution of the can body of a resin-coated aluminum alloy pressed can according to an embodiment of the present invention. [Figure 5] This table shows the results of forming the can body of a resin-coated aluminum alloy can by changing the angle of the tapered portion, according to an embodiment of the present invention. [Figure 6] This table shows the results of forming the can body of a resin-coated aluminum alloy can by changing the angle of the tapered portion, according to an embodiment of the present invention. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described in detail below with reference to the drawings. In the following description, the same reference numerals indicate parts with the same function, and redundant explanations in each figure will be omitted as appropriate.

[0014] FIG. 1 is a longitudinal sectional view along the can axis O of a drawn and ironed can made of resin-coated aluminum alloy according to an embodiment of the present invention, showing an overview of the drawn and ironed can made of resin-coated aluminum alloy. In FIG. 1, a sectional shape is shown in a diagram in which the description of the plate thickness of the can body is omitted. As shown in FIG. 1, a drawn and ironed can 1 made of resin-coated aluminum alloy includes a bottomed cylindrical can body 10.

[0015] The can body 10 is formed of a resin-coated aluminum alloy. The resin-coated aluminum alloy includes, for example, an outer surface side coating resin that becomes the outer surface side of the can body 10, an inner surface side coating resin that becomes the inner surface side of the can body 10, and an aluminum alloy provided between the outer surface side coating resin and the inner surface side coating resin.

[0016] The can body 10 has a can bottom 11 and a cylindrical can body 12 centered on the can axis O extending along the can axis O from the outer periphery of the can bottom 11, and forms a bottomed cylindrical shape by the can bottom 11 and the can body 12. The can bottom 11 and the can body 12 have the same shape over the entire circumference around the can axis O. The can body 10 is obtained by punching a plate material made of a resin-coated aluminum alloy into a circular shape, performing a drawing process to form it into a bottomed cylindrical cup member, performing a redrawing and ironing process on the cup member to integrally form the can bottom 11 and the can body 12, and then performing trimming, necking, and flanging processes on the open end of the can body 12.

[0017] The can body 10 has a can height from the grounding portion (described later) of the can bottom 11 to the upper end of the can body 12 within the range of 151 mm or more and 160 mm or less, and in the example shown in FIG. 1, it is 155.0 mm. The can body 12 has an outer diameter within the range of 45 mm or more and 59 mm or less, and in the example shown in FIG. 1, it is 57.2 mm.

[0018] The can bottom 11 includes a dome portion 111 and an annular convex portion 112. The dome portion 111 is provided at the central portion of the can bottom 11 and has a dome-shaped concave surface that is recessed toward the inner side of the can body 12 along the can axis O direction. In the example shown in FIG. 1, the dome portion 111 has a first curved surface 111A with a radius of curvature R1 at the central portion, and a second curved surface 111B that is located around the first curved surface and has a radius of curvature R2 different from the radius of curvature R1. The dome portion 111 may have a plurality of curved surfaces with different radii of curvature as in the example of FIG. 1, or may be a single curved surface with a single radius of curvature. In addition, known dome shapes can also be applied.

[0019] In a predetermined region including a point on the can axis O of the dome portion 111, it is preferable that the thickness of the outer surface side coating resin is 0.008 or more and 0.015 mm or less, the thickness of the aluminum alloy is 0.18 or more and 0.24 mm or less, and the thickness of the inner surface side coating resin is 0.010 or more and 0.020 mm or less.

[0020] The annular convex portion 112 protrudes annularly toward the outside of the can body 12 along the can axis direction around the outer periphery of the dome portion 111, and includes a grounding portion 112A that contacts the horizontal plane and supports the can body 10 when the can body 10 is placed on a horizontal plane. The tip of the annular convex portion 112 may be bent radially inward of the can body 12 in the longitudinal sectional view of FIG. 1. That is, by performing bottom reform as in the example of FIG. 1, the strength of the can bottom 11 can be further improved.

[0021] The can body 12 is formed in a cylindrical shape centered on the can axis O that extends from the outer periphery of the can bottom 11 along the can axis O. The can body 12 includes a neck portion 121 provided at the upper end portion and a taper portion 122 provided between the upper end portion and the lower end portion.

[0022] The neck portion 121 is formed such that the outer diameter of the can body 12 gradually decreases as it goes upward along the can axis O. A can lid (not shown) having a smaller diameter than the can body 12 is provided on the neck portion 121. In the example of FIG. 1, the minimum outer diameter of the neck portion 121 is 52.4 mm.

[0023] The neck portion 121 has a concave curved surface 121A with a radius of curvature r1 that is recessed radially outward at its upper end, a convex curved surface 121B with a radius of curvature r2 that is convex radially outward at its lower end, and a concave curved surface 121C with a radius of curvature r3 that is recessed radially outward between the upper and lower ends.

[0024] In the example shown in Figure 1, the radius of curvature r1 is 1.5 mm, the radius of curvature r2 is 5.0 mm, and the radius of curvature r3 is 10.0 mm. The values ​​of each radius of curvature are merely examples and are not limited to these values. Furthermore, the angle θ1 formed by the straight line L1 connecting the convex surface 121B and the concave surface 121C with the straight line parallel to the can axis O is preferably less than 27°, and in the example shown in Figure 1, it is 24°.

[0025] A flange portion 123 is formed at the open end of the can body 10, i.e., the upper end of the neck portion 121. In the example shown in Figure 1, the distance along the can axis O direction from the upper end of the flange portion 123 to the lower end of the neck portion 121 is 11 mm.

[0026] Figures 2 and 3 show enlarged views illustrating the tapered portion 122. Figure 2 shows an enlarged view of area A in Figure 1, and Figure 3 shows an enlarged view of area B in Figure 1. Note that Figure 3 is magnified to a higher degree than Figure 2.

[0027] Specifically, the tapered section 122 is provided at any position within a range of 80 mm to 140 mm (range A in Figure 1) from the contact portion 112A of the can bottom 11 toward the upper end of the can body 12. As shown in Figures 2 and 3, in at least a portion of range A in Figure 1, the thickness of the can body 12 gradually increases toward the inside of the can body 12 as it moves upward along the can axis O. The tapered section 122 is configured such that the inner surface of the can body 12 slopes inward as the thickness increases toward the top of the can body.

[0028] In the examples shown in Figures 2 and 3, the can body 12 is formed such that the thickness of the plate gradually increases from around 90 mm from the contact portion 112A of the can bottom 11 toward the upper end of the can body 12, and then increases further toward the neck portion 121 from around 135 mm. The distribution of the plate thickness of the can body 10 is shown in Figure 4.

[0029] As shown in Figures 2 and 3, the inclination angle of the tapered portion 122 on the inner surface of the can body 12, that is, the angle θ2 that the tapered portion 122 makes with a straight line parallel to the can axis O, is between 50 seconds and 1 minute 30 seconds. In this way, even when the can body 10 is made thinner, optimizing the angle of the tapered portion 122 to slow down the change in plate thickness improves the ease of stripping and prevents cracking of the can body during stripping.

[0030] Figure 5 shows the results of forming a can body with a 57.2 mm diameter from a circular plate material with a blank diameter (BD) of 143.0 mm by changing the angle of the tapered section 122 in 10-second increments from 30 seconds to 1 minute 50 seconds. Figure 6 shows the results of forming a can body with a 57.4 mm diameter from a circular plate material with a blank diameter (BD) of 143.0 mm by changing the angle of the tapered section 122 in 10-second increments from 30 seconds to 1 minute 50 seconds.

[0031] The tables in Figures 5 and 6 show the results for molding at a molding speed of 300 units per minute, with the original sheet thickness being 0.22 mm and 0.23 mm for each tapered section 122 angle. A × indicates that a crack occurred in the can body, while a ○ indicates that no crack occurred. Note that the values ​​indicating the original sheet thickness in Figures 5 and 6 represent the thickness of the aluminum alloy sheet and do not include the thickness of the outer and inner coating resins.

[0032] The presence or absence of cracks in the can body was evaluated using the ERV (Enamel Rating Value). Specifically, an enamelizer was used to create a metal exposure on the inner surface of the molded can, which was connected to the anode. The cathode was then immersed in a saline solution filling the can, and the current value was evaluated after applying a 6V DC voltage for 4 seconds at room temperature (approximately 23°C) or below. The evaluation criteria were that if the current value was 60mA or less, it was evaluated that there were no cracks in the can body, and if the current value exceeded 60mA, it was evaluated that a crack had occurred.

[0033] From the tables in Figures 5 and 6, it can be seen that when the angle of the tapered section 122 was 40 seconds or less (Comparative Examples 1-1, 1-2, 2-1, 2-2) or 1 minute 40 seconds or more (Comparative Examples 1-8, 1-9, 2-8, 2-9), cracking of the can body occurred either during the initial drawing or the re-drawing process. On the other hand, when the angle of the tapered section 122 was 50 seconds or more and 1 minute 30 seconds or less (Comparative Examples 1-3 to 1-7, 2-3 to 2-7), cracking of the can body did not occur during either the initial drawing or the re-drawing process.

[0034] As described above, according to this embodiment, even when a load is applied to the open end of the can body 12 by the fingers of the stripper during stripping in the body manufacturing process, a tapered portion 122 is provided with an optimized angle with respect to the can shaft so that the change in plate thickness becomes gradual. This improves the ease of stripping and prevents can body cracking even in can bodies with thinned plate thickness. [Explanation of symbols]

[0035] 10: Can body, 11: Can bottom, 12: Can cylinder, 111: Dome section, 112: Annular protrusion, 112A: Ground contact section, 121: Neck section, 121A: Concave curved surface, 121B: Convex curved surface, 121C: Concave curved surface, 122: Tapered section, 123: Flange section

Claims

1. The can body comprises a bottomed cylindrical can body having a can bottom and a cylindrical can body centered on the can axis, extending from the outer circumference of the can bottom along the can axis, The can body has a can height from the contact point of the can bottom to the upper end of the can body that is within the range of 151 mm to 160 mm. The aforementioned boiler body is The outer diameter is within the range of 45 mm to 59 mm, The can has a tapered section that extends from the contact point of the can bottom toward the upper end of the can body, starting from 90 mm away from the can body, in which the thickness of the can body changes continuously in the direction of the can axis. The tapered portion is such that the thickness of the can body gradually increases towards the inside of the can body as it moves upward, and as the thickness increases, the inner surface of the can body slopes inward. The angle of the tapered portion with respect to the can shaft is 50 seconds or more and 1 minute 30 seconds or less. The resin-coated aluminum alloy constituting the can body includes an outer surface coating resin that forms the outer surface of the can body, an inner surface coating resin that forms the inner surface, and an aluminum alloy provided between the outer surface coating resin and the inner surface coating resin. The bottom of the can is provided with a dome-shaped concave surface in the center that is recessed toward the inside of the can body along the axis of the can, In a predetermined region including a point on the can shaft of the dome portion, The thickness of the outer surface coating resin is 0.008 mm or more and 0.015 mm or less. The thickness of the aluminum alloy is 0.18 mm or more and 0.24 mm or less. A resin-coated aluminum alloy drawing can characterized in that the thickness of the inner surface coating resin is 0.010 mm or more and 0.020 mm or less.

2. The can body has a neck portion at its upper end, where the outer diameter of the can body decreases toward the upper part of the can shaft. The resin-coated aluminum alloy pressed can according to claim 1, wherein the neck portion has at least a convex curved surface that protrudes radially outward at the lower end of the neck portion, and a concave curved surface that is concave radially outward between the lower end and the upper end of the neck portion, and the angle of the straight line passing through the top of the convex curved surface and the top of the concave curved surface with respect to the can axis is less than 27°.

3. The tapered portion is formed over a distance of approximately 90 mm to 135 mm from the contact portion of the bottom of the can toward the upper end of the can body, as described in Claim 1 or Claim 2.

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