Metallic bottomed cylinder

Abstract

A metal bottomed cylindrical body (10) has a ground portion (5) at the bottom, a standing portion (6) extending upward from the inner side of the ground portion (5), and a dome-shaped bottom surface (7) connected to the standing portion (6). The metal bottomed cylindrical body (10) is characterized in that an annular line (11) originating from a local thin-walled portion is observed at the peripheral portion (7a) of the dome-shaped bottom surface (7).

Description

Technical Field

[0001] The present invention relates to a metal bottomed cylinder having a dome-shaped bottom surface, such as a seamless metal can, and also to a molding die for forming the dome-shaped bottom surface and a doming method using the molding die. Background Technology

[0002] Generally, for metal cylindrical bodies with bottoms obtained through metal forming processes (punching, deep drawing, and thinning), such as seamless cans, a bottom-forming process is performed to create a dome-shaped depression in order to reduce weight, improve pressure resistance, and stabilize the structure. This bottom-forming process is called dovetailing, and it is performed by pushing a dovetail die head upwards from between the annular die while holding the bottom periphery of the cylindrical body using an annular die called a retaining ring (see Patent Document 1).

[0003] Furthermore, in dome-shaped bottoms as described above, there is a tendency for wrinkles to form around the perimeter, especially noticeable in aluminum cans. Previously, these wrinkles formed only on the bottom surface and were not a significant problem. However, nowadays, beverage cans, such as seamless aluminum cans, are mostly displayed and sold with the bottom visible; therefore, the current situation requires improvement.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-177289 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Therefore, the object of the present invention is to provide a metal cylindrical body with a dome-shaped bottom without wrinkles.

[0009] Another object of the present invention is to provide a forming mold for use in dome forming (arching) of the bottom of the aforementioned metal cylindrical body, and a dome forming method using the forming mold.

[0010] Solution for solving the problem

[0011] According to the present invention, a metal cylindrical body with a bottom is provided, having a grounding portion at the bottom, an upright portion extending upward from the inside of the grounding portion, and a dome-shaped bottom surface connected to the upright portion. The metal cylindrical body with a bottom is characterized in that…

[0012] A ring-shaped line was observed at the periphery of the dome-shaped bottom surface.

[0013] In the metal-bottomed cylindrical body of the present invention, preferably,

[0014] (1) The metal bottom cylinder is a seamless aluminum can.

[0015] According to the present invention, a forming die is also provided for use in forming a dome with a bottom cylindrical body made of metal, characterized in that...

[0016] It consists of an annular retaining mold for holding the bottom periphery of a metal cylindrical body and an arched mold head for defining the dome-shaped bottom surface.

[0017] The arched die head is divided into an arched ring for defining the peripheral portion of the dome-shaped bottom surface and a base die head for defining the central portion of the dome-shaped bottom surface that is inside the peripheral portion. The arched ring and the base die head can move up and down independently.

[0018] According to the present invention, a dome forming method is also provided, which is a method for forming a dome with a bottom cylindrical body made of metal, the dome forming method being characterized in that it includes the following steps:

[0019] Prepare the molding die as described above;

[0020] The punch sleeve is lowered from the inside of the metal bottom cylinder, and the lower periphery of the cylinder is pressed against the working surface of the annular retaining mold, thereby forming a convex edge and a grounding part on the periphery of the bottom surface of the cylinder.

[0021] While using the working surfaces of the punch sleeve and the annular retaining mold to hold the convex edge and grounding part of the cylinder, the arched ring is raised to form an upright part and the periphery of the dome-shaped bottom surface inside the grounding part; and

[0022] The central part of the dome-shaped bottom surface is formed by configuring the base mold head.

[0023] Invention Effects

[0024] The metal bottom cylinder of the present invention has a dome-shaped bottom surface that is recessed into a dome shape, but there are no wrinkles on the periphery of the dome shape. Instead, annular lines are observed.

[0025] In this invention, the die used in the forming of the bottom of the cylinder, i.e., the arching forming, is divided into an arching ring for defining the peripheral portion of the dome-shaped bottom surface and a base die for defining the central portion of the dome-shaped bottom surface that is closer to the inner side of the peripheral portion. The surface of the peripheral portion of the dome-shaped bottom surface is formed by a special die called the arching ring. As a result, the surface of the peripheral portion of the dome-shaped bottom surface is extended and thinned, and wrinkles are prevented along with this thinning. In summary, the arching is performed using a special arching ring that defines the peripheral portion of the dome-shaped bottom surface; therefore, the portion thinned by the arching ring becomes an indentation, and the mark at the inner end of the arching ring is observed as a ring-shaped line.

[0026] In this way, in the metal cylindrical body of the present invention, annular lines are observed instead of wrinkles on the periphery of the dome-shaped bottom surface, thereby not compromising the appearance and ensuring high commercial value, for example, when used as a beverage can. Attached Figure Description

[0027] Figure 1 This is a schematic side sectional view showing the overall metal-based bottom cylinder body of the present invention.

[0028] Figure 2 yes Figure 1 A magnified partial side sectional view of the bottom of a metal cylinder with a base.

[0029] Figure 3 yes Figure 1 A photograph of the bottom surface of a metal cylindrical body.

[0030] Figure 4 It is a photograph of the bottom surface of a metal cylindrical body that is known from the past.

[0031] Figure 5 It shows the manufacturing process. Figure 1 A schematic diagram of the process of making a metal cylinder with a bottom.

[0032] Figure 6 It is shown in Figure 5 A diagram of the forming mold used in the arching process.

[0033] Figure 7 It is used for explanation Figure 5 The diagram shows the arching process. Detailed Implementation

[0034] <The form of a metal cylindrical body>

[0035] The metal bottomed cylindrical body of the present invention is obtained, for example, by punching, deep drawing, and re-deep drawing-thinning a thin-walled metal blank, followed by arching the bottom. Finally, after obtaining the metal bottomed cylindrical body, post-processing such as cleaning and drying, outer surface printing, topcoat varnish coating and baking, inner surface coating coating and baking, necking, and flange forming is performed. Its final shape is generally as follows: Figure 1 As shown.

[0036] Reference Figure 1 The metal bottomed cylindrical body of the present invention, generally indicated by 10, comprises: a main body 1 having a straight cylindrical shape with a flat outer surface; a grounding portion 5 formed with a convex edge 3 that slopes inward from the lower end of the main body 1; and a dome-shaped bottom surface 7 located in the area surrounded by the grounding portion 5. Furthermore, the upper part of the main body 1 is connected to a necked portion 8 formed by post-processing, and a flange portion 9 is formed at the upper end of the necked portion 8.

[0037] The dome-shaped bottom surface 7 is composed of a peripheral portion 7a connected to the upper end of the upright portion 6 that rises inward from the grounding portion 5, and a central portion 7b surrounded by the peripheral portion 7a. The peripheral portion 7a corresponds to the part that contacts the arching ring used during arching, as described later, and its length is approximately 2 mm to 30 mm when viewed in side section. When viewed in side section, the dome-shaped bottom surface 7, composed of the peripheral portion 7a and the central portion 7b, has a generally fixed large radius of curvature. By forming this type of bottom surface 7 at the bottom, the bottomed cylinder 10 can be stably installed, thereby improving the load strength relative to the axial direction.

[0038] In this invention, there are no particular limitations on the metal constituting the bottomed cylindrical body 10, and it can be any metal or alloy. However, considering factors such as lightweight and thin-walled processability, aluminum or aluminum alloy is preferred. Furthermore, in terms of maximizing the advantages of this invention, a seamless can with its inner surface coated with organic resin is preferred.

[0039] and Figure 1 Refer to together Figure 2 Enlarged partial side sectional view at the bottom and Figure 3 In the bottom photograph of the present invention, an important feature is that an annular line 11 is observed at the boundary between the peripheral portion 7a and the central portion 7b of the dome-shaped bottom surface 7.

[0040] That is, such a dome-shaped bottom surface 7 is obtained by arching, but in conventionally known metal cylindrical bodies with bottoms, such as Figure 4 As shown in the bottom photograph, wrinkles X exist in the region corresponding to the periphery 7a of the dome-shaped bottom surface 7. However, in this invention, as from... Figure 3As can be understood from the bottom photograph, an annular line 11 is formed instead of fold X. As described above, as can be understood from the periphery 7a originating from the arching ring used during arching, the annular line 11 originates from the indentation of the arching ring, with the outer region of the annular line 11 being the periphery 7a and the inner region of the annular line 11 being the center 7b. Furthermore, the thickness t0 at the annular line 11 originating from this local thin-walled portion is reduced by approximately 3% to 5% compared to the thickness t1 at a position approximately 0.5 mm inside the periphery 7a, thus eliminating fold X through extension. That is, in the present invention, an annular line 11 is formed instead of fold X.

[0041] In a metal cylindrical body 10 like this, the thickness at the center O of the dome-shaped top surface 7 is usually equivalent to the thickness of the thin-walled blank used in the forming process, and the thickness of the main body 1 is determined according to the degree of thinning process (thinning rate).

[0042] For example, in the case of seamless aluminum cans used as beverage cans, the thickness of the blank plate is about 0.180 mm to 0.350 mm, and the thickness of the thinnest part of the main body 1 is 30% to 50% of the thickness of the blank plate.

[0043] <Manufacturing of the metal bottom cylinder 10>

[0044] The metal bottom cylinder 10 of the present invention having the form described above is manufactured by molding a blank of the metal (which may also have an organic resin coating on one side corresponding to the inner surface).

[0045] The forming process using the metal blank sheet as described above is as usual, through punching, drawing, thinning, and arching, to obtain a bottomed cylindrical body 10 with a dome-shaped bottom surface 7.

[0046] The process from punching to arching is shown below. Figure 5 .

[0047] That is, such as Figure 5 As shown in (a), the blank 21 is punched using a punching punch 23 and a punching die 25 to obtain a round plate 27 (punching process). Next, as... Figure 5 As shown in (b), a deep-drawn cup (bottomed cylindrical body) 35 is obtained using a deep-drawing die 31 and a deep-drawing punch 33 (deep-drawing process). Here, the resulting deep-drawn cup 35 may also be used for the arching process described later, but usually the process from re-drawing to thinning is performed continuously as needed.

[0048] That is, such as Figure 5As shown in (c), the drawing cup 35, held by the pressing member 41 and located in the redrawing die 43, is pushed downwards using the thinning punch 45. After thinning through multiple thinning dies 47a-47c, it is arched at the lowest position. This arching is achieved using the clamping ring 51 and the arching die 61, described later. Through this arching, the dome-shaped bottom surface 7 is formed simultaneously with the aforementioned convex edge 3 and grounding portion 5.

[0049] After arching, the stripper finger 53 is used to pull the formed seamless can (metal bottom cylinder) 10 out of the punch 45, thus ending this process, and proceeding to the next process such as cleaning, drying, necking and other subsequent processes.

[0050] It should be noted that in the thinning process described above, in Figure 5 In (c), three thinning dies are configured to perform thinning in three segments. However, the number of thinning dies is not limited to three; it can be set to an appropriate number depending on the desired degree of thinning. One die can be used for thinning in one segment, or two or more dies can be configured for thinning in multiple segments. Of course, when multiple thinning dies are arranged along the processing direction and thinning is performed in multiple segments, the inner diameter (processing diameter) decreases as it moves downstream in the processing direction.

[0051] In summary, after such thinning process, arching is performed to form a dome-shaped bottom surface 7.

[0052] like Figure 6 As shown, the forming die for arching consists of a clamping ring (annular retaining die) 51 and an arching die head 60. Arching is achieved through the cooperative action of these forming dies and the punch 45. An important feature of this invention is that the arching die head 60 is divided into a base die head 61 and an arching ring 63, which are arranged to move up and down independently.

[0053] That is, as from Figure 6 As can be understood, the upper end of the clamping ring (ring-shaped retaining mold) 51 has an inward-facing and downward-sloping working surface 51a, through which a protruding edge 3 is formed that connects to the lower end of the main body 1, and a ground surface 5 is formed at the lower end of the working surface 51a.

[0054] Furthermore, the base mold 61 is a mold that defines the central portion 7b of the dome-shaped bottom surface 7, and its upper end working surface 61a corresponds to the central portion 7b of the dome-shaped bottom surface 7. Additionally, the arched ring 63 is a mold that defines the peripheral portion 7a of the dome-shaped bottom surface 7, and its upper end working surface 63a corresponds to the peripheral portion 7a of the dome-shaped bottom surface 7. These working surfaces 61a and 63a are smoothly connected to form the dome-shaped bottom surface 7.

[0055] As described above, the peripheral portion 7a of the dome-shaped bottom surface 7 is prone to wrinkling. By separating the profile defining this portion from the profile defining the central portion 7b, the stress applied to the peripheral portion 7a of the dome-shaped bottom surface 7 is concentrated, thereby extending the wrinkles and preventing their formation. A ring-shaped line 11 appears at the position corresponding to the inner end of the working surface 63a of the arched ring 63. That is, when viewed in a side section, the length of the working surface 63a is equivalent to the length of the peripheral portion 7a of the dome-shaped bottom surface 7.

[0056] The arching using the above-mentioned molding die passes through Figure 7 The process shown is carried out.

[0057] The clamping ring 51, not shown, is subjected to upward force by air, as... Figure 7 As shown in (a), in the initial stage, the working surface 63a of the arching ring 63 is located below the working surface 51a of the clamping ring 51, and the working surface 61a of the base mold head 61 is located even below the working surface 63a of the arching ring 63.

[0058] When the punch 45 is lowered and the main body 1 of the cylindrical body 10 is pressed down under the above conditions, as Figure 7 As shown in (b), the lower end of the main body 1 is pressed against the working surface 51a of the clamping ring 51, thereby forming a protruding edge 3 at the lower end of the main body 1.

[0059] Next, when the arched ring 63 is raised, as... Figure 7 As shown in (c), the grounding portion 5 is defined, and the inner side of the grounding portion 5 is pulled up to define the standing portion 6. Furthermore, the working surface 63a of the arched ring 63 pushes the surface that is closer to the inner side than the standing portion 6, thereby defining the peripheral portion 7a of the dome-shaped bottom surface 7.

[0060] When the periphery 7a of the dome-shaped bottom surface 7 is formed as described above, as Figure 7 As shown in (d), by delaying the configuration of the base mold head 61, its working surface 61a is pressed against the bottom of the cylinder 10, forming the central portion 7b of the dome-shaped bottom surface 7. Thus, the dome-shaped bottom surface 7 is defined, and at the end of the working surface corresponding to the arched ring 63, an observation is made of… Figure 2 , Figure 3 The annular line 11 shown in the figure effectively prevents wrinkles from forming by the arched ring 63.

[0061] After the arching is completed as described above, the punch 45 is pulled out, and the resulting molded body is pulled away from the punch 45 by the peeler claw 53. Subsequent processes such as cleaning, drying, necking, flange processing, and painting are then performed to obtain a bottomed cylindrical body (seamless can) with no wrinkles on the bottom surface and high commercial value.

[0062] Explanation of reference numerals in the attached figures

[0063] 1: Main body;

[0064] 3: Convex edge;

[0065] 5: Grounding part;

[0066] 6: Erecting part;

[0067] 7: Dome-shaped bottom surface;

[0068] 7a: Peripheral part;

[0069] 7b: Central section;

[0070] 10: Bottomed cylindrical body;

[0071] 51: Compression ring (ring-shaped retaining mold);

[0072] 60: Arched mold head;

[0073] 61: Base mold head;

[0074] 63: Arched ring.

Claims

1. A metal cylindrical body with a bottom, the metal cylindrical body having a grounding portion at the bottom, an upright portion extending upward from the inside of the grounding portion, and a dome-shaped bottom surface connected to the upright portion, characterized in that... The dome-shaped bottom surface is composed of a peripheral portion connected to the upright portion and a central portion surrounded by the peripheral portion. A ring-shaped line originating from the thin-walled portion is observed at the boundary between the peripheral portion and the central portion of the dome-shaped bottom surface.

2. The metal-based bottom cylinder according to claim 1, wherein, The metal-bottomed cylindrical body is a seamless aluminum can.

3. A forming die, used in forming a dome at the bottom of a metal cylindrical body, characterized in that... It consists of an annular retaining mold for holding the bottom periphery of a metal cylindrical body and an arched mold head for defining the dome-shaped bottom surface. The arched die head is divided into an arched ring for defining the peripheral portion of the dome-shaped bottom surface and a base die head for defining the central portion of the dome-shaped bottom surface that is located inside the peripheral portion. The arched ring and the base die head can move up and down independently. The arched ring is configured such that by pressing its inner end against the dome-shaped bottom surface, a ring-shaped indentation originating from the thin-walled portion is formed at the boundary between the peripheral portion and the central portion.

4. A dome forming method, wherein the dome forming method is a method for forming a dome with a bottom cylinder made of metal, the dome forming method being characterized in that it includes the following steps: Prepare the molding die as described in claim 3; The punch sleeve is lowered from the inside of the metal bottom cylinder, and the lower periphery of the cylinder is pressed against the working surface of the annular retaining mold, thereby forming a convex edge and a grounding part on the periphery of the bottom surface of the cylinder. While using the working surfaces of the punch sleeve and the annular retaining mold to hold the convex edge and grounding part of the cylinder, the arched ring is raised to form an upright part and the periphery of the dome-shaped bottom surface inside the grounding part; and The central part of the dome-shaped bottom surface is formed by configuring the base mold head.

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