METHOD FOR MANUFACTURING METAL CONTAINER, APPARATUS FOR MANUFACTURING METAL CONTAINER, AND METAL CONTAINER

Abstract

A method for manufacturing a metal container includes a first step of forming a substantially planar four-sided bag using a metal plate; a second step of sandwiching, by first and second parallel plate jigs, one surface and the other surface of the four-sided bag formed in the first step; and a third step of pressurizing an inside of the four-sided bag while maintaining a contact state by the first and second parallel plate jigs with respect to the four-sided bag sandwiched between the first and second parallel plate jigs in the second step, and expanding a volume space in the four-sided bag while increasing a distance between the first and second parallel plate jigs.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT application No. PCT/JP2021/032551, which was filed on Sep. 3, 2021 based on Japanese patent application 2020-162436 filed on Sep. 28, 2020, whose contents are incorporated herein by reference. Also, all the references cited herein are incorporated as a whole.

BACKGROUND OF THE INVENTION

Technical Field

The present invention relates to a method for manufacturing a metal container, an apparatus for manufacturing the metal container, and the metal container.

Background Art

In related art, there has been a method of performing deep drawing by sandwiching and fixing a peripheral end portion of a metal plate material such as stainless steel and pushing a central portion with a punch (for example, see PTL 1).

CITATION LIST

Patent Literature

PTL 1: JP2010-247172A

SUMMARY

The inventors of the present application have studied a hollow container including a vacuum insulated core material such as powder therein. The hollow container can be manufactured by combining two plate materials formed by the deep drawing described in PTL 1. However, in the method described in PTL 1, since elongation is locally generated in a metal plate during molding, the metal plate may be broken due to the elongation.

It is highly difficult to mold the metal plate in a manner of packaging the core material with a packaging paper, and in order to maintain a vacuum, sealing is performed at each location of the metal plate after the packaging, but it is difficult to perform sealing on a three-dimensional molded article, and there are too many locations to be sealed, which is not practical.

Therefore, an envelope shaped four-sided bag is prepared, and it is attempted to prepare a container having a substantially truncated square bipyramidal shape (shape in which bottom surface sides of two truncated quadrangular pyramids including no bottom surface are connected to each other) or a substantially rectangular parallelepiped shape by gas pressure molding. However, it has been found that even when the gas pressure molding is performed using the four-sided bag, the four-sided bag is broken due to excessive elongation of a material during the molding.

According to an embodiment, a method for manufacturing a metal container and an apparatus for manufacturing the metal container can prevent breakage due to local elongation of a metal plate when forming a container from a four-sided bag.

Solution to Problem

A method for manufacturing a metal container according to an embodiment includes: a first step of forming a substantially planar four-sided bag using a metal plate; a second step of sandwiching, by first and second parallel plate jigs, one surface and the other surface of the four-sided bag formed in the first step; and a third step of forming, using the four-sided bag, a container having a substantially truncated square bipyramidal shape or a substantially rectangular parallelepiped shape by pressurizing an inside of the four-sided bag while maintaining a contact state by the first and second parallel plate jigs with respect to the four-sided bag sandwiched between the first and second parallel plate jigs in the second step, and expanding a volume space in the four-sided bag while increasing a distance between the first and second parallel plate jigs.

An apparatus for manufacturing a metal container according to an embodiment including first and second parallel plate jigs configured to sandwich one surface and the other surface of a substantially planar four-sided bag formed of a metal plate, in which

• the first and second parallel plate jigs are capable of sandwiching the four-sided bag, and maintain a contact state with the one surface and the other surface of the four-sided bag in a process of pressurizing an inside of the four-sided bag to expand a volume space in the four-sided bag.

A metal container according to an embodiment is a metal container having a substantially truncated square bipyramidal shape or a substantially rectangular parallelepiped shape. The metal container includes: two quadrangular top plates formed as one surface of the container and the other surface opposite to the one surface; a plurality of side walls connecting the two top plates; and an ear portion having oblique sides approaching each other from opposing vertexes of the two top plates and protruding laterally or folded along the plurality of side walls, valley-folded portions are formed at boundaries between the ear portion and the plurality of side walls, and one or more valley-folded marks having the vertex as a rotation center are formed between the valley-folded portion and the oblique side.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are perspective view showing metal containers manufactured by methods for manufacturing the metal containers according to an embodiment of the present invention, in which FIG. 1A shows a first metal container, and FIG. 1B shows a second metal container.

FIG. 2 is an enlarged view of a periphery of an ear portion shown in FIG. 1A.

FIG. 3 is a perspective view showing a four-sided bag used for manufacturing the metal container.

FIGS. 4A and 4B are a schematic configuration diagrams showing a main part of an apparatus for manufacturing the metal container according to the present embodiment, in which FIG. 4A is a plan view, and FIG. 4B is a side view.

FIGS. 5A and 5B are partially enlarged views showing details of a second flap jig shown in FIGS. 4A and 4B, in which FIG. 5A shows a maximum protruding state of a wedge, and FIG. 5B shows a minimum protruding state of the wedge.

FIGS. 6A and 6B are perspective views showing an intermediate process in a process of forming a container having a substantially rectangular parallelepiped shape, in which FIG. 6A shows a first stage, and FIG. 6B shows a second stage.

FIGS. 7A, 7B and 7C are perspective views showing a forming process of the four-sided bag, in which FIG. 7A shows a metal plate, FIG. 7B shows a state in which the metal plate is folded, and FIG. 7C shows the four-sided bag.

FIGS. 8A, 8B, 8C and 8D are process diagrams showing the process of forming the container having the substantially rectangular parallelepiped shape from the four-sided bag, in which FIG. 8A shows a stage in which the four-sided bag is sandwiched, FIG. 8B shows the first stage in which an inside is pressurized, FIG. 8C shows the second stage in which the inside is pressurized, and FIG. 8D shows a completion stage of the container.

FIGS. 9A and 9B are perspective views showing other examples of the four-sided bag, in which FIG. 9A shows a first example, and FIG. 9B shows a second example.

FIG. 10 is a plan view showing an auxiliary plate.

FIG. 11 is an enlarged view of a periphery of an ear portion according to a modification.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, the present invention will be described in accordance with a preferred embodiment. The present invention is not limited to the following embodiment, and can be modified as appropriate without departing from the scope of the present invention. In the embodiment to be described below, some configurations are not illustrated or described, but it goes without saying that a known or well-known technique is applied as appropriate to details of an omitted technique within a range in which no contradiction occurs to contents to be described below.

FIGS. 1A and 1B are perspective views showing metal containers manufactured by methods for manufacturing the metal containers according to the embodiment of the present invention, in which FIG. 1A shows a first metal container, and FIG. 1B shows a second metal container.

As shown in FIG. 1A, a metal container C manufactured in the present embodiment is, for example, a container C1 having a substantially rectangular parallelepiped shape, and includes two quadrangular top plates TB formed as one surface of the container C1 and the other surface opposite to the one surface, a plurality of side walls HP connecting the two top plates TB, and a plurality of ear portions D protruding from four corners of the container C1 in a manufacturing process. A seam welding portion SW is formed at an end portion on a long side LS side. On the other hand, an end portion on a short side SS side orthogonal to the long side LS (an intermediate portion of the short side SS) is an edge side E which is not welded or the like.

As shown in FIG. 1B, the metal container C manufactured in the present embodiment is, for example, a container C2 having a substantially truncated square bipyramidal shape. In the present embodiment, a truncated square bipyramid is one obtained by connecting bottom surface sides of truncated quadrangular pyramids including no bottom surface. Similarly to the container C1, the container C2 includes two quadrangular top plates TB formed as one surface of the container C2 and the other surface opposite to the one surface, a plurality of side walls HP connecting the two top plates TB, and a plurality of ear portions D protruding from four corners of the container C2 in a process of manufacturing the container C2. A seam welding portion SW is formed at an end portion on a long side LS side. Further, an end portion on a short side SS side orthogonal to the long side LS is also an edge side E which is not welded or the like.

In each of the containers C1 and C2, the seam welding portion SW may be formed on the short side SS side by the manufacturing method, or the seam welding portions SW may be formed on both the long side LS side and the short side SS side (four sides).

FIG. 2 is an enlarged view of a periphery of the ear portion D shown in FIG. 1A. As shown in FIG. 2, the ear portions D has oblique sides HY that approach each other from opposing vertexes V of the two top plates TB and protrudes laterally. Here, opposing means opposing in a direction connecting one surface and the other surface. A valley-folded portion VF which is valley-folded is formed between such an ear portion D and the side wall HP.

Further, a plurality of valley-folded marks VT having the vertexes V as rotation centers are formed between the valley-folded portion VF and the oblique sides HY. The number of the valley-folded marks VT may be one. As will be described later, the valley-folded marks VT are portions that were the valley-folded portions VF in the past in the manufacturing process of the container C1, and are portions in which traces that had been valley-folded in the past remains.

Although FIG. 2 illustrates the periphery of one ear portion D in FIG. 1A, the same applies to other ear portions D. Although a description is omitted, similarly, in the container C2 having the substantially truncated square bipyramidal shape shown in FIG. 1B, a plurality of valley-folded marks VT having vertexes V as rotation centers are formed between valley-folded portion VF and oblique sides HY. The number of the valley-folded marks VT may be one.

Such a metal container C shown in FIGS. 1A and 1B is manufactured from a four-sided bag. FIG. 3 is a perspective view showing the four-sided bag used for manufacturing the metal container C. As shown in FIG. 3, a four-sided bag B is a bag member having a substantially planar quadrangular shape (square shape or rectangular shape) formed by folding or welding a metal plate (for example, a stainless steel plate having a thickness of about 0.1 mm) MP (see FIGS. 7A and 7C to be described later). Four sides of the four-sided bag B are in a closed state except for an opening to be described later. The opening (small hole) for internal pressurization is formed in the four-sided bag B. An inside of such a four-sided bag B is pressurized through the opening, and an internal volume space thereof is expanded. After the expansion of the volume space, the opening is sealed, and the metal container C as shown in FIGS. 1A and 1B is manufactured.

FIGS. 4A and 4B are schematic configuration diagrams showing a main part of an apparatus for manufacturing the metal container C according to the present embodiment, in which FIG. 4A is a plan view, and FIG. 4B is a side view. As shown in FIGS. 4A and 4B, a manufacturing apparatus 1 includes first and second parallel plate jigs 11 and 12. As shown in FIG. 4A, the first and second parallel plate jigs 11 and 12 are flat plates having a quadrangular (substantially square shape or rectangular shape) in a plan view. Although only one surface side of the manufacturing apparatus 1 is illustrated in FIG. 4A, the second parallel plate jig 12 and flap jigs F to be described later on the other surface side also have the same shape as the first parallel plate jig 11 and flap jigs F on the one surface side. The first and second parallel plate jigs 11 and 12 are smaller than an area of the four-sided bag B in the plan view, and sandwich one surface and the other surface of the four-sided bag B in a state of being located inside four sides of the four-sided bag B. The sides of the first and second parallel plate jigs 11 and 12 are parallel to the four sides of the four-sided bag B so as to sandwich the one surface and the other surface of the four-sided bag B. The first and second parallel plate jigs 11 and 12 form the top plates TB of the metal container C.

The manufacturing apparatus 1 further includes a plurality of flap jigs F. The flap jigs F sandwich four regions around regions sandwiched by the first and second parallel plate jigs 11 and 12 on the one surface and the other surface of the four-sided bag B, that is, end portion sides of the four-sided bag B. The flap jigs F are pivotable as indicated by arrows A1 in of FIGS. 4A and 4B, and forms side surfaces of the container C1 having the substantially rectangular parallelepiped shape or oblique surfaces of the container C2 having the substantially truncated square bipyramidal shape.

As shown in FIGS. 4A and 4B, the flap jigs F are initially in a state of being substantially parallel to the first and second parallel plate jigs 11 and 12, and pivote from the substantially parallel state to a predetermined angle with respect to the parallel state in the manufacturing process (see FIGS. 8A to 8D to be described later). The predetermined angle is 90° in the manufacturing apparatus 1 for manufacturing the container C1 having the substantially rectangular parallelepiped shape, and the predetermined angle is less than 90° in the manufacturing apparatus 1 for manufacturing the container C2 having the substantially truncated square bipyramidal shape.

As shown in FIGS. 8A to 8D, the flap jigs F are configured to move toward a center side of the four-sided bag B in the manufacturing process. Accordingly, in the manufacturing process of the metal container C, the flap jigs F move to the center side of the four-sided bag B while pivoting, and operate in a manner of folding the metal container C from the sides.

Here, the first and second parallel plate jigs 11 and 12 are connected to the flap jigs F via link mechanisms L. Therefore, the flap jigs F operate in a manner of moving toward the center side of the four-sided bag B while pivoting in accordance with the operation in which the first and second parallel plate jigs 11 and 12 move in directions away from each other. The flap jigs F are formed in a manner of gradually folding the metal container C from the sides as a space volume inside the four-sided bag B increases. Wedges W, which will be described later, also operates in conjunction with the operations of the first and second parallel plate jigs 11 and 12 via the link mechanisms L.

The plurality of flap jigs F include a plurality of first flap jigs F1 that sandwich two opposing regions (two regions on seam welding portion SW sides in the present embodiment) of the four regions, and a plurality of second flap jigs F2 that sandwich remaining two opposing regions (two regions on edge side E sides in the present embodiment) of the four regions. As shown in FIG. 4A, the first flap jig F1 has a trapezoidal shape in the plan view. On the other hand, the second flap jig F2 includes a main body portion H having a rectangular shape in the plan view, and wedges W on both end portion sides of the main body portion H (that is, corner portion sides of the four-sided bag B).

FIGS. 5A and 5B are partially enlarged views showing details of the second flap jig F2 shown in FIGS. 4A and 4B, in which FIG. 5A shows a maximum protruding state of the wedge W, and FIG. 5B shows a minimum protruding state of the wedge W.

Each of the wedges W includes a line segment portion W1 extending from a respective one of the vertexes V of the first and second parallel plate jigs 11 and 12 toward a side of the four-sided bag B on a second flap jig F2 side (that is, the edge side E). In the apparatus 1 for manufacturing the metal container C, the wedges W move the line segment portions W1 in a process of pressurizing the inside of the four-sided bag B and increasing the internal space volume.

Specifically, as shown in FIG. 5B, the wedge W moves toward a main body portion H side while rotating such that an angle θ formed by the line segment portion W1 and the side of the four-sided bag B on the second flap jig F2 side (that is, the edge side E) changes from an acute angle to a right angle. At this time, an amount of movement of the wedge W is controlled by cooperation of a spring SP shown in FIGS. 5A and 5B, an oval portion LH formed in the main body portion H, and a screw portion S integrally connected to the wedge W and fitted into the oval portion LH. The rotation of the wedge W is controlled by an appropriate means (not shown). With such a wedge W, the apparatus 1 for manufacturing the metal container C according to the present embodiment can be formed in a manner of further folding the container C, as shown in FIGS. 6A and 6B to be described later.

FIGS. 6A and 6B are perspective views showing an intermediate process in a process of forming the container C1 having the substantially rectangular parallelepiped shape, in which FIG. 6A shows a first stage, and FIG. 6B shows a second stage. In the present embodiment, the container C1 having the substantially rectangular parallelepiped shape is formed through the first stage shown in FIG. 6A and the second stage shown in FIG. 6B.

Here, as shown in FIG. 6A, in the present embodiment, the container C1 having the substantially rectangular parallelepiped shape is formed in a manner of performing folding while pressurizing the inside of the four-sided bag B, and thus the valley-folded portions VF shown in FIG. 6A are formed. Next, when the internal volume is further increased through the internal pressurization of the four-sided bag B, the valley-folded portions VF shown in FIG. 6B are formed.

When the valley-folded portions VF shown in FIGS. 6A and 6B are compared, the angles θ with respect to the edge side E are different. That is, when the container C1 is formed by folding the four-sided bag B, the angles θ of the valley-folded portions VF with respect to the edge side E change. The apparatus 1 for manufacturing the metal container C according to the present embodiment moves the line segment portion W1 of the wedge W as shown in FIG. 5B in accordance with the changing angle θ, whereby the container C1 can be formed in a manner of folding the container C1 more appropriately.

Although the container C1 having the substantially rectangular parallelepiped shape has been described above as an example, the same applies to a case where the container C2 having the substantially truncated square bipyramidal shape is formed.

Next, a method for manufacturing the metal container C according to the present embodiment will be described. FIGS. 7A, 7B and 7C are perspective views showing a forming process of the four-sided bag B, in which FIG. 7A shows the metal plate MP, FIG. 7B shows a state in which the metal plate M is folded, and FIG. 7C shows the four-sided bag B.

First, as shown in FIG. 7A, the rectangular metal plate MP is prepared. Next, as shown in FIG. 7B, short sides MP1 of the rectangular metal plate MP are bent so as to face each other. Here, bent portions are the edge sides E described above. Thereafter, as shown in FIG. 7C, the short sides MP1 are butt-welded to each other to form a butt-welded portion BW. On the other hand, sides orthogonal to the edge sides E are seam-welded to form seam welding portions SW. As described above, the metal plate MP is formed into the substantially planar four-sided bag B.

FIGS. 8A, 8B, 8C and 8D are process diagrams showing the process of forming the container C1 having the substantially rectangular parallelepiped shape from the four-sided bag B, in which FIG. 8A shows a stage in which the four-sided bag is sandwiched, FIG. 8B shows the first stage in which the inside is pressurized, FIG. 8C shows the second stage in which the inside is pressurized, and FIG. 8D shows a completion stage of the container C1.

First, as shown in FIG. 8A, the four-sided bag B is sandwiched between the first and second parallel plate jigs 11 and 12. At this time, the one surface and the other surface of the four-sided bag B are sandwiched between the first and second parallel plate jigs 11 and 12 such that the first and second parallel plate jigs 11 and 12 are located inside the four sides of the four-sided bag B and the four sides of the four-sided bag B are parallel to the respective sides of the first and second parallel plate jigs 11 and 12.

Further, as shown in FIG. 8A, the flap jigs F sandwich the four regions around the regions sandwiched by the first and second parallel plate jigs 11 and 12, that is, the end portion sides of the four-sided bag B. More specifically, as shown in FIG. 4A, the two opposing regions of the four regions are sandwiched by the first flap jigs F1, and the remaining two opposing regions of the four regions are sandwiched by the second flap jigs F2.

As shown in FIG. 8A, in the present embodiment, an air bag AB is disposed between an upper wall UW of the manufacturing apparatus 1 and the like and the first parallel plate jig 11. Accordingly, the air bag AB presses the first parallel plate jig 11, and a reaction force (force in a direction of preventing expansion) is applied when the volume space is expanded. Furthermore, the reaction force is similarly applied to the second parallel plate jig 12 that is interlocked with the first parallel plate jig 11, and the flap jigs F that are interlocked with the first and second parallel plate jigs 11 and 12 via the link mechanisms L.

Next, the inside of the four-sided bag B is pressurized from a state in FIG. 8A. Accordingly, the volume space of the four-sided bag B is expanded as shown in FIGS. 8B and 8C. When the reaction force of the air bag AB is applied in this expansion process, the four-sided bag B matches the shapes of the first and second parallel plate jigs 11 and 12 and the flap jigs F. That is, the first and second parallel plate jigs 11 and 12, and the flap jigs F increase the space volume of the four-sided bag B while maintaining a contact state with the four-sided bag B.

In the process of expanding the volume space of the four-sided bag B as shown in FIGS. 8B and 8C, the line segment portion W1 of the wedge W approaches the main body portion H while rotating as shown in FIG. 5B. Accordingly, as shown in FIGS. 6A and 6B, the valley-folded portions VF corresponding to a size of the volume space are formed.

Thereafter, the volume space is further expanded, and the container C1 having the substantially rectangular parallelepiped shape is formed as shown in FIG. 8D.

In the case of forming the container C2 having the substantially truncated square bipyramidal shape instead of the container C1 having the substantially rectangular parallelepiped shape, the process may be finished in a state in FIG. 8C, for example, without pressurizing the inside of the four-sided bag B to a state shown in FIG. 8D.

The flap jigs F are not limited to the case of sandwiching the four regions, and may sandwich only two or three of the four regions. This is because a certain folding effect can also be achieved in this case.

In this manner, according to the method and the apparatus 1 for manufacturing the metal container C according to the present embodiment, since the inside of the four-sided bag B is pressurized while maintaining the contact state by the first and second parallel plate jigs 11 and 12 with respect to the four-sided bag B and the volume space inside the four-sided bag B is expanded while increasing a distance between the first and second parallel plate jigs 11 and 12, in the four-sided bag B having relatively high rigidity on an end portion side and relatively low rigidity on a center side, the inside of the four-sided bag B is pressurized while reducing a portion having relatively low rigidity, and when the container is formed from the four-sided bag B, it is possible to prevent breakage due to local elongation of the metal plate MP.

At least two of the four regions are sandwiched by the plurality of flap jigs F that can move toward the center side of the four-sided bag while pivoting, and the inside of the four-sided bag B is pressurized while maintaining the contact state by the first and second parallel plate jigs 11 and 12 and maintaining the contact state accompanied by the pivotation by the plurality of flap jigs F. Therefore, it is possible to form an oblique surface portion of a substantially truncated square bipyramid or a side surface portion of a substantially rectangular parallelepiped using the flap jigs F. In addition, since the flap jigs F move to the center side, the container can be formed by folding the four-sided bag B, and the metal container C can be formed while further preventing the breakage.

In addition, since the two opposing regions of the four regions are sandwiched by the plurality of first flap jigs F1 and the remaining two opposing regions of the four regions are sandwiched by the plurality of second flap jigs F2, entire surfaces of the containers C1 and C2 having the substantially truncated square bipyramidal shape or the substantially rectangular parallelepiped shape can be pressed when the containers C1 and C2 are formed, the containers C1 and C2 can be formed in the manner of further folding the four-sided bag B, and possibility of the breakage can be further reduced.

In the process of expanding the volume space inside the four-sided bag B, since the wedge W is operated such that the angle θ formed by the line segment portion W1 and the edge side E changes from the acute angle to the right angle, in forming the containers C1 and C2 having the substantially truncated square bipyramidal shape or the substantially rectangular parallelepiped shape, the line segment portion W1 of the wedge W can be brought into contact with a portion to be valley-folded, the metal container C can be formed in the manner of further folding the four-sided bag B, and the possibility of the breakage can be greatly reduced.

Since the force is applied to the first and second parallel plate jigs 11 and 12 and the plurality of flap jigs F in the direction in which the expansion of the volume space due to the pressurization of the inside of the four-sided bag B is prevented, the metal container C can be formed into a shape corresponding to the first and second parallel plate jigs 11 and 12 and the plurality of flap jigs F, and can be formed into the truncated square bipyramid or the rectangular parallelepiped having a neater shape.

Further, according to the metal container C of the present embodiment, the metal container C in which the breakage due to the local elongation of the metal plate MP is prevented can be made based on the four-sided bag B.

Although various embodiments have been described above with reference to the drawings, it is needless to say that the present invention is not limited to these examples. It will be apparent to those skilled in the art that various changes and modifications may be conceived within the scope of the claims. It is also understood that the various changes and modifications belong to the technical scope of the present invention. Components in the embodiments described above may be combined freely within a range not departing from the spirit of the invention.

For example, in the above-described embodiment, the apparatus 1 for manufacturing the metal container C includes the flap jigs F. However, the present invention is not particularly limited thereto, and the manufacturing apparatus 1 may not include the flap jigs F. In the example shown in FIGS. 8A to 8D, a step of sandwiching the four-sided bag B by the first and second parallel plate jigs 11 and 12 and a step of sandwiching the four-sided bag B by the flap jigs F are performed at the same time, but the present invention is not limited thereto, and the step of sandwiching the four-sided bag B by the first and second parallel plate jigs 11 and 12 may be performed first, or the step of sandwiching the four-sided bag B by the flap jigs F may be performed first.

The four-sided bag B may be formed by a process other than the process shown in FIGS. 7A to 7C, such as superimposing two metal plates MP having the same area and welding peripheral edge portions thereof.

Furthermore, since the ear portion D is formed when the container C is formed in the present embodiment, in order to facilitate the formation of the ear portion D, it is preferable that rigidity of (at least a part of) the two opposing sides of the four-sided bag B is lower than rigidity of the remaining two sides. For example, in the four-sided bag B shown in FIG. 2, bending rigidity in the plane is high on the long side LS side where the seam welding portion SW is formed, and bending rigidity in the plane is low on the short side SS side having the edge side E. Accordingly, when the container C is manufactured from the four-sided bag B shown in FIG. 2, the ear portion D is easily formed.

On the other hand, for example, in a case where the container C is manufactured from the four-sided bag B in which the seam welding portions SW are formed on four sides, it is preferable that a process of reducing the bending rigidity in the plane is performed on one of the two opposing sides, and the bending rigidity in the plane of (at least a part of) the two sides is set to be lower than in the remaining two sides. FIGS. 9A and 9B are perspective views showing other examples of the four-sided bag B, in which FIG. 9A shows a first example, and FIG. 9B shows a second example.

As shown in FIG. 9A, for example, rectangular metal plates MP having the same area are superimposed with each other, and seam welding is performed on four sides to form the seam welding portions SW, thereby manufacturing the four-sided bag B. When the container C is manufactured from such a four-sided bag B, for example, cut portions N for reducing width of the seam welding portions SW are formed on both end sides of the seam welding portions SW on two opposing sides (short side SS sides). Accordingly, bending rigidity in the plane at positions (at least a part of the positions) of the cut portions N can be reduced, and folding can be easily performed at the positions, so that the ear portions D can be easily formed. The cut portion N is formed at a position away from an end portion VM of the seam welding portion SW by a distance corresponding to half a height of the container C to be finally manufactured, or at a position closer to the end portion VM than the position.

Further, as shown in FIG. 9B, for example, the seam welding portions SW on two opposing sides (short side SS sides) may be bent so as to rise or fall. Accordingly, bent portions BE act like the edge side E shown in FIG. 2, so that bending rigidity in the plane of the bent portions BE can be reduced, and the ear portion D can be easily formed.

Furthermore, in the present embodiment, the second flap jig F2 includes the wedge W. However, the present invention is not limited thereto, and the second flap jig F2 may not include the wedge W. When the wedge W is not provided, an auxiliary plate AP shown in FIG. 10 may be provided. FIG. 10 is a plan view showing the auxiliary plate AP. As shown in FIG. 10, the auxiliary plate AP is superimposed on the four-sided bag B so as to be aligned with a position where the valley-folded portion VF is formed. Specifically, a plurality of oval holes OV are formed in the auxiliary plate AP. The plurality of oval holes OV change such that the angle θ formed with the edge side E increases (that is, from the acute angle to the right angle) from an end portion side to a center side of the auxiliary plate AP. Such an auxiliary plate AP is superimposed in a manner of being aligned with the position where the valley-folded portion VF is formed, the formation of the valley-folded portion VF can be assisted even in the manufacturing apparatus 1 including no wedge W. The auxiliary plate AP is reinforced in the vicinity of the edge side E having lower bending rigidity in the plane than the seam welding portion SW, but is not reinforced in a portion of the oval hole OV. Accordingly, in a part (portion of the oval hole OV), the bending rigidity in the plane is set to be lower than that of the two sides including the seam welding portions SW.

The metal container C is preferably configured as shown in FIG. 11. FIG. 11 is an enlarged view of a periphery of an ear portion D according to a modification. Although the ear portion D may remain protruding laterally, it is preferable that the ear portion D is folded along the side wall HP as shown in FIG. 11. This is because a shape of the metal container C can be approximated to a substantially rectangular parallelepiped shape or a substantially truncated square bipyramidal shape. If possible, it is preferable that the seam welding portion SW is also folded along the side wall HP when the ear portion D is folded. The ear portion D is folded to a front side along the side wall HP on a side including the edge side E. However, the present invention is not limited thereto, and the ear portion D may be folded in an opposite direction.

According to an embodiment, when a container is formed from a four-sided bag, breakage due to local elongation of a metal plate can be prevented.

Claims

1. A method for manufacturing a metal container, comprising:

a first step of forming a substantially planar four-sided bag using a metal plate;

a second step of sandwiching, by first and second parallel plate jigs, one surface and the other surface of the four-sided bag formed in the first step; and

a third step of forming, using the four-sided bag, a container having a substantially truncated square bipyramidal shape or a substantially rectangular parallelepiped shape by pressurizing an inside of the four-sided bag while maintaining a contact state by the first and second parallel plate jigs with respect to the four-sided bag sandwiched between the first and second parallel plate jigs in the second step, and expanding a volume space in the four-sided bag while increasing a distance between the first and second parallel plate jigs.

2. A method for manufacturing a metal container according to claim 1, wherein

in the first step, the four-sided bag is formed such that bending rigidity in a plane of at least a part of two opposing sides is lower than bending rigidity in the plane of remaining two sides.

3. A method for manufacturing a metal container according to claim 1, wherein

in the second step, the one surface and the other surface of the four-sided bag are sandwiched by the first and second parallel plate jigs having a quadrangular shape smaller than an area of the four-sided bag formed in the first step in a plan view of the four-sided bag such that the first and second parallel plate jigs are located inside four sides of the four-sided bag and the four sides of the four-sided bag are parallel to respective sides of the first and second parallel plate jigs,

the method further comprises a fourth step, which is executed between the first step and the third step, of sandwiching at least two of four regions around each of regions sandwiched by the first and second parallel plate jigs on the one surface and the other surface of the four-sided bag by a plurality of flap jigs configured to move toward a center side of the four-sided bag while pivoting from a state of being substantially parallel to the first and second parallel plate jigs to a predetermined angle with respect to the parallel state, and

in the third step, the four-sided bag is formed with an oblique surface of a substantially truncated square bipyramid or a side surface of a substantially rectangular parallelepiped is formed by pressurizing the inside of the four-sided bag while maintaining a contact state by the plurality of flap jigs with respect to the four-sided bag, which is accompanied by pivotation and movement of the plurality of flap jigs.

4. A method for manufacturing a metal container according to claim 3, wherein

in the fourth step, with respect to a plurality of first flap jigs and a plurality of second flap jigs constituting the plurality of flap jigs, two opposing regions of the four regions are sandwiched by the plurality of first flap jigs, and remaining two opposing regions of the four regions are sandwiched by the plurality of second flap jigs.

5. A method for manufacturing a metal container according to claim 4, wherein

the plurality of second flap jigs include wedges including line segment portions extending from respective vertexes of the first and second parallel plate jigs toward respective sides of the four-sided bag on second flap jig sides on corner portion sides of the four-sided bag, and

in the third step, the wedges are operated such that angles formed by the line segment portions and the sides on the second flap jig sides change from an acute angle to a right angle in a process of expanding the volume space in the four-sided bag.

6. A method for manufacturing a metal container according to claim 2, wherein

in the third step, a force is applied to the first and second parallel plate jigs and plurality of flap jigs in a direction in which the expansion of the volume space due to the pressurization in the four-sided bag is prevented.

7. An apparatus for manufacturing a metal container including first and second parallel plate jigs configured to sandwich one surface and the other surface of a substantially planar four-sided bag formed of a metal plate, wherein

the first and second parallel plate jigs each have a quadrangular shape smaller than an area of the four-sided bag in a plan view, are capable of sandwiching the four-sided bag such that the first and second parallel plate jigs are located inside four sides of the four-sided bag and the four sides of the four-sided bag are parallel to respective sides of the first and second parallel plate jigs, and maintain a contact state with the one surface and the other surface of the four-sided bag in a process of expanding a volume space in the four-sided bag by pressurizing an inside of the four-sided bag.

8. A metal container having a substantially truncated square bipyramidal shape or a substantially rectangular parallelepiped shape, comprising:

two quadrangular top plates formed as one surface of the container and the other surface opposite to the one surface;

a plurality of side walls connecting the two top plates; and

a plurality of ear portions having oblique sides approaching each other from opposing vertexes of the two top plates and protruding laterally or folded along the plurality of side walls, wherein valley-folded portions are formed at boundaries between the plurality of ear portions and the plurality of side walls, and one or more valley-folded marks having the vertex as a rotation center are formed between the valley-folded portion and the oblique side.