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.

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.