Bottomed container and method for manufacturing the same

Abstract

A method includes a main forming step in which a blank in which creases are formed by a preforming step is set between a die and a punch such that the die and the punch correspond to the shape of the blank, and is press-formed to form a square tubular component as a bottomed container. When, in the main forming step, a rib protruding outward from between each adjacent two of the vertical walls of the bottomed container in plan view is formed in press forming, a slit is provided in each of the corner portions of the inner side surface of the die.

1 . A bottomed container comprising: a bottom portion; and a plurality of vertical walls rising from the peripheral edge of the bottom portion,
 wherein the bottomed container is formed by press-forming a blank, and has a plurality of corner portions integral with the bottom portion and the vertical walls adjacent to each other,   the corner portions are each provided with one or more ribs that protrude outward or inward from between the vertical walls adjacent to each other in plan view,   the ribs are each composed of a pair of folded flanges that are folded along creases that are preformed in the blank so as to substantially equally divide an area that will become one of the corner portions,   the amount of outward or inward protrusion of the ribs becomes larger from the bottom portion toward the open end of the vertical walls in side view, and   the ribs are provided with no flanges extending outward from the open ends of the ribs in plan view.   
     
     
         2 . The bottomed container according to  claim 1 , wherein the corner portions have a substantially arc shape in plan view, and the one or more ribs formed in each of the corner portions having a substantially arc shape are two to four ribs. 
     
     
         3 . The bottomed container according to  claim 2 , wherein recesses or protrusions that are continuous in plan view and that correspond to the ribs protruding outward or inward from the corner portions having a substantially arc shape are formed in the bottom portion. 
     
     
         4 . The bottomed container according to  claim 3 , wherein the recesses or protrusions provided in the bottom portion are formed so as to extend radially from the center of each of the corner portions having a substantially arc shape in plan view. 
     
     
         5 . The bottomed container according to  claim 1 , wherein the bottomed container is provided with flanges extending outward from the open ends of the vertical walls. 
     
     
         6 . A method for manufacturing the bottomed container according to  claim 1 , the method comprising:
 a preforming step comprising forming creases in a blank having areas that will become the bottom portion, the plurality of vertical walls, and the plurality of corner portions of the bottomed container after press forming using a preforming die, the creases being formed at borders between an area that will become the bottom portion and areas that will become the vertical walls, borders between the areas that will become the vertical walls and areas that will become the corner portions, and positions for substantially equally dividing the areas that will become the corner portions; and   a main forming step comprising setting the blank, in which creases are formed by the preforming step, between a die and a punch such that the die and the punch correspond to the shape of the blank, and press-forming said blank to form the bottomed container,   wherein in the main forming step, when one or more ribs protruding outward from between each adjacent two of the vertical walls of the bottomed container in plan view are formed in press forming, slits are provided in corner portions of the die, and when one or more ribs protruding inward from between each adjacent two of the vertical walls of the bottomed container in plan view are formed in press forming, slits are provided in corner portions of the outer side surface of the punch.   
     
     
         7 . The method for manufacturing a bottomed container according to  claim 6 , wherein in the preforming step, the number of creases formed for substantially equally dividing each of the areas that will become the corner portions is three to seven. 
     
     
         8 . The method for manufacturing a bottomed container according to  claim 6 , wherein the inside of each of the corner portions of the die is formed such that the radius of curvature of the inscribed circle is R1 in plan view, the corner portions of the outer side surface of the punch are formed in a shape having a curved surface having a radius of curvature of R2 in plan view corresponding to the inscribed circle of each of the corner portions of the die, the clearance between the punch and the die defined as R1−R2 is set to 100% to 200% of the thickness of the blank, and R1>R2. 
     
     
         9 . The method for manufacturing a bottomed container according to  claim 8 ,
 wherein in the main forming step,   when one or more ribs protruding outward from between each adjacent two of the vertical walls of the bottomed container in plan view are formed in press forming, slits are provided in the corner portions of the bottom surface of the die, and   when one or more ribs protruding inward from between each adjacent two of the vertical walls of the bottomed container in plan view are formed in press forming, slits are provided in the corner portions of the bottom surface of the punch.   
     
     
         10 . The method for manufacturing a bottomed container according to  claim 9 , wherein the slits provided in the corner portions of the bottom surface of the die or the corner portions of the bottom surface of the punch are formed so as to extend radially from the center of each corner portion. 
     
     
         11 . The method for manufacturing a bottomed container according to  claim 6 , wherein flanges extending outward from the outer side surface other than the corner portions of the punch are provided at the upper end of the punch.