Structure of opening curled portion of bottle-shaped can

Abstract

A structure of an opening curled portion of a bottle-shaped can possible to enhance the durability of a curled portion against a load applied from above so as to ensure tamper evidence function. The curled portion 10 comprises: an inner circumferential wall 16 ; an upper rounded portion 17 ; an outer circumferential wall 20 ; a lower rounded portion 21 ; a folded end 22 ; and a leading edge 23 . A tapered wall 15 is formed below the inner circumferential wall 16 to be joined to a threaded section while increasing an outer diameter thereof downwardly. A margin surface area 24 is formed between the inner circumferential wall 16 and the tapered wall 15 , in such a manner as to extend downwardly from a lowest end 25 of a contact area with the folded end 22 , to locate a curvature center P 2 thereof outside of the neck section, and to set a curvature radius R 2 thereof longer than a curvature radius R 1 of the lower rounded portion 21 in a cross-section along a center axis O of the neck section.

1 . A structure of an opening curled portion of a bottle-shaped can comprising: a shoulder section that is formed on an upper portion of a can trunk in a manner such that a diameter thereof is reduced toward an upper side; a cylindrical neck section that is formed integrally above the shoulder section; a threaded section that is formed on the neck section; a cap that is mounted on threaded section of the neck section; a bead that is formed below the threaded section to be engaged with a tamper evidence band of the cap; and the curled portion that is formed on an opening end of the neck section above the threaded section,
 wherein:   the curled portion comprises
 an inner circumferential wall leading upwardly from the threaded section, 
 an upper rounded portion bent outwardly in a radial direction of the neck section from an upper end of the inner circumferential wall, 
 an outer circumferential wall leading downwardly from the upper rounded portion in parallel to the inner circumferential wall, 
 a lower rounded portion bent inwardly in the radial direction from a lower end of the outer circumferential wall, 
 a folded end erecting upwardly from the lower rounded portion while being in contact with an outer surface of the inner circumferential wall, and 
 a leading edge leading from the folded end and confined between the inner circumferential wall and the outer circumferential wall; 
   a tapered wall is formed below the inner circumferential wall to be joined to the threaded section, an outer diameter of the tapered wall being increased toward a lower portion thereof; and   a margin surface area is formed between the inner circumferential wall and the tapered wall, in such a manner as to extend downwardly from a lowest end of a contact area of the inner circumferential wall with the folded end, to locate a curvature center of the margin surface area outside of the neck section, and to set a curvature radius of the margin surface area longer than a curvature radius of the lower rounded portion in a cross-section along a center axis of the neck section.   
     
     
         2 . The structure of the opening curled portion of the bottle-shaped can as claimed in  claim 1 , wherein the curvature center of the margin surface area is located at a same level as the curvature center of the lower rounded portion or at a level lower than the curvature center of the lower rounded portion in a direction along the center axis of the neck section. 
     
     
         3 . The structure of the opening curled portion of the bottle-shaped can as claimed in  claim 1 ,
 wherein the upper rounded portion includes an apex as a tip of the curled portion in the direction along the center axis of the neck section, and   a length from an inner surface of the inner circumferential wall to the apex of the curled portion measured in the radial direction of the neck section is shorter than a length from a starting point of the upper rounded portion in the inner circumferential wall side to the apex of the curled portion measured in the direction along the center axis of the neck section.   
     
     
         4 . The structure of the opening curled portion of the bottle-shaped can as claimed in  claim 2 ,
 wherein the upper rounded portion includes an apex as a tip of the curled portion in the direction along the center axis of the neck section, and   a length from an inner surface of the inner circumferential wall to the apex of the curled portion measured in the radial direction of the neck section is shorter than a length from a starting point of the upper rounded portion in the inner circumferential wall side to the apex of the curled portion measured in the direction along the center axis of the neck section.