Patent ID: 8091402

Claim:
A method of manufacturing a bottle can having a drum portion with a shoulder portion mounted thereon, the shoulder portion having a neck portion with a pipe sleeve portion, comprising the steps of: A) molding a skirt portion at the pipe sleeve portion of the bottle can, said molded skirt portion including an area that extends from a lower end of a male threaded portion in an opposite direction from which the male threaded portion extends over a range of at least approximately 180° along a circumferential direction from the lower end; B) molding a first circumferential wall portion at the skirt portion so as to be in contact with a bottom end of the male threaded portion, the diameter of the first circumferential wall portion being gradually enlarged as it moves downwards in the can axial direction; C) molding a convexly curved surface portion at the skirt portion so as to be adjacently joined to a bottom end of the first circumferential wall portion, the convexly curved surface portion protruding towards an outer side in the radial direction of a bottle can body and having a diameter larger than that of the bottom end of the first circumferential wall portion; and D) molding a second circumferential wall portion at the skirt portion so as to be adjacently joined to a bottom end of the convexly curved surface portion, the diameter of the second circumferential wall portion being gradually reduced as it moves downward, wherein the skirt portion is a circular protrusion comprising the first circumferential wall portion, the convexly curved surface portion, and the second circumferential wall portion, and the first circumferential wall portion and the convexly curved surface portion are molded by pressing forcefully their inner surfaces outward in the radial direction of the bottle can body.