SYNTHETIC RESIN CAP FOR CARBONATED BEVERAGE-FILLED CONTAINER, CLOSURE DEVICE, AND BEVERAGE-FILLED CLOSURE DEVICE

摘要

A synthetic resin cap mounted on a lip section of a container filled with a carbonated beverage includes a top plate section and a cylindrical section extending downward from a circumferential edge of the top plate section, wherein an annular inner seal projection fitted into the lip section and an outer seal projection abutting an outer surface of the lip section are formed at an inner surface of the top plate section. An annular abutting convex section abutting the inner surface of the lip section is formed at an outer surface of the inner seal projection. The outer seal projection has an inner surface having an inner diameter reduced toward a distal end, and a minimum inner diameter section, which is a lower end of the inner surface, abuts the outer surface of the lip section at a position spaced apart from an opening end section toward a container main body.