| 摘要 |
PURPOSE:To improve sealability by a cap member and enhance a resistance to impulsion exerted on a shoulder part of the cap member, by forming a gas- filled annular cavity in a boundary area between a flat top section and a skirted section of the cap member. CONSTITUTION:An injection-molded cap member 2 is made of suitable synthetic resin such as propylene and provided with a circular flat top section 4 and a cylindrical skirted section 6 suspended from a periphery of the flat top section 4. In a boundary area positioned between the flat top section 4 and the skirted section 6 is provided an annular cavity 18 in which gaseous substance is en closed. The annular cavity 18 is formed by blowing a suitable gas such as nitrogen into the synthetic resin during injection-molding process. Provision of such a cavity contributes to save an amount of the synthetic resin used and prevents formation of warpage and shrinkage in the boundary area thereof. The cavity further provides an elastic dampening effect against impulsion exerted on the cap member, which results in prevention of damage to sealability thereof. This construction enables the cap member to be properly fitted on a mouth part 20 of a container even though there exist some deficiencies or damages due to errors in manufacturing of the mouth part. |
