Synthetic-resin screw cap

Abstract

The object of the present invention is to provide a screw cap made of a synthetic resin that always exhibits a reliable stable function of preventing unjust unsealing. It includes: a cap main body (A) serving as a cap section, a cylindrical wall (A) of which is closely screwed on a bottle mouth cylinder () constituting a pour spout of the bottle for closely fitting thereon; and a sealing ring () having a second locking section () locked from below across a first locking section (A) formed around the outer peripheral surface of the bottle mouth cylinder () and connected to the lower end of the cylindrical wall () through a plurality of easily breakable pieces (), wherein a plurality of second pressing slopes () is disposed on the upper end of the sealing ring () so that the plurality of second pressing slope is closely opposed to a plurality of first pressing slopes () disposed on the lower end of the cylindrical wall () so as to slidably abut against the plurality of first pressing slope from an unscrewing direction and at a tilt angle (b) that is a larger acute angle than the lead angle (a) of a helical ridge (A) of the bottle mouth cylinder (), thereby forcibly depressing the sealing ring () by abutment between both the pressing slopes during the unscrewing operation of the cap main body.