Patent ID: 7484636

Claim:
A fuel cap comprising a closure unit adapted to be fitted into an opening of a filler neck, the filler neck having a plurality of ridges formed on its inner side face intermittently in the circumferential direction, so that it may be secured to the filler neck by engaging with the ridges during a turning operation, wherein the closure unit includes a closure body, a seal ring, a sleeve, a base and an elastic member, the closure body includes a trunk portion projecting from a head portion to be turned and having a plurality of closure side fitting portions on its outer side face, the sleeve is provided on its inner side face with a plurality of sleeve side fitting portions and an elastic member fitting portion and on its outer side face with a plurality of engagement protrusions adapted to be passed axially through corresponding intervals formed between the ridges of the filler neck and then turned for engaging with the upper surface of the ridges, the sleeve can be freely slid upward and downward with respect to the trunk portion of the closure body while being fitted together with the seal ring on the trunk portion and can be freely turned integrally with the closure body by fitting the closure side fitting portion and the sleeve side fitting portion together, a spacing is formed between a lower end of the sleeve and the lowermost upper surface of the base positioning right below the sleeve by fixing the base to a lower end of the trunk portion with the sleeve fitted thereon while internally sandwiching the elastic member between the elastic member fitting portion of the sleeve and the base, and the spacing is set smaller than an amount of the downward sliding of the sleeve which is caused when the engagement protrusions, formed on the outer side face of the sleeve, slip into lower faces of the ridges formed on the inner side face of the filler neck, the lower end of the sliding sleeve is lowered and comes into abutment against the base on halfway of its downward movement and the closure body integrated with the base is pushed further downward so that the seal ring is sandwiched and pressed tightly between the head portion of the closure body and the opening edge of the filler neck.