Patent ID: 7278547

Claim:
A cap device, comprising: a pipe-shaped opening formation member having a tank opening and a flow path connecting the tank opening to a tank; a cap having a closer that closes the tank opening and a handle that is mounted on the closer to rotate the closer in either of a closing direction and an opening direction; a gasket that is located between an outer circumference of the closer and a sealing face of the opening formation member; and a screw mechanism having a first threading element that is formed on an inner wall of the opening formation member and a second threading element that is formed on the outer circumference of the closer to engage with the first threading element, where the second threading element is screwed into the first threading element from a leader of the first threading element in response to rotation of the handle in the closing direction, so that the gasket is pressed against and displaced relative to the inner wall of the opening formation member to attach the cap into the opening formation member, wherein the second threading element of the screw mechanism has a stopper that comes into contact with the leader of the first threading element and is configured to restrict further rotation of the closer in the closing direction after the gasket is pressed in an axial direction by at least a predetermined displacement, the screw mechanism sets a moving distance of the cap in the axial direction to be not less than 2 mm, while the second threading element engages with the leader of the first threading element and is then screwed into the first threading element to a filly closed position where the stopper comes into contact with the leader of the first threading element, and the gasket has a reactive force of not greater than 160 N from the sealing face of the opening formation member and a sealing face pressure of not less than 0.3 MPa against the sealing face when the moving distance of the cap at the fully closed position is 3.0 mm.