Patent ID: 6997339

Claim:
A cap device for a fuel tank comprising: an operation portion, a shaft portion extending from the operation portion to be inserted into an opening of the fuel tank, a sealing member disposed on the shaft portion for sealing the opening, a movable member disposed over the shaft portion and having an engaging portion for engaging the opening of the fuel tank to fix the cap device to the fuel tank, and a cam mechanism disposed between the shaft portion and the movable member for allowing the shaft portion to move vertically and rotationally relative to the movable member by an actuation of the operation portion so that the engaging portion of the moving member engages with and disengages from the opening of the fuel tank according to a vertical and rotational movement of the shaft portion relative to the movable member through the cam mechanism, wherein the cam mechanism includes a cam groove formed in one of the shaft portion and the movable member and sized to allow the shaft portion to move vertically independent of the movable member, a cam projection formed in the other of the shaft portion and the movable member for fitting in the cam groove, and an urging member disposed between the shaft portion and the movable member for urging the movable member downward.