Filler cap

Claim 1

A filler cap for a fuel tank filler neck having a center fuel opening and an outwardly projecting helical lip formed on an outer surface thereof comprising: a cap member having a dome section and a depending cylindrical sleeve encircling said filler neck, said sleeve including helical thread adapted to engage the helical lip on the filler neck to provide a constant, low torque opening and closing movement between the cap member and the filler neck upon rotation of the former; a retaining ring rotatably carried by the cap member for relative rotation with respect thereto, said retaining ring including a center valve opening; an annular elastomeric gasket carried by the retaining ring, said gasket frictionally engaging the filler neck and swiveling with respect to the filler cap upon closing movement to thereby minimize frictional gasket wear; venting holes formed in the retaining ring; filter means carried between the gasket and the dome and disposed between the venting holes and the valve opening for filtering air passing therethrough; a vacuum relief valve disposed in the valve opening and having a valve member yieldingly biased against the gasket and adapted to normally engage the latter, the pressure differential acting on the vacuum relief valvE under predetermined vacuum conditions to permit vacuum relief in a flow path between the venting holes, the filter and the tank; and a pressure relief valve carried by the vacuum relief valve and yieldingly biased thereagainst, the pressure differential acting on the pressure relief valve under predetermined pressure conditions to permit pressure relief.