Abstract: A closure for the filler neck on a vehicle gas tank having a closure body with a central passage and an upper surface having a vent groove formed therein. The vent groove has a first end communicating with the hollow portion of the closure body and a second end adjacent the periphery of the closure body. A cap is secured to the closure body and a resilient gasket is secured between the cap and the upper surface of the closure body such that a convex surface formed on the cap engages the upper surface of the gasket adjacent the vent groove in a closure body to deflect a portion of the gasket into the groove to seal the vent groove. The gasket is sufficiently resilient to permit passage of fluid through the vent groove when a pressure differential exceeding a predetermined magnitude exists between the first and second ends of the vent groove such that pressure within the tank is vented to the atmosphere.

Abstract: A cap for a vehicle gas tank, the cap having an opening formed therein closed by a door having a smooth, continuous convex upper surface which is hingedly secured to an annular support body. The door is spring-urged into sealing engagement with a gasket and is adapted to permit passage of a gasoline nozzle through the opening to move the door out of the path of the nozzle. The sidewall of the nozzle engages the convex upper surface of the door such that the periphery of the door is maintained in spaced relation from the wall of the nozzle to permit withdrawal of the nozzle from the opening. The door is spring-urged into sealing engagement with the gasket with sufficient force to maintain a seal when a partial vacuum is formed in the tank.