Fuel system vent valve having roll-over closure with improved re- opening action for venting

摘要

A roll-over vent valve for an automobile fuel tank comprises a novel means for minimizing the force required to re-open a corked shut- off element. The disclosed embodiment comprises a thin, slightly pliable, circular disc for the shut-off element which seats against an annular seat to close the vent passage in the event of roll-over. If the pressure in the tank headspace is sufficiently positive and the disc is closed against the seat in the absence of roll-over, an extra force is required to unseat the disc because of the pressure differential acting on the seated disc. The magnitude of force required to unseat the disc is significantly attenuated in the present invention by having the force act over a limited circumferential extent of the sealing contact of the disc against the seat. This peels the disc from the seat with complete unseating being accomplished by causing the force to act progressively around the perimeter of the disc. In one embodiment the disc is caged by a set of fingers which sequentially act on the disc at different circumferential locations to transmit the re-opening force around the disc. In another embodiment tethered cords of different lengths are used.