US Patent 7007715 Pressure release valve

A shaft part is coaxially provided within a pressure release port provided in a sealing plate sealed to an opening portion of a case for a condenser or a battery, a valve body closely fitted and fixed within the pressure release port has a seal lip which is directed toward the outside of a pressure container and is closely contacted with an outer peripheral surface of the shaft part with predetermined tensional force, and in the case that internal pressure of the case is increased more than a predetermined value, the seal lip is operated so as to open the valve, thereby releasing the internal pressure to the atmospheric air.