Tank truck vent system

摘要

A vent system includes a spring-loaded closed vent valve mounted in the upper portion of the truck tank and a spring-loaded closed safety valve mounted in the bottom of the tank. The safety valve has a discharge portion carrying an actuator pin which disengagably abuts the underside of the safety valve member and is actuated to lift the valve member to permit flow of gasoline from or into the tank. The vent valve member is operatively connected to the safety valve member by an actuating rod so that the vent valve is opened or closed when the safety valve is opened or closed. The safety valve, actuating rod and vent valve are provided with an overboard vent passage which extends from an inlet in the safety valve member to an outlet in the vent valve member. When the actuator pin is actuated to open the safety valve, the inner end of the pin covers the vent passage inlet and vapors are vented from the tank through the vent valve in a normal manner. When the safety valve is closed, a small spring carried on the actuator pin urges the inner end of the actuator pin away from the safety valve member, thereby opening the vent passage so that the discharge portion of the safety valve is vented overboard. This eliminates the vacuum effect normally created in a discharge conduit connected to the safety valve, permitting it to be gravity drained after the safety valve has been closed.