Valve for relieving pressure and vacuum conditions in a tank

Abstract

A combination valve for relieving pressure and vacuum conditions in a pressurizable tank includes an elongated rod with a spring seat thereon, a body member sealingly securable to the tank, a cover member secured for axial movement with the rod, a spring mounted between the body member and rod so as to yieldably urge the rod and cover member toward the body member, and an O-ring rollably disposed in a groove in the body member. The width of the O-ring is substantially less than the width of the groove such that the O-ring is rollable within the groove between the body member and the cover member. A seal member mounts on the rod and extends between the cavity and the cover member so as to normally sealingly engage the cover member and cover the vent. In a vacuum venting mode, the flexible seal member is suctioned away from the cover member and the vents therein in response to a predetermined vacuum present in the tank. The air can then be drawn into the tank through the vent. In a pressure relieving mode, the pressure in the tank overcomes the force of the spring so as to move the cover member upwardly with respect to the body member. This relative movement causes the O-ring to roll upwardly and eventually stop on an upper shoulder of the groove. Thereafter, movement of the cover member relative to the body member causes the cover member to slide past the O-ring and open an annular pressure relieving passage between the cover member and the O-ring.