Expandable seal gate valve

Claim 1

In a valve having a body with a flow passageway therethrough, a gate member positionable in the body between an opened and a closed position, the gate member being arranged so that when in closed position fluid flow through the valve is blocked, the valve having external means of moving the gate member between opened and closed positions, the valve body including a body sealing surface, the gate member engaging said sealing surface when in closed position, improved means of effecting sealing between the body sealing surface and the gate member, wherein said body sealing surface has a continuous groove of trapazoidal dovetailed configuration encircling said body flow passageway and a pressure passageway in the body communicating said groove with the exterior of the valve body; an elongated expandable gasket member positioned in said groove in said body sealing surface, the expandable gasket member having communication with said pressure passageway, said expandable gasket including a first resilient tubular portion received in said groove and a second elastomer portion surrounding said resilient tubular portion and being boNded to said body; and means externally of said body for applying fluid pressure by way of said pressure passageway to said expandable gasket member to expand said tubular portion and thereby said elastomer portion into engagement with said gate member.