Patent ID: 7819378

Claim:
A gate valve, comprising: a body with a flow passage intersected by a gate cavity; a first seat ring at an intersection of the flow passage with the gate cavity; a second seat ring at an intersection of the flow passage with the gate cavity on an opposite side of the gate cavity from the first seat ring; a gate that is movable in the gate cavity between a closed position and an open position; a seal member in the gate having a first end that seals against the first seat ring when the gate is in the closed position and the first seat ring is downstream of the second seat ring relative to flow through the flow passage, the seal member having a second end that seals against the second seat ring when the gate is in the closed position and the second seat ring is downstream of the first seat ring relative to flow through the flow passage; and a cam member carried by the gate and in cooperative engagement with the seal member for moving the seal member in an upstream direction relative to the gate in response to beginning movement of the gate from the closed position toward the open position regardless whether the seal member is sealing against the first seat ring or the second seat ring.