| 摘要 |
<p>A gate valve has a gate that moves in a gate cavity between a lower closed position and an upper open position. A seal member in the gate seals against a downstream seat ring when the gate is in the closed position. The seal member is moveable in upward and downward directions as well as upstream and downstream directions relative to the gate. The seal member is in an upper and downstream position relative to the gate while the gate is in the closed position. A cam member is carried by the gate for movement in unison and is in engagement with the seal member. The cam member moves the seal member to an upstream and downward position in response to initial movement of the gate from the closed position toward the open position.</p> |
