Patent ID: 8777184

Claim:
An expanding gate valve, comprising: (a) a valve body having a valve chamber and inlet and outlet passages and having spaced interior sealing surfaces; (b) a gate assembly comprising first and second gate members and being movable within the valve chamber to an open position permitting flow of fluid through the inlet and outlet passages and a closed position with the gate assembly located between the sealing surfaces and blocking the flow of fluid through the inlet and outlet passages, the gate members each defining an outer-facing surface facing in the direction of a corresponding interior sealing surface of the valve body, and an inner-facing surface facing the other gate member, the inner-facing surface of each gate member further defining an upper inclined cam surface and a lower inclined cam surface, the upper inclined cam surface symmetrical with the lower inclined cam surface about a latitudinal axis, the upper and lower inclined cam surfaces of the first gate member being symmetrical with the upper and lower inclined cam surfaces of the second gate member about a longitudinal axis, the upper and lower inclined cam surfaces disposed for engagement with opposed upper and lower wedges, respectively, and causing lateral expansion of said gate assembly responsive to engagement of the upper and lower wedges with the upper and lower inclined cam surfaces; (c) a valve stem having driving connection with the upper wedge and the gate assembly for moving the gate assembly linearly to said open and closed positions; and (d) at least one lateral-force-inducing member engaging the gate members and urging them toward each other at least when the gate assembly is not in the closed position; wherein the at least one lateral-force-inducing member further comprises: (e) a first cam follower attached to the first gate member and oriented to travel against a first surface fixed inside the valve chamber, the profile of the first surface causing the first gate member to move toward the second gate member when the gate assembly is moved away from the closed position; and (f) a second cam follower attached to the first gate member and oriented to travel against the first surface fixed inside the valve chamber, the profile of the first surface causing the first gate member to move toward the second gate member when the gate assembly is moved away from the closed position.