Expanding gate valve with fluid-powered actuator

A gate valve structure having a valve body with a valve chamber therein and a flow passage extending through said valve body and communicating with said valve chamber, an expandable gate assembly mounted within said valve chamber for movement in a collapsed condition between open and closed positions with respect to said flow passage, said gate assembly including a gate element and a segment which are expanded away from each other at said open and closed positions and are provided with ports which are aligned with one another and the flow passage in said open position, said gate element and segment being each provided with an outer planar sealing surface disposed parallel to one another for sealing against valve seats provided in said valve body at opposite sides of said gate assembly when the gate assembly is expanded in the open and closed positions, said valve body having a bore extending from the exterior of the valve body into said valve chamber;

• pneumatic powered actuator means for moving said gate assembly transversely with respect to said flow passage between said open and closed positions, said actuator means comprising a housing mounted on said valve body and defining a piston chamber therewith;
• a piston slidably received in the chamber, an actuator stem connected to said piston and movable therewith in the axial direction of said stem, said actuator stem extending through said bore and connected at one end to said gate assembly;
• inlet means provided through the wall of said housing and adapted for connection to a source of pneumatic pressure whereby pressurized pneumatic fluid may be selectively admitted to the chamber on one side of the piston for urging the piston in one direction therein from one of said open or closed positions to the other;
• compression spring means in said chamber for continuously urging the piston in the opposite direction from said one direction;
• and
• hydraulic choke means operably associated with said actuator stem for imposing a constant velocity control on said actuator piston substantially throughout the actuator stroke in both directions thereof for opening and closing the valve, said hydraulic choke means comprising a hydraulic cylinder mounted on said valve body in sleeved coaxial relation to said actuator stem, said actuator stem being adapted for axial reciprocal motion through said hydraulic cylinder, a hydraulic piston fixed to said actuator stem and mounted in said hydraulic cylinder for reciprocating motion therein, said hydraulic cylinder being filled with a hydraulic fluid, and means provided through said hydraulic piston for producing a throttling effect on the flow of hydraulic fluid from one side of the hydraulic piston to the other when said actuator piston is moved by pneumatic pressure or said spring means to thereby minimize the shock effect of the actuator stroke.