Patent ID: 7455279

Claim:
A control valve comprising: a) a valve body having an inlet port, an outlet port, and a valve seat disposed between said inlet and outlet ports, said valve seat defining a valve opening to permit fluid communication between said inlet and outlet ports; b) a valve actuator housing extending from said valve body, said valve actuator housing at least partially defining a control chamber; c) a valve plug displaceable between a closed position against said valve seat, and an open position spaced apart from said valve seat, at least a portion of said valve plug extending into said control chamber, said valve plug having a valve plug shaft that extends through said control chamber; d) a primary valve actuating element deployed within said control chamber and fixedly attached to said valve plug shaft so as to form a first partition separating first and second pressure control regions within said control chamber, said primary valve actuating element being selectively and individually actuatable so as to move said valve plug through a full range of motion of said valve plug in at least one direction between said closed position and said open position; and e) a secondary valve actuating element deployed within said control chamber so as to form a second partition separating said second pressure control region and a third pressure control region within said control chamber, said secondary valve actuating element sealingly circumscribing said valve plug shaft so as to allow for movements of said valve plug shaft during displacement of the valve plug when said primary valve actuating element is moving said valve plug, said secondary valve actuating element being selectively and individually actuatable so as to move said valve plug through said full range of motion of said valve plug in at least one direction between said closed position and said open position, such that said secondary valve actuating element provides back-up control, allowing full range of motion displacement of said valve plug in the event of failure of said primary valve actuating element