Patent ID: 8286935

Claim:
A valve for a subsea wellhead assembly comprising: a valve body having a fluid flow passage; a gate selectively moveable to open and close the fluid flow passage; an actuator housing secured to the valve body, the actuator housing having an axis, a proximal end cap and a distal end cap with an axial bore extending therethrough; an axially movable valve stem extending through the axial bore in the distal end cap, the valve stem having a proximal end within the housing and a distal end exterior of the housing and coupled to the gate for moving the gate; a spring force transfer member carried within the housing, the transfer member having a cylindrical sidewall with a proximal end and a distal end, the distal end of the transfer member being mounted to the valve stem for movement in unison therewith, the cylindricai sidewall being spaced radially inward from the actuator housing, defining an annular space, the transfer member having external flange located within the annular space; a coil spring within the housing, a portion the coil spring being in the annular space surrounding the cylindrical sidewall of the transfer member, the coil spring having a proximal end in cooperative engagement with the flange and a distal end in cooperative engagement with the distal end cap of the housing, so as to exert a force against the transfer member urging the proximal end of the transfer member toward she proximal end cap; magnetized segments stacked together in alternating opposite polarity to define a magnetic segment shaft that is located in the force transfer member and coupled to the proximal end of the valve stem for movement therewith; a linear motor winding array comprising a series of axially spaced apart windings each mounted proximate the magnetized segments, the array being located within the force transfer member surrounding the shaft, the array having a proximal end that is fixed to the housing; wherein energizing the array with electrical power, causes the shaft to move axially relative to the array, thereby causing the gate to move to the open position and causing the force transfer member to contract the coil spring; and wherein removing the electrical power from the array causes the coil spring extend to move the gate to the closed position.