Semi-active damper piston valve assembly

An improved isolation system for time responsive attenuation of motion between spaced members is provided having a remotely controlled electromechanical valve assembly comprising the piston actuator of a fluid damper for generating motion attenuating forces. The piston valve assembly (22) employs a moving coil valve slider (78) moveable between first and second positions to generate damper forces independently of the fluid pressure differential between opposing fluid chambers (34, 36). Direct flow passages (68, 70) extend through the piston valve assembly between the opposing chambers. In the first position of the valve slider, fluid flow is substantially permitted through the direct flow passages to provide a substantially nonresistant damper force. In the second position, the valve slider intersects internal porting portions of the direct flow passages to substantially restrict fluid flow therethrough and provide a resistant damper force. The valving element of the slider and the internal porting portions of the direct flow passages are relatively configured so that fluid flow through the direct flow passages meets the valve element at right angles to the direction of the slider motion. In the second position, fluid flow is restricted along either the inner or outer diameter surfaces of the valve element perpendicular to the axis of motion of the slider to prevent biasing even under extreme fluid pressure conditions. The direct flow passages are radially spaced to provide radially equalized pressure forces on the slider to prevent jamming. In an alternative embodiment, the piston valve assembly includes a unidirectional flow arrangement across the valve element during both extension and retraction of the fluid damper. The arrangement of flow passages and check valves requires fluid flow across the slider radially outwardly at all times.