Patent ID: 7775240
Filing Date: 2010-08-17
Classification: F15B,F16K,Y10T

Abstract:
1. A two stage spool valve comprising: in a single assembly; a first stage spool moveable between first and second positions, the first position coupling a source of fluid under pressure to a first hydraulic area associated with a second stage spool that is moveable between third and fourth positions, and the second position coupling the first hydraulic area to a vent; the first hydraulic area being disposed so that fluid under pressure acting against the first hydraulic area encourages the second stage spool to the third position; the second stage spool having a return disposed to encourage the second stage spool to the fourth position; the second stage spool being configured to couple a first port to a second port when in one of the third and fourth positions and to not couple the first port to the second port when in the other of the third and fourth positions; a solenoid actuator disposed to move the first stage spool to one of the first and second positions when actuated, and a return spring disposed to encourage the first stage spool to the other of the first and second position; the solenoid actuator being comprised of a movable structure and a stationary structure, the stationary structure defining a magnetic flux path, including a stationary structure pole face, that together with the moveable structure, including a moveable structure pole face, define a substantially zero air gap magnetic circuit when the solenoid actuator is actuated, the pole faces of the stationary structure and the moveable structure each being defined in part by soft magnetic iron and in part by hardened steel, the hardened steel of the moveable structure contacting the hardened steel of the stationary structure and the soft magnetic iron of the moveable structure being face to face with the soft magnetic iron of the stationary structure when the solenoid actuator is actuated.