Hydraulic valve

Claim 1

A hydraulic valve for operating a double-acting fluid motor having a first drive port and a second drive port, said valve comprising a body, means providing the body with a supply pressure and a drain, first and second pairs of piston operated poppets, each poppet including a piston portion and a valve portion, each valve portion coacting with a valve seat, spring means for each poppet to normally bias the valve portion into closed position on the seat, said first pair of poppets including one poppet for selectively connecting said first drive port of the motor to said supply and one poppet for selectively connecting said second drive port of the motor to drain to drive the motor in one direction, said second pair of poppets including one poppet for selectively connecting the second drive port of the motor to said supply and one poppet for selectively connecting the first drive port of the motor to drain to drive the motor in the opposite direction, first and second means for respectively selectively connecting the supply to the upper sides of the piston portions of said first and second pairs of poppets to operate said motor, and means continually communicating the undersides of all piston portions to drain, said first and second means including first and second normally closed electromagnetic hydraulic switches connected between the supply and the respective pairs of poppets which open upon energization and close upon deenergization, whereby failure of electrical poWer to the switches and/or the means providing the supply will cause the valve to close and lock the motor in the last position, each switch including a casing having an inlet connected to supply pressure and an outlet connected to one of said pairs of piston operated poppets, a coil within the casing, a pair of pole pieces in spaced relation within the coil, an armature within the coil coacting with the pole pieces to complete the magnetic circuit therebetween when in seated position thereagainst, a ball portion for pivotally mounting the armature, an extension from the ball portion defining a valve closure member, an annular land surrounding said closure member, a port having a valve seat on said land coacting with the closure member and communicating with the outlet, means communicating the land and the closure member to the inlet of the switch, the relation between the land and closure member being such that the pressure drop due to fluid flow between the closure member and valve seat forces the closure member to seat against the valve seat when the coil is deenergized.