Servo valve

Claim 1

A SERVO VALVE COMPRISING (A) A FIRST STAGE VALVE HAVING AN EXHAUST CHAMBER, A PAIR OF PORTS LEADING INTO THE CHAMBER AND AN ELEMENT MOVABLE IN OPPOSITE DIRECTIONS FROM A NULL POSITION TO VARY IN REVERSE SENSES THE FLOW RESTRICTION AFFORDED BY THE TWO PORTS; (B) A TORQUE MOTOR OF THE STAGNANT TYPE FOR SHIFTING THE MOVABLE ELEMENT OF THE FIRST STAGE VALVE IN SAID OPPOSITE DIRECTIONS, SAID TORQUE MOTOR HAVING AN INTERNAL REGION CONTAINING AN ARMATURE AND AT LEAST ONE COOPERATING POLE PIECE; (C) A SECOND STAGE VALVE HAVING A SUPPLY PASSAGE, AN EXHAUST PASSAGE, AT LEAST ONE OUTLET PASSAGE, AND A MOVABLE MEMBER SHIFTABLE IN OPPOSITE DIRECTIONS FROM A NULL POSITION TO CONTROL COMMUNICATIONS BETWEEN THE OUTLET PASSAGE AND THE SUPPLY AND EXHAUST PASSAGES; (D) A PAIR OF OPPOSED DOUBLE-ACTING PISTON MOTORS CONNECTED WITH THE MOVABLE MEMBER OF THE SECOND STAGE VALVE FOR SHIFTING IT IN SAID OPPOSITE DIRECTIONS, EACH MOTOR COMPRISING A CYLINDER BORE AND A PISTON RECIPROCABLE IN THE CYLINDER BORE AND DIVIDING IT INTO OPPOSED WORKING CHAMBERS, THE OUTER PERIPHERY OF THE PISTON BEING SPACED RADIALLY FROM THE INNER PERIPHERY OF THE CYLINDER BORE TO DEFINE AN ANNULAR RESTRICTED PASSAGE THAT INTERCONNECTS SAID OPPOSED WORKING CHAMBERS; (E) MEANS FOR SUPPLYING FLUID UNDER PRESSURE TO ONE WORKING CHAMBER OF EACH MOTOR SO THAT THE MOTORS EXERT OPPOSITELY DIRECTED SHIFTING FORCES ON THE MOVABLE MEMBER OF THE SECOND STAGE VALVE; (F) FLOW PASSAGES CONNECTING EACH OF THE OTHER WORKING CHAMBERS WITH ONE OF THE PORTS OF THE FIRST STAGE VALVE; AND (G) MEANS DEFINING A FLUID EXCHANGE PASSAGE CONNECTING SAID INTERNAL REGION OF THE TORQUE MOTOR WITH A FLUID-CONTAINING SPACE OF THE SERVO VALVE AND INCLUDING A NARROW PASSAGE PORTION DEFINED AT LEAST IN PART BY A MAGNETIC FIELD-GENERATING PORTION OF THE TORQUE MOTOR.