Torque control apparatus for hydraulic power units

Claim 1

A TORQUE CONTROL APPARTUS FOR A HYDRAULIC POWER UNIT, SAID POWER UNIT HAVING A PRESSURE PASSAGWAY AND HAVING A SERIES OF DISPLACEMENT PISTONS, SAID POWER UNIT HAVING A MOVABLE ELEMENT ADAPTED TO BE SHIFTED IN A FLAT PLANE IN RESPONSE TO BACK PRESSURE IN THE PRESSURE PASSAGEWAY TO CONTROL THE STROKE OF SAID PISTONS AND THE DISPLACEMENT OF THE POWER UNIT, SAID CONTROL APPARATUS COMPRISING: AN AXIALLY SHIFTABLE STROKE CONTROL PISTON CONNECTED TO THE MOVABLE ELEMENT OF THE POWER UNIT AND ADAPTED TO SHIFT THE SAME FOR INCREASING OR DECREASING THE STROKE OF SAID PISTONS AND THEREBY THE DISPLACEMENT OF THE POWER UNIT; A PILOT VALVE INCLUDING AN AXIALLY SHIFTABLE VALVE SPOOL DISPOSED IN AXIAL ALIGNMENT WITH SAID STROKE CONTROL PISTON AND ENGAGING SAID MOVABLE ELEMENT IN OPPOSITION TO SAID STROKE CONTROL PISTON; A COMPRESSIBLE SPRING ELEMENT INTERPOSED BETWEEN THE AXIALLY SHIFTABLE VALVE SPOOL AND MOVABLE ELEMENT, ADAPTING THE VALVE SPOOL TO ACT UPON THE MOVABLE ELEMENT THROUGH SAID SPRING ELEMENT; SAID POWER UNIT INCLUIDNG MEANS PROVIDING HYDRAULIC COMMUNICATON BETWEEN SAID PRESSURE PASSAGEWAY AND SAID SHIFTABLE VALVE SPOOL, WHEREBY THE VALVE SPOOL IS SHIFTED TOWARD SAID MOVABLE ELEMENT IN RESPONSE TO BACK PRESSURE IN SAID PRESSURE PASSAGEWAY TO URGE THE MOVABLE ELEMENT THROUGH THE COMPRESSIBLE SPRING ELEMENT TOWARD SAID STROKE CONTROL PISTON; SAID AXIALLY SHIFTABLE VALVE SPOOL ADAPTED TO TRASMIT HYDRAULIC PRESSURE IN RESPONSE TO SAID MOVEMENT OF THE VALVE SPOOL TO SAID STROKE CONTROL PISTON IN A DIRECTION TO FORCE THE SAME TOWARD THE MOVABLE ELEMENT OPPOSITE TO THE FORCE EXERTED BY SAID VALVE SPOOL AND SPRING ELEMENT, WHEREBY THE AXIALLY SHIFTABLE VALVE SPOOL AND AXIALLY SHIFTABLE STROKE CONTROL PISTON BIAS ONE ANOTHER AGAINST SAID MOVABLE ELEMENT TO PROVIDE A SERVO ACTION AND THEREBY A BALANCED RELATIONSHIP TO HOLD THE MOVABLE ELEMENT AT A POSITION PROVIDING A GIVEN PISTON STROKE IN RESPONSE TO A GIVE BACK PRESSURE IN SAID PRESSRUE PASSAGEWAY.