Hydraulic positioning servo system

Claim 1

A HYDRAULICALLY POSITIONED SERVO SYSTEM WHICH INCLUDES A HYDRISTOR AS A POSITION FEEDBACK ELEMENT, SAID HYDRISTOR COMPRISING A CASING WITH A FLUID CHAMBER HAVING TEO INLET PORTS EACH WITH AN ORIFICE AND A METERING ELEMENT MOUNTED THEREIN, SAID INLET PORTS CONNECTED TO SAID ORIFICES, SAID METERING ELEMENT BEING FITTED AND POSITIONED WITHIN SAID FLUID CHAMBER AND PROVIDED WITH TWO OPPOSITELY SLANTED SURFACES, SAID OPPOSITELY SLANTED SURFACES POSITIONED BETWEEN SAID ORIFICES TO FORM TWO VARIABLE OPENINGS, SAID VARIABLE OPENINGS PROVIDING TWO COMPLEMENTARY HYDRAULIC RESISTANCES TO ALLOW TWO COMPLEMENTARY FLUID FLOWS OVER SAID METERING ELEMENT AND THROUGH SAID CHAMBERS IN SAID CASING TO A COMMON OUTLET, SAID SERVO SYSTEM DIVIDED INTO A POWER STAGE AND A FEEDBACK CONTROL STAGE, SAID POEER COMPRISING A POWER CYLINDER AND PISTON, A MAIN PRESSURE SOURCE AND A FOUR WAY VALVE, SAID FOUR WAY VALVE CONNECTED BY FLUID LINES TO SAID POWER CYLINDER, SAID FEEDBACK CONTROL STAGE COMPRISING SAID HYDRISTOR, AN AUXILIARY PRESSURE SOURCE, A RATIO FLOW DIVIDER SERVING AS A SIGNAL INPUT VALVE TO PROVIDE TWO COMPLEMENTARY FLUID FLOWS AND TWO COMPLEMENTARY RESISTANCES, A DIFFERENTIAL PRESSURE SENSING DEVICE WHICH IS MECHANICALLY CONNECTED TO SAID FOUR WAY VALVE AND CONNECTED BY FLUID LINES TO SAID RATIO FLOW DIVIDER AND TO SAID HYDRISTOR, SAID FOUR WAY VALVE CONNECTED TO SAID MAIN PRESSURE SOURCE AND COMPRISING A VALVE BODY WITH A CENTRAL AXIALLY MOVABLE PISTON AHVING FLUID FLOW CONTROLLING LANDS THEREON TO SEPARATE AND GUIDE SAID FLUID FLOW TO EITHER SIDE OF SAID POWER CYLINDER, SAID HYDRISTOR HAVING ITS METERING ELEMENT MECHANICALLY CONNECTED TO THE MOVING PISTON OF SAID POWER CYLINDER AS A FEEDBACK ELEMENT, SAID RATIO FLOW DIVIDER COMPRISING A CLOSED CASING WITH A FLUID INLET PORT AT ITS CENTER AND TWO FLUID OUTLET PORTS ONE AT EACH END OF SAID CASING, A PISTON AND ROD MOUNTED LOOSELY AND CENTRALLY WITHIN SAID CLOSED CASING TO PRODUCE TWO COMPLEMENTARY FLUID FLOWS SIMILAR TO THE TWO COMPLEMENTARY FLOWS PRODUCED IN SAID HYDRISTOR, SAID ROD PROVIDING THE MEANS FOR A MECHANICALLY PRODUCED INPUT SIGNAL, SAID PISTON ROD EXTENDING THROUGH SAID CYLINDER, SAID PISTON PROVIDING A METERING EFFECT TO GENERATE TWO COMPLEMENTARY HYDRAULIC RESISTANCES AND TO EFFECT TWO COMPLEMENTARY FLOWS, SAID DIFFERENTIAL PRESSURE SENSING DEVICE COMPRISING A CLOSED CYLINDER WITH TWO FLUID INLET PORTS AND TWO FLUID OUTLET PORTS AND A PISTON, ONE INLET AND ONE OUTLET PORT CONNECTED TO EACH END OF SAID CLOSED CYLINDER TO ALLOW A FLUID FLOW THERETHROUGH, AND A RESILIENT ELEMENT POSITIONED ON EACH SIDE OF SAID PISTON TO NORMALLY RETAIN SAID PISTON CENTERED WHEN SID FLUID PRESSURE ON EACH SIDE OF SAID PISTON IS EQUAL, SAID PISTON OF SAID DIFFERENTIAL PRESSURE SENSING DEVICE CONNECTED TO SAID PISTON OF SAID FOUR WAY VALVE TO CONTROL ITS MOVEMENT AND IN TURN CONTROL THE FLUID FLOW TO SAID POWER CYLINDER, SAID DIFFERENTIAL PRESSURE SENSING DEVICE PROVIDING MEANS TO COMPARE THE RATIO OF TEH TWO COMPLEMENTARY RESISTANCES OF THE HYDRISTOR WITH THE RATIO OF THE TWO COMPLEMENTARY RESISTANCES OF THE SIGNAL INPUT VALVE DURING FLUID FLOW, SAID DIFFERENTIAL PRESSURE SENSING DEVICE WHICH INCLUDES SAID RESILIENT ELEMENTS ALSO RESPONDING TO PRESSURE CHANGES TO MOVE SAID FOUR WAY VALVE TO CORRECT AN ERROR SIGNAL WHEN A PRESSURE DIFFERENTIAL EXISTS IN SAID DIFFERENTIAL SENSING DEVICE BY MOVING SID FOUR WAY VALVE IN THE DIRECTION INDICATED BY THE ERROR SIGNAL AND IN TURN MOVE SAID PISTON OF SAID POWER CYLINDER AND SAID METERING ELEMENT OF SAID HYDRISTOR TO REDUCE SAID ERROR SIGNAL TO ZERO.