Servo motor damper

Claim 1

IN A FLUID SERVO ACTUATOR SYSTEM INCLUDING A SERVO ACTUATOR RESPONSIVE TO A COMMAND SIGNAL AND ADAPTED TO DISPLACE A LOAD, SAID SERVO ACTUATOR COMPRISING A DOUBLE ACTING PISTON RECIPROCABLE IN A CYLINDER BY A FLUID PRESSURE DIFFERENTIAL BETWEEN A FIRST AND A SECOND MOTOR CHAMBERS SUBJECTING THE FACES OF SAID PISTON TO SAID FLUID PRESSURE DIFFERENTIAL, A DAMPING MECHANISM ARRANGED TO PREVENT UNDESIRABLE OSCILLATIONS AND STRESSES IN SAID SYSTEM, SAID DAMPING MECHANISM COMPRISING: A FLUID FLOW LEAKAGE PATH BETWEEN SAID MOTOR CHAMBERS AND VALVING MEANS IN SAID PATH NORMALLY INTERRUPTING THE FLOW OF FLUID THROUGH SAID PATH, SAID VALVING MEANS COMPRISING: A FIRST CYLINDRICAL BORE WITH A FIRST PORT IN FLUID COMMUNICATION WITH SAID FIRST MOTOR CHAMBER, A SECOND PORT IN FLUID COMMUNICATION WITH SAID SECOND MOTOR CHAMBER, A THIRD PORT IN FLUID COMMUNICATION WITH SAID FIRST MOTOR CHAMBER AND A FOURTH PORT IN FLUID COMMUNICATION WITH SAID SECOND MOTOR CHAMBER; A VALVE SPOOL MEMBER SLIDABLY DISPOSED IN SAID BORE AND HAVING A FIRST AND A SECOND LAND PORTIONS DEFINING AN ANNULAR CHAMBER THEREBETWEEN; MEANS DEFINING IN SAID FIRST CYLINDRICAL BORE A FIRST FLUID CHAMBER ON ONE END OF SAID VALVE SPOOL MEMBER AND A SECOND FLUID CHAMBER ON THE OTHER END OF SAID VALVE SPOOL MEMBER; COIL SPRINGS IN BOTH SAID FIRST AND SECOND FLUID CHAMBERS NORMALLY MAINTAINING SAID VALVE SPOOL MEMBER IN A NEUTRAL POSITION CAUSING SAID FIRST LAND TO OBTURATE SAID SECOND PORT, SAID SECOND LAND TO OBTURATE SAID FOURTH PORT, SAID THIRD PORT TO BE OPEN TO SAID ANNULAR CHAMBER AND SAID FIRST PORT TO BE OPEN TO SAID FIRST FLUID CHAMBER; A SECOND CYLINDRICAL BORE; A SPOOL ELEMENT SLIDABLY DISPOSED IN SAID SECOND BORE; MEANS DEFINING IN SAID SECOND BORE A THIRD FLUID CHAMBER ON ONE END OF SAID SPOOL ELEMENT AND A FOURTH FLUID CHAMBER ON THE OTHER END OF SAID SPOOL ELEMENT, SAID THIRD FLUID CHAMBER BEING AT ALL TIMES IN FLUID COMMUNICATION WITH SAID SECOND FLUID CHAMBER AND SAID FOURTH FLUID CHAMBER BEING AT ALL TIME IN FLUID COMMUNICATION WITH SAID SECOND MOTOR CHAMBER; COIL SPRING MEANS NORMALLY MAINTAINING SAID SPOOL ELEMENT IN A SUBSTANTIALLY CENTRAL POSITION IN SAID SECOND BORE; A PASSAGEWAY WITH A RESTRICTED CALIBRATBD ORIFICE PLACING SAID FIRST AND SECOND FLUID CHAMBERS IN FLUID COMMUNICATION AND CAUSING THE VARIATIONS OF FLUID PRESSURE IN SAID SECOND FLUID CHAMBER TO LAG IN TIME BEHIND THE VARIATIONS OF FLUID PRESSURE IN SAID FIRST FLUID CHAMBER, WHEREBY A SUDDEN INCREASE OF PRESSURE IN SAID FIRST FLUID CHAMBER MOMENTARILY DISPLACES SAID VALVE SPOOL MEMBER TO A FIRST POSITION AWAY FROM SAID NEUTRAL POSITION AND OPENS SAID FOURTH PORT TO SAID ANNULAR CHAMBER AND A SUDDEN DECREASE OF PRESSURE IN SAID FIRST FLUID CHAMBER MOMENTARILY DISPLACES SAID VALVE SPOOL MEMBER TO A SECOND POSITION AWAY FROM SAID NEUTRAL POSITION AND OPENS SAID SECOND PORT TO SAID ANNULAR CHAMBER, AND VARIATIONS OF PRESSURE IN SAID FOURTH FLUID CHAMBER CAUSE A DISPLACEMENT OF SAID SPOOL ELEMENT CAUSING IN TURN A FLOW OF FLUID INTO AND OUT OF SAID THIRD FLUID CHAMBER INCREASING THE DIFFERENCE IN PRESSURES BETWEEN SAID FIRST AND SECOND FLUID CHAMBERS.