Hydraulic servo control mechanism

Claim 1

A HYDRAULIC SERVO CONTROL MECHANISM COMPRISING, IN COMBINATION, A SOURCE OF FLUID PRESSURE, MAIN PISTON MEANS SLIDABLE IN AXIAL DIRECTIONS, SERVO PISTON MEANS SPACED FROM SAID MAIN PISTON MEANS ALSO SLIDABLE IN AXIAL DIRECTIONS, SAID SERVO AND MAIN PISTON MEANS EACH EXPOSED ON ONE SIDE TO SAID FLUID UNDER PRESSURE FOR BEING URGED IN ONE DIRECTION, MEANS TRANSFERRING A BIASING FORCE TO SAID MAIN PISTON MEANS TO URGE THE LATTER IN A DIRECTION OPPOSITE TO THAT URGED BY SAID FLUID UNDER PRESSURE, MECHANICAL MEANS INTERCONNECTING SAID MAIN AND SERVO PISTON MEANS (1) TO RESTRAIN THE LATTER TO MOVE SIMULTANEOUSLY WITH THE MOVEMENT OF THE FORMER IN RESPONSE TO AN EXCESS OF FLUID PRESSURE OVER SAID BIASING FORCE AND (2) TO DRIVE SAID SERVO PISTON MEANS BACK IN RESPONSE TO MOVEMENT OF SAID MAIN PISTON MEANS WHEN SAID BIASING FORCE EXCEEDS FLUID PRESSURE ON THE LATTER, CONTROL MEANS MOVABLE WITH RESPECT TO SAID SERVO PISTON MEANS, CONTROL SLOTS FORMED IN SAID CONTROL MEANS TO DISCHARGE FLUID ACTING ON SAID SERVO AND MAIN PISTON MEANS THEREBY EFFECTING A DECREASE IN FLUID PRESSURE, MEANS ATTACHED TO SAID SERVO PISTON MEANS FOR ADJUSTABLY BLOCKING FLUID FLOW THROUGH SAID CONTROL SLOTS AS A RESULT OF RELATIVE MOVEMENT OF SAID CONTROL MEANS AND SERVO PISTON MEANS, AND MEANS FOR SELECTIVELY ADJUSTING THE POSITION OF SAID CONTROL MEANS TO ALTER FLOW THROUGH SAID CONTROL SLOTS AND HENCE TO CHANGE FLUID PRESSURE ON SAID SERVO AND MAIN PISTON MEANS TO CAUSE A CHANGE IN FORCE ACTING ON SAID MAIN PISTON MEANS AS A RESULT OF CHANGE IN FLUID PRESSURE ACTING THEREON.