Control for variable displacement pump or motor

Claim 1

THE COMBINATION COMPRISING, A CROSS-CENTER AND PRESSURE TRANSLATING DEVICE HAVING TWO PORTS AND A DISPLACEMENT VARYING MEMBER SHIFTABLE IN OPPOSITE DIRECTIONS TO VARY DISPLACEMENT AND FLOW BETWEEN SAID PORTS, A FIRST TORQUE LIMITER ASSEMBLY ON ONE SIDE OF SAID MEMBER, SAID FIRST TORQUE LIMITER ASSEMBLY COMPRISING, PISTON MEANS FOR MOVING SAID MEMBER IN ONE DIRECTION AND FOR LIMITING ITS MOVEMENT IN THE OPPOSITE DIRECTION, SAID PISTON MEANS INCLUDING A CAM SURFACE, THE SHAPE OF SAID CAM SURFACES REFLECTING THE GRAPHICAL INTERRELATION BETWEEN PRESSURE, VOLUME AND TORQUE, SERVO MEANS FOR MOVING SAID PISTON MEANS IN SAID ONE DIRECTION TO SELECTIVELY POSITION SAID MEMBER, SAID SERVO MEANS INCLUDING A MOVABLE VALVE MEMBER WHICH CONTROLS APPLICATION OF MOTIVE FLUID THROUGH SAID SERVO MEANS TO SAID PISTON MEANS, SAID MOVABLE MEMBER HAVING A FACE THEREOF, DISPOSED TO PRESSURE, AN ELASTIC CAM FOLLOWER MEANS ENGAGING SAID CAM SURFACE AND APPLYING AN ELASTIC FORCE OPPOSING FLUID FORCE ACTING ON SAID FACE OF SAID MOVABLE MEMBER, THE MAGNITUDE OF SAID ELASTIC FORCE INCREASING IN INVERSE PROPORTION AS SAID DISPLACEMENT DECREASES, A SECOND TORQUE LIMITER ASSEMBLY SUBSTANTIALLY IDENTICAL TO SAID FIRST ASSEMBLY, SAID SECOND ASSEMBLY BEING LOCATED ON THE OPPOSITE SIDE OF SAID DISPLACEMENT VARYING MEMBER FOR SHIFTING SAID DISPLACEMENT VARYING MEMBER IN THE DIRECTION OPPOSITE THAT OF THE FIRST ASSEMBLY, MEANS APPLYING FLUID AT THE PRESSURE AT THE SAID RESPECTIVE PORTS TO THE RESPECTIVE MOVABLE MEMBERS OF SAID ASSEMBLIES TENDING TO MOVE SAID MOVABLE MEMBER TO APPLY FLUID TO MOVE SAID PISTON MEANS, MEANS SUPPLYING MOTIVE FLUID TO SAID SERVO MEANS, AND OPPOSED SPRING MEANS URIGING SAID DISPLACEMENT VARYING MEMBER TOWARD EACH OTHER.