Constant horsepower pump

Claim 1

A VARIABLE DISPLACEMENT PUMP HAVING A PUMP HOUSING DEFINING A FLUID CHAMBER THEREIN, AN INLET TO SAID FLUID CHAMBER AND AN OUTLET ON SAID PUMP HOUSING, A CYLINDER BLOCK SLIDABLY MOUNTED WITHIN SAID FLUID CHAMBER FOR AXIAL RECIPROCATING MOVEMENT BETWEEN MINIMUM AND MAXIMUM DISPLACEMENT POSITIONS, A PLURALITY OF CYLINDER BORES IN SAID CYLINDER BLOCK, A PISTON WITHIN EACH OF SAID CYLINDER BORES, DRIVE MEANS TO RECIPROCATE SAID PISTONS, AN INLET PORT IN SAID CYLINDER BLOCK ADAPTED TO ADMIT FLUID FROM SAID FLUID CHAMBER INTO SAID CYLINDER BORES, MEANS TO CONNECT EACH OF SAID CYLINDER BORES TO SAID PUMP OUTLET, FIRST MEANS BIASING SAID CYLINDER BLOCK TOWARD THE MINIMUM DISPLACEMENT POSITION WITH A FORCE DIRECTLY PROPORTIONAL TO THE PRESSURE AT SAID OUTLET, SECOND MEANS BIASING SAID CYLINDER BLOCK TOWARD THE MAXIMUM DISPLACEMENT POSITION IN OPPOSITION TO THE FORCE OF SAID FIRST MEANS WITH A FORCE NON-LINEAR WITH RESPECT TO THE POSITION OF SAID MOVABLE MEMBER TO MAINTAIN A COMSTANT POWER LEVEL DURING VARIATIONS OF ETHE PUMP OUTPUT DISPLACEMENT AND PRESSURE, AND PRESSURE RESPONSIVE CONTROL MEANS INCLUDING A FLUID PRESSURE MOTOR OPERATING TO OPPOSE SAID SECOND MEANS TO SHIFT SAID MOVABLE MEMBER TO THE MINIMUM DISPLACEMENT POSITION WHENEVER THE OUTPUT PRESSURE OF THE PUMP EXCEEDS A PREDETERMINED LEVEL.