Throttling control

Claim 1

A PUMP COMPRISING A PUMP HOUSING PROVIDING A FLUID CHAMBER THEREIN, AN INLET TO SAID FLUID CHAMBER, AN OUTLET ON SAID PUMP HOUSING, A CYLINDER BLOCK MOUNTED FOR SLIDABLE MOVEMENT WITHIN SAID FLUID CHAMBER ALONG A LONGITUDINAL AXIS, A PLURALITY OF CYLINDER BORES IN SAID CYLINDER BLOCK PARALLEL TO SAID LONGITUDINAL AXIS, A PISTON WITHIN EACH OF SAID CYLINDER BORES, DRIVE MEANS IN SAID PUMP HOUSING TO PROGRESSIVELY RECIPROCATE SAID PISTONS IN SAID CYLINDER BORES BETWEEN FORWARD AND RETRACTED POSITIONS, MEANS CONNECTING EACH OF SAID CYLINDER BORES TO SAID OUTLET, AN INLET PORT FOR EACH CYLINDER BORE IN SAID CYLINDER BLOCK, SAID INLET PORT HAVING FORWARD AND REARWARD AXIALLY SPACED EDGES, SAID CYLINDER BLOCK DEFINING A PREDETERMINED MAXIMUM DISPLACEMENT POSITION WHEN THE HEAD OF THE PISTON IS INTERMEDIATE SAID PORT EDGES WHEN SAID PISTON IN THE RETRACTED POSITION, CONTROL MEANS TO SHIFT SAID CYLINDER BLOCK WITH RESPECT TO SAID PUMP HOUSING AND SAID DRIVE MEANS IN THE DIRECTION TO SHIFT THE FORWARD EDGE OF SAID INLET PORT TOWARD THE RETRACTED PISTON TO DECREASE THE INLET PORT AREA EXPOSED WHEN THE PISTON IS IN THE RETRACTED POSITION TO THROTTLE FLUID FLOW INTO SAID CYLINDER BORE AND DECREASE THE EFFECTIVE OUTPUT VOLUME OF THE PUMP, AND STOP MEANS ON SAID PUMP HOUSING TO PREVENT MOVEMENT OF SAID CYLINDER BLOCK IN THE OPPOSITE DIRECTION FROM SAID MAXIMUM DISPLACEMENT POSITION.