Differential pressure poppet valve

Claim 1

IN A PUMP HAVING A PISTON MOVABLE IN A NORMAL BACK-AND-FORTH CYCLE OF FORCING A FLUID THROUGH A CYLINDIRCAL PASSAGEWAY WHICH IN PART FORMS A PUMPING CHAMBER, THE IMPROVED DISCHARGE VALVE ADAPTED TO CONTROL THE DISCHARGE OF SAID FLUID FROM SAID PUMPING CHAMBER INTO A RESERVOIR THEREFOR, SAID DISCHARGE VALVE COMPRISING: A SEAT IN THE PROXIMITY OF ONE END OF SAID PUMPING CHAMBER AND ADAPTED TO SEAT A DISCHARGE BLOCKING MEMBER; A DISCHARGE BLOCKING MEMBER MOVABLY MOUNTED BETWEEN THE PUMPING CHAMBER AND RESEVOIR, SAID SEAT AND SAID MEMBER BEING SO SIZED THAT WHEN SAID MEMBER IS SEATED THEREIN, THE FLOW OF LIQUID THROUGH SAID DISCHARGE VALVE IS SUBSTANTIALLY BLOCKED; AND FIRST AND SECOND PORTS, AT LEAST, COUPLING SAID CHAMBER TO SAID RESERVOIR TO ENABLE THE DIFFERENCE IN PRESSURE ON THE PISTON SIDE AND THE RESERVOIR SIDE OF SAID MEMBER TO SEAT SAID MEMBER DURING THE DOWNSTROKE OF SAID CYCLE WHEN THE PISTON IS MOVING IN SAID DIRECTION AWAY FROM SAID MEMBER, WHEREBY FLUID IS PREVENTED FROM FLOWING FROM SAID RESERVOIR INTO SAID PASSAGEWAY AND TO ENABLE THE PRESSURE DIFFERENCE TO HOLD SAID MEMBER AWAY FROM SAID SEAT DURING A SUBSTANTIAL PART OF THE UPSTROKE OF SAID CYLCE WHEN SAID PISTON IS MOVING TOWARDS SAID MEMBER, WHEREBY FLUID CAN FLOW THROUGH SAID FIRST PORT ITNO SAID RESERVOIR, SAID SECOND PORT BEING LOCATED CENTRALLY, AND SAID FIRST PORT BEING LATERALLY SPACED FROM SAID CENTRALLY LOCATED FIRST PORT.