Oil well pumping unit and method of using same

Claim 1

IN AN OIL WELL PUMPING UNIT THAT INCLUDES A POWER OPERATED UPWARDLY AND DOWNWARDLY MOVABLE POLISHED ROD, A STUFFING BOX IN WHICH SAID POLISHED ROD IS SLIDABLY AND SEALINGLY DISPOSED, A RECIPROCATING PUMP, A SUCKER ROD EXTENDING DOWNWARDLY FROM SAID POLISHED ROD TO SAID PUMP AND A TUBING STRING OF LARGER INTERNAL CORSS SECTION THAN THE TRANSVERSE CROSS SECTION OF SAID SUCKER ROD EXTENDING UPWARDLY FROM SAID PUMP TO A PREDETERMINED DISTANCE FROM SAID STUFFING BOX AND SURROUNDING SAID SUCKER ROD, THE COMBINATION OF: (A) A TUBING STRING EXTENSION OF LARGER INTERIOR TRANSVERSE CROSS SECTION THAN THE EXTERIOR TRANSVERSE CROSS SECTION OF SAID TUBING STRING THAT EXTENDS UPWARDLY FROM THE TOP OF SAID TUBING STRING TO A FIXED POSITION RELATIVE TO SAID STUFFING BOX; (B) A TUBULAR BARREL DISPOSED IN THE UPPER PORTION OF SAID TUBING EXTENSION WHICH BARREL AND EXTENSION COOPERATIVELY DEFINE AN ANNULUS-SHAPED SPACE THEREBETWEEN; (C) FIRST CONFINED SPACE-DEFINING MEANS DISPOSED ABOVE THE UPPER EXTREMITY OF SAID TUBING STRING EXTENSION AND IN COMMUNICATION WITH SAID ANNULUS-SHAPED SPACE; (D) WELL FLUID DISCHARGE MEANS IN COMMUNICATION WITH SAID FIRST CONFINED SPACE-DEFINING MEANS; (E) A PISTON CONNECTED TO SAID POLISHED ROD AND SLIDABLY AND SEALINGLY DISPOSED IN SAID BARREL; (F) SECOND CONFINED SPACE-DEFINING MEANS OF VARIABLE VOLUME THAT INCLUDES SAID PISTON AND AT LEAST A PORTION OF SAID BARREL; (G) A LIQUID INLET AND A LIQUID OUTLET IN COMMUNICATION WITH SAID SECOND CONFINED SPACE-DEFINING MEANS; AND (H) FIRST CHECK VALVE MEANS ON SAID INLET THAT OPENS TO ADMIT LIQUID INTO SAID SECOND CONFINED SPACE-DEFINING MEANS ON THE DOWNSTROKE OF SAID PISTON, AND CLOSES ON THE UPSTROKE OF SAID PISTON TO CAUSE SAID LIQUID IN SAID SECOND CONFINED SPACE TO DISCHARGE THEREFROM THROUGH SAID LIQUID OUTLET WHEN SAID WELL FLUID IS DISCHARGED BY SAID ROD-ACTUATED PUMP FROM SAID WELL FLUID DISCHARGE MEANS.