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Claim 1

IN A HYDRAULIC PRESSURE DEVICE THE COMBINATION OF A BODY PORTION, A PRESSURE LIQUID RECIPROCABLE DIFFERENTIAL AREA PISTON-HAMMER SLIDABLY MOUNTED IN SAID BODY PORTION, SAID PISTON HAMMBER HAVING A LARGE SURFACE AREA PORTION AT ONE END AND A SMALL AREA PORTION AT THE OTHER END, A CONTROL VALVE, SAID CONTROL VALVE INCLUDING A DIFFERENTIAL AREA FLOW CONTROL SPOOL MOUNTED FOR RECIPROCATING MOVEMENT BY PRESSURE FLUID ACTING AGAINST THE DIFFERENTIAL AREAS THEREOF, SAID DIFFERENTIAL AREAS COMPRISING THE ENTIRE END SURFACE AREAS EFFECTIVE TO SHIFT SAID SPOOL AND INCLUDING A LARGER AREA PORTION AT ONE END OF THE SPOOL AND A SMALLER AREA PORTION AT THE OTHER END OF THE SPOOL, PRESSURE LIQUID FLOW CONTROL MEANS ON SAID PISTON-HAMMER TO REVERSE THE DIRECTION OF TRAVEL OF THE FLOW CONTROL SPOOL AND THEN SAID PISTON-HAMMER, MEANS MAINTAINING THE SMALLER AREA PORTION OF SAID PISTON-HAMMER IN CONTINUOUS COMMUNICATION WITH A SOURCE OF PRESSURE LIQUID, MEANS INCLUDING SAID CONTROL VALVE FOR ALTERNATELY CONNECTING THE PRESSURE LIQUID AT THE SMALLER AREA END PORTION OF THE PISTON-HAMMER AND THE SOURCE OF PRESSURE LIQUID TO THE LARGER AREA END PORTION OF THE PISTONHAMMER AND ALTERNATELY BLOCKING COMMUNICATION BETWEEN THE LARGER AREA PORTION OF SAID PISTON-HAMMER AND THE LARGER AREA PORTION OF THE CONTROL SPOOL, MEANS CONTINUOUSLY CONNECTING THE SOURCE OF PRESSURE LIQUID WITH THE ENTIRE SMALLER AREA PORTION OF SAID CONTROL SPOOL TO THEREBY CONTINUOUSLY URGE SAID SPOOL IN A DIRECTION TOWARD THE LARGER AREA PORTION OF SAID SPOOL, SAID PRESSURE LIQUID FLOW CONTROL MEANS ON SAID PISTON-HAMMER COOPERATING WITH GROOVES IN SAID BODY PORTION AND WITH SAID CONTROL VALVE SPOOL FOR ALTERNATELY CONNECTING THE PRESSURE LIQUID AT THE SMALLER AREA PORTION OF THE SPOOL AND THE SOURCE OF PRESSURE LIQUID TO THE LARGER AREA PORTION OF SAID RECIPROCABLE SPOOL.