Piston accumulator

Claim 1

A PRESSURE VESSEL COMPRISING A CYLINDER HAVING A FIRST FLUID PORT AND A SECOND FLUID PORT, A PISTON SLIDABLY MOUNTED IN SAID CYLINDER INTERVENING BETWEEN SAID PORTS AND DEFINING A FIRST FLUID CHAMBER AND A SECOND FLUID CHAMBER ON OPPOSED SIDES OF SAID PISTON RESPECTIVELY AND EXTERNALLY OF THE LATTER, SAID PISTON HAVING A PAIR OF SPACED ANNULAR GROOVES IN ITS PERIPHERY AND A THIRD ELONGATED ANNULAR GROOVES INTERPOSED BETWEEN SAID PAIR OF SPACED ANNULAR GROOVES, A RESILIENT DEFORMABLE ANNULAR SEAL IN EACH OF SAID PAIR OF SPACED ANNULAR GROOVES, SAID SEALS ENGAGING THE INNER WALL OF SAID CYLINDER, SAID PISTON HAVING A CHAMBER THEREIN WITH A WALL AT EACH END EXPOSED IN SAID FIRST FLUID CHAMBER AND SAID SECOND FLUID CHAMBER RESPECTIVELY, SAID PISTON CHAMBER BEING IN COMMUNICATION WITH SAID THIRD ELONGATED ANNULAR GROOVE, VALVE MEANS ASSOCIATED WITH SAID PISTON CHAMBER, SAID VALVE MEANS BEING SUBJECTED TO THE PRESSURE IN SAID FIRST FLUID CHAMBER AND CONTROLLING THE FLOW OF FLUID FROM SAID PISTON CHAMBER INTO SAID SECOND FLUID CHAMBER.