Spring and fluid pressure actuator

Claim 1

A FLUID PRESSURE ACTUATOR COMPRISING: (A) A HOUSING, (B) A PISTON MEMBER MOVABLY MOUNTED IN SAID SAID ING FOR RECIPROCATIVE MOTION, (1) SAID PISTON MEMBER AND A PORTION OF SAID HOUSING TOGETHER DEFINING AT LEAST ONE SEALED CHAMBER, (2) SAID PISTON MEMBER AND ANOTHER PORTION OF SAID HOUSING TOGETHER DEFINING A SECOND CHAMBER, (C) A CONNECTING ELEMENT SECURED TO SAID PISTON MEMBER AND ADAPTED TO BE CONNECTED TO A DEVICE WHICH IS ACTUATED THEREBY (D) MEANS FOR ADMITTING FLUID UNDER PRESSURE INTO SAID SEALED CHAMBER TO URGE SAID PISTON MEMBER IN ONE DIRECTION OF MOVEMENT, (E) COMPRESSIBLE SPRING MEANS IN SAID SECOND CHAMBER FOR EXERTING A FORCE ON SAID PISTON MEMBER TO URGE SAID PISTON MEMBER IN THE OPPOSITE DIRECTION OF MOVEMENT, (F) A BEARING PLATE MOUNTED IN SAID SECOND CHAMBER FOR RECIPROCATIVE MOTION WITH SAID PISTON MEMBER FOR NORMALLY TRANSMITTING SAID FORCE FROM SAID SPRINGS MEANS TO SAID PISTON MEMBER, AND (G) MEANS, EXTENDING FROM WITHIN SAID HOUSING TO THE EXTERIOR OF SAID HOUSING ADAPTED TO ABUT THE EXTERIOR OF SAID HOUSING AND CONNECTED TO SAID BEARING PLATE BY A THREADED ROD, FOR LOCKING SAID BEARING PLATE AGAINST MOVEMENT IN SAID OPPOSITE DIRECTION BEYOND A PRESELECTED LIMIT WHEREBY SAID SPRING IS RESTRAINED FROM EXERTING FORCE ON SAID PISTON MEMBER.