Linear actuator

Claim 1

IN A POSTIONER FOR LINEARLY POSITIONING A MOVABLE REFERENCE ELEMENT IN RELATION TO A STATIONARY REFERENCE ELEMENT, WHEREIN SAID POSITIONER COMPRISES A STATIONARY ELONGATED HOUSING DEFINING THE STATIONARY REFERENCE ELEMENT HAVING A SUBSTANTIALLY CYLINDRICAL BORE WITH AN END CLOSED BY A FIRST END PLATE AND ANOTHER END PROVIDED WITH A SECOND END PLATE HAVING A SUBSTANTIALLY CENTRALLY DISPOSED OPENING, A SLIDABLE OUTPUT SHAFT DEFINING THE MOVABLE REFERENCE ELEMENT LONGITUDINALLY MOVABLE THROUGH THE OPENING IN SAID SECOND END PLATE, A PLURALITY OF CASCADED MOTOR STAGES SLIDABLY DISPOSED END-TO-END WITHIN THE BORE IN SAID HOUSING INTERMEDIATE THE CLOSED END OF SAID BORE AND THE OUTPUT SHAFT, A SOURCE OF PRESSURIZED FLUID, AND VALVING AND CONDUIT MEANS FOR SELECTIVELY CONNECTING AND DISCONNECTING THE MOTOR STAGES TO AND FROM THE SOURCE OF PRESSURIZED FLUID, THE IMPROVEMENT CHARACTERIZED BY EACH ONE OF SAID MOTOR STAGES COMPRISING: A PISTON MEMBER HAVING A BODY PORTION ADAPTED TO SLIDABLY FIT WITHIN THE BORE IN THE HOUSING AND HAVING A FIRST AND SECOND L-SHAPED EXTENSIONS PROJECTING FROM THE OPPOSITE FACES OF SAID BODY PORTION, THE FIRST OF SAID L-SHAPED EXTENSIONS DEFINING A PUSHROD ELEMENT AND THE SECOND OF SAID L-SHAPED EXTENSIONS DEFINING A CONNECTING LINK ELEMENT, BOTH SAID PUSH-ROD AND CONNECTING LINK ELEMENTS BEING PROVIDED WITH A STEM HAVING AN END FLANGE PORTION DISPOSED SUBSTANTIALLY AT RIGHT ANGLE TO THE AXIS OF THE PISTON MEMBER AND HAVING AN INNER END FACE AND AN OUTER END FACE, SAID END FLANGE PORTION OF THE PUSH-ROD ELEMENT BEING ADAPTED TO TRANSVERSELY PROJECT INTO A CORRESPONDING GROOVE-LIKE RECESS IN THE STEM OF THE CONNECTING LINK ELEMENT ASSOCIATED WITH THE NEXT PRECEDING PISTON MEMBER FOR PREVENTING CONSECUTIVE PISTON MEMBERS FROM ROTATING AND TILTING RELATIVELY TO EACH OTHER, THE INNER END FACE OF SAID END FLANGE PORTION OF THE PUSH-ROD ELEMENT BEING NORMALLY A PREDETERMINED DISTANCE AWAY FROM THE INNER END FACE OF THE END FLANGE PORTION OF THE CONNECTING ROD ELEMENT INTERLINKED THEREWITH, THE OUTER END FACE OF SAID FLANGE PORTION OF THE PUSHROD ELEMENT BEING NORMALLY ADAPTED TO ABUT AGAINST THE END FACE OF THE BODY PORTION OF THE PISTON MEMBER IMMEDIATELY PRECEDING, SAID END FLANGE PORTION OF THE CONNECTING LINK ELEMENT BEING ADAPTED TO PROJECT INTO A CORRESPONDING GROOVELIKE RECESS IN THE STEM OF THE PUSH-ROD ELEMENT ASSOCIATED WITH THE NEXT CONSECUTIVE PISTON MEMBERS FOR PREVENTING CONSECUTIVE PISTON MEMBERS FROM ROTATING AND TILTING RELATIVELY TO EACH OTHER, THE INNER END FACE OF SAID END FLANGE PORTION OF THE CONNECTING LINK ELEMENT DEFINING AN ABUTMENT BEING NORMALLY SAID PREDETERMINED DISTANCE AWAY FROM THE INNER END FACE OF THE END FLANGE PORTION OF THE PUSHROD ELEMENT AND ADAPTED TO ENGAGE THEREWITH FOR LIMITING THE PERMISSIBLE TRAVEL OF TWO CONSECUTIVE PISTON MEMBERS RELATIVELY TO EACH OTHER, THE OUTER END FACE OF SAID END FLANGE PORTION OF THE CONNECTING LINK ELEMENT BEING NORMALLY A SMALL DISTANCE AWAY FROM THE END FACE OF THE PISTON BODY PORTION OF THE NEXT CONSECUTIVE PISTON MEMBER, THE STEMS OF SAID PUSH-ROD ELEMENT AND OF SAID CONNECTING LINK ELEMENT BEING SYMMETRICALLY ARRANGED RELATIVELY TO THE LONGITUDINAL AXIS OF THE PISTON MEMBER ASSOCIATED THEREWITH AND BEING DISPOSED ON ALTERNATE SIDES OF AN IMAGINARY PLANE SITUATED IN SAID AXIS WITH THE RESPECTIVE END FLANGE PORTIONS THEREOF SUBSTANTIALLY AT RIGHT ANGLE TO SAID AXIS AND PROJECTING CENTRIPETALLY RELATIVELY THE BORE IN SAID HOUSING, A CONNECTING LINK ELEMENT PROJECTING FROM THE INNER SIDE OF THE END PLATE CLOSING THE CLOSED END OF THE BORE IN THE HOUSING WHICH IS ADAPTED TO COOPERATE WITH THE PUSH-ROD ELEMENT OF THE FIRST ONE OF SAID PISTON MEMBERS, THE LAST ONE OF SAID PISTON MEMBERS BEING DEVOID OF CONNECTING LINK ELEMENT AND BEING ATTACHED DIRECTLY TO THE OUTPUT SHAFT, THE BODY PORTIONS OF EACH OF TWO CONSECUTIVE PISTON MEMBERS DEFINING A SUBSTANTIALLY ANNULAR CHAMBER DISPOSED IN THE BORE OF SAID HOUSING BETWEEN SUCH TWO BODY PORTIONS OF CONSECUTIVE PISTON MEMBERS, PORT MEANS IN THE BORE OF THE HOUSING FOR ADMITTING PRESSURIZED FLUID INTO EACH SAID ANNULAR CHAMBER FOR CAUSING DISPLACEMENT OF THE PISTON MEMBER SITUATED TOWARDS THE OUTPUT SHAFT, THUS DISPLACING AT THE SAME TIME ALL THE PISTON MEMBERS BETWEEN SAID PISTON MEMBERS AND THE OUTPUT SHAFT BY MEANS OF THE END FACE OF THE BODY PORTION OF EACH OF SAID PISTON MEMBERS ENGAGING THE OUTER END FACE OF THE PUSHROD ELEMENT OF EACH CONSECUTIVE PISTON MEMBER, THE MAXIMUM TRAVEL OF EACH PISTON MEMBER RELATIVELY TO THE PISTON MEMBER IMMEDIATELY PRECEDING BEING LIMITED BY STOP MEANS DEFINED BY THE INNER END FACE OF THE END FLANGE PORTION OF EACH PUSH-ROD ELEMENT AND THE INNER END FACE OF THE END FLANGE PORTION OF EACH CONNECTING LINK ELEMENT, AND BIASING MEANS EXERTED UPON THE LAST PISTON MEMBER IN A DIRECTION THAT TENDS TO MAINTAIN THE OUTER END FACE OF THE FLANGE PORTION OF THE PUSH-ROD ELEMENT OF EACH PISTON MEMBER IN CONTACT WITH THE CORRESPONDING END FACE OF THE NEXT PRECEDING PISTON BODY PORTION, AND THE OUTER END FACE OF THE END FLANGE PORTION OF THE PUSH-ROD ELEMENT OF THE FIRST PISTON MEMBER IN CONTACT WITH THE INNER SIDE OF THE END PLATE THEREBY BIASING THE ACTUATOR TO ITS RETRACTED CONDITION.