Pneumatically powered linear actuator control apparatus and method

Control apparatus for a linear actuator having an extensible member, an air operated apparatus including a cylinder extending a piston carrying the extensible member for moving an external load, and an elongated threaded lead screw carried in alignment in said cylinder and driven by an electric motor for positioning the load comprising;

• a valve positioned between said electric motor and said cylinder for selectively distributing air under pressure to an extend side of said cylinder;
• a valve spool in said valve connectable on one end to and in alignment with said elongated threaded lead screw and on the other end to an in alignment with said electric motor for controlling said selectively distributing air;
• an assembly for moving said valve spool toward said electric motor responsive to rotation of said elongated threaded member in one direction;
• and
• a coupling connecting the other end of said valve spool to the electric motor permitting said moving of said valve spool and driving said elongated threaded lead screw for said rotation.

A method of controlling a linear actuator having an extensible member, an air operated apparatus including a cylinder extending and retracting a piston for moving an external load, and an elongated threaded member carried in alignment in said cylinder and driven by an electric motor for positioning the load comprising:

• positioning a valve between said electric motor and said cylinder;
• selectively distributing air under pressure to an extended side of said cylinder and to a retract side of said cylinder through said valve;
• connecting a valve spool in said valve on one end to and in axial alignment with said elongated threaded member and on the other end to and in alignment with said electric motor controlling said selectively distributing air to said cylinder;
• moving said valve spool in respect to said electric motor responsive to rotation of said elongated threaded member, and
• connecting the other end of said valve spool to the electric motor permitting said moving of said valve spool and driving said elongated threaded member for said rotation.