US Patent 7603943 Linear actuator for rotating shaft assemblies

A linear actuator for a rotating shaft assembly includes a cylinder and a piston arranged within a cavity defined by the cylinder. Faces of the piston delimit first and second chambers within the cavity. A rotatable shaft fixed to the piston defines a first main passage in fluid communication with the first chamber and a second main passage in fluid communication with the second chamber. A pressure delivery body rotatably fixed to the rotatable shaft defines a first delivery passage in fluid communication with the first main passage and a second delivery passage in fluid communication with the second main passage. A passage isolation system selectively isolates fluid communication between the first delivery passage and the first main passage and fluid communication between the second delivery passage and the second main passage. A pressure limiting system selectively blocks fluid communication through the first and second main passages.