Abstract

Helical splined rotary actuator includes a pair of cylinder housings having inboard ends rotatably mounted in coaxial alignment on opposite ends of a center sleeve member. Contained within the housings are pistons having relatively large diameter helical spline connections with the inner diameters of the housings and smaller diameter straight spline connections with opposite ends of the sleeve member, whereby simultaneous axial movement of the pistons toward and away from each other causes relative rotation between the sleeve member and cylinder housings. The sleeve member may be connected to a first support intermediate the ends of the actuator. In like manner, the cylinder housings may be connected to a second support rotatable relative to the first support adjacent opposite ends of the sleeve member. End closures at the outboard ends of the housings have barrier sleeves extending coaxially into the outboard ends of the housings between the housings and pistons to act as barriers between the internal housing seals and external piston seals. The end closures are fixed relative to a shaft pinned to the sleeve member intermediate the ends thereof, whereby the housings are rotatable relative to the barrier sleeves but not axially movable relative thereto and the pistons are axially movable relative to the barrier sleeves but not rotatable relative thereto.