Abstract

A fluid-powered helical actuator including a cylindrical body; a rotatable output member supported for rotation relative to the body and connectable to an external device; first and second independently rotatable sleeves reciprocally mounted within the body; a piston reciprocally mounted within the body for application of fluid pressure to one or the other opposing sides thereof to produce axial movement, the piston operatively engages at least one or the other of the sleeves to axially move the sleeves in response to axial movement of the piston; and torque-transmitting elements for transmitting torque between the first sleeve and the body, between the first sleeve and the output member, between the second sleeve and the output member, and between the second sleeve and the body. An adjustment member is provided for selectively moving the first sleeve relative to the second sleeve to axially preload the sleeves for eliminating backlash in the toque-transmitting elements as the piston moves from one axial direction to the other in response to selective application of fluid pressure to the piston. In one embodiment the output member has two parts which are oppositely rotated to preload the sleeves. In other embodiments ring gears are employed with one being axially movable for preloading. In yet other embodiments the axial preloading is accomplished by axial separation of the sleeves using a resilient member or set screws.

Other References

• C T. Bower, How to Provide for Backlash in Threaded Parts, 4/14/82, pp. 188-189 of Mechanisms, Linkages, & Mechanical Controls by Charonis