Relating to pressure fluid operated actuators

Claim 1

A rotary actuator comprising an enclosure having an internal rectilineal slideway along which a slide member is movable, said slide member being formed by a hollow body extending longitudinally of the slideway, first means for moving the slide member along the slideway, second means restraining the slide member from rotating during movement along the slideway, a shaft extending into the enclosure and being rotatable relative to the enclosure, the shaft axis extending longitudinally of the slideway, a worm screw carried within the enclosure by the shaft and a screw-threaded nut assembly carried by said slide member, said nut assembly and worm screw being arranged mutually to interact so that the shaft rotates when the slide member moves along the slideway, and wherein said second means comprising one of the slide member body and enclosure wall including a protrusion projecting therefrom and the other including a groove extending longitudinally relative to the slideway for receiving and cooperating with the protrusion, said nut assembly is releasably mounted within said hollow body, means for constraining the nut assembly against rotational movement, said nut assembly comprising first and second nut elements each threadedly mounted on said worm screw, at least one of the nut elements having limited axial movement relative to the worm gear and to the other nut element, and means for urging at least one of the nut elements in a direction axially opposite the other nut element for minimizing rotational backlash between the worm screw and the nut assembly.