Device and a unit for locking the sliding of the rod of a linear actuator

A device for the unidirectional locking of the sliding of a cylindrical rod of a linear actuator, the device comprising:

• an outer body fast with or adapted to be fastened to an end of a casing of the actuator in an arrangement such as to surround the rod,
• means defining, in the body, a plurality of radially inwardly facing wedging surfaces which converge towards a longitudinal axis or the body,
• a corresponding plurality of wedging rolling members consisting of diabolo-shaped rollers having two cylindrical end portions and an intermediate portion which is concave according to a generatrix in the shape of an arc of circle having a radius which corresponds to the half-diameter of the rod, in order to roll in engagement with the rod, which rollers can be wedged between the said convergent surfaces and the rod as a result of their rolling until a wedged position in one direction and as a result of a constriction of their coupling with the wedging surfaces and the rod,
• an annular unlocking piston slidable longitudinally in the fixed body and cooperating with the cylindrical end portions of the wedging rollers to urge the rollers back to an unwedged position, and
• resilient repulsion means which tend to urge the rollers back to the wedged position,
• wherein the convergent wedging surfaces which are defined in the body are convex surfaces having cross-sections in the shape of an arc of circle whose radius of curvature corresponds to the radius of curvature of the arched longitudinal profile of the intermediate concave portions of each of the rollers as well as to the half-diameter of the rod, and wherein each of the said convex surfaces is in engagement with the intermediate concave portion of one of the rollers.