Patent ID: 7412910

Claim:
A mechanism for transforming a rotational movement into a linear movement, comprising: a non-deformable nut, which is prevented from rotating but not from axially moving, the nut having an internal surface with an internal diameter; a radially deformable, tubular screw inside the nut and having an external surface and an external diameter, the screw being rotatable freely but not moveable axially, the screw external surface and the nut internal surface having respective equal pitch, the screw external diameter is slightly smaller than the internal diameter of the nut; the screw also having an internal wall defined by a respective second internal surface thereof; a pushing device placed in the tubular screw, and rotatable with respect to the screw and resting against and pushing against the second internal surface of the internal wall of the tubular screw at at least three circumferentially equidistant points, and the pushing device is operable for radially deforming the wall of the screw outward until the wall rests against and screws onto the nut at the circumferentially equidistant points; and a drag reducing device at each of the points for reducing drag between the pushing device and the second internal surface of the internal wall of the screw as the pushing device rotates; the pushing device rests against the internal surface of the tubular screw at least at the three circumferentially equidistant points; the pushing device comprises a respective independent rolling element located at the at least three circumferentially equidistant points; each of the rolling elements comprising bearings located and operable for causing a rolling movement between the screw and the nut; the rolling elements are assembled on as many cylindrical cores as the at least three points, located equidistant around and parallel to a shaft of the screw; and a support located inside the screw, rotatable with respect to the screw, and the rolling elements projecting from the support.