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Machine translation
1. (WO2016181341) LINEAR DRIVE MECHANISM OF THE SCREW AND NUT TYPE WITH PERFECT ROLLING CONTACT
Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

CLAIMS

1 . Linear drive mechanism ( 10) comprising a threaded shaft ( 12) extending along a longitudinal axis (z) and a nut ( 14) arranged coaxially with the threaded shaft ( 12), the threaded shaft ( 12) and the nut ( 14) being shifted relative to each other along the longitudinal axis (z) as a result of relative rotation of the threaded shaft ( 12) with respect to the nut ( 14) about the longitudinal axis (z), wherein the mechanism ( 10) further comprises a plurality of rolling bearings ( 18) interposed between the threaded shaft ( 12) and the nut (14), each of the bearings ( 18) comprising an outer race (22) fixed to the nut ( 14), an inner race (20) which is arranged coaxially with the outer race (22) and is rotatable relative to the outer race (22) about an axis of rotation (ζ'), and a plurality of rolling members (24) interposed between the outer race (22) and the inner race (20), and

a corresponding plurality of rings ( 16), each of which is fixed to the inner race (20) of a respective bearing ( 18) so as to rotate therewith about the same axis of rotation (ζ') and is interposed between the inner race (20) of the bearing ( 18) and the threaded shaft ( 12) in such a manner that an inner surface ( 16a) of the ring is in contact with a screw thread ( 12a) of the threaded shaft ( 12),

wherein the rings (16) and the bearings ( 18) are arranged in such a manner that their respective axes of rotation (ζ') are both inclined by a first angle (a) and positioned at a first distance (a) with respect to the longitudinal axis (z) of the threaded shaft ( 12), said first angle (a) and said first distance (a) being the same for all the rings ( 16), and

wherein the shape of the screw thread ( 12a) of the threaded shaft ( 12) and the shape of the inner surface (16a) of each ring ( 16) are configured in such a manner that each ring ( 16) is in perfect rolling contact with the threaded shaft ( 12) along a respective contact line (v) that is fixed relative to the nut ( 14) and is both inclined by a second angle ( ?) and positioned at a second distance (b) with respect to the longitudinal axis (z) of the threaded shaft ( 12),

characterized in that said first angle (a), said first distance (a), said second angle ( ?) and said second distance (b) are linked by the following equations:

\ {a) = hlb

tan( ?) = hi a,

where h is the pitch of the screw thread ( 12a) measured in lead per radian.

2. Mechanism according to claim 1 , wherein the inner surfaces ( 16a) of the rings ( 16) have, at least in a portion thereof that during operation is in contact with the threaded shaft ( 12). the same shape of a hyperboloid of one sheet, and wherein the screw thread ( 12a) of the threaded shaft ( 12) has, at least in portions thereof that during operation are in contact with the rings ( 16), a helical hyperboloid shape.

3. Mechanism according to claim 1 or claim 2, comprising at least three bearings ( 1 8) and three rings ( 16).

4. Mechanism according to any of the preceding claims, wherein said first angle (a) is greater than the helix angle of the screw thread ( 12a) of the threaded shaft ( 12) at the outer, diameter of the latter.

5. Mechanism according to any of the preceding claims, wherein the thickness of the inner surface ( 16a) of each ring ( 16) is smaller than the width, measured at the outer diameter of the threaded shaft ( 1 2), of the helical groove defined by the screw thread ( 1 2a) of the threaded shaft ( 12).

6. Mechanism according to any of the preceding claims, wherein the bearings ( 18) are ball bearings.

7. Mechanism according to any of the preceding claims, wherein the rings ( 16) are made in one piece with the inner races (20) of the respective bearings ( 18).

8. Mechanism according to any of claims 1 to 6, w herein the rings ( 16) are made as separate pieces from the inner races (20) of the respective bearings ( 1 8).

9. Mechanism according to any of the preceding claims, wherein the nut ( 14) has a corresponding plurality of seats (26). each adapted to receive a respective bearing ( 1 8), said seats (26) being positioned and orientated relative to the nut ( 14) in such a manner that the axes of rotation (ζ') of the bearings ( 18), and hence of the rings ( 16), are inclined by said first angle (a) and positioned at said first distance (a) with respect to the longitudinal axis (∑).