Splined ball screw assembly having a nested structure
AssigneeNippon Thompson Co., Ltd.
InventorKunihiko Morita
Life of this patent
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Abstract
A splined ball screw assembly having a nested structure is provided. A hollow shaft extends into an outer sleeve and a center shaft extends into the hollow portion of the hollow shaft. A ball screw structure is provided at either side of the outer and inner peripheral surfaces of the hollow shaft and a ball spline structure is provided on the other side. The outer sleeve is rotatably mounted on a housing and the center shaft is also rotatably mounted on the housing. By controlling the amount and direction of rotation of both of the outer sleeve and the center shaft, the hollow shaft may be moved longitudinally in a desired direction and/or set in rotation. The present assembly is compact in size and particularly suitable for use in a robot arm.
Claims11
A splined ball screw assembly, comprising:
- a sleeve rotatably mounted on a housing;
- a hollow shaft having an outer peripheral surface and an inner peripheral surface, said hollow shaft extending through said sleeve with a predetermined gap therebetween;
- a center shaft rotatably mounted on said housing and extending into a hollow portion of said hollow shaft with a predetermined gap therebetween;
- first engaging means provided between said sleeve and said hollow shaft for engaging both of said sleeve and said hollow shaft to provide a first predetermined relative motion between said sleeve and said hollow shaft;
- second engaging means provided between said hollow shaft and said center shaft for engaging both of said hollow shaft and said center shaft to provide a second predetermined relative motion, which is different from said first predetermined relative motion, between said hollow shaft and said center shaft;
- first rotating means for rotating said sleeve;
- second rotating means for rotating said center shaft;
- and
- wherein one of said first and second engaging means includes a ball spline engagement structure and the other of said first and second engaging means includes a ball screw engagement structure, one of said structures extending between said sleeve and said hollow shaft and the other of said structures extending between said hollow shaft and said center shaft.
Dependencies are inferred from the claim text.