Shaft with surface finished ridges
AssigneeApple Inc.
InventorsSina Mobasher Moghaddam, Troy A. Carter, Jonathan L. Hall
Life of this patent
Estimating the term…
Abstract
A ball screw spline actuator includes a shaft, a ball nut, and a ball spline. The shaft includes a helical groove and a spline groove intersecting the helical groove forming intersections having a least one ridge including a first surface finish formed by a first manufacturing operation. The ridge is subsequently reformed through a second manufacturing operation to include a second surface finish to reduce stress concentrations in the ridge from cyclical loading from at least one of the ball nut or the ball spline. In one example, the second manufacturing operation reforms the ridge to include a surface finished edge.
Claims20
A ball screw spline actuator, comprising:
- a shaft having a longitudinal axis, the shaft defining a helical groove extending along the shaft and a spline groove extending along the shaft, each of the helical groove and the spline groove having a first surface finish, the spline groove intersecting the helical groove at a plurality of intersections each defining a ridge having a second surface finish different than the first surface finish;
- a ball nut engaged with the helical groove configured to apply a first torque to the shaft about the longitudinal axis;
- and
- a ball spline engaged with the spline groove configured to apply a second torque to the shaft about the longitudinal axis to counteract the first torque to the shaft preventing a rotation of the shaft about the longitudinal axis and allowing the shaft to linearly translate along the longitudinal axis relative to the ball nut and the ball spline,
- wherein the helical groove or the spline groove comprise an arcuate cross-section,
- wherein the ridge further comprises:
- curved sidewalls formed by the helical groove and the spline groove adjacently positioned to the helical groove, and
- an edge formed by a convergence of the curved sidewalls,
- wherein the edge is reformed to include the second surface finish defining a surface finished edge configured to reduce a stress concentration in the ridge as a result of a cyclical load applied by the ball nut or the ball spline, and
- wherein the surface finished edge comprises a radius formed between the curved sidewalls.
A ball screw spline actuator, comprising:
- a shaft having a longitudinal axis, the shaft defining a helical groove and a spline groove each having an arcuate cross-section and extending along the shaft, the spline groove intersecting the helical groove at a plurality of intersections forming four ridges each having a surface finished edge extending into each intersection configured to reduce a stress concentration in the ridges when placed under a cyclical load;
- a ball nut engaged with the helical groove configured to apply a first torque to the shaft about the longitudinal axis;
- and
- a ball spline engaged with the spline groove configured to apply a second torque to the shaft about the longitudinal axis configured to linearly translate the shaft along the longitudinal axis relative to the ball nut and the ball spline and preventing rotation of the shaft about the longitudinal axis,
- wherein each of the surface finished edges comprises curved sidewalls formed at a first time by the helical groove and the spline groove adjacently positioned to the helical groove, the curved sidewalls converging to define an edge, the surface finished edge formed at the edge at a second time subsequent to the first time, and
- wherein the surface finished edge comprises a radius between the curved sidewalls.
Dependencies are inferred from the claim text.