Patent ID: 11953080
Assignee: APPLE INC.
Field: Mechanical elements (Mechanical engineering)
Classification: CPC F  B | IPC B  F

Claim 0:
1. 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.