Patent ID: 8225509
Filing Date: 2012-07-24
Classification: F16C,H01L,Y10T

Abstract:
1. A method for making a pivot arm assembly for semiconductor wafer handling robots and the like, comprising: forming from a rigid, machinable material a circular disk having a predetermined center; forming a circular aperture through the center of the disk to define an outer integral race portion of the pivot arm assembly having a cylindrically-shaped inside surface; forming a radially inwardly opening groove in the inside surface of the outer integral race portion to define a first bearing track; providing a machining apparatus having a fixturing portion which precisely retains a workpiece relative to a machining portion of the machining apparatus; positioning the apertured disk in the machining apparatus with the fixturing portion thereof engaging the first bearing track to removably, yet precisely, retain the apertured disk at a predetermined position and orientation relative to the machining portion of the machining apparatus; activating the machining portion of the machining apparatus to form in the apertured disk an annularly-shaped ring portion with a cylindrically-shaped outside surface disposed generally concentric with the inside surface of the outer integral race portion, an arm portion extending radially outwardly from the ring portion and adapted for connection with a robot articulation member, a gear segment portion extending radially outwardly from the ring portion in a circumferentially spaced apart relationship with the arm portion, and gear teeth along an outer end portion of the gear segment portion oriented precisely in a predetermined relationship with the first bearing track and adapted for meshing with an associated robot drive mechanism; forming an inner race portion of the pivot arm assembly defined by an inside surface configured to receive and retain a mounting member therein, and a cylindrically-shaped outside surface; forming a radially outwardly opening groove in the outside surface of the inner race portion to define a second bearing track which is shaped substantially similar to the first bearing track in the outer integral race portion; positioning the inner race portion inside the inside surface of the outer integral race portion such that the first and second bearing tracks are radially aligned, and the inner race portion is in an eccentric relationship with the outer integral race portion to form between the inside surface of the outer integral race portion and the outside surface of the inner race portion an eccentric gap having a wider portion and a narrower portion; sequentially inserting a plurality of rolling bearing elements through the gap at the wider portion thereof and into the first and second bearing tracks; positioning the bearing elements in a regularly spaced apart relationship around the first and second bearing tracks and contemporaneously shifting the inner race portion and the outer integral race portion into a concentric relationship; and retaining the bearing elements in the regularly spaced apart relationship in the first and second bearing tracks.