Mechanism for positioning a carrier

摘要

A mobile component carrier in an instrument includes a disk with a scalloped periphery. A larger bearing and a smaller bearing are mounted on a support structure. The larger bearing has a radius greater, and the smaller bearing has a radius less than that of each of the scallops. The disk is urged into the bearings which have a relative spacing such that the larger bearing seats against two adjacent intersections of the scallops, and the smaller bearing seats against a dished surface between two other adjacent intersections.