US Patent 7246947 Concentric radii ball bearing stack

A ball bearing stack which includes more than one bearing arranged in face to face relation and sharing a common rotational axis. Each bearing has an inner ring and a concentric outer ring. The inner ring defines an inner race. The outer ring defines an outer race. A plurality of ball bearings are captured within an annular space defined between the inner race and the outer race. Each of the more than one bearing has a ball bearing contact surface on the outer race which is radiused from face to face about a common centre point positioned on the common rotational axis.