Patent ID: 7008113

Claim:
A ball-bearing assembly which rotatably supports a hollow shaft in a stationary housing of a deep-drilling apparatus comprising a bearing unit having: radially separated inner and outer bearing races made of a first material suitable for forming a bearing raceway, the inner race being constructed and configured to be mounted in fixed relationship on the outside of the hollow shaft, and the outer race being constructed and configured to be mounted in fixed relationship on the inside of the stationary housing; a plurality of solid ceramic or ceramic coated load-bearing balls disposed in a raceway formed between the inner and outer races; a plurality of separating balls formed of a second material and disposed in the raceway in alternating relationship with the load-bearing balls, the separating balls being of a smaller diameter than the load-bearing balls; and the inner and outer races being so constructed and configured to provide communication between the hollow shaft and the bearing unit which permits drilling fluid flowing down the hollow shaft to enter the bearing unit to serve as a coolant and a lubricant.