Patent ID: 7784326
Filing Date: 2010-08-31
Classification: G01N

Abstract:
1. A four ball test apparatus, comprising: a first structure including a receptacle and at least three lower test balls disposed in the receptacle, wherein the three lower test balls are non-rotatably fixed relative to the receptacle; a second structure including a rotating powered shaft including a chuck, the chuck defining a cavity forming a chuck, the cavity having an inner portion, an outer portion, and an intermediate portion disposed between the inner and outer portions, the cavity including a tapered sidewall surface extending around the intermediate portion of the cavity; a fourth test ball disposed in the cavity in contact with the tapered sidewall portion to define a generally circular line of contact between the fourth test ball and the tapered sidewall portion, the line of contact defining a first diameter, the fourth test ball contacting the three lower test balls at three contact points, the three contact points defining a contact circle having a second diameter that is less than the first diameter, and wherein the chuck includes an opening to the cavity adjacent the outer portion of the cavity, and wherein the cavity has a shape that permits insertion of the fourth test ball through the opening and into contact with the tapered sidewall surface without movement of the tapered sidewall surface.