Dimensionally-stable ball for a ball and socket bearing assembly

摘要

A ball and socket assembly adapted to receive the rotatable shaft of a rudder installed in a boat. The assembly is composed of a journal box having a spheroidal cavity in which is socketed a ball-like bearing having an axial bore to accommodate the rudder shaft, the bearing being free to rotate within the cavity and thereby align itself with the rudder shaft as it deviates from the vertical as a result of forces imposed on the rudder. The ball-like bearing is formed by a cylindrical tube of UHMW polyethylene which is heated to an annealing temperature and thereby expanded to accept a fiber-reinforced resin sleeve which when the UHMW tube cools is compressed thereby. The resultant sleeve-lined tube is then machined to assume the ball-like shape of the bearing. Because the resin sleeve lining the machined bearing has a low coefficient of thermal expansion and the UHMW casing of the bearing, having been annealed, then also has a low coefficient of thermal expansion, the lined bearing through which the rudder shaft extends is dimensionally stable and therefore unaffected by marked changes in temperatures in the environment in which the assembly is installed.