Patent ID: 6949025

Claim:
A universal joint assembly having a longitudinal axis and adapted to be coupled to a eccentric rotor located within a well, the universal joint assembly comprising: a female coupler defining an interior cavity, the interior cavity having an end wall with a concave depression and an interior side wall; a male coupler having an exterior side wall and an engagement end with a concave depression, the engagement end being received within the interior cavity of the female coupler; each of the side walls having a plurality of circumferentially spaced recesses; a thrust ball positioned between the concave depressions of the male and female couplers; a plurality of ball members positioned in the circumferentially spaced recesses of the male and female couplers; and a seal assembly located between the side walls of the male and female couplers, defining a sealed chamber that contains the ball and the ball members and is adapted to be filled with a lubricant, the seal assembly comprising a compensating member having one side adapted to be in contact with the lubricant and another side adapted to be in contact with well fluid, the compensating member being free to move axially a limited distance toward the end wall of the female coupler to equalize pressure differential.