Patent ID: 6904835

Claim:
A coupler that is adapted to engage a cylindrical concave internal surface of a cylindrical opening of a torque receptor comprising: a shaft that rotates around a center axis, said shaft having at least two cam driving surfaces that are spaced substantially equally from said center axis and that are adapted to transmit torque applied to said shaft; at least two gripping shells having axial end portions and convex external gripping surfaces that have a cylindrical convex profile and that slidingly engage said cylindrical concave internal surface, said gripping shells further including internal cam follower surfaces that are adapted to be engaged by said cam driving surfaces so that torque applied to said shaft is transmitted from said cam driving surfaces to said internal cam follower surfaces so that said center axis of said shaft is substantially aligned with a center axis of said cylindrical opening; and retaining recesses that axially and radially retain said gripping shells on said coupler adjacent said shaft and that allow said gripping shells to move freely in a radial direction and that allow said gripping shells to automatically engage said cylindrical concave internal surface of said cylindrical opening.