The two shafts (1, 2) are joined by a universal joint and one shaft (2) is fitted with one spherical surface coupling (3) which moves inside the outer spherical surface of the second shaft. The second shaft has a slim spherical sealing surface (8) which slides inside the thicker, outer surface. The interdigitated spherical sealing surfaces provide a seal with limited ingress of dust etc. Sealing lips (8a, 9) seal the action of the shells.
