Patent ID: 6378874
Filing Date: 2002-04-30
Classification: F16J,G11B

Abstract:
A seal for sealing and electrically connecting an outer surface of a shaft to an inner surface of a hub disposed about the shaft, the shaft and hub being electrically conductive material, and the shaft being magnetically permeable, the seal comprising:(a) an annular magnet with a pair of annular pole pieces coupled to opposite poles thereof positioned between the shaft and the hub, the magnet having an interior radius that is larger than a radius of the outer surface of the shaft, and the pole pieces comprising an electrically conductive material which is magnetically permeable, and having interior radii that are larger than the radius of the outer surface of the shaft but smaller than the interior radius of the magnet; (b) a nonmagnetic electrically conductive ring to electrically couple the pole pieces to one another and to the hub wherein the electrically conductive ring comprises an annular disk having an interior radius larger than the interior radii of the pole pieces and an exterior radius with one or more tabs projecting therefrom, the exterior radius being substantially the same as exterior radii of the pole pieces and the magnet, wherein the electrically conductive ring is split axially along its outer circumference to establish a spring effect to press the ring against the inner surface of the hub and wherein the annular disk is positioned concentric with and abutting one of the pole pieces, and the tabs are folded over the magnet and the other pole piece to electrically couple the pole pieces to one another; and (c) an electrically conductive ferrofluid magnetically held between each the pole pieces and the outer surface of the shaft to form a pair of axially separated seals, and to establish parallel electrical pathways between the hub and the shaft.