FERROFLUIDDICHTUNG FUER EINE FESTSTEHENDEN WELLE UND EINE DREHNABE.

摘要

A ferrofluid seal is disclosed for use in a bearing application with a stationary shaft (2) about which a hub (4) rotates. The seal consists of a permanent magnet (30) and one or more annular pole pieces (32) which form a magnetic circuit with the bearing shaft (2). The magnetic circuit includes an annular gap (3) between the shaft (2) and the pole pieces (32) in which the magnetic flux traps a magnetic fluid (38) which bridges the gap (3) to form a seal. The shaft (2) is tapered in the gap (3) area to form a wedge-shaped gap which accommodates changes in the magnetic fluid volume due to temperature variations while holding the fluid (38) within the magnetic field to maintain the seal. The pole piece (32) which forms the gap (3) has a straight annular face located at a constant radial distance from the shaft axis. At high operating temperatures, expansion of the magnetic fluid (38) causes the fluid to fill the taper on the shaft (2), but, since the shaft (2) is stationary, fluid splash is eliminated. The straight surface of the pole piece (32) controls fluid splash caused by centrifugal force.