Patent ID: 6857635

Claim:
A ferrofluid seal suitable for sealing a magnetically-permeable rotating shaft passing from a first environment at a first pressure to a second environment at a second pressure higher than the first pressure, the seal comprising: a housing having an attachment flange and a body; a magnetically permeable annular pole piece extending close to the rotating shaft to form an air gap between the pole piece and the shaft; a coolant channel located in the interior of the pole piece and means for conducting coolant through the coolant channel wherein the means comprises a coolant channel that passes through the attachment flange and into the pole piece; a magnet generating a magnetic field that passes through the pole piece, the air gap and the shaft; ferrofluid in the gap forming a liquid O-ring seal in the gap under influence of the magnetic field in the gap; a first knife edge formed in the housing; a second knife edge formed in the pole piece opposing the first knife edge; a metal washer located between the first and second knife edges; a third knife edge formed in the housing; a fourth knife edge formed in the pole piece opposing the third knife edge; a second metal washer located between the third and fourth knife edges; and a mechanism for applying a force between the housing and the pole piece to force the first and second knife edges into the metal washer and the third and fourth knife edges into the second metal washer thereby forming a hermetic seal.