Joseph A Moses, Age 58PO Box 673, Atkinson, NH 03811

5018751, May 28, 1991

Jun 28, 1989

7/373328

Kuldip Raj - Merrimack NH
Ronald Moskowitz - Hollis NH
Joseph Moses - Tyngsboro MA
James Bonvouloir - Nashua NH
Frank Bloom - Windham NH

Ferrofluidics Corporation - NH

F16J 1540

277 80

A long-life, stacked pole-piece magnetic fluid seal for sealing between a housing and magnetically permeable shaft, in one embodiment is comprised of an annular magnet, having poles of opposite polarity on first and second end surfaces thereof, an annular, magnetically permeable primary pole-piece axially abutting the first end surface of the magnet, and one or more annular, magnetically permeable secondary pole-pieces stacked axially adjacent the primary pole-piece and separated therefrom and from each other by one or more annular spacers which define intermediate spaces between the pole-pieces. The pole-pieces are in a closely-spaced, non-contacting relationship with the shaft to define one or more radial gaps which, in conjunction with the intermediate spaces collectively form an annular ring in which a magnetic fluid is disposed and retained. In a second embodiment, the annular magnet is separated from the primary pole piece by a spacer which defines an intermediate space therebetween. The magnet and primary pole-piece are in closely-spaced, non-contacting relationships with the shaft to define first and second gaps respectively, which, in conjunction with the intermediate space, collectively form an annular ring in which a magnetic fluid is disposed and retained.

4927164, May 22, 1990

Aug 8, 1988

7/229640

Kuldip Raj - Merrimack NH
Joseph Moses - Tyngsboro MA
Ronald Moskowitz - Hollis NH
Frank Bloom - Windham NH

Ferrofluidics Corporation - Nashua NH

F16J 1540

277 80

In a ferrofluid seal which comprises a magnet and at least one pole piece, the pole piece is fabricated from a ferromagnetic material which directly bonds to the magnet face. Since the pole piece material directly bonds to the magnet, no additional adhesive is necessary. Thus, the conventional steps of applying an adhesive and mounting pole pieces on the magnet are eliminated. In addition, voids and bubbles in the adhesive are eliminated, thus, enhancing seal integrity. In one embodiment, the ferromagnetic material is a ferromagnetic epoxy compound comprising a mixture of conventional epoxy materials plus a fine powder of ferromagnetic material such as iron, cobalt, nickel or various metal alloys.