Abstract: A compact, low cost, radially polarized multiple-stage ferrofluid seal apparatus which comprises a magnetically permeable housing, a magnetically permeable shaft to be sealed extending through the housing, one or more radially polarized permanent magnets to define a plurality of separate, spaced apart radial gaps between one polarized end of the permanent magnet and the surface of the shaft, ferrofluid in the radial gaps to define one or more separate, spaced apart ferrofluid O-ring seals about the surface of the shaft and a magnetically permeable bearing assembly adjacent to and in a magnetic flux relationship with at least one of the radial polarized magnets wherein the magnetic flux circuit extends between the radial polarized magnet, the housing, the bearing assembly, the shaft, and the ferrofluid in the radial gaps.

Abstract: A single pole piece multiple-stage ferrofluid seal apparatus which comprises a non-permeable housing, an annular, axially polarized permanent magnet and a single pole piece on one side of the axially polarized permanent magnet and a magnetically permeable bearing assembly, such as a ball bearing assembly on the opposite side of the permanent magnet and a shaft extending through the housing with one end of the pole piece extending into a close, non-contacting relationship with the surface of the shaft, so as to form at the one end of the pole piece or on the surface of the shaft a plurality of separately spaced apart knife edges to define a plurality of spaced apart radial gaps and ferrofluid disposed in the radial gaps to define a plurality of spaced apart ferrofluid O-ring seals about the shaft surface, with the magnetic flux circuit passing between the permanent magnet, the pole piece, the radial gaps, the shaft, and the bearing assembly.

Abstract: A stabilized ferrofluid-ferrofluid interface seal apparatus and method, which method comprises forming a ferrofluid-ferrofluid seal interface between a magnetized ferrofluid O-ring seal and unmagnetized ferrofluid from a ferrofluid reservoir, and maintaining a pressure difference across the ferrofluid-ferrofluid seal interface to stabilize the interface.

Abstract: A low-cost, self-activating ferrofluid seal apparatus particularly useful as an exclusion seal with computer-disc-drive spindles, which seal apparatus comprises an annular, axially-polarized permanent magnet and first and second pole pieces in a magnetic-flux relationship with each side of the magnet and the one end of the pole pieces extending into a close, noncontacting relationship with the surface of a shaft element to be sealed to form a radial gap with the surface of the shaft and ferrofluid in the radial gap to effect a single-stage ferrofluid seal and wherein the annular permanent magnet has a thickness of not more than about 25 mils and the annular magnet has an energy product of about 1.8.times.10.sup.6 gauss-oersteds or greater and the ferrofluid comprises a low-vapor-pressure ferrofluid having a magnetic saturation of at least 200 gauss or more.

Abstract: A ferrofluid linear seal apparatus to provide a hermetic seal about a shaft engaged in linear motion between a first and second environment, typically between a vacuum atmosphere and atmospheric pressure, which seal apparatus comprises: a housing for a shaft element; a nonmagnetically permeable shaft element adapted for linear motion within the housing; an annular permanent magnet about the shaft element; an annular magnetically-permeable pole piece about the shaft element, the outer diameter of the pole piece extending into a close, noncontacting relationship with the inner diameter of the housing to form a plurality of separate spaced-apart radial gaps; ferrofluid retained in the radial gaps by the magnetic flux of the permanent magnet; and linear bearings to provide support for the linear movement of the shaft element within the housing.

Abstract: A ferrofluid seal apparatus and method, which ferrofluid seal apparatus comprises at least one ferrofluid seal about the surface of a rotatable shaft, the ferrofluid retained in a sealing relationship by magnetic flux from the ends of two pole pieces which define a cavity therebetween, and an interstage gap between the two pole pieces, which seal apparatus provides, within the single O-ring ferrofluid seal, a plurality of three separate regions of different magnetic-flux density, each of the regions having a different pressure value, the ferrofluid O-ring seal defining a ferrofluid exclusion seal between a first and second environment and the cavity, whereby the ferrofluid O-ring seal permits gas pressures from the cavity and the region environments to be transferred, on variations in pressures.

Abstract: A single-stage, ferrofluid magnetic seal apparatus and method which comprises: an annular, permanent-magnet ring element adapted to surround a shaft to be sealed, which shaft extends between first low-pressure and second high-pressure; first and second pole pieces in a magnetic-flux relationship with the permanent magnet, and having one and the other ends, the other end extending into a close, noncontacting relationship with the surface of the shaft, to define a radial gap therebetween; a plurality of stages formed in the radial gap under the other end of the second pole piece, which pole piece is placed toward the high-pressure side the environment, and the radial gap under the first pole piece, placed toward the low-pressure side of the environment, being shallow and generally less than about 2 mils; and ferrofluid in the radial gap under the other end of the second pole piece which forms a plurality of separate O-ring ferrofluid seals of defined pressure capacity, thereby providing a single-stage, ferroflu

Abstract: A single-pole-piece ferrofluid exclusion seal apparatus and exclusion seal system which comprises a single, annular pole piece to surround a shaft element to be sealed, and an annular permanent magnet secured to one surface of the pole piece in a magnetic-flux relationship, the single pole piece having a one end which extends into a close, noncontacting relationship with the surface of the shaft element to be sealed, to define a small radial gap between the surface of the shaft element and the one end of the pole piece, and a ferrofluid positioned within the radial gap, to provide a ferrofluid seal with the shaft element, the ferrofluid comprising a high magnetization-type ferrofluid, with the magnetic flux path of the single-pole-piece ferrofluid seal extending between the shaft, the ferrofluid in the radial gap, the single pole piece in the permanent magnet and the air gap between the magnet and the shaft.

Abstract: A nonbursting ferrofluid seal apparatus and system which comprises an annular permanent magnet and annular first and second pole pieces, one end of the pole pieces defining a single-stage ferrofluid seal under one end of one pole piece and a multiple-stage ferrofluid seal under the one end of the other pole piece with the surface of the shaft element with which the seal is employed, the first and second pole pieces and the magnet defining therebetween an interstage volume between the single-stage ferrofluid seal and the multiple-stage ferrofluid seal, and conduit means extending into the interstage volume, and means to maintain a desired pressure in the stage volume, to maintain the first-stage ferrofluid seal in a stable, nonbursting condition, when the seal apparatus is employed between high- and low-pressure environments.

Abstract: A ferrofluid rotary-shaft seal apparatus of extended seal life particularly adapted for use as an exclusion seal with a computer-disc-drive spindle, which seal apparatus comprises: an annular permanent magnet; first and second pole pieces of unequal width, one end of each pole piece extending into a close, noncontacting relationship with the surface of the shaft, to form a gap width between the one end of the pole piece and the surface of the shaft; and ferrofluid in the gap widths to form a ferrofluid O-ring seal, whereby, in operation, the ferrofluid, under the thinner pole piece, evaporates and forms an air gap, while the ferrofluid at the wider gap width provides extended seal life.

Abstract: A ferrofluid rotary-shaft seal apparatus of extended seal life particularly adapted for use as an exclusion seal with a computer-disc-drive spindle, which seal apparatus comprises: an annular permanent magnet; first and second pole pieces of unequal width, one end of each pole piece extending into a close, noncontacting relationship with the surface of the shaft, to form a gap width between the one end of the pole piece and the surface of the shaft, the pole piece of greater width characterized by a tapered one end; and ferrofluid in the gap widths to form a ferrofluid O-ring seal, whereby, in operation, the ferrofluid, under the thinner pole piece, evaporates and forms an air gap, while the ferrofluid at the wider, tapered gap width provides extended seal life.

Abstract: A ferrofluid rotary-shaft seal apparatus of extended seal life particularly adapted for use as an exclusion seal with a computer-disc-drive spindle, which seal apparatus comprises: an annular permanent magnet; first and second pole pieces, one end of each pole piece extending into a close, noncontacting relationship with the surface of the shaft, to form a gap width between the one end of the pole piece and the surface of the shaft; and ferrofluid in the gap widths to form a ferrofluid O-ring seal, whereby, in operation, the ferrofluid, under the thinner pole piece, evaporates and forms an air gap, while the ferrofluid at the wider gap width provides extended seal life.

Abstract: A ferrofluid rotary-shaft seal apparatus of extended seal life particularly adapted for use as an exclusion seal with a computer-disc-drive spindle, which seal apparatus comprises: an annular permanent magnet; first and second pole pieces of unequal length at the one end, and which one end of each pole piece extends into a close, noncontacting relationship with the surface of the shaft, to form a small-gap width and a large-gap width between the one end of the pole piece and the surface of the shaft; and a ferrofluid in the small- and large-gap widths to form a ferrofluid O-ring seal at each gap width, whereby, during rotation of the shaft, the ferrofluid at the small-gap width evaporates and forms an air gap, while the ferrofluid at the large-gap width provides extended seal life.

Abstract: A self-activating ferrofluid-seal apparatus for a memory-disc-drive shaft, which seal apparatus comprises a ring magnet and a pair of pole pieces which form a cavity therebetween, a closed loop of a plastic tubular container with ferrofluid positioned within the cavity, and a penetration clamp to penetrate the plastic container prior to installation of the shaft element.

Abstract: A self-activating seal is formed by inserting a magnetically permeable shaft into a module which comprises: a magnet, two pole pieces and a magnetic fluid. The module is so constructed that the magnet and pole pieces form a cavity for storing the magnetic fluid until the shaft or similar element is inserted. Upon insertion of the shaft, the magnetic field is altered and the flux path diverted to the small gaps separating the pole pieces and the shaft. The magnetic fluid is drawn to the gas to form hermetic seals.