Abstract: The compact ferrofluid seal and radial bearing assembly, particularly useful for the support and sealing of a shaft, such as a computer disk drive shaft, where space is at a premium, which assembly comprises a magnetically-permeable radial bearing apparatus having inner and outer race elements, moveable elements, and a cage element to retain the moveable elements, and a ferrofluid single-stage seal apparatus comprising a radially-polarized permanent magnet to retain a sealing amount of ferrofluid in a radial gap between the inner and outer race elements.

Abstract: A high-pressure rotary seal apparatus with a radially-polarized permanent magnet, which seal apparatus comprises: a housing; a magnetically-permeable shaft to be sealed extending through the housing, the shaft characterized by a plurality of separate grooves or stages on the shaft; a radially-polarized permanent magnet extending about the shaft, at least one pole piece adjacent to and in a magnetic flux relationship with the radially-polarized permanent magnet and extending about the shaft, one polarized end of the polarized magnet and one end of the pole piece extending into a close, noncontacting relationship with the grooves on the surface of the shaft to form a plurality of separate radial gaps; ferrofluid disposed in the radial gaps to define a plurality of separate, spaced-apart ferrofluid O-ring seals about the surface of the shaft; and a generally cylindrical, magnetically-permeable keeper element extending about the other polarized end of the magnet and the other end of the pole piece in order to pro

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 ferrofluid thrust and radial bearing assembly for a rotatable shaft element, which assembly comprises: a housing characterized by a shaft-receiving space, to define a radial bearing inner surface and a thrust bearing surface at the one end of the shaft-receiving space; a shaft element within the shaft-receiving space, one end of the shaft element disposed to rotate on the thrust bearing surface, and the other end of the shaft extending from the other end of the housing; a ferrolubricant in the shaft-receiving space, to form a lubricant for the thrust bearing and the radial bearing assembly; and a ferrofluid exclusion seal at the other end of the housing and about the other end of the shaft-receiving space, the exclusion seal comprising an annular permanent magnet and at least one annular pole piece, one end of which extends into a close, noncontacting relationship with the exterior surface of the shaft, to form a radial gap, and the ferrofluid within the shaft-receiving space defining a ferrofluid seal at t

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: Pole-piece-magnet apparatus for use as single- or double-pole-piece ferrofluid seal apparatus and method of manufacture, which pole-piece-magnet apparatus comprises at least one washer-type metal-pole-piece element with one flat surface having a plurality of spaced-apart raised dimple elements thereon with outwardly extending anchoring surfaces; and a washer-like hard molded permanent magnet polymer ring element molded about and secured directly to the one flat surface of the pole-piece element by the anchoring surface on the raised dimples, the permanent magnet ring element having an inner diameter greater than the inner diameter of the pole-piece element and an outer diameter of about the same dimensions as the outer diameter of the pole-piece element.

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 self-activating ferrofluid seal apparatus and method, which seal apparatus comprises a permanent-magnet ring and a pair of pole pieces which form a cavity therebetween, and which seal apparatus includes magnetically permeable, extending elements in the cavity to form a ferrofluid-retaining gap therebetween, the pole pieces forming a radial gap with the surface of the shaft to be sealed, the ferrofluid-retaining gap having a magnetic-field intensity sufficient to retain the ferrofluid therebetween and sufficiently larger in gap width than the radial gap, whereby, on insertion of the shaft element, the ferrofluid, based on the change in magnetic flux path, will move from the retaining gap to the radial gap to form a ferrofluid seal about the shaft element.

Abstract: A stable liquid composition which comprises a colloidal dispersion of finely-divided, magnetic particles in a liquid polar carrier and a dispersing amount of a surfactant, which surfactant comprises a phosphoric acid ester of a long-chain alcohol, the alcohol compatible with the polar carrier, to provide a stable ferrofluid composition.

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: An apparatus for and a method of sealing a rotating shaft in a crystal-growing furnace, wherein the crystal-growing furnace includes a chamber adapted to be maintained at a contaminant-free inert atmosphere, with an inert gas at a low pressure, a rotatable shaft element which extends into the chamber, and a seal surrounding the shaft element, to separate the atmospheric pressure outside of the chamber from the low-pressure, contaminant-free atmosphere within the chamber, the seal having a plurality of sealing elements spaced apart along the shaft and defining an annular cavity between the sealing elements, the improvement which comprises means to and a method of maintaining an inert-gas atmosphere within the sealed cavity at a pressure slightly higher than the outside atmospheric pressure or the low pressure of the chamber, whereby, on failure of the sealing elements, inert gas passes from the cavity to the atmosphere or to the low-pressure chamber, thereby preventing the contamination of the chamber with atm

Abstract: A pulling head for a Czochralski type crystal growing furnance includes a ball linked chain for suspending the growing crystal ingot, a sprocket for engaging such chain to pull the ingot from a melt, motor means for driving the sprocket and a chain storage means to receive untensioned chain discharged from the sprocket.

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 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, 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.