Ferrofluidics Corporation

Hanumaiah L Gowda

Kuldip Raj

Ronald Moskowitz

Lucian Borduz

Frank Bloom

Charles J Cheever

A sealed, rolling element bearing includes an inner race attached to a shaft, an outer race attached to a housing, a plurality of rolling elements in an annular region and a pair of shields extending inwardly from the outer race toward the inner race so as to substantially enclose the annular region. The shields have a closely-spaced, noncontacting relationship with the inner race thereby defining gaps. The elements of the bearing are of magnetically permeable material, and the sealed bearing includes means for producing a magnetic field in the gaps and in the regions where the rolling elements contact the races. A ferrofluid is retained by the magnetic field in the gaps for sealing and in the regions of contact between the rolling elements and the races for lubrication. A reservoir of ferrofluid in the regions between the two seals replenishes ferrofluid lost at the sealing and lubrication areas. The magnetic field can be produced by permanent magnetization of the bearing assembly or by axially polarized permanent magnets located on either or both ends of the outer race. Such a bearing may be used with a magnetic or nonmagnetic shaft and permits relative motion between the shaft and the housing. The housing material is of nonmagnetic type when external magnets are used.

Compact ferrofluidic electrically conducting sealed bearing

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

Ferrofluid seal for a stationary shaft and a rotating hub

An electrically conductive ferrofluid-film-bearing apparatus and seal apparatus for a shaft which employs a low-viscosity, electrically conductive ferrofluid composition, which composition comprises a liquid carrier, and contains in combination an electrically conductive amount of a cationic surfactant and dispersed carbon particles, to obtain a low-electrical-resistivity ferrofluid having a low viscosity and suitable for use in a ferrofluid bearing apparatus.

Electrically conductive ferrofluid bearing and seal apparatus and

An electrically conductive ferrofluid composition and a method of preparing and using the ferrofluid composition in a ferrofluid seal apparatus, and which ferrofluid composition comprises a liquid carrier having a colloidal dispersion of ferromagnetic particles in an amount sufficient to provide magnetic properties to the ferrofluid composition and carbon particles in an amount sufficient to provide electrical conductive properties to the ferrofluid composition, the ferromagnetic and carbon particles stabilized in the ferrofluid composition by a surface active dispersing agent. The electrically conductive ferrofluid composition is usefully employed in a ferrofluid exclusion seal apparatus to provide an electrically conductive seal apparatus particularly useful for computer disk drives and sputtering apparatus in the semiconductive industry.

Electrically conductive ferrofluid compositions and method of preparing

A compact, coaxial multiple-shaft ferrofluid seal apparatus which comprises: a housing; a central shaft and magnetically permeable coaxial shafts about the central shaft, the coaxial shafts having a pair of spaced apart nonmagnetically permeable insulator shaft sections; magnetically permeable bearings to support each shaft; pole piece elements to provide radial gaps within the inner or outer shaft surfaces; ferrofluid disposed in the radial gaps to provide a seal apparatus for the shafts of designed pressure capacity; and a single radially polarized permanent magnet to provide a source of magnetic flux for the seal apparatus.

Coaxial, multiple-shaft ferrofluid seal apparatus

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 provide a magnetic flux circuit which extends between the radially-polarized magnet, the keeper element, the shaft, and the ferrofluid in the radial gaps.

High-pressure ferrofluid seal apparatus

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.

Radially polarized multiple-stage ferrofluid seal apparatus

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.

Single pole piece multiple-stage ferrofluid seal apparatus

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.

Growing community of inventors

Nashua, NH, United States of America

Hanumaiah L Gowda