Abstract: A ferrofluid seal wherin the amount of ferrofluid which may be used is increased by tapering the gap in which the ferrofluid is retained from one end of the gap to the other. One side of this gap is the magnet and, where used, pole pieces used to generate the magnetic field retaining the sealing ferrofluid, and the other side is a wall forming the opening to be sealed. The tapering of the gap width may be achieved by tapering either side forming the gap or by tapering both sides. The taper is preferably uniform from one end of the gap to the other.

Abstract: A multi-stage ferrofluid seal incorporates a ferrofluid reservoir for extending seal life. The reservoir is located between seal stages and contains a quantity of ferrofluid sufficient to replace ferrofluid in the seal stages which is lost due to evaporation or contamination. The seal is designed to withstand a pressure drop between a high pressure area and a low pressure area and the location of the reservoir is selected so that the pressure capacity of the seal stages between the low pressure area and the reservoir is sufficient to withstand the entire pressure drop. The pressure capacity of the seal stages between the high pressure area and the reservoir is less than the entire pressure drop. Failure of the seal stages between the reservoir and low pressure area causes failure of the seal stages between the reservoir and the high pressure area.

Abstract: A compact, high-torque electric motor in which one motor element (either the stator or rotor) has magnetic poles whose effective magnetic width is substantially equal and which span equal center angles. The second motor element has a plurality of armature groups, each of which occupies a phase sector of the motor element formed by dividing the total periphery by a natural number. All of the armatures within an armature group are connected electrically in series and excited with a current of one phase (either an alternating current phase or an equivalent phase generated by commutator action). Within on pole group the poles may have equal widths or different widths.

Abstract: A compact long-life magnetic fluid seal for sealing between a housing and a magnetically permeable rotating shaft includes an annular magnet having a closely-spaced, noncontacting relationship with the shaft to define a first gap and an annular pole piece axially abutting the magnet and having a closely-spaced, noncontacting relationship with the shaft to define a second gap. The first gap has a slightly larger radial dimension than the second gap, and the first and second gaps together define an elongated annular space for retention of a magnetic fluid. The outer edges of the pole piece and magnet inner surfaces can be rounded to limit splashing of the magnetic fliud. In another embodiment, a magnetic fluid seal includes first and second pole pieces axially abutting opposite ends of an annular magnet. The magnet has a slightly larger inside diameter than either of the pole pieces. The pole pieces and the magnet together define an elongated annular gap for retention of magnetic fluid.

Abstract: A bearing and magnetic fluid seal assembly includes a shaft mounted by axially spaced-apart bearings for rotation relative to a housing. A magnetic fluid seal includes an annular magnet axially positioned between the bearings in the space that is wasted and not utilized for any purpose, and a thin, disk-like annular polepiece positioned between one of the bearings and the environment to be protected by the seal. Magnetic flux from the magnet is conducted by a magnetically permeable housing or shaft to an annular gap between the outside diameter of the polepiece and the housing. A magnetic fluid is retained in the gap by the magnetic flux, thereby providing an exclusion seal. Embodiments utilizing radially and axially polarized magets are provided. A magnetic fluid seal can be provided at each end of the assembly. The bearings supporting the shaft can be magnetically permeable or nonmagnetic. The seal(s) can be electrically conducting or nonconducting depending upon the type of ferrofluid used.

Abstract: A ferrofluid seal apparatus and a method of assembling the seal apparatus, the seal apparatus comprising a housing, an annular permanent magnet and at least one annular pole-piece element, and a sealing ring to secure and seal the permanent magnet and the pole-piece element within the housing, the sealing ring having an inwardly extending shoulder at one radial end, to retain the permanent magnet and pole piece within the sealing ring. The sealing ring is composed of a deformable material and retains, by compressive force, the permanent magnet and pole piece, by press-fitting the sealing ring into the annular space between the outer surface of the permanent magnet and the annular pole piece and the inner surface of the housing, to secure the permanent magnet and pole piece within the housing.

Abstract: 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.

Abstract: A bearing and magnetic fluid seal assembly includes a shaft mounted by axially spaced-apart bearings for rotation relative to a housing. A magnetic fluid seal includes an annular magnet axially positioned between the bearings in the space that is wasted and not utilized for any purpose, and a thin, disk-like annular polepiece positioned between one of the bearings and the environment to be protected by the seal. Magnetic flux from the magnet is conducted by a magnetically permeable housing or shaft to an annular gap between the inside diameter of the polepiece and the shaft. A magnetic fluid is retained in the gap by the magnetic flux, thereby providing an exclusion seal. Embodiments utilizing radially and axially polarized magnets are provided. A magnetic fluid seal can be provided at each end of the assembly. The bearings supporting the shaft can be magnetically permeable or nonmagnetic. The seal(s) can be electrically conducting or nonconducting depending upon the type of ferrofluid used.

Abstract: A low viscosity, electrically conductive ferrofluid composition and method of making and using same, which composition comprises: a first polar liquid carrier; a second polar liquid carrier miscible in the first polar carrier and comprising a polyol, such as a tetraethylene glycol dimethyl ether; magnetic particles to impart magnetic characteristics to the ferrofluid composition; and a surfactant, particularly a cationic surfactant in an amount sufficient to stabilize and disperse the magnetic particles, the surfactant dissociated or ionized predominately by the second polar liquid carrier.

Abstract: 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.

Abstract: A bearing assembly with an integrated single-stage ferrofluid seal incorporated therein, which assembly comprises: a bearing assembly having an inner and outer race to define a raceway and a plurality of rolling elements within the raceway to permit rotation of the inner and outer races relative to one another; and a single-stage ferrofluid seal within the raceway and positioned adjacent one side of the roller element, and which ferrofluid seal comprises a single pole piece having one end which extends into a close, noncontacting relationship with the surface of the inner and outer races to define a radial gap, ferrofluid in the radial gap to form a seal, an annular permanent magnet secured to and adjacent the single pole piece, and a nonmagnetic permeable housing extending about a portion of the pole piece and the permanent magnet, to divert magnetic flux toward the surfaces of the inner or outer race in which the ferrofluid seal is formed in the radial gap, thereby providing a compact, integrated bearing as

Abstract: A low viscosity, electrically conductive ferrofluid composition and method of making and using same, which composition comprises: a first polar liquid carrier; a second polar liquid carrier miscible in the first polar carrier and comprising a polyol, such as a tetraethylene glycol dimethyl ether; magnetic particles to impart magnetic characteristics to the ferrofluid composition; and a surfactant, particularly a cationic surfactant in an amount sufficient to stabilize and disperse the magnetic particles, the surfactant dissociated or ionized predominately by the second polar liquid carrier.

Abstract: 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.

Abstract: A pulling head adapted for use with a crystal growing furnace and a crystal growing furnace containing such pulling head, which furnace comprises a high and low speed seed lift motor, a seed rotation motor, a rotatable platform about the upper portion of the furnace, a winch mounted on the platform and adapted for rotation about its own axis to maintain a cable on a central vertical axis, a cable about the winch, one end of the cable adapted to hold a seed crystal within a sealed vacuum or inert atmosphere of the furnace and a multiple-stage planetary gear differential mechanism to receive the output motions of both seed lift motors and the seed rotation motor and to provide a first seed rotation motion output to rotate the platform and a second output to rotate the winch, the second output being the weighted sum of the input motion of the speed ranges of the seed lift motors to provide a seed lift motion which is independent of the speed rotation motor, thereby providing a pulling head which combines the inp

Abstract: A composite ferrofluid bearing and seal apparatus which comprises a ferrofluid seal apparatus which contains disposed therein a bearing element, to form a ferrofluid-film bearing with the surface of a shaft, the ferrofluid seal apparatus retaining the bearing ferrofluid film within the bearing cavity, by forming a ferrofluid O-ring seal, held by magnetic flux, at each end of the bearing element, the composite ferrofluid bearing and seal apparatus acting to contain the bearing ferrofluid film within the fluid-film bearing cavity and to exclude gases from being entrained in the ferrofluid.

Abstract: A bearing assembly with an integrated single-stage ferrofluid seal apparatus incorporated therein, which assembly comprises a bearing assembly having an inner and outer race to define a raceway, a plurality of rolling elements retained within the raceway to permit rotation of the inner and outer races relative to one another, and a single-stage ferrofluid seal apparatus within the raceway and adjacent one side of the roller elements and which ferrofluid seal apparatus comprises a single-pole piece which extends into a close, noncontacting relationship with the surface of the inner or the outer race to define a radial gap, ferrofluid in the radial gap to form a ferrofluid seal, and an annular, permanent magnet secured to and adjacent the single-pole piece, the magnet having a generally-L sectional shape and in contact with one side and about one end of the pole piece to provide both a source of magnetic flux and as a magnetically insulating housing for the pole piece.

Abstract: 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.

Abstract: A stable ferrofluid composition and the method of preparing and using the ferrofluid composition, such as in a ferrofluid seal apparatus, and which ferrofluid composition comprises: a liquid carrier; ferromagnetic particles sufficient to provide magnetic properties to the ferrofluid dispersed in the liquid carrier; and a dispersing amount of a cationic surfactant to provide a stable ferrofluid composition. The stable ferrofluid compositions have improved electrical conductivity and are useful in sealing computer disc drives and in sputtering apparatus in the semiconductive industry.

Abstract: 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.

Abstract: A multiple-shaft coaxial ferrofluid seal apparatus which comprises: a nonmagnetic housing; a central shaft element; and one or more successively coaxial shaft elements about the central shaft element with one or more of the coaxial shaft elements composed of a nonmagnetically permeable shaft section between a first and second magnetically permeable shaft sections. The seal apparatus includes an axial polarized annular permanent magnet together with first and second pole piece elements, the pole piece elements generally aligned with the magnetically permeable shaft sections to provide for a single magnetic structure within the housing and for a closed-loop magnetic flux to retain ferrofluid as a ferrofluid seal between the coaxial shaft elements which provides for hermetic sealing of the rotary motion of two or more of the coaxial shaft elements employing a single magnetic structure. The multiple-shaft coaxial ferrofluid seal apparatus also includes rotary bearings for the coaxial and central shaft element.