Ferrofluidics Corporation

Compudrive Corporation

Thomas J Black, Jr

William B Mraz

Philip Stahl

Henry Ryffel

David T Mooney

James C Toboni

Larry A Hufford

Robert C Watkins

Paul E McMahan

An on-site fillable ferrofluidic seal comprises a ferrofluidic seal having at least one ferrofluid conducting channel extending through either the magnet, through one of the pole pieces which sandwich the opposing pole ends of the magnet, or through both the magnet and a pole piece. The conducting channel extends to a location where deposited ferrofluid will be drawn to the gaps between the pole pieces and the shaft. In another embodiment a multi-stage seal is filled by displacing the pole piece/magnet assembly axially relative to the shaft so that each pole piece projection falls halfway axially between two shaft projections. The displacement alters the normal magnetic field pattern to create a substantially uniform magnetic field throughout the pole piece/shaft interface region such that ferrofluid can be drawn through the region. When the shaft is returned to its original position with respect to the pole piece/magnet assembly, that is, when the pole piece projections are re-aligned axially with the shaft projections, a series of stages of the multi-stage hermetic 'O-ring' seal are created. An alternative embodiment of the invention uses the capillary action of the liquid to maintain a multistage seal which holds the liquid in place using axially aligned wettable and non-wettable surfaces on a shaft and stator surrounding the shaft. With the wettable surfaces of the shaft axially aligned with those of the stator, the liquid congregates in the gaps formed between the wettable surfaces of the shaft and stator. Filling of the seal is accomplished by displacing the shaft relative to the stator such that each wettable surface on the shaft axially overlaps two wettable surfaces on the stator, thus providing a path of wettable surfaces which allow the liquid to flow along the length of the seal.

On-site fillable liquid magnetic seal

A ferrofluidic seal is fitted with a centering ring having an inner edge adapted for engagement with a rotating shaft for centering the seal about the rotating shaft. The centering ring automatically engages the shaft and centers the seal when the seal is fitted onto the shaft. The centering ring is affixed to the housing, and/or magnet and pole module. In one embodiment, the centering ring may be removed after it performs its centering function. In another embodiment, the centering ring is non-removable and remains within the seal permanently. According to this latter embodiment, the centering ring serves the additional purpose of retaining ferrofluid, expelled from the seal during 'bursting', within magnetic reach of the seal so as to be re-drawn into the seal, thus extending seal life. Additionally, a ferrofluid retaining ring absent a centering function may be employed. The centering ring provides for easy installation and accurate centering of a seal with which it is used, and yields a highly functional and operationally safe seal.

Ferrofluidic seal centering ring

An on-site fillable ferrofluidic seal comprises a ferrofluidic seal having at least one ferrofluid conducting channel extending through either the magnet, through one of the pole pieces which sandwich the opposing pole ends of the magnet, or through both the magnet and a pole piece. The conducting channel extends to a location where deposited ferrofluid will be drawn to the gaps between the pole pieces and the shaft. In another embodiment a multi-stage seal is filled by displacing the pole piece/magnet assembly axially relative to the shaft so that each pole piece projection falls halfway axially between two shaft projections. The displacement alters the normal magnetic field pattern to create a substantially uniform magnetic field throughout the pole piece/shaft interface region such that ferrofluid can be drawn through the region. When the shaft is returned to its original position with respect to the pole piece/magnet assembly, that is, when the pole piece projections are re-aligned axially with the shaft projections, a series of stages of the multi-stage hermetic 'O-ring' seal are created.

On-site fillable ferrofluidic seal

A ferrofluidic seal arrangement for sealing a high-speed rotary shaft which passes between an environment at atmospheric or high pressure and an environment at high-vacuum is provided, which is especially useful in a high-speed rotating anode apparatus for generating x-rays in a CAT Scan apparatus or the like. A differentially-pumped region between a multi-stage ferrofluidic seal and a single-stage seal insures that no seal bursting into the high-vacuum region occurs. Bearings supporting the shaft are arranged in a mechanically-stable arrangement but are isolated from the high-vacuum environment. Thus, neither the high-vacuum environment nor the differentially-pumped region need be continually mechanically pumped, and a relatively light-weight apparatus results. The apparatus is electrically grounded by transferring the charge on the anode through the high-speed shaft out of the vacuum environment and to a slower-rotating shaft via an electrically conductive, flexible drive belt, the slower shaft rotating at a speed at which grounding by conventional means is feasible.

Differentially-pumped ferrofluidic seal

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.

Ferrofluid exclusion seal and method of assembly

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.

Self-activating ferrofluid seal apparatus and method

A improved planetary drive employs a pair of radially inner and outer nonorbiting members between which is radially disposed an annular orbiting member. The inner nonorbiting member and the inner surface of the inner wall of the orbiting member are formed with opposing surface in meshing engagement to form one stage of a planetary drive, while the opposing surfaces of the outer nonorbiting member and the orbiting member are formed with teeth in meshing engagement to form a second stage of a planetary drive. All of the orbiting and nonorbiting members and their teeth lie in the same plane or planes disposed radially outward from the means for orbiting the orbiting member so that when that member is orbited, the forces exerted on the orbiting means are in said plane or planes. Various combinations of rollers and lobed surfaces to formed the gear stages are also described.

Growing community of inventors

Merrimack, NH, United States of America

Thomas J Black, Jr