Self-activating ferrofluid seal and method

Claim 2

A self-activating-seal apparatus adapted for use with and to seal a magnetically permeable shaft element, which seal apparatus comprises: (a) an axially polarized, permanent-magnet ring element generally disposed to be aligned axially about the shaft element; (b) first and second magnetically permeable pole pieces, each at the one end disposed in a magnetic relationship with one pole of the permanent-magnet ring element, and each disposed at the other end to extend into a close, noncontacting relationship with the surface of the shaft element and to form a small gap with the surface of the shaft element, upon the insertion of the shaft element; (c) the first and second pole pieces and the ring element forming a generally annular cavity therebetween; (d) separate, nonmagnetic, penetrable, generally peripheral container means disposed within the cavity; (e) a sealing volume of ferrofluid disposed within the container means; and (f) penetrating means to permit the penetration of the container means prior to insertion of the shaft element, thereby permitting the ferrofluid to move from the container to a sealing position, on the change in the magnetic-flux path, by insertion of the shaft element.

Claim 3

The seal apparatus of claim 1 wherein the container means comprises a closed, ring-like, tubular container.

Claim 4

The seal apparatus of claim 1 wherein the container means comprises a tubular plastic container.

Claim 5

The seal apparatus of claim 3 wherein the container means comprises a pair of tubular plastic containers disposed in a generally side-by-side relationship within the cavity and occupying a substantial portion of the cavity.

Claim 6

The seal apparatus of claim 1 wherein the container means comprises a heat-shrunk and sealed plastic tubular container.

Claim 7

The seal apparatus of claim 5 wherein the tubular container has one end heat-shrunk about and in a sealing relationship with the other heat-shrunk sealed end of the tube, to form a ring-like tubular container of defined diameter to fit within the cavity.

Claim 8

The seal apparatus of claim 1 wherein the container means comprises a preformed, generally semirigid, ring-like, plastic, tubular container.

Claim 9

The seal apparatus of claim 1 wherein the ferrofluid comprises a diester ferrofluid.

Claim 10

The seal apparatus of claim 1 wherein the penetrating means comprises a removable means disposed in a close-fitting relationship on either side of the pole pieces, and having extended penetrating elements, whereby, on radially outward movement of the prong elements, penetration of the container means occurs.

Claim 11

The seal apparatus of claim 9 wherein the penetrating elements remain in place after penetration to seal the penetration of the container, and which includes removable means to retain the penetrating means in a penetrating and sealing position.

Claim 12

The seal apparatus of claim 1 wherein the penetrating means comprises a generally U-shaped, nonmagnetic clamp, the sides of the clamp disposed in a close-fitting holding relationship on the exterior sides of the pole pieces, and a plurality of sharp prong elements disposed within the clamp, whereby, on radially outward movement, the prong elements penetrate the container means.

Claim 13

The seal apparatus of claim 11 wherein the penetrating means includes at least four, generally aligned, prong elements within the clamp, and wherein the container means comprises two, closed-loop, plastic, tubular containers within the cavity, whereby one pair of prong elements is designed to penetrate each tubular container to form a vent and discharge holes therein.

Claim 14

The seal apparatus of claim 1 which includes a magnetically permeable shaft element positioned within the seal, with the container means penetrated and the ferrofluid in the sealing position in the gaps between the other ends of the pole pieces and the surface of the shaft element.

Claim 15

The seal apparatus of claim 13 wherein the shaft element comprises a rotatable computer-disc shaft element.

Claim 16

A self-activating-seal apparatus adapted for use with and to seal a magnetically permeable shaft element, which seal apparatus comprises: (a) an axially polarized, permanent-magnet ring element generally disposed to be aligned axially about the shaft element; (b) first and second magnetically permeable pole pieces, each at the one end disposed in a magnetic relationship with one pole of the permanent-magnet ring element, and each disposed at the other end to extend into a close, noncontacting relationship with the surface of the shaft element and to form a small gap with the surface of the shaft element, upon the insertion of the shaft element; (c) the first and second pole pieces and the ring element forming a generally annular cavity therebetween; (d) separate, nonmagnetic, penetrable, generally peripheral container means disposed within the cavity, the container means comprising a pair of tubular plastic containers disposed in a generally side-by-side relationship within the cavity and occupying a substantial portion of the cavity; (e) a sealing volume of ferrofluid disposed within the container means; and (f) penetrating means comprising a generally U-shaped, non-magnetic clamp, the sides of the clamp disposed in a close-fitting holding relationship on the exterior sides of the pole pieces, and a plurality of sharp prong elements disposed within the clamp, whereby, on radially outward movement, the prong elements penetrate the container means, the penetrating means permitting the penetration of the container means prior to insertion of the shaft element, thereby permitting the ferrofluid to move from the container to a sealing position, on the change in the magnetic-flux path, by insertion of the shaft element.

Claim 17

A self-activating-seal apparatus adapted for use with and to seal a magnetically permeable shaft element, which seal apparatus comprises: (a) an axially polarized, permanent-magnet ring element generally disposed to be aligned axially about the shaft element; (b) first and second magnetically permeable pole pieces, each at the one end disposed in a magnetic relationship with one pole of the permanent-magnet ring element, and each disposed at the other end to extend into a close, noncontacting relationship with the surface of the shaft element and to form a small gap with the surface of the shaft element, upon the insertion of the shaft element; (c) the first and second pole pieces and the ring element forming a generally annular cavity therebetween; (d) separate, nonmagnetic, penetrable, generally peripheral container means disposed within the cavity, the container means comprising a pair of tubular plastic containers disposed in a generally side-by-side relationship within the cavity and occupying a substantial portion of the cavity; (e) a sealing volume of ferrofluid disposed within the container means; and (f) penetrating means comprising a generally U-shaped, non-magnetic clamp, the sides of the clamp disposed in a close-fitting holding relationship on the exterior sides of the pole pieces, and a plurality of sharp prong elements disposed within the clamp, whereby, on radially outward movement, the prong elements penetrate the container means, the penetrating means permitting the penetration of the container means prior to insertion of the shaft element, thereby permitting the ferrofluid to move from the container to a sealing position, on the change in the magnetic-flux path, by insertion of the shaft element.

Claim 18

The seal apparatus of claim 15 wherein the penetrating means includes at least four, generally aligned, prong elements within the clamp, and wherein the container means comprises two, closed-loop, plastic, tubular containers within the cavity, whereby one pair of prong elements is designed to penetrate each tubular container to form a vent and discharge holes therein.

Claim 19

A container for ferrofluid adapted for use within a peripheral cavity in a ferrofluid-seal apparatus, which container comprises a closed loop of defined diameter of a heat-shrinkable, tubular, plastic material which contains a predetermined volume of a ferrofluid, one end of the tubular plastic material in a sealed, heat-shrunk condition, and the other end heat-shrunk about and in an overlapping sealing relationship with the other heat-shrunk, sealed end, to form a closed-loop ferrofluid container.

Claim 20

A container for ferrofluid adapted for use within a peripheral cavity in a ferrofluid-seal apparatus, which container comprises a closed loop of defined diameter of a heat-shrinkable, tubular, plastic material which contains a predetermined volume of a ferrofluid, one end of the tubular plastic material in a sealed, heat-shrunk condition, and the other end heat-shrunk about and in an overlapping sealing relationship with the other heat-shrunk, sealed end, to form a closed-loop ferrofluid container.

Claim 21

The container of claim 17 which includes a diester-based ferrofluid.

Claim 22

The container of claim 17 wherein the plastic material comprises a polyolefin polymer.

Claim 25

The method of claim 20 which includes: (a) penetrating the container with at least one penetrating element and leaving the penetrating element in position to seal the penetration so made in the container; and, thereafter, (b) removing the penetrating element prior to insertion of the shaft element.

Claim 26

The method of claim 21 which includes retaining the penetrating element in a sealed position, while transporting the seal apparatus to a location for insertion of the shaft element.

Claim 27

The method of claim 20 which includes penetrating the container by a plurality of penetrating prong elements disposed to place a vent and a ferrofluid discharge hole in the container.

Claim 28

The method of claim 20 which includes penetrating the container by moving a penetrating prong element radially outwardly and into the cavity where the container is positioned.

Claim 29

The method of claim 20 which includes positioning within the cavity at least one closed-loop, sealed, plastic, tubular container of the ferrofluid.

Claim 30

The method of claim 25 which includes: (a) positioning a pair of thin-wall, penetrable, closed-loop, sealed, plastic containers within the cavity; and (b) penetrating and sealing, with at least two holes, each of the containers by a penetrating clamp; (c) retaining the clamp in position to seal the holes during transporting of the seal; and (d) removing the penetrating sealing clamp immediately prior to insertion of the shaft element.

Claim 31

The method of claim 20 which includes: (a) forming a container by inserting a volume of ferrofluid within a defined length of a heat-shrinkable plastic tube; (b) heat-shrinking and sealing one end of the plastic tube; (c) inserting the other open end of the plastic tube over and in an overlapping relationship with the sealed one end of the plastic tube; (d) heat-shrinking the other end of the plastic tube over and in a sealing relationship with one end of the plastic tube to form a closed, sealed, circular loop of the plastic tube; and (e) inserting one or more of the looped plastic tubes within the cavity as the container for the ferrofluid.

Claim 32

The method of claim 20 which includes inserting the shaft element within the seal immediately after penetrating and unsealing of the container, to permit the movement of the ferrofluid from the penetrated container to a sealing position about the surface of the shaft element.

Claim 33

The method of claim 28 wherein the shaft element comprises a computer-disc-drive shaft element.

Claim 34

The method of claim 20 which includes: (a) positioning the seal apparatus, on insertion of the shaft element, between a rotary driving means for the shaft element; and (b) a computer-memory-disc element secured to the shaft element for rotation therewith, thereby providing a sealing relationship about the shaft element to protect the memory-disc from contaminants.