US4890850A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Tapered ferrofluid seal
Assignee: Ferrofluidics Corp
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Filing: 1988-04-18
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Granted: 1990-01-02
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Expires: 2008-04-18
Abstract
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.
Inventors
- 👤 Kuldip Raj
- 👤 Ronald Moskowitz
- 👤 Frank Bloom
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 06:21
CPC Classifications
F; F16; F16J; F16J15/00; F16J15/16; F16J15/40; F16J15/43
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
113 words
A ferrofluid seal between facing walls of a shaft and a shaft and a housing, the shaft and housing being rotated relative to each other, the seal comprising: an annular magnet which is mounted to one of said walls; means, including in part said magnet, for providing a complete magnetic flux path, at least part of said means including said magnet being spaced by a predetermined gap from the other wall to which the magnet is not mounted, the flux path passing through said gap; and ferrofluid retained in and substantially filling said gap; the width of said gap tapering in the same direction from one end of the gap to the other.
Claim 2
Dependent Claim
113 words
A ferrofluid seal between facing walls of a shaft and a shaft and a housing, the shaft and housing being rotated relative to each other, the seal comprising: an annular magnet which is mounted to one of said walls; means, including in part said magnet, for providing a complete magnetic flux path, at least part of said means including said magnet being spaced by a predetermined gap from the other wall to which the magnet is not mounted, the flux path passing through said gap; and ferrofluid retained in and substantially filling said gap; the width of said gap tapering in the same direction from one end of the gap to the other.
Claim 3
Dependent Claim
27 words
A seal as claimed in claim 1 wherein the side of said gap containing said magnet tapers uniformly from one end of the gap to the other.
Claim 4
Dependent Claim
20 words
A seal as claimed in claim 2 wherein the taper angle of said gap side is between 5° and 60°.
Claim 5
Dependent Claim
19 words
A seal as claimed in claim 3 wherein the taper angle of said gap side is 10° to 25°.
Claim 6
Dependent Claim
25 words
A seal as claimed in claim 1 wherein the other wall forming said gap tapers uniformly from one end of the gap to the other.
Claim 7
Dependent Claim
25 words
A seal as claimed in claim 5 wherein the magnet is mounted to the housing and the tapered wall is a wall of the shaft.
Claim 8
Dependent Claim
20 words
A seal as claimed in claim 5 wherein the taper angle of the tapered wall is between 5° and 60°.
Claim 9
Dependent Claim
20 words
A seal as claimed in claim 7 wherein the taper angle of the tapered wall is between 10° and 25°.
Claim 10
Dependent Claim
62 words
A seal as claimed in claim 5 wherein the side of said gap containing the magnet tapers uniformly from one end of the gap to the other, the taper angle of said magnet containing side being such that both the magnet containing side and the tapered wall are at their nearest point to the other on the same side of the gap.
Claim 11
Dependent Claim
27 words
A seal as claimed in claim 9 wherein the sum of the taper angles for the containing side and the tapered wall is between 5° and 60°.
Claim 12
Dependent Claim
27 words
A seal as claimed in claim 10 wherein the sum of the taper angels for the containing side and the tapered wall is between 10° and 25°.
Claim 13
Dependent Claim
13 words
A seal as claimed in claim 1 wherein said magnet is radially polarized.
Claim 14
Dependent Claim
17 words
A seal as claimed in claim 12 wherein said magnetic field path completing means includes bearing means.
Claim 15
Dependent Claim
83 words
A seal as claimed in claim 1 wherein said magnet is axially polarized; and wherein said magnet field path completing means includes at least one pole piece adjacent a pole side of said magnet and mounted to the same wall as the magnet, ferrofluid being retained in the gap between both the magnet and pole piece on one side and the other wall on the other side, the gap tapering in the same direction from one end of the gap to the other.
Claim 16
Dependent Claim
78 words
A seal as claimed in claim 14 wherein said magnetic field path completing means includes a second pole piece, the pole pieces being adjacent opposite poles of the magnet and mounted to the same wall as the magnet, ferrofluid being retained in the gap between both the magnet and pole pieces on one side and the other wall on the other side, the gap tapering in the same direction from one end of the gap to the other.
Claim 17
Dependent Claim
15 words
A seal as claimed in claim 15 wherein the pole pieces are of unequal width.
Claim 18
Dependent Claim
23 words
A seal as claimed in claim 14 including means for securing the magnet and pole piece together, said means being substantially ferrofluid impermeable.
Claim 19
Dependent Claim
42 words
A seal as claimed in claim 14 wherein said magnetic field path completing means includes magnetically permeable bearing means positioned on the opposite side of the magnet from the pole piece, and a magnetically permeable spacer between the magnet and the bearing.
Claim 20
Dependent Claim
25 words
A seal as claimed in claim 14 wherein said one side of the gap tapers uniformly from one end of the gap to the other.
Claim 21
Dependent Claim
49 words
A seal as claimed in claim 19 wherein both sides of the gap taper uniformly from one end of the gap to the other, the taper angles being toward each other on one end of the gap and away from each other on the outer end of the gap.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-01-01 | 1993-07-03 | 1994-01-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-01-01 | 1997-07-03 | 1998-01-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-01-01 | 2001-07-03 | 2002-01-02 | $7700.00 | Window Closed / Lapsed |