US4882224A
Expired / Lapsed
US
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Magnetic particles, method for making and electromagnetic clutch using same
Assignee: TDK Corp
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Filing: 1988-04-28
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Granted: 1989-11-21
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Expires: 2008-04-28
Abstract
Abstract Magnetic particles comprising a magnetic core and a shell covering the core are provided wherein the shell is formed from titanium nitride, titanium carbide, aluminum nitride, aluminum oxide, zirconium oxide, silicon nitride, silicon carbide, or a mixture thereof by plasma-assisted chemical vapor deposition while vibrating the core.
Inventors
- 👤 Hideharu Moro
- 👤 Yoshikazu Narumiya
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 11:26
CPC Classifications
F; F16; F16D; F16D37/00; F16D37/02; B; B22; B22F; B22F1/00; B22F1/16; C; C23; C23C; C23C16/00; C23C16/44; C23C16/50; H; H01; H01F; H01F1/00; H01F1/01; H01F1/03; H01F1/032; H01F1/04; H01F1/06; H01F1/061; H01F1/12; H01F1/14; H01F1/20; H01F1/22; H01F1/24; F16D2037/002; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/29; Y10T428/2982; Y10T428/2991; Y10T428/2993
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
67 words
A magnetic particle, comprising: a magnetic core having a diameter of about 30 to about 80 μm and a shell covering the core formed from at least one member selected from the group consisting of titanium nitride, titanium carbide, aluminum nitride, aluminum oxide, zirconium oxide, siicon nitride, and silicon carbide, and having a thickness of about 2 to about 7 μm sufficient to render the particle durable.
Claim 2
Dependent Claim
67 words
A magnetic particle, comprising: a magnetic core having a diameter of about 30 to about 80 μm and a shell covering the core formed from at least one member selected from the group consisting of titanium nitride, titanium carbide, aluminum nitride, aluminum oxide, zirconium oxide, siicon nitride, and silicon carbide, and having a thickness of about 2 to about 7 μm sufficient to render the particle durable.
Claim 3
Dependent Claim
17 words
The particle of claim 1 wherein the magnetic core is formed from iron or an iron alloy.
Claim 4
Dependent Claim
30 words
The particle of claim 2, wherein the magnetic core is formed from an iron alloy selected from the group consisting of Fe-Cr, Fe-Cr-Si, Fe-B-Si, Fe-Cr-Si-Al, Fe-B-Si-Cr, Fe-P-C, and Fe-P-C-Cr alloys.
Claim 5
Dependent Claim
20 words
The particle of claim 1, wherein the thickness of said shell ranges from about 3 μm to about 5 μm.
Claim 6
Independent Claim
95 words
A method for preparing magnetic particles each having a magnetic core covered with a shell, comprising the steps of: preparing magnetic cores each having a diameter of about 30 to about 80 μm, and carrying out plasma-assisted chemical vapor deposition while vibrating the cores, thereby forming a shell of at least one member selected from the group consisting of titanium nitride, titanium carbide, aluminum nitride, aluminum oxide, zirconium oxide, silicon nitride, and silicon carbide on each of the cores to a thickness of about 2 to about 7 μm sufficient to render the particles durable.
Claim 7
Independent Claim
95 words
A method for preparing magnetic particles each having a magnetic core covered with a shell, comprising the steps of: preparing magnetic cores each having a diameter of about 30 to about 80 μm, and carrying out plasma-assisted chemical vapor deposition while vibrating the cores, thereby forming a shell of at least one member selected from the group consisting of titanium nitride, titanium carbide, aluminum nitride, aluminum oxide, zirconium oxide, silicon nitride, and silicon carbide on each of the cores to a thickness of about 2 to about 7 μm sufficient to render the particles durable.
Claim 8
Dependent Claim
24 words
The method of claim 5, wherein the core vibrating step includes placing cores on a platen as a powder layer and vibrating the platen.
Claim 9
Dependent Claim
44 words
The method of claim 5, wherein said cores are heated to a temperature within the range of 300° to about 700° C. and the pressure within the device in which plasma-assisted chemical vapor deposition is conducted ranges from about 0.1 to about 1.5 Torr.
Claim 10
Dependent Claim
24 words
The method of claim 5, wherein said shells are formed about said cores at a rate ranging from about 100 to about 500 angstroms/minute.
Claim 11
Dependent Claim
84 words
A magnetic particle comprising: a magnetic core having a diameter of about 30 to about 80 μm, and a shell covering said core formed from at least one member selected from the group consisting of titanium nitride, titanium carbide, aluminum nitride, aluminum oxide, zirconium oxide, silicon nitride and silicon carbide, and having a thickness of about 2 to about 7 μm sufficient to render the particle durable such that the Vickers hardness of the shell is at least twice the hardness of the core.
Claim 12
Dependent Claim
84 words
A magnetic particle comprising: a magnetic core having a diameter of about 30 to about 80 μm, and a shell covering said core formed from at least one member selected from the group consisting of titanium nitride, titanium carbide, aluminum nitride, aluminum oxide, zirconium oxide, silicon nitride and silicon carbide, and having a thickness of about 2 to about 7 μm sufficient to render the particle durable such that the Vickers hardness of the shell is at least twice the hardness of the core.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1992-11-20 | 1993-05-22 | 1993-11-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-11-20 | 1997-05-22 | 1997-11-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-11-20 | 2001-05-22 | 2001-11-21 | $7700.00 | Window Closed / Lapsed |