US4602957A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic powder compacts
Assignee: QED Intellectual Property Ltd
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Filing: 1985-09-06
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Granted: 1986-07-29
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Expires: 2005-09-06
Abstract
Abstract A magnetic powder core, suitable for use in a low frequency power device, is prepared by a method including the steps of coating an atomized iron powder from an aqueous solution of potassium dichromate, drying the powder, compressing the powder to form a compact and heat treating the compact until it becomes partially sintered. Cores having coercivities below 240A/m, saturation inductions exceeding 1.3 Tesla and resistivities exceeding 500 microhm cm are disclosed.
Inventors
- 👤 Harriet C. Pollock
- 👤 Andrew L. Smith
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 23:51
CPC Classifications
H; H01; H01F; H01F1/00; H01F1/01; H01F1/03; H01F1/12; H01F1/14; H01F1/20; H01F1/22; H01F1/24; B; B22; B22F; B22F1/00; B22F1/16
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
52 words
A method of preparing a magnetic powder compact including the steps of coating an iron based powder from an aqueous solution of a soluble dichromate, drying said coated powder, compressing said coated powder in a die to form said compact and heat treating said compact such that said compact becomes partially sintered.
Claim 2
Independent Claim
52 words
A method of preparing a magnetic powder compact including the steps of coating an iron based powder from an aqueous solution of a soluble dichromate, drying said coated powder, compressing said coated powder in a die to form said compact and heat treating said compact such that said compact becomes partially sintered.
Claim 3
Dependent Claim
14 words
A method according to claim 1 in which said soluble dichromate comprises potassium dichromate.
Claim 4
Dependent Claim
14 words
A method according to claim 1 in which said soluble dichromate comprises sodium dichromate.
Claim 5
Dependent Claim
22 words
A method according to claim 2 in which said dichromate solution has a strength within the range 0.2% to 10% by weight.
Claim 6
Dependent Claim
26 words
A method according to claim 1 in which said powder is an atomised iron powder whose particle diameters lie within the range 75 to 150 μm.
Claim 7
Dependent Claim
23 words
A method according to claim 1 in which said coated powder is compressed at a pressure of substantially 8.5 tonnes per square cm.
Claim 8
Dependent Claim
20 words
A method according to claim 1 in which said compact is heat treated at a temperature of substantially 600° C.
Claim 9
Dependent Claim
18 words
A method according to claim 1 in which said compact is heat treated in an atmosphere of air.
Claim 10
Dependent Claim
17 words
A method according to claim 1 in which said compact is heat treated in an inert atmosphere.
Claim 11
Dependent Claim
13 words
A method according to claim 9 in which said inert atmosphere comprises argon.
Claim 12
Dependent Claim
26 words
A method according to claim 1 in which, following heat treatment, said compact is permitted to cool at a rate of substantially 200° C. per minute.
Claim 13
Dependent Claim
21 words
A method according to claim 1 in which a lubricant is added to said dried coated powder before compressing said powder.
Claim 14
Dependent Claim
27 words
A magnetic powder contact prepared by a method according to claim 1 and which is suitable for use as a core in a low frequency power device.
Claim 15
Dependent Claim
38 words
A magnetic powder compact prepared by a method according to claim 1 and which has a coercivity not exceeding 240 A/m, a saturation induction of at least 1.3 Tesla and a resistivity of at least 500 microhm cm.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-07-28 | 1990-01-27 | 1990-07-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-07-28 | 1994-01-27 | 1994-07-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-07-28 | 1998-01-27 | 1998-07-29 | $7700.00 | Window Closed / Lapsed |