US3764539A
Expired / Lapsed
US
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Flexible ferrite permanent magnet and methods for its manufacture
Assignee: COMMUNITY BUILDING ASS OF WASH
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Filing: 1970-10-14
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Granted: 1973-10-09
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Expires: 1990-10-14
Abstract
Abstract A flexible permanent magnet is described that contains singlecrystalline ferrite particles embedded in an elastomeric binder. The ferrite particle size is much larger than that of the ferrites in the prior-art flexible magnets which results in greatly improved magnetic and mechanical properties. The largesize, single-crystalline ferrite particles are obtained by preparing a highly oriented, fully sintered hexaferrite and by pulverizing the hexaferrite into a relatively coarse powder.
Inventors
- 👤 P Cochardt
- 👤 A Cochart
- 👤 A Cochardt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 17:54
CPC Classifications
H; H01; H01F; H01F13/00; H01F13/003; H01F1/00; H01F1/01; H01F1/03; H01F1/032; H01F1/10; H01F1/11; H01F1/113; H01F1/117
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
99 words
In the method of making flexible permanent magnets, the steps comprising aligning ferrite particles in a magnetic field, said ferrite particles having the composition Mo . k Fe2O3 wherein M represents at least one element selected from the group consisting of barium and strontium and wherein k lies between 4.5 and 5.5, sintering the aligned particle agglomerate thereby producing multidomain ferrites having predominantly single crystal charactEristics, pulverizing said ferrites into a powder, preparing a mixture of elastomeric binder with at least a portion of said powder, molding the mixture, and magnetizing at least a portion of the molded pieces.
Claim 2
Dependent Claim
125 words
In the method of making lead-free flexible permanent magnets, the steps comprising reacting iron ore powder with a divalent metal oxide MO, wherein M stands for at least one element selected from the group consisting of Ba and Sr to form the ferrite MO . k Fe2O3 wherein k lies between 4.5 and 5.5, milling said ferrite in water with steel balls, pressing the slurry in a magnetic field and aligning the ferrite particles, sintering the aligned particle agglomerate into a multi-domain ferrite having predominantly single crystal characteristics, pulverizing said ferrite into a powder, preparing a mixture of elastomeric binder with at least a portion of said ferrite powder, extruding the mixture into a strip, and magnetizing at least a portion of the extruded strip.
Claim 3
Dependent Claim
79 words
The method of claim 3, wherein the ferrite component of the flexible strip has an average particle size of from at least 2 Mu m up to about 10 Mu m and contains at least one addition selected from the group consisting of from 0.1 to 1 wt% SiO2, 0.1 to 1 wt% CaO, from 0.1 to 1 wt% Al2O3 and from 0.05 to 1 wt% of a sulfate from the group consisting of SrSO4, BaSO4, CaSO4 and NaSo4.
Claim 4
Dependent Claim
72 words
A flexible permanent magnet containing multi-domain ferrite particles embedded in an elastomeric binder, said ferrite particles having predominantly single crystal characteristics and having an average particle size of from at least 2 Mu m up to about 10 Mu m, said ferrite particles having the composition MO . k Fe2O3 wherein M represents an element selected from the group consisting of barium and strontium and wherein k lies between 4.5 and 5.5.
Claim 5
Dependent Claim
40 words
The flexible magnet of claim 5 wherein M includes small amounts of one or both of lead and calcium, lead, when present, not exceeding about 1.6wt% of the ferrite and calcium, when present, not exceeding 2 wt% of the ferrite.
Claim 6
Dependent Claim
56 words
The flexible magnet of claim 5 wherein the ferrite contains at least one addition selected from the group consisting of from 0.1 to 1 wt% SiO2, 0.1 to 1 wt% CaO, from 0.1 to 1 wt% Al2O3 and from 0.05 to 1 wt% of a sulfate from the group consisting of SrSO4, BaSO4, CaSO4 and Na2SO4.
Claim 7
Dependent Claim
16 words
The flexible magnet of claim 5 wherein the ferrite contains from 0.1 to 0.5 wt% SiO2.
Claim 8
Dependent Claim
16 words
The flexible magnet of claim 5 wherein the ferrite contains from 0.1 to 1 wt% Al2O3.
Claim 9
Dependent Claim
16 words
The flexible magnet of claim 8 wherein the ferrite contains from 0.1 to 1 wt% Al2O3.
Claim 10
Dependent Claim
20 words
The flexible magnet of claim 7 wherein the ferrite particles have an average particle size of about 5 Mu m.
Claim 11
Dependent Claim
17 words
The magnet of claim 7, wherein said elastomeric binder contains a mixture of chlorosulfonated polyethylene and polyisobutylene.
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) | 1976-10-08 | 1977-04-09 | 1977-10-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-08 | 1981-04-09 | 1981-10-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-08 | 1985-04-09 | 1985-10-09 | $7700.00 | Window Closed / Lapsed |