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US4457851A
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Ferrite magnet and method of producing same
Assignee: Proterial Ltd
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Filing: 1981-12-29
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Granted: 1984-07-03
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Expires: 2001-12-29
Abstract
Abstract A ferrite magnet and a method of producing same, wherein a mixture of magnetoplumbite type ferrite particles contained as its principal constituent and at least one of a mixing medium, an organic binder and a minute particular additive which is added with water or methyl alcohol is subjected to extrusion compacting to form compacts. The formed compacts are each subjected to at least drying, sintering, orienting and magnetizing, to produce cylindrical ferrite magnets having a plurality of magnetic poles on the surface. To impart anisotropy to the magnets, at least one pulse magnetic field may be applied on the surface of each compact formed by extrusion compacting, and the oriented compact may be magnetized in the same direction as the direction in which the anisotropy has been imparted.
Inventors
- 👤 Kazunori Tabaru
- 👤 Noriyuki Noda
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 07:20
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/01; C04B35/26; C04B35/2683; H; H01; H01F; H01F41/00; H01F41/02; H01F41/0253; H01F41/0273; H01F41/028
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
105 words
A ferrite magnet of the cylindrical shape having a plurality of magnetic poles on its surface produced by subjecting at least to drying, sintering and magnetizing a mixture comprising magnetoplumbite type ferrite particles as its principal component after such mixture has been subjected to extrusion compacting, wherein said ferrite particles are oriented in anisotropic direction by applying at least one pulse magnetic field on the surface of the compact after the extrusion compacting but before the magnetizing, and the ferrite magnet has a surface magnetic flux density Bo of over 1400 G when it is ground by less than 3 mm in diameter following sintering.
Claim 2
Dependent Claim
105 words
A ferrite magnet of the cylindrical shape having a plurality of magnetic poles on its surface produced by subjecting at least to drying, sintering and magnetizing a mixture comprising magnetoplumbite type ferrite particles as its principal component after such mixture has been subjected to extrusion compacting, wherein said ferrite particles are oriented in anisotropic direction by applying at least one pulse magnetic field on the surface of the compact after the extrusion compacting but before the magnetizing, and the ferrite magnet has a surface magnetic flux density Bo of over 1400 G when it is ground by less than 3 mm in diameter following sintering.
Claim 3
Independent Claim
109 words
A method of producing a ferrite magnet comprising the steps of: extruding a mixture comprising magnetoplumbite type ferrite particles as its principal component, a mixing medium selected from the group consisting of alcohol and water, an organic binder, and at least one oxide additive selected from the group consisting of PbO, CaO and SiO 2 to form a compact; applying a pulse magnetic field to the surface of the compact to impart anisotropy thereto; drying the compact formed; sintering the dried compact; and magnetizing the compact in the same direction as the direction in which the anisotropy was imparted to the compact by application of said pulse magnetic field.
Claim 4
Independent Claim
109 words
A method of producing a ferrite magnet comprising the steps of: extruding a mixture comprising magnetoplumbite type ferrite particles as its principal component, a mixing medium selected from the group consisting of alcohol and water, an organic binder, and at least one oxide additive selected from the group consisting of PbO, CaO and SiO 2 to form a compact; applying a pulse magnetic field to the surface of the compact to impart anisotropy thereto; drying the compact formed; sintering the dried compact; and magnetizing the compact in the same direction as the direction in which the anisotropy was imparted to the compact by application of said pulse magnetic field.
Claim 5
Dependent Claim
38 words
A method of producing a ferrite magnet as claimed in claim 2, wherein said ferrite particles are non-scaly particles and/or scaly particles of a mean particle size in the range of between 0.7 and 1.5 μm in diameter.
Claim 6
Dependent Claim
31 words
A method of producing a ferrite magnet as claimed in claim 2, wherein an organic binder is added in 0.5 to 2. 0 wt % of the ferrite particles thereto .
Claim 7
Dependent Claim
35 words
A method of producing a ferrite magnet as claimed in claim 2, wherein said extrusion compacting step is carried out to form a compact having a density in the range between 2.5 and 3.28 g/cc.
Claim 8
Dependent Claim
50 words
A method of producing a ferrite magnet as claimed in claim 2, wherein a cylindrical compact is formed in the extrusion step, and at least one pulse magnetic field over about 10 K Oe is impressed on the compact in a direction at a right angle to its verticle axis.
Claim 9
Dependent Claim
47 words
A method of producing a ferrite magnet as claimed in claim 2, wherin a cylindrical compact is formed in the extrusion step, and at least one pulse magnetic field over about 10 K Oe is applied on the compact in a direction parallel to its vertile axis.
Claim 10
Dependent Claim
33 words
A method of producing a ferrite magnet as claimed in claim 2, wherein an AC magnetic field is applied to the surface of the compact immediately prior to applying said pulse magnetic field.
Claim 11
Dependent Claim
22 words
A method of producing a ferrite magnet as claimed in claim 3, wherein the proportion of scaly particles is 30-80 wt %.
Claim 12
Dependent Claim
32 words
A method of producing a ferrite magnet as claimed in claim 4, wherein said at least one oxide additive is included in an amount of 0.1-3 wt % of the ferrite particles.
Claim 13
Dependent Claim
29 words
A method of producing a ferrite magnet as claimed in claim 2, wherein said mixing medium is included in an amount of 10-30 wt % of te ferrite particles.
Claim 14
Dependent Claim
10 words
A ferrite magnet produced by the method of claim 2.
Claim 15
Dependent Claim
10 words
A ferrite magnet produced by the method of claim 3.
Claim 16
Dependent Claim
10 words
A ferrite magnet produced by the method of claim 10.
Claim 17
Dependent Claim
10 words
A ferrite magnet produced by the method of claim 11.
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) | 1987-07-03 | 1988-01-02 | 1988-07-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-07-03 | 1992-01-02 | 1992-07-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-07-03 | 1996-01-02 | 1996-07-03 | $7700.00 | Window Closed / Lapsed |