US3993972A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electro-magnetic devices
Assignee: ZF International UK Ltd
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Filing: 1975-07-02
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Granted: 1976-11-23
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Expires: 1995-07-02
Abstract
Abstract An electro-magnet includes a pole-piece having a portion of reduced cross-section. The shape of the reduced portion provides a restriction in the magnetic circuit such that the distance moved, against a biasing force, by an armature of the electro-magnet is proportional to the current in the electro-magnet winding. The pole piece comprises aligned parts of nickel-iron alloy joined by a soft iron part whose cross-section is less than that of the nickel-iron alloy parts.
Inventors
- 👤 Arthur Laurence Barbrook
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 13:21
CPC Classifications
H; H01; H01F; H01F7/00; H01F7/06; H01F7/08; H01F7/14
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
147 words
An electro-magnetic device, including a central pole piece, a winding surrounding said pole piece, an armature attractable into contact with the pole piece and a spring urging the armature away from the pole piece, the pole piece having first and second axially aligned parts of nickel iron alloy and a soft iron part joining said first and second parts and having a cross sectional area less than that of either said first or said second parts, said soft iron part defining, in combination with adjacent ends of said first and second parts, a waisted portion intermediate the ends of said pole piece, said waisted portion providing a restriction in the magnetic circuit of the device, the shape of said waisted portion being such that the distance through which the armature moves against the action of the spring is substantially proportional to the current flowing in the winding.
Claim 2
Dependent Claim
147 words
An electro-magnetic device, including a central pole piece, a winding surrounding said pole piece, an armature attractable into contact with the pole piece and a spring urging the armature away from the pole piece, the pole piece having first and second axially aligned parts of nickel iron alloy and a soft iron part joining said first and second parts and having a cross sectional area less than that of either said first or said second parts, said soft iron part defining, in combination with adjacent ends of said first and second parts, a waisted portion intermediate the ends of said pole piece, said waisted portion providing a restriction in the magnetic circuit of the device, the shape of said waisted portion being such that the distance through which the armature moves against the action of the spring is substantially proportional to the current flowing in the winding.
Claim 3
Dependent Claim
22 words
A device as claimed in claim 1 in which said first and second parts and said soft iron part are substantially cylindrical.
Claim 4
Dependent Claim
21 words
A device as claimed in claim 1 in which said first and second parts and said soft iron part are tubular.
Claim 5
Dependent Claim
28 words
A device as claimed in claim 1 in which said soft iron part is engaged in recesses in adjacent end faces of said first and second parts respectively.
Claim 6
Dependent Claim
27 words
A device as claimed in claim 4 in which one of said end faces is a frusto-conical surface which projects towards the other of said end faces.
Claim 7
Dependent Claim
21 words
A device as claimed in claim 5 in which said frusto-conical surface has an included angle of between 130° and 160°.
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) | 1979-11-23 | 1980-05-24 | 1980-11-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-11-23 | 1984-05-24 | 1984-11-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-11-23 | 1988-05-24 | 1988-11-23 | $7700.00 | Window Closed / Lapsed |