US3609530A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic leakage field flaw detector with compensation for variation in spacing between magnetizer and test piece
Assignee: United Kingdom Atomic Energy Authority
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Filing: 1969-03-06
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Granted: 1971-09-28
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Expires: 1989-03-06
Abstract
Abstract A device for sensing magnetic discontinuties comprises a magnet for inducing magnetism in a sample, and a detector and amplifier for detecting the induced magnetism. A Hall effect crystal is included in the flux path between the magnet and the specimen. The Hall effect crystal is arranged to control the detector amplifier so as to nullify the effect of variations in the gap between magnet and specimen.
Inventors
- 👤 Alan Braid Johnson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 06:09
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/72; G01N27/82
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
119 words
A magnetic device for detecting defects in a specimen comprising a magnetic circuit formed in part by said specimen, magnetizing means included in said magnetic circuit for inducing magnetism in the magnetic circuit, signal generating means responsive to leakage magnetic flux from the specimen, said signal generating means being located to detect leakage magnetic flux from part of the specimen within said magnetic circuit, amplifier means for amplifying the signals from the signal generating means, and control means responsive to changes in magnetic flux in the said magnetic circuit for controlling the effective gain of said amplifier means, said control means comprising a Hall effect crystal located in the magnetic circuit formed by said magnetizing means and the specimen.
Claim 2
Dependent Claim
119 words
A magnetic device for detecting defects in a specimen comprising a magnetic circuit formed in part by said specimen, magnetizing means included in said magnetic circuit for inducing magnetism in the magnetic circuit, signal generating means responsive to leakage magnetic flux from the specimen, said signal generating means being located to detect leakage magnetic flux from part of the specimen within said magnetic circuit, amplifier means for amplifying the signals from the signal generating means, and control means responsive to changes in magnetic flux in the said magnetic circuit for controlling the effective gain of said amplifier means, said control means comprising a Hall effect crystal located in the magnetic circuit formed by said magnetizing means and the specimen.
Claim 3
Dependent Claim
94 words
A device as claimed in claim 1 wherein said magnetizing means comprises a magnet of the horseshoe type having magnetic poles, an airgap being defined between each of the magnetic poles of the magnet and the specimen, and said Hall effect crystal being located adjacent one of said magnetic poles to sense variations in the magnetic flux in the magnetic circuit due to changes in the airgap between the specimen and said one magnetic pole, said control means controlling the effective gain of the amplifier so as to nullify the effect of gap variations.
Claim 4
Dependent Claim
51 words
A device as claimed in claim 1 wherein said signal generating means comprises a magnetic tape recording head, the recording head together with the magnetizing means being moved relatively to the specimen, whereby the recording head generates a signal which is a measure of the leakage magnetic flux from the specimen.
Claim 5
Dependent Claim
15 words
A device as claimed in claim 1, wherein the magnetizing means is a permanent magnet.
Claim 6
Dependent Claim
27 words
A device as claimed in claim 1, wherein the signal generating means comprises a fixed signal source and a probe unit comprising a further Hall effect crystal.
Claim 7
Dependent Claim
127 words
A device as claimed in claim 5, wherein the probe unit comprises a stack of three Hall effect crystals which have output signal leads for carrying the output signals indicative of the magnitude of transverse magnetic field in which the respective Hall effect crystal is situated, the output signal leads of the two outside crystals being connected so that their signals add, the output signal leads of the center crystal being connected to means for doubling the signal amplitude, and the output from the said means for doubling the signal amplitude being connected to the joined output leads of the two outside crystals so as to subtract the doubled signal output of the center crystal from the sum of the signal outputs of the two outside crystals.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-09-27 | 1975-03-29 | 1975-09-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-09-27 | 1979-03-29 | 1979-09-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-09-27 | 1983-03-29 | 1983-09-28 | $7700.00 | Window Closed / Lapsed |