US4449115A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus for detecting ferromagnetic material
Assignee: 3M Co
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Filing: 1983-08-02
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Granted: 1984-05-15
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Expires: 2003-08-02
Abstract
Abstract A convertor is used having an impedance responsive to the magnetic field intensity of the earth. The convertor may be coupled to a detector for monitoring the impedance of the convertor and generating a call signal responsive to the change in impedance. Generally, the impedance is primarily inductance and the detector is an oscillator using the convertor in a resonant circuit with a frequency monitor coupled to the detector. The convertor is an open magnetic structure having a non-linear BH curve biased by the earth's magnetic field. The open magnetic structure is a core of a highly permeable material which approaches saturation under the influence of the earth's magnetic field, with the axis of the core at least partially aligned with the magnetic flux lines of the earth's magnetic field, and a coil wound around the axis of the core.
Inventors
- 👤 Ralph J. Koerner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 03:59
CPC Classifications
G; G08; G08G; G08G1/00; G08G1/01; G08G1/042; G01; G01V; G01V3/00; G01V3/08; G01V3/10; G01V3/101
Claims Analysis
Total Claims: 46
Claim 1
Independent Claim
33 words
A passive device adapted to be connected to a detector for detecting a ferromagnetic material, said device comprising a non-linear impedance responsive to a change in the magnetic field intensity of the earth.
Claim 2
Dependent Claim
33 words
A passive device adapted to be connected to a detector for detecting a ferromagnetic material, said device comprising a non-linear impedance responsive to a change in the magnetic field intensity of the earth.
Claim 3
Dependent Claim
19 words
A device as in claim 1 wherein said change in impedance is primarily due to a change in inductance.
Claim 4
Dependent Claim
36 words
A device as in claim 2 wherein said converter comprises an open magnetic structure having a B-H curve with a non-linear portion biased by said magnetic field intensity near said non-linear portion of said B-H curve.
Claim 5
Dependent Claim
63 words
A device as in claim 3 wherein said open magnetic structure comprises: a core having an axis at least partially aligned with the magnetic flux lines of the earth's magnetic field, said core consisting essentially of a highly permeable material which approaches saturation under the influence of said magnetic field intensity; and a coil having a conductor surrounding said axis of said core.
Claim 6
Dependent Claim
116 words
A passive device adapted to be connected to a detector for detecting a ferromagnetic material in the influence of magnetic flux lines of the magnetic field intensity of the earth, comprising: a core having a major axis along its largest dimension and having orthogonal cross-sectional axes, said major axis of said core being at least partially aligned with the magnetic flux lines of the earth's magnetic field, said core consisting essentially of a permeable material which approaches saturation under the influence of said magnetic field intensity, said major axis being at least one hundred times greater than the smaller of said orthogonal cross-sectional axes; a coil having a conductor surrounding said major axis of said core.
Claim 7
Dependent Claim
116 words
A passive device adapted to be connected to a detector for detecting a ferromagnetic material in the influence of magnetic flux lines of the magnetic field intensity of the earth, comprising: a core having a major axis along its largest dimension and having orthogonal cross-sectional axes, said major axis of said core being at least partially aligned with the magnetic flux lines of the earth's magnetic field, said core consisting essentially of a permeable material which approaches saturation under the influence of said magnetic field intensity, said major axis being at least one hundred times greater than the smaller of said orthogonal cross-sectional axes; a coil having a conductor surrounding said major axis of said core.
Claim 8
Dependent Claim
22 words
A device as in claim 5 wherein said major axis of said core is larger than either of said orthogonal cross-sectional axes.
Claim 9
Dependent Claim
19 words
A device as in claim 5 wherein said core has a coercivity of less than said magnetic field intensity.
Claim 10
Dependent Claim
14 words
A device as in claim 7 wherein said coercivity is less than 0.2 oersteds.
Claim 11
Dependent Claim
15 words
A device as in claim 5 wherein said material is comprised of an iron-nickel alloy.
Claim 12
Dependent Claim
14 words
A device as in claim 9 wherein said iron-nickel alloy is approximately 80% nickel.
Claim 13
Dependent Claim
79 words
A passive apparatus for detecting a ferromagnetic material in a predetermined area comprising: conversion means having a non-linear impedance responsive to the magnetic field intensity of the earth for converting a change in said magnetic field intensity into a change in said impedance; and detection means coupled to said conversion means for monitoring said impedance and for generating a signal indicative of the detection of said ferromagnetic material in said predetermined area responsive to said change in said impedance.
Claim 14
Dependent Claim
79 words
A passive apparatus for detecting a ferromagnetic material in a predetermined area comprising: conversion means having a non-linear impedance responsive to the magnetic field intensity of the earth for converting a change in said magnetic field intensity into a change in said impedance; and detection means coupled to said conversion means for monitoring said impedance and for generating a signal indicative of the detection of said ferromagnetic material in said predetermined area responsive to said change in said impedance.
Claim 15
Dependent Claim
20 words
An apparatus as in claim 11 wherein said change in said impedance is primarily due to a change in inductance.
Claim 16
Dependent Claim
37 words
An apparatus as in claim 11 wherein said conversion means comprises an open magnetic structure having a B-H curve with a non-linear portion biased by said magnetic field intensity near said non-linear portion of said B-H curve.
Claim 17
Dependent Claim
61 words
An apparatus as in claim 13 wherein said open magnetic structure comprises: a core having an axis at least partially aligned with the magnetic flux lines of the earth's magnetic field consisting essentially of a highly permeable material which approaches saturation under the influence of said magnetic field intensity; and a coil having a conductor surrounding said axis of said core.
Claim 18
Dependent Claim
132 words
A passive apparatus for detecting a ferromagnetic material comprising: a core having a major axis along its largest dimension and having orthogonal cross-sectional axes, said major axis of said core being at least partially aligned with the magnetic flux lines of the earth's magnetic field, said core consisting essentially of a permeable material which approaches saturation under the influence of said magnetic field intensity, said major axis being much larger than the smaller of said orthogonal cross-sectional axes; a coil having a conductor surrounding said major axis of said core; said coil and said core having an impedance measured from said coil; and detection means coupled to said coil for monitoring impedance and for generating a signal indicative of the detection of said ferromagnetic material responsive to a change in said impedance.
Claim 19
Dependent Claim
132 words
A passive apparatus for detecting a ferromagnetic material comprising: a core having a major axis along its largest dimension and having orthogonal cross-sectional axes, said major axis of said core being at least partially aligned with the magnetic flux lines of the earth's magnetic field, said core consisting essentially of a permeable material which approaches saturation under the influence of said magnetic field intensity, said major axis being much larger than the smaller of said orthogonal cross-sectional axes; a coil having a conductor surrounding said major axis of said core; said coil and said core having an impedance measured from said coil; and detection means coupled to said coil for monitoring impedance and for generating a signal indicative of the detection of said ferromagnetic material responsive to a change in said impedance.
Claim 20
Dependent Claim
22 words
An apparatus as in claim 15 wherein said major axis of said core is longer than either of said orthogonal cross-sectional axes.
Claim 21
Dependent Claim
25 words
An apparatus as in claim 15 wherein said major axis is at least one hundred times greater than the smaller of said orthogonal cross-sectional axes.
Claim 22
Dependent Claim
19 words
An apparatus as in claim 17 wherein said core has a coercivity of less than said magnetic field intensity.
Claim 23
Dependent Claim
14 words
An apparatus as in claim 18 wherein said coercivity is less than 0.2 oerstads.
Claim 24
Dependent Claim
22 words
An apparatus as in claim 18 wherein said core is a strip of material wound on the inside of a nonmagnetic tube.
Claim 25
Dependent Claim
37 words
An apparatus as in claim 20 wherein said strip has a thickness of about 1 mil and a width of about 62 mils wound into a helix forming a wound length of about one and one-half inches.
Claim 26
Dependent Claim
15 words
An apparatus as in claim 17 wherein said material is comprised of an iron-nickel alloy.
Claim 27
Dependent Claim
14 words
An apparatus as in claim 22 wherein said iron-nickel alloy is approximately 80% nickel.
Claim 28
Dependent Claim
42 words
An apparatus as in claim 15 wherein said detection means comprises: an oscillator operatively coupled to said conversion means for oscillating at a frequency dependant on said impedance; and a detector operatively coupled to said oscillator for detecting changes in said frequency.
Claim 29
Dependent Claim
80 words
A passive apparatus for detecting a vehicle in a surveillance area of a roadway comprising: conversion means having a non-linear impedance responsive to the magnetic field intensity of the earth for converting changes in said magnetic field intensity into a change in said impedance; and detection means coupled to said conversion means for monitoring said impedance and for generating a signal indicative of the detection of said ferromagnetic material in said predetermined area responsive to said change in said impedance.
Claim 30
Dependent Claim
80 words
A passive apparatus for detecting a vehicle in a surveillance area of a roadway comprising: conversion means having a non-linear impedance responsive to the magnetic field intensity of the earth for converting changes in said magnetic field intensity into a change in said impedance; and detection means coupled to said conversion means for monitoring said impedance and for generating a signal indicative of the detection of said ferromagnetic material in said predetermined area responsive to said change in said impedance.
Claim 31
Dependent Claim
20 words
An apparatus as in claim 25 wherein said change in said impedance is primarily due to a change in inductance.
Claim 32
Dependent Claim
45 words
An apparatus as in claim 26 wherein said conversion means comprises an open magnetic structure having a B-H curve with a non-linear portion biased by magnetic field intensity near said non-linear portion biased by magnetic field intensity near said non-linear portion of said B-H curve.
Claim 33
Dependent Claim
139 words
A passive apparatus for detecting a vehicle in a surveillance area of a roadway comprising: a core having a major axis along its largest dimension and having orthogonal cross-sectional axes, said major axis of said core being at least partially aligned with the magnetic flux lines of the earth's magnetic field, said core consisting essentially of a permeable material which approaches saturation under the influence of said magnetic field intensity, said major axis being at 100 times the smaller of said orthogonal cross-sectional axes; a coil having a conductor surrounding said major axis of said core; said coil and said core having a impedance measured from said coil; and detection means coupled to said coil for monitoring said impedance and for generating a signal indicative of the detection of said ferromagnetic material responsive to a change in said impedance.
Claim 34
Dependent Claim
139 words
A passive apparatus for detecting a vehicle in a surveillance area of a roadway comprising: a core having a major axis along its largest dimension and having orthogonal cross-sectional axes, said major axis of said core being at least partially aligned with the magnetic flux lines of the earth's magnetic field, said core consisting essentially of a permeable material which approaches saturation under the influence of said magnetic field intensity, said major axis being at 100 times the smaller of said orthogonal cross-sectional axes; a coil having a conductor surrounding said major axis of said core; said coil and said core having a impedance measured from said coil; and detection means coupled to said coil for monitoring said impedance and for generating a signal indicative of the detection of said ferromagnetic material responsive to a change in said impedance.
Claim 35
Dependent Claim
21 words
An apparatus as in claim 28 wherein said major axis of said core is larger than either of said cross-sectional axes.
Claim 36
Dependent Claim
19 words
An apparatus as in claim 28 wherein said core has a coercivity of less than said magnetic field intensity.
Claim 37
Dependent Claim
14 words
An apparatus as in claim 30 wherein said coercivity is less than 0.2 oerstads.
Claim 38
Dependent Claim
22 words
An apparatus as in claim 28 wherein said core is a strip of material wound on the inside of a nonmagnetic tube.
Claim 39
Dependent Claim
37 words
An apparatus as in claim 32 wherein said strip has a thickness of about 1 mil and a width of about 62 mils wound into a helix forming a wound length of about one and one-half inches.
Claim 40
Dependent Claim
15 words
An apparatus as in claim 33 wherein said material is comprised of an iron-nickel alloy.
Claim 41
Dependent Claim
14 words
An apparatus as in claim 34 wherein said iron-nickel alloy is approximately 80% nickel.
Claim 42
Dependent Claim
31 words
An apparatus as in claim 28 wherein said change in said impedance is due to a decrease in said inductance as said vehicle arrives in said predetermined area of said roadway.
Claim 43
Dependent Claim
19 words
An apparatus as in claim 36 wherein said conversion means is located in vertical juxtaposition to said surveillance area.
Claim 44
Dependent Claim
28 words
An apparatus as in claim 28 wherein said change in said impedance is due to an increase in said inductance as said vehicle arrives in said surveillance area.
Claim 45
Dependent Claim
39 words
An apparatus as in claim 38 wherein said roadway has a pair of lanes each having a surveillance area located within each of said pair of lanes and wherein said conversion means is located between said pair of lanes.
Claim 46
Dependent Claim
46 words
An apparatus as in claim 28 wherein said detection means comprises: an oscillator operatively coupled to said conversion means for oscillating at a frequency dependent on said impedance of said conversion means; and a detector operatively coupled to said oscillator for detecting changes in said frequency.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-05-15 | 1987-11-14 | 1988-05-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-05-15 | 1991-11-14 | 1992-05-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-05-15 | 1995-11-14 | 1996-05-15 | $7700.00 | Window Closed / Lapsed |