US5028870A
Expired / Lapsed
US
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Sensor system method and apparatus for discrimination of metallic objects based on a variation in self inductance
Assignee: ENVIRONMENTAL PRODUCTS Corp A CORP OF
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Filing: 1989-04-18
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Granted: 1991-07-02
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Expires: 2009-04-18
Abstract
Abstract A device for discriminating metal in an object is provided including a sense coil and related circuitry, with variations in the self inductance of the sense coil being measured as the object is passed substantially through the center of the coil.
Inventors
- 👤 Michael A. Reed
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 06:56
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/08; G01V3/10; G01V3/101; G01V3/102
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
120 words
A device for discriminating metal in an object, comprising: a sense coil, said object being positioned substantially in the center of the said coil; means for generating an electrical signal having a predetermined frequency and applying said signal to said sense coil; means for measuring the self inductance of said sense coil as a function of the voltage across said coil; means for comparing said measured self inductance with a reference voltage to discriminate metal in said object; and first and second filter and rectifier circuits, said voltage across said coil being applied to said first circuit and said reference voltage being applied to said second circuit, outputs of said first and second circuits being applied to said comparing means.
Claim 2
Independent Claim
120 words
A device for discriminating metal in an object, comprising: a sense coil, said object being positioned substantially in the center of the said coil; means for generating an electrical signal having a predetermined frequency and applying said signal to said sense coil; means for measuring the self inductance of said sense coil as a function of the voltage across said coil; means for comparing said measured self inductance with a reference voltage to discriminate metal in said object; and first and second filter and rectifier circuits, said voltage across said coil being applied to said first circuit and said reference voltage being applied to said second circuit, outputs of said first and second circuits being applied to said comparing means.
Claim 3
Dependent Claim
42 words
A device according to claim 1, further comprising means for transporting said object substantially through the center of said sense coil, said measuring means measuring said self inductance when said object is positioned at a plurality of predetermine depositions within said coil.
Claim 4
Dependent Claim
14 words
A device according to claim 1, wherein said generating means is a crystal oscillator.
Claim 5
Dependent Claim
16 words
A device according to claim 1, wherein said reference voltage is generated by said generating means.
Claim 6
Dependent Claim
18 words
A device according to claim 1, wherein said first and second filter and rectifier circuits are substantially identical.
Claim 7
Dependent Claim
44 words
A device according to claim 1, wherein further comprising integration means for integrating a difference between the output of said second filter and rectifier circuit and said reference voltage and outputting an integrated signal, and for applying said integrated signal to said generating means.
Claim 8
Independent Claim
103 words
A device for discriminating metal in an object, comprising: a sense coil, said object being positioned substantially in the center of said coil; means for generating an electrical signal having a predetermined frequency and applying said signal to said sense coil, wherein said predetermined frequency is determined as a function of the metallic composition of said object, and wherein said predetermined frequency is substantially 4096 Hz; means for measuring the self inductance of said sense coil as a function of the voltage across said coil, and means for comparing said measured self inductance with a reference voltage to discriminate metal in said object.
Claim 9
Independent Claim
103 words
A device for discriminating metal in an object, comprising: a sense coil, said object being positioned substantially in the center of said coil; means for generating an electrical signal having a predetermined frequency and applying said signal to said sense coil, wherein said predetermined frequency is determined as a function of the metallic composition of said object, and wherein said predetermined frequency is substantially 4096 Hz; means for measuring the self inductance of said sense coil as a function of the voltage across said coil, and means for comparing said measured self inductance with a reference voltage to discriminate metal in said object.
Claim 10
Independent Claim
97 words
A method of discriminating metal in an object, comprising the steps of: positioning said object in substantially the center of a sense coil; generating an electrical signal having a predetermined frequency and applying said signal to said sense coil, wherein said predetermined frequency is determined as a function of the metallic composition of said object, and wherein said predetermined frequency is substantially 4096 Hz; measuring the self inductance of said sense coil as a function of the voltage across said coil; and comparing said measured self inductance with a reference voltage to discriminate metal in said object.
Claim 11
Independent Claim
97 words
A method of discriminating metal in an object, comprising the steps of: positioning said object in substantially the center of a sense coil; generating an electrical signal having a predetermined frequency and applying said signal to said sense coil, wherein said predetermined frequency is determined as a function of the metallic composition of said object, and wherein said predetermined frequency is substantially 4096 Hz; measuring the self inductance of said sense coil as a function of the voltage across said coil; and comparing said measured self inductance with a reference voltage to discriminate metal in said object.
Claim 12
Independent Claim
108 words
A method for discriminating metal in an object, comprising the steps of: positioning said object in substantially the center of a sense coil; generating an electrical signal having a predetermined frequency and applying said signal to said sense coil; measuring the self inductance of said sense coil as a function of the voltage across said coil; comparing said measured self inductance with a reference voltage to discriminate metal in said object; applying said voltage across said coil to a first filter and rectifier circuit; applying said reference voltage to a second filter and rectifier circuit; and applying outputs of said first and second circuits to said comparing means.
Claim 13
Independent Claim
108 words
A method for discriminating metal in an object, comprising the steps of: positioning said object in substantially the center of a sense coil; generating an electrical signal having a predetermined frequency and applying said signal to said sense coil; measuring the self inductance of said sense coil as a function of the voltage across said coil; comparing said measured self inductance with a reference voltage to discriminate metal in said object; applying said voltage across said coil to a first filter and rectifier circuit; applying said reference voltage to a second filter and rectifier circuit; and applying outputs of said first and second circuits to said comparing means.
Claim 14
Dependent Claim
49 words
The method as defined in claim 9, wherein said positioning step includes a step of transporting said object substantially through the center of said sense coil, and wherein said measuring step measures said self inductance when said object is positioned at a plurality of predetermined positions within said coil.
Claim 15
Dependent Claim
19 words
The method as defined in claim 9, wherein said generating step generates said electrical signal using a crystal oscillator.
Claim 16
Dependent Claim
15 words
The method as defined in claim 9, wherein said generating step generates said reference voltage.
Claim 17
Dependent Claim
19 words
The method as defined in claim 9, wherein said first and second filter and rectifier circuits are substantially identical.
Claim 18
Dependent Claim
43 words
The method as defined in claim 9, further comprising the steps of: integrating a difference between the output of said second filter and rectifier circuit and said reference voltage and outputting an integrated signal; and applying said integrated signal to said generating means.
Claim 19
Dependent Claim
13 words
A device according to claim 1, wherein said predetermined frequency is 4,150 Hz.
Claim 20
Dependent Claim
21 words
A method according to claim 9, wherein said generating step includes generating an electrical signal having a frequency of 4,150 Hz.
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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) | 1994-07-01 | 1994-12-31 | 1995-07-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-07-01 | 1998-12-31 | 1999-07-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-07-01 | 2002-12-31 | 2003-07-02 | $7700.00 | Window Closed / Lapsed |