US3911389A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic gradient vehicle detector
Assignee: United States Department of Transportation
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Filing: 1974-03-21
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Granted: 1975-10-07
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Expires: 1994-03-21
Abstract
Abstract A metallic object detection apparatus is disclosed. The detection apparatus comprises a transmitter which radiates electromagnetic energy to a receiving means which has a substantially zero voltage induced therein when a metallic object is not magnetically coupled to the transmitter and the receiving means. When a metallic object becomes magnetically coupled to the electromagnetic field radiating from the transmitter, eddy currents are induced in the metallic structure of the metallic object which in turn induce a non zero voltage within the receiving means. The transmitter is constructed from a nondistributed element which produces a dipole like electromagnetic field. The output signal produced by the receiving means is amplified and applied to either a phase responsive and/or amplitude responsive indicating means to signal when an object has caused the inducement of a non zero voltage in the receiving means.
Inventors
- 👤 Milton K Mills
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 03:58
CPC Classifications
G; G08; G08G; G08G1/00; G08G1/01; G08G1/042; G06; G06V; G06V10/00; G06V10/20; G06V10/255
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
137 words
In an object detection system of the type which senses metallic structure of objects, the combination comprising: an alternating current generator comprising oscillator means having a predetermined oscillation frequency and constant current amplifier means; a non-distributed element transmitter radiating electromagnetic energy at the predetermined frequency, said transmitter being electrically coupled to said alternating current generator; receiving means being electromagnetically coupled to said transmitter, said receiving means producing a substantially zero magnitude output signal when a metallic object is not magnetically coupled with said receiving means and said transmitter and producing a non-zero level output signal in response to eddy currents induced in a metallic object magnetically coupled with said receiver; and indicating means responsive to the output signal produced by said receiving means for signalling when a non zero output signal is produced by said receiving means.
Claim 2
Dependent Claim
137 words
In an object detection system of the type which senses metallic structure of objects, the combination comprising: an alternating current generator comprising oscillator means having a predetermined oscillation frequency and constant current amplifier means; a non-distributed element transmitter radiating electromagnetic energy at the predetermined frequency, said transmitter being electrically coupled to said alternating current generator; receiving means being electromagnetically coupled to said transmitter, said receiving means producing a substantially zero magnitude output signal when a metallic object is not magnetically coupled with said receiving means and said transmitter and producing a non-zero level output signal in response to eddy currents induced in a metallic object magnetically coupled with said receiver; and indicating means responsive to the output signal produced by said receiving means for signalling when a non zero output signal is produced by said receiving means.
Claim 3
Dependent Claim
77 words
In an object detection system as recited in claim 1 wherein said receiving means comprises at least one pair of series connected receiving coils wound in magnetic phase opposition to each other to produce a zero magnitude output signal when a metallic object is not magnetically coupled with said transmitter and said coils and producing a non zero level output signal when eddy currents induced in the object are magnetically coupled with said transmitter and said coils.
Claim 4
Dependent Claim
49 words
In an object detection system as recited in claim 2 further comprising: a triaxial transmission line electrically coupling said transmitter and said alternating generator; a triaxial transmission line electrically coupling said receiving means with said indicating means and; separate electrostatic shielding means enclosing said transmitter and said receiving means.
Claim 5
Dependent Claim
53 words
In an object detection system as recited in claim 3 further comprising: a longitudinally slotted magnetic shield disposed around the section of said triaxial transmission line coupled between said receiving means and said indication means which is located closest to said transmitter to minimize the induction of interference in said triaxial transmission line.
Claim 6
Dependent Claim
40 words
In an objection detection system as recited in claim 2 wherein each coil of said at least one pair of receiving coils has its axis substantially parallel to the other coils within said at least one pair of receiving coils.
Claim 7
Dependent Claim
162 words
In an object detection system as recited in claim 2 wherein said indicating means comprises: a phase detector having two inputs and an output, the first input of said phase detector being coupled to said receiving means, said second input being coupled to an output of said alternating current generator; a threshold detection circuit having an input and an output, the input being coupled to the output of said phase detector, said threshold circuit producing an output signal of a first level when the level of the signal of said phase detector is below the threshold of said detection circuit and producing an output signal of a second level when the level of the signal of said phase detector is above the threshold of said detection circuit; and a relay having an input and an output, said input being coupled to the output of said threshold detector, the output of said relay driver being adapted to be connected to a signalling device.
Claim 8
Dependent Claim
131 words
In an object detection system as recited in claim 2 wherein said indicating means comprises: a threshold detection circuit having an input and an output, said input being coupled to the output of said receiving means, said threshold circuit producing an output signal of a first level when the level of the output signal produced by said receiving means is below the threshold of said detection circuit and producing an output signal of a second level when the level of the output signal produced by said receiving means is above the threshold of said detection circuit; and a relay having an input and an output, said input being coupled to the output of said threshold detector, the output of said relay driver being adapted to be connected to a signalling device.
Claim 9
Dependent Claim
41 words
An objecT detection device as recited in claim 4 wherein said object detection device is buried in the pavement of a roadway, said object detection device having a longitudinal axis oriented transverse to the direction of traffic flow of the roadway.
Claim 10
Dependent Claim
95 words
In an object detection device as recited in claim 2 wherein each of said at least one pair of series connected receiving coils has a distributed capacitance, said coil of said at least one pair of coils which is disposed closest to said transmitter comprising an RF choke, said coil disposed farthest from said transmitter having a ferrite core, said series connection of receiving coils having a pair of terminals with said terminals located closest to said receiving coil disposed farthest from said transmitter, and said transmitter comprising a coil and an associated ferrite core.
Claim 11
Dependent Claim
52 words
In an object detection system as recited in claim 3 further comprising: impedance matching means coupled between said transmitter and output terminals of said triaxial cable at said transmitter; and impedance matching means coupled between output terminals of said receiving means and terminals of said triaxial transmission line at said receiving means.
Claim 12
Dependent Claim
25 words
An object detection system as recited in claim 1 wherein said electromagnetic energy is radiated from said transmitter in a dipole like spatial field pattern.
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) | 1978-10-06 | 1979-04-07 | 1979-10-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-10-06 | 1983-04-07 | 1983-10-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-10-06 | 1987-04-07 | 1987-10-07 | $7700.00 | Window Closed / Lapsed |