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US4818944A
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Magnetic locating and tracing system and method using dual-antenna transmitter to distinguish between concealed adjacent objects
Assignee: Schonstedt Instrument Co LLC
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Filing: 1987-05-06
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Granted: 1989-04-04
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Expires: 2007-05-06
Abstract
Abstract Locating and tracing of a concealed, elongated, conductive object, such as a buried pipe or cable, is enhanced, when a second such object is adjacent to the first, by employing a transmitter having a pair of antennae that induce distinguishable currents in the respective objects. A receiver movable with respect to the transmitter and with respect to the objects produces an output signal dependent upon the sensing of fields associated with both currents. The position of the transmitter relative to the objects is adjusted to optimize the output signal.
Inventors
- 👤 John B. Rippingale
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-10 01:26
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/02; G01V3/06
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
98 words
A system for locating at least one of a pair of concealed, elongated, conductive, adjacent objects, comprising, in combination, a transmitter and a receiver, said transmitter having means including a pair of spaced antennae for generating electromagnetic fields coupled to said objects for inducing a pair of distinguishable alternating currents in said objects, respectively said receiver being movable relative to said transmitter and to said objects, having means for sensing magnetic fields associated with said currents, respectively, and having means for producing an output signal dependent upon the sensing of both of said fields associated with said currents.
Claim 2
Independent Claim
98 words
A system for locating at least one of a pair of concealed, elongated, conductive, adjacent objects, comprising, in combination, a transmitter and a receiver, said transmitter having means including a pair of spaced antennae for generating electromagnetic fields coupled to said objects for inducing a pair of distinguishable alternating currents in said objects, respectively said receiver being movable relative to said transmitter and to said objects, having means for sensing magnetic fields associated with said currents, respectively, and having means for producing an output signal dependent upon the sensing of both of said fields associated with said currents.
Claim 3
Dependent Claim
14 words
A system in accordance with claim 1, wherein said currents have different carrier frequencies.
Claim 4
Dependent Claim
16 words
A system in accordance with claim 1, wherein said currents are pulsed at different pulsation rates.
Claim 5
Dependent Claim
19 words
A system in accordance with claim 1, wherein said currents have the same carrier frequency but different modulation frequencies.
Claim 6
Dependent Claim
25 words
A system in accordance with claim 1, wherein said output signal producing means comprises means for producing a beat frequency signal related to said currents.
Claim 7
Dependent Claim
17 words
A system in accordance with claim 1, wherein said antennae are separated horizontally by about 3-5 feet.
Claim 8
Dependent Claim
49 words
A system in accordance with claim 1, wherein said sensing means comprises a coil for sensing both of said magnetic fields associated with said currents and for producing a combined signal, and wherein said output signal producing means produces said output signal only when said combined signal is present.
Claim 9
Dependent Claim
42 words
A system in accordance with claim 7, wherein said currents have different carrier frequencies and said combined signal has components corresponding to said different carrier frequencies, respectively, and wherein said output signal producing means produces a beat frequency signal from said components.
Claim 10
Dependent Claim
42 words
A system in accordance with claim 7, wherein said currents have different pulsation rates and said combined signal has components corresponding to said different pulsation rates, respectively, and wherein said output signal producing means produces a beat frequency signal from said components.
Claim 11
Dependent Claim
42 words
A system in accordance with claim 7, wherein said currents have different modulation frequencies and said combined signal has components corresponding to said different modulation frequencies, respectively, and wherein said output signal producing means produces a beat frequency signal from said components.
Claim 12
Dependent Claim
30 words
A system in accordance with claim 1, wherein said output signal producing means produces said output signal only upon the sensing of both of said fields associated with said currents.
Claim 13
Independent Claim
77 words
A method of locating at least one of a pair of concealed, elongated, conductive, adjacent objects, comprising, producing in said objects a pair of distinguishable alternating currents, respectively, moving with respect to said objects a receiver sensitive to a pair of magnetic fields associated with said currents, respectively, and producing an output signal from said receiver dependent upon the sensing by said receiver of both of said fields, and only when both of said fields are present.
Claim 14
Independent Claim
77 words
A method of locating at least one of a pair of concealed, elongated, conductive, adjacent objects, comprising, producing in said objects a pair of distinguishable alternating currents, respectively, moving with respect to said objects a receiver sensitive to a pair of magnetic fields associated with said currents, respectively, and producing an output signal from said receiver dependent upon the sensing by said receiver of both of said fields, and only when both of said fields are present.
Claim 15
Dependent Claim
30 words
A method in accordance with claim 12, wherein said output signal is produced in response to a beat frequency signal generated by the sensing of both of said magnetic fields.
Claim 16
Dependent Claim
20 words
A method in accordance with claim 12 wherein said currents are induced in said objects by a pair of antennae.
Claim 17
Dependent Claim
14 words
A method in accordance with claim 12, wherein said currents have different carrier frequencies.
Claim 18
Dependent Claim
16 words
A method in accordance with claim 12 wherein said currents are pulsed at different pulsation rates.
Claim 19
Dependent Claim
19 words
A method in accordance with claim 12 wherein said currents have the same carrier frequency modulated at different frequencies.
Claim 20
Dependent Claim
27 words
A method in accordance with claim 12 wherein said receiver is moved back and forth transversely of said objects and is also moved longitudinally of said objects.
Claim 21
Dependent Claim
49 words
A method in accordance with claim 18, wherein said output signal from said receiver is produced by sensing said magnetic fields in a sensor coil, producing a combined signal from said coil that includes components corresponding to said magnetic fields, and producing a beat frequency signal from said components.
Claim 22
Dependent Claim
14 words
A method in accordance with claim 19, wherein said components have different carrier frequencies.
Claim 23
Dependent Claim
14 words
A method in accordance with claim 19, wherein said components have different pulsation rates.
Claim 24
Dependent Claim
14 words
A method in accordance with claim 19 wherein said components have different modulation frequencies.
Claim 25
Independent Claim
103 words
A method of locating at least one of a pair of concealed, elongated, conductive, adjacent objects, comprising, producing in said objects a pair of distinguishable alternating currents, respectively, moving with respect to said objects as receiver sensitive to a pair of magnetic fields associated with said currents, respectively, and producing an output signal from said receiver dependent upon the sensing by said receiver of both of said fields, said currents being inducted in said objects by a transmitter that is positioned over said objects and that is provided with a pair of spaced antennae and said receiver being moved relative to said transmitter.
Claim 26
Independent Claim
103 words
A method of locating at least one of a pair of concealed, elongated, conductive, adjacent objects, comprising, producing in said objects a pair of distinguishable alternating currents, respectively, moving with respect to said objects as receiver sensitive to a pair of magnetic fields associated with said currents, respectively, and producing an output signal from said receiver dependent upon the sensing by said receiver of both of said fields, said currents being inducted in said objects by a transmitter that is positioned over said objects and that is provided with a pair of spaced antennae and said receiver being moved relative to said transmitter.
Claim 27
Dependent Claim
29 words
A method in accordance with claim 23, wherein the position of said transmitter relative to said objects is adjusted to optimize the sensing of said fields by said receiver.
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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) | 1992-04-03 | 1992-10-03 | 1993-04-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-04-03 | 1996-10-03 | 1997-04-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-04-03 | 2000-10-03 | 2001-04-04 | $7700.00 | Window Closed / Lapsed |