US3872380A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Metal detector distinguishing between different metals by using a bias circuit actuated by the phase shifts caused by the metals
Assignee: Individual
•
Filing: 1974-01-02
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Granted: 1975-03-18
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Expires: 1994-01-02
Abstract
Abstract A metal detector is described utilizing a transmitting and receiving coil for detecting the presence of metal objects positioned in the field of the coils. As oscillator is utilized to generate a signal to be transmitted by the first of the coils and the signals detected by the second of the coils is amplified and applied to an indicator circuit. The detected signal is also applied to a wave shaping circuit which, in turn, switches flipflop. The output of the oscillator is applied to a phase shifting circuit and a wave shaping circuit to shift the phase of the signal in a predetermined fashion. The shifted and shaped signal is applied to the above-mentioned flip-flop. The flip-flop output is applied to the indicator circuit. The type of metal present in the field of the coils will affect the amplitude and phase of the signal detected by the receiving coil. The phase change and the amplitude changes are thus detected and are utilized to determine the amplitude of the output of the indicator circuit which, in turn, is applied to a meter to present an indication of the type of metal being detected.
Inventors
- 👤 Robert F Gardiner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 17:40
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/08; G01V3/10; G01V3/104; G01V3/105; G01V3/107
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
257 words
A metal detector for detecting the presence of, and distinguishing between, certain types of metallic objects, comprising: an oscillator; a transmitting coil connected to said oscillator for transmitting electromagnetic signals generated by said oscillator; a receiving coil mounted in proximity to said transmitting coil for receiving electromagnetic signals transmitted by said transmitting coil, the received electromagnetic signals being changed in amplitude and phase when a metallic object is placed in the path of said electromagnetic signal transmitted by said transmitting coil; an indicator means for providing a reading to an operator when a metallic object has been detected, said indicator means including a meter and an indicator circuit for receiving electromagnetic signals from said receiving coil and providing a DC current to said meter in response thereto, said indicator circuit responsive to biasing to reduce said DC current and reduce the meter reading; means connected to said indicator means and to said receiving coil responsive to an increase in amplitude of said received signals for increasing the reading of said indicator means; first wave shaping means connected to said receiving coil for producing a first short duration pulse; a phase shift circuit connected to said oscillator for imposing a predetermined phase shift upon electromagnetic signals generated by said oscillator; a second wave shaping means connected to said phase shift circuit for producing a second short duration pulse; and means connected to receive said first and second short duration pulses and connected to said indicator circuit for applying the biasing thereto for decreasing the reading of said meter.
Claim 2
Dependent Claim
257 words
A metal detector for detecting the presence of, and distinguishing between, certain types of metallic objects, comprising: an oscillator; a transmitting coil connected to said oscillator for transmitting electromagnetic signals generated by said oscillator; a receiving coil mounted in proximity to said transmitting coil for receiving electromagnetic signals transmitted by said transmitting coil, the received electromagnetic signals being changed in amplitude and phase when a metallic object is placed in the path of said electromagnetic signal transmitted by said transmitting coil; an indicator means for providing a reading to an operator when a metallic object has been detected, said indicator means including a meter and an indicator circuit for receiving electromagnetic signals from said receiving coil and providing a DC current to said meter in response thereto, said indicator circuit responsive to biasing to reduce said DC current and reduce the meter reading; means connected to said indicator means and to said receiving coil responsive to an increase in amplitude of said received signals for increasing the reading of said indicator means; first wave shaping means connected to said receiving coil for producing a first short duration pulse; a phase shift circuit connected to said oscillator for imposing a predetermined phase shift upon electromagnetic signals generated by said oscillator; a second wave shaping means connected to said phase shift circuit for producing a second short duration pulse; and means connected to receive said first and second short duration pulses and connected to said indicator circuit for applying the biasing thereto for decreasing the reading of said meter.
Claim 3
Dependent Claim
35 words
The combination set forth in claim 1, wherein said means for increasing the reading of said indicator includes an amplifier for receiving, amplifying, and transmitting electromagnetic signals from said receiving coil to said indicator means.
Claim 4
Dependent Claim
23 words
The combination set forth in claim 1 wherein said means connected to receive said first and second short duration pulses is a flip-flop.
References Cited (Backward Citations)
US3020470A
Cited
US3676772A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-03-17 | 1978-09-16 | 1979-03-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-03-17 | 1982-09-16 | 1983-03-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-03-17 | 1986-09-16 | 1987-03-18 | $7700.00 | Window Closed / Lapsed |