Apparatus and method for locating metal objects and minerals in the ground with return of energy from transmitter coil to power supply
First Claim
1. In apparatus for locating a metal object or mineral in the ground:
- a searchcoil adapted to be moved over the surface of the earth, a transmitter connected to the searchcoil for energizing the coil with a voltage of generally rectangular waveform to produce a magnetic field which alternately builds up and collapses, a receiver connected to the searchcoil responsive to signals induced in the searchcoil by metal objects or minerals in the magnetic field, a power supply with an energy storage element for supplying operating power to the transmitter, and means interconnecting the power supply and the searchcoil for returning energy from the searchcoil to the energy storage element during collapse of the magnetic field.
2 Assignments
0 Petitions
Accused Products
Abstract
Eddy current type metal detector for locating and distinguishing between different classes of metal objects, and geophysical apparatus for measuring various properties of soil and rock. A nonsinusoidal transmit voltage energizes a transmit coil which transmits a nonsinusoidal alternating magnetic field into the soil, rocks or metal objects to be located. Distortion of the magnetic field caused by the presence of these materials in the field induces corresponding voltage waveforms in a receive coil. The induced waveform is analyzed in order to deduce certain electrical properties of the materials, or in order to distinguish buried metal objects from the soil in which they are buried. The circuit which energizes the transmit coil returns energy from the collapse of the magnetic field to the power supply, minimizing the power consumption of the apparatus.
52 Citations
43 Claims
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1. In apparatus for locating a metal object or mineral in the ground:
- a searchcoil adapted to be moved over the surface of the earth, a transmitter connected to the searchcoil for energizing the coil with a voltage of generally rectangular waveform to produce a magnetic field which alternately builds up and collapses, a receiver connected to the searchcoil responsive to signals induced in the searchcoil by metal objects or minerals in the magnetic field, a power supply with an energy storage element for supplying operating power to the transmitter, and means interconnecting the power supply and the searchcoil for returning energy from the searchcoil to the energy storage element during collapse of the magnetic field.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. In apparatus for locating a metal object or mineral in the ground:
- a searchcoil adapted to be moved over the surface of the earth, a power supply having positive and negative terminals, a transmitter having controlled switching elements connected between a first end of the searchcoil and the power supply terminals, energy storage elements connected between the second end of the searchcoil and the power supply terminals, means for applying a timing signal of generally rectangular waveform to the control inputs of the switching elements to condition the switching elements to alternately connect the first end of the searchcoil to the positive and negative power supply terminals and thereby apply a voltage of generally rectangular waveform to the searchcoil to produce a magnetic field which alternately builds up and collapses, means for delivering energy from the searchcoil to the energy storage elements upon collapse of the magnetic field, and a receiver for monitoring the searchcoil for signals induced therein by metal objects or minerals in the magnetic field.
- View Dependent Claims (17, 18, 19, 20, 21, 22)
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23. In apparatus for locating a metal object or mineral in the ground:
- a searchcoil having separate transmitting and receiving windings arranged in such manner that signals are not induced directly in the receiving winding from the transmitting winding, a power supply having positive and negative terminals, a transmitter having switching elements connected between a first end of the transmitting winding and the power supply terminals, energy storage elements connected between the second end of the transmitting winding and the power supply terminals, means for applying a generally rectangular timing signal which alternates between first and second levels to the switching elements to alternately actuate the switching elements to connect the first end of the transmitting winding to the positive and negative terminals of the power supply and thereby apply a voltage of generally rectangular waveform to the searchcoil to produce a magnetic field which alternately builds up and collapses, means for delivering energy from the transmitting winding to the energy storage elements upon collapse of the magnetic field, and a receiver connected to the receiving winding for continuously monitoring said winding for signals induced therein by metal objects or minerals in the magnetic field.
- View Dependent Claims (24, 25, 26)
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27. In apparatus for locating a metal object or mineral in the ground:
- a searchcoil having separate transmitting and receiving windings arranged in such manner that signals are not induced directly in the receiving winding by the transmitting winding, a power supply having positive and negative terminals, a transmitter having switching elements connected between the second end of the transmitting winding and the power supply terminals, means for applying a timing signal comprising a series of temporally separated pulses of alternate level to the switching elements to alternately actuate the switching elements to connect the first end of the transmitting winding to the positive and negative terminals of the power supply to produce a magnetic field which alternately builds up and collapses, means for delivery energy from the transmitting winding to the energy storage elements during the time intervals between successive ones of the temporally separated pulses, and a receiver connected to the receiving winding with means for monitoring the receiving winding for signals induced therein only during the time intervals between the temporally separated pulses.
- View Dependent Claims (28, 29, 30, 31)
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32. In a method for locating a metallic object or a mineral in the ground, the steps of:
- moving a searchcoil over the surface of the earth, energizing the searchcoil with a voltage of generally rectangular waveform to produce a magnetic field which alternately builds up and collapses, monitoring the searchcoil for signals induced therein by metallic objects or minerals in the magnetic field, supplying operating power to the searchcoil from a power supply having an energy storage element, and returning energy from the searchcoil to the energy storage element during collapse of the magnetic field.
- View Dependent Claims (33, 34, 35)
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36. In apparatus for locating metal and detecting minerals:
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an inductive nonresonant transmitter coil; a D.C. power supply having positive and negative output terminals and capacitive energy storage means connected between said output terminals; said storage means having sufficient electrical capacitance to store the energy of flyback currents from the transmitter coil; low impedance means coupling a first end of the transmitter coil to the output terminals of the power supply; positive and negative switching means for coupling a second end of the transmitter coil to the positive and negative output terminals of the power supply, respectively; timing means for actuating the positive and negative switching means alternately at predetermined times to cause a nonsinusoidal driving current of alternating polarity to flow in the transmitter coil and produce a nonsinusoidal alternating magnetic field in the vicinity of the transmitter coil; positive and negative current steering means coupling the second end of the transmitter coil to the power supply output terminals for steering positive and negative flyback currents from the transmitter coil to the positive and negative power supply output terminals, respectively, said flyback currents occurring when the positive switching means for the negative switching means is turned off allowing the magnetic field to collapse; receiver means responsive to variations in the magnetic field caused by the presence of metal or minerals within the magnetic field; and indicator means responsive to the receiver means for indicating the presence of the metal or minerals within the magnetic field. - View Dependent Claims (37, 38, 39, 40, 41, 42, 43)
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Specification