Induction-type metal detector with increased scanning area capability
First Claim
1. An induction-type metal detector apparatus, comprising:
- a primary coil;
transmit circuit means connected to said primary coil for controllably outputting electromagnetic radiation therethrough;
a plurality of secondary coils, disposed within the vicinity of said primary coil, and having voltages induced therein by electromagnetic radiation from said primary coil;
means for establishing a predetermined reference voltage level;
receive circuit means, connected to said secondary coils, for detecting differences between voltage levels induced in said secondary coils and said predetermined reference voltage level, which difference is due to and indicative of the presence of metallic objects in the vicinity of said apparatus because such presence affects said electromagnetic radiation; and
support means for supporting said primary coil and said secondary coils substantially in a common plane with all secondary coils being disposed within the periphery of said primary coil, and in a mutually non-overlapping configuration.
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Accused Products
Abstract
A metal detector includes a detector head having a primary or transmit coil for the transmission of electromagnetic radiation therefrom, and having a plurality of secondary or receiving coils associated therewith for having voltages induced therein by transmissions from said primary coil. The presence of metallic objects within the detector head affects the voltage level induced in the secondary coils, a condition which may be detected as indicative of such presence of metallic objects. Each detector head preferably includes a primary coil about the periphery thereof, with a plurality of secondary coils, all in the same plane with the primary coil, situated axially in from the periphery of the detector head in a mutually non-overlapping configuration, preferably about the center of such detector head. A plurality of such detector heads may be supported in co-planar alignment by a common non-metallic support structure for scanning relatively larger areas at a time. The primary coil of each respective detector head may be sequentially pulsed and selectively spaced to avoid interference with adjacent detector heads, thereby avoiding certain inherent disadvantages in applying conventional single detector head frequency-dependent tuned coil technology to multiple head use in an integral metal detector system.
39 Citations
19 Claims
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1. An induction-type metal detector apparatus, comprising:
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a primary coil; transmit circuit means connected to said primary coil for controllably outputting electromagnetic radiation therethrough; a plurality of secondary coils, disposed within the vicinity of said primary coil, and having voltages induced therein by electromagnetic radiation from said primary coil; means for establishing a predetermined reference voltage level; receive circuit means, connected to said secondary coils, for detecting differences between voltage levels induced in said secondary coils and said predetermined reference voltage level, which difference is due to and indicative of the presence of metallic objects in the vicinity of said apparatus because such presence affects said electromagnetic radiation; and support means for supporting said primary coil and said secondary coils substantially in a common plane with all secondary coils being disposed within the periphery of said primary coil, and in a mutually non-overlapping configuration. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A multi-head metal detector device, comprising:
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an array of plural transmit-sense heads, each head having respective transmit and sense winding portions; transmit circuit means for controllably pulsing at different times respective transmit winding portions for each of said heads; sensing circuit means for obtaining, processing, and outputting signals from the sense winding portions of each respective head induced therein by their respective transmit winding portions; and comparator circuit means for comparing said signals output from said sensing circuit means for each of said respective heads with a predetermined reference signal, and for indicating differences of a predetermined amount therebetween, which differences are caused by the presence of metal objects within the vicinity of each respective head resulting in partial disruption of transmissions between a given transmit winding portion and its respective head sense winding portion; wherein each of said heads is substantially planar, and has said transmit winding portion thereof generally about its periphery, with said sense winding portion thereof within said periphery; and
wherein said sense winding portion includes at least four respective sensing windings disposed in a mutually non-overlapping configuration within the plane of their respective head. - View Dependent Claims (11, 12, 13)
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14. A multi-coil, multi-head pulse induction metal detection system, comprising:
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generally non-metallic support structure for supporting an array of a plurality of substantially planar detector heads in co-planar alignment, each such detector head having a primary coil disposed within its plane and about the periphery thereof for transmitting signals therefrom upon being pulsed, and a plurality of secondary coils also disposed within its plane for receiving signals transmitted from its respective primary coil, said secondary coils being symmetrically supported about the center of their respective detector head axially inward from its periphery and without overlapping one another; sequential transmit means for sequentially pulsing the primary coil of each respective detector head in discrete pulse time periods so that there is no overlap of pulse time periods for the respective heads; and secondary coil sensor means, operatively associated with said detector heads, for indicating differences between signals received by secondary coils of each respective detector head and a predetermined reference signal, such differences indicating the presence of metallic objects relatively near such detection head; wherein said co-planar alignment of said detector heads is generally in a 1×
n array of such heads, with n being the number of such heads, whereby in general a relatively large area may be scanned at a given time across the n width of said array. - View Dependent Claims (15, 16, 17, 18, 19)
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Specification