Method and apparatus for generating alternating magnetic fields to produce harmonic signals from a metallic strip
First Claim
1. Apparatus for generating an alternating magnetic field in a detection zone to produce harmonic signals from a metallic strip therein, comprising:
- a first and a second coil of conductive material, each of said coils configured to have a plurality of essentially linear segments, a first group of said segments having each one thereof oriented at an acute angle relative to horizontal and a second group of said segments each one thereof oriented essentially vertically, said first and said second coils spaced apart to form the detection zone therebetween,means for producing an alternating current in said first coil, andmeans for producing in said second coil an alternating current which alternates between being in-phase and out-of-phase with the current in said first coil.
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Accused Products
Abstract
A system (10) produces an alternating magnetic field in a detection zone between a pair of doorways (346, 348) to produce harmonic signals from a marker (330) when the marker (330) is activated and located in the detection zone. Each of the doorways (346, 348) is provided with a trapezoidally shaped coil which is in a resonant circuit. The coils in the doorways (346, 348) are driven at periodic time periods with in-phase currents to produce aiding magnetic fields perpendicular to doorways in the detection zone. At alternate time periods the coils in the doorways are driven with out-of-phase signals which produce opposing magnetic fields perpendicular to the doorways (346, 348) and aiding magnetic fields parallel to the planes of the doorways. The magnetic fields thus produced in the detection zone cause the marker (330) when activated to produce harmonic signals despite the orientation of the marker (330) as it passes through the detection zone.
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Citations
11 Claims
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1. Apparatus for generating an alternating magnetic field in a detection zone to produce harmonic signals from a metallic strip therein, comprising:
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a first and a second coil of conductive material, each of said coils configured to have a plurality of essentially linear segments, a first group of said segments having each one thereof oriented at an acute angle relative to horizontal and a second group of said segments each one thereof oriented essentially vertically, said first and said second coils spaced apart to form the detection zone therebetween, means for producing an alternating current in said first coil, and means for producing in said second coil an alternating current which alternates between being in-phase and out-of-phase with the current in said first coil. - View Dependent Claims (2, 3, 4, 5, 6)
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7. Apparatus for generating an alternating magnetic field in a detection zone to produce harmonic signals from a metallic strip therein, comprising:
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a first and a second coil positioned parallel and spaced apart forming the detection zone therebetween, each of said coils trapezoidally shaped and having elongate sections thereof oriented at an acute angle from horizontal and the remaining sections thereof oriented vertically, means for producing an alternating current in said first coil, and means for producing in said second coil an alternating current which alternates between being in-phase and out-of-phase with the current in said first coil. - View Dependent Claims (8)
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9. A method for generating an alternating magnetic field in a detection zone to produce harmonic signals from a metallic strip therein, comprising the steps of:
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positioning first and second coils in vertical planes and parallel at spaced apart locations to define the detection zone therebetween, each of said coils configured to have a plurality of essentially linear segments, a first group of said segments have each one thereof oriented at an acute angle relative to horizontal and a second group of said segments each one thereof oriented essentially vertically, producing an alternating current in said first coil, and producing in said second coil an alternating current which alternates between being in-phase and out-of-phase with the current in said first coil.
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10. A method for generating an alternating magnetic field in a detection zone to produce harmonic signals from a metallic strip therein, comprising the steps of:
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positioning first and second coils in vertical planes and parallel at spaced apart locations to define the detection zone therebetween, each of said coils being trapezoidally shaped and having a greater horizontal dimension than vertical dimensions, producing an alternating current in said first coil, and producing in said second coil an alternating current which alternates between being in-phase and out-of-phase with the current in said first coil.
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11. A method for generating an alternating magnetic field in a detection zone to produce harmonic signals from a metallic strip therein, comprising the steps of:
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positioning first and second coils vertically and spaced apart to define the detection zone therebetween, said coils having elongate segments thereof oriented at an acute angle relative to horizontal, driving in-phase alternating currents through said coils to produce aiding horizontal magnetic field from said coils during first periodic time periods, said aiding horizontal magnetic fields perpendicular to said coils, and driving out-of-phase alternating currents through said coils to produce opposing horizontal magnetic fields perpendicular to said coils and aiding magnetic fields parallel to the plane of said coils during second periodic time periods occurring alternately with said first periodic time periods.
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Specification