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US 5,432,444 AGranted
Inspection device having coaxial induction and exciting coils forming a unitary coil unit
AssigneeKaisei Engineer Co., Ltd.
InventorsKazuhiko Yasohama, Hiroaki Kohama, Hirofumi Takahashi
Life of this patent
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Abstract
An inspection device has an exciting coil for generating an electromagnetic field and an induction coil which are integrally connected to each other a coaxial relation so as to induce mutual inductance in the induction coil by the electromagnetic field. The mutual inductance caused in the induction coil varies with a given object to be inspected which is present in the electromagnetic field. The object can be inspected by analyzing the change in inductance.
Claims5
A device for inspecting an object according to a change in electromagnetic induction, comprising:
- a unitary detection coil unit having an inspection path extending therethrough through which the object to be tested is passed and consisting essentially of a first coil structure containing an exciting coil which is responsive to an alternating current applied thereto to generate an electromagnetic field that varies according to the object as the object is passed through said inspection path, and a second coil structure containing an induction coil which directly receives said electromagnetic field generated by said exciting coil and in which an electromotive current is induced responsive to said electromagnetic field generated by said exciting coil, said electromotive current denoting the electromagnetic induction of said unitary detection coil unit;
- and
- a decision unit coupled to said induction coil for receiving said electromotive current induced in said induction coil, for comparing said electromotive current with a predetermined reference value to obtain a comparison result, and for detecting an abnormality in the object to be tested according to the comparison result,
- wherein said second coil structure is directly fixed to said first coil structure to form said unitary detection coil unit, and wherein one of said induction coil and said exciting coil is coaxially wound around the other of said induction coil and said exciting coil, and wherein said exciting coil contained by said first coil structure is electrically insulated from said induction coil contained by said second coil structure,
- wherein said first coil structure is cylindrical having an inner peripheral surface and an outer peripheral surface, said inner peripheral surface of said first coil structure surrounding said inspection path, and said second coil structure is directly fixed to said first coil structure along said outer peripheral surface of said first coil structure such that said induction coil is located coaxially around said exciting coil.
2 more elements
A device for inspecting an object according to a change in electromagnetic induction, comprising:
- a unitary detection coil unit having an inspection path extending therethrough through which the object to be tested is passed and consisting essentially of a first coil structure containing an exciting coil which is responsive to an alternating current applied thereto to generate an electromagnetic field that varies according to the object as the object is passed through said inspection path, and a second coil structure containing an induction coil which directly receives said electromagnetic field generated by said exciting coil and in which an electromotive current is induced responsive to said electromagnetic field generated by said exciting coil, said electromotive current denoting the electromagnetic induction of said unitary detection coil unit;
- and
- a decision unit coupled to said induction coil for receiving said electromotive current induced in said induction coil, for comparing said electromotive current with a predetermined reference value to obtain a comparison result, and for detecting an abnormality in the object to be tested according to the comparison result,
- wherein said second coil structure is directly fixed to said first coil structure to form said unitary detection coil unit, and wherein one of said induction coil and said exciting coil is coaxially wound around the other of said induction coil and said exciting coil, add wherein said exciting coil contained by said first coil structure is electrically insulated from said induction coil contained by said second coil structure,
- wherein said first coil structure is cylindrical having an inner peripheral surface and an outer peripheral surface, and said second coil structure is directly fixed to said first coil structure along said inner peripheral surface of said first coil structure such that said exciting coil is located coaxially around said induction coil, an inner peripheral surface of said second coil structure surrounding said inspection path.
2 more elements
Dependencies are inferred from the claim text.