Rotating magnetic field device for detecting cracks in metal
First Claim
1. Eddy current inspection apparatus for detecting cracks in a metallic article having a flat surface, comprising:
- (a) a central magnetic core extending longitudinally along a central axis, the central core having two ends designated the first and second ends, respectively;
(b) at least three L-shaped peripheral magnetic cores,(i) each peripheral core having first and second leg portions joined to form the two legs of an L-shaped member, the first leg portion being magnetically coupled to the first end of the central core and extending radially away from the central axis, and the second leg portion extending parallel to the central axis and terminating in a foot, and(ii) the feet of each of the peripheral cores and the second end of the central core being substantially coplanar;
(c) a drive coil wound on each of the peripheral cores;
(d) means for electrically energizing each drive coil with an alternating-current signal, the signals applied to the different drive coils having at least two different electrical phases so as to produce in the metallic article, when the feet of the peripheral cores are positioned abutting the surface of the article, a magnetic field rotating about the central axis;
(e) a sensor coil wound on the central core; and
(f) means for detecting the voltage appearing across the sensor coil, the value of the voltage indicating whether a crack exists in the metallic article.
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Accused Products
Abstract
An eddy current type of inspection device having input signal coils on cores radially arranged around a center and having outer ends of the cores which rest against a surface of a metal assembly to be tested for defects. The input coils are energized by an AC signal of different phase for each respective coil so that a rotating magnetic field is produced in the assembly being tested. An output sensor coil is mounted at the center of the tester immediately adjacent to such test surface for coupling out a signal induced from the rotating field. A specific embodiment has three coils physically spaced 120° apart, for energizing by a three-phase power source.
51 Citations
14 Claims
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1. Eddy current inspection apparatus for detecting cracks in a metallic article having a flat surface, comprising:
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(a) a central magnetic core extending longitudinally along a central axis, the central core having two ends designated the first and second ends, respectively; (b) at least three L-shaped peripheral magnetic cores, (i) each peripheral core having first and second leg portions joined to form the two legs of an L-shaped member, the first leg portion being magnetically coupled to the first end of the central core and extending radially away from the central axis, and the second leg portion extending parallel to the central axis and terminating in a foot, and (ii) the feet of each of the peripheral cores and the second end of the central core being substantially coplanar; (c) a drive coil wound on each of the peripheral cores; (d) means for electrically energizing each drive coil with an alternating-current signal, the signals applied to the different drive coils having at least two different electrical phases so as to produce in the metallic article, when the feet of the peripheral cores are positioned abutting the surface of the article, a magnetic field rotating about the central axis; (e) a sensor coil wound on the central core; and (f) means for detecting the voltage appearing across the sensor coil, the value of the voltage indicating whether a crack exists in the metallic article. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification