Method and apparatus for examining a workpiece
First Claim
Patent Images
1. Apparatus for testing a metallic workpiece comprising:
- a test coil mounted in proximity to a workpiece and coupled to means for cyclically energizing said coil;
field modifying means comprising an electrically conductive sleeve defining at least one aperture for selectively modifying a magnetic field created by said coil;
means coupled to said coil for creating a shape indicating signal related to a distance between an outer workpiece surface and said coil as said magnetic field is modified, andmeans coordinated with said field modifying means for scaling the shape signal to provide an indicating signal which varies with changes in workpiece shape.
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Abstract
An eddy current inspector for imaging of a workpiece shape. A differentially wound test coil mounted next to a workpiece path of travel is energized with a time varying signal to set up eddy currents in the workpiece. A field modifying sleeve is rotated with the field to periodically disrupt the eddy current inducing field. Two signals from the coil, a flaw signal and a shape signal, are time multiplexed and scaled to present a real time image of a workpiece surface as well as the orientation and severity of flaws existing at the workpiece surface.
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Citations
17 Claims
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1. Apparatus for testing a metallic workpiece comprising:
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a test coil mounted in proximity to a workpiece and coupled to means for cyclically energizing said coil; field modifying means comprising an electrically conductive sleeve defining at least one aperture for selectively modifying a magnetic field created by said coil; means coupled to said coil for creating a shape indicating signal related to a distance between an outer workpiece surface and said coil as said magnetic field is modified, and means coordinated with said field modifying means for scaling the shape signal to provide an indicating signal which varies with changes in workpiece shape. - View Dependent Claims (2, 3)
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4. In a flaw detection system having means for producing a flaw signal related to a flaw position on a workpiece, workpiece imaging apparatus comprising:
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means for generating a shape signal varying with a shape of a workpiece outer surface; means for time multiplexing said shape and flaw signals; scaling means for scaling said time multiplexed signals into component signals relative to a reference; and display means for displaying said component signals on an imaging screen to yield a real time image of a workpiece cross-section. - View Dependent Claims (5, 6)
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7. In eddy current testing, a method for displaying an image of a workpiece comprising the steps of:
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positioning a probe coil next to a workpiece path of movement; energizing said probe coil with a time varying signal to create an electromagnetic field that induces an eddy current in said workpiece; modifying said field by rotating a field modifying object comprising an electrically conductive slotted sleeve around the workpiece; monitoring induced signals in said coil due to said eddy currents and generating a first signal related to a presence of a flaw in said workpiece and a second signal related to a distance between the coil and a workpiece surface; time multiplexing said first and second signals and scaling said first and second signals by a factor related to an instantaneous position of said rotating object; and displaying a visible indication of said cross-section using the scaled first and second signals as control signals to position the indication on a display. - View Dependent Claims (8)
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9. Apparatus for imaging a metallic workpiece comprising:
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a test coil mounted in proximity to a workpiece path and coupled to means for cyclically energizing said coil; field modifying means comprising an electrically conductive sleeve defining an aperture for selectively modifying a magnetic field created by said coil at time varying locations about a workpiece surface to create a shape indicating signal related to a distance between an outer workpiece surface and said coil; and imaging means co-ordinated with said modifying means for displaying an indication of said shape indicating signal as said coil and field modifying means scan the workpiece to present a real time representation of said workpiece surface. - View Dependent Claims (10)
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11. In eddy current testing, a method for displaying an image of a workpiece comprising the steps of:
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positioning a probe coil next to a workpiece path of movement; energizing said probe coil with a time varying signal to create an electromagnetic field that induces an eddy current in said workpiece; modifying said field at varying locations around the workpiece by use of an electrically conductive apertured sleeve; monitoring signals in said coil induced by said modified field and generating a signal related to a distance between the coil and a workpiece surface; and displaying said signal on a screen to present a visible indication of the shape of the workpiece'"'"'s outer surface. - View Dependent Claims (12, 13)
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14. Apparatus for imaging a metallic workpiece comprising:
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a differentially wound test coil having two portions mounted as spaced locations along a workpiece travel path and coupled to means for cyclically energizing said coil; a rotatably mounted electrically conductive sleeve having apertures at said spaced locations for selectively modifying an electromagnetic field created by said coil portions to produce a flaw indicating signal across said coil portions; means coupled across one of said coil portions for creating a shape indicating signal related to a distance between an outer workpiece surface and said one coil portion in a region of electromagnetic field modification; means coordinated with rotation of said sleeve for scaling the shape and flaw signals to provide orthogonal components of said shape and flaw signals, and display means for displaying said orthogonal components of one or the other or both said flaw signals as said coil and field modifying means scan the workpiece. - View Dependent Claims (15, 16)
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17. In eddy current testing, a method for displaying an image of a workpiece comprising the steps of:
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positioning a probe coil next to a workpiece path of movement; energizing said probe coil with a time varying signal to create an electromagnetic field that induces an eddy current in said workpiece; modifying said field by rotating a field modifying object comprising an electrically conductive sleeve defining at least one aperture around the workpiece, and monitoring induced signals in said coil due to said eddy currents and generating a signal related to a distance between the coil and a workpiece surface at the region the field is modified.
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Specification