Measuring and testing – Vibration – By mechanical waves
Reexamination Certificate
2000-10-18
2001-10-09
Williams, Hezron (Department: 2856)
Measuring and testing
Vibration
By mechanical waves
C073S642000, C073S661000
Reexamination Certificate
active
06298727
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus and method for acoustically inspecting a workpiece in arbitrary orientation.
BACKGROUND OF THE INVENTION
Nondestructive Inspection (NDI) determines the quality of a workpiece without causing damage to the workpiece. One NDI technique uses acoustic waves to inspect a work-piece. This technique directs an incident acoustic wave at a workpiece, senses a reflection from the workpiece and analyzes the reflection to determine the quality of the workpiece. Acoustic inspection is helpful, for example, to determine the integrity of airplane components including the wing, fuselage and empennage by detecting disbonded lap splices, corroded rivet joints and similar structural defects.
A typical apparatus for acoustically inspecting a workpiece includes a pulse generator electrically connected to a transducer assembly which generates a focused acoustic wave (practical ultrasonic transducers have an inherent focus and the selection of a useful focus is application dependant). The acoustic wave travels through a transmission medium and onto the workpiece. Acoustic reflections from the workpiece radiate back to the transducer and causes the transducer to generate a corresponding electrical signal. A processor then analyzes the electrical signal to determine the quality of the workpiece.
Ultrasonic NDI, in particular can improve the inspection spatial resolution and the signal to noise by using a focused acoustic beam and a scanner to move the transducer assembly in a raster scan over the workpiece. This type of NDI requires good and reliable acoustic coupling and is most effective when applied in an immersion mode.
A known inspection apparatus as described by Patton in the U.S. Pat. No. 5,469,744 uses an acoustic apparatus called a Contact Adaptive Bubbler (CAB) consisting of a tubular member containing an ultrasonic transducer and a couplant chamber (first chamber) and a couplant reservoir (second chamber) between the transducer and the workpiece. Couplant is continuously supplied to replenish couplant leaks. A vacuum chamber (opening) recovers couplant that leaks from the couplant reservoir (second chamber).
However, in practice, it was found that the prior art inspection device operates reliably on horizontal and slightly angled workpiece surfaces, but not on rough surfaces, and in vertical and underside orientations (inverted) with respect to workpiece surfaces. Further, the couplant and vacuum lines connected to prior art devices easily disturbs the horizontal and slightly angled orientations of those device with respect to the workpiece, thus minimizing the reliability of the prior art devices even in those orientations. Additionally, the prior art devices cannot reliably be used on rough surfaces, or vertical or under side surfaces as a result of shortcomings of the interface of those devices to the surface of interest. The acoustic inspection device of the present invention overcome the problems experienced by the prior art thus permitting use on rough surfaces and in any orientation from horizontal to inverted.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an acoustic inspection device that: (1) interfaces reliably with uneven or rough workpiece surfaces; (2) interfaces reliably with all workpiece surface orientations from horizontal on top of the workpiece to inverted on the underside surfaces of the workpiece; and (3) provides a superior and reliable acoustic coupling with the workpiece independent of the orientation and condition of the workpiece surface being inspected. Accordingly, the acoustic inspection device of the present invention is compatible with surfaces that are rough or oriented at any angle including inverted on the under-side of a workpiece.
Another, object of the present invention is to provide an acoustic inspection device with a smaller diameter, flexible vacuum and couplant supply lines, and positions for the ports on the acoustic inspection device of the present invention that allow for more accurate alignment to the orientation of the workpiece, regardless of that orientation.
Yet another object of the present invention is the provision of a small footprint of the acoustic inspection device of the present invention.
The acoustic inspection device of the present invention is designed for use on a broad range of workpiece surfaces including those that have unevenness that disturb the desired orientation of the prior art devices as they pass over the rough areas. Additionally, it has been observed with the prior art devices that the surface unevenness can spoil the integrity between the couplant and the workpiece. The objective of the present invention is to greatly improve the capability for scanning uneven surfaces by using improved couplant distribution and vacuum recovery in the their respective chambers.
Each of these objects result from the combination of the various features of the present invention.
REFERENCES:
patent: 4058000 (1977-11-01), Ries et al.
patent: 5469744 (1995-11-01), Patton et al.
patent: 5473943 (1995-12-01), Barry
patent: 5631425 (1997-05-01), Wang et al.
patent: 5948985 (1999-09-01), Brautigan et al.
Fleming Marvin F.
Patterson Peter M.
Jones Allston L.
Saint-Surin Jacques
Sierra Matrix, Inc.
Williams Hezron
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