Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Distributive type parameters
Reexamination Certificate
1998-08-17
2001-02-06
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Distributive type parameters
C324S636000, C324S637000
Reexamination Certificate
active
06184694
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the non-destructive thickness measurements of the paint and coating thickness for metals, graphite/epoxy composites, and other conductive substrates. in particular, the invention may be used to measure the dry paint film thickness of paint film thickness of paint applied by conventional or electrostatic spraying of primer, paint, or other coatings on a conductive or poorly conductive surface.
2. Statement of the Problem
In the spray application of many paints, it is difficult to maintain a uniform thickness application of the primer or paint. The difference in paint film thickness results in appearance changes in which the substrate shows. As a result of the substrate showing through, users tend to apply primer and paint thicker than specified on graphite/epoxy composites. Current methods for measuring dry film thickness on metal substrates do not work on graphite/epoxy composites. There is no good and accurate non-destructive method or device for quickly and accurately measuring the primer, paint and coating thickness on graphite/epoxy composites.
There is a need for a dry film thickness measurement instrument and method for graphite/epoxy composites which does not destroy the paint and coating and accurately measures the dry film thickness on metal and graphite/epoxy composites surfaces.
3. Object of the Invention
One of the objects of the present invention is to provide a measuring instrument which is able to measure thickness of the primer, paint, and coating on metal and graphite/epoxy composites without destroying the dry film layer. To this end, the present invention uses a measurement cavity that oscillates at a fixed frequency dependent on the apparent length of the cavity.
However, it is difficult for users to correlate a given frequency change with a thickness measurement. Therefore, another object of the invention is to provide a measuring instrument which converts the frequency changes due to the apparent length change of the cavity into a thickness measurement.
SUMMARY OF THE INVENTION
An electrical instrument and method for measuring the dry paint and coating thickness on conductive and poorly conductive substrates non-destructively which instrument contains the following components:
a. a measurement cavity that oscillates at frequency dependent on the apparent length of the cavity when the sixth wall is formed by the conductive substrate;
b. a reference cavity connected to the above measurement cavity to convert the frequency changes to dc level changes;
c. a data acquisition circuit whereby the dc level changes are converted to thickness measurements and displayed to the user;
c. a power supply circuit to provide power to the measurement and reference cavities and the data acquisition circuit. The power supply circuit may be de-energized when the enclosure pressure approaches ambient pressure. The power supply circuit is monitored by the data acquisition circuit to notify the operator when the voltage lever drops below threshold.
REFERENCES:
patent: 3562642 (1971-02-01), Hochschild
patent: 5057781 (1991-10-01), Arkins et al.
patent: 5384543 (1995-01-01), Bible et al.
patent: 5539322 (1996-07-01), Zoughi et al.
patent: 5748003 (1998-05-01), Zoughi et al.
Loren F. Root and Irving Kaufman, “Noncontacting low-cost instrument for film thickness measurement” Dec. 1992, IEEE Transactions on Instrumentation and Measurement, vol. 41, No. 6, pp. 1014-1019.
Anderson Patrick L.
Bjorkegren Christer E.
Howard Bruce S.
Kovarik (Forner) Lori E.
Deb Anjan K
Gardner Conrad O.
Metjahic Safet
The Boeing Company
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