Stock material or miscellaneous articles – Structurally defined web or sheet – Including aperture
Reexamination Certificate
1999-08-03
2001-06-19
Watkins, III, William P. (Department: 1772)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including aperture
C428S220000, C428S338000, C181S213000, C181S214000, C181S222000, C181S293000, C181S286000, C181S296000
Reexamination Certificate
active
06248423
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to microporous metallic and non-metallic sheets, and in particular to a microporous sheet and a process for its production and use where the sheet has both acoustical and structural functionality by having form ed therethrough a plurality of apertures of a size and number sufficient to enable the sheet to function as an acoustical noise suppressor while retaining capability of functioning as a structural element.
BACKGROUND OF THE INVENTION
Certain elements of manufacture require both acoustical and structural qualities in particular applications. One example of such a requirement is found in a jet engine housing for an airplane in particular, an engine housing must function as both a noise suppressor and a structurally sound encasement of the engine therewithin disposed. This dual task now is accomplished by employing two-sheet fabrication comprising a porous first sheet or “skin” for acoustical control and a second perforated skin for structural stability. Both functions cannot be accomplished by present porous-sheet construction since normal laser-drilled or chemically-etched apertures yield sheets that are poor in structural and fatigue strength and thus require a second perforated sheet for structural capability. Specifically, apertures formed by normal laser drilling or chemical etching have rough edges and cannot be tailored to indicated geometric and size characteristics for particular applications, and the sheets so constructed experience poor fatigue life and structural integrity. Further, because of the limited quality and geometric choice of these prior-art apertures, friction-to-surface values can be relatively high which can cause clogging and resultant airflow disruption.
In view of the above considerations, it is apparent that a need is present for a metallic or non-metallic sheet having both acoustical and structural functionality, and for a process for producing such a sheet. Accordingly, a primary object of the present invention is to provide an acoustically and structurally functional porous sheet and a process for its formation.
Another object of the present invention is to provide such a sheet wherein a plurality of apertures therethrough are formed by a free-electron laser beam.
Yet another object of the invention is to provide such a sheet wherein the plurality of apertures are of a size and number sufficient to enable the sheet to function as an acoustical noise suppressor while retaining capability of functioning as a structural element.
Still another object of the present invention is to provide a jet engine housing constructed of a single sheet of the inventive acoustically and structurally functional porous sheet defined herein.
These and other object of the present invention will become apparent throughout the description thereof which now follows.
SUMMARY OF THE INVENTION
The present invention is a microporous metallic or non-metallic sheet having both acoustical and structural functionality and a process for producing the sheet. Construction of the microporous sheet comprises, first of all, providing a sheet capable of functioning as a structural element of a component. A laser device capable of producing a free electron laser beam is provided, and the free electron laser beam is directed to a surface of the sheet to penetrate the sheet at a plurality of sites and thereby form a plurality of apertures. These apertures are generally uniformly dispersed and of a size and number sufficient to enable the sheet to function as an acoustical noise suppressor while retaining capability of functioning as a structural element. Use of free electron laser technology permits formation of smooth-walled, circular or non-circular apertures tailored to exact geometry specifications controlled to a nanometer in size. This methodology results in the production of a microporous sheet having structural functionality while meeting acoustic requirements with clean, unclogged apertures and with low friction-to-surface and/or boundary-layer control airflow.
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Clarke James A.
Parente Charles A.
Stetina Brunda Garred & Brucker
Vought Aircraft Industries, Inc.
Watkins III William P.
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