Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Headed fastener element with nut – washer – securing means or cap – Cap over the head
Reexamination Certificate
2001-02-28
2004-01-20
Saether, Flemming (Department: 3679)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Headed fastener element with nut, washer, securing means or cap
Cap over the head
36
Reexamination Certificate
active
06679667
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
(Not Applicable)
STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT
(Not Applicable)
BACKGROUND OF THE INVENTION
The present invention relates in general to fillers for placement over countersunk fasteners disposed in surface openings, and in particular to a hot-melt fastener filler fabricated as a sheet of a non-woven electrically conductive mat impregnated within a thermoplastic elastomer and sizable to fit atop an in-place fastener.
A typical manner of fastening one structural component to another is to employ standard bolts and nuts which are countersunk within voids of the surfaces of the components being joined. Once the fasteners are properly tightened, the countersink voids are filled with a fastener filler to thereby produce a generally smooth surface as nut and bolt ends are covered.
One particularly important application where such a filler is used in the construction and maintenance of aircraft where surface characteristics must be substantially compatible over entire expanses. Present fillers typically are dielectric fillers having relatively long cure times, and, upon curing, are prone to be brittle which results in premature cracking thereof to produce cracks leading to the conductive layer of the filler. A large number of such cracks can easily lead to untoward surface behavior. Additionally, because of the long cure times associated with aircraft repairs, non-availability of such airplanes under repair along with associated costs significantly reduces operation efficiency.
In view of the above deficiencies in current filler material, it is apparent that a need is present for a fastener filler whose application procedures and longevity of use are beneficial in aircraft construction and repair. Accordingly, a primary object of the present invention is to provide an electrically smooth fastener filler that can be applied and cured within seconds within a countersink hole which houses a fastener end.
Another object of the present invention is to provide such a fastener filler in sheet form and easily sizable to fit within a countersink void in the surface.
Yet another object of the present invention is to provide such a filler fastener wherein one side of the sheet is provided with a pressure sensitive adhesive for initial secured placement against the fastener end prior to filler curing.
These and other objects of the present invention will become apparent throughout the description thereof which now follows.
BRIEF SUMMARY OF THE INVENTION
The present invention is a hot-melt fastener filler for placement within a void atop an in-place fastener which is countersunk within a surface, with the filler comprising an electrically-conductive mat fabricated of at least one ply sizable by cutting to a cross-sectional dimension of the void. The at least one ply comprises a plurality of non-woven electrically conductive fibers each comprising a core strand coated with a layer of nickel, with the plurality of fibers generally uniformly dispersed within a thermoplastic elastomer. Preferably, electrically conductive carbon black particulate is substantially uniformly distributed throughout the thermoplastic elastomer, and the electrically conductive mat is fabricated of two such plies oriented at 0° and 90° to each other. The electrically conductive nickel-coated fibers additionally can be coated with a layer of copper layer followed by a second layer of nickel. A pressure sensitive adhesive can be provided on one side of the sheet to thereby permit secured placement, such as in an overhead application, prior to completion of installation.
Placement of the fastener filler within the void atop the fastener is easily and rapidly accomplished. Preferably, the fastener filler is provided as a large sheet from which is punched a portion equal cross-sectionally to the cross sectional dimension, usually circular, of the void. When adhesive is supplied to one side of the sheet, a release layer typically is provided for ease of handling. Once the properly sized piece is cut, the release layer is removed and the filler is placed within the void such that the adhesive abuts the exposed end of the fastener there within and finger pressure is applied for the adhesive to engage the fastener end. A non-porous cover patch is then positioned over the filler and heat is applied, as with an iron, on the patch to thereby cause the elastomer of the filler to flow and complete filler set. Usual time involved is generally less than one minute, as opposed to hours required for curing prior art fillers. As a result, the fastener filler of the present invention allows not only regularly scheduled maintenance and repairs, but also permits quick and generally uncomplicated field-level repairs for assuring aircraft availability at remote sites.
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Brown Mark D.
Case George V.
Tully John W.
Wade Susan LaColla
Northrop Grumman Corporation
Saether Flemming
Stetina Brunda Garred & Brucker
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