Patent Application
20080081149
The accompanying drawings which are incorporated in and which constitute a portion of this specification illustrate an exemplary embodiment of the invention which, together with the general description above and the detailed description set forth below will serve to explain the principles of the invention wherein;
While embodiments of the invention have been illustrated and generally described above and will hereinafter be described in connection with certain potentially preferred procedures and practices, it is to be understood and appreciated that in no event is the invention to be limited to such embodiments and procedures as may be illustrated and described herein. On the contrary, it is intended that the present invention shall extend to all alternatives and modifications as may embrace the broad principles of the invention within the true spirit and scope thereof.
Reference will now be made to the various drawings wherein to the extent possible, like elements are designated by corresponding reference numerals in the various views. In
The polymeric layer 16 may be formed of any polymeric resinous material suitable for lamination to the surface layers 12, 14 and with strength and glass transition temperature characteristics suitable to function under normal operating conditions. By way of example only, and not limitation, exemplary polymers may include ethylene polymers and co-polymers and propylene polymers and co-polymers. Such materials include polypropylene, low density or high density polyethylene, ethylene/vinyl acetate co-polymer, ethylene/acrylic copolymer, and ethylene/butene-1 and other alkene-1 co-polymers. Visco-elastic resins and aramid epoxy resins may be particularly preferred. The polymeric resin material can be bonded directly to the surface layers 12, 14 or can be held in place by an intermediate adhesive layer. The thickness of the polymeric layer 16 is preferably in the range of about 0.025 to about 0.040 mm although greater or lesser thickness may be used if desired.
In an alternative construction 10′ illustrated in
As will be appreciated, the welding process will typically result in melting of a portion of the polymeric layers in the vicinity of the spot welds 24. The welding process thus results in the release of combustion byproducts from the polymeric layers including gaseous components. These gaseous components occupy much greater volume under standard room temperature conditions than the original polymer precursor. Consequently, accommodating the gaseous byproducts within the original internal structure of the laminated panel is problematic. Pressure resulting from gaseous byproducts can compromise both weld integrity by forming blowholes at weld locations and sheet integrity by forcing open the metal surface layers forming bulges or delaminations. Delaminations are particularly harmful as they allow moisture to enter the laminate initiating crevice corrosion, which compromises panel durability.
The invention disclosed herein derives from the observation that the released gases will equilibrate at lower pressures when cavity structures or reservoirs are incorporated in the enclosed volume between the surface layers 12, 14 of the laminate construction.
Of course, the configuration illustrated in
As will be appreciated from the exemplary constructions as set forth above, the cavities in the polymeric layer may have non-zero initial volume or they may have essentially zero initial volume. The cavities may be discrete or interconnected and they can even provide open paths for gas to easily flow to the atmosphere. The cavities may be created in the polymer layer mechanically (e.g. punching holes, slicing channels), chemically (e.g. chemical etch or spray), or thermally (laser or heated probe) removing a small amount of polymer material from the layer in a pattern distributed across the entire surface or concentrated in a pattern at strategic locations. Cavities may also be formed by initially limiting the area covered by polymeric material, such as by applying polymer in a predetermined pattern leaving desired areas of the surface layers uncovered with the polymeric material. The cavities may be created by slicing short or long channels or slits in connecting or non-connecting patterns across the entire surface or concentrated in a pattern at strategic locations. The cavities also may be intentionally introduced during curing and rolling operations used to produce the sandwich structure of the metal-polymer laminate structures. The polymeric material may be formulated or processed so that the layer or layers may form dimples or holes within the layer or on the surface of the polymer layer during curing or rolling pressures. The cavities may be one sided, that is cavities may not appear on both surfaces of the polymer layer. If more than one polymer sheet is applied with the laminate structures, the cavities may be created in one or more of the layers. The cavities may be incorporated in the polymer materials before being applied to the metal panel, or after. Any combination of the aforementioned cavities is permissible as well as any and all combinations of cavities which fall within the spirit and scope of the invention.
Regardless of the structure of the formed cavities, the result is the development of gas accepting reservoirs that can accept gases produced during welding or other assembly processes. By way of example only, the resulting characteristic of gas collection is illustrated in
As previously noted, the high temperature of the welding process results in the liberation of gaseous by-products as material within the polymer layer is melted. As shown in
Although the welding arrangement illustrated in
It is to be understood that while the present invention has been illustrated and described in relation to potentially preferred embodiments, constructions, and procedures, that such embodiments, constructions, and procedures are illustrative only and that the invention is in no event limited thereto. Rather, it is contemplated that modifications and variations embodying the principals of the invention will no doubt occur to those of skill in the art. It is therefore contemplated and intended that the present invention shall extend to all such modifications and variations as may incorporate the broad aspects of the invention within the true spirit and scope thereof.
