Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Washer structure – Corrugated
Patent
1996-07-26
1999-09-14
Saether, Flemming
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Washer structure
Corrugated
411531, 52410, F16B 4302
Patent
active
059512253
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a large-area washer with an aperture for insertion of a fastener, with stiffeners such as reinforcement indentations or beads and/or reinforcement elevations or ribs being formed on the washer.
Such washers, which are known from U.S. Pat. No. 4,763,456 and from U.S. Pat. No. 4,787,188, are used for fastening roofing sheets with one or more layers and/or an insulation layer to a solid infrastructure. In order to achieve a corresponding hold of the covering roofing sheet, the washer known from U.S. Pat. No. 4,763,456 has points as meshing elements, which bore into the roofing sheet, and the washer known from U.S. Pat. No. 4,787,188 has teeth, which do not bore through the roofing sheet, but only increase the friction between the washer and the roofing sheet. Relatively high forces occur between the roofing sheets and the bottom of the washers, particularly if strong forces occur on the roofing sheet due to corresponding suction stress, which forces attempt to pull the roofing sheet out from under the fastener and/or under the washer.
Furthermore, it has always proved to be a problem that, with a corresponding suction stress on the roofing sheets, they are lifted practically in the axis direction of the fastener used, with a correspondingly great force. Since the large-area washers have a limited area, for one thing, the corner regions of the washers, in particular, engage relatively strongly with the sheet material. Particularly, if a firm hold is achieved between the bottom of the washer and the roofing sheet and thus the roofing sheet cannot be pulled out from under the washer, there is greater stress in the corner regions of the washer when the roofing sheet is lifted, so that it has happened repeatedly that these corner regions of the washers, in particular, cause damage to the roofing sheet.
In the known embodiments, attention has been paid, repeatedly, to making reinforcement or stiffening elements available particularly in the edge region, in order to be able to distribute the force proceeding from the fastener over a relatively large surface and in a reliable manner. But at the same time, this creates the risk that the corner regions of the washer will press into the sheet to be fastened, if there is too much stress, and can damage it.
It is therefore an object of the present invention to create a large-area washer, with which damage of roofing sheets in the corner region of the washer can be avoided.
Pursuant to the invention, it is proposed, for this purpose, that the corner regions of the washer be arranged outside of the segments, which have the stiffeners, and can be elastically bent down about an imaginary line at an acute angle to the two central axes of the washer as far as a given load region.
If, therefore, suction forces cause undue stress on the roofing sheet and therefore lift it from the insulation underneath, the corner regions of the washer have the possibility of moving in the elastic range, in order thereby to prevent damage to the roofing sheet. If a really excessive force should attack at some time, then it would also be conceivable, and this possibility exists, that the corner regions undergo plastic deformation. This provides at least a corresponding safety factor, which also takes into consideration cases with a particular storm effect. With the wind stresses, which usually occur, the corner regions can bend elastically and subsequently always return to their original position.
Furthermore, it is proposed that to improve the friction and/or the meshing, a coating be provided and/or protruding elements be constructed in the corner regions at the surface. Since corresponding elements to improve the friction and/or the meshing are formed in these corner regions, the necessary friction or the necessary meshing between the bottom of the washer and the top of the roofing sheet is always maintained, even when corresponding elastic bending of the corner regions occurs.
With the present invention, particularly that region of the large-area washer, which always c
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Baumgartner Stefan
Osterle Helmut
Saether Flemming
SFS Industrie Holding AG
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