Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Externally threaded fastener element – e.g. – bolt – screw – etc. – Pilot end having means enhancing fastening or installation
Patent
1994-08-11
1996-09-03
Wilson, Neill R.
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Externally threaded fastener element, e.g., bolt, screw, etc.
Pilot end having means enhancing fastening or installation
411 29, F16B 1304, F16B 2500
Patent
active
055518184
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a self-drilling fastener, comprising a fastener element with a slot, formed at its free end and constructed parallel to the axis of the fastener, and a platelet-shaped drilling insert, the end of which is inserted into the slot at the fastening element, the drilling insert being connected positively and non-positively due to the deformation of the jaws forming the boundary of the slot at the fastening element.
A self-drilling screw is already known (DE-C-28 01 962), the drilling part of which is formed by a cutting insert inserted into a longitudinal slot of the screw shaft. The side edges of the cutting insert are provided with recesses, into which the edge region or partial region in question of the jaws of the screw shaft, forming the boundary of the slot, is or are pressed in order to form a solid positive and non-positive connection between the cutting insert and the screw shaft. The corresponding regions of the jaws are thus pressed into indentations at the surface of the platelet-shaped cutting insert until they lie against the base of this recess. There is thus only a slight deformation of the edge regions of the jaws and no particularly strong plastic deformation of the jaws due to the solid counter-surface at the cutting insert. Many years of practical use have shown that this type of fastening of the cutting insert has been entirely optimum in the past and that the required safety against loss is provided by this positive and non-positive holding of the cutting insert. Furthermore, the necessary torque during the drilling can be transferred properly.
As a result of the optimum use of such self-drilling screws with a platelet-shaped cutting insert, the range of uses is constantly being enlarged. The drilling is not restricted only to thin sheet metal. This means that the depths of drilling, which can be managed by such self-drilling fasteners, are also constantly being extended. In order to be able to use such self-drilling fasteners also in thick material that is, for example, in steel girders with a wall thickness of 8 mm, 12 mm or more, it is necessary to make the steel inserts correspondingly longer.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a self-drilling fastener of the aforementioned type, for which cutting inserts with a larger axial length can be connected sufficiently firmly with the fastener element, without requiring additionally welding, soldering or bonding operations.
Pursuant to the invention the drilling insert has, at its end region engaging the slot of the fastener element at one or both lateral boundary surfaces, one or more notches, incisions, grooves or channels, which are continuous over the thickness of the drilling insert and into which an edge region of the jaw or the edge regions of both jaws of the fastening element is or are pressed with plastic deformation.
In the case of cutting inserts of longer axial length, the sideways tilting of the cutting insert during the drilling process is a problem. By means of the inventive measures, the cutting insert is clamped at the two mutually opposite narrow sides positively and non-positively between the jaws forming the boundary of the slot, so that the cutting insert can no longer tilt sideways.
When the jaws, forming the boundary at the slot fastener element, are pressed merely into recesses of low depth, these regions of the jaws are deformed plastically only insignificantly and can spring back partially once again after the pressing process. This was adequate for holding cutting inserts of relatively short axial length.
Due to the inventive measures, the corresponding edge region of the jaws is pressed with plastic deformation into the channel extending over the thickness of the drilling insert, so that elastic recovery is no longer possible. It has been shown experimentally, that the shearing-out value can, at least, be doubled by the inventive measures. With this, the present invention can also provide the possibility of be
REFERENCES:
patent: 4257307 (1981-03-01), Regensburger
patent: 4480951 (1984-11-01), Regensburger
patent: 5183357 (1993-02-01), Palm
patent: 5213459 (1993-05-01), Palm
patent: 5383753 (1995-01-01), Palm
SFS Industrie Holding AG
Wilson Neill R.
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