FIXING ELEMENT FOR KNOCKING INTO A DRILLED HOLE

Abstract: Fixing device for knocking into a pre-drilled hole in concrete or the like, including a plug (1) and a nail (2) coacting therewith. The purpose of the device is to provide a fixing element giving the greatest possible contact surface and the greatest possible surface pressure against the wall of the pre-drilled hole, and thereby maximum resistance to withdrawal. This purpose has been achieved by the expansion zone (3) of the plug including longitudinal ridges (9) arranged internally in the nail hole and longitudinal grooves (10) arranged in the exterior surface, ridges and grooves being formed such that a substantially constant cross-sectional area is obtained in the expansion zone (3) along the greater portion of its length.

Description: FIXING ELEMENT FOR KNOCKING INTO A DRILLED HOLE TECHNICAL FIELD The present invention relates to a fixing element of the kind disclosed in the preamble to claim 1. BACKGROUND ART In known fixing elements for knocking into pre-drilled holes it has been attempted to achieve great resistance to withdrawal by supplying the expandable portion with a large amount of material which, since the outside diameter is determined with respect to the hole diameter, has only been able to be arranged by reducing the extension of the nail hole in the expandable portion or by heavily reducing its diameter within this portion. Further to this it has been in many cases attempted to increase the resistance to withdrawal by forming cutouts of different shapes at right angles to the longitudinal axis and on the exterior surface of the expandable portion, these being expected to form claw-like engagement means which will grip into the wall of the hole when the plug expands. Fastening elements intended for knocking in, of the type described here, are intended to replace fastening means of the type plug + screw, with the object of reducing the time and input of work in di ferent kinds of installation or erection where plugging is necessary. However, it has been found that in many types of such erection or installation, fastening elements of the type plug + screw are still preferred, since these give greater resistance to withdrawal. DISCLOSURE OF INVENTION The object of the present invention is to provide a fastening element with the aid of which it is possible to achieve values for withdrawal resistance which correspond to those achieved with a screw + plug fastening of high quality. This object has been achieved by the exterior surface of the expandable portion of the plug being provided with longitudinal grooves corresponding to internal longitudinal ridges arranged in the tapering part of the nail hole, ridges and grooves being implemented such that the expandable portion has a substantially constant cross-sectional area along the greater portion of its length. There is thus achieved uniform expansion along practically the whole of the expandable portion. In a preferred embodiment there is also obtained large contact surface and large contact pressure against the wall of the hole. In the preferred embodiment the sum of the cross-sectional areas of the expandable portion and the steel nail are substantially equal or fall to a minor extent below the cross- sectional area of the pre-drilled hole. This relationship between said areas may be denoted as the filling factor of the fastening element, and the following relationship applies to it: Nail area + plug area = f ing factQrj hole area the plug area relating to the expansion zone. For filling factors equal to, or less than 1, only a radial redistribution of the plastics in the expansion zone takes place, and thereby radial filling-out of the cavities between plug and hole wall. To achieve the greatest possible withdrawal value, the filling factor must be close to 1 along the entire length of the expandable portion. If the filling factor should exceed 1, an axial expansion occurs when the nail is driven in, i.e. material is pressed in front of the nail towards the end of the plug. When the nail is in movement during driving-in, the radial expansion does not have time to develop to its fullest extent, and poor withdrawal values are obtained as a result. Added to this, large forces are required to overcome the inner resistance of the plastics, and the plug may be damaged when the nail is driven in. DESCRIPTION OF FIGURES The invention will now be described with reference to the accompanying drawing, on which Figure 1 is a side view of a device in accordance with the invention, including nail and plug, the latter in longitudinal section, Figure 2 are side and end views of the plug, Figure 3 is a cross section along the line III— III in Figure 2 and Figure 4 is a cross section along the line IV-IV in Figure 2. PREFERRED EMBODIMENT The device in accordance with the invention consists of a plug 1 with a coacting nail or the like 2 adjusted to the length of the plug. The plug comprises an expandable portion 3 provided with a diametral slit 8, the portion 3 extending from the inner end 4 of the plug and to an unexpandable portion 5, which may have different lengths depending on the field of use of the plug. At the outer end of the plug the portion 5 merges into a collar 6 in which there is the mouth of a hole 7 suited to the nail, and this hole tapers towards the inner end 4 of the plug in the expandable portion 3, which is provided with four internal, longitudinal ridges 9. Corresponding to these ridges 9 there are four grooves 10 arranged in the cylindrical outer surface of the expandable portion. The increase in the cross-sectional area of the expandable portion, which occurs in a direction towards the inner end 4 of the plug, as a result of the taper of the hole 7, is compensated by the grooves at the inner end 4 of the plug having greater width and depth, which is illustrated by Figures 3 and 4, showing two different cross-sections of the expandable portion 3. By keeping the cross-sectional area constant, and, together with the nail area, in correspondence with the hole area, i.e. with the filling factor 1, the material in the expandable portion of the plug will be redistributed and will assume an annular appearance when the plug is placed in a hole and the nail is driven in. There is thus achieved a large contact surface against the hole wall as well as high pressure on the contact surface, and thereby maximum resistance to withdrawal. The forces in withdrawal stresses will be taken up by the head of the nail. In order to transmit larger forces between the expanded portion of the plug and the nail, the latter can be provided with a shallow, claw-like rolled thread over the portion coacting with the expandable portion of the plug. Screwing the nail _OMPI out and removing the plug is thus enabled. The thread is formed such that it does not retard driving in the nail. OMPI ' WiPO

Claims: CLAIMS 1 Fixing element for knocking into a pre-drilled hole in concrete or the like material in so-called straight-through fixing for fastening wall panels, studs etc., said fixing element consisting of a plug (1) with a nail or the like (2) coacting therewith, said plug preferably being manufactured in a rigid plastic material and including an expandable portion (3) extending from the inner end (4) of the plug in a fixed condition and preferably provided with a diametral slit (8), said portion (3) merging into a non-expandable zone (5) terminating at the outer end of the plug in a collar (6), the plug being formed with a central hole (7) starting from the end provided with the collar (6), the hole being adapted to the nail (2) and preferably tapering conically towards the inner end of the plug (4) in the expandable portion (3), in which it is provided with four internal longitudinal ridges (9), characterized in that the exterior surface of the expandable portion is provided with a plurality of longitudinal grooves (10), ridges (9) and grooves (10) being formed such that the expandable portion has a substantially constant cross-sectional area along the greater portion of is length. 2 Fastening element as claimed in claim 1, characterized in that the sum of the cross-sectional areas of the expandable portion, and the steel nail are substantially equal to or fall to a minor extent below the cross-sectional area of the pre-drilled hole.

Inventors: LINDELL JAN ANDERS, LINDELL, JAN, ANDERS
Applicants: ERICSSON TELEFON AB L M, TELEFONAKTIEBOLAGET L M ERICSSON
Application year: 1984
Main classification: F16B13
IPC codes: F16B13