Tensile Force Absorbing Anchoring in Concrete

The present invention relates to a tensile force absorbing anchoring in concrete or another hard material, comprising an anchoring member and a hole in the material for receiving said member.

For anchoring a structure in concrete, such as a ceiling suspended from a concrete joist, plugs and/or expanding members are used which are entered into holes sunk into the concrete and which are tightened in the holes with the aid of screw or bolt means. Whether plugs or expanding members are employed, the anchoring in concrete is difficult and time-consuming and costly, as well, not the least by reason of the holes required for these known anchoring members having to be comparatively deep for affording the necessary strength, and of such depth, as a rule, that the reinforcements below the concrete surface are often encountered on sinking the holes. This considerably delays and makes costlier the sinking of the holes to a depth required for proper strength, or may entail breaking off the preparing of the holes before reaching the necessary depth, thereby causing the anchoring strength to be insufficient.

It is an object of the present invention, therefore, to provide a concrete anchoring free from the afore mentioned drawbacks and being such that it does not require any screw or bolt means for its securing or clamping in a hole, thus making for a quicker mounting than when known plugs or expanding members are used, which further requires only a considerably lesser depth of hole than the known anchoring members and in spite of this affords a strength which is improved over that attained with known anchoring means of the plug or expanding-member type, and which can be mounted quickly and in a simple manner. To a speedy mounting an important contribution is offered therethrough that the depth of the anchoring hole may be reduced considerably when practising the invention.

These objects and others are attained by providing a structure according to the present invention the characteristics defined in the claims.

Preferred embodiments of the present invention are described hereinafter, reference being had to the drawing. In the drawing:

FIG. 1 is a perspective view of an anchoring member according to the invention,

FIG. 2 is a section view of an anchoring member received in an anchoring hole sunk into a concrete joist,

FIG. 3 is a perspective view of a modified embodiment of the anchoring member and,

FIG. 4 is a section view of a further embodiment according to the present invention received in an anchoring hole.

In the drawing an anchoring member 1 is shaped integrally of resilient steel wire, such as music-wire (pianosteel wire) or the like, and includes an anchoring portion 2 and a leg portion 3. This leg portion 3 is shaped as a substantially U-shaped fastening eye or loop and comprises more specifically two shanks 5 connected by an arcuate portion 4, whereas the anchoring portion 2 comprises two opposed gripping members 6 formed integrally with an associated shank 5 by being bent inward towards the shank. The gripping members 6 subtend an angle with the associated shank 5 which should be less than 90.degree. and should be in the range 20.degree.-70.degree., preferably 29.degree.-61.degree., and being about 45.degree. in the preferred embodiment illustrated in the drawing. Further, in the illustrated embodiment gripping members 6 having their free ends 7 pointing in opposite directions are overlapping in planes which are substantially parallel with the leg portion (the drawing plane in FIG. 2) and cross each other. In a further embodiment (FIG. 4), the gripping members 6 are staggered vertically. This entails the drawback of having to provide deeper holes for anchoring the member, however.

In FIG. 2 an anchoring member according to the invention is shown introduced into an anchoring hole 9 sunk into a concrete surface 8 from below. This anchoring hole should have a diameter, according to the invention, which has to be somewhat smaller (e.g. 1 to 5 millimeters) than the perpendicular distance between the free terminal surface 7 of the gripping member and the side of the corresponding shank facing away from said terminal surface, in the unloaded or non-activated state of the anchoring member. When entering the anchoring member 1 in the hole 9 thus the gripping members 6 will be resiliently forced towards the associated shank 5 by the hole wall 10. The gripping members 6 are consequently subjected to a prestressing action which will strive to make the free ends 7 of members 6 engage the hole wall 10 when the anchoring member 1 is pushed home into the hole 9. This engagment becomes stronger as soon as the shank portion 5 is subjected to a vertical pulling load. Such pulling load acts on the end of the gripping members facing away from its free end 7, and thereby the anchoring portion 2 will be pulled into a rigid engagement about the free ends 7 of the gripping members abutting the hole wall 10. The gripping members thus are wedged and clamped immovably between the hole walls with a force which grows greater with an increasing pulling load. This clamping force is somewhat dependent on the bending strength of the gripping members, but since these portions comprise a material of high stiffness such as spring steel and may be very short the flexural strength of the gripping members will be more than adequate for accommodating without rupture the pulling forces acting on the shanks 5 of the anchoring portion 2.

With regard to the hole depth, this need not be, in principle, greater than a few millimeters, for example 5 to 10 millimeters greater than the height of the anchoring portion. The latter, in its turn, can be as short as 4 to 10 millimeters. Thus a hole depth of about 15 millimeters is quite sufficient for this anchoring, and tests have proved that an anchoring member according to the invention, made of a spring-steel wire having a diameter of 2 millimeters and secured in a hole made in a concrete joist having a diameter of 8 millimeters and a depth of 15 millimeters, can take up a load of at least 300-350 kiloponds without giving way.

In FIG. 3 a modified embodiment of the anchoring member 1 according to the invention is shown, which differs from the member 1 shown in FIG. 1 only in that the two clamping or gripping members 6 each formed integral with its shank 5 are facing in the same direction and are in parallel with each other. Also at this embodiment the leg portion 3 is shaped as a fastening eye.

The invention is not restricted to the embodiments described above and illustrated on the drawing, but can be altered and modified in many different respects within the scope of the claims. This also applies for the measurements given above which are only given by way of example. Thus it may be pointed out that the angle subtended between the gripping member 6 and the associated shank 5 does not need to be that shown in the drawing, but may vary somewhat. In such case the length of the gripping members has to be made such as to suit the angle thereof, to make the distance between the free terminal face 7 and the associated shank the same for both gripping members.

The anchoring member according to the invention can be used for anchoring in concrete walls and ceilings, as well, provided that the load acts in the direction of the leg, and it can also be used for anchoring in sheet metal.