A TENSILE FORCE ABSORBING ANCHORING IN CONCRETE

Abstract: For anchoring in concrete, plugs and/or expanders are used, which require relatively deep holes for providing the strength required. In order to reduce the necessary hole depth without deteriorating the strength, and in general to facilitate and render cheaper the anchoring in concrete and other hard material, the present tensile force absorbing anchoring comprises an anchoring member (1) formed integral of music-wire, with an anchoring portion (2) located in a hole in the material, which portion (2) comprises two gripping members (6), each with a free end (7) engaging with the hole wall, which members are formed integral, with each of their two shanks (5) abutting an opposed side of the hole wall against the engaging surface of the free end of the respective gripping member (6) and extending axially out of the hole, which shanks (5) constitute parts of the leg portion of the anchoring member (1) and form and acute angle with the respective gripping member (6), and that each gripping member (6) has a length between its free end and the associated shank which exceeds the hole diameter, and is stiff against bending along its entire length, and that the free end (7) of the respective gripping member (6) prior to the application of the anchoring member (1) in its hole is located at a perpendicular distance from the associated shank (5) which exceeds the hole diameter, for obtaining an initial clamping force at the application of the anchoring member in its hole.

Description: A 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 invention, therefore, to provide a con¬ crete 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 re¬ duced considerably when practising the invention. These objects are attained by providing a structure having the characteristics defined in the claims. The invention is described hereinafter, reference being had to the drawing. In the drawing Fig. 1 is a perspective vie of an anchoring member according to the invention, Fig. is a section view of an anchoring member received in an anchoring hole sunk into a concrete joist, and Fig. 3 is a perspective view of a modified embodiment of the anchoring member. In the drawing numeral 1 denotes in general an anchoring me shaped integrally of resilient steel wire, such as music-wi or the like, and comprising an anchoring portion 2 and a le portion 3. This leg portion 3 is shaped as a substantially U-shaped fastening eye or loop and comprises more specifica two shanks 5 connected by an arcuate portion 4, whereas the anchoring portion 2 comprises two opposed gripping members 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 tha 90° and should be in the range 20°-70°, preferably 29°-61°, and being about 45° in the preferred embodiment illustrated the drawing. Further, in the illustrated embodiment grippin members 6 having their free ends 7 pointing in opposite directions are overlapping in planes which are substantiall parallel with the leg portion (the drawing plane in Fig. 2 ) and cross each other. In other, non-illustrated embodiments gripping members 6 may be staggered vertically. This entail the drawback of having to provide deeper holes for anchorin the member, however. In Fig. 2 an anchoring member according to the invention is shown introduced into an anchoring hole 9 sunk into a concr surface 8 from below. This anchoring hole should have a dia meter, 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 grippin member and the side of the corresponding shank facing away from said terminal surface, in the unloaded or non-activate state of the anchoring member. When entering the anchoring OMP 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 sub- jected 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 engagement becomes stronger as soon as the shank portion 5 is subjected to a vertikal pulling load. Such pulling load acts on the end of the gripping members facing away from its free . e ^ 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 accomodating 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 H 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 a in a concrete joist having/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 describe above and illustrated on the drawing, but can be altered an 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 poin out that the angle subtended between the gripping member 6 and the associated shank 5 does not need to be that shown i 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 termin 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, pro¬ vided that the load acts in the direction of the leg, and i can also be used for anchoring in sheet metal.

Claims: Claims 1. A tensile force absorbing anchoring in hard material, such as for example concrete, rock, sheet metal or the like, comprising an anchoring member with an anchoring portion in a hole made in the material for δo-operation with opposed wall portions of the hole, and a leg portion extending from the hole and integral with the anchoring portion for applying tensile force producing load, c h a r a c t e r i z e d i n that the anchoring portion formed integral of music-wire comprises two gripping members, each with a free end engaging with the hole wall, which members are formed integral, with each of their two shanks abutting an opposed side of the hole wall against the engaging surface of the free end of the respective gripping member and extending axially out of the hole, which shanks constitute parts of the leg portion of the anchoring member and form an acute angle with the respective gripping member, and that each gripping member has a length between its free end and the associated shank which exceeds the hole diameter,and is stiff against bending along its entire length, and that the free end of the resp¬ ective gripping member prior to the application of the anchor¬ ing member in the -hol 'is ' .located at a perpendicular distance from the associated shank which exceeds the hole diameter, for obtaining an initial clamping force at the application of the anchoring member in its hole. 2. An anchoring as defined in claim 1, c h a r a c t e r ¬ i z e d n that the two gripping members are directed in the same direction. 3. An anchoring as defined in claim 1, c h a r a c t e r - i z e d i n that the gripping members are in parallel with each other. 4. An anchoring as defined in claim 1, c h a r a c t e r ¬ i z e d i n that the two gripping members are directed opposed to each other. OΪ-.:PI 5. An anchoring as defined in claim 4, c h a r a c t e r ¬ i z e d i n that the gripping members are located over¬ lapping in planes substantially in parallel with the leg portion. 6. A device according to any one of the preceding claims, c h a r a c t e r i z e d i n that the gripping members located offset in vertical direction relative to each other. 7. A device as defined in any one of the preceding claims, c h a r a c t e r i z e d i n that the angle between the gripping members and associated shanks is the same for the two gripping members. 8. A .device as defined in any one of the preceding claims, c h a r a c t e r i z e d i n that the shanks (5) formin the leg portion are connected to each other to form a substa ially U-shaped fastening eye. O

Inventors: BERGGREN A, KLINGSTEDT H, KLINGSTEDT I
Applicants: BERGGREN A, KLINGSTEDT H, KLINGSTEDT I, MILJOETAKMONTAGE AB
Application year: 1980
Main classification: F16B2
IPC codes: E04B9, F16B2, F16B13