ANCHOR RAIL WITH A TIE

Abstract

An anchoring rail is disclosed. The anchoring rail includes a rail body that has a holding space extending in the longitudinal direction of the rail body, a filler body that is provided in the holding space of the rail body, and at least one fiber-reinforced tear strip that is arranged between the rail body and the filler body for removing the filler body from the holding space. The tear strip has a matrix of modified natural rubber at least partially surrounding the fibers.

Description

This application claims the priority of International Application No. PCT/EP2011/059474, filed Jun. 8, 2011, and German Patent Document No. 10 2010 031 636.9, filed Jul. 21, 2010, the disclosures of which are expressly incorporated by reference herein.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a moldable anchoring rail. Such an anchoring rail, which can be molded in a component, is designed with a rail body having a holding space extending in the longitudinal direction of the rail body, a filler body, which is provided in the holding space of the rail body, and at least one fiber-reinforced tear strip arranged between the rail body and the filler body for removing the filler body from the holding space.

Anchoring rails introduced into the formwork before concreting must usually be sealed to prevent the penetration of concrete so as not to lose their function. This can be accomplished by introducing foam-type materials, such as PE foam, polystyrene, etc., into the anchoring rail. The foam filler is usually removed before using the anchoring rail. Anchoring rails with temporary fillers are known from DE 87 05 644 U and U.S. Pat. No. 4,532,740 A, for example. In addition, DE 295 15 152 U1 discloses a plastic foam filler made of LDPE for anchoring rails.

To facilitate removal of the temporary rail filler, tear strips applied to the bottom side of the filler in the longitudinal direction of the rail are known from U.S. Pat. No. 4,532,740 A, for example. According to U.S. Pat. No. 4,532,740 A, the strips may also be provided with adhesive and may contain reinforcing fibers.

However, it has been found that when using fiber-reinforced tear strips in cemented anchoring rails, the tear strips partially tear even under loads far below the theoretical tensile force, which may result in failure of the tear strips before the filler has been reliably released.

The object of the present invention is to provide an anchoring rail, which will allow an especially simple and reliable removal of the filler material.

The invention is characterized in that the tear strip has a matrix of modified natural rubber at least partially surrounding the fibers.

Experiments have surprisingly shown that the failure which has been observed with known fiber-reinforced tear strips in some cases often cannot be attributed to a failure of the fibers per se but rather must be attributed to a failure of the matrix in which the fibers are embedded. In the undamaged state, this matrix presents a shearing resistance, which makes it possible to distribute the load to the fibers, so that as many fibers as possible are involved in the load transfer. If the matrix fails then, the load is no longer being distributed to all the fibers but instead is being applied to only a few fibers. These fibers then break prematurely, with the result that the load is again applied to only a few fibers, which break again, etc. In a weakened matrix, the fibers which are subjected to uneven loads will thus fail successively until the entire strip has failed.

Experiments have also surprisingly shown that the observed weakness of the matrix can often be attributed to the liquid concrete, which can attack the matrix due to its high pH, i.e., its strongly alkaline pH. However, release agents applied to the formwork to reduce sticking of the concrete to the formwork boards can also have a negative effect on the matrix.

It should also be pointed out here that the tear strip may be exposed to the harmful effects of the laitance, i.e., the soupy liquid concrete mix, on the protruding straps and the end faces of the anchoring rail as well as at its nail holes. Experiments have shown that under some circumstances, even nail holes with a diameter of only 3 mm can cause permanent damage to the strip, with the result that the strip tears exactly at the locations of the nail holes, and the functionality of the strip is no longer ensured. It has also been observed that in cases in which the filler material has not completely sealed off the interior of the rail, liquid concrete was able to penetrate through the end faces, so that the tear strip at the bottom of the anchoring rail was completely wetted with liquid concrete. That could make the strip completely useless under some circumstances.

The present invention begins with the surprising finding that failure of the tear strips can be attributed to a failure of the matrix, and this failure of the matrix may itself be due to harmful effects of the concrete itself. The invention proposes using modified natural rubber as the matrix material. Experiments have surprisingly shown that natural rubber is only marginally damaged by the alkaline attack by the concrete.

It has been found that natural rubber is not only especially resistant to chemical attack, but also can advantageously serve at the same time to attach the tear strip on the filler body, preferably comprising a foam material. Due to this type of attachment, slippage of the strip beneath the filler body when the rail pieces are short can be prevented without requiring an additional adhesive layer. It is thus especially preferable for the tear strip to be attached to the filler body at its matrix of modified natural rubber. The matrix is thus suitably in direct contact with the filler body, i.e., without any layers such as adhesive layers in between.

The tear strip suitably has a backing strip on which the matrix and/or fibers are arranged. This backing strip may comprise polyethylene (PE), polypropylene (PP) or polyethylene terephthalate (PET) in particular.

The fibers are preferably glass fibers. These fibers are especially chemically resistant to the natural rubber matrix according to the invention but also to the liquid concrete. Continuous filaments in particular may be used as the fibers. The fibers usually run in the longitudinal direction of the tear strip.

In addition, it is expedient for the filler body to have an extruded foam, which has an extrusion membrane at least in the area of the tear strip. Such an extrusion membrane ensures especially good adhesion of the tear strip to the filler body. At the same time, the extrusion membrane may prevent liquid concrete from penetrating into the filler body in an unwanted manner, which under some circumstances could make it difficult to extract the filler body.

To counteract spreading of the liquid concrete in the filler body in particular, it may also be advantageous for the filler body to have a closed-cell extruded foam.

With respect to the manufacturing costs, for example, it may be provided that the filler body comprises low-density polyethylene (LDPE). It should be pointed out here that LDPE does not have especially high tensile strength, so that removal of an LDPE filler body in one stroke is often impossible if the tear strip has been weakened. Instead, when the tear strip has been damaged, this often results in numerous individual foam pieces that must be disposed of individually. The use of a natural rubber matrix which counteracts weakening of the tear strip according to the invention is thus especially advantageous, in particular in conjunction with LDPE filler bodies. Experiments have shown that this combination makes it possible to extract the foam even when the rails have been nailed to it, and the nails have penetrated through the tear strip as well as through the filler body.

Experiments have also shown that a tear strip with natural rubber matrix can withstand the blows of a hammer in removing the concrete crust, which is formed when the anchoring rail is installed too deeply, for example, or in a search for the start of the tear strip. With the material combination described above, the tear strip together with the filler body is capable of forming a unit that has tensile strength and cooperates in removal of the filler body, permitting easy removal of the filler body.

Another improvement in the stability of the tear strip may be achieved through the following approach: in manufacturing the tear strip, two strips of natural rubber may be provided with a glass fiber layer sandwiched between them to insulate the glass fibers from the external aggressive environment. The natural rubber strips may then be rolled together and bonded by an adhesive or by the action of heat, so that they surround the glass fiber layer on both sides.

The invention is explained in greater detail below on the basis of exemplary embodiments diagrammed schematically in the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an anchoring rail according to the invention in cross section; and

FIG. 2 shows an enlarged cross-sectional view of the tear strip in the anchoring rail from FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an anchoring rail 11 according to the invention that can be molded in a component. The anchoring rail 11 shown here has a rail body 12, comprising a holding space 13 extending in the longitudinal direction of the rail body 12, such that in the case of the cross-sectional view in FIGS. 1 and 2, the longitudinal direction runs perpendicular to the plane of the drawing. The anchoring rail 11 also has multiple anchoring elements protruding on the lower side of the rail body 12, only one of these anchoring elements 14 being shown in FIG. 1, covering the remaining anchoring elements. A filler body 16, which may be made of LDPE foam, for example, and preferably has an extrusion membrane, is provided in the holding space 13 in the rail body 12.

A tear strip 21 is provided between the filler body 16 and the rail body 12 in the holding space 13, with the tear strip being attached adhesively to the filler body 16. The tear strip 21 runs in the longitudinal direction of the rail body 12 on the bottom of the holding space 13 facing the anchoring elements 14. Forces may be exerted on the filler body 16 serving to remove the filler body 16 at least partially from the holding space 13 by means of the tear strip 21.

FIG. 2 shows a detailed view of the tear strip 21. As shown in FIG. 2, the tear strip 21 has a backing strip 30, which extends in the longitudinal direction of the rail body 12 and which may be made of a polyester film, for example. A matrix 35 of modified natural rubber is arranged on the backing strip 30; fibers 36, which are embodied as continuous filaments, are embedded in this matrix. The fibers 36, which are embodied as glass fibers, also extend in the longitudinal direction of the rail body 12. The matrix 35 serves to distribute the forces that occur with tensile loading on the tear strip 21 onto the fibers 36, so that ideally the load is borne by all the fibers 36.

The matrix 35, made of modified natural rubber, may also serve as an adhesive, so that the tear strip 21 can be attached directly on the top side 39 of the matrix 35 to the filler body 16.

The width of the tear strip 21 may typically be 5 mm to 40 mm. The total thickness of the tear strip 21 is typically 0.1 mm to 0.5 mm, in particular approximately 0.25 mm. It is preferable for the tear strip 21 to be able to withstand a tensile force of at least 50 kg, in particular 100 kg, from the standpoint of reliability and in order to ensure the functioning, even when the anchoring rail 11 is cemented deeper than usual, for example, and thus higher pull-away forces are needed for the tear strip 21.

Claims

1-7. (canceled)

8. An anchoring rail, comprising:

a rail body defining a holding space, wherein the holding space extends in a longitudinal direction of the rail body;

a filler body disposed in the holding space of the rail body; and

a tear strip which is reinforced with fibers and which is disposed between the rail body and the filler body;

wherein the tear strip includes a matrix of modified natural rubber which at least partially surrounds the fibers.

9. The anchoring rail according to claim 8, wherein the tear strip is attached to the filler body by the matrix of modified natural rubber.

10. The anchoring rail according to claim 8, wherein the tear strip includes a backing strip, wherein the matrix and the fibers are disposed on the backing strip, and wherein the backing strip is polyethylene (PE), polypropylene (PP) or polyethylene terephthalate.

11. The anchoring rail according to claim 8, wherein the fibers are glass fibers.

12. The anchoring rail according to claim 8, wherein the filler body is an extruded foam which has an extrusion membrane at least in an area of the tear strip.

13. The anchoring rail according to claim 8, wherein the filler body is a closed-cell extruded foam.

14. The anchoring rail according to claim 8, wherein the filler body is low-density polyethylene (LDPE).