GB2232618A

GB2232618A - Process for manufacturing bundles of steel wire pieces

Info

Publication number: GB2232618A
Application number: GB9010869A
Authority: GB
Inventors: Yves Vancraeynest
Original assignee: Bekaert NV SA
Current assignee: Bekaert NV SA
Priority date: 1989-05-16
Filing date: 1990-05-15
Publication date: 1990-12-19
Anticipated expiration: 2010-05-15
Also published as: GB9010869D0; NL193324B; LU87737A1; DK118690D0; SE9001609L; SE9001609D0; NO902161D0; AT405491B; CA2016298C; PT94031A; IT1239613B; CH683200A5; ATA107690A; GR900100359A; CA2016298A1; NO300785B1; SE501425C2; NL193324C; DK171873B1; DE4014891A1

Description

0 1:2:2::::2 ( -1- a 1 433.515 PROCESS FOR MANUFACTURING BUNDLES OF STEEL

WIRE PIECES The invention relates to a process for manufacturing bundles of steel wire pieces for the strengthening of building elements, such as beams or roadway surfaces.

In order to be usable in the strengthening of building elements, wire pieces should have an essentially oblong form, with a thickness of 0.3 to 1.5 mm, a length-to- thickness ratio between 40 and 120, and a maximum length of 120 mm. By "oblong" it is mean t that the wire piece is not so bent, curled or distorted that it would no longer be possible to distinguish the general length direction in which the wire piece is intended to exert its strengthening effect. In this respect, the apparent length of the wire piece, i.e. the spatial distance between each end of the wire piece, should not be less than 0.7 times the actual length of the wire piece. The thickness of the wire piece, for non-circular crosssections, is calculated as the diameter of a circle having the same area.

Such steel wire pieces are used for the reinforcement of cementitious concrete. The wire pieces are mixed into the wet mixture, that is thereafter dumped, deformed and compacted and which then hardens in the desired form. When such wire pieces are introduced into the mixture without any further precautions, this leads to the conglomeration of the wire pieces into balls, rather than an equal distribution of wire pieces in the concrete. For this reason, the steel wire pieces are introduced into the wet mixture in the form of bundles thereof that are held together in a bundle by means of a binding substance that loses its binding power during mixing with the concrete, for example. More specifically the binding substance dissolves, 2 totally or partially, in the water present in the cementitious mortar or concrete. Such bundles preferably each contain 5 to 40 steel wire pieces. The bundle need not necessarily have a nearly circular cross-section, but may also be a flat bundle of wire pieces that are glued together side by side.

It is known from US Patent No 4284667 to manufacture such bundles of wire pieces by a method in which a number of wires are bundled and glued together, by applying an emulsion or solution in water of a binding substance that thereafter, after drying, will be capable of dissolving and/or emulgating again in the concrete. The thus obtained bundle is subsequently dried in a drying furnace, and is finally cut transversely into pieces.

However, the known methods have the disadvantages that they are limited in terms of the binding/glueing agent that may be used and that the speed of production not as fast as it could be.

According to one aspect of the present invention there is provided a process for manufacturing bundles of steel wire pieces for the strengthening of building elements, said process comprising the step of bundling and binding together a number of steel wires and the subsequent step of cutting the thus obtained bundle transversely into pieces, characterized in that said binding is effected by means of a binder which is applied in molten state and which solidifies thereafter on cooling down. 30 According to a further aspect there is provided a bundle of steel wire pieces when manufactured by A process as described above. The present invention is based on the finding that the binding or glueing substance, although previously known as a substance that has to be totally or partially soluble in water, does not for that reason necessarily have to be applied in the form of an emulsion or 6 1 k 3 solution in water, but can also be applied in the form of a hot molten liquid. The process of the present invention may even be operated using substances or mixtures of substances that are not soluble in water at all, but that may be caused to lose their binding or glueing ability by melting. This is interesting for applications where the steel wire pieces must be mixed into hot mixtures, such as hot bituminous concretes, and where the fibre bundles disintegrate or fall apart by 10 virtue of the temperature of the mixture.

Applying the glue in a molten form has the advantage that the binder need no longer be dried in a drying furnace, since it can solidify simply by rapid cooling before the bundle is transversely cut into pieces. In this way the production speed can be raised and drying energy may be saved. Furthermore, the method of applying a molten binder or glue does not prevent the use of a glue that is totally or partially soluble in water, in such a way that the bundles of wire nieces are usable both in cold cementitious mortar or concrete and in hot bituminous concrete. A further advantage lies in the fact that a glue which is to be applied by melting takes up much less room for storage, and can be preserved for an indefinite period.

The binder in a "molten state" is to be understood here in the sense that the binder, under influence of temperature, has lost its solidity, not necessarily completely by heating above a sharply defined melting point that the binder should have, but that it has lost sufficient solidity so as to enable it to be applied to the wire bundle. For substances that are composed of different molecules with different melting points, as e.g. for synthetic resins, the loss of solidity occurs by gradually softening through a softening temperature range, and it is sufficient that the substance is sufficiently soft to be applied as a glue. For such substances the temperature level of softening may be 4 determined here by the softening point according to the Ring & Ball Test. In addition, for the substances with a sharply defined melting point the "softening" occurs at the melting point. This is what is meant hereinafter 5 by softening point.

When the fibre bundles are intended for use in bituminous concrete, a binder will conveniently be chosen that is capable of or adapted to lose its binding or glueing ability by melting when mixed into such hot bituminous concrete. This means that the binder, under the influence of temperature, loses sufficient of its solidity to allow the bundles of wire pieces to fall apart into individual wire pieces under the movement caused by mixing, where this loss of solidity is due to the substance passing wholly or partially from the solid into the molten state. As the mixing temperature of bituminous concrete ranges from about 800C to 200C, and as the mixing temperature preferably has to be 30 to 50 degrees centigrade above the softening point, a glue will conveniently be chosen having a softening point in the range between 50'C and 170C. Below 500C, the risk increases that the bundles begin to stick to each other when exposed to the sun or to a warm climate.

As a binding substance, a bitumen may be chosen, preferably having the same composition as used in the bituminous concrete, if the fibre bundles are intended for mixing into a bituminous concrete. Bitumens are a mixture mainly of hydrocarbons with residual impurities, obtained as residues from refining coal or petroleum, such as pitch, tar or asphalt. They are hard at room temperature and sufficiently liquid at the mixing temperature to flow between the other components of the bituminous concrete (that further comprises a mixture of filling material, such as sand, lime, and/or stone pieces of a dimension of 2 mm up to 20 mm) and to form, after hardening, the binding component for the bituminous concrete.

j k It is also possible for the binding substance to be a thermoplastic polymer or copolymer, preferably in the form of a conventional hot melt glue, which, depending on the manufacturer thereof, also comprises resins, waxes, softeners, stabilizers and possibly fillers, in addition. Accordingly', a polyester-polyurethane glue may be used, e.g. according to U.S. Patent No. 2801648, of which the softening point may be set by adding more or less di-isocyanate during the manufacturing of the glue. An EVA-glue (ethylene-vinylacetate copolymer) may also be used, of which the softening point may be adapted by means of the proportion ethylene/vinylacetate. When a hot melt glue is required that can dissolve or form an emulsion in water, then a typical hot melt glue may be used, as used for applying in molten state to paper or cardboard, where the glue can thereafter become tacky again by moistening with water. In practice, a choice may be made among the ho4- ne -I --le on an- di- lues ava4lal,, that are e.g. described in the book of D.L. BATEMAN "Hot melt adhesives", Third Edition (Noyes Data Corporation).

The binder may be applied in different ways. It is possible to pass a bundle of wires continuously through a bath of molten binder, and to wipe off the excess of glue at the exit of the bath before cooling the bundle, e.g. in an air jet or in water, when a glue is used that is not soluble in water. Another method, when the binder is in powder form, consists of heating up a continuous bundle of wires and passing this hot bundle through a fluidized bed of such powder. The powder then melts against the wire bundle, and the glue solidifies again at the exit of the fluidized bed. It is also possible to use conventional applicators having a nozzle that continuously delivers the molten binder under pressure on or around the bundle and a wiping piece. It is also possible to apply the binder on the individual wires first, and to bundle the wires thereafter, where 6 the wires can be glued together, e.g. by heating up and cooling down again.

In order to glue the wire pieces easily together, and so that the wire pieces can easily be separated thereafter, it is preferred to glue the wires side by side into a flat bundle. It is however also possible to manufacture a round bundle, in which the glue does not penetrate completely towards the core of the bundle, but keeps all the wires together because it acts as a tight sleeve around the bundle. Glueing the wires together consequently does not necessarily mean that all wire pieces are brought in contact with the glue, but only that, after solidification of the glue, the wires are maintained together in a bundle.

When the wires are conducted side by side in order to be grouped into one flat bundle in one plane, and when the wire pieces are to be provided with undulations or deformations and/or hooks or bendings at the extremities, those deformations shall preferably be applied on the continuous bundle, before the cutting thereof. This is then preferably done by conducting the flat bundle continuously between two rotating rollers with an undulating cross-sectional circumference or with another profile, where the protrusions of one profile match the indentations of the other one. In such a way, deformations are applied in a plane that comprises the longitudinal direction of the bundle, and that is perpendicular to the plane of this bundle.

It is clear that the process of the present invention is highly adapted for a continuous process, in which a number of wires are unwound from their respective spools, and in which these wires after unwinding are caused to converge towards the entrance of a machine, in which they are bundled and glued. In this machine, the bundle passes a glueing station first, where the glue is applied, and then passes a cooling station, where the glue is caused to cool down for 4 11 7 solidification, and then further optionally passes a deforming station, where the bundle is deformed between two rotating wheels, and finally passes a cutting station, where the bundle is cut into pieces, and the bundles of wire pieces are collected in a container.

8

Claims

1. A process for manufacturing bundles of steel wire pieces for the strengthening of building elements, said process comprising the step of bundling and binding together a number of steel wires and the subsequent step of cutting the thus obtained bundle transversely into Pieces, characterized in that said binding is effected by means of a binder which is applied in molten state and which solidifies thereafter on cooling down.

2. A process as claimed in claim 1, wherein said binder is capable of or adapted to lose its binding ability by melting when mixed into a hot bituminous is concrete mixture.

3. A process as claimed in claim 1, wherein said binder is capable of or adapted to lose its binding ability by dissolving or forming an emulsion in water when mixed into a cementitious concrete.

4. A process as claimed in any one of the preceding claims, wherein said wires are bound to each other side by side into a flat bundle.

5. A process as claimed in claim 4, wherein said wires are subsequently deformed in a plane comprising the longitudinal direction of the bundle and perpendicular to the plane of said flat bundle.

6. A process as claimed in cla_im 1 substantially as herein described.

7. A bundle of steel wire pieces when manufactured by a process as claimed in claim 1.

8. A process for the preparation of a castable hot 9 mixture of bituminous concrete, which comprises introducing bundles of steel wire pieces manufactured by a process as claimed in claim 1 into a mixture for said bituminous concrete.

Published 1990 at The Patent Office. Sts.'Pllouse,6671 High Holborn. London WCIR4TP.Further copies maybe obtained from The Patent OfficeSales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques lt(L St Mary Cray, Kent, Con. 1/87