DE2727427A1 - COVERED METAL WIRE AND PROCESS AND DEVICE FOR ITS PRODUCTION - Google Patents

Description

Isenmann Drahterzeugnisse GmbH, Geruigstra3s 67, 75 Karlsruhe

Sheathed metal wire and method and apparatus for its manufacture

The invention relates to a plastic coated with a high molecular weight plastic which has a low viscosity at the melting temperature Metal wire for wire mesh, wire mesh or wire mesh for dewatering, sorting and / or classifying corrosive, granular material, with the sheathing firmly seated on the metal wire, as well as a method and a device for its production.

Wire mesh, wire mesh and wire mesh are widely used in the processing of minerals, e.g. gravel, ores or coal widespread use. The profitability of the processing depends essentially on a large open sieve area and a long service life of these machine parts.

808 ^ 81/0182

Well-known wire mesh, wire mesh and wire grids made of metal wires have a large open sieve area. However they often only have a very limited service life. In addition, she checks at short intervals Need to become. However, since the end of their service life is not readily recognizable, they are often too early or too late exchanged.

In order to avoid the last-mentioned disadvantages, it is known from US Pat. No. 2,533,339, the metal wires with a To provide protective cover. The protective coating has a small thickness and consists of an organic, thermoplastic resin. Such wire mesh, wire mesh or wire grids have, however, been used during processing Corrosive goods also not proven. With these sieve elements, too, the metal wire must be next to absorb the impact work of the material to be screened to withstand the high tensile and swell loads. The sheath could only last a short time limit the abrasion through the screenings. In addition, the mesh accuracy and mesh strength corresponded not the requirements.

The invention was based on the object of providing a sheathed metal wire for wire mesh, wire mesh and wire mesh to create, the latter having a high mesh accuracy, mesh strength and stability and inexpensive can be produced.

This object is achieved in that the jacket thickness of the plastic is at least 0.3 times the Metal wire diameter. The metal wire is thus essentially no longer surrounded by a protective layer. Rather, the metal wire forms a support for the plastic of the sheathing. This makes it possible that the Plastic sheathing in the first place

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absorbs the impact work of the material being screened, while the metal wire only absorbs the tensile and swell loads. Furthermore, when the grains of the material to be screened hit the casing, such high stress peaks no longer occur on, whereby the abrasion and thus the service life can be influenced favorably.

For the processing of particularly corrosive minerals, e.g. ore, coal or gravel, it has proven to be beneficial when the jacket thickness of the plastic is 0.3 to 5 », preferably 0.5 to 4.0 times the metal wire diameter.

Sine substantial simplification and savings in manufacture of the sheathed ketallic wire results when the plastic of the casing directly without an intermediate adhesive layer is upset. The coating is advantageously applied as a single layer.

It is particularly advantageous for the plastic to have a matt surface that deviates from a high-gloss surface. The resulting higher roughness of the surface leads to a higher coefficient of friction. This allows the wire mesh made from these coated metal wires, Wire mesh or wire mesh a better mesh accuracy and mesh strength can be achieved.

Because of its high elasticity and thus the ability to absorb shocks and because of its high abrasion resistance, a polyester, preferably a polyester-elastomer, has proven itself as a plastic.

Additives for UV and hydrolysis resistance can be added to the plastic. This becomes a premature Prevents it from becoming brittle or swelling as a result of light or water.

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The mesh accuracy and mesh strength can be increased if the plastic is on its surface has a profile running in the longitudinal and / or in the transverse direction. At the same time, it can influence the sieve hole geometry and the volume resistance can be taken. The sheathed metal wire can, for example, in cross section trapezoidal or grooves can be provided on the surface of the plastic. The cross section of the internal metal wire remains unaffected.

In contrast to wire grids made only of metal wire, in which the warp wires are pre-cranked by 30 % and the weft wires by 70 % before processing on a lattice chair, a sheathed metal wire is pre-formed in such a way that the warp wires and the weft wires made from it each have a cranking of 50 f » . The cranking takes place after the unmantle.

If the sheathed metal wire becomes a wire mesh on a loom with a plug arm device or a Processed with a comparable device, a high mesh accuracy and mesh strength can be achieved as a result be that only the weft wires are slightly cranked.

If, on the other hand, the coated metal wire is processed into a wire mesh on a loom with a shuttle, the warp and weft wires are uncranked. It is advantageously possible to use a sheathed metal wire to weave a comparatively large overall diameter.

An extrusion process is particularly suitable for sheathing the metal wire with the plastic. Included the metal wire is cold to a cross-head with a mouthpiece and the plastic

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fed to the mouthpiece under pressure and heat at the same time. The fact that the metal wire in the cold state, z.3. with Room temperature, is supplied, there are significant advantages. First of all, it does not require energy-consuming Provide heating devices for the metal wire. In addition, the cold metal wire accelerates the cooling process of the plastic. Therefore, especially in the area of the parting line between the metal wire and the sheathing in the plastic Tensions are generated and "frozen", which ensure good adhesion of the sheath to the metal wire.

The adhesion between the sheath and metal wire can be increased if the sheathed metal wire is applied directly After leaving the mouthpiece, it is cooled down quickly and through and through to almost ambient temperature will. The cooling medium used must be selected and supplied at such a temperature and speed that that from the sheathing depending on the Yfärconductivity of the plastic to the free surface Any heat that arrives is removed continuously and quickly without accumulation.

Deviating from a high gloss surface matte surface can be created especially when the mouthpiece is held on an at least 5% _t preferably to a 10 to 15% lower temperature than the melt temperature of the plastic material during the Ummanteins.

It has been shown that a homogeneous and perfect sheathing can be achieved especially when the required high extrusion pressure for the pressure jacket is precisely maintained in the mouthpiece. This The higher the pressure, the more difficult it is to maintain close to the end of the mouthpiece the desired jacket thickness of the plastic is selected.

80 * 481/0182

This problem occurs especially when it is very low viscous plastics; i.e. plastics that are very thin at melting temperature are processed. this applies particularly to polyester and polyester elastomers. Nevertheless, apply around the coating in one operation to be able to, it has proven to be particularly advantageous when carrying out the above-mentioned process proved that the length of the cylindrical nozzle portion of the mouthpiece is 10 to 40 times, preferably 20 to 30 times the jacket thickness of the jacket is.

The invention is described below with the aid of the exemplary embodiments shown schematically in the drawings explained in more detail.

They show: FIG. 1 an encased according to the invention

Metal wire in cut and

FIG. 2 shows a cross-sectional spray head according to the invention in section.

In Figure 1 is a section of a sheathed according to the invention Metal wire shown. The metal wire 1 is embedded concentrically in the casing 2. The sheath 2 has a jacket thickness 3 which is preferably 0.5 to 4.0 times the metal wire diameter 4. The diameter of the coated metal wire results from the sum of the metal wire diameter 4 and the double the jacket thickness 3. The surface 5 of the jacket is not designed with a high-gloss finish. It has a surface roughness for example about 20 to 50 ^. The metal wire 1 is preferably a bright drawn, round spring steel wire from 0.3 to 5 mm in diameter.

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A coated metal wire according to the invention is turned into wire meshes, Wire meshes or wire grids for dewatering, sorting and / or classifying corrosive, granular material, e.g. gravel, sand, coal or ores, processed. This usually involves high kinetic energy on these machine parts Material to be screened that hits it causes high abrasion and considerable dynamic and static loads. According to the invention these stresses are absorbed by the casing. The casing absorbs it largely reduces the impacts that occur through the material to be screened and, because of its high abrasion resistance, limits wear and tear essential one.

Before further processing the coated metal wire, it is usually straightened. In order to achieve a high mesh accuracy and mesh strength, the sheathed metal wires according to the invention must be more or less pre-cranked depending on their processing. When processing on a lattice chair, it has proven to be beneficial if the warp wires and the weft wires are each given a pre-cranking of 50 % . When used on a loom with a plug-in arm device or a comparable device, an optimal wire mesh is obtained when the Xett wires are not cranked and the weft wires are only slightly cranked. The final cranking of the warp and weft wires is created by the tension applied during weaving. When pre-cranking, care must be taken that with a given mesh size the pitch is reduced by approx. 5 to 30% and the cranking depth is increased by approx. 30 to 90 % depending on the thickness of the sheathing. This also applies to wire mesh. If the sheathed metal wire according to the invention is woven on a loom with a shuttle, neither the warp nor the weft wires are cranked. Sheathed metal wires according to the invention up to a comparatively large overall diameter can be processed on such looms.

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A coated metal wire according to the invention can be processed within wide limits. Its possible uses are wide-ranging due to its high load-bearing capacity and abrasion resistance. Wire mesh, wire meshes or wire grids produced therefrom can advantageously be provided with tensioning devices. The warp and weft wires touch each other without play. They lie firmly and immovably against each other at the nodes and thus improve the load-bearing capacity and wear resistance of the sieves. The composite is highly elastic and has great torsional rigidity in all temperature ranges of interest, for example in a temperature range from −50 to over + 100 ^° C. Such screens are ideally suited for outdoor use. They have a high flexural fatigue strength with perfect adhesion between metal wire and sheathing. They are characterized by high abrasion resistance and have a high notch resistance against cracking due to deformation.

The low specific weight of the plastic also saves a considerable amount of weight compared to pure plastic Steel sieves of the same mesh size. The elasticity of the plastic, in particular a polyester elastomer, is improved due to its resilient effect, the acceleration and the transportability of the material to be screened.

In Figure 2 is a section of a cross-head according to the invention shown for the sheathing of the metal wire according to the invention. The cross-head has a tool body 6. An adapter 7 is used in the tool body as a connection for the supply of the plastic, e.g. a polyester elastomer 6 the metal wire is guided in a quill 9. The mouthpiece 10 adjoining the quill 9 contains the nozzle area 11. The DUsenbereich 11 has a conical part 12, which merges into a cylindrical nozzle area 13. The length of the cylindrical nozzle area 13 is preferably 10 to 40 20 to 30 times the jacket thickness 14 of the jacket 15. The length (12 + 13) of the entire nozzle area

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depends on the flow properties of the plastic, the extrusion speed (wire speed), the jacket thickness of the jacket and the diameter of the finished, coated metal wire. Temperature measurement devices for measuring the melt temperature can be installed in the cross-head of the plastic may be provided. The mouthpiece 10 can be a cooling and / or heating device (not shown) to control its operating temperature. The arrow drawn indicates the direction of travel of the metal wire 8. The cross-head works on the principle of pressure jacketing.

This cross-head is particularly suitable for sheathing a metal wire after an extrusion process. In the production of the sheathed metal wire according to the invention, this is done at high speed, e.g. at approx. 300 meters per minute, fed to the cross-head. At the same time, an extrusion screw presses the plastic, e.g. a polyester elastomer, via the adapter 7 into the nozzle area 11 of the mouthpiece 10. For Polyester elastomers, this pressure is approx. 200 to 250 bar. The great length of the cylindrical nozzle area enables the required back pressure on the extrusion screw. The back pressure is with the Melting temperature of low viscosity plastic is of great importance. The metal wire is at ambient temperature supplied and immediately after leaving the mouthpiece 10 at least approximately back to ambient temperature cooled down quickly and through and through. The rapid cooling of the plastic both inwards and outwards is prevented it is true that the plastic is post-tempered, as is the case, for example, in the manufacture of electrical Cables is carried out. However, this creates stresses in the plastic and "freezes" them, in particular in the case of high molecular weight plastics lead to the

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sheath has a high degree of adhesion to the metal wire. A high degree of adhesion, being between the metal wire and the sheath no capillaries or other cavities are formed, is an essential prerequisite for a long service life. Of the Finished, sheathed metal wire can be wound up in the usual way on drums or rolls.

The stability as well as the mesh accuracy and mesh strength of the wire cloth, wire mesh and wire mesh produced from the sheathed metal wire can be further increased if the surface of the sheath is not designed with a high-gloss finish. The high gloss on the free surface is usually achieved by reheating the casing in the mouthpiece. Extensive tests have shown, however, that it is precisely the reheating of the plastic in the area of the free surface that is adversely affected. One explanation for this lies in the fact that the excessive local heating destroys the molecular chains of the plastic. As a result, the plastic loses its abrasion resistance in this important area. Excessively strong abrasion is the result. This can be avoided by keeping the mouthpiece 10 at a temperature which is approximately 10 to 15 % below the cash temperature of the plastic during the coating. Is used as the plastic material is a polyester elastomer, the optimum mass temperature during encasing about 235 ° C and the temperature of the mouthpiece 200 ⁰ C. During the encasing of the metal wire, it is particularly important that the optimum mass temperature is always maintained. The optimum melt temperature is in the range which, on the one hand, enables a largely homogeneous coating and, on the other hand, excludes overheating of the plastic, which can lead to the destruction of molecular chains. Careful monitoring and compliance with the mass temperature of the plastic and the temperature of the mouthpiece is crucial for the good properties of the coating.

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With the stated ratios for the jacket thicknesses of the plastic, the smaller values preferably apply in particular those from 0.3 to 2.5 for metal wires with a diameter greater than 2 mm and the larger values in particular those from 1 to 5 for metal wires less than 2 mm in diameter.

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Claims (14)

Isenmann Wire Products GmbH, Gerwigstr. 67, 75 Karlsruhe Claims Metal wire for wire mesh, coated with a high molecular weight plastic that has a low viscosity at melting temperature, Wire meshes or wire grids for dewatering, sorting and / or classifying corrosive, granular material, the Sheath sits firmly on the metal wire, thereby characterized in that the jacket thickness (3) of the plastic is at least 0.3 times the Ketal wire diameter (4) is. 2. Sheathed metal wire according to claim 1, characterized in that the sheath thickness (3) of the Plastic 0.3 to 5.0, preferably 0.5 to 4.0 times the metal wire diameter (4). 3. Sheathed metal wire according to claim 1 or 2, characterized in that the plastic is applied directly without an intermediate adhesive layer. 4. Sheathed metal wire according to one of claims 1 to 3 »characterized in that the Plastic has a matt surface that differs from a high-gloss surface. -2- 809881/0182 ORIGINAL INSPECTED 2727 * 27 5. Sheathed metal wire according to one of claims 1 to 4, characterized in that the plastic is a polyester, preferably a polyester elastomer is. 6. Sheathed metal wire according to one of claims 1 to 5, characterized in that the plastic additives for UV and hydrolysis resistance are attached. 7. Sheathed metal wire according to one of claims 1 to 6, characterized in that the Plastic has a profile running in the longitudinal and / or transverse direction on its surface. 8. Sheathed metal wire designed as a warp and weft wire for a wire mesh according to one of claims 1 to 7, characterized in that the warp and weft wires have a cranking of 50 % each. 9. Sheathed metal wire designed as warp and weft wire for a wire mesh according to one of the claims 1 to 7, characterized in that only the weft wires are slightly cranked are. 10. Sheathed, formed as a warp and weft wire for a wire mesh metal wire according to one of the claims 1 to 7, characterized in that 80 ^ 881/0182 that the warp and weft wires are uncranked. 11. Method of manufacturing the covered metal wire according to one of claims 1 to 10, characterized in that that the metal wire (8) in the cold state to a Cuerspritzkopf (6) having a mouthpiece (10) and the plastic to the mouthpiece (10) is supplied under pressure and heat at the same time. 12. The method according to claim 11, characterized in that that the coated metal wire immediately after leaving the mouthpiece (10) to is cooled rapidly and through and through to approximately ambient temperature. 13. The method according to claim 11 or 12, characterized in that the mouthpiece (10) is kept at a temperature by at least 5%, preferably at a temperature 10 to 15% lower than the melt temperature of the plastic during the sheathing. 14. Device for performing the method according to one of claims 11 to 13 »characterized in that that the length (13) of the cylindrical nozzle area of the mouthpiece (10) is 10 to 40 preferably 20 to 30 times the jacket thickness (14) of the jacket. -4- 808881/0182