EP0852634B1 - Process for producing a steel cord - Google Patents

Abstract

PCT No. PCT/EP96/03884 Sec. 371 Date Jul. 17, 1998 Sec. 102(e) Date Jul. 17, 1998 PCT Filed Sep. 4, 1996 PCT Pub. No. WO97/12091 PCT Pub. Date Apr. 3, 1997Process for producing a steel cord for pneumatic tires comprising a bunch of wires, the core of which consists of wire filaments 10 arranged bunched juxtaposed in parallel. Preferably at least three wire filaments 10, 20 are provided, at least two wire filaments located juxtaposed in parallel being spirally shaped as core filaments 10 forming a core 60 and at least one wire filament spirally surrounding the two core filaments 10 as a sheathing wire 20. Spirally shaping the wire filaments 10 is achieved in accordance with the invention by false twisters 40. Due to this spiral shaping of the wire filaments 10 migration of the filaments from the core composite is avoided more particularly. The residual torsional stresses of the core filaments among each other and in conjunction with the restoring forces of the sheathing wire are advantageously cancelled. In addition, the steel cord features to advantage a flattened, more particularly, oval shape.

Description

The invention relates to a method for producing a steel cord and a steel cord made by this method.

Steel cords as inserts in pneumatic tires for motor vehicles for improvement their driving characteristics, dynamics, stability and extension their lifespan are known and are usually made of strands constructed, one strand a bundle of at least two, usually however, there is several individual wires that are laid around and / or are twisted around each other. The production takes place by means of a Bunching machine and is quite complex.

Steel cords are also known, their soul from a central, folded wire bundle, which is no longer in a separate Stranding process is produced, but immediately during stranding can be formed.

DE-A 26 19 086 describes a method for producing a Steel cords are known in which several serve as soul filaments Wire filaments are pulled off the spools. The soul filaments are combined into a strand and on the edges of a Guide eyes sharply bent and deformed helically. In principle, a sheathed wire is pulled off a coil is also helical on the edges of another Guide eyes sharply bent and also helical deformed. The soul filaments bent together are on Rope formation point wrapped in the preformed sheathed wires. The the resulting rope runs over a pair of rollers to a false twist device, which plastically deformed the steel cord obtained and the existing ones Residual torsional stresses reduced. In the known method it can affect the brass coating of the Wire filaments caused by those on the edges of the guide eye helical deformation. The impairment of Brass coating leads to an impairment of liability the tire rubber. Furthermore, it can in the manufacturing process The individual filaments are impaired when local pressure points occur occur. This affects the fatigue strength, which makes the individual filaments unsuitable for cyclical loads because such local deformations are the starting points for the Fatigue fractures occur.

EP 0 492 682 describes a manufacturing method for a steel cord known in which serving as soul filaments Coils are withdrawn and twisted around their longitudinal axis become. The soul filaments are then in a single plane merged in parallel and with a sheathed wire envelops. One or more of the core filaments arranged in one plane or the plane of the core filaments as a whole exhibits elastic Residual torsional stresses. The elastic residual torsional stresses are chosen such that the wire bundle in its entire length remains essentially flat as long as no external forces attack it. The size and direction of the residual torsional stresses are so chosen that the elastic residual torsional stresses of the core filaments with the restoring forces of the sheath filaments. The production such a flat wire bundle is difficult and technical expensive because the parallel single filaments are kept on one level Need to become.

The invention has for its object a method for manufacturing to propose a steel cord where no interference wire coating or local pressure marks.

To solve this problem, a method with the features of Claim 1 proposed. In the method according to the invention are the soul filaments around each other using a false twister twisted to obtain a spiral plastic deformation. After the false twister, the spiral-shaped soul filaments are formed parallel to each other with at least one sheath wire wrapped around. The main advantage of the manufacturing method according to the invention lies in the gentle plastic deformation of the Soul filaments by means of a false twister, with neither impairment local pressure marks still occur in the coating. Consequently stands out the manufactured by the inventive method Steel cord through good grip with the tire rubber and on characterized by high fatigue strength.

In a further embodiment of the manufacturing method according to the invention it is suggested that in step B two, three or four soul filaments twisted together and that two or more strands with two, three or four twisted soul filaments combined in an additional step C to form a soul become.

According to claims 4 and 5 can in the inventive method be provided that the steel cord is pressed so that it gets an oval shape. The deformation is expediently carried out by a Pair of roles.

A steel cord produced by the method according to the invention has in its simplest form three wire filaments, one of which two soul filaments are spirally shaped and one too spiral-shaped sheathed wire are surrounded. Here are the soul filaments in a suitable manner using a false twister the desired speed twisted around to get after the false twister again parallel to each other, but with spiral preforming to be brought together. To make this bundle more parallel Soul filament becomes another filament with the same pitch and Direction of thread to the spiral shape of the preforming of the individual filaments. This inventive formation of a wire bundle the individual filaments are neither damaged nor deformed locally, so that a steel cord of this type for a tire, in particular when subjected to compression, has very good fatigue properties.

In a particularly advantageous embodiment of the invention, one or several layers of sheathed wires are provided which cover the at least two Soul filaments surround. This creates a wire bundle for a tire cord provided, in which the wires of the bundle of souls also Do not migrate from the rope assembly when used in the tire belt. The wire bundle according to the invention can be produced very inexpensively because the bundle of souls does not need its own work process, but be produced in line with the entire production can.

To further solve the problem is a steel cord according to claim 16 proposed with a wire bundle, with at least two Wire filaments as a soul-forming bundle of soul filaments running parallel to each other and elastic residual torsional stresses have in connection with the restoring forces Pick up at least one sheath wire surrounding the core filaments. The wire bundle according to the invention can be easily produced because the wire filaments of the soul are not parallel in parallel one level, which is technically with some effort is connected, but can be summarized in the form of a bundle. Through the appropriate choice of the residual elastic torsional stresses easy processing with rubber coating is achieved because the wire bundle according to the invention lie flat in the rubber coating remains.

In a further advantageous embodiment of the invention, the steel cord has a flattened, essentially oval shape. This invention oval shape has significant for use in tires Advantages, especially due to the different stiffness of the Steel cords in radial and lateral directions. The flattened, essentially oval shape can, for example, by squeezing of the steel cord can be reached with a pair of rollers.

Further advantageous refinements of the invention and that of the invention Procedures are described in the subclaims.

Figur 1

veranschaulicht in schematischer Darstellung ein erfindungsgemäßes Verfahren zur Herstellung eines erfindungsgemäßen Stahlcords gemäß der Figur 4.

Figur 2

veranschaulicht in schematischer Darstellung ein erfindungsgemäßes Verfahren zur Herstellung eines erfindungsgemäßen Stahlcords gemäß der Figur 3.

Figur 3

zeigt in schematischer perspektivischer Darstellung einen erfindungsgemäßen Stahlcord mit zwei spiralförmig vorgeformten und parallel aneinanderliegenden Seelenfilamenten, die von einem Hülldraht spiralförmig umgeben sind.

Figur 4

zeigt einen erfindungsgemäßen Stahlcord gemäß Figur 3, jedoch mit sechs spiralförmig vorgeformten und parallel aneinanderliegenden Seelenfilamenten.

Figur 5

zeigt in schematischer und perspektivischer Darstellung einen erfindungsgemäßen Stahlcord mit drei spiralförmig vorgeformten und parallel aneinanderliegenden Drahtfilamenten als Seele, die von einer Lage von sechs Hülldrähten umgeben ist.

Figur 6

zeigt einen weiteren erfindungsgemäßen Stahlcord mit einer Seele aus zwölf spiralförmig vorgeformten Drahtfilamenten, die von einer Lage von Hülldrähten umgeben ist, die wiederum spiralförmig mit einem Wendeldraht umgeben ist.

The invention is illustrated in the drawing using several exemplary embodiments and is explained in more detail below.

Figure 1

illustrates a schematic representation of a method according to the invention for producing a steel cord according to the invention according to FIG. 4.

Figure 2

illustrates a schematic representation of a method according to the invention for producing a steel cord according to the invention according to FIG. 3.

Figure 3

shows a schematic perspective view of a steel cord according to the invention with two spirally preformed and parallel core filaments, which are surrounded by a sheathed wire spiral.

Figure 4

shows a steel cord according to the invention according to Figure 3, but with six spirally preformed and parallel adjacent soul filaments.

Figure 5

shows a schematic and perspective view of a steel cord according to the invention with three spirally preformed and parallel adjacent wire filaments as a core, which is surrounded by a layer of six sheathed wires.

Figure 6

shows another steel cord according to the invention with a core of twelve spirally preformed wire filaments, which is surrounded by a layer of sheathed wires, which is in turn spirally surrounded by a helical wire.

Figures 3 to 6 show different embodiments of the invention Steel cords with different numbers of the soul of the wire filament forming the steel cord. In Figure 3 is one first embodiment of a steel cord according to the invention shown with a wire bundle with two core filaments 10 as core 60, the are spirally shaped and run parallel to each other. The two soul filaments 10 are of another filament than Surrounding sheath wire 20, namely the sheath wire 20 is the same Pitch height and direction to the spiral shape of the soul filaments 10 placed. In the illustrated embodiment, the soul filaments are 10 left-handed spiral shaped, and the sheath wire 20 is also left-handed wound around the two soul filaments 10. The aisle is typically about 14 mm in such a steel cord, the diameter of the core filaments 10 and the sheath wire 20 is about 0.28 mm.

Figure 4 shows another embodiment of an inventive Steel cords according to FIG. 3, in which the core 60 consists of six spirally shaped and parallel to each other Soul filaments 10 is formed, the left-hand spiral shaped are and wrapped by a seventh filament as a sheath 20 left-handed are. In this embodiment, the pitch can be, for example 18 mm and the diameter of the used Filaments 0.35 mm.

Of course, steel cords with wire bundles are also conceivable, one have an even greater number of wire filaments. With increasing Number of wire filaments in the soul becomes the diameter of the filaments chosen smaller. The pitch can be specified as required and the diameter of the sheath wire can be chosen the same like the diameter of the wire filaments of the soul, however, can also differ from their diameter. With a bundle of soul wires, which is formed from twelve spirally shaped wire filaments the pitch z. B. advantageously 12.5 mm, the diameter the wire filaments 0.22 mm and the diameter of the bundle of soul wires surrounding sheath wire 0.15 mm.

Figure 5 shows a further embodiment of an inventive Steel cords in a schematic perspective view. The Core 60 of the steel cord is made from three spirally preformed core filaments 10 formed, which run parallel to each other. This are made from a layer of six closely spaced sheathed wires 20 surround, which have the same direction as that Soul filaments 10. For reasons of clarity the soul filaments 10 shown longer than the sheathed wires 20. Die Direction of the soul filaments 10 can also be in opposite directions the thread direction of the sheathed wires 20.

Such a tight covering of the core 60 with a layer of sheathed wires 20 has the advantage that the soul filaments 10 of the bundle of souls even when used as a steel belt, not from the rope assembly can migrate. In addition, the manufacture of such a steel cord very inexpensive since the bundle of souls 60, as below will not be described, but needed can be produced in line with the steel cord production.

In the embodiment shown in Figure 5, the Soul filaments 10 advantageously over a diameter of 0.2 mm, the sheathed wires 20 over a diameter of 0.35 mm.

FIG. 6 shows an embodiment of the invention which is similar to the exemplary embodiment in FIG Steel cord shown over a soul 60 out of twelve has left-hand spiral preformed core filaments 10, the again from a left-handed position from fifteen sheathed wires 20 are surrounded. In this embodiment, all wires advantageously have same diameter of 0.175 mm. The one in FIG. 6 Steel cord shown is additionally with a spiral wire 30 wrapped right-handed. The diameter of the spiral wire 30 is 0.15 mm, for example. The direction of the soul filaments 10 can of course also work in opposite directions in this exemplary embodiment to the thread direction of the sheathed wires.

Figure 1 illustrates a schematic representation of an inventive Process for producing an inventive device shown in FIG Steel cords. To make this steel cord with a Bundles of six wire filaments are used in a first Step A, the core filaments 10 drawn from six spools 11. In a further step B, three of the six Core filaments 10 are combined into a strand 50 by means of deflection rollers 15, to then in a third step C of two false twists 40 each clockwise with one set Pitch (here: 18 mm) to be preformed spirally. After this Leaving the false twister 40, the two bundles with each three core filaments in a further work step D using pulleys 15 assembled into a wire bundle from six wire filaments, that forms the core 60 of the steel cord to be produced. The soul 60 from six soul filaments 10, the right-hand spiral are formed in the same operation with a sheath wire 20 surrounded, which is withdrawn from a coil 21 in step E. and right-handed in step F with a predetermined pitch (for example 18 mm) is wound around the core 60. The result this manufacturing process is a steel cord according to the invention, such as he is shown in Figure 4, wherein the steel cord shown in Figure 4 just like the steel cord shown in Figure 3 on left-handed Soul filaments 10 and sheathed wires 20 has.

The wire filaments used as core filaments in this manufacturing process are advantageously made of wire rod with a steel quality of 0.6 to 0.9% C, 0.4 to 0.8% Mn and 0.1 to 0.3% Si and a maximum of 0.03% S, P and other usual accompanying elements. The wire rod is in advance rolled in several steps from 5.5 mm to thinner diameters, drawn, heat-treated and before the subsequent, final stage, mostly a wet drawing step, brassed. The brass is called "Lubricant" used when pulling, but primarily serves as liability of the steel cord with the rubber compound of the tire. The production the steel cords are made by twisting and stranding the Wire filaments in a suitable number and shape, with the choice of Machine parameters a suitable combination of coil size and Engine speed must be found because of a high speed with small insert coils and accordingly a low one Speed is connected with large insert coils.

The method according to the invention for producing a Steel cords are suitable for the production of steel cords with bundles of souls from two to thirty wire filaments, including cord constructions same type imaginable with more than thirty wire filaments are.

Figure 2 illustrates a method for producing an inventive Steel cords as shown in Figure 3. In a first Step A becomes two core filaments 10 from two spools 11 deducted and merged in a second step B. The two soul filaments 10 are in a further step C in a false twister 40 right-handed with a set pitch (e.g. 14 mm) right-hand spiral shaped. This two spirally twisted soul filaments 10 form the 60 core of the steel cord to be produced. In a next step E a wire filament is drawn off a spool 21, which as a sheath wire 20 in a last step F around the soul 60 right-handed with a pitch of 14 mm, for example becomes.

In a further embodiment of the invention, those described above are described Steel cords according to the invention pressed into an oval shape. This is particularly suitable for steel cords as in the Figures 5 and 6 are shown. The oval shape of the steel cord can for example by pressing the cord together using a pair of rollers be preserved. Due to the different stiffness in the radial and lateral direction the oval shape of the steel cord has an application in tires has considerable advantages.

The proposed steel cord according to the invention is simple and inexpensive producible and is characterized by excellent properties, especially in the case of compressive stress. He lets himself rubberize slightly, as the residual torsional stresses are released to the outside are and thus lie flat during the gumming process remains. The migration ability of the wire filaments used is also great from the rope assembly when used as a belt very low. With the A variety of configurations proposed according to the invention are numerous of steel cord constructions that can be used in a wide range of applications cover, starting with steel cords for car tires from light truck tires to truck and bus tires.

Claims (18)

1. A process of producing a steel cord characterized by the following steps:

   A:uncoiling from reels (11) at least two wire filaments serving as core filaments (10),

   B:combining said uncoiled core filaments (10) in a false twister (40) into a strand (50) and initially intertwining the core filaments to spirally preshape them,

   C: sheathing said spirally preshaped individual filaments (10) located downstream of said false twister (40) juxtaposed in parallel in the form of a core (60) with at least one wire filament serving as the sheathing wire (60) uncoiled from a reel (21).
2. The process as set forth in claim 1, characterized in that in step B two, three or four core filaments (10) are mutually intertwined and in that two or more stands (50) incorporating two, three or four intertwined core filaments (10) are combined into a core (60) in an additional step C.
3. The process as set forth in claim 1 or 2, characterized in that said at least two core filaments (10) are intertwined left-handedly or right-handedly and in that at said least one sheathing wire (20) is likewise wound left-handedly or right-handedly about said preshaped core filaments (10).
4. A process for producing a steel cord, characterized in that a steel cord produced as set forth in any of the claims 1 to 3 is compressed such that it receives an oval shape.
5. The process as set forth in claim 4, characterized in that said steel cord is compressed into an oval shape through a pair of rolls.
6. A steel cord produced by a process as set forth in any of the -claims 1 to 5.
7. The steel cord as set forth in claim 6, characterized in that at said least two core filaments (10) are shaped as right-handed or left-handed spirals and said at least one sheathing wire (20) surrounding said at least two core filaments (10) likewise right-handedly or left-handedly.
8. The steel cord as set forth in claim 6 or 7, characterized in that the pitch of the spiral preshape of said core filaments (10) corresponds to the pitch of said sheathing wire (20) surrounding the latter.
9. The steel cord as set forth in any of the claims 6 to 8, characterized in that the pitch of said preshape and the pitch of said surrounding sheathing wire (20) is between 6 mm and 30 mm.
10. The steel cord as set forth in any of the claims 6 to 9, characterized in that the outer diameter of the spirals of each preshaped core filament (10) is between 0.1 and 0.5 mm.
11. The steel cord as set forth in any of the claims 6 to 10, characterized in that the diameter of said core filaments (10) is between 0.12 and 0.5 mm.
12. The steel cord as set forth in any of the claims 6 to 11, characterized in that one or more plies of sheathing wires (20) are provided surrounding said at least two core filaments (10).
13. The steel cord as set forth in any of the claims 6 to 12, characterized in that said core filaments (10) and said sheathing wires (20) are the same in diameter.
14. The steel cord as set forth in any of the claims 6 to 12, characterized in that said core filaments (10) and said sheathing wires (20) differ in diameter.
15. The steel cord as set forth in any of the claims 6 to 14, characterized in that a spiral wire (20) surrounding said sheathing wires (20) is provided.
16. The steel cord as set forth in any of the claims 6 to 15, characterized in that at least two wire filaments as core filaments (10) forming a core (60) are oriented bunched juxtaposed in parallel and feature elastic residual torsional stresses which are cancelled in conjunction with the restoring forces of at least one sheathing wire (20) surrounding the core filaments (10).
17. The steel cord as set forth in any of the claims 6 to 16, characterized in that said steel cord features a flattened, substantially oval shape.
18. The steel cord as set forth in claim 17, characterized in that the ratio of width to height of said flattened steel cord is 1.15 to 1.50.

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