Abstract:
A high-security cable is provided, wherein the high-security cable is capable of achieving a smoothing of a work-to-break energy curve. The high-security cable is manufactured of a mixture of plastic yarns or of plastic yarns and metal wires, wherein the cable comprises a first constituent part of untwisted or twisted yarns, or untwisted or twisted yarns and metal wires, a second constituent part of doubled yarn, the doubled yarn manufactured of plastic yarns or of plastic yarns and metal wires, and a third constituent part of cord manufactured from the doubled yarns, wherein the doubled yarn is manufactured from plastic yarns or of plastic yarns and metal wires. The high-security cable can be used as a safety arrester cable, and can also be used to form a netting to serve as safety arrester netting or falling-rock protection netting.

Description:
[0001]    The present application is a National Stage filing and claims priority to PCT/CH2006/000292 having an international filing date of Jun. 1, 2006. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a high-security cable, which is manufactured of a mixture of plastic yarns or of plastic yarns and metal wires. 
         [0003]    High-security cables are used in many applications. Today, in particular, high-security cables are known, which are used as safety arrester cables, in particular for connecting a wheel of a racing car to its chassis. Such a safety arrester cable is known from WO 03/048602. The mentioned cable consists of a mixed yarn of threads with relatively rigid plastic filaments with an extension until breakage of 2 to 5%, and of relatively elastic plastic filaments with an extension to breakage of 12 to 25%. Here, the various plastic filaments are twisted into yarn strands, wherein the yarn strands are twisted in a balanced manner, whilst the cable manufactured of these yarn strands is twisted in an unbalanced manner. Such a cable not only has large tensile strength, but also an increased extension, by which means one may achieve an improved energy uptake. Given a full loading, the total energy is not transmitted directly to the anchoring, which often represents the critical location in the complete system, thanks to the accordingly increased energy uptake by the cable itself. 
         [0004]    The known safety arrester cable which used in Formula 1 racing, may only have a relatively short extension path for reasons of safety, in order to prevent the broken-off wheel which now hangs on the arrester cable, from being thrown onto the cockpit or the head of the driver. However, a longer extension path would not only be acceptable, but, as the case may be, even desirable with other racing vehicles, or in other applications. The applicant has carried out further research and development in this direction, and has particularly sought after solutions which practically permit the creation of a customer-specific adaptation to the specifications. 
         [0005]    Considering the so-called work-to-break-energy curve of any material, then such a curve in principle has the shape of an acute triangle in a coordinate system, with which the force is plotted on the abscissa and the elasticity E on the ordinate. The tensile strength of the material is reflected in the height of the triangle, and the elasticity of the material is represented by the inclination of the hypotenuse of the right-angled triangle. If then, different materials are processed into a cable, then usually the material-specific peaks are clearly recognisable in the complete enveloping curve. This leads to extremely unfavourable tear behaviour, depending on the load. 
         [0006]    It is therefore the object of the present invention to provide a high-security cable which, on account of its special manufacture, is capable of achieving a smoothing of the work-to-break-energy curve, by which means, as a whole, the energy which may be absorbed until breakage is to be increased. This object is achieved by a high-security cable with the features claimed herein. The invention relates also to the use of such a high-security cable for different applications, which until now have not been considered for cable of this type. In particular, the expanded application also results due to the fact that the cables may be manufactured of a combination of filaments of one or more plastics, as well as of wires of one or more metals or metal alloys. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0007]    The present invention solves the aforementioned problem by providing a high-security cable capable of achieving a smoothing of the work-to-break energy curve. 
         [0008]    According to one aspect of the invention, a high-security cable is manufactured of a mixture of plastic yarns or of plastic yarns and metal wires, wherein the cable comprises a first constituent part of untwisted or twisted yarns, or untwisted or twisted yarns and metal wires, a second constituent part of doubled yarn, the doubled yarn manufactured of plastic yarns or of plastic yarns and metal wires, and a third constituent part of cord manufactured from the doubled yarns, wherein the doubled yarn is manufactured from plastic yarns or of plastic yarns and metal wires. 
         [0009]    Further advantageous designs of the subject-matter of the invention are to be deduced from the dependent claims. Their design, purpose and effect are explained in the subsequent description with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The drawings illustrate one preferred embodiment presently contemplated for carrying out the invention. 
           [0011]    In the drawings: 
           [0012]      FIG. 1  is a force-extension diagram for various materials, in a symbolic representation. 
           [0013]      FIG. 2  is a further force-extension diagram of a single material, consisting of yarn, of double yarn and of cord. 
           [0014]      FIG. 3  shows a force-extension diagram of a high-security cable, which is designed according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0015]    High-security cables in most cases are manufactured of a single material, wherein one usually assumes the greatest force application which is capable of acting on the cable. Until now, one has used two or three different materials in a mixed manner only for reasons such as weather-durability, UV-durability and temperature-durability or other demands of a specific nature. Thereby, one has consistently limited oneself either to textile cables of natural fibres and plastic fibres, or purely metal cables. Cables which consist of both types of fibres and wires in a mixed manner, are not obtainable on the market. 
         [0016]    As is schematically represented in the force-extension diagram of  FIG. 1  the different materials which are indicated here as M 1 , M 2 , M 3  or M 4 , have different modules of elasticity and different maximal loads-to-break (load-to-break curves). The respective curves symbolically represent mono-filament or multi-filament cables without twisting. Such curves have a more or less steep flank, a relatively small maximum plateau up to maximal extension, which leads to breakage. 
         [0017]    In a large series of trials, the applicant has now found that the curves change, if instead of a simple yarn in a twisted form or untwisted form, one processes this further into doubled yarns or to cord. With this, it has been found that this form of further processing permits the flank of the gradient curve to become less steep, and, depending on the type of processing, one may maintain the maximal force transmission over a longer extension path. In other words, the previously pointed curves, as are known from  FIG. 1 , may be stretched out. By way of this, the curves flatten inasmuch as the extension path also increases given an increasing increase of the force, wherein this occurs in the initial phase, as well as further increasing with the maximal force which may be applied. The total work which such a cable is capable of absorbing, is represented by the area below the enveloping curve. 
         [0018]    However, depending on the application, it is however not at all desirable to obtain a respective extension already before the maximum force is present. The object of the invention is to be seen in providing a cable which has an as small as possible extension path up to reaching the maximal applicable force, but to permit an as large as possible extension up to breakage when applying the maximal force. The maximal work which may be absorbed, may be optimised by way of this. 
         [0019]    Now, an example is shown by way of the force-extension diagram according to  FIG. 3 , with which four different materials symbolised by M 1  to M 4  are processed, wherein all materials are present in the form as a yarn or wires, as well as in the form of doubled yarns, and finally in the form of cord. One may realise a curve which may be symbolically displayed practically as a rectangle, by way of the presence of these materials in all three processed forms, wherein each material does not necessarily have to be present in all three processed forms, although this definitely represents the most optimal design. 
         [0020]    Since the definitions of the terms used here are not uniform on an international level, the terms are hereinafter defined as are to be understood in the present invention. The smallest element is a monofilament or a single wire. Here, the fineness of the wire is not fixed. In the present invention, yarn is to be understood as an endless product consisting of several filaments. Here, the yarn may be non-twisted or twisted. A yarn according to the invention may analogously also consist of a multitude of fine metal wires. These metal wires too may be non-twisted or twisted. 
         [0021]    With regard to the invention, a doubled yarn is to be understood as a product which consists of two yarns which are wound with one another. Each yarn may be S-twisted or Z-twisted. Here, S-twisting is to be understood as a left-hand twisting and Z-twist is to be understood as a right-hand twisting. 
         [0022]    The individual yarns not only vary in the twist direction in which they are twisted, but they also differ in the number of twists per meter. This measure number may vary in the magnitude from about 30 twists per meter up to maximally 600 twists per meter. Whilst the S-twisting or the Z-twisting may be used independently of the type of material, the variation of the twists per meter may be dependent on different factors, such as for example the stiffness of the materials and of course on the effect to be achieved. Basically it is the case, that the lower the twisting, the lower is the extension path until breakage, wherein however one should additionally take into account the fact that although the extension path until breakage increases with a very large number of twists per meter, the maximal force until breakage is however reduced. The latter is particularly the case with yarns, which are completely manufactured of metal, or for yarns which contain a metal component. 
         [0023]    As already mentioned, with regard to the invention, one advantageously assumes cords which consist of three yarns. Thereby, within a cord, the variation of the yarns applied therein, with regard to the properties of the materials, as well as with regard to the number of twists per meter, should not be too great. One may deduce various cords as well as their composition of different yarns, from the subsequent table, wherein only the details with regard to the twists of the yarn are specified, but not their material composition. 
         [0024]    With regard to the materials being considered here, one may essentially ignore the purely natural fibres. Apart from the known carbon fibres with tensile strength of 20 cN/dtex, the essentially more elastic m-aramide fibres which have a tensile strength of 4.7 CN/dtex are of course also considered here. The mentioned elastic m-aramide fibres may also be combined very well with the relatively rigid p-aramide fibres, which have a tensile strength of 19 cN/dtex. The very modern PBP-fibres which even have a tensile strength of about 37 cN/dtex, have a particularly high tensile strength. Cables which are manufactured of such high tensile fibres are capable of accommodating tensile forces which far exceed the usually occurring forces. Despite this, often such high-security cables which are manufactured of such high tensile materials, are extremely problematic on application. The smallest elastic extension up to breakage of only 1.5 to maximal 3.5% limits their application. The cables must be able to absorb a part of the energy via the extension, wherever very high forces may occur during a relatively short period of time, since otherwise the occurring brief, enormously high forces only lead to a destruction of the fastening points of the cables. Even then, when these fastening points are able to be dimensioned significantly greater than the cables in many cases, according to experience, problems occur at the fixation points. 
         [0025]    In order to increase the deformation work which is undergone by the cable, the admixture of metal wires which may be integrated either in the yarn or the cord, in particular by way of a so-called core-spinning method, is particularly suitable, wherein the metal wire or wires lie in the centre, whilst the plastic yarns run around them. With regard to the metal wires of interest here, of course various steel wires are to be considered, but in particular also wires of nickel or of an austenitic nickel-chrome alloy have proven their worth. Austenitic nickel-chrome alloys were processed in the form of wires with a diameter of below 0.5 mm into doubled yarns, and these processed further into a cable with a diameter of 12 to 13 mm. Such a cable with a length of 600 mm permits the transmission of a maximal force of 57.8 kN. The work-to-break here was also 10′000 Nm. 
         [0026]    What is essential according to the present invention, is the fact that the cable must consist of three different constituent parts, specifically on the one hand of yarns, on the other hand of doubled yarns, and thirdly of cords, wherein simultaneously, of each material constituent part, this material should be present as yarn as well as doubled yarn and as cord. Only thus is it ensured that the three different extension regions of the same material may also be utilised. 
         [0027]    It is only due to the combination of all three processing steps that the maximal extendibility of the material is also fully utilised. Although the processing of metal wires in the high-security cable according to the invention is not absolutely necessary, such wires have been found to be extremely advantageous for covering certain extension ranges. In the case that the high-security cable contains shares of p-aramide fibres, m-aramide fibres or PBO-fibres, then the share of these fibres which have a tensile strength of more than * cN/dtex energy, must consist mostly of the constituent parts of yarn and cord, but to a lower extend as pure cord. 
         [0028]    The application of such high-security cables according to the invention is hardly suitable for cables which merely need to transmit a relatively constant high tensile force. However, the high-security cables according to the invention may be applied wherever extreme high peak loads of a high-security cable occur. In particular, tests have shown that such safety arrester cables are suitable for application in sports car racing, for connecting a wheel to the chassis of the racing car. It has been found that with such an application, it makes sense to design the cable according to the invention such that several windings are shaped into parallel loops, so that at least one open loop is formed at the open end. 
         [0029]    A further field of application of these cables according to the invention lies in the fact that these may be used in order to make safety arrester cables therefrom, which may be attached along ski slopes, and in particular along the race circuits in alpine sports. 
         [0030]    High-security cables may only fulfil the safety standards demanded of them when these are applied under clear conditions. Accordingly, they are hardly suitable for long-term falling-stone arrester structures or avalanche protective structures. The prevailing environmental influences over a longer period would manifest themselves with regard to the performance of the high-security cable. However, the high-security cables may be advantageously be processed into nettings which may serve as a temporary avalanche protector netting. Accordingly, such cables may also be processed into nettings as temporary falling-stone arrester netting. 
         [0031]    The present invention has been described in terms of the preferred embodiment, and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appending claims.