Abstract:
A flexible traction organ that can be wound and unwound, in particular for passenger and/or goods lifts, said organ comprising at least one stranded cable consisting of a tensile resistant material. The core strand of each stranded cable is surrounded by a flexible thermoplastic plastic layer. A production line for embedding several stranded cables in a flexible thermoplastic layer comprises a respective reel for unwinding the stranded cable, a device for accurately aligning the stranded cable, a heating element for pre-heating the stranded cable, at least one extruder for co-extruding the stranded cable in a flexible plastic sheathing, a cooling vat, a reel storage unit, a cutting unit and a reserve reel. The extruder, a wire guide and at least one die can be adjusted individually, conjointly and in relation to one another on a plane (P) that runs at an angle to the cable plane (E). The unwound stranded cables are degreased and/or pre-treated to improve the adhesion of the plastic sheathing, and pre-heated to a temperature of approximately ±20° C. in relation to the melting temperature of the flexible, thermoplastic plastic that surrounds the core strand and are sheathed with liquefied plastic in the extruder.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The invention relates to a flexible traction element which can be wound and unwound, in particular for passenger and/or goods lifts, which comprises at least one stranded cable made of a material guaranteeing tensile strength. The invention also relates to a production line for embedding a plurality of stranded cables in a flexible thermoplastic plastics material, which production line comprises, in each case, a reel for unwinding the stranded cables, a device for the precise orientation of the stranded cables, a heater for preheating the stranded cables, at least one extruder for co-extrusion of the stranded cables in a flexible plastics material jacket, a cooling trough, a roller store, a cutting device and a storage roller. Finally, the invention relates to a method for embedding at least one stranded cable in a flexible thermoplastic material.  
         [0002]     U.S. Pat. No. 3,348,585 relates to a method and a device for producing industrially usable bands made of rubber with strands, also called wires or threads, made of ferromagnetic material, embedded therein and running approximately in parallel in the longitudinal direction. The strands consist in particular of steel, with their magnetic properties being used as tensile and spacing forces.  
         [0003]     GB 1362514 relates to a coiler for band-shaped lifting cables, in which steel bands are sheathed by a synthetic plastics material, in particular by polyurethane. Various flat lifting cables are shown in the drawings.  FIG. 1  shows a broad, flat cable with steel strands, which are sheathed by polyurethane. Longitudinally running recesses  17  are also shown in the plastics material jacket, these being designated as insignificant. In  FIG. 2 , a band-shaped lifting cable with longitudinally extending steel strands is also shown in a plastics material jacket, which has smooth surfaces on either side, in other words has no longitudinally extending recesses.  
         [0004]     WO 03/042085 A2 describes a method for producing a lift band with a plurality of bands or braids (cords) in a flat jacket, in which the braids are oriented in a selected arrangement. A special jacket material is selected and the strands are finally individually tensioned such that they are at a uniform distance everywhere from the smooth surface of the plastics material band. The band-shaped lift band minimises the production of disturbing noises and vibrations during lift operation.  
         [0005]     The inventor has set himself the object of providing a traction element, a production line and a method for the production thereof according to the manner mentioned at the outset, which ensure increased flexibility in a traction element with a plurality of stranded cables and also improved adhesion over the long term between the stranded cables and the plastics material jacket, and more precisely and reliably control the spacing of the stranded cables guaranteeing tensile strength from the band surfaces even at increased production speed, and deliver band-shaped traction elements of the best commercially available quality.  
       SUMMARY OF THE INVENTION  
       [0006]     With respect to the traction element, the object is achieved according to the invention in that the core strand of each stranded cable is sheathed by a flexible thermoplastic plastics material layer.  
         [0007]     In order to produce stranded cables, at least six peripheral strand cords are wound around a central strand cord designated a core strand. The strand cords themselves, which are in turn stranded, consist of individual fibres or wires of a material guaranteeing tensile strength. The flexibility of a conventional stranded cable can be considerably increased again according to the invention; the coating of the core strands prior to applying the peripheral strand cords also opens the way to higher flexibility without conventional lubricants. The thermoplastic plastics material is made at least partially capable of flowing, but without becoming highly liquid, and applied.  
         [0008]     The thickness of the thermoplastic plastics material layer is expediently in the range of 0.1 to 1 mm, the diameter of the core strands being one of the determining factors. The temperature region applied during stranding, for example 100 to 200° C., can cause penetration of the plastics material into cable grooves, but discharge from the surface of the stranded cable is avoided as far as possible. The outer surface of the stranded cables remains bare and is expediently degreased. Individual cables are preferably covered with a protective covering, in particular in the case of larger external diameters of the stranded cable in the range of about 5 mm or more.  
         [0009]     Stranded cables of smaller diameter, for example with a diameter of approximately 1 to 3 mm, are in practice sheathed, running in parallel, with a flexible thermoplastic plastics material, for example by a co-extrusion method, while observing optimum adhesion conditions for the plastics material jacket. The degreasing mentioned, a plasma treatment or the application of an adhesion-promoting layer, for example, contribute substantially to this. Lift bands, have, for example, eight stranded cables of 2 mm in diameter arranged on a plane, with a plastics material jacket of 25×4 mm in cross-section. The lift band is a stable composite, which is extremely flexible and forms a traction element which can easily be wound and unwound.  
         [0010]     The individual fibres guaranteeing tensile strength, of the stranded cables are, for example steel, aramid, glass, ceramic or carbon fibres. The flexible thermoplastic plastics material sheathing the core strands of the stranded cables consists of polythene, polypropylene, polyurethane or polystyrene, for example. The stranded cables with coated core strands are preferably embedded in the same flexible thermoplastic plastics material.  
         [0011]     In relation to the production line for sheathing at least one stranded cable with a flexible thermoplastic plastics material, the object is achieved according to the invention in that the extruder has a thread guide for the stranded cables and at least one matrix, which can be adjusted with and in relation to one another, individually, in a plane P angled with respect to the cable plane. Special and refined embodiments are in turn the subject of dependent claims.  
         [0012]     The stranded cables run through the extruder and the outlet opening of the matrix, lying on one plane E. Above all in the case of flat traction elements, it is of substantial significance that the stranded cables lie on one plane so the parallel surfaces of the plastics material jacket have approximately the same spacing everywhere from the embedded stranded cables. By means of a relative displacement of the thread guide, which is also called a wire guide, relative to the matrix, the relative position of the stranded cables changes in the nozzle outlet opening and therefore the position of the stranded cables in the plastics material jacket also changes. The thread guide and the matrix can also be displaced together, in other words with respect to height, without their spacing changing. The plane P which is angled with respect to the cable plane E has an angle of preferably 45 to 135°; in particular, the two planes extend at an angle of about 90°.  
         [0013]     If a plurality of stranded cables arranged in parallel run on a plane through the production line, pressure rollers may be arranged directly downstream from the extruder. These consist, for example, of at least one pair of rollers, in particular two pairs of rollers, which can be adjusted in a direction which is at right angles to the traction element passing through. Thus, the position of the stranded cables can be corrected in the still soft plastics material, but only in the fine range of a few tenths of millimetres. The pressure rollers may, however, also be arranged offset in the longitudinal direction of the traction element and thus act on the still soft composite.  
         [0014]     Further details of the production line are shown in the drawings and correspondingly described.  
         [0015]     Obviously, the production line can also be used for sheathing individual stranded cables or a plurality of stranded cables not located on a plane. The devices which are important to the invention, in this case, are not operated or removed if superfluous.  
         [0016]     Finally, the object is achieved in relation to the method for embedding at least one stranded cable with a plastics material-coated core strand according to the invention in that the unwound stranded cables are degreased and/or pretreated to improve the adhesion of the plastics material jacket, preheated to a temperature of about ±20° C. of the melting temperature of the flexible thermoplastic plastics material sheathing the core strands and sheathed in the extruder with the liquefied plastics material. Special and refined embodiments are the subject of dependent claims.  
         [0017]     The preheating takes place, for example, with an induction heater, a flame burner and/or a hot air heater. In this case, residual gases inter alia are removed and the adhesion of the plastics material sheathing and the stranded cables is improved.  
         [0018]     The sheathing of stranded cables with a flexible thermoplastic plastics material for producing a traction element by means of co-extrusion is possible in an optimal manner owing to the inventive knowledge. The degreasing or coating of the free surface of the stranded cables with an adhesion promoting layer and the preheating to about ±20° C. of the melting temperature of the liquefied plastics material play a decisive role and overall, a sharp improvement in the adhesion between the stranded cables and the plastics material jacket is achieved. The improvement also lasts over long-term and intensive use. Even the lasting deflection around comparatively narrow radii at high tensile forces, which is the case during operation of lifts, does not impair the adhesion between the stranded cables and plastics material, or only to a negligible extent, viewed over the long term.  
         [0019]     With the method according to the invention, the economy of the process can also be improved. A very high running speed in the region of 10 to 60 m/min. is achieved.  
         [0020]     Each individual stranded cable is tensioned, preferably with a tensile force of 5 to 100 N, in particular 35 to 45 N. If an extruder is used with a cable guide which can be displaced in relation to the matrix, the tensioning of the stranded cables is less critical.  
         [0021]     The geometrical cross-sectional shape of the traction elements is decisively determined by the outlet opening of the extruder, in particular when a plurality of parallel stranded cables are being sheathed with a joint plastics material. A band form is preferred with stranded cables arranged on a plane, which generally have cross-sectional external dimensions in the region of 15×1, 5 to 100×20 mm. The cross-sectional dimensions also depend, in particular, on the external diameter of the stranded cables, which is most frequently 1 to 5 mm in particular about 2 mm. The position of the stranded cables, guided in parallel, in the embedded plastics material, can be adjusted by the relative adjustment of the cable guide/matrix to ±0.1 mm accuracy. The correction range is ±0.5 to 2 mm.  
         [0022]     In the case of stranded cables located on a plane with a jacket, which has two outer faces located parallel to the plane of the stranded cables, the relative position of the stranded cables and the outsides of the jacket can still be modified. At least two pressure rollers are preferably arranged for this purpose directly downstream from the extruder, as already mentioned. These can also provide the surface of the traction element running through with a certain structure, for example a roughened surface. In the case of traction elements located on top of one another, the coefficient of friction is thus substantially increased and the band-shaped traction elements can thus be wound to form more dimensionally stable band rolls.  
         [0023]     The traction elements according to the invention have a wide range of use. They are particularly suitable for the lifting and pulling of loads when the traction element is deflected once or repeatedly and/or stored on a coiler. Lift bands or cables are an important application area and have to meet high safety requirements. In the case of a strand diameter of about 2 mm, they have a tensile strength of at least about 4000 kN/steel stranded cable. In the case of appropriate strand material, the traction elements may also be used as electric conductors.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     The invention will be described in more detail with the aid of embodiments shown in the drawings, which are also the subject of dependent claims. In the drawings, schematically:  
         [0025]      FIG. 1  shows a production line for producing band-shaped traction elements,  
         [0026]      FIG. 2  shows a cross-section through various traction elements,  
         [0027]      FIG. 3  shows a horizontal section through a thread guide and a matrix,  
         [0028]      FIG. 4  shows a vertical section through a thread guide and a matrix with a holder, along a stranded cable,  
         [0029]      FIG. 5  shows a vertical section through a thread guide and a matrix,  
         [0030]      FIG. 6  shows a vertical section through a thread guide and a two-part matrix,  
         [0031]      FIG. 7  shows a variant of  FIG. 6  and  
         [0032]      FIG. 8  shows a cross-section through a stranded cable. 
     
    
     DETAILED DESCRIPTION  
       [0033]     A production line  10  shown in  FIG. 1  for producing band-shaped traction elements  38  with stranded cables  16  according to  FIG. 8  made of twisted steel fibres and a rectangular jacket  39  made of a flexible thermoplastic plastics material begins at a system  12  with, in the present case, two times eight reels  14  for unwinding the flexible stranded cables  16  and ends with a storage roller  18  for winding the band-shaped traction elements  38 . In industrial production systems, the production line  10  is several dozen metres long.  
         [0034]     For the production of traction elements  38 , for example lift bands, the diameter Ø of the flexible stranded cables  16  is 2 mm in the present case. All the stranded cables  16  have to have the same, constant, diameter Ø so they can be positioned precisely in the middle of the jacket  39  made of plastics material. The diameter tolerance is at most ±0.05 mm. The stranded cable  16  must not be welded nor have twisting defects. Finally, the stranded cable  16  must be faultlessly wound onto the reel  14 .  
         [0035]     The individual control of the tensile force of the stranded cables  16 , which is held at about 50 N, takes place in a manner which is known per se with a pneumatic or electromagnetic system.  
         [0036]     After unrolling, the stranded cables  16  are firstly moved into a plane by way of a stand  20  with a horizontal guide slot. As the stranded cables  16  should be clean and whenever possible without volatile gas components on the surface, they are guided in-line through a cleaning system  22 .  
         [0037]     Directly downstream from the cleaning system  22 , the stranded cables  16  pass through a further stand  24  with a device for the exact orientation of the stranded cables  16  at a constant horizontal spacing. Oriented in this way, the stranded cables  16  pass through an induction heater  26 , a flame burner  28  and a hot air heater  30  and after this preheating, the stranded cables  16  have a surface temperature in the region of 100 to 200° C. and all residual gases are removed for the subsequent plastics material coating.  
         [0038]     The oriented, cleaned and preheated stranded cables  16  pass through an extruder  32  with a wire or thread guide and matrix according to the invention, shown in detail in FIGS.  3  to  6 . The liquefied plastics material, in the present case polyurethane, is supplied perpendicularly to the running direction  80  of the stranded cables  16  shown by an arrow. The plastics material is poured, in powder or granulate form, into a filter  34 , whence the bulk material, which is not visible, pours into a horizontal feed screw  36 . During the feed, the plastics material is liquefied and pressed by way of the thread guide into the matrix, where the stranded cables  16  passing through in parallel are sheathed with plastics material. The extruder  32 , which is known per se with the exception of the thread guide and the matrix, ensures a constant supply of plastics material and excellent quality without gelled or crystallised plastics material particles. The discharge opening  90  ( FIGS. 5, 6 ) of the matrix defines the outer dimensions of a traction element  38  which is sheathed with plastics material.  
         [0039]     The final dimensions of a traction element  38  are established by the subsequent pressure rollers  40  made of tetrafluoroethylene (TEFLON, Du Pont) or a material coated with TEFLON. Two pairs of rollers  40  also establish the surface structure of the traction element  38 . The pressure rollers  40  must not bind with the still warm, soft material of the traction elements and have to be precisely adjustable with respect to the roller gap and the height, and be dimensionally stable. The roller surfaces are roughened in the present case and precisely cylinder jacket-shaped. This produces traction bands of elongate rectangular shape and with a roughened surface according to  FIG. 2   a.    
         [0040]     Downstream from the pressure rollers  40 , the still warm traction element  38  runs into a cooling trough  42  of 20 to 40 m in length, for example. In  FIG. 1 , the cooling trough  42  is shown in very shortened form. In a first section of the cooling trough  42 , the traction element  38  can be introduced into hot water of, for example, 65° C. In one or more further sections of the cooling trough  42 , the traction element  38  is guided through cooler and cooler water, finally through normal mains or industrial water at tap temperature. According to a variant, the entire cooling trough  42  may contain unheated mains or industrial water. While passing through, the traction element  38  is guided straight, with application of a tensile stress, so contact with the side walls of the cooling system can be avoided. The cooling trough  42  may also comprise one or more returns for the traction element  38 .  
         [0041]     Upstream and downstream from the cooling trough  42  is arranged a control apparatus  44 ,  46 , in each case for controlling the thickness d of the traction element  38 , in particular. The measured dimensions are recorded and stored for the fully or partially automatic control of the production line  10  (for example adjustment of the wire unwinding  12 , the preheating  26 ,  28 ,  30 , the extruder  32  and the pressure rollers  40 ). Furthermore, the stored data can be used for statistical evaluations and quality reports.  
         [0042]     The traction elements  38  are marked when passing through an automatically or manually operable inscription device  48 , for example through an inkjet printer with an ink which adheres well on the surface of the traction element  38 .  
         [0043]     A caterpillar conveyor  50  with two continuously circulating bands ensures that a constant tractive force is exerted on the band-shaped traction element  38  and a constant running speed is maintained.  
         [0044]     A subsequent roller store  52 , also called an accumulator, has a plurality of rollers  58  held on a static stand  54  and on a mobile stand  56 . The two stands  54 ,  56  are shown with a minimal spacing, in the normal working state. In the event of a change of roller, the roller store  52  has to receive the extruded traction element  38  for about 2 minutes, while the mobile stand  56  is displaced as indicated by dashed lines counter to the running direction  80 . This mobile stand  56  is also used as a dancer and any irregularities in the band speed can be compensated by its displacement. When the roller store  52  is, for example, 70 to 75% filled, the band speed is reduced to the minimum value, which is about 10 m/min. By increasing the band speed downstream from the roller store  52  the normal working state shown by a continuous line  38  in  FIG. 1  is produced as quickly as possible again.  
         [0045]     Downstream from the roller store  52  a second caterpillar conveyor  60  is arranged according to the present embodiment with a preceding guide roller  62  on a holder  64 . A cutting device  66  arranged downstream from the second caterpillar conveyor  60  cuts the traction element  38  to length when the storage roller  18  is full. The change of the storage roller  18  is matched to the roller store  52  and the change should be complete within 2 minutes. A guide roller  68  ensures regular winding of the traction element  38  onto the storage roller  18 .  
         [0046]     In the cross-section through a traction element  38  according to  FIG. 2   a , eight stranded cables  16  with a diameter Ø of 2.00 mm are embedded on a plane E at regular intervals a of 0.5 mm. These stranded cables  16  each have a core strand  124  and six peripheral strand cords  128  of in turn seven steel fibres  130 , in each case (cf.  FIG. 8 ). The stranded cables  16  have the same spacing a from the surfaces  70 ,  72 . The traction element  38  has an overall thickness d of 3 mm and a width b of 25 mm.  
         [0047]     A traction element  38  according to  FIG. 2   b  has a longitudinal groove  17  on either side in the centre. A constriction  15  is formed thereby.  
         [0048]     In the embodiment according to  FIG. 2   c , the traction element  38  has longitudinally extending constrictions  15  formed between the stranded cables  16  by longitudinal grooves  17  in the jacket  39 . The longitudinal grooves  17  do not impair the tensile strength of the traction element  38 , or only marginally. The traction element  38  is more flexible, however, as a whole, for example in the use as a tensioning element for fixing articles.  
         [0049]     The outer contours of the jacket  39  are also fixed by the pressure rollers  40  ( FIG. 1 ), which have a correspondingly structured jacket surface. The matrix opening of the extruder can be configured accordingly, but may also be elongate rectangular.  
         [0050]      FIG. 2   d  shows a traction element  38  with stranded cables  16  of different thicknesses. The inner stranded cables  16  are smaller, the outer ones larger. On one side, the surface  72  of the jacket  39  is adapted to the diameter of the stranded cables  16 , a broad longitudinal groove  17  is formed, and on the other side, the surface  70  is continuously smooth. This embodiment is suitable in turn for special purposes and the outer form of the jacket  39  is established in turn by the pressure rollers  40  ( FIG. 1 ).  
         [0051]     The embodiment according to  FIG. 2   e , in contrast to the previous examples, is asymmetrical in cross-section. The stranded cables  16  of different thicknesses are connected to one another by a connection web  15  and have a jacket  39  of approximately the same thickness everywhere.  
         [0052]      FIG. 3  shows a horizontal section through a thread guide  74  and a matrix  76  at the level of the eight bores  78  corresponding to the thread diameter Ø for the stranded cables  16  running with little play in the running direction of the arrow  80 , of which stranded cables only one is indicated as a part piece. Bores  84  run parallel to the screws  82  detachably connecting the thread guide  74  and the matrix  76 , the bores having a diameter in the present case of 6 mm for feeding liquefied plastics material compound  86 , which—invisibly on the sectional plane—is pressed into a matrix cavity  88  with the stranded cables  16  running through. The liquefied plastics material  86  sheaths the stranded cables  16 . The composite leaves the discharge slot  116 , which is elongate rectangular in cross-section, through the matrix opening  90  as a sheathed traction element  38 .  
         [0053]      FIG. 4  shows a vertical sectional plane placed through a stranded cable  16 , through the thread guide  74  and matrix  76  according to  FIG. 3 . The stranded cables  16  are in turn guided in the running direction  80  through the thread guide  74  and the matrix  76 . Prior to entry into the bore  78 , the stranded cable  16  firstly passes through an outer inlet groove  92  and an inner smaller inlet groove  94 , which simplify the production of the precise bores  78 , lying closely together, for the stranded cables  16 . A V-shaped inlet slot  96  is fed by way of the bores  84  according to  FIG. 3  with liquefied plastics material compound  86 .  
         [0054]     By means of adjusting screws  98 ,  100 , which act by way of guide plates  102 ,  104  on the matrix  76 , the latter can be displaced in the vertical position by Δt of at most about 0.5 mm relative to the matrix  76 . This displacement can take place at a precision of about 0.05 mm or less. In the case of a displacement of the matrix  76  by Δt, the stranded cable  16  is displaced inside the discharge slot  116  or the matrix opening  90  by the same amount. The stranded cable  16  can thus be positioned precisely inside the matrix opening  90 . The position of the stranded cables in the traction element  38  is correspondingly precise ( FIG. 2 ). The thread guide  74  can also be positioned by adjusting screws  108  and guide plates  110  in the same holder  106  as the matrix  76 , if, instead of a continuous bore  112 , adjusting screws are also arranged at the bottom in the thread guide  74 . If the thread guide  74  is also displaceable, the mutual displacement range Δt can be correspondingly enlarged between the thread guide  74  and matrix  76 .  
         [0055]     In  FIG. 5 , the thread guide  74  and matrix  76  located on one another along a plane P are shown enlarged. The continuous, tensioned stranded cable  16  runs in the direction  80  through the thread guide  74  and the matrix  76 . On displacement of the thread guide  74  along the plane P, the stranded cable  16  is entrained, because it is guided with very little play through the bore  78  ( FIG. 4 ). If the matrix  76  is displaced with the thread guide  74  fixed, the stranded cable  16  remains untouched thereby. However, as the vertical position of the discharge slot  116  with the matrix opening  90  changes, the distance of the stranded cable  16  from the upper and lower limitation of the discharge slot  116  is changed. Thus the position of the stranded cable  16  in the centre of the discharge slot  116  can be established precisely by a simple displacement of the matrix  76  along the plane P in the vertical direction by one or a few tenths of millimetres. Therefore, the stranded cable  16  is adjusted precisely in the centre of the traction element  38 , i.e. the jacket  39  is the same size on the upper and lower apex of the stranded cable.  
         [0056]     In the embodiment according to  FIG. 6 , for co-extrusion, a further matrix  75  is arranged between the thread guide  74  and the matrix  76  and the same plastics material jacket  39  ( FIG. 5 ) is applied consecutively in a spatially separated manner.  
         [0057]     The matrix  76  for the traction element  38  ( FIG. 5 ) has a projecting collar  114  with a lengthened discharge slot  116  and a discharge opening  90 . Owing to the arrangement of the collar  114 , the plastics material jacket  39  can cool better and harden better before discharge from the matrix opening  90 .  
         [0058]     The thread guide  74  comprises two peripheral bores  118  and two V-shaped inlet slots  96 , also for the liquefied plastics material  86 . The holes  78  for passage of the stranded cables  16  remain substantially unchanged, as do the outer and inner inlet groove  92 ,  94 .  
         [0059]     The further matrix  75  arranged between the thread guide  74  and the matrix  76  comprises two V-shaped inlet slots  96 , which guide the fed liquefied plastics material  86  from the peripheral bores  118  to the matrix cavity  88 . An advanced matrix cavity  120  is fed through the V-shaped inlet slot  96  in the thread guide  74 . From this matrix cavity  120 , a connection channel  122  leads to the matrix cavity  88  in the matrix  76 , this connection channel  122  having a slightly larger diameter than the advanced bore  78 . The stranded cable  16  passing through reaches the matrix cavity  88  already precoated.  
         [0060]     According to a variant shown in  FIG. 7 , the thread guide  74  according to  FIG. 6  is designed such that an impregnation means  87  for the stranded cable  16  is guided through the inlet slots  96  into the advanced matrix cavity  120 . The liquefied plastics material compound  86  is guided through the inlet slots  97  into the matrix cavity  88 . Obviously, various liquefied plastics material compounds  86  can also be guided through the inlet slots  96 ,  97 .  
         [0061]      FIG. 8  shows a cross-section through a stranded cable  16 . A central strand cord, the core strand  124  is sheathed with a flexible thermoplastic plastics material layer  126 , in the present case polyurethane. When stranding with six strand cords, the peripheral strand cords  128 , the plastics material layer which is capable of flowing or viscous deforms and flows into the cable grooves. The individual fibres  130  of the core strand  124  and peripheral strand cords  128  are stranded in a manner which is known per se.  
         [0062]     A stranded cable  16  with an outer diameter of at least about 5 mm, for example, can, as a single cable, achieve the tensile force required for a traction element. The stranded cable is preferably protected with an outer jacket made of plastics material.  
         [0063]     Stranded cables  16  with a smaller diameter are guided in parallel through a production line  10  according to  FIG. 1 , sheathed with a plastics material  39  and used as a traction element  38  with a plurality of stranded cables  16 .  
         [0064]     The coating of a stranded part  16  or a core strand  124  can take place in any manner which is known per se or preferably with a modified production line according to  FIG. 1 , using the method according to the invention.