METHOD OF MANUFACTURING A CABLE-LIKE PLASTIC COMPOSITE BODY

Abstract: A cable-like synthetic composite body which can be used as a support element for technical cables comprises a string of endless filaments of high modulus of elasticity which extend parallel to one another and to the cable axis, with the string being impregnated with a first thermoplastic material (12) in the form of a hot melt adhesive. The string (11′) which is held together in this way is then sleeved by extrusion with the second thermoplastic material (13) which is filled with staple fibers (23) of a high modulus of elasticity. A sleeve of a third thermoplastic material (14) is then applied by means of extrusion onto the sleeve layer.

Description: The invention relates to a method of manufacturing a cable-like plastic composite body in accordance with the preamble of claim 1 and to a cable-like plastic composite support body resistant to kinking. Such synthetic composite bodies are used in technology as support elements for cables, in particular for optical waveguide cables, such as optical fiber cables. They are widely used in cable technology and are mainly used in rod form as a central core or as armouring in cables (sea-cables, communication cables, air cables etc.). Other applications are also known. Such synthetic composite bodies can for example also be used as armouring in other structures, for example in concrete in bridge building. It is important, in particular when using the composite body as a support element for an optical waveguide cable, however also when using the composite body as armouring in concrete structures and in other fields, that the composite body is able to accommodate both tensile stresses and also compressive stresses, in particular stresses which are directed in the axial direction, without excessive extension or compression of the composite body occurring. From this point of view it is desirable that the composite body behaves approximately as an iron rod. By way of example in an optical waveguide cables each individual glass filament which transmits the light signals is inserted into a thin tube or cannula which is filled with petrolatum. In the normal state the optical fibers have a length which is fractionally larger than that of the tubes so that the fibers extend in slightly wave-like manner through the tubes. In this way a certain degree of extension of the tube, for example as a result of tensile stresses or temperature fluctuations, can be tolerated without longitudinal loadings of the optical fibers arising which could lead to breakage of the fibers. Under compressive stresses, which predominantly arise as a result of temperature fluctuations, the tubes tend to shrink more than the glass fibers. This excessive shrinkage of the tube then leads to the optical fibers extending in a more pronounced waveform within the tubes so that they contact the inner side of the tubes at least point-wise. This results in a very high optical attenuation which is undesired since the signal strength reduces. A preferred practical application of a cable-like synthetic composite body of the present species is the prevention of this excessive shrinkage of the tubes. This can be achieved by arranging the tubes around a cable-like synthetic composite body manufactured in accordance with the method of the present invention and securing them to it, which can for example be done by means of an adhesive (preferably of a hot melt adhesive). In the prior art the cable-like synthetic composite body has a core string consisting of endless filaments which are embedded by pultrusion into a matrix of a duroplastic plastic, i.e. of a synthetic material which can be cured by heat. This core string is then surrounded by a winding or two crossed windings of a yarn which cause depressions and raised portions at the boundary between the core string and the yarn which ensure a form-locked connection with the core string. This winding, or these windings, is, or are, then mainly provided with a sleeve layer of a thermoplastic material in order to form the finished synthetic composite body. This sleeve layer, which is frequently applied later during the manufacture of the actual cable is likewise connected as a result of the depressions and raised portions of the winding or windings with the latter, so that tensile or compressive forces acting on the sleeve layer can be transmitted via the form-locked connection to the core string, with essentially only the core string contributing to the tensile strength of the composite body. When used as a support element for an optical waveguide cable the sleeve layer serves to thicken the core string and can be applied in various diameters in order to make available support elements of different diameters for the subsequent cable manufacture. When using the known composite body as armouring for concrete structures the sleeve layer can be dispensed with. The manufacture of the core string takes place by means of so-called pultrusion and the requirement to cure the thermosetting plastic (duroplastic) by means of heat leads, with a reasonable length for the plant, to a relatively low manufacturing speed of approximately 4 m/min. As a result of the low speed of manufacture the product is relatively expensive. Moreover, heat curable duroplastics always contain solvents which are to be regarded as noxious materials and are poisonous for human beings. It is thus necessary to go to great expense to keep the volatile solvents away from the environment or to recover them. As duroplasts have a relatively high stiffness the composite body also has a relatively high bending strength. This is admittedly desirable from some points of view, however, it leads to certain difficulties when handling the composite body or the finished cable since the composite body tends to spring away from the coil and it is relatively difficult to bend the cable itself around relatively small radii. Thus the installation of the cable is made unnecessarily difficult for certain applications. Nevertheless the known composite body has a good resistance against kinking as a result of the high bending stiffness which is desirable, in particular with optical waveguide cables. The principal object underlying the present invention is to provide a method for the economical manufacture of a cable-like synthetic composite body which satisfies the requirements of being able to bear relatively high tensile and compressive forces in every respect, which has adequate bending stiffness and a good resistance to kinking, but which is nevertheless easy to handle during further processing, and in particular also permits small bending radii, and which can moreover be produced in an environmentally friendly manufacturing process and does not represent any danger for the environment in later use. In order to satisfy this object there is provided, in accordance with the present invention, a method in accordance with any one of the claims 1 to 11 and a cable-like plastic composite support body resistant to kinking in accordance with claims 12 to 19. The preambles of the independent method and apparatus claims 1 and 12 are based on the prior art discussed in detail in the introduction to the present invention. The present teaching thus relates to the manufacture of a composite body suitable for use as a cable core with absolute watertightness along its full length. The endless filaments consist, in accordance with the invention, preferably of E-glass (aluminoborosilicate glass), S-glass (magnisium aluminosilicate), aramid, or carbon. The first thermoplastic plastic is preferably hot melt adhesive, for example a hot melt adhesive based on ethylene vinyl acetate, polyester, polyamide, polypropylene or polyester. The fact that the plastic surrounding the endless filaments is a thermoplastic avoids the need to operate with environmentally noxious solvents such as styrol. For the sake of completeness it should be pointed out that DE-A-32 07 083 shows a plant for making an electrical or an optical cable in which the leads of the cable are led through a guide tube into filling device for a filling composition and then into an extruder for providing a sleeve around the filling composition and the leads. The material of the filling composition is not specified it is simply said to achieve longitudinal sealing of the interior of the sleeve. It is not made clear against which medium the filling composition is intended to seal. The invention will later be more closely described in the following by way of example only with reference to Figs. 5 to 8 of the accompanying drawings, this description will however be preceded by assignees which is helpful in provided a better understanding of the present invention, in particular with respect to some items of the apparatus and the thermoplastics that are used. More specifically the drawings show: Fig. 1 a schematic perspective illustration of an earlier non-prior published apparatus proposed by the assignees for manufacturing a cable-like composite body, Fig. 2 a schematic perspective illustration of the build-up of the cable-like synthetic composite body of Fig. 1, with the individual layers being partly cut-away for the sake of clarity, Fig. 3 a cross-section through the cable-like synthetic composite body of Fig. 1 in accordance with the arrows III-III of Fig. 2, Fig. 4 a longitudinal section in accordance with arrows IV-IV of Fig. 1 in order to show a detail of the string impregnating device that is used. Fig. 5 a plan view of a plant for producing a core string using the method of the present invention which is particularly suitable for use in optical cables, Fig. 6 a sideview of the plant of Fig. 5, Fig. 7 a schematic illustration of a part of a plant for producing an optical fiber cable particularly suited for use as a drop line, and Fig. 8 a broken away perspective view of an optical fiber drop line cable manufactured using the plant of Fig. 7. At the start of the apparatus of Fig. 1 there is located a spool carrier arrangement 17 in the form of a delivery frame with a plurality of reels 16 which are rotatably arranged on spigots. Each individual reel 16 carries a bundle of filaments (which can consist of several hundreds filaments) and is braked in order to keep the take-off of the filaments uniform. The individual filaments of the filament bundle are wound during the manufacturing process of the filaments without adhesive or other securing or binding agents onto the reel 16. The drawing shows four rows arranged above one another and each consisting of four reels 16. The four filament bundles 15' located on the reels 16 of each row are drawn through a guide 24 and are led from this guide to the input of the nozzle 26 of a string impregnation device in order to form a string 11. In the drawing there are thus a total of 16 reels, many more or fewer can however also be provided depending on how many filaments as a whole are required and how many filaments belong to each bundle. The nozzle 26 which is shown in detail in a longitudinal section in Fig. 4 serves for the application of the hot melt adhesive which is kept ready in the liquid state in a container 30 and is pressed by means of a dispensing pump 31 in the form of a motor-driven gear pump through the line 32 in metered quantities. As shown in Fig. 4 the nozzle 26 has a funnel-like channel 27 which is of circular cross-section. The bundles 15' run through the funnel and are simultaneously impregnated with the hot melt adhesive which flows through the line 32 and the bore 33, with the individual endless filaments 15 extending parallel to one another and to the longitudinal axis of the string 11 at the output of the nozzle in order to ensure the desired extendability and compressability of the finished composite body. The endless filaments impregnated with hot melt adhesive thus form the so-called core string 11'. With reference to the example of a cable-like synthetic composite body with 3 mm cross-section of the core string 11' ten such bundles are combined with each bundle having 1200 Tex (g/1000m) and being composed of individual filaments with a diameter in the region from 14 to 15 µ. These filaments are high module fibers, i.e. fibers with a high modulus of elasticity and consist in the present example of E-glass. When using ten bundles 15' the string 11 so formed thus has a weight of 12 g/m. The absolute speed of the core string 11' emerging from the nozzle 26 and the supply speed of the dispensing pump 31 are so matched to one another that the conveyed hot melt adhesive fully bonds to the string 11, so that no excess of melt adhesive is lost or has to be returned to the container. The liquid hot melt adhesive in the string impregnation device 18 is an Esso hot melt adhesive on ethylene vinyl acetate basis of the type JU 2514 which is kept liquid at a temperature of 190°C and has a low viscosity at this temperature, so that it can flow between the endless filaments. The core string 11' impregnated with the hot melt adhesive emerges from the string impregnation device 18, or from its nozzle 26, with a weight of 13.5 g/m. The relatively low increase in weight indicates that relatively little hot melt adhesive is contained in the core string, in other words, that the degree of filling of the core string with the high module fibers is very high. The core string 11' cools rapidly in the environmental air, so that the hot melt adhesive already has a certain strength after leaving the string impregnation device 18. The core string 11' then runs into a first extruder 19, with the distance between the string impregnation device 18 and the first extruder 19 amounting to 4 m. The first extruder 19 is formed as a so-called cross-head extruder which is known for the coating of a string with a sleeve of synthetic material. The first extruder 19 serves to apply a sleeve layer of a second thermoplastic material 13 filled with short reinforcement elements 23 such as staple fibers of glass, to the core string. The second thermoplastic material can be a glass fiber filled polypropylene of the Hoechst type PPN 7790 GV2/20, i.e. polypropylene filled with 20% E-glass staple fibers which are chemically coupled to the polypropylene. This thermoplastic material is brought in the extruder 19 to a temperature of 240°C and in this manner heats the surface of the hot melt adhesive lying beneath it, so that the latter is reactivated, i.e. becomes adhesive, with an intimate bond being generated between the first thermoplastic material of the hot melt adhesive and the second thermoplastic material 13 of the sleeve layer. This bond is made stronger by the staple fiber filling of the second thermoplastic material, since individual fibers of the quasi randomly distributed staple fibers bridge the boundary layer between the two thermoplastic materials, and thus ensure that compressive and tensile forces can be transmitted from the sleeve layer of second plastic 13 to the core string 11'. On leaving the first extruder the now formed string 11" with sleeve layer has a diameter of 4 mm and a weight of 17.5 g/m, i.e. a weight increase relative to the core string 11' of 4 g/m. The string 11" then leads, after cooling in the environmental air, into a second extruder 22 which is arranged at a distance of 1.5 m from the first extruder 19. A sleeve of a third thermoplastic material 14 is applied to the sleeve layer of the second plastic 13 of the string 11" and consists in the present example of polyethylene from the company Neste type DFDS 1169. In the extruder 22 this polyethylene reaches a temperature as it is applied to the string 11" of 190°. After the second extruder the string then has a diameter of 6 mm and a weight of 34 g/m, i.e. an increase in weight of 16.5 g/m relative to the string 11". The so formed string 11"' is then drawn by means of the driven drawing device 29 through a cooling device 20 in the form of an open channel of 30 m length, with cooling water flowing at a temperature of approximately 20°C through the channel in order to cool the string to the environmental temperature. In order to save water it is recirculated by means of a pump through the intermediary of a storage container. The driven drawing device consists of two recirculating conveyor bands which form an entry gap and which run in opposite directions so that the lower run of the upper conveyor belt and the upper run of the lower conveyor belt run in the same direction. With this drawing device the string 11"", and thus also the endless filaments are pulled at a constant speed of 100 m/min. through the apparatus. The finished string 11"" is then coiled into the reel 21. This reel 21 is so driven that the string 11"" is reeled with constant tension onto the reel. A drive of this kind can be realised in relatively simple manner. An embodiment of the invention is now shown in Figs. 5 and 6 in which parts common to the earlier figures are identified by the same reference numerals. The object of the plant of Figs. 5 and 6 is to provide a core string 11' with a high density of high modulus fibers, and in which hot melt adhesive is present in all interstices between individual high modulus fibers so that absolute watertightness of the core string 11' can be guaranteed. This is sometimes difficult to obtain with the string impregnation device 18 of Figs. 1 and 4. Once again the endless high modulus filaments are drawn from a plurality of reels 16 provided on a spool carrier arrangement 17. The spool carrier arrangement 17, the spools and also the filaments wound thereon can, and preferably are, precisely the same as those described with reference to Fig. 1. The four filament bundles 15' located on the reels 16 of each row are again drawn through a respective guide 24 but instead of passing directly to the extruder nozzle 18 they now first pass beneath a roller 41 and over the surface of a drum roller 42. The drum roller 42 is mounted so that its lower portion runs through a tank 43 containing the same hot melt adhesive as was supplied to the string impregnation device 18 of Fig. 1. The drum roller 42 is heated to the same temperature as the molten hot melt adhesive 44 in the tank 43 (190°C for the Esso hot melt adhesive on ethylene vinyl acetate basis of the type JU 2514) so that a thin film of molten hot melt adhesive forms on the surface of the drum roller 42. The individual filaments of the individual filament bundles 15' are brought into intimate contact with the film of hot melt adhesive on the surface of the drum roller 42 as a result of the position of the roller 41, which causes the filaments to wrap around the drum over an angular extent α. The wrap angle α (Fig. 6) can be varied by varying the position of the roller 41 relative to the drum roller 42 and also by varying the position of the extruder 18 relative to the drum roller 42. Because of the tension in the filaments the indivudual filament bundles tend to flatten out on the surface of the drum, as can be seen from Fig. 5, and this ensures that each thin filament comes into contact with the thin film of hot melt adhesive on the surface of the drum. Furthermore, the drum roller 42 is driven with a surface speed slightly less than the linear speed of the individual high modulus fibers in the direction of the core string 11' so that a certain degree of slip occurs between the individual fibers and the surface of the drum. This slippage beneficially affects the coating of the individual fibers with the hot melt adhesive. On leaving the drum roller 42 the individual fibers pass once again into a string impregnation device 18 which can be constructed precisely in the same manner as was described with reference to Fig. 1. The only difference now is that the dispensing pump 31 is set to deliver smaller quantities of hot melt adhesive via the line 32, since some of the hot melt adhesive is already supplied via the drum roller 42. The core string 11' emerging from the string impregnation device 18 of Fig. 5 can either be passed directly into the cross-head extruder 19 of Fig. 1, from which it subsequently passes into the cross-head extruder 22 (optionally present) into the cooling device 20 and then through the caterpillar drawing device 29 prior to being wound onto a spool 21. However, it is anticipated that many cable manufacturers would like to be supplied with a core string 11' so that they may build the core string up themselves in accordance with their requirements. This poses a certain problem since the core string 11' is not at all resistant to kinking, since the sleeve layer 13 is missing. The Applicants have however made the surprising discovery that it is possible to protect the core string against kinking by winding it with a helical outer thread which is achieved using the winding apparatus 45 of Fig. 5. This winding apparatus comprises a hollow axle 46 through which the core string 11' is free to slide with the hollow axle 46 being supported at its two ends in bearings in a stand (not shown). The axle is driven via a pulley 47 using a V-belt and a motor which, for the sake of simplicity, are not shown here. It will be understood that the motor is arranged inside the stand for the axle beneath the winding device 45 in Fig. 6. A flyer 48 is mounted on the pulley and has two arms one of which forms a guide for the winding yarn and the other of which forms a counter-weight to keep assembly dynamically balanced. A cross-wound spool package 49 of endless polyester filaments is mounted on the hollow axle 46 and is rotatable relative thereto. A friction clutch 50 is however provided between the cross-wound package 49 and the axle 46 to prevent overrunning of the package and tangling of the polyester filaments. The polyester filaments 51 wound on the package typically comprise 50 individual endless polyester filaments each of 5 D.Tex, i.e. the polyester filament yarn used for winding around the core string has a total weight of 250 D.Tex. In operation the motor drives the flyer via the V-belt and pulley arrangement and the flyer draws yarn 51 from the package and winds it helically around the core string 11' as illustrated at 52. A second winding device 53 can be provided downstream of the first winding device 45 and can be used to cross-wind the core string 11' with a second polyester yarn 51' identical to that used for the winding device 45. It will be appreciated that to achieve the cross-winding the winding device 53 is rotated in the opposite direction to the winding device 45. Since the winding takes place whilst the hot melt adhesive used to impregnate the core string 11' is still soft, the winding yarn is reliably retained on the surface of the core string 11'. It has been found that this simple act of winding the core string has a beneficial effect on preventing the cross-section of the core string becoming oval when subjected to potential kinking loads, so that improved protection against kinking is present. It should be noted that although the winding indeed of a core string, and also cross-winding of a core string, is known per se in connection with the prior art filaments the winding there took place for a completely different purpose. In the prior art the windings have no effect on the resistance of the core string to kinking since the core string is impregnated with a rigid thermosetting plastic or resin which is so hard that kinking does not occur. On the contrary, the core string of the prior art is liable to brittle fracture if subjected to loads which would ordinarily produce kinking. The winding of the core string in the prior art was done solely to provide a mechanical anchorage for a sleeve layer subsequently applied thereto. On leaving the winding device 45, or also the further winding device 53, if such is provided, the core string then again passes through a caterpillar drawing device 29 and is wound onto drums such as 56. The process described with reference to Figs. 5 and 6 is not as fast as the process described with reference to Fig. 1. Experiments presently show that it is possible to drive the process of Figs. 5 and 6 at a linear speed of the core string of up to 20 m/min. The apparatus of Fig. 1 can however be driven at speeds of up to 100 m/min. In view of this, and, assuming that the core string 11' produced by the plant of Figs. 5 and 6 is to be further treated in the cross-head extruder 19 (and optionally in the cross-head extruder 22 with subsequent cooling in the water channel 20), it is desirable to provide say five installations of the type shown in Figs. 5 and 6 so that the total production of these five installations is again 100 m/min. of core string, which is sufficient to run the plant of Fig. 1 continuously. Although the production rate of the plant of Figs. 5 and 6 is reduced relative to that of Fig. 1 the core string is of a higher quality since absolute watertightness of the core is guaranteed. Moreover, the speed of production of the plant of Figs. 5 and 6 is four or five times greater than the speed of production of the plants used to produce the known cable cores with thermosetting material. The reason for this is to be found not only in the difference in material but also in the different process approaches. In the prior art the endless filaments are impregnated with the thermosetting plastic material in the cold state and heat is then applied to cure the thermosetting plastic at elevated temperature which takes a relatively long time. In the present invention the impregnation of the fibers takes place at an elevated temperature and the hot melt adhesive starts to cool immediately it leaves the extruder 18. Moreover, further processes can be carried out on the cable core (winding, cross-winding) while the core is still hot, or at least warm, without disadvantage. The plant of the present invention, i.e. of Figs. 5 and 6, is substantially more economical than the plant used for the prior art cable cores. The plant used for prior art cable cores is not only much slower, as explained above, but it also requires extensive solvent capture and reprocessing equipment to protect the environment. It also needs a lot of thermal energy for the curing of the thermosetting plastic material. As explained above the hot melt adhesive and thermoplastics used for the present invention do not involve solvents and the manufacturing process involves only relatively small quantities of energy. Although the core strings and coated core strings previously described are principally used as support cores for large optical cables, they can also be used for the production of optical fiber cables suitable for use as drop lines, and for local connections between apparatus handling optical signals. An apparatus for producing such a drop line cable is illustrated in Fig. 7. Again, common reference numerals are used to indicate parts of the apparatus of Fig. 7 which have already been described earlier. As seen in Fig. 7 the endless filaments 15' again pass beneath a roller 41 and then over the surface of a heated drum roller 42, which once again bears a thin layer of a molten hot melt adhesive drawn from the tank 43. Instead of passing directly into the extruding head 18 the endless filament bundles 15' first pass through a die plate 61 having a plurality of guide holes equidistantly distributed around its central opening 63. A plastic, preferably thermoplastic, tube 64 containing an optical transmission fiber is drawn from a supply reel 65 and passes through the central orifice 63 of the die-plate 61 so that on emergence from the extruder head 18 the tube 64 is located at the center of the core string 11. The core string 11' can be bound in the manner previously described and can subsequently be sleeved with a thermoplastic sleeving layer (optionally with or without staple fiber filling), to produce the cable shown in section in Fig. 8. The sleeving of the wound (or unwound) core string 11' can of course take place in the cross-head extruder 19 of the plant of Fig. 1. The materials used for the sleeve are the same as those previously described with reference to the other embodiments. Thus the build-up of the drop line cable of Fig. 8 comprises at the very center the optical fiber 66 within its support tube 64, with the tube 64 lying coaxially within the core string 11'. The core string 11' is again reinforced against kinking by cross-wound polyester filament yarns as described in connection with Figs. 5 and 6, and a first thermoplastic sleeving layer 13 is disposed concentrically around the cross-wound core string 11'. A cable of this kind has substantial strength and resistance to damage and can for example be laid in a building during the building stage, without being susceptible to damage through rough treatment such as can occur on building sites. This is particularly the case when the sleeve layer 13 is reinforced with high modulus staple fibers and covered with a further protective sleeve 14 (not shown in Fig. 8).

Claims: A method of manufacturing a cable-like plastic composite body in which a string of endless filaments of high modulus of elasticity which are gathered together and extend parallel to one another and to the cable axis is impregnated with a liquid, solidifiable plastic and the plastic is subsequently solidified, characterised in that the string (11) is impregnated with a hot melt adhesive (12) which can be made liquid by heating; and in that the string (11') impregnated with the hot melt adhesive (12) is wound with a high strength yarn (51). A method in accordance with claim 1, characterised in that the winding with a high strength yarn takes place while the hot melt adhesive is still soft. A method in accordance with claim 1 or claim 2, wherein said wound core string is cross-wound with a second high strength yarn (51). A method in accordance with any one of the claims 1 to 3, wherein said endless filaments are passed over the surface of a heated rotating drum roller (42) carrying a film of liquid hot melt adhesive (44) in order to wet the filaments with adhesive on all sides to ensure complete watertightness of said cable-like plastic composite body. A method in accordance with claim 4, wherein said endless filaments coated with hot melt adhesive are gathered together on leaving said heated drum roller (42) and are passed through an extruding device (18) to form said core string (11'). A method in accordance with claim 4 or claim 5, wherein said rotating drum roller (42) rotates with a surface speed slightly different from the linear speed of said core string (11') whereby a degree of slippage occurs between the core string (11') and the surface of said drum (42). A method in accordance with any one of the claims 4, 5 or 6, wherein said endless filaments pass beneath a roller (41) prior to contacting the surface of said heated drum roller (42). A method in accordance with claim 7, wherein the position of said roller (41) before said heated drum roller (42) is variable to vary the angle of wrap of the endless filaments around the surface of said heated drum roller. A method in accordance with one of the preceding claims, wherein said endless high modulus filaments are gathered together into bundles and pass through apertures (62) in a die plate (61) positioned between said heated drum roller (42) and said extruder (18); and in that said die plate has a central opening (63) through which a tube (64) containing an optical fiber (66) is drawn, whereby said tube (64) becomes substantially concentrically embedded in said core string (11'). A method in accordance with claim 9, wherein said tube containing said optical fiber is drawn from a supply reel (65) which is preferably positioned so that said optical tube (64) does not pass over said heated drum roller (42). A method in accordance with claim 10, wherein said core string (11') containing said optical fiber (66) is subsequently sleeved with a further thermoplastic material (13), preferably in a cross-head extruder (19) and preferably, after being wound with high strength yarn (51, 51') to improve the resistance of said core string (11') to kinking. A high strength cable-like plastic composite support body resistant to kinking and made in accordance with any one of the method claims 1 to 10, said support body having a longitudinal axis and comprising a plurality of substantially endless filaments (15, 15') of high modulus of elasticity gathered together into a cores string (11') so that said filaments and said core string extend parallel to one another in a direction of said longitudinal axis, and an impregnation between the filaments of said core string, characterised in that said impregnation comprising a hot melt adhesive which can be made liquid by heating and solidifies on cooling, and at least one winding (51, 51') extending around said core string (11'), said at least one winding comprising a high strength yarn wound around said core string while said hot-melt adhesive is in a soft state. A high strength cable-like plastic composite support body in accordance with claim 12, characterised in that the endless filaments (15, 15') comprise E-glass (aluminoborosilicate glass), S-glass (magnisium aluminosilicate), aramid, or carbon. A high strength cable-like plastic composite support body in accordance with claim 12 or claim 13, characterised in that said hot melt adhesive is based on ethylene vinyl acetate, polyester, polyamide, polypropylene or polyester. A high strength cable-like plastic composite support body in accordance with one of claims 12 to 14, characterised in that said high strength yarn (51, 51') comprises polyester filament yarn. A high strength cable-like plastic composite support body in accordance with claim 15, wherein said polyester filament yarn comprises endless filaments. A high strength cable-like plastic composite support body in accordance with any one of the preceding claims 12 to 16, characterised in that a plastic tube (64) containing an optical transmission fibre (66) is located at the centre of said core string (11'). A high strength cable-like plastic composite support body in accordance with any one of the preceding claims 12 to 17, characterised in that a thermoplastic sleeving layer (13), optionally reinforced with high modulus fibres, is provided around said wound core string (11'). A high strength cable-like plastic composite support body in accordance with claim 18, characterised in that a further protective layer (14) is provided around said sleeving layer (13).

Inventors: JORGENSEN, JORGEN, OLESEN, JOHN
Applicants: ROBLON A/S
Application year: 1988
Main classification: B29C47
IPC codes: B29C47, B29C70, G02B6, B29C53, B29D99