CABLES AND METHOD FOR MAKING A CABLE

Description

[0001] The invention relates to a cable and a method for manufacturing a cable.

[0002] Cables are commonly used in electrical and information technology and typically consist of a single- or multi-core bundle of conductors (individual wires) sheathed in insulating material. The cable serves to transmit energy and / or information.

[0003] Typically, different plastics are used as insulating materials, which surround and insulate the conductors.

[0004] Electrical conductors are mostly made of copper, sometimes of aluminum or suitable metal alloys.

[0005] However, electrical conductors made of heavy materials such as copper are a disadvantage, particularly in the fields of aerospace, aviation, and medicine.

[0006] For some years now, it has been known in practice to use carbon nanotubes (also called Carbon Nanotubes - CNT) as electrical conductors.

[0007] Carbon nanotubes are microscopically small, tube-shaped structures (molecular nanotubes) made of carbon.

[0008] The walls of carbon nanotubes consist solely of carbon, with the carbon atoms forming a honeycomb-like structure with hexagons and three bonding partners per hexagon. The diameter of the tubes typically ranges from 1 to 50 nm (nanometers), although tubes with a diameter of only 0.4 nm also exist. They can be single- or multi-walled, open or closed, and can be either empty or filled. Filling with silver, liquid lead, or noble gases is possible.

[0009] These carbon nanotubes exhibit electrical conductivity. Depending on the detail of the structure, the electrical conductivity within the tube is metallic or semiconducting. Carbon nanotubes that are superconducting at low temperatures are also known.

[0010] Single-walled carbon nanotubes typically have a density of 1.3 to 1.4 g / cm³. Multi-walled carbon nanotubes typically have a density of approximately 1.8 g / cm³ and a tensile strength of 30 GPa (giga-pascals) for single-walled and up to 63 GPa for multi-walled versions.

[0011] A coaxial cable and a method for its manufacture are known from the prior art (EP 2 085 979 B1). This coaxial cable has the following structure: a core comprising a plurality of carbon nanotubes with at least one coating surrounding the carbon nanotubes, wherein the carbon nanotubes and the coating are combined in the form of at least one carbon nanotube composite wire and the carbon nanotubes are systematically arranged; an insulating layer enclosing the core; a shielding layer enclosing the insulating layer; and a sheathing layer enclosing the shielding layer, wherein the conductive coating comprises a conductive layer and a wetting layer located between the carbon nanotubes and the conductive layer. This state-of-the-art cable is a so-called coaxial cable. It features a conductive coating around the carbon nanotubes and an additional wetting layer, making its construction very complex.

[0012] Furthermore, a cable for leak detection is part of the state of the art (EP 3 471 112 A1).

[0013] This cable is used in devices for detecting leaks of various liquids, such as moisture, liquid chemicals, and organic liquids.

[0014] This state-of-the-art leak detection cable has a core containing detection elements, which in turn comprise a metal core surrounded by a conductive polymer coating. Insulating elements, also with metal cores, are positioned between these elements. These detection elements are surrounded by a braid. A layer of conductive polymer is applied to the braid; this layer expands when it comes into contact with hydrocarbons. This conductive polymer layer also expands when it comes into contact with an organic liquid. An additional outer layer, acting as a boundary element, restricts the inward expansion of the conductive polymer layer, thus coupling and connecting the connecting elements.The sensor cable detects contact with an organic liquid, causing a short circuit between the various detection elements. This state-of-the-art cable for leak detection is not designed for electrical and information technology applications because it creates a short circuit upon contact with a liquid.

[0015] The prior art (US 2018 / 315521 A1) includes a cable with a conductive core comprising a strand of electroplated carbon nanotubes. A shield surrounds the core along the length of the cable, and a jacket surrounds the shield along the same length. This prior art cable always features an electrically conductive shielding jacket. Furthermore, a dielectric, which can be configured as an insulator, is arranged around the core. Embedding the carbon nanotubes in a plastic dielectric that subsequently hardens has the disadvantage that the carbon nanotube fibers bond with the plastic, preventing the plastic from being cut to length without tearing the carbon fibers.Wrapping the carbon nanotubes with a tape of expanded polytetrafluoroethylene has the disadvantage that the carbon nanotubes can very easily slip out of the sheathing, so that under certain circumstances no conductor is arranged in the cable.

[0016] The technical problem underlying the invention is to provide a cable with at least one electrical conductor, wherein the electrical conductor consists of carbon nanotubes, which is simple in structure and easy to manufacture, which ensures a certain tensile strength, and which provides cut protection when the insulating material is cut. Furthermore, a method for manufacturing such a cable is to be provided, by which a cable with an electrical conductor consisting of carbon nanotubes can be produced in such a way that an insulating layer at the end of the cable can be easily removed without destroying or damaging the electrical conductor.

[0017] This technical problem is solved by a cable having the features according to claim 1 and by a method having the features according to claim 8.

[0018] The cable according to the invention, which has one or more electrical conductors, wherein at least one electrical conductor is formed from a plurality of electrically conductive carbon nanotubes, In which a braid made of non-conductive material is provided enclosing the at least one electrical conductor and in which a further insulating layer is provided enclosing the braid made of non-conductive material, is characterized in that the braid enclosing the at least one electrical conductor is arranged directly on the at least one electrical conductor and that the braid is made of a textile material, or that the braid consists of aramid fibers.

[0019] The cable according to the invention has the advantage that the at least one electrical conductor is encased in a braid of non-conductive material. This protects the sensitive carbon nanotubes. At the same time, the carbon nanotubes are arranged in the braid in such a way that they cannot slip out of the braid. The braid is held in contact with the at least one electrical conductor with appropriate pressure.

[0020] The mesh is further encased in another insulating layer made of a non-conductive material.

[0021] This inventive design ensures that the insulating layer at the end of a cable can be cut in a circular, i.e. radial, manner and that the insulating layer can then be separated from the braid so that the braid can be opened in such a way that the at least one electrical conductor can be exposed in order to electrically connect the electrical conductor to another electrical element, for example a terminal.

[0022] An electrical conductor is understood to be an arrangement of electrically conductive carbon nanotubes. These carbon nanotubes can form a strand to create an electrical conductor. The carbon nanotubes can be arranged in a predetermined structure to form an electrical conductor. The cable can contain a single electrical conductor formed from a multitude of electrically conductive carbon nanotubes, or it can contain multiple electrical conductors, each consisting of a multitude of electrically conductive carbon nanotubes.

[0023] If multiple electrical conductors are arranged within the cable, they are not electrically insulated from each other within the cable, i.e., within the braid. Multiple electrical conductors refers to the fact that each conductor is formed from a specific structure or arrangement of carbon nanotubes. For example, the multitude of carbon nanotubes can be arranged twisted around a longitudinal axis, thus forming a single electrical conductor.

[0024] The terms conductive material or non-conductive material refer to electrically conductive or electrically non-conductive material.

[0025] A braid is understood to be a structure made of fibers or thread-like material, which is interwoven in such a way that it forms a sheath-like shape, which is produced by interlacing several strands of flexible material.

[0026] According to an advantageous embodiment of the invention, the braid sheathing the at least one electrical conductor is arranged directly on the at least one electrical conductor.

[0027] No additional material is arranged between the at least one electrical conductor and the braid sheathing the conductor. No further layer is provided between the at least one electrical conductor and the braid sheathing the conductor. The braid directly surrounds the at least one electrical conductor.

[0028] The network has the following functions: 1. To prevent the at least one electrical conductor from sticking to the material of the further insulating layer, 2. to ensure a certain tensile strength of the cable, 3. to ensure protection against cutting when the insulating material is cut.

[0029] Furthermore, the arrangement of the braid surrounding the at least one electrical conductor directly on the at least one electrical conductor has the advantage that the braid and the conductor are connected to each other in a slip-resistant manner, so that the electrical conductor cannot slip out of the braid.

[0030] For this purpose, the braid is arranged around the electrical conductor with the required tension during manufacturing.

[0031] Another advantageous embodiment of the invention provides that the braid is formed from fibers or a thread-like material. Since the braid consists of an intertwined material, it is advantageous to use elongated fibers or thread-like material.

[0032] According to the invention, the braid is to be formed from a textile material. Textile material has the advantage that, firstly, it is electrically non-conductive. Secondly, a braid can be easily produced from the textile material.

[0033] According to the invention, the braid is provided to consist of aramid fibers.

[0034] Aramid fibers have the advantage of being heat-resistant and are very strong synthetic fibers with high tensile strength.

[0035] The aramid fibers also ensure that there is a certain degree of adhesion between the plastic of the insulating layer and the aramid fibers of the braid.

[0036] If the carbon nanotubes were arranged in the plastic of the outer insulating layer without the interposition of the braid, the insulating layer would be fused to the carbon nanotubes and removing the insulating layer - for example to contact the conductor element - would not be possible.

[0037] According to a further advantageous embodiment of the invention, the braid is designed to completely enclose the at least one electrical conductor on a cladding surface.

[0038] The braid completely encases or sheaths the electrical conductor. This means that the additional insulating layer has no contact with the at least one electrical conductor. The braid completely encases the electrical conductor. The braid forms a complete sheath of the electrical conductor.

[0039] According to a further preferred embodiment of the invention, it is provided that the at least one electrical conductor is sheathed by the braid in such a way that a contactless structure is provided between the at least one electrical conductor and the further insulating layer.

[0040] As already explained, at least one electrical conductor does not come into contact with the further insulating layer. This ensures that the adhesion provided by the braid remains continuous.

[0041] It is also advantageous that the insulating layer is made of a thermoplastic material.

[0042] Insulating materials consist of an electrically non-conductive material. The insulating material exhibits extremely low and therefore negligible electrical conductivity.

[0043] Electrical insulating materials have a high specific electrical resistance, for example at least 10< Ω · cm, and are non-conductors.

[0044] Plastics, such as thermosets, thermoplastics, or elastomers, are advantageously used as electrical insulating materials. Thermoplastic materials are advantageous due to their ease of processing.

[0045] For example, polyethylene, such as foamed polyethylene, can be used for the insulating layer.

[0046] According to a further advantageous embodiment of the invention, the additional insulating layer and the braid are firmly connected to each other, or the additional insulating layer and the braid are connected to each other by an adhesive bond.

[0047] The bond between the insulating layer and the braid should be strong enough to prevent the braid from slipping within the insulating layer. If the insulating layer needs to be removed from the end of a cable, it must be easy to peel off the braid, for example, after making a circular cut in the insulating layer.

[0048] According to a further advantageous embodiment of the invention, it is provided that, although the electrical conductor has a tensile strength of less than 2 N, the cable according to the invention can be used well and without damage.

[0049] The inventive method for producing a cable comprising one or more electrical conductors, wherein the at least one electrical conductor is formed from a plurality of electrically conductive carbon nanotubes and wherein a braid of non-conductive material is provided enclosing the at least one electrical conductor and wherein a further insulating layer enclosing the braid of non-conductive material is provided, is characterized in that the at least one electrical conductor consisting of a plurality of electrically conductive carbon nanotubes is braided with non-conductive fibers and that a further insulating layer made of a plastic is subsequently arranged on the braid.

[0050] This method for manufacturing a cable is characterized by the fact that a non-slip connection is formed between the at least one electrical conductor, which consists of carbon nanotubes, and the braid, and that an additional insulating layer made of a plastic is placed on the braid, so that the insulating layer can be at least partially removed from the cable if necessary.

[0051] The process ensures the simple and inexpensive production of such a cable.

[0052] A particularly preferred embodiment of the method according to the invention is characterized in that the at least one electrical conductor and the braid are encased with the plastic, preferably a thermoplastic plastic, and that the plastic, preferably the thermoplastic plastic and the braid form a firm connection or an adhesive connection.

[0053] This ensures, firstly, that at least one electrical conductor is securely positioned within the braid and, secondly, that the braid and the plastic form an adhesive bond, preventing the braid and its electrical conductor from slipping out of the insulating layer. Nevertheless, a detachable connection is maintained to allow the insulating layer to be separated from the braid.

[0054] According to an advantageous embodiment of the invention, the plastic is arranged on the braid using a cable extrusion process. However, other methods can also be used.

[0055] Another advantageous embodiment of the invention provides that the at least one electrical conductor is completely encased in the braid. In this case, during the production of the braid, for example, a complete sheathing is formed by guiding the threads with spindles, so that the at least one electrical conductor does not come into contact with the further insulating layer.

[0056] A significant advantage of the cable according to the invention is that when the cable is laid down, i.e. when the insulating material is cut in a circular fashion, the insulating material can be easily pulled away from the braid in order to establish an electrically conductive connection to other components with the at least one electrical conductor located inside the cable.

[0057] These cables are used, for example, as high-frequency cables or power cables. They can also be used in switching technology as switch wires.

[0058] As already explained, the mesh is not electrically conductive and has a certain tensile strength.

[0059] The cables can be manufactured on an extrusion line, for example a full extrusion line.

[0060] Further features and advantages of the invention will become apparent from the accompanying drawings, which show a cable according to the invention, without limiting the invention to these embodiments. The drawings show: Fig. 1 a longitudinal section through a cable according to the invention; Fig. 2 a cross-section through a cable according to the invention; Fig. 3 a longitudinal section through a cable with a partially removed insulating layer; Fig. 4 a longitudinal section through a modified embodiment.

[0061] Fig. 1 Figure 1 shows a cable 1 which has an electrical conductor 2. The electrical conductor 2 consists of a multitude of carbon nanotubes 3.

[0062] The electrical conductor 2 is surrounded by a braid 4. The braid 4 consists of a non-conductive material, preferably aramid fibers.

[0063] The braid 4 made of aramid fibers ensures that the braid firmly holds the electrical conductor 2.

[0064] The electrical conductor 2 and the braid 4 are surrounded by an insulating layer 5. The insulating layer 5 completely encloses the braid 4.

[0065] Likewise, the mesh 4 completely encloses the electrical conductor 2, so that the insulating layer 5 does not come into contact with the electrical conductor 2.

[0066] Fig. 2 The cable 1 shows the electrical conductor 2, which has a multitude of carbon nanotubes 3. In the Fig. 2 Only a portion of the carbon nanotubes 3 is shown. The electrical conductor 2 is entirely composed of the carbon nanotubes 3.

[0067] The electrical conductor 2 is sheathed with the braid 4, which also consists of individual threads 6. The threads are made, for example, of aramid or another textile material.

[0068] The entire layer 4, which is in Fig. 2 The structure shown consists of the mesh and the threads 6.

[0069] The braid 4 is completely encased by a layer 5, which acts as an insulating layer. The layer 5 has no contact with the electrical conductor 2.

[0070] Fig. 3 Kabel 1 shows how it is in Fig. 1 is shown. Identical parts are marked with the same reference symbols. According to Fig. 3 The insulating layer 5 is cut off at one end 7. For this purpose, a circular incision is made in the insulating layer at this end 7. The threads 6 of the braid 4 and the carbon nanotubes 3 protrude beyond an end face 8 of the insulating layer 5. The carbon nanotubes 3 can be electrically connected to another component. They can, for example, be arranged in a clamp (not shown).

[0071] Fig. 4 Figure 1 shows cable 1 with braid 4 and insulating layer 5. The construction is analogous to the embodiment shown in Figure 1. Fig. 1 .

[0072] Cable 1 has several electrical conductors 2. For this purpose, the carbon nanotubes 3 are entangled, interwoven, braided, or similarly connected to form three different strands. This creates three electrical conductors. These are in Fig. 4 This is only a schematic representation. There is generally no spacing between the electrical conductors 2; they lie close together, as do the individual carbon nanotubes 3. Fig. 1 . Reference figures

[0073] 1 Cable 2 Electrical conductor 3 Carbon nanotubes 4 Braid 5 Insulating layer 6 Threads 7 End 8 End face

Claims

1. Cable which has one or more electrical conductors, wherein the at least one electrical conductor is formed from a plurality of electrically conductive carbon nanotubes, - in which a braid (4) surrounding the at least one electrical conductor (2) is provided, - and in which a further insulating layer (5) sheathing the braid (4) composed of non-conductive material is provided, characterized in that the braid (4) is formed from non-conductive material, and in that the braid (4) sheathing the at least one electrical conductor (2) is arranged directly on the at least one electrical conductor (2), and in that the braid (4) is formed from a textile material or in that the braid (4) consists of aramid fibres.

2. Cable according to Claim 1, characterized in that the braid (4) is formed from fibres or a filamentous material.

3. Cable according to either of the preceding claims, characterized in that the braid (4) is designed so as to completely surround the at least one electrical conductor (2) on a lateral surface.

4. Cable according to any of the preceding claims, characterized in that the at least one electrical conductor (2) is sheathed by the braid (4) in such a way that a contactless structure is provided between the at least one electrical conductor (2) and the further insulating layer (5).

5. Cable according to any of the preceding claims, characterized in that the further insulating layer (5) is formed from a thermoplastic.

6. Cable according to any of the preceding claims, characterized in that the further insulating layer (5) and the braid (4) are fixedly connected to each other, or in that the further insulating layer (5) and the braid (4) are connected to each other by means of an adhesive connection.

7. Cable according to any of the preceding claims, characterized in that the electrical conductor (2) has a tensile strength of less than two Newtons.

8. Method for producing a cable according to Claim 1, characterized in that the at least one electrical conductor (2) consisting of a plurality of electrically conductive carbon nanotubes (3) is braided with non-conductive fibres, and in that a further insulating layer (5) composed of a plastic is then arranged on the braid (4).

9. Method according to Claim 8, characterized in that the at least one electrical conductor (2) and the braid (4) are sheathed with the plastic, and in that the plastic and the braid (4) form a fixed connection or an adhesive bond.

10. Method according to Claim 8 or 9, characterized in that the plastic is arranged on the braid (4) by means of a cable extrusion process.

11. Method according to any of Claims 8 to 10, characterized in that the at least one electrical conductor (2) is fully sheathed with the braid (4).