A coaxial cable having a conductive plastic shield

Abstract

The present application relates to coaxial cable technical field, particularly to a kind of coaxial cable with conductive plastic shielding layer, including inner conductor, the outer covering of the inner conductor has insulating layer, the outer covering of the insulating layer has conductive plastic shielding layer, the outer covering of the conductive plastic shielding layer has outer sheath, the conductive plastic shielding layer is made by conductive filler incorporation extrudable plastic, the conductive plastic shielding layer is seamless tubular structure, by extrusion process whole covering in the outside of the insulating layer, the present application replaces traditional aluminum foil and braided wire by adopting conductive plastic shielding layer, conductive plastic shielding layer is once formed by extrusion process by conductive filler incorporation extrudable plastic, form seamless tubular shielding structure, eliminate aluminum foil lap joint gap and braided mesh, significantly improve the shielding effectiveness when high-frequency signal transmission, avoid electromagnetic leakage, ensure signal integrity.

Description

Technical Field

[0001] This invention relates to the field of coaxial cable technology, and in particular to a coaxial cable with a conductive plastic shielding layer. Background Technology

[0002] In applications such as robot joints, high-frequency signal transmission, and dynamic bending, coaxial cables need to simultaneously meet multiple requirements, including stable high-frequency signal transmission, high shielding effectiveness, good flexibility, and resistance to torsional fatigue.

[0003] The shielding layer of existing coaxial cables typically uses an aluminum foil wrapping structure with metal braided wires. Gaps exist at the aluminum foil overlaps, and meshes exist between the braided wires, allowing high-frequency signals to easily leak through these gaps, leading to decreased shielding effectiveness. Furthermore, the aluminum foil and braided wires require multiple processes such as wrapping and braiding, resulting in slow production speeds and high manufacturing costs. In addition, the braided wires are prone to breakage during repeated bending and twisting, creating gaps in the shielding layer and further deteriorating shielding performance. To meet torsion resistance requirements, existing cables often employ increased braiding density or the addition of an anti-torsion layer. However, increased braiding density increases copper usage and cable weight, while the anti-torsion layer increases structural complexity and outer diameter. Some cables use conductive plastic as the shielding layer, but existing conductive plastic shielding layers are mostly extruded from a single material, resulting in insufficient bonding strength between the shielding layer and the inner insulation layer and outer sheath, making them prone to interlayer slippage during dynamic bending. Simultaneously, the conductive plastic shielding layer itself has limited torsion resistance and may crack after prolonged torsion. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention provides a coaxial cable with a conductive plastic shielding layer.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: an anti-torsion coaxial cable with a conductive plastic shielding layer, comprising an inner conductor, an insulation layer covering the outer side of the inner conductor, a conductive plastic shielding layer covering the outer side of the insulation layer, and an outer sheath covering the outer side of the conductive plastic shielding layer. The conductive plastic shielding layer is made by incorporating conductive filler into extrudable plastic, and the conductive plastic shielding layer is a seamless tubular structure that is integrally covered on the outside of the insulation layer by an extrusion process.

[0006] As a preferred embodiment of the present invention, a tensile reinforcing core is provided at the center of the inner conductor, and the inner conductor is formed by multiple tin-plated copper wires twisted around the tensile reinforcing core.

[0007] As a preferred embodiment of the present invention, an easily separable insulating layer is provided between the insulating layer and the conductive plastic shielding layer.

[0008] As a preferred embodiment of the present invention, an anti-torsion wrapping layer is provided between the conductive plastic shielding layer and the outer sheath. The anti-torsion wrapping layer is a fiber spiral wrapping layer, and the wrapping direction of the anti-torsion wrapping layer is opposite to the twisting direction of the inner conductor.

[0009] As a preferred technical solution of the present invention, the anti-torsion wrapping layer is wrapped in a unidirectional spiral wrapping, a bidirectional cross wrapping, or a mesh braided wrapping.

[0010] As a preferred embodiment of the present invention, the conductive plastic shielding layer is a circular tubular structure, a polygonal tubular structure, or a spiral corrugated tubular structure, and the longitudinal ribs are disposed on the outer wall of the tubular structure.

[0011] As a preferred embodiment of the present invention, the conductive plastic shielding layer is a circular tubular structure, a polygonal tubular structure, a tubular structure with longitudinal ribs, or a spiral corrugated tubular structure.

[0012] As a preferred embodiment of the present invention, the outer sheath has a double-layer structure, including an inner TPU layer and an outer TPU layer, wherein the hardness of the inner TPU layer is lower than that of the outer TPU layer.

[0013] As a preferred embodiment of the present invention, an adhesive layer is further provided between the conductive plastic shielding layer and the outer sheath.

[0014] As a preferred embodiment of the present invention, a water-blocking layer is further provided between the insulating layer and the conductive plastic shielding layer.

[0015] Compared with the prior art, the beneficial effects that this invention can achieve are: 1. This invention replaces traditional aluminum foil and braided wire with a conductive plastic shielding layer. The conductive plastic shielding layer is formed in one step by incorporating conductive filler into extrudable plastic through an extrusion process, forming a seamless tubular shielding structure. This eliminates the gaps in aluminum foil overlaps and braided mesh, significantly improving the shielding effectiveness during high-frequency signal transmission, avoiding electromagnetic leakage, and ensuring signal integrity.

[0016] 2. The conductive plastic shielding layer of the present invention is integrally coated on the outside of the insulation layer through an extrusion process, eliminating the traditional wrapping and braiding processes, breaking through the production bottleneck of low-speed braiding, and greatly improving production efficiency; at the same time, the conductive plastic shielding layer replaces most of the copper material, significantly reducing the amount of copper material used, making the overall weight of the coaxial cable lighter and meeting the requirements for lightweighting.

[0017] 3. This invention provides an anti-torsion wrapping layer between the conductive plastic shielding layer and the outer sheath. The anti-torsion wrapping layer is a fiber spiral wrapping layer with the wrapping direction opposite to the twisting direction of the inner conductor, forming a reverse torque cancellation structure. When the cable is torsioned, the anti-torsion wrapping layer bears the main torsional stress, protecting the internal conductive plastic shielding layer and the inner conductor, and effectively improving the cable's resistance to torsional fatigue.

[0018] 4. This invention provides longitudinal ribs on the outer wall of the conductive plastic shielding layer. The longitudinal ribs are integrally extruded with the conductive plastic shielding layer and embedded in the inner wall of the outer sheath, forming a mechanical interlocking structure to prevent relative rotation between the conductive plastic shielding layer and the outer sheath. At the same time, the longitudinal ribs improve the axial tensile strength and heat dissipation area of ​​the conductive plastic shielding layer, further enhancing the reliability of the cable in dynamic bending situations.

[0019] 5. This invention employs a double-layer TPU outer sheath structure, with the inner TPU layer having a lower hardness than the outer TPU layer. The inner layer provides flexibility, while the outer layer provides abrasion resistance, allowing the cable to remain flexible while providing sufficient mechanical protection during repeated bending and twisting. Combined with a tensile reinforcing core and a water-blocking layer, this further improves the overall tensile strength, waterproof performance, and cyclic bending life of the cable, meeting the long-term usage requirements of robot joints and high-frequency dynamic bending applications. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the outer TPU layer of the present invention; Figure 2 This is a schematic diagram of the inner TPU layer of the present invention; Figure 3 This is a schematic diagram of the structure of the conductive plastic shielding layer of the present invention; Figure 4 This is a schematic diagram of the adhesive layer structure of the present invention; Figure 5 This is a schematic diagram of the anti-torsion wrapping layer of the present invention; Figure 6 This is a schematic diagram of the structure of the insulating layer of the present invention; Figure 7 This is a schematic diagram of the tensile strengthening core of the present invention.

[0021] Among them: 1. Inner conductor; 2. Insulation layer; 3. Conductive plastic shielding layer; 4. Outer sheath; 41. Inner TPU layer; 42. Outer TPU layer; 5. The insulation layer is easy to separate; 6. Anti-torsion cladding; 7. Longitudinal reinforcing bars; 8. Adhesive layer; 9. Tensile-strength reinforced core. Detailed Implementation

[0022] To make the technical means, creative features, and achieved objectives and effects of this invention easier to understand, the invention is further described below with reference to specific embodiments. However, the following embodiments are merely preferred embodiments of this invention and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments described herein without creative effort are all within the protection scope of this invention. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods, and the materials and reagents used in the following embodiments are commercially available unless otherwise specified.

[0023] Example: Figure 1 As shown, this embodiment provides an anti-torsion coaxial cable with a conductive plastic shielding layer. Its structure, from the inside out, includes: an inner conductor 1, an insulation layer 2, a water-blocking layer, an easily separable insulation layer 5, a conductive plastic shielding layer 3, an anti-torsion wrapping layer 6, an adhesive layer 8, and an outer sheath 4. The outer wall of the conductive plastic shielding layer 3 is integrally extruded with several longitudinal ribs 7, and the outer sheath 4 is a double-layer TPU structure. The material, function, and manufacturing method of each layer are described in detail below.

[0024] refer to Figure 7 As shown, the inner conductor 1 is made of multiple tin-plated copper wires twisted together, with a twist pitch of 8 to 12 times the outer diameter of the inner conductor 1. The tin plating layer is used to prevent the copper wires from oxidizing and to ensure stable conductivity during long-term use. The twisted structure gives the inner conductor 1 high flexibility, allowing it to withstand repeated bending without easily breaking. A tensile reinforcing core 9 is set in the center of the inner conductor 1. The tensile reinforcing core 9 is made of aramid fiber rope, which has high tensile strength and good flexibility. Multiple tin-plated copper wires are twisted around the tensile reinforcing core 9 to form a composite inner conductor structure. While ensuring signal transmission capability, it significantly improves the overall tensile strength of the cable, making it suitable for applications such as robot joints that require tensile and bending resistance.

[0025] Manufacturing method: Using a conventional stranding machine, multiple tin-plated copper wires are simultaneously stranded with aramid fiber rope, and the stranding pitch is controlled to be 8 to 12 times the outer diameter of the inner conductor, and then wound up for later use.

[0026] refer to Figure 6 As shown, the insulation layer 2 covers the outside of the inner conductor 1 and is made of foamed polyethylene material with a thickness of 0.8 mm. Foamed polyethylene has a low dielectric constant and dielectric loss, which can effectively reduce the transmission attenuation of high-frequency signals and ensure the stability of the characteristic impedance of the coaxial cable. The insulation layer 2 also serves to isolate the inner conductor 1 from the subsequent shielding layer to prevent short circuits.

[0027] Manufacturing method: Using an extruder, foamed polyethylene material is extruded and coated on the outside of the inner conductor 1. By controlling the degree of foaming and the extrusion temperature, the thickness of the insulation layer 2 is made uniform and the surface is smooth.

[0028] refer to Figure 5 and Figure 6 As shown, the water-blocking layer is set between the insulation layer 2 and the easily separable insulation layer 5, and is made by wrapping with water-blocking tape. The water-blocking tape can expand rapidly when it comes into contact with water, fill the gaps inside the cable, and prevent water from penetrating along the axial direction, thereby improving the waterproof performance and service life of the cable.

[0029] Manufacturing method: Using a wrapping machine, the water-blocking tape is spirally wrapped around the outside of the insulation layer 2, and the wrapping overlap rate is controlled at 20%~30% to ensure that the water-blocking layer is continuous and without gaps.

[0030] refer to Figure 5 As shown, the easily separable insulation layer 5 covers the outside of the water-blocking layer. It is made of easily peelable polypropylene thin layer with a thickness of 0.1mm. The main function of this layer is to facilitate stripping during field termination, and at the same time to prevent the subsequent conductive plastic shielding layer 3 from excessively adhering to the water-blocking layer or insulation layer 2 during extrusion. The peel strength of the easily separable insulation layer 5 is moderate, which can ensure that the layers of the cable do not separate during manufacturing and use, and also allows operators to easily strip it with ordinary wire stripping tools.

[0031] Manufacturing method: Using an extruder, a thin layer of polypropylene material is extruded and coated onto the outside of the water-blocking layer. The extrusion temperature is controlled to create a suitable peel force between the thin layer and the water-blocking layer.

[0032] refer to Figure 3 As shown, the conductive plastic shielding layer 3 is the core innovative layer of this invention, covering the outside of the easily separable insulation layer 5. This layer is made by incorporating conductive filler into extrudable plastic. Specifically, the matrix resin is a thermoplastic elastomer, and the conductive filler is nickel-plated carbon fiber, with the conductive filler accounting for 25% of the mass. Through an extrusion process, the conductive plastic shielding layer 3 completely covers the outside of the easily separable insulation layer 5, forming a seamless circular tubular structure with a thickness of 0.3 mm and a resistivity of no more than 10 Ω·m. This layer completely replaces the aluminum foil and metal braided wire in traditional coaxial cables and has the following functions: Seamless electromagnetic shielding: Traditional aluminum foil has gaps at the overlaps and woven mesh, which can easily lead to the leakage of high-frequency signals; the conductive plastic shielding layer has a continuous tubular structure without any gaps, which significantly improves the shielding effectiveness.

[0033] Lightweight: Replacing most of the copper with conductive plastic significantly reduces the weight of the cable.

[0034] High-efficiency manufacturing: The extrusion process is used for one-time molding, eliminating the wrapping and weaving processes, which greatly increases the production speed.

[0035] Torsional resistance: Conductive plastic itself has a certain degree of elasticity, which can disperse some of the torsional stress through elastic deformation.

[0036] refer to Figure 1 ,refer to Figure 2 ,refer to Figure 3 and reference Figure 5 As shown, during the extrusion of the conductive plastic shielding layer 3, several longitudinal ribs 7 are uniformly formed along the circumferential direction on its outer wall using a shaped extrusion die. The longitudinal ribs 7 are integral with the conductive plastic shielding layer 3, with a semi-circular cross-section, and extend continuously along the cable axis. The functions of the longitudinal ribs 7 include: increasing the axial tensile strength of the shielding layer; increasing the heat dissipation area; and embedding into the inner wall of the outer sheath 4 during subsequent wrapping to form a mechanical interlock and prevent relative rotation between layers.

[0037] refer to Figure 1 ,refer to Figure 2 ,refer to Figure 3 and reference Figure 5 As shown, the manufacturing method is as follows: The thermoplastic elastomer and nickel-plated carbon fiber are mixed in proportion and added to the extruder using a co-extrusion or single extrusion process. The conductive plastic shielding layer 3 is extruded through a circular tubular die, and longitudinal ribs 7 are formed by the grooves on the die. After extrusion, the material is water-cooled and shaped, and then wound up.

[0038] refer to Figure 5 As shown, the anti-torsion wrapping layer 6 is disposed outside the conductive plastic shielding layer 3. It is made of aramid fiber wire with unidirectional spiral wrapping. The wrapping direction is opposite to the twisting direction of the inner conductor 1. The aramid fiber wire has high strength, high modulus and excellent fatigue resistance. It can withstand the main torsional stress when the cable is repeatedly twisted. Since the wrapping direction is opposite to the twisting direction of the inner conductor, when the cable is twisted, the anti-torsion wrapping layer 6 generates a reverse torque, which offsets part of the torsional stress and protects the inner conductive plastic shielding layer 3 and the inner conductor 1 from damage.

[0039] Manufacturing method: A high-speed wrapping machine is used to wrap aramid fiber threads around the outside of the conductive plastic shielding layer 3 in a unidirectional spiral manner, controlling the wrapping pitch and tension to ensure that the wrapping layer fits tightly without damaging the shielding layer.

[0040] refer to Figure 4 As shown, the adhesive layer 8 is disposed between the anti-torsion wrapping layer 6 and the outer sheath 4. It is a hot melt adhesive layer with a thickness of 0.05mm. The adhesive layer 8 is used to firmly bond the anti-torsion wrapping layer 6 and the outer sheath 4 to prevent slippage and delamination between the layers during dynamic bending of the cable.

[0041] Manufacturing method: A hot melt coating process is used to uniformly coat the outside of the anti-torsion wrapping layer 6 with hot melt adhesive, and then the outer sheath 4 is immediately extruded and wrapped so that the adhesive layer 8 is firmly bonded to the outer sheath 4 in a hot state.

[0042] refer to Figure 1 and Figure 2 As shown, the outer sheath 4 has a double-layer TPU structure, including an inner TPU layer 41 and an outer TPU layer 42. The inner TPU layer 41 has a hardness of 80A and a thickness of 0.3mm, providing flexibility; the outer TPU layer 42 has a hardness of 95A and a thickness of 0.4mm, providing abrasion resistance. TPU material has excellent abrasion resistance, oil resistance, hydrolysis resistance and low temperature resistance, making it suitable for dynamic bending applications such as robot joints. The inner TPU layer 41 is wrapped around the outside of the adhesive layer 8 during extrusion, and the longitudinal ribs 7 on the conductive plastic shielding layer 3 are embedded in the inner TPU layer 41 to form a mechanical interlock, further preventing relative rotation between layers.

[0043] Manufacturing method: The inner TPU material and the outer TPU material are fed into two extruders respectively and extruded simultaneously through a double-layer co-extrusion die, so that the inner TPU layer 41 and the outer TPU layer 42 are tightly bonded. After extrusion, the material is cooled by water, drawn, and wound up.

[0044] refer to Figure 1 As shown, the coaxial cable produced in this embodiment has an overall outer diameter of 5mm and a cyclic bending life of not less than 10 million cycles. It is suitable for robot joints, high-frequency signal transmission, and dynamic bending applications. Its shielding layer is seamless and has high shielding effectiveness. Conductive plastic is used instead of aluminum foil and braided wire, which makes it lightweight and efficient in production. The anti-torsion wrapping, longitudinal ribs, and double-layer TPU sheath work together to give the cable excellent resistance to torsional fatigue.

[0045] Working principle: Before use: Refer to Figure 1 As shown, check whether the structure of each layer of the coaxial cable is intact. Confirm that the inner conductor (1), insulation layer (2), water-blocking layer (10), easily separable insulation layer (5), conductive plastic shielding layer (3), anti-torsion wrapping layer (6), adhesive layer (8), outer sheath (4), longitudinal ribs (7) and tensile reinforcing core (9) are undamaged. Cut the cable according to the actual wiring length, remove the easily separable insulation layer (5) and outer sheath (4) at the end to expose the inner conductor (1) and conductive plastic shielding layer (3). Weld or crimp the inner conductor (1) to the connector center pin, and connect the conductive plastic shielding layer (3) to the grounding terminal of the connector shell to form a signal circuit and a shielding grounding circuit. After checking and confirming that there is no short circuit between the inner conductor (1) and the conductive plastic shielding layer (3), pre-bend and fix the cable according to the movement trajectory of the robot joint or dynamic bending equipment.

[0046] When using: Refer to Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 As shown, high-frequency signals are transmitted through the inner conductor (1), the insulation layer (2) ensures stable characteristic impedance, the conductive plastic shielding layer (3) is a seamless tubular structure, which suppresses external electromagnetic interference from entering the inner conductor (1) and prevents internal signals from radiating outward, thus ensuring signal integrity. When the cable is twisted, the anti-torsion wrapping layer (6) bears the main torsional stress, and its wrapping direction is opposite to the twisting direction of the inner conductor (1), forming a reverse torque cancellation. The longitudinal ribs (7) are embedded in the inner wall of the outer sheath (4) to form a mechanical interlock, preventing relative rotation between layers. In the double-layer TPU outer sheath (4), the inner TPU layer (41) provides flexibility, and the outer TPU layer (42) provides abrasion resistance, so that the cable remains stable in repeated bending and twisting. The tensile strengthening core (9) bears axial tension, and the water-blocking layer (10) prevents moisture from penetrating along the axial direction.

[0047] After use: Reference Figure 1 As shown, disconnect the connector and inspect the cable's appearance and the structure of each layer. Pay special attention to whether the outer sheath (4) is worn or cracked, whether the conductive plastic shielding layer (3) is exposed or cracked, whether the anti-torsion wrapping layer (6) is loose, and whether the inner conductor (1) is broken. If the cable needs to be rewired or stored, coil it into a loop with a coiling diameter not less than 10 times the outer diameter of the cable. Avoid excessive bending and twisting. Store it in a dry and cool environment. If the outer sheath (4) is found to be severely worn or the conductive plastic shielding layer (3) is cracked, the cable should be replaced.

[0048] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A torsion-resistant coaxial cable with a conductive plastic shielding layer, comprising an inner conductor (1), characterized in that, The inner conductor (1) is covered with an insulating layer (2), the insulating layer (2) is covered with a conductive plastic shielding layer (3), the conductive plastic shielding layer (3) is covered with an outer sheath (4), the conductive plastic shielding layer (3) is made by incorporating conductive filler into extrudable plastic, the conductive plastic shielding layer (3) is a seamless tubular structure, and is entirely covered with the outside of the insulating layer (2) by an extrusion process.

2. The anti-torsion coaxial cable with a conductive plastic shielding layer according to claim 1, characterized in that, The inner conductor (1) is provided with a tensile reinforcing core (9) at its center. The inner conductor (1) is formed by multiple tin-plated copper wires twisted around the tensile reinforcing core (9).

3. The anti-torsion coaxial cable with a conductive plastic shielding layer according to claim 1, characterized in that, An easily separable insulating layer (5) is provided between the insulating layer (2) and the conductive plastic shielding layer (3).

4. The anti-torsion coaxial cable with a conductive plastic shielding layer according to claim 1, characterized in that, An anti-torsion wrapping layer (6) is provided between the conductive plastic shielding layer (3) and the outer sheath (4). The anti-torsion wrapping layer (6) is a fiber spiral wrapping layer, and the wrapping direction of the anti-torsion wrapping layer (6) is opposite to the twisting direction of the inner conductor (1).

5. The anti-torsion coaxial cable with a conductive plastic shielding layer according to claim 4, characterized in that, The anti-torsion wrapping layer (6) is wrapped in a unidirectional spiral wrapping, a bidirectional cross wrapping, or a mesh braided wrapping.

6. The anti-torsion coaxial cable with a conductive plastic shielding layer according to claim 1, characterized in that, The conductive plastic shielding layer (3) is a circular tubular structure, a polygonal tubular structure or a spiral corrugated tubular structure, and the longitudinal ribs (7) are provided on the outer wall of the above-mentioned tubular structure.

7. The anti-torsion coaxial cable with a conductive plastic shielding layer according to claim 1, characterized in that, The conductive plastic shielding layer (3) is a circular tubular structure, a polygonal tubular structure, a tubular structure with longitudinal ribs, or a spiral corrugated tubular structure.

8. The anti-torsion coaxial cable with a conductive plastic shielding layer according to claim 1, characterized in that, The outer sheath (4) has a double-layer structure, including an inner TPU layer (41) and an outer TPU layer (42). The hardness of the inner TPU layer (41) is lower than that of the outer TPU layer (42).

9. A torsion-resistant coaxial cable with a conductive plastic shielding layer according to claim 1, characterized in that, An adhesive layer (8) is also provided between the conductive plastic shielding layer (3) and the outer sheath (4).

10. A torsion-resistant coaxial cable with a conductive plastic shielding layer according to claim 1, characterized in that, A water-blocking layer is also provided between the insulating layer (2) and the conductive plastic shielding layer (3).

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