Flame-retardant low-standing-wave low-loss leaky coaxial cable and its processing technology

Abstract

The application belongs to the technical field of leaky coaxial cables, and discloses a kind of flame-retardant low standing wave low-loss leaky coaxial cable and its processing technology, coaxial cable includes the inner conductor, insulating layer, outer conductor and sheath layer sequentially arranged from inside to outside;Outer conductor is formed by longitudinal wrapping of metal strip with leaky hole, multiple corrugations extending along the width direction of the metal strip are formed on the metal strip, each corrugation is arranged at intervals along the length direction of the metal strip, at least one corrugation is formed with two positioning protrusions at the crest and / or trough, and the two positioning protrusions are located at both ends of the width direction of the metal strip;Both ends of the width direction of the metal strip are stacked together to form a lap joint area, the two positioning protrusions at the crest and / or trough of each corrugation are stacked together to form a lock structure in the lap joint area, and a welding point is formed at each lock structure by laser spot welding. Through the application, the problem that the current leaky coaxial cable cannot simultaneously consider the stitching welding effect and the flame-retardant and heat-insulating effect can be solved.

Description

Technical Field

[0001] This application belongs to the field of leaky coaxial cable technology, and more specifically, relates to a flame-retardant, low standing wave, low loss leaky coaxial cable and its processing technology. Background Technology

[0002] Leaky coaxial cables serve a dual function of signal transmission and antenna radiation, making them a core transmission component in closed or semi-closed wireless communication systems. They are widely used in high-risk, enclosed communication scenarios such as subways, mines, high-rise buildings, and tunnels. With the continuous iteration and upgrading of communication technologies, the market has placed more stringent demands on the overall performance of leaky coaxial cables. They must not only possess excellent flame-retardant properties to address sudden safety hazards such as fires, but also achieve low VSWR and low transmission loss to ensure the stability and efficiency of signal transmission.

[0003] As one of the core structures of leaky coaxial cables, the outer conductor's processing quality directly determines the cable's electrical performance, mechanical reliability, and bending adaptability. Currently, the industry commonly uses a perforated copper strip longitudinal wrapping process to manufacture the outer conductor. To meet the bending requirements of subways, tunnels, and other scenarios, the outer conductor is usually designed with a small corrugated structure. However, due to the small corrugated structure, an irregular surface with alternating peaks and troughs forms at the overlap of the copper strip longitudinal wrapping. This not only significantly increases the difficulty of welding, but the heat input generated during welding can also easily cause corrugation deformation and copper strip damage, thereby compromising the cable's bending performance. Therefore, when using a small corrugated outer conductor longitudinal wrapping process, welding is usually not performed; the overlap is achieved solely through the tension of the copper strip itself and the subsequent compression of the sheath layer.

[0004] While the aforementioned non-welding treatment method can avoid the damage to bending performance caused by welding, it has many fatal flaws: the unwelded overlap is only held together by tension and sheath compression, resulting in extremely poor structural stability. This not only leads to a higher VSWR and increased transmission loss in the cable, but also significantly reduces the sealing performance and mechanical strength of the outer conductor. More importantly, in a fire scenario, the gap of the unwelded outer conductor is in an open state, and flames can easily penetrate from the longitudinal overlap, directly burning the internal insulation core. This ultimately leads to excessive heat release indicators of the cable, burning drips, and other safety hazards, seriously threatening the safety of personnel and equipment in the usage scenario.

[0005] In addition, some companies have tried to use simplified welding processes to make up for the above defects. However, due to the limitations of the small-scale serrated structure, the laser head position is fixed and cannot adaptively adjust to the changes in the peaks and troughs of the serrated surface. This makes it easy to produce welding defects: over-welding and copper strip burning are likely to occur at the peaks, while incomplete welding and incomplete penetration are likely to occur at the troughs. This not only fails to completely solve the core problem of loose lap joints, but also further deteriorates the bending and electrical performance of the cable due to copper strip damage.

[0006] Currently, the industry generally adopts the method of increasing the amount of flame retardant added to the sheath layer to improve the flame retardancy rating of cables. However, this method can only improve the flame retardancy properties of the sheath material itself. In addition to significantly increasing the manufacturing cost of cables, it cannot prevent flames from entering and burning the insulation core from the longitudinal gaps of the outer conductor. It still cannot solve the core problem of excessive heat release data of cables under fire conditions.

[0007] Therefore, developing a leaky coaxial cable and its processing technology that can simultaneously achieve excellent bending performance, low standing wave and low loss transmission, high flame retardancy and heat insulation, and meet heat release standards, has become an urgent technical challenge to be solved in this field. Summary of the Invention

[0008] In response to the deficiencies or improvement needs of existing technologies, this application provides a flame-retardant, low-standing-wave, low-loss leaky coaxial cable and its processing technology, aiming to solve the problem that current leaky coaxial cables cannot simultaneously achieve both lap joint welding effect and flame-retardant and heat-insulating effect.

[0009] The above-mentioned technical objectives of this application are mainly achieved through the following technical solutions.

[0010] On one hand, this application provides a flame-retardant, low-VSWR, low-loss, leaky coaxial cable, comprising an inner conductor, an insulation layer, an outer conductor, and a sheath layer arranged sequentially from the inside out. The outer conductor is formed by longitudinally wrapping a metal strip with leakage holes. The width of the metal strip is greater than the circumference of the insulation layer. The metal strip is rolled with multiple grooves extending along its width direction. Each groove is spaced apart along the length direction of the metal strip. At least one groove has two positioning protrusions rolled at its crest and / or trough, located at both ends of the metal strip in the width direction. The two ends of the metal strip in the width direction are stacked together to form an overlap area. The two positioning protrusions at the crest and / or trough of each groove are stacked together in the overlap area to form a locking structure. Each locking structure is welded by laser spot welding to weld and fix the two layers of metal strip stacked together in the overlap area.

[0011] By setting positioning protrusions at the crests and / or troughs of the metal strip's corrugations, these protrusions overlap in the overlap area after longitudinal wrapping to form a locking structure. This provides a precise positioning reference for laser spot welding, ensuring accurate welding position and a strong weld, effectively sealing the longitudinal wrapping gaps in the outer conductor. The laser spot welding process involves low and concentrated heat input, which does not damage the small corrugated structure and preserves the cable's excellent bending performance. The welded and sealed outer conductor has a complete structure and good electrical continuity, effectively reducing the standing wave ratio and transmission loss. Simultaneously, the sealed outer conductor prevents flames from entering through the gaps in the overlap area and burning the internal insulation core, ensuring that the cable's heat release indicators meet standards. This eliminates the need for significantly increasing the amount of flame retardant used in the sheath, effectively controlling production costs.

[0012] In a preferred embodiment of this application, the lengths of the two positioning protrusions along the width direction of the metal strip are equal to the perimeter of the insulating layer. By precisely controlling the distance between the two positioning protrusions to be equal to the outer diameter of the insulating layer, it is ensured that the two positioning protrusions are accurately aligned and overlapped in the overlapping area after the metal strip is longitudinally wrapped, forming a stable locking structure. This provides a reliable positioning reference for subsequent laser spot welding, ensuring the consistency and stability of welding quality.

[0013] In a preferred embodiment of this application, the thickness of the metal strip is 0.1 mm, the height of the corrugations is 0.3 mm to 0.5 mm, and the width of the overlap area in the circumferential direction is 2 mm to 5 mm. The 0.1 mm thickness of the metal strip ensures both the conductivity and mechanical strength of the outer conductor, and facilitates longitudinal wrapping and laser welding; the 0.3 mm to 0.5 mm corrugation height effectively improves the bending flexibility of the cable, adapting to the bending laying requirements of scenarios such as subways and tunnels; the 2 mm to 5 mm overlap area ensures sufficient welding area, guaranteeing weld strength, while avoiding excessively wide overlap areas that would lead to material waste and an increase in the cable's outer diameter.

[0014] In a preferred embodiment of this application, the leakage hole on the metal strip is either a figure-eight hole or a straight hole. Figure-eight and straight holes are commonly used leakage hole types in leaky coaxial cables, ensuring uniform signal leakage and radiation, and meeting the signal coverage requirements of different application scenarios. Figure-eight holes offer better signal radiation uniformity, while straight holes have a simple structure and high processing efficiency, allowing for flexible selection based on actual application needs.

[0015] In a preferred embodiment of this application, the insulation layer is made of low-dielectric composite foamed insulation material through an extrusion process. The thickness of the insulation layer is 6mm to 13mm, the outer diameter is 22mm to 45mm, and the foaming degree is 86% to 92%. The low-dielectric composite foamed insulation material uses polyethylene as a base material and is composed of high-density polyethylene, low-density polyethylene, and a nucleating agent, exhibiting excellent dielectric properties and foaming stability. Controlling the foaming degree to 86% to 92% minimizes dielectric loss during signal transmission, laying the foundation for low VSWR and low-loss transmission. The design of an insulation layer thickness of 6mm to 13mm and an outer diameter of 22mm to 45mm ensures both the electrical performance and mechanical strength of the cable while meeting the application requirements of different specifications.

[0016] In a preferred embodiment of this application, the sheath layer is made of low-smoke halogen-free flame-retardant polyolefin material, and the thickness of the sheath layer is 1.5mm to 2.5mm. Low-smoke halogen-free flame-retardant polyolefin material has excellent flame-retardant properties, achieving a flame-retardant rating that meets the B1 (d0) level requirements specified in GB 31247-2014. It releases no toxic or harmful fumes during combustion, ensuring high safety. The sheath layer thickness of 1.5mm to 2.5mm ensures both mechanical protection and environmental resistance to the internal structure, while avoiding excessive thickness that could lead to an increased cable outer diameter and decreased bending performance. Since the outer conductor is effectively sealed by welding to prevent flame intrusion, the sheath layer can meet the usage requirements using a conventional flame-retardant formulation, eliminating the need for large amounts of additional flame retardant and effectively controlling production costs.

[0017] On the other hand, this application also provides a process for manufacturing a flame-retardant, low-standing-wave, low-loss leaky coaxial cable, used to prepare the aforementioned flame-retardant, low-standing-wave, low-loss leaky coaxial cable. The process includes: preparing an inner conductor; extruding foamed insulating material to cover the inner conductor to form an insulating layer, thereby obtaining an insulated cable core; pre-treating a metal strip to process leakage holes, corrugations, and positioning protrusions on the metal strip; then longitudinally covering the insulating layer with the pre-treated metal strip, with the two ends of the metal strip overlapping in the width direction to form an overlap area, and the positioning protrusions forming a locking structure in the overlap area; performing laser spot welding at the locking structure to form an outer conductor; and extruding protective material to cover the outer conductor to form a sheath layer.

[0018] This processing technology pre-treats the metal strip, creating positioning protrusions at the crests and / or troughs of the rolled grooves. After longitudinal wrapping, these protrusions form a locking structure in the overlap area, providing a precise positioning reference for laser spot welding. The laser spot welding process employs adaptive tracking technology, with the laser welding head synchronously rising and falling according to the position information of the positioning protrusions. This ensures the laser welding head is always precisely aligned with the overlap area for spot welding, avoiding the defects of traditional fixed laser heads that result in over-welding at crests and incomplete welding at troughs. This process features low and concentrated heat input, without damaging the small rolled groove structure, preserving the cable's excellent bending performance. Simultaneously, it achieves precise and robust welding of the outer conductor overlap area, effectively blocking flame intrusion channels, ensuring the cable's heat release indicators meet standards, and significantly reducing VSWR and transmission loss.

[0019] In a preferred embodiment of this application, the pretreatment process of the metal strip includes: opening the drainage holes on the metal strip using a punching device, wherein the drainage holes are either figure-eight holes or straight holes; rolling multiple grooves extending along the width direction on the metal strip using rolling rollers on a embossing machine, wherein each groove is spaced apart along the length direction of the metal strip; and forming two positioning protrusions at the crest and / or trough of at least one groove using two sets of dot-rolling rollers on the embossing machine, wherein the two positioning protrusions are located at both ends in the width direction of the metal strip. The drainage holes are opened using specialized punching equipment to ensure uniform distribution and precise dimensions; the rolling rollers of the embossing machine roll wavy grooves to improve the flexibility and bending performance of the metal strip; and the dot-rolling rollers form positioning protrusions at the crests and / or troughs of the grooves, providing a precise positioning reference for the locking structure and laser spot welding after longitudinal wrapping.

[0020] In a preferred embodiment of this application, the outer diameter of the insulated cable core is measured in real time using a diameter gauge. The distance between the two sets of knurling wheels is adjusted according to the outer diameter of the insulated cable core, ensuring that the distance between the two positioning protrusions rolled by the knurling wheels is equal to the circumference of the insulated cable core. After longitudinal wrapping, the positions of the two positioning protrusions on the outer conductor are superimposed and fixed to facilitate subsequent laser spot welding. By measuring the outer diameter of the insulated cable core in real time using a diameter gauge, the actual circumference after longitudinal wrapping of the metal strip can be accurately calculated, and the distance between the knurling wheels can be adjusted accordingly to ensure that the distance between the two rolled positioning protrusions is equal to the circumference of the insulated cable core. In this way, after longitudinal wrapping, the two positioning protrusions are precisely aligned and superimposed in the overlap area, forming a stable locking structure, providing a reliable positioning reference for laser spot welding, and ensuring the consistency and stability of welding quality.

[0021] In a preferred embodiment of this application, the process of laser spot welding the outer conductor after the longitudinal wrapping includes: real-time acquisition of information on the peaks, troughs, and positioning protrusions of the rolled surface using a laser vision sensor to obtain the height and position of the positioning protrusions in real time; based on the information acquired by the laser vision sensor, a servo lifting mechanism is used to drive the laser welding head to move up and down synchronously to ensure that the laser welding head is always accurately aligned with the overlapping area, and spot welding is continuously performed on each of the positioning protrusions to fix the stacked metal strips together; wherein, the laser power during the laser spot welding process is 100W to 150W, the spot welding time is 10ms to 30ms, and the shielding gas flow rate is 5L / min to 8L / min. The laser vision sensor acquires information on the peaks, troughs, and positioning protrusions of the rolled surface in real time, the calculation and control module performs data calculations in real time, identifies the height and position of the positioning protrusions, and drives the servo lifting mechanism to drive the laser welding head to move up and down synchronously to track, with an adjustment accuracy of ±0.01mm, ensuring that the laser welding head is always accurately aligned with the overlapping area for spot welding. The controlled parameters of laser power (100W to 150W) and spot welding time (10ms to 30ms) ensure weld strength while preventing excessive heat input that could lead to warping and metal strip burn-out. Argon gas protection at a flow rate of 5L / min to 8L / min effectively prevents oxidation during welding, guaranteeing weld quality. Through adaptive tracking laser spot welding, precise and robust welding of the outer conductor overlap area is achieved, effectively blocking flame intrusion channels, ensuring cable heat release parameters meet standards, and significantly reducing VSWR and transmission loss.

[0022] In summary, compared with the prior art, the technical solutions conceived in this application mainly possess the following technical features and advantages: 1. By setting positioning protrusions at the crests and / or troughs of the corrugated metal strip, and then stacking these protrusions in the overlap area after longitudinal wrapping to form a locking structure, combined with adaptive tracking laser spot welding technology, precise and robust welding of the outer conductor overlap area is achieved, effectively sealing the longitudinal wrapping gaps of the outer conductor. In fire scenarios, the sealed outer conductor can prevent flames from entering through the gaps in the overlap area and burning the internal insulation core, solving the problem of excessive heat release in the cable from the source, eliminating burning dripping, and ensuring flame-retardant safety. Compared to the traditional approach of simply increasing the amount of flame retardant in the sheath to improve the flame retardant rating, this application uses a conventional flame retardant ratio to meet high-level flame retardant requirements without significantly increasing the amount of flame retardant in the sheath, effectively controlling production costs.

[0023] 2. This application retains the small corrugated structure of the outer conductor, with a metal strip thickness of 0.1mm and a corrugation height of 0.3mm to 0.5mm, ensuring the cable has good bending and laying performance, adapting to the laying requirements of subways, tunnels, and other scenarios. The laser spot welding process has low and concentrated heat input, which does not damage the small corrugated structure and preserves the cable's excellent bending performance. At the same time, the outer conductor structure is intact and has good electrical continuity after welding and sealing, which can effectively reduce the standing wave ratio and reduce transmission loss. Actual measurements have verified that, compared with traditional non-welded leaky cables, the leaky coaxial cable prepared by this application has a standing wave ratio of less than 1.2034 in the 3.3GHz to 3.7GHz frequency band, with a stable improvement of 5% to 10% in standing wave ratio and transmission attenuation indicators, effectively solving the inherent contradiction in the industry of "preserving bending results in poor electrical performance and easy insulation burnout."

[0024] 3. This application uses a low-dielectric composite foamed insulation material, with polyethylene as the base material, composed of high-density polyethylene, low-density polyethylene, and a nucleating agent. The foaming degree of the insulation layer is controlled between 86% and 92%, which can minimize dielectric loss during signal transmission. The inner conductor is formed by longitudinally wrapping corrugated copper strip and then spot welding, resulting in a dense structure and uniform conductivity, which can effectively reduce contact loss. Laser spot welding of the outer conductor overlap area optimizes the continuity of electrical transmission. Excellent signal transmission performance can be achieved without changing the insulation material formula, ensuring stable and efficient signal transmission.

[0025] 4. This application employs an adaptive tracking laser spot welding process. A laser vision sensor collects real-time information on the peaks, troughs, and positioning protrusions of the rolled surface. A servo lifting mechanism drives the laser welding head to move synchronously up and down, with an adjustment accuracy of ±0.01mm, ensuring the laser welding head is always precisely aligned with the lap area for spot welding. Parameter control of laser power from 100W to 150W and spot welding time from 10ms to 30ms ensures weld strength while avoiding excessive heat input that could lead to rolled surface deformation and metal strip burn-out. The entire processing parameters are controllable and the process is standardized, resulting in good product performance consistency and a high finished product qualification rate during mass production, meeting the needs of large-scale industrial production. Compared to traditional fixed laser head welding processes, this application's process consumes less energy and effectively avoids thermal deformation of the metal strip, solving the dilemma of traditional welding damaging bending performance while neglecting welding degrades electrical performance.

[0026] 5. The leaky coaxial cable prepared in this application adopts a corrugated flexible structure for both the inner and outer conductors, combined with a polyethylene-based foam insulation layer of appropriate thickness. The cable exhibits excellent overall flexibility, strong tensile and deformation resistance, and is less prone to loosening or cracking during long-term laying, maintaining stable electrical performance over the long term. The outer conductor overlap area is welded and sealed, resulting in high mechanical strength and a long service life. The product is widely applicable to high-risk, enclosed communication scenarios such as subways, tunnels, mines, and high-rise buildings, meeting the stringent requirements of curved laying, low-loss communication, and high flame-retardant safety, thus demonstrating broad market application prospects.

[0027] 6. Traditional longitudinally wrapped leaky cables are prone to loosening of the outer conductor layer during combustion, leading to easy melting of the internal insulation and providing a large air contact surface for the burning surface, resulting in poor cable combustion performance. This application estimates the circumference of the longitudinally wrapped metal strip by measuring the circumference of the insulated cable core, and then forms positioning protrusions and locking points on the outer conductor at this circumference distance. This facilitates laser spot welding and ensures the tightness between the cable's insulation layer, outer conductor, and sheath layer. During combustion, the outer conductor will not loosen, and there is almost no air layer between the layers, thus inhibiting the occurrence of continuous combustion and further improving the cable's flame-retardant safety performance. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the flame-retardant, low-VSWR, low-loss, leaky coaxial cable described in this application; Figure 2 for Figure 1 A magnified schematic diagram of the local structure; Figure 3 This is an axial cross-sectional view of the flame-retardant, low-VSWR, low-loss, leaky coaxial cable described in this application. Figure 4 for Figure 3 A magnified view of part A in the middle; Figure 5 for Figure 3 A magnified view of part B in the middle; Figure 6 This is a radial cross-sectional view of the flame-retardant, low-standing-wave, low-loss, leaky coaxial cable described in this application at the crest of the corrugation. Figure 7 for Figure 6 A magnified view of part C in the middle; Figure 8 This is a radial cross-sectional view of the flame-retardant, low-standing-wave, low-loss, leaky coaxial cable described in this application at the trough of the corrugations. Figure 9 for Figure 8 A magnified view of part D in the middle; Figure 10 This is a schematic diagram of the adaptive tracking laser welding device. Figure 11 This is a schematic diagram of the patterning wheel on the patterning machine.

[0029] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 10. Inner conductor; 20. Insulation layer; 30. Outer conductor; 31. Positioning protrusion; 32. Locking structure; 33. Overlap area; 40. Sheath layer; 50. Adaptive tracking laser welding device; 51. Lifting motor; 52. Laser; 53. Copper strip forming mold; 54. Insulated cable core; 55. Corrugated copper strip; 60. Grating machine; 61. Grating wheel; 62. Drive motor. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0031] Implementation Method 1: This application provides a flame-retardant, low-VSWR, low-loss, leaky coaxial cable, such as... Figures 1 to 9 As shown, the coaxial cable includes, from the inside out, an inner conductor 10, an insulation layer 20, an outer conductor 30, and a sheath layer 40.

[0032] The outer conductor 30 is formed by longitudinally wrapping a metal strip with a leakage hole. The width of the metal strip is greater than the circumference of the insulation layer 20. Multiple grooves extending along the width direction are rolled on the metal strip. Each groove is spaced apart along the length direction of the metal strip. Two positioning protrusions 31 are rolled at the crests and / or troughs of the multiple grooves. The two positioning protrusions 31 are located at both ends of the width direction of the metal strip. The two ends of the width direction of the metal strip are stacked together to form an overlap area 33. The two positioning protrusions 31 at the crests and / or troughs of each groove are stacked together in the overlap area 33 to form a locking structure 32. Each locking structure 32 is formed by laser spot welding to form a welding point. The welding point welds and fixes the two layers of metal strips stacked together in the overlap area 33.

[0033] The flame-retardant, low-standing-wave, low-loss, leaky coaxial cable described in this application employs positioning protrusions at the crests and / or troughs of the corrugated metal strip. After longitudinal wrapping, these positioning protrusions overlap in the splice area to form a locking structure. Combined with adaptive tracking laser spot welding technology, this achieves precise and robust welding of the outer conductor splice area 33, effectively sealing the longitudinal wrapping gaps in the outer conductor. In a fire scenario, the sealed outer conductor can prevent flames from entering through the gaps in the splice area and burning the internal insulation core, thus addressing the problem of excessive heat release in the cable at its source, preventing burning drips, and ensuring flame-retardant safety.

[0034] The following will describe in detail the specific structure of each part of the flame-retardant, low-VSWR, low-loss, and leaky coaxial cable described in this application, as well as the positional relationship between each part and the molding process, with reference to the embodiments shown in the accompanying drawings.

[0035] The coaxial cable includes an inner conductor 10 located at the innermost layer. The inner conductor 10 can be integrally manufactured using a copper strip welding and corrugating process. Specifically, qualified copper strip is selected, and the inner conductor 10 is prepared through an integrated forming process of copper strip edge cutting, longitudinal wrapping, welding, and corrugating. Strict control of process parameters during the forming process ensures that the inner conductor 10 has a uniform structure, a round surface, and stable conductivity. In other embodiments of this application, the inner conductor 10 can also be a solid metal wire made of high-purity copper or copper alloys, such as annealed copper wire, annealed copper tube, or copper-clad aluminum wire.

[0036] After molding, the inner conductor 10 has a dense and uniform structure, excellent conductivity continuity, and good overall flexibility. It can flexibly adapt to the bending and laying requirements of cables in various scenarios, effectively reduce its own contact resistance and signal transmission loss, and ensure the stability of signal transmission.

[0037] The coaxial cable also includes an insulation layer 20 formed on the outer circumferential surface of the inner conductor 10. The insulation layer 20 is a hollow cylindrical sleeve covering the outside of the inner conductor 10, and is made of a low-dielectric composite foamed insulation material. This material is based on polyethylene and is composed of high-density polyethylene, low-density polyethylene, and a nucleating agent. It is formed by extrusion and has excellent dielectric properties and foaming stability.

[0038] The insulation layer 20 has a thickness of 6 mm to 13 mm, an outer diameter of 22 mm to 45 mm, and a foaming degree of 86% to 92%. In this embodiment, the insulation layer 20 has a thickness of approximately 10 mm, an outer diameter of approximately 33 mm, and an insulation foaming degree controlled at 89%. During the extrusion process of the insulation layer 20, the traction speed is controlled at 15 m / min to strictly ensure that the thickness, outer diameter, and foaming degree of the insulation layer 20 meet the design requirements.

[0039] After extrusion, the insulated cable core 54, consisting of the inner conductor 10 and the insulation layer 20, is placed in a cooling water bath for cooling and curing. The cooling temperature is controlled at 20 to 24°C, and the time spent in the cooling water bath is 10 to 20 minutes to ensure the stable molding of the insulation layer 20. The high foaming degree design can minimize the dielectric loss during signal transmission, laying the foundation for low standing wave ratio and low loss transmission.

[0040] The coaxial cable also includes an outer conductor 30 longitudinally wrapped around the outer periphery of the insulation layer 20. The outer conductor 30 is a hollow metal cylinder wrapped around the outside of the insulation layer 20, and it is formed by longitudinally wrapping a perforated and corrugated metal strip. In this embodiment, the outer conductor 30 is formed by longitudinally wrapping a corrugated copper strip 55, and the nominal thickness of the corrugated copper strip 55 is approximately 0.1 mm.

[0041] The width of the metal strip is greater than the outer circumference of the insulating layer (20mm), such as... Figure 6 and Figure 8As shown, after longitudinal wrapping, the two ends of the metal strip in the width direction are stacked together to form an overlap area 33, which includes upper and lower metal strips. The width (arc length) of the overlap area 33 in the circumferential direction is designed to be 2mm-5mm; in this embodiment, the width of the overlap area 33 formed by the corrugated copper strip 55 is 3mm.

[0042] Before longitudinal wrapping, the metal strip has drainage holes, which can be either figure-eight or straight holes, formed by punching with specialized punching equipment. In this embodiment, the corrugated copper strip 55 has multiple evenly distributed groups of figure-eight holes to ensure uniform signal leakage and transmission stability.

[0043] Before longitudinal wrapping, the metal strip is rolled to form multiple grooves. The grooves extend along the width of the metal strip and are evenly spaced along its length. The grooves are formed by a groove rolling mill. After longitudinal wrapping, the ends of each groove on the metal strip are overlapped and joined to form a complete annular groove. The height of the formed grooves on the metal strip is set to 0.3mm-0.5mm; in this embodiment, the groove height on the grooved copper strip 55 is 0.4mm, which can effectively ensure the overall bending performance of the cable.

[0044] After the metal strip is formed by corrugation and before longitudinal wrapping, two positioning protrusions 31 are formed at the crest and / or trough of at least one corrugation. The two positioning protrusions 31 are located at both ends in the width direction of the metal strip, and the positioning protrusions 31 are formed by corrugation rolling. After longitudinal wrapping, as... Figures 3 to 5 As shown, the two positioning protrusions 31 at the crests and / or troughs of each roll are radially outward and are stacked together in the overlap area 33 to form a locking structure 32. Each locking structure 32 is formed by laser spot welding to form a welding point, which welds and fixes the two layers of metal strips stacked together in the overlap area 33.

[0045] In this embodiment, two positioning protrusions 31 are rolled at each crest of the groove, every two crests; and two positioning protrusions 31 are rolled at each trough of the groove, every two troughs. Between each positioning protrusion 31 at a crest and a trough, there is one crest without a positioning protrusion 31 and one trough without a positioning protrusion 31. The number of positioning protrusions 31 can be rolled according to actual design needs and is not specifically limited here.

[0046] Furthermore, the length of the two positioning protrusions 31 at each peak or trough along the width of the metal strip is equal to the perimeter of the insulating layer 20. By precisely controlling the distance between the two positioning protrusions 31 to be equal to the perimeter of the insulating layer 20, it is ensured that after the metal strip is longitudinally wrapped, the two positioning protrusions 31 are precisely aligned and overlapped in the overlap area 33, forming a stable locking structure 32. This provides a reliable positioning reference for subsequent laser spot welding, ensuring the consistency and stability of welding quality.

[0047] After the metal strip is longitudinally wrapped, laser spot welding is performed on the locking structure 32 at the overlap area 33 to form a welding point. The welding point fixes the two layers of metal strips stacked together in the overlap area 33. The connection structure of using a locking structure combined with precise spot welding to fix the overlap area not only avoids the rolling deformation and metal strip damage caused by welding in the existing technology, but also meets the high-level flame retardant requirements without significantly increasing the amount of flame retardant in the sheath.

[0048] The coaxial cable also includes a sheath layer 40 formed on the outer circumferential surface of the outer conductor 30. The sheath layer 40 is a hollow cylindrical sleeve covering the outside of the outer conductor 30, which is used to protect the cable from environmental factors such as mechanical damage, chemical corrosion, moisture intrusion and ultraviolet radiation, improve the service life and reliability of the cable, and provide additional insulation performance to ensure the safety of the cable during use.

[0049] The sheath layer 40 is made of low-smoke, halogen-free, flame-retardant polyolefin material through extrusion, exhibiting excellent flame-retardant properties. Its flame-retardant rating meets the B1 (d0) level requirements specified in GB 31247-2014, releasing no toxic or harmful fumes during combustion, ensuring high safety. The thickness of the sheath layer 40 is 1.5mm to 2.5mm, ensuring both mechanical protection and environmental resistance for the internal structure while avoiding excessive thickness that could increase the cable's outer diameter and reduce bending performance. Since the outer conductor 30 is effectively sealed by welding to prevent flame intrusion, the sheath layer 40 can meet usage requirements using a conventional flame-retardant formulation, eliminating the need for large amounts of additional flame retardant and effectively controlling production costs. In this embodiment, the sheath layer 40 is 2.0mm thick, with a smooth surface, providing excellent mechanical protection and environmental resistance, effectively protecting the internal structure from external damage.

[0050] Implementation Method Two: This application also provides a processing method for flame-retardant, low-standing-wave, low-loss, leaky coaxial cable, which is used to prepare the flame-retardant, low-standing-wave, low-loss, leaky coaxial cable described in Embodiment 1. The processing method for the flame-retardant, low-standing-wave, low-loss, leaky coaxial cable includes the following steps: Step S10: Prepare inner conductor 10.

[0051] Step S20: Extrude foamed insulating material onto the inner conductor 10 to form an insulating layer 20, thereby obtaining an insulated cable core 54.

[0052] Step S30: The metal strip is pre-treated to process leakage holes, embossed lines and positioning bumps 31 on the metal strip. Then, the pre-treated metal strip is longitudinally wrapped with an insulating layer 20. The two ends of the metal strip in the width direction are stacked together to form an overlap area 33. The positioning bumps 31 form a locking structure 32 in the overlap area 33. Laser spot welding is performed at the locking structure 32 to form the outer conductor 30.

[0053] Step S40: Extrude protective material over the outer conductor 30 to form a sheath layer 40.

[0054] The flame-retardant, low VSWR, low-loss, and leaky coaxial cable processing technology described in this application pre-treats the metal strip used for longitudinal wrapping, machining positioning protrusions at the crests and / or troughs of the rolled corrugations. After longitudinal wrapping, these positioning protrusions form a locking structure in the overlap area, providing a precise positioning reference for laser spot welding. The laser spot welding process employs adaptive tracking technology, with the laser welding head synchronously rising and falling according to the position information of the positioning protrusions. This ensures that the laser welding head is always precisely aligned with the overlap area for spot welding, avoiding the defects of traditional fixed laser heads, such as over-welding at crests and incomplete welding at troughs. This process has low and concentrated heat input, does not damage the small rolled corrugation structure, preserves the cable's excellent bending performance, and simultaneously achieves precise and strong welding of the outer conductor overlap area, effectively blocking flame intrusion channels, ensuring that the cable's heat release indicators meet standards, and significantly reducing VSWR and transmission loss.

[0055] The following section will provide a detailed description of each step in the processing technology for the flame-retardant, low-VSWR, low-loss, and leaky coaxial cable described in this application.

[0056] In step S10, the inner conductor 10 is prepared.

[0057] Qualified copper strips are selected, and the inner conductor 10 is prepared through an integrated forming process of copper strip edge cutting, longitudinal wrapping, welding, and corrugation. The process parameters during the forming process are strictly controlled to ensure that the inner conductor 10 has a uniform structure, a round surface, and stable conductivity. After forming, the inner conductor 10 has good flexibility and can adapt to the bending laying conditions of the overall cable, effectively reducing transmission loss.

[0058] In step S20, an insulating layer 20 is formed over the inner conductor 10.

[0059] A low-dielectric composite foamed insulation material based on polyethylene (PE) (composed of high-density polyethylene, low-density polyethylene, and a nucleating agent) is fed into an extruder and heated to melt. The prepared inner conductor 10 is fed into the extruder die at a uniform speed, and the molten insulation material is uniformly coated on the outside of the inner conductor 10 through the extrusion process to form a foamed insulation layer. During the extrusion process, the traction speed is controlled at 6m / min-20m / min (adapted to different specifications), strictly ensuring that the insulation layer thickness is approximately 6mm-13mm, the outer diameter is approximately 22mm-45mm, and the insulation foaming degree is controlled at 86%-92%. After extrusion, the insulated cable core 54, composed of the inner conductor 10 and the insulation layer 20, is sent to a cooling water tank for cooling and solidification. The cooling temperature is controlled at 20℃-24℃, and the time in the cooling water tank is 10min-20min to ensure the stability of the insulation layer formation, laying a solid foundation for the subsequent welding of the outer conductor and the realization of low standing wave and low loss performance.

[0060] In step S30, the metal strip is pretreated and the pretreated metal strip is longitudinally wrapped around the insulating layer 20 to form the outer conductor 30.

[0061] Step S30 is the core of the entire processing technology. It aims to achieve precise and firm welding of the overlapping area 33 on the outer conductor 30 while preserving the small rolling bending performance. Specifically, it includes three processes: metal strip pretreatment, longitudinal wrapping, and laser spot welding.

[0062] First, the metal strip is pretreated.

[0063] Oxygen-free copper strip with a nominal thickness of 0.1mm is selected. Drainage holes in the shape of either a figure-eight or a straight line are punched into the copper strip using specialized punching equipment, ensuring uniform distribution of the drainage holes to effectively guarantee uniform signal radiation. Subsequently, the copper strip undergoes small-scale ribbed processing. Multiple ribs extending along the width of the metal strip are rolled onto the strip using rollers on a ribbed mill. These ribs are spaced apart along the length of the metal strip, ensuring uniform rib height between 0.3mm and 0.5mm to guarantee the cable's bending performance. Afterward, positioning bumps 31 are processed on the copper strip, such as... Figure 11 As shown, two sets of dot-rolling wheels 61 on the rolling mill 60 are used to simultaneously roll two positioning protrusions 31 at the crests and troughs of multiple rolls. The two positioning protrusions 31 are located at both ends in the width direction of the metal strip.

[0064] Preferably, the distance between the two positioning protrusions 31 rolled by the dot-rolling wheel 61 is equal to the longitudinal circumference of the outer conductor 30 (the outer circumference of the insulated cable core 54). For example... Figure 11As shown, the corrugating machine 60 is equipped with a drive motor 62 for adjusting the distance between two sets of corrugating wheels 61. After step S20 is completed, the outer diameter of the insulated cable core 54 is measured in real time by a photoelectric induction diameter measuring instrument. The outer diameter data is transmitted to the microcontroller module, from which the circumference of the insulated cable core 54 can be calculated. This allows the estimation of the actual circumference of the copper strip after longitudinal wrapping. The drive motor 62 drives the two sets of corrugating wheels 61 to move closer or further apart according to the instructions of the microcontroller module so that the distance between them is equal to the longitudinal wrapping circumference of the outer conductor 30.

[0065] After pretreatment, the copper strip is degreased and derusted to remove surface oil and oxide layer, improve the quality of subsequent welding, and avoid welding defects.

[0066] Secondly, the pretreated metal strip is longitudinally wrapped around the outer periphery of the insulating layer 20.

[0067] like Figure 10 As shown, the front end of the adaptive tracking laser welding device 50 integrates a copper strip forming mold 53. A tensioned active strip feeding method is used to feed the pre-treated corrugated copper strip 55. The feeding speed is synchronized with the traction speed of the insulated cable core 54. The copper strip forming mold 53 precisely wraps the corrugated copper strip 55 longitudinally around the outer periphery of the insulated cable core 54, ensuring that the corrugated copper strip 55 is tightly bonded to the insulation layer 20 without wrinkles or loosening, and that the leakage holes are oriented uniformly, thus guaranteeing the subsequent welding quality and signal transmission stability. After longitudinal wrapping, the two ends of the corrugated copper strip 55 in the width direction are stacked together to form an overlap area 33. The overlap area 33 includes upper and lower copper strips. The two ends of each corrugation on the copper strip are overlapped and joined to form a complete annular corrugation. The two positioning protrusions 31 at the crest and trough of each corrugation protrude radially outward and are stacked together in the overlap area 33 to form a locking structure 32.

[0068] Finally, the locking structure 32 on the overlapping area 33 is laser-spot welded to form multiple welding points.

[0069] like Figure 10 As shown, the adaptive tracking laser welding device 50 integrates a lifting motor 51 and a laser 52 (laser welding head) at its rear end, with the laser 52 located at the output end of the lifting motor 51. During the welding process, the laser vision sensor collects information on the peaks, troughs, and positioning protrusions 31 of the rolled surface in real time. The calculation and control module performs data calculations in real time, identifies the height and position of the positioning protrusions 31, and drives the lifting motor 51 to synchronously lift and track the laser 52. The adjustment accuracy can reach ±0.01mm, ensuring that the laser 52 is always accurately aligned with the locking structure 32 on the overlapping area 33 and continuously performs spot welding on the positioning protrusions 31, fixing the upper and lower copper strips together in the overlapping area 33.

[0070] Welding parameters are strictly controlled as follows: laser power 100W to 150W, spot welding time 10ms to 30ms, and shielding gas flow rate 5L / min to 8L / min. By controlling these parameters, defects such as incomplete welds and lack of penetration are ensured. Weld spots are evenly distributed with spacing matching the crest-trough spacing of the rolled wave, guaranteeing weld strength. The outer conductor 30, after welding and sealing, exhibits a complete structure and good electrical continuity, effectively reducing the standing wave ratio and transmission loss.

[0071] Meanwhile, the sealed outer conductor 30 can prevent flames from penetrating through the gaps in the overlap area and burning the inner insulation layer 20, thus solving the problem of excessive heat release in the cable at the source, eliminating burning drips, and ensuring flame-retardant safety. The laser spot welding process has a small and concentrated heat input, which will not damage the small corrugated structure and preserves the cable's excellent bending performance.

[0072] In step S40, a sheath layer 40 is formed over the outer conductor 30.

[0073] During the extrusion molding of the sheath layer 40, low-smoke, halogen-free, flame-retardant polyolefin material is fed into the extruder, heated, and melted. The traction speed is synchronized with the previous process to ensure that the thickness deviation of the sheath layer 40 is ≤ ±0.1mm. Using a conventional flame-retardant formula, high-level flame-retardant requirements can be achieved without adding large amounts of flame-retardant to the sheath.

[0074] After extrusion, a segmented cooling process is adopted: first, hot water is used for cooling, then cold water is used for cooling to room temperature, and finally the wire is dried to ensure that the sheath layer 40 is stably formed and has a smooth surface. Since the outer conductor 30 has been effectively blocked from flame intrusion by welding and sealing, the sheath layer 40 can meet the usage requirements with a conventional flame retardant ratio, without the need to add a large amount of additional flame retardant, thus effectively controlling production costs.

[0075] The finished cable prepared in this embodiment underwent comprehensive testing, including flame retardancy, standing wave ratio, transmission attenuation, and structural dimensions. The flame retardant heat release performance test results showed that it met relevant specifications, exhibited no dripping or flame propagation during combustion, the gaps in the overlapping area 33 of the outer conductor 30 were well sealed and did not spread, the insulation layer 20 was not directly burned by the flame, and the heat release indicators were qualified.

[0076] The VSWR test results show that the cable in this embodiment has a VSWR of no more than 1.2034 in the 3.3 to 3.7 GHz frequency band. In comparison, the leaky cable manufactured using the traditional non-soldering process has a VSWR of approximately 1.2816 in the same frequency band, representing an improvement of about 6.1%, which is within the design improvement range of 5% to 10%.

[0077] Transmission attenuation test results show that the cable in this embodiment has a loss of 10.621 dB / 100m in the 3.3 GHz band. In comparison, the leaky cable manufactured using the traditional non-soldering process has a loss of 11.192 dB / 100m in the 3.3 GHz band, representing an improvement of approximately 5.1%, which meets the improvement requirement of 5% to 10%.

[0078] Welding and mechanical performance tests show that there are no defects such as incomplete welding or lack of penetration at the seam of the lap area 33 on the outer conductor 30, the structure is solid, the overall bending performance of the cable remains excellent, and there are no problems such as rolling deformation or copper strip damage. The thickness, outer diameter, and foaming degree of the insulation layer 20 all meet the design parameter requirements, and the overall performance is stable.

[0079] It should be understood that expressions such as "comprising" and "may include" as used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as "comprising" and / or "having" may be interpreted as indicating a specific characteristic, number, operation, constituent element, component, or combination thereof, but should not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0080] It should be understood that the terms “center,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0081] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0082] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0083] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A flame-retardant low standing wave low loss leaky coaxial cable characterized by, It includes an inner conductor (10), an insulation layer (20), an outer conductor (30), and a sheath layer (40) arranged sequentially from the inside to the outside. The outer conductor (30) is formed by longitudinally wrapping a metal strip with a leakage hole. The width of the metal strip is greater than the circumference of the insulating layer (20). The metal strip is rolled with multiple grooves extending along its width direction. Each groove is spaced apart along the length direction of the metal strip. At least one groove has two positioning protrusions (31) rolled at its peak and / or trough. The two positioning protrusions (31) are located at both ends of the width direction of the metal strip. The two ends of the metal strip in the width direction are stacked together to form an overlap area (33). The two positioning protrusions (31) at the crests and / or troughs of each of the rolled patterns are stacked together in the overlap area (33) to form a locking structure (32). Each locking structure (32) is formed by laser spot welding to form a welding point. The welding point welds and fixes the two layers of metal strips stacked together in the overlap area (33).

2. The flame-retardant low-resonance-loss leaky coaxial cable according to claim 1, characterized by The length of the two positioning protrusions (31) along the width direction of the metal strip is equal to the perimeter of the insulating layer (20).

3. The flame-retardant low-resonance-loss leaky coaxial cable according to claim 1, wherein The metal strip has a thickness of 0.1 mm, the groove height is 0.3 mm to 0.5 mm, and the overlap area (33) has a width of 2 mm to 5 mm in the circumferential direction.

4. The flame-retardant low-standing-wave, low-loss leaky coaxial cable according to any one of claims 1 to 3, characterized in that, The leakage hole on the metal strip is either a figure-eight hole or a straight hole.

5. The flame-retardant low-resonance-loss leaky coaxial cable according to claim 1, wherein The insulation layer (20) is made of low dielectric composite foamed insulation material by extrusion process. The thickness of the insulation layer (20) is 6mm-13mm, the outer diameter of the insulation layer (20) is 22mm-45mm, and the degree of foaming of the insulation layer (20) is 86%-92%.

6. The flame-retardant low-resonance-loss leaky coaxial cable according to claim 1, wherein The sheath layer (40) is made of low-smoke, halogen-free, flame-retardant polyolefin material, and the thickness of the sheath layer (40) is 1.5mm-2.5mm.

7. A process for making a flame-retardant low standing wave low loss leaky coaxial cable characterized by, For the preparation of the flame-retardant, low-VSW, low-loss, leaky coaxial cable according to any one of claims 1 to 6, the processing technology of the flame-retardant, low-VSW, low-loss, leaky coaxial cable includes: Prepare the inner conductor (10); Foamed insulating material is extruded over the inner conductor (10) to form an insulating layer (20), thereby obtaining an insulated cable core (54). The metal strip is pretreated to form leakage holes, embossed patterns and positioning bumps (31). The pretreated metal strip is then longitudinally wrapped around the insulating layer (20). The two ends of the metal strip are stacked together in the width direction to form an overlap area (33). The positioning bumps (31) form a locking structure (32) in the overlap area (33). Laser spot welding is performed at the locking structure (32) to form the outer conductor (30). A protective material is extruded over the outer conductor (30) to form a sheath layer (40).

8. The process for making a flame-retardant low-resonance-loss leaky coaxial cable of claim 7, wherein, The pretreatment process of the metal strip includes: The leakage hole is made on the metal strip using a punching device. The leakage hole is either a figure-eight hole or a straight hole. Multiple grooves extending along the width direction are rolled on the metal strip using the rolling rollers on the rolling mill, and the grooves are spaced apart along the length direction of the metal strip. Two positioning protrusions (31) are formed by rolling two sets of dot-rolling wheels on the rolling mill at the crests and / or troughs of multiple grooves. The two positioning protrusions (31) are located at both ends in the width direction of the metal strip.

9. The process for making a flame-retardant low-resonance- wave low-loss leaky coaxial cable according to claim 8, wherein The outer diameter of the insulated cable core (54) is measured in real time using a diameter measuring instrument, and the distance between the two sets of dot-rolling wheels is adjusted according to the outer diameter of the insulated cable core (54) so ​​that the distance between the two positioning protrusions (31) rolled by the dot-rolling wheels is equal to the circumference of the insulated cable core (54).

10. The process for making a flame-retardant low-residence-wave low-loss leaky coaxial cable of claim 7 wherein, The process of laser spot welding the outer conductor (30) after longitudinal wrapping includes: The laser vision sensor collects information on the peaks, troughs and positioning protrusions (31) of the rolled pattern in real time to obtain the height and position of the positioning protrusions (31) in real time. Based on the information collected by the laser vision sensor, the servo lifting mechanism drives the laser welding head to move up and down synchronously to ensure that the laser welding head is always accurately aligned with the overlapping area (33) and continuously spot welds on each positioning protrusion (31) to fix the metal strips stacked together. The laser power during laser spot welding is 100W-150W, the spot welding time is 10ms-30ms, and the flow rate of the shielding gas is 5L / min-8L / min.

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