Leaky coaxial cable, intercom system and method of manufacture

Abstract

The present application relates to a kind of leaky coaxial cable, intercom system and manufacturing method.The present application includes inner conductor;Insulating layer, the outer surface of inner conductor is covered;Outer conductor, the outer surface of insulating layer is covered;POM sheath layer, the outer surface of outer conductor is covered, wherein, along POM sheath layer outer surface radially outwardly integrally formed thereon extend with multiple support columns;Non-woven fabric wrapping layer, wrapping on the outer surface formed by each support column, so that the air path gap is formed between every two adjacent support columns;Flame-retardant sheath layer, the outer surface of non-woven fabric wrapping layer is covered;Pressure pump, arranged at one end of leaky coaxial cable, for into the air path gap with pressurized gas, to cool POM sheath layer;When the leaky coaxial cable is laid on ground, the minimum gap between the slot hole on outer conductor and ground is not less than 28mm.The present application can meet the signal coverage requirement of fire intercom system in actual use.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of leaky coaxial cable, in particular to a leaky coaxial cable, a intercom system and a manufacturing method. BACKGROUND

[0002] Leaky coaxial cable (for short, leaky cable) is a coaxial communication cable with an incompletely closed outer conductor, and part of the signals transmitted or received on the cable can be coupled or radiated into the transmission system composed of the outer conductor and the external environment.

[0003] Referring to Figure 7 , during the underground site rescue process, the firefighters need to use intercoms to maintain normal communication with the internal personnel and the outside world. The intercom system is mainly composed of a signal source (signal source) dedicated to the intercom frequency band, a leaky coaxial cable (signal transmission carrier), a load (excess signal absorption), and an intercom (receiving end, transmitting end). When the firefighters are working on site, they hold an intercom in one hand, and the working range is within 1.5 meters around the leaky coaxial cable. There are firefighters working on both sides of the leaky coaxial cable at the same time. In addition, the leaky coaxial cable is laid on the ground, and the length of the cable is adjusted in time along with the change of the position of the fire fighting operation.

[0004] According to the energy coupling mechanism, the leaky coaxial cable is divided into coupling type and radiation type. Referring to Figure 8 , in the coupling mode leaky coaxial cable, there is a row of slots along the entire length of the cable, and the spacing of the slots is much smaller than the working wavelength. The electromagnetic field diffracts through the slots to excite the electromagnetic field outside the outer conductor, so there is current on the outer surface of the outer conductor, and thus electromagnetic radiation exists. Because in this mode the electromagnetic field diffracts through the small holes to excite the electromagnetic field outside the outer conductor. The resonant charge caused by the skin effect only moves along the outer surface of the shield conductor. The working principle of the coupling type leaky coaxial cable is the surface wave effect on the outer conductor.

[0005] Referring to Figure 9 , the radiation type leaky coaxial cable has a slot on the outer conductor with a spacing comparable to the wavelength (or half wavelength). The slot structure causes the signals at the slot to produce in-phase superposition. The leaked electromagnetic energy has directionality, so the field strength distribution along the line is less affected by environmental conditions, and the radial decay characteristics of the field are good.

[0006] Because the coupling type leaky cable slot excites "surface electromagnetic wave", the ground as a conductive medium will absorb and reflect electromagnetic waves, resulting in that the surface wave cannot be effectively transmitted and the signal decays quickly.

[0007] And the electromagnetic energy of the radiation type leaky cable has directionality. When the field firemen work, because the left and right sides of the cable need to be operated at the same time, the laying of the cable is randomly performed, the slots cannot be ensured to be consistent, and thus the intercom signals of the personnel on the left and right sides are unstable.

[0008] Therefore, in order to ensure that the field firemen can obtain stable signals and maintain the normal communication of the internal personnel and the normal communication between the internal and external personnel, a new coupling type leaky cable is urgently needed to be developed for the fire intercom system used by the field firemen. SUMMARY

[0009] Therefore, the application provides a leaky coaxial cable, an intercom system and a manufacturing method, which meet the signal coverage requirements of the fire intercom system in actual use.

[0010] To solve the above technical problems, the application provides a leaky coaxial cable, which comprises:

[0011] an inner conductor;

[0012] an insulating layer covering the outer surface of the inner conductor;

[0013] an outer conductor covering the outer surface of the insulating layer, wherein slots are arranged on the surface of the outer conductor and spaced along the axial direction, and the distance between adjacent slots is less than the working wavelength, so that electromagnetic fields are diffracted through the slots to form surface waves on the outer conductor;

[0014] a POM (polyoxymethylene) sheath layer covering the outer surface of the outer conductor, wherein a plurality of support columns are integrally formed and extend radially outward from the outer surface of the POM sheath layer, each of the support columns extends along the length direction of the outer conductor, and adjacent two support columns are spaced by 45 degrees along the circumferential direction of the POM sheath layer;

[0015] a non-woven fabric wrapping layer wrapped around the outer surface of each support column to form an air gap between each adjacent two support columns;

[0016] a flame-retardant sheath layer covering the outer surface of the non-woven fabric wrapping layer;

[0017] a booster pump arranged at one end of the leaky coaxial cable for introducing pressurized gas into the air gap to cool the POM sheath layer;

[0018] The radial length of the support column is limited to be not less than 28 mm so that the minimum gap between the slots on the outer conductor and the ground is not less than 28 mm when the leaky coaxial cable is laid on the ground.

[0019] In an embodiment of the application, the inner conductor is made of copper-clad aluminum material.

[0020] In one embodiment of the present application, the support column is in the shape of a rectangular thin plate, and the end surface in contact with the POM sheath layer is rectangular or arc-shaped.

[0021] In one embodiment of the present application, the radial length of the support column is not less than 28 mm, and the circumferential width is 3 mm ± 1 mm; the outer diameter of the POM sheath layer is 15.7 mm ± 0.25 mm.

[0022] In one embodiment of the present application, the outer diameter of the insulating layer is 12.6 mm ± 0.20 mm.

[0023] In one embodiment of the present application, the outer conductor is in the shape of a ring-shaped corrugated copper pipe, and the slot hole is arranged at the wave crest position; the outer diameter of the outer conductor is 13.9 mm ± 0.25 mm, and the diameter of the wave trough is 12.9 mm ± 0.25 mm.

[0024] In one embodiment of the present application, the non-woven fabric is a wrapping tape with a thickness of 0.18 mm ± 0.01 mm and a width of 35 mm ± 1 mm, and the wrapping coverage rate is 30% to 50%; the outer diameter of the non-woven fabric wrapping layer is 44.3 mm ± 0.35 mm.

[0025] In one embodiment of the present application, the flame-retardant sheath layer uses a low-smoke halogen-free flame-retardant sheath material with a density of 1.50 g / cm³, and the outer diameter of the flame-retardant sheath layer is 45.1 mm ± 0.35 mm.

[0026] The present application also provides a speakerphone system comprising the leaky coaxial cable; wherein the two ends of the leaky coaxial cable are respectively provided with a first connector and a second connector, and the first connector and the second connector are respectively connected to a speakerphone signal source and a load through a jumper wire;

[0027] The side wall of the first connector is provided with a gas injection hole and is threadedly connected with a gas injection valve through the gas injection hole, and the gas injection valve is connected with the output end of the booster pump through a pipeline;

[0028] The side wall of the second connector is threadedly connected with a check valve communicating with the air gap.

[0029] The present application also provides a method for manufacturing a leaky coaxial cable, comprising:

[0030] S1, inner conductor preparation: providing copper-clad aluminum as the inner conductor;

[0031] S2, insulation process: high-density foaming material, low-density foaming material and nucleating agent are mixed in a mass ratio of 71:25:4, and at the same time, high-purity carbon dioxide is injected into the mixture of foaming material and gas to form a bubble layer, and the bubble layer is cooled and shaped in a hot water tank and a cold water tank to form a foam material insulation layer, the outer diameter of the insulation layer is 12.6mm±0.20mm;

[0032] S3, copper strip rolling groove slotting process: the copper strip with a thickness of 0.18mm is sequentially cleaned, edge cut, longitudinally wrapped, formed, welded, rolled into a ring-shaped corrugated copper pipe, and continuously milled and opened at the wave peak position to form an outer conductor with a hole distance, the outer diameter of the outer conductor is 13.9mm±0.25mm, and the valley diameter is 12.9mm±0.25mm;

[0033] S4, POM sheath extrusion process: an extrusion die set is provided, the extrusion die set includes an extrusion cavity, the extrusion cavity includes a hole part and an extrusion groove extending radially outward every 45° along the circumferential direction of the hole part;

[0034] The POM material sheath material is extruded through the extrusion die set on the surface of the outer conductor to form a POM sheath layer, and a support column is extruded every 45° along the circumferential direction, the length of the support column is not less than 28mm, the width is 3mm±1mm, the outer end face is rectangular or arc-shaped, and the outer diameter of the sheath layer is 15.7mm±0.25mm;

[0035] S5, sheath wrapping process: a concentric wrapping device is used to wrap non-woven fabric with a thickness of 0.18mm±0.01mm and a width of 35mm±1mm on the outer surface formed by each support column at a lap rate of 30%-50% to form a non-woven fabric wrapping layer, and the outer diameter of the non-woven fabric wrapping layer is 44.3mm±0.35mm;

[0036] S6, semi-finished product detection process: the semi-finished product formed in step S4 is detected, and after passing the detection, subsequent processes are carried out;

[0037] S7, flame-retardant sheath layer extrusion process: low-smoke halogen-free flame-retardant sheath material with a density of 1.50g / cm³ is extruded through a sheath extruder and pushed to the surface of the non-woven fabric wrapping layer through a die, the extrusion temperature is 125℃-165℃, and a flame-retardant sheath layer with an outer diameter of 45.1mm±0.35mm is formed;

[0038] S8, detection and disc forming: after disc forming, the finished product is detected, and after passing the detection, packaging, warehousing and delivery detection are carried out.

[0039] The above technical scheme of the present application has the following advantages compared with the prior art:

[0040] The leaky coaxial cable, intercom system and manufacturing method, by integrally forming support columns every 45 degrees in the circumferential direction of the POM sheath layer, when the leaky coaxial cable is laid on the ground, the minimum gap between the outer conductor slot hole and the ground is not less than 28mm, 28mm can meet the requirement of margin, effectively reduce the absorption and reflection loss of the surface wave signal on the ground, the leaky coaxial cable can be directly laid on the ground, without additional overhead; through field test and test field verification, when the height from the ground reaches 28mm or more, the signal can be stably received, with the increase of the height, the signal strength gradually increases, and when the height reaches 500mm, the signal strength tends to be stable.

[0041] The application utilizes the air path gap formed between the support columns, sets a booster pump at one end of the cable, and introduces booster gas into the air path, so as to realize rapid cooling of the POM sheath layer, improve the heat dissipation performance of the leaky cable, thereby prolong the service life of the cable and maintain the signal transmission quality.

[0042] The POM sheath layer of the application adopts POM material to replace the traditional low-smoke and halogen-free flame-retardant sheath material, which significantly improves the hardness, wear resistance and impact resistance of the outer sheath, and can adapt to the working conditions such as frequent dragging and bending in the fire scene; the support column and the sheath layer are integrally extruded, reducing the assembly process and improving the overall structural strength and stability.

[0043] The application wraps the non-woven fabric with a thickness of 0.18mm and a width of 35mm around the outer surface of the support column, and the wrapping coverage rate is 30%~50%, which plays a continuous supporting role in the extrusion molding process of the flame-retardant sheath layer, prevents the local collapse or uneven thickness of the outer sheath caused by the gap between the support columns, and improves the geometric consistency and appearance quality of the finished product.

[0044] In each process of the inner conductor foamed insulation layer, the outer conductor corrugated forming and slotting, the sheath layer and the flame-retardant sheath layer extrusion, the material specifications, outer diameter size and process parameters are limited, the outer diameter of the insulation layer is 12.6mm±0.20mm, the outer diameter of the outer conductor is 13.9mm±0.25mm, and the outer diameter of the flame-retardant sheath layer is 45.1mm±0.35mm, which cooperates with multiple detections of semi-finished products and finished products to ensure the dimensional accuracy and performance stability in batch production.

[0045] The first connector and the second connector are respectively arranged at both ends of the leaky coaxial cable, which can be conveniently connected to the intercom signal source, terminal load and booster pump system, adapt to the commonly used fire intercom interface, and facilitate rapid deployment and maintenance. BRIEF DESCRIPTION OF DRAWINGS

[0046] In order to make the content of the application more easily understood, the application will be further described in detail below according to the specific embodiments of the application and in conjunction with the drawings.

[0047] Figure 1is a schematic diagram of a cross-sectional structure of a leaky coaxial cable of the present application.

[0048] Figure 2 is a schematic diagram of a longitudinal cross-sectional structure of a leaky coaxial cable of the present application.

[0049] Figure 3 is a schematic diagram of an axial side structure of a POM sheath layer of the present application.

[0050] Figure 4 is a schematic diagram of a structure of a speakerphone system of the present application.

[0051] Figure 5 is a schematic diagram of a structure of an extrusion die of the present application.

[0052] Figure 6 is a flow chart of a manufacturing method of a leaky coaxial cable of the present application.

[0053] Figure 7 is a schematic diagram of a cable leakage application scenario for a fire-fighting speakerphone system.

[0054] Figure 8 is a schematic diagram of a coupling type cable leakage radiation principle.

[0055] Figure 9 is a schematic diagram of a radiation type cable leakage radiation principle.

[0056] Figure 10 is a signal loss diagram obtained by testing when a leaky coaxial cable of the present application is placed on the ground.

[0057] Figure 11 is a signal loss diagram obtained by testing when a leaky coaxial cable of the present application is placed 28 mm away from the ground.

[0058] Figure 12 is a signal loss diagram obtained by testing when a leaky coaxial cable of the present application is placed 42 mm away from the ground.

[0059] Figure 13 is a signal loss diagram obtained by testing when a leaky coaxial cable of the present application is placed 56 mm away from the ground.

[0060] Figure 14 is a signal loss diagram obtained by testing when a leaky coaxial cable of the present application is placed 80 mm away from the ground.

[0061] Figure 15 is a signal loss diagram obtained by testing when a leaky coaxial cable of the present application is placed 500 mm away from the ground.

[0062] Figure 16 is a picture of a leaky coaxial cable of the present application during testing (overhead cushion test).

[0063] Explanation of the drawing marks in the specification:

[0064] 100, leaky coaxial cable; 110, first connector; 111, gas injection hole; 120, second connector; 130, load; 140, intercom; 150, gas injection valve; 160, check valve;

[0065] 200, extrusion die; 210, hole; 220, extrusion groove;

[0066] 1, inner conductor;

[0067] 2, insulating layer;

[0068] 3, outer conductor; 31, slot hole;

[0069] 4, POM sheath layer; 41, support column;

[0070] 5, non-woven fabric wrapping layer;

[0071] 6, air path gap;

[0072] 7, flame-retardant sheath layer;

[0073] 8, booster pump; 82, pipeline. DETAILED DESCRIPTION

[0074] The present application will be further described below in conjunction with the drawings and specific embodiments, so that those skilled in the art can better understand the present application and implement it.

[0075] In the present application, if the direction (up, down, left, right, front and back) is described, it is only for the convenience of describing the technical solutions of the present application, and is not intended to indicate or imply that the indicated technical features must have a specific orientation, be constructed and operated in a specific orientation, therefore, it cannot be understood as a limitation of the present application.

[0076] In the present application, the meaning of "several" is one or more, the meaning of "multiple" is two or more, "greater than", "less than", "more than" and the like are not included in the number; "above", "below", "within" and the like are understood to include the number. In the description of the present application, if "first" and "second" are described, they are only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or implicitly indicating the order of indicated technical features.

[0077] In the present application, unless otherwise explicitly defined, the words such as "arrange", "mount", "connect" and the like should be understood in a broad sense, for example, can be directly connected, or indirectly connected through an intermediate medium; can be fixedly connected, or can be detachably connected, or can be integrally formed; can be mechanically connected, or can be electrically connected or capable of communicating with each other; can be the communication or interaction relationship between two elements. The skilled in the art can reasonably determine the specific meaning of the above words in the present application in combination with the specific content of the technical solution.

[0078] Referring to Figures 1 to 3 The leaky coaxial cable 100 of the present embodiment comprises:

[0079] an inner conductor 1;

[0080] an insulating layer 2 covering the outer surface of the inner conductor 1;

[0081] an outer conductor 3 covering the outer surface of the insulating layer 2, and a plurality of slot holes 31 are formed along the surface of the outer conductor 3 and spaced along the axial direction, the distance between adjacent slot holes 31 is less than the working wavelength, so that the electromagnetic field is diffracted through the slot holes 31, thereby forming a surface wave on the outer conductor 3;

[0082] a POM sheath layer 4 covering the outer surface of the outer conductor 3, wherein a plurality of support columns 41 are integrally formed and extend radially outward from the outer surface of the POM sheath layer 4, each support column 41 extends along the length direction of the outer conductor 3, and adjacent two support columns 41 are spaced 45° along the circumferential direction of the POM sheath layer 4;

[0083] a non-woven fabric wrapping layer 5 wrapped around the outer surface of each support column 41 to form an air gap 6 between each adjacent two support columns 41;

[0084] a flame-retardant sheath layer 7 covering the outer surface of the non-woven fabric wrapping layer 5;

[0085] a booster pump 8 arranged at one end of the leaky coaxial cable 100 for introducing pressurized gas into the air gap 6 to cool the POM sheath layer 4;

[0086] wherein the radial length of the support column 41 is limited so that when the leaky coaxial cable 100 is laid on the ground, the minimum gap between the slot holes 31 on the outer conductor 3 and the ground is not less than 28mm.

[0087] It should be noted that through on-site debugging, it is found that when the coupling type leaky coaxial cable 100 is kept at a certain height interval from the ground, the receiving signal of the intercom 140 can be obviously improved; when the height of the leaky cable from the ground reaches 28mm, the intercom 140 can stably receive the signal, meeting the normal communication demand.

[0088] The test verification is carried out on site, and the test conditions are as follows: the leakage cable transmission power is 15 dBm; the test frequency (frequency 1) is 450 MHz; the test distance is 50 m; the judgment standard: the coupling loss is generally lower than 80 db, which is better; the test height from the ground: placed on the ground, 28 mm from the ground, and the overhead section is about 14-28 m, 42 mm from the ground, and the overhead section is about 13-32 m, 56 mm from the ground, and the overhead section is about 7-28 m, 80 mm from the ground, and the overhead section is about 5-37 m, 500 mm from the ground, and the overhead section is about 18-43 m. Referring to Figures 10 to 16 .

[0089] It should be noted that during the leakage cable test, a measurement is taken every 1 mm, and the computer automatically records the corresponding test point number and test value. Taking a 50 m length as an example, a total of 5000 test data can be obtained. The so-called 95% coupling loss value is that after arranging the 5000 test data in descending order, taking the test value corresponding to the 4750th point (i.e. 5000x0.95=4750) as the 95% coupling loss value of the whole cable. In specific operation, the host computer system will automatically collect all test data and automatically select the data point value at the 95% position after sorting as the final result. The coupling loss value is directly derived from the data collected by the computer and corresponds to the test point one by one. According to the total number of collected points, the corresponding coupling loss value can be quickly determined according to the total number of points x 0.95.

[0090] Referring to Figures 10 to 15 It can be seen that when the leakage cable is placed on the ground, the received signal strength is poor (i.e. the coupling loss is high); when the leakage cable is 28 mm from the ground, the received signal strength has been significantly improved (within 28 mm from the ground, it is not much different from when the leakage cable is placed on the ground, so it is not shown, 28 mm can meet the margin requirement); with the increase of the height from the ground, the received signal strength continues to increase; when the height from the ground reaches 500 mm, the signal strength tends to be stable and does not increase significantly. Therefore, the leakage cable can realize stable coverage of the intercom 140 when the height from the ground is more than 28 mm, meeting the communication requirements of the fire intercom system in complex underground environment.

[0091] Therefore, through the arrangement of the support column 41, the cable can naturally maintain a gap of more than 28 mm when laid on the ground, meeting the signal coverage requirements of the fire intercom system in actual use.

[0092] In addition, by introducing the booster pump 8 into the air passage gap 6 formed between the support columns 41 to introduce pressurized gas into the air passage, the POM sheath layer 4 can be quickly cooled, prolonging the service life and maintaining the signal transmission quality.

[0093] Specifically, the inner conductor 1 is a copper-clad aluminum material.

[0094] Specifically, the support column 41 is in a rectangular thin plate shape, and the end face in contact with the POM sheath layer 4 is in a rectangular or arc shape. The radial length of the support column 41 is not less than 28 mm, and the circumferential width is 3 mm ± 1 mm; the outer diameter of the POM sheath layer 4 is 15.7 mm ± 0.25 mm. The radial length of the support column 41 is arranged to ensure that the minimum gap between the cable slot hole 31 and the ground is not less than 28 mm, avoiding the absorption of the surface wave signal by the ground; the width design ensures sufficient support strength under the action of gravity, preventing the cable from collapsing and stabilizing the ground clearance.

[0095] Referring to Figure 3 The end face of the support column 41 adopts a rectangular or arc structure, which can increase the contact area with the material of the non-woven fabric wrapping layer 5, so that the non-woven fabric can uniformly and stably cover the outer surface of the support column 41 in the subsequent wrapping process.

[0096] In addition, the POM (polyoxymethylene) material is used to replace the original low-smoke halogen-free flame-retardant sheath material to coat the outer conductor 3, so as to improve the mechanical strength, wear resistance and overall protection performance of the sheath.

[0097] Specifically, the outer diameter of the insulating layer 2 is 12.6 mm ± 0.20 mm.

[0098] Specifically, the outer conductor 3 adopts a ring-shaped corrugated copper pipe, and the slot hole 31 is arranged at the wave peak position; the outer diameter of the outer conductor 3 is 13.9 mm ± 0.25 mm, and the valley diameter is 12.9 mm ± 0.25 mm.

[0099] Specifically, the non-woven fabric is a wrapping tape with a thickness of 0.18 mm ± 0.01 mm and a width of 35 mm ± 1 mm, and the wrapping coverage rate is 30% to 50%; the outer diameter of the non-woven fabric wrapping layer 5 is 44.3 mm ± 0.35 mm.

[0100] By coating a layer of non-woven fabric material on the outer surface of each support column 41, local collapse caused by the gap between the support columns 41 during the extrusion molding of the flame-retardant sheath layer 7 is prevented, so as to ensure the molding integrity and flatness of the outer sheath.

[0101] Specifically, the flame-retardant sheath layer 7 adopts a low-smoke halogen-free flame-retardant sheath material with a density of 1.50 g / cm³, and the outer diameter of the flame-retardant sheath layer 7 is 45.1 mm ± 0.35 mm.

[0102] Referring to Figure 4As shown, the embodiment also provides an intercom system, comprising the leaky coaxial cable 100; wherein the two ends of the leaky coaxial cable 100 are respectively provided with a first connector 110 and a second connector 120, the first connector 110 and the second connector 120 are respectively connected to the signal source of the intercom 140 and the load 130 through the jumper wires; the sidewall of the first connector 110 is provided with a gas injection hole 111 and is threadedly connected with a gas injection valve 150 through the gas injection hole 111, the gas injection valve 150 is connected with the output end of the booster pump 8 through the pipeline 82; the sidewall of the second connector 120 is threadedly connected with a check valve 160 which is connected with the air gap 6.

[0103] Specifically, the first connector 110 and the second connector 120 are conveniently connected with the signal source of the intercom 140 and the load 130, facilitating deployment and maintenance. The gas injection valve 150 and the check valve 160 are both single-leaf swing valves made of stainless steel, which has strong corrosion resistance. The check valve 160 is a one-way flow automatic valve to prevent the backflow of the medium in the pipeline, which is opened or closed by the pressure of the pipeline medium flow.

[0104] Exemplarily, the gas injection power of the booster pump 8 is set to 3kw, which can meet the cooling requirement of the POM sheath layer 4.

[0105] Referring to Figure 6 It should be noted that when the booster pump 8 is working, the high-pressure gas flows at high speed along the air gap 6, and the injected gas flow is ambient temperature air (or low-temperature gas), which can take away the heat in the cable and reduce the surface temperature of the POM sheath layer 4.

[0106] The embodiment also provides a manufacturing method of the leaky coaxial cable 100, comprising:

[0107] S1, preparing the inner conductor 1: providing copper-clad aluminum as the inner conductor 1;

[0108] S2, insulation process: mixing high-density foaming material, low-density foaming material and nucleating agent according to the mass ratio of 71:25:4, and simultaneously injecting high-purity carbon dioxide to form a mixture of foaming material and gas, using an extrusion die to push the extruder die module to form a cell layer, and cooling and shaping in a hot water tank and a cold water tank to form an insulation layer 2 of foam material, the outer diameter of the insulation layer 2 is 12.6mm±0.20mm;

[0109] S3, copper strip corrugation and slotting process: the copper strip with a thickness of 0.18mm is sequentially washed, edge cut, longitudinally wrapped, formed, and welded to be rolled into an annular corrugated copper pipe, and a hole is continuously milled at the wave crest position according to the set hole pitch to form an outer conductor 3, the outer diameter of the outer conductor 3 is 13.9mm±0.25mm, and the valley diameter is 12.9mm±0.25mm;

[0110] S4, POM sheath extrusion process: provide an extrusion die set 200, which includes an extrusion cavity, the extrusion cavity includes a hole part 210 and an extrusion groove 220 extending outwardly and radially every 45° along the circumferential direction of the hole part 210; refer to Figure 5 as shown;

[0111] The sheath material of POM material is extruded through the extrusion die set 200 on the surface of the outer conductor 3 to extrude the POM sheath layer 4, and at the same time, an integral support column 41 is extruded every 45° along the circumferential direction, the length of the support column 41 is not less than 28mm, the width is 3mm±1mm, the outer end face is rectangular or arc-shaped, and the outer diameter of the sheath layer is 15.7mm±0.25mm;

[0112] S5, sheath wrapping process: using a concentric wrapping device, a non-woven fabric with a thickness of 0.18mm±0.01mm and a width of 35mm±1mm is wrapped on the outer surface formed by each support column 41 at a lap rate of 30%~50% to form a non-woven fabric wrapping layer 5, the outer diameter of the non-woven fabric wrapping layer 5 is 44.3mm±0.35mm;

[0113] S6, semi-finished product detection process: the semi-finished product formed in step S4 is detected, and after passing the detection, subsequent processes are carried out;

[0114] S7, flame-retardant sheath layer 7 extrusion process: low-smoke halogen-free flame-retardant sheath material with a density of 1.50g / cm³ is extruded through a sheath extruder and pushed through a die to the surface of the non-woven fabric wrapping layer 5, the extrusion temperature is 125℃~165℃, forming a flame-retardant sheath layer 7 with an outer diameter of 45.1mm±0.35mm;

[0115] S8, detection and disc forming: after disc forming, the finished product is detected, and after passing the detection, packaging, warehousing and delivery detection are carried out.

[0116] Through each process of the inner conductor 1 foamed insulation layer 2, the outer conductor 3 corrugated forming and slotting, the sheath layer and the flame-retardant sheath layer 7 extrusion, the material specifications, the outer diameter size and the process parameters are limited, and the semi-finished product and the finished product are detected multiple times, so as to ensure the size precision and the performance stability in batch production.

[0117] Finally, it should be explained that the above specific embodiments are only used to illustrate the technical solutions of the present application and not to limit, although the present application is described in detail with reference to examples, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application, which should be covered in the scope of the claims of the present application.

Claims

1. A speakerphone system, characterized by The leaky coaxial cable comprises: an inner conductor (1); an insulating layer (2) covering the outer surface of the inner conductor (1); an outer conductor (3) covering the outer surface of the insulating layer (2), and a plurality of slot holes (31) are formed on the surface of the outer conductor (3) and are distributed along the axial direction, the distance between adjacent slot holes (31) is less than the working wavelength, and the electromagnetic field is diffracted through the slot holes (31), so that a surface wave is formed on the outer conductor (3); a POM sheath layer (4) covering the outer surface of the outer conductor (3), wherein a plurality of support columns (41) are integrally formed on the outer surface of the POM sheath layer (4) and extend radially outward, each support column (41) extends along the length direction of the outer conductor (3), and adjacent two support columns (41) are spaced apart by 45° along the circumferential direction of the POM sheath layer (4); a non-woven fabric wrapping layer (5) wrapped on the outer surface of each support column (41) to form an air gap (6) between every adjacent two support columns (41); a flame-retardant sheath layer (7) covering the outer surface of the non-woven fabric wrapping layer (5); a booster pump (8) arranged at one end of the leaky coaxial cable for introducing pressurized gas into the air gap (6) to cool the POM sheath layer (4); wherein the radial length of the support column (41) is limited so that when the leaky coaxial cable is laid on the ground, the minimum gap between the slot holes (31) on the outer conductor (3) and the ground is not less than 28mm; wherein the two ends of the leaky coaxial cable are respectively provided with a first connector (110) and a second connector (120), and the first connector (110) and the second connector (120) are respectively connected to a speakerphone (140) signal source and a load (130) through a jumper; the side wall of the first connector (110) is provided with a gas injection hole (111), and a gas injection valve (150) is threadedly connected through the gas injection hole (111), and the gas injection valve (150) is connected to the output end of the booster pump (8) through a pipeline (82); the side wall of the second connector (120) is threadedly connected with a check valve (160) connected with the air gap (6).

2. A system according to claim 1, wherein The inner conductor (1) is made of copper-clad aluminum material.

3. A system according to claim 1, wherein The support column (41) is in the shape of a rectangular thin plate, and the end surface in contact with the POM sheath layer (4) is in the shape of a rectangle or an arc.

4. A system according to claim 1, wherein The radial length of the support column (41) is not less than 28mm, and the circumferential width is 3mm±1mm; the outer diameter of the POM sheath layer (4) is 15.7mm±0.25mm.

5. A system according to claim 1, wherein The outer diameter of the insulating layer (2) is 12.6mm±0.20mm.

6. A system according to claim 1, wherein The outer conductor (3) is made of a ring-shaped corrugated copper pipe, and the slot holes (31) are arranged at the wave crest positions; the outer diameter of the outer conductor (3) is 13.9mm±0.25mm, and the valley diameter is 12.9mm±0.25mm.

7. A system according to claim 1, wherein The non-woven fabric is a wrapping tape with a thickness of 0.18mm±0.01mm and a width of 35mm±1mm, and the wrapping coverage is 30%-50%, and the outer diameter of the non-woven fabric wrapping layer (5) is 44.3mm±0.35mm.

8. A system according to claim 1, wherein, The flame-retardant sheath layer (7) is made of low-smoke halogen-free flame-retardant sheath material with a density of 1.50g / cm³, and the outer diameter of the flame-retardant sheath layer (7) is 45.1mm±0.35mm.

9. A method of making a leaky coaxial cable for a intercom system as claimed in any one of claims 1 to 8, characterised in that, Comprise: S1, inner conductor (1) preparation: provide copper-clad aluminum as the inner conductor (1); S2, insulation process: mix high-density foaming material, low-density foaming material and nucleating agent according to the mass ratio of 71:25:4, and simultaneously inject high-purity carbon dioxide to prepare a mixture of foaming material and gas, push the extruder die module through the extrusion die, form a bubble layer, and cool and shape the foam material insulation layer (2) through a hot water tank and a cold water tank, the outer diameter of the insulation layer (2) is 12.6mm±0.20mm; S3, copper strip corrugation slotting process: the copper strip with a thickness of 0.18mm is sequentially cleaned, edge cut, longitudinally wrapped, formed, and welded, and is rolled into an annular corrugated copper pipe, and a continuous hole is formed at the wave peak position according to the set hole pitch to form an outer conductor (3), the outer diameter of the outer conductor (3) is 13.9mm±0.25mm, and the valley diameter is 12.9mm±0.25mm; S4, POM sheath extrusion process: provide an extrusion die set (200), the extrusion die set (200) comprises an extrusion cavity, the extrusion cavity comprises a hole portion (210) and an extrusion groove (220) extending radially outward every 45° along the circumferential direction of the hole portion (210); The sheath material of POM material is extruded through the extrusion die set (200) on the surface of the outer conductor (3) to form the POM sheath layer (4), and at the same time, a support column (41) is extruded every 45° along the circumferential direction, the length of the support column (41) is not less than 28mm, the width is 3mm±1mm, the outer end face is rectangular or arc-shaped, and the outer diameter of the sheath layer is 15.7mm±0.25mm; S5, sheath wrapping process: using a concentric wrapping device, a non-woven fabric with a thickness of 0.18mm±0.01mm and a width of 35mm±1mm is wrapped on the outer surface formed by each support column (41) with a coverage of 30%-50% to form a non-woven fabric wrapping layer (5), and the outer diameter of the non-woven fabric wrapping layer (5) is 44.3mm±0.35mm; S6, semi-finished product detection process: the semi-finished product formed in step S4 is detected, and after passing the detection, subsequent processes are carried out; S7, flame-retardant sheath layer (7) extrusion process: low-smoke halogen-free flame-retardant sheath material with a density of 1.50g / cm³ is extruded through a sheath extruder and pushed to the surface of the non-woven fabric wrapping layer (5) through a die, the extrusion temperature is 125℃-165℃, and a flame-retardant sheath layer (7) with an outer diameter of 45.1mm±0.35mm is formed; S8, detection and disc forming: after disc forming, the finished product is detected, and after passing the detection, packaging, warehousing and delivery detection are carried out.

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