Fire Resistant Coaxial Cable

Abstract

The present invention relates to a fire-resistant coaxial cable that can stably maintain communication functions for a certain period of time by having an insulator capable of maintaining the shape of the inner conductor and the outer conductor at a high temperature of 750°C or higher in the event of a fire.

Description

Technology Field

[0001] The present invention relates to a fire-resistant coaxial cable. More specifically, the present invention relates to a fire-resistant coaxial cable capable of stably maintaining communication functions for a certain period of time at a high temperature of 750°C or higher in the event of a fire. Background Technology

[0002] Materials such as PE and PTFE, which are used as insulators for general coaxial cables, have a melting point of 100 to 325°C. This causes a problem in that they melt in a fire environment of at least 750°C or higher, failing to adequately perform the role of insulation between the inner conductor and the outer conductor.

[0003] Therefore, an insulation structure is required that forms concentric circles between the inner and outer conductors and implements a dielectric constant equivalent to that of materials such as PE and PTFE, so that communication functions can be maintained for a certain period of time or longer by ensuring insulation performance by maintaining the structure between the inner and outer conductors in a fire-affected environment, and simultaneously allows the communication cable to faithfully perform its role as a transmission line even in a fire-free environment. Additionally, a fire-resistant coaxial cable including the same is required.

[0004] In particular, firefighting wireless communication auxiliary equipment is essential for high-rise and large buildings. To ensure smooth wireless communication for firefighters at the scene of a fire, it is desirable for the fire-resistant coaxial cables used in these auxiliary equipment to satisfy fire resistance performance according to standards IEC 60331-11 and IEC 60331-23. IEC 60331-11 and IEC 60331-23, which are fire resistance standards for fire-resistant coaxial cables, evaluate whether there is a short circuit between the inner conductor and the outer conductor for a certain period of time when a test voltage is applied at a flame temperature of at least 750°C.

[0005] Accordingly, there is a need for a fire-resistant coaxial cable that can be used as a coaxial cable for firefighting wireless communication auxiliary equipment by stably maintaining the function of the coaxial cable for a certain period of time at high temperatures of 750°C or higher in the event of a fire. The problem to be solved

[0006] The present invention aims to solve the problem of providing a fire-resistant coaxial cable that can stably maintain communication functions for a certain period of time at a high temperature of 750°C or higher in the event of a fire. means of solving the problem

[0007] To solve the above problem, the present invention may provide a fire-resistant coaxial cable comprising: an inner conductor disposed in the center; an insulator transversely wound on the outer side of the inner conductor; an outer conductor surrounding the outer side of the insulator and forming a coaxial structure with the inner conductor; and a cable jacket surrounding the outer side of the outer conductor, wherein the insulator comprises an insulating core and a fire-resistant layer surrounding the insulating core, and the fire-resistant layer comprises silicone rubber.

[0008] In addition, to solve the above problem, the present invention may provide a fire-resistant coaxial cable comprising: an inner conductor disposed in the center; an insulator transversely wound on the outer side of the inner conductor; an outer conductor surrounding the outer side of the insulator and forming a coaxial structure with the inner conductor; and a cable jacket surrounding the outer side of the outer conductor; wherein the insulator comprises an insulating core and a fire-resistant layer surrounding the insulating core, and the fire-resistant layer comprises a fire-resistant elastomer.

[0009] In addition, to solve the above problem, the present invention may provide a fire-resistant coaxial cable comprising: an inner conductor disposed in the center; an insulator transversely wound on the outer side of the inner conductor; an outer conductor surrounding the outer side of the insulator and forming a coaxial structure with the inner conductor; and a cable jacket surrounding the outer side of the outer conductor; wherein the insulator comprises an insulating core and a fire-resistant layer surrounding the insulating core, the insulating core of the insulator comprises polyethylene, and the fire-resistant layer of the insulator comprises at least one of basalt fiber, silica fiber, ceramic fiber, glass fiber, and mica tape.

[0010] In addition, the fire-resistant layer of the insulator may include silicone rubber.

[0011] Here, the insulating core of the insulator may include a tension member.

[0012] In this case, the tensile strength of the insulating core including the above-mentioned tensile member may be 5 g / TEX or more.

[0013] In addition, the tensile member may include at least one of basalt fiber, glass fiber, silica fiber, ceramic fiber, or aramid fiber material.

[0014] In addition, the above-mentioned tension member may include glass yarn.

[0015] In addition, the insulating core may have a higher temperature at which shape deformation occurs at a higher temperature than the refractory layer.

[0016] Here, the maximum load applied when fixing the outer conductor of a fire-resistant coaxial cable with a specimen length of 500 mm and pulling the inner conductor in the axial direction of the inner conductor at a speed of 50.0 mm / min may be 2 kgf or more.

[0017] In this case, the insulator may include a low dielectric constant layer having a dielectric constant of 2.5 or less that surrounds the insulator.

[0018] In addition, the low dielectric constant layer may include at least one of PE (Polyethylene), HDPE (High-Density Polyethylene), PTFE (Polytetrafluoroethylene) and FEP (Fluorinated ethylene propylene).

[0019] In addition, it may include an insulating fire-resistant reinforcing layer that surrounds the insulator and reinforces the fire-resistant performance of the fire-resistant coaxial cable.

[0020] Here, the insulating fire-resistant reinforcing layer may include at least one of basalt fibers, silica fibers, ceramic fibers, glass fibers, and mica tape.

[0021] In this case, one or more fire-resistant tape layers covering the outer side of the outer conductor may be further included to reinforce the fire-resistant performance of the fire-resistant coaxial cable.

[0022] In addition, the fire-resistant tape layer may include at least one of mica tape, glass tape, and metal tape.

[0023] In addition, to reinforce the fire resistance performance of the above-mentioned fire-resistant coaxial cable, a conductor fire-resistant reinforcing layer surrounding the inner conductor may be further included.

[0024] In addition, the conductor refractory reinforcing layer may include at least one of basalt fibers, silica fibers, ceramic fibers, glass fibers, and mica tape.

[0025] Here, the inner conductor and the outer conductor may be made of copper or a copper alloy.

[0026] In this case, the outer conductor may have a corrugated tube structure in which corrugated peaks and corrugated grooves are repeatedly formed. Effects of the invention

[0027] According to the fire-resistant coaxial cable of the present invention, the insulator disposed between the inner conductor and the outer conductor comprises a fire-resistant layer composed of a specific fire-resistant material and an insulating core embedded therein, thereby maintaining insulation between the inner conductor and the outer conductor at a high temperature of 750°C or higher in the event of a fire, thereby enabling excellent fire-resistant performance.

[0028] In addition, according to the fire-resistant coaxial cable of the present invention, the insulator is arranged to be transversely wound on the outside of the inner conductor to form an air layer, and a low dielectric constant layer is added on the outside of the insulator to secure a low dielectric constant, thereby enabling excellent communication performance of the fire-resistant coaxial cable.

[0029] In addition, according to the fire-resistant coaxial cable of the present invention, the fire-resistant properties can be further improved by adding an insulating fire-resistant reinforcing layer to the outer side of the insulator. Brief explanation of the drawing

[0030] FIG. 1 illustrates a configuration diagram of a firefighting wireless communication auxiliary facility including a fire-resistant coaxial cable according to the present invention. FIG. 2 shows a multi-stage stripped perspective view of one embodiment of a fire-resistant coaxial cable according to the present invention. Figure 3 shows a partial enlarged cross-sectional view of the fire-resistant coaxial cable shown in Figure 2. FIG. 4 shows a cross-sectional view of one embodiment of the fire-resistant coaxial cable shown in FIG. 2. FIG. 5 shows a cross-sectional view of another embodiment of a fire-resistant coaxial cable according to the present invention. FIG. 6 shows the results of the Pulling Force Test for specimens of Examples 1 to 3 and Comparisons 1 to 3. FIG. 7 illustrates a cross-sectional view of another embodiment of a fire-resistant coaxial cable according to the present invention. FIG. 8 shows a cross-sectional view of another embodiment of a fire-resistant coaxial cable according to the present invention. FIG. 9 shows a cross-sectional view of another embodiment of a fire-resistant coaxial cable according to the present invention. Specific details for implementing the invention

[0031] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete, and to ensure that the spirit of the invention is sufficiently conveyed to those skilled in the art. Throughout the specification, the same reference numerals indicate the same components.

[0032] FIG. 1 illustrates a configuration diagram of a firefighting wireless communication auxiliary facility including a fire-resistant coaxial cable according to the present invention.

[0033] As illustrated in FIG. 1, the firefighting wireless communication auxiliary equipment may be configured to include a fire-resistant coaxial cable (100) forming a wired communication network, a fire-resistant leak-proof coaxial cable (100L) forming a wireless communication network, an indoor antenna (200) that transmits and receives wireless signals with a wireless terminal (t) carried by a firefighting and disaster prevention officer, a central amplifier (300) installed in a disaster prevention room (d) etc. to amplify and relay wireless signals transmitted and received, a line amplifier (400) for amplifying signals on a transmission and reception line, a distributor (500) for distributing signals, an outdoor antenna (600) that transmits and receives wireless signals with a wireless terminal (t) outside the building, and a power supply device (700) for supplying power to the line amplifier (400).

[0034] As illustrated in FIG. 1, the firefighting wireless communication auxiliary equipment may be equipped with a fire-resistant coaxial cable (100) for constructing a wired communication network composed of various equipment used for fire prevention and control, such as an indoor antenna (200), a central amplifier (300), a line amplifier (400), a distributor (500), an outdoor antenna (600), a power supply device (700), and lines connecting these to each other. In underground spaces such as underground parking lots with a large area inside a building and undivided space, a fire-resistant leakage coaxial cable (100L) may be laid to construct a wireless communication network. Of course, if necessary, an indoor antenna (200) may be installed together with the fire-resistant leakage coaxial cable in the underground space of the building.

[0035] For reference, according to the fire safety standards for wireless communication auxiliary equipment (NFSC 505), the leaky coaxial cable and indoor antenna (200) can transmit and receive electromagnetic waves in the range of 440 MHz to 450 MHz, which is the communication frequency for firefighting.

[0036] Through such a wireless communication network, it is possible to enable communication between firefighting personnel and the fire command center or control room.

[0037] The above-mentioned firefighting wireless communication auxiliary equipment is installed above and below ground of the building (b) and may be equipped with multiple indoor antennas (200) capable of wireless communication with each wireless terminal (t) carried by a firefighting and disaster prevention officer.

[0038] The above indoor antenna (200) can be provided in an indoor space on each floor of the building (b), and enables mutual communication between firefighting and disaster prevention personnel carrying a wireless terminal (t) or mutual communication between a firefighting and disaster prevention personnel carrying a wireless terminal (t) and personnel inside the disaster prevention room (d).

[0039] Here, the indoor antenna (200) can be connected to a central amplifier (300) of a fire control room (d) located within the building (b) via a fire-resistant coaxial cable (100).

[0040] In addition, the above firefighting wireless communication auxiliary equipment may be configured to include a plurality of line amplifiers (400) that are connected via the indoor antenna (200) and the fire-resistant coaxial cable (100) and amplify the signal transmitted and received from the indoor antenna (200).

[0041] Additionally, the firefighting wireless communication auxiliary equipment illustrated in FIG. 1 may be configured to include a plurality of distributors (500) for branching signals transmitted and received from a plurality of indoor antennas (200).

[0042] The above-mentioned splitter (500) may be provided in each area where signals are branched into multiple coaxial cables, and the splitter (500) may synthesize the signals received from the indoor antenna (200) or branch the signals provided from the central amplifier and transmit each branched signal to the indoor antenna (200).

[0043] Additionally, the above-mentioned firefighting wireless communication auxiliary equipment may be configured to include an outdoor antenna (600) installed outdoors. The outdoor antenna (600) enables voice communication between a wireless terminal (t) held by a firefighting officer or fire commander outside the building and a firefighting officer inside the building, or communication with a central amplifier (300) in the firefighting control room (d).

[0044] Here, even if the outdoor antenna (600) is not provided, the firefighting wireless communication auxiliary equipment can be connected via a wire to a wireless terminal (t) held by a firefighting officer or fire commander outside the building to enable voice communication with a firefighting officer inside the building or communication with a central amplifier (300) in the firefighting control room (d).

[0045] Additionally, the above-mentioned firefighting wireless communication auxiliary equipment may be configured to include a power supply device (700) for supplying commercial power or emergency power. The power supply device (700) may provide power to a line amplifier (400), etc., through a fire-resistant coaxial cable (100) or a separate power cable.

[0046] Meanwhile, the overall configuration of the firefighting wireless communication auxiliary equipment to which the fire-resistant coaxial cable (100) according to the present invention is applied is not limited to the items shown in FIG. 1, and may be configured by selectively combining at least some of the indoor antenna (200), central amplifier (300), line amplifier (400), distributor (500), outdoor antenna (600), and power supply device (700), or may be configured to additionally include various equipment that constitutes a conventional firefighting wireless communication auxiliary equipment in addition to the configuration described above.

[0047] Meanwhile, Figure 1 shows an embodiment in which a fire-resistant coaxial cable (100) according to the present invention is applied to a firefighting wireless communication auxiliary facility, but in addition to that, the fire-resistant coaxial cable according to the present invention can be applied to various environments where communication functions need to be maintained when high temperatures occur.

[0048] Hereinafter, with reference to FIG. 2 and below, the structure of the fire-resistant coaxial cable (100) according to the present invention will be examined in detail.

[0049] FIG. 2 shows a multi-stage stripped perspective view of one embodiment of a fire-resistant coaxial cable according to the present invention, FIG. 3 shows a partially enlarged cutaway view of the fire-resistant coaxial cable shown in FIG. 2, and FIG. 4 shows a cross-sectional view of the fire-resistant coaxial cable shown in FIG. 2.

[0050] As illustrated in FIGS. 2 to 4, a fire-resistant coaxial cable (100) according to the present invention may be configured to include: an inner conductor (10) disposed in the center; an insulator (20) that is transversely wound on the outside of the inner conductor (10) and includes an insulating core (21) and a fire-resistant layer (23) that surrounds the insulating core (21) and is composed of a fire-resistant composition; an outer conductor (30) that surrounds the outside of the insulator (20) and forms a coaxial structure with the inner conductor (10); and a cable jacket (40) that surrounds the outside of the outer conductor (30).

[0051] The inner conductor (10) is provided in the center and serves to transmit communication signals. Typically, copper or aluminum is used as the material for the inner conductor (10) of a coaxial cable, but since the melting point of copper is 1,084°C while the melting point of aluminum is 660°C, the inner conductor (10) is preferably made of copper or a copper alloy. The cross-section of the inner conductor (10) is circular, and the diameter can be configured to be in the range of 5.0 millimeters (mm) or less.

[0052] An insulator (20) is provided on the outer side of the inner conductor (10), and the insulator (20) may be configured in the form of a rope or wire and may be provided by being wound transversely on the outer side of the inner conductor (10) in a preset pitch range. The insulator (20) performs the function of maintaining a constant distance between the inner conductor (10) and the outer conductor (30) and insulating the inner conductor (10). The insulator (20) may be configured to include an insulating core (21) and a fire-resistant layer (23), wherein the insulating core (21) is configured in the form of a rope, wire, or a long extended fiber, and the fire-resistant layer (23) is provided in a form that wraps around the insulating core (21) with a certain thickness, so that the insulator (20) can be implemented in the form of a rope or wire.

[0053] In this way, the fire-resistant coaxial cable (100) according to the present invention is configured such that the insulator (20) is not filled entirely around the outer circumference of the inner conductor (10) as in the conventional form, but is formed in the form of a rope or wire and spirally wound around the outer side of the inner conductor (10). Accordingly, the cross-sectional area of ​​the insulator (20) is reduced, thereby reducing the absolute amount of the insulator (20) which has relatively weak fire resistance compared to the inner conductor (10) and the outer conductor (30), thereby improving flame retardant properties and simultaneously improving the flexibility of the cable and minimizing the cable manufacturing cost, while stably maintaining the coaxial structure between the inner conductor (10) and the outer conductor (30) through the insulator (20).

[0054] Furthermore, by configuring the insulator (20) in a shape that is transversely wound on the outside of the inner conductor (10), a void space is formed between the inner conductor (10) and the outer conductor (30), and the dielectric constant of the space between the inner conductor (10) and the outer conductor (30) is reduced by the air layer of the void space formed around the insulator (20), thereby improving the transmission characteristics of electromagnetic wave signals transmitted and received through the fire-resistant coaxial cable (100).

[0055] Although the insulator (20) itself has a high dielectric constant, the dielectric constant of the entire insulation structure between the inner conductor (10) and the outer conductor (30) of the fire-resistant coaxial cable can be lowered by winding it transversely around the outer surface of the inner conductor (10) to include an air layer. In addition, as described below with reference to FIG. 5 and below, the dielectric constant of the insulation structure can be lowered by further including a low dielectric constant layer (50) on the outside of the insulator (20). At this time, it is preferable that the dielectric constant of the low dielectric constant layer (50) be 2.5 or less. When the low dielectric constant layer (50) is formed on the outside of the insulator (20), the dielectric constant of the fire-resistant coaxial cable is further lowered, thereby reducing the signal attenuation of the fire-resistant coaxial cable. A detailed explanation of the low dielectric constant layer (50) is deferred to later.

[0056] Specifically, the inclination angle (θ) at which the insulator (20) is transversely wound around the outer side of the inner conductor (10) may be 20 to 60°. The inclination angle (θ) can be defined as the angle between the base and the hypotenuse in a right-angled triangle, as shown in FIG. 3, where the base is half the pitch (P) of the insulator (20) during transverse winding and the height is the inner diameter (D) of the outer conductor (30). The inner diameter (D) of the outer conductor (30) may be the inner diameter between the grooves of the corrugations in the corrugated outer conductor (30).

[0057] Here, if the inclination angle (θ) is greater than 60°, the structure of the cable is stable, but the dielectric constant between the inner conductor (10) and the outer conductor (30) is increased by the insulator (20), so the communication characteristics of the cable are degraded, the cable is excessively stiff, so the flexibility is reduced, and the manufacturing cost may increase due to an increase in unnecessary material costs.

[0058] On the other hand, when the above-mentioned inclination angle (θ) is less than 20°, manufacturing costs are reduced due to material cost reduction and communication characteristics are improved due to lower dielectric constant, but the structure is unstable, such as when the outer conductor is easily crushed when the cable is bent, and a short circuit may occur when the inner conductor and the outer conductor come into contact.

[0059] Meanwhile, the outer diameter of the insulator (20) may be 75 to 95% of the diameter of the inner conductor (10). Here, if the outer diameter of the insulator (20) is less than 75% of the diameter of the inner conductor (10), it is difficult to secure a gap between the inner conductor (10) and the outer conductor (30) to satisfy a characteristic impedance of 50±5 Ω, and if it exceeds 95%, when the insulator (20) is wound transversely on the outside of the inner conductor (10), excessive tension is applied to the inner conductor (10), making it difficult for the inner conductor (10) to maintain a straight line in the longitudinal direction, which may reduce structural stability.

[0060] Detailed experimental results of the above-mentioned insulator (20) structure will be described below.

[0061] Meanwhile, it is desirable for fire-resistant coaxial cables for signal transmission within firefighting wireless communication auxiliary equipment to satisfy fire resistance performance according to standards IEC 60331-11 and IEC 60331-23 as specified in international standards. As mentioned above, standards IEC 60331-11 and IEC 60331-23 evaluate whether there is a short circuit between the inner conductor and the outer conductor when a test voltage is applied at a flame temperature of at least 750°C.

[0062] Accordingly, in order to satisfy the fire resistance performance according to standards IEC 60331-11 and IEC 60331-23, the insulator (20) constituting the fire resistance coaxial cable (100) according to the present invention can be designed to secure excellent fire resistance performance at high temperatures of 750°C or higher when a fire occurs, while simultaneously maintaining the internal structure of the insulator at high temperatures.

[0063] In addition, the fire-resistant coaxial cable (100) including the insulator (20) may be designed and manufactured to maintain a constant structure between the inner conductor (10) and the outer conductor (30), so that the unique function of the communication cable can be properly performed even in an environment where no fire occurs.

[0064] The insulator (20) constituting the fire-resistant coaxial cable (100) according to the present invention may be composed of an insulating core (21) formed by being embedded along the longitudinal direction and a fire-resistant layer (23) that surrounds the insulating core (21) and is composed of a fire-resistant elastomer material.

[0065] The above-mentioned refractory layer (23) may be a refractory elastomer material. For example, the refractory layer may include at least one of silicone rubber, fluoroelastomer (FKM), fluorosilicone (FVMQ), ethylene acrylic rubber (AEM), acrylic rubber (ACM), etc. If the refractory layer (23) is a refractory elastomer material, it can be easily deformed, so that when the insulator (20) is wound transversely on the outside of the inner conductor (10), the insulator (20) can adhere to the outer surface of the inner conductor (10). In this way, the insulator (20) provides adhesion based on material properties, so that the coaxial structure between the outer conductor and the inner conductor can be stably maintained even when the refractory coaxial cable is bent or under stress due to external force.

[0066] The adhesion of the above insulator (20) can be verified through a pulling force test.

[0067] The pulling force test is performed by preparing a fire-resistant coaxial cable specimen with a length of 500 mm, and determining the maximum load at which the pulling load becomes maximum when the inner conductor (10) is pulled in the axial direction of the inner conductor (10) at a speed of 50.0 mm / min while the outer conductor (30) is fixed.

[0068] In this case, if the fire-resistant layer (23) is configured to include a fire-resistant elastomer material, the maximum load can be at least 2 kgf. If the maximum load is less than 2 kgf, the outer conductor (30) and the inner conductor (10) can be easily separated by a small force, and structural damage between the inner conductor (10) and the outer conductor (30) can easily occur due to external tensile force, and the reliability of the cable cannot be guaranteed during installation and use.

[0069] When the insulator (20) is constructed using refractory materials such as basalt, ceramic, or glass as the main material, it lacks flexibility, so when the insulator is wound horizontally on the outside of the inner conductor (10), cracks easily occur and it breaks, and the adhesion between the inner conductors is poor, and when the insulator is formed by weaving it in the form of fibers, it is not easy to achieve a sufficient thickness.

[0070] On the other hand, when silicone rubber is used as the refractory elastomer material constituting the refractory layer (23), it was confirmed that the processability during manufacturing is excellent, making it easy to achieve the thickness in the shape of the insulator, and the workability of the product processed into the shape of the insulator is excellent, so the adhesion is better when the inner conductor (10) is wound transversely.

[0071] Specifically, when a pulling force test was performed to measure the adhesion of the insulator (20) by using a specimen of a fire-resistant coaxial cable with a length of 500 mm and a test speed of 50.0 mm / min, the maximum load was measured to be 16.2 kgf, confirming that the insulator (20) was sufficiently adhered to the outer surface of the inner conductor (10) and the inner surface of the outer conductor (30), respectively.

[0072] In addition, silicone rubber has significantly superior fire resistance performance compared to general elastic polymer materials, and as a thermosetting material, it hardens at high temperatures, so it can maintain the separation structure between the inner conductor (10) and the outer conductor (30) even in a high-temperature environment, thereby allowing the fire-resistant coaxial cable to maintain its function.

[0073] The above refractory layer (23) can be formed to have a circular cross-section on the outside of the insulating core (21) by means such as extrusion of a refractory elastomer material. As an example of a refractory elastomer material constituting the above refractory layer (23), it can be composed of various refractory fillers, such as magnesium hydroxide (MDH), aluminum hydroxide (ATH), mineral powders such as quartz or wollastonite, mineral fibers, and glass fibers, added to silicone rubber as a base resin.

[0074] The silicone rubber used as the above-mentioned refractory elastomer material may be a polymer in which silicon (Si) containing organic groups and oxygen are chemically bonded and connected to each other by siloxane bonds. Due to these siloxane bonds, it exhibits excellent bonding stability at high temperatures, making it suitable as a refractory material. In addition, silicone rubber has a relatively low heat release rate and does not emit toxic gases during combustion, thus having the advantage of being an eco-friendly refractory material.

[0075] The refractory silicone rubber as a refractory elastomer material constituting the refractory layer (23) may include silicone rubber as a base resin and a refractory filler, and thus, even if the refractory coaxial cable (100) is placed in a high-temperature environment and the silicone rubber undergoes some thermal decomposition, oxidation, or combustion, it can achieve sufficient fire resistance performance to maintain a separation structure between the inner conductor (10) and the outer conductor (30) of the refractory coaxial cable (100).

[0076] Meanwhile, since the refractory silicone rubber constituting the refractory layer (23) has relatively high flexibility and ductility, shape deformation such as stretching of the refractory layer (23) may occur during the process of winding the insulator (20) around the outside of the inner conductor (10).

[0077] Accordingly, the insulator (20) is provided with an insulating core (21) in the shape of a long wire, rope, or thread embedded inside, so that tension is applied in the longitudinal direction when the insulator (20) is wound transversely, thereby preventing the sagging of the fire-resistant layer (23).

[0078] To apply the above tension, the insulating core (21) may be configured to include a tension member. The tension member may be composed of fiber yarns such as reinforcing fibers, for example, basalt fibers, glass fibers, silica fibers, ceramic fibers, or aramid fiber materials. In particular, it may include glass yarn, which has high fire resistance and is easy to process.

[0079] The glass yarn constituting the insulating core (21) can be formed by twisting hundreds of fine inorganic glass fibers of 5 μm to 13 μm, obtained by melting and spinning selected raw materials at a high temperature of 1,200 to 1,500°C, into a yarn shape.

[0080] The insulating core (21) may have a long fiber, wire, or rope shape to maintain the shape of the insulator (20) and reinforce tensile strength, and may include a tensile member to have a higher tensile strength than the fire-resistant layer (23), and preferably, the tensile strength may be 5 g / TEX or higher. The tensile strength of the insulating core (21) including the tensile member may be a value measured by the ASTM D885 standard test method. If the tensile strength of the insulating core (21) is less than 5 g / TEX, the insulator (20), which mainly consists of the fire-resistant layer (23) made of an elastomer material, may easily stretch and deform, making it difficult to maintain a constant coaxial structure between the inner conductor and the outer conductor in the cable manufacturing and usage environment.

[0081] The outer diameter of the insulating core (21) may be 30% or less of the outer diameter of the refractory layer (23). If the outer diameter of the insulating core (21) is 30% or more of the outer diameter of the refractory layer (23), the flexibility of the insulator (20) decreases, the adhesion between the insulator (20) and the inner conductor (10) decreases, and workability may be reduced or cracks may occur during transverse winding. That is, if the outer diameter of the insulating core (21), which is made of a non-flexible material and is embedded inside the refractory layer (23) made of a flexible material constituting the insulator (20), is too large, the structural stability of the coaxial structure in which the insulator (20) is interposed decreases, a large force is required during transverse winding, and the insulator (20) may be damaged during the transverse winding process.

[0082] Additionally, the insulating core (21) may contain an insulating material with higher fire resistance performance than the fire-resistant layer (23), so that the temperature at which shape deformation occurs in a high-temperature environment may be higher. For example, even if the fire-resistant layer (23) deforms in extreme conditions of 1000°C or higher, the insulating core (21) may be configured to separate the inner conductor (10) and the outer conductor (30) so that the fire-resistant coaxial cable maintains its function as a cable.

[0083] In this way, the insulator (20) constituting the fire-resistant coaxial cable (100) according to the present invention is configured to include an insulating core (21) and a fire-resistant layer (23) that surrounds the insulator and is composed of a fire-resistant composition, thereby ensuring excellent fire resistance performance at high temperatures of 750°C or higher, which is the test temperature of standards IEC 60331-11 and IEC 60331-23, while maintaining the internal structure between the inner and outer conductors by the insulator (20).

[0084] The outer conductor (30) forms a coaxial structure with the inner conductor (10) and is provided spaced apart from the inner conductor (10).

[0085] In this way, the fire-resistant coaxial cable (100) according to the present invention is formed in a coaxial structure in which the inner conductor (10) and the outer conductor (30) have the same central axis.

[0086] Typically, a coaxial cable is generally made of a flexible and thin metal material as the outer conductor (30), but the outer conductor (30) constituting the fire-resistant coaxial cable (100) according to the present invention may be made of a metal material with excellent rigidity to maintain a gap with the inner conductor (10) to secure electrical characteristics, and preferably, the outer conductor (30) may be made of copper or a copper alloy material, just like the inner conductor (10).

[0087] And, the outer conductor (30) is formed with a corrugation structure in which corrugated peaks and corrugated grooves are repeatedly formed, and the flexibility and rigidity of the outer conductor (30) can be reinforced by the corrugation structure.

[0088] Additionally, the thickness of the outer conductor (30) may be configured in the range of 0.14 millimeters (mm) to 0.45 millimeters (mm). If the thickness of the outer conductor (30) is less than 0.14 millimeters (mm), the rigidity is insufficient and the gap between the inner conductor (10) and the outer conductor (30) cannot be maintained effectively, whereas if the thickness is greater than 0.45 millimeters (mm), the bending characteristics are reduced and damage to the outer conductor (30) may easily occur due to cable bending or kinking.

[0089] The outer side of the above outer conductor (30) may be covered with a cable jacket (40). The cable jacket (40) may be made of polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polyethylene (PE), etc., as a base resin, and may be composed of an insulating composition in which a refractory filler is added to the base resin as needed.

[0090] FIG. 5 shows a cross-sectional view of another embodiment of a fire-resistant coaxial cable according to the present invention.

[0091] As illustrated in FIG. 5, another embodiment of the fire-resistant coaxial cable (100) according to the present invention is configured to include an inner conductor (10), an insulator (20) including an insulating core (21) and a fire-resistant layer (23), an outer conductor (30), and a cable jacket (40), similar to the embodiment illustrated in FIG. 4, wherein the fire-resistant coaxial cable (100) may further include a low dielectric constant layer (50) surrounding the outer circumference of the insulator (20). A detailed description of the inner conductor (10), insulator (20), outer conductor (30), and cable jacket (40) constituting the fire-resistant coaxial cable (100) of the present invention in the embodiment illustrated in FIG. 5 is omitted as it overlaps with the description with reference to FIG. 4.

[0092] The fire-resistant coaxial cable (100) according to the present invention may additionally have a low dielectric constant layer (50) that wraps around the outer surface of the insulator (20) in the longitudinal direction. The low dielectric constant layer (50) may be configured to reduce the dielectric constant of the coaxial cable.

[0093] The low dielectric constant layer (50) may be composed of a layer having a dielectric constant of 2.5 or less. The low dielectric constant layer (50) may be composed of one or at least two low dielectric constant materials selected from PE (Polyethylene), HDPE (High-Density Polyethylene), PTFE (Polytetrafluoroethylene), and FEP (Fluorinated ethylene propylene). Additionally, the low dielectric constant material may be coated on the outside of the insulator (20).

[0094] When the fire-resistant coaxial cable (100) according to the present invention further comprises a low dielectric constant layer (50) that wraps around the outer surface of the insulator (20), the fiber yarn constituting the insulating core (21) of the insulator (20) may include glass yarn, and the fire-resistant layer (23) of the insulator (20) may be composed of fire-resistant silicone rubber.

[0095] In this way, a low dielectric constant material is coated on the outside of the insulator (20) to form a low dielectric constant layer (50), and the insulator (20) is wound transversely on the outside of the inner conductor (10) in a preset pitch range to form an insulating structure between the inner conductor (10) and the outer conductor (30), thereby reducing the dielectric constant while maintaining fire resistance performance, and through this reduction in dielectric constant, the original communication performance of the coaxial cable can be improved.

[0096] Additionally, an insulating fire-resistant reinforcing layer (not shown) having high fire resistance characteristics may be further provided, which wraps around the outer side of the insulator (20) in the longitudinal direction on the outer side of the low dielectric constant layer (50) or on the inner side of the low dielectric constant layer (50). Furthermore, since the insulating fire-resistant reinforcing layer wraps around the outer side of the insulator (20), mutual contact between the inner conductor (10) and the outer conductor (30) can be blocked, thereby strengthening the insulation function between the inner conductor (10) and the outer conductor (30).

[0097] The above-mentioned insulation fire-resistant reinforcing layer may be composed of one or at least two high-fire-resistant insulating materials selected from basalt fibers, mica tape, silica fibers, ceramic fibers, and glass fibers.

[0098] The basalt fibers constituting the above insulating fire-resistant reinforcing layer can be manufactured by melting basalt powder made of basalt material at 1,500°C and spinning it into filaments with a size of 9㎛ to 20㎛ using centrifugal force.

[0099] The chemical composition of basalt is high in CaO, MgO, FeO+Fe2O3, and has a SiO2 content of 52% or less. Due to this chemical composition, basalt has excellent chemical properties and is characterized by excellent heat resistance at high temperatures.

[0100] The basalt fibers constituting the above-mentioned insulating fire-resistant reinforcing layer may be configured in a braided form or in a coated form by applying a coating material such as a carbon-based, silicone-based, or urethane-based coating material to the basalt fibers.

[0101] The mica tape constituting the above-mentioned insulation fire-resistant reinforcement layer can be manufactured in the form of a tape by adhering white mica powder (soft mica, hard mica) obtained from the natural mineral muscovite onto a PE film or glass fiber fabric. At this time, the number of windings of the mica tape can be varied depending on the required fire-resistant performance, cable structure, and application.

[0102] The glass fibers constituting the above insulating fire-resistant reinforcing layer can be either long fibers produced by drawing molten glass at high speed and winding it, or short fibers produced by blowing molten glass into a planar shape using a centrifugal force method or a flame method.

[0103] Here, the glass fiber constituting the insulating fire-resistant reinforcing layer may be provided in the form of a glass tape by bonding glass fibers coated with silicone adhesive or acrylic adhesive, etc. to a polymer substrate. Additionally, the glass fiber constituting the insulating fire-resistant reinforcing layer may be provided in the form of glass fibers wound transversely on the outer surface of the fire-resistant layer (23) and glass yarn coated using a non-metallic or metallic coating material.

[0104] The fire-resistant coaxial cable (100) according to the present invention may further reinforce the fire-resistant and insulation functions through the insulator by additionally providing an insulation fire-resistant reinforcing layer on the outer side of the insulator (20) or on the outer side of the low dielectric constant layer (50). For example, the fire-resistant coaxial cable (100) according to the present invention can maintain cable functions for a certain period of time even at high temperatures of 1000°C or higher.

[0105] Additionally, the insulating fire-resistant reinforcing layer surrounding the outer side of the insulator (20) may include an insulating material with higher fire resistance performance than the fire-resistant layer (23), so that the temperature at which shape deformation occurs in a high-temperature environment may be higher. For example, even if the fire-resistant layer (23) deforms in extreme conditions of 1000°C or higher, the insulating fire-resistant reinforcing layer may be configured to separate the inner conductor (10) and the outer conductor (30) so that the cable can maintain its communication function.

[0106] To verify the performance of the insulation of the fire-resistant coaxial cable constructed in this manner, coaxial cables were manufactured by configuring the insulation of Examples 1 to 3 and Comparative Examples 1 to 3 with various materials, and transverse winding workability of the insulation being transversely wound on the outer side of the inner conductor, a pulling force test to measure the adhesion of the insulation, a fire resistance test to verify fire resistance performance, and a test to measure the amount of attenuation according to the spiral insulation structure and the material of the insulation were performed. Here, the outer diameter of the inner conductor of Examples 1 to 3 and Comparative Examples 1 to 3 was 3.6 mm, the outer diameter of the insulation was 3.1 mm, and the transverse winding pitch of the insulation was 25 mm for the tests. The results in Table 1 below are the results of the above tests for Examples 1 to 3 and Comparative Examples 1 to 3.

[0107] [Table 1]

[0108]

[0109] Specifically, Example 1 is an example in which an insulating core (21) constituting an insulator (20) comprises glass yarn and a refractory layer (23) comprises silicone rubber, and a low dielectric constant layer (50) surrounding the outer surface of the insulator (20) is provided, and the material of the low dielectric constant layer (50) is an HDPE coating; Example 2 is an example in which an insulating core (21) constituting an insulator (20) comprises glass yarn and a refractory layer (23) comprises silicone rubber; Example 3 is an example in which an insulating core (21) constituting an insulator (20) comprises glass yarn and a refractory layer (23) comprises fluororubber; Comparative Example 1 is a comparative example in which the entire insulator (20) is composed of basalt; Comparative Example 2 is a comparative example in which the entire insulator (20) is composed of polyethylene (PE) material; and Comparative Example 3 is a comparative example in which an insulating core (21) constituting an insulator (20) comprises silica and a refractory layer (23) comprises a ceramic refractory layer. This is a comparative example.

[0110] The evaluation of the transverse winding workability of the insulator on the outer side of the inner conductor was classified into good and poor by visually assessing the degree to which the insulator breaks or surface damage occurs when the insulator is transversely wound on the inner conductor. In the case of poor transverse winding workability, when the insulator is transversely wound on the outer side of the inner conductor, the transversely wound insulator cannot stably maintain the separation structure between the inner conductor and the outer conductor.

[0111] Examples 1 to 3, in which the refractory layer (23) constituting the insulator comprises silicone rubber or fluororubber, and Comparative Example 2, in which the insulator is composed of polyethylene (PE), had good transverse winding workability because there was no damage to the insulator when the insulator was transversely wound due to the flexibility of the material. However, Comparative Examples 1 and 3, in which the insulator is composed of a basalt or ceramic refractory layer that is not flexible and is hard, had poor transverse winding workability because fracture of the insulator and destruction of the surface occurred when the insulator was transversely wound on the outside of the inner conductor.

[0112] In addition, as previously mentioned, when the maximum pulling force in the pulling force test for measuring the adhesion of the aforementioned insulator (20) is less than 2 kgf, the outer conductor and the inner conductor are easily separated by a small force, and structural damage between the inner conductor and the outer conductor can easily occur due to external tensile force, and it is difficult to guarantee the reliability of the cable during installation and use.

[0113] Examples 1 to 3 and Comparative Example 2, which have flexible insulators, have excellent transverse winding workability as well as insulator adhesion, and have a maximum pulling force of 2 kgf or more, whereas Comparative Examples 1 and 3, which are made of a rigid material without insulator flexibility, have poor transverse winding workability and consequently fail to adhere between the inner conductor and the outer conductor, resulting in a maximum pulling force of less than 2 kgf and thus failing to pass the pulling force test.

[0114] FIG. 6 shows the results of the Pulling Force Test for specimens of Examples 1 to 3 and Comparisons 1 to 3.

[0115] As described above, for the Pulling Force Test, a fire-resistant coaxial cable specimen with a length of 500 mm is prepared, and while the outer conductor is fixed, the inner conductor is pulled at a speed of 50.0 mm / min in the axial direction of the inner conductor, the elongation (mm) of the inner conductor and the load at that time are measured, and the load at the moment when the load becomes maximum is measured as the Max Pulling Force.

[0116] As shown in FIG. 6, in the case of Examples 1 to 3 and Comparative Example 2, the maximum pulling force was 16.2 kgf, 20.7 kgf, 7.1 kgf, and 4.9 kgf, respectively, satisfying the acceptance criterion of 2 kgf or more for the pulling force test; however, in the case of Comparative Examples 1 and 3, the maximum pulling force was 1.4 kgf and 1.0 kgf, respectively, failing the pulling force test, which confirms that the adhesion of the insulator is poor.

[0117] The fire resistance test is conducted by applying the aforementioned international standard fire resistance specifications IEC 60331-11 and IEC 60331-23. A coaxial cable specimen (length: 1,200 mm) is installed horizontally on the ground on a support, and the jackets at both ends of the specimen are stripped by about 100 mm. Then, the inner conductor and the outer conductor are connected to a voltage application device so that they do not come into contact with each other. The center of the burner that applies the flame is positioned 70 ± 10 mm below the bottom edge of the specimen, and the front surface of the burner and the vertical center surface of the specimen are spaced 45 mm apart. A flame of 750°C is applied for 90 minutes. During the application of the flame, the voltage must be maintained, the inner conductor and the outer conductor must not short-circuit, and the conductor must not rupture or break.

[0118] Examples 1 to 3 and Comparative Examples 1 and 3, in which a refractory material was applied as the insulator, passed the fire resistance test, but Comparative Example 2, in which a material with a low melting point was used, failed the fire resistance test.

[0119] The attenuation measurement test to determine the attenuation amount based on the spiral insulation structure and the material of the insulator was performed by measuring the attenuation amount when transmitting a 450 MHz test signal. A lower attenuation amount indicates superior performance of the communication cable.

[0120] In particular, excellent communication performance can be guaranteed when the attenuation is less than 16 (dB / 100m) based on a 450MHz test signal. As a result of the test, the attenuation of Examples 1 to 3 and Comparative Example 2 was measured at 10.9 (dB / 100m), 13.87 (dB / 100m), 15.29 (dB / 100m), and 9.18 (dB / 100m), respectively, which is lower than the passing criterion of 16 (dB / 100m), thus ensuring excellent communication performance. However, Comparative Examples 1 and 3 were measured at 18.3 (dB / 100m) and 16.6 (dB / 100m), respectively, which is relatively high and did not satisfy the condition of being less than 16 (dB / 100m), which is the test criterion. It is believed that this is because the insulator is composed of a material with a high dielectric constant.

[0121] Therefore, summarizing the results of Table 1, Examples 1 to 3 satisfy the fire resistance performance of the insulator during a fire, while also satisfying the condition that the transverse winding workability of the insulator is good and the maximum pulling force in the pulling force test is 2 kgf or more, thereby ensuring close contact between the insulator and the conductor, and thus it is judged that the structure of the fire-resistant coaxial cable including the insulator can be maintained stably.

[0122] In particular, it can be confirmed that Examples 1 and 2, which use silicone rubber as the main material for the insulator, have a low attenuation amount and can perform communication functions more advantageously. In particular, Example 1 has the characteristic of being able to perform fire-resistant functions while having a low attenuation amount because an HDPE coating, which is a low dielectric constant layer, is applied to the outer side of the insulator, so the dielectric constant between the inner conductor and the outer conductor is low.

[0123] FIG. 7 illustrates a cross-sectional view of another embodiment of a fire-resistant coaxial cable according to the present invention.

[0124] As illustrated in FIG. 7, another embodiment of the fire-resistant coaxial cable (100) according to the present invention is configured to include an inner conductor (10), an insulator (20) including an insulating core (21) and a fire-resistant layer (23), an outer conductor (30), a cable jacket (40), a low dielectric constant layer (50), and an insulating fire-resistant reinforcing layer, similar to the embodiment illustrated in FIG. 5, and may further include a fire-resistant tape layer (60) that wraps around the outer circumference of the outer conductor (30) to reinforce the fire-resistant performance of the fire-resistant coaxial cable (100).

[0125] In the embodiment illustrated in FIG. 7, content that overlaps with the description with reference to FIG. 4 and FIG. 5 will be omitted.

[0126] The fire-resistant coaxial cable (100) according to the present invention may have a fire-resistant tape layer (60) having high fire resistance characteristics that wraps around the outer side of the outer conductor (30) in the longitudinal direction.

[0127] The fire-resistant tape layer (60) may be composed of one or at least two high-fire-resistant materials, such as fire-resistant tape, for example, mica tape, glass tape, and metal tape. In this way, the fire-resistant tape layer (60) is composed of a tape member, which can secure the flexibility and bending characteristics of the fire-resistant coaxial cable (100).

[0128] The description regarding the mica tape or glass tape constituting the above fireproof tape layer (60) is the same as that described in the insulation fireproof reinforcing layer.

[0129] The metal tape constituting the above fireproof tape layer (60) may be made of a fireproof metal material such as copper, aluminum, iron and copper alloy, aluminum alloy, etc.

[0130] As illustrated in FIG. 7, when the fire-resistant coaxial cable (100) according to the present invention is equipped with the fire-resistant tape layer (60), the fire-resistant tape layer (60) additionally performs a fire-resistant function in addition to the insulator (20) and the insulation fire-resistant reinforcing layer, so that the fire-resistant coaxial cable (100) according to the present invention has excellent fire resistance even at high temperatures of 1000°C or higher and can maintain the cable function for a certain period of time.

[0131] FIG. 8 shows a cross-sectional view of another embodiment of a fire-resistant coaxial cable according to the present invention.

[0132] As illustrated in FIG. 8, another embodiment of the fire-resistant coaxial cable (100) according to the present invention is configured to include an inner conductor (10), an insulator (20) including an insulating core (21) and a fire-resistant layer (23), an outer conductor (30), a cable jacket (40), a low dielectric constant layer (50), an insulating fire-resistant reinforcing layer, and a fire-resistant tape layer (60), similar to the embodiment illustrated in FIG. 7, wherein the fire-resistant coaxial cable (100) may further be provided with a conductor fire-resistant reinforcing layer (70) that wraps around the outer circumference of the inner conductor (10) to further improve fire-resistant performance.

[0133] In the embodiment illustrated in FIG. 8, content that overlaps with the description with reference to FIG. 4, FIG. 5, and FIG. 7 will be omitted.

[0134] The fire-resistant coaxial cable (100) according to the present invention may be provided with a conductor fire-resistant reinforcing layer (70) having high fire resistance characteristics that wraps around the outer surface of an inner conductor (10) placed in the center in the longitudinal direction.

[0135] The above conductor fire-resistant reinforcing layer (70) may be composed of one or at least two high-fire-resistant insulating materials such as basalt fiber, silica fiber, ceramic fiber, glass fiber, and mica tape, similar to the insulating fire-resistant reinforcing layer. Each fire-resistant material of the above conductor fire-resistant reinforcing layer (70) is as described in the insulating fire-resistant reinforcing layer.

[0136] As illustrated in FIG. 8, when the fire-resistant coaxial cable (100) according to the present invention is equipped with a conductor fire-resistant reinforcing layer (70), the conductor fire-resistant reinforcing layer (70) additionally performs a fire-resistant function in addition to the insulator (20), the insulating fire-resistant reinforcing layer and the fire-resistant tape layer (60), so that the fire-resistant coaxial cable (100) according to the present invention has excellent fire resistance even at high temperatures of 1000°C or higher and can maintain the fire-resistant coaxial cable function for a certain period of time.

[0137] Furthermore, in addition to the function of further improving the fire resistance performance of the cable, the conductor fire-resistant reinforcing layer (70) can reinforce the insulation function of the inner conductor (10) by preventing a short circuit caused by mutual contact between the inner conductor (10) and the outer conductor (30).

[0138] The above conductor fire-resistant reinforcing layer (70) may include an insulating material with higher fire resistance performance than the fire-resistant layer (23), so that the temperature at which shape deformation occurs in a high-temperature environment may be higher. For example, even if the fire-resistant layer (23) deforms in extreme conditions of 1000°C or higher, the conductor fire-resistant reinforcing layer (70) may be configured to separate the inner conductor (10) and the outer conductor (30) so that the fire-resistant coaxial cable (100) maintains the function of the cable for a certain period of time.

[0139] Here, the fire-resistant coaxial cable (100) according to the present invention is presented as including all of the low dielectric constant layer (50), the insulating fire-resistant reinforcing layer, the fire-resistant tape layer (60), and the conductor fire-resistant reinforcing layer (70), but in addition to this, it may be configured to include one or at least two of the low dielectric constant layer (50), the insulating fire-resistant reinforcing layer, the fire-resistant tape layer (60), and the conductor fire-resistant reinforcing layer (70).

[0140] FIG. 9 shows a cross-sectional view of another embodiment of a fire-resistant coaxial cable according to the present invention.

[0141] As illustrated in FIG. 9, the fire-resistant coaxial cable (100) according to the present invention is configured to include an inner conductor (10), an insulator (20) comprising an insulating core (21') inside and a fire-resistant layer (23') outside, an outer conductor (30), and a cable jacket (40), as in the embodiment illustrated in FIG. 4. In the embodiment illustrated in FIG. 9, the insulator (20) may be configured to include a material other than glass yarn as the insulating core (21') material and a fire-resistant material other than fire-resistant silicone rubber as the fire-resistant layer (23') material.

[0142] Specifically, the insulating core (21') of the insulator (20) comprises flexible polyethylene with a low dielectric constant, and the refractory layer (23') of the insulator (20) may be composed of one or at least two high-refractory insulating materials selected from basalt fibers, silica fibers, ceramic fibers, glass fibers, and mica tape. Accordingly, an insulator (20) can be constructed that maintains refractory performance while achieving low dielectric constant and flexibility.

[0143] If the above refractory layer (23') includes basalt fibers, the basalt fibers may be configured in a braided or coated form.

[0144] If the above refractory layer (23') includes glass fibers, it may be configured in the form of a tape or a coated form of glass fibers.

[0145] The above refractory layer (23') may be composed of a refractory member having high fire resistance characteristics that wraps around the outer surface of the insulating core (21') in the longitudinal direction. The insulator (20) is provided with a refractory layer (23') composed of one or at least two high fire resistance insulating materials among basalt fiber, mica tape, and glass fiber, so that even if the insulating core (21'), which has a relatively low melting point, is completely burned or melted at a high temperature, the refractory layer (23') placed on the outside of the insulating core (21') remains and can perform the fire resistance function.

[0146] Here, in the fire-resistant coaxial cable according to the present invention, a low dielectric constant layer (50) (see FIG. 5, FIG. 7 and FIG. 8) or an insulating fire-resistant reinforcing layer provided on the outside of the insulator (20) may be omitted. This is because the insulating core (21') of the insulator (20) already contains polyethylene and thus has a sufficiently low dielectric constant, and the fire-resistant layer (23') is already composed of a fire-resistant material such as basalt fiber, mica tape, or glass fiber. In addition, as shown in FIG. 9, the fire-resistant coaxial cable (100) according to the present invention applies a high fire-resistant material to the fire-resistant layer (23') of the insulator (20), and further includes one or more of a fire-resistant tape layer (60) surrounding the outer conductor (30) or a conductor fire-resistant reinforcing layer (70) surrounding the inner conductor (10), thereby securing excellent fire-resistant performance even at high temperatures of 1000°C or higher and maintaining the cable function for a certain period of time.

[0147] The fire-resistant coaxial cable (100) according to the present invention can be applied to various environments, such as specific fire-fighting targets where wireless communication auxiliary equipment must be installed, other buildings, road tunnels, hazardous material storage and processing facilities, and underground facilities.

[0149] [Examples according to the structure of the insulator]

[0151] 1. Preparation Example

[0153] Coaxial cable specimens were manufactured according to the design described in Table 2 below. Examples 4 to 7 and Comparative Examples 4 to 6 follow the structure of FIG. 4, and the inner conductor and outer conductor were made of copper, and the insulator was made by applying silicone rubber and glass yarn as the refractory layer and insulating core, respectively.

[0155] [Table 2]

[0156]

[0158] 2. Evaluation of physical properties

[0160] 1) Evaluation of fire resistance properties

[0161] Each of the coaxial cable specimens (length: 1,200 mm) of Examples 4 to 7 and Comparative Examples 4 to 6 is installed horizontally on the ground on a support, and the jackets at both ends of the specimen are stripped by about 100 mm so that the inner conductor and the outer conductor do not come into contact with each other. Then, the center of the burner that applies the flame is positioned 70 ± 10 mm below the bottom of the specimen and the front of the burner is spaced 45 mm apart from the center of the specimen, and a flame of 750°C is applied for 90 minutes. During the application of the flame, the voltage must be maintained and the conductor must not rupture or break.

[0163] 2) Characteristic Impedance Evaluation

[0164] For each of the coaxial cable specimens (length: 100 m) of Examples 4 to 7 and Comparative Examples 4 to 6, the characteristic impedance was measured by measuring the average value of the corresponding frequency in the frequency band of 30 to 1000 MHz using a network analyzer, and it must be 45 to 55 Ω.

[0166] 3) Flexibility evaluation

[0167] Each of the coaxial cable specimens in Examples 4 to 7 and Comparative Examples 4 to 6 was wound once on a circular mandrel with a diameter of 120 mm when the corrugation shape of the coaxial cable was spiral, and once on a circular mandrel with a diameter of 280 mm when the corrugation shape of the coaxial cable was annular, and the workability of the operator was evaluated. If excessive force was required when wound once compared to a cable of similar size, it was evaluated as defective.

[0169] 4) Structural Stability (Short) Evaluation

[0170] Each of the coaxial cable specimens of Examples 4 to 7 and Comparative Examples 4 to 6 was wound once on a circular mandrel with a diameter of 120 mm when the corrugation shape of the coaxial cable was spiral, and once on a circular mandrel with a diameter of 280 mm when the corrugation shape of the coaxial cable was annular. A multimeter was connected to the inner conductor and the outer conductor to evaluate whether the inner conductor and the outer conductor were in contact, and if they were in contact, it was evaluated as a failure.

[0172] The results of the above physical property evaluation are as described in Table 3 below.

[0174] [Table 3]

[0175]

[0176] As described in Table 3 above, the coaxial cable specimens of Examples 4 to 7, in which the inclination angle and outer diameter of the insulator were precisely designed during transverse winding, were confirmed to have excellent fire resistance, characteristic impedance, flexibility, and structural stability.

[0177] Meanwhile, it was confirmed that in the coaxial cable specimen of Comparative Example 4, a short circuit occurred due to contact between the inner conductor and the outer conductor when bent because the inclination angle during transverse winding of the insulator did not meet the standard, in the coaxial cable specimen of Comparative Example 5, the characteristic impedance exceeded the standard value and flexibility decreased and manufacturing costs increased because the inclination angle during transverse winding of the insulator exceeded the standard, and in the coaxial cable specimen of Comparative Example 6, the characteristic impedance decreased due to insufficient spacing between the inner conductor and the outer conductor because the outer diameter of the insulator did not meet the standard.

[0178] Although this specification has been described with reference to preferred embodiments of the present invention, those skilled in the art may modify and change the present invention in various ways without departing from the spirit and scope of the present invention as described in the claims below. Therefore, if a modified embodiment basically includes the components of the claims of the present invention, it should be considered to be included within the technical scope of the present invention. Explanation of the symbols

[0179] 100 : Fireproof coaxial cable 10: Internal conductor 20 : Insulator 30: Outer conductor 40: Cable Jacket

Claims

Claim 1 A fire-resistant coaxial cable comprising: an inner conductor disposed in the center; an insulator transversely wound on the outer side of the inner conductor; a low dielectric constant layer disposed to surround the outer surface of the insulator; an outer conductor surrounding the outer side of the low dielectric constant layer and forming a coaxial structure with the inner conductor; and a cable jacket surrounding the outer side of the outer conductor; wherein the insulator comprises an insulating core and a fire-resistant layer surrounding the insulating core, the fire-resistant layer comprises silicone rubber, the outer diameter of the insulating core is 30% or less of the outer diameter of the fire-resistant layer, the insulating core of the insulator comprises a tension member, the tension member comprises at least one of basalt fiber, glass fiber, silica fiber, ceramic fiber, or aramid fiber material, and the low dielectric constant layer comprises HDPE (High-Density Polyethylene). Claim 2 A fire-resistant coaxial cable comprising: an inner conductor disposed in the center; an insulator transversely wound on the outer side of the inner conductor; a low dielectric constant layer disposed to surround the outer surface of the insulator and having a dielectric constant of 2.5 or less; an outer conductor surrounding the outer side of the low dielectric constant layer and forming a coaxial structure with the inner conductor; and a cable jacket surrounding the outer side of the outer conductor; wherein the insulator comprises an insulating core and a fire-resistant layer surrounding the insulating core, the fire-resistant layer comprises silicone rubber, the insulating core comprises a tension member, the tension member comprises at least one of basalt fiber, glass fiber, silica fiber, ceramic fiber, or aramid fiber material, and the low dielectric constant layer comprises HDPE (High-Density Polyethylene). Claim 3 delete Claim 4 delete Claim 5 delete Claim 6 A fire-resistant coaxial cable according to claim 1 or 2, characterized in that the tensile strength of the insulating core including the tensile member is 5 g / TEX or higher. Claim 7 delete Claim 8 A fire-resistant coaxial cable according to claim 1 or 2, characterized in that the tension member comprises glass yarn. Claim 9 A fire-resistant coaxial cable according to claim 1 or 2, characterized in that the insulating core has a higher temperature at which shape deformation occurs at a higher temperature than the fire-resistant layer. Claim 10 A fire-resistant coaxial cable according to claim 1 or 2, characterized in that the maximum load applied when fixing the outer conductor of the fire-resistant coaxial cable, which has a specimen length of 500 mm, and pulling the inner conductor in the axial direction of the inner conductor at a speed of 50.0 mm / min is 2 kgf or more. Claim 11 delete Claim 12 delete Claim 13 A fire-resistant coaxial cable according to claim 1 or 2, characterized by including an insulating fire-resistant reinforcing layer that surrounds the insulator and reinforces the fire-resistant performance of the fire-resistant coaxial cable. Claim 14 A fire-resistant coaxial cable according to claim 13, characterized in that the insulation fire-resistant reinforcing layer comprises at least one of basalt fiber, silica fiber, ceramic fiber, glass fiber, and mica tape. Claim 15 A fire-resistant coaxial cable according to claim 1 or 2, further comprising one or more fire-resistant tape layers wrapping around the outer side of the outer conductor to reinforce the fire-resistant performance of the fire-resistant coaxial cable. Claim 16 A fire-resistant coaxial cable according to claim 15, characterized in that the fire-resistant tape layer comprises at least one of mica tape, glass tape, and metal tape. Claim 17 A fire-resistant coaxial cable according to claim 1 or 2, further comprising a conductor fire-resistant reinforcing layer surrounding an inner conductor to reinforce the fire-resistant performance of the fire-resistant coaxial cable. Claim 18 A fire-resistant coaxial cable according to claim 17, characterized in that the conductor fire-resistant reinforcing layer comprises at least one of basalt fiber, silica fiber, ceramic fiber, glass fiber, and mica tape. Claim 19 A fire-resistant coaxial cable according to claim 1 or 2, characterized in that the inner conductor and the outer conductor are made of copper or a copper alloy. Claim 20 A fire-resistant coaxial cable according to claim 1 or 2, wherein the outer conductor has a corrugated tube structure in which corrugated peaks and corrugated grooves are repeatedly formed.

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