CN116953867A - Self-extinguishing type flame-retardant fire-resistant optical cable - Google Patents

Abstract

The application belongs to the technical field of optical cables, and provides a self-extinguishing type flame-retardant and fire-resistant optical cable, wherein a cladding sheath sequentially comprises a water blocking layer, an inner sheath layer, a fire extinguishing layer, an expandable graphite layer, a nonmetallic woven layer and an outer sheath layer from inside to outside, and the multi-layer cladding sheath layer has more excellent flame-retardant and fire-resistant performances; the cable core includes central skeleton unit and light unit, has the arc recess through the design surface, and inside has the central skeleton unit of reinforcing element and metal support to the inside strap and the flexible graphite paper of being provided with of arc recess can guarantee on the one hand that light unit keeps stable structure in less space, and on the other hand strap and flexible graphite paper form a fire prevention area, further play fire-retardant fire prevention's effect.

Description

Self-extinguishing type flame-retardant fire-resistant optical cable

Technical Field

The application relates to the technical field of optical cables, in particular to a self-extinguishing type flame-retardant fire-resistant optical cable.

Background

Fiber optic cable (optical fiber cable) is a communications cable assembly that utilizes one or more optical fibers disposed in a covering sheath as a transmission medium and may be used alone or in groups. In recent years, due to the rapid development of communication services in China, people are always concerned by producers and users while the demand for optical fiber products is continuously increasing. The flame-retardant optical cable is a novel optical cable capable of delaying fire and slowing down the propagation speed of fire, and after the flame-retardant optical cable is separated from the influence range of open fire, the combustion flame can be automatically extinguished rapidly, so that further fire damage can be avoided. The prior flame-retardant optical cable has been applied to the special communication occasions of comprehensive wiring in buildings, power communication industry, aviation industry, navigation industry, mining industry, rail transportation industry and various fire accidents easily caused.

A common measure for improving the combustion performance of conventional flame-retardant optical cables is to enhance the flame-retardant performance of the cable jacket material. However, because other non-flame-retardant substances or constituent elements are also present in the optical cable, even if expensive flame-retardant materials are adopted, the flame spread cannot be completely delayed when a fire disaster occurs; meanwhile, the internal structure of the optical cable can be easily damaged, so that transmission signals are interrupted, and the application of the optical cable in some occasions with higher safety level is affected.

Disclosure of Invention

In view of this, the present application provides a self-extinguishing flame-retardant fire-resistant optical cable.

In a first aspect, an embodiment of the present application provides a self-extinguishing flame-retardant and fire-resistant optical cable, including a cable core and a cladding sheath that cladding the cable core, where the cladding sheath is a water-blocking layer, an inner sheath, a fire extinguishing layer, an expandable graphite layer, a non-metal woven layer, and an outer sheath in order from inside to outside, the fire extinguishing layer includes a thermoplastic resin material attached between the expandable graphite layer and the inner sheath, a fire extinguishing capsule is disposed in the thermoplastic resin material, and a fire extinguishing agent is filled in the fire extinguishing capsule; the outer protective layer and the inner protective layer are made of low-smoke halogen-free flame retardant materials; the cable core comprises a central framework unit and a light unit, wherein an arc-shaped groove is formed in the outer surface of the central framework unit along the extending direction of the optical cable, the light unit is arranged in the arc-shaped groove, a reinforcing element is arranged in the center of the central framework unit along the extending direction of the optical cable, a metal supporting piece is embedded in the central framework unit along the extending direction of the optical cable, and the metal supporting piece is arranged on the periphery of the reinforcing element.

In some embodiments, the maximum outer diameter of the metal support is in contact with the lowest point of the arcuate groove.

In some embodiments, the metal support is a stainless steel wire armored helically along the periphery of the reinforcing element.

In some embodiments, the inner surface of the arc-shaped groove is attached with a metal belt, one side of the metal belt, facing the light unit, is attached with flexible graphite paper, the metal belt is a corrugated steel belt or a corrugated aluminum belt, the thickness of the flexible graphite paper is 0.03-0.08 mm, and the flexible graphite paper is completely attached to the surface of the metal belt.

In some embodiments, the expandable graphite layer is formed by bonding expandable graphite with a high temperature resistant adhesive on a side of the non-metallic braid facing the fire extinguishing layer.

In some embodiments, the fire-extinguishing capsules are uniformly arranged in the thermoplastic resin material along the circumferential direction, and capillary communication is used between the fire-extinguishing capsules to form a whole.

In some embodiments, the fire extinguishing agent is at least one of a flame retardant ultra-fine solid powder mixture, a nano-substrate composite metal oxide, an inert gas, and a non-combustible gas having a particle size of 0.5 μm or less.

In some embodiments, the light unit sequentially comprises a first plastic layer, a fire-resistant layer, a second plastic layer, a water-blocking material and an optical fiber from outside to inside, wherein the thermal deformation temperature, the thermal decomposition temperature and the melting point of the first plastic layer are all greater than those of the second plastic layer, the fire-resistant layer is a polyimide composite adhesive tape coated by mica powder, and the first plastic layer, the fire-resistant layer and the second plastic layer are formed by three-layer coextrusion; the water-blocking material is water-blocking yarn.

In some embodiments, the optical fibers within the light unit are bound by a binding element to form a whole.

In some embodiments, the optical fiber has a plastic coating or a resin coating.

The application has the beneficial effects.

The self-extinguishing type flame-retardant fire-resistant optical cable provided by the application has excellent flame retardant property and self-extinguishing property, and the cladding sheath sequentially comprises a waterproof layer, an inner protective layer, a fire extinguishing layer, an expandable graphite layer, a nonmetallic woven layer and an outer protective layer from inside to outside. The outer protective layer and the inner protective layer are made of low-smoke halogen-free flame retardant materials, so that flame spread and toxic smoke generation can be restrained. The expandable graphite layer can expand in the flame combustion process, so that flame is choked, and meanwhile, the generated graphite expansion body material covers the surface of the inner protective layer, so that contact between the inner material and oxygen can be isolated, and heat energy transmission inwards is delayed. The non-metal braiding layer has a multi-mesh and fluffy fiber structure, so that space can be provided for graphite expansion, and meanwhile, the glass fiber braiding belt can ensure that expandable graphite does not fall off in the combustion expansion process, so that the structural stability of the fireproof layer is improved. When the temperature of the fire extinguishing layer rises when encountering heat, the thermoplastic resin material can be slowly softened and even gradually decomposed to provide an expansion space for the expandable graphite, and meanwhile, the fire extinguishing capsule is influenced by the extrusion and high temperature of the expandable graphite, and the thin-wall plastic layer of the fire extinguishing capsule can be damaged, so that the filled fire extinguishing agent is released, the temperature of the fire extinguishing agent is reduced or the oxygen is isolated, the flame retardant effect is further achieved, and the flame or heat transfer to the inner protective layer is delayed or prevented. The cable core comprises a central skeleton unit and an optical unit, wherein an arc-shaped groove is formed in the surface of the cable core, a reinforcing element and a central skeleton unit of a metal support piece are arranged in the cable core, so that the position stability of the optical unit in the cable core is enhanced, even if an internal thermoplastic material is melted at a high temperature, the position of the optical unit is limited in a certain range due to the support of the metal support piece, the situation that the optical unit cannot maintain the original stable position and moves in the cable core due to the fact that the thermoplastic material in the cable core is melted at a high temperature is avoided, the situation of distortion occurs, and the risk of embrittlement and fracture of an optical fiber caused by damage of the external environment or mechanical stress of the optical fiber is reduced. The self-extinguishing type flame-retardant fire-resistant optical cable has the advantages that the multi-layer cladding sheath layer and the cable core are designed in structure, and the flame-retardant and fire-resistant performances are more excellent.

In addition, in some embodiment examples, the inside strap and the flexible graphite paper of being provided with of arc recess, strap and flexible graphite paper form a fire prevention area, and the strap improves the compressive property of recess, also can not take place to warp when meeting high temperature, and flexible graphite paper utilizes graphite to meet high temperature or burning, can take place to expand, can cladding recess internal light unit, further plays fire-retardant fire prevention's effect.

In order to make the above objects, features and advantages of the present application more comprehensible, preferred embodiments accompanied with figures are described in detail below.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic view showing the structure of a self-extinguishing flame-retardant and fire-resistant optical cable according to the present application;

fig. 2 shows a schematic structure of a light unit according to the application.

Wherein: 1-outer sheath, 2-nonmetallic braid, 3-expandable graphite layer, 4-fire extinguishing layer, 5-inner sheath, 6-water blocking layer, 7-light unit, 8-metal support, 9-reinforcing element, 10-metal tape, 11-flexible graphite paper, 12-fire-proof layer, 13-cable core, 14-fire extinguishing unit, 15-central skeleton unit, 16-arc groove, 17-first plastic layer, 18-fire-proof layer, 19-second plastic layer, 20-optical fiber, 21-water blocking material.

Detailed Description

The term "comprising" in the description of the application and in the claims and in the drawings is synonymous with "including", "containing" or "characterized by", and is inclusive or open-ended and does not exclude additional unrecited elements or method steps. "comprising" is a technical term used in claim language to mean that the recited element is present, but other elements may be added and still form a construct or method within the scope of the recited claims.

It should be noted that: like reference numerals and letters in the following figures denote like items, and thus once an item is defined in one figure, no further definition or explanation of it is required in the following figures, and furthermore, the terms "first," "second," "third," etc. are used merely to distinguish one description from another and are not to be construed as indicating or implying relative importance. The term "about" in the present application is meant to encompass minor variations (up to +/-10%) from the stated values.

With the rapid development of communication services in China, people are concerned by producers and users all the time while the demand for optical products is continuously increased. It has been found in the present application that at present flame retardant optical cables: the heat insulation effect between the coating layer and the cable core is poor, so that external heat during combustion cannot be effectively prevented from being transmitted inwards, and the flame retardant property of the optical cable is affected; the position stability of the internal light unit is poor, the optical fiber surface of the optical cable is easy to wear, even damage and fracture in the fire disaster, and the communication safety in the fire disaster is affected; the fire-resistant flame-retardant material has poor adhesion and tightness, and is easy to fall off, so that the fire-resistant material cannot effectively resist fire.

In view of this, some embodiments of the present application provide a self-extinguishing flame-retardant and fire-resistant optical cable, including a cable core and a covering sheath covering the cable core, where the covering sheath is a water-resistant layer, an inner protective layer, a fire extinguishing layer, an expandable graphite layer, a nonmetallic woven layer, and an outer protective layer in order from inside to outside, the fire extinguishing layer includes a thermoplastic resin material adhered between the expandable graphite layer and the inner protective layer, a fire extinguishing capsule is disposed in the thermoplastic resin material, and the fire extinguishing capsule is covered with a thin-wall plastic layer, and is filled with a fire extinguishing agent; the outer protective layer and the inner protective layer are made of low-smoke halogen-free flame retardant materials; the cable core comprises a central framework unit and a light unit, wherein an arc-shaped groove is formed in the outer surface of the central framework unit along the extending direction of the optical cable, the light unit is arranged in the arc-shaped groove, a metal belt is attached to the inner surface of the arc-shaped groove, and flexible graphite paper is attached to one side, facing the light unit, of the metal belt; the center of the center skeleton unit is provided with a reinforcing element along the extending direction of the optical cable, the center skeleton unit is internally provided with a metal support piece along the extending direction of the optical cable, and the metal support piece is arranged at the periphery of the reinforcing element.

The application provides a self-extinguishing flame-retardant fire-resistant optical cable, which comprises a water-resistant layer, an inner protective layer, a fire extinguishing layer, an expandable graphite layer, a nonmetallic woven layer and an outer protective layer from inside to outside. The outer protective layer and the inner protective layer are made of low-smoke halogen-free flame retardant materials, so that flame spread and toxic smoke generation can be restrained. The expandable graphite layer can expand in the flame combustion process, so that flame is choked, and meanwhile, the generated graphite expansion body material covers the surface of the inner protective layer, so that contact between the inner material and oxygen can be isolated, and heat energy transmission inwards is delayed. The non-metal braiding layer has a multi-mesh and fluffy fiber structure, so that space can be provided for graphite expansion, and meanwhile, the glass fiber braiding belt can ensure that expandable graphite does not fall off in the combustion expansion process, so that the structural stability of the fireproof layer is improved. When the temperature of the fire extinguishing layer rises when encountering heat, the thermoplastic resin material can be slowly softened and even gradually decomposed to provide expansion space for the expandable graphite, meanwhile, the fire extinguishing unit is affected by extrusion and high temperature of the expandable graphite, and the thin-wall plastic layer of the fire extinguishing unit can be damaged, so that the filled fire extinguishing agent is released, the temperature of the fire extinguishing agent is reduced or the oxygen is isolated, the flame retardant effect is further achieved, and flame or heat transfer to the inner protective layer is delayed or prevented. The cable core includes central skeleton unit and optical unit, there is the arc recess through the design surface, there is the central skeleton unit of reinforcing element and metal support in inside, and the inside strap and the flexible graphite paper of being provided with of arc recess, can guarantee on the one hand that the optical unit keeps stable structure in less space, strengthen the position stability of inside optical unit promptly, avoid the inside plastics material of optical cable to melt the back optical unit because of the high temperature and can not maintain original stable position and remove in inside, the circumstances of distortion appears, reduce the destruction of optic fibre external environment or mechanical stress and lead to the fracture risk of optic fibre embrittlement, on the other hand strap and flexible graphite paper form a fire-proof belt, the compressive property of strap improvement recess is met to the strap, also can not take place to warp, flexible graphite paper meets high temperature or burning with graphite, can take place to expand, can cladding recess internal optical unit, further play fire-retardant fire prevention's effect. The self-extinguishing type flame-retardant fire-resistant optical cable has the advantages that the multi-layer cladding sheath layer and the cable core are designed in structure, and the flame-retardant and fire-resistant performances are more excellent.

The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are some, but not all embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those of skill in the art will explicitly and implicitly appreciate that the embodiments described herein may be combined with other embodiments.

A common measure for improving the combustion performance of conventional flame-retardant optical cables is to enhance the flame-retardant performance of the cable jacket material. However, because other non-flame-retardant substances or component elements are also present in the optical cable, even if expensive flame-retardant materials are adopted, flame spread cannot be completely delayed when a fire disaster occurs, and meanwhile, the internal structure of the optical cable can be easily damaged, so that transmission signals are interrupted, and the application of the optical cable in some occasions with higher safety levels is affected.

For example, the present application has found that the existing optical cable has poor heat insulation effect, the optical cable is subject to licking by flame, no way is provided for preventing external heat generated during combustion from being transferred to the loose tube, the plastic loose tube is melted after being heated, and then shrinkage external force can cause the attenuation of the optical fiber to be increased or broken sharply during the cooling process of the material of the loose tube. For example, the application also finds that the position stability of the internal light unit of the existing optical cable is poor in the burning process, the internal plastic material is easy to melt or carbonize at high temperature, the optical fiber in the optical cable cannot maintain the original stable position and moves in the optical cable, the optical fiber is easy to twist, the optical fiber is easy to be extruded and bent sideways to deform, the surface of the optical fiber is further worn, and the optical fiber is damaged and broken, so that the normal use of the optical fiber is affected. For example, the application also finds that the existing fire-resistant flame-retardant material of the optical cable has poor adhesion and tightness and is easy to fall off, for example, ceramic polyolefin material is introduced as a sheath layer, and the loose tube material of the optical unit is still burnt and carbonized at high temperature in the continuous burning process, so that the burning residues of the outer layer material of the optical fiber are collapsed inwards, thereby affecting the transmission performance of the optical fiber and even causing the problem of fiber breakage.

In view of the above problems, the application provides a self-extinguishing type flame-retardant fire-resistant optical cable which has excellent flame retardance, can delay flame to burn into the optical cable when a fire disaster occurs, ensures that the optical fiber is prevented from being damaged by high temperature, and maintains the integrity of a communication line of the optical cable.

As shown in fig. 1, a self-extinguishing type flame-retardant and fire-resistant optical cable comprises an outer protective layer 1, a fireproof layer 12, a fire extinguishing layer 4, an inner protective layer 5, a waterproof layer 6 and a cable core 13 from outside to inside. Wherein the fireproof layer 12 is composed of a nonmetallic woven layer 2 and an expandable graphite layer 3. The water blocking layer 6 is a water blocking tape. A plurality of fire extinguishing units 14 are uniformly arranged in the circumferential direction inside the fire extinguishing layer 4. The cable core 13 comprises a central skeleton element 15, and the radial circumferential surface of the central skeleton element 15 is provided with at least 1 arc-shaped groove 16 which is not completely closed, and 6 arc-shaped grooves 16 are shown in fig. 1. In other embodiments the arcuate grooves 16 may be provided in 1, 2, 3, 4, 5, 7, 8, etc. (natural numbers) depending on the number of light units and the size of the cable. The inner surface of the arc-shaped groove 16 is sequentially attached with the metal belt 10 and the flexible graphite paper 11. At least 1 light unit 7 is accommodated in the arcuate recess 16. In this embodiment one light unit 7 is accommodated in one arcuate recess 16. In other embodiments, depending on the size of the arcuate recess 16 and the size of the light unit 7, more than 1, e.g. 2, 3, 4, 5, 6, 7, 8, etc. (natural number) light units 7 may be provided. The central skeleton element 15 contains inside the reinforcing element 9 and the metal support 8.

The fire-proof layer 12 in the application is composed of a nonmetallic woven layer 2 and an expandable graphite layer 3. The nonmetallic braiding layer 2 is made of glass fiber braiding belt, mica tape, ceramic silicon rubber fire-resistant tape, high flame-retardant fire-proof oxygen-proof glass cloth tape, polyimide film tape and the like. The expandable graphite is bonded to the non-metallic braid 2 with a high temperature resistant adhesive using the non-metallic braid 2 (e.g., fiberglass braid, etc.) as a carrier, thereby forming a fire-resistant layer, which is coated between the outer and inner sheaths 1 and 5. The high temperature resistant adhesive can be, for example, organic polyimide adhesive, phenolic resin adhesive, urea-formaldehyde resin adhesive, heat-resistant epoxy adhesive, organic silica gel and the like, and inorganic adhesive, for example, common ZS-1071 high temperature resistant inorganic adhesive and the like.

The graphite crystal has a hexagonal network planar layered structure composed of carbon elements. The carbon atoms on the layer plane are bonded by strong covalent bonds, while the layers are bonded by van der Waals forces between the layers, the bond is very weak, and the interlayer distance is large. Thus, under appropriate conditions, various chemical species such as acids, alkali metals, salts, etc. can intercalate between graphite layers and combine with carbon atoms to form new chemical phase-graphite intercalation compounds (Graphite Intercalation on Compounds, abbreviated GIC). When heated to a proper temperature, the interlayer compound can be instantaneously and rapidly decomposed to generate a large amount of gas, so that the graphite is expanded into a worm-like new substance along the axial direction, namely, expanded graphite. The unexpanded graphite intercalation compound is an expandable graphite.

In the flame combustion process, the expandable graphite expands rapidly, flame can be choked, and meanwhile, the generated graphite expansion body material covers the surface of the inner protective layer, so that contact between the inner material and oxygen can be isolated, and heat energy transmission inwards is delayed. The non-metal braiding layers 2 such as glass fiber braiding belts and the like have a multi-mesh and fluffy fiber structure, so that space can be provided for graphite expansion, and meanwhile, the glass fiber braiding belts can ensure that expandable graphite does not fall off in the combustion expansion process, so that the structural stability of the fireproof layer is improved.

The inner sheath 5 and the outer sheath 1 are made of polyolefin materials with high flame retardance and low smoke generation. For example, low smoke zero halogen polyolefin materials, such as low smoke zero halogen polyethylene materials, low smoke zero halogen crosslinked polyethylene materials, low smoke zero halogen irradiation crosslinked polyethylene materials, etc., low Smoke Zero Halogen (LSZH) materials can control flame spread and toxic smoke generation.

In the application, the fire extinguishing layer 4 is made of thermoplastic resin material and is closely adhered between the fire-proof layer 12 and the inner protective layer 5. A plurality of fire extinguishing units 14 are provided at regular intervals in the circumferential direction inside the thermoplastic resin material. The plurality of fire extinguishing units 14 are communicated by adopting fine capillaries to form a whole. The fire extinguishing unit 14 is provided, for example, in the form of a fire extinguishing capsule, which is covered with a thin-walled plastic layer, the interior of which is filled with a fire extinguishing agent. The wall thickness of the thin-walled plastic layer is less than 1mm. When the temperature of the fire-extinguishing layer 4 increases upon exposure to heat, the thermoplastic resin material will slowly soften or even gradually decompose, providing expansion space for the expandable graphite in the fire-resistant layer 12. Meanwhile, the fire extinguishing unit 14 is affected by extrusion and high temperature of the expandable graphite, and the thin-wall plastic layer of the fire extinguishing unit is damaged, so that the filled fire extinguishing agent is released, the fire retarding effect is further achieved through the function of reducing the temperature of the fire extinguishing agent or isolating oxygen, and flame or heat transfer to the inner protective layer is delayed or prevented.

The fire extinguishing agent is a flame-retardant superfine solid powder mixture with the particle size less than or equal to 0.5 mu m, for example, flame-retardant superfine solid powder with the particle size less than or equal to 0.5 mu m, and comprises sodium bicarbonate or ammonium phosphate, magnesium stearate, white carbon black powder, silicon dioxide powder and talcum powder, and the fire extinguishing agent has the functions of decomposing after being subjected to high temperature, absorbing heat, playing a role in chemically inhibiting flame combustion and playing a role in choking flameless combustion.

In other embodiments, the fire extinguishing agent may be a nano-base material composite metal oxide, such as nano-dihydroxy composite magnesium hydroxide material, with a particle size less than or equal to 0.1 μm, and the composite metal oxide releases crystal water when heated, evaporates, decomposes and emits water vapor to absorb a large amount of combustion heat energy, thereby greatly reducing the surface temperature of the material, delaying or preventing the material from burning or thermally decomposing, and simultaneously, utilizing the huge specific surface area of the nano-particles, also can inhibit the material from fuming and reduce the smoke density.

In other embodiments, the fire suppression agent may also be an inert or non-flammable gas, such as N2, CO2, that is released to reduce the oxygen content of the combustion site, thereby preventing combustion.

The cable core 13 comprises a central skeleton unit 15, light units 7, metal supports 8 and reinforcing elements 9. The central skeleton element 15 is a solid cylinder with a surface with incompletely closed arc-shaped grooves 16 extruded with a thermoplastic elastomer material to a certain thickness. The reinforcing member 9 is filled in the center of the center frame unit 15 to improve tensile properties. For example, the reinforcing element 9 may be a rod of non-metallic fiber reinforced plastic, such as a glass fiber reinforced plastic rod, an aramid fiber reinforced plastic rod, a carbon fiber reinforced plastic rod, or the like. The metal support 8 extends longitudinally along the periphery of the reinforcing element 9 and is embedded in the central skeleton unit 15 to improve the lateral pressure resistance, and the metal support 8 is also used for limiting the positions of the light units after the thermoplastic materials in the cable core are melted, so that twisting or twisting among the light units is avoided. Wherein the reinforcing element 9 is a metal or nonmetal rod material with certain tensile strength, preferably a nonmetal fiber reinforced plastic rod, the tensile strength is not less than 1450MPa, the elastic modulus is not less than 55GPa, the bending strength is not less than 1100MPa, the diameter deviation is +/-0.02 mm, the density range is 2.05-2.15g/cm < 3 >, the reinforcing element is a round rod with the required diameter, the color is uniform and consistent, the surface is free from cracks and burrs, and the hand feeling is smooth.

In some embodiments, the metal support 8 is formed by spiral armouring with a stainless steel wire, and the maximum outer diameter of the metal support is in contact with the lowest point of the arc-shaped groove 16, so as to provide a certain support for the groove, especially under the condition of high temperature or fire, the central skeleton unit 15 extruded by the thermoplastic elastomer material can be softened or even structurally damaged, and the metal support 8 cannot be deformed, so that the stability of the arc-shaped groove 16 can be ensured, and the stability of the light unit 7 in the arc-shaped groove 16 can be improved.

In the application, the arc-shaped groove 16 is sequentially attached to the inner surface of the metal belt 10 and the flexible graphite paper 11, namely, the metal belt 10 is taken as a base material, and the flexible graphite paper 11 is taken as a substrate, so that a fireproof belt is formed. The metal strip 10 is a corrugated steel strip or a corrugated aluminum strip, improves the compression resistance of the grooves, and does not deform even at high temperatures. The flexible graphite paper 11 is completely attached to the surface of the metal belt 10, the thickness of the flexible graphite paper is 0.03-0.08 mm, and the flexible graphite paper can expand when being subjected to high temperature or combustion by utilizing graphite, so that the flexible graphite paper can cover the light unit 7 in the groove and further has the flame-retardant and fireproof effects. In other embodiments of the present application, a high temperature resistant adhesive may be used to adhere the flexible graphite paper 11 to the surface of the metal strip 10 to enhance the adhesion.

The light unit 7 in the present application, as shown in fig. 2, comprises, in order from the outside to the inside, a first plastic layer 17, a fire-resistant layer 18, a second plastic layer 19, a water-blocking material 21, and an optical fiber 20. In the process, the first plastic layer 17, the fire-resistant layer 18 and the second plastic layer 19 are formed by three layers of coextrusion and synchronous molding, and compared with the conventional loose tube, the heat resistance is better. Wherein the heat distortion temperature, the thermal decomposition temperature and the melting point of the first plastic layer 17 are all greater than those of the second plastic layer 19. For example, the first plastic layer 17 is nylon, FEP, ETFE, PFA, LCP, or the like. For example, the second plastic layer 19 is PC, PE, PBT, LSZH, PVC, TPE. The refractory layer 18 is a polyimide composite tape coated with mica powder.

The optical fiber 20 has a core number of at least 1 core, and is one of single mode and multimode, for example, bare fiber with a coating layer having an outer diameter of 200 μm to 255 μm, and a common coating material is one of acrylic resin and polyamide resin. For example, a coated optical fiber having a plastic coating layer with an outer diameter of 500 μm to 1000 μm may be used, and the plastic layer is usually one of LSZH, PA, TPE, ETFE, PTFE, FEP. Further, in other embodiments, the optical fiber 20 may be a temperature resistant optical fiber to accommodate a coating or plastic cladding. For example, a high temperature resistant optical fiber coated with a special polyester (polyimide coating) which can withstand high temperatures of 300 ℃.

Further, in some embodiments, the plurality of optical fibers 20 may be independent, dispersed inside the light unit 7. Or may be arranged in a sequence and bound by a suitable material to form a unitary body, the binding element including but not limited to one of a fiber optic bundle or a fiber optic ribbon.

The water-blocking material 21 is water-blocking yarn, has a dry structure, can reduce the use of ointment, and is clean and environment-friendly.

It can be seen that the overall thickness of the optical unit provided by the application is 230-600 μm, which is basically similar to the thickness of the loose tube of the conventional optical cable, but has heat resistance, flame retardance, fire resistance and mechanical strength which are obviously superior to those of the conventional loose tube.

The self-extinguishing type flame-retardant fire-resistant optical cable has the advantages of more excellent flame retardance and fire resistance due to the design of a multi-layer structure. When the optical cable burns, flame and heat can easily break through the outer protective layer, and at the moment, the optical cable structure is not damaged yet, and fire prevention is critical. Therefore, the fire-proof layer is designed, flame is prevented or delayed from spreading inwards at the first time, the fire is reduced, a flame-retardant effect is achieved, and the inner cable core structure is protected again. When the optical cable burns and breaks through the fireproof layer, the existence of the fire extinguishing layer can help the optical cable to extinguish fire by itself, and the second protection is achieved for the inner cable core structure. When the fire is further deteriorated, after the fire layer is broken by the burning of the optical cable, the structure of the optical cable is also damaged, and the optical cable can not prevent flame or heat from spreading basically in the aspect of flame retardance; therefore, it is critical to maintain the integrity of the communication line, ensuring that no interruption of the optical fiber occurs. Through the cable core that design surface has the recess, inside has metal support piece, lay expandable fire prevention area in the recess to and the light unit of resistant temperature, can further guarantee that the light unit keeps stable structure in less space, reduce the risk that the destruction of external environment or mechanical stress leads to the optical fiber embrittlement fracture promptly, third triple protection.

The foregoing has outlined rather broadly the more detailed description of embodiments of the application, wherein the principles and embodiments of the application are explained in detail using specific examples, the above examples being provided solely to facilitate the understanding of the method and core concepts of the application; meanwhile, as those skilled in the art will have variations in the specific embodiments and application scope in accordance with the ideas of the present application, the present description should not be construed as limiting the present application in view of the above.

Claims (10)

1. The self-extinguishing type flame-retardant fire-resistant optical cable comprises a cable core and a cladding sheath for cladding the cable core, and is characterized in that the cladding sheath sequentially comprises a water-resistant layer, an inner sheath, a fire extinguishing layer, an expandable graphite layer, a nonmetallic woven layer and an outer sheath from inside to outside, wherein the fire extinguishing layer comprises a thermoplastic resin material attached between the expandable graphite layer and the inner sheath, a fire extinguishing capsule is arranged in the thermoplastic resin material, and a fire extinguishing agent is filled in the fire extinguishing capsule; the outer protective layer and the inner protective layer are made of low-smoke halogen-free flame retardant materials;

the cable core comprises a central framework unit and a light unit, wherein an arc-shaped groove is formed in the outer surface of the central framework unit along the extending direction of the optical cable, the light unit is arranged in the arc-shaped groove, a reinforcing element is arranged in the center of the central framework unit along the extending direction of the optical cable, a metal supporting piece is embedded in the central framework unit along the extending direction of the optical cable, and the metal supporting piece is arranged on the periphery of the reinforcing element.

2. A self-extinguishing flame-retardant fire-resistant optical cable as recited in claim 1 wherein said metal support member has a maximum outer diameter in contact with the lowest point of the arcuate groove.

3. A self-extinguishing flame-retardant and fire-resistant optical cable according to claim 1, wherein the metal support is a stainless steel wire helically armored along the periphery of the reinforcing element.

4. A self-extinguishing flame retardant and fire resistant optical cable as recited in claim 1 wherein a metal tape is attached to the inner surface of said arcuate groove, said metal tape being attached to a side of said optical unit facing said flexible graphite paper; the metal belt is a corrugated steel belt or a corrugated aluminum belt, the thickness of the flexible graphite paper is 0.03-0.08 mm, and the flexible graphite paper is completely attached to the surface of the metal belt.

5. A self-extinguishing flame retardant and fire resistant fiber optic cable as recited in claim 1, wherein said expandable graphite layer is formed of expandable graphite bonded with a high temperature resistant adhesive on a side of said non-metallic braid facing said fire extinguishing layer.

6. A self-extinguishing flame retardant and fire resistant optical cable according to claim 1, wherein said fire extinguishing capsules are uniformly arranged in said thermoplastic resin material in the circumferential direction, and said fire extinguishing capsules are communicated with each other by capillary tubes to form a whole.

7. The self-extinguishing flame-retardant and fire-resistant optical cable according to claim 1, wherein the fire-extinguishing agent is at least one of flame-retardant superfine solid powder mixture with the particle size less than or equal to 0.5 μm, nano-base material composite metal oxide, inert gas and nonflammable gas.

8. The self-extinguishing type flame-retardant and fire-resistant optical cable as claimed in claim 1, wherein the optical unit comprises a first plastic layer, a fire-resistant layer, a second plastic layer, a water-blocking material and an optical fiber from outside to inside in sequence, the thermal deformation temperature, the thermal decomposition temperature and the melting point of the first plastic layer are all higher than those of the second plastic layer, the fire-resistant layer is a polyimide composite adhesive tape coated by mica powder, and the first plastic layer, the fire-resistant layer and the second plastic layer are synchronously molded by three layers of coextrusion; the water-blocking material is water-blocking yarn.

9. A self-extinguishing flame-retardant fire-resistant optical cable according to claim 8, wherein the optical fibers in the light unit are bound by a binding element to form a single body.

10. A self-extinguishing flame-retardant and fire-resistant optical fiber cable according to claim 8, wherein the optical fiber has a plastic coating layer or a resin coating layer.