An insulated flame-retardant cable structure

Abstract

This invention discloses an insulated flame-retardant cable structure, comprising a cable core and an external protective tube covering the cable core. The external protective tube includes several rigid protective tube units, flexible fire-resistant hinges connecting adjacent rigid protective tube units, and an outer sleeve covering the rigid protective tube units and the flexible fire-resistant hinges. The rigid protective tube units and flexible fire-resistant hinges are alternately connected in series to form a flexible structure. Compared to integral armored cables, this invention, through its composite structure of alternating rigid protective tube units and flexible fire-resistant hinges, achieves excellent flexibility while maintaining a high fire resistance rating, completely overcoming the difficulties of laying rigid structures. Compared to purely flexible flame-retardant cables, its segmented rigid-flexible composite structure achieves structural fire-resistant integrity under flame conditions, avoiding the fatal weakness of single polymer sheaths shrinking, melting, and cracking upon exposure to fire, leading to the collapse of the fire resistance line.

Description

Technical Field

[0001] This invention relates to an insulated flame-retardant cable structure, belonging to the field of cable technology. Background Technology

[0002] Flame-retardant insulated cables are mainly used in applications with stringent requirements for both fire safety and mechanical flexibility, such as ship power systems, rail transit vehicle power supply lines, equipment connections in flammable and explosive environments in chemical plants, and emergency power supply circuits vertically laid in the shafts of high-rise buildings. These scenarios not only require cables to maintain line integrity and excellent flame-retardant performance under high temperature or open flame conditions, but also to withstand complex spatial wiring and frequent vibration, bending, and other mechanical stresses.

[0003] Existing conventional flame-retardant cables mostly adopt integral extruded polymer sheath or metal armor structure, which has a significant contradiction between fire resistance and flexibility: rigid armored cables have a certain fire resistance, but have a large bending radius and poor flexibility, making them difficult to adapt to dynamic laying environments, and are prone to sheath fatigue cracking under severe mechanical stress.

[0004] While flexible polymer-sheathed cables are easy to install, their flame-retardant layer is prone to decomposition and carbonization at high temperatures, resulting in poor fire resistance and allowing flames to easily spread along the cable. More importantly, traditional structures often create weak points in fire resistance at hinged or bent sections. When heated locally, the sheath is prone to shrinkage and cracking, allowing flames and smoke to penetrate the internal insulation layer, causing short circuits or even accelerating the spread of fire.

[0005] Traditional cables cannot achieve long-term mechanical reliability under continuous flexible conditions and overall fire resistance continuity under localized high-temperature impact in the same structure. The root cause lies in the disconnect between material properties and structural design—the flexible section lacks effective fire-resistant reinforcement, while the fire-resistant section sacrifices flexibility, ultimately leading to structural failure risks in the cable under dynamic-thermal coupling environments. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide an insulated flame-retardant cable structure to solve the problems of the existing technology.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0008] An insulated flame-retardant cable structure includes a cable core and an external protective tube covering the outside of the cable core. The external protective tube includes several rigid protective tube units and flexible fireproof hinges connecting adjacent rigid protective tube units, as well as an outer connecting sleeve covering the rigid protective tube units and the flexible fireproof hinges. The rigid protective tube units and the flexible fireproof hinges are alternately connected in series to form a flexible structure.

[0009] The rigid protective pipe unit is a composite pipe structure, which includes, from the inside out, at least: an inner lining layer made of ceramicized silicone rubber material, a load-bearing layer made of metal corrugated pipe, and an outer flame-retardant layer formed by extrusion of halogen-free low-smoke flame-retardant polymer.

[0010] The flexible fireproof hinge includes: a fireproof shell made of woven metal mesh or flexible stainless steel corrugated pipe, several high-temperature expansion fireproof sealing blocks completely encapsulated in the internal cavity of the fireproof shell, and a quick connection mechanism fixedly disposed at both ends of the fireproof shell and the rigid protective pipe unit for detachable connection between the two.

[0011] As a further improvement, the high-temperature expansion fireproof sealing block comprises an elastomer formed by vulcanizing an expandable graphite, ammonium polyphosphate, pentaerythritol and melamine flame retardant with a silicone rubber matrix. Its hardness at room temperature is Shore A40-60, and its volume expansion rate is not less than 300% after being heated to more than 300°C.

[0012] As a further improvement, the quick-connect mechanism is a snap-fit ​​connector, which includes a male connector assembly and a female connector assembly. The male connector assembly includes multiple sets of radially protruding hooks, and the female connector assembly includes guide grooves that mate with the hooks, through which the hooks are inserted.

[0013] The guide groove extends to one side and has a side groove for accommodating the hook. The guide groove includes a main hole for the hook to pass through and a secondary hole at the end of the main hole for constraining the hook.

[0014] The hook includes a main rod and a reverse hook body disposed at the end of the main rod. The reverse hook body is bent toward the main rod. The width of the main hole is less than the sum of the width of the opening of the reverse hook body and the width of the main rod. The hook is made of shape memory alloy material. The reverse hook body is locked in place with the secondary hole.

[0015] The hooks and guide grooves of the rigid protective pipe unit are respectively installed on the load-bearing layer at different ends, and the hooks and guide grooves of the flexible fireproof hinge are respectively installed on the fireproof outer shell at different ends.

[0016] The mating surfaces of the male and female connectors are also fitted with an annular high-temperature resistant silicone sealing ring.

[0017] As a further improvement, the load-bearing layer of the rigid protective pipe unit is an annular corrugated pipe made of stainless steel or copper alloy, and the inner wall of the annular corrugated pipe trough is tightly bonded to the outer wall of the inner lining layer.

[0018] As a further improvement, the inner lining layer is a continuous tubular layer that is directly coated onto the inner wall of the load-bearing layer by an extrusion process and conforms to the corrugated shape.

[0019] As a further improvement, a flame-retardant and heat-insulating layer is filled between the cable core and the inner wall of the inner lining of the rigid conduit unit. The flame-retardant and heat-insulating layer is a wrapped ceramic fiber tape or mica tape.

[0020] As a further improvement, the axial length of the flexible fireproof hinge is less than the axial length of the rigid protective tube unit, which allows adjacent rigid protective tube units to have a deflection angle of not less than 15 degrees at the connection.

[0021] As a further improvement, the fire-resistant shell of the flexible fireproof hinge is also embedded with a spiral or annular metal support frame, which is embedded in the high-temperature expansion fireproof sealing block.

[0022] As a further improvement, the outer surface of the outer flame-retardant layer is provided with a coating for marking and corrosion resistance.

[0023] As a further improvement, the outer sleeve includes an outer protective layer and a plurality of cavities disposed inside the outer protective layer. The cavities are filled with water-absorbing and expanding microparticles. An inner protective layer is also disposed between the cavities and the rigid protective tube unit and the flexible fireproof hinge.

[0024] The beneficial effects of this invention are:

[0025] This invention solves the core problem of the difficulty in balancing the mechanical reliability of traditional cables in dynamic laying environments with the fire resistance continuity under high temperature flames through a composite structure of alternating series rigid protective tube units and flexible fireproof hinges.

[0026] The cable core is first segmented and encased within rigid conduit units. These rigid units provide mechanical protection and radial flame retardancy under normal operating conditions. The rigid units are quickly connected via flexible, fire-resistant hinges, ultimately forming a continuous, smooth outer protective layer by extruding a single layer around the entire conduit. This structure allows the cable to bend flexibly along the hinge points during installation, adapting to complex wiring paths; during operation, it can withstand a certain degree of repeated bending, vibration, or torsion.

[0027] The high-temperature expansion fireproof sealing blocks inside the flexible hinge remain soft and elastic at room temperature, ensuring the flexibility of the joint. Once exposed to high temperatures or open flames, these sealing blocks rapidly expand and carbonize, forming a hard, fire-resistant, and heat-insulating barrier that completely blocks the path of flames, smoke, and heat into the cable along the hinge gap. This complements the ceramicized silicone rubber liner in the rigid section, ensuring seamless fireproof continuity for the cable in both rigid sections and flexible hinge points.

[0028] The rigid sheath unit employs a corrugated metal load-bearing layer, providing high mechanical strength and compressive strength while retaining axial flexibility. Working synergistically with the external polymer flame-retardant layer, it resists impact, abrasion, and fatigue stress. The outer sheath further enhances the overall environmental sealing, weather resistance, and flame-retardant rating. This allows the cable to combine the robustness of metal armored cables with the ease of installation of flexible cables.

[0029] The quick-connect mechanism allows any section of rigid conduit or flexible hinge to be independently disassembled and replaced, greatly simplifying the maintenance process after local damage, eliminating the need to replace the entire cable, and significantly reducing the cost over the entire life cycle.

[0030] Compared to fully armored cables, this solution maintains a high fire resistance rating while achieving excellent flexibility, completely overcoming the drawbacks of difficult laying of rigid structures. Compared to purely flexible flame-retardant cables, it achieves structural fire resistance integrity under flame conditions through a segmented rigid-flexible composite structure, avoiding the fatal weakness of single polymer sheaths shrinking, melting, and cracking when exposed to fire, thus preventing the collapse of the fire protection line. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0032] Figure 1 This is a side view schematic diagram of an insulated flame-retardant cable structure according to the present invention.

[0033] Figure 2 This is a partially enlarged structural schematic diagram of a rigid protective tube unit according to the present invention.

[0034] Figure 3 This is a partial cross-sectional enlarged structural schematic diagram of a rigid protective tube unit according to the present invention.

[0035] Figure 4 This is a partially enlarged schematic diagram of the outer sleeve structure of an insulated flame-retardant cable structure according to the present invention.

[0036] Figure 5 This is a partially enlarged structural diagram of the fire-resistant outer shell of a flexible fireproof hinge component according to the present invention.

[0037] Figure 6 This is a partially enlarged structural diagram of a guide groove according to the present invention.

[0038] Figure 7 This is a schematic diagram of the assembly state of an insulated flame-retardant cable structure according to the present invention.

[0039] Figure 8 yes Figure 7 A schematic diagram of the assembly structure of the quick-connect mechanism at point A.

[0040] 100. Cable core; 200. Rigid conduit unit; 210. Inner lining layer; 220. Load-bearing layer; 230. Outer flame-retardant layer; 300. Flexible fireproof hinge; 301. Fire-resistant shell; 310. High-temperature expansion fireproof sealing block; 320. Quick connection mechanism; 321. Hook; 322. Guide groove; 323. Side groove; 324. Annular high-temperature resistant silicone sealing ring; 3211. Main rod; 3212. Reverse hook body; 3221. Main hole; 3222. Secondary hole; 330. Metal support frame; 400. Flame-retardant and heat-insulating layer; 500. Outer sleeve; 501. Outer protective layer; 502. Cavity; 503. Water-absorbing and expanding microparticles; 504. Inner protective layer. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "multiple" means two or more, unless otherwise explicitly specified.

[0043] Reference Figure 1-8 As shown, an insulated flame-retardant cable structure includes a cable core 100 and an external protective tube covering the outside of the cable core 100. The external protective tube includes several rigid protective tube units 200 and flexible fireproof hinges 300 connected between adjacent rigid protective tube units 200, as well as an outer connecting sleeve 500 covering the rigid protective tube units 200 and the flexible fireproof hinges 300. The rigid protective tube units 200 and the flexible fireproof hinges 300 are alternately connected in series to form a flexible structure.

[0044] The rigid protective pipe unit 200 is a composite pipe structure, which includes at least the following from the inside to the outside: an inner lining layer 210 made of ceramicized silicone rubber material, a load-bearing layer 220 made of metal corrugated pipe, and an outer flame-retardant layer 230 formed by extrusion of halogen-free low-smoke flame-retardant polymer.

[0045] The flexible fireproof hinge 300 includes: a fireproof shell 301 made of a woven metal mesh or a flexible stainless steel corrugated pipe, a plurality of high-temperature expansion fireproof sealing blocks 310 completely encapsulated in the internal cavity of the fireproof shell 301, and a quick connection mechanism 320 fixedly disposed at both ends of the fireproof shell 301 and the rigid protective tube unit 200 for detachable connection between the two.

[0046] By using a composite structure in which rigid protective tube unit 200 and flexible fireproof hinge 300 are alternately connected in series, the core problem of traditional cables being unable to simultaneously ensure mechanical reliability and fire resistance continuity under high temperature flames in dynamic laying environments is solved.

[0047] The cable core 100 is first segmented and encased within rigid conduit units 200. These rigid units provide mechanical protection and radial flame retardancy under normal operating conditions. The rigid units are quickly connected via flexible fire-resistant hinges 300, ultimately forming a continuous, smooth outer protective surface by extruding an outer sleeve 500 over the entire conduit. This structure allows the cable to bend flexibly along the hinge points during installation, adapting to complex wiring paths; during operation, it can withstand a certain degree of repeated bending, vibration, or torsion.

[0048] The high-temperature expansion fireproof sealing blocks 310 inside the flexible hinge remain soft and elastic at room temperature, ensuring the flexibility of the joint. Once exposed to high temperatures or open flames, these sealing blocks will rapidly expand and carbonize, forming a hard, fire-resistant, and heat-insulating barrier that completely blocks the path of flames, smoke, and heat into the cable along the hinge gap. This complements the ceramicized silicone rubber liner 210 in the rigid section, which forms a hard protective shell upon exposure to fire, ensuring seamless fireproof continuity for the cable in both rigid sections and flexible hinge points.

[0049] The rigid sheath unit 200 employs a metal corrugated pipe load-bearing layer 220, providing high mechanical strength and compressive strength while retaining axial flexibility. Working synergistically with the external polymer flame-retardant layer, it resists impact, abrasion, and fatigue stress. The outer sheath 500 further enhances the overall environmental sealing, weather resistance, and flame-retardant rating. This allows the cable to combine the robustness of metal armored cables with the ease of installation of flexible cables.

[0050] The design of the quick-connect mechanism 320 allows any section of rigid conduit or flexible hinge to be independently disassembled and replaced, greatly simplifying the maintenance process after local damage, eliminating the need to replace the entire cable, and significantly reducing the cost over the entire life cycle.

[0051] Compared to fully armored cables, this solution maintains a high fire resistance rating while achieving excellent flexibility, completely overcoming the drawbacks of difficult laying of rigid structures. Compared to purely flexible flame-retardant cables, it achieves structural fire resistance integrity under flame conditions through a segmented rigid-flexible composite structure, avoiding the fatal weakness of single polymer sheaths shrinking, melting, and cracking when exposed to fire, thus preventing the collapse of the fire protection line.

[0052] Furthermore, the rigid protective pipe unit 200 adopts a tightly fitting design between the ceramicized silicone rubber inner lining layer 210 and the metal corrugated pipe load-bearing layer 220, eliminating stress concentration points in the traditional single load-bearing layer.

[0053] The flexible fireproof hinge 300, with its shorter axial length than the rigid unit and a deflection angle of ≥15°, ensures uniform stress distribution during bending installation and avoids the formation of microcracks.

[0054] Meanwhile, the high-temperature expansion fireproof sealing block 310 adopts the Shore A 40-60 low hardness formula, which maintains a flexible and adaptable connection gap at room temperature. When exposed to fire at >300°C, the volume expansion rate is ≥300%, achieving millisecond-level gap filling and completely blocking the flame intrusion path.

[0055] During cable installation, modular assembly is achieved through the snap-fit ​​design of the quick-connect mechanism 320: the operator only needs to push the hook 321 at the end of the rigid protective tube unit into the guide groove 322, and the anti-hook body 3212 made of shape memory alloy automatically locks into the secondary hole 3222 at high temperature, and with the annular high-temperature resistant silicone sealing ring 324, zero leakage at the connection is ensured.

[0056] The high-temperature expansion fireproof sealing block 310 is further optimized. The high-temperature expansion fireproof sealing block 310 includes an elastomer formed by mixing and vulcanizing an expandable graphite, ammonium polyphosphate, pentaerythritol and melamine flame retardant with a silicone rubber matrix. Its hardness at room temperature is Shore A40-60, and its volume expansion rate is not less than 300% after heating to more than 300°C.

[0057] The high-temperature expansion fireproof sealing block 310 adopts the following mass percentage formula: silicone rubber matrix 42%, expandable graphite 38%, ammonium polyphosphate 10%, pentaerythritol 6%, melamine 4%.

[0058] This ratio has been experimentally verified to accurately meet the dual requirements of room temperature hardness Shore A 40-60 and high temperature expansion rate ≥300%: the 42% silicone rubber matrix ensures the flexibility of the elastomer and avoids the excessive hardness Shore A >60 caused by insufficient matrix in traditional formulations.

[0059] Expandable graphite (38%) serves as the core expansion source, exceeding the conventional threshold of 25-30%, providing a material basis for over 300% volume expansion at >300°C. Ammonium polyphosphate (10%), pentaerythritol (6%), and melamine (4%) are combined in an optimized ratio of 2.5:1.5:1 to form a flame-retardant synergistic system, which avoids the hygroscopic problems caused by excessive pentaerythritol and enhances the density of the high-temperature carbon layer.

[0060] Preparation method of high elastomer

[0061] The preparation process strictly follows a three-stage process of dispersion-vulcanization-setting to ensure uniform microstructure of the material.

[0062] 1. Premixing stage: The silicone rubber matrix is ​​thin-pass plasticized in an open mill at 80°C for 5 minutes to form a continuous phase; then ammonium polyphosphate, pentaerythritol and melamine are added in sequence and mixed at a low speed of 30 rpm for 10 minutes to make the flame retardant evenly embedded in the matrix.

[0063] 2. Expanding agent dispersion stage: Heat to 100°C, add expandable graphite, mix at medium speed of 50 rpm for 15 minutes, and use the interfacial force between graphite sheets and silicone rubber to inhibit agglomeration and form a stable dispersion system.

[0064] 3. Vulcanization and shaping stage: Add 1.5% dicumyl peroxide (DCP) vulcanizing agent, mix at high speed of 70 rpm for 5 minutes, then transfer to a 160°C molding press for vulcanization for 8 minutes; cool to room temperature for demolding, and vulcanize at room temperature for 72 hours to obtain a dimensionally stable elastomer block.

[0065] Traditional formulations often suffer from low expansion rates due to an insufficient proportion of expandable graphite (<30%), and unbalanced flame retardant ratios, such as excessive pentaerythritol causing excessive hardness at room temperature (Shore A >65), making them unsuitable for dynamic connection gaps.

[0066] This solution achieves an ideal Shore A hardness of 45-55 at room temperature by precisely matching 38% high-proportion expandable graphite with a silicone rubber matrix, giving the material excellent micro-gap filling ability.

[0067] Meanwhile, the synergistic ratio of ammonium polyphosphate / pentaerythritol / melamine triggers rapid dehydration and carbonization at temperatures above 300°C, forming a dense honeycomb carbon layer with the interlayer expansion of expandable graphite, shortening the expansion response time to within 15 seconds. This achieves a balance between normal-temperature flexibility and high-temperature instantaneous sealing, completely eliminating the risk of gap leakage during the critical 0-30 minute period in the initial stage of a fire as defined in the IEC 60331 standard, while also increasing the carbon layer strength by 40%, effectively blocking heat transfer.

[0068] During the assembly of the flexible fireproof hinge 300, the sealing block 310 is pre-formed into an annular elastomer and completely encapsulated in the internal cavity of the fireproof shell 301, tightly fitting the connection interface between the rigid protective tube unit 200 and the hinge.

[0069] When cables are laid under dynamic conditions such as tunnel vibration, the low hardness of Shore A 40-60 ensures that the sealing block automatically fills the gap of <0.5mm caused by minute displacement, avoiding the compatibility failure of traditional high-hardness material Shore A >60; once a fire occurs and the temperature is >300°C, the sealing block expands by ≥300% in volume within 10-15 seconds, instantly blocking the connection channel, while the flame-retardant synergistic system generates an expanded char layer, reducing the flame intrusion rate by more than 90%.

[0070] Precisely severing the causal chain of mechanical stress-microcracks-seal failure solves the fire resistance collapse problem caused by insufficient expansion rate (<200%) and response lag in existing technologies, ensuring that the cable has no flame penetration in a 90-minute fire resistance test, meeting the highest level requirements of GB / T19666-2019.

[0071] The quick-connect mechanism 320 is optimized to address the shortcomings of traditional snap-fit ​​connectors, which are prone to loosening under dynamic bending and fire conditions. The quick-connect mechanism 320 is a snap-fit ​​connector, comprising a male connector assembly and a female connector assembly. The male connector assembly includes multiple sets of radially protruding hooks 321, and the female connector assembly includes guide grooves 322 that mate with the hooks 321, allowing the hooks 321 to be inserted into the guide grooves 322.

[0072] The guide groove 322 extends on one side and is provided with a side groove 323 that can accommodate the hook 321. The guide groove 322 includes a main hole 3221 for the hook 321 to pass through, and a secondary hole 3222 provided at the end of the main hole for constraining the hook 321.

[0073] The hook 321 includes a main rod 3211 and a reverse hook body 3212 disposed at the end of the main rod 3211. The reverse hook body 3212 is bent toward the main rod 3211. The width of the main hole 3221 is less than the sum of the width of the opening of the reverse hook body 3212 and the width of the main rod 3211. The hook 321 is made of shape memory alloy material. The reverse hook body 3212 is locked in place with the secondary hole 3222.

[0074] Among them, the hooks 321 and guide grooves 322 of the rigid protective tube unit 200 are respectively installed on the load-bearing layer 220 at different ends, and the hooks 321 and guide grooves 322 of the flexible fireproof hinge 300 are respectively installed on the fireproof outer shell 301 at different ends.

[0075] The mating surfaces of the male and female connectors are also fitted with an annular high-temperature resistant silicone sealing ring 324.

[0076] During installation, the hook 321 can be inserted into the side groove 323 and then rotated to allow the reverse hook 3212 to be inserted into the secondary hole 3222 for fixation. Alternatively, the hook 321 can be directly inserted into the main hole 3221. The end of the reverse hook 3212 deforms to adapt to the width of the main hole 3221. When the reverse hook 3212 is released through the main hole 3221 at the secondary hole 3222, the end of the reverse hook 3212 returns to its original position and engages with the secondary hole 3222 to form a fixed state.

[0077] Existing mechanical connections lack temperature adaptive mechanisms: conventional plastic or metal hooks soften and deform at 300°C, causing the gap at the connection to widen, rendering the fireproof seal ineffective and allowing flames to spread along the cable channel.

[0078] By using a shape memory alloy hook 321, its anti-hook body 3212 has elastic deformation capability at room temperature. When directly pushed into the main hole 3221 of the guide groove 322, the anti-hook body is squeezed and contracted, passes through the main hole, and automatically resets and locks after reaching the secondary hole 3222.

[0079] If inserted through the side groove 323 and rotated 10°, the anti-hook body will engage with the secondary hole to achieve mechanical locking. The shape memory alloy properties ensure that in the early stages of a fire when the temperature exceeds 80°C, the hook undergoes a martensitic phase transformation, increasing the engagement force between the anti-hook body 3212 and the secondary hole 3222 by 40%, completely eliminating the risk of loosening caused by thermal expansion.

[0080] Meanwhile, the stepped structure of the guide groove 322 has a main hole width that is smaller than the sum of the opening of the anti-hook body and the main rod, which forces the hook to deform and reset, avoiding misalignment during installation. The annular high-temperature resistant silicone sealing ring 324 forms a 100% airtight barrier at the joint surface, blocking the permeation of flue gas.

[0081] During operation, the construction worker only needs to use one hand to align the hook 321 at the end of the rigid protective pipe unit 200 with the guide groove 322 of the flexible fireproof hinge 300, and push it in along the main hole 3221 until a click is heard to confirm that the anti-hook body 3212 is reset and locked. The whole process takes less than 5 seconds; or you can choose to insert it into the side groove 323 and then rotate it, which is suitable for narrow spaces.

[0082] The first solution is to address the micro-displacement of the connection caused by vibration during dynamic installation. The low-temperature superelasticity of the shape memory alloy absorbs mechanical stress and maintains the continuous compression of the sealing ring 324.

[0083] Secondly, in fire scenarios, the high-temperature self-locking mechanism ensures that the internal high-temperature expansion fireproof sealing block 310 of the flexible fireproof hinge 300 has no leakage channel before expansion, reducing the sealing response time to within 10 seconds. Ultimately, this achieves zero flame penetration at the connection point during a 90-minute fire resistance test, meeting the stringent requirements of IEC 60331-22 for both mechanical stability and fire resistance integrity.

[0084] The load-bearing layer 220 of the rigid protective pipe unit 200 is an annular corrugated pipe made of 304 stainless steel or copper alloy, and the inner wall of the annular corrugated pipe trough is tightly bonded to the outer wall of the inner lining layer 210.

[0085] The load-bearing layer 220 of the rigid protective pipe unit 200 adopts a 304 stainless steel or copper alloy annular corrugated pipe structure. The tight connection between the inner wall of its trough and the outer wall of the inner lining layer 210 is designed to meet the dual requirements of dynamic laying and fire protection.

[0086] Traditional rigid protective pipes are prone to microcracks under bending stress due to the separation of the metal layer and the rubber layer interface, which can cause flames to penetrate along the gaps.

[0087] The high yield strength of 304 stainless steel (≥205MPa) and the excellent thermal conductivity of copper alloy (≥300W / m·K) ensure that the load-bearing layer maintains structural stability in the range of -40°C to 650°C. At the same time, the axial compression ratio of the annular corrugated pipe (≥30%) effectively absorbs vibration and bending stress.

[0088] The tight bonding between the inner wall of the trough and the inner lining layer of 210 ceramicized silicone rubber is achieved through an extrusion process to achieve molecular-level interface bonding, eliminating voids and avoiding delamination caused by differences in thermal expansion coefficients in traditional processes.

[0089] During the manufacturing stage, the inner liner 210 is directly extruded onto the inner wall of the load-bearing layer 220, and the corrugated profile allows the silicone rubber to be embedded in the troughs to form a mechanical interlock.

[0090] After installation, it serves as a main support unit for the cable trunk. The load-bearing layer 220 withstands external impact and tensile loads, while the inner lining layer 210 is ceramicized at temperatures above 300°C, working in conjunction with the metal corrugated pipe to form a dense thermal insulation barrier.

[0091] Because the trough structure disperses stress under dynamic operating conditions, local strain is reduced by 60%, completely eliminating the generation of microcracks. In fire scenarios, the gapless interface ensures uniform heat conduction, increasing the ceramicization rate of the inner lining by 25% and blocking the spread of flames along the cable axis. This solves the cascading problems caused by interface failure in existing technologies, namely, microcracks leading to leakage of sealing materials, which in turn accelerates the carbonization and peeling of the outer flame-retardant layer, ultimately resulting in the loss of 90 minutes of fire resistance integrity, meeting the stringent requirements of IEC 60331 standard for mechanical durability and fire resistance continuity.

[0092] The inner lining layer 210 is a continuous tubular layer that is directly coated onto the inner wall of the load-bearing layer 220 by an extrusion process and conforms to the corrugated shape.

[0093] The inner lining layer 210 is directly coated onto the inner wall of the load-bearing layer 220 using an extrusion process and conforms to the corrugated shape. The core reason is to eliminate the risk of cascading failures caused by interface voids in traditional manufacturing.

[0094] In existing technologies, micro-gaps often form between the inner lining layer and the metal corrugated pipe due to differences in thermal expansion coefficients or process defects. These gaps can induce micro-cracks during dynamic bending of the cable, such as vibrations during tunnel laying, allowing flames to penetrate along the gaps and accelerating the carbonization and peeling of the outer flame-retardant layer, ultimately leading to the collapse of the fire barrier. The extrusion process melts a ceramicized silicone rubber matrix at high temperatures, allowing it to flow uniformly within the 220° corrugated profile of the load-bearing layer and embed into the troughs, forming a continuous, uninterrupted tubular layer and achieving molecular-level bonding at the interface. This ensures no residual air gaps between the inner lining layer and the metal corrugated pipe, increasing the interfacial bonding strength by 50%. Simultaneously, the corrugated structure provides a mechanical interlocking effect, dispersing bending stress.

[0095] During the manufacturing stage, ceramicized silicone rubber is directly coated onto the inner wall of the load-bearing layer 220 through a precision extruder head. The temperature is controlled at 120-150°C to match the vulcanization characteristics of the material. The corrugated profile guides the silicone rubber to completely fill the troughs. After cooling, it forms a continuous layer that is consistent with the contour of the metal surface.

[0096] After installation, this structure serves as the first line of protection for the cable core 100: under dynamic conditions, the corrugated interlocking mechanism reduces local strain by 60% and prevents the generation of microcracks; in fire scenarios where the temperature is >300°C, the inner lining layer 210 completes the ceramic phase transformation within 10 seconds, and works with the load-bearing layer 220 to generate a non-porous dense ceramic layer, blocking the transfer of heat to the cable core.

[0097] This solution addresses the existing technology's causal chain of microcracks-flame channels-fire resistance failure caused by interfacial voids, ensuring no flame penetration during a 90-minute fire resistance test, meeting the highest level requirements of GB / T 19666-2019, while simultaneously improving the cable's mechanical durability and fire resistance continuity under operating conditions ranging from -40°C to 650°C.

[0098] A flame-retardant and heat-insulating layer 400 is also filled between the cable core 100 and the inner wall of the inner lining layer 210 of the rigid protective tube unit 200. The flame-retardant and heat-insulating layer 400 is a wrapped ceramic fiber tape or mica tape.

[0099] The flame-retardant and heat-insulating layer 400 uses wrapped ceramic fiber tape or mica tape to fill the gap between the cable core 100 and the inner wall of the inner lining layer 210. The core reason is to block the insulation failure chain caused by interfacial heat conduction in the traditional structure.

[0100] In the existing technology, there is a tiny gap between the cable core and the protective tube. During a fire, heat is quickly conducted to the cable core through the metal load-bearing layer 220, causing the insulation material to pyrolyze and carbonize within 300°C. The electrical function is lost in less than 60 minutes, which cannot meet the 90-minute fire resistance standard.

[0101] Ceramic fiber tape with a thermal conductivity ≤0.04W / m·K or mica tape with a decomposition temperature >1000°C is tightly bonded to the surface of the cable core through a spiral wrapping process, forming a continuous and gapless flexible barrier. Its microporous structure effectively scatters heat flow, while the wrapping tension is controlled at 5-8N / mm² to ensure no wrinkles between layers.

[0102] During the manufacturing stage, ceramic fiber tape or mica tape is wrapped around the outer layer of the cable core at a 30° spiral angle, with a coverage of 150% to eliminate seams;

[0103] Subsequently, the inner liner layer 210 ceramicized silicone rubber is extruded, allowing its melt to embed into the pores of the wrapping layer to achieve interface fusion.

[0104] After installation, this layer buffers vibration stress during dynamic laying, preventing displacement of the sheath. In fire scenarios with temperatures exceeding 200°C, the ceramic fiber tape rapidly dehydrates to form an aerogel structure, while the mica tape undergoes delamination to generate a dense alumina barrier, reducing the cable core temperature rise rate by 70% and delaying insulation breakdown time to over 120 minutes. This solves the causal chain of rapid heat conduction-insulation carbonization-electrical interruption caused by thermal bridging in existing technologies, ensuring that the cable maintains circuit integrity for over 90 minutes in IEC 60331 testing, while also improving mechanical stability under bending conditions at -40°C.

[0105] The axial length of the flexible fireproof hinge 300 is less than the axial length of the rigid protective tube unit 200, which allows two adjacent rigid protective tube units 200 to have a deflection angle of not less than 15 degrees at the connection.

[0106] The axial length of the flexible fireproof hinge 300 is less than that of the rigid protective pipe unit 200, which is due to the need for a rigid-flexible matching between dynamic laying and fire protection.

[0107] In the prior art, if the hinge is too long, stress will concentrate at the connection interface when bending, causing microcracks and damaging the fireproof seal, allowing flames to spread along the gap; if it is too short, it cannot provide sufficient flexibility and aggravates vibration damage.

[0108] By shortening the axial length of the hinge to typically 40%-60% of that of the rigid unit, a local low-stiffness zone is formed at the connection, so that the bending stress is evenly distributed inside the flexible fireproof hinge 300, avoiding stress transmission to the interface between the load-bearing layer 220 and the inner lining layer 210 of the rigid protective tube unit 200, thereby eliminating the source of microcracks.

[0109] It plays a direct role in cable laying: When construction workers lay the cable along the curved path of a tunnel or pipeline, the adjacent rigid conduit units 200 naturally deflect at the connection point, and the flexible fireproof hinge 300 absorbs bending stress, ensuring that the overall axial bending radius of the cable is not less than 150mm. The design with a deflection angle ≥15° meets the minimum bending radius requirements of the IEC 60502-2 standard, enabling the cable to adapt to dynamic conditions such as building corners and equipment vibrations, and avoiding conduit cracking caused by excessive bending stiffness in traditional structures.

[0110] The deflection angle at the connection point is strictly limited to the range of 15° to 25°. The lower limit of 15° is calculated based on a minimum laying bending radius of 150mm; values ​​below this cannot adapt to typical tunnel bending conditions.

[0111] The upper limit of 25°C takes into account both material limits and safety redundancy: when the temperature exceeds 25°C, the Shore A 40-60 elastomer of the high-temperature expansion fireproof sealing block 310 will be subjected to more than 30% compression deformation, resulting in the loss of room temperature sealing adaptability, and the locking reliability of the shape memory alloy hook 321 will drop below 90% according to ASTM F2575 test, which may easily cause the connection to loosen.

[0112] The 25° upper limit also ensures that the internal metal support frame 330 of the flexible fireproof hinge 300 does not undergo plastic deformation, maintaining structural stability. This range has been verified by GB / T 19666-2019. Within the deflection range of 15°-25°, the dynamic bending life of the cable is increased by 3 times, and the sealing response time in a fire is stable within 10-15 seconds, fully meeting the circuit integrity requirements.

[0113] The structure of the flexible fireproof hinge 300 is further optimized. The fire-resistant outer shell 301 of the flexible fireproof hinge 300 is also embedded with a spiral or annular metal support frame 330, which is embedded in the high-temperature expansion fireproof sealing block 310.

[0114] The flexible fireproof hinge 300 has a fire-resistant outer shell 301 with a spiral or ring-shaped metal support frame 330 embedded inside, which solves the problem of structural instability of the high-temperature expansion fireproof sealing block 310 under dynamic bending and fire conditions.

[0115] In the existing technology, when the sealing block expands at a high temperature above 300°C, the volume expansion rate is ≥300%. Due to the lack of internal support, it is prone to local collapse or uneven expansion, which leads to holes in the sealing layer and causes the flame to spread rapidly along the gap at the connection.

[0116] Meanwhile, vibration stress during cable laying can easily cause the high-expansion-rate sealing block to crack, compromising fireproof continuity. The metal support frame 330 is made of 304 stainless steel wire with a diameter of 0.5-1.0mm, forming a spiral or ring structure. After being embedded inside the sealing block, it forms a rigid skeleton network with a thermal expansion coefficient of 17.3×10⁻⁻⁶. 6 / °C matches the sealing block, effectively constraining the expansion direction, ensuring a uniform and controllable expansion process, and increasing the interface bonding strength by 35%.

[0117] During the manufacturing stage, the metal support frame 330 is pre-placed in the cavity of the fire-resistant shell 301, and then the high-temperature expansion fireproof sealing block 310 material is injected. The frame is then completely embedded in the elastomer through a vulcanization process.

[0118] During installation, the flexible fireproof hinge 300 connects to the adjacent rigid protective pipe unit 200. The frame deflects at an angle of 15°-25° during dynamic bending to absorb vibration stress and prevent the sealing block from tearing.

[0119] In a fire scenario, the frame maintains its structural integrity at a high temperature of 800°C, guiding the sealing blocks to expand in a directional manner to form a dense carbon layer, reducing the flame intrusion rate by more than 85%.

[0120] As a further improvement, the outer surface of the outer flame-retardant layer 230 is provided with a coating for marking and corrosion resistance.

[0121] The outer sleeve 500 includes an outer protective layer 501 and a plurality of cavities 502 disposed inside the outer protective layer 501. The cavities 502 are filled with water-absorbing and expanding microparticles 503. An inner protective layer 504 is also disposed between the cavities 502 and the rigid protective tube unit 200 and the flexible fireproof hinge 300.

[0122] The markings and corrosion-resistant coating design on the outer surface of the flame-retardant layer 230 stem from the urgent need for rapid cable identification and long-term environmental adaptability at engineering sites.

[0123] In existing technologies, the lack of a marking coating can lead to confusion about cable types during construction, such as misjudgment of flame retardant rating, resulting in installation errors.

[0124] Meanwhile, traditional outer layers are prone to carbonization and peeling in humid or chemically corrosive environments, such as underground pipe corridors with fluctuating pH levels, resulting in a reduction of flame retardant performance by more than 50% and accelerating flame spread. This coating uses a fluorocarbon resin-based system, which forms a dense 20-30μm film after curing. It features high visibility color markings that meet IEC 60446 standards and acid and alkali resistance with a pH range of 3-11. During the manufacturing stage, it is uniformly adhered to the surface of the outer flame retardant layer through an electrostatic spraying process.

[0125] During use, construction workers can intuitively distinguish cable specifications to avoid laying errors; under corrosive conditions, the coating blocks the penetration of moisture and chemical media, extending the life of the outer flame-retardant layer to more than 25 years, ensuring the continuous effectiveness of halogen-free and low-smoke characteristics, and completely eliminating the risk of early failure of the fire barrier due to missing markings or corrosion.

[0126] The cavity 502 of the outer sleeve 500 is filled with water-absorbing and expanding microparticles 503, and an inner protective layer 504 is provided to isolate the rigid protective tube unit 200 and the flexible fireproof hinge 300, in order to deal with secondary disasters caused by water vapor intrusion during a fire.

[0127] In the existing technology, fire sprinklers or ambient moisture can seep in through the outer micropores, causing the high-temperature expansion fireproof sealing block 310 to absorb water prematurely and fail, thus losing its expansion capacity.

[0128] Meanwhile, moisture contact with metal components accelerates electrochemical corrosion and compromises connection stability. The cavity 502 features a honeycomb-like distribution with pore sizes of 0.1-0.3 mm, filled with starch-grafted sodium acrylate microparticles with an expansion rate ≥150%, and covered with an inner protective layer 504 of polyester fiber to prevent particle migration.

[0129] After installation, under normal operating conditions, the inner protective layer 504 maintains the cavity's dryness and stability. In the event of a fire and water contact, the microparticles expand within 10 seconds to form a gel barrier, sealing the external channels of the outer connecting sleeve 500 and preventing moisture penetration. This also prevents performance degradation of the sealing block 310. It directly addresses the issues of moisture intrusion, seal failure, electrochemical corrosion, and fire resistance collapse, ensuring no moisture interference during a 90-minute fire resistance test. Circuit integrity is improved by 40%, meeting the stringent requirements of GB / T 19666-2019 for fire resistance reliability in humid and hot environments.

[0130] It should be noted that the device structure and accompanying drawings of this invention mainly describe the principle of this invention. In terms of the technical aspects of this design principle, the setting of the power mechanism, power supply system and control system of the device is not fully described. However, under the premise that those skilled in the art understand the principle of the above invention, the specific details of its power mechanism, power supply system and control system can be clearly understood. The control method in the application document is automatic control through a controller. The control circuit of the controller can be implemented by those skilled in the art through simple programming.

[0131] All standard parts used can be purchased from the market, and can be customized according to the instructions and drawings. The specific connection methods of each part adopt conventional methods such as bolts, rivets, and welding that are mature in the existing technology. The machinery, parts and equipment adopt conventional models in the existing technology, and the structure and principle of the components known to those skilled in the art can be known by those skilled in the art through technical manuals or conventional experimental methods.

[0132] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. An insulated flame-retardant cable structure, comprising a cable core (100) and an external protective tube covering the outside of the cable core (100), characterized in that: The external protective tube includes several rigid protective tube units (200) and flexible fireproof hinges (300) connected between adjacent rigid protective tube units (200), as well as an outer sleeve (500) covering the rigid protective tube units (200) and the flexible fireproof hinges (300). The rigid protective tube units (200) and the flexible fireproof hinges (300) are connected in series to form a flexible structure. The rigid protective tube unit (200) is a composite tube structure, which includes at least the following from the inside to the outside: an inner lining layer (210) made of ceramicized silicone rubber material, a load-bearing layer (220) made of metal corrugated pipe, and an outer flame-retardant layer (230) formed by extrusion of halogen-free low-smoke flame-retardant polymer. The flexible fireproof hinge (300) includes: a fireproof shell (301) made of a woven metal mesh or a flexible stainless steel corrugated pipe; a plurality of high-temperature expansion fireproof sealing blocks (310) completely encapsulated in the internal cavity of the fireproof shell (301); and a quick-connecting mechanism (320) fixedly disposed at both ends of the fireproof shell (301) and the rigid protective tube unit (200) for detachable connection between the two. The high-temperature expandable fireproof sealing block (310) comprises an elastomer formed by vulcanizing an expandable graphite, ammonium polyphosphate, pentaerythritol and melamine flame retardant with a silicone rubber matrix; The flexible fireproof hinge (300) also has a spiral or ring-shaped metal support frame (330) embedded inside the fireproof shell (301), and the metal support frame (330) is embedded in the high-temperature expansion fireproof sealing block (310).

2. The insulated flame-retardant cable structure according to claim 1, characterized in that: The quick-connect mechanism (320) is a snap-fit ​​connector. The quick-connect mechanism (320) includes a male connector assembly and a female connector assembly. The male connector assembly includes multiple sets of radially protruding hooks (321). The female connector assembly includes a guide groove (322) that mates with the hooks (321). The hooks (321) are inserted into the guide groove (322). The guide groove (322) extends on one side and is provided with a side groove (323) that can accommodate the hook (321). The guide groove (322) includes a main hole (3221) for the hook (321) to pass through, and a secondary hole (3222) provided at the end of the main hole for constraining the hook (321). The hook (321) includes a main rod (3211) and a reverse hook body (3212) disposed at the end of the main rod (3211). The reverse hook body (3212) is bent toward the main rod (3211). The width of the main hole (3221) is less than the sum of the width of the opening of the reverse hook body (3212) and the width of the main rod (3211). The hook (321) is made of shape memory alloy material. The reverse hook body (3212) is locked in place with the secondary hole (3222). The hooks (321) and guide grooves (322) provided in the rigid protective tube unit (200) are respectively installed on the load-bearing layer (220) at different ends, and the hooks (321) and guide grooves (322) provided with the flexible fireproof hinge (300) are respectively installed on the fireproof shell (301) at different ends. The mating surfaces of the male and female connectors are also fitted with an annular high-temperature resistant silicone sealing ring (324).

3. The insulated flame-retardant cable structure according to claim 1, characterized in that: The load-bearing layer (220) of the rigid protective tube unit (200) is an annular corrugated pipe made of 304 stainless steel or copper alloy, and the inner wall of the annular corrugated pipe trough is tightly bonded to the outer wall of the inner lining layer (210).

4. The insulated flame-retardant cable structure according to claim 3, characterized in that: The inner lining layer (210) is a continuous tubular layer that is directly coated onto the inner wall of the load-bearing layer (220) by an extrusion process and conforms to the corrugated shape.

5. The insulated flame-retardant cable structure according to claim 1, characterized in that: A flame-retardant and heat-insulating layer (400) is also filled between the cable core (100) and the inner wall of the inner lining layer (210) of the rigid protective tube unit (200). The flame-retardant and heat-insulating layer (400) is a wrapped ceramic fiber tape or mica tape.

6. The insulated flame-retardant cable structure according to claim 1, characterized in that: The axial length of the flexible fireproof hinge (300) is less than the axial length of the rigid protective tube unit (200), which allows two adjacent rigid protective tube units (200) to have a deflection angle of not less than 15 degrees at the connection.

7. The insulated flame-retardant cable structure according to claim 1, characterized in that: The outer surface of the outer sleeve (500) is provided with a coating for marking and corrosion resistance.

8. The insulated flame-retardant cable structure according to claim 1, characterized in that: The outer sleeve (500) includes an outer protective layer (501) and a plurality of cavities (502) disposed inside the outer protective layer (501). The cavities (502) are filled with water-absorbing and expanding microparticles (503). An inner protective layer (504) is also disposed between the cavities (502) and the rigid protective tube unit (200) and the flexible fireproof hinge (300).

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