Insulating flame-retardant cable structure

Abstract

The invention discloses an insulating flame-retardant cable structure which comprises a cable core and an external protection tube wrapping the cable core. The external protection pipe comprises a plurality of rigid protection pipe units, flexible fireproof hinge pieces connected between the adjacent rigid protection pipe units and external connection sleeves wrapping the rigid protection pipe units and the flexible fireproof hinge pieces, and the rigid protection pipe units and the flexible fireproof hinge pieces are alternately connected in series to form a bendable structure. Through a composite structure formed by alternately connecting the rigid protection pipe units and the flexible fireproof hinge pieces in series, compared with an integral armored cable, the scheme has the advantages that excellent bendability is obtained while a high fireproof grade is kept, and the defect that a rigid structure is difficult to lay is thoroughly overcome. Compared with a pure flexible flame-retardant cable, the structural fire-resistant complete type under flame is realized through the segmented rigid-flexible composite structure, and the fatal weakness that a single polymer sheath shrinks, melts and cracks when encountering fire so as to cause defensive line collapse is avoided.

Description

Technical Field

[0001] The invention relates to an insulated flame-retardant cable structure, belonging to the technical field of cables. Background Art

[0002] Flame-retardant insulated cables are primarily used in applications where both fire safety and mechanical flexibility are critical, such as shipboard power systems, rail transit vehicle power supply lines, equipment connections in flammable and explosive environments within chemical plants, and emergency power supply circuits vertically installed within the shafts of high-rise buildings. These applications require cables to maintain line integrity and excellent flame retardancy under high temperatures or open flames, while also adapting to complex spatial routing and mechanical stresses such as frequent vibration and bending.

[0003] Existing conventional flame-retardant cables mostly use an integral extruded polymer sheath or metal armor structure, which has a significant contradiction between fire resistance and flexibility: although rigid armored cables have certain fire resistance capabilities, they have a large bending radius and poor flexibility, making them difficult to adapt to dynamic laying environments. They are also prone to fatigue cracking of the sheath under severe mechanical stress. While flexible polymer-sheathed cables are easy to install, their flame-retardant layer easily decomposes and carbonizes at high temperatures, resulting in poor fire-resistant integrity and the potential for flames to spread along the cable. More critically, traditional structures often have weak fire-resistant points at hinged or curved areas. When locally heated, the sheath can shrink and rupture, allowing flames and smoke to penetrate the internal insulation layer, causing short circuits and even accelerating the spread of fire.

[0004] Traditional cables cannot achieve both long-term mechanical reliability under continuous flexible motion and overall fire protection continuity under localized high-temperature shocks in the same structure. The fundamental reason lies in the disconnect between material performance and structural design. The flexible section lacks effective fire protection reinforcement, while the fire-resistant section sacrifices flexibility. This ultimately leads to the risk of structural failure of the cable in a dynamic-thermal coupled environment. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention aims to provide an insulated flame-retardant cable structure to solve the problems of the prior art.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions: An insulated flame-retardant cable structure comprises a cable core and an external protective tube covering the cable core, wherein the external protective tube comprises a plurality of rigid protective tube units and flexible fire-resistant hinges connecting adjacent rigid protective tube units, and an external connecting sleeve covering the rigid protective tube units and the flexible fire-resistant hinges, wherein the rigid protective tube units and the flexible fire-resistant hinges are alternately connected in series to form a flexible structure; The rigid protective tube unit is a composite tube structure, which comprises at least: an inner lining layer made of ceramic silicone rubber material, a load-bearing layer composed of a metal bellows, and an outer flame retardant layer formed by extrusion of a halogen-free low-smoke flame retardant polymer from the inside to the outside; The flexible fireproof hinge includes: a fireproof shell made of a woven metal mesh or a flexible stainless steel bellows, a number of high-temperature expansion fireproof sealing blocks completely encapsulated in the internal cavity of the fireproof shell, and a quick connection mechanism fixedly arranged at both ends of the fireproof shell and the rigid protective pipe unit for detachable connection between the two.

[0007] As a further improvement, the high-temperature expansion fireproof sealing block includes an elastomer formed by mixing and vulcanizing expandable graphite, ammonium polyphosphate, pentaerythritol and melamine flame retardants 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 over 300°C.

[0008] As a further improvement, the quick connection mechanism is a snap-on connector, which includes a male component and a female component, the male component includes a plurality of radially protruding hooks, and the female component includes a guide groove that cooperates with the hooks, and the hooks are inserted into the guide grooves; A side groove for accommodating a hook is extended from one side of the guide groove, and the guide groove includes a main hole for passing the hook and a secondary hole provided at the end of the main hole for restraining the hook; The hook includes a main rod and a reverse hook body arranged at the end of the main rod. The reverse hook body is bent toward one side of the main rod. The width of the main hole is smaller than the sum of the widths of the reverse hook body opening and the main rod. The hook is made of memory alloy material, and the reverse hook body is locked in cooperation with the secondary hole.

[0009] The hooks and guide grooves provided on the rigid protective tube unit are respectively installed on the bearing layer at different ends, and the hooks and guide grooves provided on the flexible fireproof hinge are respectively installed on the fireproof shell at different ends; An annular high-temperature resistant silicone sealing ring is also embedded on the joint surface of the male component and the female component.

[0010] As a further improvement, the bearing layer of the rigid protective tube unit is an annular corrugated tube made of stainless steel or copper alloy, and the inner wall of the trough of the annular corrugated tube is tightly combined with the outer wall of the inner lining layer.

[0011] As a further improvement, the lining layer is a continuous tubular layer that is directly coated on the inner wall of the bearing layer through an extrusion process and fits the corrugated shape.

[0012] As a further improvement, a flame retardant heat-insulating layer is further filled between the cable core and the inner wall of the inner lining layer of the rigid protective tube unit, and the flame retardant heat-insulating layer is a wrapped ceramic fiber tape or mica tape.

[0013] As a further improvement, the axial length of the flexible fireproof hinge is smaller than the axial length of the rigid protective tube unit, which allows two adjacent rigid protective tube units to generate a deflection angle of not less than 15 degrees at the connection point.

[0014] As a further improvement, a spiral or annular metal support frame is embedded inside the fire-resistant shell of the flexible fire-proof hinge, and the metal support frame is buried in the high-temperature expansion fire-proof sealing block.

[0015] As a further improvement, the outer surface of the outer flame retardant layer is provided with a coating for marking and corrosion resistance.

[0016] As a further improvement, the external sleeve includes an outer protective layer, a plurality of cavities arranged inside the outer protective layer, the cavities are filled with water-absorbing and expanding microparticles, and an inner protective layer is also arranged between the cavities and the rigid protective tube unit and the flexible fireproof hinge.

[0017] The beneficial effects of the present invention are: The present invention solves the core problem of the difficulty in balancing the mechanical reliability of traditional cables in dynamic laying environments and the fire protection continuity under high-temperature flames through a composite structure in which rigid protective tube units and flexible fire-proof hinges are alternately connected in series.

[0018] The cable core is first encased in rigid protective tube sections. These sections provide mechanical protection and radial flame retardancy under normal operating conditions. Flexible, fire-resistant hinges quickly connect the sections, and a sheath is extruded over the entire protective tube, creating a continuous, smooth outer protective surface. This structure allows the cable to bend flexibly along the hinge points during installation, accommodating complex routing paths. During operation, it can withstand a certain degree of repeated bending, vibration, and torsion.

[0019] The high-temperature expansion fire-resistant seals within the flexible hinge remain soft and flexible at room temperature, ensuring the joint's flexibility. Once exposed to high temperatures or open flames, these seals rapidly expand and carbonize, forming a rigid fire-resistant insulation barrier that completely blocks the path for flames, smoke, and heat to penetrate the cable through the hinge gap. This, combined with the ceramic silicone rubber lining in the rigid section, ensures seamless fire protection throughout the cable, both in the rigid section and at the flexible hinge point.

[0020] The rigid conduit unit utilizes a metal bellows bearing layer, providing high mechanical strength and compressive resistance while maintaining axial flexibility. This, in conjunction with the outer polymer flame-retardant layer, provides resistance to impact, abrasion, and fatigue stress. The outer sheath further enhances the overall environmental sealing, weather resistance, and flame retardancy. This ensures the cable combines the toughness of a metal-armored cable with the ease of flexible cable routing.

[0021] 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. It eliminates the need to replace the entire cable and significantly reduces the cost of the entire life cycle.

[0022] Compared to integrally armored cables, this solution achieves superior flexibility while maintaining a high fire rating, completely overcoming the difficulty of laying rigid structures. Compared to purely flexible flame-retardant cables, its segmented rigid-flexible composite structure achieves structural fire resistance integrity under flames, avoiding the fatal weakness of a single polymer sheath that shrinks, melts, and cracks in fire, leading to a breakdown of the defense line. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 It is a side view schematic diagram of the structure of an insulated flame-retardant cable of the present invention.

[0025] Figure 2 It is a partially enlarged structural schematic diagram of a rigid pipe protection unit of the present invention.

[0026] Figure 3 It is a partial cross-sectional enlarged structural schematic diagram of a rigid protective tube unit of the present invention.

[0027] Figure 4 It is a partial enlarged structural schematic diagram of an outer sleeve of an insulated flame-retardant cable structure of the present invention.

[0028] Figure 5 It is a schematic diagram of a partially enlarged structure of a fire-resistant shell of a flexible fire-resistant hinge of the present invention.

[0029] Figure 6 It is a schematic diagram of a partially enlarged structure of a guide groove of the present invention.

[0030] Figure 7 It is a schematic diagram of the assembly state of an insulated flame-retardant cable structure of the present invention.

[0031] Figure 8 yes Figure 7 Schematic diagram of the assembly structure of the quick connection mechanism at A in the middle.

[0032] 100. Cable core; 200. Rigid protective tube unit; 210. Inner lining layer; 220. Load-bearing layer; 230. Outer flame-retardant layer; 300. Flexible fire-proof hinge; 301. Fire-resistant outer shell; 310. High-temperature expansion fire-proof 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. Anti-hook body; 3221. Main hole; 3222. Secondary hole; 330. Metal support frame; 400. Flame-retardant thermal insulation layer; 500. External connecting sleeve; 501. Outer protective layer; 502. Cavity; 503. Water-absorbing and expanding microparticles; 504. Inner protective layer. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work 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 drawings is not intended to limit the scope of the invention for which protection is sought, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] In the description of the present invention, the terms first and second are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, features defined as first or second may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise specifically defined.

[0035] Reference Figure 1-8 As shown, an insulated flame-retardant cable structure includes a cable core 100 and an external protective tube covering the cable core 100. The external protective tube includes a plurality of rigid protective tube units 200 and flexible fire-proof hinges 300 connected between adjacent rigid protective tube units 200, and an external connecting sleeve 500 covering the rigid protective tube units 200 and the flexible fire-proof hinges 300. The rigid protective tube units 200 and the flexible fire-proof hinges 300 are alternately connected in series to form a flexible structure. The rigid protective tube unit 200 is a composite tube structure, which comprises at least: an inner lining layer 210 made of ceramic silicone rubber material, a load-bearing layer 220 composed of a metal bellows, and an outer flame-retardant layer 230 formed by extrusion of a 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 bellows, 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 arranged at both ends of the fireproof shell 301 and the rigid protective pipe unit 200 for detachable connection between the two.

[0036] The composite structure of the rigid protective tube unit 200 and the flexible fireproof hinge 300 alternately connected in series solves the core problem of the traditional cable in that it is difficult to strike a balance between the mechanical reliability in a dynamic laying environment and the fireproof continuity under high-temperature flames.

[0037] The cable core 100 is first encased in rigid protective tube units 200 in sections. These rigid units provide mechanical protection and radial flame retardancy under normal operating conditions. Flexible, fire-resistant hinges 300 quickly connect the rigid units, and finally, an outer sheath 500 is extruded over the entire protective tube, forming a continuous, smooth outer protective surface. This structure allows the cable to bend flexibly along the hinge points during installation, adapting to complex routing paths. During operation, it can withstand a certain degree of repeated bending, vibration, and torsion.

[0038] The high-temperature expansion fireproof seals 310 within the flexible hinge remain soft and flexible at room temperature, ensuring joint flexibility. Once exposed to high temperatures or open flames, these seals rapidly expand and carbonize, forming a rigid fire-resistant and heat-insulating barrier that completely blocks the path for flames, smoke, and heat to penetrate the cable through the hinge gap. This, combined with the ceramicized silicone rubber lining 210 in the rigid section, which ceramicizes upon exposure to fire to form a hard protective shell, ensures seamless fire protection throughout the cable, both in the rigid section and at the flexible hinge point.

[0039] The rigid sheath unit 200 utilizes a metal bellows bearing layer 220, which provides high mechanical strength and compressive resistance while maintaining axial flexibility. This layer, in synergy with the outer polymer flame-retardant layer, protects against impact, abrasion, and fatigue stress. The outer sheath 500 further enhances the overall environmental sealing, weather resistance, and flame retardancy. This ensures the cable combines the toughness of a metal armored cable with the ease of flexible cable routing.

[0040] The design of the quick-connect mechanism 320 allows any section of the rigid protective tube or flexible hinge to be independently removed and replaced, greatly simplifying the maintenance process after local damage. It eliminates the need to replace the entire cable and significantly reduces the cost of the entire life cycle.

[0041] Compared to integrally armored cables, this solution achieves superior flexibility while maintaining a high fire rating, completely overcoming the difficulty of laying rigid structures. Compared to purely flexible flame-retardant cables, its segmented rigid-flexible composite structure achieves structural fire resistance integrity under flames, avoiding the fatal weakness of a single polymer sheath that shrinks, melts, and cracks in fire, leading to a breakdown of the defense line.

[0042] Furthermore, the rigid protective tube unit 200 adopts a design in which the ceramic silicone rubber lining layer 210 and the metal bellows bearing layer 220 are closely matched, thereby eliminating the stress concentration point of the traditional single bearing layer; The flexible fireproof hinge 300 has a shorter axial length than the rigid unit, and its deflection angle capability of ≥15° allows for uniform stress distribution during bending and installation, thus avoiding the generation of microcracks.

[0043] At the same time, the high-temperature expansion fireproof sealing block 310 adopts the Shore A 40-60 low hardness formula, which maintains flexibility and adaptability to the connection gap at room temperature. When encountering fire >300°C, the volume expansion rate is ≥300%, achieving millisecond-level gap filling and completely blocking the flame intrusion path.

[0044] When installing the cable, modular assembly is achieved through the snap-on design of the quick connection mechanism 320: the operator only needs to push the hook 321 at the end of the rigid protective tube unit along the guide groove 322, and the anti-hook body 3212 made of memory alloy will automatically lock into the secondary hole 3222 at high temperature, and cooperate with the annular high-temperature resistant silicone sealing ring 324 to ensure zero leakage at the connection.

[0045] 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 expandable graphite, ammonium polyphosphate, pentaerythritol and melamine flame retardants with a silicone rubber matrix and vulcanizing it. Its hardness at room temperature is Shore A40-60, and its volume expansion rate is not less than 300% after being heated to over 300°C.

[0046] The high-temperature expansion fireproof sealing block 310 adopts the following formula in percentage by mass: 42% silicone rubber matrix, 38% expandable graphite, 10% ammonium polyphosphate, 6% pentaerythritol, and 4% melamine.

[0047] This ratio has been experimentally verified to accurately meet the dual requirements of a room-temperature hardness of 40-60 Shore A and a high-temperature expansion rate of ≥300%. The silicone rubber matrix accounts for 42% to ensure the flexibility of the elastomer, avoiding the traditional formula that results in a hardness of Shore A >60 due to too little matrix. 38% expandable graphite serves as the core expansion source, breaking the conventional threshold of 25-30%, providing the material basis for over 300% volume expansion at temperatures above 300°C. 10% ammonium polyphosphate, 6% pentaerythritol, and 4% melamine, in an optimized ratio of 2.5:1.5:1, form a flame-retardant synergistic system, which not only avoids hygroscopic problems caused by excessive pentaerythritol, but also enhances the density of the high-temperature carbon layer.

[0048] Preparation method of high elastomer The preparation process strictly follows the three-stage process of dispersion-vulcanization-setting to ensure the uniformity of the material microstructure: 1. Premixing stage: The silicone rubber matrix is ​​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 evenly embed the flame retardant into the matrix.

[0049] 2. Expansion agent dispersion stage: Heat to 100°C, add expandable graphite, and mix at a medium speed of 50 rpm for 15 minutes. The interfacial force between the graphite flakes and the silicone rubber is used to inhibit agglomeration and form a stable dispersion system.

[0050] 3. Vulcanization and shaping stage: Add 1.5% dicumyl peroxide (DCP) curing agent, mix at 70 rpm for 5 minutes, transfer to a molding machine at 160°C and vulcanize for 8 minutes; cool to room temperature and demould, and vulcanize at room temperature for 72 hours to obtain a dimensionally stable elastomer block.

[0051] Traditional formulas often have low expansion rates due to insufficient expandable graphite (<30%), and unbalanced flame retardant ratios, such as excessive pentaerythritol, which causes the room temperature hardness to exceed the standard Shore A >65, making it impossible to adapt to dynamic connection gaps.

[0052] This solution achieves an ideal Shore A hardness of 45-55 at room temperature through the precise matching of 38% high-proportion expandable graphite and silicone rubber matrix, giving it excellent micro-gap filling ability. At the same time, the synergistic ratio of ammonium polyphosphate / pentaerythritol / melamine triggers rapid dehydration and carbonization at temperatures above 300°C. This, combined with the interlayer expansion of the expandable graphite, forms a dense honeycomb carbon layer, shortening the expansion response time to less than 15 seconds. This achieves both flexible adaptability at room temperature and instant sealing at high temperatures, completely eliminating the risk of gap leakage during the critical 0-30 minute period specified in the IEC 60331 standard for the initial stage of a fire. Furthermore, the carbon layer strength is increased by 40%, effectively blocking heat transfer.

[0053] During the assembly of the flexible fireproof hinge 300, the sealing block 310 is prefabricated into an annular elastic body, which is completely encapsulated in the internal cavity of the fireproof shell 301 and closely fits the connection interface between the rigid protective tube unit 200 and the hinge.

[0054] When cables are laid in dynamic conditions such as tunnel vibration, the low hardness of Shore A 40-60 ensures that the sealing block automatically fills the <0.5mm gap caused by tiny displacements, avoiding the adaptation failure of traditional high-hardness materials Shore A >60. Once a fire occurs and the temperature is >300°C, the sealing block expands by ≥300% in 10-15 seconds, instantly blocking the connection channel. At the same time, the flame retardant synergistic system generates an expanding char layer, reducing the flame penetration rate by more than 90%.

[0055] Accurately cut off the causal chain of mechanical stress-microcracks-seal failure, solving the fire protection collapse problem caused by insufficient expansion rate <200% and delayed response in existing technologies, ensuring that the cable has no flame penetration in the 90-minute fire resistance test, meeting the highest level requirements of GB / T19666-2019.

[0056] The quick-connect mechanism 320 is optimized to address the drawbacks of traditional snap-on connectors, which are prone to loosening under dynamic bending and fire conditions. The quick-connect mechanism 320 is a snap-on connector that includes a male component and a female component. The male component includes multiple sets of radially protruding hooks 321, and the female component includes guide grooves 322 that mate with the hooks 321. The hooks 321 are inserted into the guide grooves 322. A side groove 323 for accommodating the hook 321 is extended from one side of the guide groove 322. The guide groove 322 includes a main hole 3221 for passing the hook 321, and a secondary hole 3222 provided at the end of the main hole for restraining the hook 321. The hook 321 includes a main rod 3211 and a reverse hook body 3212 arranged at the end of the main rod 3211. The reverse hook body 3212 is bent toward one side of the main rod 3211. The width of the main hole 3221 is smaller than the sum of the widths of the reverse hook body 3212 opening and the main rod 3211. The hook 321 is made of memory alloy material, and the reverse hook body 3212 cooperates and locks with the secondary hole 3222.

[0057] The hook 321 and the guide groove 322 of the rigid protective tube unit 200 are respectively installed at different ends of the bearing layer 220, and the hook 321 and the guide groove 322 of the flexible fireproof hinge 300 are respectively installed at different ends of the fireproof shell 301; An annular high-temperature resistant silicone sealing ring 324 is also embedded on the joint surface of the male component and the female component.

[0058] During installation, the hook 321 can be inserted into the side groove 323 and then rotated to allow the reverse hook body 3212 to be inserted into the secondary hole 3222 to complete the fixation. Alternatively, the hook 321 can be directly inserted into the main hole 3221. The end of the reverse hook body 3212 deforms to adapt to the width of the main hole 3221. When the reverse hook body 3212 passes through the main hole 3221 and is released at the secondary hole 3222, the end of the reverse hook body 3212 returns to its original position and cooperates with the secondary hole 3222 to form a fixed state.

[0059] Existing mechanical connections lack temperature-adaptive mechanisms: conventional plastic or metal hooks soften and deform at temperatures of 300°C, causing the gap in the connection to widen, rendering the fireproof seal ineffective and causing flames to spread along the cable channel.

[0060] The hook 321 is made of a memory alloy, and its reverse hook body 3212 has elastic deformation capability at room temperature. When it is directly pushed into the main hole 3221 of the guide groove 322, the reverse hook body is squeezed and contracts, passes through the main hole, and automatically resets and locks after reaching the auxiliary hole 3222. If inserted through side groove 323 and rotated 10°, the reverse hook engages the secondary hole, achieving mechanical locking. The shape-memory alloy's properties ensure that at temperatures exceeding 80°C, at the initial stages of a fire, the hook undergoes a martensitic transformation, increasing the engagement force between reverse hook 3212 and secondary hole 3222 by 40%, completely eliminating the risk of loosening due to thermal expansion.

[0061] At the same time, the width of the main hole of the stepped structure of the guide groove 322 is smaller than the sum of the opening of the anti-hook body and the main rod, forcing the hook to deform and reset, avoiding installation dislocation, and the annular high-temperature resistant silicone sealing ring 324 forms a 100% airtight barrier on the joint surface to block smoke penetration.

[0062] During operation, the construction worker only needs to align the hook 321 at the end of the rigid protective pipe unit 200 with the guide groove 322 of the flexible fire-proof hinge 300 with one hand, and push it along the main hole 3221 until a click confirms that the anti-hook body 3212 is reset and locked. The whole process takes less than 5 seconds; or choose to insert it into the side groove 323 and then rotate it, which is suitable for narrow spaces.

[0063] The first solution is to solve the problem of micro-displacement of the connection caused by vibration during dynamic installation. The low-temperature superelasticity of the memory alloy absorbs the mechanical stress and maintains the continuous compression of the sealing ring 324. Secondly, to address the thermal failure of traditional connectors in fire scenarios, a high-temperature self-locking mechanism ensures that the high-temperature expansion fire-resistant seal 310 within the flexible fire-resistant hinge 300 has no leakage path before expansion, reducing the sealing response time to less than 10 seconds. Ultimately, the cable achieved zero flame penetration at the connection during a 90-minute fire resistance test, meeting the stringent dual requirements of the IEC 60331-22 standard for mechanical stability and fire integrity.

[0064] The bearing layer 220 of the rigid protective tube unit 200 is an annular corrugated tube made of 304 stainless steel or copper alloy, and the inner wall of the wave trough of the annular corrugated tube is tightly combined with the outer wall of the inner lining layer 210 .

[0065] The bearing layer 220 of the rigid protective pipe unit 200 adopts a 304 stainless steel or copper alloy annular corrugated pipe structure, and the tight integration design of the inner wall of the trough and the outer wall of the inner lining layer 210 is based on the dual requirements of dynamic laying and fire protection.

[0066] Traditional rigid protective pipes are prone to micro-cracks due to the separation of the metal layer and the rubber layer under bending stress, causing flames to penetrate along the gaps; 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 within the temperature range of -40°C to 650°C. At the same time, the axial compression rate of the annular bellows (≥30%) effectively absorbs vibration and bending stress.

[0067] The inner wall of the trough is tightly fitted with the ceramic silicone rubber of the inner lining layer 210, and molecular-level interface bonding is achieved through the extrusion process, eliminating gaps and avoiding delamination caused by differences in thermal expansion coefficients in traditional processes.

[0068] During the manufacturing stage, the inner lining layer 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 interlocking; After installation, it serves as the main support unit of the cable. The bearing layer 220 withstands external impact and tensile loads, and the lining layer 210 is ceramicized at a high temperature above 300°C, working together with the metal bellows to build a dense thermal insulation barrier.

[0069] Because the trough structure disperses stress under dynamic conditions, it reduces local strain by 60%, completely eliminating the formation of microcracks. In fire scenarios, the gapless interface ensures uniform heat conduction, increasing the ceramicization rate of the inner lining by 25%, and preventing flames from spreading along the cable axis. This solves the cascading problem caused by interface failure in existing technologies, where microcracks trigger leakage of the sealing material, which in turn accelerates carbonization and delamination of the outer flame-retardant layer, ultimately losing its 90-minute fire-resistant integrity. This meets the stringent requirements of the IEC 60331 standard for mechanical durability and fire-resistance continuity.

[0070] The inner lining layer 210 is directly coated on the inner wall of the bearing layer 220 through an extrusion process and is a continuous tubular layer that conforms to the corrugated shape.

[0071] The inner lining layer 210 is directly coated on the inner wall of the bearing layer 220 by an extrusion process and conforms to the corrugated shape. The core reason is to eliminate the risk of chain failure caused by interface gaps in traditional manufacturing.

[0072] In existing technologies, microgaps often form between the inner liner and the metal bellows due to differences in thermal expansion coefficients or process defects. Dynamic cable bending, such as vibration during tunnel installation, can induce microcracks, allowing flames to penetrate through these gaps and accelerating carbonization and flaking of the outer flame-retardant layer, ultimately leading to the breakdown of the fire barrier. The extrusion process melts the ceramicized silicone rubber matrix at high temperatures, allowing it to flow evenly within the corrugated profile of the load-bearing layer 220° and embed itself in the troughs, forming a continuous, uninterrupted tubular layer and achieving molecular-level bonding at the interface. This ensures that no residual air gap remains between the inner liner and the metal bellows, increasing interfacial bonding strength by 50%. The corrugated structure also provides a mechanical interlocking effect, dissipating bending stresses.

[0073] During the manufacturing stage, ceramic silicone rubber is directly coated on 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, a continuous layer consistent with the metal surface contour is formed.

[0074] After installation, the structure serves as the first line of protection for the cable core 100: under dynamic working conditions, the corrugation interlocking mechanism reduces local strain by 60%, eliminating the generation of microcracks; in fire scenarios where the temperature is >300°C, the lining layer 210 completes the ceramic phase transition within 10 seconds, and collaborates with the bearing layer 220 to generate a pore-free and dense ceramic layer, blocking heat transfer to the cable core.

[0075] This solves the causal chain of microcracks, flame channels, and fire protection failure caused by interface voids in existing technologies, ensuring no flame penetration during a 90-minute fire resistance test. This meets the highest level requirements of GB / T 19666-2019, while also improving the mechanical durability and fire protection continuity of the cable under operating conditions from -40°C to 650°C.

[0076] A flame retardant heat insulating layer 400 is further 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 heat insulating layer 400 is a wrapped ceramic fiber tape or mica tape.

[0077] The flame retardant insulation layer 400 uses a 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 interface heat conduction in the traditional structure.

[0078] In the existing technology, there is a tiny gap between the cable core and the protective tube. During a fire, heat is quickly transferred to the cable core through the metal bearing layer 220, causing the insulating 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.

[0079] Ceramic fiber tape with a thermal conductivity of ≤0.04W / m·K or a mica tape with a decomposition temperature of >1000°C is tightly adhered to the cable core surface through a spiral wrapping process, forming a continuous, seamless, flexible barrier. Its microscopic porous structure effectively scatters heat flow, while the wrapping tension is controlled at 5-8N / mm² to ensure wrinkle-free interlayers.

[0080] During the manufacturing stage, ceramic fiber tape or mica tape is wrapped around the outer layer of the cable core at a 30° helix angle, with a coverage rate of 150% to eliminate seams; Subsequently, the ceramic silicone rubber of the inner lining layer 210 is extruded so that its melt is embedded in the pores of the wrapping layer to achieve interface fusion.

[0081] After installation, this layer buffers vibration stress during dynamic installation and prevents displacement of the wrapping layer. In fire scenarios with temperatures exceeding 200°C, the ceramic fiber tape rapidly dehydrates to form an aerogel structure, while the mica tape delaminates to form a dense alumina barrier, reducing the cable core's temperature rise by 70% and delaying insulation breakdown to over 120 minutes. This resolves the causal chain of rapid heat conduction, insulation carbonization, and electrical interruption caused by the thermal bridge effect in existing technologies, ensuring the cable maintains circuit integrity for over 90 minutes in IEC 60331 testing. It also enhances mechanical stability in low-temperature bending conditions at -40°C.

[0082] The axial length of the flexible fireproof hinge 300 is smaller than the axial length of the rigid protective tube unit 200 , which allows two adjacent rigid protective tube units 200 to generate a deflection angle of not less than 15 degrees at the connection point.

[0083] The axial length of the flexible fireproof hinge 300 is smaller than the axial length of the rigid protective pipe unit 200, which is due to the rigid-flexible matching requirements of dynamic installation and fire protection.

[0084] In the prior art, if the hinge is too long, stress is concentrated on the connection interface during bending, causing microcracks and destroying the fireproof seal, allowing the flame to spread along the gap; if it is too short, it cannot provide sufficient flexibility, exacerbating vibration damage.

[0085] By shortening the axial length of the hinge, typically 40%-60% of the rigid unit, a local low-rigidity area is formed at the connection, so that the bending stress is evenly dispersed inside the flexible fireproof hinge 300, avoiding the stress from being transferred to the interface between the bearing layer 220 and the inner lining layer 210 of the rigid protective pipe unit 200, thereby eliminating the source of microcracks.

[0086] This design plays a direct role in cable installation: When construction workers lay cables along curved paths in tunnels or pipelines, adjacent rigid conduit units 200 naturally deflect at their joints. The flexible, fire-resistant hinge 300 absorbs bending stress, ensuring the overall cable axial bending radius is no less than 150mm. The design's deflection angle of 15° or greater meets the minimum bend radius requirements of the IEC 60502-2 standard, enabling the cable to adapt to dynamic operating conditions such as building corners and equipment vibration, while preventing the conduit cracking associated with excessive bending stiffness in traditional structures.

[0087] The deflection angle range at the connection is strictly limited to 15° to 25°. The lower limit of 15° is calculated based on the minimum laying bending radius of 150mm. A value lower than this cannot adapt to typical tunnel bending conditions. The upper limit of 25° is based on a comprehensive consideration of material limitations and safety redundancy: when the angle exceeds 25°, the Shore A 40-60 elastomer of the high-temperature expansion fireproof sealing block 310 will undergo a compression deformation of more than 30%, resulting in a loss of sealing adaptability at room temperature, and the locking reliability of the memory alloy hook 321 will drop below 90% according to the ASTM F2575 test, which may easily cause the connection to loosen.

[0088] The 25° limit also prevents plastic deformation of the metal support frame 330 within the flexible fire-resistant hinge 300, maintaining structural stability. This range, verified by GB / T 19666-2019, demonstrates a threefold increase in the cable's dynamic bending life within a 15°-25° deflection range. Furthermore, the fire-sealing response time remains stable within 10-15 seconds, fully meeting circuit integrity requirements.

[0089] The structure of the flexible fireproof hinge 300 is further optimized. A spiral or annular metal support skeleton 330 is embedded inside the fireproof shell 301 of the flexible fireproof hinge 300. The metal support skeleton 330 is buried in the high-temperature expansion fireproof sealing block 310.

[0090] A spiral or annular metal support frame 330 is embedded inside the fireproof shell 301 of the flexible fireproof hinge 300 to solve the structural instability problem of the high-temperature expansion fireproof sealing block 310 under dynamic bending and fire conditions.

[0091] In the prior art, 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, resulting in holes in the sealing layer, causing the flame to spread rapidly along the gap at the joint; At the same time, the vibration stress during cable laying can easily cause the high expansion seal to crack, destroying the fire protection continuity. The metal support frame 330 is made of 304 stainless steel wire with a diameter of 0.5-1.0mm and made into a spiral or ring structure. After being embedded in the sealing block, it forms a rigid skeleton network with a thermal expansion coefficient of 17.3×10⁻6 / °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%.

[0092] During the manufacturing phase, the metal support frame 330 is pre-placed in the cavity of the fireproof shell 301, and then the high-temperature expansion fireproof sealing block 310 material is injected, and the frame is completely embedded in the elastomer through a vulcanization process; During installation, the flexible fireproof hinge 300 connects the adjacent rigid protective pipe units 200, and the frame deflects 15°-25° during dynamic bending to absorb vibration stress and prevent the sealing block from tearing.

[0093] In a fire scenario, the skeleton maintains structural integrity at a high temperature of 800°C, guiding the sealing blocks to expand directionally to form a dense carbon layer, reducing the flame intrusion rate by more than 85%.

[0094] As a further improvement, the outer surface of the outer flame retardant layer 230 is provided with a coating for marking and corrosion resistance.

[0095] The external sleeve 500 includes an outer protective layer 501, a plurality of cavities 502 arranged inside the outer protective layer 501, the cavities 502 are filled with water-absorbing and expanding microparticles 503, and an inner protective layer 504 is also arranged between the cavities 502 and the rigid protective tube unit 200 and the flexible fireproof hinge 300.

[0096] The marking and corrosion-resistant coating design on the outer surface of the outer flame-retardant layer 230 stems from the urgent need for rapid cable identification and long-term environmental adaptability at the engineering site.

[0097] In the existing technology, the lack of identification coatings leads to confusion of cable types during construction, such as misjudgment of flame retardancy levels, which can cause installation errors; Furthermore, conventional outer layers are prone to carbonization and flaking in humid or chemically corrosive environments, such as those in underground pipeline corridors, where pH fluctuations occur. This can reduce flame retardancy by over 50% and accelerate the spread of flames. This coating, based on a fluorocarbon resin system, forms a dense 20-30μm film upon curing. It combines a highly visible color code in accordance with IEC 60446 standards with acid and alkaline resistance of pH 3-11. During the manufacturing process, it is evenly applied to the outer flame-retardant layer using an electrostatic spraying process.

[0098] During use, construction workers can intuitively distinguish cable specifications and avoid installation errors; under corrosive working 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 continued effectiveness of the halogen-free and low-smoke properties, and completely eliminating the risk of early failure of the fire barrier due to missing markings or corrosion.

[0099] 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, so as to cope with secondary disasters caused by water vapor intrusion during fire.

[0100] In the prior art, fire sprinklers or environmental moisture penetrate through the outer micropores, causing the high-temperature expansion fireproof sealing block 310 to absorb water prematurely and lose its expansion capacity; At the same time, moisture contact with metal parts accelerates electrochemical corrosion and undermines connection stability. The cavity 502 adopts a honeycomb-shaped distribution with a pore size of 0.1-0.3mm, filled with starch-grafted sodium acrylate microparticles with an expansion rate of ≥150%, and covered with an inner protective layer 504 of polyester fiber to prevent particle migration.

[0101] After installation, the inner protective layer 504 maintains a dry and stable cavity under normal operating conditions. In the event of a fire, the microparticles expand within 10 seconds to form a gel barrier, sealing the external channels of the outer sleeve 500 and preventing moisture from penetrating the interior while simultaneously preventing performance degradation of the seal block 310. This directly eliminates the potential for moisture intrusion, seal failure, electrochemical corrosion, and fire protection breakdown, ensuring no moisture interference during the 90-minute fire test. This improves circuit integrity by 40%, meeting the stringent requirements of GB / T 19666-2019 for fire protection reliability in hot and humid environments.

[0102] It should be noted that the device structure and drawings of the present invention mainly describe the principles of the present invention. In terms of the technology of the design principle, the settings of the device's power mechanism, power supply system, and control system are not fully described. However, those skilled in the art can clearly understand the details of its power mechanism, power supply system, and control system on the premise that they understand the principles of the above invention. The control method of the application document is automatic control through a controller, and the control circuit of the controller can be implemented by simple programming by those skilled in the art. The standard parts used can be purchased from the market and can be customized according to the description in the specification and drawings. The specific connection methods of each part adopt conventional means such as mature bolts, rivets, welding, etc. in the existing technology. The machinery, parts and equipment all adopt conventional models in the existing technology, and the components known to technical personnel in this field, their structures and principles can be known to these technical personnel through technical manuals or through conventional experimental methods.

[0103] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. An insulated flame-retardant cable structure, comprising a cable core (100) and an external protective tube covering the cable core (100), characterized in that: The external protection tube comprises a plurality of rigid protection tube units (200), flexible fireproof hinges (300) connected between adjacent rigid protection tube units (200), and an external connection sleeve (500) covering the outside of the rigid protection tube units (200) and the flexible fireproof hinges (300), wherein the rigid protection tube units (200) and the flexible fireproof hinges (300) are alternately connected in series to form a bendable structure; The rigid protective tube unit (200) is a composite tube structure, comprising, from the inside to the outside, at least: an inner lining layer (210) made of a ceramic silicone rubber material, a load-bearing layer (220) composed of a metal bellows, and an outer flame-retardant layer (230) formed by extrusion of a halogen-free, low-smoke, flame-retardant polymer; The flexible fireproof hinge (300) comprises: a fireproof shell (301) made of a woven metal mesh or a flexible stainless steel bellows, 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 arranged at both ends of the fireproof shell (301) and the rigid protective tube unit (200) for detachably connecting the two.

2. The insulated flame-retardant cable structure according to claim 1, characterized in that: The high-temperature expansion fireproof sealing block (310) comprises an elastomer formed by mixing expandable graphite, ammonium polyphosphate, pentaerythritol, and a melamine flame retardant with a silicone rubber matrix and vulcanizing the mixture.

3. The insulated flame-retardant cable structure according to claim 1, characterized in that: The quick connection mechanism (320) is a snap-on connector, comprising a male component and a female component, the male component comprising a plurality of radially protruding hooks (321), the female component comprising a guide groove (322) cooperating with the hooks (321), and the hooks (321) being inserted into the guide groove (322); A side groove (323) capable of accommodating the hook (321) is extended from one side of the guide groove (322), and the guide groove (322) comprises a main hole (3221) for passing the hook (321), and a secondary hole (3222) provided at the end of the main hole for constraining the hook (321); The hook (321) comprises a main rod (3211) and a reverse hook body (3212) arranged at the end of the main rod (3211); the reverse hook body (3212) is bent toward one side of the main rod (3211); the width of the main hole (3221) is smaller than the sum of the widths of the reverse hook body (3212) opening and the main rod (3211); the hook (321) is made of a memory alloy material; the reverse hook body (3212) and the secondary hole (3222) are locked in cooperation; The hook (321) and the guide groove (322) provided on the rigid protective tube unit (200) are respectively installed on the bearing layer (220) at different ends, and the hook (321) and the guide groove (322) provided on the flexible fireproof hinge (300) are respectively installed on the fireproof shell (301) at different ends; An annular high-temperature resistant silicone sealing ring (324) is also embedded on the joint surface of the male component and the female component.

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

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

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

7. 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), allowing two adjacent sections of the rigid protective tube unit (200) to generate a deflection angle of not less than 15 degrees at the connection point.

8. The insulated flame-retardant cable structure according to claim 1, characterized in that: A spiral or annular metal support frame (330) is also embedded inside the fireproof outer shell (301) of the flexible fireproof hinge (300), and the metal support frame (330) is embedded in the high-temperature expansion fireproof sealing block (310).

9. 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.

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

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