An ultra-thin bend-resistant elevator cable and a method of making the same

Abstract

The application relates to the technical field of electric wire and cable, in particular to an ultrathin bending-resistant elevator cable and a preparation method thereof. The cable comprises five layers of functional structures, namely a center reinforcing layer, a stranded core unit, a cabling filling system, a shielding layer and an outer sheath layer. The center reinforcing layer is made of 400D para-aramid fiber and coated with a polyurethane coupling agent coating, and the center reinforcing layer is twisted with the cable core and serves as a load-bearing framework. The preparation method comprises five steps of conductor twisting, insulation extrusion, center cabling, shielding wrapping and flat sheath extrusion. Through compact layout and differential wall thickness design, the thickness and width of the cable are reduced by about 30-40% compared with the same specification elevator cable, the center aramid framework effectively bears longitudinal tension and radial shear force, the alternating twist direction design offsets the torsional stress, the bending resistance and service life of the cable are significantly improved, and the cable can be applied to harsh installation space scenes such as household elevators and sightseeing elevators.

Description

Technical Field

[0001] This invention belongs to the field of wire and cable technology, specifically an ultra-thin, bend-resistant elevator cable and its preparation method. Background Technology

[0002] Elevator traveling cables are a critical component of elevator systems, responsible for providing power transmission and control signal communication to the elevator car. With the trend towards high-rise and miniaturized buildings in modern architecture, and the rapid growth of the home elevator market, higher performance requirements are being placed on elevator cables. Currently, elevator cables face technical challenges such as large thickness requiring significant space, susceptibility to damage after prolonged bending, and insufficiently optimized structural design.

[0003] Patent CN104810090A discloses an elevator cable that meets RS485 / 232 communication functions. It includes a flat outer sheath and a cable core located in the middle of the outer sheath. An RS485 communication cable and an RS232 communication cable are respectively arranged on both sides of the cable core. Both the RS485 and RS232 communication cables are twisted pairs, and their twisting directions are opposite. The RS485 communication cable has a first shielding layer, and the RS232 communication cable has a second shielding layer. This patent, through its design of opposite twisting directions, can ensure the elevator cable's bending resistance to a certain extent. However, this technical solution has the following shortcomings: First, the overall thickness of the cable is relatively large, and the flat outer sheath structure occupies a large amount of space in the elevator shaft wiring, making it difficult to adapt to the compact installation requirements of small home elevators and ultra-high-rise high-speed elevators; Second, the design of the multi-layer shielding structure increases the rigidity of the cable, and there is still room for improvement in bending performance; Third, this solution mainly focuses on optimizing the communication function and does not comprehensively solve the technical problem of balancing ultra-thinness and bending resistance from both material and structural perspectives.

[0004] Patent CN103531278A discloses a traveling elevator cable, comprising several conductive cores and an insulating outer sheath. Each conductive core includes several copper-clad steel conductors and several copper conductors, which are twisted together. This patent claims to overcome the shortcomings of existing elevator cables, such as poor bending performance leading to conductor breakage. It claims to improve the bending performance of the conductors while maintaining other original performance characteristics, thereby increasing conductor strength and preventing breakage. However, this technical solution also has the following shortcomings: First, the cable structure design is not optimized for ultra-thin characteristics; the twisted structure of the copper-clad steel and copper conductors increases the overall thickness and weight of the cable. Second, although the bending performance at the conductor level is improved, the design of the outer sheath and insulation layer does not consider the directional optimization of bending stress, which may still lead to problems such as loosening of the cable core and damage to the shielding layer under long-term repeated bending conditions. Third, this solution does not provide a systematic ultra-thin manufacturing process, making it difficult to meet the requirements of compact installation.

[0005] In summary, although there are patents in the existing technology that involve improving the bending performance of elevator cables, none of them have been able to simultaneously solve the two major technical problems of ultra-thin design and excellent bending resistance. Summary of the Invention

[0006] This invention provides an ultra-thin, bend-resistant elevator cable and its preparation method, aiming to solve the technical problems of existing elevator cables, such as large thickness occupying shaft space, easy core wire breakage and shielding layer damage after long-term bending, traditional structural design not being optimized for bending stress, and poor bending performance due to increased cable rigidity caused by multi-layer structure superposition.

[0007] In a first aspect, the present invention provides an ultra-thin, bend-resistant elevator cable, comprising a central reinforcing layer, stranded core units, a cabling filling system, a shielding layer, and an outer sheath layer; The surface of the central reinforcing layer is coated with a polyurethane coupling agent coating. The stranded core unit includes a main signal core and an auxiliary signal core; the main signal core includes a conductor formed by stranding several oxygen-free copper wires and an insulation layer; the auxiliary signal core includes a conductor formed by stranding several oxygen-free copper wires and a low-dielectric PVC insulation layer. The cable filling system includes high-density polyethylene rope filling and a flow guiding structure made of several tin-plated copper wires twisted together. The shielding layer is a single-sided aluminum foil wrapping structure; The outer sheath layer is a flat sheath.

[0008] Furthermore, the insulating layer of the main signal core is composed of the following components in parts by weight: 70 parts of SG-5 type resin, 25 parts of dioctyl phthalate, 3 parts of calcium zinc stabilizer, 0.5 parts of antioxidant 1010, and 1.5 parts of carbon black; the outer diameter after extrusion is 2.2±0.1mm.

[0009] Furthermore, the insulating layer of the auxiliary signal core is composed of the following components in parts by weight: 65 parts of SG-5 type resin, 30 parts of dioctyl terephthalate, 3 parts of epoxidized soybean oil, 0.5 parts of antioxidant, and 2 parts of titanium dioxide; the outer diameter after extrusion is 1.9±0.1mm.

[0010] Furthermore, the main signal core is left-hand stranded with a stranding pitch of 23mm; the auxiliary signal core is right-hand stranded with a stranding pitch of 18mm.

[0011] Furthermore, the stranding pitch of the flow guiding structure is 29 mm, and the thickness of the tin plating layer on the surface is 3 to 5 μm.

[0012] Furthermore, the shielding layer uses aluminum foil with a width of 14 mm in the two-core winding area and aluminum foil with a width of 21 mm in the remaining areas, with a wrapping overlap rate of 25%.

[0013] Furthermore, the outer sheath layer is composed of the following components in parts by weight: 60 parts of SG-7 type resin, 32 parts of dioctyl terephthalate, 5 parts of tricresyl phosphate, 3 parts of calcium-zinc stabilizer, and 0.5 parts of antioxidant; after extrusion, it forms a flat structure with a width of 5.6±0.5 mm and a thickness of 1.5±0.1 mm.

[0014] By adopting the above technical solution, in the ultra-thin and bend-resistant elevator cable, the 400D para-aramid fiber in the central reinforcing layer is twisted with the center of the cable core as a load-bearing skeleton. During the cabling process, a pretension of 5 to 8 N is applied to keep the aramid fiber in a constant tension state, thereby directly bearing the longitudinal tensile force and radial shear force during elevator lifting and lowering, and protecting the internal copper conductor from being stretched and broken.

[0015] In the ultra-thin, bend-resistant elevator cable, 24 core wires are arranged in a single row around the aramid fiber in the central reinforcing layer. There are gaps between adjacent core wires, and high-density polyethylene filler rope is filled in the gaps. This ensures the roundness of the cable core and avoids friction and wear caused by relative displacement between the core wires.

[0016] In the ultra-thin, bend-resistant elevator cable, the main signal core and the auxiliary signal core adopt an alternating stranding design. The main signal core is stranded to the left with a stranding pitch of 23mm, and the auxiliary signal core is stranded to the right with a stranding pitch of 18mm. The torsional stress during cabling and movement is offset by the stranding design in opposite directions.

[0017] In the ultra-thin, bend-resistant elevator cable, the 37 tin-plated copper wires of the current-conducting structure are simultaneously implanted inside the cable core, forming an electrical connection with the shielding layer. This effectively discharges the static electricity generated during elevator operation, preventing static electricity accumulation from interfering with signal transmission.

[0018] In the ultra-thin, bend-resistant elevator cable, the outer sheath layer adopts a flat structure design. Compared with the traditional round cable sheath, it significantly reduces the thickness and width of the cable while maintaining the same electrical performance, thus saving wiring space in the elevator shaft.

[0019] Secondly, the present invention provides a method for preparing the ultra-thin, bend-resistant elevator cable, comprising the following steps: S1: Take oxygen-free copper wire and twist it into the main signal core conductor and the auxiliary signal core conductor respectively; S2: Extruding insulating layers with different formulations onto the surfaces of the main signal core conductor and the auxiliary signal core conductor; S3: Place the aramid fiber coated with polyurethane coupling agent at the center of the cable core, arrange the core wires in a single row around the aramid fiber, fill the gaps between adjacent core wires with high-density polyethylene filler rope, and simultaneously implant the guide wire made of tin-plated copper wire twisted together. S4: A shielding layer is formed by wrapping a single-sided aluminum foil around the cable core; S5: Extruded flat weather-resistant and flame-retardant PVC sheath.

[0020] In the S1 conductor stranding step, two opposite stranding methods, left-hand stranding and right-hand stranding, are used so that the torsional stress generated by the main signal core and the auxiliary signal core during subsequent cabling and movement can cancel each other out, thus preventing the cable from becoming loose due to the accumulation of torsional stress during long-term reciprocating bending.

[0021] In the S2 insulation extrusion step, a differentiated wall thickness design is achieved by adjusting the insulation layer formulation and extrusion outer diameter of the main signal core and the auxiliary signal core: the main signal core adopts an insulation formulation with higher tensile strength and a larger outer diameter, which can withstand greater mechanical stress; the auxiliary signal core adopts a low dielectric constant formulation and a smaller outer diameter, which reduces signal transmission attenuation while providing space for overall thickness compression.

[0022] In the S3 center cabling step, 400D aramid fiber is placed at the center of the cable core, making the aramid fiber the longitudinal load-bearing skeleton of the cable, directly bearing the longitudinal tension during elevator lifting; the polyurethane coupling agent coating enables the aramid fiber to form a good interface bond with the surrounding materials, ensuring that stress can be effectively transferred and dispersed; high-density polyethylene filler rope fills the gaps between the core wires, maintaining the roundness of the cable core while preventing relative movement of the core wires; the synchronous implantation of the guide wire enables effective discharge of static electricity.

[0023] In the S4 shielding wrapping step, a differentiated design of the shielding layer is achieved by using a narrower aluminum foil in the two-core winding area and a wider aluminum foil in the remaining areas. This ensures the shielding effect in the critical areas while avoiding the increase in thickness caused by using a wide aluminum foil across the entire cross section. The 25% overlap rate ensures the continuity of the shielding without increasing the cable thickness due to excessive overlap.

[0024] In the S5 flat sheath extrusion step, tricresyl phosphate is used as a flame retardant, which, together with SG-7 type resin, forms a flame retardant system, enabling the cable to achieve the UL VW-1 flame retardant rating. The design of the flat die head realizes the flat structure of the cable, and the width and thickness are significantly reduced compared with round cables of the same specification. The extrusion temperature is controlled within the range of 165 to 170°C, which can ensure the full plasticization of PVC material without causing material decomposition due to excessive temperature.

[0025] Furthermore, in step S1, the 20 main signal cores are twisted in a left-hand direction with a twist pitch controlled at 23mm; the 4 auxiliary signal cores are twisted in a right-hand direction with a twist pitch controlled at 18mm.

[0026] Furthermore, in step S5, the extrusion temperature is controlled within the range of 165 to 170°C, and after extrusion, the material is shaped by passing it through a cooling water tank, with the cooling water temperature controlled within the range of 15 to 20°C.

[0027] The present invention achieves the following beneficial effects through the above technical solution: By adopting a compact layout and differentiated wall thickness design, combined with a central aramid reinforcement structure, the multi-layer sheath stacking of the transmission cable is eliminated, making the cable thickness and width significantly thinner than elevator cables of the same specification. This reduces the space occupied by the shaft wiring and makes it suitable for scenarios with demanding installation space, such as home elevators and sightseeing elevators. It solves the technical problems mentioned in the background technology, such as the large thickness occupying elevator shaft wiring space and the difficulty in adapting to the compact installation requirements of small home elevators and ultra-high-rise high-speed elevators.

[0028] By placing 400D aramid fiber in the cable core as a tensile skeleton, it directly bears the longitudinal tensile force and radial shear force during elevator lifting and lowering, protecting the internal copper conductor from being stretched and broken. The alternating stranding design of the main signal core and auxiliary signal core offsets the torsional stress during cabling and movement, significantly improving the cable's bending resistance and service life, and solving the technical problems mentioned in the background technology, such as core wire breakage, shielding layer damage, and cable core loosening after long-term reciprocating bending.

[0029] Through a dual-shielding design in both material formulation and structure, the attenuation of weak electrical signals is reduced, improving the integrity and reliability of signal transmission. The outer sheath uses a weather-resistant and flame-retardant PVC formula, which can maintain stable performance in harsh environments, and the flame retardant rating meets the UL VW-1 standard. Fourth, by adopting a flat sheath structure and standardized manufacturing process, the cable can be mass-produced, resulting in stable and reliable product quality that meets the needs of modern elevator systems for high-performance special cables. Detailed Implementation

[0030] The various embodiments or implementation schemes in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Example

[0031] This embodiment provides a method for preparing an ultra-thin, bend-resistant elevator cable, including the following steps: S1: Conductor stranding steps TU1 grade oxygen-free copper wire with a copper content of not less than 99.99% is used, and two types of conductors are stranded together. The main signal core uses 20 strands of 61×0.12mm gauge, stranded in a left-hand direction with a stranding pitch of 23mm. The auxiliary signal core uses 4 strands of 41×0.12mm gauge, stranded in a right-hand direction with a stranding pitch of 18mm. A frame-type stranding machine is used, with a stranding speed controlled at 15-20 meters per minute. An electronic tensioner controls the tension, with the main signal core tension controlled at 3N and the auxiliary signal core tension controlled at 2N. During stranding, the copper wire is drawn from the pay-off stand and passes through the stranding die to form the stranded conductor. The die aperture is selected according to the conductor specifications to ensure a tight and secure strand. After stranding, an online testing instrument is used to measure the conductor outer diameter. The outer diameter of the main signal core is controlled at 1.05±0.02mm, and the outer diameter of the auxiliary signal core is controlled at 0.85±0.02mm.

[0032] S2: Insulation extrusion step The main signal core uses a mixture of 70 parts SG-5 resin, 25 parts dioctyl phthalate, 3 parts calcium-zinc stabilizer, 0.5 parts antioxidant 1010, and 1.5 parts carbon black. First, the SG-5 resin is added to a high-speed mixer, and the mixer speed is set to 800-1000 rpm for 2-3 minutes to ensure the resin is loose and uniform. Then, dioctyl phthalate, calcium-zinc stabilizer, antioxidant 1010, and carbon black are added sequentially, mixing for 2-3 minutes after each addition until a homogeneous mixture is obtained. The mixture is then added to the hopper of an extruder using a 50mm diameter screw with a length-to-diameter ratio of 25:1 and a compression ratio of 3:1. The extrusion temperatures are set as follows: Zone 1: 160℃, Zone 2: 170℃, Zone 3: 175℃, and Die Head: 170℃. The insulation extrusion uses an extrusion die, with the die orifice diameter designed according to the target outer diameter. After extrusion, the outer diameter of the main signal core insulation is controlled within the range of 2.2±0.1mm. After extrusion, it passes through a cooling water tank with the water temperature controlled at 15 to 20℃ and a cooling length of 3 meters to ensure that the insulation layer is fully cooled and shaped.

[0033] The auxiliary signal core uses a mixture of 65 parts SG-5 resin, 30 parts dioctyl terephthalate, 3 parts epoxidized soybean oil, 0.5 parts antioxidant, and 2 parts titanium dioxide. The mixing process is the same as for the main signal core, with extrusion temperatures set at 155℃ in zone one, 165℃ in zone two, 170℃ in zone three, and 165℃ at the die head. The outer diameter of the auxiliary signal core insulation after extrusion is controlled within the range of 1.9±0.1mm. After extrusion, the insulation layer thickness is checked online using a thickness gauge. The insulation layer thickness for the main signal core is controlled between 0.55 and 0.6mm, and for the auxiliary signal core, it is controlled between 0.5 and 0.55mm. The tensile strength of the insulation layer is tested using a tensile testing machine. The tensile strength of the main signal core insulation layer is not less than 15MPa, and the dielectric constant of the auxiliary signal core insulation layer does not exceed 3.5.

[0034] S3: Center Cable Formation Steps 400D aramid fibers coated with a polyurethane coupling agent are placed at the center of the cable core. The coating process for the aramid fibers is as follows: the polyurethane coupling agent is dissolved in ethyl acetate to prepare a 15% to 20% solution. The aramid fibers are then dip-coated through a coating tank to ensure the coating adheres evenly to the fiber surface. The fibers are then dried in an oven at 80 to 100°C to allow the solvent to evaporate, with the coating thickness controlled at 0.2 mm. After coating, the aramid fibers enter the cable-laying section, where a pretension of 5 to 8 N is applied as a load-bearing framework. The tension is precisely set using a tension controller.

[0035] Twenty-four core wires are arranged in a single row around the aramid fiber, with 20 as main signal cores and 4 as auxiliary signal cores. During the arrangement, gaps exist between adjacent core wires, which are filled with high-density polyethylene filler ropes. The filler ropes are produced using an extrusion molding process, with high-density polyethylene as the raw material, a melt flow index of 2 to 5 grams per 10 minutes, an extrusion temperature controlled at 190 to 210°C, and a filler rope diameter controlled at 0.8 to 1.0 mm. During the filling process, the filler ropes are introduced from the filling station and simultaneously enter the cabling mold along with the core wires. The cabling mold is designed according to the cable core structure to ensure uniform filling and a round cable core.

[0036] A current-carrying wire, composed of 37 strands of 0.125mm diameter tin-plated copper wire, is simultaneously implanted, with the tin plating thickness controlled within the range of 3 to 5μm. The current-carrying wire is fabricated using a stranding method; the 37 tin-plated copper wires are stranded together by a stranding machine with a stranding pitch of 29mm and a left-hand stranding direction. The current-carrying wire forms an electrical connection with the shielding layer to discharge static electricity. After cabling, the outer diameter of the cable core is controlled within the range of 4.2 to 4.5mm.

[0037] S4: Shielding Wrapping Steps In the two-core parallel winding area, aluminum foil with a width of 14mm and a thickness of 0.038mm is used for wrapping, while in the remaining areas, aluminum foil with a width of 21mm and a thickness of 0.038mm is used. The aluminum foil is single-sided, with an aluminum layer thickness of 0.038mm and a polyester layer thickness of 0.025mm, the polyester layer located outside the aluminum layer. A high-speed wrapping machine is used, with a wrapping speed controlled at 80 to 100 meters per minute and a wrapping tension controlled at 2 to 3N. The wrapping overlap rate is controlled at 25%, achieved by controlling the difference between the aluminum foil supply speed and the cable core advance speed. After wrapping, the outer diameter of the shielding layer is controlled within the range of 4.6 to 4.9mm. The shielding attenuation is not less than 60dB in the frequency range of 1MHz to 30MHz and not less than 50dB in the frequency range of 30MHz to 100MHz.

[0038] S5: Flat Sheath Extrusion Step A flame-retardant formulation was prepared using 60 parts SG-7 resin, 32 parts dioctyl terephthalate, 5 parts tricresyl phosphate, 3 parts calcium-zinc stabilizer, 0.5 parts antioxidant, and a certain amount of colorant. The mixing process was the same as in the aforementioned insulation extrusion step, and the mixture was fed into the extruder after thorough mixing. The extruder used a 65mm diameter screw with a length-to-diameter ratio of 25:1 and a compression ratio of 3:1. The extrusion temperature was controlled at 160℃ in zone one, 165℃ in zone two, 170℃ in zone three, and 165-170℃ at the die head. A flat die head was used for extrusion, with the die designed as a rectangular structure 5.6mm wide and 1.5mm thick. After extrusion, the material was set in a cooling water bath, with the cooling water temperature controlled at 15-20℃ and the cooling time controlled at 5-10 seconds. After extrusion and setting, a flat structure with a width of 5.6±0.5mm and a thickness of 1.5±0.1mm was formed. The flame retardant rating met the UL VW-1 standard. The outer sheath layer has 0.5 parts of UV protectant added to the formula, and the addition of colorant gives the sheath a specific color marking. Example

[0039] This embodiment further optimizes the cable structure based on Embodiment 1.

[0040] A buffer layer formed by high-density polyethylene filler rope, with a thickness of approximately 0.3 mm, is placed between the central reinforcing layer and the stranded core unit. This buffer layer provides a cushioning effect between the aramid fibers and the core wire, absorbing some bending stress and further improving the cable's bending resistance. The preparation method of the buffer layer is the same as the filling step in Example 1. The filling density is controlled to ensure that there are no obvious gaps between adjacent core wires, thus ensuring the roundness of the cable core and avoiding an increase in cable diameter due to overfilling.

[0041] In the cabling filling system, the current-guiding structure is composed of 37 tin-plated copper wires twisted together. The tin plating thickness of the copper wires is controlled within the range of 3 to 5 μm, ensuring good solderability without compromising the flexibility of the current-guiding wires due to excessive tin plating. The current-guiding wires form an electrical connection with the shielding layer, effectively dissipating static electricity generated during elevator operation and preventing static electricity accumulation from interfering with signal transmission.

[0042] The main signal core and auxiliary signal core adopt an alternating stranding design. The main signal core is stranded to the left with a stranding pitch of 23mm; the auxiliary signal core is stranded to the right with a stranding pitch of 18mm. The opposite stranding design cancels out the torsional stress during cabling and movement, preventing the cable from becoming structurally loose due to the accumulation of torsional stress during long-term reciprocating bending.

[0043] In the shielding wrapping process, a differentiated shielding layer design was achieved by using narrower aluminum foil in the two-core winding area and wider aluminum foil in the remaining areas. In the single-sided aluminum foil used for wrapping, the polyester layer, with a thickness of 0.025mm, is located on the outside of the aluminum layer, protecting it from scratches or oxidation during cabling and subsequent use; the aluminum layer itself is 0.038mm thick, providing sufficient shielding effectiveness. A 25% overlap rate is achieved through precise control of the wrapping tension; excessive overlap increases the thickness, while insufficient overlap affects shielding continuity.

[0044] Appearance and size test The cable width and thickness were measured using a projector. The results showed that the cable width was 5.55 to 5.65 mm and the cable thickness was 1.48 to 1.52 mm, which met the design requirements of 5.6 ± 0.5 mm width and 1.5 ± 0.1 mm thickness. Microscopic observation of the cable cross-section revealed that the central reinforcing layer was located at the exact center of the cable core, with 24 core wires evenly distributed around it. Filler ropes filled the gaps between the core wires, the shielding layer completely covered the cable core, and the outer sheath had a uniform shape.

[0045] Electrical performance testing Use a multimeter to measure the DC resistance of the conductors. The resistance of the main signal core conductor should not exceed 0.021 Ω / m, and the resistance of the auxiliary signal core conductor should not exceed 0.036 Ω / m. Use a withstand voltage tester to test the insulation layer. The insulation layer should withstand AC 2000V for 1 minute without breakdown. Use an insulation resistance tester to measure the insulation resistance. The insulation resistance of the main signal core should not be less than 100 MΩ·km, and the insulation resistance of the auxiliary signal core should not be less than 80 MΩ·km. Use a network analyzer to measure the shielding attenuation. The shielding attenuation should be 62 to 65 dB in the frequency range of 1 MHz to 30 MHz, and 52 to 56 dB in the frequency range of 30 MHz to 100 MHz.

[0046] Mechanical performance testing Tensile strength tests were conducted using an electronic universal testing machine. The results showed that the tensile strength was 520 to 580 N, which is sufficient to withstand the longitudinal tension during elevator lifting and lowering; the short-term tensile strength was 1050 to 1150 N, which meets the load-bearing requirements of the elevator in case of emergencies.

[0047] The bending resistance performance was tested using a bending tester. The test conditions were: bending radius of 6 times the cable thickness (9 mm); bending angle of ±90 degrees; and bending frequency of 20 times per minute. The test results are shown in the table below. 10,000 times The conductor resistance increases by 2%. Sheath without cracks 30,000 times The conductor resistance increased by 4%. Sheath without cracks 50,000 times The conductor resistance increased by 6%. Sheath without cracks 80,000 times The conductor resistance increased by 8%. Sheath without cracks 100,000 times The conductor resistance increases by 10%. The sheath has no cracks, the core wires have no breaks, and the shielding layer has no damage. Test results show that the ultra-thin, bend-resistant elevator cable provided by this invention can withstand at least 100,000 reciprocating bending tests. After the test, the electrical performance of the cable decreases by no more than 10%, the structural integrity remains good, and there are no core wire breaks, shielding layer damage, or cable core loosening.

[0048] Environmental performance testing The cable was placed in a -30°C environment for 24 hours, followed by a bending test; no significant change in bending performance was observed. The cable was then placed in a +70°C environment for 24 hours, followed by a tensile test; no significant decrease in tensile strength was observed. The cable underwent a flame retardancy test according to UL VW-1 standards; the flame spread time did not exceed 60 seconds, and the flame spread distance did not exceed 25mm, achieving the UL VW-1 flame retardancy rating.

[0049] The performance of the ultra-thin, bend-resistant elevator cable provided by this invention is compared with that of existing elevator cables. Comparative Example 1 is a traditional circular elevator cable, and Comparative Example 2 is a common thin-walled elevator cable. The test results are shown in the table below: As shown in the table above, the ultra-thin, bend-resistant elevator cable provided by this invention is significantly thinner and narrower than existing elevator cables, saving approximately 30% to 40% of shaft wiring space. Regarding tensile strength, the cable provided by this invention has higher tensile strength and can withstand greater longitudinal tension. In terms of bend resistance, the cable provided by this invention has a significantly higher number of bends than existing technologies, capable of withstanding at least 100,000 reciprocating bends. Regarding shielding performance, the cable provided by this invention has better shielding attenuation performance, more effectively suppressing electromagnetic interference. Example

[0050] This embodiment optimizes the preparation process parameters to further improve product performance.

[0051] In the S1 conductor stranding step, the stranding pitch was optimized. The stranding pitch of the main signal core was adjusted from 23mm to 22mm, and the stranding pitch of the auxiliary signal core was adjusted from 18mm to 17mm. The adjusted stranding pitch resulted in a tighter stranding between the conductors, improving the tensile strength and flexibility of the conductors. Test results showed that the tensile strength of the cable increased by approximately 8% and the bending performance increased by approximately 5% after the adjustment.

[0052] In the S2 insulation extrusion step, the extrusion temperature was optimized. The extrusion temperature of the main signal core was adjusted from 160℃ in zone 1, 170℃ in zone 2, 175℃ in zone 3, and 170℃ at the die head to 165℃ in zone 1, 175℃ in zone 2, 180℃ in zone 3, and 175℃ at the die head. Increasing the extrusion temperature improved the surface finish of the insulation layer, reduced bubbles and impurities, and increased tensile strength by approximately 10%. The extrusion temperature of the auxiliary signal core was adjusted from 155℃ in zone 1, 165℃ in zone 2, 170℃ in zone 3, and 165℃ at the die head to 160℃ in zone 1, 170℃ in zone 2, 175℃ in zone 3, and 170℃ at the die head. After adjustment, the dielectric constant of the insulation layer decreased by approximately 5%, improving signal transmission performance.

[0053] In the S3 center-laying process, the pretension was optimized. The pretension of the aramid fiber was adjusted from 5-8 N to 6-9 N. Increasing the pretension allowed the aramid fiber to maintain a more constant tension within the cable core, enhancing its ability to directly withstand the longitudinal tensile and radial shear forces during elevator movement. Test results showed that the tensile strength of the cable increased by approximately 12% after the adjustment.

[0054] In the S4 shielding wrapping step, the wrapping overlap rate was optimized. The overlap rate was adjusted from 25% to 28%. Increasing the overlap rate improves the continuity of the shielding layer and increases shielding attenuation by approximately 3dB. However, an excessively high overlap rate leads to an increase in cable thickness, so a trade-off needs to be struck based on actual requirements.

[0055] In the S5 flat sheath extrusion process, the extrusion temperature was optimized. The extrusion temperature was adjusted from 160℃ in zone 1, 165℃ in zone 2, 170℃ in zone 3, and 165-170℃ at the die head to 165℃ in zone 1, 170℃ in zone 2, 175℃ in zone 3, and 170-175℃ at the die head. Increasing the extrusion temperature resulted in more complete plasticization of the PVC material and improved surface smoothness of the sheath; however, excessively high temperatures could lead to material decomposition, thus requiring precise control. Example

[0056] This embodiment optimizes the material formulation to further improve product performance.

[0057] In the main signal core insulation layer formulation, the carbon black content was adjusted from 1.5 parts to 2 parts. Increasing the carbon black content improves the insulation layer's weather resistance and UV resistance, enabling it to maintain stable performance even after long-term exposure to sunlight within the elevator shaft. Test results show that after 1000 hours of aging in a UV aging chamber, the tensile strength retention rate of the insulation layer increased from 85% to 92%.

[0058] In the auxiliary signal core insulation layer formulation, the titanium dioxide content was adjusted from 2 parts to 2.5 parts. Increasing the titanium dioxide content resulted in a more uniform white appearance of the insulation layer and further improved weather resistance. Simultaneously, the low dielectric constant of titanium dioxide helps reduce signal transmission loss. Test results showed that signal transmission attenuation was reduced by approximately 8%.

[0059] In the outer sheath formulation, the UV stabilizer content was adjusted from 0.5 parts to 0.8 parts. Increasing the UV stabilizer content further improved the sheath's aging performance under long-term UV exposure within the elevator shaft. Test results showed that after 2000 hours of aging in a UV aging chamber, the sheath's tensile strength retention increased from 80% to 88%.

[0060] In the outer sheath formulation, the content of tricresyl phosphate was adjusted from 5 parts to 6 parts. Increasing the flame retardant content further improved the flame retardant performance of the cable, reducing the flame spread time by approximately 15%. However, excessively high flame retardant content can affect the mechanical properties of the sheath, so a trade-off needs to be struck based on actual requirements. Example

[0061] This embodiment adapts the ultra-thin, bend-resistant elevator cable provided by the present invention to different application scenarios.

[0062] For home elevators, due to their lower lifting speeds and relatively lower cable bending frequency, the requirements for cable thickness and width are more stringent. Therefore, in this embodiment, the cable thickness and width are further reduced. The cable thickness is reduced from 1.5mm to 1.3mm, and the width from 5.6mm to 5.0mm. This is achieved by reducing the insulation layer thickness and filler density. Test results show that the adjusted cable thickness is reduced by approximately 13%, and the width by approximately 11%, better meeting the compact installation requirements of home elevators. Although the cable thickness is reduced, through optimized structural design, the cable can still withstand at least 80,000 reciprocating bending tests, meeting the usage requirements of home elevators.

[0063] For sightseeing elevator scenarios, since the elevator shafts are typically transparent, cables may be exposed to direct sunlight, thus requiring higher UV resistance. In this embodiment, the UV resistance of the outer sheath is further improved. The UV stabilizer content in the outer sheath formulation is increased from 0.5 parts to 1 part, while the carbon black content is increased to 2.5 parts. Test results show that after 3000 hours of aging in a UV aging test chamber, the tensile strength retention rate of the sheath still reaches over 85%, meeting the long-term use requirements of sightseeing elevators.

[0064] For ultra-high-rise high-speed elevators, the high lifting speed and bending frequency of these elevators result in high longitudinal tensile forces and bending frequencies on the cables, thus requiring higher tensile strength and bending resistance. In this embodiment, the tensile strength and bending resistance of the cable are further improved. The aramid fiber density in the central reinforcing layer is increased from 400D to 500D, and the pretension is increased from 5-8N to 8-12N. Test results show that the adjusted cable tensile strength increases from 550N to 680N, and the number of bends increases from 100,000 to over 120,000, meeting the requirements for use in ultra-high-rise high-speed elevators.

[0065] For high-temperature environments, such as elevator shafts in some industrial buildings where temperatures can be high, cables with better high-temperature resistance are required. In this embodiment, the material formulation is adjusted to adapt to high-temperature environments. The SG-7 resin in the outer sheath formulation is replaced with high-temperature resistant PVC resin, increasing the heat resistance from 70℃ to 90℃. The SG-5 resin in the insulation layer formulation of the main signal core and auxiliary signal core is replaced with high-temperature resistant PVC resin. Test results show that the adjusted cable's operating temperature range expands from -30℃ to +70℃ to -40℃ to +90℃, maintaining stable performance at higher temperatures.

[0066] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An ultra-thin, bend-resistant elevator cable, characterized in that, It includes a central reinforcement layer, stranded core units, cabling filling system, shielding layer, and outer sheath layer; The surface of the central reinforcing layer is coated with a polyurethane coupling agent coating. The stranded core unit includes a main signal core and an auxiliary signal core; the main signal core includes a conductor formed by stranding several oxygen-free copper wires and an insulation layer; the auxiliary signal core includes a conductor formed by stranding several oxygen-free copper wires and a low-dielectric PVC insulation layer. The cable filling system includes high-density polyethylene rope filling and a flow guiding structure made of several tin-plated copper wires twisted together. The shielding layer is a single-sided aluminum foil wrapping structure; The outer sheath layer is a flat sheath.

2. The ultra-thin, bend-resistant elevator cable according to claim 1, characterized in that, The insulating layer of the main signal core is composed of the following components in parts by weight: 70 parts of SG-5 type resin, 25 parts of dioctyl phthalate, 3 parts of calcium zinc stabilizer, 0.5 parts of antioxidant 1010, and 1.5 parts of carbon black; the outer diameter after extrusion is 2.2±0.1mm.

3. The ultra-thin, bend-resistant elevator cable according to claim 2, characterized in that, The insulating layer of the auxiliary signal core is composed of the following components in parts by weight: 65 parts of SG-5 type resin, 30 parts of dioctyl terephthalate, 3 parts of epoxidized soybean oil, 0.5 parts of antioxidant, and 2 parts of titanium dioxide; the outer diameter after extrusion is 1.9±0.1mm.

4. The ultra-thin, bend-resistant elevator cable according to claim 3, characterized in that, The main signal core is left-hand stranded with a stranding pitch of 23mm; the auxiliary signal core is right-hand stranded with a stranding pitch of 18mm.

5. The ultra-thin, bend-resistant elevator cable according to claim 4, characterized in that, The stranding pitch of the flow guiding structure is 29 mm, and the thickness of the tin plating layer on the surface is 3 to 5 μm.

6. The ultra-thin, bend-resistant elevator cable according to claim 5, characterized in that, The shielding layer uses aluminum foil with a width of 14 mm in the two-core winding area and aluminum foil with a width of 21 mm in the remaining areas, with a wrapping overlap rate of 25%.

7. The ultra-thin, bend-resistant elevator cable according to claim 6, characterized in that, The outer sheath layer is composed of the following components in parts by weight: 60 parts of SG-7 type resin, 32 parts of dioctyl terephthalate, 5 parts of tricresyl phosphate, 3 parts of calcium-zinc stabilizer, and 0.5 parts of antioxidant; after extrusion, it forms a flat structure with a width of 5.6±0.5 mm and a thickness of 1.5±0.1 mm.

8. A method for preparing the ultrathin, bend-resistant elevator cable according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1: Take oxygen-free copper wire and twist it into the main signal core conductor and the auxiliary signal core conductor respectively; S2: Extruding insulation layers with different formulations on the surfaces of the main signal core conductor and the auxiliary signal core conductor; S3: Placing aramid fibers coated with polyurethane coupling agent at the center of the cable core, arranging core wires in a single row around the aramid fibers, filling the gaps between adjacent core wires with high-density polyethylene filler rope, and simultaneously implanting guide wires made of tin-plated copper wires twisted together. S4: A shielding layer is formed by wrapping a single-sided aluminum foil around the cable core; S5: A flat, weather-resistant, flame-retardant PVC sheath is extruded.

9. The method according to claim 8, characterized in that, In step S1, the 20 main signal cores are twisted in a left-hand direction with a twist pitch of 23mm; the 4 auxiliary signal cores are twisted in a right-hand direction with a twist pitch of 18mm.

10. The method according to claim 8, characterized in that, In step S5, the extrusion temperature is controlled within the range of 165 to 170°C, and after extrusion, the material is shaped by passing it through a cooling water bath, with the cooling water temperature controlled within the range of 10°C to 30°C.