A flexible mineral insulated pre-branched fireproof cable

Abstract

The present invention discloses a flexible mineral insulated pre-branched fireproof cable, comprising: a trunk cable and a branch cable. A fixing device is further provided at the connection between the trunk cable and the branch cable. The fixing device comprises: a protective box, a C-shaped clamp, two first reinforcement cable clamps, and a plurality of second reinforcement cable clamps. The protective box is filled with a dense injection-molded solid material, which completely covers the cable body of the trunk cable, the cable body of the branch cable, the connection between the trunk cable and the branch cable, the first reinforcement cable clamp, and the second reinforcement cable clamp within the protective box. The present invention synergistically improves the tensile strength of the branch connection portion of the mineral prefabricated branch cable through three aspects, significantly improving the tensile strength while also providing sealing performance.

Description

Technical Field

[0001] The invention belongs to the technical field of mineral cables, and in particular relates to a flexible mineral insulated pre-branched fireproof cable. Background Art

[0002] Prefabricated branch cables offer numerous advantages, including low power distribution costs, short on-site construction periods, and freedom from site spatial and environmental constraints. They are widely used as main and trunk cables for power supply and distribution in residential, office, and commercial buildings, as well as high-rise buildings. Currently, the national standard for prefabricated branch cables, JB / T 10636-2006, "Rated Voltage 0.6 / 1kV (Um=1.2kV) Copper Core Plastic Insulated Prefabricated Branch Cables," has been promulgated. However, no national standard for mineral-based prefabricated branch cables has been issued.

[0003] Mineral-insulated prefabricated branch cables connect the main line and branch lines through crimping, which requires removing the sheath and insulation material at the connection point. Because mineral-insulated cables are made of mineral insulation, even the slightest ingress of moisture can dramatically degrade the cable's insulation performance, leading to cable breakdown. Therefore, research and development efforts in mineral-insulated prefabricated branch cables are primarily focused on waterproofing the branch connection areas.

[0004] For example, the Chinese invention patent with announcement number CN113689982A discloses a mineral insulated fireproof and water-resistant pre-branching cable, comprising a main cable, a branch cable, and a connector. The branch cable is connected to the main cable via the connector. The main cable and the branch cable have the same structure, consisting of a conductive core, an insulation layer, a copper metal isolation sleeve, and an outer sheath. The connector comprises, from the inside out, a C-shaped copper crimping ring, a mineral insulation layer, a connector copper metal isolation layer, a water-blocking layer, and an outer sheath, arranged at the connection between the main cable and the branch cable. Heat-shrinkable waterproof sleeves are provided at the connection ends of the connector, the main cable, and the branch cable. This invention claims to completely solve the problem of frequent operational failures such as cable breakdown caused by water ingress, making it easier to promote and use.

[0005] However, the applicant has found through research that existing mineral prefabricated branch cables generally have a branch connector injection-molded at the branch connection position to protect the connection between the main line and the branch line. However, the branch connector obtained by the conventional injection molding method has poor tensile strength. When the prefabricated branch cable is laid, the pulling force or multiple bending of the branch line may cause the connection between the main line and the branch line to be unstable, affecting the use of the cable. In severe cases, the branch line may break at the branch connection position.

[0006] Chinese utility model patent publication number CN201449769U discloses an improved prefabricated branch cable, comprising a main cable and a connected branch cable. The connection between the main and branch cables is covered with a wrapping layer, and the conductors of the main and branch cables are welded together. Compared to crimping, this design omits the crimping accessories, resulting in a more compact structure and higher strength. Its tensile strength is increased from 80% to 110% of the pre-crimping method, providing improved fastening performance.

[0007] Chinese utility model patent publication number CN213601662U discloses a prefabricated branch cable, comprising a protective box, a main cable disposed at the bottom of the protective box, the top of the main cable extending through the top of the protective box, a branch cable located on the left side of the main cable and connected to the inner cavity of the protective box, the end of the branch cable distal from the main cable extending through the top of the protective box, and both the main cable and the branch cable comprising a base layer, an insulating layer fixedly attached to the surface of the base layer via an adhesive, and a reinforcing layer fixedly attached to the surface of the insulating layer via an adhesive. By providing a protective box, a base layer, an insulating layer, a reinforcing layer, a tensile layer, a flame-retardant layer, a corrosion-resistant layer, an aging-resistant layer, a knob, a threaded rod, a pressure plate, a toothed plate, a thermoplastic polyurethane elastomer layer, and a nitrile rubber layer, the prefabricated branch cable solves the problem of low strength and susceptibility to breakage under external tensile forces in existing prefabricated branch cables. This prefabricated branch cable offers the advantages of high strength and tensile resistance.

[0008] The Chinese invention patent with announcement number CN113724927A discloses a method for manufacturing a prefabricated branch cable and a prefabricated branch cable. The method for manufacturing the prefabricated branch cable includes the following steps: A1. Stripping off the insulation layer and protective layer at the connection part of the main line cable, and stripping off the insulation layer and protective layer at the connection end of the branch line cable; A2. Connecting the conductor of the connection end of the branch line cable to the conductor at the connection part of the main line cable; A3. Clamping the C-type connector to the connection part between the branch line cable and the main line cable; A4. Wrapping the insulation wrapping layer around the connection part of the main line cable; A5. Moving the main line cable, the branch line cable, the C-type connector and the insulation wrapping layer into the injection mold, and injecting the hot-melt polyolefin into the injection mold through a screw injection molding machine, and solidifying it after pressure holding and cooling to form a branch connector; A6. Opening the injection mold and taking out the completed prefabricated branch cable; The advantage is that it effectively improves the tensile strength and sealing performance of the connection between the main line and the branch line.

[0009] Existing technologies are not specifically designed for MI cables, and their relatively conventional methods are difficult to apply to the production of prefabricated branches for MI cables. Furthermore, while these technologies have improved the tensile strength of prefabricated branch cables, they are still far from meeting the requirements for MI cables, and the tensile strength design of branch connection points needs to be improved. Summary of the Invention

[0010] The purpose of the present invention is to solve the technical problems that the branch connection parts of the existing mineral prefabricated branch cables have low tensile strength, are easily damaged by external forces during the laying process, and have a connection structure or sealing and water-blocking performance, and to provide a flexible mineral insulated pre-branched fire-resistant cable.

[0011] In order to solve the above problems, the present invention is implemented according to the following technical solutions:

[0012] The present invention provides a flexible mineral insulated pre-branched fireproof cable, comprising:

[0013] A trunk cable, wherein a cutout portion is provided on the cable body of the trunk cable, and the cutout portion only includes the conductor portion of the trunk cable;

[0014] A branch cable, the end of which is provided with a connecting wire core, the connecting wire core being wound and fixedly connected to the conductor portion of the cutout portion;

[0015] A fixing device is also provided at the connection between the trunk cable and the branch cable, and the fixing device includes:

[0016] a protection box that completely covers the connection between the trunk cable and the branch cable; and a device disposed in the protection box,

[0017] A C-type clamp, which covers the connection between the trunk cable and the branch cable, and is used to tightly clamp the connection between the trunk cable and the branch cable;

[0018] Two first reinforcing cable clamps, which are respectively clamped on the cable body of the trunk cable adjacent to the left and right of the cutout portion, and the cutout portion is located between the two first reinforcing cable clamps;

[0019] a plurality of second reinforcement cable clamps, which are clamped on the cable body of the branch cable;

[0020] The protective box is filled with dense injection-molded solids, which completely cover the cable body of the trunk cable, the cable body of the branch cable, the connection between the trunk cable and the branch cable, the first reinforcement cable clamp and the second reinforcement cable clamp in the protective box.

[0021] Preferably, the cross-section of the first and second reinforcing cable clamps are both C-shaped, and the inner surfaces of the first and second reinforcing cable clamps are both provided with a plurality of conical punctures for piercing the sheath of the cable.

[0022] Preferably, the second reinforcement cable clamp comprises a C-shaped body and a plurality of conical punctures arranged on the inner surface of the C-shaped body;

[0023] The length of the C-shaped body is 80-100 mm, and the thickness of the C-shaped body is 8-15 mm.

[0024] Preferably, the outer surface of the C-shaped body is provided with a plurality of semi-annular grooves, which are arranged at equal intervals along the axis of the C-shaped body; the plurality of semi-annular grooves make the outer surface of the C-shaped body uneven, so that the C-shaped body and the injection molded solid form a chimeric structure.

[0025] Preferably, a high-temperature resistant water-blocking tape is provided between the inner surface of the first reinforcing cable clamp and the outer surface of the trunk cable, and before connecting the first reinforcing cable clamp to the cable body of the trunk cable, the high-temperature resistant water-blocking tape is wrapped around the cable body corresponding to the trunk cable;

[0026] A high-temperature resistant water-blocking tape is provided between the inner surface of the second reinforcing cable clamp and the outer surface of the branch cable; before connecting the second reinforcing cable clamp to the cable body of the branch cable, the high-temperature resistant water-blocking tape is wrapped around the cable body corresponding to the branch cable, and the length of the wrapped area of ​​the high-temperature resistant water-blocking tape on the branch cable is not less than 80 mm.

[0027] Preferably, before the injection molded solid is filled into the protective box, a covering cushion layer is provided on the exposed portion of the cable body at the connection between the trunk cable and the branch cable; the covering cushion layer is made by sequentially wrapping double-sided synthetic mica tape, high-voltage insulating tape, waterproof tape and protective tape around the exposed portion of the cable body.

[0028] Preferably, the injection-molded solidified product is formed by injection molding and filling of a low-smoke, halogen-free, flame-retardant polyolefin material.

[0029] Preferably, the trunk cable comprises a twisted cable core, an inorganic filling layer, a high-strength protective layer, a copper sheath, a high-temperature resistant insulation layer and an outer sheath, which are sequentially arranged from the inside to the outside;

[0030] Each cable of the trunk cable comprises a conductor, a mineral insulation fire-resistant layer and an insulation layer which are arranged in sequence from the inside to the outside.

[0031] Preferably, the branch cable comprises a twisted cable core, an inorganic fiber filler, a copper sheath and an outer sheath arranged in sequence from the inside to the outside;

[0032] Each cable of the branch cable comprises a conductor and an inorganic insulating wrapping tape which are arranged in sequence from the inside to the outside.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] A flexible mineral insulated pre-branched fireproof cable of the present invention, in a first aspect, is provided with a C-type clamp at the connection between the trunk cable and the branch cable, and the C-type clamp is used as the first structure for improving the tensile performance, and the tensile performance of the connection is enhanced by tightly clamping the two cables at the branch connection position.

[0035] Secondly, the present invention fills the protective box with dense injection-molded solids, and the injection-molded solids fully penetrate into the structure and gap formed by the various components of the branch connection part. After the injection-molded solids are cooled and solidified, they form a physical fixed structure with the branch connection part and are combined into a whole. Under the wrapping and reinforcement of the protective box, a second physical structure is formed to improve the tensile performance, thereby improving the tensile strength of the branch connection part; at the same time, it also has excellent sealing performance.

[0036] Thirdly, the present invention innovatively clamps a plurality of second reinforcement cable clamps on the cable body of the branch cable. Since the end face of the second reinforcement cable clamp has a certain thickness, an uneven structure is formed on the surface of the cable body of the branch cable. In conjunction with the dense filling and cooling and solidification of the injection molded solid, the surface of the branch cable and the solidified injection molded solid form a physical interlocking structure. The sheath of the branch cable and the injection molded solid are wedged and joined together by the interlocking structure, thereby improving the tensile strength. During the cable laying process, when the branch cable is pulled, the interlocking structure can disperse the stress generated by the pulling of the branch cable, avoiding the stress being mainly concentrated on the connecting wire core of the branch cable, and solving the problem of the connecting wire core being broken due to excessive stress.

[0037] The present invention synergistically improves the tensile strength of the branch connection portion of the mineral prefabricated branch cable through three aspects, the tensile strength is significantly improved, and the sealing performance is also achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, wherein:

[0039] Figure 1 It is a three-dimensional schematic diagram of the branch connection portion of the flexible mineral insulated pre-branched fireproof cable of the present invention;

[0040] Figure 2 It is a schematic diagram of the assembly of the branch connection portion of the flexible mineral insulated pre-branched fireproof cable of the present invention;

[0041] Figure 3 It is a schematic cross-sectional view of the branch connection portion of the flexible mineral insulated pre-branched fireproof cable of the present invention;

[0042] Figure 4 It is a schematic cross-sectional view of the trunk cable and the first reinforced cable clamp of the flexible mineral insulated pre-branched fireproof cable of the present invention;

[0043] Figure 5 It is a schematic cross-sectional view of a branch cable and a second reinforced cable clamp of the flexible mineral insulated pre-branched fireproof cable of the present invention;

[0044] In the picture:

[0045] 10-trunk cable, 11-cutout;

[0046] 20- branch cable, 21- connecting wire core;

[0047] 30-protection box;

[0048] 40-C-type clamp;

[0049] 50-first reinforcement cable clamp;

[0050] 60-first reinforcement cable clamp;

[0051] 70-injection molded solid;

[0052] 80-chimeric structure;

[0053] 90-High temperature resistant water blocking tape. DETAILED DESCRIPTION

[0054] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0055] In this field, there are three national and industry standards for mineral insulated cables. Table 1 shows the mineral insulated cables of different product standards.

[0056] Table 1 Mineral insulated cables of different product standards

[0057]

[0058] The patent of the present invention mainly provides a YTTW series of flexible mineral insulated pre-branching fireproof cables. The applicant's research found that the country has currently promulgated the relevant standard JB / T 10636-2006 "Rated voltage 0.6 / 1kV (Um=1.2kV) copper core plastic insulated prefabricated branch cable" for pre-branching cables, but there is currently no relevant national standard for mineral prefabricated branch cables. The research and development hotspots for mineral pre-branching cables in this field are mainly concentrated on the waterproof and water-blocking design of the branch connection parts. However, when laying the mineral insulated prefabricated branch cable, the tension or multiple bending of the branch line will cause the connection between the main line and the branch line to be unstable, affecting the use of the cable. In severe cases, the branch line breaks at the branch connection part, causing the cable to be scrapped. The existing conventional pre-branching technologies are not targeted at mineral insulated cables, and cannot effectively improve the tensile strength of the branch connection part of the mineral insulated cable, making it difficult to meet the needs of use.

[0059] Example 1

[0060] To this end, the purpose of this patent is to provide a flexible mineral insulated pre-branched fire-resistant cable with good tensile strength performance at the branch connection part.

[0061] like Figures 1 to 5 As shown, it is the preferred structure of a flexible mineral insulated pre-branched fire-resistant cable described in the present invention.

[0062] like Figure 1 As shown, the flexible mineral insulated pre-branched fireproof cable includes a trunk cable 10 and a branch cable 20. The manufacturing process of the flexible mineral insulated pre-branched fireproof cable includes many steps, mainly including the conductor connection of the trunk cable 10 and the branch cable 20, and the insulation and outer sheath treatment of the connection parts.

[0063] The trunk cable 10 has a cutout 11 on its body, which contains only the conductor portion of the trunk cable 10. A connecting wire core 21 is provided at the end of the branch cable 20, which is wound around and fixedly connected to the conductor portion of the cutout 11 to achieve conductor connection.

[0064] As for the insulation and external red treatment of the connection parts, a fixing device is mainly provided at the connection between the main cable 10 and the branch cable 20. This patent realizes the insulation, sealing, water blocking and tensile strength of the branch connection parts of the flexible mineral insulated pre-branched fireproof cable through the fixing device.

[0065] like Figure 2As shown, the fixing device includes a protective box 30, a C-clip 40, two first reinforcing cable clamps 50, and a plurality of second reinforcing cable clamps 60. When manufacturing a branch cable, the C-clip 40, the first reinforcing cable clamp 50, and the second reinforcing cable clamp 60 are all located within the protective box 30. Specifically, the protective box 30 is filled with a dense injection-molded cured material 70, which completely covers the cable body of the trunk cable 10, the cable body of the branch cable 20, the connection between the trunk cable 10 and the branch cable 20, the first reinforcing cable clamp 50, and the second reinforcing cable clamp 60 within the protective box 30.

[0066] The present invention fills the protective box with dense injection-molded solids, and the injection-molded solids fully penetrate into the structure and gap formed by the various components of the branch connection parts. After the injection-molded solids are cooled and solidified, they form a physical fixed structure with the branch connection parts and are combined into a whole. Under the wrapping and reinforcement of the protective box, a physical structure with improved tensile performance is formed, thereby improving the tensile strength of the branch connection parts; at the same time, it also has excellent sealing performance.

[0067] like Figure 3 As shown, the protection box 30 of the present invention completely covers the connection between the trunk cable 10 and the branch cable 20.

[0068] In one embodiment, the protective box 30 includes an upper box body and a lower box body, the upper box body and the lower box body are connected to each other, and the protective box 30 is made of copper or aluminum alloy. As an embodiment, the upper box body and the lower box body can be fixedly connected by bolts or welding, etc., which is not limited by the present invention.

[0069] Specifically, the upper and lower box bodies cover the cutout portion of the trunk cable and the conductors adjacent to the cutout portion, as well as the connecting cores of the branch cables and the cable bodies adjacent to the connecting cores, so that the cutout portion of the trunk cable and the cable bodies adjacent to the cutout portion, as well as the connecting cores of the branch cables and the cable bodies adjacent to the connecting cores, are all placed within the box cavity of the protection box. The protection box is provided with through holes for the trunk cable and the branch cables to pass through, and an injection molding hole is reserved on the protection box, which is connected to the box cavity of the protection box.

[0070] like Figure 2 As shown, the C-type clamp 40 of the present invention covers the connection between the trunk cable 10 and the branch cable 20 , and the C-type clamp 40 is used to tightly clamp the connection between the trunk cable 10 and the branch cable 20 .

[0071] The C-clip is made of metal and has a C-shaped cross-section. C-clip technology is well known to those skilled in the art. Specifically, the length of the C-clip is less than the length of the conductor segment in the cutout, and slightly longer than the coiled length of the connection. Specifically, the C-clip wraps around the connection between the main cable and the branch cable, interfering with the coiled connecting wires. Those skilled in the art can compress the C-clip using hydraulic pliers to secure the main cable and branch cable securely.

[0072] In order to improve the tensile strength of the branch connection part of the flexible mineral insulated pre-branched fire-resistant cable, the present invention provides a C-type clamp 40 at the connection between the trunk cable 10 and the branch cable 20. The C-type clamp 40 is used as the first structure to improve the tensile performance, and the two cables at the branch connection part are tightly clamped to enhance the tensile performance of the connection.

[0073] like Figure 2 As shown, the two first reinforcing cable clamps 50 of the present invention are respectively clamped on the cable body of the trunk cable 10 adjacent to the left and right of the cutout portion 11 , and the cutout portion 11 is located between the two first reinforcing cable clamps 50 .

[0074] When the trunk cable 10 is branched, all the sheaths outside the conductor need to be removed, resulting in only the conductor remaining in the cutout portion 11 of the trunk cable 10. Since most cables are laid vertically, during the laying process of the trunk cable 10, the stress on the cutout portion 11 of the trunk cable 10 is concentrated, which can easily cause defects in the conductor. To this end, the present invention innovatively clamps a first reinforcement cable clamp 50 on the cable body of the trunk cable 10. Because the end face of the first reinforcement cable clamp 50 has a certain thickness, it forms an uneven structure on the surface of the cable body of the trunk cable 10. In conjunction with the dense filling and cooling and solidification of the injection molded solid 70, the surface of the trunk cable 10 and the solidified injection molded solid 70 form a physical interlocking structure 80. During the cable laying process, when the trunk cable 10 is pulled, the interlocking structure 80 can disperse the stress generated by the pulling of the trunk cable 10, and can disperse the stress to the sheath of the trunk cable 10, avoiding the stress being mainly concentrated on the conductor of the trunk cable 10.

[0075] like Figure 2 and Figure 3 As shown, in a specific implementation of the present invention, the cable is provided with a second reinforcing cable clamp 60 , which is clamped on the cable body of the branch cable 20 .

[0076] When branching the branch cable 20, the entire sheath at the end needs to be removed, leaving only the connecting wire core 21 at the end of the branch cable 20. During the laying process of the branch cable 20, it needs to be pulled or bent multiple times. The connecting wire core 21 is the root of the branch cable 20 and serves as the part connecting to the main cable 10. Due to the removal of the sheath, the connecting wire core 21 is subjected to concentrated stress during the pulling and laying process. To this end, the present invention innovatively clamps a plurality of second reinforcing cable clamps 60 on the cable body of the branch cable 20. Since the end face of the second reinforcing cable clamp 60 has a certain thickness, an uneven structure is formed on the surface of the cable body of the branch cable 20. Combined with the dense filling and cooling and solidification of the injection-molded solid 70, the surface of the branch cable 20 and the solidified injection-molded solid 70 form a physical interlocking structure 80. The interlocking structure 80 is used to wedge the sheath of the branch cable 20 and the injection-molded solid 70 into each other and connect them, thereby improving the tensile strength.

[0077] During the cable laying process, when the branch cable 20 is pulled, the mosaic structure 80 can disperse the stress generated by the pulling of the branch cable 20, and disperse the stress to the sheath of the branch cable 20, thereby avoiding the stress being mainly concentrated on the connecting core 21 of the branch cable 20, and solving the problem of the connecting core 21 being broken due to excessive stress.

[0078] The present invention synergistically improves the tensile strength of the branch connection portion of the mineral prefabricated branch cable through the above three aspects, and the tensile strength is significantly improved while also having sealing performance.

[0079] In one embodiment, the injection molded solidified material 70 is formed by injection molding and filling with a low-smoke, halogen-free, flame-retardant polyolefin material to fully guarantee the insulation and flame-retardant properties of the cable. The low-smoke, halogen-free, flame-retardant polyolefin material is selected to have high fluidity for easy injection molding, and to achieve as close-to-gap filling as possible, thereby achieving dense filling.

[0080] Example 2

[0081] The second embodiment provides a flexible mineral insulated pre-branched fireproof cable, the structure and principle of which are exactly the same as those of the first embodiment, except that the present application provides a specific implementation structure of the first reinforcement cable clamp 50 and the second reinforcement cable clamp 60 based on the first embodiment.

[0082] The first and second reinforcing cable clamps 50 and 60 both have C-shaped cross-sections. Their inner surfaces are equipped with multiple tapered puncture points for piercing the cable sheath. Because cables typically have a cylindrical, circumferential structure, the tapered puncture points ensure a secure grip on the cable. The clamps and cable body are less likely to shift or slide relative to each other, ensuring structural strength and stress dispersion.

[0083] In one implementation, the first reinforcement cable clamp 50 and the second reinforcement cable clamp 60 are made of metal materials, such as aluminum or aluminum alloy, which have the advantages of light weight and good strength.

[0084] Specifically, in order to ensure the stability of the connection between the second reinforcement cable clamp 60 and the branch cable 20, in a specific implementation, the second reinforcement cable clamp 60 includes a C-shaped body and a plurality of conical punctures arranged on the inner surface of the C-shaped body; the length of the C-shaped body is 80 to 100 mm, and the thickness of the C-shaped body is 8 to 15 mm.

[0085] In a preferred embodiment, the length of the C-shaped body is 80 mm, and the thickness of the C-shaped body is 8 mm.

[0086] Specifically, a pre-branched cable is a cable that is prefabricated as a branch line according to a user's design drawings during the production of the main cable 10 by the cable manufacturer. The branch lines are prefabricated within the main cable 10 and the branch cable 20, and their cross-sectional dimensions, length, and other parameters are determined based on design requirements. Therefore, the specific dimensions of the first and second reinforcing cable clamps 50, 60 can be adjusted by those skilled in the art based on specific design requirements. This is not a limitation of the present invention.

[0087] like Figure 2 and Figure 5 As shown, in a preferred structure, the outer surface of the C-shaped body is provided with a plurality of semi-annular grooves, which are arranged in sequence and at equal intervals along the axis of the C-shaped body; the plurality of semi-annular grooves make the outer surface of the C-shaped body uneven, so that the C-shaped body and the injection-molded solidified object 70 form a mosaic structure 80.

[0088] This design increases the contact area between the second reinforcing cable clamp 60 and the injection-molded cured article 70, and increases the number of interlocking structures 80 formed between the second reinforcing cable clamp 60 and the injection-molded cured article 70, thereby enhancing stress dispersion. Furthermore, the increased contact area further enhances the strength of the fixed structure between the second reinforcing cable clamp 60 and the injection-molded cured article 70, further contributing to improved tensile strength.

[0089] Example 3

[0090] The third embodiment provides a flexible mineral insulated pre-branched fireproof cable, the structure and principle of which are exactly the same as those of the second embodiment. The difference is that, based on the second embodiment, the present application provides a specific implementation structure of the trunk cable 10 combined with the first reinforced cable clamp 50, and the branch cable 20 with the second reinforced cable clamp 60.

[0091] like Figure 4As shown, a high-temperature resistant water-blocking tape 90 is provided between the inner surface of the first reinforcing cable clamp 50 and the outer surface of the trunk cable 10. Before connecting the first reinforcing cable clamp 50 to the cable body of the trunk cable 10, the high-temperature resistant water-blocking tape 90 is wrapped around the corresponding cable body of the trunk cable 10.

[0092] like Figure 5 As shown, a high-temperature resistant water-blocking tape 90 is provided between the inner surface of the second reinforcing cable clamp 60 and the outer surface of the branch cable 20; before connecting the second reinforcing cable clamp 60 to the cable body of the branch cable 20, the high-temperature resistant water-blocking tape 90 is wrapped around the cable body corresponding to the branch cable 20, and the length of the wrapped area of ​​the high-temperature resistant water-blocking tape 90 on the branch cable 20 is not less than 80 mm.

[0093] The present invention forms a sealing and protective layer structure by injection molding a cured product 70. In order to enhance the water-blocking performance of the branch connection part, before injection molding, 5 to 8 layers of high-temperature resistant water-blocking tape 90 are overlapped and wrapped around the two cable bodies adjacent to the cutout portion 11 of the trunk cable 10 and the cable body adjacent to the connecting core 21 of the branch cable 20, and then clamped and fixed with a first reinforcement cable clamp 50 and a second reinforcement cable clamp 60.

[0094] This design prevents the formation of gaps between the injection-molded cured material 70 and the cable body surface, as well as gaps between the tapered puncture point and the sheath, after long-term use of the branch cable. This prevents moisture from penetrating through these gaps. When moisture enters longitudinally through the cable gaps, the water-blocking powder absorbs and expands, preventing further spread.

[0095] The wrapping position of the high temperature resistant water blocking tape 90 is preferably 30 mm adjacent to the through hole of the protection box 30 through which the main cable 10 and the branch cable 20 pass.

[0096] Example 4

[0097] This embodiment four provides a flexible mineral insulated pre-branched fireproof cable, whose structure and principle are exactly the same as those of embodiment three. The difference is that this application provides a preferred structure of the connection part between the trunk cable 10 and the branch cable 20 based on embodiment three.

[0098] Before the protective box 30 is filled with the injection molded solid 70, a covering cushion is provided on the exposed portion of the cable body at the connection between the trunk cable 10 and the branch cable 20; the covering cushion is made by sequentially wrapping double-sided synthetic mica tape, high-voltage insulation tape, waterproof tape and protective tape around the exposed portion of the cable body.

[0099] When insulating the branch connection, first manually wrap the exposed portion with double-sided synthetic mica tape. To ensure the cable's fire resistance, the mica tape should be wrapped in at least two layers, overlapping at least 50%. The fire-resistant mica tape used for wrapping should preferably be double-sided synthetic mica tape with excellent fire resistance, capable of withstanding temperatures exceeding 1000°C, close to the melting point of copper.

[0100] Then wrap with high-voltage insulation tape, waterproof tape and protective tape in sequence, and finally cover all the insulated cores of the trunk and branch cables with the cushion layer to ensure the insulation, waterproofness and flame retardancy of the branch connection parts.

[0101] Example 5

[0102] The fifth embodiment provides a flexible mineral insulated pre-branched fireproof cable, the structure and principle of which are exactly the same as those of the fourth embodiment, except that the present application provides an optimal structural design of the trunk cable 10 and the branch cable 20 based on the fifth embodiment.

[0103] The trunk cable 10 comprises, from the inside out, four twisted cable cores, an inorganic filler layer, a high-strength protective layer, a copper sheath, a high-temperature insulation layer, and an outer sheath. Each cable of the trunk cable 10 comprises, from the inside out, a conductor, a mineral insulation fire-resistant layer, and an insulation layer.

[0104] The conductors are unmetallized, twisted copper conductors with a Class 2 compressed circular structure, as specified in GB / T 3956-2008, "Conductors for Cables." During the design process, the twist pitch is precisely controlled to ensure excellent electrical conductivity. During production, continuous online monitoring technology is implemented throughout the drawing, annealing, and twisting processes to ensure the copper wires are defect-free.

[0105] The mineral insulation fire-resistant layer applied to the conductor is made of mica tape specified in GB / T 5019 for fire-resistant safety cables. This ensures the cable's electrical performance while enhancing its heat resistance. The mineral mica tape is made from high-temperature resistant materials such as mica paper and glass cloth, compounded and dried. The tape is wrapped around the conductor with an overlap ratio of 25% of the tape width to ensure the conductor's ability to withstand sustained high temperatures. The insulation layer is made of ceramic mineral insulation material using a continuous extrusion process. When exposed to temperatures exceeding 500°C, the insulation layer rapidly forms a dense, hard ceramic armor, which not only seals the internal structure and ensures a tight, non-detachable internal fire-resistant layer, but also enhances thermal insulation and provides a certain degree of impact resistance.

[0106] The inorganic filling layer is densely filled with inorganic filling ropes, which have heat insulation and temperature resistance. The inorganic filling ropes are made of alkali-free glass fiber filling ropes and asbestos ropes twisted into ropes according to a certain ratio and evenly and tightly distributed in the gaps between the conductors.

[0107] The high-strength protective layer is composed of impregnated, reinforced, inorganic, alkali-free glass fiber tape, which is flame-resistant. The tape has a breaking strength of 875N / 25mm or greater, meeting the breaking strength requirements of Article 4.1.5 of JC / T 174-2005, "Alkali-Free Glass Fiber Tape," effectively protecting the cable core structure.

[0108] The high-temperature insulation layer is composed of alkali-free glass fiber tape and highly flame-retardant wrapping tape. The material components are inorganic and have good high-temperature resistance.

[0109] Among them, the thickness of the outer sheath can be relatively large, so that the conical puncture of the first reinforced cable clamp 50 can pierce the outer sheath and be clamped on the outer sheath. The outer sheath can adopt the conventional outer sheath of the flexible mineral insulated cable in this field, and can also preferably adopt polyetheretherketone. The outer sheath manufactured has the following advantages: 1. The temperature resistance grade is 260°C and excellent hydrolysis resistance; it can be used continuously in high temperature, high pressure water vapor or water environment. And the cable produced itself is halogen-free, low-smoke, flame-retardant, non-toxic and environmentally friendly. 2. Excellent chemical corrosion resistance and excellent radiation resistance; the corrosion resistance is similar to that of nickel steel, and it can still maintain good insulation performance under high radiation. 3. Fatigue resistance to alternating stress is comparable to that of alloy materials. It also has certain self-lubrication and wear resistance; it greatly reduces the wear and damage of the cable during the dragging operation.

[0110] Those skilled in the art can use hydraulic pliers to compress the first reinforcing cable clamp 50 so that the first reinforcing cable clamp 50 is tightly clamped on the trunk cable 10. If necessary, the tapered piercing end of the first reinforcing cable clamp 50 can pierce and be fixed on the copper sheath.

[0111] The branch cable 20 includes a twisted cable core, an inorganic fiber filler, a copper sheath and an outer sheath arranged in sequence from the inside to the outside; each cable of the branch cable 20 includes a conductor and an inorganic insulating wrapping tape arranged in sequence from the inside to the outside.

[0112] Among them, the thickness of the outer sheath can be relatively large, so that the conical puncture of the second reinforced cable clamp 60 can pierce the outer sheath and be clamped on the outer sheath. The outer sheath can adopt the conventional outer sheath of the flexible mineral insulated cable in this field, and can also preferably adopt polyetheretherketone. The outer sheath manufactured has the following advantages: 1. The temperature resistance grade is 260°C and excellent hydrolysis resistance; it can be used continuously in high temperature, high pressure water vapor or water environment. And the cable produced itself is halogen-free, low-smoke, flame-retardant, non-toxic and environmentally friendly. 2. Excellent chemical corrosion resistance and excellent radiation resistance; the corrosion resistance is similar to that of nickel steel, and it can still maintain good insulation performance under high radiation. 3. Fatigue resistance to alternating stress is comparable to that of alloy materials. It also has certain self-lubrication and wear resistance; it greatly reduces the wear and damage of the cable during the dragging operation.

[0113] Those skilled in the art can use hydraulic pliers to compress the second reinforcing cable clamp 60 so that the second reinforcing cable clamp 60 is tightly clamped on the trunk cable 10. If necessary, the tapered piercing end of the second reinforcing cable clamp 60 can pierce and be fixed on the copper sheath.

[0114] Preparation method

[0115] The present invention also provides a method for preparing a flexible mineral insulated pre-branched fireproof cable, which is used to produce the flexible mineral insulated pre-branched fireproof cables of the above-mentioned embodiments 1 to 5. Specifically, the method for preparing the flexible mineral insulated pre-branched fireproof cable comprises the following steps:

[0116] (1) Use a cable stripper to remove the inorganic filler layer, high-strength protective layer, copper sheath, high-temperature insulation layer, and outer sheath from the middle section of the trunk cable; as well as the mineral insulation fire-resistant layer and insulation layer to obtain a cut portion. Remove any debris from the cut portion to expose the cable core. The total length of the cut portion should not exceed 20 cm.

[0117] (2) Wrap the connecting wire core of the branch cable around the conductor of the cutout part of the main cable, use a C-type clamp at the connection between the main cable and the branch cable, and use hydraulic pliers to press it tightly.

[0118] (3) Align the lower box body of the protection box with the connection between the trunk cable and the branch cable, and estimate the installation position of the first reinforcement cable clamp and the second reinforcement cable clamp. Put the first reinforcement cable clamp and the second reinforcement cable clamp on the corresponding positions of the trunk cable and the branch cable respectively, and use hydraulic pliers to tighten them.

[0119] (4) The exposed parts of the cable body at the connection between the trunk cable and the branch cable are wrapped with double-sided synthetic mica tape, high-voltage insulation tape, waterproof tape and protective tape in sequence.

[0120] (5) Assemble the protection box so that the cutout portion of the trunk cable and the cable body adjacent to the cutout portion, the connecting core of the branch cable and the cable body adjacent to the connecting core are all placed in the protection box.

[0121] (6) Using injection molding equipment, the halogen-free flame-retardant polyolefin material is injected and filled through the injection molding hole of the protection box, so that the gap between the protection box and the trunk cable and the branch cable is completely filled with the injection molding filling body.

[0122] Test methods

[0123] Test 1: Testing the tensile strength of the branch connection of the flexible mineral insulated pre-branched fire-resistant cable

[0124] Comparative Example 1: The raw materials, cable structure and preparation process used in Comparative Example 1 are exactly the same as those in Example 5. The difference is that the branch cable in Comparative Example 1 does not include the second reinforcing cable clamp.

[0125] During the tear resistance test of the cable, a clamp is used to fix the branch connection of the flexible mineral insulated branch fire-resistant cable, and the branch cable of the sample is cut to a uniform length. A tensile testing machine is used to pull the branch cable until the branch cable of the sample breaks, and the maximum force value (unit: N) is recorded.

[0126] Table 2 Maximum force of pre-branch cable specimens pulled to break

[0127] sample Example 5 Comparative Example 1 Maximum force N 153.1 107.3

[0128] Test 2: Performance test of the branch connection of the flexible mineral insulated pre-branched fire-resistant cable

[0129] Based on some technical requirements of JB / T 10636-2006 "Rated voltage 0.6 / 1kV (Um=1.2kV) copper core plastic insulated prefabricated branch cable", the flexible mineral insulated branch fireproof cable of Example 3 and Example 4 was tested; the test structure is shown in Table 3.

[0130] Table 3 Pre-branched fireproof cable performance test

[0131]

[0132] For other structures of the flexible mineral insulated pre-branched fireproof cable described in this embodiment, refer to the prior art.

[0133] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Therefore, any modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A flexible mineral insulated pre-branched fireproof cable, characterized in that: include: A trunk cable having a cutout portion provided on the cable body, wherein the cutout portion contains only the conductor portion of the trunk cable; the trunk cable comprises, arranged from the inside out, a stranded cable core, an inorganic filler layer, a high-strength protective layer, a copper sheath, a high-temperature resistant thermal insulation layer, and an outer sheath; each wire of the trunk cable comprises, arranged from the inside out, a conductor, a mineral insulated fire-resistant layer, and an insulating layer; the high-strength protective layer comprises an impregnated alkali-free glass fiber tape, and the breaking strength of the alkali-free glass fiber tape is ≥875N / 25mm; A branch cable having a connecting core at its end, the connecting core being wound and fixedly connected to the conductor portion of the cutout portion; the branch cable comprising a twisted cable core, an inorganic fiber filler, a copper sheath, and an outer sheath arranged sequentially from the inside to the outside; each cable of the branch cable comprising a conductor and an inorganic insulating wrapping tape arranged sequentially from the inside to the outside; A fixing device is also provided at the connection between the trunk cable and the branch cable, and the fixing device includes: a protection box that completely covers the connection between the trunk cable and the branch cable; and a device disposed in the protection box, A C-type clamp, which covers the connection between the trunk cable and the branch cable, and is used to tightly clamp the connection between the trunk cable and the branch cable; Two first reinforcing cable clamps, each clamped on the cable body of the trunk cable adjacent to the left and right sides of the cutout portion, with the cutout portion located between the two first reinforcing cable clamps; the first reinforcing cable clamp and the second reinforcing cable clamp both have a C-shaped cross-section, and the inner surfaces of the first reinforcing cable clamp and the second reinforcing cable clamp are each provided with a plurality of tapered punctures for piercing the sheath of the cable; the tapered punctures of the first reinforcing cable clamp can pierce the outer sheath of the trunk cable and be fixed to the outer sheath of the trunk cable; A plurality of second reinforcing cable clamps, which are clamped on the cable body of the branch cable; the second reinforcing cable clamps include a C-shaped body and a plurality of conical punctures arranged on the inner surface of the C-shaped body; the length of the C-shaped body is 80 mm, and the thickness of the C-shaped body is 8 mm; the conical punctures of the second reinforcing cable clamps can pierce the outer sheath of the branch cable and clamp on the outer sheath of the branch cable; The protective box is filled with a dense injection-molded solid material, which completely covers the cable body of the trunk cable, the cable body of the branch cable, the connection between the trunk cable and the branch cable, the first reinforcement cable clamp and the second reinforcement cable clamp in the protective box; The outer surface of the C-shaped body is provided with a plurality of semi-annular grooves, which are arranged at equal intervals along the axis of the C-shaped body; the plurality of semi-annular grooves make the outer surface of the C-shaped body uneven, so that the C-shaped body and the injection-molded solidified object form a chimeric structure; 5 to 8 layers of high-temperature resistant water-blocking tape are provided between the inner surface of the first reinforcing cable clamp and the outer surface of the trunk cable. Before connecting the first reinforcing cable clamp to the cable body of the trunk cable, the high-temperature resistant water-blocking tape is wrapped around the cable body corresponding to the trunk cable; A high-temperature resistant water-blocking tape is provided between the inner surface of the second reinforcing cable clamp and the outer surface of the branch cable; before connecting the second reinforcing cable clamp to the cable body of the branch cable, 5 to 8 layers of high-temperature resistant water-blocking tape are wrapped around the cable body corresponding to the branch cable, and the length of the wrapped area of ​​the high-temperature resistant water-blocking tape on the branch cable is not less than 80 mm.

2. A flexible mineral insulated pre-branched fireproof cable according to claim 1, characterized in that: Before the protective box is filled with the injection-molded solidified material, a covering cushion is provided on the exposed portion of the cable body at the connection between the trunk cable and the branch cable; the covering cushion is made by sequentially wrapping double-sided synthetic mica tape, high-voltage insulating tape, waterproof tape and protective tape around the exposed portion of the cable body.

3. The flexible mineral insulated pre-branched fireproof cable according to claim 1, characterized in that: The injection-molded solidified product is formed by injection molding and filling of a low-smoke, halogen-free, flame-retardant polyolefin material.

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