Intrinsic safety computer cable and preparation method thereof

Abstract

This invention discloses an intrinsically safe computer cable. The intrinsically safe computer cable includes an inner layer of several core groups and an outer sheath. Each core group consists of two twisted single cores, and each core group is wrapped with a shielding layer. The sheath, from the inside out, consists of a heat insulation layer, a fire-resistant layer, a waterproof shielding layer, and an outer sheath. Heat-insulating filler material is used between the core groups and between the core groups and the sheath. In use, this invention employs both individual and overall shielding. The shielding layer not only suppresses electromagnetic wave emissions but also serves as a path for short-circuit current, protecting the neutral core and providing excellent shielding. It also has anti-static properties, preventing flammable and explosive accidents caused by sparks.

Description

Technical Field

[0001] This invention relates primarily to the technical field of cables, and particularly to an intrinsically safe computer cable and its preparation method, especially to an explosion-proof and fire-resistant intrinsically safe computer cable and its preparation method. Background Technology

[0002] With the rapid development of industrial automation in my country, the application scope of explosion-proof cables as power supply equipment for communication, monitoring, detection, alarm, and control systems, as well as computer cables, is constantly expanding in the production process. For example, cables are also needed in environments containing flammable and explosive mixtures, such as coal mines, petroleum, chemical, and textile industries, which places higher demands on cable performance.

[0003] Therefore, there is an urgent need in the market for an explosion-proof safety cable that has safety properties such as anti-interference, fire resistance, radial waterproofing, environmental protection, antistatic properties, and explosion protection, and can be suitable for applications in various environments. At the same time, due to the influence of the usage environment, the requirements for the shielding performance of the cable are also more stringent. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides an intrinsically safe computer cable and its manufacturing method. By improving the cable structure and employing both partial and overall shielding, the cable protects the neutral core while also providing explosion-proof and fire-proof protection, making it suitable for environments containing flammable and explosive mixtures.

[0005] The objective of this invention can be achieved through the following technical solution: an intrinsically safe computer cable, characterized in that the intrinsically safe computer cable includes an inner layer of several core groups and an outer layer of wrapping layer, each core group is formed by twisting two single cores together, and each core group is wrapped with a shielding isolation layer; the wrapping layer consists of a heat insulation layer, a fire-resistant layer, a waterproof shielding layer and an outer sheath from the inside out, and heat insulation filler material is filled between the several core groups and between the core groups and the wrapping layer.

[0006] Preferably, the single wire core is composed of an oxygen-free copper conductor and a ceramicized polyolefin insulation layer extruded on the outside of the oxygen-free copper conductor. The shielding and isolation layer has a two-layer structure, consisting of a polyester tape isolation layer and a copper-plastic tape shielding layer from the inside out.

[0007] Furthermore, the copper-plastic tape shielding layer is composed of an inner copper tape layer and an outer plastic layer, with the copper tape layer having a thickness of ≥0.06mm.

[0008] A method for manufacturing an intrinsically safe computer cable, characterized by the following steps: a) Fabricating core assemblies: First, ceramicized polyolefin insulating material is extruded onto the surface of a copper conductor to form single cores. Two single cores are twisted together and then wrapped with a shielding layer to form a core assembly; b) Several core assemblies are arranged clockwise and assembled into a cable. Alkali-free glass fiber rope is filled between adjacent core assemblies, and alkali-free glass fiber rope is wrapped around the core assemblies to make the cable round; c) A fire-resistant layer is extruded onto the core assemblies. The fire-resistant layer is ceramicized polyolefin insulating material with a thickness of 2.5-5mm; d) A copper strip is longitudinally wrapped around the fire-resistant layer. The copper strip is sealed by argon arc welding and then corrugated to form a threaded shape; e) An antistatic outer sheath is extruded onto the fire-resistant layer.

[0009] Compared with the prior art, the technical solution of the present invention not only improves the overall technical solution, but also includes many improvements in details. Specifically, it has the following beneficial effects:

[0010] 1. In the improved scheme of the present invention, each core group is composed of two single cores twisted together, and each core group is wrapped with a shielding isolation layer. The wrapping layer consists of a heat insulation layer, a fire-resistant layer, a waterproof shielding layer and an outer sheath from the inside out. The present invention adopts separate shielding and overall shielding. The shielding layer not only suppresses the external emission of electromagnetic waves, but also serves as a channel for short-circuit current, thus providing protection for the neutral core and excellent shielding effect.

[0011] 2. In the technical solution described in this invention, the shielding isolation layer outside the single wire core has a two-layer structure, consisting of a polyester tape isolation layer and a copper-plastic composite tape shielding layer from the inside out. The copper-plastic composite tape serves as a secondary shield to shield the communication wire core from electromagnetic interference. The shielding layer plays a blocking role, ensuring that the core wire is only electromagnetically coupled to the shielding layer.

[0012] 3. The improved preparation method of this invention is fast, safe, efficient, and has a high yield, improving product quality while reducing production costs and production cycle.

[0013] 4. The cable structure and process of this invention have great commercial value and are easy to promote and utilize. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the present invention.

[0015] The following labels are marked on the image:

[0016] 1. Oxygen-free copper conductor; 2. Ceramicized polyolefin insulation layer; 3. Polyester tape isolation layer; 4. Copper-plastic tape shielding layer; 5. Alkali-free glass rope; 6. Heat insulation layer; 7. Fire-resistant layer; 8. Waterproof shielding layer; 9. Outer sheath.

[0017] 11 single wire cores, 12 wire core groups. Detailed Implementation

[0018] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings, so that those skilled in the art can more clearly understand how to practice the present invention. Although the present invention has been described in conjunction with its preferred embodiments, these embodiments are merely illustrative and not intended to limit the scope of the invention.

[0019] like Figure 1 As shown, an intrinsically safe computer cable differs from existing technologies in that it comprises an inner layer of several core groups and an outer layer of wrapping. Each core group consists of two twisted single cores, and each core group is wrapped with a shielding isolation layer. The wrapping layer consists of, from the inside out, a heat insulation layer, a fire-resistant layer, a waterproof shielding layer, and an outer sheath. Heat insulation filler material is used between the core groups and between the core groups and the wrapping layer.

[0020] In practice, the number of core groups is always odd, typically 5, 7, 9, or 11. During cabling, one core group is placed in the center, with the remaining core groups arranged clockwise around it, twisted to the right. The cable employs individual shielding structures for each core group and an overall shielding structure after cabling. The shielding layer not only suppresses electromagnetic wave emissions but also serves as a path for short-circuit current, protecting the neutral core. It also provides anti-static properties, preventing flammable and explosive accidents caused by sparks, allowing the cable to be used in complex environments with excellent explosion-proof and fire-resistant performance.

[0021] Example 1

[0022] like Figure 1 As shown, the cable of the present invention includes an inner layer of 7 sequentially arranged core groups and an outer layer of wrapping. Each core group is composed of two single cores twisted together, and each core group is wrapped with a shielding isolation layer. The wrapping layer consists of a heat insulation layer, a fire-resistant layer, a waterproof shielding layer and an outer sheath from the inside out. Heat insulation filler material is used between adjacent core groups and between core groups and wrapping layers.

[0023] Preferably, the single wire core consists of an oxygen-free copper conductor and a ceramicized polyolefin insulation layer extruded around the oxygen-free copper conductor. The shielding layer has a two-layer structure: a polyester tape insulation layer and a copper-plastic tape shielding layer from the inside out. The copper-plastic tape shielding layer is composed of an inner copper tape layer and an outer plastic layer, with the copper tape layer having a thickness greater than or equal to 0.06 mm. During wrapping, the copper tape layer is wrapped close to the wire core, while the plastic layer is the outer layer. The copper-plastic composite tape acts as a secondary shield, protecting the communication wire core from electromagnetic interference. The shielding layer acts as a barrier, ensuring that the core wire only undergoes electromagnetic coupling with the shielding layer, while the distributed capacitance between the shielding layer and external metal objects is irrelevant to the core wire. Copper wire guides are placed between the copper tape layer and the plastic layer. These copper wire guides are arranged longitudinally or spirally wound around the outside of the copper tape layer. Longitudinal arrangement uses 4-6 copper wire guides evenly distributed along the outside of the copper tape layer to improve current transmission efficiency.

[0024] Furthermore, the shielding layer is equipped with pressure relief grooves. Specifically, 2-4 pressure relief grooves are evenly distributed on the copper-plastic tape shielding layer. The pressure relief groove structure is Y-shaped, with the upper half of the Y (i.e., the V-shaped groove) on the copper tape layer and the lower half of the Y (i.e., the L-shaped groove) on the plastic layer. The bottom of the V-shaped groove is connected to the L-shaped groove. Under normal circumstances, the L-shaped groove is just a gap. When it encounters changes in the environment such as high temperature and high pressure, the single-core structure can automatically relieve pressure to ensure safety and explosion-proof operation.

[0025] Furthermore, 2-4 pressure relief grooves corresponding to the Y-shaped pressure relief groove structure can be arranged on the polyester tape isolation layer, resulting in better pressure relief. Meanwhile, the heat insulation layer is made of alkali-free glass fiber rope wrapped around it; the fire-resistant layer is a ceramicized polyolefin insulation layer with a thickness of 2.5-5mm. The waterproof shielding layer is made of longitudinally wrapped copper tape using argon arc welding, forming a spiral structure; the outer sheath is an antistatic outer sheath with a thickness of 1.8-3.0mm.

[0026] Example 2

[0027] A method for manufacturing an intrinsically safe computer cable includes the following steps: a) Fabricating core assemblies: First, ceramicized polyolefin insulating material is extruded onto the surface of a copper conductor to form single cores. Two single cores are twisted together and then wrapped with a shielding layer to form a core assembly; b) Several core assemblies are arranged clockwise and assembled into a cable. Alkali-free glass fiber rope is filled between adjacent core assemblies, and alkali-free glass fiber rope is wrapped around the assembled core assemblies to make the cable round; c) A fire-resistant layer is extruded onto the assembled core assemblies. The fire-resistant layer is ceramicized polyolefin insulating material with a thickness of 2.5-5mm; d) A copper strip is longitudinally wrapped around the fire-resistant layer. The copper strip is sealed by argon arc welding and then corrugated to form a threaded shape; e) An antistatic outer sheath is extruded onto the fire-resistant layer.

[0028] Preferably, in step a, the twisting pitch is 20-30mm, and each pair of cores is distinguished by different colored ribbons. In step b, after the two single cores are twisted together, a shielding isolation layer is wrapped around them. The shielding isolation layer has a pressure relief groove. The shielding isolation layer has a two-layer structure: an inner polyester tape isolation layer and an outer copper-plastic tape shielding layer. The copper-plastic tape shielding layer is composed of a copper tape layer and a plastic layer. A copper wire guide is provided between the copper tape layer and the plastic layer. The thickness of the copper tape layer is greater than or equal to 0.06mm. During wrapping, the copper tape layer is wrapped close to the single core.

[0029] In step d, the copper strip is made of 0.4-0.6mm thick pure copper strip, and the spiral pattern on the surface of the copper strip appears in a sparse-dense-sparse-dense pattern, which is more conducive to the bending angle of the cable. In step e, the antistatic outer sheath is made of antistatic PVC or low-smoke halogen-free sheath material with added antistatic agent.

[0030] The present invention has the following advantages in use:

[0031] 1. Excellent shielding effect: It adopts partial shielding and overall shielding. The shielding layer not only suppresses the external emission of electromagnetic waves, but also serves as a channel for short-circuit current, protects the neutral core, and has anti-static properties to prevent flammable and explosive accidents caused by sparks.

[0032] 2. Environmentally friendly: Free of heavy metals, non-toxic, odorless, and has no impact on human health or the environment; ant-proof, rodent-proof, waterproof, and oil-resistant.

[0033] 3. Excellent thermal insulation with a thermal conductivity of 0.09 W / mk. In particular, the interior after ablation has a uniform honeycomb structure, which provides better fire resistance and thermal insulation.

[0034] 4. Excellent fire resistance, with a fire resistance rating that meets the Class A standard of GB12666.6, meaning that a 3A fuse will not blow after burning in a flame at 950~1000℃ for 90 minutes; it can also meet the highest level of CWZ of British BS6387, namely C - burning in a flame at 950℃ for 3 hours, W - water spray, and Z - vibration.

[0035] 5. In summary, high-performance intrinsically safe computer cables possess safe performance characteristics such as anti-interference, fire resistance, radial waterproofing, environmental friendliness, antistatic properties, and explosion-proof properties.

[0036] Example 3

[0037] The cable of the present invention includes 11 inner core groups arranged in sequence and an outer wrapping layer. Each core group is composed of two single cores twisted together. Each core group is wrapped with a shielding isolation layer. The wrapping layer consists of a heat insulation layer, a fire-resistant layer, a waterproof shielding layer and an outer sheath from the inside out. Heat insulation filler material is filled between adjacent core groups and between core groups and wrapping layers.

[0038] Specifically, the conductor material is oxygen-free copper wire with a specification of 0.5-4mm². Depending on the application conditions, Class 1, Class 2, or Class 5 conductors can be used. The copper conductor surface is extruded with ceramicized polyolefin insulation material, which has excellent insulation properties and a volume resistivity ≥2×10⁻⁶. 15 Ω·cm. It forms a hard, solid shell quickly; under flame and extinguishing conditions at 350-1600℃, it can be fired into a hard, armor-like shell. The higher the temperature and the longer the firing time, the harder the ceramic-like shell becomes. The residue is pure ceramic inorganic matter. During the ablation process, the ceramic-like shell can form dense honeycomb-like micropores, and a "porcelain enamel" film can be formed on the surface, which can play a good role in fire resistance, fire blocking, heat insulation, and temperature insulation. It can pass the spray and vibration test requirements of Class A (950~1100℃×180min) and the highest level CWZ of BS6387.

[0039] Then, each core group consists of two single cores forming a pair, with each pair of cores twisted together. The twisting pitch varies from 20 to 30 mm, and each pair of core groups is distinguished by a different colored ribbon. Each core group is wrapped with two overlapping layers of 0.05 mm thick polyester tape, with an overlap rate of not less than 20%, as part of the shielding layer. A 0.1 mm thick copper-plastic composite tape is then wrapped around each of the polyester tapes, with the copper layer in the composite tape being at least 0.06 mm thick. During wrapping, the copper tape layer is close to the core, and the plastic layer is the outer layer. The copper-plastic composite tape acts as a secondary shield, protecting the communication core from electromagnetic interference. The shielding layer acts as a barrier, ensuring that the core wire only undergoes electromagnetic coupling with the shielding layer, while the distributed capacitance between the shielding layer and external metal objects is irrelevant to the core wire.

[0040] During cabling, the core groups are arranged clockwise, with the outermost layer twisted to the right. Simultaneously, alkali-free glass fiber rope is filled between the cores, and two layers of 0.2mm thick alkali-free glass tape are wrapped around the cores and secured tightly, ensuring a rounded cable. The alkali-free glass fiber rope and wrapping tape provide heat insulation. A fire-resistant layer is extruded over the core groups. This fire-resistant layer is made of ceramicized polyolefin insulation material. This ceramicized polyolefin insulation material is self-extinguishing and does not propagate flame when burned horizontally, with an oxygen index ≥35. Under flame and extinguished conditions at 350-1600℃, it does not melt, drip, or detach, and will not cause secondary fires. It can be fired into a hard ceramic-like armor. The higher the temperature and the longer the firing time, the harder the ceramic-like armor becomes. The residue is composed of inorganic ceramic material, with a residue content greater than 80%. The ceramic-like armor can form honeycomb-like ceramic micropores, providing excellent fire and heat insulation effects. Its excellent flame retardancy also provides good fire protection.

[0041] Next, using argon arc welding equipment, a layer of copper strip is longitudinally wrapped around the fire-resistant layer of the cable core. After the copper strip is longitudinally wrapped by argon arc welding, it is rolled into a thread shape to make the cable easy to bend. The thickness of the copper strip is selected from 0.4mm to 0.6mm depending on the outer diameter of the fire-resistant layer. Pure copper strip is used. After the cable core is covered with a threaded copper tube, it serves several purposes: first, it shields against interference from internal and external electric and magnetic fields; second, the sealed copper tube provides radial water resistance; third, the copper tube can be used as a grounding wire to shield against static electricity and prevent fires caused by leakage current; and fourth, the copper tube acts as an armor layer, protecting the cable core.

[0042] Finally, the outer sheath is extruded onto the fireproof layer, with a thickness of 1.8–3.0 mm. Depending on the specific requirements, PVC or low-smoke halogen-free sheath material can be selected. Antistatic agents are added to the sheath material to prevent electrostatic sparks from being generated during installation and use.

[0043] It should be noted that the present invention, as fully described, can have various modifications and variations, and is not limited to the specific embodiments described above. The above embodiments are merely illustrative of the invention and not intended to limit it. In short, the scope of protection of the present invention should include those modifications, substitutions, and alterations that are obvious to those skilled in the art, and the appended claims shall prevail.

Claims

1. An intrinsically safe computer cable, characterized in that, Intrinsically safe computer cables consist of several core groups in the inner layer and an outer wrapping layer. Each core group is composed of two twisted single cores, and each core group is wrapped with a shielding layer. The wrapping layer consists of, from the inside out, a heat insulation layer, a fire-resistant layer, a waterproof shielding layer, and an outer sheath. Heat-insulating filler material is used between the core groups and between the core groups and the wrapping layer. Each single core consists of an oxygen-free copper conductor and a ceramicized polyolefin insulation layer extruded on the outside of the oxygen-free copper conductor. The shielding layer has a two-layer structure, consisting of a polyester tape shielding layer and a copper-plastic tape shielding layer from the inside out. The copper-plastic tape shielding layer is composed of an inner copper tape layer and an outer plastic layer, with the copper tape layer having a thickness of ≥0.06mm. A copper wire guide is provided between the copper strip layer and the plastic layer. The copper wire guide is arranged longitudinally or spirally wrapped around the outside of the copper strip layer. When arranged longitudinally, 4-6 copper wire guides are evenly laid along the outside of the copper strip layer. Two to four pressure relief grooves are evenly distributed on the copper-plastic strip shielding layer. The pressure relief grooves are Y-shaped, with the upper V-shaped groove on the copper strip layer and the lower L-shaped groove on the plastic layer. The bottom of the V-shaped groove is connected to the L-shaped groove.

2. The intrinsically safe computer cable according to claim 1, characterized in that, The heat insulation layer is made of alkali-free glass fiber rope wrapped around it; the fire-resistant layer is a ceramicized polyolefin insulation layer with a thickness of 2.5-5mm.

3. The intrinsically safe computer cable according to claim 1, characterized in that, The waterproof shielding layer is made of longitudinally wrapped copper strip by argon arc welding, and has a threaded structure; the outer sheath is an antistatic outer sheath with a thickness of 1.8-3.0mm.

4. The method for preparing an intrinsically safe computer cable according to claim 1, characterized in that, The preparation method includes the following steps: a) Fabricating core groups: First, ceramicized polyolefin insulating material is extruded onto the surface of a copper conductor to form a single core. Two single cores are twisted together and then wrapped with a shielding isolation layer to form a core group; b) Several core groups are arranged clockwise and assembled into a cable. Alkali-free glass fiber rope is filled between adjacent core groups, and alkali-free glass fiber rope is wrapped around the core groups of the cable to make the cable round; c) A fire-resistant layer is extruded onto the core groups of the cable. The fire-resistant layer is ceramicized polyolefin insulating material with a thickness of 2.5-5mm; d) A copper strip is longitudinally wrapped around the fire-resistant layer. The copper strip is sealed by argon arc welding, and then the copper strip is corrugated to form a thread. The copper strip is 0.4-0.6mm thick and the corrugated pattern on the surface of the copper strip appears in a sparse-dense-sparse-dense pattern; e) An antistatic outer sheath is extruded onto the fire-resistant layer.

5. The method for manufacturing an intrinsically safe computer cable according to claim 4, characterized in that, In step a, the twist pitch is 20-30mm, and each pair of wire cores is distinguished by different colored ribbons.

6. The method for manufacturing an intrinsically safe computer cable according to claim 4, characterized in that, In step b, after the two single wire cores are twisted together, a shielding isolation layer is wrapped around the outside. The shielding isolation layer is provided with a pressure relief groove. The shielding isolation layer has a two-layer structure: the inner layer is a polyester tape isolation layer, and the outer layer is a copper-plastic tape shielding layer. The copper-plastic tape shielding layer is composed of a copper tape layer and a plastic layer. A copper wire guide is set between the copper tape layer and the plastic layer. The thickness of the copper tape layer is greater than or equal to 0.06mm. When wrapping, the copper tape layer is wrapped close to the single wire core.

7. The method for preparing an intrinsically safe computer cable according to claim 4, characterized in that, In step e, the antistatic outer sheath is made of PVC or low-smoke halogen-free sheath material with added antistatic agent.

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