An intrinsically safe control cable and its preparation method

Abstract

The present invention relates to an intrinsically safe control cable. The cable includes a plurality of core groups and an outer sheath extruded outside the core groups. The outer sheath includes, from the inside to the outside, a braided shielding layer, an isolation layer, a fire-resistant layer, a copper sheath shielding layer, and an outer sheath; between adjacent core groups and between the core groups and the outer sheath, non-alkali glass fiber ropes are filled. When in use, the cable of the present invention has excellent shielding effects. The shielding layer not only plays a role in suppressing the external emission of electromagnetic waves, but also can serve as a channel for short-circuit current, can play a role in protecting the neutral core, and at the same time has an antistatic effect, avoiding combustible and explosive accidents caused by sparks.

Description

Technical Field

[0001] The present invention relates to the technical field of cables, specifically to an intrinsically safe control cable and its preparation method, and particularly to an antistatic and explosion-proof intrinsically safe control cable and its preparation method. Background Art

[0002] Static electricity is an objective natural phenomenon, which can be generated in various ways, such as contact, friction, peeling, etc. Static electricity protection technologies are used to reduce the losses caused by static electricity in fields such as the electronics industry, semiconductor industry, petroleum industry, ordnance industry, textile industry, rubber industry, and the military.

[0003] With the rapid development of industrial automation in China, during the production process, as a power supply device for communication, monitoring, detection, alarm, and control systems, the application scope of antistatic and explosion-proof control cables is constantly expanding.

[0004] At the same time, with the expansion of the application scope of cables, many high-voltage, high-temperature, and explosive environments also require the use of cables. Therefore, there is an urgent need in the market for a safe cable with excellent antistatic effect and capable of explosion-proof and fire-proof functions. Summary of the Invention

[0005] The purpose of the present invention is to provide an improved intrinsically safe control cable and its preparation method. Through structural improvement, the cable has excellent shielding effect. The multiple shielding structures play a comprehensive role, which not only inhibits the external emission of electromagnetic waves but also serves as a channel for short-circuit current, can protect the neutral core, and at the same time has an antistatic effect, avoiding combustible and explosive accidents caused by sparks.

[0006] To achieve the above purpose, the technical solution of the present invention is: an intrinsically safe control cable, characterized in that: the cable includes a plurality of core groups and an outer sheath extruded outside the core groups. The outer sheath is composed of a braided shielding layer, an isolation layer, a fire-resistant layer, a copper sheath shielding layer, and an outer sheath from inside to outside; between adjacent core groups and between the core groups and the outer sheath, non-alkali glass fiber ropes are filled.

[0007] Preferably, each core group is composed of oxygen-free copper wires and a ceramized polyolefin insulation layer extruded on the surface of the oxygen-free copper wires. The plurality of core groups are arranged in a clockwise direction, and a heat insulation layer is wound around the outside.

[0008] Further, the heat insulation layer is wound by a polyester tape; the fire-resistant layer is a ceramized polyolefin insulation layer with a thickness of 2.5 - 5 mm.

[0009] Furthermore, the copper sheath shielding layer is made by longitudinally wrapping copper tape by argon arc welding, showing a spiral structure; the outer sheath is an antistatic outer sheath with a thickness of 1.8 - 3.5 mm.

[0010] A preparation method of intrinsically safe control cable, characterized in that: the preparation method comprises the following steps: a. Making a core group, first extruding a ceramifiable polyolefin insulating material on the surface of an oxygen-free copper wire to form a single core; b. Arranging several core groups in a clockwise direction for overall cabling, filling an alkali-free glass fiber rope between adjacent core groups, and wrapping an alkali-free glass fiber tape around the outside of the cabled core groups to make the cable round; c. Wrapping a braided shielding layer and a polyester tape isolation layer around the outside of the cabled core groups in sequence; d. Extruding a fire-resistant layer on the outside of the isolation layer, the fire-resistant layer being a ceramifiable polyolefin insulating material with a thickness of 2.5 - 5 mm; e. Longitudinally wrapping a copper tape on the outside of the fire-resistant layer, sealing and welding the copper tape by argon arc welding, and then corrugating the copper tape to form a spiral shape; f. Extruding an antistatic outer sheath on the outside of the copper sheath shielding layer.

[0011] Compared with the prior art, the technical solution of the present invention includes not only improvements in the overall technical solution but also many improvements in details. Specifically, it has the following beneficial effects:

[0012] 1. In the improvement scheme of the present invention, the cable includes several core groups and an outer sheath extruded on the outside of the core groups. The outer sheath is composed of a braided shielding layer, an isolation layer, a fire-resistant layer, a copper sheath shielding layer, and an outer sheath from inside to outside; an alkali-free glass fiber rope is filled between adjacent core groups and between the core groups and the outer sheath; it has excellent shielding effect. The shielding layer not only plays a role in suppressing the external emission of electromagnetic waves but also can serve as a channel for short-circuit current, can play a role in protecting the neutral core, and at the same time has an antistatic effect, avoiding combustible and explosive accidents caused by sparks.

[0013] 2. In the technical solution of the present invention, each core group is composed of an oxygen-free copper wire and a ceramifiable polyolefin insulating layer extruded on the surface of the oxygen-free copper wire, having good fireproof performance, and the fire resistance level can reach the A level standard of GB12666.6, that is, it burns in a 950 - 1000 °C flame for 90 min and the 3A fuse does not blow.

[0014] 3. The manufacturing process of the present invention is simple, the finished product rate is high, the production cost is reduced, the work efficiency is improved, and it is convenient for popularization and utilization.

[0015] 4. The high-performance intrinsically safe control cable of the present invention has the safe use properties of anti-interference, fire resistance, radial waterproof, environmental protection, antistatic, and explosion protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic structural diagram of the present invention.

[0017] Reference numerals:

[0018] 1 Oxygen-free copper wire, 2 ceramicized polyolefin insulation layer, 3 heat insulation layer, 4 braided shielding layer, 5 isolation layer, 6 fire-resistant layer, 7 copper sheath shielding layer, 8 outer sheath. Detailed implementation mode

[0019] The technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work shall fall within the protection scope of the present invention.

[0020] The present invention provides an intrinsically safe control cable. For details, please refer to Figure 1 , which is different from the prior art in that: the cable includes a plurality of core groups and an outer sheath extruded outside the core groups. The outer sheath is, from inside to outside, a braided shielding layer 4, an isolation layer 5, a fire-resistant layer 6, a copper sheath shielding layer 7, and an outer sheath 8; between adjacent core groups and between the core groups and the outer sheath, non-alkali glass fiber ropes are filled.

[0021] During implementation, a plurality of core groups are arranged in three layers. One core group is arranged in the innermost layer, five core groups are arranged in the middle layer, and twelve core groups are arranged in the outermost layer. After arranging in sequence, they are cabled. Non-alkali glass fiber ropes are filled between adjacent core groups, and a non-alkali glass tape is wrapped outside the outermost core group to form a heat insulation layer. The cable made in this way has excellent shielding effect. The shielding layer not only plays a role in suppressing the external emission of electromagnetic waves, but also can be used as a channel for short-circuit current, can play a role in protecting the neutral core, and at the same time has an antistatic effect, avoiding combustible and explosive accidents caused by sparks.

[0022] Example 1

[0023] The cable includes a plurality of core groups and an outer sheath extruded outside the core groups. The outer sheath is, from inside to outside, a braided shielding layer, an isolation layer, a fire-resistant layer, a copper sheath shielding layer, and an outer sheath; between adjacent core groups and between the core groups and the outer sheath, non-alkali glass fiber ropes are filled. The non-alkali glass fiber ropes are filled with silver-plated glass microspheres. The silver-plated glass microspheres are provided with a silver-plated layer with a thickness of 0.1 - 0.01 ohm-cm. The hollow silver-plated glass microspheres are used here not only to improve the electromagnetic shielding effect, but also due to the setting of the microspheres, the friction between adjacent core groups and the friction between the core groups and the non-alkali glass fiber ropes are reduced, so that the cable will not have local heating and serious wear during use, rotation, etc., and the service life is extended.

[0024] Preferably, each core group is composed of oxygen-free copper wires 1 and a ceramized polyolefin insulating layer 2 extruded on the surface of the oxygen-free copper wires. A number of core groups are arranged in a clockwise direction, and a heat insulation layer 3 is wrapped around the outside. The heat insulation layer is made of ceramized polyolefin insulating material, which has excellent insulation performance and a volume resistivity ≥ 2×10 15 Ω·cm. In the presence or absence of flames at 350 - 1600°C, it can be fired into a hard armor-like shell. The higher the temperature and the longer the time, the harder the fired ceramic-like armor will be. The residue is pure ceramic inorganic matter. During the ablation process of the ceramic-like armor, dense honeycomb-like micropores can be formed, and a "porcelain glaze" film can be formed on the surface, which can achieve good fire resistance, fire blocking, heat insulation, and temperature insulation effects, and can pass the A-level and the highest level CWZ-level spray and vibration test requirements of 950~1100°C × 180 min or more.

[0025] Furthermore, when extruding the heat insulation layer, the extrusion thickness of the core group arranged in the middle layer is increased. The extrusion thickness of the core group in the middle layer is increased by 0.05 - 0.15 mm compared with the extrusion thickness of the inner and outer core layers, increasing the wear resistance and protection effect.

[0026] Furthermore, in this embodiment, the braided shielding layer can be woven from copper wires with a diameter of 0.2 mm, and the braiding density is greater than or equal to 80%. The braided shielding layer plays a role in shielding the electromagnetic interference received by the communication core wires. The shielding layer plays a blocking role, which makes the core wire only have electromagnetic coupling with the shielding layer, and the distributed capacitance between the shielding layer and external metal objects has no relation to the core wire.

[0027] In another embodiment, the braided shielding layer is woven from copper wires with a diameter of 0.2 mm and silver-plated carbon fibers with a diameter of 0.2 mm. The ratio of the two is 1:0.3, and the braiding density is greater than or equal to 80%. Using the two materials for braiding has a better shielding effect.

[0028] Even further, the heat insulation layer is formed by winding polyester tape; the fire-resistant layer is a ceramized polyolefin insulating layer with a thickness of 2.5 - 5 mm. The copper sheath shielding layer is made by longitudinally wrapping copper tape by argon arc welding and has a spiral structure; the outer sheath uses an antistatic outer sheath with a thickness of 1.8 - 3.5 mm.

[0029] Embodiment 2

[0030] A preparation method of intrinsically safe control cable, the preparation method comprising the following steps: a. Making a core group, first extruding a ceramizable polyolefin insulating material on the surface of oxygen-free copper wire to form a core group; b. Arranging a plurality of core groups in a clockwise direction for overall cabling, filling an alkali-free glass fiber rope between adjacent core groups, and wrapping an alkali-free glass fiber tape around the outside of the cabled core groups to make the cabling round; c. Wrapping a braided shielding layer and a polyester tape isolation layer around the outside of the cabled core groups in sequence; d. Extruding a fire-resistant layer on the outside of the isolation layer, the fire-resistant layer being a ceramizable polyolefin insulating material with a thickness of 2.5-5 mm; e. Longitudinally wrapping a copper tape on the outside of the fire-resistant layer, hermetically welding the copper tape by argon arc welding, and then corrugating the copper tape to form a thread-like shape; f. Extruding an antistatic outer sheath on the outside of the copper sheath shielding layer.

[0031] Preferably, in step b, silver-plated glass microspheres are filled in the alkali-free glass fiber rope, and the silver-plated glass microspheres are provided with a silver-plated layer of 0.1-0.01 ohm-cm; in step c, a plastic layer is coated on the outside of the braided shielding layer, and 3-5 longitudinally arranged ultra-fine carbon black conductive strips are coated on the inner wall of the plastic layer. Here, the ultra-fine carbon black conductive strips are made of a conductive coating prepared from ultra-fine carbon black powder and coated on the inner wall of the plastic layer, with a shielding effect reaching more than 50 dB. It is light while having good electromagnetic shielding effect, and can also reduce the thickness of the braided shielding layer and save materials.

[0032] In step e, the copper tape is a purple copper tape with a thickness of 0.4-0.6 mm, and the thread-like corrugations on the surface of the copper tape appear in the form of sparse-dense-sparse-dense intervals. In step f, the antistatic outer sheath is made of a polymerization-resistant polyvinyl chloride or low-smoke and halogen-free sheath material added with an antistatic agent.

[0033] The cable produced by the present invention has the following advantages:

[0034] 1. Excellent shielding effect. The shielding layer not only plays a role in suppressing the external emission of electromagnetic waves, but also can serve as a channel for short-circuit current, can play a role in protecting the neutral core, and at the same time has an antistatic effect, avoiding combustible and explosive accidents caused by sparks.

[0035] 2. Environmentally friendly: It contains no heavy metals, is non-toxic, odorless, and has no impact on the human body and the environment; it is ant- and rodent-proof, waterproof, and oil-resistant.

[0036] 3. Good heat insulation, with a thermal conductivity of 0.09 W / Mk. Especially after ablation, the inside is a uniform honeycomb shape, having better fire resistance and heat insulation.

[0037] 4. Excellent fire resistance performance, the fire resistance rating can reach Class A standard of GB12666.6, that is, it burns in the flame of 950 - 1000 °C for 90 minutes and the 3A fuse does not blow; it can also reach the highest level of CWZ of British BS6387, that is, C - burns in the flame of 950 °C for 3H, W - water spray, Z - vibration.

[0038] 5. In summary, the high-performance intrinsically safe control cable has the safe use performance of anti-interference, fire resistance, radial waterproof, environmental protection, anti-static, and explosion-proof.

[0039] Example 3

[0040] First, make a single core group. The conductor uses oxygen-free copper wire with a specification of 0.5 - 10 mm2. According to the use conditions, Class 1, Class 2, or Class 5 conductors can be used. Then extrude ceramizable polyolefin insulating material on the surface of the conductor to form a core group. The ceramizable polyolefin insulating material has excellent insulation performance, and the volume resistivity ≥ 2×10 15 Ω·cm. It has a fast crusting speed and a hard crust; in the presence or absence of flame at 350 - 1600 °C, it can be burned into a hard armor-like shell. The higher the temperature and the longer the time, the harder the burned ceramic-like armor will be. The residue is pure ceramic inorganic matter. The ceramic-like armor can form dense honeycomb-like micropores during the ablation process, and a layer of "porcelain glaze" film can be formed on the surface, which can play a very good role in fire resistance, fire blocking, heat insulation, and temperature insulation, and can pass the A-level and the highest level CWZ-level spray and vibration test requirements of 950 - 1100 °C × 180 min or more. The made core groups can be distinguished by numbers or colors.

[0041] Next, arrange the core groups in a clockwise direction, and the outermost layer has a right-handed lay. During cabling, non-alkali glass fiber ropes are filled between the cable cores, and two layers of non-alkali glass tapes with a thickness of 0.2 mm are wound around the outermost core group and tied tightly to make the cable cores round. The non-alkali glass fiber ropes and non-alkali glass tapes play a role in heat insulation. For the braided shielding layer process, copper wires with a diameter of 0.2 mm are used for braiding shielding, and the braiding density is not less than 80%. The braided shielding layer plays a role in shielding the electromagnetic interference received by the communication core wires. The shielding layer plays a blocking role. It makes the core wires only have electromagnetic coupling with the shielding layer, and the distributed capacitance between the shielding layer and external metal objects has nothing to do with the core wires.

[0042] Then, two layers of polyester tapes with a thickness of 0.05 mm are overlapped and wrapped around the braided shielding layer, and the lapping rate is not less than 20%, serving as the polyester tape isolation layer. A fire-resistant layer is extruded outside the isolation layer. The fire-resistant layer is made of ceramizable polyolefin insulating material with a thickness of 3 mm. The ceramizable polyolefin insulating material can self-extinguish and does not spread when horizontally burned, and the oxygen index is ≥35; in the presence or absence of flames at 350 - 1600 °C, it does not melt, does not drip, does not fall off, and will not cause a secondary fire. It can be burned into a hard ceramic-like armor body. The higher the temperature and the longer the time, the harder the burned ceramic-like armor body. The residue is ceramic inorganic matter, and the residue amount is greater than 80%. The ceramic-like armor body can form honeycomb-like ceramic micropores, which can play a good role in fire separation and heat insulation, and its excellent flame retardancy can also play a good role in fire prevention.

[0043] A copper tape is longitudinally wrapped outside the fire-resistant layer and sealed by argon arc welding. Then the copper tape is corrugated into a spiral shape. Specifically, an argon arc welding production device is used to longitudinally wrap a copper tape outside the fire-resistant layer of the cable core. After the copper tape is longitudinally wrapped by argon arc welding, it is corrugated into a spiral shape to make the cable easy to bend. The thickness of the copper tape is selected from 0.4 mm to 0.6 mm according to the outer diameter of the fire-resistant layer. The copper tape is selected as a purple copper tape. After the cable core is coated with the spiral copper tube, firstly, it can shield the interference of internal and external electric and magnetic fields; secondly, the sealed copper tube can block water radially; thirdly, the copper tube can be used as a grounding wire to shield static electricity and avoid fire caused by leakage current;

[0044] Fourthly, the copper tube acts as an armor layer to protect the cable core.

[0045] Finally, an antistatic outer sheath is extruded outside the copper sheath shielding layer. The outer sheath is extruded onto the fireproof layer by extrusion, with a thickness of 1.8 - 3.5 mm. According to different needs, flame-retardant polyvinyl chloride or low-smoke and halogen-free sheath materials can be selected, and antistatic agents are added to the sheath material to prevent static sparks during installation and use. The outer sheath plays a protective role.

[0046] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. An intrinsically safe control cable, Characterized in that: The cable includes a plurality of core groups and an outer sheath extruded outside the core groups. The outer sheath is successively composed of a braided shielding layer, an isolation layer, a fire-resistant layer, a copper sheath shielding layer, and an outer sheath from the inside to the outside; between adjacent core groups and between the core groups and the outer sheath, non-alkali glass fiber ropes are filled; silver-plated glass microspheres are filled in the non-alkali glass fiber ropes, and the silver-plated glass microspheres are provided with a silver-plated layer with a thickness of 0.1 - 0.01 ohm-cm; the outside of the braided shielding layer is coated with a plastic layer, and the inner wall of the plastic layer is coated with 3 - 5 longitudinally arranged ultra-fine carbon black conductive strips.

2. An intrinsically safe control cable according to claim 1, Characterized in that: Each core group is composed of oxygen-free copper wires and a ceramized polyolefin insulation layer extruded on the surface of the oxygen-free copper wires. A plurality of core groups are arranged in a clockwise direction, and a heat insulation layer is wound around the outside.

3. An intrinsically safe control cable according to claim 1, Characterized in that: The braided shielding layer is woven from copper wires with a diameter of 0.2 mm, and the braiding density is greater than or equal to 80%.

4. An intrinsically safe control cable according to claim 1, Characterized in that: The braided shielding layer is woven from copper wires with a diameter of 0.2 mm and silver-plated carbon fibers with a diameter of 0.2 mm together, and the braiding density is greater than or equal to 70%.

5. An intrinsically safe control cable according to claim 1, Characterized in that: The heat insulation layer is wound by a polyester tape; the fire-resistant layer is a ceramized polyolefin insulation layer with a thickness of 2.5 - 5 mm.

6. An intrinsically safe control cable according to claim 1, Characterized in that, The copper sheath shielding layer is made by longitudinally wrapping a copper strip by argon arc welding, presenting a threaded structure; the outer sheath is an antistatic outer sheath with a thickness of 1.8 - 3.5 mm.

7. A preparation method of an intrinsically safe control cable according to claim 1, Characterized in that: The preparation method includes the following steps: a. Making core groups, first extruding a ceramized polyolefin insulating material on the surface of oxygen-free copper wires to form single cores; b. A plurality of core groups are arranged in a clockwise direction for overall cabling. Non-alkali glass fiber ropes are filled between adjacent core groups. The outside of the cabled core groups is wound with non-alkali glass fiber tapes to make the cabling round. Silver-plated glass microspheres are filled in the non-alkali glass fiber ropes; c. Winding a braided shielding layer and a polyester tape isolation layer on the outside of the cabled core groups in sequence. The outside of the braided shielding layer is coated with a plastic layer, and the inner wall of the plastic layer is coated with a plurality of longitudinally arranged ultra-fine carbon black conductive strips; d. Extruding a fire-resistant layer on the outside of the isolation layer. The fire-resistant layer is a ceramized polyolefin insulating material with a thickness of 2.5 - 5 mm; e. Longitudinally wrapping a copper strip on the outside of the fire-resistant layer, using argon arc welding to seal and weld the copper strip, and then corrugating the copper strip to form a threaded shape; f. Extruding an antistatic outer sheath on the outside of the copper sheath shielding layer.

8. A preparation method of an intrinsically safe control cable according to claim 7, Characterized in that: In step e, the copper strip is a purple copper strip with a thickness of 0.4 - 0.6 mm, and the threaded corrugations on the surface of the copper strip appear in the form of sparse - dense - sparse - dense intervals.

9. A preparation method of an intrinsically safe control cable according to claim 7, characterized in that: In step f, the antistatic outer sheath is made of a polymerization-inhibited polyvinyl chloride or a low-smoke and halogen-free sheath material added with an antistatic agent.

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