Method of using a mineral extruder for mineral fire-resistant insulation cable

Abstract

The application relates to a method for using a mineral extruder for mineral fireproof insulation cable, and steps include: step one, introducing liquid medium for air isolation into a shell; step two, ensuring that the liquid fills the shell; step three, rotating a rotor to discharge residual air in a cavity; step four, putting mineral raw materials into a front cavity; step five, rotating the rotor to discharge the liquid until mineral extrusion appears; and step six, rotating the rotor at a working speed to start the extrusion operation. Before starting the mineral extrusion operation, the liquid medium for air isolation is introduced into the extruder to fill the shell, the air in the extruder is preliminarily discharged, the air in the interior is then discharged through slow rotation of the extruder, and then the mineral extrusion operation is started, so that the extruded mineral is free of bubbles, and the mineral wrapping layer has better heat insulation and oxygen isolation effects, and is suitable for cable manufacturing with higher fireproof grade and higher application safety level.

Description

Technical Field

[0001] This invention relates to the field of cable production equipment technology, and specifically to a method of using a mineral extruder for mineral fireproof insulated cables. Background Technology

[0002] Using mineral coatings to insulate cables from external air and minimize heat transfer to the conductor is a common method for fire-resistant insulated cables. In high-level projects, the fire resistance requirements for cables are very stringent. For example, a B1-class cable requires that the duration of droplet particles within 20 minutes of burning does not exceed 10 seconds. This necessitates a very high level of heat insulation and gas barrier properties in the protective layer. However, existing cable mineral coatings are applied using an extruder. During extrusion, gases are easily compressed into the mineral material, creating cavities. This reduces the heat insulation and barrier properties of the mineral coating. Furthermore, due to the extrusion structure, it is difficult to create a vacuum between the feed and discharge chambers. Since the front and rear chambers are almost completely isolated by the extrusion mechanism, it is even more difficult to create a vacuum by evacuating the interior using a vacuum pump. Additionally, because there are residues from the extrusion process within the chambers, vacuuming would also draw these residues into the pump body, making vacuuming extremely difficult.

[0003] By isolating air through a liquid medium, such as an organic liquid, if air can be expelled from inside the extruder through the liquid and no gas can enter during the extrusion operation, a vacuum-like effect will be created inside the extruder. At the same time, without the negative pressure effect of a vacuum, a tight coating layer can be formed well, so that the coating layer does not contain air bubbles and has better heat insulation and oxygen barrier effects. However, there is no corresponding technology to achieve this effect.

[0004] Existing technologies also include processes for producing cables using vacuum technology. For example, Chinese patent document CN105014920A describes a twin-screw extruder for preparing 105℃ polyvinyl chloride cable material, which includes a frame, a main motor, a barrel, and an electrical control cabinet mounted on the frame. An automatic feeding device and a vacuum degassing device are installed in the vertical direction of the barrel. However, its vacuum device is used to form a polyvinyl chloride insulating rubber layer, which is very different from the mineral insulating layer in this application. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method of using a mineral extruder for fireproof and insulating mineral cables. The method can vent the air in the extruder by coordinating the operation of the pipe valves in the housing with the rotation of the rotor and the input of liquid medium through the pipes, and separate the material from the air to form a vacuum-like effect without the negative pressure of a vacuum.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: The method of using a mineral extruder for fire-resistant mineral-insulated cables includes the following steps: Step 1: Close the discharge valve and keep the twin-screw rotor stationary. Open the pipe valve and introduce the liquid medium to isolate the air into the shell. The liquid medium flows from the front chamber to the rear chamber along the gap between the two screws of the twin-screw rotor. After the first liquid level sensor senses the liquid medium, continue to introduce the liquid medium into the interior until the second liquid level sensor senses the liquid. Step 2: Close the valve and wait. The liquid level may drop because it did not flow completely into the rear chamber. At this time, reopen the valve and raise the liquid level to the position of the second liquid level sensor. Repeat this process until the reading of the second liquid level sensor stabilizes within the set time. Keep the valve open and proceed to Step 3. Step 3: Start the twin screw rotor to rotate at the set exhaust speed, and open the discharge valve. During this process, keep the valve open and continuously introduce liquid medium into the front chamber. Continue this process until the set time is reached, then proceed to Step 4. Step 4: Stop the twin-screw rotor, simultaneously close the pipe valve and discharge valve, and add the set amount of mineral raw material into the feed box. Since the mineral raw material has a higher specific gravity than the liquid medium, it enters the front chamber from the inlet, gathers in the front chamber, and overflows the inlet. Step 5: Start the twin-screw rotor to rotate at the set speed, and at the same time open the discharge valve. The mineral raw materials in the front chamber will "flow" to the rear chamber under the compression of the twin-screw rotor, squeezing out the liquid medium in the rear chamber. Step Six: After a stable extrusion of mineral raw materials flows out of the outlet, mineral raw materials are added to the liquid medium in the feed box. At the same time, the twin-screw rotor is accelerated to rotate at the working speed, and the cable feeding mechanism to be wrapped is activated to start the mineral wrapping cable operation. The extruder mentioned above includes a housing, inside which is a rotatably connected twin-screw rotor. The spiral part of the twin-screw rotor is wrapped by the housing wall but with a gap. The spiral part of the twin-screw rotor divides the inner cavity of the housing into a front cavity and a rear cavity. The top of the front cavity has a feed port located in the feed box. The rear cavity has a discharge port at the tail end, and a discharge valve is installed at the discharge port. The bottom of the front cavity has a pipe with a pipe valve. The top of the front cavity has a first liquid level sensor, and the side wall of the feed box has a second liquid level sensor. The discharge port is connected to the die for wrapping the cable.

[0007] Step four above includes step six, in which the mineral raw material put into the feed box is a raw material that has been mixed with the adhesive.

[0008] A feed valve is provided at the aforementioned feed inlet.

[0009] In step one above, first open the feed valve; In step three above, before starting the twin-screw rotor to rotate at the set exhaust speed, the feed valve is closed first. Then, in step four, the feed valve is opened at the same time the twin-screw rotor stops rotating.

[0010] The aforementioned twin-screw rotor has one end extending out of the housing and driven by a drive motor, while the other end is rotatably connected to the inside of the housing. Both ends of the twin-screw rotor are sealed to the housing, and a first liquid level sensor is provided at the top of the front cavity.

[0011] The aforementioned feed valve and discharge valve are telescopic valves.

[0012] The above-mentioned feed valve and discharge valve have the following structure: an electromagnetic coil fixedly connected to the outer wall of the housing, the upper end of the valve stem passing through the electromagnetic coil, a limiting plate in the middle section of the valve stem, a spring between the limiting plate and the inner wall of the housing, and a door at the end of the valve stem.

[0013] This invention provides a method for using a mineral extruder for mineral fire-resistant insulated cables. Before starting the mineral extrusion operation, a liquid medium for isolating air is introduced into the extruder to fill the shell, initially purging the air inside the extruder. Then, the air inside is purged by rotating the extruder at a slow speed before starting the mineral extrusion operation. This ensures that there are no air bubbles or air chambers inside the extruded mineral, giving the mineral coating layer better heat insulation and oxygen isolation. This method is suitable for the manufacture of cables with high fire resistance and high safety requirements in applications. Attached Figure Description

[0014] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a schematic diagram of the structure of the mineral extruder of the present invention; Figure 2 This is a side view of a mineral extruder. Figure 3 for Figure 1 A magnified view of a portion of the image.

[0015] The components include: housing 1, twin screw rotor 2, feed box 3, feed inlet 4, feed valve 5, first liquid level sensor 6, second liquid level sensor 7, discharge port 8, discharge valve 9, pipe 10, pipe valve 11, electromagnetic coil 12, valve stem 13, limit plate 14, spring 15, and door 16. Detailed Implementation

[0016] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0017] like Figure 1-3 The method of using a mineral extruder for mineral fire-resistant insulated cables, as shown in the figure, includes the following steps: Step 1: Close the discharge valve 9, keep the twin-screw rotor 2 stationary, open the pipe valve 11, and introduce the liquid medium for isolating air into the housing 1 through the pipe 10. The liquid medium flows from the front chamber along the gap between the two screws of the twin-screw rotor 2 to the rear chamber. When the first liquid level sensor 6 senses the liquid medium, continue to introduce the liquid medium into the interior until the second liquid level sensor 7 senses the liquid. Step 2: Close valve 11 and wait. The liquid level may drop because it did not flow completely into the rear chamber. At this time, valve 11 is reopened and the liquid level is raised to the position of the second liquid level sensor 7. Repeat this process until the reading of the second liquid level sensor 7 is stable and unchanged within the set time. Keep valve 11 open and proceed to step 3. At this time, the liquid medium fills the interior of the shell 1. Only in the closed gap formed by mineral residue between the two screws of the twin screw rotor 2, and in the pipe connected to the rear cavity before the discharge valve 9, a small amount of air is present because the liquid seal prevents it from being discharged upwards in time. Step 3: Start the twin screw rotor 2 to rotate at the set exhaust speed, and open the discharge valve 9. During this process, the pipe valve 11 remains open and liquid medium is continuously introduced into the front chamber. This process is maintained until the set time is reached, then proceed to step 4. Step 4: The twin screw rotor 2 stops rotating, and at the same time, the pipe valve 11 and the discharge valve 9 are closed. The set amount of mineral raw material is put into the feed box 3. Since the specific gravity of the mineral raw material is greater than that of the liquid medium, the mineral raw material enters the front chamber from the feed port 4 and gathers in the front chamber and overflows the feed port 4. The amount of mineral raw material overflowing the feed inlet 4 needs to be sufficient to ensure that the mineral raw material in the front chamber can still fill the front chamber when the material extrusion is started in step six. This ensures that the mineral raw material with a higher specific gravity always enters the rear chamber. In step three, the air involved in the process is discharged through the flow of liquid medium and the incompressibility of liquid. This is done by using the flow of liquid medium to discharge all the air involved in the process between rotors and in the pipes connected to the rear chamber before the discharge valve 9. Step 5: Start the twin-screw rotor 2 to rotate at the set speed, and at the same time open the discharge valve 9. The mineral raw materials in the front chamber are squeezed into the rear chamber by the twin-screw rotor 2, and the liquid medium in the rear chamber is squeezed out. Step Six: After a stable mineral extrusion flows out of the discharge port 8, mineral raw materials are added into the liquid medium in the feed box 3. At the same time, the twin-screw rotor 2 is accelerated to rotate at the working speed, and the cable feeding mechanism to be wrapped is activated to start the mineral wrapping cable operation. The extruder mentioned above includes a housing 1, and a twin-screw rotor 2 is rotatably connected inside the housing 1. The spiral part of the twin-screw rotor 2 is wrapped by the wall of the housing 1 but with a gap. The spiral part of the twin-screw rotor 2 divides the inner cavity of the housing 1 into a front cavity and a rear cavity. The top of the front cavity is provided with a feed port 4, which is located inside the feed box 3. The rear cavity is provided with a discharge port 8, and a discharge valve 9 is provided at the discharge port 8. The bottom of the front cavity is provided with a pipe 10, and a pipe valve 11 is provided on the pipe 10. The top of the front cavity is provided with a first liquid level sensor 6, and the side wall of the feed box 3 is provided with a second liquid level sensor 7. The discharge port 8 is connected to the die for wrapping the cable.

[0018] The first liquid level sensor 6 is used to sense whether the inside of the housing 1 is filled with a liquid medium that isolates the gas.

[0019] The second liquid level sensor 7 is used to sense the liquid level of the liquid medium inside the housing 1. The liquid medium in the housing 1 is used to isolate the fed minerals from the air. Since the liquid medium has a much lower specific gravity than the minerals, the liquid medium always keeps the minerals isolated from the air on the surface of the feed tank 3.

[0020] In step four, which includes step six, the mineral raw material put into the feed box 3 is a raw material that has been mixed with the adhesive.

[0021] Feed valve 5 is provided at the above-mentioned feed inlet 4.

[0022] The feed valve 5 can be used during air intake and exhaust operations, i.e. when the twin screw rotor rotates and drives the liquid medium to be extruded backward. The valve is closed so that the liquid medium in the feed box 3 is not disturbed by the extrusion operation, which facilitates the subsequent feeding of materials. The undisturbed liquid is more conducive to the material settling to the bottom.

[0023] The liquid medium used to isolate gases mentioned above can be a sodium silicate solution, which can simultaneously serve as a mineral binder and an air-isolating liquid.

[0024] In step one above, first open the feed valve 5; In step three above, before starting the twin-screw rotor 2 to rotate at the set exhaust speed, the feed valve 5 is closed first. Then, in step four, the feed valve 5 is opened at the same time the twin-screw rotor 2 stops rotating.

[0025] The aforementioned twin-screw rotor 2 extends out of the housing 1 at one end and is driven by a drive motor, while the other end is rotatably connected to the inside of the housing 1. Both ends of the twin-screw rotor 2 are sealed to the housing 1, and a first liquid level sensor 6 is provided at the top of the front cavity.

[0026] The feed valve 5 and discharge valve 9 mentioned above are telescopic valves.

[0027] When feeding and discharging materials, the telescopic valve retracts into the wall, reducing the impact of the material on the valve.

[0028] The above-mentioned feed valve 5 and discharge valve 9 have the following structure: an electromagnetic coil 12 fixedly connected to the outer wall of the housing 1, the upper end of the valve stem 13 passing through the electromagnetic coil 12, a limiting plate 14 in the middle section of the valve stem 13, a spring 15 between the limiting plate 14 and the inner wall of the housing 1, and a door 16 at the end of the valve stem 13.

[0029] Pipe 10 is used to input an air-isolated liquid medium into the housing 1. The specific gravity of the liquid medium is less than that of the mineral itself. Before the mineral extrusion operation, pipe 10 and discharge valve 9 are used to fill the housing 1 with the liquid medium, allowing most of the air to be discharged from the inlet 4. Then, while the liquid medium continues to be input into pipe 10, the twin-screw rotor 2 rotates to discharge the air from the outlet 8, ensuring that there is no air in the housing 1. The outlet valve 9 is closed, and the twin-screw rotor 2 stops rotating. Then, the mineral raw material is put into the inlet 4. Since its specific gravity is greater than that of the liquid medium, the mineral raw material will fill the front cavity. At this time, the twin-screw rotor 2 starts the extrusion operation and opens the outlet valve 9. When the mineral raw material reaches the outlet 8, it is a completely gas-free mineral extrusion material, which is equivalent to production in a vacuum environment. The extrusion material is wrapped around the cable using a mold, which not only ensures that there are no air holes in the mineral coating layer, but also greatly increases the heat insulation and gas isolation effect of the mineral layer.

[0030] Before extrusion, liquid medium is introduced into the front chamber through pipe 10 and valve 11. The liquid medium enters the rear chamber through the gap between the twin screw rotors 2, filling the shell 1. At this time, the discharge valve 9 is closed, and gas is discharged from the feed port 4. At this time, there is still some gas in the pipe connecting the discharge port 8 and the rear chamber, as well as in the gap between the twin screws due to the isolation caused by residual material. While the liquid medium continues to be introduced into pipe 10, the discharge valve 9 is opened, the twin screw rotors 2 are started, and the liquid medium in the front chamber is discharged to the rear chamber. The residual gas is discharged towards the discharge port 8 due to the extrusion of the liquid. Then the discharge valve 9 is closed, and the twin screw rotors 2 are stopped from rotating. At this point, the gas is completely discharged from the shell 1, and the material extrusion operation can be carried out.

Claims

1. A method of using a mineral extruder for mineral-fire-resistant insulated cables, characterized in that, The steps involved include: Step 1: Close the discharge valve (9), keep the twin screw rotor (2) stationary, open the pipe valve (11), and introduce the liquid medium used to isolate air into the housing (1) through the pipe (10). The liquid medium flows from the front chamber along the gap between the two screws of the twin screw rotor (2) to the rear chamber. When the first liquid level sensor (6) senses the liquid medium, continue to introduce the liquid medium into the interior until the second liquid level sensor (7) senses the liquid. Step 2: Close the pipe valve (11) and wait. The liquid level may drop because it did not flow completely into the rear chamber before. At this time, the pipe valve (11) is reopened and the liquid level is raised to the position of the second liquid level sensor (7). Repeat this until the reading of the second liquid level sensor (7) is stable and unchanged within the set time. Keep the pipe valve (11) in the open state and proceed to step 3. Step 3: Start the twin screw rotor (2) and rotate it at the set exhaust speed. At the same time, open the discharge valve (9). During this process, the pipe valve (11) remains open and liquid medium is continuously introduced into the front chamber. This process is maintained until the set time is reached and then proceed to step 4. Step 4: The twin screw rotor (2) stops rotating, and at the same time closes the pipe valve (11) and the discharge valve (9). The set amount of mineral raw material is put into the feed box (3). The mineral raw material has a higher specific gravity than the liquid medium. Therefore, the mineral raw material enters the front chamber from the feed port (4) and gathers in the front chamber and overflows the feed port (4). Step 5: Start the twin-screw rotor (2) to rotate at the set speed, and at the same time open the discharge valve (9). The mineral raw materials in the front chamber are squeezed into the rear chamber by the twin-screw rotor (2), and the liquid medium in the rear chamber is squeezed out. Step 6: After a stable mineral raw material extrusion flows out of the discharge port (8), put the mineral raw material into the liquid medium in the feed box (3). At the same time, the twin screw rotor (2) speeds up and rotates according to the working speed, and the cable feeding mechanism to be wrapped starts the mineral wrapping cable operation. The extruder includes a housing (1), and a rotatably connected twin-screw rotor (2) is provided inside the housing (1). The spiral part of the twin-screw rotor (2) is wrapped by the wall of the housing (1) but with a gap. The spiral part of the twin-screw rotor (2) divides the inner cavity of the housing (1) into a front cavity and a rear cavity. The top of the front cavity is provided with a feed port (4), which is located inside the feed box (3). The rear cavity is provided with a discharge port (8), and a discharge valve (9) is provided at the discharge port (8). The bottom of the front cavity is provided with a pipe (10), and a pipe valve (11) is provided on the pipe (10). The top of the front cavity is provided with a first liquid level sensor (6), and the side wall of the feed box (3) is provided with a second liquid level sensor (7). The discharge port (8) is connected to the mold that wraps the cable.

2. The method of using the mineral extruder for mineral fire-resistant insulated cables according to claim 1, characterized in that, Step four includes step six, in which the mineral raw material put into the feed box (3) is a raw material that has been mixed with the binder.

3. The method of using the mineral extruder for mineral fire-resistant insulated cables according to claim 2, characterized in that, A feed valve (5) is provided at the feed inlet (4).

4. The method of using the mineral extruder for mineral fire-resistant insulated cables according to claim 3, characterized in that, In step one, the feed valve (5) is opened first. In step three, before starting the twin-screw rotor (2) to rotate at the set exhaust speed, the feed valve (5) is closed first. Then, in step four, the feed valve (5) is opened at the same time the twin-screw rotor (2) stops rotating.

5. The method of using the mineral extruder for mineral fire-resistant insulated cables according to claim 4, characterized in that, The twin-screw rotor (2) extends out of the housing (1) at one end and is driven by a drive motor, while the other end is rotatably connected to the inside of the housing (1). Both ends of the twin-screw rotor (2) are sealed to the housing (1), and a first liquid level sensor (6) is provided at the top of the front cavity.

6. The method of using the mineral extruder for mineral fire-resistant insulated cables according to claim 5, characterized in that, The feed valve (5) and discharge valve (9) are telescopic valves.

7. The method of using the mineral extruder for mineral fire-resistant insulated cables according to claim 6, characterized in that, The feed valve (5) and discharge valve (9) are structured as follows: including an electromagnetic coil (12) fixedly connected to the outer wall of the housing (1), the upper end of the valve stem (13) passes through the electromagnetic coil (12), a limiting plate (14) is provided in the middle section of the valve stem (13), a spring (15) is provided between the limiting plate (14) and the inner wall of the housing (1), and a door (16) is provided at the end of the valve stem (13).

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