Extruder mixing and feeding device and optical cable double jacket

Abstract

The application discloses a plastic extruder mixing feeding device which comprises a mixing feeding cylinder, a body material hopper, a color master batch bottle and a rotating material changing component. The inside of the mixing feeding cylinder is provided with a mixing feeding channel along the axial direction thereof and a mixing feeding component in the mixing feeding channel. The top of the mixing feeding cylinder is respectively provided with a body material discharging interface and a color master batch discharging interface along the radial direction thereof and both of the interfaces are communicated with the mixing feeding channel. The body material discharging interface is connected with the body material hopper. The rotating material changing component is rotatably arranged on the circumferential side of the mixing feeding cylinder at the position of the color master batch discharging interface. The rotating material changing component is provided with a plurality of bottle interfaces and connected with the color master batch bottle. The application can greatly reduce the space required for equipment installation, reduce the material consumption during the color changing of the sleeve, configure the rotating material changing component to reduce the operation time and operation difficulty of the color master batch replacement, reduce the energy consumption and improve the production efficiency.

Description

Technical Field

[0001] This invention relates to the technical field of optical cable secondary sheathing equipment, specifically to an extruder mixing and feeding device and an optical cable double-layer sheath. Background Technology

[0002] Currently, in the secondary plastic sheathing process of optical fibers in optical cable products, the sheath material is mainly a single layer of engineering plastic. To meet the requirements of optical fiber splicing and optical cable line maintenance, the surface of the optical fiber needs to be color-coded, and the sheath wrapping the optical fiber also needs to be color-coded. For existing color-coded sheath structures, see [link to existing structures]. Figure 1 As shown, the color is uniformly distributed within the sleeve wall. The processing method for this type of sleeve involves mixing a certain proportion of color masterbatch into the raw material (mainly PBT, or polybutylene terephthalate) to form a homogeneous mixture. This mixture is then melt-extruded through an extruder, molded, and stretched to the required specifications. Since the sleeve's color development primarily relies on the reflection of the color masterbatch from the surface after exposure to external light, the color masterbatch in the deeper layers of the sleeve wall absorbs and reflects light less effectively. Therefore, the color masterbatch uniformly distributed deep within the sleeve wall has a weaker color development effect, resulting in waste in this area. Furthermore, the uniform distribution of the color masterbatch within the sleeve wall has a certain impact on the performance of PBT, and the impact varies depending on the color of the masterbatch, increasing the difficulty of quality control for optical cable sleeves. Moreover, because the screw diameter of the melt extrusion equipment used for the sleeve raw materials in the production line is relatively large, color changes during sleeve production require significant raw material and time consumption, leading to material waste and reduced efficiency.

[0003] To address the waste and time-consuming issues inherent in traditional optical fiber secondary coating processes, engineers have proposed a novel method for color development of the sleeve. This method involves including only the color masterbatch component on the outer surface of the sleeve. During processing, an extruder for the outer sleeve material and a double-layer co-extrusion die are added to the existing system. The resulting double-layer co-extrusion production line features two extruders: a main extruder for extruding the primary material (PBT) for the sleeve, and an auxiliary extruder for extruding the outer sleeve material. Typically, the main extruder is horizontally mounted, while the auxiliary extruder is vertically mounted. Existing extruders rely on the gravity of the plastic particles for feeding, which can lead to uneven entry into the extruder's feed inlet. This results in reduced and unstable extrusion output, ultimately causing product scrap. For the aforementioned double-layer co-extrusion production line, since the auxiliary extruder 1 for extruding the outer sleeve material is vertically mounted, the hopper guide pipe 2 needs to be installed at an angle. (See the installation diagram below.) Figure 2 As shown, in order to enable it to mix functional materials such as color masterbatch, in addition to the main material hopper 3, a color masterbatch hopper 4 is also required, along with a color masterbatch feeder 5. However, this configuration structure has the following drawbacks:

[0004] 1. The feed inlet of the vertically installed auxiliary extruder is located at a high position. Considering that the plastic granules need to be guided by an inclined guide pipe to enter the feed inlet of the auxiliary extruder, the hopper of the main material needs to be set at a higher position, which requires more space for equipment installation.

[0005] 2. The added color masterbatch hopper and feeding equipment need to be installed at a high position to cooperate with the main material hopper, which increases the difficulty of subsequent color masterbatch feeding or material replacement operations.

[0006] 3. Due to the long inclined feed tube, the plastic granules are greatly affected by the friction of the inclined feed tube wall when flowing in it. This can easily cause the plastic granules to be bridged and unable to enter the feed inlet of the auxiliary extruder smoothly, resulting in unstable extrusion output and affecting the extrusion quality. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a mixing and feeding device for an extruder and a double-layer sheath for optical cables produced by a double-layer extrusion production line using the mixing and feeding device, so as to solve the problems existing in the prior art.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A mixing and feeding device for an extruder includes a mixing and feeding cylinder, a main material hopper, a masterbatch bottle, and a rotary material changing component. The mixing and feeding cylinder has an axial mixing and feeding channel inside, and a mixing and feeding component is located within it. The top of the mixing and feeding cylinder has a main material discharge port and a masterbatch discharge port radially connected to the mixing and feeding channel. The main material hopper is connected to the main material discharge port. The rotary material changing component is rotatably mounted on the circumferential side of the mixing and feeding cylinder at the position of the masterbatch discharge port. The rotary material changing component has multiple bottle ports connected to the masterbatch bottles. By rotating the rotary material changing component circumferentially along the mixing and feeding cylinder, any one of the masterbatch bottles can be connected to the masterbatch discharge port.

[0010] Preferably, the mixing feeding channel is divided into a color masterbatch feeding channel and a mixed material feeding channel along the axial direction of the mixing feeding cylinder. The connection between the color masterbatch feeding channel and the mixed material feeding channel adopts a conical transition or a straight-edge stepped transition. The main material feeding interface is located in the part of the mixing feeding cylinder located in the mixed material feeding channel and communicates with the mixed material feeding channel. The color masterbatch feeding interface is opened in the part of the mixing feeding cylinder located in the color masterbatch feeding channel and communicates with the color masterbatch feeding channel.

[0011] Preferably, the mixing and feeding component includes a screw drive, a masterbatch feeding screw, and a mixture feeding screw. The masterbatch feeding screw is rotatably disposed in the masterbatch feeding channel, and the mixture feeding screw is rotatably disposed in the mixture feeding channel. One end of the masterbatch feeding screw is threadedly connected to the mixture feeding screw, and the other end passes through the mixing and feeding cylinder and is drivenly connected to the screw drive.

[0012] Preferably, the outer diameter of the spiral blade of the mixture feeding screw is larger than the outer diameter of the spiral blade of the color masterbatch feeding screw, and the two are in a multiple relationship; the inner diameter of the mixture feeding channel is larger than the inner diameter of the color masterbatch feeding channel, and the two are in a multiple relationship; the screw groove depth of the mixture feeding screw is larger than the screw groove depth of the color masterbatch feeding screw, and the two are in a multiple relationship; and the screw groove pitch of the mixture feeding screw is larger than the screw groove pitch of the color masterbatch feeding screw, and the two are in a multiple relationship.

[0013] Preferably, the distance from the connection point between the main material feeding interface and the mixed material feeding channel to the connection point between the mixed material feeding channel and the color masterbatch feeding channel is not less than two screw groove pitches of the mixed material feeding screw, and the distance from the connection point between the color masterbatch feeding interface and the color masterbatch feeding channel to the screw drive is not less than three screw groove pitches of the color masterbatch feeding screw.

[0014] Preferably, the end of the mixture feeding screw that is not connected to the color masterbatch feeding screw is a clamping end. The clamping end is flush with at least the end of the mixing feeding cylinder that is not provided with the screw drive component. The surface of the rod of the mixture feeding screw near the clamping end is provided with a wrench clamping surface along its axial direction.

[0015] Preferably, the rotary material changing component includes a rotary ring and a bottle base. The rotary ring is rotatably sleeved on the mixing feed cylinder at the position of the color masterbatch discharge interface and is limited by a positioning retaining ring or a pin. The inner side of the rotary ring cooperates with the outer circumferential side of the mixing feed cylinder. Multiple pairs of centrally symmetrical bottle interfaces are opened on the rotary ring along its radial direction. Each bottle interface is threadedly connected to the bottle base, and the color masterbatch bottle is threadedly connected or snapped onto the bottle base.

[0016] Preferably, the opening of the masterbatch bottle adopts a wide-mouth structure, and both the masterbatch bottle and the bottle base are provided with multiple transparent windows.

[0017] Meanwhile, this application also provides a double-layer optical cable sheath, which is manufactured using the extruder mixing and feeding device described in any of the above claims. It includes a natural-colored inner sheath and a colored outer sheath, wherein the natural-colored inner sheath is wholly or partially wrapped with the colored outer sheath and the two are coaxially arranged to form a double-layer structure.

[0018] Preferably, the overall outer diameter of the double-layer sleeve is 1.2 to 10 mm, the wall thickness of the inner layer of the sleeve is 0.3 to 0.6 mm, and the wall thickness of the outer layer of the sleeve is 0.02 to 0.08 mm.

[0019] Compared with existing technologies, the extruder mixing and feeding device provided by this invention can significantly reduce the space required for equipment installation when using a vertical extruder to extrude the outer layer of a sleeve in a double-layer extrusion production line. The feeding screw for conveying the masterbatch has a smaller diameter, reducing material consumption during sleeve color changes. It also includes a rotating material changing component to reduce the operation time and difficulty of changing the masterbatch, thereby reducing energy consumption and improving production efficiency. This feeding device adopts an active feeding method, and the feeding speed can be linked and controlled with the production speed of subsequent production lines. It also eliminates the phenomenon of plastic pellets bridging and bridging that may occur during natural feeding of the extruder, ensuring extrusion stability and improving the quality of the extruded product.

[0020] Furthermore, this invention also provides a double-layer sleeve for optical cables produced using a double-layer extrusion production line equipped with the aforementioned mixing and feeding device. Through color development on the outer layer of the sleeve, it fully meets the color-coding requirements for optical cable sleeves. In the production of large-core-count optical cables, it can overcome the limitations of the existing 12-color spectrum and provide a flexible color-coding scheme for large-core-count optical cable sleeves. The double-layer structure with a color-developing outer layer eliminates performance differences between sleeves of different colors, improves the consistency of optical cable cabling control commands, and significantly reduces the amount of masterbatch used in the sleeve manufacturing process compared to existing single-layer color-developing sleeves, thereby saving material costs. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the existing colorimetric sleeve;

[0023] Figure 2 This is a schematic diagram of the installation of an existing vertical extruder and feeding device;

[0024] Figure 3 A schematic diagram of a double-layer optical cable sheath provided by the present invention, in which the outer surface of the inner layer of the sheath is completely covered by the outer layer of the sheath in a colored manner.

[0025] Figure 4 A schematic diagram of a structure in which the outer part of the inner layer of the optical cable double-layer sheath is wrapped with a colored outer layer of the sheath, provided by the present invention;

[0026] Figure 5 This invention provides a schematic diagram of the structure of a mixing and feeding device for an extruder;

[0027] Figure 6 This is a cross-sectional view of the rotating ring in a mixing and feeding device for an extruder provided by the present invention.

[0028] Explanation of reference numerals and components in the accompanying drawings:

[0029] 1. Auxiliary extruder; 2. Hopper guide pipe; 3. Main material hopper; 4. Masterbatch hopper; 5. Masterbatch feeder; 6. Inner layer of sleeve (natural color); 7. Outer layer of sleeve (colored); 8. Mixing feed cylinder; 9. Masterbatch bottle; 10. Masterbatch feeding channel; 11. Mixed material feeding channel; 12. Main material discharge interface; 13. Masterbatch discharge interface; 14. Bottle interface; 15. Rotating ring; 16. Bottle base; 17. Transparent window; 18. Mixed material feeding screw; 19. Masterbatch feeding screw; 20. Screw drive component; 21. Wrench clamping surface; 22. Discharge interface. Detailed Implementation

[0030] The technical solution of the present invention will now be clearly and completely described through specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0031] To address the problems of existing single-layer color-developing sleeves, a double-layer optical cable sleeve is provided, comprising a natural-colored inner layer 6 extruded from PBT bulk material and a colored outer layer 7 extruded from a mixture of PBT bulk material and color masterbatch. The two layers are coaxially arranged in a double-layer structure, and the color rendering index of the colored outer layer can be adjusted by controlling the concentration of the color masterbatch in the mixture. Figure 3 As shown, the entire exterior of the inner, uncolored layer 6 of the casing is covered by the colored outer layer 7 of the casing. Figure 4As shown, the outer surface of the innermost layer 6 of the sheath can also be partially covered by a colored outer layer 7. This allows direct observation of the body color of the innermost layer 6, which is generally white after cooling. Consequently, the surface of the sheath will display a combination of colored and white stripes, thus providing a more flexible color-coding scheme for the sheath. The overall outer diameter of the double-layer sheath can be rationally designed according to the requirements of the fiber core count and structural design of the optical cable, with a preferred range of 1.2–10 mm. The wall thickness of the innermost layer 6 is 0.3–0.6 mm, and the wall thickness of the colored outer layer 7 is 0.02–0.08 mm.

[0032] The manufacturing of the aforementioned double-layer optical cable sheath utilizes a main extruder for extruding PBT bulk material and an auxiliary extruder 1 for extruding a mixture of PBT bulk material and color masterbatch. The base material is simultaneously melted, and a melt tube is formed under the action of a double-layer co-extrusion die. Supported by the optical cable and fiber paste passing through the melt tube, as well as external cooling water, the material is stretched and pulled by a traction machine to form a double-layer optical cable sheath that meets the requirements. However, the auxiliary extruder 1 used in this double-layer extrusion production line is vertically installed, thus presenting the problems described in the background art. Therefore, this embodiment also provides an extruder mixing and feeding device to solve the aforementioned problems.

[0033] See Figures 5-6 As shown, an extruder mixing and feeding device includes a mixing and feeding cylinder 8, a main material hopper 3, a color masterbatch bottle 9, and a rotary material changing component. The mixing and feeding cylinder 8 has a mixing and feeding channel along its axial direction, and a mixing and feeding component is located within it. The mixing and feeding channel is sequentially divided along the axial direction of the mixing and feeding cylinder 8 into a color masterbatch feeding channel 10 and a mixed material feeding channel 11, with the connection between the two using a tapered transition or a straight-edge stepped transition to ensure that the color masterbatch in the color masterbatch feeding channel 10 can smoothly enter the mixed material feeding channel 11.

[0034] At the top of the mixing feed cylinder 8, corresponding to the positions of the mixing material feeding channel 11 and the masterbatch feeding channel 10, a main body material feeding port 12 and a masterbatch feeding port 13 are respectively opened radially. The main body material feeding port 12 is connected to the mixing material feeding channel 11, and the masterbatch feeding port 13 is connected to the masterbatch feeding channel 10. A main body material hopper 3 is connected to the main body material feeding port 12, and the main body material hopper 3 contains PBT main body material.

[0035] To enable rapid color changing, a rotating material changing component is rotatably mounted on the circumferential side of the mixing feed cylinder 8 at the position of the masterbatch dispensing interface 13. This rotating material changing component has multiple bottle interfaces 14 connected to masterbatch bottles 9. By rotating the rotating material changing component circumferentially along the mixing feed cylinder 8, any one of the masterbatch bottles 9 can be connected to the masterbatch dispensing interface 13. The aforementioned material changing component includes a rotating ring 15 and a bottle base 16. The rotating ring 15 is rotatably mounted on the mixing feed cylinder 8 at the position of the masterbatch dispensing interface 13 and is limited by a positioning retaining ring or pin. The inner surface of the rotating ring 15 cooperates with the outer circumferential surface of the mixing feed cylinder 8 to allow the rotating ring 15 to rotate relative to the mixing feed cylinder 8 without leakage. The rotating ring 15 has multiple pairs of centrally symmetrical bottle interfaces 14 along its radial direction. Each bottle interface 14 is threadedly connected to a bottle base 16, and a color masterbatch bottle 9 is threadedly connected or snapped onto the bottle base 16. In actual production, it is preferable to install four bottle bases 16. By rotating the rotating ring 15, the color masterbatch bottle 9 of the desired color is aligned with the color masterbatch feeding interface 13 for feeding. When one color masterbatch bottle 9 is aligned with the color masterbatch feeding interface 13, the other color masterbatch bottle 9, which is centrally symmetrical to it, is located at the bottom of the mixing feed cylinder 8, making it easy for the operator to manually rotate and remove it from the bottle base 16. Each color masterbatch bottle 9 contains a different color of color masterbatch. To facilitate observation of the amount of color masterbatch, both the color masterbatch bottle 9 and the bottle base 16 are provided with multiple transparent windows 17. At the same time, the opening of the color masterbatch bottle 9 adopts a wide-mouth structure, which facilitates both adding material into the bottle and cleaning the inside of the bottle.

[0036] Corresponding to the mixed material feeding channel 11 and the masterbatch feeding channel 10 are the mixing feeding components, including a mixed material feeding screw 18, a masterbatch feeding screw 19, and a screw drive 20. The masterbatch feeding screw 19 is rotatably disposed within the masterbatch feeding channel 10, and the mixed material feeding screw 18 is rotatably disposed within the mixed material feeding channel 11. One end of the masterbatch feeding screw 19 is threadedly connected to the mixed material feeding screw 18, and the other end passes through the mixing feeding cylinder 8 and is driven by the screw drive 20. Thus, the screw drive 20 simultaneously drives both the mixed material feeding screw 18 and the masterbatch feeding screw 19 to rotate and feed materials, saving installation space and simplifying the control system.

[0037] The end of the mixing feed screw 18 that is not connected to the masterbatch feed screw 19 is the clamping end. The clamping end is flush with the end of the mixing feed cylinder 8 that is not provided with the screw drive 20. The surface of the rod of the mixing feed screw 18 near the clamping end is provided with a wrench clamping surface 21 along its axial direction, which facilitates the disassembly and installation of the combination of the mixing feed screw 18 and the masterbatch feed screw 19. At the same time, the wrench clamping surface 21 has a certain disturbance effect on the plastic granules at the discharge interface 22 of the mixing feed channel 11.

[0038] The masterbatch in the masterbatch bottle 9 falls from the masterbatch discharge port 13 into the masterbatch mixing channel 10 and is conveyed to the mixing material feeding channel 11 by the masterbatch feeding screw 19. The PBT body material in the body material hopper 3 falls from the body material discharge port 12 into the mixing material feeding channel 11. During the continuous rotation and pushing process of the mixing material feeding screw 18, it is mixed with the masterbatch and output to the discharge port 22 of the mixing material feeding channel 11.

[0039] The material of the colored outer layer 7 of the aforementioned optical cable double-layer sheath is a mixture of PBT bulk material and color masterbatch. The PBT bulk material and color masterbatch are mixed in a certain proportion and then fed into the feed inlet of the auxiliary extruder 1. Since the rotational angular velocity of the mixture feeding screw 18 and the color masterbatch feeding screw 19 is the same, the mixing ratio of PBT bulk material and color masterbatch can be adjusted by adjusting the outer diameter of the spiral blade, the screw pitch, and the screw depth of the mixture feeding screw 18 and the color masterbatch feeding screw 19, thereby meeting the product quality requirements. To facilitate adjustment of the mixing ratio, the outer diameter of the spiral blade of the mixing material feeding screw 18 is larger than the outer diameter of the spiral blade of the color masterbatch feeding screw 19, and the two are in a multiple relationship. Correspondingly, the inner diameter of the mixing material feeding channel 11 is also larger than the inner diameter of the color masterbatch feeding channel 10, and the two are also in a multiple relationship. The screw groove depth and screw groove pitch of the mixing material feeding screw 18 are both larger than the screw groove depth and screw groove pitch of the color masterbatch feeding screw 19, and both are in a multiple relationship.

[0040] To facilitate the entry of PBT bulk material into the mixing material feeding channel 11 via the bulk material hopper 3, the mixing material feeding channel 11 is designed to have a large internal space. When the mixing material feeding screw 18 is stationary, the PBT bulk material will flow irregularly after entering the mixing material feeding channel 11. To prevent it from flowing to the connection between the mixing material feeding channel 11 and the masterbatch feeding channel 10, or even into the masterbatch feeding channel 10 and the screw drive unit 20, specific requirements must be made for the setting position of the bulk material unloading interface 12. Preferably, the distance from the connection point between the interface 12 and the mixing material feeding channel 11 to the connection point between the mixing material feeding channel 11 and the masterbatch feeding channel 10 is not less than two screw groove pitches of the mixing material feeding screw 18. Similarly, specific requirements for the position of the masterbatch feeding interface 13 can also prevent the masterbatch entering the masterbatch feeding channel 10 from flowing towards the screw drive 20. Therefore, the distance from the connection between the masterbatch feeding interface 13 and the masterbatch feeding channel 10 to the screw drive 20 is not less than three screw groove pitches of the masterbatch feeding screw 19.

[0041] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A mixing and feeding device for an extruder, characterized in that: The device includes a mixing and feeding cylinder, a main material hopper, a masterbatch bottle, and a rotary material changing component. The mixing and feeding cylinder has an axial mixing and feeding channel inside, and a mixing and feeding component is located within it. The top of the mixing and feeding cylinder has a main material discharge port and a masterbatch discharge port radially connected to the mixing and feeding channel. The main material hopper is connected to the main material discharge port. The rotary material changing component is rotatably mounted on the circumferential side of the mixing and feeding cylinder at the position of the masterbatch discharge port. The rotary material changing component has multiple bottle ports connected to the masterbatch bottles. By rotating the rotary material changing component circumferentially along the mixing and feeding cylinder, any one of the masterbatch bottles can be connected to the masterbatch discharge port. The mixing feeding channel is divided into a color masterbatch feeding channel and a mixed material feeding channel along the axial direction of the mixing feeding cylinder. The connection between the color masterbatch feeding channel and the mixed material feeding channel adopts a conical transition or a straight-edge stepped transition. The main material feeding interface is located in the part of the mixing feeding cylinder located in the mixed material feeding channel and communicates with the mixed material feeding channel. The color masterbatch feeding interface is opened in the part of the mixing feeding cylinder located in the color masterbatch feeding channel and communicates with the color masterbatch feeding channel. The rotating material changing component includes a rotating ring and a bottle base. The rotating ring is rotatably sleeved on the mixing feed cylinder at the position of the color masterbatch discharge interface and is limited by a positioning retaining ring or a pin. The inner side of the rotating ring cooperates with the outer circumferential side of the mixing feed cylinder. Multiple pairs of centrally symmetrical bottle interfaces are opened on the rotating ring along its radial direction. Each bottle interface is threadedly connected to the bottle base, and the color masterbatch bottle is threadedly connected or snapped onto the bottle base.

2. The extruder mixing and feeding device according to claim 1, characterized in that: The mixing and feeding component includes a screw drive, a masterbatch feeding screw, and a mixture feeding screw. The masterbatch feeding screw is rotatably disposed in the masterbatch feeding channel, and the mixture feeding screw is rotatably disposed in the mixture feeding channel. One end of the masterbatch feeding screw is threadedly connected to the mixture feeding screw, and the other end passes through the mixing and feeding cylinder and is drivenly connected to the screw drive.

3. The extruder mixing and feeding device according to claim 2, characterized in that: The outer diameter of the spiral blade of the mixture feeding screw is greater than that of the outer diameter of the spiral blade of the color masterbatch feeding screw, and the two are in a multiple relationship. The inner diameter of the mixture feeding channel is greater than that of the color masterbatch feeding channel, and the two are in a multiple relationship. The screw groove depth of the mixture feeding screw is greater than that of the color masterbatch feeding screw, and the two are in a multiple relationship. The screw groove pitch of the mixture feeding screw is greater than that of the color masterbatch feeding screw, and the two are in a multiple relationship.

4. The extruder mixing and feeding device according to claim 2, characterized in that: The distance from the connection point between the main material feeding interface and the mixed material feeding channel to the connection point between the mixed material feeding channel and the color masterbatch feeding channel is not less than two screw groove pitches of the mixed material feeding screw, and the distance from the connection point between the color masterbatch feeding interface and the color masterbatch feeding channel to the screw drive is not less than three screw groove pitches of the color masterbatch feeding screw.

5. The extruder mixing and feeding device according to claim 2, characterized in that: The end of the mixing feed screw that is not connected to the color masterbatch feed screw is a clamping end. The clamping end is flush with at least one end of the mixing feed cylinder that is not provided with the screw drive component. The surface of the rod of the mixing feed screw near the clamping end is provided with a wrench clamping surface along its axial direction.

6. The extruder mixing and feeding device according to claim 1, characterized in that: The opening of the masterbatch bottle adopts a wide-mouth structure, and both the masterbatch bottle and the bottle base are provided with multiple transparent windows.

7. A double-layer sheath for optical cables, characterized in that: The product manufactured using the extruder mixing and feeding device according to any one of claims 1 to 6 includes a natural-colored inner layer of the sleeve and a colored outer layer of the sleeve, wherein the natural-colored inner layer of the sleeve is wholly or partially wrapped with the colored outer layer of the sleeve and the two are coaxially arranged to form a double-layer structure.

8. The optical cable double-layer sheath according to claim 7, characterized in that: The overall outer diameter of the double-layer sleeve is 1.2~10mm, the wall thickness of the inner layer of the sleeve is 0.3~0.6mm, and the wall thickness of the outer layer of the sleeve is 0.02~0.08mm.

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