Extruding machine head and extruding equipment for forming multi-layer plastic light pipe

Abstract

The invention discloses an extruding machine head and extruding equipment for forming a multi-layer plastic light pipe, relates to the technical field of plastic waste recycling and forming, and aims to solve the technical problem that the interlayer bonding strength is insufficient when the multi-layer plastic light pipe is generated. According to the extrusion machine head and the extrusion equipment for forming the multi-layer plastic light pipe, the quality and the efficiency are optimized from multiple aspects of mixing, defoaming, function expansion and production adaptation. Through a multi-stage shear mixing structure, interlaminar molecular chain entanglement is strengthened, the bonding strength is improved, and layering is avoided; spiral guide negative pressure bubble removal and buffering acceleration auxiliary bubble removal are cooperated, melt bubbles are efficiently removed, and the optical performance and the forming quality of the light pipe are guaranteed; the embossing mode can be used for processing specific textures on the surface of the light pipe, embossing and bubble removing are synchronously carried out, and functions and quality are both considered; and a shaft side moving mechanism of the extrusion equipment can be conveniently butted with the material guide barrel for maintenance. And the problems of insufficient interlayer bonding, bubble residues and the like of traditional equipment are integrally solved, and the production convenience and the product stability are improved.

Description

Technical Field

[0001] This invention relates to the field of plastic waste recycling and molding technology, and more specifically, to an extruder head and extrusion equipment for forming multi-layer plastic tubes. Background Technology

[0002] In the intersection of plastic recycling and optical applications, recycling and regenerating plastic waste to fabricate multilayer plastic optical tubes is an important path to achieve efficient resource recycling and reduce the production cost of optical products, while also aligning with environmental policies and sustainable development needs. This production process relies on co-extrusion technology, which can process different types of plastic waste (such as waste PET, PP, ABS, etc.) through crushing, screening, and modification, and then use a layered co-extrusion process to prepare multilayer plastic optical tubes with light transmission capabilities. These tubes are widely used in landscape lighting, short-distance light transmission, and other scenarios. The core of this process is the synergistic effect of the "micro-bump mixing structure" and "back pressure adjustment technology" within the extrusion equipment's feed block, ensuring tight bonding between different recycled plastic melt layers. The micro-bump mixing structure, through the concave-convex design on the flow channel walls and mandrel, creates localized disturbances at the melt interface, promoting the entanglement of different recycled plastic molecular chains. The back pressure adjustment technology, through pressure control, eliminates interface bubbles and strengthens interlayer bonding. Together, these two technologies support the basic molding quality and light transmission stability of the recycled multilayer plastic optical tube.

[0003] However, existing micro-bump hybrid structures and back pressure adjustment technologies have significant drawbacks in the practical application of recycling plastic waste to produce multilayer plastic tubes. Plastic waste itself has a complex composition, often containing aged molecular chains, trace impurities, and varying degrees of degradation components. Even after modification, its melt flowability and compatibility are still lower than virgin materials. Multilayer plastic tubes, on the other hand, have higher requirements for interlayer bonding strength and structural uniformity, which existing technologies struggle to meet. When co-extruding waste PET and PP waste to produce multilayer plastic tubes, the micro-bump hybrid structure frequently causes problems: due to the initially designed excessively large micro-bump spacing, coupled with the differences in the flowability of recycled plastic melt, some areas of the melt are not effectively disturbed when flowing through the feed block, resulting in insufficient molecular chain entanglement at the interface and directly reducing interlayer bonding strength. Subsequent performance testing revealed that the shear strength and peel strength of these weakly bonded areas were significantly insufficient, and the uneven interlayer bonding led to a significant decrease in light transmission efficiency. In durability tests simulating real-world usage environments, after a certain period of light exposure and thermal cycling, delamination easily occurred in these weakly bonded areas, resulting not only in secondary resource waste but also a substantial increase in the company's recycling and processing costs. Therefore, we propose an extruder head and extrusion equipment for forming multilayer plastic tubes. Summary of the Invention

[0004] The purpose of this invention is to provide an extruder head for forming multilayer plastic tubes, so as to solve the technical problem of insufficient interlayer bonding strength during the formation of multilayer tubes.

[0005] To solve the above technical problems, the present invention provides the following technical solution: an extrusion head for forming multi-layer plastic tubes, comprising a co-extrusion head, wherein the co-extrusion head is composed of a pre-forming section, a forming section and an extrusion section, wherein an outlet end is provided at the center of one end of the extrusion section, and a central inner support column is provided inside the end of the co-extrusion head near the outlet end. The other end of the co-extrusion die head is connected to a buffer end pipe, one end of which is connected to a shearing end pipe. The shearing end pipe is provided with a back pressure adjustment part at its end. The shearing end pipe has a conical cross-section. The shearing end pipe and the buffer end pipe are provided with gaps for the flow of multiple layers of materials. Multiple guide cylinders are connected to the outer periphery of the shearing end pipe. Multiple beak shearing components are provided inside the shearing end pipe. The beak shearing components are spirally distributed along the axis of the gaps in the shearing end pipe. The preformed section has a defoaming structure on its sidewall. The defoaming structure includes an inner cavity formed in the inner wall of the preformed section. A negative pressure chamber is provided on one side of the inner cavity. A negative pressure mechanism is provided inside the negative pressure chamber. Multiple bubble-absorbing grooves are connected between the negative pressure chamber and the inner cavity. A spiral guide plate is provided inside the inner cavity.

[0006] Preferably, the beak shearing component consists of a sealing section and a gradient section. The gradient section has a gradually decreasing thickness from the shearing end tube towards the co-extrusion head. The outer wall of the gradient section has multiple serrated protrusions. The sealing section fits into the inner wall of the gap.

[0007] Preferably, the inner side of the spiral guide plate is a pointed tip, the spiral guide plate is distributed around the outer surface of the preformed light tube, and the pointed tip of the spiral guide plate is in contact with the outer surface of the preformed light tube.

[0008] Preferably, the negative pressure mechanism is a negative pressure suction device.

[0009] Preferably, the negative pressure mechanism includes an outer ring plate fixed to the inner wall of the negative pressure chamber. A side frame is connected to one side of the outer ring plate. The side frame is made of elastic material and forms a closed annular frame with the outer ring plate. Multiple one-way valves that allow air to enter are provided on the inner wall of the annular frame. Multiple one-way valves that allow air to exit are provided on the outer wall of the annular frame. A differential pressure valve is installed on the outer wall of the annular frame. Multiple stabilizing telescopic rods are provided between the side frame and the outer ring plate.

[0010] Preferably, the inner wall of the side frame is integrally formed with a concave section, and a plurality of extrusion blocks are provided inside the concave section, with hydraulic rods connected to the inner circumference of the extrusion blocks.

[0011] Preferably, the negative pressure chamber is further provided with an embossing mechanism, which includes a fixing ring. An embossed metal is connected to one side of the fixing ring. The embossed metal is made of an elastic material and is in close contact with the side wall of the negative pressure chamber on one side. The embossed metal is composed of a straight edge section and a conical tip section. The conical tip section is in the shape of a cone. The hydraulic rod drive end is located on one side of the embossed metal.

[0012] Preferably, the buffer end tube includes multiple acceleration chambers and buffer chambers. The acceleration chambers have a gradually decreasing gap from the input direction to the output direction. The buffer chambers have several concave areas on the outer wall of the material fluid. Multiple adjacent concave areas are connected by a groove. A negative pressure ring is installed at the end of the buffer end tube, and the negative pressure ring is connected to the groove.

[0013] Preferably, a low-pressure component is provided inside the concave area. The low-pressure component includes a hemisphere, which is an elastic hemispherical capsule. An elastic pull rope is connected inside the hemisphere. A sealing sleeve penetrating the adjacent gap is provided on the outer periphery of the elastic pull rope. The rear part of the penetrating end of the elastic pull rope is thickened and fixed to the side wall of the adjacent gap.

[0014] Preferably, the extrusion equipment for the above-mentioned multi-layer plastic tube forming extruder head includes a plurality of such extrusion devices, wherein a shaft-side moving mechanism is installed at the bottom of the extrusion device, and the output port of the extrusion device is connected to the guide cylinder.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention addresses the characteristics of complex composition, uneven melt flow, and easy aging and breakage of molecular chains in plastic waste. It constructs a multi-stage shearing and mixing system using a beak-shaped shearing component. The spirally distributed sealing section allows the recycled plastic melt to flow along a spiral trajectory, generating circumferential shear force to break the disordered arrangement and parallel aggregation of aged molecular chains, promoting initial entanglement between different types of recycled plastic layers. The gradually decreasing thickness of the gradient section reduces the flow channel space, causing the melt to compress against each other, effectively offsetting the insufficient contact caused by impurities in the recycled plastic melt and expanding the actual contact area between layers. The serrated protrusions generate precise micro-shear at the melt interface, segmenting melt clumps formed by waste degradation and enhancing local shear force. This simultaneously improves the mixing effect from both macroscopic compression and microscopic disturbance levels, ensuring sufficient entanglement of aged molecular chains between layers. This significantly improves the interlayer bonding strength of multi-layer tubes formed from recycled plastic waste, avoiding subsequent delamination problems caused by poor waste compatibility and low molecular activity, and solving the problem of insufficient interlayer bonding strength when preparing multi-layer tubes from plastic waste.

[0016] 2. This invention addresses the problem of bubbles generated during the recycling of plastic waste due to residual impurities and degradation of volatiles. It utilizes a spiral guide plate and a negative pressure system for defoaming. The tip of the spiral guide plate contacts the surface of the light tube, generating shear force that propels bubbles encased in the recycled melt outwards along a spiral trajectory. Polishing of the inner cavity reduces bubble adhesion to the wall surface (especially addressing the bubble adsorption problem caused by trace amounts of oil in the waste). A stable pressure difference is formed between the bubble suction tank and the negative pressure chamber, quickly capturing and extracting the migrated bubbles. The annular frame of the negative pressure mechanism continuously provides stable negative pressure through periodic contraction and expansion. Combined with the wedge-shaped inlet design of the bubble suction tank, it ensures no dead zones in the capture area. This structure efficiently removes bubbles from the inside of the plastic waste-molded light tube, avoiding light transmission efficiency degradation caused by bubble residue. It solves the industry pain point of numerous and difficult-to-remove bubbles in recycled plastic melt, ensuring the optical performance and molding quality of multilayer light tubes prepared from recycled plastic waste.

[0017] 3. This invention addresses the issue of limited functionality in plastic waste recycled light tubes by designing a negative pressure mechanism that can switch to embossing mode. A hydraulic rod pushes the conical tip of the embossing metal to press annular wavy patterns onto the light tube surface, meeting the needs of special applications such as landscape lighting and anti-slip protection. During embossing, the negative pressure system operates continuously, both fixing the light tube through negative pressure adsorption to prevent embossing deviation caused by uneven recycled plastic material, and instantly adsorbing tiny air bubbles generated during embossing (recycled plastic melt easily precipitates hidden air bubbles under pressure), achieving simultaneous embossing and debubbling. The elastic embossing metal avoids scratching the light tube surface, which has reduced toughness after waste modification treatment. A stable telescopic rod ensures uniform deformation of the annular frame, guaranteeing negative pressure stability and embossing consistency. This design enriches the functionality of recycled plastic waste light tubes while also considering molding quality, significantly improving the equipment's adaptability and practicality to recycled plastic raw materials, and expanding the application scenarios of multi-layer recycled light tubes.

[0018] 4. This invention addresses the problem of uneven distribution of bubbles and impurities in plastic waste melt before entering the co-extrusion die head. It optimizes pretreatment through a buffer end tube and employs a decreasing gap design in the acceleration chamber to increase the flow rate of the recycled plastic melt. A radial pressure gradient forces bubbles to migrate outwards (especially targeting small, low-density bubbles in the waste). The concave area of ​​the buffer chamber forms a localized low-pressure zone, which, combined with continuous suction from the negative pressure ring, efficiently captures the migrating bubbles. The elastic hemisphere of the low-pressure component deforms flexibly under the impact of the melt, increasing the volume of the concave area and creating a momentary strong negative pressure, enhancing the capture effect on small bubbles generated by waste degradation in the recycled melt. This structure pre-treats bubbles before the melt enters the co-extrusion die head, further removing bubbles and some small impurities from the recycled plastic melt, optimizing melt uniformity, and providing high-quality recycled melt raw materials for subsequent co-extrusion molding. This improves the molding quality and optical performance of multilayer optical tubes made from recycled plastic waste from the source.

[0019] 5. This invention addresses the need for adaptability to different types and specifications of waste materials in plastic waste recycling production. It enhances equipment adaptability through an axially moving mechanism and a segmented design. The axially moving mechanism at the bottom of the extrusion equipment allows for flexible movement, facilitating quick connection or separation from the guide cylinder. This simplifies the raw material switching process for different types of plastic waste (such as waste PET, PP, ABS, etc.) and reduces equipment installation, debugging, and maintenance costs. The co-extrusion die head adopts a segmented design, with each component having an independent structure, facilitating the replacement of corresponding components according to the optical tube specifications, adapting to the production needs of recycled multilayer optical tubes with different thicknesses and layers. The back pressure adjustment unit utilizes existing mature technology, reducing equipment development difficulty and maintenance costs. Simultaneously, it allows for precise adjustment of parameters based on the flow characteristics of different recycled plastic melts. The overall structural design balances adaptability and convenience, meeting the production needs of multilayer optical tubes from recycled plastic waste of different specifications and raw material types. This significantly improves operational efficiency during production, reduces enterprise recycling and processing costs, and promotes the efficient resource utilization of plastic waste in the field of optical products. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the co-extrusion die head of the present invention.

[0021] Figure 2 This is a schematic diagram of the shear end tube in this invention.

[0022] Figure 3 This is a schematic diagram of the structure when the outermost layer of the sheared end tube is removed in this invention.

[0023] Figure 4 This is a schematic diagram of the structure of a single eagle beak shearing component in this invention.

[0024] Figure 5 This is a schematic diagram of a half-section of the buffer end tube in this invention.

[0025] Figure 6 This is a schematic diagram of the low-pressure component in this invention.

[0026] Figure 7 This is a schematic diagram of the internal structure of the preformed section in this invention.

[0027] Figure 8 This is a schematic diagram of the internal cavity of the preformed section in this invention.

[0028] Figure 9 This is a schematic diagram of the defoaming structure in this invention.

[0029] Figure 10 This is a half-section diagram of the defoaming structure in this invention.

[0030] Figure 11 This is a schematic diagram of the ring frame structure in this invention.

[0031] Figure 12 This is a schematic diagram of the embossing mechanism in this invention.

[0032] Figure 13 This is a schematic diagram of the connection structure between the extrusion equipment and the co-extrusion die head in this invention.

[0033] Explanation of the labels in the diagram: 1. Co-extrusion die head; 101. Preforming section; 102. Forming section; 103. Extrusion section; 2. Outlet tube end; 3. Central inner support column; 4. Buffer end tube; 5. Shear end tube; 6. Back pressure adjustment section; 7. Guide cylinder; 8. Beak shear component; 9. Defoaming structure; 10. Embossing mechanism; 11. Extrusion equipment; 12. Axial side moving mechanism; 401. Acceleration chamber; 402. Buffer chamber; 403. Negative pressure ring; 43. Low-pressure component; 431. Hemisphere; 432. Elastic pull rope; 433. Sealing sleeve; 801. Sealing section; 802. Gradient section; 91. Inner cavity; 92. Negative pressure chamber; 93. Bubble absorption groove; 94. Spiral guide plate; 95. Negative pressure mechanism; 951. Outer ring plate; 952. Side frame; 9521. Concave section; 953. Stabilizing telescopic rod; 954. Extrusion block; 955. Hydraulic rod; 111. Fixing ring; 112. Embossed metal; 1121. Straight edge section; 1122. Conical tip section. Detailed Implementation

[0034] like Figures 1 to 13 As shown, the present invention relates to an extruder head for forming multi-layer plastic tubes, including a co-extrusion head 1. The co-extrusion head 1 is composed of a pre-forming section 101, a forming section 102 and an extrusion section 103. An outlet end 2 is provided at the center of one end of the extrusion section 103. A central inner support column 3 is provided inside the end of the co-extrusion head 1 near the outlet end 2. The central inner support column 3 penetrates the extrusion section 103 and is used to support the inner hole shape of the tube and prevent it from collapsing during forming.

[0035] The other end of the co-extrusion die head 1 is connected to a buffer end pipe 4. One end of the buffer end pipe 4 is connected to a shear end pipe 5. A back pressure adjustment part 6 is provided at the end of the shear end pipe 5. The shear end pipe 5 and the buffer end pipe 4 are provided with gaps for the flow of multiple layers of materials. Multiple guide cylinders 7 are connected to the outer periphery of the shear end pipe 5. The back pressure adjustment part 6 adopts existing technology, so the structure here will not be described in detail.

[0036] The shearing end tube 5 has a conical cross-section and multiple beak shearing components 8 are installed inside the shearing end tube 5. The beak shearing components 8 are spirally distributed along the axis of the gap in the shearing end tube 5. The beak shearing components 8 are composed of a sealing section 801 and a transition section 802. The transition section 802 has a gradually decreasing thickness from the shearing end tube 5 to the co-extrusion head 1. Multiple serrated protrusions are opened on the outer wall of the transition section 802. The sealing section 801 fits against the inner wall of the gap.

[0037] The working principle is as follows: The shearing effect of the spiral trajectory: When the melt flows along the spiral trajectory formed by the sealing section 801, it is subjected to the dual action of back pressure and spiral channel, generating circumferential shear force. The eagle beak shear component 8 is "spirally distributed along the gap of the shear end tube 5". This distribution method causes the melt to be continuously scraped and squeezed by the circumferential wall of the spiral channel while advancing axially, which initially breaks the parallel arrangement of the melt molecular chains, promotes the initial entanglement of interlayer molecular chains, and completes the first shear mixing.

[0038] The convergence of trajectories and secondary extrusion in the transition section: As the melt flows from the shear end tube 5 toward the co-extrusion die head 1, it enters the transition section 802 of the beak shear component 8. The thickness of this section gradually decreases from the shear end tube 5 toward the co-extrusion die head 1, causing the originally independent spiral channel space to gradually shrink. Melts with different spiral trajectories begin to approach and contact each other. The design of "gradually decreasing thickness of transition section 802" causes the melt to be subjected to continuous axial extrusion during the flow process. The interlayer contact area expands from local contact to full adhesion, and the molecular chain entanglement density is further improved, completing the second extrusion mixing.

[0039] Enhanced shearing by the serrated protrusions: Multiple serrated protrusions on the outer wall of the gradient section 802 play a "micro-shearing" role during melt flow and extrusion. When the melt flows through the serrated protrusions, the edges of the protrusions will cause local disturbances to the melt interface, dividing the originally large melt clumps into small streams, while increasing the flow resistance of the melt. Combined with the back pressure, this forms a stronger local shearing force, ensuring sufficient entanglement of interlayer molecular chains.

[0040] The “trajectory limitation” of the sealing section 801 and the “pressure guarantee” of the back pressure work together: the fitting design of the sealing section ensures the stability of the spiral trajectory, while the back pressure provides the pressure required for shearing. Together, they prevent shear failure caused by “pressureless flow” of the melt.

[0041] The "spatial contraction" of the gradient section 802 and the "micro-disturbance" of the serrated protrusion work together: the thickness reduction of the gradient section achieves interlayer compression, and the serrated protrusion strengthens local shearing. The two improve the mixing effect from the levels of "macro compression" and "micro-disturbance" respectively, and finally solve the core problem of insufficient interlayer bonding strength of multilayer optical tubes.

[0042] To further improve the quality of the fluorescent tube and avoid the residue of air bubbles.

[0043] The preforming section 101 has a defoaming structure 9 on its side wall. The defoaming structure 9 includes an inner cavity 91 formed in the inner wall of the preforming section 101. A negative pressure chamber 92 is provided on one side of the inner cavity 91. A negative pressure mechanism 95 is provided inside the negative pressure chamber 92. Multiple bubble suction grooves 93 are connected between the negative pressure chamber 92 and the inner cavity 91. A spiral guide plate 94 is provided inside the inner cavity 91. The inner side of the spiral guide plate 94 is pointed. The spiral guide plate 94 is distributed around the outer surface of the preformed tube. The tip of the spiral guide plate 94 contacts the outer surface of the preformed tube. The negative pressure mechanism 95 can be an existing negative pressure suction device, such as a vacuum pump.

[0044] The specific implementation method for defoaming is as follows: Negative pressure system startup and pressure calibration.

[0045] Start the external vacuum pump and stabilize the pressure inside the negative pressure chamber 92 at -0.09 to -0.08 MPa by installing a pressure regulating valve on the negative pressure chamber 92 or by using the vacuum pump (real-time monitoring by a vacuum gauge, error ≤ ±0.005 MPa); at the same time, check whether the bubble absorption groove 93 between the negative pressure chamber 92 and the inner cavity 91 is unobstructed - this can be tested by introducing compressed air (0.2 MPa) to ensure there is no blockage (if there is a blockage, it needs to be cleaned by back-blowing with high-pressure nitrogen).

[0046] Defoaming: Internal cleaning of the structure and inspection of components.

[0047] Clean the inner wall of the inner cavity 91 and the surface of the spiral guide plate 94 to remove residual molten impurities (use a copper brush with alcohol to wipe, avoiding scratching the surface). Confirm that the tip of the spiral guide plate 94 is unworn (the contact gap between the tip and the outer surface of the preformed tube should be controlled between 0.1 and 0.2 mm; if the wear exceeds 0.3 mm, the guide plate needs to be replaced). Check the spiral guide plate 94 to ensure that it is coaxial with the axis of the inner cavity 91 to prevent the tube from shifting during transport, which could lead to bubble guidance failure.

[0048] Temperature-coordinated preheating.

[0049] Preheat the pre-forming section 101 and the defoaming structure 9 (the temperature is matched with the forming temperature of the tube, such as the PA / EVOH / PE five-layer structure with a suitable temperature of 180 to 200℃). The temperature of the inner wall of the inner cavity 91 is monitored by a temperature sensor. Temperature control is existing technology and will not be described in detail. It can be omitted under normal temperature conditions. Ensure that the temperature difference is ≤5℃ - to avoid the melt viscosity from rising sharply due to excessively low temperature, which would make it difficult for bubbles to migrate.

[0050] Light tube delivery stage: Stable feed provides initial positioning (laying the foundation for bubble guidance).

[0051] Under the action of the traction mechanism, the multi-layer composite optical tube (such as a five-layer PA / EVOH / PE structure) moves smoothly along the annular channel axis of the inner cavity 91 at a speed of 0.5 to 2 m / min (the feed speed is adjusted according to the diameter of the optical tube: 0.5 to 1 m / min for diameter ≤ 20 mm, and 1 to 2 m / min for diameter > 20 mm). At this time, the gap between the outer layer of the optical tube and the inner wall of the inner cavity 91 remains uniform (0.5 to 1 mm), and the optical tube is kept in the center position of the inner cavity 91 by the limiting of the optical tube guide ring, avoiding excessive friction with the tip of the spiral guide plate 94 and causing scratches on the surface of the optical tube.

[0052] Bubble guidance stage: spiral trajectory migration and directional aggregation (core pre-debubbling step).

[0053] The combined effect of shear force and tip force: When the light tube moves, its outer layer and the tip of the spiral guide plate 94 generate a slight shear force. At the same time, the spiral guide plate 94, which is distributed around the outer surface of the pre-formed light tube, causes the residual bubbles inside the light tube (within the range of 0.05 to 0.5 mm in diameter) to be subjected to "circumferential thrust + radial component force" - the circumferential thrust pushes the bubbles to move along the trajectory of the spiral guide plate 94, while the radial component force causes the bubbles to migrate towards the outer layer of the light tube (away from the center of the light tube, and gather towards the side wall of the inner cavity 91).

[0054] Bubble path optimization and anti-escape design: The tip of the spiral guide plate 94 has a sharp structure that can penetrate the melt boundary layer of the outer layer of the light tube and break the adsorption force between the bubble and the melt; at the same time, the inner wall of the inner cavity 91 is polished (roughness Ra≤0.1μm) to reduce the adhesion of bubbles to the wall surface. Under the dual effect, the migration efficiency of the bubble along the spiral trajectory is increased by 40%, avoiding the bubble from being stuck inside the light tube or escaping along the axis.

[0055] Negative pressure capture stage: When bubbles migrate along the spiral trajectory to the bubble-absorbing groove 93 area outside the inner cavity 91, a pressure difference (pressure difference ≥ 0.08MPa) is formed between the inner cavity (normal pressure or slightly positive pressure) - bubble-absorbing groove - negative pressure chamber (-0.09 to -0.08MPa) because the bubble-absorbing groove 93 is directly connected to the negative pressure chamber 92. Under the action of this pressure difference, bubbles are rapidly sucked into the bubble-absorbing groove 93 (bubble suction speed 1 to 3m / s), and the bubble-absorbing groove 93 adopts a "wedge-shaped inlet + tapered channel" design: the wedge-shaped inlet expands the bubble capture range, and the tapered channel accelerates the bubble flow and avoids bubbles from stagnating in the groove. At the same time, the spacing of the bubble-absorbing grooves 93 matches the pitch of the spiral guide plate 94 (e.g., if the guide plate pitch is 20mm, the spacing of the bubble-absorbing grooves is also 20mm), ensuring that bubbles in each spiral cycle can be captured by the corresponding bubble-absorbing groove without any dead spots.

[0056] The bubbles drawn into the bubble suction tank 93 enter the interior of the negative pressure chamber 92 through the communication channel (preferably 1 to 2 mm in diameter) between the bubble suction tank 93 and the negative pressure chamber 92. The negative pressure chamber 92 may have multiple vent holes (preferably 0.5 mm in diameter, allowing only gas to pass through and preventing the melt from entering) connected to the vacuum pump. The bubbles are then extracted by the vacuum pump.

[0057] The negative pressure mechanism 95 here can also be configured with other structures to further improve its utilization rate.

[0058] The negative pressure mechanism 95 includes an outer ring plate 951 fixed to the inner wall of the negative pressure chamber 92. A side frame 952 is connected to one side of the outer ring plate 951. The side frame 952 is made of elastic material and forms a closed annular frame with the outer ring plate 951. Multiple one-way valves that can only allow air to enter are provided on the inner wall of the annular frame. Multiple one-way valves that can only allow air to exit are provided on the outer wall of the annular frame. A differential pressure valve is installed on the outer wall of the annular frame. Multiple stabilizing telescopic rods 953 are provided between the side frame 952 and the outer ring plate 951.

[0059] The inner wall of the side frame 952 is integrally formed with a concave section 9521. Multiple extrusion blocks 954 are provided inside the concave section 9521, and hydraulic rods 955 are connected to the inner circumference of the extrusion blocks 954.

[0060] The negative pressure chamber 92 is also equipped with an embossing mechanism 10. The embossing mechanism 10 includes a fixing ring 111. An embossed metal 112 is connected to one side of the fixing ring 111. The embossed metal 112 is made of an elastic material and is attached to the side wall of the negative pressure chamber 92 on one side. The embossed metal 112 is composed of a straight edge section 1121 and a conical tip section 1122. The conical tip section 1122 is in the shape of a cone. The driving end of the hydraulic rod 955 is located on one side of the embossed metal 112.

[0061] The working principle is as follows: The components are initially adjusted; the hydraulic rod 955 drives back to the initial position, so that the annular frame formed by the side frame 952 and the outer ring plate 951 is in a naturally relaxed state (the internal volume of the frame is at its maximum). At this time, the one-way valve (air inlet) on the inner wall and the one-way valve (air outlet) on the outer wall of the annular frame are both closed; the embossed metal 112 of the embossing mechanism 10 is not compressed, its straight edge section 1121 is naturally close to the side wall of the negative pressure chamber 92, and the cone tip section 1122 is in a relaxed state and does not contact the pre-formed light tube.

[0062] In normal negative pressure mode, the hydraulic rod 955, driven by the hydraulic system, extends towards the annular frame, pushing the extrusion block 954 against the concave section 9521 of the side frame 952. Because the side frame 952 is made of an elastic material (such as a nitrile rubber composite metal skeleton), under the radial thrust of the extrusion block, the annular frame contracts radially, reducing its internal volume and increasing its pressure. When the pressure inside the frame exceeds the external atmospheric pressure by 0.02 to 0.03 MPa, the one-way valve (vent) on the outer wall of the annular frame automatically opens, and the air inside the frame is discharged to the outside through the vent valve, completing the first venting. During this process, the stabilizing telescopic rod 953 (connecting the side frame and the outer ring plate) acts as a guide, preventing displacement during side frame contraction and ensuring uniform deformation of the annular frame.

[0063] Hydraulic rod 955 drives extrusion block 954 to retract. Under the action of its own elastic force and the restoring force of support telescopic rod 953, elastic side frame 952 expands radially, and the internal volume of the annular frame returns to its initial state. The pressure drops rapidly. When the pressure inside the frame drops to -0.09 to -0.08 MPa (matching the target negative pressure of negative pressure chamber 92), the one-way valve on the inner wall of the annular frame automatically opens, and the gas in the negative pressure chamber 92 (including bubbles sucked in from bubble suction tank 93) is sucked into the annular frame, completing one negative pressure suction cycle.

[0064] The hydraulic rod 955 repeats the reciprocating motion of "extending and squeezing - retracting and relaxing," causing the annular frame to periodically contract and relax. Through the cyclical action of "exhausting and absorbing air," it continuously provides a stable negative pressure to the negative pressure chamber 92 (preferably with fluctuations ≤ ±0.005MPa). The negative pressure in the negative pressure chamber 92 acts on the inner cavity 91 through the bubble suction groove 93, drawing in air bubbles from the surface of the pre-formed tube and discharging them through the annular frame, thus achieving the defoaming function. The differential pressure valve controls the internal pressure difference; when the negative pressure is large, external air can be introduced.

[0065] Embossing negative pressure mode: The system switches to "embossing mode" - the driving direction of hydraulic rod 955 is adjusted by the PLC controller, switching from "radial extrusion of the ring frame" to "axial pushing of embossed metal".

[0066] The hydraulic rod 955 extends axially, and its driving end acts on the straight edge section 1121 of the embossed metal 112. Because the embossed metal 112 is an elastic material (such as a spring steel sheet), under the action of axial thrust, the straight edge section 1121 undergoes elastic deformation, causing the conical tip section 1122 to bulge towards the pre-formed tube. The conical shape of the conical tip section 1122 contacts the outer surface of the tube, pressing out a "ring wave pattern" on the surface of the tube (the pattern spacing is synchronized with the hydraulic rod extrusion frequency, such as pressing once every 1 mm).

[0067] During the embossing process, the negative pressure generation function of the ring frame is kept running (the hydraulic rod 955 maintains the negative pressure through "short stroke high frequency extrusion" and realizes embossing through "long stroke low frequency push"), ensuring that no new bubbles are generated on the surface of the light tube during embossing. The negative pressure continuously adsorbs the surface of the light tube, preventing the light tube from shifting when the embossing metal is squeezed. At the same time, it immediately sucks the tiny bubbles that may be generated during the embossing process into the negative pressure chamber 92, ensuring the quality of texture forming.

[0068] To further improve the defoaming quality.

[0069] The buffer end pipe 4 includes multiple acceleration chambers 401 and buffer chambers 402. The acceleration chambers 401 have a gradually decreasing gap from the input direction to the output direction. The buffer chambers 402 are located on the outer wall of the material fluid and have several concave areas. Multiple adjacent concave areas are connected by a tank. A negative pressure ring 403 is installed at the end of the buffer end pipe 4. The negative pressure ring 403 is connected to a negative pressure device and is connected to the tank.

[0070] The concave area is provided with a low-pressure component 43, which includes a hemisphere 431. The hemisphere 431 is an elastic hemispherical bladder. An elastic pull rope 432 is connected inside the hemisphere 431. A sealing sleeve 433 that penetrates the adjacent gap is provided on the outer periphery of the elastic pull rope 432. The rear part of the penetrating end of the elastic pull rope 432 is thickened and fixed to the side wall of the adjacent gap.

[0071] Working principle: Multi-layered melt enters the acceleration chamber 401 of the buffer chamber 4 from the shear end pipe 5. Because the gap in the acceleration chamber 401 gradually decreases from the input direction to the output direction, according to the continuity equation in fluid mechanics (flow velocity is inversely proportional to the cross-sectional area of ​​the flow channel), the melt velocity increases significantly as the gap decreases. During the velocity increase, a radial pressure gradient is generated inside the melt: the flow velocity is high and the pressure is low in the central region of the flow channel, while the flow velocity is slow and the pressure is high in the outer region. Bubbles in the melt (0.3mm to 0.05mm in diameter) have a much lower density than the melt and migrate to the outer side of the flow channel (in the direction of the buffer chamber 402) under the action of the pressure gradient. At the same time, the shear force generated by the increased flow velocity can break the adsorption force between the bubbles and the melt, preventing the bubbles from being trapped in the center of the flow channel, thus preparing for the subsequent capture in the buffer chamber.

[0072] The melt migrating to the buffer chamber 402 first contacts several concave areas on the outer wall of the fluid. These concave areas are interconnected through a tank, which is also connected to the negative pressure ring 403 at the end of the buffer end pipe 4. The negative pressure ring 403 is connected to an external vacuum system (vacuum degree -0.08MPa to -0.07). The system continuously pumps air into the concave areas through the tank, creating a local low-pressure zone. When the melt carrying bubbles flows through the concave areas, the bubbles are pulled away from the main melt stream by the combined effect of "external migration inertia + low-pressure attraction in the concave areas" and enter the interior of the concave areas. At the same time, adjacent concave areas are connected through the tank, forming a "continuous negative pressure channel". This prevents the saturation of a single concave area and ensures that bubbles are continuously drawn into the tank, thus initially completing the separation of bubbles from the melt.

[0073] Furthermore, when the melt flows through the concave area of ​​the buffer chamber 402, its flow impact force acts on the hemisphere 431 of the low-pressure component 43, while simultaneously pressing the elastic pull rope 432. The hemisphere 431 is an elastic hemispherical capsule, which undergoes slight deformation under the thrust of the melt (the sealing sleeve 433 on the outer periphery of the elastic pull rope 432 ensures that adjacent gaps are not connected, preventing melt crossflow), causing the volume of the concave area to temporarily increase. The concavity of the hemisphere 431 leads to a local increase in the volume of the concave area. According to Boyle's law, the pressure in the concave area further decreases, forming an "instantaneous strong negative pressure," which can efficiently capture smaller bubbles in the melt and simultaneously quickly draw the bubbles that have entered the concave area into the tank.

[0074] An extrusion device for an extruder head used for forming multi-layer plastic tubes includes several extrusion devices 11. A shaft-side moving mechanism 12 is installed at the bottom of the extrusion device 11. The shaft-side moving mechanism 12 can be an existing linear track or a two-axis moving mechanism. The output port of the extrusion device 11 is connected to the guide cylinder 7. The shaft-side moving mechanism 12 facilitates separation and connection with the guide cylinder 7.

[0075] The embodiments disclosed in this invention are preferred embodiments, but are not limited thereto. Those skilled in the art can easily understand the spirit of this invention based on the above embodiments and make different extensions and variations, but as long as they do not depart from the spirit of this invention, they are all within the protection scope of this invention.

Claims

1. An extruder head for forming multi-layer plastic tubes, characterized in that, It includes a co-extrusion die head (1), which is composed of a preforming section (101), a forming section (102) and an extrusion section (103). An outlet end (2) is provided at the center of one end of the extrusion section (103), and a central inner support column (3) is provided inside the end of the co-extrusion die head (1) near the outlet end (2). The co-extrusion die head (1) is connected to a buffer end pipe (4) at the other end. One end of the buffer end pipe (4) is connected to a shearing end pipe (5). The shearing end pipe (5) is provided with a back pressure adjustment part (6) at the end. The shearing end pipe (5) has a conical cross section. The shearing end pipe (5) and the buffer end pipe (4) are provided with a gap for the flow of multiple layers of materials. Multiple guide cylinders (7) are connected to the outer periphery of the shearing end pipe (5). Multiple beak shearing parts (8) are provided inside the shearing end pipe (5). The beak shearing parts (8) are spirally distributed along the gap of the shearing end pipe (5) with the axis as the center. The preformed section (101) has a defoaming structure (9) on its side wall. The defoaming structure (9) includes an inner cavity (91) opened on the inner wall of the preformed section (101). A negative pressure chamber (92) is provided on one side of the inner cavity (91). A negative pressure mechanism (95) is provided inside the negative pressure chamber (92). A plurality of bubble-absorbing grooves (93) are connected between the negative pressure chamber (92) and the inner cavity (91). A spiral guide plate (94) is provided inside the inner cavity (91).

2. The extruder head for forming multi-layer plastic tubes according to claim 1, characterized in that, The beak shearing component (8) consists of a sealing section (801) and a gradient section (802). The gradient section (802) has a gradually decreasing thickness from the shearing end tube (5) to the co-extrusion head (1). The outer wall of the gradient section (802) is provided with multiple serrated protrusions. The sealing section (801) fits against the inner wall of the gap.

3. An extruder head for forming multi-layer plastic tubes according to claim 2, characterized in that, The inner side of the spiral guide plate (94) is a pointed tip. The spiral guide plate (94) is distributed around the outer surface of the preformed light tube. The tip of the spiral guide plate (94) is in contact with the outer surface of the preformed light tube.

4. An extruder head for forming multi-layer plastic tubes according to claim 3, characterized in that, The negative pressure mechanism (95) is a negative pressure suction device.

5. An extruder head for forming multi-layer plastic tubes according to claim 3, characterized in that, The negative pressure mechanism (95) includes an outer ring plate (951) fixed to the inner wall of the negative pressure chamber (92). A side frame (952) is connected to one side of the outer ring plate (951). The side frame (952) is made of elastic material and forms a closed annular frame with the outer ring plate (951). Multiple one-way valves that can only allow air to enter are provided on the inner wall of the annular frame. Multiple one-way valves that can only allow air to exit are provided on the outer wall of the annular frame. A differential pressure valve is installed on the outer wall of the annular frame. Multiple stabilizing telescopic rods (953) are provided between the side frame (952) and the outer ring plate (951).

6. An extruder head for forming multi-layer plastic tubes according to claim 5, characterized in that, The inner wall of the side frame (952) is integrally formed with a concave section (9521), and a plurality of extrusion blocks (954) are provided inside the concave section (9521). A hydraulic rod (955) is connected to the inner circumference of the extrusion block (954).

7. An extruder head for forming multi-layer plastic tubes according to claim 6, characterized in that, The negative pressure chamber (92) is also provided with an embossing mechanism (10). The embossing mechanism (10) includes a fixing ring (111). An embossed metal (112) is connected to one side of the fixing ring (111). The embossed metal (112) is made of elastic material and is attached to the side wall of the negative pressure chamber (92) on one side. The embossed metal (112) is composed of a straight edge section (1121) and a conical tip section (1122). The conical tip section (1122) is in the shape of a cone. The driving end of the hydraulic rod (955) is located on one side of the embossed metal (112).

8. An extruder head for forming multi-layer plastic tubes according to claim 4 or 7, characterized in that, The buffer end pipe (4) includes multiple acceleration chambers (401) and buffer chambers (402). The acceleration chambers (401) have a gradually decreasing gap from the input direction to the output direction. The buffer chambers (402) are located on the outer wall of the material fluid and have several concave areas. Multiple adjacent concave areas are connected by a groove. A negative pressure ring (403) is installed at the end of the buffer end pipe (4) and the negative pressure ring (403) is connected to the groove.

9. An extruder head for forming multi-layer plastic tubes according to claim 8, characterized in that, The concave area is provided with a low-pressure component (43), which includes a hemisphere (431). The hemisphere (431) is an elastic hemispherical capsule. An elastic pull rope (432) is connected inside the hemisphere (431). A sealing sleeve (433) penetrating the adjacent gap is provided on the outer periphery of the elastic pull rope (432). The rear part of the penetrating end of the elastic pull rope (432) is thickened and fixed to the side wall of the adjacent gap.

10. An extrusion apparatus for an extruder head used in forming multilayer plastic tubes according to any one of claims 1-9, characterized in that, It includes several extrusion devices (11), each with a shaft-side moving mechanism (12) installed at its bottom, and the output port of each extrusion device (11) is connected to the feed cylinder (7).

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