A civilian PET-specific screw

Abstract

This application relates to the field of feeding screws, and particularly to a screw specifically designed for civilian PET applications. It includes a mixing section and a homogenizing section. The homogenizing section is located at the rear end of the mixing section. The mixing section has several sets of barrier grooves, all inclined to the screw axis. Each set of barrier grooves includes a first barrier groove and a second barrier groove. A material channel is provided on the side of the first barrier groove, connecting to the second barrier groove in the same set. The cross-sectional area of ​​the material channel is smaller than that of the first and second barrier grooves. One end of the second barrier groove extends into the homogenizing section. Pins are provided on the homogenizing section, arranged in a diamond pattern. This application provides a civilian PET-specific screw that solves the problem of reduced product strength due to uneven plasticization caused by traditional screws, and offers high plasticization efficiency, energy saving, durability, and uniform plasticization.

Description

Technical Field

[0001] This application relates to the field of feeding screws, and in particular to a screw specifically designed for civilian PET applications. Background Technology

[0002] With increasing global environmental awareness and the development of the circular economy, the demand for polyethylene terephthalate (PET) materials continues to grow in the consumer product sector (such as beverage bottles, food packaging, and daily chemical containers) due to their excellent recyclability, lightweight, and high transparency. Statistics show that global PET consumption exceeded 40 million tons in 2022, with the proportion of recycled PET (rPET) increasing year by year.

[0003] However, PET processing places higher demands on the performance of the core component of injection molding equipment—the screw. Firstly, regarding the need for recycled material processing: rPET contains many impurities and has large viscosity fluctuations, making it easy for traditional screws to cause uneven plasticization, leading to a decrease in product strength. Secondly, regarding energy consumption and efficiency bottlenecks: existing general-purpose screws have low plasticization efficiency (specific energy consumption reaches 0.4~0.5 kWh / kg), making it difficult to meet the production needs of high-capacity, low-cost consumer products. Therefore, it is evident that screws in related technologies suffer from uneven plasticization or low plasticization efficiency.

[0004] To address the aforementioned issues, a high-efficiency, energy-saving, durable, and uniformly plasticized PET-specific screw for civilian use is proposed. Utility Model Content

[0005] The purpose of this application is to solve the problems that traditional screws are prone to uneven plasticization, which leads to a decrease in product strength, and that existing general-purpose screws have low plasticization efficiency, making it difficult to meet the production needs of high-capacity, low-cost civilian products.

[0006] The following technical solution is adopted in this application:

[0007] A civilian-grade PET-specific screw includes a mixing section and a homogenization section. The homogenization section is located at the rear end of the mixing section. Several sets of barrier grooves are provided on the mixing section, and the entire set is inclined to the screw axis. Each set of barrier grooves includes a first barrier groove and a second barrier groove. Both the first and second barrier grooves are semi-enclosed structures. The opening of the first barrier groove faces the feed end, and the opening of the second barrier groove faces the discharge end. A material channel is provided on the side of the first barrier groove, connecting to the second barrier groove in the same set. The cross-sectional area of ​​the material channel is smaller than that of the first and second barrier grooves, and the groove depth of the material channel is smaller than that of the first and second barrier grooves. One end of the second barrier groove extends into the homogenization section. Pins are provided on the homogenization section, and the pins are arranged in a diamond pattern on the homogenization section.

[0008] Furthermore, there are several pins, which are evenly distributed on the homogenization section. The bottom of each pin is set as a rhombus, and the multiple pins arranged in rhombuses form multiple intersecting cross-shaped passage slots for material passage.

[0009] Furthermore, a compression section is provided at the front end of the mixing section, and the screw edges of the compression section are all blunted, with the outer diameter of the compression section gradually increasing from the feed end to the discharge end.

[0010] Furthermore, the front end of the compression section is provided with a feeding section, the feeding section having the same outer diameter and depth from the feeding end to the discharge end.

[0011] Furthermore, the front end of the feeding section is provided with a connecting section for connecting the overall screw to an external power source.

[0012] Furthermore, both the feed end and the discharge end of the mixing section are chamfered to reduce blockage at the feed and discharge points.

[0013] This application has at least one of the following beneficial effects:

[0014] 1. Material enters through a barrier trough with its opening facing the feed end. Moving along the inclined barrier trough, the material enters a second barrier trough with its opening facing the discharge end via a material channel on the side of the first barrier trough, and then moves out of the mixing section from this second barrier trough, thus achieving barrier mixing. One end of the second barrier trough extends into the homogenization section, and the length of its end opening exceeds that of the mixing section, further facilitating barrier mixing and making it easier for material to enter the homogenization section. The inclined trough design of the mixing section refines the melt through a shear-stretch synergistic effect.

[0015] 2. The material passes through the homogenization section with the help of pins to eliminate melt pulsation and ensure uniform discharge.

[0016] 3. This application solves the problems of plasticization uniformity, thermal degradation control, and energy consumption in PET processing through screw structure innovation. This application provides a high-efficiency, energy-saving, durable, and uniformly plasticized screw specifically for civilian PET applications. Attached Figure Description

[0017] Figure 1 A schematic diagram of the overall structure of a civilian PET-specific screw is provided for application.

[0018] Figure 2 This is an enlarged schematic diagram of a portion of the structure of a civilian PET-specific screw.

[0019] In the diagram: 1. Connecting section; 2. Feeding section; 3. Compression section; 4. Mixing section; 5. Mixing section; 6. Homogenization section; 7. Barrier trough; 8. Pin; 9. First barrier trough; 10. Second barrier trough; 11. Material channel; 12. Chamfer. Detailed Implementation

[0020] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0022] In the description of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances. Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0023] Example 1

[0024] Reference Figure 1 and Figure 2 A civilian-grade PET-specific screw includes a connecting section 1, a feeding section 2, a compression section 3, a mixing section 4, and a homogenizing section 6. The feeding section 2 has a connecting section 1 at its front end, which connects the entire screw to an external power source. The compression section 3 has the feeding section 2 at its front end, and the feeding section 2 has a uniform outer diameter from the inlet to the outlet. The feeding section 2 employs a deep screw groove and rectangular thread design to enhance solid conveying efficiency and prevent bridging. The mixing section 4 has the compression section 3 at its front end, and the screw edges of the compression section 3 are all blunted. The outer diameter of the compression section 3 gradually increases from the inlet to the outlet. The compression section 3 separates unmelted solids from the melt, reducing thermomechanical degradation.

[0025] The mixing section 4 is equipped with a homogenization section 5 at its rear end. The mixing section 4 also has several sets of barrier grooves 7, all inclined at 45 degrees to the screw shaft. The inclined groove design of the mixing section 4 refines the melt through a shear-stretch synergy. Each set of barrier grooves 7 includes a first barrier groove 9 and a second barrier groove 10. Both the first and second barrier grooves 9 and 10 are semi-enclosed structures. The opening of the first barrier groove 9 faces the feed end, and the opening of the second barrier groove 10 faces the discharge end. A material channel 11 is provided on the side of the first barrier groove 9, connecting to the second barrier groove 10 in the same group. The cross-sectional area of ​​the material channel 11 is smaller than that of the first and second barrier grooves 9 and 10. Material enters through the barrier trough 7, which opens towards the feed end, and moves along the inclined barrier trough 7. The material then enters the second barrier trough 10, which opens towards the discharge end, via the material channel 11 on the side of the first barrier trough 9. It then moves out of the mixing section 4 through the second barrier trough 10, achieving barrier mixing. One end of the second barrier trough 10 extends into the homogenization section 6, with its end opening exceeding the length of the mixing section 4, further facilitating barrier mixing and allowing material to enter the homogenization section 6. The depth of the second barrier trough 10 is greater than that of the first barrier trough 9, allowing one end of the second barrier trough 10 to extend into the homogenization section 6. The second barrier trough 10 and the first barrier trough 9 have the same width. Material first enters the first barrier trough 9, and under the compression of subsequent material, it is progressively compressed within the first barrier trough 9 through the material channel 11, and then enters the second barrier trough 10 through the material channel 11. As the material enters the material channel 11 from the first barrier trough 9, it undergoes a progressive increase in extrusion pressure. As it enters the second barrier trough 10 from the material channel 11, the extrusion pressure is released, and then it experiences a further increase in extrusion pressure at the end of the homogenization section 6 before entering the homogenization section 6. Thus, the process of the material passing through the mixing section 4 and entering the homogenization section 6 involves an increase, release, and re-extrusion of extrusion pressure, thereby improving the mixing effect of the material.

[0026] The end opening length of the second barrier tank 10 extends beyond the mixing section 4, improving barrier mixing efficiency and prolonging the residence time of materials in the barrier zone 7. This increases the shearing time, allowing the melt to undergo more thorough shearing and mixing within the barrier tank 7. The extended portion forms a longer shear path, increasing shear strength and promoting molecular chain breakage and recombination, resulting in more effective mixing. It also improves melt homogeneity by extending the mixing path, making the melt temperature and component distribution more uniform and reducing temperature gradients and component inhomogeneities. The design of the second barrier tank 10's end opening length extending beyond the mixing section 4 optimizes the melt flow path, forming a gradual transition zone. This allows for a smoother transition of the melt from the barrier tank 7 to the homogenization section 6, reducing flow resistance. It also prevents material stagnation zones at the junction of the mixing section 4 and the barrier tank 7, eliminating dead zones and preventing localized degradation due to stagnation. Furthermore, it improves flow uniformity, ensuring a more uniform flow state before entering the homogenization section 6, thus increasing the plasticizing efficiency of the homogenization section. This ultimately improves both plasticizing quality and efficiency. This reduces melt viscosity, increases plasticizing speed and efficiency, reduces plasticizing energy consumption, and improves product uniformity. Similarly, the front end of the first barrier groove 9 can also be designed to extend beyond the mixing section 4.

[0027] Both the inlet and outlet ends of the mixing section 4 are equipped with chamfers 12 to reduce blockages at these points. The chamfer 12 at the outlet end, in particular, allows the mixed material to transition more smoothly from the mixing section 4 to the subsequent homogenization section 6, reducing material accumulation and stagnation at the outlet. The chamfer 12 design makes the material flow within the mixing section 4 more dynamically balanced, reducing the possibility of localized accumulation. Due to the smooth flow at the inlet and outlet ends, the material is more evenly distributed within the mixing section 4, avoiding uneven mixing caused by uneven flow. The stable flow of material within the mixing section 4 results in more uniform shearing action, improving mixing efficiency. Reducing material stagnation at the inlet and outlet ends leads to a more uniform temperature distribution within the mixing section 4, preventing degradation caused by localized overheating. When used in conjunction with the design where the end opening of the second barrier trough 10 extends beyond the mixing section 4, the chamfer 12 design further optimizes the material flow path, forming a more efficient mixing system.

[0028] The homogenization section 6 is equipped with pins 8 arranged in a diamond pattern. There are several pins 8 evenly distributed on the homogenization section 6, each pin 8 having a diamond-shaped base. The diamond-shaped arrangement of the pins 8 forms multiple intersecting cross-shaped passageways for material passage. The material passing through the homogenization section, in conjunction with the pins, eliminates melt pulsation and ensures uniform discharge.

[0029] This application employs a split-type two-stage compression structure, with compression section 3 performing the first stage of compression and mixing section 4 performing the second stage of compression. Furthermore, thermodynamic simulation optimization was conducted using ANSYS Polyflow to simulate melt flow, optimizing the screw tip angle (25°~30°) and compression ratio (2.8:1), balancing the ratio of shear heat to conduction heat (target ratio 6:4), and avoiding localized overheating.

[0030] This application designs the screw parameters as follows: 1. Length-to-diameter ratio (L / D): 25:1 (traditional screws are 20:1), extending plasticizing time and improving the filtration capacity of rPET impurities. 2. Compression ratio: 2.8:1, adapting to the low melt density characteristics of PET. 3. Screw clearance: 0.1~0.15mm, reducing melt backflow and improving volumetric efficiency.

[0031] This application designs the barrel as follows: 1. Axial grooves on the inner wall: 0.5mm deep, 8mm spacing, to enhance the friction coefficient of solid conveying (μ≥0.4). 2. Zoned temperature control system: using ceramic heating coils and PID closed-loop control to achieve five-stage temperature control (accuracy ±1℃). 3. Wear-resistant bushing: inlaid with tungsten carbide alloy strips (hardness ≥62HRC) to reduce barrel wear rate.

[0032] This application optimizes and improves the processing technology: 1. Screw manufacturing: adopts "precision forging + CNC grinding" process, with straightness error ≤0.02mm / m. 2. Surface treatment: plasma spraying of WC-10Co coating (thickness 50μm, porosity ≤1%) to improve corrosion resistance. 3. Dynamic balancing test: residual imbalance ≤5g·mm, ensuring stability during high-speed operation (≥150rpm).

[0033] How this application works:

[0034] In operation, the integral screw extends into the barrel and is mounted on an external power source via connecting section 1. Material is fed into the feed section 2 and enters the compression section 3 along the feed section 2. The compression section 3 has an appropriate ratio, which neither increases shear heat nor causes obstruction of material flow. The material then enters the mixing section 4. Both the feed and discharge ends of the mixing section 4 are equipped with chamfers 12 to reduce blockage at the feed and discharge points. The material enters from the barrier groove 7 with its opening facing the feed end and moves along the 45-degree inclined barrier groove 7 to its end. The material then flows along the mixing section 4... The material enters the mixing section 4 through the first barrier trough 9, which faces the feed end, and then enters the second barrier trough 10 along the side material channel 11. Because there is a large amount of material at the feed end of the mixing section 4, it is squeezed into the first barrier trough 9, where it is compressed. The side material channel 11 further mixes the material. The material moves along the opening of the second barrier trough 10 to the discharge end, leaving the mixing section 4, thus achieving barrier mixing. It then enters the homogenization section 6, where the pins 8 eliminate melt pulsation and ensure uniform discharge. Through the barrier mixing of the mixing section 4 and the homogenization section 6, both plasticizing and mixing are ensured, as well as the full uniformity of the material.

[0035] This application optimizes the screw structure design, developing a separable screw tailored to the characteristics of PET, and optimizing the structural parameters of the feeding section, compression section, and homogenization section. Regarding material selection and surface treatment, this application uses a bimetallic alloy, such as 38CrMoAlA with a tungsten carbide coating, to improve wear and corrosion resistance. This application also optimizes the barrel's inner wall groove structure and temperature control system through a co-design of the barrel, achieving efficient heat conduction and melt homogenization. Furthermore, this application constructs a process parameter database, establishing a mapping model between screw speed, back pressure, temperature, and product quality.

[0036] This application utilizes a two-stage barrier mixing technology, employing a separation-mixing two-stage structure to overcome the plasticization uniformity bottleneck of traditional screw processors, improving melt temperature uniformity by 40%. Through an intelligent temperature control compensation algorithm, heating power is dynamically adjusted based on melt pressure feedback to reduce the risk of thermal degradation (yellowing index ΔYI≤2). A recycled material adaptability design has been implemented: a melt filter chamber (120~150 mesh) is added to accommodate high-proportion rPET processing. Furthermore, a composite coating technology is added, increasing wear resistance by 3 times and extending the maintenance cycle to 6000 hours. This application addresses the issues of plasticization uniformity, thermal degradation control, and energy consumption in PET processing through screw structure innovation, material optimization, and process upgrades. Firstly, it improves PET melt quality, ensuring product transparency and mechanical properties (tensile strength ≥55 MPa, turbidity ≤3%). Secondly, it achieves stable processing compatible with 30%~50% rPET proportions, reducing raw material costs. Thirdly, it reduces unit energy consumption by more than 15%, with a target specific energy consumption ≤0.35 kWh / kg. The fourth aspect is to extend the screw's service life to over 20,000 hours, approximately 2.3 years, which is far greater than the 1.5-2 years of traditional screws.

[0037] This application can bring economic benefits to injection molding machine manufacturers and PET product companies, with an estimated annual electricity saving of approximately 86,000 kWh per injection molding machine (based on 300 days / year), reducing production costs by 12%. It also improves the environmental friendliness of products, promoting the use of rPET to 35% and reducing the consumption of petroleum-based raw materials. The products produced by this application are competitive in the market, filling the gap in domestically produced high-end PET-specific screws, replacing imported high-end PET-specific screws, and reducing prices by approximately 40%.

[0038] In summary, this application solves the problems of plasticization uniformity, thermal degradation control, and energy consumption in PET processing through screw structure innovation. This application provides a high-efficiency, energy-saving, durable, and uniformly plasticized screw specifically for civilian PET applications.

[0039] The foregoing has shown and described the basic principles, main features, and advantages of this application. The various components mentioned in this application are common technologies in the existing field. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed. The scope of protection of this application is defined by the appended claims and their equivalents.

Claims

1. A special screw for civil PET characterized in that, The system includes a mixing section (4) and a homogenization section (6). The homogenization section (6) is located at the rear end of the mixing section (4). The mixing section (4) is provided with barrier grooves (7). There are several sets of barrier grooves (7), and they are inclined to the screw shaft. Each set of barrier grooves (7) includes a first barrier groove (9) and a second barrier groove (10). The first barrier groove (9) and the second barrier groove (10) are both semi-closed structures. The opening of the first barrier groove (9) faces the feed end, and the opening of the second barrier groove (10) faces the discharge end. A material channel (11) is provided on the side of the barrier trough (9) and connected to the second barrier trough (10) in the same group. The cross-sectional area of ​​the material channel (11) is smaller than that of the first barrier trough (9) and the second barrier trough (10), and the depth of the material channel (11) is smaller than that of the first barrier trough (9) and the second barrier trough (10). One end of the second barrier trough (10) extends into the homogenization section (6). A pin (8) is provided on the homogenization section (6), and the pin (8) is arranged in a diamond shape on the homogenization section (6).

2. A special screw for PET for civil use according to claim 1, characterized in that, There are several pins (8) evenly distributed on the homogenization section (6). The bottom of each pin (8) is set as a rhombus. Multiple cross-shaped passage grooves are formed between the multiple pins (8) arranged in a rhombus shape for material passage.

3. A special screw for PET for civil use according to claim 2, characterized in that, The mixing section (4) is provided with a compression section (3) at the front end. The screw edges of the compression section (3) are all blunted, and the outer diameter of the compression section (3) gradually increases from the feed end to the discharge end.

4. A special screw for PET for civil use according to claim 3, characterized in that, The front end of the compression section (3) is provided with a feeding section (2), and the feeding section (2) has the same outer diameter and depth from the feeding end to the discharge end.

5. A special screw for PET for civil use according to claim 4, characterized in that, The front end of the feeding section (2) is provided with a connecting section (1) for connecting the overall screw to an external power source.

6. A special screw for PET for civil use according to claim 5, characterized in that, The mixing section (4) is equipped with chamfers (12) at both the feed end and the discharge end to reduce blockage at the feed and discharge points.

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