A rubber cold feed extruder screw structure

Abstract

The present application relates to rubber processing equipment, and particularly relates to a screw structure of a rubber cold-feeding extruder; the screw structure comprises a feeding section, a plasticizing section connected with the feeding section, and an extruding section connected with the plasticizing section; the plasticizing section comprises a plurality of shearing sections and a plurality of mixing sections with the same number of shearing sections, and the shearing sections and the mixing sections are alternately distributed; two head main screw ribs are arranged on the mixing section, the two head main screw ribs are spirally arranged along the outer circumferential side of the mixing section, the starting points of the two head main screw ribs are different but the pitches of the two head main screw ribs are the same, and a main screw groove is arranged between the two head main screw ribs; the width of the main screw rib at the widest part is 1.3-2 times the width of the screw rib of the shearing section, the depth of the main screw rib is 55-65% of the depth of the screw rib of the shearing section, and the helix angle of the main screw rib is the same as the helix angle of the screw rib of the shearing section. Through continuous distribution, shearing and combination, the rubber generates heat quickly and uniformly in the plasticizing process, the rubber quality is improved, and the energy consumption is low.

Description

Technical Field

[0001] This invention relates to rubber processing equipment, and more specifically to a screw structure for a rubber cold-feed extruder. Background Technology

[0002] Rubber extruders are indispensable key equipment in the rubber processing industry, playing a decisive role in the production efficiency and quality of rubber products. In recent years, with continuous technological advancements, cold-feed extrusion technology, with its numerous advantages, has gradually replaced the traditional hot-feed extrusion technology and has been widely used in the rubber industry. Compared with the working mode of hot-feed extruders, cold-feed extruders differ in structure, adding at least one plasticizing (or softening) functional unit.

[0003] The core component of cold feed extruders is the screw, which plays a decisive role in the extruder's performance parameters. The screw design typically includes a feeding section, a compression section, and a homogenization section, where the material is melted and plasticized in a single extrusion. The screw's rotation not only propels the material forward but also generates pressure within the screw channels, subjecting the rubber raw material to shearing and mixing actions, thereby achieving plasticization and softening effects.

[0004] The core requirement for the plasticizing function of cold-feed extruders is uniform plasticizing. However, in existing screw plasticizing modes, a "non-flowing layer" exists in the central region, creating a so-called "cold core" phenomenon. This causes temperature differences within the screw channel, coupled with uneven shear rates, resulting in poor plasticizing (uniform and inefficient plasticizing). Ultimately, this affects extrusion stability, rubber product precision, and final overall performance, leading to rapid failure in operational applications and significant resource waste, thus hindering the development of high-end rubber product molding technology. Therefore, the plasticizing method plays a crucial role in the quality of the rubber compound.

[0005] To address these issues and improve energy efficiency, numerous cold-feed extruders with different screw configurations have been designed and invented. Pin-type cold-feed extruders, with their superior distribution and mixing advantages, are widely used in rubber cold-feed extrusion processes. However, the multiple rows of screw grooves on the screw (for the pins to pass through the rotating screw) can cause backflow, resulting in a significantly lower conveying capacity compared to ordinary fully threaded screws. Increasing the screw speed to increase the output of pin-type barrel cold-feed extruders inevitably leads to higher extrusion temperatures and a higher risk of scorching.

[0006] Therefore, in practice, in order to meet the requirements of larger production volume and higher extrusion quality, such as the extrusion of large-size tire crowns, only hot-feed extruders of the same size or larger-size pin barrel extruders can be used, which will increase equipment costs and operating expenses.

[0007] To overcome the shortcomings of traditional pin-barrel cold-feed extruders, it is necessary to invent a new type of screw. Compared with the performance of pin-barrel cold-feed extruders, this screw should not only have a better-distributed mixing plasticizing section, but also have higher output and lower energy consumption. Summary of the Invention

[0008] This invention provides a screw structure for a rubber cold-feed extruder, which aims to solve the problems of poor distribution and mixing, low output and high energy consumption of existing screws.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows:

[0010] This invention provides a screw structure for a rubber cold feed extruder, comprising a feeding section, a plasticizing section connected to the feeding section, and an extrusion section connected to the plasticizing section;

[0011] The plasticizing section includes several shearing sections and a mixing section of the same number as the shearing sections, with the shearing sections and the mixing sections distributed alternately.

[0012] The mixing section is provided with two main spiral ridges at both ends, which are spirally arranged along the outer periphery of the mixing section. The starting points of the two main spiral ridges are different, but the pitch is the same. A main spiral groove is provided between the two main spiral ridges. The width of the main spiral ridge is gradually set. The width of the main spiral ridge at its widest point is 1.3 to 2 times the width of the spiral ridge of the shearing section. The depth of the main spiral ridge is 55 to 65% of the depth of the spiral ridge of the shearing section. The helix angle of the main spiral ridge is the same as that of the spiral ridge of the shearing section.

[0013] The surface of the main spiral ridge is staggered with four to eight overlapping spiral ridges, forming at least four overlapping spiral grooves interrupted by the main spiral groove on each main spiral ridge; the four to eight overlapping spiral ridges are spirally arranged along the surface of the main spiral ridge, and the overlapping spiral ridges are parallel to each other after the mixed section is expanded in the outer circle; the width of the overlapping spiral ridge is 1 / 3 to 3 / 5 of the width of the widest part of the main spiral ridge, and equal to 7 / 9 of the width of the shearing section spiral ridge; the height of the overlapping spiral ridge is 7 / 4 times the total depth of the main spiral groove; the helix angle of the overlapping spiral ridge is 5-12° larger than the helix angle of the main spiral ridge.

[0014] Furthermore, the screw structure also includes a fixed section, which is connected to the other end of the feeding section.

[0015] Furthermore, the number of both the sheared segments and the mixed segments is less than or equal to five.

[0016] Furthermore, the number of both the shearing segment and the mixing segment is two.

[0017] Furthermore, the shearing section has a double-headed continuous helical ridge configuration, with a helical ridge width of 4-5mm, a thread depth of 10-12mm, and a helix angle of 20-25°.

[0018] Furthermore, the width of the widest part of the main screw thread is 1.7 times the width of the shearing section screw thread.

[0019] Furthermore, the depth of the main screw thread is 60% of the depth of the shearing section screw thread.

[0020] Furthermore, the width of the overlapping spiral edges is half the width of the widest part of the main spiral edge.

[0021] Furthermore, the depth of the overlapping spiral edges is 2 / 3 of the depth of the main spiral edge.

[0022] Furthermore, the helix angle of the overlapping spiral edges is 1.5 times that of the helix angle of the main spiral edge.

[0023] The beneficial effects achieved by this invention are as follows:

[0024] (1) Under the same operating conditions, the present invention has better distribution mixing and uniform plasticizing effect compared with the traditional pin machine barrel screw.

[0025] (2) Under the same operating conditions, this invention has lower power consumption compared to traditional pin-type barrel screws. This is mainly because the pin-type barrel screw has barrel pins in the screw groove that resist the flow of the rubber compound. In contrast, this invention mixes the rubber compound through continuous splitting, merging, and shearing in the mixing section, reducing the resistance encountered by the rubber compound and thus resulting in lower power consumption.

[0026] (3) Under the same operating conditions, this invention has a lower extrusion temperature and better low-temperature extrusion performance compared with traditional pin-type barrel screws. This is mainly because this invention uses a narrow or shallow screw groove design in the mixing section, allowing more heat generated during extrusion to be conducted away through the screw and barrel, thus resulting in better low-temperature extrusion performance.

[0027] (4) Under the same operating conditions, this invention achieves almost the same extrusion output as a traditional pin-barrel screw extruder. Because this invention possesses better low-temperature extrusion performance, the extrusion output can be further increased by increasing the screw speed, overcoming the problem of low output in cold-feed pin-barrel extruders.

[0028] (5) Under the same operating conditions, compared with the traditional pin machine barrel screw, the present invention improves the quality of the rubber material by continuously splitting-shearing-merging the flow, which results in faster and more uniform heat generation of the rubber material during the plasticizing process.

[0029] (6) Under the same operating conditions, compared with the traditional pin machine barrel screw, the present invention uses multiple sets of identical and alternately distributed shearing sections and mixing sections. The modular plasticizing method can play a supplementary mixing effect. Attached Figure Description

[0030] 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 the structures shown in these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0032] Figure 2 This is a schematic diagram of the three-dimensional structure of the hybrid segment of the present invention.

[0033] Figure 3 This is a schematic diagram of the mixed section thread of the present invention unfolded along the outer circle; in the figure, the direction of the thick solid line arrow represents the direction of rubber flow.

[0034] Figure 4 yes Figure 3 Cross-sectional view of the AA position.

[0035] Figure 5 yes Figure 3 Cross-sectional view of the BB location.

[0036] Figure 6 yes Figure 3 Cross-sectional view of the CC position.

[0037] Figure 7 Part a is a cross-sectional image of the rubber strip in the screw groove at an axial position near the outlet of the mixing section in the last mixing section of the present invention, obtained in a screw pulling test; Part b is a cross-sectional image of the rubber strip in the screw groove at the same position on the screw of a conventional pin machine.

[0038] Figure 8 This is a comparison diagram of the extrusion temperature of the screw structure disclosed in this application and that of a traditional pin screw.

[0039] Figure 9 This is a comparison diagram of the power consumption of the screw structure disclosed in this application and the traditional pin screw.

[0040] Figure 10 This is a comparison diagram of the extrusion output of the screw structure disclosed in this application and that of a traditional pin screw.

[0041] In the diagram, 1 is the screw structure; 2 is the feeding section; 3 is the plasticizing section; 4 is the extrusion section; 5 is the shearing section; 6 is the mixing section; 7 is the main screw edge; 8 is the overlapping screw edge; 9 is the main screw channel; 10 is the overlapping screw channel; 11 is the non-flowing layer of rubber compound; and 12 is the segmented non-flowing layer of rubber compound. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0043] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0044] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, if the word "and / or" appears throughout the text, it means including three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution that simultaneously satisfies A and B. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0045] like Figures 1-8 As shown, the present invention provides a screw structure 1 for a rubber cold feed extruder, including a feeding section 2, a plasticizing section 3 connected to the feeding section 2, and an extrusion section 4 connected to the plasticizing section 3;

[0046] The plasticizing section 3 includes a number of shearing sections 5 and a number of mixing sections 6 equal to the number of shearing sections 5, wherein the shearing sections 5 and the mixing sections 6 are distributed alternately.

[0047] The mixing section 6 is provided with two main spiral ridges 7, which are spirally arranged along the outer periphery of the mixing section 6. The starting points of the two main spiral ridges 7 are different, but the pitch is the same. A main spiral groove 9 is provided between the two main spiral ridges 7. The width of the main spiral ridge 7 is gradually set (that is, its width gradually changes along the spiral line). The width of the main spiral ridge 7 at its widest point is 1.3 to 2 times the width of the spiral ridge of the shearing section 5. The depth of the main spiral ridge 7 is 55 to 65% of the depth of the spiral ridge of the shearing section 5. The helix angle of the main spiral ridge 7 is the same as the helix angle of the spiral ridge of the shearing section 5.

[0048] The surface of the main threaded edge 7 is staggered with four to eight overlapping threaded edges 8. The four to eight overlapping threaded edges 8 have different starting points but the same pitch, forming at least four overlapping threaded grooves 10 interrupted by the main threaded groove 9 on each main threaded edge 7; the four to eight overlapping threaded edges 8 are spirally arranged along the surface of the main threaded edge 7, and after the mixing section 6 is expanded outwards, the overlapping threaded edges 8 are parallel to each other (e.g., ...). Figure 3 (as shown); the width of the overlapping screw ridge 8 is 1 / 3 to 3 / 5 of the widest width of the main screw ridge 7, and equal to 7 / 9 of the width of the screw ridge of the shearing section 5; the height of the overlapping screw ridge 8 is greater than the total depth of the main screw groove 9, and is approximately 7 / 4 times the total depth of the main screw groove 9 (the depth of the main screw groove 9 is set with reference to existing pin screws); the helix angle of the overlapping screw ridge 8 is 5-12° larger than the helix angle of the main screw ridge 7.

[0049] The screw structure 1 also includes a fixing section, which is connected to the other end of the feeding section 2; the screw structure 1 is fixed in the rubber cold feed extruder through the fixing section; the fixing section is existing technology and is a general configuration, so the specific structure will not be described in detail.

[0050] Both the feeding section 2 and the extrusion section 4 adopt existing technology and can have the same configuration as the screw of a conventional rubber cold feed extruder (e.g., a pin barrel cold feed extruder); naturally, other configurations with better performance can also be adopted.

[0051] Furthermore, the feeding section 2 has a four-headed spiral ridge and a double-headed spiral groove configuration, and the extrusion section 4 has a common double-headed continuous spiral ridge configuration; since the above two configurations are existing technologies, the specific structures will not be described in detail.

[0052] The plasticizing section 3 of the screw structure 1 is designed based on an interrupted shear mixing mode. All the mixing sections 6 have the same configuration, and all the shearing sections 5 also have the same configuration.

[0053] Furthermore, the number of shearing sections 5 and mixing sections 6 depends on the screw length-to-diameter ratio, and the number of shearing sections 5 and mixing sections 6 is generally less than or equal to five.

[0054] Furthermore, the number of shearing segments 5 and mixing segments 6 are both two.

[0055] Furthermore, the shearing section 5 has a double-ended continuous helical ridge configuration, with a ridge width of 4-5 mm, a thread depth of 10-12 mm, and a helix angle of 20-25°. In addition, the lead of the shearing section 5 is greater than that of the extrusion section 4, and it is designed with reference to the configuration of existing pin screws.

[0056] Furthermore, the width of the widest part of the main thread 7 is 1.7 times the width of the thread 7 of the shearing segment 5.

[0057] Furthermore, the depth of the main thread 7 is 60% of the depth of the thread of the shearing section 5.

[0058] The function of the overlapping helical ridges 8 is to divert the flow, and therefore they can also be called diverting helical ridges. The overlapping helical ridges 8 are based on the screw diameter. Because the height of the overlapping helical ridges 8 is greater than the total depth of the main screw groove 9, the helix angle of the overlapping helical ridges 8 is large, and the multiple overlapping helical ridges 8 are arranged in an alternating pattern, when the rubber material reaches the overlapping helical ridges 8 at the inlet of the mixing section 6, the material flow is diverted. At the same time, the rubber material micro-elements parallel to the root diameter surface of the helical ridges in the overlapping helical grooves 10 and the main screw grooves 9 are reoriented along the depth direction of the screw grooves. This results in a greater increase in the interface area caused by shearing in the subsequent overlapping helical grooves 10 and the main screw grooves 9, causing an interruption of shear mixing. The overlapping helical groove 10 is interrupted by the main screw groove 9, and the rubber material in the main screw groove 9 flows into the overlapping helical groove 10 through the break, or the rubber material in the overlapping helical groove 10 flows out from the break and into the main screw groove 9 with the rubber material flow, thus achieving the purpose of diversion / merging.

[0059] Furthermore, the width of the overlapping helical ridge 8 is half the width of the widest part of the main helical ridge 7.

[0060] Furthermore, the depth of the overlapping helical ridge 8 is 2 / 3 of the depth of the main helical ridge 7.

[0061] Furthermore, the helix angle of the overlapping helix 8 is 1.5 times that of the helix angle of the main helix 7.

[0062] The mixing section 6 is similar to a typical two-end continuous main screw ridge 7 configuration; in the mixing section 6, the repeated flow orientation and shearing also constitute an interrupted shear mixing action. In the plasticizing section 3, which is composed of the mixing section 6 and the shearing section 5, an interrupted shear mixing mode occurs, and each of the mixing sections 6 is a mixer with an interrupted shear mixing action. Therefore, a compound interrupted shear mixing mode will be generated throughout the entire screw plasticizing section 3.

[0063] Figure 2The specially designed screw rib configuration of the mixing section 6 is demonstrated. Taking a 60mm diameter, 12L / D cold-feed extruder as an example, the length of the mixing section 6 is 100-140mm, and the length of the shearing section 5 is 90-120mm. In each of the mixing sections 6, there are two main screw ribs 7 that are wider than the screw ribs of the shearing section 5. The depth of the main screw ribs 7 is approximately 60% of the depth of the shearing screw ribs, and the helix angle of the main screw ribs 7 is the same as that of the screw ribs of the shearing section 5. On each main screw rib 7, four to eight overlapping screw ribs 8 with a larger helix angle than the main screw rib 7 are designed (the number of diverting screw ribs depends on the screw diameter). Four overlapping screw grooves 10, interrupted by main screw grooves 9, are formed on the main screw ribs 7. The width of the overlapping screw ribs 8 is smaller than the width of the main screw ribs 7 in the mixing section 6, and slightly smaller than the screw rib width of the shearing section 5. Therefore, the volume of the new screw plasticizing section 3 is basically the same as that of the plasticizing section 3 of a pin extruder of the same length.

[0064] like Figure 2 As shown, in the plasticizing section 3 composed of the two mixing sections 6 and the two shearing sections 5, the interrupted shear mixing mode, which involves two shearing cycles, will occur, significantly increasing the interfacial area of ​​the material micro-elements and enhancing the distribution mixing effect. This is because the interfacial area of ​​the initial randomized interface increases linearly with shear deformation, while the interrupted shear mixing mode causes an exponential increase in the interfacial area (Equation (1)):

[0065]

[0066] In the formula, A is the new interface area, A0 is the initial interface area, γ is the shear deformation (assuming that all shear segments 5 have the same shear deformation), and N is the number of shear segments 5 in the interrupted shear hybrid mode (in the above specific embodiment of the invention, N = 2).

[0067] like Figure 2 As shown, although the overlapping screw ridges 8 are interrupted by the main screw grooves 9, continuous forward conveying screw grooves are formed between the overlapping screw ridges 8, which will give the mixing section 6 a large forward conveying capacity.

[0068] like Figure 3 As shown, during operation, the rubber compound enters the mixing section 6 after passing through the shearing section 5. The main screw ridge 7, overlapping screw ridge 8, main screw groove 9, and overlapping screw groove 10 form a multiple splitting-shearing-merging mixing process. Thus, in each of the mixing sections 6, two interrupted shearing mixing actions occur, significantly increasing the distribution mixing effect of the mixing section 6. The mechanism by which this interrupted shearing mixing action causes the interface area to increase is shown in equation (1).

[0069] Throughout the plasticizing section 3, a compound interrupted mixing mode occurs, which greatly improves the distribution mixing and uniform plasticizing effect of the plasticizing section 3.

[0070] like Figure 3 As shown, when the overlapping screw ridges 8 divert material, the height of the overlapping screw ridges 8 is greater than one-third of the total depth of the main screw groove 9. Therefore, the non-flowing layer adhesive 11 in the central region of the main screw groove 9 is diverted by the overlapping screw when passing through the overlapping screw ridges 8. A portion of the divided non-flowing layer adhesive 12 enters the overlapping screw groove 10, while a portion of the non-flowing layer adhesive 11 remains in the main screw groove 9 for the next stage of diversion. The divided non-flowing layer adhesive 12 entering the overlapping screw groove 10 merges with another portion of the adhesive in the main screw groove 9, and this process repeats continuously.

[0071] like Figure 4 As shown, when the material enters the overlapping screw groove 10 from the main screw groove 9, the cross section that becomes smaller along the streamline direction will cause tensile flow, which will cause the interface area to grow rapidly (Equation (2)), and further promote the distribution mixing and uniform plasticizing effect.

[0072]

[0073] In the formula, ε represents the tensile deformation.

[0074] Furthermore, due to the higher shear rate in the shallower overlapping spiral grooves 10, there is an enhanced plasticizing effect in the mixing section 6.

[0075] To verify the mixing capacity of the screw plasticizing section 3 of this invention, two colors of tire sidewall rubber, black and white, were used on a Φ60×12D pin-barrel extruder. Under the same extrusion parameters and die head profile, the mixing capacity of the pin-barrel screw and the screw of this invention was compared at different screw speeds. Using black and white tire sidewall rubber, a screw pull-out experiment was conducted at a certain screw speed under the same temperature setting and die head profile conditions: black and white rubber strips were fed into the extruder side by side. After stabilization, the screw rotation was suddenly stopped. The barrel and screw were heated using a temperature control device, and the rubber compound vulcanized in the screw grooves was vulcanized. After cooling the barrel and screw, the screw was pulled out of the barrel, and the slicing position was marked along the screw axis. The rubber strip was spirally removed from the screw, and the cross-sectional area was observed. The rheological properties of the black and white tire sidewall rubber used were almost identical, with a Mooney viscosity of 55±5 mL1+4 (100℃). The comparison shows that the new screw has a better distribution and mixing effect than the pin-type barrel screw because the area where white glue appears is much smaller. Figure 7 As shown.

[0076] Table 1 shows a comparison of the extrusion test data of the rubber compound of the present invention and the pin screw at different speeds. Based on the special split-shear-convergence structure of the new screw, the dispersion is significantly higher than that of the pin screw, and the tensile strength is also significantly greater than that of the pin screw, as shown in Table 2.

[0077] Table 1 Comparison of rubber dispersion of two screw extrusions at different speeds.

[0078] Rotational speed (r / min) 20 30 40 50 60 Screw of the present invention 6.8 6.9 6.8 7.1 6.8 Pin screw 5.2 5.3 6.1 6.3 6.2

[0079] Table 2 Comparison of tensile strength of two types of extruded rubber compounds at different screw speeds.

[0080] Rotational speed (r / min) 20 30 40 50 60 Screw of the present invention 19.5 19.8 18.8 19.5 18.6 Pin screw 17.6 18.2 18.5 18.3 17.9

[0081] like Figure 8 As shown, with the increase of screw speed, the extrusion temperature of both screws exhibits an almost slow linear increase, and the extrusion temperature of the new screw is significantly lower than that of the pin-barrel screw, by approximately 4-6°C. The difference in extrusion temperature is mainly due to the narrower or shallower screw channel design in the mixing section 6 of the new screw, allowing more viscous heat to be conducted away through the screw. This significantly reduces the extrusion temperature of the new screw and indicates that the enhanced distributed mixing structure in the new screw can effectively promote heat conduction. Compared to the pin-barrel screw, the new screw has better low-temperature extrusion performance and can be used for extruding heat-sensitive rubbers, avoiding scorching or molecular decomposition. Figures 9-10 As shown, with the increase of screw speed, the two screws have almost the same output, but the power consumption of the new screw disclosed in this application is significantly lower than that of the pin barrel screw, making it more energy-efficient.

[0082] The above description is merely an optional embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A screw structure (1) for a rubber cold-feed extruder, characterized in that: It includes a feeding section (2), a plasticizing section (3) connected to the feeding section (2), and an extrusion section (4) connected to the plasticizing section (3); The plasticizing section (3) includes several shearing sections (5) and a number of mixing sections (6) equal to the number of shearing sections (5), with the shearing sections (5) and the mixing sections (6) distributed alternately. The mixing section (6) is provided with two main spiral ridges (7), which are spirally arranged along the outer periphery of the mixing section (6). The starting points of the two main spiral ridges (7) are different, but the pitch is the same. A main spiral groove (9) is provided between the two main spiral ridges (7). The width of the main spiral ridge (7) is gradually set. The width of the main spiral ridge (7) at its widest point is 1.3 to 2 times the width of the spiral ridge of the shearing section (5). The depth of the main spiral ridge (7) is 55 to 65% of the depth of the spiral ridge of the shearing section (5). The helix angle of the main spiral ridge (7) is the same as the helix angle of the spiral ridge of the shearing section (5). The surface of the main thread (7) is provided with four to eight overlapping threaded edges (8), forming at least four overlapping threaded grooves (10) interrupted by the main threaded groove (9) on each main threaded edge (7); the four to eight overlapping threaded edges (8) are spirally arranged along the surface of the main threaded edge (7), and the overlapping threaded edges (8) are parallel to each other after the outer circle of the mixing section (6) is expanded; the width of the overlapping threaded edge (8) is 1 / 3 to 3 / 5 of the width of the widest part of the main threaded edge (7), and equal to 7 / 9 of the width of the threaded edge of the shearing section (5); the height of the overlapping threaded edge (8) is 7 / 4 times the total depth of the main threaded groove (9); the helix angle of the overlapping threaded edge (8) is 5-12° larger than the helix angle of the main threaded edge (7).

2. The screw structure (1) of a rubber cold feed extruder according to claim 1, characterized in that: The screw structure (1) also includes a fixed section, which is connected to the other end of the feeding section (2).

3. The screw structure (1) of a rubber cold feed extruder according to claim 1, characterized in that: The number of each shear segment (5) and the number of each mixing segment (6) are less than or equal to five.

4. The screw structure (1) of a rubber cold feed extruder according to claim 3, characterized in that: The number of shearing segments (5) and mixing segments (6) are both two.

5. The screw structure (1) of a rubber cold feed extruder according to claim 1, characterized in that: The shearing section (5) has a double-headed continuous spiral configuration, with a spiral width of 4-5 mm, a thread depth of 10-12 mm, and a helix angle of 20-25°.

6. The screw structure (1) of a rubber cold feed extruder according to claim 1, characterized in that: The width of the widest part of the main thread (7) is 1.7 times the width of the thread of the shearing segment (5).

7. The screw structure (1) of a rubber cold feed extruder according to claim 1, characterized in that: The depth of the main thread (7) is 60% of the depth of the thread of the shear section (5).

8. The screw structure (1) of a rubber cold feed extruder according to claim 1, characterized in that: The width of the overlapping helical edge (8) is half the width of the widest part of the main helical edge (7).

9. The screw structure (1) of a rubber cold feed extruder according to claim 1, characterized in that: The depth of the overlapping spiral edge (8) is 2 / 3 of the depth of the main spiral edge (7).

10. The screw structure (1) of a rubber cold feed extruder according to claim 1, characterized in that: The helix angle of the overlapping helix (8) is 1.5 times that of the helix angle of the main helix (7).

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