Variable cross-section asymmetric multi-screw extruder

Abstract

The invention discloses a variable cross-section asymmetric multi-screw extruder, and relates to the technical field of screw extruders. The variable-cross-section asymmetric multi-screw extruder comprises a machine barrel and a screw assembly, the screw assembly comprises a first screw and a second screw which are meshed with each other, the first screw comprises a first unit rod section, and the second screw comprises a second unit rod section; a transition arc with the radius increasing and then decreasing in the axial direction is introduced into the cross section contour of the first unit rod section, so that when materials flow in the same screw groove and between the front and back adjacent screw grooves, a topological splitting and integrating iterative melting mixing mechanism similar to a static mixer can be introduced; and meanwhile, unsteady disturbance and a two-way stretching effect of a flow field are generated in the whole extrusion process, so that the efficiency of melting plasticizing, mixing and exhausting is improved. In addition, due to the fact that the screw assembly has high melting and mixing capacity, use of a traditional kneading block can be omitted, and therefore the installation, disassembly and replacement process of the screw is simplified, and the device is more convenient and economical.

Description

Technical Field

[0001] This invention relates to the field of screw extruder technology, and in particular to a variable cross-section asymmetric multi-screw extruder. Background Technology

[0002] Co-rotating twin-screw extruders have been widely used in polymer material processing and other fields. However, existing screws typically have a cross-sectional shape that remains constant along the axial direction. Their melting and mixing effects mainly rely on the disturbance effect of the screw meshing zone, while in the flow channel far from the meshing zone, there is a lack of effective tumbling and disturbance, resulting in near-steady-state material conveying and limited heat and mass transfer efficiency. To enhance the melt mixing effect, existing technologies usually require the addition of specialized reinforcing elements such as kneading blocks to the screw. However, this not only complicates the screw assembly but also often requires transition elements for connection, making it difficult to precisely control the material residence time distribution and causing inconvenience for on-site installation and disassembly. Summary of the Invention

[0003] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a variable cross-section asymmetric multi-screw extruder, which constructs flow channels with varying shapes and areas of the left and right screws at different axial positions. This enables continuous changes in the flow channels, such as splitting into two, merging into one, and then splitting into two again and merging into one. This further realizes the topological splitting and merging iterative melt mixing and compounding mechanism. At the same time, due to the continuous changes in the cross-sectional shape and area of ​​the screw combination at different axial positions, unsteady disturbances and bidirectional stretching effects on the flow field are generated throughout the extrusion process, improving the efficiency of melt plasticizing, mixing and compounding, and degassing, and achieving precise control of the phase morphology and nanostructure of polymer material processed products.

[0004] According to an embodiment of the present invention, a variable cross-section asymmetric multi-screw extruder includes: a barrel, comprising a conveying section, a melting section, a venting section and a mixing extrusion section arranged sequentially along the length of the barrel, wherein the conveying section is provided with a feed inlet, the venting section is provided with a venting outlet, and the mixing extrusion section is provided with a discharge outlet; A screw assembly is disposed inside the barrel and passes through the conveying section, the melting section, the venting section and the mixing extrusion section. The screw assembly includes a first screw and a second screw that mesh with each other. The first screw includes a plurality of first unit segments connected in sequence, and the second screw includes a plurality of second unit segments connected in sequence. The cross-sectional profile of the first unit segment includes a top arc, a bottom arc, and a transition arc. The radius of the top arc is greater than the radius of the bottom arc. The transition arc is located between the top arc and the bottom arc. Along the axial direction of the first unit segment, the radius of the transition arc first increases and then decreases. The cross-sectional profile of the second unit segment is conjugately meshed with the cross-sectional profile of the first unit segment.

[0005] The variable cross-section asymmetric multi-screw extruder according to embodiments of the present invention has at least the following beneficial effects: By introducing a transition arc with an axial radius that first increases and then decreases in the cross-sectional profile of the first unit segment, the material flows within the same screw channel and between adjacent screw channels, creating flow channels with varying shapes and areas of the left and right screws at different axial positions. This allows for the introduction of a static mixer-like mechanism to achieve continuous changes in the flow channels, such as splitting into two, merging into one, and then splitting into two again and merging into one. This further realizes the topological splitting and merging iterative melt mixing and compounding mechanism. Simultaneously, due to the continuous changes in the cross-sectional shape and area of ​​the screw combinations at different axial positions, unsteady disturbances and bidirectional stretching of the flow field are generated throughout the extrusion process. These complex flow field effects enhance the folding, stretching, and reorientation of the fluid interface, thereby improving the efficiency of melt plasticizing, mixing, and degassing. Because the screw assembly itself has a strong melting and mixing capability, the use of traditional kneading blocks can be eliminated, and a streamlined screw channel can be constructed. This not only makes the distribution of material residence time more precise and enables precise control of the phase morphology and nanostructure of polymer material processed products, but also simplifies the installation, disassembly and replacement process of the screw because there is no need to set up a component such as a kneading block, making it more convenient and economical.

[0006] According to some embodiments of the present invention, the radius of the top arc is R, the radius of the bottom arc is r, and the radius of the transition arc is r. m Along the axial direction of the first screw and within the axial length range of the first unit segment, the radius r of the transition arc m From r gradually increasing to R, Then gradually decrease it to r.

[0007] According to some embodiments of the present invention, the length of the first unit rod segment is the lead length of the first screw, the length of the second unit rod segment is the lead length of the second screw, and along the flow direction of the material, the cross-sectional area of ​​the first unit rod segment first gradually increases and then gradually decreases, while the cross-sectional area of ​​the second unit rod segment first gradually decreases and then gradually increases.

[0008] According to some embodiments of the present invention, the first screw includes a plurality of first unit segments connected in sequence, the axial length of the first unit segment being the lead length of the first screw, and the cross-sectional profiles of the two ends of the first unit segment along the axial direction being the same; and / or, The second screw includes a plurality of second unit segments connected in sequence. The length of the second unit segment along the axial direction is the lead length of the second screw. The cross-sectional profiles of the two ends of the second unit segment along the axial direction are the same.

[0009] According to some embodiments of the present invention, the lead length of the first unit rod segment and the second unit rod segment, which are at least partially located in the conveying section, is L1; the lead length of the first unit rod segment and the second unit rod segment, which are at least partially located in the melting section, is L2; ​​the lead length of the first unit rod segment and the second unit rod segment, which are at least partially located in the venting section, is L3; and the lead length of the first unit rod segment and the second unit rod segment, which are at least partially located in the compounding extrusion section, is L4, satisfying: L3 > L1 > L2 = L4.

[0010] According to some embodiments of the present invention, the lead length of the first unit rod segment and the second unit rod segment, which are at least partially located in the melting section, is L2, and the lead length of the first unit rod segment and the second unit rod segment, which are at least partially located in the venting section, is L3, satisfying: L3 > L2.

[0011] According to some embodiments of the present invention, the leads of the plurality of first screws and the plurality of second screws located within the conveying section remain constant; or, The leads of multiple first screws and multiple second screws located within the conveying section gradually decrease, gradually increase, or are arranged in alternating sizes along the material flow direction; or, The leads of the multiple first screws and multiple second screws located in the compounding extrusion section remain constant; or, The leads of the multiple first screws and multiple second screws located in the compounding extrusion section gradually decrease, gradually increase, or are arranged in alternating sizes along the material flow direction.

[0012] According to some embodiments of the present invention, the radius of the top arc is R, the radius of the bottom arc is r, the center distance between the first screw and the second screw is C, satisfying: C = R + r, and the radius of the transition arc is r. m The radius of the meshing arc between the second unit segment and the transition arc is Cr. m .

[0013] According to some embodiments of the present invention, the rotational speed ratio of the first screw and the second screw is M:1, where M is an integer greater than or equal to 1; and / or, The first screw has 1 thread, and the second screw has M thread, where M is an integer greater than or equal to 1.

[0014] According to some embodiments of the present invention, the radius of the top arc is R, and the corresponding central angle is... The radius of the bottom arc is r, and the corresponding central angle is . The radius of the transition arc is r. m The corresponding central angle is The outer diameter of the first screw is D, which satisfies: D=2R; the center distance between the first screw and the second screw is C, which satisfies: C=R+r. The cross-sectional profile of the first unit segment also includes three curved arcs. Along the circumference of the cross-sectional profile of the first unit segment, the intersection points of each arc are sequentially marked J1, J2, J3, J4, J5, and J6. The top arc is denoted as the top arc. The bottom arc is denoted as the bottom. The transition arc is denoted as the transition arc. The three curves mentioned are respectively denoted as curve arcs. , curves and arcs and curve arc The top circular arc The curve arc The bottom The curve arc The transition arc and the curve arc Connect sequentially along the circumference of the first unit segment; Wherein, the curve arc The corresponding central angle is ,satisfy:

[0015] The curve arc The corresponding central angle is ,satisfy: ,

[0016] The central angle corresponding to the arc J6J1 of the curve is: ,satisfy: ,

[0017] The top arc central angle The bottom central angle The transition arc central angle The curve arc central angle The curve arc central angle The central angle of the arc J6J1 of the curve satisfy: .

[0018] According to some embodiments of the present invention, the rotation center O1 of the first screw and the starting point of the bottom diameter are connected. With the ray as the polar axis, given variables The direction in which the radius of the first screw gradually increases is the polar angle. Let the curve arc For any point P1, the corresponding polar radius is = The curve arc The polar coordinate parametric equations satisfy:

[0019]

[0020] In the formula

[0021] Connecting the rotation center O1 of the first screw and the starting point of the bottom diameter With the ray as the polar axis, given variables The direction in which the radius of the first screw gradually increases is the polar angle. Given the curve arc any point The corresponding polar radius is = The curve arc The polar coordinate parametric equations satisfy:

[0022]

[0023] In the formula ,

[0024] Connecting the rotation center O1 of the first screw and the starting point of the bottom diameter The ray is the polar axis, and the curve arc is given. any point Given variables The corresponding polar radius is = The direction in which the screw radius gradually increases is the polar angle. The curve arc The polar coordinate parametric equations satisfy:

[0025]

[0026] In the formula , .

[0027] According to some embodiments of the present invention, The cross-sectional profile of the second unit segment includes a series of connected bottom circular arcs. , curves and arcs ,top , curves and arcs Transition arc , curves and arcs ( i =1,2), bottom arc , curves and arcs Top arc , curves and arcs Transition arc ( i =1,M), curve arc (i=2, M-1), bottom arc , curves and arcs ,top , curves and arcs Transition arc and curve arc ; Wherein, the bottom arc The corresponding central angle is The top arc The corresponding central angle is , curves and arcs The corresponding central angle is , curve arc ( i The central angle corresponding to =1,M-1) is , curve arc The corresponding central angle is Transition arc ( i The central angle corresponding to =1,M is .

[0028] According to some embodiments of the present invention, the second screw rotation center O2 and the starting point of the bottom diameter are connected. or ( i The ray (=1,M) is the polar axis, given the variable... The direction in which the radius of the second screw gradually increases is the polar angle. Given the curve arc ( i =1, M ) Take office at a point The corresponding polar radius is = The curve arc ( i =1, MThe polar coordinate parameters of ) satisfy:

[0029]

[0030] In the formula .

[0031] Connecting the rotation center O2 of the second screw and the starting point of the bottom diameter ( i The ray (=1,M) is the polar axis, given the variable... The direction in which the radius of the second screw gradually increases is the polar angle. , curve arc any point The corresponding polar radius is = The curve arc The polar coordinate parametric equations satisfy:

[0032]

[0033] In the formula , .

[0034] Given curve arc ( i =1, M -1) any point Given variables The corresponding polar angle is The corresponding polar radius is = The curve arc ( i =1, M -1) The polar coordinate parametric equations satisfy:

[0035]

[0036] In the formula , .

[0037] According to some embodiments of the present invention, the screw assembly further includes at least a third screw, the third screw and the second screw engaging in conjugate meshing; or, The screw assembly further includes a third screw and a fourth screw, wherein the first screw, the second screw, the third screw, and the fourth screw are sequentially conjugate meshed.

[0038] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0039] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 This is a schematic diagram of an asymmetric multi-screw extruder with a transition arc and a variable cross-section according to an embodiment of the present invention. Figure 2 This is an embodiment of the present invention with different speed ratios M and transition circle radii r. m / R represents the fixed angle relationship of the first screw; Figure 3 This is a schematic diagram of the arbitrary axial cross-sectional geometry of the first and second unit segments when M=1 according to an embodiment of the present invention; Figure 4 This is a three-dimensional geometric model of the first unit segment and the second unit segment when M=1 according to an embodiment of the present invention; Figure 5 This is a schematic diagram of another three-dimensional geometric shape of the first unit segment and the second unit segment when M=1 according to one embodiment of the present invention; Figure 6 This is a schematic diagram of the arbitrary axial cross-sectional geometry of the first and second unit segments when M=2 according to an embodiment of the present invention; Figure 7 This is a three-dimensional geometric model of the first unit segment and the second unit segment when M=2 according to an embodiment of the present invention; Figure 8 This is a schematic diagram of another three-dimensional geometric shape of the first unit segment and the second unit segment when M=2 according to one embodiment of the present invention; Figure 9 This is a schematic diagram of the arbitrary axial cross-sectional geometry of the first and second unit segments when M=3 according to an embodiment of the present invention; Figure 10 This is a three-dimensional geometric model of the first unit segment and the second unit segment when M=3 according to an embodiment of the present invention; Figure 11 This is a schematic diagram of another three-dimensional geometric shape of the first unit segment and the second unit segment when M=3 according to one embodiment of the present invention; Figure 12 This is a schematic diagram of a screw assembly structure according to another embodiment of the present invention; Figure 13 This is a trend diagram of the cross-sectional area variation of a screw assembly according to an embodiment of the present invention; Figure 14This is a top view of a screw assembly according to an embodiment of the present invention; Figure 15 yes Figure 14 Cross-sectional views of the screw assembly at different locations.

[0040] Figure label: Barrel 100; Transport space 101; Conveying section 110; Feed inlet 102; Melting section 120; Exhaust section 130; Exhaust port 103; Mixing and extrusion section 140; Discharge port 104; Screw assembly 200; first screw 210; first unit segment 211; second screw 220; second unit segment 221; third screw 230. Detailed Implementation

[0041] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0042] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0043] In the description of this invention, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0044] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0045] Reference Figure 1As shown, an embodiment of the variable cross-section asymmetric multi-screw extruder of the present invention includes a barrel 100 and a screw assembly 200. The barrel 100 includes a conveying section 110, a melting section 120, a venting section 130, and a compounding extrusion section 140 arranged sequentially along the length of the barrel 100. The conveying section 110 is provided with a feed inlet 102, the venting section 130 is provided with a vent 103, and the compounding extrusion section 140 is provided with a discharge outlet 104. The screw assembly 200 is disposed within the barrel 100 and penetrates the conveying section 110, the melting section 120, the venting section 130, and the compounding extrusion section 140. A material transport space 101 is formed between the screw assembly 200 and the inner wall of the barrel 100. The screw assembly 200 may include multiple screws, such as two or three screws. The two meshing screws are a first screw 210 and a second screw 220. The first screw 210 includes a first unit segment 211, and the second screw 220 includes a second unit segment 221. (Refer to...) Figure 3 and Figure 4 As shown, the cross-sectional profile of the first unit segment 211 includes a top arc, a bottom arc, and a transition arc. The radius of the top arc is greater than the radius of the bottom arc. The transition arc is located between the top arc and the bottom arc. Along the axial direction of the first unit segment 211, the radius of the transition arc first increases and then decreases. The cross-sectional profile of the second unit segment 221 is conjugately meshed with the cross-sectional profile of the first unit segment 211.

[0046] By introducing a transition arc with an axial radius that first increases and then decreases in the cross-sectional profile of the first unit segment 211, the material flows within the same screw channel and between adjacent screw channels, creating flow channels with varying shapes and areas of the left and right screws at different axial positions. This allows for continuous changes in the flow channels, such as splitting into two, merging into one, and then splitting into two again and merging into one. This further realizes the topological splitting and merging iterative melt mixing and compounding mechanism. Simultaneously, due to the continuous changes in the cross-sectional shape and area of ​​the screw combinations at different axial positions, unsteady disturbances and bidirectional stretching of the flow field are generated throughout the extrusion process. These complex flow field effects enhance the folding, stretching, and reorientation of the fluid interface, thereby improving the efficiency of melt plasticizing, mixing, and venting. Because the screw assembly 200 itself has a strong melting and mixing capability, the use of traditional kneading blocks can be eliminated, and a streamlined screw channel can be constructed. This not only makes the distribution of material residence time more precise and enables precise control of the phase morphology and nanostructure of polymer material processed products, but also simplifies the installation, disassembly and replacement process of the screw because there is no need to set up components such as kneading blocks, making it more convenient and economical.

[0047] Reference Figure 12As shown, in another embodiment of the present invention, the screw assembly 200 further includes at least a third screw 230, the shape of which is the same as that of the first screw 210. The third screw 230 and the second screw 220 are conjugate meshing, that is, the first screw 210 and the third screw 230 are conjugate meshing with the second screw 220 respectively. In this arrangement, by utilizing the variable cross-section geometry with a transition arc, the two meshing areas formed by the middle second screw 220 and the two side screws will generate a multiplied topological splitting and iterative mixing effect. Since the radius of the transition arc changes periodically with the axial direction, the shapes and cross-sectional areas of the three meshing screws at different axial positions form a periodic change of expansion-contraction-expansion. When the material flows in the flow channels of the three screws and between adjacent flow channels, it will experience a stronger "unsteady disturbance enhancement effect" and a "bidirectional stretching effect" of the flow field, thereby significantly improving the folding, stretching and reorientation effect of the fluid interface. This structure enables efficient melting, plasticizing, and mixing without the use of kneading blocks. Furthermore, because the central screw meshes with both sides simultaneously, the frequency of the flow channel changing between closing and opening increases, resulting in more precise control of residence time distribution. This significantly improves exhaust efficiency and heat and mass transfer efficiency, while maintaining the ease of assembly and disassembly due to the consistent end faces of the components.

[0048] In another embodiment of the present invention, the screw assembly 200 further includes a third screw 230 and a fourth screw. The first screw 210 and the third screw 230 have the same shape, and the second screw 220 and the fourth screw have the same shape. The first screw 210, the second screw 220, the third screw 230, and the fourth screw are sequentially conjugate-meshing. In the sequentially meshing four-screw configuration, the variable cross-section asymmetric screw technology constructs a longer, fully streamlined screw channel. When the material is transported axially, a continuous macroscopic topological separation and iteration effect is generated between multiple adjacent screw channels. As the material passes through each meshing zone sequentially, the periodic changes in geometric space continuously introduce a bidirectional stretching flow field and an unsteady cutting and tumbling effect along the longer path. This not only enhances melting and degassing efficiency but also provides a longer-term, finely controlled capability for the dispersed phase morphology and scale of the multiphase system. Furthermore, this configuration, through the combination of lead of multiple elements and the extrusion action of sequential meshing, can more effectively introduce disturbances at positions far from the meshing zone, overcoming the shortcomings of the limited heat and mass transfer effect of traditional screw near-steady-state conveying. Moreover, it can realize complex mixing processes without transition elements, improving the economy of engineering applications.

[0049] Reference Figure 3 and Figure 4As shown in the embodiment of the present invention, the rotation center of the first screw 210 is O1, and the rotation center of the second screw 220 is O2. The top diameter of both the first screw 210 and the second screw 220 is R, which is the largest radius, and the corresponding outer diameter of the screw is D, where D=2R. The bottom diameter of both the first screw 210 and the second screw 220 is r, which is the smallest radius. Therefore, the center distance O1O2 between the first screw 210 and the second screw 220 is... C ,and C = R + r The first screw 210 and the second screw 220 mesh and rotate in the same direction, with a speed ratio M:1. And M is an integer), such as combinations like 2:1, 3:1, 4:1, 5:1, etc. The first screw 210 has 1 head, and the second screw 220 has M heads, for example... Figure 3 , Figure 4 and Figure 5 The second screw 220 shown has 1 thread. Figure 6 , Figure 7 and Figure 8 The number of heads in the second screw 220 is 2; Figure 9 , Figure 10 and Figure 11 The number of heads in the second screw 220 is 3. It should be noted that the number of heads M in the second screw 220 and the M in the speed ratio are the same.

[0050] It should be noted that, Figure 3 , Figure 4 , Figure 6 , Figure 7 , Figure 9 and Figure 10 In the scheme shown, the first and second screws are threaded, thus providing better axial conveying capability. Figure 5 , Figure 8 and Figure 11In the illustrated scheme, the first and second screws lack threads, effectively making their lead infinite. Although this section lacks active axial conveying capacity, with material forward flow primarily relying on upstream pressure, this structure significantly enhances the squeezing and kneading effect. Because this scheme retains the variable cross-section geometry with a transition arc—meaning the transition arc radius changes periodically axially—the screw's cross-sectional area continuously pulsates with expansion and contraction. In the absence of threaded helical flow guidance, this periodic volume change forces the material to endure high-intensity radial compression, circumferential shearing, and forced kneading between the barrel and screw. Compared to threaded embodiments, this threadless variable cross-section structure sacrifices conveying efficiency for stronger unsteady-state disturbances and bidirectional stretching, greatly improving the material's grinding and dispersing capabilities and the mixing and compounding levels. The appropriate scheme should be selected based on the specific circumstances.

[0051] Wherein, the radius of the top arc is R, and the corresponding central angle is... The radius of the bottom arc is r, and the corresponding central angle is . The radius of the transition arc is r. m The corresponding central angle is The center distance between the first screw 210 and the second screw 220 is C, which satisfies: C=R+r; the cross-sectional profile of the first unit segment 211 also includes three curved arcs. Along the circumference of the cross-sectional profile of the first unit segment 211, the intersection points of each arc are marked J1, J2, J3, J4, J5, and J6 in sequence, and the top arc is denoted as the top arc. The bottom arc is denoted as the base. The transition arc is denoted as the transition arc. The three curved arcs are denoted as curve arcs respectively. , curves and arcs and curve arc Among them, the top arc , curves and arcs ,end , curves and arcs Transition arc and curve arc Connect sequentially along the circumference of the first unit segment 211.

[0052] The cross-sectional profile of the second unit segment 221 includes a series of connected bottom circular arcs. , curves and arcs ,top , curves and arcs Transition arc , curves and arcs ( i =1,2), bottom arc ( i =1,M), curve arc ( i =1,M), Top arc ( i =1,M), curve arc ( i =1,M), transition arc ( i =1,M), curve arc (i=2, M-1), bottom arc , curves and arcs ,top , curves and arcs Transition arc and curve arc .

[0053] For example, when M=1, such as Figure 3 and Figure 4 As shown, the cross-sectional profile of the second unit segment 221 includes a series of connected bottom circular arcs. , curves and arcs ,top , curves and arcs Transition arc , curves and arcs .

[0054] When M=2, such as Figure 6 and Figure 7 As shown, the cross-sectional profile of the second unit segment 221 includes a series of connected bottom circular arcs. , curves and arcs ,top , curves and arcs Transition arc , curves and arcs Bottom arc , curves and arcs Top arc , curves and arcs Transition arc , curves and arcs .

[0055] When M=3, such as Figure 9 and Figure 10 As shown, the cross-sectional profile of the second unit segment 221 includes a series of connected bottom circular arcs. , curves and arcs ,top , curves and arcs Transition arc , curves and arcs Bottom arc , curves and arcs Top arc , curves and arcs Transition arc , curves and arcs Bottom arc , curves and arcs ,top , curves and arcs Transition arc and curve arc .

[0056] To ensure conjugate meshing, the first screw 210 has a top arc. radius is R The corresponding central angle is The second screw 220 with which it meshes has a bottom arc. ( i The radius of (=1, M) is r The corresponding central angle is The bottom arc of the first screw 210 The radius is r The corresponding central angle is The second screw 220 that meshes with it has a top arc. The radius of (i=1, M) is R， The corresponding central angle is ; First screw 210 transition arc radius is The central angle is The transition arc of the second screw 220 that meshes with it. ( i =1, M The radius of ) is The corresponding central angle is .For example Figure 2 As shown, for any axial section, there are three types of circular arcs (top circular arc). Bottom arc and transition arc The central angle of the first screw 210 is adjustable under the condition that the first screw 210 is fixed, where the apex angle of the first screw 210 is... bottom corner and the angle of the transition arc There are multiple combination relationships. By selecting different combination relationships, various geometric shapes of the first screw 210 with variable cross-section can be formed. Under the action of the meshing conjugate relationship, the geometric shape of the second screw 220 is also determined accordingly.

[0057] In an embodiment of the present invention, the radius of the top arc is R, the radius of the bottom arc is r, and the radius of the transition arc is r. m Along the axial direction of the first screw 210 and within the axial length of the first unit segment 211, the radius r of the transition arc m From r gradually increasing to R, Then gradually decrease it to r. This is achieved by using the transition arc radius r. m The variation range is set to start from the base diameter r, change to the maximum value, and then return to r, ensuring that the axial end faces of the first unit segment 211 and the corresponding second unit segment 221 constituting the screw have the same geometry. This design eliminates the need for additional transition elements when assembling screw components, greatly simplifying the on-site installation, disassembly, and replacement process, and reducing usage and maintenance costs.

[0058] It should be noted that the corresponding second unit segment 221 is shaped to achieve different axial cross-sectional geometric profiles according to the conjugate meshing condition. Under the premise of satisfying the fixed angle condition of the first screw 210 given later, the initial radius of the given transition arc is the screw base diameter r, and the initial value of the central angle of the given transition arc is 0, which undergoes a change from increasing to decreasing to the initial value; or the central angle of the given transition arc is kept constant, thereby ensuring that the geometric shapes of the two end faces of the first unit segment 211 and the second unit segment 221 are completely consistent.

[0059] Reference Figure 1 As shown, in an embodiment of the present invention, the first screw 210 includes a plurality of first unit segments 211 connected in sequence, the axial length of which is the lead length of the first screw 210. The second screw 220 includes a plurality of second unit segments 221 connected in sequence, the axial length of which is the lead length of the second screw 220. The lead lengths of the first unit segments 211 and 221 located in the conveying section 110 are L1, the lead lengths of the first unit segments 211 and 221 located in the melting section 120 are L2, the lead lengths of the first unit segments 211 and 221 located in the venting section 130 are L3, and the lead lengths of the first unit segments 211 and 221 located in the compounding extrusion section 140 are L4, satisfying that L3 > L2.

[0060] In other embodiments, L3 > L1 > L2 = L4. Of course, in other embodiments, the leads of the plurality of first screws 210 and second screws 220 located in the conveying section 110 remain constant; or, the leads of the plurality of first screws 210 and second screws 220 located in the conveying section 110 gradually decrease, gradually increase, or are arranged in alternating sizes along the material flow direction; or, the leads of the plurality of first screws 210 and second screws 220 located in the compounding extrusion section 140 remain constant; or, the leads of the plurality of first screws 210 and second screws 220 located in the compounding extrusion section 140 gradually decrease, gradually increase, or are arranged in alternating sizes along the material flow direction. The specific arrangement depends on the material being processed.

[0061] For example, the working principle of a variable cross-section asymmetric multi-screw extruder is as follows: The first screw 210 and the second screw 220 rotate in the same direction around their respective axes and mesh with each other. Their speeds can be the same or different, but they have a constant speed ratio. The material is fed into the conveying section 110 through the feed inlet 102. Under the combined action of the positive displacement generated by the screw assembly 200 and the friction between the material and the barrel 100, it moves towards the outlet. Due to the continuous change of the flow channel cross-section, the extrusion and kneading action generates strong frictional heat between the materials. Under the combined action of external heating, the material temperature continues to rise.

[0062] Afterwards, the material enters the melting section 120. Due to the continuous change in the radius of the transition arc, the shape and area of ​​the screw cross-section continuously change. During the material conveying in the same screw channel, a topological splitting and iterative action similar to a static mixer is generated. When the material moves away from the meshing zone, an unsteady strengthening effect is introduced, and it is subjected to strong cutting and tumbling action, reducing the heat transfer distance between materials, and the material undergoes a melting process. On the other hand, the transition arc of the first screw 210 and the second screw 220 meshing with each other undergoes a continuous increase and decrease in radius at different axial positions. The flow channel in the meshing zone appears to be closed and open at times, which leads to a further macroscopic topological splitting and iterative action of the material between adjacent screw channels. The periodic change in geometric space also leads to a bidirectional stretching effect in the flow field, which accelerates the peeling of the melt film and the peeling of the melt interface. The material is subjected to the combined effect of external heating and frictional heat generation, which greatly improves the melting efficiency. In the later stage of the melting process, the unmelted material particle aggregates participate in mixing and stirring in the melt to enhance heat transfer, and the material further melts into a melt.

[0063] When the molten material reaches the exhaust section 130, the filling degree of the material decreases sharply under the conveying action of the screw assembly 200, creating a negative pressure space. In particular, the unsteady disturbance and squeezing and tumbling action of the screw assembly 200 far from the meshing zone causes the entrained gas and small volatile molecules to be discharged from the melt, improving the exhaust efficiency.

[0064] The molten material enters the mixing and extrusion section 140. Due to the reduced lead of the screw thread, it is gradually compacted and depressurized during forward conveying. During the conveying process within the same screw channel, the material undergoes a topological splitting and merging iterative process, splitting into two, merging again, and so on. Because the flow channel shape and cross-sectional area continuously change at different axial positions, the material is simultaneously subjected to unsteady-state intensification as it moves away from the meshing zone, experiencing intense cutting and turbulence. On the other hand, the radius of the transition arc where the first screw 210 and the second screw 220 mesh with each other continuously increases and decreases at different axial positions, causing the flow channel in the meshing zone to sometimes close and sometimes open, further generating macroscopic topological splitting and merging iterative processes between different screw channels. The periodic changes in geometric space also lead to a bidirectional stretching effect in the flow field. The molten material, subjected to the above-mentioned mixing and blending processes, further completes the microscopic phase morphology and structure regulation of the multiphase system.

[0065] By linking the axial length of the screw unit with the lead length and configuring different leads for different functional sections, precise control of the extrusion process is achieved. For example, setting the maximum lead in the venting section 130 can reduce the material filling rate, create a negative pressure space, and significantly improve the efficiency of venting and volatilization; while setting a smaller lead in the melting section 120 and the compounding extrusion section 140 helps with material compaction, pressure building, and shearing, thereby enhancing the melting and mixing effect.

[0066] Reference Figure 13 , Figure 14 and Figure 15 As shown, in the embodiment of the present invention, the length of the first unit rod segment 211 is the lead length of the first screw 210, and the length of the second unit rod segment 221 is the lead length of the second screw 220. Along the flow direction of the material, the cross-sectional area of ​​the first unit rod segment 211 gradually increases and then gradually decreases, while the cross-sectional area of ​​the second unit rod segment 221 gradually decreases and then gradually increases.

[0067] It should be noted that, Figure 13 In the x-axis (z / L), z represents the axial length at any position on the first unit segment 211 or the second unit segment 221, L represents the maximum axial length of the first unit segment 211, and M represents the reduction ratio. The y-axis represents the ratio of the cross-sectional area of ​​the first unit segment 211 or the second unit segment 221 to the area of ​​a single hole in the barrel 100. A single hole in the barrel 100 refers to the cross-sectional area of ​​the hole accommodating the corresponding screw. For example, when there are only two screws, the barrel 100 has two connected holes, and a single hole refers to one of those holes. From... Figure 13 and Figure 15 As can be seen from this, along the direction of material flow, that is... Figure 15 In the direction from the CC section to the HH section, the cross-sectional area of ​​the first unit segment 211 first gradually increases and then gradually decreases, while the cross-sectional area of ​​the second unit segment 221 first gradually decreases and then gradually increases. The cross-sectional areas of the first unit segment 211 and the second unit segment 221 differ under different reduction ratios.

[0068] This configuration, with its periodically changing cross-sectional area, causes the screw's cross-sectional shape and area to continuously change. It introduces a topological splitting and merging iteration effect, similar to a static mixer, into the material conveying process, and generates an unsteady-state intensification effect far from the meshing zone, subjecting the material to intense cutting and tumbling, reducing heat transfer distance and accelerating the island melting process. Simultaneously, because the flow channels in the meshing zone exhibit alternating closed and open states due to geometric spatial changes, it further promotes macroscopic topological splitting and merging iteration between adjacent screw channels, triggering a bidirectional stretching effect in the flow field and accelerating the peeling of the melt film from the melt interface. Ultimately, this configuration significantly improves melting, plasticizing, mixing, and venting efficiency, and allows for more precise control of residence time distribution.

[0069] Reference Figure 3 As shown in the embodiment of the present invention, the radius of the top arc is R, the radius of the bottom arc is r, the center distance between the first screw 210 and the second screw 220 is C, satisfying: C=R+r, and the radius of the transition arc is r. m The radius of the meshing arc between the second unit segment 221 and the transition arc is Cr. m By ensuring that the center distance C between the first screw 210 and the second screw 220 satisfies C=R+r, and by setting the radius of the corresponding meshing arc on the second unit segment 221 to Cr... m This ensures that even when the cross-sectional shape of the first unit segment 211 changes continuously along the axial direction, the first screw 210 and the second screw 220 can still maintain mutual sweeping and close fit, thereby guaranteeing the self-cleaning function and stable operation of the extruder.

[0070] Reference Figure 3 As shown, in an embodiment of the present invention, the curve arc The corresponding central angle is ,satisfy:

[0071] Curve Arc The corresponding central angle is ,satisfy: ,

[0072] The central angle corresponding to the arc J6J1 of the curve is ,satisfy: ,

[0073] Top arc central angle ,end central angle Transition arc central angle , curves and arcs central angle , curves and arcs central angle The central angle of the arc J6J1 of the curve satisfy: .

[0074] Continue to refer to Figure 3 As shown, in an embodiment of the present invention, the rotation center O1 of the first screw 210 and the starting point of the bottom diameter are connected. With the ray as the polar axis, given variables The direction in which the radius of the first screw 210 gradually increases is the polar angle. Let the curve arc For any point P1, the corresponding polar radius is = , curve arc The polar coordinate parametric equations satisfy:

[0075]

[0076] In the formula

[0077] Connecting the rotation center O1 of the first screw 210 and the starting point of the bottom diameter With the ray as the polar axis, given variables The direction in which the radius of the first screw 210 gradually increases is the polar angle. Given a curve arc any point The corresponding polar radius is = , curve arc The polar coordinate parametric equations satisfy:

[0078]

[0079] In the formula ,

[0080] Connecting the rotation center O1 of the first screw 210 and the starting point of the bottom diameter With the ray as the polar axis, given variables Given a curve arc any point The corresponding polar radius is = The direction in which the screw radius gradually increases is the polar angle. , curve arc The polar coordinate parametric equations satisfy:

[0081]

[0082] In the formula , .

[0083] Continue to refer to Figure 3 As shown in the embodiment of the present invention, the bottom arc The corresponding central angle is Top arc central angle , curves and arcs The corresponding central angle is , curve arc ( i The central angle corresponding to =1,M-1) is , curve arc The corresponding central angle is Transition arc ( i The central angle corresponding to =1,M is It should be noted that the curve arc , curves and arcs ( i =1,M) and curve arc They are used to refer to multiple corresponding curves, for example, when M=1, the curve arc Referring to the aforementioned curve arc , curve arc ( i =1,M-1) refers to the curve arc , curve arc Refers to the curve arc When M=2, the curve arc Referring to the aforementioned curve arc and curve arc Any one of them, curve arc ( i =1,M-1) refers to the curve arc and curve arc Any one of them, curve arc Refers to the curve arc and curve arc Any one of them. When M=3, the curve arc Referring to the aforementioned curve arc , curves and arcs and curve arc Any one of them, curve arc ( i=1,M-1) refers to the curve arc Curve Arc and curve arc Any one of them, curve arc Refers to the curve arc , curves and arcs and curve arc Any one of them.

[0084] Connecting the rotation center O2 of the second screw 220 and the starting point of the bottom diameter or ( i The ray (=1,M) is the polar axis, given the variable... The direction in which the radius of the second screw 220 gradually increases is the polar angle. Given a curve arc ( i =1, M ) Take office at a point The corresponding polar radius is = , curve arc ( i =1, M The polar coordinate parameters of ) satisfy:

[0085]

[0086] In the formula .

[0087] Connecting the rotation center O2 of the second screw 220 and the starting point of the bottom diameter ( i The ray (=1,M) is the polar axis, given the variable... The direction in which the radius of the second screw 220 gradually increases is the polar angle. , curve arc any point The corresponding polar radius is = , curve arc The polar coordinate parametric equations satisfy:

[0088]

[0089] In the formula , .

[0090] Given curve arc ( i =1, M -1) any point Given variables The corresponding polar angle is The corresponding polar radius is = , curve arc ( i =1, M -1) The polar coordinate parametric equations satisfy:

[0091]

[0092] In the formula , .

[0093] It is understood that, through the above formulas, the embodiments of the present invention provide a complete and accurate mathematical model and polar coordinate parametric equations for defining and constructing the complex geometric contours of the first unit segment 211 and the second unit segment 221. This mathematical method is not only the theoretical basis for achieving all the aforementioned technical effects, but more importantly, it provides a specific and reproducible technical path for the design and manufacture of such complex variable cross-section screws, ensuring that the fixed angle relationship and conjugate meshing conditions are satisfied in the design, thus enabling the concept of the present invention to be accurately transformed into industrial products.

[0094] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A variable cross-section asymmetric multi-screw extruder, characterized in that, include: The barrel includes a conveying section, a melting section, a venting section and a mixing and extrusion section arranged sequentially along the length of the barrel. The conveying section is provided with a feed inlet, the venting section is provided with a venting outlet, and the mixing and extrusion section is provided with a discharge outlet. A screw assembly is disposed inside the barrel and passes through the conveying section, the melting section, the venting section and the mixing extrusion section. The screw assembly includes a first screw and a second screw that mesh with each other. The first screw includes a plurality of first unit segments connected in sequence, and the second screw includes a plurality of second unit segments connected in sequence. The cross-sectional profile of the first unit segment includes a top arc, a bottom arc, and a transition arc. The radius of the top arc is greater than the radius of the bottom arc. The transition arc is located between the top arc and the bottom arc. Along the axial direction of the first unit segment, the radius of the transition arc first increases and then decreases. The cross-sectional profile of the second unit segment is conjugately meshed with the cross-sectional profile of the first unit segment.

2. The variable cross-section asymmetric multi-screw extruder according to claim 1, characterized in that: The radius of the top arc is R, the radius of the bottom arc is r, and the radius of the transition arc is r. m Along the axial direction of the first screw and within the axial length range of the first unit segment, the radius r of the transition arc m From r gradually increasing to R, Then gradually decrease it to r.

3. The variable cross-section asymmetric multi-screw extruder according to claim 1, characterized in that: The length of the first unit segment is the lead length of the first screw, and the length of the second unit segment is the lead length of the second screw. Along the flow direction of the material, the cross-sectional area of ​​the first unit segment gradually increases and then gradually decreases, while the cross-sectional area of ​​the second unit segment gradually decreases and then gradually increases.

4. The variable cross-section asymmetric multi-screw extruder according to claim 1, characterized in that: The first screw comprises a plurality of first unit segments connected in sequence, the axial length of the first unit segment being equal to the lead length of the first screw, and the cross-sectional profiles of the two ends of the first unit segment along the axial direction being identical; and / or, The second screw includes a plurality of second unit segments connected in sequence. The length of the second unit segment along the axial direction is the lead length of the second screw. The cross-sectional profiles of the two ends of the second unit segment along the axial direction are the same.

5. The variable cross-section asymmetric multi-screw extruder according to claim 4, characterized in that: The lead lengths of the first and second unit rod segments, which are at least partially located in the conveying section, are L1; the lead lengths of the first and second unit rod segments, which are at least partially located in the melting section, are L2; the lead lengths of the first and second unit rod segments, which are at least partially located in the venting section, are L3; and the lead lengths of the first and second unit rod segments, which are at least partially located in the compounding extrusion section, are L4, satisfying: L3 > L1 > L2 = L4.

6. The variable cross-section asymmetric multi-screw extruder according to claim 4, characterized in that: The lead lengths of the first unit rod segment and the second unit rod segment, which are at least partially located in the melting section, are L2, and the lead lengths of the first unit rod segment and the second unit rod segment, which are at least partially located in the venting section, are L3, satisfying that: L3 > L2.

7. The variable cross-section asymmetric multi-screw extruder according to claim 6, characterized in that: The leads of the multiple first screws and multiple second screws located within the conveying section remain constant; or, The leads of multiple first screws and multiple second screws located within the conveying section gradually decrease, gradually increase, or are arranged in alternating sizes along the material flow direction; or, The leads of the multiple first screws and multiple second screws located in the compounding extrusion section remain constant; or, The leads of the multiple first screws and multiple second screws located in the compounding extrusion section gradually decrease, gradually increase, or are arranged in alternating sizes along the material flow direction.

8. The variable cross-section asymmetric multi-screw extruder according to claim 1, characterized in that: The radius of the top arc is R, the radius of the bottom arc is r, the center distance between the first screw and the second screw is C, satisfying: C = R + r, and the radius of the transition arc is r. m The radius of the meshing arc between the second unit segment and the transition arc is Cr. m .

9. The variable cross-section asymmetric multi-screw extruder according to claim 1, characterized in that: The rotational speed ratio of the first screw and the second screw is M:1, where M is an integer greater than or equal to 1; and / or, The first screw has 1 thread, and the second screw has M thread, where M is an integer greater than or equal to 1.

10. The variable cross-section asymmetric multi-screw extruder according to claim 9, characterized in that: The radius of the top arc is R, and the corresponding central angle is . The radius of the bottom arc is r, and the corresponding central angle is . The radius of the transition arc is r. m The corresponding central angle is The outer diameter of the first screw is D, which satisfies: D=2R; the center distance between the first screw and the second screw is C, which satisfies: C=R+r. The cross-sectional profile of the first unit segment also includes three curved arcs. Along the circumference of the cross-sectional profile of the first unit segment, the intersection points of each arc are sequentially marked J1, J2, J3, J4, J5, and J6. The top arc is denoted as the top arc. The bottom arc is denoted as the bottom. The transition arc is denoted as the transition arc. The three curves mentioned are respectively denoted as curve arcs. , curves and arcs and curve arc The top circular arc The curve arc The bottom The curve arc The transition arc and the curve arc Connect sequentially along the circumference of the first unit segment; Wherein, the curve arc The corresponding central angle is ,satisfy: The curve arc The corresponding central angle is ,satisfy: , The central angle corresponding to the arc J6J1 of the curve is: ,satisfy: , The top arc central angle The bottom central angle The transition arc central angle The curve arc central angle The curve arc central angle The central angle of the arc J6J1 of the curve satisfy: 。 11. The variable cross-section asymmetric multi-screw extruder according to claim 10, characterized in that: Connecting the rotation center O1 of the first screw and the starting point of the bottom diameter With the ray as the polar axis, given variables The direction in which the radius of the first screw gradually increases is the polar angle. Let the curve arc For any point P1, the corresponding polar radius is = The curve arc The polar coordinate parametric equations satisfy: In the formula Connecting the rotation center O1 of the first screw and the starting point of the bottom diameter With the ray as the polar axis, given variables The direction in which the radius of the first screw gradually increases is the polar angle. Given the curve arc any point The corresponding polar radius is = The curve arc The polar coordinate parametric equations satisfy: In the formula , Connecting the rotation center O1 of the first screw and the starting point of the bottom diameter The ray is the polar axis, and the curve arc is given. any point Given variables The corresponding polar radius is = The direction in which the screw radius gradually increases is the polar angle. The curve arc The polar coordinate parametric equations satisfy: In the formula , .

12. The variable cross-section asymmetric multi-screw extruder according to claim 11, characterized in that: The cross-sectional profile of the second unit segment includes a series of connected bottom circular arcs. , curves and arcs Top arc , curves and arcs Transition arc , curves and arcs ( i =1,2), bottom arc , curves and arcs Top arc , curves and arcs Transition arc ( i =1,M), curve arc (i=2, M-1), bottom arc , curves and arcs Top arc , curves and arcs Transition arc and curve arc ; Wherein, the bottom arc The corresponding central angle is The top arc The corresponding central angle is , curves and arcs The corresponding central angle is , curve arc ( i The central angle corresponding to =1,M-1) is , curve arc The corresponding central angle is Transition arc ( i The central angle corresponding to =1,M is .

13. The variable cross-section asymmetric multi-screw extruder according to claim 12, characterized in that: Connecting the rotation center O2 of the second screw and the starting point of the bottom diameter or ( i The ray ( =1, M) is the polar axis, given the variable... The direction in which the radius of the second screw gradually increases is the polar angle. Given the curve arc ( i =1, M ) Take office at a point The corresponding polar radius is = The curve arc ( i =1, M The polar coordinate parameters of ) satisfy: In the formula ; Connecting the rotation center O2 of the second screw and the starting point of the bottom diameter ( i The ray ( =1, M) is the polar axis, given the variable... The direction in which the radius of the second screw gradually increases is the polar angle. , curve arc any point The corresponding polar radius is = The curve arc The polar coordinate parametric equations satisfy: In the formula , ; Given curve arc ( i =1, M -1) any point Given variables The corresponding polar angle is The corresponding polar radius is = The curve arc ( i =1, M -1) The polar coordinate parametric equations satisfy: In the formula , .

14. The variable cross-section asymmetric multi-screw extruder according to claim 1, characterized in that: The screw assembly further includes at least a third screw, which engages conjugately with the second screw; or... The screw assembly further includes a third screw and a fourth screw, wherein the first screw, the second screw, the third screw, and the fourth screw are sequentially conjugate meshed.

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