A split screw mechanism for preventing viscosity drop in twin-screw extruder

Abstract

A split screw mechanism for preventing viscosity drop for a twin-screw extruder relates to the technical field of extruder screws, comprising a feeding section, a first compression section, a vacuum conveying section, a first homogenizing section, a second homogenizing section and a second compression section which are sequentially connected and arranged in a barrel in the axial direction along a material transportation direction; the feeding section and the first compression section are both twin-screw structures, and the pitch of the feeding section is greater than the pitch of the first compression section; the screw mechanism after the first compression section adopts a split design, the barrel is divided into two branches from the tail end of the first compression section, and each branch is sequentially connected and arranged with a vacuum conveying section, a first homogenizing section, a second homogenizing section and a second compression section along the material transportation direction; the first homogenizing section, the second homogenizing section and the second compression section are all single-screw structures; the entire screw mechanism is placed in a high-temperature heating environment, wherein the ambient temperature of the first homogenizing section and the second homogenizing section is lower than the ambient temperature of the feeding section and the first compression section; the vacuum conveying section on the barrel is connected to a vacuum machine.

Description

Technical Field

[0001] The invention relates to the technical field of extruder screws, in particular to a split screw mechanism for preventing viscosity drop for a twin-screw extruder. Background Art

[0002] The twin-screw extruder is developed on the basis of the single-screw extruder. It is composed of two parallel screws rotating in a heated barrel with an "∞"-shaped cross-section. Due to its good feeding performance, mixing and plasticizing performance, exhaust performance, extrusion stability and other characteristics, it has been widely used in the molding and processing of extruded products. When the current twin-screw extruder is in production, the viscosity value of the material itself will decrease after being melted and extruded by the extruder. This decrease is called the viscosity drop. Too low viscosity is easy to cause film breakage in the subsequent stretching process. In order to ensure the stable performance of the final product, the viscosity drop needs to be reduced in production. For example, the Chinese utility model with announcement number CN220362961U discloses a screw combination structure for reducing the viscosity drop of a twin-screw extruder, including a feeding section, a compression section, a meshing section and a homogenizing section, which are arranged in sequence along the material transportation direction in the axial direction. The feeding section is a screw structure with a larger pitch, the compression section is a screw structure with a smaller pitch, the meshing section is a structure with axial sheets superimposed, and the homogenizing section is a rod structure with a single spiral element. Although the screw structure of the above utility model can reduce the viscosity drop, it has limited effect on the stirring and homogenizing of the material. Based on this, a split screw mechanism for a twin-screw extruder that prevents viscosity drop is proposed to make the stirring and homogenizing effect more sufficient and ensure more stable performance of the finished product. Summary of the invention

[0003] In view of the above problems, the present invention proposes a split screw mechanism for a twin-screw extruder to prevent viscosity drop, and the technical solution used is:

[0004] A split screw mechanism for preventing viscosity drop for a twin-screw extruder comprises a feeding section, a first compression section, a vacuum conveying section, a first homogenizing section, a second homogenizing section and a second compression section which are sequentially connected and arranged in a barrel in the axial direction along the material transportation direction; the feeding section and the first compression section are both twin-screw structures, and the pitch of the feeding section is greater than the pitch of the first compression section; the screw mechanism after the first compression section adopts a split design, the barrel is divided into two branches from the tail end of the first compression section, and each branch is sequentially connected and arranged with a vacuum conveying section, a first homogenizing section, a second homogenizing section and a second compression section along the material transportation direction; the first homogenizing section, the second homogenizing section and the second compression section are all single-screw structures; the entire screw mechanism is placed in a high-temperature heating environment, wherein the ambient temperature of the first homogenizing section and the second homogenizing section is lower than the ambient temperature of the feeding section and the first compression section;

[0005] The vacuum conveying section on the barrel is connected to the vacuum machine; the first homogenizing section is provided with a first homogenizing mechanism, and the second homogenizing section is provided with a second homogenizing mechanism; the second homogenizing mechanism includes a plurality of pairs of limiting inclined slide rails fixedly mounted on the spiral groove edge of the screw of the second homogenizing section and having an angle with the radial direction of the screw, a moving plate elastically connected to the screw in the radial direction through a spring 1, a linkage rack slidably mounted in the moving plate along the axial direction of the screw, a linkage gear rotatably mounted on the moving plate and meshing with the linkage rack, a stirring block fixedly mounted on the linkage gear, and a limiting push plate that slides and is elastically mounted on the barrel through a spring 2 and intermittently pushes the moving plate.

[0006] Furthermore, the first homogenizing mechanism includes a sliding frame slidably mounted on the screw of the first homogenizing section along the axial direction, and a limited rotary slide rail fixedly mounted in the barrel; the sliding frame is slidably connected to the limited rotary slide rail; and a plurality of stirring support rods extending radially are fixedly arranged on the sliding frame along the spiral trajectory of the screw.

[0007] Furthermore, a relief opening is provided on the edge of the spiral groove of the screw of the first homogenizing section corresponding to the stirring support rod.

[0008] Furthermore, the end point of the movable plate is mounted on the limiting inclined slide rail in a chimeric manner, and the elastic coefficient of the second spring is greater than the elastic coefficient of the first spring.

[0009] Furthermore, two ends of the linkage rack are respectively in contact with the limiting inclined slide rails on both sides of the movable plate.

[0010] Furthermore, the two screws of the first compression section are connected to the screws of the first homogenization section in the two branches respectively through a universal shaft.

[0011] Furthermore, the screw of the second compression section in each branch is connected with the screw of the second homogenization section through a universal shaft.

[0012] Furthermore, the ends of the two branches of the barrel merge, and the ends of the screws of the two second compression sections both point to the confluence port.

[0013] Since the present invention adopts the above technical solution, the present invention has the following advantages:

[0014] 1. The present invention is provided with a feeding section, a first compression section, a vacuum conveying section, a first homogenizing section, a second homogenizing section and a second compression section which are sequentially connected in the axial direction along the material transport direction in the barrel. The granular material is transported from the feeding section to the first compression section and melted into a fluid. The water and volatiles generated after high-temperature melting are extracted by the vacuum conveying section. The first homogenizing section and the second homogenizing section stir and homogenize the fluid material. The second compression section compresses the homogenized material again and extrude the material. The whole process can ensure that the material is melted and plasticized.

[0015] 2. The ambient temperature of the first homogenizing section and the second homogenizing section of the present invention is lower than the ambient temperature of the feeding section and the first compression section, which prevents the viscosity of the fluid material from further decreasing during the stirring and homogenizing process in the first homogenizing section and the second homogenizing section, thereby reducing the viscosity drop.

[0016] 3. The present invention adopts a split design. After the granular material is melted into a fluid through the feeding section and the first compression section, the split design can divide the fluid material into two parts, and perform vacuum treatment and homogenization treatment respectively, so that the treatment effect is more sufficient and effective, thereby ensuring the quality of the final product.

[0017] 4. The stirring and homogenizing effects of the first homogenizing section and the second homogenizing section of the present invention are achieved by the rotation of the screw itself, without the need for other power drives, thus reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0019] Figure 2 It is a schematic diagram of the structure of the present invention installed in a barrel.

[0020] Figure 3 It is a schematic diagram of the assembly structure of the first homogenizing section, the second homogenizing section and the second compression section of the present invention.

[0021] Figure 4 It is a schematic diagram of the overall structure of the first homogenization section of the present invention.

[0022] Figure 5-Figure 6 It is a partial structural schematic diagram of the first homogenization section.

[0023] Figure 7-Figure 8 It is a schematic diagram of the overall structure of the second homogenization section of the present invention.

[0024] Figure 9-11 It is a partial structural schematic diagram of the second homogenization section of the present invention.

[0025] Fig.12 It is a cross-sectional schematic diagram of the AA section of the limiting push plate and the push plate slide groove in the second homogenizing section of the present invention.

[0026] Figure Number:

[0027] 1-feeding section; 2-first compression section; 3-vacuum conveying section; 4-first homogenization section; 5-second homogenization section; 6-second compression section; 7-barrel;

[0028] 401-sliding frame; 4011-connecting sliding rod; 4012-stirring support rod; 402-limited rotary slide rail;

[0029] 501-limiting inclined slide rail; 502-moving plate; 503-spring one; 504-linked rack; 505-linked gear; 506-stirring block; 507-limiting push plate; 508-spring two; 509-push plate slide groove. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further specifically described below by way of embodiments and in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0031] In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "up", "down", "in", "out", "front", "back", etc. are based on the directions or positional relationships shown in the accompanying drawings, or are the directions or positional relationships in which the inventive product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0032] Example:

[0033] like Figure 1-Figure 2 As shown, the screw mechanism of the present invention includes a feeding section 1, a first compression section 2, a vacuum conveying section 3, a first homogenizing section 4, a second homogenizing section 5 and a second compression section 6 which are sequentially connected in the axial direction along the material transportation direction in the barrel 7; the entire screw mechanism is placed in a high-temperature heating environment; the feeding section 1 and the first compression section 2 are both twin-screw structures, and the pitch of the feeding section 1 is greater than the pitch of the first compression section 2; the screw mechanism after the first compression section 2 adopts a split design, and the barrel 7 is divided into two branches from the tail end of the first compression section 2, and each branch is sequentially connected with a vacuum conveying section 3, a first homogenizing section 4, a second homogenizing section 5 and a second compression section 6 along the material transportation direction; the first homogenizing section 4, the second homogenizing section 5 and the second compression section 6 are all single-screw structures;

[0034] The barrel 7 is provided with a feed port at the beginning of the feeding section 1. The granular material enters the feeding section 1 from the feed port. The feeding section 1 transports the granular material to the first compression section 2. Under the compression action of the first compression section 2, the material is squeezed, piled up, and compacted. The granular material melts into a fluid in a high temperature environment.

[0035] The vacuum conveying section 3 is connected to the first compression section 2 and the first homogenizing section 4 by setting a universal shaft. The two screws of the first compression section 2 are connected with the screws of the first homogenizing section 4 in the two branches through the universal shaft respectively; the vacuum conveying section 3 on the barrel 7 is connected to a vacuum machine (not shown in the figure). When the fluid material is quickly conveyed in the vacuum conveying section 3, a cavity will be formed. The vacuum machine extracts the moisture and volatiles generated after the material is melted at high temperature to prevent affecting the quality of the final product.

[0036] like Figure 4-Figure 6 As shown, a sliding frame 401 is slidably installed on the screw of the first homogenizing section 4 along the axial direction, and both ends of the screw are provided with a limit rotary slide rail 402 fixedly installed in the barrel 7; the front and rear ends of the sliding frame 401 are fixedly provided with a connecting slide rod 4011 corresponding to the limit rotary slide rail 402, and the connecting slide rod 4011 is slidably installed on the limit rotary slide rail 402 at the corresponding end; a plurality of stirring support rods 4012 extending radially are fixedly provided on the sliding frame 401 along the spiral track, and an avoidance opening is provided on the edge of the spiral groove of the screw corresponding to the stirring support rod 4012;

[0037] Specifically, when the screw of the first homogenizing section 4 rotates, the sliding frame 401 will rotate accordingly, and the connecting slide rod 4011 will slide along the limited rotary slide rail 402, driving the entire sliding frame 401 to slide back and forth axially on the screw, and the stirring support rod 4012 will move accordingly and stir the fluid material to make the material evenly blended.

[0038] like Figure 7-Figure 12 As shown, a plurality of pairs of limiting inclined rails 501 are fixedly provided on the edge of the spiral groove of the screw of the second homogenizing section 5 (there is an angle between the limiting inclined rails 501 and the radial direction of the screw), and a moving plate 502 is slidably installed between each pair of limiting inclined rails 501;

[0039] The movable plate 502 is elastically connected to the screw of the second homogenizing section 5 in the radial direction through the spring 1 503. The spring 1 503 is a compression spring. The movable plate 502 can only move in the radial direction of the screw. The end point of the movable plate 502 is mounted on the limiting inclined slide rail 501 in a chimeric manner. When the movable plate 502 moves in the radial direction of the screw, the chimeric area between the end point of the movable plate 502 and the limiting inclined slide rail 501 will change in real time.

[0040] Each movable plate 502 is provided with a linkage rack 504 which is slidably mounted along the axial direction of the screw rod, and the two ends of the linkage rack 504 are respectively in contact with the limiting inclined slide rails 501 on both sides of the movable plate 502, that is, when the movable plate 502 moves along the radial direction of the screw rod, the linkage rack 504 can slide along the limiting inclined slide rails 501, and the linkage rack 504 moves along the axial direction of the screw rod relative to the movable plate 502;

[0041] The linkage rack 504 is a double-sided rack, and the two sides are respectively meshed with two linkage gears 505 rotatably mounted on the moving plate 502; a stirring block 506 is fixedly mounted on each linkage gear 505;

[0042] Three groups of push plate slide grooves 509 are provided at the second homogenizing section 5 on the barrel 7, and each group of push plate slide grooves 509 is evenly distributed with six push plate slide grooves along the circumference and are fixedly installed on the inner wall of the barrel 7; a limited push plate 507 is installed in each push plate slide groove 509 along the radial direction of the screw for sliding movement, and the limited push plate 507 is elastically connected to the push plate slide groove 509 through a second spring 508; the second spring 508 is a compression spring, and the elastic coefficient of the second spring 508 is greater than the elastic coefficient of the first spring 503; the middle part of the limited push plate 507 is convex and smoothly transitions to both sides;

[0043] Specifically, the screw of the second homogenizing section 5 rotates, and the movable plate 502 rotates accordingly. When the movable plate 502 contacts the limit push plate 507, the movable plate 502 moves along the limit push plate 507. Since the elastic coefficient of the second spring 508 is greater than the elastic coefficient of the first spring 503, the first spring 503 is compressed, and the limit push plate 507 pushes the movable plate 502 to move radially inward along the screw first, and then moves radially outward until the movable plate 502 is disengaged from the limit push plate 507. In the above process, the linkage rack 504 moves along the limit inclined slide rail 501 and The relatively movable plate 502 moves along the axial direction of the screw, thereby driving the linkage gear 505 to rotate, and driving the stirring block 506 to rotate. The stirring block 506 stirs the fluid material to make the material evenly blended; it is worth noting that when the spiral groove edge of the screw contacts the limit push plate 507, the spiral groove edge will push the limit push plate 507 into the push plate slide groove 509, and the spring 2 508 is compressed until the limit push plate 507 is separated from the spiral groove edge, and the limit push plate 507 extends out of the push plate slide groove 509. Therefore, the limit push plate 507 will not affect the rotation of the screw.

[0044] like Figure 1-Figure 3 As shown, the screw of the second compression section 6 in each branch is connected to the screw of the second homogenizing section 5 through a universal shaft; the ends of the two branches merge, and the ends of the screws of the two second compression sections 6 both point to the confluence port; the second compression section 6 compresses the fluid material after homogenization by the first homogenizing section 4 and the second homogenizing section 5 again, and transports the fluid material to the extrusion port to ensure that the fluid material can be extruded evenly.

[0045] In this embodiment, since the first homogenizing section 4 and the second homogenizing section 5 will stir the fluid material, this process will reduce the viscosity of the fluid material. Too low viscosity will easily lead to film breakage during the subsequent stretching process. Therefore, the ambient temperature of the first homogenizing section 4 and the second homogenizing section 5 is lower than the ambient temperature of the feeding section 1 and the first compression section 2 to prevent the viscosity of the fluid material from further decreasing in the first homogenizing section 4 and the second homogenizing section 5, thereby reducing the viscosity drop (the decrease in the viscosity value of the material itself after being melted and extruded through the extruder).

[0046] In this embodiment, the granular material enters the feeding section 1 through the feeding port of the barrel 7; the feeding section 1 conveys the granular material to the first compression section 2, and heats the granular material at the same time, so that the granular material gradually melts into a fluid; the first compression section 2 extrude, stack, and compact the material, and the granular material completely melts into a fluid; when the fluid material passes through the vacuum conveying section 3, the vacuum machine extracts the moisture and volatiles generated after the material is melted at high temperature; the fluid material passes through the first homogenizing section 4 and the second homogenizing section 5 for homogenization; finally, the homogenized fluid material enters the second compression section 6 for re-compression and extrusion;

[0047] The split design can divide the fluid material into two parts, and perform vacuum treatment and homogenization treatment separately, making the treatment effect more complete and effective.

Claims

1. A split screw mechanism for preventing viscosity drop for a twin-screw extruder, characterized in that: The invention comprises a feeding section, a first compression section, a vacuum conveying section, a first homogenizing section, a second homogenizing section and a second compression section which are sequentially connected in the axial direction along the material transport direction in the barrel; the feeding section and the first compression section are both twin-screw structures, and the pitch of the feeding section is greater than the pitch of the first compression section; the screw mechanism after the first compression section adopts a split design, and the barrel is divided into two branches from the tail end of the first compression section, and each branch is sequentially connected along the material transport direction with a vacuum conveying section, a first homogenizing section, a second homogenizing section and a second compression section; the first homogenizing section, the second homogenizing section and the second compression section are all single-screw structures; the entire screw mechanism is placed in a high-temperature heating environment, wherein the ambient temperature of the first homogenizing section and the second homogenizing section is lower than the ambient temperature of the feeding section and the first compression section; The vacuum conveying section on the barrel is connected to the vacuum machine; the first homogenizing section is provided with a first homogenizing mechanism, and the second homogenizing section is provided with a second homogenizing mechanism; the second homogenizing mechanism includes a plurality of pairs of position-limiting inclined slide rails fixedly mounted on the spiral groove edge of the screw of the second homogenizing section and having an angle with the radial direction of the screw, a moving plate elastically connected to the screw in the radial direction through a spring 1, a linkage rack slidably mounted in the moving plate along the axial direction of the screw, a linkage gear rotatably mounted on the moving plate and meshing with the linkage rack, a stirring block fixedly mounted on the linkage gear, and a position-limiting push plate that slides and is elastically mounted on the barrel through a spring 2 and intermittently pushes the moving plate; The first homogenizing mechanism comprises a sliding frame slidably mounted on the screw of the first homogenizing section along the axial direction, and a position-limiting rotary slide rail fixedly mounted in the barrel; the sliding frame is slidably connected to the position-limiting rotary slide rail; a plurality of stirring support rods extending radially are fixedly arranged on the sliding frame along the spiral track of the screw; connecting slide rods are fixedly arranged at the front and rear ends of the sliding frame corresponding to the position-limiting rotary slide rails, and the connecting slide rods are slidably mounted on the position-limiting rotary slide rails at the corresponding ends; A relief opening is provided on the side of the spiral groove of the first homogenizing section screw corresponding to the stirring support rod; The end points of the movable plate are mounted on the limiting inclined slide rail in a chiming manner, and the elastic coefficient of the second spring is greater than the elastic coefficient of the first spring.

2. According to claim 1, a split screw mechanism for preventing viscosity drop for a twin-screw extruder, characterized in that: The two ends of the linkage rack are respectively in contact with the limiting inclined slide rails on both sides of the moving plate.

3. According to claim 1, a split screw mechanism for preventing viscosity drop for a twin-screw extruder, characterized in that: The two screws of the first compression section are connected with the screws of the first homogenization section in the two branches respectively through a universal shaft.

4. The split screw mechanism for preventing viscosity drop for a twin-screw extruder according to claim 1, characterized in that: The screw of the second compression section in each branch is connected with the screw of the second homogenization section through a universal shaft.

5. The split screw mechanism for preventing viscosity drop for a twin-screw extruder according to claim 1, characterized in that: The ends of the two branches of the barrel merge, and the ends of the screws of the two second compression sections both point to the confluence port.

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