Extruder vent stuffer and extruder

Abstract

This vent stuffer 20 for an extruder according to one embodiment has a cylinder 21 having a cylinder hole 30a, and a screw 23a disposed inside the cylinder hole 30a. An inner wall 31 of the cylinder hole 30a has an upper surface part 31a and a lower surface part 31b, and the screw 23a is positioned between the upper surface part 31a and the lower surface part 31b. A clearance C1 between the screw 23a and the upper surface part 31a is larger than a clearance C2 between the screw 23a and the lower surface part 31b.

Description

Technical Field

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[0001] The present invention relates to a vent stuffer for an extruder and an extrusion apparatus.

Background Art

[0002] An extruder that melts, kneads, or thermally decomposes raw materials and materials and extrudes them from a cylinder is known. Patent Document 1 describes an extruder equipped with a vent stuffer. The vent stuffer is a degassing device that removes gas from the cylinder of the extruder. The vent stuffer includes a cylinder connected to the cylinder of the extruder and a screw disposed within the cylinder.

[0003] <{0000012}The gas generated within the cylinder of the extruder flows into the cylinder of the vent stuffer, is recovered through the cylinder of the vent stuffer, or is released into the atmosphere. Also, a part of the raw materials and materials that flow out from the cylinder of the extruder and into the cylinder of the vent stuffer is stopped within the cylinder of the vent stuffer by the screw of the vent stuffer or returned to the cylinder of the extruder.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] It is required to prevent the raw materials and materials from blowing out from their respective cylinders in the vent stuffer for an extruder and the extruder.

[0006] Other problems and novel features will become apparent from the description of this specification and the accompanying drawings.

Means for Solving the Problems

[0007] According to one embodiment, the vent stuffer for an extruder includes a cylinder having a cylinder bore and a screw positioned within the cylinder bore. The inner wall of the cylinder bore has an upper and a lower portion, and the screw is located between the upper and lower portions. The clearance between the screw and the upper portion is greater than the clearance between the screw and the lower portion. [Effects of the Invention]

[0008] According to one embodiment, the blowing out of raw materials or other materials from the extruder vent stuffer or the extruder cylinder is prevented. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram showing the configuration of an extrusion apparatus according to one embodiment. [Figure 2] This is a cross-sectional view of the extrusion apparatus along line AA in Figure 1. [Figure 3] This is an enlarged cross-sectional view along line XX in Figure 2. [Figure 4] This is an enlarged cross-sectional view along the YY line in Figure 2. [Figure 5] This is an enlarged cross-sectional view along the ZZ line in Figure 2. [Figure 6] This is a cross-sectional view showing the height of the internal space of a cylinder according to one embodiment. [Figure 7] This is a cross-sectional view showing the relationship between the maximum diameter of the main screw and the maximum diameter of the screw in one embodiment. [Figure 8] This is a cross-sectional view showing a chamber and its vicinity according to one embodiment. [Figure 9] This is another cross-sectional view showing a chamber and its vicinity according to one embodiment. [Modes for carrying out the invention]

[0010] Hereinafter, one embodiment will be described in detail with reference to the drawings. In all drawings used to illustrate the embodiment, the same reference numerals will be used for equipment and components that have the same or substantially the same function. Furthermore, equipment and components that have already been described will not be described again in principle.

[0011] <Extruder configuration> Figure 1 is a schematic diagram showing the configuration of the extrusion apparatus 1 according to this embodiment. The extrusion apparatus 1 includes an extruder body 10 and an extruder vent stuffer 20. In the following description, the extruder vent stuffer 20 may be abbreviated as "vent stuffer 20".

[0012] The extruder 1 according to this embodiment can process waste plastics by the following process. More specifically, the extruder 1 according to this embodiment can recycle waste plastics by the following process.

[0013] First, the crushed waste plastic is supplied to the extruder body 10. More specifically, the waste plastic is supplied into the cylinder 11 through a raw material supply port 12 located at or near the rear end of the cylinder 11. Although not shown in the illustration, a hopper into which the waste plastic is fed is connected to the raw material supply port 12.

[0014] The waste plastic supplied to the extruder body 10 is, for example, plastic fragments discarded as household waste or industrial waste and crushed by a crusher. In the following description, the waste plastic supplied to the extruder body 10 may be referred to as "raw material".

[0015] The raw material supplied to the extruder body 10 is kneaded and conveyed toward the tip of the cylinder 11. More specifically, the raw material supplied into the cylinder 11 is melted and kneaded as it is moved forward by the rotation of a screw located inside the cylinder 11.

[0016] The raw material (kneaded material / melted resin) kneaded by the extruder main body 10 is extruded to the outside through a die head attached to the tip of the cylinder 11. The kneaded material is formed into a strand shape (string shape, rope shape) by passing through the nozzle of the die head.

[0017] The strand-shaped kneaded material extruded from the die head is cut by a cutting device (pelletizer). Viewed from another perspective, the strand-shaped kneaded material extruded from the die head is divided into pellets. As a result, resin pellets of a desired size (length and thickness) are obtained.

[0018] In the above process, gas may be generated in the cylinder 11 of the extruder main body 10. For example, volatile gas may be generated during the kneading and melting of the raw material. In particular, waste plastic often contains moisture and a large amount of gas may be generated.

[0019] The vent staffer 20 includes a cylinder 21 connected to the cylinder 11 of the extruder main body 10, and extracts gas from the cylinder 11 of the extruder main body 10. In the following description, the cylinder 11 of the extruder main body 10 may be referred to as the "main cylinder 11" to distinguish it from the cylinder 21 of the vent staffer 20.

[0020] The main cylinder 11 of the extruder main body 10 and the cylinder 21 of the vent staffer 20 communicate with each other. Therefore, the gas generated in the main cylinder 11 flows into the cylinder 21 of the vent staffer 20, and in some cases, a part of the kneaded material or particles (hereinafter sometimes collectively referred to as "ejecta") may flow in together with the gas.

[0021] Therefore, a screw is provided inside the cylinder 21 of the vent stuffer 20. The ejected material that flows from the main cylinder 11 into the cylinder 21 is stopped inside the cylinder 21 or returned to the main cylinder 11 by the rotation of the screw provided inside the cylinder 21. In the following description, the screw provided in the extruder body 10 may be referred to as the "main screw" to distinguish it from the screw provided in the vent stuffer 20.

[0022] Although not shown in the diagram, the extruder body 10 is placed on a bed. On the other hand, the vent stuffer 20 is placed on a support base 22 to match the height of the extruder body 10. However, there are also embodiments in which the vent stuffer 20 is equipped with support parts or support legs instead of the support base 22.

[0023] <Extruder body> Next, the extruder body 10 will be described in more detail. Figure 2 is a cross-sectional view of the extruder 1 along line AA in Figure 1. Note that the support base 22 shown in Figure 1 is omitted in Figure 2.

[0024] As shown in Figures 1 and 2, the extruder body 10 includes a main cylinder 11, a raw material supply port 12, main screws 13a and 13b, and a drive unit 14. Alternatively, the extruder body 10 is a twin-screw extruder equipped with two parallel screws.

[0025] The main cylinder 11 is formed by multiple blocks arranged in a row. More specifically, the main cylinder 11 is formed by seven blocks 15a, 15b, 15c, 15d, 15e, 15f, and 15g arranged in a row.

[0026] Each of the blocks 15a, 15b, 15c, 15d, 15e, 15f, and 15g is provided with a through hole. The through holes in each of the blocks 15a to 15g communicate with each other, forming a cylinder bore 16 inside the main cylinder 11.

[0027] The cylinder bore 16 includes a cylinder bore 16a where the main screw 13a is located, and a cylinder bore 16b where the main screw 13b is located. The cylinder bore 16a and the cylinder bore 16b are parallel to each other and communicate with each other.

[0028] Between cylinder bore 16a and cylinder bore 16b, there are two opposing projections 17. One projection 17 protrudes downward, and the other projection 17 protrudes upward. In other words, the main cylinder 11 is spectacle-shaped. Alternatively, the top and bottom surfaces of the cylinder bore 16 are not flat.

[0029] The drive unit 14 includes a motor and a reduction gear. The main screws 13a and 13b are rotationally driven by the driving force output from the motor and input via the reduction gear.

[0030] The raw material fed into the hopper falls into the cylinder hole 16 through the raw material supply port 12. The raw material that falls into the cylinder hole 16 is kneaded and carried forward by the main screws 13a and 13b that rotate within the cylinder hole 16. At the same time, the raw material is melted by the heat emitted from the heater installed in the main cylinder 11 and the heat generated by shear heating.

[0031] The raw material supply port 12 is located on the upper surface of the last block 15g, and the drive unit 14 is positioned further rearward from the block 15g.

[0032] <Overview of Bent Stuff> Figure 3 is an enlarged cross-sectional view along the XX line in Figure 2. Figure 4 is an enlarged cross-sectional view along the YY line in Figure 2. Figure 5 is an enlarged cross-sectional view along the ZZ line in Figure 2.

[0033] The ventstaffer 20 comprises a cylinder 21, screws 23a and 23b, a drive unit 24, and a chamber 25. Alternatively, the ventstaffer 20 is a twin-screw degassing device with two parallel screws.

[0034] <Cylinder> The cylinder 21 of the vent stuffer 20 is connected to one of the blocks that make up the main cylinder 11 of the extruder body 10. More specifically, the cylinder 21 is connected to the side of block 15c. Alternatively, the cylinder 21 of the vent stuffer 20 is perpendicular to the main cylinder 11 of the extruder body 10.

[0035] In other embodiments, the cylinder 21 of the vent stuffer 20 may be connected to the upper surface of block 15c or another block.

[0036] <Cylinder bore> The cylinder 21 of the vent staff 20 has a cylinder bore 30 that communicates with the cylinder bore 16 of the main cylinder 11. As mainly shown in Figure 4, the cylinder bore 30 includes a cylinder bore 30a where a screw 23a is located and a cylinder bore 30b where a screw 23b is located.

[0037] Cylinder bore 30a and cylinder bore 30b are parallel to each other and communicate with each other. Furthermore, cylinder bore 30a and cylinder bore 30b have the same cross-sectional shape and cross-sectional area. More specifically, cylinder bore 30a and cylinder bore 30b have cross-sectional shapes that are symmetrical with respect to the virtual straight line VL shown in Figure 4.

[0038] Each cylinder bore 30a, 30b has an inner wall 31 including an upper surface 31a, a lower surface 31b, and a side surface 31c. Screw 23a is located between the upper surface 31a and the lower surface 31b of the inner wall 31 of cylinder bore 30a. Screw 23b is located between the upper surface 31a and the lower surface 31b of the inner wall 31 of cylinder bore 30b.

[0039] From another perspective, the upper surface 31a and the lower surface 31b of the inner wall 31 of the cylinder bore 30a face each other with the screw 23a in between. Similarly, the upper surface 31a and the lower surface 31b of the inner wall 31 of the cylinder bore 30b face each other with the screw 23b in between.

[0040] The side portion 31c of cylinder bore 30a connects one side of the upper portion 31a and one side of the lower portion 31b of cylinder bore 30a. Similarly, the side portion 31c of cylinder bore 30b connects one side of the upper portion 31a and one side of the lower portion 31b of cylinder bore 30b. As a result, the side portion 31c of cylinder bore 30a and the side portion 31c of cylinder bore 30b face each other with screws 23a and 23b in between.

[0041] From another perspective, the upper surface 31a of the cylinder hole 30a forms the ceiling surface of the cylinder hole 30a, the lower surface 31b forms the bottom surface of the cylinder hole 30a, and the side surface 31c forms the inner surface of the cylinder hole 30a. Similarly, the upper surface 31a of the cylinder hole 30b forms the ceiling surface of the cylinder hole 30b, the lower surface 31b forms the bottom surface of the cylinder hole 30b, and the side surface 31c forms the inner surface of the cylinder hole 30b.

[0042] The upper surfaces 31a of each cylinder bore 30a and 30b are flat. Furthermore, the upper surface 31a of cylinder bore 30a and the upper surface 31a of cylinder bore 30b form a continuous, seamless plane. Alternatively, the upper surfaces 31a of cylinder bore 30a and the upper surface 31a of cylinder bore 30b are continuous, forming a flat ceiling surface of cylinder bore 30.

[0043] The lower surfaces 31b of each cylinder bore 30a and 30b are curved. More specifically, the lower surface 31b of cylinder bore 30a is a curved surface that follows the screw 23a, and the lower surface 31b of cylinder bore 30b is a curved surface that follows the screw 23b.

[0044] Between the lower surface 31b of cylinder bore 30a and the lower surface 31b of cylinder bore 30b, there is a mountain-shaped projection 32 that protrudes upward. Alternatively, the bottom surface of cylinder bore 30 has a sharp projection 32 that protrudes toward the ceiling. In other words, the ceiling surface of cylinder bore 30 is flat, while the bottom surface of cylinder bore 30 is not. Note that the virtual straight line VL shown in Figure 4 is also a vertical line passing through the apex of the projection 32.

[0045] <Connection hole> As shown in Figure 2, the main cylinder 11 of the extruder body 10 is provided with a connection hole 18 that connects the main cylinder 11 to the cylinder 21 of the vent stuffer 20. The connection hole 18 is provided in the block 15c to which the cylinder 21 is connected. The connection hole 18 penetrates the side wall of the block 15c and connects to the cylinder hole 16 and the cylinder hole 30.

[0046] As shown in Figures 3 and 4, the connection hole 18 and the cylinder hole 30 have the same cross-sectional shape and area. The tips of the screws 23a and 23b protruding from the cylinder 21 of the vent stuffer 20 are inserted into the connection hole 18. More specifically, the tip of screw 23a protruding from cylinder hole 30a is inserted into one side of the connection hole 18 that continues from cylinder hole 30a, and the tip of screw 23b protruding from cylinder hole 30b is inserted into the other side of the connection hole 18 that continues from cylinder hole 30b.

[0047] From another perspective, the screws 23a and 23b of the venting staff 20 straddle the cylinder 21 and the main cylinder 11 (see Figure 2).

[0048] <Clearance> As shown in Figure 4, the clearance C1 between the screw 23a and the upper surface 31a of the cylinder bore 30a is greater than the clearance C2 between the screw 23a and the lower surface 31b of the cylinder bore 30a. Similarly, the clearance C1 between the screw 23b and the upper surface 31a of the cylinder bore 30b is greater than the clearance C2 between the screw 23b and the lower surface 31b of the cylinder bore 30b. Alternatively, the clearance C1 between the screws 23a, 23b and the ceiling surface of the cylinder bore 30 is greater than the clearance C2 between the screws 23a, 23b and the bottom surface of the cylinder bore 30.

[0049] The above-mentioned relationship between clearance C1 and clearance C2 (C1 > C2) is always maintained regardless of the rotation angle of screws 23a and 23b. Furthermore, this relationship (C1 > C2) is maintained throughout the entire length of cylinder 21. Moreover, the same or substantially the same relationship is maintained within the connecting hole 18, which has the same cross-sectional shape and cross-sectional area as cylinder hole 30.

[0050] Figure 6 is a cross-sectional view showing the internal height of the cylinder 21. In this embodiment, the above-mentioned relationship between clearance C1 and clearance C2 (C1 > C2) is achieved by flattening the ceiling surface of the cylinder bore 30. Alternatively, by flattening the ceiling surface of the cylinder bore 30, the internal height of the cylinder 21 is increased.

[0051] More specifically, the distance Fd between the upper surface 31a and the lower surface 31b of the cylinder bore 30a shown in Figure 6 is set to be 1.1 times or more the maximum diameter (peak diameter / long diameter) d of the screw 23a. Alternatively, the ratio of the distance Fd to the maximum diameter d (Fd / d) is set to be 1.1 or more.

[0052] Furthermore, the distance Fd between the upper surface 31a and the lower surface 31b of the cylinder bore 30b, which is not shown in Figure 6, is set to be 1.1 times or more the maximum diameter (peak diameter) d of the screw 23b.

[0053] As previously described, the upper surface 31a of each cylinder hole 30a, 30b forms the ceiling surface of the cylinder hole 30, and the lower surface 31b of each cylinder hole 30a, 30b forms the bottom surface of the cylinder hole 30. Therefore, the distance Fd between the upper surface 31a and the lower surface 31b corresponds to the height of the internal space of the cylinder 21.

[0054] In this embodiment, the internal space height of the cylinder 21 is set to a height that satisfies the condition (Fd / d≧1.1), and the centers of the screws 23a and 23b are offset downward with respect to the center of the cylinder bore 30.

[0055] From another perspective, in this embodiment, a larger space is secured above the screws 23a and 23b in the cylinder bore 30 than below the screws 23a and 23b. Therefore, the flow velocity of the gas flowing from the cylinder bore 16 into the cylinder bore 30 via the connection hole 18 is reduced, or at least its acceleration is suppressed. As a result, the ejection material flowing from the main cylinder 11 into the cylinder 21 is prevented or suppressed from being blown out of the cylinder 21.

[0056] Furthermore, any ejected material that flows into cylinder 21 along with the gas flow is either stopped within cylinder 21 by the rotating screws 23a and 23b, or returned to the main cylinder 11.

[0057] Here, from the viewpoint of slowing down the gas flow, it is preferable to increase the space around the screws 23a and 23b (the gap between the cylinder bore 30 and the screws 23a and 23b). Specifically, it is preferable to increase the above ratio (Fd / d). However, according to the inventors' studies, when the above ratio (Fd / d) exceeds 2.0, the gas flow velocity becomes almost constant. Furthermore, if the opposing distance Fd is increased to increase the above ratio (Fd / d), there is a concern that the strength and durability of the cylinder 21 will decrease, and there is also a concern that the cylinder 21 will become larger. From this viewpoint, it is preferable that the ratio (Fd / d) is between 1.1 and 2.0, and more preferably between 1.5 and 2.0.

[0058] Furthermore, even if clearance C1 and clearance C2 are the same, the gas flow will slow down if the space around screws 23a and 23b expands. However, if the space around screws 23a and 23b is too large, the transport capacity of screws 23a and 23b may decrease. In other words, the ability to retain the ejected material in cylinder 21 or return it to main cylinder 11 may decrease.

[0059] From the standpoint of maintaining and improving the conveying capacity of screws 23a and 23b, it is preferable that the clearance C2 be as small (narrow) as possible. In other words, it is preferable to achieve the desired ratio (Fd / d) by minimizing clearance C2 while maximizing clearance C1.

[0060] In this embodiment, flattening the ceiling surface of the cylinder bore 30 contributes to achieving the desired ratio (Fd / d) by minimizing the clearance C2 and maximizing the clearance C1. However, flattening the bottom surface of the cylinder bore 30 is not ruled out.

[0061] On the other hand, the gas flow that enters the cylinder bore 30, particularly the flow of volatile gases, passes through the upper part of the cylinder bore 30. In contrast, most of the ejected material that enters the cylinder bore 30 falls to the lower part of the cylinder bore 30 due to its own weight. Therefore, from the viewpoint of maintaining the conveying capacity of screws 23a and 23b and slowing down the gas flow, it is preferable to achieve the desired ratio (Fd / d) by minimizing clearance C2 and maximizing clearance C1. To this end, it is effective to make the top surface of the cylinder bore 30 flat and the bottom surface curved.

[0062] <Ensuring clearance through screw diameter> The above relationship between clearance C1 and clearance C2 (C1 > C2) can also be achieved by reducing the diameters of screws 23a and 23b. Figure 7 is a cross-sectional view showing the relationship between the maximum diameter D of the main screws 13a and 13b of the extruder body 10 and the maximum diameter d of the screws 23a and 23b of the vent stuffer.

[0063] It is clear that if the maximum diameter d of the screw 23a shown in Figure 7 is reduced, the clearance C1 will increase. Alternatively, reducing the maximum diameter d of the screw 23a will create a larger space above the screw 23a in the cylinder bore 30.

[0064] However, if the maximum diameter d of screw 23a is too small, the conveying capacity of screw 23a will be insufficient. Therefore, when attempting to achieve the above-mentioned size relationship (C1 > C2) by reducing the diameter of screw 23a, the maximum diameter d of screws 23a and 23b is preferably 0.2 times or more and 0.8 times or less, and more preferably 0.4 times or more and 0.8 times or less, the maximum diameter D of main screws 13a and 13b.

[0065] <Chamber> Figure 8 is a cross-sectional view showing the chamber 25 and its vicinity. The chamber 25 has a cylindrical buffer chamber 40 and an exhaust pipe 41 extending from the buffer chamber 40. An opening 43 communicating with the cylinder hole 30 is provided at the bottom of the buffer chamber 40, and the exhaust pipe 41 is connected to the vacuum pump P.

[0066] The gas generated in the main cylinder 11 passes through the cylinder 21 (cylinder bore 30) to the bottom of the opening 43 and flows into the buffer chamber 40 from the opening 43. Subsequently, the gas is drawn out of the buffer chamber 40 via the exhaust pipe 41.

[0067] In this case, to prevent the ejected material that reaches below the opening 43 along with the gas from flowing out of the buffer chamber 40, it is effective to enlarge the area of ​​the opening 43. Alternatively, to prevent the ejected material from flowing into the exhaust pipe 41 via the buffer chamber 40, it is effective to enlarge the area of ​​the opening 43.

[0068] The gas and ejected material flow through the cylinder bore 30 from the front end to the rear end along the axial direction of the screws 23a and 23b, reaching the opening 43. Therefore, in order to prevent the ejected material from flowing out, it is effective to enlarge the area of ​​the opening 43 by increasing the length L shown in Figure 8. The length L shown in Figure 8 is the length along the axial direction of the screws 23a and 23b from one side (front end) to the other side (rear end) of the opening 43.

[0069] Figure 9 is a cross-sectional view showing the chamber 25 and its vicinity with an enlarged opening 43. As shown in Figure 9, by enlarging the length L of the opening 43, the probability that ejected material reaching the opening 43 will fall into the cylinder bore 30 by its own weight without flowing into the buffer chamber 40 increases. Also, the probability that ejected material that has flowed into the buffer chamber 40 will fall into the cylinder bore 30 by its own weight increases. Overall, the probability that ejected material will be sucked out of the buffer chamber 40 along with the gas is reduced.

[0070] From the viewpoint of enhancing the recovery effect of ejected material due to free fall as described above, it is preferable to make the length L 2.0 times or more the maximum diameter d of screws 23a and 23b, and more preferably 3.0 times or more.

[0071] Furthermore, when the ejection section is small (light), it is preferable to increase the length L to increase the possibility of the ejected material free-falling. On the other hand, when the ejection section is large (heavy), it is preferable to shorten the length L to increase the conveying capacity of screws 23a and 23b.

[0072] The present invention has been described in detail above based on embodiments and examples, but it goes without saying that the present invention is not limited to the above embodiments or examples, and can be modified in various ways without departing from the spirit of the invention.

[0073] For example, the applications of extruders are not limited to the processing of waste plastics. Extruders can be used for melting, kneading, and degassing various raw materials and substances.

[0074] The form of raw materials and materials processed by the extruder is not particularly limited. The extruder can process raw materials and materials in various forms, such as pellets, granules, and powders.

[0075] The screws on the extruder body and the extruder vent stuffer may be of the meshing type or the non-meshing type. However, the extruder body and the extruder vent stuffer are not limited to twin-screw types. [Explanation of Symbols]

[0076] 1…Extruder, 10…Extruder body, 11…Cylinder (main cylinder), 12…Raw material supply port, 13a,13b…Screw (main screw), 14…Drive unit, 15a~15g…Block, 16,16a,16b…Cylinder hole, 17…Protrusion, 18…Connection hole, 20…Extruder vent stuffer (vent stuffer), 21…Cylinder, 22…Support base, 23a,23b…Screw, 24…Drive unit, 25…Chamber, 30,30a,30b…Cylinder hole, 31…Inner wall, 31a…Top surface, 31b…Bottom surface, 31c…Side surface, 32…Protrusion, 40…Buffer chamber, 41…Exhaust pipe, 43…Opening, C1,C2…Clearance, d…Maximum diameter (peak diameter), D…Maximum diameter, Fd…Opposite spacing, P…Vacuum pump, VL…Imaginary straight line

Claims

1. Extruder venting stuffers, including the following: A cylinder having a cylinder bore, connected to the extruder body; and Screw, positioned in the cylinder bore, Here, The inner wall of the cylinder bore has an upper portion and a lower portion. The screw is located between the upper portion and the lower portion. The clearance between the screw and the upper portion is greater than the clearance between the screw and the lower portion. The screw includes a first screw and a second screw, The cylinder bore includes a first cylinder bore in which the first screw is located and a second cylinder bore in which the second screw is located. The upper surface of the first cylinder bore and the upper surface of the second cylinder bore are a series of planes, The lower surface of the first cylinder bore is a curved surface that follows the first screw, The lower surface of the second cylinder bore is a curved surface that follows the second screw.

2. In the extruder vent stuffer according to claim 1, An extruder vent staff, wherein the distance between the upper and lower portions is 1.1 times or more the maximum diameter of the screw.

3. In the extruder vent stuffer according to claim 1, An extruder venting staff, wherein the maximum diameter of the screw is 0.8 times or less the maximum diameter of the screw provided in the extruder body.

4. A vent stuffer for an extruder comprising the following: A cylinder having a cylinder bore, connected to the extruder body; Screw positioned within the cylinder bore; and A chamber positioned above the cylinder, Here, The chamber comprises a buffer chamber and an exhaust pipe extending from the buffer chamber. An opening communicating with the cylinder bore is provided at the bottom of the buffer chamber. The length of the screw along the axial direction from one side to the other of the opening is 2.0 times or more the maximum diameter of the screw.

5. Extruder including the following: Extruder body; and The extruder venting staff connected to the extruder body, Here, The extruder body comprises a main cylinder having a cylinder bore and a main screw positioned within the cylinder bore. The extruder vent stuffer comprises a cylinder having a cylinder bore connected to the main cylinder, and a screw positioned within the cylinder bore. The inner wall of the cylinder bore of the extruder vent stuffer has an upper portion and a lower portion. The screw of the extruder vent stuffer is located between the upper and lower portions. The clearance between the screw and the upper portion is greater than the clearance between the screw and the lower portion. The screw of the vent stuffer for the extruder includes a first screw and a second screw. The cylinder bore of the extruder vent stuffer includes a first cylinder bore where the first screw is located and a second cylinder bore where the second screw is located. The upper surface of the first cylinder bore and the upper surface of the second cylinder bore are a series of planes, The lower surface of the first cylinder bore is a curved surface that follows the first screw, The lower surface of the second cylinder bore is a curved surface that follows the second screw.

6. In the extrusion apparatus according to claim 5, An extruder in which the maximum diameter of the screw of the extruder vent stuffer is 0.8 times or less the maximum diameter of the main screw of the extruder body.

7. In the extrusion apparatus according to claim 5, The main cylinder of the extruder body is provided with a connection hole that connects the main cylinder to the cylinder of the extruder vent stuffer. The connection hole has the same cross-sectional shape and cross-sectional area as the cylinder hole of the extruder vent stuffer. An extrusion apparatus in which the tip of the screw of the extruder vent stuffer, which protrudes from the cylinder of the extruder vent stuffer, is inserted into the connection hole.

8. Extrusion apparatus comprising: Extruder body; and The extruder venting staff connected to the extruder body, Here, The extruder body comprises a main cylinder having a cylinder bore and a main screw positioned within the cylinder bore. The extruder vent stuffer comprises a cylinder having a cylinder bore connected to the main cylinder, a screw positioned within the cylinder bore, and a chamber positioned above the cylinder. The chamber comprises a buffer chamber and an exhaust pipe extending from the buffer chamber. An opening communicating with the cylinder bore is provided at the bottom of the buffer chamber. The length of the screw along the axial direction from one side to the other of the opening is 2.0 times or more the maximum diameter of the screw.

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