Extruder screw, extruder and extrusion process

Abstract

Extruder screw (2), comprising: a transfer section (11a) which conveys continuously supplied materials; a melting and mixing section (11b) which continuously melts and mixes the conveyed materials; and a kneading section (11c) which continuously kneads raw materials obtained by melting and mixing the materials, wherein the transfer section (11a), the melting and mixing section (11b) and the kneading section (11c) are provided in a screw main body (11) which rotates about a straight axis (10), where a part of the screw main body (11) in which the kneading section (11c) is provided is composed of a rotary shaft (14) extending coaxially from the section provided with the melting and mixing section (11b) and cylindrical tubes (13) fitted into and supported by the rotary shaft (14), the cylindrical tubes (13) which are coaxially coupled to each other on the rotary shaft (14) have conveying sections (22) which convey the raw materials and blocking sections (23) which restrict the conveyance of the raw materials arranged alternately thereon, each of the barrier sections (23) has a path (37) and is arranged between two conveyor sections (22) adjacent to both sides of the barrier section (23), the path (37) is provided within the cylindrical tube (13) and has an inlet (38) and an outlet (40), wherein the entrance (38) in an outer peripheral surface of the cylindrical tube (13) in the conveying section (22) adjacent to the barrier section (23) is open from a base end side of the screw main body (11) in such a way as to force the raw materials, the conveyance of which is restricted by the barrier section (23) to increase pressure on the raw materials, to flow into the entrance (38), the path (37) is designed to force the raw materials flowing from the inlet (38) to flow to the outlet (40) in a direction same as a conveying direction of the conveying section (22), and the exit (40) in the peripheral surface of the cylindrical tube (13) in the conveying section (22) adjacent to the barrier section (23) is open from a tip end side of the screw main body (11).

Description

Background of the inventionTechnical field

[0001] The present invention relates to an extrusion technique capable of improving the degree of kneading without lengthening an extruder (screw). State of the art

[0002] Conventionally, an extrusion technique for improving the degree of kneading by utilizing the extension action imparted to raw materials when the raw materials pass from a wide portion through a narrow portion is known. For example, JP H07-227836 A and JP 2010-137405 A disclose an extrusion technique in which an extension action imparting the extension action to the raw materials at a tip of an extruder (screw) is additionally provided. Furthermore, JP 2013-123841 A discloses an extrusion technique for securing an extension action imparting the extension action to the raw materials at a tip of an extruder (screw). Furthermore, JP 2013-123841 A discloses an extrusion technique for securing an extension action imparting a flow having a high degree of extension between a pair of screws provided with spiral flight.

[0003] Another previously known design of an extruder screw is disclosed in JP S52-72 573 U. Description of the inventionTechnical problem

[0004] However, in the extrusion technique disclosed in JP H07-227836 A and JP 2010-137405 A, the entire extruder is elongated by an amount corresponding to the addition of the elongation-imparting mechanism. Specifically, paragraph

[0027] of JP 2010-137405 A discloses that the elongation effect is imparted to the raw materials by forcing the raw materials to pass through a gap between parallel opposing surfaces multiple times. Accordingly, further elongation of the entire extruder is unavoidable to realize such a specification.

[0005] Furthermore, the extrusion technique of JP 2013-123841 A includes, as raw materials to be conveyed by the pair of screws, the raw material flowing along the spiral flight while avoiding the extension conveying section, in addition to the raw material passing through the extension conveying section. Accordingly, it is unclear whether all the raw materials conveyed by the pair of screws pass through the extension conveying section in JP 2013-123841 A. In this case, it is necessary to secure the extension conveying section sufficiently long to force all the raw material to pass through the extension conveying section. However, this causes the extruder (screw) to be elongated by an amount corresponding to the extension of the extension conveying section.

[0006] The invention is therefore based on the object of providing an extrusion technique in which the screw itself has a function of imparting an elongation effect to the raw materials, the elongation effect being fully transmitted to all the raw materials to be conveyed by the screw and the degree of kneading of the raw material being improved without elongation of the extruder (screw). Solution to the problem

[0007] To achieve this object, an extruder screw according to claim 1, an extruder according to claim 6 and an extrusion method according to claim 7 are disclosed. Further preferred embodiments emerge from the dependent claims. Advantageous effects of the invention

[0008] According to the present invention, an extrusion technique for manufacturing a screw itself has the function of imparting the elongation effect to the raw materials, whereby the elongation effect is consistently imparted to all the raw materials conveyed by the screw, and the improvement of the kneading degree can be achieved without elongation of an extruder (screw). Short description of the drawings Fig. 1 is a transverse cross-sectional view showing an external structure of an extruder screw in an overall structure of a single-screw extruder according to one of the embodiments of the present invention. Fig. 2 is a transverse cross-sectional view showing an internal structure of the extruder screw in a kneading section in the single-screw extruder according to the embodiment of the present invention. Fig. 3 is a cross-sectional view along the line F3-F3 of Fig. 2 considered. Fig. 4 is an enlarged perspective view showing a part of an annular locking body of Fig. 2 shows. Fig. 5 is an enlarged fragmentary view showing a part of a structure of a path formed to extend along two pipes. Fig. 6 is a diagram schematically showing a flow state of the raw materials generated by the extruder screw. Fig. 7 is an enlarged partial view showing a part of the flow state of the raw materials in a cylinder of the extruder. Fig. Fig. 8 (A) is an enlarged partial view showing the structure of an input portion of the path in a modification example of the present invention, and Fig. 8 (B) is a cross-sectional view taken along the line F8B-F8B in Fig. 8 (A). Fig. 9 (A) is an enlarged partial view showing the structure of an output portion of the path in the modification example of the present invention, and Fig. 9 (B) is a cross-sectional view taken along the line F9B-F9B in Fig. 9 (A). Fig. 10 (A) is an enlarged partial view showing the structure of the input portion of the path in the modification example of the present invention, and Fig. 10 (B) is a cross-sectional view taken along the line F10B-F10B in Fig. 10 (A). Fig. 11 (A) is an enlarged partial view showing the structure of the exit portion of the path in the modification example of the present invention, and Fig. 11 (B) is a cross-sectional view taken along the line F11B-F11B in Fig. 11 (A). Fig. 12 (A) is an enlarged partial view showing the structure of the input portion of the path in the modification example of the present invention, and Fig. 12 (B) is a cross-sectional view taken along the line F12B-F12B in Fig. 12 (A). Fig. 13 (A) is an enlarged partial view showing the structure of the exit portion of the path in the modification example of the present invention, and Fig. 13 (B) is a cross-sectional view taken along the line F13B-F13B in Fig. 13 (A). Fig. 14 is a partial longitudinal view schematically showing the structure of the extruder screw in which a path is provided along the inner peripheral surface of a pipe forming a kneading section in a modification example of the present invention. Fig. 15 is a partial longitudinal view schematically showing the configuration of the extruder screw in which a path is provided along the outer peripheral surface of a rotating shaft forming a kneading section in the modification example of the present invention. Fig. 16 is a partial longitudinal view schematically showing the structure of the extruder screw in which a path is provided along a surface of a key constituting a kneading portion in the modification example of the present invention. Fig. 17 is a partial longitudinal view schematically showing the structure of the extruder screw in which a screw main body is formed of a shaft-like member in the modification example of the present invention. Fig. 18 is a partial transverse view showing the external configuration of an extruder screw in the overall structure of the twin-screw extruder according to the modification example of the present invention. Fig. 19 is a partial enlarged view showing a part of a structure of a locking portion configured with a worm gear in the modification example of the present invention. Description of the embodiments

[0009] One of the embodiments of the present invention will be described below with reference to the accompanying drawings.

[0010] Fig. 1 and Fig. 2 shows a structure of a single-screw extruder 1 according to the present embodiment. The single-screw extruder 1 includes an extruder screw 2 and a barrel 4 with a cylinder 3 in which the screw 2 is rotatably mounted.

[0011] A supply port 5 through which materials 6 such as thermoplastic resin are supplied is provided in one end of the drum 4. The supply port 5 penetrates the drum 4 to communicate with the cylinder 3. Further, a discharge port 7 is provided in the other end of the drum 4. The discharge port 7 is formed in a lid 8 to be coupled to the drum 4 to cover the opening in the other end of the drum 4. Kneaded materials produced by the extruder screw 2 are continuously extruded through the discharge port 7.

[0012] Further, the drum 4 is configured with a coolant path through which cooling water is caused to flow, a heater, a temperature sensor, and the like (all not shown). The inside of the cylinder 3 can be heated to a set temperature by controlling the heater to heat the drum 4. When the temperature of the drum 4 exceeds the set temperature, the inside of the cylinder 3 is cooled to the set temperature by flowing cooling water through the coolant path of the drum 4.

[0013] The extruder screw 2 extends straight from the base end to the tip, and its total length is set to a length corresponding to the total length of the cylinder 3 of the barrel 4. The extruder screw 2 can be arranged such that the screw 2 is rotatably inserted into the cylinder 3 of the barrel 4. The base end of the extruder screw 2 is positioned at one end side of the barrel 4 on which the feed port 5 is provided, and the tip of the extruder screw 2 is arranged at the other end side of the barrel 4 on which the discharge port 7 is provided, in a state where the extruder screw 2 is rotatably inserted into the cylinder 3 of the barrel 4.

[0014] A stopper portion 9 is coaxially provided at the base end of the extruder screw 2. The stopper portion 9 is configured to close the opening of the barrel 3 on the base end side of the extruder screw 2 in a state where the extruder screw 2 is rotatably inserted and arranged in the barrel 3 of the drum 4. The materials 6 to be supplied to the inside of the barrel 3 can thereby be prevented from leaking to the outside. The stopper portion 9 can be coupled to a rotating device such as a motor via a coupling (not shown). When the torque from the rotating device is transmitted to the stopper portion 9, the extruder screw 2 is rotated about a straight axis 10 extending from its base end to its tip.

[0015] Further, the extruder screw 2 includes a screw main body 11 that rotates integrally with the extruder screw 2. In the following descriptions, the rotation direction (left rotation or right rotation) of the screw main body 11 means the rotation direction (left rotation or right rotation) viewed from the base end of the screw main body 11, in other words, viewed from the supply port 5 of the barrel 4 in the direction of the discharge port 7. Likewise, the twisting direction (clockwise or counterclockwise) of each of the screw flights 12, 25, and 26 is the twisting direction (clockwise, counterclockwise) of each of the screw flights 12, 25, and 26 viewed from the base end side of the screw main body 11.

[0016] The screw main body 11 includes a transfer section 11a, a melting and mixing section 11b, and a kneading section 11c, in order from the base end to the tip of the screw main body 11. The transfer section 11a continuously conveys the materials 6 supplied from the supply port 5 to the inside of the cylinder 3 to the melting and mixing section 11b. The melting and mixing section 11b continuously melts and mixes the materials 6. Then, the materials 6 obtained by melting and mixing each of the materials 6 are continuously introduced into the kneading section 11c as raw materials for kneading. Desired kneaded materials are continuously produced in the kneading section 11c.

[0017] The part of the screw main body 11 in which the kneading section 11c is provided is formed not only by arranging sections (shearing action areas) that impart a shearing action to the raw materials, but also, in particular, by arranging sections (expansion action areas) that impart an expansion action to the raw materials at locations in the axial direction. The degree of dispersion of the raw materials is thereby improved, and as a result, kneaded materials excellent in the degree of kneading can be produced. Then, the kneaded materials produced in the cylinder 3 are continuously extruded through the discharge port 7.

[0018] A spirally twisted flight is continuously formed on the outer peripheral surfaces M1 and M2 of the screw main body 11, extending from the transfer section 11a to the melting and mixing section 11b. The flight 12 is configured to continuously convey each of the materials 6 supplied from the supply port 5 to the inside of the cylinder 3 from the transfer section 11a to the melting and mixing section 11b. For this reason, the flight 12 is twisted in a direction opposite to the rotation direction of the screw main body 11.

[0019] The drawings show the screw flight 12 in a case where each of the materials 6 is conveyed by the counterclockwise rotation of the screw main body 11. In this case, the twisting direction of the screw flight 12 is set to the clockwise direction, like a right-handed screw. When each of the materials 6 is conveyed by the clockwise rotation of the screw main body 11, the twisting direction of the screw flight 12 can be set to the counterclockwise direction, like a left-handed screw.

[0020] The outer peripheral surface M1 of the screw main body 11 in the transfer section 11a has a columnar shape, and a gap between the outer peripheral surface M1 and the inner surface 3s of the cylinder 3 is set to be wide. The outer peripheral surface M2 of the screw main body 11 in the melting and mixing section 11b has a shape that widens from the transfer section 11a to the kneading section 11c, and a gap between the outer peripheral surface M2 and the inner surface 3s of the cylinder 3 is set to continuously decrease from the transfer section 11a to the kneading section 11c.

[0021] Each of the materials 6 supplied from the supply port 5 to the cylinder 3 is conveyed through the screw flight 12 from the transfer section 11a to the melting and mixing section 11b by means of the screw flight 12 in a state where the extruder screw 2 is rotated counterclockwise. In the melting and mixing section 11b, each of the materials 6 is subjected to compression mainly from the narrowing gap while being heated by the heater, thereby forming a melted and mixed raw material for kneading. The raw materials are continuously conveyed from the melting and mixing section 11b to the kneading section 11c.

[0022] The part of the screw main body 11 in which the kneading section 11c is provided is composed of cylindrical tubes 13 and a rotary shaft 14 that supports the tubes 13. Also, the kneading section 11c includes an introduction section 15 for introducing the raw materials conveyed from the melting and mixing section 11b into the kneading section 11c. The introduction section 15 is formed to be adjacent to an end surface 16 of the melting and mixing section 11b. Details of the introduction section 15 will be described later.

[0023] The rotary shaft 14 is provided in a region extending from the tip of the screw main body 11 to the end surface 16 of the melting and mixing section 11b. The rotary shaft 14 extends straight from the base end to the tip, and the base end is coaxially connected to the end surface 16 of the melting and mixing section 11b. The rotary shaft 14 has a columnar shape, and its contour is set to be smaller than that of the end surface 16 of the melting and mixing section 11b.

[0024] Regarding the method of connecting the base end of the rotary shaft 14 to the end surface 16 of the melting and mixing section 11b, for example, any of the existing methods such as a method of coaxially and integrally forming the rotary shaft 14 together with the screw skin body 11 from the transmission section 11a to the melting and mixing section 11b, and a method of separately forming the screw main body 11 from the transmission section 11a to the melting and mixing section 11b and the rotary shaft 14 and then coaxially coupling the base end of the rotary shaft 14 to the end surface 16 of the melting and mixing section 11b can be appropriately selected.

[0025] As in Fig. 3 and Fig. As shown in Fig. 4, a pair of keys 17 are provided on an outer peripheral surface of the rotary shaft 14 as an example of a support structure that forces the rotary shaft to support the tubes 13. The keys 17 are fitted into a pair of groove portions 18 formed at positions offset from each other by 180° in the circumferential direction along the outer peripheral surface of the rotary shaft 14. Each of the groove portions 18 is formed by partially removing the outer peripheral surface of the rotary shaft 14 in the axial direction.

[0026] Furthermore, each of the tubes 13 is configured to force the rotating shaft 14 to coaxially penetrate the tubes 13 along their inner circumferential surfaces. Keyways 19 (also called keyways or keyways) are formed at positions circumferentially offset by 180° from each other on an inner circumferential surface of each of the tubes 13. The pair of keyways 19 are formed by partially cutting the inner circumferential surfaces of the tube 13 in the axial direction.

[0027] As in Fig. 1 to Fig. As shown in Fig. 4, the rotary shaft 14 is made to penetrate all the tubes 13 along the inner peripheral surfaces while aligning the keys 17 with the keyways 19. Thereafter, a fastening screw 21 is screwed through a collar 20 into the tip of the rotary shaft 14. At this time, all the tubes 13 are clamped between the tip collar 20 and the end surface 16 of the melting and mixing section 11b and are sandwiched by the clamping force, and are held in a state of being in close contact with each other without gaps by means of the forces exerted by the sandwiching.

[0028] All the tubes 13 are coaxially coupled to each other on the rotating shaft 14 through the support structure explained above, and each of the tubes 13 and the rotating shaft 14 are thereby integrally assembled. The screw main body 11 is formed as a rod-shaped member extending from the base end to the tip in the axial direction (longitudinal direction) by integrally assembling each of the tubes 13 and the rotating shaft 14.

[0029] Thus, each of the tubes 13 can be rotated around the axis 10 together with the rotating shaft 14, that is, the screw main body 11 can be rotated around the axis 10. Moreover, the base end of the screw main body 11 corresponds to the base end of the rotating shaft 14, and the tip of the screw main body 11 corresponds to the tip of the rotating shaft 14. In other words, the base end of the screw main body 11 corresponds to the base end of the extruder screw 2 corresponding to one end of the barrel 4, and the tip of the screw main body 11 corresponds to the tip of the extruder screw 2 corresponding to the other end of the barrel 4.

[0030] At this time, each of the tubes 13 serves as a structural element having an outer diameter D1 (see Fig. 3) of the screw main body 11 in the portion of the screw main body 11 where the kneading section 11c is provided. In the kneading section 11c, the outer diameters D1 of the tubes 13 coaxially coupled along the rotating shaft 14 are set to be equal to each other. The outer diameter D1 of the screw main body 11 (each tube 13) is defined as a diameter passing through the axis 10, which is a rotation center of the rotating shaft 14.

[0031] A segmented screw 2 in which the outer diameter D1 of the screw main body 11 (each tube 13) in the kneading section 11c is a fixed value is thereby formed. In the segmented screw 2, the screw elements can be held in any order and combination along the rotating shaft 14. Regarding the screw elements, for example, each of the tubes 13 on which at least parts of the screw flights 12, 25, and 26 described later are formed can be defined as a screw element.

[0032] Convenience, for example, in making changes and adjustments in the specifications or maintenance and service of the screw 2, can be remarkably improved by segmenting the screw 2.

[0033] In the present embodiment, the structure in which the tubes 13 and the rotary shaft 14 are fixed and held non-rotatably is not limited to the structure associated with the combination of the keys 17 and the keyways 19, but a wedge structure (not shown) may be used instead.

[0034] Furthermore, the segment-like screw 2 is coaxially housed in the cylinder 3 of the drum 4. Specifically, the screw main body 11, on which the screw elements are supported along the rotating shaft 14, is rotatably housed in the cylinder 3. In this state, a conveying path 29 for conveying the raw materials is formed between the outer peripheral surface of the screw main body 11 (tubes 13) and the inner surface 3s of the cylinder 3. The conveying path 29 has an annular cross-sectional shape in the radial direction of the cylinder 3 and extends in the axial direction along the cylinder 3.

[0035] In the present embodiment, the above-described introduction section 15, conveying sections 22 that convey the raw materials introduced through the introduction section 15, and barrier sections 23 that restrict the flow of the raw materials conveyed by the conveying sections 22 are provided in the part of the screw main body 11 where the kneading section 11c is provided. The conveying sections 42 and the barrier sections 43 are alternately arranged in the axial direction (longitudinal direction) of the screw main body 11 in the kneading section 11c.

[0036] In other words, the locking portion 23 is disposed on the base end side of the screw main body 11 in the kneading portion 11c. The locking portion 23 is also used as a constituent part of the introduction portion 15. The conveying portions 22 and the locking portions 23 are alternately arranged from this locking portion 23 toward the tip of the screw main body 11.

[0037] On the other hand, a discharge conveyor section 24 is arranged on the tip side of the screw main body 11 at the kneading section 11c. The discharge conveyor section 24 is configured to convey the kneaded materials kneaded in the cylinder 21a in the same direction as the conveying direction of the other conveyor sections 22.

[0038] A spirally twisted screw flight 25 is provided at each of the conveying sections 22. The screw flight 25 protrudes from the outer peripheral surface of the pipe 13 in the circumferential direction toward the conveying path 29. The screw flight 25 extends in a direction opposite to the direction of rotation of the screw main body 11 from the base end to the tip of the screw main body 11.

[0039] A spirally twisted screw flight 26 is provided on the discharge conveyor section 24. The screw flight 26 protrudes from the outer peripheral surface of the pipe 13 in the circumferential direction toward the conveyor path 29. The screw flight 26 is in a direction opposite to the direction of rotation of the screw main body 11.

[0040] When raw materials are kneaded by rotating the screw main body 11 counterclockwise, the screw flight 25 of each of the conveying sections 22 is twisted to convey the raw materials from the base end to the tip of the screw main body 11. In other words, the twisting direction of the screw flight 25 is set clockwise, similar to a right-hand screw.

[0041] Further, when the raw materials are kneaded by rotating the screw main body 11 counterclockwise, the screw flight 26 of each of the discharge conveyor sections 24 is rotated to convey the raw materials from the base end to the tip of the screw main body 11. In other words, the twisting direction of the screw flight 26 is set clockwise, similar to a right-hand screw.

[0042] In contrast, when raw materials are kneaded by rotating the screw main body 11 clockwise, the screw flight 25 of each of the conveying sections 22 is twisted to convey the raw materials from the base end to the tip of the screw main body 11. In other words, the twisting direction of the screw flight 25 is set counterclockwise, similar to a left-turning screw.

[0043] Further, when the raw materials are kneaded by rotating the screw main body 11 clockwise, the screw flight 26 of each discharge conveyor section 24 is twisted to convey the raw materials from the base end to the tip of the screw main body 11. In other words, the twisting direction of the screw flight 25 is set counterclockwise, similar to a left-turning screw.

[0044] An annular locking body 28, which is continuous in the circumferential direction along the outer peripheral surface of the screw main body 11, is provided at each of the locking portions 23. The annular locking body 28 includes a cylindrical surface 28s which is coaxial in the circumferential direction around the axis 10 (see Fig. 4). The cylinder surface 28s protrudes from the outer peripheral surface of the pipe 13 in the circumferential direction toward the conveying path 29.

[0045] In this case, a gap 27 (see FIG. 7) between an outer diameter portion 23s of each barrier portion 23 and the inner surface 3s of the cylinder 3 is desirably set to fall within a range of 0.05 mm or greater and 2 mm or less. Further, the gap 27 is more desirably set to fall within a range of 0.05 mm or greater and 0.7 mm or less. The conveyance of the raw materials through the gap 27 can thereby be securely restricted. Therefore, the raw materials do not overflow each of the barrier portions 23.

[0046] In each of the locking areas 23, a spirally twisted screw thread 41 can be provided instead of the annular locking body 28, as for example in Fig. 19. The screw flight 41 protrudes from the outer peripheral surface of the pipe 13 in the circumferential direction toward the conveying path 29. The screw flight 41 is twisted in the same direction as the rotation direction of the screw main body 11.

[0047] When raw materials are kneaded by rotating the screw main body 11 counterclockwise, the screw flight 41 of each of the conveying sections 23 is twisted to convey the raw materials from the base end to the tip of the screw main body 11. In other words, the twisting direction of the screw flight 41 is set counterclockwise, similar to a left-turning screw.

[0048] In contrast, when raw materials are kneaded by rotating the screw main body 11 clockwise, the screw flight 41 of each of the conveying sections 23 is twisted to convey the raw materials from the base end to the tip of the screw main body 11. In other words, the twisting direction of the screw flight 41 is set clockwise, similar to a right-hand screw.

[0049] At each locking portion 23, a twist of the screw flight 41 is set to be equal to or smaller than a twist of the screw flights 25 and 26 at the conveying portions 22 and 24. Further, a gap between an upper part of the screw flight 41 and the inner surface 3s of the cylinder 3 is set to fall within the above-explained range of the gap 27.

[0050] Incidentally, the length of each of the conveying sections 22 and 24 in the axial direction of the screw main body 11 is adjusted according to, for example, the type of raw materials, the degree of kneading of the raw materials, the amount of kneaded materials produced per unit time, and the like. The conveying sections 22 and 24 denote regions where the screw flights 25 and 26 are formed at least on the outer peripheral surfaces of the tubes 13, but are not limited to regions between a starting point and an end point of the screw flights 25 and 26.

[0051] In other words, areas remote from the flights 25 and 26 of the outer peripheral surfaces of the tubes 13 can be considered as the conveying sections 22 and 24. For example, if a cylindrical spacer or a cylindrical collar is disposed at a position adjacent to the tubes 13 having the flights 25 and 26, the spacer or the collar, the spacer or the collar can also be included in the conveying sections 22 and 24.

[0052] In addition, the lengths of the barrier portions 23 in the axial direction of the screw main body 11 are appropriately set according to, for example, the type of raw material, the degree of kneading of the raw material, the production amount of the kneaded material per unit time, and the like. The barrier portions 23 serve to restrict the flow of the raw materials conveyed by the conveying portions 22. The barrier portions 23 are adjacent to the conveying portions 22 on the downstream side in the conveying direction of the raw materials and are configured to prevent raw materials fed from the conveying portions 22 from being conveyed through the above-mentioned gap 27.

[0053] Each of the screw flights 25, 26, and 41 and the annular locking body 28 (cylinder surface 28s) protrudes from the outer peripheral surfaces of the tubes 13 having outer diameters D1 equal to each other toward the conveying path 29 in the part of the above-mentioned screw 2 (screw main body 11) in which the kneading section 11c is provided. For this reason, the outer peripheral surface in the circumferential direction of each of the tubes 13 defines a core diameter of the screw 2 in the kneading section 11c. The core diameter coincides with the above-mentioned outer diameter D1 and is maintained at a fixed value over the entire length of the portion of the screw main body 11 in which the kneading section 11c is provided.

[0054] In this case, the core diameter of the kneading section 11c can be made larger to reduce the core depth. According to such a structure, the kneaded materials produced by the screw 2 can be stably discharged from the discharge port 7. The core depth can be defined as a height dimension in the radial direction from the outer peripheral surface of the screw main body 11 (pipe 13) to the outer diameter of each of the screw flights 25, 26, and 41 and the annular locking body 28 (cylindrical surface 28s).

[0055] Further, axially extending paths 37 are provided within the part of the screw main body 11 where the kneading section 11c is provided. The paths 37 are arranged in the axial direction and the circumferential direction of the screw main body 11. The figures show, as an example, a structure in which two paths 37 arranged at regular intervals in the circumferential direction of the screw main body 11 are arranged at regular intervals in the axial direction.

[0056] Each path 37 is provided at a position eccentric from the axis 10, which is the rotation center of the screw 2. In other words, the paths 37 are spaced from the axis 10. For this reason, the paths 37 rotate around the axis 10 in conjunction with the rotation of the screw main body 11.

[0057] The shape of the path 37 can be set, for example, as a circular shape, a rectangular shape, an elliptical shape, and the like as its cross-sectional shape if the shape allows the flow of raw materials. The figures show, as an example, the paths 37 having portions formed in circular holes. In this case, an inner diameter (bore) of the holes is desirably greater than or equal to 1 mm and less than 6 mm. More desirably, the inner diameter (bore) of the holes is greater than or equal to 1 mm and less than 5 mm.

[0058] In the screw main body 11 (kneading section 11c), the tubes 13 of the conveying sections 22 and the blocking sections 23 have tubular wall surfaces 30 (see Fig. 3 to Fig. 5) that define the paths 37, which are the holes. In other words, the paths 37 are the hole consisting only of cavities. The wall surfaces 30 continuously surround the hollow paths 37 in the circumferential direction. The paths 37 are formed as cavities that only allow the flow of raw materials. In other words, no other elements constituting the screw main body 11 exist in the paths 37. In this case, the wall surfaces 30 rotate around the axis 10 without rotating around the axis 10 when the screw main body 11 rotates.

[0059] When the raw materials conveyed through the conveying path 29 through each of the conveying sections 22 flow through the paths 37 according to the paths 37, the "expansion effect" generated when the raw materials pass from a wide section (conveying path 29) to a narrow section (paths 37) can be effectively imparted to the raw materials. Therefore, the paths 37 are defined as sections (expansion effect areas) that impart the expansion effect to the raw materials.

[0060] A specific structure of the paths 37 described above is described below.

[0061] As in Fig. 2 and Fig. As shown in Fig. 5, the paths 37 are arranged in the axial direction (longitudinal direction) and spaced from each other within the screw main body 11 (kneading section 11c), in which the conveying sections 22 and the barrier sections 23 are alternately arranged in the axial direction (longitudinal direction) in the extruder screw 2 according to the present embodiment. The raw materials, whose conveyance is restricted by the barrier sections 23, flow to each of the paths 37. In each of the paths 37, the raw materials flow in the same direction as the conveying direction of the conveying sections 22. The screw 2, which has the screw main body 11 (kneading section 11c), which has the function of continuously imparting the shearing action and expansion action to the raw materials, is achieved by such a screw structure.

[0062] When a barrier section 23 and two conveyor sections 22 are arranged adjacent to both sides of the barrier section 23, a path 37 is provided in the above-explained screw structure via the tube 13 of the barrier section 23 and the tubes 13 of two conveyor sections 22. This structure can be recognized as a structurally integrated unit.

[0063] The screw main body 11 (kneading section 11c) according to the present embodiment is formed by arranging the units in the axial direction (longitudinal direction). In the above-explained screw structure, a conveying section 22 and a barrier section 23 are adjacent to each other in a pipe 13 (see Fig. 4). The above-mentioned units can be arranged in the axial direction (longitudinal direction) by arranging the tubes 13 in the axial direction (longitudinal direction). Thus, a unidirectional screw structure in which raw materials never pass the section they once passed can be achieved by tracking the specific passage of the raw materials.

[0064] In other words, the above-described unit can be recognized as a functionally integrated module. As functions of one module, for example, the function of imparting a shearing action to the raw materials, the function of imparting an elongating action to the raw materials, the function of damming the conveyance of the raw materials by the barrier section 23, the function of guiding the raw materials with a pressure increased by the barrier section to the paths 37, the function of forming a raw material reservoir R in which the filling rate of the raw materials is 100% immediately before the barrier section 23, and the like are assumed.

[0065] Furthermore, the path 37 includes an entrance 38, an exit 40, and a path main body 39 connecting the entrance 38 and the exit 40 in the above-mentioned screw structure. The entrance 38 and the exit 40 are provided on both sides of a barrier region 23 in a unit as described above. In other words, the entrance 38 is provided on one side of the path main body 39 (the portion closer to the base end of the screw main body 11). The exit 40 is provided on the other side of the path main body 39 (the portion closer to the tip of the screw main body 11).

[0066] Specifically, the entrance 38 is opened to the outer peripheral surface of the conveying section 22 in the conveying section 22 adjacent to the blocking section 23 from the base end side of the screw main body 11. In contrast, the exit 40 is opened to the outer peripheral surface of the conveying section 22 in the conveying section 22 adjacent to the blocking section 23 from the tip side of the screw main body 11.

[0067] In this case, the positions where the entrance 38 and the exit 40 are formed can be freely set within the range of the conveying section 22. For example, both the entrance 38 and the exit 40 can be closer to the barrier section 23 or farther from the barrier section 23. Furthermore, either the entrance 38 or the exit 40 can be arranged closer to the barrier section 23 or farther from the barrier section 23. The figures show, as an example, a structure in which the entrance 38 is provided closer to the barrier section 23, while the exit 40 is provided farther from the barrier section 23.

[0068] The entrance 38 is a hole drilled from the outer peripheral surface of the tube 13 (screw main body 11) in the kneading section 11c in the radial direction. The entrance 38 can be formed, for example, by machining using a drill. As a result, a bottom portion 38a of the entrance 38 is formed as an inclined surface cut into a conical shape by the tip of the drill. In other words, the conical bottom portion 38a is an inclined surface that widens toward the outer peripheral surface of the screw main body 11.

[0069] The exit 40 is a hole drilled from the outer peripheral surface of the tube 13 (screw main body 11) in the kneading section 11c in the radial direction. The exit 40 can be formed, for example, by machining using a drill. As a result, the bottom portion 40a of the entrance 40 is formed as an inclined surface cut into a conical shape by the tip of the drill. In other words, the conical bottom portion 38a is an inclined surface that widens toward the outer peripheral surface of the screw main body 11.

[0070] The path main body 39 is formed along two tubes 13 adjacent to each other. The path main body 39 consists of first and second sections 39a and 39b. The first section 39a is formed in one of the tubes 13. The second section 39b is formed within the other tube 13.

[0071] In the tube 13, the first portion 39a is formed along a surface opposite the blocking portion 23. The first portion 39a extends parallel along the axis 10. One end of the first portion 39a is open in an end face 13a of the tube. The other end of the first portion 39a is closed at an inner portion (i.e., an end wall 13b) of the tube 13. Further, the other end of the first portion 39a is connected to the above-mentioned inlet 38 to communicate with the inlet 38.

[0072] In the other pipe 13, the second portion 39b is formed along the region opposite the conveying portion 22. The second portion 39b extends parallel along the axis 10. One end of the second portion 39b is open at an end surface 13a of the pipe 13. In contrast, the other end of the second portion 39b is closed at an inner portion (i.e., an end wall 13b) of the pipe 13. Further, the other end of the second portion 39b is connected to the above-mentioned outlet 40 to communicate with the outlet 40.

[0073] The path main body 39 can be formed by fixing the pipe 13 in which the first portion 39a is formed and the pipe 13 in which the second portion 39b is formed in the axial direction, and bonding their end surfaces 13a in close contact with each other. In this state, the path main body 39 extends linearly and continuously in the axial direction of the screw main body 11 without branching in the middle. Both sides of the path main body 39 are connected to the entrance 38 and the exit 40 to communicate with the entrance 38 and the exit 40.

[0074] In this case, the bore of the path main body 39 may be set to be smaller than or equal to the bores of the inlet 38 and the outlet 40. In either case, the path cross-sectional area defined by the bore of the path main body 39 is set to be much smaller than the annular cross-sectional area of ​​the above-mentioned conveying path 29 in the radial direction.

[0075] In the present embodiment, each of the tubes 13 on which at least parts of the screw flights 25, 26 and 41 and the annular locking body 28 are formed can be recognized as a screw element corresponding to each of the conveying sections 22 and 24 and the locking section 23.

[0076] Accordingly, the portion of the screw main body 11 in which the kneading section 11c is provided can be formed by sequentially arranging the tubes 13 on the outer periphery of the rotating shaft 14 as the screw elements. For this reason, the conveying sections 22 and 24 and the locking sections 23 can be exchanged and rearranged, and the work for exchange and rearrangement can be easily performed, for example, in accordance with the degree of kneading of the raw materials.

[0077] Further, the path main body 39 of each of the paths 37 is formed, and the entrance 38 and the exit 40 of the path 37 are integrally connected by the path main body 39 by extending the tubes 13 serving as screw elements in the axial direction and bringing the tubes 13 into close contact with each other. Accordingly, to form the path 37 in the screw main body 11, processing can be performed to provide the path 37 for each of the tubes 13 with a length sufficiently shorter than the entire length of the screw main body 11 (kneading section 11c). Therefore, processing and handling in forming the path 37 can be facilitated.

[0078] Further, the above-explained introducing section 15 in the screw structure of the extruder screw 2 has a structure for continuously introducing the raw materials conveyed from the melting and mixing section 11b to the kneading section 11c. Fig. 1 and Fig. 2 shows an example of such an introduction structure. The introduction section 15 is configured to have an introduction pipe 13p instead of the conveying section 22 on the upstream side in the above-mentioned unit. An entrance 38 communicating with the path 37 is formed on the outer peripheral surface of the introduction pipe 13p. The introduction pipe 13p is disposed adjacently between a barrier section 23 provided at the base end of the screw main body 11 in the kneading section 11c and the end surface 16 of the melting and mixing section 11b.

[0079] According to such an introduction structure, the pressure of the raw materials conveyed from the melting and mixing section 11b is increased by restricting their conveyance by the barrier section 23. The raw materials forced to flow into the inlet 38 of the introduction pipe 13p pass through the path 37 (path main body 39), and then flow out the outlet 40 of the conveying section 22 on the downstream side. The raw materials conveyed from the melting and mixing section 11b can thereby be continuously introduced into the kneading section 11c.

[0080] Next, the process of kneading raw materials by the single-screw extruder screw 2 will be explained below. In this functional explanation, the "outer peripheral surface of the screw main body 11" refers to the outer peripheral surface of the screw main body 11 in the circumferential direction, excluding both end surfaces in the longitudinal direction. Furthermore, in this functional explanation, it is assumed that kneading is performed while the extruder screw 2 rotates counterclockwise in the left direction at a rotation speed of, for example, 50 rpm to 100 rpm.

[0081] As in Fig. 6 and Fig. 7, materials 6 (see Fig. 1) is fed from the feed port 5 into the cylinder 3 in a state where the extruder screw 2 is rotated counterclockwise.

[0082] The pellet-like resin fed into the cylinder 3 is conveyed from the transfer section 11a through the screw flight 12 to the melting and mixing section 11b. In the melting and mixing section 11b, the resin is mainly subjected to pressure from the continuously narrowed gap while being heated by the heater. As a result, the raw materials formed by melting and mixing two types of resins are conveyed from the melting and mixing section 11b.

[0083] The raw materials conveyed from the melting and mixing section 11b are introduced into the kneading section 11c via the introduction section 15. The pressure of the raw materials conveyed from the melting and mixing section 11b is increased by restricting its conveyance by the barrier sections 23, and the raw materials flow into the inlet 38 of the introduction pipe 13p, pass through the path main body 39, and flow out the outlet 40 of the conveying section 22 on the downstream side.

[0084] The raw materials flowing out of the outlet 40 are continuously supplied to the outer peripheral surface of the screw main body 11 at the kneading section 11c. The supplied raw materials are conveyed from the base end toward the tip of the screw main body 11 in the direction S1 through the screw flight 25 of the conveying section 22.

[0085] The "shearing effect" caused by the speed difference between the screw flights 25 of the conveying sections 22 rotating along the conveying path 29 and the inner surface 3s of the cylinder 3 is imparted to the raw materials, and the stirring effect caused by the rotation of the spiral screw flights 25 themselves is also imparted to the raw materials while the raw materials are conveyed in the direction S1. The kneading degree of the raw materials is thereby increased.

[0086] The conveyance of the raw materials conveyed in the direction S1 is restricted by the barrier sections 23. In other words, the barrier sections 23 act to press the raw materials from the tip toward the base end of the screw main body 11 in the direction opposite to the direction S1. As a result, the flow of the raw materials is dammed by the barrier sections 23.

[0087] At this time, the pressure exerted on the raw materials is increased by damming the flow of the raw materials. More specifically, the filling rate of the raw materials at a part of the conveying path 29 corresponding to the conveying section 22 of the screw main body 11 (kneading section 11c) is Fig. 7 is expressed by a gradation. In other words, the filling rate of the raw materials in the conveying path 29 becomes higher when the clay is thicker. As can be seen from Fig. As is clearly shown in Figure 7, the filling rate of the raw materials becomes higher as the raw materials are produced closer to the barrier areas 23 in the conveying path 29 corresponding to the conveying sections 22. The filling rate of the raw materials is 100% just before the barrier section 23.

[0088] For this reason, a "raw material reservoir R" in which the filling rate of raw materials is 100% is formed immediately before the barrier sections 23. In the raw material reservoir R, the pressure of the raw materials is increased by damming the raw material flow. The raw materials, the pressure of which is increased, continuously flow into the path main body 39 from the inlet 38 opened on the outer peripheral surface of the conveying sections 22 (pipes 13), and then flow from the base end toward the tip of the screw main body 11 through the interior of the path main body 39 in a direction S2, that is, in the same direction as the direction S1.

[0089] As explained above, the path cross-sectional area defined by the bore of the path main body 39 is much smaller than the annular cross-sectional area of ​​the conveying path 29 in the radial direction of the cylinder 3. The expanded area based on the bore of the path main body 39 is much smaller than the expanded area of ​​the annular conveying path 29, depending on the other aspect. For this reason, when the raw materials flow from the entrance 38 into the path main body 39, the raw materials are radically narrowed, thereby imparting the "expansion effect" to the raw materials.

[0090] Furthermore, because the path cross-sectional area is sufficiently smaller than the annular cross-sectional area, the raw materials collected in the raw material reservoir R do not disappear. In other words, the raw materials collected in the raw material reservoir R partially flow continuously into the entrance 38. During this time, new raw materials are supplied to the barrier sections 23 through the screw flights 25 of the conveying sections 22. As a result, the filling rate in the raw material reservoir R just before the barrier sections 23 is always maintained at 100%. At this time, even if the discharge amount of the raw materials conveyed by the screw flights 25 is slightly varied, the variation state is absorbed by the raw materials remaining in the raw material reservoir R. The raw materials can thereby be continuously and stably supplied to the path main body 39.The expansion effect can thus be imparted uninterruptedly and continuously to the raw materials in the path main body 39.

[0091] The raw materials flowing through the path main body 39 flow from the exit 40 onto the outer peripheral surface of the screw main body 11 (kneading section 11c). Since the above-mentioned conveying sections 22 and the barrier sections 23 are alternately arranged in the axial direction on the screw main body 11 (kneading section 11c), the raw materials in the cylinder 3 are continuously conveyed from the base end to the tip of the screw main body 11 (kneading section 11c) in a state where the shear flow and the extension flow are repeated by repeating a sequence of the shear flow and the extension flow. The kneading degree of the raw materials is thereby increased.

[0092] The conveyed kneaded materials are conveyed in the direction S1 through the screw flight 26 of the discharge conveyor section 24 and continuously from the discharge opening 7 (see Fig. 1 and Fig. 2) extruded.

[0093] As described above, according to the present embodiment, the kneading degree of the raw materials can be improved without elongating the screw 2 or the single-screw extruder by allowing the extruder screw 2 to have the function of exerting the stretching action on the raw materials.

[0094] According to the present embodiment, the shearing action and the stretching action can be continuously imparted to the raw materials multiple times. Therefore, the number of times and the duration of the shearing action and the stretching action can be increased. As a result, the degree of kneading can be controlled more precisely than in the conventional method.

[0095] According to the present embodiment, in an existing extruder screw having a feeding section, a compression section, and a measuring section from the base end toward the tip and lacking paths through which the raw materials flow, the feeding section is replaced by a transfer section 11a, the compression section by a melting and mixing section 11b, and the measuring section by a kneading section 11c in which a combination of the conveying sections 22, the barrier sections 23, and the paths 37 is arranged. The existing extruder screw can thereby exhibit both the function of imparting the shearing action and the function of imparting the stretching action. As a result, an extruder screw in which the handling facility is maintained and increased can be implemented.

[0096] In addition, the extruder screw 2 according to the present embodiment includes a unidirectional screw structure in which raw materials at the kneading section 11c do not flow through the same section again when the specific flow is followed. For this reason, the stretching effect can be uniformly imparted to all raw materials in the kneading section 11c. Furthermore, according to the unidirectional screw structure, the specific flow of raw materials is not mixed with the flow of raw materials that differ in the kneading state existing before or after the specific flow of raw materials. All raw materials can thereby be equally and uniformly kneaded.

[0097] According to the present embodiment, a segmented screw 2 that can hold screw elements in an arbitrary order and combination is implemented by setting the outer diameter D1 of the screw main body 11 (each tube 13) to a fixed value, that is, setting the core diameter of the screw 2 to a fixed value at the portion where the kneading section 11c is provided. Convenience in, for example, changes or adjustments in specifications or maintenance and service of the screw 2 can be remarkably improved by segmenting the screw 2.

[0098] Furthermore, according to the present embodiment, the stretching action can be uniformly, stably, and efficiently transmitted to the raw materials passing through the paths 37 (path main body 39) by setting the sectional area of ​​the paths 37 (path main body 39) much smaller than the sectional area of ​​the conveying path 29 configured to convey the raw materials.

[0099] While one of the embodiments of the present invention has been described, the present invention is not limited to the embodiment, and the following modified examples are also included in the technical scope of the present invention.

[0100] In the embodiment described above, Fig. 2 and Fig. 5, the paths 37 in which both ends of the path main body 39 are connected to the entrance 38 and the exit 40 at positions offset from the bottom parts 38a and 40a of the entrance 38 and the exit 40. However, the relationship in connection of the path main body 39 with the entrance 38 and the exit 40 is not limited to the above-described embodiment, but the following relationship in connection with the technical scope of the present invention is also included.

[0101] Fig. 8 to Fig. 13 shows, as examples, the path 37 in which both sides of the path main body 39 are connected to the bottom portions 38a and 40a of the entrance 38 and the exit 40. Specifically, one of the ends of the path main body 39, that is, the other end of the first portion 39a, is connected to the bottom portion 38a of the entrance 38. Further, the other side of the path main body 39, that is, the other end of the second portion 39b, is connected to the bottom portion 40a of the exit 40.

[0102] Fig. 8 (A) and (B) and Fig. 9 (A) and (B) show the path 37 according to a first modified example. In the path 37, an end face of one side (the other end of the first portion 39a) of the path main body 39 is connected to the bottom portion 38a of the entrance 38. The opening 38b communicating with the path main body 39 (the first portion 39a) is formed in the bottom portion 38a. In contrast, an end face of the other side (the other end of the second portion 39b) of the path main body 39 is connected to the bottom portion 40a of the exit 40. The opening 40b communicating with the path main body 39 (second portion 39b) is formed in the bottom portion 40a.

[0103] An opening 38b of the inlet 38 is formed in a region opposite the bottom portion 38a that widens toward the outer peripheral surface of the screw main body 11. In contrast, an opening 40b of the outlet 40 is formed in a region opposite the bottom portion 40a that widens toward the outer peripheral surface of the screw main body 11.

[0104] In this case, the raw materials flowing into the entrance 38 are guided to the opening 38b along the slope of the bottom portion 38a. As a result, all the raw materials continuously and evenly flow into the path main body 39 without stagnating inside the entrance 38. The raw materials that have passed through the path main body 39 then flow into the exit 40. The raw materials flowing into the exit 40 are guided to the outer peripheral surface of the screw main body along the slope of the bottom portion 40a. As a result, all the raw materials continuously and evenly flow to the outer peripheral surface of the screw main body 11 without stagnating inside the exit 40.

[0105] Thus, the stretching effect can be imparted to the raw materials passing through the path 37 without any omission, uniformly and continuously, while preventing the raw materials from stagnating locally within the path 37.

[0106] Fig. 10 (A) and (B) and Fig. 11 (A) and (B) show the path 37 according to a second modified example. In the path 37, the part closer to an end surface 39s of one side of the path main body 39 (the other end of the first portion 39a), that is, the portion in front of the end surface 39s, is connected to the bottom portion 38a of the entrance 38. Two openings 38b communicating with the path main body 39 (first portion 39a) are formed in the bottom portion 38a. In contrast, the part closer to an end surface 39s of the other side of the path main body 39 (the other end of the second portion 39b), that is, the portion in front of the end surface 39s, is connected to the bottom portion 40a of the exit 40. Two openings 40b communicating with the path main body 39 (second portion 39b) are formed in the bottom portion 40a.

[0107] Two openings 38b of the entrance 38 are formed in a region opposite the bottom portion 38a, which widens toward the outer peripheral surface of the screw main body 11. In contrast, two openings 40b of the exit 40 are formed in a region opposite the bottom portion 40a, which widens toward the outer peripheral surface of the screw main body 11. Since the function and advantage of the path 37 according to the second modified example are the same as those of the path 37 according to the first modified example, their explanations are omitted.

[0108] In the above-explained embodiment and the modified examples, it is assumed that the opening direction of the inlet 38 and the outlet 40 is a direction perpendicular to the axis 10, but is not limited thereto. For example, as in Fig. 12 (A) and (B) and Fig. 13 (A) and (B), the opening directions of the entrance 38 and the exit 40 can be set in the directions (directions indicated by dashed lines) intersecting the axis 10. In this case, both sides of the path main body 39 can be opened in directions, and the entrances 38 and 38-1 and the exits 40 and 40-1 can thereby be provided.

[0109] Furthermore, the inlet 38 may preferably be formed so as to be recessed from the outer peripheral surface of the screw main body 11. This allows the raw materials to flow more easily into the inlet 38.

[0110] Furthermore, in the above-explained embodiment and modified examples, the path 37 having the path main body 39 parallel to the axis 10 is assumed, but the path 37 is not limited thereto, and the path 37 having the path main body 39 intersecting the axis 10 is also included in the technical scope of the present invention. For example, the other side of the path main body 39, one side of which is connected to the inlet 38, is directly opened to the outer peripheral surface of the screw main body 11 (pipe 13) by removing the outlet 40. In this case, the path main body 39 is formed with a gradient that increases from one side to the other.

[0111] According to such a structure, the raw materials flowing from the entrance 38 into the path main body 39 receive a centrifugal action during the rotation of the screw main body 11, thereby flowing more smoothly through the path main body 39 and flowing to the outer peripheral surface of the screw main body 11 (pipe 13). At this time, the stretching effect is imparted to the raw materials more efficiently and continuously. As a result, the degree of kneading of the raw materials can be further increased.

[0112] In addition, in the above-explained embodiment, the paths 37 (specifically, the path main bodies 39) are formed inside the screw main body 11 (pipe 13) at the kneading portion 11c, but instead, the paths 37 (path main bodies 39) may be formed at the boundary portion between each of the pipes 13 and the rotary shaft 14 when the rotary shaft 14 is caused to penetrate along the inner peripheral surface of each of the pipes 13 constituting the screw main body 11 (kneading portion 11c). Fig. 14 to Fig. 17 show the structure of the section according to Fig. 3 as the structure of the present modified example.

[0113] The paths 37, which in Fig. 14 are composed of wall surfaces 30a formed by depressing portions of the inner peripheral surfaces of the tubes 13 in the shape of a depression in the axial direction. In this case, the paths 37 surrounded by the wall surfaces 30a and the outer peripheral surface of the rotary shaft 14 can be defined by driving the rotary shaft 14 to penetrate the inner peripheral surfaces of the tubes 13.

[0114] The paths 37, which in Fig. 15 are composed of wall surfaces 30a formed by depressing portions of the outer peripheral surface of the rotary shaft 14 into a concave shape in the axial direction. In this case, the paths 37 surrounded by the wall surfaces 30b and the inner peripheral surface of the tube 13 can be defined by forcing the rotary shaft 14 to penetrate the inner peripheral surfaces of the tubes 13.

[0115] The paths 37, which in Fig. 16 are composed of wall surfaces 30c formed by depressing portions of the outer peripheral surfaces of the keys 17 in the shape of a depression in the axial direction. In this case, the paths 37 surrounded by the wall surfaces 30c and the groove bottom surfaces of the keyways 19 can be defined by causing the rotary shaft 14 to penetrate the inner peripheral surfaces of the tubes 13.

[0116] Since the wall surfaces 30a, 30b, and 30c can be formed into a recessed shape in one of the paths 37 only by machining the outwardly exposed portions, the molding work can be easily performed. In this case, for example, various shapes such as a semicircular shape, a triangular shape, an elliptical shape, a rectangular shape, and the like can be used as the shapes of the concave wall surfaces 30a, 30b, and 30c.

[0117] Further, in the above-described embodiment, the part of the screw main body 11 where the kneading section 11c is provided is composed of the tubes 13 and the rotary shaft 14, but instead, the screw main body 11 (kneading section 11c) may be composed of a straight shaft-like member 2t as shown in Fig. 11. In this case, the above-mentioned conveying sections and locking sections are provided on the outer peripheral surface of the screw main body 11 (kneading section 11c), and the above-mentioned paths 37 are provided inside the screw main body 11 (kneading section 11c). The figure shows, as an example, a pair of paths 37 provided at positions eccentric from the axis 10 and defined by cylindrical wall surfaces 30d, but the arrangement of each of the paths 37 is not limited to this.

[0118] Furthermore, in the above-explained embodiment, the single-screw extruder 1 in which one extruder screw 2 is rotatably inserted into the cylinder 3 of the barrel 4 is adopted, but instead, the technical idea of ​​the present invention can also be applied to a twin-screw extruder 34 in which two extruder screws 31 are rotatably inserted into the cylinder 33 of the barrel 32, and the same advantages can be obtained.

[0119] Fig. 18 shows an example of the twin-screw extruder 34. The figure shows only one extruder screw 31 of two extruder screws 31. The other extruder screw is not shown because it is hidden behind the extruder screw 31.

[0120] In the twin-screw extruder 34, two extruder screws 31 can rotate in the same direction in engagement with each other. Similar to the above-mentioned embodiment, the screw main body 11 is provided on each of two extruder screws 31 to rotate integrally with the screw 31. The transfer section 11a, the melting and mixing section 11b, and the kneading section 11c are formed between the screw main bodies 11 in order from the base end to the tip of the screw main body 11 in a state where the extruder screws 31 are engaged with each other.

[0121] The transfer section 11a continuously feeds the materials 6 fed from the feed port 5 into the cylinder 33 to the melting and mixing section 11b. A spiral flight 35 is continuously formed on the outer peripheral surface of each of the screw main bodies 11 in the transfer section 11a. The flight 35 is configured to continuously feed each of the materials fed from the feed port 5 into the cylinder 33 from the transfer section 11a to the melting and mixing section 11b. For this reason, the flight 35 is twisted opposite to the rotation direction of the screw bodies 11.

[0122] The melting and mixing section 11b continuously melts and mixes each of the materials 6 conveyed from the transfer section 11a. Each of the screw main bodies 11 in the melting and mixing section 11b is configured to have disks 36 adjacent in the axial direction. The disks 36 are arranged in a state where the phase difference is applied to the adjacent disks 36.

[0123] Similar to the above-described embodiment, the conveying sections 22 and the locking sections 23 are arranged alternately in the axial direction in each of the screw bodies 11 in the kneading section 11c. On the drum 4, an inner surface 33s of the cylinder 33 is formed to have a shape that can accommodate both of the two extruder screws 31 meshing with each other and simultaneously rotate the extruder screws 31 in the same direction. The other constituent elements are the same as those of the above-described embodiment and are therefore not explained.

[0124] According to such a twin-screw extruder 34, the materials 6 fed from the feed port 5 into the cylinder 33 are continuously conveyed from the transfer section 11a to the melting and mixing section 11b in a state where two extruder screws 31 are conveyed in the same direction at a rotation speed of, for example, 100 rpm to 300 rpm. Each of the materials 6 is continuously melted and mixed in the melting and mixing section 11b. At this time, the melted and mixed materials 6 become raw materials for kneading, which are conveyed from the melting and mixing section 11b to the kneading section 11c. The conveyed raw materials are introduced into the kneading section 11c through the above-mentioned introduction section 15 and then become kneaded materials with an increased degree of kneading and are continuously extruded from the discharge port 7.

[0125] When the conveying efficiency of feeding the raw materials from the melting and mixing section 11b to the introduction section 15 on the twin-screw extruder 34 is insufficient, a raw material feeding mechanism is preferably provided between the melting and mixing section 11b and the introduction section 15. Regarding the raw material feeding mechanism, for example, a pipe 13 may be prepared in which the same screw flight as the screw flight 35 provided on the transfer section 11a is formed, and such a barrel 13 may be inserted between the melting and mixing section 11b and the introduction section 15. The raw materials can thereby be sufficiently fed from the melting and mixing section 11b to the introduction section 15.

[0126] In the embodiment described above, the technical idea (extrusion technique for improving the degree of kneading) of the present invention is applied to the kneading of materials 6, but is not limited thereto, and the technique is also applicable to a case where the generation of minute remelted parts is prevented or the generation of uneven parts with a minute resin temperature is prevented when one kind of material is melted. List of reference symbols 2 extruder screws 10 axis 11 Snail main body 11a Transmission section 11b Melting and mixing section 11c Kneading section 12 worm gear 13 pipe 14 Rotating shaft 15 Introductory section 22 conveyor section 23 restricted section 24 discharge conveyor section 25 and 26 worm gear 27 gap 28 annular locking body 29 funding path 37 Path 38 Entrance 39 Path main body 40 Exit

Claims

[1] Extruder screw (2), comprising: a transfer section (11a) which conveys continuously supplied materials; a melting and mixing section (11b) which continuously melts and mixes the conveyed materials; and a kneading section (11c) which continuously kneads raw materials obtained by melting and mixing the materials, wherein the transfer section (11a), the melting and mixing section (11b) and the kneading section (11c) are provided in a screw main body (11) which rotates about a straight axis (10), where a part of the screw main body (11) in which the kneading section (11c) is provided is composed of a rotary shaft (14) extending coaxially from the section provided with the melting and mixing section (11b) and cylindrical tubes (13) fitted into and supported by the rotary shaft (14), the cylindrical tubes (13) which are coaxially coupled to each other on the rotary shaft (14) have conveying sections (22) which convey the raw materials and blocking sections (23) which restrict the conveyance of the raw materials arranged alternately thereon, each of the barrier sections (23) has a path (37) and is arranged between two conveyor sections (22) adjacent to both sides of the barrier section (23), the path (37) is provided within the cylindrical tube (13) and has an inlet (38) and an outlet (40), wherein the entrance (38) in an outer peripheral surface of the cylindrical tube (13) in the conveying section (22) adjacent to the barrier section (23) is open from a base end side of the screw main body (11) in such a way as to force the raw materials, the conveyance of which is restricted by the barrier section (23) to increase pressure on the raw materials, to flow into the entrance (38), the path (37) is designed to force the raw materials flowing from the inlet (38) to flow to the outlet (40) in a direction same as a conveying direction of the conveying section (22), and the exit (40) in the peripheral surface of the cylindrical tube (13) in the conveying section (22) adjacent to the barrier section (23) is open from a tip end side of the screw main body (11). [2] The extruder screw (2) according to claim 1, wherein the part of the screw main body (11) in which the kneading section (11c) is provided is configured to have an outer diameter at a fixed value over a complete length of the part. [3] The extruder screw (2) according to claim 1, wherein a bore of the path (37) is set to be equal to or smaller than a bore of the entrance (38) of the path (37). [4] Extruder screw (2) according to claim 1, wherein a bore of the path (37) is set to be greater than or equal to 1mm and less than 6mm. [5] Extruder screw (2) according to claim 1, wherein the screw main body extends from a base end connected to a rotating device to a tip in an axial direction, a screw flight (12, 25, 26) which is spirally twisted along the outer peripheral surface of the screw main body (11) is provided on the conveying section (22), and the screw flight (12, 25, 26Pfa) is twisted from the base end to the tip of the screw main body (11) in a direction opposite to a rotational direction of the screw main body (11) as viewed from the base end side. [6] Extruder with the extruder screw (2) according to one of claims 1 to 5, wherein the extruder comprises: a drum with a cylinder in which the extruder screw (2) is rotatably inserted; a feed opening provided on the drum through which materials are fed to the cylinder; and a discharge opening provided in the drum through which the kneaded materials produced by the screw are continuously extruded. [7] An extrusion method for kneading raw materials with the extruder screw (2) according to any one of claims 1 to 5, and continuously producing and extruding kneaded materials, wherein in the kneading section, the raw materials conveyed along the outer peripheral surface of the screw main body (11) flow through the path (37) and then return to an outer peripheral surface of the screw while continuously extruding the kneaded materials. [8] Extrusion method according to claim 7, wherein in the kneading section (11c) the conveyance of the raw materials conveyed along the outer peripheral surface of the screw main body (11) is restricted by the barrier portion (23) provided in the kneading portion (11c), and the pressure on the raw materials is thereby increased, and the raw materials whose pressure has been increased flow from the inlet (38) into the path (37). [9] The extrusion method according to claim 8, wherein in the kneading section (11c), the raw materials flowing from the inlet (38) into the path (37) flow through the inside of the path (37) in a direction same as the conveying direction executed by the conveying section (22). [10] The extrusion method according to claim 9, wherein in the kneading section (11c), the raw materials passing through the path (37) flow from the exit (40) to the outer peripheral surface of the screw main body (11) at a position offset from the conveying section (22) at which the entrance (38) is open.

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