Extruder, extruder screw, and method for disassembling extruder screw

Abstract

To facilitate the disassembly of screws for an extruder.SOLUTION: The extruder includes a screw 3 housed within a cylinder. The screw 3 comprises a screw shaft 11, a plurality of screw pieces 12 attached to the screw shaft 11, and a screw cap attached to the tip of the screw shaft 11. The screw cap includes a bolt member 14, a cover member 15, and a threaded member 16. The bolt member 14 has a main body portion 14c inserted into a bore portion 11a of the screw shaft 11, a head portion 14a located outside the bore portion 11a, a protruding portion 14b extending from the head portion 14a, and a threaded bore portion 14d formed on the surface of the protruding portion 14b. The cover member 15 is positioned on the head portion 14a of the bolt member 14 such that the protruding portion 14b of the bolt member 14 fits into a recess portion of the cover member 15. The screw member 16 is inserted through a through hole in the cover member 15 into the screw hole portion 14d of the bolt member 14.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an extruder, a screw for an extruder, and a method for disassembling a screw for an extruder. [Background technology]

[0002] The extruder has a cylinder with a built-in screw. Resin material is introduced into the cylinder, where it is mixed and conveyed by the rotating screw and then extruded through a die attached to the tip of the cylinder.

[0003] For example, Japanese Patent Application Laid-Open No. 2023-151221 (Patent Document 1) describes a technique relating to a screw for an extruder. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-151221 Summary of the Invention [Problem to be solved by the invention]

[0005] An extruder screw has a screw shaft, multiple screw pieces attached to the screw shaft, and a screw cap attached to the tip of the screw shaft. When the extruder is operating, the screw cap comes into contact with the resin material inside the extruder cylinder. If the resin material in contact with the screw cap is a molten resin and the viscosity of the molten resin is relatively low, malfunctions in the screw cap are unlikely to occur. However, if the resin material in contact with the screw cap is an unmelted resin material with an extremely high viscosity, a load caused by the resin material may be applied to the screw cap, potentially causing malfunctions in the screw cap. If a malfunction occurs in the screw cap, it becomes difficult to remove the screw cap from the screw shaft during maintenance, making it difficult to disassemble or perform maintenance on the screw.

[0006] Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0007] According to one embodiment, the extruder includes a screw built into a cylinder. The screw has a screw shaft, a plurality of screw pieces attached to the screw shaft, and a screw cap attached to the tip of the screw shaft. The screw cap has a bolt member, a cover member, and a screw member. The bolt member has a body portion inserted into a hole in the screw shaft, a head portion positioned outside the hole, a protrusion portion protruding from the head portion, and a threaded hole portion formed in the surface of the protrusion portion. The cover member has a recess portion and a through hole. The cover member is arranged on the head of the bolt member so that the protrusion portion is fitted into the recess portion. The screw member is inserted into the threaded hole portion of the bolt member through the through hole of the cover member. [Effects of the Invention]

[0008] According to one embodiment, the disassembly work of the screw for the extruder can be easily performed. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is an explanatory diagram showing an extruder according to the present embodiment. [Figure 2] FIG. 2 is a side view of a screw provided in the extruder according to the present embodiment. [Figure 3] FIG. 3 is a partially exploded side view of the screw in FIG. 2. [Figure 4] FIG. 3 is a partially enlarged cross-sectional view showing an enlarged tip portion of the screw in FIG. 2. [Figure 5] FIG. 3 is a cross-sectional view of a screw cap provided on the screw of FIG. 2. [Figure 6] FIG. 6 is a cross-sectional view of the screw cap taken along line A1-A1 in FIG. 5. [Figure 7] FIG. 6 is a cross-sectional view of the screw cap taken along line A2-A2 in FIG. 5. [Figure 8] FIG. 6 is a plan view of the screw cap of FIG. 5. [Figure 9] FIG. 6 is a cross-sectional view of a bolt member that constitutes the screw cap of FIG. 5. [Figure 10] FIG. 10 is a plan view of the bolt member of FIG. 9. [Figure 11] FIG. 6 is a cross-sectional view of a cover member that constitutes the screw cap of FIG. 5. [Figure 12] FIG. 12 is a plan view of the cover member of FIG. [Figure 13] 5A to 5C are explanatory diagrams of a method for removing a screw cap in the present embodiment. [Figure 14] 5A to 5C are explanatory diagrams of a method for removing a screw cap in the present embodiment. [Figure 15] 4A to 4C are explanatory diagrams of a method for attaching a screw cap in the present embodiment. [Figure 16] FIG. 1 is a cross-sectional view of a screw cap of a study example. [Figure 17] FIG. 17 is a cross-sectional view of the screw cap of the study example taken along the line E1-E1 shown in FIG. 16. [Figure 18] FIG. 17 is a cross-sectional view of the screw cap of the study example taken along line E2-E2 in FIG. 16. [Figure 19] FIG. 1 is a plan view of a screw cap of a study example. [Figure 20] FIG. 10 is an explanatory diagram of a method for removing a screw cap in the study example. [Figure 21] FIG. 1 is an explanatory diagram of a problem with the screw cap of the study example. [Figure 22] 10A and 10B are explanatory diagrams illustrating the effect of the screw cap of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described in detail with reference to the drawings. In all drawings for explaining the embodiments, components having the same functions are designated by the same reference numerals, and repeated explanations thereof will be omitted. In the following embodiments, explanations of the same or similar parts will not be repeated unless particularly necessary.

[0011] (Embodiment) <Overall structure of extruder 1> FIG. 1 is an explanatory diagram (side view) showing an extruder 1 in this embodiment.

[0012] The schematic configuration of an extruder (resin extruder, extrusion device) 1 will be described with reference to Fig. 1. The extruder 1 shown in Fig. 1 has a cylinder (barrel) 2, a screw 3 rotatably arranged within the cylinder 2, a rotation drive mechanism 4 for rotating the screw 3 within the cylinder 2, a hopper (resin material input section, resin material supply section) 5 arranged on the upstream side (rear end side) of the cylinder 2, and a die (metal mold) 6 attached to the tip of the cylinder 2 on the downstream side.

[0013] The hopper 5 is connected to the upper surface of the cylinder 2, and a resin material (raw resin) can be supplied into the cylinder 2 via the hopper 5. The temperature of the cylinder 2 is controlled by a temperature adjustment mechanism (not shown), such as a heater.

[0014] Two screws 3 are rotatably (freely rotatably) inserted and built into the cylinder 2. For this reason, the extruder 1 can also be considered a twin-screw extruder. Within the cylinder 2, the two screws 3 are arranged to intermesh with each other and rotate. The extension direction (longitudinal direction, axial direction) of the cylinder 2 and the extension direction (longitudinal direction, axial direction) of the screws 3 within the cylinder 2 are the same, which is the X direction in this case.

[0015] In this embodiment, the case where the number of screws 3 in the cylinder 2 is two is described, but as another embodiment, the number of screws 3 in the cylinder 2 can also be one. However, when the number of screws 3 in the cylinder 2 is two, a larger spatial volume can be secured, and therefore, for the same screw diameter, a twin-shaft (two screws 3) can have a higher raw material supply capacity than a single-shaft (one screw 3).

[0016] The cylinder 2 is made up of multiple cylinder blocks, which are arranged and connected in a direction from upstream to downstream (X direction). Therefore, the cylinder 2 extends in a direction from upstream to downstream. Of the multiple cylinder blocks that make up the cylinder 2, the cylinder block to which the hopper 5 is connected has an opening (resin supply port) on its top surface, and the hopper 5 is connected so as to communicate with this opening. As a result, the resin material put into the hopper 5 is supplied into the cylinder block from the opening (resin supply port) on the top surface of the cylinder block to which the hopper 5 is connected.

[0017] The die 6 functions to form the molten resin extruded from the cylinder 2 of the extruder 1 into a predetermined cross-sectional shape (for example, a string shape) and discharge it. For this reason, the die 6 is a die (die, metal mold) for extrusion molding.

[0018] In this application, "melting" is not limited to melting by heat, but also includes melting with a solvent or the like. Therefore, not only when a resin is melted by heating, but also when a resin is melted with a solvent or by microwaves can be included in the "molten resin." Furthermore, a liquid resin can also be included in the "molten resin."

[0019] Furthermore, when referring to the cylinder 2 and the screw 3 as "downstream side" and "upstream side," the "downstream side" refers to the downstream side of the flow of resin in the cylinder 2, and the "upstream side" refers to the upstream side of the flow of resin in the cylinder 2. Therefore, in the cylinder 2 and the screw 3, the side closer to the tip of the cylinder 2 is the downstream side, and the side farther from the tip of the cylinder 2 is the upstream side. The tip of the cylinder 2 corresponds to the end of the cylinder 2 from which the kneaded product of resin and filler is extruded.

[0020] Furthermore, composite materials that contain a resin as a base material and a non-resin material such as calcium oxide or wood flour as a filler can also be included in the "resin material".

[0021] Next, an outline of the operation of the extruder 1 shown in FIG. 1 will be described.

[0022] Raw resin material (resin material, thermoplastic resin) is supplied from the hopper 5 into the cylinder 2. The raw resin material supplied from the hopper 5 into the cylinder 2 is melted (i.e., becomes molten resin) while being sent forward (downstream) within the cylinder 2 by the rotation of the screw 3. When a filler is supplied from a filler supply device (not shown) into the cylinder 2, the resin (molten resin) and filler are kneaded within the cylinder 2 by the rotation of the screw 3, and the molten resin within the cylinder 2 comes to contain the filler.

[0023] The molten resin sent forward inside the cylinder 2 by the rotation of the screw 3 is extruded from a die 6 attached to the tip of the cylinder 2. A resin product is manufactured from the resin material extruded from the die 6. For example, the resin material (molten resin) is formed into a string shape by the die 6, extruded from the die 6 as a strand (resin strand), and cut by a cutting device (cutter) to manufacture pellets (resin pellets) as a resin product.

[0024] Therefore, the process of manufacturing a resin product (e.g., resin pellets) using the extruder 1 includes a step of supplying a resin material from a hopper 5 into the cylinder 2, a step of kneading the resin material using the screw 3 in the cylinder 2 after the step of supplying the resin material, and a step of extruding the resin material out of the cylinder 2 after the kneading step.

[0025] <Screw 3 structure> Fig. 2 is a side view of the screw 3 provided in the extruder 1 in this embodiment. Fig. 3 is also a side view of the screw 3, but Fig. 3 shows a state in which a part of the screw 3 is disassembled. Fig. 4 is a partially enlarged cross-sectional view showing an enlarged tip portion of the screw 3.

[0026] 2 to 4 and the following figures, the X, Y, and Z directions are shown as necessary, but the X, Y, and Z directions are mutually orthogonal. Of these, the X and Y directions are horizontal directions, and the Z direction is the height direction.

[0027] The structure of the screw 3 in the cylinder 2 of the extruder 1 in this embodiment will be described with reference to FIGS.

[0028] As can be seen from Figures 2 to 4, the screw 3 has a screw shaft (shank portion) 11, a plurality of screw pieces (screw portion) 12 attached to the screw shaft 11, and a screw cap (cap portion) 13 attached to the tip of the screw shaft 11. The plurality of screw pieces 12 and the screw cap 13 are attached to a portion of the screw shaft 11 located inside the cylinder 2. The screw cap 13 is composed of a bolt member (bolt-shaped member, bolt portion) 14, a cover member (cover portion) 15, and a screw member 16. Note that Figure 3 corresponds to a state in which the screw cap 13 and two screw pieces 12 have been removed from the screw shaft 11. The tip of the screw 3 corresponds to the downstream end of the screw 3.

[0029] The screw shaft 11 has a columnar or cylindrical shape. The extension direction (longitudinal direction, axial direction) of the screw shaft 11 and the extension direction (longitudinal direction, axial direction) of the screw 3 are the same, which is the X direction in this example.

[0030] Each of the multiple screw pieces 12 has an opening 12b through which the screw shaft 11 can pass (insert) (see FIG. 4). The multiple screw pieces 12 are inserted into the screw shaft 11 and lined up in the X direction. That is, the multiple screw pieces 12 are arranged lined up in the X direction so that the screw shaft 11 passes through the openings of the multiple screw pieces 12. When the screw shaft 11 rotates, the multiple screw pieces 12 and screw caps 13 attached to the screw shaft 11 also rotate together with the screw shaft 11. The rotation drive mechanism 4 rotates the entire screw 3 by rotating the screw shaft 11.

[0031] The flights of the screw 3 are formed on the screw pieces 12. As a result, within the cylinder 2, flights are formed on the surface of the screw 3 (the surface formed by the screw pieces 12).

[0032] The multiple screw pieces 12 can include screw pieces composed of flight screws and screw pieces composed of kneading screws. A flight screw corresponds to a screw with a spiral flight formed on its side. A kneading screw has a structure in which multiple kneading disks are stacked with their rotational positions shifted.

[0033] The screw cap 13 functions as a stopper that holds down (fixes) the multiple screw pieces 12 attached to the screw shaft 11. That is, after the multiple screw pieces 12 are inserted into the screw shaft 11, the screw cap 13 is attached to the tip of the screw shaft 11, thereby preventing the screw pieces 12 from coming off the screw shaft 11.

[0034] <About the structure of the screw cap 13> FIG. 5 is a cross-sectional view of the screw cap 13 provided on the screw 3. FIG. 6 is a cross-sectional view of the screw cap 13 taken along line A1-A1 in FIG. 5. FIG. 7 is a cross-sectional view of the screw cap 13 taken along line A2-A2 in FIG. 5. FIG. 8 is a plan view (front view) of the screw cap 13 when viewed from direction 10a in FIG. 5. The cross-sectional views of the screw cap 13 taken along line B1-B1 in FIGS. 6 to 8 correspond to FIG. 5. FIG. 9 is a cross-sectional view of the bolt member 14 constituting the screw cap 13 in FIG. 5. FIG. 10 is a plan view (front view) of the bolt member 14 when viewed from direction 10b in FIG. 9. The cross-sectional view of the bolt member 14 taken along line C1-C1 in FIG. 10 corresponds to FIG. 9. FIG. 11 is a cross-sectional view of the cover member 15 constituting the screw cap 13 in FIG. 5. Fig. 12 is a plan view of cover member 15 when cover member 15 is viewed from direction 10c shown in Fig. 11. The cross-sectional view of cover member 15 taken along line D1-D1 shown in Fig. 12 corresponds to Fig. 11.

[0035] The structure of the screw cap 13 in this embodiment will be described with reference to FIGS.

[0036] The screw cap 13 is composed of a bolt member 14, a cover member 15, and a screw member 16 (see FIGS. 4 to 7). The bolt member 14, the cover member 15, and the screw member 16 are each independent parts (members) and are each made of a metal material. For example, the cover member 15 and the screw member 16 can each be made of stainless steel (SUS), and the bolt member 14 can be made of chrome molybdenum steel.

[0037] The bolt member 14 is a bolt-shaped member. Specifically, the bolt member 14 has a main body 14c, a head 14a connected to the main body 14c and having a larger planar dimension than the main body 14c, a protrusion (convex portion) 14b protruding from the upper surface of the head 14a, and a screw hole (hole) 14d formed in the surface (tip surface, top surface, upper surface) of the protrusion 14b (see FIGS. 5 to 7, 9, and 10). The main body 14c, the head 14a, and the protrusion 14b can be integrally formed.

[0038] The main body 14c has a circular planar shape. That is, the main body 14c has a substantially cylindrical shape. A screw thread is formed on the side surface of the main body 14c. In addition, a screw thread is formed on the side surface (inner wall surface) of the screw hole 14d of the bolt member 14.

[0039] Note that when referring to the components of the screw 3 (screw shaft 11, screw piece 12, screw cap 13, bolt member 14, cover member 15, and screw member 16) in a planar view, this refers to a view on a plane substantially perpendicular to the axial direction of the screw 3 (here, the X direction). Furthermore, when referring to the planar shape of the components of the screw 3, this refers to the shape on a plane substantially perpendicular to the axial direction of the screw 3 (here, the X direction). Furthermore, when referring to the planar dimensions of the components of the screw 3, this refers to the dimensions on a plane substantially perpendicular to the axial direction of the screw 3 (here, the X direction).

[0040] A hole (opening) 11a is formed in the tip surface of the screw shaft 11 (see Figure 4). The planar shape of the hole 11a of the screw shaft 11 is circular. That is, the hole 11a is a cylindrical space. A screw thread is formed on the side surface (inner wall surface) of the hole 11a. Therefore, the hole 11a can also be considered a screw hole, and the main body 14c of the bolt member 14 can also be considered a screw portion to be inserted into the hole 11a (screw hole).

[0041] In the bolt member 14, the main body 14c is a portion that is located inside the hole 11a of the screw shaft 11 when the screw cap 13 is attached to the tip of the screw shaft 11. That is, when the screw cap 13 is attached to the tip of the screw shaft 11, the main body 14c of the bolt member 14 is inserted into the hole 11a of the screw shaft 11. Therefore, the diameter of the main body 14c is approximately the same as or slightly smaller than the diameter of the hole 11a of the screw shaft 11. The depth (dimension in the X direction) of the hole 11a is equal to or greater than the length (dimension in the X direction) of the main body 14c. The extending direction (axial direction) of the main body 14c, the extending direction (axial direction) of the hole 11a, the extending direction (axial direction) of the screw hole 14d, and the extending direction (axial direction) of the screw shaft 11 are all the same, which is the X direction in this example.

[0042] The head 14a of the bolt member 14 has a circular planar shape (see Figures 9 and 10). That is, the head 14a has a substantially disk-like or cylindrical shape. The planar dimensions of the head 14a are larger than the planar dimensions of the main body 14c. That is, the diameter of the head 14a is larger than the diameter of the main body 14c and larger than the diameter of the hole 11a of the screw shaft 11. From another perspective, in plan view, the planar area of ​​the head 14a is larger than the planar area of ​​the main body 14c and larger than the planar area of ​​the hole 11a of the screw shaft 11. When the screw cap 13 is attached to the tip of the screw shaft 11, the head 14a and the protrusion 14b of the bolt member 14 are located outside the hole 11a of the screw shaft 11, not inside the hole 11a.

[0043] The planar dimensions of the head 14a of the bolt member 14 are larger than the planar dimensions of the tip of the screw shaft 11. That is, the diameter of the head 14a of the bolt member 14 is larger than the diameter of the tip of the screw shaft 11. Furthermore, the planar area of ​​the head 14a of the bolt member 14 is larger than the planar area of ​​the tip of the screw shaft 11 (including the area of ​​the hole 11a). In a planar view, the outer periphery of the head 14a of the bolt member 14 is located outside the outer periphery of the tip face of the screw shaft 11. From another perspective, in a planar view, the outer periphery of the tip face of the screw shaft 11 is located inside the outer periphery of the head 14a of the bolt member 14, and the tip face of the screw shaft 11 is enclosed within the head 14a of the bolt member 14.

[0044] The protrusion 14b of the bolt member 14 is formed on the upper surface of the head 14a so as to protrude from the upper surface of the head 14a (protrude in the X direction). The upper surface of the head 14a has an upper surface and a lower surface positioned opposite each other, and the protrusion 14b is formed on the upper surface of the head 14a, and the main body 14c is connected to the lower surface of the head 14a.

[0045] The planar shape of the protrusion 14b is a polygonal shape having three or more corners, and is a hexagonal shape (more specifically, a regular hexagonal shape) in the case of Fig. 10. In this case, the protrusion 14b is a substantially hexagonal column shape.

[0046] The cover member 15 is a separate member from the bolt member 14. The overall planar shape of the cover member 15 is circular (see Figures 8 and 12). The planar dimensions of the cover member 15 are approximately the same as the planar dimensions of the head 14a of the bolt member 14. In other words, the diameter of the cover member 15 is approximately the same as the diameter of the head 14a of the bolt member 14. From another perspective, the planar area of ​​the cover member 15 is approximately the same as the planar area of ​​the head 14a of the bolt member 14 in a plan view.

[0047] The cover member 15 is disposed on the upper surface of the head 14a of the bolt member 14 so as to cover the upper surface of the head 14a and the protrusion 14b (see FIGS. 5, 11, and 12). The cover member 15 has a recess (concave portion) 15a that matches the protrusion 14b, and when the cover member 15 is disposed on the upper surface of the head 14a of the bolt member 14, the protrusion 14b of the bolt member 14 is housed (fitted) in the recess 15a of the cover member 15. In other words, the cover member 15 is disposed on the upper surface of the head 14a of the bolt member 14 so that the protrusion 14b of the bolt member 14 is fitted into the recess 15a of the cover member 15. The recess 15a is formed on the surface of the cover member 15 that faces the bolt member 14. The cover member 15 covers almost the entire head 14a and protrusion 14b of the bolt member 14.

[0048] The planar shape of recess 15a of cover member 15 approximately matches the planar shape of protrusion 14b of bolt member 14 (see FIGS. 10 and 12). Since the planar shape of protrusion 14b of bolt member 14 is polygonal, the planar shape of recess 15a of cover member 15 is also polygonal. In other words, the planar shape of recess 15a of cover member 15 is a polygon that matches the planar shape of protrusion 14b of bolt member 14.

[0049] The number of corners of the polygon that forms the planar shape of recessed portion 15a is the same as the number of corners of the polygon that forms the planar shape of protruding portion 14b. When the planar shape of protruding portion 14b of bolt member 14 is hexagonal, the planar shape of recessed portion 15a of cover member 15 is also hexagonal, and when the planar shape of protruding portion 14b of bolt member 14 is regular hexagonal, the planar shape of recessed portion 15a of cover member 15 is also regular hexagonal.

[0050] Furthermore, the cover member 15 has a through-hole 15b that penetrates the cover member 15 (see FIGS. 11 and 12). In a plan view, the through-hole 15b is formed in the center of the cover member 15. The through-hole 15b reaches the bottom surface of the recessed portion 15a. No threads are formed on the side surface (inner wall surface) of the through-hole 15b.

[0051] The screw hole 14d of the bolt member 14 is formed in approximately the center of the surface of the protruding portion 14b (see FIGS. 9 and 10). The surface of the protruding portion 14b is the surface opposite to the side connected to the head portion 14a. A screw thread is formed on the side surface (inner wall surface) of the screw hole 14d of the bolt member 14.

[0052] When the cover member 15 is placed on the top surface of the head 14a of the bolt member 14 so that the protrusion 14b of the bolt member 14 fits into the recess 15a of the cover member 15, the through hole 15 of the cover member 15 overlaps (aligns with) the screw hole portion 14d of the bolt member 14 in a planar view.

[0053] The screw member 16 is a separate member from the cover member 15 and also from the bolt member 14. A thread is formed on the side of the screw member 16. The screw member 16 passes through a through hole 15b of the cover member 15 and is inserted into a threaded hole portion 14d of the bolt member 14 (see FIG. 5). The head of the screw member 16 presses against the cover member 15, thereby fixing the cover member 15 to the bolt member 14.

[0054] When the extruder 1 is in operation, the screw cap 13 is attached to the tip of the screw shaft 11 inside the cylinder 2, as shown in Figures 2 and 4. Specifically, as shown in Figure 4, the main body 14c of the bolt member 14 is inserted into the hole 11a of the screw shaft 11. Then, the cover member 15 is placed on the upper surface of the head 14a of the bolt member 14 so that the protrusion 14b of the bolt member 14 is fitted into the recess 15a of the cover member 15. Then, the screw member 16 is inserted into the threaded hole 14d of the bolt member 14, passing through the through hole 15b of the cover member 15.

[0055] As described above, the planar dimensions of the head 14a of the bolt member 14 are larger than the planar dimensions of the tip of the screw shaft 11, and in a plan view, the outer periphery of the head 14a of the bolt member 14 is located outside the outer periphery of the tip surface of the screw shaft 11. Therefore, the screw piece 12 located at the front of the multiple screw pieces 12 inserted into the screw shaft 11 (corresponding to the screw piece 12a shown in FIG. 4) comes into contact with the head 14a of the bolt member 14, and the head 14a of the bolt member 14 prevents the screw piece 12a from moving in the X direction. Specifically, the outer periphery of the head 14a of the bolt member 14 is adjacent to the screw piece 12a.

[0056] In Fig. 4, if the bolt member 14 were not present, the screw piece 12a would be able to move forward (downstream) in the X direction, preventing stable operation of the screw 3. As shown in Fig. 4, the head 14a of the bolt member 14 presses the screw piece 12a, preventing the screw piece 12a from moving forward in the X direction, thereby enabling stable operation of the screw 3.

[0057] The screw hole portion 14d of the bolt member 14 is used when removing (pulling out) the bolt member 14 from the screw shaft 11 during maintenance or the like, as will be described in detail later.

[0058] The cover member 15 and the screw member 16 function to prevent the resin material (molten resin) in the cylinder 2 from entering the threaded hole 14d of the bolt member 14 during operation of the extruder 1. In FIG. 4, if the screw member 16 were not present, the resin material (molten resin) in the cylinder 2 would enter the threaded hole 14d of the bolt member 14 during operation of the extruder 1. If the resin material (molten resin) enters the threaded hole 14d of the bolt member 14, it would be difficult to use the threaded hole 14d of the bolt member 14 when removing the bolt member 14 from the screw shaft 11 during maintenance, etc. Furthermore, in FIG. 4, if the cover member 15 were not present, the resin material (molten resin) in the cylinder 2 would easily enter the gap between the threaded hole 14d of the bolt member 14 and the screw member 16 during operation of the extruder 1. If the resin material (molten resin) enters the gap between the threaded hole portion 14d of the bolt member 14 and the screw member 16, it becomes difficult to use the threaded hole portion 14d of the bolt member 14 when removing the bolt member 14 from the screw shaft 11 during maintenance, etc. In this embodiment, the cover member 15 and the screw member 16 are attached to the bolt member 14, thereby preventing the resin material (molten resin) in the cylinder 2 from entering the threaded hole portion 14d of the bolt member 14 during operation of the extruder 1. As a result, the bolt member 14 can be easily and accurately removed from the screw shaft 11 using the threaded hole portion 14d of the bolt member 14 during maintenance, etc.

[0059] <How to remove screw cap 13> There are cases where the screw cap 13 is removed from the screw 3 (more specifically, the screw shaft 11 of the screw 3) for maintenance of the screw 3. This is because, with the screw cap 13 attached to the tip of the screw shaft 11, the screw piece 12 cannot be removed from the screw shaft 11. In order to remove the screw piece 12 from the screw shaft 11, it is necessary to first remove the screw cap 13 from the screw shaft 11, and then remove the screw piece 12 from the screw shaft 11.

[0060] A method for removing the screw cap 13 in this embodiment will be described with reference to FIGS.

[0061] 13 and 14 are explanatory views of a method for removing the screw cap 13 in this embodiment. Cross sections corresponding to those in FIGS. 4 and 5 are shown in FIGS. 13 and 14. For the sake of simplicity, the screw shaft 11 and the screw pieces 12 are omitted from FIG. 13, whereas the screw shaft 11 and the screw pieces 12 are also shown in FIG. 14. In reality, similar to FIG. 14, multiple screw pieces 12 are inserted into the screw shaft 11, and the main body 14c of the bolt member 14 is inserted into the hole 11a of the screw shaft 11 in FIG. 13 as well.

[0062] Figure 13 is composed of a first cross-sectional view, a second cross-sectional view, a third cross-sectional view, and a fourth cross-sectional view. The first cross-sectional view in Figure 13 shows the same state as Figure 4 above, but as mentioned above, the screw shaft 11 and the screw piece 12 are not shown. When the extruder 1 is in operation, as shown in Figures 2 and 4 above, the screw cap 13 is attached to the tip of the screw shaft 11, and the main body 14c of the bolt member 14 that constitutes the screw cap 13 is inserted into the hole 11a of the screw shaft 11. In this way, the bolt member 14 is fixed to the screw shaft 11. 13, cover member 15 is placed on the top surface of head 14a of bolt member 14 so that protrusion 14b of bolt member 14 fits into recess 15a of cover member 15, and screw member 16 is inserted through through hole 15b of cover member 15 and into threaded hole 14d of bolt member 14. In this way, screw member 16 is fixed to bolt member 14. In addition, the head of screw member 16 presses cover member 15, so that cover member 15 is pressed against bolt member 14. In this way, cover member 15 is fixed to bolt member 14.

[0063] The screw cap 13 is removed as follows.

[0064] First, as shown in the cross-sectional view in the second row of Fig. 13, the screw member 16 is rotated. At this time, the rotation direction 10d of the screw member 16 is the direction in which the screw member 16 loosens. As a result, the screw member 16 is removed (pulled out) from the threaded hole portion 14d of the bolt member 14, as shown in the cross-sectional view in the third row of Fig. 13.

[0065] Next, as shown in the cross-sectional view in the fourth row of Fig. 13, the cover member 15 is removed from the bolt member 14. After the screw member 16 is removed from the threaded hole portion 14d of the bolt member 14, the cover member 15 is no longer pressed by the screw member 16, and therefore, the cover member 15 can be easily removed from the bolt member 14 by moving the cover member 15 in the direction 10e. The direction 10e is approximately parallel to the X direction and corresponds to the direction away from the screw shaft 11.

[0066] In this way, the screw member 16 and the cover member 15 can be removed from the bolt member 14. Even at this stage, the main body 14c of the bolt member 14 remains inserted in the hole 11a of the screw shaft 11 (see FIG. 14).

[0067] Next, the screw 3 is removed (pulled out) from the cylinder 2 by using the bolt member 14, and the method for this is as follows, for example.

[0068] A jig 21 for pulling out the screw 3 is prepared in advance, and the threaded portion 21a of the jig 21 is inserted into the threaded hole 14d of the bolt member 14 (see FIG. 14). The jig 21 has the threaded portion 21a, and a thread is formed on the side of the threaded portion 21a. Then, by pulling the jig 21 in direction 10f, the bolt member 14 is pulled in direction 10f together with the jig 21 and the threaded portion 21a. Because the threads on the side of the main body 14c of the bolt member 14 are fitted with the threads on the side (inner wall surface) of the hole 11a of the screw shaft 11, when the bolt member 14 is pulled in direction 10f, the screw shaft 11 and the multiple screw pieces 12 attached to the screw shaft 11 are also pulled in direction 10f together with the bolt member 14. As a result, the screw 3 (bolt member 14, screw shaft 11, and multiple screw pieces 12) can be removed (pulled out) from the cylinder 2. The direction 10f is approximately parallel to the X direction and corresponds to the direction away from the cylinder 2.

[0069] Unlike the present embodiment, if the bolt member 14 does not have a threaded hole portion 14d, it is not easy to pull the bolt member 14 with a strong force in the direction 10f, and therefore it is not easy to pull the screw 3 out of the cylinder 2.

[0070] In contrast, in the present embodiment, the bolt member 14 has a threaded hole portion 14d, and therefore, as described above, the screw 3 (bolt member 14, screw shaft 11 and multiple screw pieces 12) can be easily pulled out from the cylinder 2 by utilizing the threaded hole portion 14d.

[0071] In this manner, the screw 3 can be removed (pulled out) from the cylinder 2.

[0072] Thereafter, if necessary, the bolt member 14 is removed from the screw shaft 2. As a result, the screw cap 13, which is made up of the screw member 16, the cover member 15, and the bolt member 14, is removed from the screw shaft 11.

[0073] After the bolt member 14 is removed from the screw shaft 2, the screw piece 12 can be removed (pulled out) from the screw shaft 11 as needed. This allows the screw 3 to be disassembled and maintenance of the screw 3 to be performed.

[0074] Therefore, a method for disassembling a screw 3 for an extruder includes the steps of preparing a screw 3 having a screw shaft 11, a plurality of screw pieces 12 attached to the screw shaft 11, and a screw cap 13 attached to the tip of the screw shaft 11, followed by the steps of removing the screw cap 13 from the screw shaft 11, and then removing one or more of the plurality of screw pieces 12 from the screw shaft 11.

[0075] In the step of preparing the screw 3, the body 14c of the bolt member 14 is inserted into the hole 11a of the screw shaft 11, and the head 14a of the bolt member 14 is positioned outside the hole 11a. Then, the cover member 15 is placed on the head 14a of the bolt member 14 so that the protrusion 14b of the bolt member 14 is fitted into the recess 15b of the cover member 15, and the screw member 16 is inserted into the threaded hole 14d of the bolt member 14, passing through the through hole 15b of the cover member 15. In the step of preparing the screw 3, the screw 3 is placed in the cylinder 2.

[0076] The step of removing the screw cap 13 from the screw shaft 11 includes the step of removing the screw member 16 from the bolt member 14, followed by the step of removing the cover member 15 from the bolt member 14, and then the step of removing the bolt member 14 from the screw shaft 11. After the step of removing the cover member 15 from the bolt member 14 and before the step of removing the bolt member 14 from the screw shaft 11, a step of inserting the threaded portion 21a of the jig 21 into the threaded hole portion 14d of the bolt member 14 and using the jig 21 to pull out the screw 3 from the cylinder 2 is performed.

[0077] <How to install screw cap 13> After disassembling the screw 3 and performing maintenance on the screw 3, the screw 3 is assembled. When assembling the screw 3, a plurality of screw pieces 12 are attached to the screw shaft 11, and then a screw cap 13 is attached to the tip of the screw shaft 11. In other words, after the plurality of screw pieces 12 are inserted into the screw shaft 11, the screw cap 13 is attached to the tip of the screw shaft 11.

[0078] A method for attaching the screw cap 13 in this embodiment will be described with reference to FIG.

[0079] Fig. 15 is an explanatory diagram of a method for attaching the screw cap 13 in this embodiment. Fig. 15 shows a cross section corresponding to Fig. 4 and Fig. 5. Fig. 15 is composed of a first cross-sectional view, a second cross-sectional view, a third cross-sectional view, and a fourth cross-sectional view.

[0080] 13, the screw shaft 11 and the screw pieces 12 are omitted from Fig. 15 for the sake of simplicity. In reality, as in Fig. 4 and Fig. 14, a plurality of screw pieces 12 are inserted into the screw shaft 11, and the main body 14c of the bolt member 14 is inserted into the hole 11a of the screw shaft 11 in Fig. 15 as well.

[0081] The screw cap 13 is attached as follows.

[0082] First, the main body 14c of the bolt member 14 is inserted into the hole 11a of the screw shaft 11. A screw thread is formed on the side surface of the main body 14c of the bolt member 14 and on the side surface (inner wall surface) of the hole 11a of the screw shaft 11. By inserting the main body 14c of the bolt member 14 into the hole 11a of the screw shaft 11 while rotating the bolt member 14, the screw thread on the side surface of the main body 14c of the bolt member 14 and the screw thread on the side surface (inner wall surface) of the hole 11a of the screw shaft 11 are fitted together. In this way, the bolt member 14 is fixed to the screw shaft 11.

[0083] Next, the screw 3 (bolt member 14 , screw shaft 11 and multiple screw pieces 12 ) is placed (inserted) into the cylinder 2 .

[0084] It is easier to insert the screw 3 into the cylinder 2 than to pull out the screw 3 from the cylinder 2. Therefore, the screw hole portion 14d of the bolt member 14 does not need to be used when inserting the screw 3 into the cylinder 2.

[0085] Next, as shown in the first and second cross-sectional views of Fig. 15, the cover member 15 is placed on the upper surface of the head 14a of the bolt member 14 so that the protrusion 14b of the bolt member 14 fits into the recess 15a of the cover member 15. At this time, the cover member 15 is moved in direction 10g so that the recess 15a of the cover member 15 is aligned with the protrusion 14b of the bolt member 14. Note that direction 10g is approximately parallel to the X direction and corresponds to the direction approaching the screw shaft 11.

[0086] Next, as shown in the cross-sectional views from the third row to the fourth row in FIG. 15 , the screw member 16 is inserted into the threaded hole 14d of the bolt member 14 while being rotated. The rotation direction 10h of the screw member 16 at this time is the rotation direction in which the screw member 16 is tightened. The screw member 16 passes through the through-hole 15b of the cover member 15 and is inserted into the threaded hole 14d of the bolt member 14. This fixes the screw member 16 to the bolt member 14. Furthermore, the head of the screw member 16 presses the cover member 15, so that the cover member 15 is pressed against the bolt member 14. This fixes the cover member 15 to the bolt member 14.

[0087] In this way, the screw cap 13 can be attached to the tip of the screw shaft 11.

[0088] <About the study example> Next, the screw cap 13 of the example studied by the present inventor will be described.

[0089] FIG. 16 is a cross-sectional view of the screw cap 113 of the study example, and shows a cross section corresponding to FIG. 5 above. FIG. 17 is a cross-sectional view of the screw cap 113 at the position of the E1-E1 line shown in FIG. 16. FIG. 18 is a cross-sectional view of the screw cap 113 at the position of the E2-E2 line shown in FIG. 16. FIG. 19 is a plan view (front view) of the screw cap 113 when viewed from the direction 10i shown in FIG. 16. The cross-sectional views of the screw cap 113 at the position of the F1-F1 line shown in FIGS. 17 to 19 correspond to FIG. 16.

[0090] The structure of a screw cap 113 as an example studied by the present inventors will be described with reference to FIGS.

[0091] The screw cap 113 of the examined example is composed of a bolt member 114 and a cover member 115 (see FIGS. 16 to 19).

[0092] The structure of the bolt member 114 is substantially the same as that of the bolt member 14. Therefore, the bolt member 114 has a main body 114c corresponding to the main body 14c, a head 114a corresponding to the head 14a, a protrusion 114b corresponding to the protrusion 14b, and a screw hole 114d corresponding to the screw hole 14d (see FIG. 16). As with the bolt member 14 of this embodiment, the main body 114c of the bolt member 114 is inserted into the hole 11a of the screw shaft 11.

[0093] Cover member 115 is a separate member from bolt member 114. The entire planar shape of cover member 115 is circular, and the planar dimensions of cover member 115 are approximately the same as the planar dimensions of head 114a of bolt member 114. Cover member 115 is disposed on the upper surface of head 114a of bolt member 114 so as to cover the upper surface of head 114a and protrusion 114b (see FIG. 16).

[0094] The cover member 115 has a threaded portion 115a and a recessed portion (concave portion) 115b. The threaded portion 115a is not a separate member (component) from the cover member 115, but is formed integrally with the cover member 115. The threaded portion 115a is formed in the center of the bottom surface of the recessed portion 115b. A screw thread is formed on the side surface of the threaded portion 115a. The threaded portion 115a of the cover member 115 is inserted into the screw hole portion 114d of the bolt member 114.

[0095] The planar shape of recess 115b of cover member 115 is circular (see FIG. 17). On the other hand, the planar shape of protrusion 114b of bolt member 114 is hexagonal (see FIG. 17). Therefore, in plan view, a gap is generated between the inner wall (side surface) of recess 115b of cover member 115 and the side surface of protrusion 114b of bolt member 114 (see FIG. 7). The reason why the planar shape of recess 115b of cover member 115 is circular will be explained later.

[0096] The threaded hole 114d of the bolt member 114 is used when removing the bolt member 114 from the screw shaft 11 during maintenance, etc. The cover member 115 has the function of preventing the resin material (molten resin) in the cylinder 2 from entering the threaded hole 114d of the bolt member 114 when the extruder 1 is operating.

[0097] A method for removing the screw cap 113 in the study example will be described with reference to FIG.

[0098] Fig. 20 is an explanatory diagram of a method for removing the screw cap 113 of the study example. Fig. 20 shows a cross-sectional view corresponding to Fig. 13 above. As in Fig. 13 above, Fig. 20 also omits the illustration of the screw shaft 11 and the screw pieces 12 to simplify the drawing. In reality, as in Figs. 4 and 14 above, in Fig. 20 also, a plurality of screw pieces 12 are inserted into the screw shaft 11, and the main body 114c of the bolt member 114 is inserted into the hole 11a of the screw shaft 11.

[0099] The screw cap 13 is removed as follows.

[0100] First, the cover member 115 is rotated as shown in the cross-sectional views from the first row to the second row in Fig. 13. The rotation direction 10j of the cover member 115 at this time is the rotation direction that loosens the threaded portion 115a. As a result, the threaded portion 115a of the cover member 115 is removed (pulled out) from the screw hole portion 14d of the bolt member 14 as shown in the cross-sectional view from the third row in Fig. 13, and the cover member 115 can be removed from the bolt member 114.

[0101] Because the cover member 115 has a threaded portion 115a, in order to remove the cover member 115 from the bolt member 114, it is necessary to rotate the cover member 115 relative to the bolt member 114. In the case of the screw cap 13 of the studied example, the planar shape of the recessed portion 115b of the cover member 115 is circular, so the rotation of the cover member 115 is not hindered by the protruding portion 114b of the bolt member 114. For this reason, in the case of the screw cap 13 of the studied example, the planar shape of the recessed portion 115b of the cover member 115 needs to be circular.

[0102] 14 above, the screw 3 (bolt member 114, screw shaft 11, and multiple screw pieces 12) is pulled out from the cylinder 2, and then the bolt member 114 is removed from the screw shaft 11. As a result, the screw cap 113 consisting of the cover member 115 and the bolt member 114 is removed from the screw shaft 11.

[0103] Next, the problem with the screw cap 113 of the studied example will be described with reference to FIG.

[0104] Figure 21 is an explanatory diagram of the problem with the screw cap 113 of the study example, and shows a cross section corresponding to Figure 16. As with Figures 13 and 20 above, the screw shaft 11 and screw pieces 12 are omitted from Figure 21 to simplify the drawing. In reality, as with Figures 4 and 14 above, multiple screw pieces 12 are inserted into the screw shaft 11, and the main body 114c of the bolt member 114 is inserted into the hole 11a of the screw shaft 11 in Figure 21 as well.

[0105] 21 corresponds to the resin material in the cylinder 2. When the extruder is in operation, the surface (upper surface) of the cover member 115 of the screw cap 113 attached to the tip of the screw shaft 11 is covered with the resin material 131 in the cylinder 2.

[0106] When the screw shaft 11 rotates, the multiple screw pieces 12 and the screw cap 113 also rotate together with the screw shaft 11, and therefore the bolt member 114 and cover member 115 that constitute the screw cap 113 also rotate together with the screw shaft 11. Because the surface of the cover member 115 is covered with a resin material 131, when the cover member 115 rotates together with the screw shaft 11, the resin material 131 acts to hinder the rotation of the cover member 115, and torque caused by the resin material 131 is generated in the cover member 115. If the resin material 131 is a molten resin and the viscosity of the molten resin is relatively low, even if torque caused by the resin material 131 is generated in the cover member 115, the magnitude of the torque is sufficiently small so that no malfunction occurs in the screw cap 113.

[0107] However, if the resin material 131 covering the surface of the cover member 115 is an unmelted resin material with an extremely high viscosity, a large torque due to the resin material 131 is generated in the cover member 115. As a result, the cover member 115 rotates relative to the bolt member 114, and excessive force is applied to the threaded portion 115a inserted into the threaded hole portion 114d of the bolt member 114, which may cause galling or damage to the threaded portion 115a inserted into the threaded hole portion 114d. Furthermore, the inventors have found that galling or damage may also occur at the contact point between the outer periphery of the cover member 115 and the outer periphery of the head portion 114a of the bolt member 114. For example, when the operation of the extruder is temporarily stopped and then resumed, the resin material 131 covering the surface of the cover member 115 may be an unmelted resin material. If the threaded portion 115a inserted into the screw hole portion 14d is galled or damaged, it becomes difficult to remove the cover member 115 from the bolt member 114 when removing the screw cap 113 from the screw shaft 11, making it difficult to disassemble the screw or perform maintenance on the screw. Furthermore, galling or damage occurring at the contact point between the outer periphery of the cover member 115 and the outer periphery of the head portion 114a of the bolt member 114 may also make it difficult to remove the cover member 115 from the bolt member 114.

[0108] <Main features and effects> One of the main features of this embodiment is that the screw cap 13 attached to the tip of the screw shaft 11 has a bolt member 14, a cover member 15, and a screw member 16. The bolt member 14, the cover member 15, and the screw member 16 are separate members (components), and the screw cap 13 is assembled by these bolt member 14, the cover member 15, and the screw member 16.

[0109] The bolt member 14 has a main body 14c inserted into the hole 11a of the screw shaft 11, a head 14a connected to the main body 14c and positioned outside the hole 11a, a protrusion 14b protruding from the head 14a, and a threaded hole 14d formed in the surface of the protrusion 14b. The cover member 15 has a recess 15a and a through hole 15b. The cover member 15 is disposed on the head 14a of the bolt member 14 so that the protrusion 14b fits into the recess 15a. The screw member 16 passes through the through hole 15b of the cover member 15 and is inserted into the threaded hole 14d of the bolt member 14. The planar shape of the protrusion 14b is polygonal, and the planar shape of the recess 15a is polygonal to match the protrusion 14b.

[0110] Next, the effect of applying the screw cap 13 in this embodiment will be described with reference to FIG.

[0111] Figure 22 is an explanatory diagram of the effect of the screw cap 13 of this embodiment, showing a cross section corresponding to Figure 5. As in Figures 13, 20, and 21, the screw shaft 11 and screw pieces 12 are omitted from Figure 22 to simplify the drawing. In reality, as in Figures 4 and 14, a plurality of screw pieces 12 are inserted into the screw shaft 11, and the main body 14c of the bolt member 14 is inserted into the hole 11a of the screw shaft 11 in Figure 22 as well.

[0112] 22 corresponds to the resin material in the cylinder 2. When the extruder 1 is in operation, the surface (top surface) of the cover member 14 of the screw cap 13 attached to the tip of the screw shaft 11 and the surface of the screw member 16 exposed from the cover member 15 are covered with the resin material 31 in the cylinder 2.

[0113] When the screw shaft 11 rotates, the plurality of screw pieces 12 and the screw cap 13 also rotate together with the screw shaft 11, and therefore the bolt member 14, cover member 15 and screw member 16 that constitute the screw cap 13 also rotate together with the screw shaft 11.

[0114] Because the surface of the cover member 115 is covered with the resin material 31, when the bolt member 14 and the cover member 15 rotate together with the screw shaft 11, the resin material 31 acts to hinder the rotation of the cover member 15, and torque caused by the resin material 31 is generated in the cover member 15. If the resin material 31 covering the surface of the cover member 15 is an unmelted resin material with an extremely high viscosity, a large torque caused by the resin material 31 will be generated in the cover member 15.

[0115] However, the large torque generated in the cover member 15 due to the resin material 31 has almost no effect on the screw member 16 inserted into the screw hole portion 14d. This is because the cover member 15 and the screw member 16 are separate members (components), and therefore the torque (rotational force) generated in the cover member 15 is not easily transmitted to the screw member 16.

[0116] Furthermore, even if a large torque caused by resin material 31 is applied to cover member 15, cover member 15 will not rotate relative to bolt member 14. This is because protrusion 14b of bolt member 14 is fitted into recess 15a of cover member 15, the planar shape of protrusion 14b is polygonal, and the planar shape of recess 15a is a polygon that matches protrusion 14b. As a result, even if an attempt is made to forcibly rotate cover member 15 relative to bolt member 14, protrusion 14b prevents cover member 15 from rotating relative to bolt member 14.

[0117] Unlike this embodiment, if the planar shape of recessed portion 15a of cover member 15 were circular, protrusion 14b would not hinder the relative rotation of cover member 15, and it would be possible to forcibly rotate cover member 15 with respect to bolt member 14. In contrast, in this embodiment, the planar shape of recessed portion 15a is a polygonal shape that matches protrusion 14b, and protrusion 14b prevents the relative rotation of cover member 15, making it difficult to forcibly rotate cover member 15 with respect to bolt member 14.

[0118] Therefore, in this embodiment, even if a large torque caused by the resin material 31 is applied to the cover member 15, almost no problems occur.

[0119] On the other hand, in this embodiment, the surface of the screw member 16 exposed from the cover member 15 is covered with the resin material 31, so that when the bolt member 14 and the screw member 16 rotate together with the screw shaft 11, the resin material 31 acts to hinder the rotation of the screw member 16, and torque caused by the resin material 31 is generated in the screw member 16. If the resin material 31 that covers the surface of the screw member 16 exposed from the cover member 15 is an unmelted resin material with an extremely high viscosity, there is a concern that the torque generated in the screw member 16 due to the resin material 31 will become large.

[0120] However, the planar dimensions of the screw members 16 exposed from the cover member 15 are significantly smaller than the planar dimensions of the cover member 15. That is, the diameter of the head of the screw member 16 (the diameter of the screw member 16 exposed from the cover member 15) is smaller than the diameter of the cover member 15 (see FIG. 8, etc.). Also, the planar area of ​​the head of the screw member 16 (the planar area of ​​the screw member 16 exposed from the cover member 15) is smaller than the planar area of ​​the cover member 15. In a plan view, the outer periphery of the screw member 16 exposed from the cover member 15 is located inside the outer periphery of the cover member 15.

[0121] For this reason, the torque generated in the screw member 16 due to the resin material 31 is considerably smaller than the torque generated in the cover member 15 due to the resin material 31. Therefore, even if the resin material 31 is an unmelted resin material with an extremely high viscosity, the torque generated in the screw member 16 due to the resin material 31 can be suppressed, so that the force applied to the screw member 16 inserted into the threaded hole portion 14d of the bolt member 14 can be suppressed, and galling or damage to the screw member 16 inserted into the threaded hole portion 14d can be prevented. Furthermore, because the cover member 15 cannot rotate relative to the bolt member 14 as described above, galling or damage can be prevented from occurring at the contact point between the outer periphery of the cover member 15 and the outer periphery of the head portion 14a of the bolt member 14.

[0122] Therefore, when removing the screw cap 13 from the screw shaft 11, the cover member 15 can be easily and accurately removed from the bolt member 14. This makes it easier to disassemble the screw 3 and perform maintenance on the screw 3. It also reduces the workload required for disassembling the screw 3 and performing maintenance on the screw 3. It also reduces the time required for disassembling the screw 3 and performing maintenance on the screw 3.

[0123] In the above-described example, threaded portion 115a is formed integrally with cover member 115, and therefore, if resin material 131 is an unmelted resin material with an extremely high viscosity, a large torque generated in cover member 115 due to resin material 131 is applied to threaded portion 115a. This can cause galling of threaded portion 115a inserted into screw hole 14d.

[0124] In this embodiment, cover member 15 and screw member 16 are separate members, and screw member 16 can rotate independently of cover member 15. Therefore, when resin material 31 is an unmelted resin material with an extremely high viscosity, the large torque generated in cover member 15 due to resin material 31 is not applied to screw member 16, so that it is possible to prevent galling or damage to screw member 16 inserted into screw hole portion 14d.

[0125] In this embodiment, the planar shape of protrusion 14b of bolt member 14 is polygonal, and the planar shape of recess 15a of cover member 15 is polygonal to match protrusion 14b, so that cover member 15 does not rotate relative to bolt member 14. The polygonal shape that forms the planar shape of protrusion 14b is not limited to a hexagonal shape, but a hexagonal shape can reliably prevent rotation of cover member 15 relative to bolt member 14 and makes it easier to form screw hole 14d. Also, machining of bolt member 14 becomes easier.

[0126] The invention made by the inventor has been specifically described above based on the embodiments thereof, but it goes without saying that the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the invention. [Explanation of symbols]

[0127] 1. Extruder 2 cylinders 3 screws 4 Rotation drive mechanism 5 Hopper 6 Die 10a,10b,10c,10e,10f,10g,10i direction 10d, 10h, 10j Rotation direction 11 Screw shaft 11a Hole 12,12a Screw Piece 12b opening 13,113 screw caps 14,114 bolt components 14a,114a Head 14b,114b Projection 14c,114c Main body 14d, 114d screw hole 15,115 Cover material 15a, 115b recess 15b Through hole 16 Screw member 21 Jig 21a Threaded part 31,131 Resin materials 115a Threaded part

Claims

1. Extruder including: cylinder; and a screw housed in the cylinder; Here, the screw has a screw shaft, a plurality of screw pieces attached to the screw shaft, and a screw cap attached to the tip of the screw shaft, The screw cap has a bolt member, a cover member, and a screw member, The bolt member has a main body portion inserted into a hole portion of the screw shaft, a head portion connected to the main body portion and positioned outside the hole portion, a protrusion portion protruding from the head portion, and a screw hole portion formed on a surface of the protrusion portion, the cover member has a recess and a through hole, The planar shape of the protrusion is a polygonal shape, a planar shape of the recessed portion is a polygonal shape that matches with the protruding portion, the cover member is placed on the head of the bolt member so that the protrusion fits into the recess; The screw member passes through the through hole of the cover member and is inserted into the screw hole portion of the bolt member.

2. 2. The extruder according to claim 1, The planar shape of the protrusion is a hexagonal shape, The planar shape of the recessed portion is hexagonal.

3. 2. The extruder according to claim 1, An extruder, wherein a screw thread is formed on a side surface of the screw member, a side surface of the screw hole portion, a side surface of the main body portion, and a side surface of the hole portion.

4. 2. The extruder according to claim 1, an extruder, wherein the outer peripheral portion of the head portion is adjacent to a leading screw piece among the plurality of screw pieces.

5. 2. The extruder according to claim 1, The cover member covers the head and the protrusion.

6. 2. The extruder according to claim 1, an extruder, wherein when the cover member is placed on the head of the bolt member so that the protrusion is fitted into the recess of the cover member, the cover member does not rotate relative to the bolt member.

7. A screw for an extruder, including: screw shaft; a plurality of screw pieces attached to the screw shaft; and a screw cap attached to the tip of the screw shaft; Here, the screw cap has a bolt member, a cover member, and a screw member, The bolt member has a main body portion inserted into a hole portion of the screw shaft, a head portion connected to the main body portion and positioned outside the hole portion, a protrusion portion protruding from the head portion, and a screw hole portion formed on a surface of the protrusion portion, the cover member has a recess and a through hole, The planar shape of the protrusion is a polygonal shape, a planar shape of the recessed portion is a polygonal shape that matches with the protruding portion, the cover member is placed on the head of the bolt member so that the protrusion fits into the recess; The screw member passes through the through hole of the cover member and is inserted into the screw hole portion of the bolt member.

8. The screw for an extruder according to claim 7, The planar shape of the protrusion is a hexagonal shape, The screw for an extruder, wherein the recess has a hexagonal planar shape.

9. The screw for an extruder according to claim 7, A screw for an extruder, wherein a screw thread is formed on a side surface of the screw member, a side surface of the screw hole portion, a side surface of the main body portion, and a side surface of the hole portion.

10. The screw for an extruder according to claim 7, A screw for an extruder, wherein the outer periphery of the head portion is adjacent to the leading screw piece of the plurality of screw pieces.

11. The screw for an extruder according to claim 7, The cover member covers the head and the protrusion.

12. The screw for an extruder according to claim 7, A screw for an extruder, wherein when the cover member is placed on the head of the bolt member so that the protrusion fits into the recess of the cover member, the cover member does not rotate relative to the bolt member.

13. A method for disassembling a screw for an extruder, comprising the steps of: (a) preparing a screw having a screw shaft, a plurality of screw pieces attached to the screw shaft, and a screw cap attached to the tip of the screw shaft; (b) removing the screw cap from the screw shaft after the step (a); and (b) after the step (b), removing one or more of the plurality of screw pieces from the screw shaft; Here, the screw cap has a bolt member, a cover member, and a screw member, The bolt member has a main body, a head connected to the main body, a protrusion protruding from the head, and a screw hole formed in a surface of the protrusion, the cover member has a recess and a through hole, The planar shape of the protrusion is a polygonal shape, a planar shape of the recessed portion is a polygonal shape that matches with the protruding portion, In step (a), the main body portion is inserted into the hole portion of the screw shaft, the head portion is positioned outside the hole portion, the cover member is placed on the head portion of the bolt member so that the protrusion portion fits into the recess portion, and the screw member is inserted into the screw hole portion of the bolt member through the through hole of the cover member.

14. The method for disassembling an extruder screw according to claim 13, The step (b) comprises: (b1) removing the screw member from the bolt member; (b2) after the step (b1), removing the cover member from the bolt member; (b3) after the step (b2), removing the bolt member from the screw shaft; A method for disassembling a screw for an extruder, comprising:

15. The method for disassembling an extruder screw according to claim 14, In the step (a), the screw is disposed in a cylinder, After the step (b2) and before the step (b3), (b4) inserting a threaded portion of a jig into the threaded hole portion of the bolt member and pulling the screw out of the cylinder using the jig; The method for disassembling a screw for an extruder further comprises:

16. The method for disassembling an extruder screw according to claim 13, The planar shape of the protrusion is a hexagonal shape, A method for disassembling a screw for an extruder, wherein the planar shape of the recessed portion is hexagonal.

17. The method for disassembling an extruder screw according to claim 13, A method for disassembling a screw for an extruder, wherein a screw thread is formed on a side surface of the screw member, a side surface of the screw hole portion, a side surface of the main body portion, and a side surface of the hole portion.

18. The method for disassembling an extruder screw according to claim 13, In the step (a), the outer periphery of the head portion is adjacent to the leading screw piece of the plurality of screw pieces.

19. The method for disassembling an extruder screw according to claim 13, In the step (a), the cover member covers the head and the protrusion.

20. The method for disassembling an extruder screw according to claim 13, In the step (a), the cover member does not rotate relative to the bolt member.

Images