extruder

Abstract

The extruder is equipped with a cylinder and a screw housed in the cylinder. The inner circumferential surface of the cylinder has a first groove formation region 22e and a second groove formation region 22f, in each of which grooves are formed. In the first groove formation region 22e, the height of the crests 22g forming the grooves 22d is constant. In the second groove formation region 22f, when viewed from the circumferential direction, at least a portion overlaps with a material supply port 22a and the height of the crests 22g forming the grooves 22d is lower than the crests 22g of the first groove formation region 22e.

Description

Technical Field

[0001] The present invention relates to an extruder.

Background Art

[0002] An extruder is known that includes a cylinder to which a heater is attached and a screw accommodated in the cylinder, melts a molding material by heating with the heater, etc., and extrudes the melted molding material from an extrusion port of the cylinder.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] There is a demand to increase the extrusion amount per unit time of an extruder. If the inflow amount of the molding material into the cylinder per unit time increases, the extrusion amount also increases. If the inner diameter of the cylinder is increased, the inflow amount increases, but the extruder becomes larger and the space required for installation becomes larger, and the manufacturing cost of the extruder also increases.

[0005] The present invention has been made in view of such a situation, and an exemplary object of one aspect thereof is to provide a technique capable of increasing the inflow amount of a molding material into an extruder without increasing the size of the extruder.

Means for Solving the Problems

[0006] To solve the above problems, an extruder according to one aspect of the present invention comprises a cylinder and a screw housed in the cylinder. The inner circumferential surface of the cylinder has first and second groove-forming regions, each having a groove formed therein. In the first groove-forming region, the height of the peaks that form the groove is constant, and in the second groove-forming region, at least a portion overlaps with the material supply port when viewed in the circumferential direction, and the height of the peaks that form the groove is lower than that of the peaks in the first groove-forming region.

[0007] Furthermore, any combination of the above components, or any substitution of the components or expressions of the present invention between methods, apparatus, systems, etc., are also valid embodiments of the present invention. [Effects of the Invention]

[0008] According to the present invention, the amount of molding material flowing into the extruder can be increased without increasing the size of the extruder. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view of an extruder according to an embodiment. [Figure 2] This is a perspective view of the main body of the first cylinder section shown in Figure 1. [Figure 3] This is an end view of the main body of the first cylinder section shown in Figure 1. [Figure 4] This is an unfolded view of the main body section after cutting along line AA in Figure 3. [Figure 5] Figure 4 is a cross-sectional view along line BB. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant explanations are omitted as appropriate.

[0011] Figure 1 is a cross-sectional view of an extruder 100 according to an embodiment. Figure 1 is a cross-sectional view of the extruder 100 cut in a vertical section including the central axis C of the cylinder 10 (described later). The extruder 100 is connected to an inflation film molding machine, a cast film molding machine, a laminator, or other device, and supplies molten molding material to them.

[0012] The extruder 100 comprises a cylindrical cylinder 10, a screw 12 housed in the cylinder 10, a hopper 14 filled with molding material and for supplying the molding material to one end of the cylinder 10 (hereinafter referred to as the upstream side), and a support member 16 that supports the upstream side of the cylinder 10 and also supports the hopper 14.

[0013] Hereafter, the direction parallel to the central axis C of the cylindrical internal space S of the cylinder 10 will be referred to as the axial direction, any direction passing through the central axis C on a plane perpendicular to the central axis C will be referred to as the radial direction, and the direction along the circumference of a circle centered on the central axis C on a plane perpendicular to the central axis C will be referred to as the circumferential direction.

[0014] The cylinder 10 includes a first cylinder section 18 and a second cylinder section 20, in order from upstream. The first cylinder section 18 and the second cylinder section 20 are cylindrical members having substantially the same inner diameter and are connected coaxially.

[0015] The first cylinder section 18 includes a cylindrical main body section 22, a cooling section 23 that surrounds the downstream side of the main body section 22, and a cover section 24 that surrounds the cooling section 23. The main body section 22 and the cooling section 23, and the cooling section 23 and the cover section 24 are joined together by welding.

[0016] On the upstream side of the outer peripheral surface of the main body portion 22, a material supply port 22a which is an opening is formed. In the cooling portion 23, a refrigerant flow path (not shown) is formed. A refrigerant such as cooling water flows through this flow path. The cooling portion 23 surrounds the downstream side of the main body portion 22 as described above, and thus cools the downstream side of the main body portion 22. A refrigerant flow path (not shown) is also formed in the support member 16. The upstream side of the main body portion 22 is cooled by the support member 16 surrounding the upstream side. When the molding material melts in the first cylinder portion 18, the driving force is lost and the molding material cannot advance to the downstream side. By cooling the main body portion 22 by the cooling portion 23, this can be avoided.

[0017] A plurality of heaters 26 are wound around the outer periphery of the second cylinder portion 20. The heater 26 warms the inside of the second cylinder portion 20 to the temperature at which the molding material melts. An extrusion port 20a through which the melted molding material is extruded is formed at the downstream end surface of the second cylinder portion 20.

[0018] The bolt 32 is inserted axially through the flange portion 20b of the second cylinder portion 20 and the cover portion 24 of the first cylinder portion 18 and screwed into the screw hole 16b formed in the support member 16, whereby the second cylinder portion 20 and the first cylinder portion 18 are jointly fastened and fixed to the support member 16.

[0019] The screw 12 is accommodated in the internal space S of the cylinder 10. The screw 12 includes a screw shaft 28 having a circular cross-section extending in the axial direction and a screw flight 30 extending spirally formed on the outer periphery of the screw shaft 28. The screw 12 is rotationally driven by a rotational drive device (not shown) connected to one end side thereof and rotates inside the internal space S about the central axis of the screw shaft 28. The screw 12 moves the molding material toward the extrusion port 20a by its rotation.

[0020] The support member 16 supports the upstream side of the cylinder 10 and also supports the hopper 14. The upstream side of the main body 22 of the first cylinder part 18 is fitted inside the support member 16, and the material supply port 22a is located inside the support member 16. A communication hole 16a that communicates the inside of the hopper 14 and the inside of the main body 22 of the first cylinder part 18 is formed in the support member 16.

[0021] The hopper 14 is filled with a molding material. The molding material falls from the hopper 14 into the communication hole 16a of the support member 16 and is supplied through the material supply port 22a to the inside of the main body 22, that is, the internal space S of the cylinder 10.

[0022] The above is the basic configuration of the extruder 100. Next, its operation will be described. The molding material filled in the hopper 14 falls into the communication hole 16a of the support member 16 and flows into the internal space S of the cylinder 10 through the material supply port 22a. The flowed-in molding material moves to the downstream side by the rotation of the screw 12. At that time, the molding material melts due to the heat from the inner wall surface of the cylinder 10 (that is, the heating by the heater 26) and the shear heat generated by being sheared by the screw 12. The melted molding material is extruded from the extrusion port 20a.

[0023] Next, the configuration of the main body 22 of the first cylinder part 18 will be described in more detail.

[0024] Figs. 2 to 4 are views showing the main body 22. Fig. 2 is a perspective view of the main body 22. Fig. 3 is an end view of the main body 22 cut by a vertical cross-section perpendicular to the central axis C and cutting across the material supply port 22a. The arrow in Fig. 3 indicates the rotation direction of the screw 12 (not shown in Fig. 3). Fig. 4 is a developed view of the main body 22 cut along the line A-A in Fig. 3 and developed. In Fig. 4, the display of the groove 22d is omitted.

[0025] The inner circumferential surface 22b of the main body portion 22 has a groove-forming region 22c, which is the area in which grooves 22d are formed. The main body portion 22 in this embodiment is not particularly limited, but it has a groove-forming region 22c that extends over the entire inner circumferential surface 22b. By forming grooves 22d on the inner circumferential surface 22b of the main body portion 22, the shape friction effect between the inner circumferential surface 22b of the main body portion 22 and the molding material is increased, and the transport force of the molding material is improved.

[0026] The groove 22d is a groove that extends spirally along the axial direction. The spiral shape of the groove 22d provides a higher dimensional friction effect compared to a non-spiral groove. Furthermore, the spiral direction of the groove 22d is opposite to that of the screw flight 30, resulting in a higher dimensional friction effect compared to a groove in the same direction. A higher dimensional friction effect improves the conveying force of the molding material. Note that the groove 22d is not limited to a spiral groove; for example, it may be a groove that extends linearly in the axial direction.

[0027] The groove-forming region 22c comprises a first groove-forming region 22e and a second groove-forming region 22f. In Figure 4, the region enclosed by the dotted line is the first groove-forming region 22e, and the region enclosed by the dashed line is the second groove-forming region 22f.

[0028] The first groove-forming region 22e is a region where the height of the peaks 22g that form the groove 22d is constant. In other words, the first groove-forming region 22e is a region where the distance from the central axis C to the top of the peaks 22g is constant. The "height" of the peaks 22g is the radial distance between the cylindrical reference plane P centered on the central axis C and the top of the peaks 22g. In this example, the reference plane P is a cylindrical plane passing through the deepest part of the groove.

[0029] The second groove-forming region 22f is a region where the height of the peaks 22g that form the groove 22d is lower than that of the peaks 22g in the first groove-forming region 22e. In other words, the second groove-forming region 22f is a region where the distance from the central axis C to the peaks 22g is long. The second groove-forming region 22f is not particularly limited, but in this example, the peaks 22g that are further from the material supply port 22a are higher. In other words, the distance from the central axis C to the peaks 22g is longer for peaks 22g that are further from the material supply port 22a. Also, the second groove-forming region 22f is not particularly limited, but in this example, each peak 22g is higher the further it is from the material supply port 22a. In other words, the distance from the central axis C to each peak 22g is longer the further it is from the material supply port 22a.

[0030] The second groove-forming region 22f is provided such that its axial range Rf (left-right direction in Figure 4) at least partially overlaps with the axial range Ra of the material supply port 22a.

[0031] In the illustrated example, the second groove-forming region 22f is provided such that its axial range Rf is wider than the axial range Ra of the material supply port 22a and overlaps with the entire range Ra. In other words, the second groove-forming region 22f is provided such that its axial range Rf encompasses the axial range Ra of the material supply port 22a. To put it another way, the second groove-forming region 22f is provided to extend from upstream of the material supply port 22a (specifically, from the upstream end face 22h of the main body portion 22) to downstream of the material supply port 22a.

[0032] The second groove-forming region 22f is located near the material supply port 22a in the circumferential direction and is provided on both sides of the material supply port 22a in the circumferential direction. Preferably, the second groove-forming region 22f is provided so as to extend circumferentially from the material supply port 22a (i.e., be continuous with the material supply port 22a). In this example, the second groove-forming region 22f is provided on both sides of the material supply port 22a in the circumferential direction, but the second groove-forming region 22f may be provided only on one side of the material supply port 22a in the circumferential direction.

[0033] On the other hand, in the axial direction, the portion of the inner circumferential surface 22b adjacent to the material supply port 22a (the portions to the right and left of the material supply port 22a in Figure 4) does not have a second groove forming region 22f, and in this example, only the first groove forming region 22e is formed. Of course, this is not the only option, and the second groove forming region 22f may be formed in these portions as well.

[0034] The second groove-forming region 22f may be formed by removing the peak portion 22g of the first groove-forming region 22e. That is, the entire groove-forming region 22c may first be formed as the first groove-forming region 22e, and then the second groove-forming region may be formed by removing a portion of the peak portion 22g within it; in other words, a portion of the first groove-forming region may be changed into the second groove-forming region 22f.

[0035] By making the groove-forming region 22c near the material supply port 22a a second groove-forming region 22f, which has a lower peak 22g than the first groove-forming region 22e, the internal space S of the cylinder 10 near the material supply port 22a is widened accordingly. In other words, a space (pocket) Sa is formed between a virtual circle passing through the peak 22g of the first groove-forming region 22e and a line connecting the peaks of the peaks of the second groove-forming region, which extends in an arc shape and into which the molding material can enter. As the internal space S widens, the amount of molding material flowing in per unit time increases, and as a result, the extrusion amount increases.

[0036] Furthermore, since the second groove-forming region 22f extends downstream of the material supply port 22a, the internal space S is also widened downstream of the material supply port 22a due to the formation of the second groove-forming region 22f. Some of the molding material falls diagonally downstream from the material supply port 22a, and because the internal space S on the downstream side of the material supply port 22a (i.e., the side of the extrusion port 20a) is widened, the amount of molding material flowing in per unit time increases further, and as a result, the amount of extrusion increases further.

[0037] Even if the second groove-forming region 22f extends upstream of the material supply port 22a, it is on the opposite side from the extrusion port 20a and therefore contributes little to no increase in the extrusion amount. However, when forming the second groove-forming region 22f by cutting the peak portion 22g of the first groove-forming region 22e, if the second groove-forming region extends from the end face 22h of the main body portion 22, the processing to form the second groove-forming region 22f becomes easier.

[0038] Figure 5 is a cross-sectional view along line BB in Figure 4. In the axial direction, the peaks 22g of the second groove-forming region 22f are connected to the peaks of the first groove-forming region 22e via inclined portions so that no step is formed between the peaks 22g of the first groove-forming region 22e and the peaks 22g of the second groove-forming region 22f. This reduces the flow resistance of the molding material and improves the conveying force of the molding material compared to the case where a step is formed.

[0039] According to the embodiment described above, a higher extrusion rate can be achieved with an extruder 100 of the same size as a conventional extruder. Conversely, a smaller extruder 100 can achieve the same extrusion rate as a conventional extruder.

[0040] The present invention has been described above based on embodiments. These embodiments are illustrative, and it will be understood by those skilled in the art that various modifications are possible in combinations of these components and processing processes, and that such modifications also fall within the scope of the present invention. Modifications will be described below.

[0041] Any combination of the embodiments and modifications described above is also useful as an embodiment of the present invention. The new embodiments resulting from these combinations possess the combined effects of the respective embodiments and modifications. [Industrial applicability]

[0042] This invention relates to an extruder. [Explanation of symbols]

[0043] 10 Cylinder, 12 Screw, 18 First cylinder section, 20 Second cylinder section, 22 Main body section, 22a Material supply port, 22b Inner circumferential surface, 22c Groove forming area, 22d Groove, 22e First groove forming area, 22f Second groove forming area, 22g Ridge section, 100 Extruder.

Claims

1. Cylinder and A screw housed in a cylinder, The inner circumferential surface of the cylinder has first and second groove-forming regions, where grooves are formed. The first groove-forming region has a constant height for the peaks that form the grooves. The second groove-forming region has an axial extent that at least partially overlaps with the axial extent of the material supply port, and the height of the groove-forming peaks is lower than that of the peaks in the first groove-forming region. An extruder characterized in that, in a cross-section perpendicular to the axial direction, the peaks formed in the second groove-forming region are higher the further away they are from the material supply port.

2. The extruder according to claim 1, characterized in that the second groove forming region is provided near the material supply port in the circumferential direction.

3. The extruder according to claim 1 or 2, characterized in that the second groove-forming region extends in the axial direction to a downstream side of the material supply port.

4. Cylinder and A screw housed in a cylinder, The inner circumferential surface of the cylinder has a first groove-forming region, a second groove-forming region, and a second groove-forming region separate from the first groove-forming region, in a cross section perpendicular to the axial direction and crossing the material supply port, respectively, where grooves are formed. The first groove-forming region has a constant height for the peaks that form the grooves. The second groove-forming region and the other second groove-forming region have a height of the groove-forming peak that is lower than the peak of the first groove-forming region. An extruder characterized in that, in the circumferential direction, the second groove-forming region is located between the material supply port and the first groove-forming region, and the other second groove-forming region is located between the material supply port and the first groove-forming region on the opposite side of the material supply port from the second groove-forming region.

5. The extruder according to claim 4, characterized in that the second groove-forming region and the other second groove-forming region extend in the axial direction downstream of the material supply port.

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