Screws, injection devices, and injection molding machines for injection molding machines

Abstract

A stepped ladder plate (28) is formed on the screw (18) of the injection molding machine (1). The stepped ladder plate (28) is attached to a stepped ladder plate (21) with a stepped portion at its top (29). The top (29) of the ladder plate (21) is composed of a large-diameter portion (31) on the upstream side and a flat portion (32) on the downstream side. Regarding the gap H1 between the flat portion (32) and the bore (35) of the heating cylinder (17), and the gap H2 between the large-diameter portion (31) and the bore (35), when the gap ratio m = H1 / H2 is set, the gap ratio m is selected to be 2.3 ≤ m ≤ 6.4.

Description

Technical Field

[0001] The present invention relates to a screw for an injection molding machine having a stepped, flat (land) portion formed at the top of a ladder plate, an injection device having the screw, and an injection molding machine thereof. Prior Technology

[0002] The injection unit of an injection molding machine consists of a heating cylinder and a screw inserted into the bore of the heating cylinder. A flight plate is formed on the screw to melt and measure the injected material; the flight plate can have various shapes.

[0003] For example, the screw described in Patent Document 1 is a stepped ladder plate with a stepped section formed at the top of the ladder plate. The stepped ladder plate is located at the top of the ladder plate, with the upstream side of the stepped section, i.e., the hopper side, becoming a large diameter section, and the downstream side, i.e., the injection nozzle side, becoming a flat section. [Previous Technical Documents] [Patent Literature]

[0004] [Patent Document 1] Japanese Patent No. 4977258 Summary of the Invention

[0005] (The problem the invention aims to solve)

[0006] However, the inventors have discovered that in injection molding devices equipped with the screw described in Patent Document 1, there is a problem with screws having stepped plates to improve plasticizing capacity. Screws with stepped plates produce a smaller amount of extruded material compared to conventional screws of the same diameter that do not have a stepped section at the top of the plate. This is because, at the top of the plate, only the large-diameter portion has a smaller gap with the heating cylinder bore, while the gap is larger in the flat portion. This is because the sealing effect at the top of the plate is inferior to that of conventional screws.

[0007] Therefore, the present invention provides a screw with high plasticizing capacity, an injection device, and an injection molding machine. (Technical means to solve the problem)

[0008] This invention relates to a screw for an injection molding machine, configured as follows: a stepped section is formed on the screw. The stepped section is configured such that a stepped portion is formed at the top of the section, and a large-diameter portion on the upstream side and a flat portion on the downstream side are formed. If the gaps between the flat portion and the large-diameter portion and the bore of the heating cylinder are respectively set as H1 and H2, and the gap ratio m = H1 / H2, then a value of 2.3 ≤ m ≤ 6.4 is selected. (Compared to the effectiveness of previous technologies)

[0009] According to the present invention, for a screw with a stepped plate, if the clearance ratio m is selected to be 2.3 or more and 6.4 or less, an increase in extrusion volume can be obtained. That is, the plasticizing capacity will be higher. Simple Explanation of the Diagram

[0010] Figure 1 is a front view of the injection molding machine of this embodiment. Figure 2 is a front cross-sectional view of the injection device in this embodiment. Figure 3 is a front view of a portion of the screw in this embodiment. Figure 4 is a cross-sectional view of the stepped plate of the screw in this embodiment. Figure 5 is a cross-sectional view of the stepped plate of the screw in this embodiment, and a graph showing the lubrication pressure generated at the top of the stepped plate by the injected material flowing between the stepped plate and the bore of the heating cylinder. Figure 6 is a schematic diagram illustrating the movement of a viscous fluid flowing in the gap between the moving plate and the stationary plate. Figure 7 is a graph showing the change in the load capacity coefficient of the lubrication pressure at the top of the ladder plate when the shape factor β is varied in the stepped section. Figure 8 is a graph showing the change in the load capacity coefficient of the lubrication pressure at the top of the ladder plate when the gap ratio m is varied in the stepped section. Figure 9 is a graph showing the amplitude of the screws at various screw positions, including three screws with different gap ratios m and a conventional screw, in a stepped plate with different gap ratios m. When the screw is rotated in the heating cylinder, it generates an amplitude, and the rotation axis is eccentric relative to the central axis of the heating cylinder. Figure 10 is a cross-sectional view of the stepped plate of the screw in the present embodiment of the heating cylinder. Figure 11 is a graph showing the relationship between the clearance ratio m and the load capacity factor. Figure 12 is a cross-sectional view of the upper half of the central axis of the screw in the stepped section of the screw in this embodiment of the heating cylinder. Implementation

[0011] The specific embodiments will now be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. For clarity, the following descriptions and drawings will be appropriately simplified. In each drawing, the same elements will be indicated by the same symbols, and repeated descriptions will be omitted as necessary. Furthermore, to avoid complicating the drawings, some parts with shading lines will be omitted.

[0012] The following describes this embodiment. Injection Molding Machine As shown in Figure 1, the injection molding machine 1 of this embodiment is roughly composed of a clamping device 2 disposed on the base (bed) B and an injection device 3 of this embodiment, which will be described later. The clamping device 2 is composed of a fixed platen 7, a movable platen 8, a clamping housing 9, connecting rods 10, 10, ... connecting the clamping housing 9 and the fixed platen 7, and a clamping mechanism 11 composed of a toggle mechanism. Molds 13 and 14 are disposed on the fixed platen 7 and the movable platen 8. If the clamping mechanism 11 is driven, molds 13 and 14 are clamped.

[0013] <Injection device> In this embodiment, the injection device 3 is designed to move freely forward and backward relative to the clamping device 2, injecting material into the molds 13 and 14 clamped by the clamping device 2. As shown in Figure 2, the injection device 3 consists of a heating cylinder 17 and a screw 18 as described in this embodiment. A hopper 19 is located near the rear end of the heating cylinder 17, and an injection nozzle 20 is located at the front end. When the injection material is fed into the hopper 19 and the screw 18 is rotated, the injection material is melted and conveyed forward for measurement. That is, in the injection device 3, the hopper 19 side is the upstream side, and the injection nozzle 20 side is the downstream side.

[0014] <Screw> In this embodiment, the screw 18, regarding the step plate 21, has a characteristic shape that will be described below, but the overall system is as follows. The depth of the groove formed by the step plate 21 on the screw 18 varies in different parts of the screw 18 and is divided within the heating cylinder 17. That is, on the upstream side of the screw 18, the groove is formed to be deeper, becoming the supply section 23 where the injected material is heated and transported downstream. Moreover, the groove depth gradually becomes shallower in the middle section, becoming the compression section 24 where the injected material is melted and compressed, and the groove is formed to be shallower in the downstream section, becoming the measuring section 25 where the injected material is measured.

[0015] The screw 18 of this embodiment is partially shown enlarged in FIG. 3, characterized in that a portion of the ladder plate 21 is a stepped ladder plate 28. A cross-section of the stepped ladder plate 28 obtained by cutting along line AA in FIG. 3 is shown in FIG. 4, revealing a distinctive top 29. Specifically, the top 29 of the stepped ladder plate 28 is formed as a stepped portion, consisting of a large-diameter portion 31 on the upstream side and a flat portion 32 on the downstream side. Since the flat portion 32 has a smaller diameter than the large-diameter portion 31 by a small step 33, the gap H1 between the bore 35 of the heating cylinder 17 and the flat portion 32 is larger than the gap H2 between the bore 35 of the heating cylinder 17 and the large-diameter portion 31. Because it is formed in this manner, the molten injection material enters the stepped ladder plate 28 and generates appropriate lubrication pressure at the top 29, preventing contact between the heating cylinder 17 and the screw 18.

[0016] Furthermore, in this embodiment, the stepped plate 28 is provided in both the compression section 24 and the measuring section 25. This is because when the screw 18 rotates, it generates amplitude, and its rotation axis deviates from the axis of the heating cylinder 17. The amplitude is relatively large in the compression section 24, and second only to the compression section 24 in the measuring section 25. Therefore, although the stepped plate 28 is provided within these intervals, even if it is only provided in the compression section 24 where the amplitude is larger, it is still effective in preventing contact between the heating cylinder 17 and the screw 18.

[0017] When the screw 18 rotates and delivers the injected material forward, the stepped plate 28 has a flat portion 32 compared to the stepped plate of a conventional screw, resulting in a larger gap H1. This makes the injected material flow more easily, but its plasticizing ability is lower than that of a conventional screw. However, the screw 18 of this embodiment has a characteristic range of gap ratio m, and even with the stepped plate 28, its plasticizing ability remains high. The gap ratio m is the ratio of gap H1 to gap H2, i.e., m = H1 / H2, and is specifically selected within the following range of values. 2.3≦m≦6.4 (numerical range A)

[0018] If the clearance ratio m is selected in this way, the plasticizing capacity is improved. This fact has been determined by the experiments described later. However, according to theoretical considerations based on the model described below, the ideal range for the clearance ratio m is 1.65 or higher and 2.15 or lower. This is because a higher lubrication pressure can be obtained within this range. The range A of the clearance ratio m selected in this embodiment is a larger range.

[0019] Two questions arise here. The first question is that even if the numerical range A is greater than the ideal range, the plasticizing capacity of the screw is still higher than that of the screw within the ideal range. Logically, a larger clearance ratio m should result in a larger clearance H1 in the flat portion 32, making the resin material flow more easily and reducing the plasticizing capacity. However, this is contrary to expectation. The second question is whether the required lubrication pressure will still be generated even if the clearance ratio m exceeds the ideal range. Regarding the first question, experiments have shown that the screw 18 of this embodiment has a higher plasticizing capacity than screws with a clearance ratio m within the ideal range. Regarding the second question, experiments have also confirmed that the required lubrication pressure can be obtained. These will be explained below.

[0020] First, the movement of the injected material in the stepped plate 28 of the step difference section is theoretically examined using a model.

[0021] <Mechanism of generating lubrication pressure and lubrication load capacity (W)> First, the mechanism of generating lubricating pressure in the stepped plate 28 is explained. The repulsive force that prevents the top 29 of the stepped plate 28 from contacting the bore of the heating cylinder 17, i.e., the lubricating load capacity W, is expressed by a formula.

[0022] As the screw 18 rotates within the heating cylinder 17, the stepped plate 28 is driven relative to the bore of the heating cylinder 17 at a predetermined speed. This speed can be divided into a component parallel to the stepped plate 28 and a component perpendicular to the stepped plate 28. Considering the component perpendicular to the stepped plate 28, the stepped plate 28 appears to move to the left relative to the heating cylinder 17 at a speed U', as shown in Figure 5. If the stepped plate 28 is considered fixed, the heating cylinder 17 can be considered to move to the right at a speed U. The speed U is equal in magnitude but opposite in direction to the speed U'.

[0023] The molten injection material enters gap H1 and exits from gap H2. Lubricating pressure is generated at this point. Figure 5 schematically illustrates the velocity distribution v of the injection material in gaps H1 and H2. The lubricating pressure p reaches its maximum value Ps at the boundary between the large-diameter section 31 and the flat section 32, i.e., near the stepped section, and is essentially zero at both ends of the stepped plate 28 in the stepped section. Furthermore, the lubricating pressure p in both the large-diameter section 31 and the flat section 32 exhibits a linear variation. This linear variation in lubricating pressure p is due to the laminar flow of the high-viscosity molten resin, where pressure is lost proportionally to the distance of laminar flow.

[0024] Here, we consider the typical movement of a viscous fluid between two relatively moving planes. Figure 6 shows a model consisting of a fixed plate 37 and a moving plate 38 that slides relative to the fixed plate 37 at a velocity V, with a Newtonian fluid filling the space between the fixed plate 37 and the moving plate 38. Considering the balance of forces acting on the fluid's minute element 39, Equation 1 can be obtained based on the balance of forces along the x-axis. Here, p is pressure, and τ is shear force. (Equation 1)

[0025] The shear force τ is given by Equation 2, which sets the viscosity of the fluid as μ and the velocity in the x-direction as v. (Equation 2) Based on equations 1 and 2, equation 3 can be obtained. (Equation 3) Equation 3 can also be derived from the so-called Navier-Stokes equations, thus becoming an equation representing the steady flow of an incompressible fluid.

[0026] If the gap in the y-direction between the fixed plate 37 and the moving plate 38 is set as h, then the fluid velocity v = 0 when y = h. Also, when y = 0, the fluid velocity v = V. By setting these as boundary conditions to solve Equation 3, the relationship between the flow velocity v and the pressure distribution can be obtained, i.e., Equation 4. (Equation 4) If we consider a unit width perpendicular to the paper, the flow rate Q of the fluid flowing through the gap h is given by equation 5, which is obtained by integrating equation 4. (Equation 5)

[0027] According to Equation 5, the flow rate Qx of the molten resin flowing through gaps H1 and H2 in the model shown in Figure 5 is calculated. The flow rate Qx is equal in gaps H1 and H2. Here, if the width of the stepped plate 28 in the stepped section is set to B1, and the width of the flat section 32 is set to B2, then the pressure gradient dp / dx is given by Ps / B2 in gap H1, and by (0-Ps) / (B1-B2) in gap H2. In this way, the flow rate Qx is given by Equation 6. (Equation 6)

[0028] If we solve equation 6 for the maximum value of the lubrication pressure Ps, we can obtain equation 7. (Equation 7)

[0029] The lubrication load capacity W per unit length of the stepped section 28 is obtained by integrating the lubrication pressure p along the width direction of the stepped section 28. However, as shown in Figure 5, the lubrication pressure p varies in the form of a triangle with a base length of B1 and a height of Ps. In this way, the load capacity W is given by the area. The load capacity W calculated in this way is shown in Equation 8. (Equation 8) Furthermore, Kw is the load capacity coefficient, m is the gap ratio, i.e., the ratio of gap H1 to H2, and β is the shape factor, i.e., the ratio of the width of the ladder plate B1 to the width of the flat part 32 B2.

[0030] The stepped plate 28, by means of the lubrication load capacity W shown in Equation 8, generates a repulsive force between the top 29 and the bore of the heating cylinder 17, thereby preventing such contact.

[0031] The lubrication load capacity W is proportional to the load capacity coefficient Kw, which varies according to the ratio of clearance H1 to H2 (i.e., clearance ratio m) and the ratio of the ladder width B1 to the width B2 of the flat portion 32 (i.e., shape factor β). Therefore, the variation of shape factor β with respect to various clearance ratios m for the load capacity coefficient Kw assigned by Equation 8 is shown in the graph of Figure 7. Furthermore, the variation of the load capacity coefficient Kw with respect to various shape factor β for the clearance ratio m is shown in the graph of Figure 8.

[0032] When the gap ratio m and shape factor β are below the following conditions, the load capacity coefficient Kw is 0.2 or higher. 1.65≦m≦2.15 0.63≦β≦0.79 At this point, the load capacity W becomes maximum, and the high lubrication pressure effectively prevents the top 29 of the stepped plate 28 from contacting the bore 35 of the heating cylinder 17. The above is based on a theoretical examination using the model.

[0033] As previously stated, in the stepped plate 28 of the screw 18 in this embodiment, the clearance ratio m is selected within the numerical range A. This selection is based on the following experiment. The first experiment will be described.

[0034] <Experiment 1> Experimental objective: In the screw 18 with the stepped plate 28, the relationship between the clearance ratio m and the plasticizing capacity will be clarified. Experimental preparation: Prepare a heating cylinder 17 with an inner diameter of 91.8 mm, and five screws X, Y, A, B, and C with the same screw diameter and the same depth of the stepped plate groove. Screw X is a conventional screw with a flat top of the stepped plate, while screws Y, A to C are screws 18 of this embodiment, which have stepped stepped plates 28 formed in the compression section 24 and the measuring section 25. Furthermore, for screws Y, A, B, and C, change the clearance ratio m = H 1 / H 2. Specifically, set it to 2.00, 2.33, 4.33, and 6.33, respectively.

[0035] Experimental methods: Screws X, Y, A, B, and C are sequentially mounted in heating cylinder 17. Polypropylene (PP) and polyethylene (PE) are supplied as resin materials, and the extrusion volume is measured. This extrusion volume serves as an indicator of the plasticizing capacity at the same screw rotation speed. That is, the higher the extrusion volume, the higher the plasticizing capacity. The extrusion volume is measured according to the following conditions 1 and 2. "Condition 1": Measure the weight of the resin material extruded by the rotating screw in 90 seconds. "Condition 2": The weight of the extruded resin material is measured by rotating the screw for 10 seconds and stopping for 10 seconds, then rotating the screw for 10 seconds and stopping for 10 seconds, and so on, repeated 10 times. The experimental results are shown in Table 1.

[0036] [Table 1] Screw X Screw Y Screw A Screw B Screw C Gap ratio m (H1 / H2) - 2.00 2.33 4.33 6.33 PP Condition 1 4568 3996 4207 4385 4501 Condition 2 5386 4925 5036 5148 5388 PE Condition 1 5806 5343 5410 5657 5764 Condition 2 6838 6310 6455 6487 6769 Unit g

[0037] Experimental investigation: Although the clearance ratio m of screw Y falls within the ideal value range obtainable through theoretical examination based on the model, the extrusion volume is smaller compared to the traditional screw, i.e., screw X. In contrast, although the clearance ratio m of screws A, B, and C exceeds the ideal value range and becomes larger, the extrusion volume is greater than that of screw Y.

[0038] However, if we consider the flow rate Q1 of the ejected material flowing in the gap H1 of the flat section 32 according to formula 5, we can obtain the following formula 9. (Equation 9) Originally, since increasing the gap ratio (m) would necessarily increase the gap H1, according to the first term of Equation 9, the flow rate Q1 should increase. Since the flow rate Q1 might be due to leakage of the injected material at the top 29 of the ladder plate 21, increasing the gap ratio (m) should decrease the extrusion rate. However, the results of this experiment showed the opposite effect to this prediction.

[0039] The following analysis is conducted using Figure 10. When the gap ratio m is large, i.e., when the gap H1 is larger than the gap H2, material retention occurs in the area indicated by symbol 41 near the step difference 33. This retention has the effect of pushing the injected material back, resulting in a thinner flow thickness of the injected material in the flat portion 32. Consequently, the apparent gap H1' is smaller than the actual gap H1. Therefore, the flow rate Q1 shown in Equation 9 decreases. The larger the gap ratio m, the larger the retention area 41, and the smaller the apparent gap H1' is than the actual gap H1. As a result, the flow rate Q1 decreases while the extrusion volume increases.

[0040] Conclusion of the experiment: It is known that among the screws 18 equipped with stepped plates 28, screws A, B, and C with clearance ratios m of 2.33, 4.33, and 6.33 all have higher plasticizing capacity than screw Y with a clearance ratio m of 2.00. From the viewpoint of plasticizing capacity, the clearance ratio m is preferably within the above-mentioned value range A. More preferably, the clearance ratio m is 2.3 or higher and 4.3 or lower.

[0041] Secondly, for the screw 18 with such a numerical range A and a clearance ratio m, a second experiment was conducted to confirm whether the required lubrication pressure would be generated.

[0042] <Experiment 2> The purpose of the experiment: When measuring the injected material by rotating the screw 18 within the heating cylinder 17 with a clearance ratio m within the numerical range A, it is confirmed whether the lubrication pressure is properly generated to reliably prevent the top 29 of the ladder plate 21 from contacting the bore 35.

[0043] Preparation for the experiment: In the injection device 3 of this embodiment shown in Figure 2, sensors for detecting the distance to the screw are embedded in several parts G7, G8, ..., G12 of the heating cylinder 17. Parts G7 to G9 correspond to the compression section 24, while parts G10 to G12 correspond to the measuring section 25. The screws X, A, B, and C used in Experiment 1 are provided.

[0044] The order and results of the experiment: In the heating cylinder 17, screws X, A, B, and C are sequentially arranged and rotated to measure the injected material. The screw amplitude ratio at each location is obtained from the distances detected at G7, G8, ..., G12. The results are shown in the graph in Figure 9. Symbols 46, 47, and 48 represent the curves for screws A, B, and C, i.e., the curves with clearance ratios m of 2.33, 4.33, and 6.33, respectively. Symbol 49 represents the curve for screw X, i.e., the curve of a conventional screw. Furthermore, when the central axis of screw 18 coincides with the central axis of the heating cylinder 17, the screw amplitude ratio is 0.0; then, when screw 18 contacts the bore of the heating cylinder 17, the screw amplitude ratio is 1.0. According to the graph in Figure 9, the screw amplitude ratio in this embodiment is in the range of 0.17 to 0.82.

[0045] Investigation: Even with a clearance ratio m of 6.4, the screw amplitude of screw C is significantly smaller than that of a conventional screw, and the required lubrication pressure can be obtained. However, this screw C has a form factor β of 0.94, and according to formula 8 (which serves as a theoretical expression), the load capacity coefficient Kw is 0.056, which theoretically predicts may not necessarily result in sufficient lubrication pressure. But in reality, experiments have confirmed that the required lubrication pressure can be obtained. If we speculate on the reason, as examined in the first experiment shown in Figure 10, it may be because when the clearance ratio m is large, the apparent clearance H1' is thinner than the clearance H1 of the flat portion 32. As a result, as illustrated in Figure 11, for example, the curve shown in Figure 8 representing the relationship between the clearance ratio m and the load capacity coefficient Kw when the form factor β is 0.9 will actually become a dashed curve 50.

[0046] Conclusion of the experiment: It can be confirmed that among the screws 18 equipped with the stepped plate 28, screws A, B, and C with clearance ratios m of 2.33, 4.33, and 6.33 can all obtain the required lubrication pressure, while appropriately preventing contact with the bore 35 of the heating cylinder 17. It is clear that selecting a clearance ratio m from the numerical range A will not cause any problem in obtaining the required lubrication pressure.

[0047] According to the second experiment, even with a shape factor β of 0.94, sufficient lubrication pressure can be obtained. From the curves in Figure 8, it can be seen that when the shape factor β is 0.5 and the clearance ratio m is 4.6 or less, the theoretical load capacity coefficient Kw is 0.056 or more. Furthermore, it can be seen that when the shape factor β is 0.6 and the clearance ratio m is 5.2 or less, the theoretical load capacity coefficient Kw is 0.056 or more. Additionally, it can be seen that when the shape factor β is 0.95 and the clearance ratio m is 6.5 or less, the theoretical load capacity coefficient Kw is 0.056 or more. It is clear that when the clearance ratio m is large, the actual load capacity coefficient Kw is greater than the theoretical value, and the required lubrication pressure can be obtained. Therefore, it can be said that the optimal range for the shape factor β is 0.5 or more and 0.95 or less.

[0048] Secondly, the optimal conditions for the diameter of the screw 18 are also considered. As shown in Figure 12, in the compression section 24, the solid injection material 51 and the molten injection material 52 are mixed together in the heating cylinder 17. The solid injection material 51 accumulates on the back of the ladder plate 21, i.e., the upstream side, thereby forming a solid bed 54. A melt film 55 composed of molten injection material is formed between the solid bed 54 and the bore 35 of the heating cylinder 17, and a molten pool 57 composed of molten injection material is formed on the upstream side of the solid bed 54.

[0049] When the screw 18 rotates, lubrication pressure is generated at the top 29 of the stepped plate 28 as described above, but negative pressure is generated on the molten film 55. This negative pressure causes the screw 18 to vibrate when it rotates, and the thinner the thickness H3 of the molten film 55, the larger its size. That is, if the thickness H3 of the molten film 55 is thin, there is a risk that the screw 18 will come into contact with the bore 35 of the heating cylinder 17.

[0050] However, the thickness H3 of the molten film 55 increases with the increase of the diameter of the screw 18. That is, if the injection device 3 becomes larger, the thickness H3 of the molten film 55 will become thicker. This is because the larger the machine, the more efficient it is to melt the injection material and to heat the heating cylinder 17. Also, the larger the machine, the lower the rotation speed of the screw 18, and the longer the melting time of the injection material. The industry generally considers a screw 18 with a diameter of 70 mm or more to be a large machine, but for a screw 18 with a diameter of 70 mm or more, the thickness H3 of the molten film 55 is large enough that the effect of the negative pressure caused by the molten film 55 does not need to be considered. Therefore, the diameter of the screw 18 is preferably 70 mm or more. For example, the diameter of the large diameter portion 31 of the screw 18 is 70 mm or more. Furthermore, the diameter of the large diameter portion 31 of the screw 18 is, for example, 450 mm or less, preferably 200 mm or less, and more preferably 130 mm or less.

[0051] Although the invention completed by the inventor in this case has been specifically described above according to the embodiments, the present invention is not limited to the aforementioned embodiments, and various modifications can naturally be made within the scope of its spirit. The several examples described above can also be appropriately combined and implemented.

[0052] 1: Injection molding machine 2: Mold clamping device 3: Injection device 7: Fixed plate 8: Movable disc 9: Mold Locking Housing 10: Connecting rod 11: Mold clamping mechanism 13: Mold 14: Mold 17: Heating cylinder 18: Screw 19: Hopper 20: Injection nozzle 21: Ladder board 23: Supply Department 24: Compression section 25: Measurement Department 28: Stepped section of the ladder plate 29: Top 31: Large diameter section 32: Flat area 33: Step difference 35: Pipeline 37: Fixing plate 38: Sports Film 39: Tiny elements 41: Area 46, 47, 48, 49, 50: Curve graphs 51, 52: Injection Material 54: Solid Bed 55: Melting film 57: Molten Pool A: Numerical range / screw B: Base / Screw B 1: Ladder width B 2: Width of the flat section C,X,Y: Screw G7, G8, G9, G10, G11, G12, G13: Location H1, H2, h: gaps H 1': Apparent gap H 3: Thickness m: clearance ratio P: Lubrication pressure Ps: Maximum lubrication pressure p: pressure Q: Traffic U,U': speed V: Speed v: velocity of the ejected material x, y: Direction β: Shape factor τ: Shear force

Claims

1. A screw that is inserted into the bore of a heating cylinder of an injection molding machine; the screw has a ladder plate, and a stepped portion is formed at the top of the ladder plate on a portion of the screw, the ladder plate forming the stepped portion is a stepped portion ladder plate, the stepped portion ladder plate is composed of a large-diameter portion on an upstream side and a flat portion on a downstream side, the gap ratio (m = H1 / H2) of the gap (H2) between the large-diameter portion and the bore and the gap (H1) between the flat portion and the bore is 2.3 or more and 6.4 or less, the width (B1) of the ladder plate in the direction perpendicular to the lead angle and the width (B2) of the flat portion are both 0.5 times and 0.95 times the width (B1).

2. As in request item 1, the screw, wherein, The diameter of the aforementioned large-diameter section is 70 mm or more.

3. As in request item 1 or 2, the screw, wherein, When the screw rotates in the heating cylinder, the heating cylinder is divided into a supply section upstream of the injected material, a compression section where the injected material is melted and compressed, and a measuring section where the molten injected material is measured. The stepped plate is formed at least throughout the compression section.

4. As in request item 3, the screw, wherein, The aforementioned stepped plate is continuously formed in such a way that it extends from the aforementioned compression section toward the aforementioned measuring section.

5. An injection device comprising a heating cylinder having a bore and a screw; wherein a stepped portion is formed at the top of a stepped plate in a portion of the screw, the stepped plate in the portion of the screw being a stepped plate, the stepped plate being composed of a large-diameter portion on an upstream side and a flat portion on a downstream side, the gap ratio (m = H1 / H2) of the gap (H2) between the large-diameter portion and the bore and the gap (H1) between the flat portion and the bore is 2.3 or more and 6.4 or less, and the width of the stepped plate (B1) in the direction perpendicular to the lead angle and the width of the flat portion (B2) are both 0.5 times and 0.95 times the width (B1).

6. The injection device as claimed in claim 5, wherein, The diameter of the aforementioned large-diameter section is 70 mm or more.

7. The injection device as claimed in claim 5 or 6, wherein, When the screw rotates in the heating cylinder, the heating cylinder is divided into a supply section upstream of the injected material, a compression section where the injected material is melted and compressed, and a measuring section where the molten injected material is measured. The stepped plate is formed at least throughout the compression section.

8. The injection device as claimed in claim 7, wherein, The aforementioned stepped plate is continuously formed in such a way that it extends from the aforementioned compression section toward the aforementioned measuring section.

9. An injection molding machine comprising a mold clamping device for clamping a mold and an injection device for injecting material into the mold; the injection device comprising a heating cylinder having a bore and a screw, wherein a portion of the screw has a stepped portion formed at the top of a stepped plate to form a stepped plate, the stepped plate being composed of a large-diameter portion on an upstream side and a flat portion on a downstream side, wherein the gap ratio (m = H1 / H2) of the gap (H2) between the large-diameter portion and the bore and the gap (H1) between the flat portion and the bore is 2.3 or more and 6.4 or less, and the width (B1) of the stepped plate in the direction perpendicular to the lead angle and the width (B2) of the flat portion are both 0.5 times or more and 0.95 times the width (B1).

10. The injection molding machine as described in claim 9, wherein, The diameter of the aforementioned large-diameter section is 70 mm or more.

11. The injection molding machine as described in claim 9 or 10, wherein, When the screw rotates in the heating cylinder, the heating cylinder is divided into a supply section upstream of the injected material, a compression section where the injected material is melted and compressed, and a measuring section where the molten injected material is measured. The stepped plate is formed at least throughout the compression section.

12. The injection molding machine as claimed in claim 11, wherein, The aforementioned stepped plate is continuously formed in such a way that it extends from the aforementioned compression section toward the aforementioned measuring section.

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