Injection device

Abstract

The present invention provides an injection device (20) comprising a heating cylinder (27), a screw (29), an injection table (26) that supports the heating cylinder (27), a drop port bushing (40) that is attached to the injection table (26), a hopper holding member (50) that is disposed on the drop port bushing (40), and a hopper (28) that is disposed on top of the hopper holding member (50), wherein a resin material stored in the hopper (28) is dropped into the heating cylinder (27) via the hopper holding member (50) and the drop port bushing (40). The drop port bushing (40) is provided with a first gas passage (42) extending upward and leading a gas generated from the resin material in the heating cylinder (27). The hopper holding member (50) is provided with a second gas passage (57) connected to the first gas passage (42) and leading the gas as well as a gas outlet from which to discharge the gas.

Description

injection device

[0001] The present invention relates to an injection device that kneads and injects a resin material in a heating barrel.

[0002] The solid resin material is kneaded and melted by the screw inside the heating barrel of the injection device. During this process, a small amount of gas may be generated from the resin material. This gas is injected into the mold along with the molten resin material. The resulting resin product contains a small amount of gas.

[0003] General-purpose resin products are allowed to contain trace amounts of gas. However, some resin products require a certain level of purity. Therefore, there is a need to reduce the amount of gas contained in resin products. One technique that meets this requirement is known, for example, as disclosed in Patent Document 1.

[0004] Patent Document 1 will be described with reference to the following figure. Figure 6 is a diagram illustrating the basic structure of a conventional injection device. As shown in Figure 6, an injection device 100 includes a barrel 101, a hopper 102, a hopper base 103 that supports the hopper 102, a screw 104, a barrel support base 105 that supports the barrel 101, and a barrel presser 106 that holds the barrel 101. In the technology of Patent Document 1, such an injection device 100 is further equipped with the following elements.

[0005] That is, it comprises a nitrogen gas supply source 111 that supplies nitrogen gas to the drop port 107 below the hopper 102, a first exhaust passage 112 that extends upward from the tail of the barrel support base 105, a first vacuum generator 113 provided in this first exhaust passage 112, a second exhaust passage 114 that extends upward from the barrel retainer 106, and a second vacuum generator 115 provided in this second exhaust passage 114.

[0006] Gas generated when resin material 116 is kneaded and plasticized by screw 104 is forcibly discharged to the atmosphere (i.e., outside) by first vacuum generator 113 and second vacuum generator 115 via first exhaust passage 112 and second exhaust passage 114. As a result, the resin product obtained by the technology of Patent Document 1 maintains a certain level of purity or higher.

[0007] However, the technology of Patent Document 1 has the following problem. When the resin material 116 is a powder, a portion of the resin material 116 is sucked by the first vacuum generator 113 and the second vacuum generator 115 and discharged to the outside. This reduces the yield, which is expressed as (weight of resin product / weight of resin material). This reduction in yield undesirably reduces the effective utilization rate of the resin material 116.

[0008] The first vacuum generator 113 and the second vacuum generator 115 are devices that are driven by compressed air (Patent Document 1, paragraph 0052), which is typically installed in factories. Alternatively, the first vacuum generator 113 and the second vacuum generator 115 are vacuum pumps that are driven by electric motors. When the driving source is compressed air, energy (electrical energy, etc.) is required to compress the air. In the case of a vacuum pump, electrical energy is required. As a result, the technology of Patent Document 1 requires high operating costs.

[0009] Therefore, there is a need for an injection device that can produce resin products of required purity without the risk of powdered resin material being discharged to the outside and that can reduce operating costs.

[0010] Patent No. 5138183

[0011] An object of the present invention is to provide an injection device that eliminates the risk of powdered resin material being discharged to the outside and that can reduce operating costs.

[0012] The invention of claim 1 is an injection device comprising a heating barrel, a screw rotatably and axially movable in the heating barrel, an injection stand supporting the heating barrel, a drop inlet bushing attached to the injection stand, a hopper holding member arranged on the drop inlet bushing, and a hopper arranged on the hopper holding member, wherein resin material stored in the hopper is dropped into the heating barrel via the hopper holding member and the drop inlet bushing, wherein the drop inlet bushing is provided with a first gas passage extending upward to guide gas generated from the resin material in the heating barrel, and the hopper holding member is provided with a second gas passage connected to the first gas passage to guide the gas, and a gas outlet for discharging the gas to the outside.

[0013] The invention according to claim 2 is preferably the injection device according to claim 1, wherein the second gas passage of the hopper holding member comprises a vertical passage that is connected to the first gas passage and extends upward, and a horizontal passage that extends horizontally from the upper end of the vertical passage, and the gas outlet is provided at the outlet of the horizontal passage, and the gas is discharged horizontally from this gas outlet.

[0014] A third aspect of the present invention is preferably the injection device according to the first or second aspect, wherein the gas outlet is provided with a filter for capturing powder discharged along with the gas.

[0015] A fourth aspect of the present invention is preferably the injection device according to the first aspect, wherein the drop inlet bushing is made of a corrosion-resistant material that is resistant to corrosion by the gas.

[0016] A fifth aspect of the present invention is preferably the injection device according to the first aspect, wherein the hopper holding member and the drop inlet bushing are made of a corrosion-resistant material that is resistant to corrosion by the gas.

[0017] In the invention according to claim 1, a first gas passage is provided in the drop inlet bushing and a second gas passage is provided in the hopper holding member, so that gas is discharged to the outside via the first gas passage and the second gas passage. No vacuum pump or the like is used for this discharge. That is, in this invention, the gas is discharged by the so-called natural exhaust method. Because a vacuum pump or the like is not used, electrical energy is not required, and operating costs can be reduced.

[0018] The natural exhaust method is a gentler exhaust method than the forced exhaust method, and with this type of exhaust method, no powdered resin material is discharged to the outside, or even if it is, it is only a small amount. Therefore, the present invention provides an injection device that does not have to worry about powdered resin material being discharged to the outside and can reduce operating costs.

[0019] In the invention according to claim 2, the second gas passage comprises a vertical passage extending upward together with the first gas passage and a horizontal passage extending horizontally from the upper end of the vertical passage. The second gas passage is provided in the hopper holding member, and because the second passage is a simple passage consisting of a vertical passage and a horizontal passage, the processing costs of the hopper holding member can be reduced.

[0020] In the invention according to claim 3, a filter is provided at the gas outlet of the side passage to capture powder discharged with the gas. In principle, powder is not discharged to the outside in this invention, but there is a possibility that a small amount of powder may be discharged. Even in this case, providing a filter prevents the powder from being discharged to the outside, which is preferable.

[0021] In the invention according to claim 4, the drop inlet bushing is made of a corrosion-resistant material. When the resin material is polyvinyl chloride, a small amount of chlorine-based gas is generated. Chlorine-based gas is corrosive. If the drop inlet bushing is made of a corrosion-resistant material, polyvinyl chloride can be added to the resin material. As a result, the types of resin materials that can be processed can be increased.

[0022] In the invention according to claim 5, the hopper holding member and drop inlet bushing are made of a corrosion-resistant material. When the resin material is polyvinyl chloride, a small amount of chlorine-based gas is generated. Chlorine-based gas is corrosive. If the hopper holding member and drop inlet bushing are made of a corrosion-resistant material, polyvinyl chloride can be added to the resin material. As a result, the types of resin materials that can be processed can be increased.

[0023] 1 is a side view of an injection molding apparatus including an injection apparatus according to the present invention. (a) is a plan view of a drop inlet bushing, (b) is a cross-sectional view of the drop inlet bushing, and (c) is a bottom view of the drop inlet bushing. (a) is a plan view of a hopper holding member, (b) is a cross-sectional view of the hopper holding member, and (c) is a bottom view of the hopper holding member. 2 is a diagram explaining the operation of the injection apparatus according to the present invention. (a) and (b) are diagrams for examining the height of the drop inlet bushing. 3 is a diagram explaining the basic structure of a conventional injection apparatus.

[0024] An embodiment of the present invention will be described below with reference to the accompanying drawings.

[0025] 1, an injection molding apparatus 10 is an apparatus whose main components are a mold clamping device 11, an injection device 20, and a bed 12 that supports the mold clamping device 11 and the injection device 20. The mold clamping device 11 is an apparatus that clamps a mold 13, and only a portion of it is shown for convenience of drawing.

[0026] [Injection Unit] Rails 21 are laid on the bed 12, and a movable table 22 is supported by the rails 21. The injection unit 20 is supported by the movable table 22 so as to be horizontally movable. For example, an injection unit moving cylinder 23 is placed between the movable table 22 and the fixed platen 14. The injection unit moving cylinder 23 moves the nozzle 24 back and forth between a position where it touches the mold 13 and a position sufficiently separated from the mold 13 (the position shown in FIG. 1). A hydraulic cylinder or an electric cylinder can be used as the injection unit moving cylinder 23.

[0027] The injection device 20 includes an injection table 26 supported by a movable table 22, a heating barrel 27 supported by the injection table 26, a hopper 28 that supplies resin material to the heating barrel 27, a screw 29 that is housed in the heating barrel 27 so as to be rotatable and axially movable, a screw moving cylinder 31 attached to the injection table 26, a moving plate 33 supported by a piston rod 32 of the screw moving cylinder 31, and a screw rotation mechanism 34 that is supported by the moving plate 33 and rotates the screw 29.

[0028] A hydraulic cylinder or an electric cylinder can be used as the screw moving cylinder 31. An electric motor or a hydraulic motor can be used as the screw rotating mechanism 34.

[0029] The injection device 20 further includes the following elements: a drop inlet bushing 40 attached to the injection table 26, and a hopper holding member 50 disposed on the drop inlet bushing 40. The hopper 28 is disposed on the hopper holding member 50.

[0030] [Plasticization and metering process] Plasticization and metering process: While the screw 29 is rotated in a predetermined direction by the screw rotation mechanism 34, the resin material is supplied from the hopper 28 to the heating barrel 27. The resin material moves within the heating barrel 27 along the spiral groove of the screw 29 to the vicinity of the nozzle 24. During this movement, the resin material is kneaded and plasticized, and the plasticized resin material accumulates in the front part of the heating barrel 27. The reaction force of this accumulated resin material causes the screw 29 to retreat (move away from the nozzle 24). When the screw 29 retreats to a predetermined position, the rotation of the screw 29 is stopped. In this manner, plasticization and metering are performed.

[0031] [Injection Process] Injection process: With the nozzle 24 in contact with the mold 13, the screw 29 is advanced by the screw moving cylinder 31. Due to this advancement, the resin material is injected into the mold 13 through the nozzle 24.

[0032] [Resin Material] The resin material is not particularly limited, but resin materials that generate gas during the plasticization and metering process can be processed by the injection device 20 of the present invention. Examples of resins that generate gas include polyvinyl chloride (PVC), polyphenylene sulfide (PPS), polycarbonate (PC), polyether ether ketone (PEEK), acrylonitrile butadiene styrene resin (ABS), and polymethacrylate (PMMA).

[0033] [Drop Inlet Bush] The structure of the drop inlet bush 40 will be described in detail with reference to Figures 2(a) to 2(c). Figure 2(a) is a plan view of the drop inlet bush 40, Figure 2(b) is a cross-sectional view of the same, and Figure 2(c) is a bottom view of the same.

[0034] As shown in Fig. 2(a), the drop inlet bushing 40 has a drop inlet 41 in the center, through which the resin material drops. The drop inlet bushing 40 has a plurality of first gas passages 42 (eight in this example) surrounding the drop inlet 41. As shown in Fig. 2(b), the drop inlet bushing 40 has a flange 43. As shown in Fig. 2(c), the plurality of first gas passages 42 can be seen surrounding the drop inlet 41.

[0035] [Material of Drop Inlet Bush] The material of the drop inlet bush 40 may be ordinary carbon steel, mechanical structural steel, or cast iron, but when the resin material being handled contains polyvinyl chloride, it is recommended to use a corrosion-resistant material such as stainless steel that is resistant to corrosion by chlorine-based gases.

[0036] 2(a) to 2(c), the drop inlet bushing 40 has an extremely simple shape. It does not have any particularly fine threads (also called taps). Therefore, the drop inlet bushing 40 can be easily machined.

[0037] [Hopper Holding Member] The structure of the hopper holding member 50 will be described in detail with reference to Figures 3(a) to 3(c). Figure 3(a) is a plan view of the hopper holding member 50, Figure 3(b) is a cross-sectional view of the same, and Figure 3(c) is a bottom view of the same.

[0038] As shown in Figure 3(a), the hopper holding member 50 is a square thick plate with a through hole 51 in the center having the same diameter as the drop opening (Figure 2(a), symbol 41), a bar 52 that crosses this through hole 51, and a screw portion 53 and a bolt hole 54 at each of the four corners.

[0039] Arranging the bars 52 in a grid pattern prevents objects larger than the mesh of the grid (including an operator's hand) from falling from the hopper (FIG. 1, reference numeral 28) into the drop opening. Hopper holding members with a falling object prevention mechanism are general-purpose products, and the hopper holding member 50 can be easily obtained by machining this general-purpose product.

[0040] 1 is threaded into the threaded portion 53, the hopper 28 can be fixed to the hopper holding member 50. In addition, the hopper holding member 50 can be fixed to the injection platform 26 shown in FIG. 1 by passing a hexagon socket head bolt 55 through the bolt hole 54.

[0041] In FIG. 1, the drop inlet bushing 40 is dropped into the launching platform 26, the hopper holding member 50 is placed on top of it, and the hopper holding member 50 is fixed to the launching platform 26 with a hexagon socket bolt (FIG. 3(a), symbol 55). The drop inlet bushing 40 is simply placed on the launching platform 26 by the flange 43. The drop inlet bushing 40 is prevented from coming off upward by the hopper holding member 50. Therefore, as mentioned above, the structure of the drop inlet bushing 40 is simplified.

[0042] As shown in Fig. 3(b), the hopper holding member 50 has a second gas passage 57. The second gas passage 57 is made up of a vertical passage 58 that is connected to the upper end of the first gas passage (Fig. 2(b), reference numeral 42) and extends upward, and a horizontal passage 59 that extends horizontally from the upper end of the vertical passage 58.

[0043] As shown in Fig. 3(c), the vertical passage 58 is an annular groove. If it is an annular groove, the first gas passage 42 will always be connected to the vertical passage 58 shown in Fig. 3(a) even if the drop inlet bushing 40 shown in Fig. 2(a) rotates. As shown in Fig. 3(a), a plurality of horizontal passages 59 (four in this example) are connected to this annular groove-shaped vertical passage 58.

[0044] As shown in FIG. 3B, a female thread 62 may be provided at the gas outlet 61 of the horizontal passage 59, and a cylindrical filter 63 may be attached to this female thread 62.

[0045] Whether or not to attach the filter 63 is optional, but the following criteria are recommended: Attach the filter 63 when the resin material being handled is a powder. Do not attach the filter 63 when the resin material being handled is not a powder. In this case, the female thread portion 62 may be omitted.

[0046] [Powder and beads] When the resin material is a powder, the particle size of the powder is 200 μm to 300 μm. Beads are known as a non-powder resin material. The particle size of beads is several mm. When powder or beads are subjected to wind pressure, the wind pressure acts in proportion to the cross-sectional area (the square of the radius). On the other hand, the mass (weight) of powder or beads is proportional to the cube of the radius. Depending on the balance between this mass and wind pressure, beads are less likely to fly away and powder is more likely to fly away. Therefore, in the case of beads, filter 63 is not necessary, but in the case of powder, it is recommended to install filter 63.

[0047] [Material of Hopper Holding Member] The material of the hopper holding member 50 is preferably a corrosion-resistant material such as stainless steel that is resistant to corrosion by chlorine-based gases.

[0048] However, as explained in Figures 3(a) to 3(c), the hopper holding member 50 has a somewhat complicated structure, so ordinary carbon steel, mechanical structural steel, or cast iron may also be used. Carbon steel and the like are inexpensive and can be replaced with new ones as needed. Therefore, whether the material for the hopper holding member 50 is made of expensive stainless steel or inexpensive carbon steel or the like can be selected arbitrarily in consideration of cost-effectiveness.

[0049] The operation of the injection device 20 configured as described above will be described with reference to Fig. 4. In Fig. 4, the resin material stored in the hopper 28 passes through the through hole 51 and the drop port 41 and falls into the heating barrel 27. The resin material is kneaded and plasticized by the screw 29. Gas may be generated during this process.

[0050] Fluids containing gas flow where it is easiest to flow. Fluids containing gas also flow toward the outlet. Gases that are lighter than air rise in the atmosphere. Gases behave according to these laws of nature. The gas outlet of the present invention (Figure 3(b), reference numeral 61) is the outlet toward which the fluid flows.

[0051] That is, the gas generated in the heating barrel 27 flows toward the first gas passage 42 as indicated by an arrow G1. The gas passes through the first gas passage 42 and the second gas passage 57 and is discharged to the outside as indicated by an arrow G2.

[0052] The amount of gas in the heating cylinder 27 is reduced by the amount of gas discharged. As a result, the amount of gas contained in the resin product falls within an allowable range, and the quality of the resin product is maintained.

[0053] The flow of arrow G1 is based on natural exhaust and is therefore very gentle. Therefore, unlike forced exhaust, powder is not actively exhausted to the outside along with the gas, and even if it is, it is only a small amount. Because the amount is small, the filter 63 is not essential. However, providing the filter 63 is more preferable as it can reliably capture the small amount of powder.

[0054] [Height Dimension of Drop Inlet Bush] Next, the height dimension of drop inlet bushing 40 will be considered. The bottom surface of drop inlet bushing 40 shown in Fig. 5(a) extends to inner circumferential surface 27a of heating barrel 27. Although gas can be vented with this structure, there is a risk that the lower opening of first gas passage 42 will be blocked by the resin material.

[0055] The bottom surface of the drop inlet bushing 40 shown in Figure 5(b) extends to the outer peripheral surface 27b of the heating barrel 27. As a result, a cylindrical space 65 (see Figure 4) is secured in the heating barrel 27, calculated by multiplying the wall thickness of the heating barrel by the bottom area of ​​the drop inlet bushing. The resin material 64 dropping from the drop inlet 41 spreads out in a truncated cone shape, but subspaces 66 with triangular cross sections remain at the corners of the space 65. The presence of these subspaces 66 keeps the first gas passage 42 open, allowing the gas to smoothly enter the first gas passage 42. Therefore, Figure 5(b) is recommended over Figure 5(a).

[0056] The first gas passage 42 shown in Fig. 2(b) may extend vertically upward or may be an inclined passage, as long as it extends upward. Similarly, the vertical passage 58 shown in Fig. 3(b) may extend vertically upward or may be an inclined passage, as long as it extends upward. Furthermore, the horizontal passage 59 shown in Fig. 3(b) may extend horizontally or may be inclined relative to the horizontal, as long as it extends horizontally.

[0057] In addition, the drop inlet bushing 40 and the hopper holding member 50 are separate components, but they may also be integrated into a single component. That is, the flange 43 shown in FIG. 2( b) may be enlarged and the second gas passage 57 may be formed in the enlarged flange 43.

[0058] The present invention is suitable for an injection device that injects a powdered resin material.

[0059] 20...injection device, 26...injection table, 27...heating barrel, 28...hopper, 29...screw, 40...drop inlet bushing, 42...first gas passage, 50...hopper holding member, 57...second gas passage, 58...vertical passage, 59...horizontal passage, 61...gas outlet, 63...filter, 64...resin material.

Claims

1. An injection device comprising: a heating barrel; a screw rotatably and axially movable in the heating barrel; an injection stand supporting the heating barrel; a drop inlet bushing attached to the injection stand; a hopper holding member placed on the drop inlet bushing; and a hopper placed on the hopper holding member, wherein resin material stored in the hopper is dropped into the heating barrel via the hopper holding member and the drop inlet bushing; the drop inlet bushing is provided with a first gas passage extending upward to guide gas generated from the resin material in the heating barrel; and the hopper holding member is provided with a second gas passage connected to the first gas passage to guide the gas, and a gas outlet for discharging the gas to the outside.

2. An injection device as set forth in claim 1, wherein the second gas passage of the hopper holding member comprises a vertical passage that connects to the first gas passage and extends upward, and a horizontal passage that extends horizontally from the upper end of the vertical passage, the gas outlet being provided at the outlet of the horizontal passage, and the gas being discharged horizontally from this gas outlet.

3. An injection device according to claim 1 or 2, wherein a filter is provided at the gas outlet for capturing powder discharged along with the gas.

4. An injection device according to claim 1, wherein the drop port bushing is made of a corrosion-resistant material that is resistant to corrosion by the gas.

5. An injection device according to claim 1, wherein the hopper holding member and the drop port bushing are made of a corrosion-resistant material that is resistant to corrosion by the gas.

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