Injection device

Abstract

To provide an injection device which eliminates the risk of powdered resin material being discharged to the outside and can reduce operation costs.SOLUTION: In this injection device (20), resin material stored in a hopper (28) is dropped into a heating barrel (27) via a hopper holding member (50) and a drop port bushing (40). The drop port bushing (40) is provided with a first gas passage (42) that extends upward and guides gas generated from the resin material in the heating barrel (27). The hopper holding member (50) is provided with a second gas passage (57) that connects to the first gas passage (42) and guides the gas, and a gas outlet that discharges the gas to the outside. Natural exhaust rather than forced exhaust is used, so exhaust is gentle and powder is less likely to be discharged to the outside. Natural exhaust does not require electrical energy, etc.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[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 together with the molten resin material. The resulting resin material contains a small amount of gas.

[0003] General-purpose resin products are allowed to contain trace amounts of gas, but some resin products require a certain level of purity, and so gas content must be reduced. One technique that meets this demand is known, for example, as disclosed in Patent Document 1.

[0004] Patent Document 1 will be explained with reference to the following figure. FIG. 6 is a diagram illustrating the basic structure of a conventional injection device. As shown in FIG. 6, Patent Document 1 discloses an injection device 100 including 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 presses down the barrel 101, and the injection device 100 is further provided 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 and second vacuum generators 113 and 115 via first and second exhaust passages 112 and 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 problems. When the resin material 116 is a powder, part of the resin material 116 is sucked by the first and second vacuum generators 113 and 115 and discharged to the outside. This reduces the yield, which is expressed as (weight of resin product / weight of resin material). This is undesirable because it reduces the effective utilization rate of the resin material 116.

[0008] Furthermore, the first and second vacuum generators 113, 115 may be devices powered by compressed air (Patent Document 1, paragraph 0052) that is normally installed in factories, or may be vacuum pumps powered 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 also required. As a result, operating costs increase.

[0009] When manufacturing resin products of required purity, there is a need for an injection device that does not involve the risk of powdered resin material being discharged to the outside and that can reduce operating costs. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent No. 5138183 Summary of the Invention [Problem to be solved by the invention]

[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. [Means for solving the problem]

[0012] The invention according to claim 1 comprises a heating barrel, a screw housed in the heating barrel so as to be rotatable and axially movable, an injection stand supporting the heating barrel, a drop inlet bush attached to the injection stand, a hopper holding member disposed on the drop inlet bush, and a hopper disposed on the hopper holding member, An injection device in which the resin material stored in the hopper is dropped into the heating barrel through the hopper holding member and the drop port bushing, the drop port bushing is provided with a first gas passage extending upward to guide gas generated from the resin material in the heating barrel; The hopper holding member is characterized in that a second gas passage connected to the first gas passage for guiding the gas and a gas outlet for discharging the gas to the outside are provided.

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

[0014] The invention according to claim 3 is the injection device according to claim 1 or claim 2, The gas outlet is provided with a filter for capturing powder discharged with the gas.

[0015] The invention according to claim 4 is the injection device according to claim 1, The drop inlet bushing is characterized by being made of a corrosion-resistant material that is resistant to corrosion by the gas.

[0016] The invention according to claim 5 is the injection device according to claim 1, The hopper holding member and the drop port bushing are characterized by being made of a corrosion-resistant material that is resistant to corrosion by the gas. [Effects of the Invention]

[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, and gas is discharged to the outside via the first gas passage and the second gas passage. This exhaust does not require a vacuum pump or the like. That is, in the present invention, the gas is exhausted by the so-called natural exhaust method. Since no vacuum pump or the like is used, no electrical energy is required, and operating costs can be reduced.

[0018] Compared to the forced evacuation method, the natural evacuation method is a gentler evacuation method, and with this type of evacuation 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 eliminates the risk of powdered resin material being discharged to the outside and that 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, but since the second passage is a simple passage consisting of a vertical passage and a horizontal passage, the processing cost 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 lateral passage to capture powder discharged along with the gas. In the present invention, in principle, the powder is not discharged to the outside, but there is a possibility that a small amount of powder may be discharged. Even in this case, the provision of a filter is preferable because it prevents the powder from being discharged to the outside.

[0021] In the invention according to claim 4, the drop inlet bushing is made of a corrosion-resistant material. If 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 the drop inlet bushing are made of a corrosion-resistant material. If 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 port bushing are made of corrosion-resistant materials, polyvinyl chloride can be added to the resin material. As a result, the types of resin materials that can be processed can be increased. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a side view of an injection molding apparatus including an injection device according to the present invention. [Figure 2] 1(a) is a plan view of the drop inlet bushing, FIG. 1(b) is a cross-sectional view of the drop inlet bushing, and FIG. 1(c) is a bottom view of the drop inlet bushing. [Figure 3] 1A is a plan view of a hopper holding member, FIG. 1B is a cross-sectional view of the hopper holding member, and FIG. 1C is a bottom view of the hopper holding member. [Figure 4] 5A to 5C are diagrams illustrating the operation of the injection device according to the present invention. [Figure 5] (a) and (b) are diagrams for examining the height of the drop inlet bush. [Figure 6] FIG. 1 is a diagram illustrating the basic structure of a conventional injection device. DETAILED DESCRIPTION OF THE INVENTION

[0024] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings, in which the drawings are to be viewed in the direction indicated by the reference numerals. [Example]

[0025] [Injection molding equipment] As shown in FIG. 1, the injection molding apparatus 10 is an apparatus including, as its main components, a mold clamping unit 11, an injection unit 20, and a bed 12 that supports the mold clamping unit 11 and the injection unit 20. The mold clamping device 11 is a device for clamping a mold 13, and only a part of it (fixed platen 14) is shown for convenience of drawing.

[0026] [Injection device] The injection unit 20 is supported so as to be horizontally movable by a movable table 22 supported by rails 21 laid on the bed 12. For example, an injection unit moving cylinder 23 spanning the movable table 22 and the fixed platen 14 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 the figure). The injection unit moving cylinder 23 may be a hydraulic cylinder or an electric cylinder.

[0027] The injection device 20 includes an injection table 26 supported by a movable table 22, a heating cylinder 27 supported by the injection table 26, a hopper 28 that supplies resin material to the heating cylinder 27, a screw 29 that is rotatably housed in the heating cylinder 27 and movable in the axial direction, 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] The screw moving cylinder 31 can be a hydraulic cylinder or an electric cylinder. The screw rotation mechanism 34 can be an electric motor or a hydraulic motor.

[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 / metering process] Plasticization and metering process: The screw 29 is rotated in a predetermined direction by the screw rotation mechanism 34, while 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 way, plasticization and metering are performed.

[0031] [Injection process] Injection step: 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-in bush] The structure of drop inlet bushing 40 will be described in detail with reference to Figures 2(a) to 2(c), where Figure 2(a) is a plan view of drop inlet bushing 40, Figure 2(b) is a cross-sectional view thereof, and Figure 2(c) is a bottom view thereof.

[0034] As shown in FIG. 2(a), the drop port bushing 40 has a drop port 41 in the center for dropping the resin material, and has a plurality of first gas passages 42 (eight in this example) surrounding this drop port 41. As shown in FIG. 2( b ), the drop inlet bushing 40 has a flange 43 . As shown in FIG. 2( c ), a plurality of first gas passages 42 can be seen surrounding the drop port 41 .

[0035] [Material of drop bush] The material of the drop inlet bushing 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 that it be made of a corrosion-resistant material such as stainless steel that is resistant to corrosion by chlorine-based gases.

[0036] [Machining of drop port bushings] 2(a) to 2(c), drop inlet bushing 40 has an extremely simple shape. It does not have any particularly fine threads (also called taps). Therefore, 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 that has the same diameter as the drop opening (Figure 2(a), symbol 41), a bar 52 that crosses this through hole 51, and a threaded portion 53 and a bolt hole 54 at each of the four corners.

[0039] By arranging the bars 52 in a grid pattern, it is possible to prevent objects larger than the meshes of the grid (including the worker's hand) from falling from the hopper (FIG. 1, reference numeral 28) into the drop opening. The hopper holding member having the falling object prevention mechanism is a general-purpose product, and the hopper holding member 50 can be easily obtained by machining this general-purpose product.

[0040] The hopper 28 can be fixed to the hopper holding member 50 by screwing the bolt 36 shown in FIG. Moreover, by passing a hexagon socket head bolt 55 through the bolt hole 54, the hopper holding member 50 can be fixed to the injection platform 26 shown in FIG.

[0041] In FIG. 1, the drop port bushing 40 is dropped into the launch pad 26, and the hopper holding member 50 is placed on top of it, and this hopper holding member 50 is fixed to the launch pad 26 with a hexagon socket bolt (FIG. 3(a), symbol 55). The drop inlet bushing 40 is simply resting on the launch pad 26 by the flange 43. The drop inlet bushing 40 is prevented from falling out 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 this vertical passage 58.

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

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

[0045] While the installation of filter 63 is optional, the following criteria are recommended: When the resin material to be handled is in powder form, a filter 63 is attached. If the resin material to be handled is not a powder, the filter 63 is not attached. In this case, the female thread portion 62 may be omitted.

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

[0047] [Hopper holding material] 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, so they can be replaced with new ones as needed. Therefore, whether the material of the hopper holding member 50 is expensive stainless steel or inexpensive carbon steel or the like may be selected arbitrarily in consideration of cost-effectiveness.

[0049] The operation of the injection device 20 having the above configuration will be described with reference to FIG. 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 cylinder 27. The resin material is kneaded and plasticized by the screw 29. Gas may be generated during this process.

[0050] Gas behaves according to the natural laws that fluids containing gas flow where it is easiest to flow, that fluids flow toward an outlet, and that gases that are lighter than air rise in the atmosphere. 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 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 arrow G2.

[0052] The amount of gas inside the heating cylinder 27 is reduced by the amount of gas that has been 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 outside along with the gas, and even if it is, it is only a small amount. Because the amount is small, filter 63 is not essential. However, providing filter 63 is more preferable as it can reliably capture the small amount of powder.

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

[0055] 5(b), the bottom surface of drop inlet bushing 40 extends to outer peripheral surface 27b of heating barrel 27. As a result, a cylindrical space 65 (see FIG. 4) calculated by (wall thickness of heating barrel x bottom area of ​​drop inlet bushing) is secured in heating barrel 27. The resin material 64 dropping from the drop port 41 spreads out in a truncated cone shape, but sub-spaces 66 with triangular cross sections remain at the corners of the space 65. The existence of these sub-spaces 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. Moreover, the horizontal passage 59 shown in FIG. 3(b) may extend horizontally or may be inclined with respect to the horizontal, as long as it extends horizontally.

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

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

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

Claims

1. a heating barrel, a screw housed in the heating barrel so as to be rotatable and axially movable, an injection stand supporting the heating barrel, a drop inlet bush attached to the injection stand, a hopper holding member disposed on the drop inlet bush, and a hopper disposed on the hopper holding member; An injection device in which the resin material stored in the hopper is dropped into the heating barrel through the hopper holding member and the drop port bushing, the drop port bushing is provided with a first gas passage extending upward to guide gas generated from the resin material in the heating barrel; The injection device is characterized in that the hopper holding member is provided with a second gas passage connected to the first gas passage to guide the gas therethrough, and a gas outlet for discharging the gas to the outside.

2. 2. The injection device according to claim 1, the second gas passage of the hopper holding member comprises a vertical passage connected to the first gas passage and extending upward, and a horizontal passage extending horizontally from an upper end of the vertical passage, The gas outlet is provided at the outlet of the horizontal passage, and the gas is discharged horizontally from the gas outlet.

3. 3. The injection device according to claim 1 or 2, The injection device is characterized in that a filter is provided at the gas outlet for capturing powder discharged with the gas.

4. 2. The injection device according to claim 1, The injection device is characterized in that the drop inlet bush is made of a corrosion-resistant material that is resistant to corrosion by the gas.

5. 2. The injection device according to claim 1, The injection device is characterized in that 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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