Nozzle for injection molding device, and injection molding device

Abstract

Provided is a nozzle for an injection device capable of stably cooling a tip of the nozzle.　The nozzle for the injection device includes a nozzle body and a tip part formed continuously with the nozzle body. A nozzle tip in which a nozzle hole is formed and an annular groove surrounding the nozzle tip are formed at the tip part. The annular groove forms an air thermal insulation layer surrounding the nozzle tip, thereby suppressing excessive heating of the nozzle tip.

Description

Nozzle for injection molding apparatus, and injection molding apparatus

[0001] The present invention relates to a nozzle for an injection apparatus and an injection molding apparatus.

[0002] An injection molding apparatus according to the prior art is described, for example, in Patent Document 1. Patent Document 1 describes an injection apparatus including a heating cylinder, a screw rotatably and axially movably housed in the heating cylinder, an injection base that supports the heating cylinder, and a material supply unit that supplies a resin material to the heating cylinder.

[0003] Japanese Patent No. 7189222

[0004] In resin injection molding using an injection molding apparatus, a nozzle attached to the tip of a heating cylinder is brought into contact with a cooled mold, molten resin is injected into the mold from the nozzle, and the molten resin is cooled and solidified into a molded product. At this time, the nozzle is constantly heated by heat transfer from the heating cylinder. However, since the nozzle is in continuous contact with the mold, it is cooled from the contact surface with the mold, and the temperature of the nozzle decreases.

[0005] FIG. 7 is a schematic cross-sectional view showing a state where a conventional nozzle and a mold are in contact with each other. Here, the screw is omitted for ease of illustration. In the conventional nozzle, the distal end portion is formed in a hemispherical shape that is convex toward a substantially concave nozzle receiving opening formed in the mold, and the proximal end portion is formed in a cylindrical shape and connected to the end of the heating cylinder. The nozzle has a nozzle hole penetrating along an axis, and the nozzle hole is connected to a substantially conical resin flow path formed in the internal space of the nozzle. The resin flow path is connected to a cylindrical resin heating flow path formed in the heating cylinder. A band heater for heating the nozzle is provided on the outer periphery of the nozzle.

[0006] As indicated by the arrows in Figure 7, the heat from the nozzle's band heater and the molten resin in the resin channel is transferred to the nozzle and further to the mold via the nozzle socket. The nozzle is more affected by the mold's temperature the closer it is to the tip of the nozzle, so the temperature of the molten resin in the nozzle hole is lower than the temperature of the molten resin in the resin channel. If the temperature of the molten resin in the nozzle hole is appropriate, the molten resin in the nozzle hole will cool and solidify, and when injection is complete and the movable mold and molded product retract (moving to the left in Figure 7), it will be cut off at the point where the base end of the nozzle hole connects to the tip end of the resin channel.

[0007] However, depending on the type and composition of the resin material used, and the temperature conditions of the heating cylinder, the nozzle tip may not be properly cooled, or the temperature of the nozzle tip may not be stable, resulting in the molten resin inside the nozzle hole not reaching a temperature suitable for solidification. In this case, when injection is complete and the movable mold and molded product retract, a molding defect occurs in which the molten resin is not cut but remains in a continuous, thread-like manner, also known as stringing.

[0008] Conventional nozzles have a shape that tapers from the base to the tip, so the nozzle is cooled by the mold as it approaches the tip, and the molten resin inside the nozzle hole is cooled more towards the tip.

[0009] Therefore, conventional nozzles have the problem that the temperature difference between the molten resin temperature inside the nozzle hole and the molten resin temperature inside the resin flow path is small. Consequently, conventional nozzles have the problem that they cannot stably cool the tip where the nozzle hole is formed.

[0010] The present invention aims to provide an injection nozzle that can stably cool the tip of the nozzle.

[0011] The present invention relates to an injection nozzle for an injection device, comprising a heating cylinder, a screw rotatably and axially movable within the heating cylinder, and a hopper for supplying resin material to the heating cylinder, wherein the nozzle includes a nozzle body and a tip portion formed in connection with the nozzle body, and the tip portion has a nozzle tip where a nozzle hole is formed and an annular groove surrounding the nozzle tip.

[0012] The present invention is further characterized by including a groove cover that covers the annular groove.

[0013] The present invention is an injection molding apparatus characterized by comprising the nozzle for the injection device.

[0014] According to the present invention, since the nozzle for the injection device has an annular groove, an air insulating layer can be formed surrounding the nozzle tip, and the path for heat conduction can be narrowed. As a result, the heat from the heater that heats the nozzle can be insulated by the air insulating layer, and heat conduction can be suppressed, so that excessive heat is not transferred to the nozzle tip and the nozzle tip does not overheat. Therefore, a nozzle that can stably cool the nozzle tip can be realized. As a result, the temperature difference between the temperature of the molten resin in the nozzle hole and the temperature of the molten resin in the resin flow path can be increased, so that stringing and nozzle clogging can be suppressed.

[0015] Furthermore, according to the present invention, the nozzle for the injection device has a groove cover that covers the annular groove, so that foreign matter can not enter the annular groove.

[0016] According to the present invention, the injection device of the injection molding apparatus is equipped with a nozzle for the injection device, so that stringing and nozzle clogging can be suppressed, and the occurrence of molding defects can be reduced.

[0017] This is a side view of an injection molding apparatus. This is a perspective view of the nozzle. This is a schematic cross-sectional view showing the nozzle and mold in contact. This is a diagram illustrating a groove cover. This is a schematic cross-sectional view showing the groove cover installed. This is a perspective view showing a band heater with a groove cover installed. This is a schematic cross-sectional view showing the nozzle and mold in contact in the prior art.

[0018] <Injection Molding Apparatus> Figure 1 is a side view of an injection molding apparatus 1 according to the present invention. The injection molding apparatus 1 comprises a bed 2, an injection device 3 disposed on the upper surface of the bed 2, and a clamping device (not shown) disposed on the upper surface of the bed 2.

[0019] The injection device 3 comprises a heating cylinder 7 having a nozzle 5 at its tip and a built-in screw 6, a hopper 8 that supplies resin material into the heating cylinder 7, and a rotary drive means 9 that rotates the screw 6 and moves it back and forth in the forward and backward directions, injecting resin material from the nozzle 5 with each forward movement of the screw 6.

[0020] The clamping device comprises a fixed platen 10 fixed to the bed 2, a pressure receiving platen (not shown), a tie bar 12 positioned between the fixed platen 10 and the pressure receiving platen, a movable platen 13 attached to the tie bar 12 so as to be movable in the longitudinal direction of the tie bar 12, a toggle link (not shown) connecting the pressure receiving platen and the movable platen 13, and a toggle driving means for driving the toggle link. The fixed platen 10 and the pressure receiving platen are positioned on the upper surface of the bed 2.

[0021] The tie bar 12 consists of four rod-shaped bars, with one pair provided on the upper and lower sides, and is stretched between the fixed platen 10 and the pressure receiving platen. A fixed mold 16 is attached to the fixed platen 10. A movable mold 17 is attached to the movable platen 13. The mold 18 is formed by the fixed mold 16 and the movable mold 17. The mold 18 is clamped when the movable mold 17 is pressed against the fixed mold 16 by the operation of the mold clamping device, and the mold is opened when the movable mold 17 is separated from the fixed mold 16.

[0022] The injection molding apparatus 1 includes a control unit 20 that controls the injection device 3 and the clamping device. The control unit 20 includes a display unit 23 for displaying the operating status of the injection molding apparatus 1 and for inputting control signals to the control unit 20.

[0023] The injection device 3 rotates the screw 6 using a rotary drive means 9, supplying resin material from the hopper 8 to the heating cylinder 7. The resin material moves through the heating cylinder 7 along the helical groove formed in the screw 6 to the nozzle 5. The resin material is plasticized as it moves from the introduction to the nozzle 5. The plasticized resin material accumulates at the front of the heating cylinder 7.

[0024] At this time, the screw 6 retracts due to the reaction force of the resin material accumulated at the front. When the screw 6 retracts to a predetermined position, the injection device 3 stops the rotation of the screw 6. In this way, the resin material is plasticized and metered.

[0025] The injection device 3 advances the screw 6 while the nozzle 5 is in contact with the mold 18. This advance causes the resin material (molten resin) accumulated in the front of the heating cylinder 7 to be injected into the mold 18 through the nozzle hole 54 of the nozzle 5. Once injection is complete, the injection device 3 performs plasticization and metering of the resin material for the next molding.

[0026] <Nozzle> Figure 2 is a perspective view of the nozzle 5 according to the present invention, and Figure 3 is a schematic cross-sectional view showing the state in which the nozzle 5 and the mold 18 are in contact. In Figure 3, the screw 6 is omitted for the sake of illustration. The nozzle 5 is composed of a cylindrical nozzle body 50, a connecting portion 51 connected to one end of the nozzle body 50, a tool gripping portion 52 formed between the nozzle body 50 and the connecting portion 51, and a tip portion 53 connected to the other end of the nozzle body 50. A screw is formed on the outer surface of the connecting portion 51. The nozzle 5 is fixed by screwing the connecting portion 51 to the tip of the heating cylinder 7. A band heater 11 is provided surrounding the nozzle 5.

[0027] A nozzle hole 54 is formed at the tip 53, extending in the axial direction of the nozzle 5. The nozzle hole 54 communicates with a resin flow path 56. The resin flow path 56 is a cylindrical flow path that tapers towards the nozzle hole 54. The resin flow path 56 is also called a resin reservoir, as it is where molten resin accumulates before injection. The molten resin in the resin flow path 56 is at a high temperature, and this heat is transferred to the tip 53.

[0028] The outer surface of the nozzle body 50 is heated by a band heater 11 provided on the nozzle body 50, and this heat is transferred to the molten resin in the resin channel 56 via the nozzle body 50. The tool gripping portion 52 is formed in a hexagonal prism shape in cross-section, making it easy to grip with a tool such as a monkey wrench. By gripping the tool gripping portion 52 with a tool and rotating the nozzle 5, the nozzle 5 can be firmly screwed and fixed to the tip of the heating cylinder 7.

[0029] The tip portion 53 includes a nozzle tip 57 having a substantially hemispherical outer surface and an annular groove 55 formed surrounding the base end of the nozzle tip 57. The outer surface of the radially outer side wall of the annular groove 55 is smoothly continuous with the outer surface of the nozzle body 50. The depth of the annular groove 55 may be selected in the range of, for example, 2.5 mm to 5 mm. The formation of the annular groove 55 creates an air insulation layer surrounding the nozzle tip 57. The annular groove 55 may be formed, for example, by machining the area around the nozzle tip 57.

[0030] A recess 60 into which the nozzle 5 is inserted is formed in the fixed mold 16. A nozzle receiving port 61 into which the nozzle tip 57 abuts is formed in the recess 60. A sprue gate 62 communicating with the nozzle hole 54 is formed in the nozzle receiving port 61. The fixed mold 16 is cooled by a cooling device to solidify the injected molten resin. Therefore, the nozzle tip 57 is cooled via the nozzle receiving port 61, and the molten resin in the nozzle hole 54 is also cooled.

[0031] The nozzle 5 has an annular groove 55 formed in it, which creates an air insulation layer surrounding the nozzle tip 57 and narrows the path for heat conduction. This allows the heat from the band heater 11 to be insulated by the air insulation layer while suppressing heat conduction, thus preventing the nozzle tip 57 from overheating. The molten resin in the nozzle hole 54 is cooled by the fixed mold 16. Therefore, compared to conventional nozzles, the nozzle tip 57 of the nozzle 5 can be cooled stably. As a result, the temperature difference between the temperature of the molten resin in the nozzle hole 54 and the temperature of the molten resin in the resin flow path 56 can be increased, thus suppressing stringing and nozzle clogging.

[0032] <Performance Test> Using an injection molding machine manufactured by Nissei Plastic Industrial Co., Ltd. (model number: FNX80III-12A), the nozzle of the present invention (with annular groove) was evaluated as a comparative example with a conventional nozzle (without annular groove) attached to the tip. The conditions for the performance test were as follows: 1. Material used in the experiment (pellets) PBT (polybutylene terephthalate) 2. Injection conditions Heating cylinder temperature 250℃ Meter value 80mm Injection speed 120m / s Rotation speed 150rpm Back pressure 5MPa Injection time 8sec VP switching position 13mm Holding pressure 5MPa

[0033] <Evaluation> Molding was performed six times, and the molded products were visually inspected for the presence or absence of strings. If stringing was observed in all six attempts, it was evaluated as × (stringing present). If stringing was observed in one or two out of six attempts, it was evaluated as △ (partial stringing present). If no stringing was observed in any of the six attempts, it was evaluated as ○ (no stringing present). The test results are summarized in Table 1.

[0034]

[0035] As a measure to suppress stringing, the nozzle temperature is generally lowered to be lower than the heating cylinder temperature. As shown in Table 1, nozzles with annular grooves 55 were able to suppress stringing over a wide range of nozzle temperature ranges.

[0036] <Modification> Figure 4 is a diagram illustrating the groove cover 70, where (a) is a perspective view showing the groove cover 70 installed, and (b) is a perspective view showing the groove cover 70. Figure 5 is a schematic cross-sectional view showing the groove cover 70 installed.

[0037] In this embodiment, the nozzle 5 has a groove cover 70 that covers the annular groove 55. The groove cover 70 has a disc-shaped portion 71 that faces the bottom edge of the annular groove 55 and a rising portion 72 that rises from the edge of the disc-shaped portion 71. An opening 73 is formed in the disc-shaped portion 71 through which the tip portion 53 is inserted. With the tip portion 53 inserted through the opening 73, the groove cover 70 is attached so that the rising portion 72 surrounds the tip portion of the nozzle body 50, and a band heater 11 is further attached so as to cover the rising portion 72. By providing the groove cover 70, the annular groove 55 is covered. In this embodiment, since there is a groove cover 70 that covers the annular groove 55, it is possible to prevent foreign matter from entering the annular groove 55.

[0038] Figure 6 is a perspective view showing a band heater 11 with a groove cover portion 75 installed. The groove cover that covers the annular groove 55 may be configured with the groove cover portion 75 provided on the band heater 11 side. The groove cover portion 75 is formed by bending from the edge of the band heater 11, and its free end is located near the nozzle body 50. Because the band heater 11 has a groove cover portion 75, the annular groove 55 is covered. In this embodiment, since the band heater 11 has a groove cover portion 75 that covers the annular groove 55, it is possible to prevent foreign matter from entering the annular groove 55.

[0039] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above, and various modifications and improvements are possible without departing from the spirit of the invention. It goes without saying that all or part of each of the above embodiments can be combined as appropriate and in a non-contradictory manner.

[0040] 1 Injection molding apparatus 3 Injection device 5 Nozzle 7 Heating cylinder 11 Band heater 18 Mold 50 Nozzle body 51 Connecting part 53 Tip part 54 Nozzle hole 55 Annular groove 56 Resin flow path 57 Nozzle tip 61 Nozzle receiving port 70 Groove cover 75 Groove cover part

Claims

1. An injection nozzle comprising a heating cylinder, a screw rotatably and axially movable within the heating cylinder, and a hopper for supplying resin material to the heating cylinder, wherein the nozzle includes a nozzle body and a tip portion formed in connection with the nozzle body, and the tip portion has a nozzle tip where a nozzle hole is formed and an annular groove surrounding the nozzle tip.

2. The nozzle for an injection device according to claim 1, further comprising a groove cover that covers the annular groove.

3. An injection molding apparatus characterized by comprising an injection nozzle according to claim 1 or 2.

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