JP2016221887A - Plunger type injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plunger type injection device capable of enhancing injection pressure and injection speed while maintaining merits of a plunger.SOLUTION: A plunger type injection device (1) comprises: a heating cylinder (2); a plunger (4) disposed in the heating cylinder (2); a melting device (5); and a transport piston (8) disposed in the heating cylinder (2). The melting device (4) is provided in a state of being integrated with the plunger (4), and the transport piston (8) is configured to drive similar to a reciprocating motion, in the heating cylinder (2) independently from the plunger (4). The transport piston (8) is preferably formed of an annular body, and is provided on a shaft part (18) having a constant diameter, and being formed in a prescribed zone close to a rear side of the plunger (2). The plunger comprises a backflow prevention device (7).SELECTED DRAWING: Figure 2

Description

  The present invention comprises a heating cylinder, a plunger that is reciprocatingly driven in the heating cylinder, a backflow prevention device, and a melter provided with a plurality of injection material melting holes or grooves. The present invention relates to a plunger type injection device that is driven integrally with the plunger.

  The injection device can be roughly classified into an inline screw type and a plunger type. The in-line screw type is composed of a heating cylinder, a screw that can be driven in the rotation direction and the axial direction in the heating cylinder, a drive device that drives the screw in the rotation direction and the axial direction, and the like, as is conventionally known. Has been. An injection nozzle is provided in front of the heating cylinder, a hopper is provided at the rear end, and a band heater is provided at the outer periphery of the heating cylinder. Therefore, when the screw is rotated and the resin material is supplied from the hopper, the resin material is melted by the heat from the band heater, the frictional heat due to the rotation of the screw, the shear heat, etc. in the process of being sent forward, and the front of the heating cylinder. Accumulated in the weighing chamber or storage chamber. As a result, the screw is retracted by the pressure of the accumulated molten resin and the measurement is completed. When the screw is driven in the axial direction, molten resin is injected and filled into a mold that has been clamped, and after cooling and solidification, the movable mold is opened to obtain a molded product.

  The plunger type is also well known in the art and includes a heating cylinder, a plunger provided in the cylinder so as to be driven, a melting device for melting pellets, a driving device for driving the plunger, and the like. Plunger-type injection devices are of various types and have been proposed in various patent documents.

JP-A-53-106765 Japanese Patent No. 4817402

  As shown in FIG. 4, Patent Document 1 discloses a plunger-type injection device that includes a heating cylinder 50 having a predetermined length in the axial direction and a plunger 56 that is driven forward in the cylinder 50. ing. An injection nozzle 51 is provided in front of the heating cylinder 50, and a hopper 52 is provided in the rear. Further, between the injection nozzle 51 and the hopper 52, a melter, that is, first and second stage torpedos 53 and 55 are fixedly provided to the heating cylinder 50 at a predetermined interval. The first stage torpedo 53 is heated by a heater, and a plurality of small diameter gradient holes at the tip, that is, tapered resin passage holes 54, 54,... Yes. On the other hand, a plurality of spiral grooves 56, 56,... Are formed on the outer peripheral surface of the second stage torpedo 55. Therefore, when the plunger 56 is driven forward, the pellets P, P,... Supplied from the hopper 52 are pushed forward and pass through the plurality of resin passage holes 54, 54,. pass. At this time, the pellets P, P,... Are pressed against the inner peripheral walls of the passage holes 54, 54,. When passing through the spiral grooves 56, 56,... Of the second torpedo 55, it is further melted by heat generated by shearing or kneading action, and then injected and filled from the injection nozzle 51 into the mold cavity that has been clamped. The When the movable mold is opened after cooling and solidification, a molded product is obtained.

  As shown in FIG. 5, the plunger-type injection device proposed in Patent Document 2 is provided with a heating cylinder 60 provided with an injection nozzle 61 at its tip, and is driven in the heating cylinder 60. The plunger 66, the melter 63 in which a plurality of resin passage holes 64, 64,... Are formed, the air vent 67 provided in the vicinity of the resin supply port, and the like. A heater 68 is attached to the outer peripheral portion of the heating cylinder 60, and the resin passage holes 64, 64,... Therefore, when the plunger 66 is driven downward, that is, forward, the pellets supplied from the hopper 62 are pushed forward and consolidated when passing through the plurality of resin passage holes 64, 64,... 64, and so on. At this time, it is efficiently melted by heat applied from the heating cylinder 60, frictional heat generated when passing through the resin passage holes 64, 64,. When melted in this way, the air retained between the pellets is exhausted from the air vent 67. Next, the mold is clamped and filled from the injection nozzle 61. When the movable mold is opened after cooling and solidification, a molded product is obtained in the same manner.

  In this way, there are inline screw type and plunger type in the injection device, and each has advantages and disadvantages, and which is better, it can not be determined immediately. Since it is small, it takes time to melt. Therefore, there is a problem that the screw or the heating cylinder must be elongated in the axial direction in order to melt the pellet. On the other hand, since the pellet type or the molten resin passes through the plurality of passage holes of the melting device, the plunger type has a wide contact area between the pellet and the melting device and is easily melted. Therefore, it is not necessary to lengthen the heating cylinder and the plunger in the axial direction, and an advantage that the injection device can be configured compactly is recognized. Although the present invention is directed to a plunger type injection device that can be configured in this compact manner, there is a problem with the plunger type injection device. The plunger type injection device described in Patent Documents 1 and 2 will be described as an example. Both of them are designed to simultaneously perform melting and injection of resin when the plungers 56 and 66 are driven forward. In other words, since the melting and the injection are performed simultaneously by driving in one direction, the pressing force of the plungers 56 and 66 is distributed to the pressure loss and the injection pressure when the pellets are melted. That is, in order to increase the injection pressure, it is necessary to increase the pressing force of the plungers 56 and 66. However, as the pressing force of the plungers 56 and 66 increases, the pressure loss of the melters 53 and 63 also increases. The conventional plunger-type injection device that performs the above simultaneously has a problem that it is difficult to obtain a high injection pressure. There is also a problem with the injection speed. The injection speed may be increased by increasing the driving speed of the plungers 56 and 66, but the pellets must be reliably melted in the melters 53 and 63. However, there is a limit in trying to shorten the melting time in the melting units 53 and 63. That is, there is a problem that the melters 53 and 63 are rate limiting and the injection speed cannot be increased sufficiently.

  An object of the present invention is to provide a plunger type injection device that solves the above-mentioned conventional drawbacks or problems. Specifically, a plunger that can increase the injection pressure and the injection speed by taking advantage of the advantages of the plunger type. It aims at providing a type injection device.

  In order to achieve the above object, the present invention provides a heating cylinder, a plunger provided in the heating cylinder, a melter in which a plurality of injection material melting holes or melting grooves are formed, and a heating cylinder. A plunger-type injection device is constituted by the transport piston provided. The melter is provided integrally with the plunger, and the transport piston is configured to be reciprocally driven in the heating cylinder independently of the plunger. The transport piston is preferably composed of an annular body, and is provided on a shaft portion having a constant diameter formed in a predetermined section near the rear of the plunger. The plunger is provided with a backflow prevention device.

That is, in order to achieve the above-mentioned object, the invention according to claim 1 is a heating cylinder in which a tip end portion serves as a storage portion for molten injection material and a rear end portion serves as a supply portion for injection material to be supplied. And a plunger provided in the heating cylinder, a melter in which a plurality of injection material melting holes or melting grooves are formed, and a transport piston provided in the heating cylinder. A container is provided integrally with the plunger, and the transport piston is configured to be reciprocatingly driven in the heating cylinder independently of the plunger. Is done.
The invention according to claim 2 is the plunger-type injection device according to claim 1, wherein the plunger is provided with a backflow prevention device for preventing backflow of the injection material measured in the accumulation portion. It is comprised as a plunger type injection device.
According to a third aspect of the present invention, in the plunger-type injection device according to the first or second aspect, the plunger includes a shaft portion in which a predetermined section closer to the rear is formed with a constant diameter, and the transport piston is The plunger-type injection device is constituted by an annular body provided coaxially in the shaft portion.
According to a fourth aspect of the present invention, in the plunger type injection device according to any one of the first to third aspects, the injection material melting hole or the melting groove of the melter is a number toward the tip. It is constituted as a plunger type injection device characterized by having increased.

  As described above, according to the present invention, a heating cylinder is provided in the heating cylinder in which the front end portion serves as a storage portion for the molten injection material and the rear end portion serves as a supply portion for the injection material supplied. And a plunger having a plurality of injection material melting holes or melting grooves, and a transport piston provided in a heating cylinder. The melter is provided integrally with the plunger, and the transport piston is reciprocally driven in the heating cylinder independently of the plunger. Since the transport piston is provided in this way, when the transport piston is driven in the axial direction in the heating cylinder, the pellets can be fed forward, and the pellets can be melted in the melter and metered in the accumulator. At this time, it is not necessary to drive the plunger. When the plunger is driven in the axial direction at the time of injection, since there is no resistance in the melter, the axial force of the plunger acts as the injection pressure as it is. Since it is not necessary to melt the pellets with a melter at the time of injection, the injection speed can be increased. That is, the plunger type injection device according to the present invention has an effect of increasing the injection pressure and the injection speed. According to another invention, the plunger is provided with a backflow prevention device for preventing backflow of the injection material measured in the accumulator. Therefore, the molten injection material weighed in the accumulating portion is efficiently injected by receiving the axial force of the plunger without flowing backward at the time of injection. According to still another invention, the plunger includes a shaft portion in which a predetermined section near the rear is formed with a constant diameter, and the transport piston is formed of an annular body provided coaxially with the shaft portion. That is, the transport piston is provided coaxially with the plunger. Then, when the pellets are fed forward by the transport piston, a pressing force acts on the pellets in a well-balanced manner in the heating cylinder, and the pellets can be efficiently melted by the melter and the injection material can be measured. According to still another invention, the number of injection material melting holes or melting grooves of the melting device increases toward the tip. The pellets are melted in contact with the injection material melting holes and the wall of the melting groove, but as the number of injection material melting holes and melting grooves increases, the area of the wall surface increases. As a result, the injection material is easily melted.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows typically the plunger type injection device which concerns on embodiment of this invention, The (a) is front sectional drawing of a plunger type injection device, The (a)-(D) is the (a), respectively. It is sectional drawing of the plunger seen in arrow AA, BB, CC direction in FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the effect | action of the plunger type injection device which concerns on embodiment of this invention typically, (a)-(d) is front sectional drawing of the plunger type injection device in each process of injection | emission. It is front sectional drawing of the plunger type injection device which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows the conventional plunger type injection device. It is sectional drawing which shows the other conventional plunger type injection device.

  Embodiments of the present invention will be described below. As shown in FIG. 1A, the plunger injection device 1 according to this embodiment includes a heating cylinder 2 having a predetermined length in the axial direction and a screw provided inside the heating cylinder 2. A plunger 4 having a head, a melter 5 provided in the plunger 4, a backflow prevention device 7 having a conventionally well-known structure provided in the vicinity of the tip of the plunger 4, a member unique to the present invention and later It is comprised from the transportation piston 8 etc. which are demonstrated. The heating cylinder 2 is a storage portion where the injection material in a molten state is measured at the tip, and an injection nozzle 10 is provided at the tip. The rear part is a supply part to which pellets of the injection material are supplied, and a hopper 11 is provided in the supply part. Although not shown in the drawing, a plurality of band heaters are wound around the outer peripheral surfaces of the heating cylinder 2 and the injection nozzle 10 so that the heating cylinder 2 and the injection nozzle 10 can be heated.

  The melter 5 includes fins 13, 14, and 15 fixedly provided in a predetermined section of the plunger 4, and when the plunger 4 is driven, the melter 5 is driven back and forth integrally with the plunger 4. The fins 13, 14, 15 are provided on the plunger 4 so as to be parallel to the axial direction and even in the circumferential direction, but the fins 13, 14, 14 provided in the respective sections of the melter 5 are provided. The number of 15 is different. That is, six fins 13, 14, 15,... Are provided in the section closer to the rear of the melter 5, as shown in FIG. 1D, and in FIG. As shown in FIG. 1, 8 sheets are provided, and in the section closer to the front, 12 sheets are provided as shown in FIG. The injection material is melted when it flows through a groove between adjacent fins 13, 14, 15,. That is, the heat of the heating cylinder 2 heated by the band heater is conducted to the fins 13, 14, and 15 and is efficiently melted by this heat. Since the injection material is supplied as pellets, the number of fins 13, 13,... Is small and the gap between the melt grooves is large so that the pellets can easily pass through the rear part. In order to melt reliably, the number of sheets is increased so that the contact area between the injection material and the fins 15, 15,. That is, the number of the melt grooves increases as it approaches the tip. As a result, the injection material is sufficiently melted as it is sent to the tip.

  The transport piston 8 according to the present embodiment will be described. The transport piston 8 is made of an annular body having a predetermined thickness. A predetermined section in the rear portion of the plunger 4 is a shaft portion 18 having a constant diameter, and the transport piston 8 is slidably provided on the shaft portion 18. Although the drive mechanism is not shown in FIG. 1A, the transport piston 8 is reciprocally driven in a predetermined section in the heating cylinder 2 independently of the plunger 4. When such a transport piston 8 is driven in the axial direction, the pellets of the injection material supplied from the hopper 11 can be sent forward in the heating cylinder 2, whereby the injection material is melted in the melter 5 and heated. 2 is stored in the storage unit.

  The operation of the plunger type injection device 1 according to the present embodiment will be described with reference to FIG. The heating cylinder 2 is heated by a band heater, and pellets of the injection material are supplied from the hopper 11 as shown in FIG. Then, the transport piston 8 is driven in the axial direction as shown in FIG. Then, the pellets are sent forward in the heating cylinder 2 by the pressing force of the transport piston 8. The pellets are melted when passing through the melter 5 to become a molten injection material. The transport piston 8 is retracted. The driving of the transport piston 8 in the axial direction may be performed only once or a plurality of times. When the driving piston 8 is driven in the axial direction, the molten injection material is measured in the accumulation portion at the tip of the heating cylinder 2. Then, as shown in FIG. 2C, the plunger 4 is retracted by the pressure of the injection material. That is, the weighing is completed. The plunger 4 is driven in the axial direction as shown in FIG. Then, the measured injection material is prevented from backflow by the backflow prevention device 7 and is injected from the injection nozzle 10 under the pressing force of the plunger 4. Although not shown in the figure, a molded product is obtained by being injected into a clamped mold.

  The plunger-type injection device 1 according to the present embodiment includes a transport piston 8 that is driven independently of the plunger 4 in the heating cylinder 2, so that the injection material is sent forward without driving the plunger 4. Can be melted. When the plunger 4 is driven at the time of injection, most of the pressing force of the plunger 4 can act as the injection pressure. The plunger-type injection device 1 according to the present embodiment only needs to include the transport piston 8 that is driven independently of the plunger 4 in the heating cylinder 2, so that various modifications are possible. For example, FIG. 3 shows a plunger-type injection device 1 ′ according to the second embodiment. In this embodiment, the transport piston 8 ′ is not an annular body. In the heating cylinder 2 ′, an extended section 20 having a wide bore in a predetermined rear section is formed, and a transport piston 8 ′ is provided in the expanded section 20. Those skilled in the art can easily understand that, as long as the cross-sectional shapes of the expansion section 20 and the transport piston 8 ′ are equal, these may be any shape, and the transport piston 8 ′ can be pivoted. If driven in the direction, the pellets can be fed forward in the heating cylinder 2 'to melt it and the injection material can be weighed. Other modifications are possible, and the melter 5 can also be modified. In this embodiment, the melter 5 is composed of fins 13, 14, 15,... And is melted when the injection material flows through these grooves, that is, the melt grooves. On the other hand, the melter 5 can be configured to include a plurality of axial holes, that is, injection material melting holes.

DESCRIPTION OF SYMBOLS 1 Plunger type injection device 2 Heating cylinder 4 Plunger 5 Melting device 7 Backflow prevention device 8 Transport piston 10 Injection nozzle 11 Hopper 13, 14, 15 Fin 18 Shaft

Claims (4)

A heating cylinder that serves as an injection material supply unit to which the front end portion is a molten injection material accumulation portion and a rear end portion is supplied, a plunger provided in the heating cylinder, and a plurality of injection materials A melter in which a melt hole or a melt groove is formed, and a transport piston provided in the heating cylinder,
The melter is provided integrally with the plunger;
The plunger type injection device, wherein the transport piston is driven reciprocally in the heating cylinder independently of the plunger.   2. The plunger type injection device according to claim 1, wherein the plunger is provided with a backflow prevention device for preventing a backflow of the injection material measured in the accumulation portion.   3. The plunger type injection device according to claim 1, wherein the plunger includes a shaft portion in which a predetermined section near the rear is formed with a constant diameter, and the transport piston is provided coaxially with the shaft portion. A plunger-type injection device comprising an annular body.   The plunger type injection device according to any one of claims 1 to 3, wherein the number of the injection material melting holes or the melting grooves of the melter increases toward the tip. Plunger type injection device.

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