JP2019063999A - Hot runner unit for injection molding machine - Google Patents

Abstract

To provide a hot runner unit for an injection molding machine capable of effectively discharging gas in a molten material.SOLUTION: In a hot runner unit for an injection molding machine comprising a material passage 8 through which a molten material passes, a discharge port 6 for discharging the molten material into a cavity 103 of a molding die 100, and a valve pin 3 provided so as to be inserted from the outside into the material passage 8 and axially advancing and retracting to open and close the discharge port 6, the valve pin 3 is provided with a degassing passage 11 for discharging gas in the molten material to the outside.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hot runner unit for an injection molding machine.

  As an injection molding method of injecting a molten material into a mold cavity to form a molded article, the material passage up to the gate (inlet) of the cavity is heated to melt the material in the material passage An injection molding method called a hot runner method of maintaining is known (see Patent Document 1).

  According to this method, only the material of the part (in the cavity) to be a molded article is cured, and the other parts are not cured, so that there is no extra part associated with the molded article, and after molding There is an advantage that processing cost and material cost can be reduced.

  However, in the hot runner method, since the material is constantly heated in the material passage, the components in the material are vaporized by heat, and a gas (bubble) is easily generated in the material. Then, when such a gas is supplied into the cavity together with the material and the material is cured as it is, there is a problem that the quality such as the surface condition and the strength of the molded product is deteriorated.

  With respect to such a problem, Patent Document 2 proposes a method of providing a gas venting path between the manifold and the valve casing, and discharging the gas generated in the material passage to the outside through the gas venting path.

JP, 2013-99860, A Unexamined-Japanese-Patent No. 2003-145587

  In the configuration provided with the gas vent as described above, in order to effectively discharge as much gas as possible, it is preferable to provide the gas vent at a position where gas is likely to be generated. However, it is not easy to identify locations where gasses are likely to occur. Further, it is also conceivable that the gas is dispersed throughout the material passage, so that the dispersed gas can not be effectively discharged only by providing the degassing passage at a specific location. On the other hand, it is not preferable to form the gas venting passage at many places in order to effectively discharge the gas, which leads to a decrease in the strength of the valve casing. As described above, in the conventional measures, it has been difficult to effectively discharge the gas generated in the molten material to the outside.

  Therefore, an object of the present invention is to make it possible to effectively discharge the gas in the molten material.

  In order to solve the above-mentioned problems, according to the present invention, a material passage through which the molten material passes, a discharge port for discharging the molten material into the cavity of the molding die, and the material passage are externally inserted into the material passage. In a hot runner unit for an injection molding machine including a valve pin provided and axially advancing and retracting to open and close the discharge port, the valve pin is provided with a gas venting path for discharging gas in the molten material to the outside. Provided is a molding machine hot runner unit.

  Thus, the provision of the degassing passage in the valve pin increases the opportunity for the degassing passage to contact the gas in the molten material by axially moving the valve pin. This makes it possible to discharge more gas over a wide range in the molten material, and the amount of gas contained in the molten material can be effectively reduced.

  According to the present invention, since the amount of gas contained in the molten material can be effectively reduced, it is possible to reduce the defects of the injection molded product and to improve the quality.

It is a sectional view of a hot runner unit for injection molding machines concerning one embodiment of the present invention. It is sectional drawing of the hot runner unit which concerns on the said embodiment. It is a perspective view of a valve pin. It is a cross-sectional view of a valve pin.

  Hereinafter, an embodiment of the present invention will be described based on the attached drawings.

  1 and 2 show cross-sectional views of a hot runner unit for an injection molding machine according to an embodiment of the present invention.

  The hot runner unit 1 shown in FIGS. 1 and 2 includes a hot runner block 2 having a material passage 8 through which a molten material (for example, a thermoplastic resin) passes and a discharge port 6 provided in the hot runner block 2. A valve pin 3 that opens and closes, a piston cylinder mechanism 4 as a drive device that drives the valve pin 3, and a heater 5 that heats the molten material in the material passage 8 are provided as main components.

  The hot runner block 2 is provided on a molding die 100. The molding die 100 is composed of a fixed die 101 forming the cavity 103 and a movable die 102, and the hot runner block 2 is provided so as to be embedded in the fixed die 101. The hot runner block 2 has a nozzle portion 7 provided with a discharge port 6 at its tip. In addition, the nozzle part 7 may be provided with the some nozzle part 7 by branching the material channel | path 8 according to the magnitude | size, shape, etc. of a cast not only one. The discharge port 6 is provided to face the cavity 103, and in this case, the opening constituting the discharge port 6 also serves as the gate (inlet) of the cavity 103.

  The heater 5 is disposed around the hot runner block 2 and heats the molten material in the material passage 8. Thereby, the material in the material passage 8 is maintained in the molten state. In FIG. 1 and FIG. 2, the heater 5 is mainly disposed around the nozzle portion 7, but the heater 5 is appropriately disposed at other places, and the material is melted throughout the material passage 8. It is configured to be maintained at.

  The valve pin 3 is provided to penetrate the hot runner block 2 and be inserted into the material passage 8 from the outside. The rear end (upper end in FIG. 1) of the valve pin 3 exposed to the outside is connected to the piston rod 9 constituting the piston cylinder mechanism 4, and the valve pin 3 is axially moved by driving the piston rod 9. Advance to As shown in FIG. 1, when the valve pin 3 advances, the tip (lower end in FIG. 1) of the valve pin 3 is fitted to the discharge port 6, and the discharge port 6 is closed. On the contrary, as shown in FIG. 2, when the valve pin 3 is retracted, the fitting of the valve pin 3 to the discharge port 6 is released, and the discharge port 6 is opened. Pressure is always applied to the molten material in the material passage 8 by an injection molding machine (not shown), and as shown in FIG. 2, when the discharge port 6 is opened, the molten material 10 in the material passage 8 is discharged. 6 and discharged into the cavity 103.

  Here, also in the hot runner unit according to the present embodiment, as in the conventional case, the molten material in the material passage is warmed by the heater, so that the components in the molten material are vaporized by heat, so that the inside of the material passage is Gas (air bubbles) is generated. Such a gas, if supplied together with the molten material into the cavity, can lead to defects in the molding. Therefore, in the hot runner unit according to the present embodiment, as shown in FIG. 1 and FIG. 2, the valve pin 3 is provided with the degassing passage 11 for discharging the gas in the molten material.

  The degassing passage 11 includes a plurality of inlets 11a opening in the material passage 8, a plurality of outlets 11b opening outside the material passage 8 (outside the hot runner block 2), an inlet 11a and an outlet 11b And a flow passage portion 11c connecting the two.

  As shown in the perspective view of FIG. 3, the plurality of inlets 11 a are formed by linear slits 12 extending in the axial direction of the valve pin 3. The width (the width in the direction orthogonal to the longitudinal direction) of each slit 12 is set to, for example, several tens of micrometers (less than 0.1 mm) so as to allow passage of gas but prevent passage of molten material. ing. As shown in the cross-sectional view of FIG. 4, the plurality of slits 12 are arranged at equal intervals in the circumferential direction of the valve pin 3 and extend in the radial direction and communicate with the flow passage portion 11 c. In the example shown in FIG. 3 and FIG. 4, two sets of slits 12 formed in the circumferential direction are arranged in the axial direction, but the number and arrangement of the slits 12 can be changed as appropriate. Further, the shape of the inlet portion 11 a is not limited to the elongated slit shape, and may be another shape such as a round hole.

  Thus, by providing the degassing passage 11 in the valve pin 3, the gas in the material passage 8 is discharged to the outside through the degassing passage 11 (see the arrows in FIGS. 1 and 2). . Further, in the present embodiment, the outlet portion 11b of the degassing passage 11 is always exposed to the outside regardless of the advancing and retracting motion of the valve pin 3, so either the closed state or the open state of the discharge port 6 can be obtained. In any case, it is possible to carry out the exhaust of the gas.

  Further, since the gas vent passage 11 is provided in the valve pin 3, when the valve pin 3 is moved in the axial direction, the chance of the inlet portion 11 a of the gas vent passage 11 contacting the gas in the material passage 8 increases. This makes it possible to effectively discharge more gas over a wide range.

  As described above, according to the hot runner unit according to the present invention, by providing the gas venting path in the movable valve pin, the gas venting path is provided in the (non-moving) valve casing as proposed in Patent Document 2 described above. Compared to the configuration, the outgassing passage is more likely to come into contact with the gas in the molten material, so that more gas can be discharged over a wide range. As a result, since the amount of gas contained in the molten material can be effectively reduced, it is possible to reduce the defects of the injection molded article due to the gas being filled in the cavity together with the molten material, and the quality Can be improved. Furthermore, if the valve pin can be removed from the hot runner block, the maintainability is also improved. That is, even when the material adheres to the inlet of the gas vent and the gas vent function is deteriorated, the valve pin can be easily removed to clean the gas vent. Thereby, it is possible to restore the degassing function to a good state.

  As mentioned above, although the embodiment of the present invention was described, the hot runner unit concerning the present invention is not restricted to the above-mentioned embodiment. It goes without saying that various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 hot runner unit 2 hot runner block 3 valve pin 4 piston cylinder mechanism 5 heater 6 discharge port 8 material passage 10 molten material 11 degassing passage 100 molding die 101 fixed die 102 movable die 103 cavity

Claims (1)

A material passage through which the molten material passes, a discharge port for discharging the molten material into the cavity of the molding die, and the material discharge passage is provided so as to be inserted into the material passage from the outside and advanced and retracted axially A hot runner unit for an injection molding machine comprising a valve pin for opening and closing the
A hot runner unit for an injection molding machine, wherein the valve pin is provided with a degassing passage for discharging the gas in the molten material to the outside.

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