JPH11333898A - Injection mold - Google Patents

Abstract

(57) [Problem] To provide an injection molding die capable of rapidly solidifying a resin filled in a resin flow path. SOLUTION: The nozzle gate, the runner, the first and the sprue of the injection molding die have a cross-sectional shape having a high air cooling effect, and have an uneven surface which can increase the area of each heat transfer wall to increase the cooling efficiency. It has a certain cross-sectional shape.
The cross section of the runner 24 has any one of the cross-sectional shapes shown in FIG. 1, for example, the cross-sectional shape 70 shown in FIG. The nozzle gate, the runner, and the first and second sprues have a high air cooling effect, and the resin in the resin flow path is quickly cooled by the air outside the mold. Therefore, the resin in the resin flow path is quickly solidified and can be taken out as a resin solid, so that the time required for the injection molding cycle is shortened and the productivity is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an injection mold for plastic molding, and more particularly to an injection mold capable of shortening an injection molding cycle.

[0002]

2. Description of the Related Art Many types of plastic products are currently formed by injection molding. The injection molding method
In principle, the molding material heated and fluidized in the cylinder is injected into the mold at high pressure, solidified by cooling if the material is a thermoplastic resin, and cured if the material is a thermosetting resin, and then This is a molding method in which a mold is opened and a molded product is taken out of the mold.

Here, a method of injection-molding a plastic product using an injection molding machine will be described with reference to FIG. FIG. 4 is a schematic sectional view showing a general configuration of the injection molding machine. The molding material supplied to the hopper, for example, plastic pellets, is sent to the front of the injection cylinder as the screw rotates. The temperature of the cylinder is adjusted to a predetermined temperature by a heater according to the type of plastic material, for example, 190 to 220 ° C. for polystyrene. The material is compressed, kneaded and plasticized as it is sent to the front of the cylinder. The screw retreats with the increase in the amount of plasticization at the front of the cylinder, and when the screw reaches a predetermined amount, stops the rotation of the screw, then sends high-pressure oil to the injection cylinder to advance the screw, and removes the material at the front of the cylinder. It is injected into a mold at a high pressure, for example, 500 to 2,000 kgf / cm ² , and the molded product is taken out after cooling.

Here, with reference to FIGS. 5 to 9,
The configuration and function of the injection mold will be described. As shown in FIG. 5, an injection mold (hereinafter simply referred to as a mold) 10 includes a fixed mold 12 fixed to an injection molding machine (not shown) and a driving device (not shown). 1) fixed mold 1
2 and a movable mold 14 which contacts the fixed mold 12 and forms a cavity 15 therebetween.

[0005] The fixed mold 12 includes a fixed mounting plate 16.
And a runner plate 18 fixed to the fixed-side mounting plate 16.
And a fixed mold 20 which can be separated from the runner plate 18. The nozzle gate 22, into which the resin flows from the cylinder (see FIG. 4) of the injection molding machine, penetrates through the fixed-side mounting plate 16 and communicates with the runner 24 provided in the fixed mold 20 in a groove shape. The plate surface of the runner plate 18
A resin flow path is formed by covering the upper surface of the runner 24 provided in the fixed mold 20. The runner 24 is connected at both ends to a first sprue 26 and a second sprue 27 penetrating the fixed mold 20, and communicates with the cavity 15 via the first and second sprues 26 and 27.

The runner 24 is a cold runner type runner, as shown in FIG.
It has a groove-shaped cross-sectional shape such as a trapezoid, and has an area ratio and an equivalent pipe diameter shown in the figure with respect to a circular cross section. The numerical value shown in FIG.
It is a numerical value of the unit. The runner 24 having a circular cross section has one semicircular cross section in the fixed mold 20 and the other semicircular cross section in the runner plate 18 side. The runner 24 having a cross-sectional shape other than the circular cross-section is provided on the fixed die 20 side. The molten resin is
From the cylinder of the injection molding machine (see FIG. 4) to the nozzle gate 2
2 and press-fitted into the mold 10, the runner 24 and the first
The cavity 15 passes through the sprue 26 and the second sprue 27.
To fill the cavity 15.

[0007] The movable mold 14 includes a movable mounting plate 28.
And a movable back plate 32 fixed to the movable side mounting plate 28 via a spacer block 30, and a movable mold 34 fixed to the movable back plate 32. The cavity 15 is formed between the movable mold 34 and the fixed mold 20. An ejector driving mechanism 38 for driving the ejector 36 to move forward and backward is provided in the inner hollow portion of the spacer block 30. The ejector 36 projects from the movable mold 34 toward the cavity 15 by the ejector driving mechanism 38, and is moved into the movable mold 34. fall back.

As a guide for moving the movable mold 14 toward and away from the fixed mold 12, the guide pin 40 is used to guide the guide pin 40 into the fixed mold 12.
Are provided on the movable mold 14. Further, a runner plate blur pin mechanism 44 is provided as a guide when the fixed mold 20 separates from the runner plate 18.

In molding, first, the movable mold 14 is brought into close contact with the fixed mold 12 as shown in FIG. Next, the molten resin is pressed into the mold 10 from the cylinder (see FIG. 4) of the injection molding machine, and the nozzle gate 22 and the runner 2 are pressed.
4 and the first sprue 26 and the second sprue 27 are fed into the cavity 15 and filled therein. The resin filled in the cavity 15 while being kept in this state for a predetermined time is cooled and solidified. Then, as shown in FIG.
The movable mold 14 is retracted from the fixed mold 12, then the ejector 36 is projected into the cavity 15, the molded product 46 is separated from the movable mold 14, and then dropped downward. Subsequently, as shown in FIG. 9, the fixed mold 20 is separated from the runner plate 18, and the fixed mold 20 is advanced toward the movable mold 14 while being guided by the guide pins 40 and the guide holes 42. The cavity 15 is formed in close contact with the movable mold 34. When the fixed die 20 advances, the runner plate blur pin mechanism 44 defines the distance between the runner plate 18 and the fixed die 20. Further, by moving the fixed mold 20 forward, the resin solids 48 solidified in the resin flow path including the first and second sprues 26 and 27, the runner 24 and the nozzle gate 22 are separated from the fixed mold 20. The solid resin 48 is removed from the movable mold 14 by the automatic runner / sprue takeout mechanism or the like (not shown).
Remove from. Next, the runner plate blur pin mechanism 44
Then, the movable mold 14 and the fixed mold 20 are advanced toward and adhered to the runner plate 18 while being guided to the state shown in FIG. 7, and the press-fitting of the resin is started again. Thus, one injection molding cycle of the injection mold 10 is completed.

[0010]

However, in the above-described conventional injection mold, the resin in the cavity 15 is cooled and solidified to form a molded product 46, and even when the molded product 46 can be taken out. , Nozzle gate 22 and runner 24
And the first and second sprues 26 and 27 and the temperature in and around the resin flow path are high temperatures close to the resin melting temperature. Therefore, the resin filled in the resin flow path does not solidify, and in order to remove the molded product 46 from the mold, it is necessary to wait for the resin flow path to cool and fill the resin flow path and solidify the resin. there were. For this reason, it is difficult to shorten the time required for the injection molding cycle, which is a problem in improving productivity. Further, if the resin in the resin flow path is taken out before the resin in the resin flow path is cooled and sufficiently solidified in order to shorten the time required for the injection molding cycle, the deformation becomes large. For this reason, when trying to take out the resin solidified in the resin flow path by using the automatic runner / sprue take-out mechanism, as shown in FIGS. Could not.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an injection molding die capable of rapidly solidifying a resin filled in a resin flow path.

[0012]

The present inventor has attempted to reduce the amount of resin in the resin flow path by reducing the cross-sectional area of the sprue or runner in order to shorten the time for cooling and solidifying the resin. However, if the sprue or runner is too thin, sufficient pressure cannot be transmitted to the resin in the cavity through the runner and sprue, and defects such as voids will occur in the molded product and the defective product rate will increase. Was.
Therefore, it was considered that the cross-sectional shape of the runner and the sprue was made to have a high air-cooling effect along the runner and the sprue, and that the air was cooled by the outside air through the mold. Was.

In order to achieve the above object, based on the above-mentioned knowledge, an injection molding die according to the present invention has a fixed mold and a movable mold which is movable with respect to the fixed mold. In contact with the mold, a movable mold that forms a cavity between the fixed mold and a movable gate, a nozzle gate that penetrates the fixed mold, a resin flow path including a runner and a sprue, and a resin flow path In a mold for injection molding in which a resin is press-fitted into a cavity through a cavity, a nozzle gate, a runner, and a sprue each have a cross-sectional shape having a high air-cooling effect.

The injection molding die according to the present invention has a cross section having a high air cooling effect so that the cooling of the resin in the nozzle gate, the runner and the sprue is promoted. Thereby, the time in which the resin in the resin flow path is air-cooled by the air outside the mold and solidified is reduced. Preferably, the nozzle gate, the runner, and the sprue each have a cross-sectional shape having a convex portion or a concave portion in a specific direction or radially so that a heat transfer area is large, and the nozzle gate, the runner, and the sprue have a longitudinal shape. Provided along the direction. Further, preferably, a convex portion or a concave portion having a cross-sectional shape is provided in a fin shape. The specific direction is a direction regulated based on the arrangement of the nozzle gate, runner and sprue in the mold,
It is determined according to the shape of the mold.

In a preferred embodiment of the present invention, further, the nozzle gate and the sprue each have an air flow path around the nozzle gate and the sprue, and the runner has an air flow path along the bottom of the runner. ing. In this embodiment, by providing the air flow path, external air can flow into or out of the air flow path by natural convection or forcibly, thereby cooling the resin in the resin flow path. More preferably,
When the cooled air is fed into the air flow path to cool the resin in the resin flow path, the cooling effect is enhanced.

[0016]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Embodiment 1 This embodiment is an example of an embodiment of an injection mold according to the present invention. FIG. 1 is a diagram showing a cross-sectional shape of a runner, and FIG. 2 is a cross-sectional shape of a nozzle gate and a sprue. FIG. The injection mold according to the present embodiment includes a nozzle gate 22, a runner 24, first and second sprues 26,
Except for the configuration of 27, the conventional injection mold 1 described above
0 is provided. In the present embodiment, the nozzle gate 22, the runner 24, the first and the sprues 26, 2
Numeral 7 has a cross-sectional shape having a concavo-convex shape capable of increasing the area of each heat transfer wall and increasing the cooling efficiency as a cross-sectional shape having a high air cooling effect. The cross section of the nozzle gate 22 may be any of the cross-sectional shapes shown in FIG.
The cross-sectional shape 68 shown in (5) and the cross-section of the runner 24 are any of the cross-sectional shapes shown in FIG. 1, for example, the cross-sectional shape 70 shown in FIG. 1 (1), and the cross-sections of the first and second sprues 26 and 27 are Any of the cross-sectional shapes shown in FIG.
A cross-sectional shape 72 shown in 1) is provided.

Each of the cross-sectional shapes shown in FIG. 1 has a fin-shaped convex portion extending radially or in a specific direction, in FIG. 1, in the horizontal or vertical direction, and has a high air cooling effect. For example,
The cross-sectional shape 70 shown in FIG. 1A has a fin-shaped convex portion 78 extending in the vertical direction, a heat transfer area per cross-sectional unit volume is large, and the air cooling effect is high. Each of the cross-sectional shapes shown in FIG. 2 has a fin-shaped convex portion extending radially or in a specific direction, in FIG. 2, in a horizontal direction or a vertical direction, and has a high air cooling effect. For example, the cross-sectional shape 68 shown in FIG.
Is provided with fin-shaped protrusions 74 extending radially in four directions, whereby the heat transfer area per unit volume of the cross section is increased and the air cooling effect is high. The cross-sectional shape 72 shown in FIG. 2 (11) includes fin-shaped protrusions 76 extending radially in four directions, thereby increasing the heat transfer area per unit volume of the cross-section and increasing the air cooling effect.

By providing the above-mentioned cross-sectional shape, the nozzle gate 22, the runner 24, and the first and second sprues 26 and 27 have a high air cooling effect, and the nozzle gate 22, the runner 24 and the first and second sprues 24 and 27 have a high air cooling effect. Sprue 26,
The resin in the resin flow path constituted by 27 is quickly cooled by air outside the mold. Therefore, the resin in the resin flow path is quickly solidified and can be taken out as a resin solid, so that the time required for the injection molding cycle is shortened and the productivity is improved.

The nozzle gate 22, the runner 24, and the first and second sprues 26 and 27 of the embodiment are shown in FIG.
The runner 24 may have any of the cross-sectional shapes shown in FIG. In FIG. 1, the runners having the cross-sectional shapes from (1) to (12) are provided on the fixed mold 20, and from (13) to (3).
In the runners having the cross-sectional shapes up to 0), half of the cross-section is provided on the fixed mold 20 and the other half is provided on the runner plate 18.

Embodiment 2 This embodiment is another example of the embodiment of the injection mold according to the present invention. FIG. 3 is a view showing the main part of the injection mold of this embodiment. FIG. 3 is a cross-sectional view of a fixed mold showing a configuration. The injection molding die of this embodiment has the same configuration as the above-described conventional injection molding die 10 except for the configuration of the nozzle gate 22, the runner 24, and the first and second sprues 26 and 27. . In the present embodiment, the nozzle gate 22, the runner 24, and the first and second sprues 26 and 27 have the same cross-sectional shape as in the first embodiment. Further, in the present embodiment, as shown in FIG. 3, in order to cool the resin in the nozzle gate 22, an air flow passage 52 is formed in a double pipe form around the nozzle gate 22, and a hollow portion of the runner plate 18 is formed around the nozzle gate 22. The wall between the nozzle gate 22 and the air flow path 52 is a heat transfer wall. Further, an inflow hole 54 for flowing air into the air flow path 52 and an outflow hole 56 for discharging air from the air flow path 52 are provided to penetrate the runner plate 18, and cooled air flows from the inflow hole 54. It flows into the air passage 52 and flows out of the outflow hole 56 while cooling the resin in the nozzle gate 22.

In order to cool the resin in the first sprue 26 and the second sprue 27, as shown in FIG.
6 and the second sprue 27 are provided as hollow portions of the fixed mold 20 around the first and second sprues 26 and 27, and the walls between the air passages 58 and 60 serve as heat transfer walls. Has become. Further, in order to cool the resin in the runner 24, an air flow path 62 communicating with the air flow paths 58 and 60 is provided along the bottom of the runner 24 as a hollow portion of the fixed die 20, and the air flow path 62 The wall between the flow path 62 is a heat transfer wall. Further, an inflow hole 64 through which air flows into the air flow path 58 and an outflow hole 66 through which air flows out from the air flow path 60 are provided so as to penetrate the fixed die 20. Flows into the air passage 58 from the air passage 58 while cooling the resin in the first sprue 26.
0, enters the air passage 62 while cooling the resin in the runner 24, and flows out of the outflow hole 66 while cooling the resin in the second sprue 27.

The sectional shape of the nozzle gate 22, the first and second sprues 26, 27 of this embodiment may be other than the sectional shape shown in FIG. 2, and the sectional shape of the runner 24 is shown in FIG. The cross-sectional shape shown in FIG.

With the above configuration, in the present embodiment, the resin in the resin flow path constituted by the nozzle gate 22, the runner 24 and the first and second sprues 26 and 27 is supplied to the air flow path 5
2, 58, 62 and 62, the resin can be rapidly cooled by the cooling air flowing therein, and the resin in the resin flow path can be solidified and taken out as a resin solid, so that the time required for the injection molding cycle is shortened, and the productivity is reduced. improves.

[0024]

According to the present invention, a resin is press-fitted into a cavity through a resin flow path, and a movable mold having a cavity formed between the fixed mold and the fixed mold. In the injection mold, the nozzle gate, the runner, and the sprue have a high cross-sectional shape with an air-cooling effect, so that the resin in the resin flow path is quickly air-cooled, and the resin in the resin flow path is solidified. Since it can be taken out as a resin solid, the time required for the injection molding cycle is reduced without providing a complicated mechanism, and the productivity is improved. In addition, since the resin can be solidified reliably to form a resin solid that is not easily deformed, the resin solid can be automatically and efficiently removed from the resin flow path by a robot or the like. Since the injection molding cycle is shortened and the residence time in the cylinder of the injection molding machine is shortened, the properties of the resin press-fitted into the injection mold are stable, and a molded product having no variation in quality can be formed. .

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross-sectional shape of a runner according to a first embodiment.

FIG. 2 is a diagram illustrating a cross-sectional shape of a nozzle gate and a sprue according to the first embodiment.

FIG. 3 is a cross-sectional view illustrating a configuration of a fixed mold according to a second embodiment.

FIG. 4 is a schematic diagram showing a configuration of an injection molding machine.

FIG. 5 is a cross-sectional view showing a configuration of a conventional injection mold.

FIG. 6 is a view showing the shape and dimensions of a runner.

FIG. 7 is a cross-sectional view of the injection molding die showing a first step of the injection molding.

FIG. 8 is a cross-sectional view of the injection molding mold showing a second step following the first step shown in FIG. 7;

FIG. 9 is a cross-sectional view of the injection molding mold showing a step subsequent to the second step shown in FIG.

FIGS. 10 (a) and (b) are schematic diagrams for explaining the problems of the conventional injection mold.

[Explanation of symbols]

10: a conventional mold for injection molding (hereinafter simply referred to as a mold), 12: a fixed mold, 14: a movable mold, 15
... Cavity, 16 ... Fixed side mounting plate, 18 ...
Runner plate, 20: fixed type, 22: nozzle gate,
24 runner, 26 first sprue, 27 second sprue, 28 movable mounting plate, 30 spacer block, 32 movable back plate, 34 movable type, 3
6 Ejector, 38 Ejector drive mechanism, 40
... Guide pins, 42 ... Guide holes, 44 ... Runner plate blur pin mechanism, 46 ... Molded products, 48 ... Resin solids, 52 ... Air flow path, 54 ... Inflow holes, 56 ... Outflow holes , 58, 60, 62 ... air flow path, 64 ... inflow hole,
66: Outflow hole.

Claims (4)

[Claims] 1. A fixed mold, a movable mold that is movable back and forth with respect to the fixed mold and forms a cavity between the fixed mold and the fixed mold. A nozzle gate penetrating the fixed mold, a resin flow path comprising a runner and a sprue, an injection molding die for press-fitting a resin into a cavity through the resin flow path to form a nozzle, a nozzle gate, a runner, and Sprue,
An injection molding die having a cross section having a high air cooling effect. 2. The nozzle gate, the runner, and the sprue each have a sectional shape having a convex portion or a concave portion in a specific direction or radially so that the heat transfer area is large. The injection mold according to claim 1, wherein the mold is provided along a longitudinal direction. 3. The injection-molding mold according to claim 2, wherein the convex portion or the concave portion in the cross-sectional shape has a fin shape. 4. The nozzle gate and the sprue each have an air flow path around the nozzle gate and the sprue, and the runner has an air flow path along the bottom of the runner. 2. The mold for injection molding according to 1.