JP2002103382A - Heat insulating structure of hot runner for injection molding die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat insulating structure of a hot runner for an injection molding die which upgrades the heat radiating effect of the hot runner and prevents a molding failure due to the heat radiation of the hot runner from occurring. SOLUTION: In the injection molding die which is equipped with the hot runner 5 and is installed in a freely clamping and opening manner, at least the region exposed to an atmosphere, of the hot runner 5 when the die is opened, is covered with a heat insulating means 7. This heat insulating means 7 comprises a metallic heat insulating layer 71 made up of a metallic member arranged, spaced as specified, on the outer peripheral surface of the hot runner 5 and an air heat insulating layer 72 formed between the metallic heat insulating layer 71 and the outer peripheral surface of the hot runner 5. In addition, the heat insulating means 7 is structured of the metallic heat insulating layer 71, the air heat insulating layer 72 and a resin heat insulating layer 73 formed of a resin member laminated on the outer peripheral surface of the metallic heat insulating layer 71. The air heat insulating layer 72 is formed in a cylindrical shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection mold having a hot runner, and to a heat insulating structure for the hot runner.

[0002]

2. Description of the Related Art Conventionally, as an injection mold having a hot runner, as shown in FIG. 6, an intermediate plate 3 is provided between a fixed die 1 and a movable die 2, and the intermediate plate 3 and the movable die 2 is provided so that the mold can be opened and clamped freely.

The contact surface (parting line) PL between the fixed mold 1 and the intermediate plate 3 and the contact surface (parting line) PL between the intermediate plate 3 and the movable mold 2 have:
Cavities 4 corresponding to the shape of the molded product are formed, and each cavity 4 is configured to be filled with a molten resin injected from an injection nozzle (not shown) through a hot runner 5 and a gate 6 ( For example, see JP-A-6-848).

[0004]

However, in the above conventional injection mold, when the intermediate plate 3 and the movable mold 2 are opened as shown in FIG. 7, a part of the hot runner 5 (in the example shown in the drawing). (From the middle part to the tip part in the structure), it is exposed to the outside air. When a part of the hot runner 5 is exposed to the outside air as shown by the hatched line 5a in FIG. 8, a significant temperature drop occurs in the part due to the heat radiation action, causing a problem such as a decrease in the fluidity of the molten resin. Runner 5
There is a problem that a molded product formed by the cavity 4 on the side of the movable die 2 leading to the above-mentioned problem has an appearance defect such as a short shot.

The present invention has been made in view of the above problems, and has as its object to improve the heat radiating effect of a hot runner and prevent molding defects due to the heat radiating of the hot runner.

[0006]

According to a first aspect of the present invention, a heat insulating structure for a hot runner for an injection molding die according to the present invention comprises an injection molding die provided with a hot runner and provided so as to be mold-clamped and mold-openable. When the injection mold is opened, at least a portion of the hot runner exposed to the outside air is covered with a heat insulating means.

According to a second aspect of the invention, there is provided a heat insulating structure for a hot runner for an injection molding die, wherein the heat insulating means comprises a metal member disposed at a predetermined interval on an outer peripheral surface of the hot runner. It comprises a heat insulating layer and an air heat insulating layer formed between the metal heat insulating layer and the outer peripheral surface of the hot runner.

According to a third aspect of the invention, there is provided a heat insulating structure for a hot runner for an injection mold, wherein the heat insulating means comprises a metal member arranged at a predetermined interval on an outer peripheral surface of the hot runner. A heat insulating layer, an air heat insulating layer formed between the metal heat insulating layer and the outer peripheral surface of the hot runner, and a resin heat insulating layer formed of a resin member laminated on the outer peripheral surface of the metal heat insulating layer. It is.

According to a fourth aspect of the present invention, in the heat insulating structure of the hot runner for an injection mold, the air heat insulating layer is formed in a cylindrical shape.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. Since an example of the configuration of the injection mold is basically the same as the configuration of the injection mold described in the conventional example, the same members are given the same reference numerals and description thereof will be omitted.

FIG. 1 shows a heat insulating structure of a hot runner for an injection mold according to the present invention.

The heat insulating structure of this hot runner for injection molding is provided with a heat insulating means 7 on the outer peripheral surface of the hot runner 5.

As shown in FIG. 2, a specific structure of the heat insulating means 7 is a metal heat insulating layer 71 disposed on the outer peripheral surface of the hot runner 5 at a predetermined interval, and the metal heat insulating layer 71 and the hot runner 5 And a resin heat-insulating layer 73 laminated on the outer periphery of the metal heat-insulating layer 71.

The metal heat insulating layer 71 is formed of a metal member in a cylindrical shape. By forming the cylindrical metal heat insulating layer 71 one size larger than the outer peripheral surface of the hot runner 5, the hot metal is formed. The runner 5 is disposed on the outer peripheral surface of the runner 5 with a predetermined gap therebetween, and is fixed to the fixed mold 1 in this state.

The thickness of the metal heat insulating layer 71 is preferably as small as possible. However, if the thickness is too small, positioning with respect to the hot runner 5 becomes difficult or the strength becomes weak.
mm is preferable.

By disposing the metal heat insulating layer 71 with respect to the hot runner 5, the cylindrical air heat insulating layer 72 described above is inevitably provided between the metal heat insulating layer 71 and the outer peripheral surface of the hot runner 5. Is formed. Air insulation layer 72
Is made cylindrical in order to suppress the convection of the air and prevent the temperature of the hot runner 5 from decreasing due to the convection.

The thickness of the air heat insulating layer 72 is preferably as large as possible. However, if the air heat insulating layer 72 is too thick, convection of air is generated and the temperature balance of the entire layer becomes uneven. 1 mm to 4 to facilitate transmission to layer 71
mm is preferable. That is, the thickness of the air heat insulating layer 72 is 1
The size of the metal heat insulating layer 71 is set so as to be about mm to 4 mm.

The resin heat-insulating layer 73 is made of a resin material and is formed in a cylindrical shape, for example, like the metal heat-insulating layer 71. The resin heat-insulating layer 73 is laminated on the outer periphery of the metal heat-insulating layer 71 to form the fixed mold 1. It is fixed. As the thickness of the resin heat insulating layer 73 is larger, the heat of the hot runner 5 is not deprived, and a resin having heat resistance that does not melt even at the continuous use temperature of the hot runner 5 is used.

The air forming the air insulating layer 72 is preferably air having a low thermal conductivity. In this case, the air is preferably sealed in the air insulating layer 72. As a method for enclosing air, for example, as shown in FIG. , The air heat insulating layer 72 is sealed, and air having poor thermal conductivity is sealed therein. By forming the flange 71a, the positioning of the metal heat insulating layer 71 with respect to the hot runner 5 can be easily performed.

By providing the heat insulating structure on the outer peripheral surface of the hot runner 5 as described above, when the intermediate plate 3 and the movable mold are opened with respect to the fixed mold 1 as shown in FIG.
The tip of the hot runner 5 projecting outward from the middle is not exposed to the outside air, and is protected by the above-described three-layer heat insulating structure. That is, the heat radiation from the outer peripheral surface of the hot runner 5 can be confined by the air heat insulating layer 72 in combination with the use of the heat reflected by the metal heat insulating layer 71. Further, heat radiation from the metal heat insulating layer 71 to the outside is performed by the resin heat insulating layer 73.
Is suppressed. Thereby, the heat insulating effect of the hot runner 5 is remarkably improved, the temperature of the hot runner 5 can be easily controlled, and molding defects due to heat radiation of the hot runner 5 can be prevented.

FIG. 4 shows another embodiment of the heat insulating structure of the hot runner for an injection mold according to the present invention.

The heat insulation structure of the hot runner for an injection mold includes a metal heat insulation layer 71 in which a heat insulating means 7 is arranged on the outer peripheral surface of the hot runner 5 at a predetermined interval, and the metal heat insulation layer 71 and the hot runner. 5 and a cylindrical air heat insulating layer 72 formed between the outer peripheral surface 5 and the outer peripheral surface. That is, it has a two-layer heat insulating structure.

In the case where the heat insulating structure has two layers as described above, the thickness of the heat insulating structure needs to be larger than that of the metal heat insulating layer having the three-layer structure in order to avoid heat radiation to the outside by the metal heat insulating layer 71. is there.

The other components such as the shape and thickness of the metal heat insulating layer 71 and the gaps between the air heat insulating layers 72 are the same as those of the above-described embodiment, and a description thereof will be omitted.

The above-described three-layer heat-insulating structure also enables
Although it is inferior to the heat insulating effect of the hot runner 5 due to the heat insulating structure of the layers, a sufficient heat insulating effect of the hot runner 5 can be exhibited, and the same effect as the heat insulating structure of the three layers can be obtained.

FIG. 5 shows a heat insulating structure having the heat insulating means 7 (three layers) shown in FIG. 2, a heat insulating structure having the heat insulating means 7 (two layers) shown in FIG. 4, and a conventional heat insulating means shown in FIG. The comparison is made between the temperature change in each part a to e (see FIGS. 1 and 8) of the hot runner when the mold is opened for each of the hot runners having no mold. The set temperature of the hot runner 5 was 240 ° C., and molding was performed using PC + ABC as a raw material.

As can be seen from FIG. 5, in the case where the conventional heat insulating means is not provided, the hot runner 5 is used at points c and d.
2 is extremely lower than the set temperature, whereas the heat insulating means 7 (three layers) having the heat insulating structure shown in FIG. 2 is in a state very close to the set temperature, and the heat insulating means 7 (2) shown in FIG.
In the case of the layer having the heat insulating structure, although a drop of about 10 ° C. to 20 ° C. from the set temperature is observed at the points c and d, the change with respect to the set temperature is far less than that of the layer having no heat insulating structure. .

[0028]

As described above, according to the present invention, when the injection mold is opened, at least a portion exposed to the outside of the hot runner is covered by the heat insulating means, so that the heat insulating means can cover the hot runner. The heat radiation to the outside of the runner can be suppressed, whereby the heat insulation effect of the hot runner is improved, the temperature of the hot runner can be easily controlled, and molding defects due to the heat radiation of the hot runner can be prevented. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an embodiment of a heat insulating structure of a hot runner for an injection mold of the present invention.

FIG. 2 is an enlarged view showing a specific configuration of a heat insulating means.

FIG. 3 is an enlarged view showing a modification of the heat insulating means.

FIG. 4 is an enlarged view showing another embodiment of the heat insulating means.

FIG. 5 is a diagram comparing temperature changes between a hot runner having a heat insulating structure of the present invention and a hot runner having no conventional heat insulating structure.

FIG. 6 is a cross-sectional view showing a configuration of a conventional injection mold having a hot runner.

FIG. 7 is a cross-sectional view showing a state where a conventional injection mold is opened.

FIG. 8 is an enlarged sectional view showing a state in which the hot runner is exposed to the outside air when the conventional injection mold is opened.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed type 2 Movable type 5 Hot runner 7 Heat insulation means 71 Metal heat insulation layer 72 Air heat insulation layer 73 Resin heat insulation layer

Claims (4)

[Claims] 1. An injection molding die provided with a hot runner and provided so as to be mold-clampable and mold-openable, wherein at least a portion of the hot runner exposed to the outside air when the injection molding die is opened is a heat insulating means. A heat insulating structure for a hot runner for an injection mold, characterized by being coated with: 2. The heat insulating means includes: a metal heat insulating layer formed of a metal member disposed at a predetermined interval on an outer peripheral surface of the hot runner; and a heat insulating layer between the metal heat insulating layer and the outer peripheral surface of the hot runner. The heat insulating structure of a hot runner for an injection molding die according to claim 1, comprising an air heat insulating layer formed on the hot runner. 3. The heat insulating means includes: a metal heat insulating layer made of a metal member disposed at a predetermined interval on an outer peripheral surface of the hot runner; and a metal insulating layer between the metal heat insulating layer and the outer peripheral surface of the hot runner. 2. The hot runner for an injection molding die according to claim 1, wherein the hot runner for an injection molding die comprises an air heat insulating layer formed on the outer surface of the metal heat insulating layer and a resin heat insulating layer formed of a resin member laminated on an outer peripheral surface of the metal heat insulating layer. Insulation structure. 4. The heat insulation structure for a hot runner for an injection mold according to claim 2, wherein the air heat insulation layer is formed in a cylindrical shape.