JPH07290509A - Injection mold and injection molding method - Google Patents

Abstract

PURPOSE:To manufacture a molded piece having excellent finish appearance by arranging a pressurized gas injecting passage communicating with a resin reservoir at a sprue tip so as to integrate a melting resin injecting gate with a pressurized gas injecting opening, thereby eliminating a gas passage as needed in a conventional one and reducing the extra number of man-hours needed for finishing. CONSTITUTION:In an injection mold, a melting resin is injected into a cavity formed by a fixed mold 1 and a movable mold 2 and a pressurized gas is injected so as to mold a molded piece 3 having a hollow 3a. A sprue 4 for injecting the melting resin is provided in the fixed mold 1 and a resin reservoir 4a is arranged at the tip of the sprue 4 in the movable mold 2. At the resin reservoir 4a of the movable mold 2, a passage 5 having a cross section almost the same as that of the resin reservoir 4a is extended. The tip of the passage 5 is connected with an injection opening 6a at a tip of a pressure gas injecting nozzle 6 passing through the movable mold 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding die for a molded article having a hollow portion and an injection molding method.

[0002]

2. Description of the Related Art Conventionally, an injection mold for molding a molded product having a hollow portion by injecting a molten resin into a cavity formed by a fixed mold and a movable mold and injecting a pressurized gas into the mold and its molding. For example, as described in Japanese Patent Publication No. 03-47171, a method is adopted in which a pressurized gas injection section is provided on the movable mold side in addition to the molten resin injection gate provided on the fixed mold side. .

In order to prevent the pressurized gas from being directly blown into the cavity from the injection nozzle, the injection portion for the pressurized gas is provided with a gas flow path from the tip of the injection nozzle to the cavity. Cavity is created by creating a padded part, passing pressurized gas through the padded part filled in the flow path filled with this molten resin, avoiding direct pressure, and applying resistance to provide cushioning properties. It is designed to be injected into.

[0004]

However, in the conventional method of injecting the pressurized gas as described above, the pad portion of the molten resin formed by the gas flow path of the pressurized gas adheres to the molded product. Since it is formed, it is necessary to perform a finishing process by cutting and removing it after the forming process, which requires extra man-hours, and there is a problem that the cut mark is whitened and the appearance is deteriorated.

The present invention has been made by paying attention to the above problems, and an object thereof is to solve these problems and to inject a molten resin injection gate and a pressurized gas. (EN) An injection molding die and an injection molding method by which a gas passage as in the past is eliminated by reducing the number of finishing steps by integrating the inlets, and a molded product having an excellent finished appearance can be obtained. .

[0006]

According to another aspect of the present invention, there is provided an injection molding die according to the present invention, characterized in that a passage for a pressurized gas is provided in communication with a resin reservoir at the tip of the sprue. In the injection molding die method of the present invention according to item 2, the injection mold of the present invention according to claim 1 is used to inject a molten resin into a cavity and to inject a pressurized gas to form a hollow portion. It is characterized in that a molded product having the above is molded.

Further, in the injection molding die of the present invention as defined in claim 3, a pressurized gas passage is provided in communication with the resin reservoir at the tip of the sprue, and the pressurized gas passage is pressurized. Characterized in that a gas shut-off means is provided,
In the injection molding method of the present invention according to claim 4, the injection molding die of the present invention according to claim 3 is used to inject the molten resin into the cavity, and at the same time the shut-off means adjusts the timing. A feature is that a molded product having a hollow part is molded by injecting a pressurized gas.

[0008]

[Function] A molten resin is injected into a cavity by using an injection mold provided with a flow path for a pressurized gas in communication with a resin reservoir at the tip of a sprue, and a hollow portion is formed by injecting the pressurized gas. By molding a molded product, a molten resin is injected into the cavity by using an injection molding die in which a shutoff means for the pressurized gas is further provided in the flow path of the pressurized gas, and a shutoff means is provided. By injecting pressurized gas while adjusting the timing to form a molded product with a hollow part, the extra finishing man-hours for the pressurized gas injection gate are reduced, and a molded product with an excellent finished appearance is obtained. be able to.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an example of the injection molding die of the present invention according to claim 1. In FIG. 1, 1 is a fixed mold, 2 is a movable mold, and 3 is a molded product. Molten resin is injected into a cavity formed by the fixed mold 1 and the movable mold 2, and a pressurized gas is injected. Is an injection mold for molding a molded product 3 having a hollow portion by injecting.

The stationary die 1 is provided with a sprue 4 for injecting a molten resin, and a resin reservoir 4a is provided at the tip of the sprue 4 on the movable die 2 side. A gate 4b extending from the space between the resin reservoir 4a and the sprue 4 to the cavity for molding the molded product 3 is provided on the movable mold 2 side so that the molten resin is filled therein.

The resin reservoir 4a of the movable mold 2 is provided with a flow passage 5 extending in substantially the same cross section as the resin reservoir 4a. The tip of this flow path 5 is connected to an injection port 6a at the tip of an injection nozzle 6 for injecting a pressurized gas that penetrates the movable mold 2.

When the injection molding die is closed and the molten resin is injected from the sprue 4 into the cavity for molding the molded article 3, the molten resin is filled into the entire cavity. At this time, the molten resin is filled from the resin reservoir 4a into the flow path 5 provided at the tip thereof. Then, when the pressurized gas is sent from the injection nozzle 6 for the pressurized gas in the movable mold 2 while observing the timing, the pressurized gas flows into the flow path 5 through the injection port 6a at the tip of the injection nozzle 6. It is possible to form the hollow portion 3a to be a gas channel through the resin reservoir 4a and the gate 4b by advancing while opening the passage.

[Embodiment 1] FIG. 2 is a perspective view of a molded article produced by the injection molding die of the present invention according to claim 1.
FIG. 3 is a perspective view showing a main part of the molded product shown in FIG. 2. Figure 2
2 is a molded product, and this molded product 20 is composed of a main body 21 having a space 21a in the substantially central portion and a hollow portion 22 in which a hollow portion is formed.
A sprue 23 for injecting the molten resin and a gate 24 for filling the molded product 20 with the molten resin are provided below the la 1a.

Reference numeral 25 is a flow path for the pressurized gas.
5 is the sprue 2 from the resin reservoir 23a at the tip of the sprue 23.
3 and the same cross section. Pressurized gas is injected from the tip of the flow path 25.

The injection molding test described below was carried out using a test mold for molding the above-mentioned molded article 20. The length of the flow path 25 at the injection portion of the pressurized gas is 35 mm, and the thickness is 7 mm.
And A polypropylene resin (PPF OX-560-K3B, manufactured by Mitsubishi Yuka) was used as a resin for injection molding, and the injection time was 2.5 seconds. A porous body having a diameter of 4 mm was used as the injection nozzle for the pressurized gas. The injection conditions of the pressurized gas in this injection molding test were as follows: gas charge pressure 19.5 kg / cm ² , gas injection pressure 65.0 kg / cm ² .
cm ² , gas injection time 4.2 seconds, gas injection delay time 4.
The gas holding time was 0 seconds and the gas holding time was 18.0 seconds.

As a result of the above test, a good hollow portion 22a could be obtained as shown in FIG. Further, the flow path 25 that was molded at the same time and adhered to the molded product 20 was cut together with the gate 24, leaving only the gate mark 24a.

[Comparative Example 1] FIG. 4 is a perspective view of a molded product using a conventional injection molding die, and FIG. 5 is a perspective view showing a main part of the molded product shown in FIG. In FIG. 3, reference numeral 30 denotes a molded product, and this molded product 30 has a space 3 at the center thereof.
A main body 31 having 1a and a hollow portion 32 in which a hollow portion is formed
The sprue 33 for injecting the molten resin, the gate 34 for filling the molded product 30 with the molten resin, and the resin reservoir 35 are provided below the space 31a of the main body 31.

Reference numeral 36 denotes a flow passage, which is provided above the gate 34 at approximately the center of the hollow portion 32.
Pressurized gas is injected from the tip of the flow path 36.

The injection molding test described below was carried out using a test mold for molding the above-mentioned molded product 30. The flow path 36 of the pressurized gas injection part has a length of 35 mm and a thickness of 7 mm.
And A polypropylene resin (PPF OX-560-K3B, manufactured by Mitsubishi Yuka) was used as a resin for injection molding, and the injection time was 2.5 seconds. A porous body having a diameter of 4 mm was used as the injection nozzle for the pressurized gas. The injection conditions of the pressurized gas in this injection molding test were the same as in Example 1.

As a result of the above test, as shown in FIG. 5, a good hollow portion 32a could be obtained. In addition, the flow path 36 formed at the same time and adhering to the molded product 30 is the gate 2
It was cut together with No. 4 to leave a cut mark 36a. A whitening phenomenon occurred in the cut traces 36a, and the cut traces 36a also remained large, which was not preferable in appearance. When the gas charge pressure was increased, flow marks were found on the surface (design surface) of the molded product. This flow mark was not recognized in Example 1.

FIG. 6 is a sectional view showing an example of the injection molding die of the present invention according to claim 3. In FIG. 6, 11 is a fixed mold, 12 is a movable mold, and 13 is a molded product. Molten resin is injected into the cavity formed by the fixed mold 11 and the movable mold 12, and pressurized gas is supplied. Is an injection mold for molding a molded product 13 having a hollow portion.

The fixed die 11 is provided with a sprue 14 for injecting the molten resin, and a resin reservoir 14a is provided at the tip of the sprue 14 on the movable die 12 side. A gate 14b extending from the space between the resin reservoir 14a and the sprue 14 to the cavity for molding the molded product 13 is provided on the movable mold 12 side so as to be filled with the molten resin.

The resin reservoir 14a of the movable mold 12 is provided with a passage 15 for pressurized gas having a cross section substantially the same as that of the resin reservoir 4a. The tip of the flow path 15 is connected to an injection port 16 a at the tip of a pressurized gas injection nozzle 16 provided through the movable die 12.

In the present invention, a shutoff gate operated by a hydraulic cylinder is used as the shutoff means for the pressurized gas. Reference numeral 17 denotes a hydraulic cylinder attached to the upper surface of the movable die 12, and the hydraulic cylinder 17 is provided with a shutoff gate 18 penetrating the inside of the movable die 12.

The tip portion 18 of this shut-off gate 18
The a is provided so as to cross the flow path 15 described above from the right angle direction, and at this position, the tip end portion 18 a has the flow path 15 a.
The molten resin is prevented from entering the injection nozzle 16 side by shutting off or opening it, and at the same time, injection and stop of the pressurized gas can be performed at a suitable timing.

Example 2 The following test was carried out using an injection molding test die having the structure shown in FIG. As in Example 1, the length of the channel 15 at the injection portion of the pressurized gas was 35 mm, and the thickness was 7 mm. ABS resin was used as the resin for injection molding, and the injection time was 2.5 seconds. A porous body having a diameter of 4 mm was used as the injection nozzle for the pressurized gas. The injection conditions of the pressurized gas in this injection molding test were as follows: gas charge pressure of 19.5 kg / cm ² ,
Gas injection pressure 65.0 kg / cm ² , gas injection time 4.
2 seconds, gas injection delay time 4.0 seconds, gas pressure holding time 18.
It was set to 0 seconds.

After the completion of the mold closing and before the start of injection of the molten resin,
The shut-off gate 18 shown in FIG. 6 is closed to prevent the molten resin from entering the injection nozzle 16 through the gas passage 15. Next, immediately after the injection of the molten resin is completed, or after a few seconds, the hydraulic cylinder 17 is operated to open the shut-off gate 18, and the pressurized gas is injected from the injection nozzle 16, and the pressurized gas is discharged when the gas holding pressure is completed. Done,
It was cooled and the product was taken out. By repeating this one cycle process, almost 100 shots were molded.

As a result of the above test, it was confirmed that the molten resin was not clogged in the injection nozzle 16 and the injection port 16a, and that a molded product having a good hollow portion could be injection-molded.

[0029]

INDUSTRIAL APPLICABILITY A molten resin is injected into a cavity and a pressurized gas is injected into a hollow by using an injection molding die in which a flow path of the pressurized gas communicates with a molten metal pool at the tip of a sprue. By molding a molded product having a portion, further, by using an injection molding die in which a pressurized gas shutoff means is provided in the pressurized gas flow path, while injecting a molten resin into the cavity, The shut-off means injects pressurized gas while adjusting the timing to form a molded product with a hollow portion, reducing the extra finishing man-hours for the injection gate for pressurized gas, resulting in an excellent finished appearance. You can get the goods. Furthermore, the shut-off means of the pressurized gas eliminates the clogging of the molten resin in the gas nozzle portion, enabling the high-speed resin filling necessary for ensuring a high hollow ratio. Therefore, it is suitable as an injection mold and an injection molding method.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of an injection molding die of the present invention according to claim 1.

FIG. 2 is a perspective view of a molded product produced by the injection molding die according to the first aspect of the present invention.

FIG. 3 is a perspective view showing a main part of the molded product shown in FIG.

FIG. 4 is a perspective view of a molded product by a conventional injection molding die.

5 is a perspective view showing a main part of the molded product shown in FIG.

FIG. 6 is a sectional view showing an example of an injection molding die of the present invention according to claim 3;

[Explanation of symbols]

 1, 11 Fixed mold 2, 12 Movable mold 3, 13, 20, 30 Molded product 3a, 13a, 22, 32 Hollow part 4, 14, 23, 33 Sprue 4a, 14a, 35 Resin reservoir 4b, 14b, 24, 34 Gate 5, 15, 25, 36 Flow path 6, 16 Injection nozzle 6a, 16a Injection port 17 Hydraulic cylinder 18 Shut-off gate 18a Tip part 21, 31 Main body 21a, 31a Space 23 36a Cutting trace

Claims (4)

[Claims] 1. An injection mold for injecting a molten resin into a cavity formed by a fixed mold and a movable mold, and injecting a pressurized gas to form a molded article having a hollow portion. An injection mold, wherein a flow path for injection is provided in communication with a resin reservoir at the tip of the sprue. 2. A method of injection molding, which comprises using the injection molding die according to claim 1 to inject a molten resin into a cavity and inject a pressurized gas to form a molded article having a hollow portion. . 3. An injection molding die for injecting a molten resin into a cavity formed by a fixed die and a movable die, and injecting a pressurized gas to form a molded article having a hollow portion. An injection molding die, wherein a flow passage is provided in communication with a resin reservoir at the tip of the sprue, and a pressurizing gas shutoff means is provided in the pressurizing gas passage. 4. A molded article having a hollow portion is produced by using the injection molding die according to claim 3 to inject a molten resin into a cavity and to inject a pressurized gas while adjusting timing by a shutoff means. An injection molding method characterized by molding.