JPH0236372B2 - TADANKASANEAWASESHIKIKANAGATAOJUSHITASHASHUTSUSEIKEIKI - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention injects molding material in a hot runner manifold that communicates with the molding cavities of molds arranged in a multistage stacked manner, and at the same time injects the molding material from the entire area of the runner. This invention relates to an injection molding machine having a device for extracting all generated gas.

Multi-stage overlapping molding molds can quickly produce a larger number of molded products under the same mold clamping force.
In accordance with the increasing number of molding cavities in the mold, it is necessary to increase the plasticized material capacity and injection capacity of the hot runner manifold applied to it, which increases the influence of residual pressure in the hot runner and the molding material flowing into the hot runner. The moment I entered,
Due to the evaporation of moisture in the molding material, gas components become finely gasified, causing gas phenomena, etc. Also, gas is mixed into the interior of the injected molded product, leading to deterioration of physical properties and poor insulation, resulting in long-term deformation of the molded product. This may cause inconveniences such as

[Conventional technology and its problems]

Conventionally, multi-stage stacking has succeeded in simply solving the problem of fine gas generation due to residual pressure and gas generated during injection (gas generated when plasticized material is overheated and vaporization of moisture in the material). Injection molding machines with mating molds have not yet been seen.

That is, conventionally known injection molding machines of this type include Japanese Patent Publication Nos. 50-8109 and 50-5216, and other commonly used molding machines have an injection nozzle that is slightly retracted immediately after injection. (decompression)
Alternatively, attempts are made to reduce the residual pressure on the molding cavity side, but the residual pressure in the hot runner may still cause a so-called dripping phenomenon on the molding cavity side, and there is also a problem with injection into the molding cavity. As mentioned above, the actual situation is that black spots and cloud-like patterns may be produced in molded products due to the infiltration of fine gases due to gas generation due to gasification of moisture contained in plasticized materials during overheating decomposition. Furthermore, even if the appearance and precision are good, a small amount of moisture remains as a gas inside the molded product, leading to poor insulation.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide an injection molding machine having a multistage overlapping mold that can easily solve problems such as residual pressure in a hot runner and generation of fine gases.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an injection molding machine having an extension part that serves as an accumulator and an injection part, the tip of which reaches near the center of a hot runner manifold for molding cavities of molds arranged in a multistage stacked manner. A space is provided at the tip of the screw heating tube, and a sintered metal member is provided as a gas venting means at a location facing the hot runner corresponding to the extension of the screw heating tube tip, and a means is provided to remove any gas from the plasticized material. It is characterized by

〔Example〕

Next, embodiments of the present invention will be described with reference to the accompanying drawings.

A mold clamping device B is arranged in a T-shape with respect to the injection device A, and the mold clamping device B includes a fixed platen 1, a movable platen 3 attached to the tip of a hydraulically driven mold clamping rod 2, and these fixed plates 1. and an intermediate movable plate 4 disposed between the movable plate 3, one of the split molds is attached to the fixed plate 1, the other is attached to the intermediate movable plate 4, and one of the other split die is attached to the movable plate 3. , the other is attached to the intermediate movable platen 4, respectively. When the movable platen 3 is moved to the left in the direction of FIG. 1 by the mold clamping rod 2,
Along with this, the intermediate movable platen 4 is moved in the same direction via a known interlocking means (not shown), and the mold is opened.
When the mold clamping rod 2 pushes the movable platen 3 to the right as shown in Fig. 1, the mold is clamped.

The intermediate movable platen 4 is provided with a hot runner manifold 6 for the molding cavity 5, and the tip of the screw heating cylinder 7 in the injection device A is extended to near the center of the hot runner manifold 6.
Extension part 8 space 1 as an accumulator and injection part
5, and a degassing means 10 facing the hot runner 9 at a location corresponding to the extension part 8 is provided on an intermediate movable platen 4 which is a hot runner manifold block. As the gas venting means 10, a sintered metal part having continuous gaseous fine holes (approximately 0.25 mm) can be provided and connected to a vacuum pump. The gas venting means 1
0 is communicated with the atmosphere through a pipe 11 using a reduced pressure source (not shown) such as a vacuum pump.

In the illustrated injection molding machine of the present invention, during injection, the screw 12 in the injection device A functions as an injection plunger as in conventional in-line injection molding, and after injection, the screw 12 serves as an extension of the tip of the screw heating cylinder 7 as an accumulator and injection section. The screw is retracted to the home position while storing the plasticized material in the hot runner 9 including the hot runner 8.

The plasticized material injected into the hot runner 9 from the extension part 8, which serves as the accumulator and injection part, passes through the branch runners 13, 13 and the sprue gates 14, 14 of the hot runner 9, and is degassed until the cavities 5, 5 are filled. The plasticized product is injected all at once into molding cavities 5, 5 in a multistage overlapping mold.

In this injection molding, since the extension part 8 reaches near the center of the hot runner manifold 6, a hot runner with a short flow path, in other words, a small capacity is sufficient, and the injection rate is also increased, resulting in an extra high pressure No injection required. Therefore, the residual pressure inside the hot runner is also small. Therefore, the residual stress of the plasticized material filled in the cavity is minimal, and distortion of the molded product does not occur over a long period of time.

In addition, in the above injection molding, at the moment when the molding material is injected into the hot runner 9 from the extension part 8 which serves as an accumulator and an injection part, when the gas generating components and gas components in the molding material are finely gasified in the hot runner 9, the fine gaseous components are The gas is discharged from the entrance of the cavity 5 through the degassing means 10 and the piping 11 under reduced pressure or atmospheric pressure until the cavity is filled. In this case, the degassing means 10 has an extension 8 that reaches near the center of the hot runner manifold.
Since the hot runner 9 is heated at a high temperature between the heating tube 7 and the screw, the gas-generating components or gas components in the molding material are turned into fine gases and are exhausted outside the mold, allowing for degassing. This is carried out effectively and the residual pressure within the cavity is also reduced by the degassing.

〔Effect of the invention〕

As described above, according to the present invention, the degassing means performs effective gas degassing, which contributes to reducing the residual pressure inside the hot runner. This method has the advantage that the problems of internal residual pressure and fine gas generation can be easily solved, and molded products with high precision and excellent quality can be obtained.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view showing an embodiment of the present invention;
2 is a longitudinal sectional view of the vicinity of the center of the hot runner manifold in the injection molding machine of FIG. 1. FIG. A... Injection device, B... Mold clamping device, 1... Fixed plate, 2... Mold clamping rod, 3... Movable plate, 4... Intermediate movable plate, 5... Molding cavity, 6... Hot runner Manifold, 7... Screw heating cylinder, 8
... Extension part, 9 ... Hot runner, 10 ... Gas venting means, 11 ... Piping, 12 ... Screw,
13... Branch runner, 14... Sprue gate.

Claims (1)

[Claims] 1 Run the runners vertically toward the molding cavities of the molds arranged in a multi-stage stacked manner until near the center of the hot runner manifold, and at the center of the mold clamping, the left and right runners are branched, and the gates are installed in the stacked cavities on both sides. is opened, and the runner and sprue gate are provided with a sintered metal member as a degassing means while reaching the cavity, and means for continuously degassing the gas of the plasticized material until it fills the cavity, passing through the runner, and injecting it into the cavity. An injection molding machine equipped with a multi-stage overlapping mold.