JPH0478514A - Resin blow molding equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a resin blow molding apparatus that injects gas into a resin to form a hollow part when molding a resin product by injection molding. This invention relates to improvements to make the wall thickness uniform and to prevent appearance defects such as sink marks.

(Prior art) Conventionally, molten resin such as plastic was injected into the cavity of an injection mold, and before the resin was completely cooled, high pressure gas was injected into the resin to make a part of the product hollow. There are known molding methods for forming parts. In this molding method, for example, molten resin is injected into a cavity formed by a fixed mold body and a movable mold body, and the surface layer of the resin is semi-solidified, and the internal resin is still unsolidified. A hole is made in a part of the surface layer by a gas injection mechanism to form a gas injection hole, and high-pressure gas is injected from this gas injection hole toward the unsolidified portion inside to form a hollow portion. This high-pressure gas is pressurized to about 600 atmospheres, for example.
When it enters the resin through the gas injection hole, it presses the unsolidified molten resin inside and penetrates deep into the resin, forming a gas flow path. This gas pressure is used to prevent sink marks due to molding shrinkage, and the gas-occupied space is formed as a hollow part to ensure the strength of the product.

(ilB to be solved by the invention) However, in the conventional case, when a hollow part is formed by such a method,
There was a problem in that the molten resin pushed by the gas pressure accumulated on the downstream side of the gas flow path and became thick, causing sink marks and the like in the openings, impairing the aesthetic appearance. In other words, as mentioned above, the gas injected from the gas injection hole permeates the unsolidified molten resin while pressing it around, forming a gas flow path, but in the downstream region where the gas pressure decreases, it penetrates the unsolidified molten resin. The spreading force of the pipe was also weakened, and the resin flowing from the upstream side began to coagulate, forming a thick wall in some parts. In such thick-walled parts, sufficient pressure is not applied during molding and the cooling rate tends to be unbalanced, so molding shrinkage does not occur uniformly, causing sink marks, etc. This resulted in appearance defects such as color unevenness.

(Means for Solving the Problem) In order to solve the problem, the present invention provides a product shape in the cavity at the farthest point from the gas injection hole among the gas flow paths formed in the molten resin by gas injection. A non-product thick wall part is provided that connects to the part.

(Function) The non-product thick wall portion is used as an escape area for the resin pushed by the gas, and the wall thickness of the hollow portion of the product shape portion is made uniform. That is, a sufficient volume of the non-product thick-walled portion provided in the portion where the gas pressure decreases is taken, and the molten resin pressed by the gas is forced into this non-product thick-walled portion, thereby delaying cooling and solidification around the opening. Therefore, the wall thickness of the hollow part of the product shape becomes uniformly thin,
Sink marks and the like due to molding shrinkage occur only in thick parts such as non-products, and do not impair the appearance quality of the product itself.

The non-product thick part is cut off after molding and solidification.

(Example) An example of the resin blow molding apparatus of the present invention will be described based on the attached drawings.

FIG. 1 is a longitudinal cross-sectional view of the entire resin blow molding apparatus, FIG. 2 is an enlarged view of a non-product thick part, and FIG. 3 is an enlarged view of a non-product thick part of another embodiment.

As shown in FIG. 1, the resin blow molding apparatus 1 of the present invention includes a fixed main body 3 attached to a fixed mounting plate 2, and a movable main body 6 attached to a movable mounting plate 4 via a support 5. The movable mold main body 6 is configured to be able to move vertically to open and close the mold. The cavity 7 formed at the dividing surface between the fixed main body 3 and the movable main body 6 is provided with a product-shaped part 8 in the shape of a product and a non-product thick part 9 as a discarded shape, which will be described later. .

Injection mechanism 11 that fills the cavity 7 with molten resin
is provided on the side of the fixed body 3 and is constructed using a hot runner method. That is, a hot runner block 12 equipped with a heater for heating the runner, such as a cartridge heater, and a hot nozzle 13 are provided, and the lunch resin kept in a molten state is injected into the cavity 7 from a sprue 14.

Further, a ninth gas injection mechanism 15 for injecting high pressure gas into the molten resin is provided on the movable mold main body 6 side. This gas injection mechanism 15 includes a piston that slides within the cylinder of a hydraulic cylinder unit 16, and a bottle 18 that can freely move in and out of the cavity 7 by this piston. The gas supply path 22 is always sealed. Then, the piston 17 is moved downward to project the tip of the bottle 18 into the cavity, and a gas injection hole 25 is opened in the surface layer of the filled resin 21.
Next, the bottle 18 is moved upward to communicate the nozzle hole I9 with the gas supply path 22.

On the other hand, an extrusion mechanism for releasing the mold is provided in order to open the mold and take out the product after molding and solidification is completed. This extrusion mechanism consists of an extrusion plate 23 that is provided to be slidable up and down with respect to the movable mold mounting plate 4, and an extrusion bottle 24 that is attached to this extrusion plate 23. It pierces through, with its tip facing the cavity surface.

On the other hand, the aforementioned non-product thick wall portion 9 is provided to protrude outward from the product-shaped portion 8, and its position is located at the gas injection hole 2, which is bored by the bottle 18 of the gas injection mechanism 15.
It is provided at the position of the gas flow path farthest from 5. or,
As shown in FIG.
2 (j21>u2), and the root portion is made slightly thinner to facilitate cutting.

The outline of the operation of the resin blow molding apparatus thus constructed is as follows.

When the cavity 7 is filled with molten resin by the injection mechanism 11, high pressure gas is injected by the gas injection mechanism 15. That is, by hydraulically operating the bottle 18 of the gas injection mechanism 15, a gas injection hole 25 is provided in the semi-solidified resin surface layer within the cavity, and high-pressure gas permeates into the resin 21 through this hole 25. That is, the high-pressure gas penetrates the unsolidified portion of the resin 21 and advances to the deep part, and a portion of the unsolidified molten resin is pushed by the gas and flows downstream. On the upstream side, where the gas pressure is relatively high, the gas pressure has sufficient pushing and spreading force, allowing a good hollow shape, that is, a thin, uniform wall thickness of the hollow portion. On the other hand, on the downstream side, the molten resin pushed by the gas flows into the non-product thick wall portion 9. In other words, since the non-product thick interior 9 has a sufficient thickness of ℃1, the molten resin in the non-product thick wall part 9, which has high heat retention ability, is less likely to solidify than the surrounding product-shaped part 8, and the pressed resin can be easily removed. I can accept it. Therefore, the hollow shape of the hollow portion 26 of the product-shaped portion 8 can be made good even on the downstream side of the gas flow path.

This non-product thick wall portion 9 is cut off after molding and solidification.

Next, in FIG. 3, the root portion is made thicker, and a hollow portion 26 is formed up to the vicinity of the non-product thick wall portion 9. In this case, the communicating hole 27 will be naturally formed when it is cut out using X-X rays after molding, and depending on the location, it is convenient because the step of separately drilling the hole can be omitted. That is, the communication hole 27 is usually provided for venting gas from the hollow part, etc.
It is effective in preventing product deformation.

(Effects of the Invention) As described above, in the resin blow molding apparatus of the present invention, a non-product thick wall portion connected to the product shape portion is provided in the cavity located at the farthest downstream side of the gas flow path from the gas injection hole. , excess molten resin is pushed into this, and thick parts do not occur in the product, which does not cause deterioration in quality in appearance. Further, it is possible to prevent defects due to unbalanced shrinkage during thickening, such as deformation due to residual stress, reduction in product strength, and occurrence of cracks.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of the entire resin blow molding apparatus, and FIGS. 2 and 3 are enlarged views of non-product shaped parts. In the figure, 1 is a resin blow molding device, 7 is a cavity, and 8 is a resin blow molding device.
1 is the product shape part, 9 is the non-product thick part, 11 is the injection mechanism, 1
5 is a gas injection mechanism, 21 is a resin, 25 is a gas injection hole, 2
6 indicates a hollow part. Patent applicant: Agent for Honda Motor Co., Ltd.
Patent Attorney Part 2 1) Part 1 Patent Attorney
Kuni Ohashi Patent Attorney Small
Yama Yu Figure 3

Claims (1)

[Scope of Claims] In a resin blow molding apparatus that injects molten resin into a product-shaped portion of a mold cavity and injects gas into the molten resin to mold a hollow molded product, this apparatus includes A resin blow molding apparatus characterized in that a non-product thick-walled part connected to the product-shaped part is provided in a cavity at a position farthest from the gas injection hole in the formed gas flow path.