JPH05185453A - Hollow injection molding apparatus - Google Patents

Abstract

PURPOSE:To prevent a pressurized fluid path from back-flow of a molten resin and to perform efficiently to inject and discharge a pressurized fluid through a pressurized fluid path. CONSTITUTION:A porous stopper 4 is mounted on an opening on the mold space 2, side of a pressurized fluid path 3. Therefore, a pressurized fluid can pass through but a molten resin can not flow into the pressurized fluid path 3 side by means of the porous stopper 4 and it is possible to perform smoothly injection and discharge of the pressurized fluid by adjusting the exposed area in the mold space 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow injection molding apparatus for molding a hollow injection molding by pressurizing a pressurized fluid into a molten resin in a mold. More specifically, instead of pressurizing the pressurizing fluid from the pressurizing fluid nozzle built into the injection nozzle, the pressurizing fluid can be directly pressurized into the mold space from the pressurizing fluid passage provided in the mold. The present invention relates to a molding device.

[0002]

2. Description of the Related Art Conventionally, as a hollow injection molding apparatus capable of directly pressurizing a pressurized fluid into a mold space, as disclosed in Japanese Patent Publication No.
Those disclosed in Japanese Patent No. 41264 and Japanese Patent Publication No. 59-19017 are known.

The hollow injection molding apparatus disclosed in Japanese Patent Publication No. 48-41264 is as shown in FIG. 3, in which the rear end is connected to a pressurized fluid source and the inside is a pressurized fluid passage 101.
The thin cylindrical protrusion 102 is provided so as to project and retract toward the inside of the mold 103. When this hollow injection molding apparatus is used, molten resin is injected in a state where the projection 102 is projected into the mold 103, and a pressurized fluid is press-fitted to form a hollow portion. After cooling and solidification, the pressurized fluid is applied. Is discharged from the hollow portion through the pressurized fluid passage 101, and the protrusion 102 is retracted from the inside of the mold 103 to take out the molding product.

The hollow injection molding apparatus disclosed in Japanese Patent Publication No. 59-19017 is as shown in FIG. 4, and the molten resin passage 105 for guiding the injected molten resin to the mold cavity 104 is provided. The cylinder device 106
A valve 107 for opening and closing the pressurized fluid passage 101 is provided, and the pressurized fluid is pressed in and discharged through the valve 107.

[0005]

However, these hollow injection molding apparatuses have the advantage that the pressurized fluid can be press-fitted from any position of the mold, but have the following problems.

In the case of the hollow injection molding apparatus of Japanese Patent Publication No. 48-41264, the protrusion 10 is formed when the molten resin is injected.
There is a problem that the molten resin flows back into the pressurized fluid passage 101 in the inside 2 and the pressurized fluid passage 101 is clogged. In order to prevent the backflow of the molten resin, it is possible to reduce the hole diameter of the pressurized fluid passage. However, with this method, it takes time to pressurize and discharge the pressurized fluid, and the molding cycle becomes long. There is a problem that the molding efficiency decreases.

In the case of the hollow injection molding apparatus of Japanese Patent Publication No. 59-19017, when the valve 107 is opened at the time of pressurizing the pressurized fluid, the molten resin flows backward from the opened valve 107 into the pressurized fluid passage 101, There is a problem that the pressure fluid passage 101 is clogged.

The present invention has been made in view of the above problems, and an object of the present invention is to prevent the backflow of the molten resin into the pressurized fluid passage and to efficiently pressurize and discharge the pressurized fluid. To do.

[0009]

The means taken by the present invention for this purpose will be described with reference to FIG. 1 corresponding to one embodiment.
According to the present invention, in a hollow injection molding apparatus for injecting a molten resin and pressurizing a pressurized fluid into a mold 1, one end has a mold space 2
Is provided with a pressurized fluid passage 3 whose other end is connected to a pressurized fluid source (not shown), and the opening of the pressurized fluid passage 3 on the mold space 2 side has a diameter of 0.5 mm. The hollow injection molding apparatus is provided with the following porous plug body 4 having a large number of fine through holes.

[0010]

In the present invention, the mold space 2 of the pressurized fluid passage 3
The porous plug body 4 provided in the side opening portion has a minute through hole, so that the flow of the pressurized fluid is allowed but the intrusion of the molten resin is prevented and the molten resin is not added. It is intended to prevent backflow to the pressure fluid passage 3. Further, even if the exposed area of the porous plug body 4 to the mold space 2 is large, the above-mentioned backflow preventing effect can be obtained, and by making this exposed area large, the pressurization fluid can be smoothly inserted and discharged. It is a thing.

[0011]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention.
The mold 1 is composed of a fixed mold 1a and a movable mold 1b. A pressurized fluid passage 3 is provided on the movable die 1b side. However, the pressurized fluid passage 3 does not have to be provided on the movable die 1b side, but may be provided on the fixed die 1a side.

One end of the pressurized fluid passage 3 opens into the mold space 2, and the other end of the pressurized fluid passage 3 is connected to a pressurized fluid source (not shown). In the present embodiment, the mold space 2 in which one end of the pressurized fluid passage 3 is open is a mold cavity, but as the mold space 2 in which one end of the pressurized fluid passage 3 is opened in the present invention, , Other than this mold cavity,
A space such as a sprue, a runner, or another space may be used as long as it is a space in the mold 1 into which the molten resin flows.

A porous plug body 4 is fitted into the opening of the pressurized fluid passage 3 on the side of the mold space 2. The porous plug 4 has a large number of fine through holes, and has a function of allowing the pressurized fluid to flow therethrough but preventing the molten resin from entering.

The through holes of the porous plug 4 need to have a diameter of 0.5 mm or less in order to allow the pressurized fluid to flow through but prevent molten resin from entering. When the through hole of the porous plug body 4 is larger than this, it is impossible to prevent the molten resin from flowing back to the pressurized fluid passage 3. The cross-sectional shape of the through hole in the present invention is not limited to a circular shape and may be a non-circular cross section. The diameter of a through hole having a non-circular cross section is determined by the flow resistance value of the molten resin in the through hole corresponding to the diameter of the through hole having a circular cross section.

The size of the through hole of the porous plug 4 differs depending on the property of the pressurized fluid used, particularly the viscosity of the pressurized fluid. As the pressurized fluid, a gas or liquid that does not react with the resin under the temperature and pressure at the time of injection can be used, and specifically, an inert gas such as nitrogen gas, air, high-temperature and high-pressure water, liquid paraffin, oligomer, etc. Although it can be used, the larger the viscosity difference from the molten resin is, the easier it is to prevent the molten resin from backflowing by the porous plug body 4. From that point, a fluid having a viscosity as low as possible is preferable, and a gas such as nitrogen is particularly preferable. When a gas such as nitrogen is used as the pressurized fluid, the through holes of the porous plug body 4 preferably have a diameter of 0.001 mm or more, more preferably 0.001 mm or more and 0.2 mm or less.

The porous plug 4 is not particularly limited as long as it is a porous body that can withstand the temperature and pressure of injection molding, and for example, a porous body made of metal, ceramic, ceramics, resin or the like can be used. Among these, a sintered metal porous body is preferable because it is easy to obtain a material that withstands the temperature and pressure during injection molding and that satisfies the size of the through hole. Further, the porous plug body 4 may be fitted and fixed to the pressurized fluid passage 3 or may be fixed by welding or the like.

When the porous plug 4 is attached, the porous plug 4 may be directly attached to the hole formed as the pressurized fluid passage 3 in the mold 1, but as shown in the drawing, at least the mold space is provided. The pressurizing fluid passage 3 on the second side is composed of a tubular body 5 inserted into the die 1, and the end of the tubular body 5 on the die space 2 side is projected into the die space 2. It is preferable to carry out.
This makes it easier to pressurize the pressurized fluid into the center of the molten resin in the mold space 2.

Further, it is preferable that the porous plug body 4 is attached so as to project from the pressurized fluid passage 3 into the mold space 2. By doing so, the exposed area of the porous plug body 4 in the mold space 2 becomes wider, and it becomes easier to smoothly press-fit and discharge the pressurized fluid.

Hollow injection molding by the present hollow injection molding apparatus can be carried out in the same manner as in the past. That is, the molten resin is injected, and at the same time as or after injecting a predetermined amount of the molten resin, the pressurized fluid is pressed from the pressurized fluid passage 3 to form the hollow portion, and the resin in the mold 1 is solidified by cooling. Then, the pressurized fluid in the hollow portion is discharged from the hollow portion, and then the mold 1 is opened to take out the hollow product. The pressurized fluid can be discharged from the hollow portion by causing the pressurized fluid to flow backward through the pressurized fluid passage 3. The discharge of the pressurized fluid from the hollow portion may be performed by disconnecting the connection between the pressurized fluid passage 3 and the pressurized fluid source and opening the pressurized fluid passage to the atmosphere. The pressurized fluid can be recovered and reused by switching the connection of from the pressurized fluid source to a recovery container (not shown).

FIG. 2 shows another attachment state of the porous plug body 4, and the attached state of the porous plug body 4 shown in FIG. 1 is the best, but FIGS. It is also possible to have the porous plug body 4 attached as shown in FIG.

(A) to (c) are obtained by directly inserting and fixing the porous plug body 4 into the hole provided as the pressurized fluid passage 3 in the mold 1, and (a) is the porous plug body 4. The mold 1 is slightly retracted from the inner wall surface of the mold 1, and (b) is the porous plug 4 and the mold 1.
Of the inner wall surface of the porous plug 4 is substantially the same, (c) is the porous plug 4
The projections are shown respectively from the inner wall surface of the mold 1.

(D) to (h) are those in which the pressurizing fluid passage 3 is constituted by the tubular body 5 inserted in the mold 1 and the porous plug body 4 is attached, and (d) to (f). ) Indicates that the tip of the tubular body 5 is substantially aligned with the inner wall surface of the mold 1 and the porous stopper 4 is slightly retracted from the tip of the tubular body 5, the porous stopper 4 and the tubular body 5 respectively. 3 and the porous plug 4 is projected from the end of the cylindrical body 5, respectively. Also,
In (g) and (h), the end of the tubular body 5 is projected from the inner wall surface of the mold 1 and the porous stopper 4 is slightly retracted from the end of the tubular body 5, and the porous stopper 4 is shown. And the tip end of the tubular body 5 are substantially aligned with each other.

[0023]

The present invention is as described above, and since the molten resin is prevented from flowing back to the pressurized fluid passage 3 by the porous plug body 4, the backward flow of the molten resin causes the pressure to flow. It is possible to stably supply the pressurized fluid without clogging the fluid passage 3. In addition, by adjusting the exposed area of the porous plug body 4 into the mold space 2, it is possible to quickly press-fit and discharge the pressurized fluid, which results in a decrease in molding efficiency due to a longer molding cycle. Can be prevented.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing another attachment state of the porous plug body.

FIG. 3 is an explanatory diagram of a conventional technique.

FIG. 4 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

 1 Mold 1a Fixed Type 1b Moving Type 2 Mold Space 3 Pressurized Fluid Passage 4 Porous Plug 5 Cylindrical

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Claims (5)

[Claims] 1. A hollow fluid injection molding apparatus for injecting a molten resin and pressurizing a pressurized fluid into a mold, wherein one end is opened to a mold space and the other end is connected to a pressurized fluid source. Hollow injection molding characterized in that a porous plug having a passage and provided with a large number of fine through holes having a diameter of 0.5 mm or less is provided at the opening of the pressurized fluid passage on the mold space side. apparatus. 2. The hollow injection molding apparatus according to claim 1, wherein the through hole of the porous plug has a diameter of 0.2 mm or less and 0.01 mm or more. 3. The hollow injection molding apparatus according to claim 1, wherein the porous plug body is made of a sintered metal. 4. A pressurizing fluid passage on at least the space inside the mold is composed of a cylindrical body inserted into the mold, and the end of the cylindrical body on the mold space side is the mold. The hollow injection molding device according to any one of claims 1 to 3, wherein the hollow injection molding device projects into the space. 5. The hollow injection molding apparatus according to claim 1, wherein the porous plug body projects into the mold space.