JPH07100854A - Method for blocking gas channel of gas blowing molding method - Google Patents

Abstract

PURPOSE:To block a hole generated at a gas exit/ entrance such as a gate, etc., in a gas blowing molding method. CONSTITUTION:A movable pin 5, disposing its tip in a gate 3a and movable in a vertical direction, is disposed in molds 6 a synthetic resin 2 is substantially fully injected in a cavity of the molds 6, and a high pressure inert gas is thereafter blown through a sprue 3 before the resin 2 is entirely solidified. After dwelling, the pin 5 is moved upward to seal up the gate 3a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for injecting a synthetic resin into a cavity of a molding die, and before the synthetic resin is solidified,
In a gas injection molding method for injecting an inert gas into a molded body to form a void, a method for closing a gas passage which can easily close a hole which is one end of a gas passage formed at a gas inlet and outlet such as a gate .

[0002]

2. Description of the Related Art As one of the methods for manufacturing synthetic resin products,
There is an injection molding method that involves injecting a synthetic resin into the cavity of a molding die and injecting a high-pressure inert gas into the inside of the molded body to form a void therein before the synthetic resin is solidified. According to this gas injection molding method, the gas flows into the low-pressure portion of the synthetic resin, etc., and the appropriate pressure reaches the corner of the molded body by the gas holding pressure, and the stress inside the molded body is relaxed and uniformed. By doing so, sink marks, warpage, and the like that occur in the molded body are prevented.

However, in the above-mentioned gas injection molding method, when the inert gas is injected through the gate and other parts, a gas flow path is formed inside the gate and the like, so that when the gate and the like are cut, the molding is performed. There has been a problem that a hole, which is one end of the gas flow path, is exposed on the cut surface of the gas inlet and outlet of the body.

Since the hole formed on the cut surface is inferior in aesthetics and water may infiltrate during cleaning, it is necessary to attach a seal or a name plate to this hole or weld a synthetic resin piece of another piece. Alternatively, the hole is closed by a method such as welding a gate left behind for a long time.

[0005]

However, in the method of closing the holes described above, for example, in the case of a molded product that is washed with a high-pressure water stream, there is a possibility that the seal or the synthetic resin piece of another piece may come off. Moreover, it is difficult to say that the treatment of gas inlets and outlets such as gates by welding is aesthetically excellent.

Therefore, the present invention provides a method for closing a gas passage in a gas injection molding method capable of surely closing a hole formed in a cut surface of a gas inlet / outlet while maintaining excellent aesthetics. With the goal.

[0007]

In order to achieve the above-mentioned object, the method of closing the gas flow path in the gas injection molding method of the present invention is such that the inert gas is injected after the synthetic resin is injected into the cavity of the molding die. In a gas injection molding method of injecting and forming a void inside a molded body, disposing a movable movable pin at a gas inlet / outlet portion inside a molding die, and injecting the movable pin into the gas inlet / outlet portion to seal the gas inlet / outlet. It is characterized by.

Alternatively, in a gas injection molding method in which a synthetic resin is injected into a cavity of a molding die and then an inert gas is injected to form a void inside the molding, a cavity portion corresponding to a gas inlet / outlet inside the molding die. A movable pin is formed so as to form an extra region in the cavity, and the movable pin moves in the cavity to fill the synthetic resin in the extra space into the gap at the gas inlet / outlet portion. .

Further, the movable pin may be moved while being vibrated in the moving direction by the driving means.

[0010]

In a gas injection molding method in which a synthetic resin is injected into a cavity of a molding die and then an inert gas is injected to form a void inside the molding, a movable pin movable to a gas inlet / outlet portion inside the molding die. By disposing the movable pin into the gas inlet / outlet portion and sealing the gas inlet / outlet, the synthetic resin molded article can cut the gas inlet / outlet without forming a hole in the gas inlet / outlet in the molding cycle. .

In a gas injection molding method in which a synthetic resin is injected into a cavity of a molding die and then an inert gas is injected to form a void inside the molding, a cavity portion corresponding to a gas inlet / outlet inside the molding die is left over. A gas inlet / outlet port in a synthetic resin molded product is formed by forming a movable region and arranging a movable pin that is movable, and by moving the movable pin in the cavity to fill the synthetic resin in the extra region into the gap of the gas inlet / outlet part. Part of the void is filled with synthetic resin in the extra area,
As a result, even if the gas inlet / outlet is cut, no hole is formed in the gas inlet / outlet portion.

By moving the movable pin while vibrating it in the moving direction by the driving means, the synthetic resin can be smoothly moved in the molding die.

[0013]

1 and 2 are cross-sectional views showing a first embodiment of a method for closing a gas flow path in the gas injection molding method of the present invention, in which 1 in the gas injection molding method of the present invention. A molded body injection-molded by a method of closing a gas flow path, 2 is a synthetic resin injected into a cavity of a molding die 6 to mold the molded body 1, and 3 is a synthetic resin that connects an injection nozzle and the molded body 1. The sprue 3a in the molding die 6 through which the resin 2 and the inert gas such as nitrogen gas are passed is a gate which is so-called a side gate and which is formed linearly on the side surface of the molded body 1. The voids 5 formed by injecting an inert gas and the gas flow passages are movable pins which are arranged in the molding die 6 so as to be movable in the vertical direction and whose tips are located at the gate 3a. In the present invention, the cavity includes not only the space of the molded body but also the sprue and runner into which the synthetic resin is injected.

When molding the molded body 1, first, the synthetic resin 2 is poured into the cavity of the molding die 6 almost completely, and thereafter, as shown in FIG. 1, while the synthetic resin 2 is not completely solidified. A high pressure inert gas is injected through the sprue 3. As a result, not only in the molded body 1 but also in the sprue 3 and the gate 3a, a void 4 is formed by the gas flow path.

After holding the pressure, as shown in FIG. 2, the movable pin 5 whose tip is located at the gate 3a is moved upward to seal off the gate 3a, so that the synthetic resin 2 located at the gate 3a is removed. The gap 4 is not exposed at the cut surface of the movable pin 5 by being pushed into the gate portion of the molded body 1 and the sprue 3. The molded body 1 molded in this way is released from the mold through a cooling process.

3 and 4 show a second embodiment of the method for closing the gas flow path in the gas injection molding method of the present invention, in which the gate 3a extends horizontally from the side edge of the lower surface of the molded body 1. It is called a jump gate that goes out, and the tip of the movable pin 5 is located below the gate 3a. And FIG.
After the synthetic resin 2 and the inert gas are injected and the pressure is maintained as shown in FIG. 4, the movable pin 5 moves upward to the bottom surface of the molded body 1 and seals the gate 3a as shown in FIG.

5 and 6 show a third embodiment of the method for closing the gas flow path in the gas injection molding method of the present invention, in which the gate 3a has the sprue 3 positioned above the molded body 1. It is called a direct gate and has a movable pin 5
Is located on the lower surface of the molded body 1 facing the gate 3a, and the extra area 1a is provided on the outer peripheral surface of the molded body 1. Then, as shown in FIG. 5, after the synthetic resin 2 and the inert gas are injected and the pressure is maintained, the movable pin 5 moves upward to the bottom surface of the molded body 1 as shown in FIG. Is pushed to the gate. As a result, even if the gate 3a is cut, no void is created in the gate cut portion.
The position of the movable pin 5 is not limited to the lower surface of the molded body 1 facing the gate 3a, but may be any position as long as the synthetic resin in the extra area can be pushed into the gate portion. .

7 and 8 show a fourth embodiment of the method for closing the gas flow path in the gas injection molding method of the present invention, in which the gate 3a is provided above the molded body 1 with a large number of fine sprues 3. Is a pin gate that is automatically gate-cut when the mold is released from the mold. The tip of the movable pin 5 is provided on the lower surface of the molded body 1 facing the gate 3a and the extra area 1a is provided on the outer peripheral surface of the molded body 1. Is located. Then, as shown in FIG. 7, after the synthetic resin 2 and the inert gas are injected and the pressure is maintained, the movable pin 5 moves upward to the bottom surface of the molded body 1 as shown in FIG. The synthetic resin 2 in 1a is filled.

Further, in the above-mentioned first and second embodiments, the tip of the movable pin 5 is located at the gate 3a (a gas inlet / outlet other than the gate is also possible), but of course it is not limited to this. However, the movable pin 5 is formed after forming the spare area in the gate 3a as in the third and fourth embodiments.
May be arranged. By forming this extra area, the voids in the gas inlet / outlet portion are more surely filled with the synthetic resin in the extra area.

In the first to fourth embodiments described above, when the movable pin 5 is moved while being vibrated in the moving direction by the driving means (not shown), the synthetic resin 2 is smooth. It moves to and fills the gate part.

Further, in each of the above-mentioned embodiments, the inert gas is injected through the gate, but of course, the present invention is not limited to this, and it may be injected from any cavity portion other than the gate. In this case, the movable pin is arranged not at the gate portion but at a position corresponding to the gas inlet / outlet port.

[0022]

As described above in detail, according to the method of closing the gas flow path in the gas injection molding method of the present invention, the movable pin is arranged at the gas inlet / outlet portion in the molding die, and the movable pin is provided. By injecting the gas into the gas inlet / outlet portion and sealing the gas inlet / outlet, the synthetic resin molded article can cut the gate without forming holes in the gate cut portion in the molding cycle. In addition, a movable pin is formed in the cavity corresponding to the gas inlet / outlet inside the molding die, and a movable pin is provided, and the movable pin moves in the cavity to allow the synthetic resin in the gas inlet / outlet portion to move. By filling the voids, the voids in the gas inlet / outlet part of the synthetic resin molded product are filled with the synthetic resin in the extra area, so that even if the gas inlet / outlet is cut, no hole is created in the gas inlet / outlet part. Is.

Thus, in the gas injection molding method, which is an excellent synthetic resin molding method capable of preventing sink marks, warpage, etc., it is necessary to treat the gas inlet / outlet hole portion such as the gate cut portion, which cannot be dealt with conventionally. This eliminates the need for a separate piece of synthetic resin, a sticking process, a welding process, etc., and it is possible to provide a molded product that retains its excellent aesthetics while reducing the manufacturing cost of the molded product in the gas injection molding method. became.

Further, when the movable pin is moved while vibrating in the moving direction, the synthetic resin moves smoothly in the molding die to surely fill the gas inlet / outlet portion.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of a method for closing a gas passage in a gas injection molding method of the present invention.

FIG. 2 is a cross-sectional view showing a first embodiment of a method for closing a gas flow path in the gas injection molding method of the present invention.

FIG. 3 is a cross-sectional view showing a second embodiment of the method for closing the gas flow path in the gas injection molding method of the present invention.

FIG. 4 is a cross-sectional view showing a second embodiment of the method for closing the gas passage in the gas injection molding method of the present invention.

FIG. 5 is a cross-sectional view showing a third embodiment of the method for closing the gas flow path in the gas injection molding method of the present invention.

FIG. 6 is a cross-sectional view showing a third embodiment of the method for closing the gas flow path in the gas injection molding method of the present invention.

FIG. 7 is a cross-sectional view showing a fourth embodiment of the method of closing the gas flow path in the gas injection molding method of the present invention.

FIG. 8 is a cross-sectional view showing a fourth embodiment of the method for closing the gas flow path in the gas injection molding method of the present invention.

[Explanation of symbols]

 1 Molded Body 2 Synthetic Resin 3 Sprue 3a Gate 4 Void 5 Movable Pin 6 Mold

Claims (3)

[Claims] 1. In a gas injection molding method in which a synthetic resin is injected into a cavity of a molding die and then an inert gas is injected to form a void inside the molding, the gas injection molding method is movable to a gas inlet / outlet portion inside the molding die. A method for closing a gas flow path in a gas injection molding method, wherein a movable pin is provided, and the movable pin is allowed to enter a gas inlet / outlet portion to seal the gas inlet / outlet. 2. In a gas injection molding method in which a synthetic resin is injected into a cavity of a molding die and then an inert gas is injected to form a void inside the molding, a cavity portion corresponding to a gas inlet / outlet inside the molding die. A gas injection molding, characterized in that a movable pin is formed to form a free space in the space and the movable pin moves in the cavity to fill the synthetic resin in the free space into the gap at the gas inlet / outlet part. Method to block the gas flow path in the method. 3. The movable pin moves while being vibrated in the moving direction by the driving means.
Alternatively, a method of closing the gas flow path in the gas injection molding method according to 2 above.