JPH0712623B2 - Injection molding method and apparatus for molded article having hollow portion - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As a conventional injection molding method for a molded product having a hollow portion, there is one as disclosed in Japanese Patent Publication No. 57-14968. The injection molding method of a molded product having a hollow portion shown in this figure is performed by injecting a gas body into the cavity during or after injecting a predetermined amount of molten resin insufficient to fill the cavity. Trying to meet. Thereby, a molded product having a hollow portion can be injection-molded.

[0003]

However, in the conventional injection molding method for a molded article having a hollow portion as described above, the pressure of the gas body to be injected is as high as 150 kg / square cm, and therefore the apparatus Maintenance and management is troublesome,
In addition, since the device handles high pressure, it becomes large in size and expensive. In addition, JP-A-6
There are injection molding methods as disclosed in Japanese Patent Application Laid-Open No. 0-24913 and Japanese Patent Application Laid-Open No. 64-14012, but both of them have the same problem as above because high-pressure pressurized gas is injected into the cavity. There was a point. The present invention aims to solve such problems.

[0004]

According to the present invention, a smaller amount of molten resin is injected into a cavity, and a vaporizable fluid is injected into the molten resin during or after the injection. The above problems are solved. That is, the injection molding method for a molded product having a hollow portion of the present invention has a method of injecting a molten resin in an amount smaller than its capacity into a mold cavity and having vaporization property inside the molten resin during or after the injection. At the same time, a predetermined amount of fluid such as water that does not dissolve the resin used is injected, and the injected fluid is evaporated by the heat of the molten resin in the mold cavity to generate vapor pressure, and this vapor pressure causes the outer surface of the molten resin to rise. Press into the mold to make a hollow molded product. Water or the like may be supplied in a liquid state to the flow path reaching the mold cavity, heated in the middle of the flow path to be vaporized, and then injected into the mold cavity. Further, an apparatus for carrying out the above method comprises a fixed mold (10), a movable mold (12), and an injection device (14) capable of injecting a molten resin into the cavity (C).
An inner annular member (22) arranged in the nozzle part of this,
In the case of a device having a passage member (24) connected thereto via an injection device (14) and a pump (26) connected thereto, a depressurization valve (28) and vaporization And a tank (32) containing a liquid such as water that does not dissolve the resin used, and the passage member (24) has two passages (24) on the upstream side thereof.
a.24b), and the pump (26)
Is attached to the passage member (24) so that its discharge port communicates with one passage (24a) of the passage member (24), and the pressure relief valve (28) is attached to one port of the passage member (24). (P) is attached to the passage member (24) so as to communicate with the other passage (24b) of the passage member (24), and the suction port of the pump (26) and the pressure relief valve (28) are connected to each other. The other port (T) is connected to the tank (32). In addition, fixed type (1
0), the movable mold (12), the injection device (14) capable of injecting the molten resin into the cavity (C), and the passage member (4).
4) and a pump (26) connected thereto, the passage opening / closing valve (12a.3)
8), a depressurization valve (28), and a tank (3) containing a liquid such as water that has a vaporizing property and does not dissolve the resin used.
2) and a heater (48) fixed to the passage member (44)
And a passage (12d) communicating with the cavity (C) is formed in the movable mold (12), and the passage opening / closing valves (12a, 38) are provided in the passage (12d).
Is provided at a position where the passage member (4
4) is fixed to the movable die (12) so that the passage on the downstream side of the passage communicates with the passage (12d), and the upstream side of the passage is branched into two passages (44a, 44b). The pump (26) includes the passage member (4
4) The pressure release valve (28) is attached to the passage member (44) so as to be connected to one of the passages (44a).
Is attached to the passage member (44) so as to be connected to the other passage (44b) of the passage member (44), and the suction port of the pump (26) and the pressure relief valve (2).
The other port (T) of 8) is connected to the above tank (3).
2) is connected. The reference numerals in parentheses indicate the corresponding members of the embodiment.

[0005]

When a vaporizable fluid (eg, water) is injected into the molten resin during or after the injection of the molten resin in an amount smaller than the capacity of the molten resin, the fluid is surrounded by the molten resin. The heat increases the volume of the molten resin and causes the gas pressure to be generated, whereby the molten resin is pressed against the wall surface of the mold. As a result, a molded product having a hollow portion can be injection-molded without using a high pressure gas device which is troublesome to handle. In addition, when the fluid is supplied to the flow path reaching the cavity in a liquid state, it is vaporized by heating in the middle of the flow path, and is injected into the molten resin in the cavity in a gas state, it is melted. The steam pressure applied to the resin can be further increased.

[0006]

FIG. 1 shows the first embodiment of the present invention. Fixed type 1
The cavity C is formed by 0 and the movable die 12. The fixed mold 10 is fixed to a fixed portion (not shown), and the movable mold 12 is driven by a mold clamping device (not shown), so that the movable mold 12 is at the closed position shown in the drawing and the left side thereof. It is movable between the two mold open positions. Fixed type 1
The injection device 14 is arranged so as to face the 0 inlet portion 10a. The injection device 14 includes an injection cylinder 16, a screw 18 rotatably and axially movably fitted to the injection cylinder 16, a heater 20 attached to an outer peripheral portion of the injection cylinder 16, and the like. A nozzle portion 16a is formed at the left end of the injection cylinder 16 in the figure. Injection device 1
4 is capable of pressing the nozzle portion 16a of the injection cylinder 16 against the inlet portion 10a of the fixed mold 10 by being driven by an injection device moving device (not shown). An inner annular member 22 is arranged on the inner diameter side of the nozzle portion 16a, whereby the nozzle portion 16a has a double annular shape. The passage of the inner annular member 22 is connected to the passage 16b that penetrates the wall portion of the injection cylinder 16 to the outer peripheral portion. A passage member 24 is fixed to the outer peripheral portion of the injection cylinder 16 corresponding to the passage 16b. The passage member 24 is formed with a passage that bifurcates from the middle, a pump 26 is connected so as to communicate with one passage 24a, and a depressurization valve 28 so as to communicate with the other passage 24b. Are connected. The suction port 26a of the pump 26 is
It is connected to the tank 32 via the check valve 30.
The tank 32 contains water. The pressure release valve 28 has a tank port T and a passage 24b of the passage member 24 when the spool 28a of the pressure release valve 28 is located at the shut-off position shown in the drawing.
Can be shut off, and when it is positioned at the communication position on the right side of the drawing with respect to the shut-off position shown in the figure, the tank port T of this can be communicated with the passage 24b of the passage member 24.
The tank port T of the pressure relief valve 28 is also connected to the tank 32. The passage member 24, the pump 26, the pressure release valve 28, the check valve 30 and the like constitute a liquid supply / drainage device.
The liquid supply / drainage device can drive the pump 26 by a reciprocating motor (not shown) to suck up the water in the tank 32 and supply it into the cavity C through the passage 16b of the injection cylinder 16 and the inner annular member 22. Further, as will be described later, the water vapor in the cavity C can be discharged as drain to the tank 32 through the pressure relief valve 28.

Next, the operation of the first embodiment will be described.
In the case of the first embodiment, there are two ways of use, so they will be described separately.

(First Example of First Embodiment) The first example shown in FIGS.
The conceptual working steps of the example are shown. The apparatus shown in FIGS. 2 to 6 is partially different from that of FIG. 1 in that a fixed ring 10 has a locate ring 34 attached thereto, and a nozzle portion of the injection device 14 has a locate ring 34.
The liquid supply / drainage device is not shown in the figure. First, the pressure release valve 28 is placed in the shut-off position shown in FIG. 1, and the molds 10 and 14 are closed. A predetermined amount of molten resin is injected from the injection device 14 into the cavity C of both molds 10 and 14 (FIG. 2). The amount of this molten resin is smaller than the capacity of the cavity C. The pump 26 is operated in a state where the molten resin in the cavity C is cooled and solidified to some extent, and the water sucked into the cylinder of the pump 26 from the tank 32 through the check valve 30 in the suction process is passed through the passage 24 in the discharge process.
While passing through a and 16b, it is made into hot water by the heat from the injection device 14, and the inner annular member 22 makes a cavity C
The required amount is injected into the inside. As a result, hot water enters the molten resin (Fig. 3). Cavity C
The hot water inside is heated by the heat from the surrounding molten resin and becomes steam, so that the volume thereof increases and the molten resin is pressed against the mold wall surface (FIG. 4). After the cooling step, the pressure relief valve 28 is positioned from the shutoff position shown in FIG. 1 to the communication position to the right of this, and the water vapor in the cavity C is returned to the tank 32 as a drain to depressurize the hollow chamber 50a (see FIG. 5). The mold is opened and the molded product 50 is projected from the mold (FIG. 6). As a result, the hollow molded product 50 can be injection-molded. In the case of the work procedure of the first example, the molded product 50
The hollow chamber 50a is communicated with the outside.

(Second Example of First Embodiment) FIGS. 7 to 12 show conceptual working steps of the first example. Note that FIG. 7 is the same work step corresponding to FIG. 2 of the first example, and similarly FIG. 8 is FIG. 3, FIG. 9 is FIG. 4, and FIG. The description of the steps from the injection of the molten resin to the depressurization of the water vapor in the cavity C is omitted. In the second example, the molded product 5 is obtained by injecting a small amount of molten resin again after the depressurization.
The opening of the hollow chamber 50a of No. 0 is sealed (FIG. 11). The mold is opened and the molded product 50 is projected from the mold (FIG. 12). As a result, the hollow molded product 50 can be injection-molded. In the case of the working procedure of the second example, the hollow chamber 50 of the molded product 50 is
a is shielded from the outside. That is, hollow sealing molding is performed.

Next, FIG. 13 shows a second embodiment of the present invention. A locate ring 34 is fixed to the fixed mold 10, and the injection device 14 is of a type having a shutoff nozzle 36 capable of opening and closing a passage. Movable type 12
The valve chamber 12a is formed in the valve body 3 and the valve body 3
The piston integrated with 8 is fitted. As a result, as shown in FIG. 16, the valve chamber 12a includes a valve closing oil chamber 12a1 on the left side of the drawing and a valve opening oil chamber 12a2 on the right side of the drawing.
It is divided into and. The movable mold 12 includes a valve closing oil chamber 1
A passage 12b communicating with 2a1, a passage 12c communicating with the valve opening oil chamber 12a2, and a passage 12d opening toward the valve body 38 are formed. A hydraulic pump 40 and a hydraulic switching valve 42 are arranged above the movable die 12 in FIG. The hydraulic pump 40, the hydraulic switching valve 42, and the movable die 12 are sequentially connected by piping. Movable type 1
The passage member 44 is fixed to the lower portion of the drawing in FIG. The passage member 44 includes a pump 26, a pressure release valve 28, and a check valve 3
0 is attached in the same arrangement relationship as in the first embodiment. The lower end of the passage member 44 in the figure is located below the liquid surface of the tank 32. However, in the case of the second embodiment, the passage member 44 is provided with the discharge side check valve 46 in the passage 44a, and the heater 4 is further provided on the outer peripheral portion.
8 are provided. The cavity C is connected to the passage 12d when the valve body 38 is located at the valve closing position shown in FIG. 13 because the hydraulic pressure is supplied from the hydraulic pump 40 to the passage 12b via the hydraulic pressure switching valve 42. Although the valve 1 is shut off, the hydraulic pressure is supplied from the hydraulic pump 40 to the passage 12c through the hydraulic switching valve 42, so that when the valve body 38 is in the valve open position shown in FIG.
It is in communication with 2d. As a result, the water in the tank 32 can be supplied to the cavity C via the check valve 30, the pump 26, and the check valve 46. Further, in the subsequent process, water vapor from the cavity C can be supplied to the tank 32 via the pressure relief valve 28.
Can be discharged to.

Next, the operation of the second embodiment will be described with reference to FIGS. In these figures, the hydraulic switching valve 42 is omitted, and lines such as the pipes related to the passage 12c are shown by broken lines. The passage member 44 is heated in advance by energizing the heater 48. First, the pressure relief valve 28 is placed in the shutoff position shown in FIG.
Is switched to a position where the passage 12b side communicates with the discharge side of the hydraulic pump 40, and both molds 10 and 14 are closed. The shutoff nozzle 36 of the injection device 14 is shown in FIG.
3 is positioned from the closed position to the open position, and a predetermined amount of molten resin is injected from the injection device 14 into the cavity C of both molds 10 and 14 (FIG. 14). The amount of this molten resin is smaller than the capacity of the cavity C. After the injection is completed, the shutoff nozzle 36 of the injection device 14 is located at the closed position (FIG. 15). When the molten resin in the cavity C is cooled and solidified to some extent, the hydraulic pressure switching valve 42 is switched, whereby the hydraulic pressure of the hydraulic pump 40 is supplied to the passage 12c and the valve body 38 is positioned at the passage open position. At the same time, the pump 26 is operated, and the tank 32 is operated in the suction process.
The water sucked into the cylinder of the pump 26 through the check valve 30 is injected into the cavity C by the required amount while being heated and vaporized by the heater 48 through the passage 44a, the check valve 46 and the passage 12d in the discharge process. To be done. As a result, water vapor enters the molten resin (FIG. 16). The water vapor in the cavity C is further heated by heat from the surrounding molten resin,
Since it becomes high-pressure steam, its volume increases, and the molten resin is pressed against the mold wall surface (FIG. 17). After the cooling step, the depressurization valve 28 is positioned from the shutoff position shown in FIG. 17 to the communication position to the right of this, and the water vapor in the cavity C is returned to the tank 32 as a drain to depressurize the inside of the hollow chamber 50a (see FIG. 18). The mold is opened and the molded product 50 is ejected from the mold.
As a result, the hollow molded product 50 can be injection-molded. In the case of the second embodiment, the hollow chamber 50a of the molded product 50 is formed.
Is in communication with the outside.

In the description of the first embodiment,
Although the hot water is injected into the molten resin in the cavity C, the injection speed and the passage 1 are set so that the molten resin is vaporized while passing through the passage 16b and injected in the state of water vapor.
A temperature such as 6b may be set. Further, in the above description of each embodiment, the hot water or steam is injected after the injection of the molten resin, but the hot water or steam may be injected during the injection of the molten resin. Further, although water (hot water or steam) is used as the fluid in the description of each of the above embodiments, any fluid other than water may be used as long as it does not dissolve the resin used. Although the hollow chamber 50a is depressurized in the above description of each embodiment, the depressurizing step may be omitted.

[0013]

As described above, according to the present invention, a hollow molded article can be injection molded without using a high pressure gas device or a gas recovery device. Since a device for injecting liquid does not need to have a high pressure, the device can be made compact and inexpensive.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a state where molten resin is injected into a mold cavity (first example).

FIG. 3 is a diagram showing a state of injecting a fluid into a molten resin in a mold cavity (first example).

FIG. 4 is a view showing a state of being hollow-formed by the vaporizing pressure of a fluid (first example).

FIG. 5 is a diagram showing a state in which the vaporizing pressure in the mold cavity is released (first example).

FIG. 6 is a view showing a state in which a molded product is projected from a mold (first example).

FIG. 7 is a view showing a state where molten resin is injected into a mold cavity (second example).

FIG. 8 is a diagram showing a state of injecting a fluid into the molten resin in the mold cavity (second example).

FIG. 9 is a view showing a state where a small amount of molten resin is injected again into the mold cavity (second example).

FIG. 10 is a diagram showing a state of being hollow-formed by the vaporizing pressure of a fluid (second example).

FIG. 11 is a view showing a state where the inside of the mold cavity is depressurized (second example).

FIG. 12 is a view showing a state where a molded product is projected from the mold (second example).

FIG. 13 is a diagram showing a second embodiment of the present invention.

FIG. 14 is a diagram showing a state in which a shut-off nozzle is opened and molten resin is injected into a mold cavity.

FIG. 15 is a diagram showing a state in which a shutoff nozzle is closed.

FIG. 16 is a view showing a state where water vapor is injected into the molten resin in the mold cavity.

FIG. 17 is a view showing a state of being hollow-formed by the vaporizing pressure of a fluid.

FIG. 18 is a view showing a state where the inside of the mold cavity is depressurized.

[Explanation of symbols]

 10 Fixed type 12 Movable type 14 Injection device 22 Inner annular member 24 Passage member 26 Pump 28 Pressure release valve 30 Check valve 32 Tank 36 Shutoff valve 38 Valve body (passage opening / closing valve) 40 Hydraulic pump 42 Hydraulic switching valve 44 Passage member 46, 48 Check valve 48 Heater

Claims (4)

[Claims] 1. A molten resin in an amount smaller than its capacity is injected into a mold cavity, and a fluid such as water which has vaporizing property and does not dissolve the resin used is vaporized inside the molten resin during or after the injection. A predetermined amount is injected, vapor pressure is generated by evaporating the injected fluid by the heat of the molten resin in the mold cavity, and the outer surface of the molten resin is pressed against the mold by this vapor pressure to form a hollow molded product. An injection molding method for a molded product having a hollow portion. 2. The hollow according to claim 1, wherein the fluid is supplied in a liquid state to a flow path reaching a mold cavity, heated in the middle of the flow path to be vaporized, and then injected into the mold cavity. A method of injection molding a molded article having a portion. 3. A fixed mold (10), a movable mold (12),
An injection device (14) capable of injecting a molten resin into the cavity (C), an inner annular member (22) arranged in a nozzle portion of the injection device, and a passage member connected to the injection device (14) via the injection device (14). (24) and the pump (2
And a tank (32) containing a liquid, such as water, which is vaporizable and does not dissolve the resin used, and is provided in the injection molding device having the above-mentioned passage member. The upstream side of (24) is branched into two passages (24a, 24b),
The pump (26) is attached to the passage member (24) so that its discharge port communicates with one passage (24a) of the passage member (24), and the pressure relief valve (28) is One of the ports (P) is attached to the passage member (24) so that it communicates with the other passage (24b) of the passage member (24), and the suction port of the pump (26) and the pressure. The other port (T) of the outlet valve (28) is an injection molding device connected to the tank (32). 4. A fixed mold (10), a movable mold (12),
In an injection molding apparatus having an injection device (14) capable of injecting a molten resin into a cavity (C), a passage member (44), and a pump (26) connected to the passage member, a passage opening / closing valve (12a 38), a depressurization valve (28), a tank (32) containing a liquid such as water that is vaporizable and does not dissolve the resin used, and a heater (48) fixed to the passage member (44). The movable mold (12) has a passage (12) leading to the cavity (C).
d) is formed, and the passage opening / closing valve (12a.3) is formed.
8) is provided at a position where the passage (12d) can be opened and closed, and the passage member (44) has the movable member (12) so that a passage on the downstream side of the passage member (44) communicates with the passage (12d). ) And its upstream side is branched into two passages (44a, 44b). The pump (26) is provided with one passage (44) of the passage member (44).
The pressure release valve (28) is attached to the passage member (44) so as to be connected to the passage member (44).
4) is attached to the passage member (44) so as to be connected to the other passage (44b) of the pump 4).
Suction port and the other port (T) of the pressure relief valve (28)
Is an injection molding apparatus connected to the tank (32).