JPH07119007B2 - Injection compression molding method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection compression molding method and apparatus.

[0002]

2. Description of the Related Art A conventional injection compression molding apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. 61-283520. In the injection compression molding method shown therein, a fixed mold and a movable mold are attached to the fixed plate and the movable plate of the mold clamping device, and when the mold is closed, the convex and concave portions of the fixed mold and the movable mold fit together. However, when the molds are not completely in close contact with each other, that is, when there is a gap between the parting surfaces of the two dies, the molds are temporarily closed, injection is performed in this stopped state, and then The movable platen is moved forward and the mold is clamped to compress the molded product. This makes it possible to obtain a molded product with less distortion and high shape accuracy.

[0003]

However, the conventional injection compression molding apparatus as described above has a problem in that a hollow molded article cannot be manufactured. That is, although it is possible to manufacture a solid molded product by an injection compression molding method or a porous molded product by using a foamable resin, the advantages of the injection compression molding method can be utilized to obtain dimensional accuracy. It has hitherto not been possible to produce a good hollow molded article.

[0004]

According to the present invention, a molten resin is injected into a cavity before the mold is closed so as to form a solid mass, and a gas is injected into the solid mass according to the injection state of the molten resin. Further, the above problem is solved by ending the injection of gas in accordance with the injection state of the molten resin, and then clamping the mold to compress the molded product. That is, according to the injection compression molding method of the present invention, the molten resin (30) is injected into the cavity (C) of the mold (14, 16) before completion of mold closing so as to form a molten resin (30). A gas is injected into the interior of the molten resin (30) according to the injection state of the molten resin (30), and the injection of the gas is terminated according to the injection state of the molten resin (30) to form a balloon-shaped resin (30a). The balloon-shaped resin (30a) is compressed to form a molded product (30b) by performing mold clamping during or after the injection. The apparatus for carrying out the above method is a fixed plate (10).
And a mold clamping device (46) having a movable plate (12), a fixed mold (14) attached to the fixed plate (10), and a movable mold (16) attached to the movable plate (12). The fixed mold (14) or the movable mold (16) is formed with a resin passageway (18) passing through this and opening to the wall surface forming a part of the wall of the cavity (C). A gas passage having an opening (20a) passing through the mold (14) or the movable mold (16) and passing through the wall surface forming a part of the wall of the cavity (C) and extending into the cavity (C). (20) is formed, and an injection device (28) capable of injecting the molten resin (30) into the cavity (C) through the resin passage (18) and air to the molten resin (30). The air supply device (44) capable of supplying the air and the cavity (C) Means for detecting an injection state of melting resin (30), an air supply device based on a future signal (4
4) and the mold clamping device (46), and a controller (48) for outputting a control signal, respectively. The means for detecting the injection state is a position detector (32) for detecting the position of the injection plunger of the injection device, a movable mold (16).
Alternatively, it may be a position detector (34) that detects the position of the movable member (12) of the mold clamping device (46), a timer that starts timing with the start of injection, or the like. The reference numerals in parentheses indicate the corresponding members of the embodiment.

[0005]

Function: Molten resin is injected into the cavity before the mold is closed so as to form a solid mass. A gas such as air is injected into this mass according to the injection state of the molten resin, and the injection of gas is terminated according to the injection state of the molten resin. As a result, the molten resin becomes a balloon-shaped resin that bulges like a balloon. In this state, the mold is clamped to compression-mold the balloon-shaped resin. After cooling the mold, it is opened and the molded product is taken out. By doing so, a hollow molded article can be manufactured.

[0006]

1 to 4 show a first embodiment of the present invention. FIG. 6 shows the molding process of the first embodiment. The fixed platen 10 and the movable platen 12 of the mold clamping device 46 are provided so as to face each other. The movable platen 12 can be moved by a mold clamping cylinder (not shown) in a direction toward and away from the fixed platen 10. A fixed die 14 is attached to the fixed platen 10, and a movable die 16 is attached to the movable platen 12. The fixed mold 14 is formed in a columnar shape having two stepped protrusions. The movable mold 16 has a "concave" cross section. The middle outer diameter portion of the fixed mold 14 can be fitted into the cylindrical hole of the movable mold 16. With the movable mold 16 and the fixed mold 14 fitted together, the space C between the molds 14 and 16 forms a cavity C having a U-shaped cross section. The size of the fitting portion between the fixed mold 14 and the movable mold 16 is such that a gap that allows the air in the cavity C to be discharged when the movable mold 16 further moves in the mold closing direction from the position shown in FIG. Has been selected. Fixed mold 14
A resin passage 18 opening to the cavity C is formed therein. That is, the resin passage 18 is the same as that of the fixed mold 14 shown in FIG.
It is provided from the wall surface on the left side toward the center of the mold, bends upward in the middle, and opens at the center of the upper surface of the mold. From the injection device 28 to the resin passage 18 in the cavity C.
It is possible to inject molten resin therethrough. Further, the movable mold 16 is formed with an air passage 20 extending into the cavity C. That is, the air passage 20 extends into the cavity C by penetrating the upper surface and the lower surface of the movable mold 16 in the figure. Opening 20 of air passage 20
The a is arranged at a position facing the opening of the resin passage 18. An air supply device 44 is connected to the air passage 20. As will be described later, in a state where the molten resin 30 is supplied into the cavity C in a solid state so as to surround the opening 20a, air is supplied from the air supply device 44 through the air passage 20 into the molten resin 30. Is possible. A position detector 32 is attached to the injection plunger 28 a of the injection device 28. A comparator 36 that receives a signal from the position detector 32 and a setter 38 that sets a predetermined stroke position of the injection plunger 28a in advance.
And a controller 48 for receiving the signal from the comparator 36. It is possible to set two positions in the setting device 38, a gas injection start position and a gas injection end position. The position detector 32 is the injection plunger 28.
It is possible to detect the position of a and output a signal to the comparator 36. The comparator 36 can compare the signal from the setter 38 with the signal from the position detector 32 and output a signal to the controller 48 when both signals are equal. The controller 48 can output a command signal to the air supply device 44 and the mold clamping device 46 based on the signal from the comparator 36.

Next, the operation of the first embodiment will be described with reference to the control block diagram of FIG. Pre-setting device 3
The gas injection start position set value S1 (see FIG. 6) and the gas injection end position set value S2 are set in FIG. Controller 4
In response to a command signal from 8, the movable platen 12 is temporarily stopped in a state where it is moved from the mold open position to the mold closing position shown in FIG. Next, from the injection device 28 to the molten resin 30
Is injected into the cavity C through the resin passage 18 (injection step of FIG. 6). As a result, the molten resin 30 has a solid shape that encloses the opening 20a of the air passage 20.
Since the injection of the molten resin 30 is performed before the molds 14 and 16 are closed, the injection is performed at a low pressure. The injection plunger 28a moves to the right in FIG. 4 in accordance with the injection, but the movement position of the injection plunger 28a is detected by the position detector 32 (injection state detection means) and is input to the comparator 36 (FIG. 9). reference). Of the two set values set in the setter 38, the gas injection start position set value S1 (see FIG. 6) and the detected value of the position detector 32 are compared by the comparator 36, and when the two match, comparison is made. A signal is output from the device 36 to the controller 48, and in response to a command signal from the controller 48, blowing of air into the molten resin 30 from the air supply device 44 through the gas passage 20 into the molten resin 30 is started (gas injection). Process). Further, the injection of resin progresses and the gas injection end position set value S of the two set values set in the setter 38 is set.
2 (see FIG. 6) and the detected value of the position detector 32 match, a signal is output from the comparator 36 to the controller 48,
The command signal from the controller 48 terminates the blowing of air from the air supply device 44. As a result, the molten resin 30 becomes a balloon-shaped resin 30a having air therein, as shown in FIG. After the air injection is completed, the controller 4
The movable plate 12 is driven again by the command signal from 8 to perform mold clamping as shown in FIG. 3 (compression process). As a result, the balloon-shaped resin 30a becomes a hollow molded product 30b having a "U" -shaped cross section. Both molds 14 and 16 are cooled, the movable platen 12 is moved in the mold opening direction to open the movable mold 16, and the molded product 30b is taken out.

Next, a second embodiment of the present invention will be described with reference to FIGS.
It will be described based on. The fixed platen 10, the movable platen 12, the fixed mold 14, the movable mold 16, the resin passage 18 formed in the fixed mold 18, the air passage 20 formed in the movable mold 16, and the inlet of the resin passage 18 are arranged. The injection device 28, etc.
It is similar to that of the first embodiment. Position detector 3 on the fixed part
4 is attached to the movable platen 1 of which a detection rod is attached.
It is fixed at 2. A setting device 42 that sets the moving position of the movable platen 12 in advance, a comparator 40 that receives a signal from the position detector 34, and a controller 48 that receives a signal from the comparator 40 are provided. It is possible to set two positions in the setting unit 42, a gas injection start position and a gas injection end position. The position detector 34, the comparator 40, and the setting device 42 are the same as the position detector 3 of the first embodiment.
2. The comparator 36 and the setter 38 are similar to each other.

Next, the operation of the second embodiment will be described with reference to FIGS.
This will be described with reference to FIGS. The movable platen 12 is temporarily stopped in a state where it is moved from the mold open position to the mold closing position shown in FIG. Next, the molten resin 30 is injected from the injection device 28 through the resin passage 18 into the cavity C in a highly viscous state. The position of the movable platen 12 is detected by the position detector 34 and input to the comparator 40.
After the injection is finished, the movable platen 12 is moved in the compression direction.
When the gas injection start position set value M1 (see FIG. 7) of the two set values set in the setter 42 in advance and the detected value of the position detector 34 are compared by the comparator 40, and the two match. , Air supply device 44 to air passage 20
Air is blown into the molten resin 30 through the opening 20a (gas injection step). When the movable platen 12 further moves and the gas injection end position set value M2 (see FIG. 7) of the two set values set in the setter 42 matches the detected value of the position detector 34. , The blowing of air is ended. As a result, the molten resin 30 becomes a balloon-shaped resin 30a having air therein, as shown in FIG. Subsequently, the mold is clamped as shown in FIG. 3 (compression step). As a result, the balloon-shaped resin 30a becomes a hollow molded product 30b having a "U" -shaped cross section. Double mold 14.1
6 is cooled, the movable platen 12 is moved in the mold opening direction to open the movable mold 16, and the molded product 30b is taken out.

Next, a third embodiment of the present invention will be described based on the molding process of FIG. The injection compression device is provided with a timer that starts timing at the same time when the injection device 28 starts injection. The steps from the mold opening position to the start of resin injection during mold closing are performed in the same manner as in the first embodiment. At the same time when the injection of the resin into the cavity C is started (injection process), the timer starts counting time. When the gas injection start time TX1 has elapsed, the gas injection is started (gas injection step), and when the gas injection end time TX2 has elapsed, the gas injection is ended. The movable platen 12 starts to move in the compression direction at a predetermined timing during the gas injection process or after the gas injection is completed, and subsequently the mold clamping is performed (compression process).
After completion of the compression process, a cooling process is performed, and the mold opening and molded product removal are performed as in the case of the first embodiment and the like.

In the above description, the fixed mold 14 is provided with the resin passage 18 and the movable mold 16 is provided with the air passage 20, but these may be arranged in reverse.
Alternatively, the resin passage 18 and the air passage 20 may be provided in one mold, for example, the fixed mold 14, and nothing may be provided, for example, in the movable mold 16 on the other side.
Further, in the above description, the movable platen 12 is stopped at an intermediate position of mold closing to inject the molten resin 30, but the movable platen 12 is not stopped, and the molten resin 30 is moving at a slight speed in the mold closing direction. It is also possible to perform 30 injections. In the above description, the compression process is started after the injection process is finished, but the compression process may be started during the injection process. Further, in the above description, air is used as the gas to be injected into the molten resin, but a gas other than air, for example, nitrogen can be used.

[0012]

As described above, according to the present invention, it is possible to manufacture a hollow molded article having a uniform thickness by the injection compression molding method. Even if the molded product has a thin portion or a rib portion, these portions can be surely made hollow. Since the molten resin is injected into the cavity before the mold is closed, the injection pressure may be low and the mechanical device can be inexpensive. The gas pressure acts inside the molded product until it solidifies, and the internal gas pressure after compression can be adjusted by controlling the injection of gas, so a molded product with a good surface without sink marks can be obtained. .

[0013]

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a state in which a molten resin is injected into an injection compression device.

FIG. 2 is a cross-sectional view showing a state in which a gas is injected into a molten resin in a cavity to form a balloon-shaped resin.

FIG. 3 is a cross-sectional view showing a state where the balloon-shaped resin in the cavity is compression-molded.

FIG. 4 is a view showing an injection compression device in which a position detector is provided on an injection plunger.

FIG. 5 is a diagram showing an injection compression device in which a movable platen is provided with a position detector.

FIG. 6 is a diagram illustrating a process of detecting the position of an injection plunger and controlling the start and end of gas injection.

FIG. 7 is a diagram illustrating a process of detecting the position of a movable plate and controlling the start and end of gas injection.

FIG. 8 is a diagram illustrating a process of controlling start and end of gas injection using a timer.

FIG. 9 is a control block diagram of the present invention.

[Explanation of symbols]

 10 Fixed Plate 12 Movable Plate 14 Fixed Mold 16 Movable Mold 18 Resin Passage 20 Gas Passage 20a Opening 28 Injection Device 30 Molten Resin 30a Balloon Resin 30b Molded Product 32/34 Position Detector C Cavity

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B29C 49/06 7619-4F // B29L 22:00

Claims (5)

[Claims] 1. A molten resin (30) is injected into a cavity (C) of a mold (14, 16) before completion of mold closing so that the molten resin (30) becomes a solid state, and the molten resin (30) is injected in accordance with the injection state. A balloon-shaped resin (30a) is formed by starting to inject gas into the inside of the resin and ending injection of the gas in accordance with the injection state of the molten resin (30), and mold clamping during or after the gas injection. An injection compression molding method for molding a molded product (30b) by compressing the balloon-shaped resin (30a) by performing. 2. A mold clamping device (46) having a fixed plate (10) and a movable plate (12), a fixed mold (14) attached to the fixed plate (10), and a movable plate (12). A movable mold (16), and a fixed mold (1
4) or the movable mold (16) is formed with a resin passageway (18) passing through this and opening to the wall surface forming a part of the wall of the cavity (C), and the fixed mold (14) or the movable mold. Formed in the mold (16) is a gas passage (20) having an opening (20a) extending through the wall surface forming a part of the wall of the cavity (C) and extending into the cavity (C). An injection device (28) capable of injecting the molten resin (30) into the cavity (C) through the resin passage (18), and an air supply capable of supplying air to the gas passage (20). The device (44), a means for detecting the injection state of the molten resin (30) in the cavity (C), and a control signal to the air supply device (44) and the mold clamping device (46) based on the signals from this. Output controller (48)
And an injection compression molding device provided with. 3. A position detector (3) for detecting the position of an injection plunger of an injection device, said means for detecting the injection state.
2) The injection compression molding apparatus according to claim 2. 4. The means for detecting the injection state is a movable member (12) of a movable mold (16) or a mold clamping device (46).
The injection compression molding apparatus according to claim 2, which is a position detector (34) for detecting the position of the. 5. The injection compression molding apparatus according to claim 2, wherein the means for detecting the injection state is a timer that starts timing with the start of injection.