JPH05131498A - Injection molding nozzle - Google Patents

Abstract

PURPOSE:To collect or discharge a pressurized fluid pressed in a mold cavity via a fluid conduit having structure hard to be clogged up with the counterflow of synthetic resin or its chips, and simultaneously enhance the degree of freedom in the pressure control of pressurized fluid within the mold cavity. CONSTITUTION:An injection molding nozzle 12 includes an operation valve 5 for opening and closing a resin conduit 3, a fluid conduit 7 provided via a check valve 6 within the operation valve 5, and fluid discharge opening and closing means for releasing the check valve 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding nozzle used for injection molding of synthetic resin.
The present invention relates to an injection molding nozzle used for molding a molded body having a hollow portion formed by a fluid by pressurizing a molten synthetic resin and a pressurized fluid such as a gas body into a mold cavity of a mold.

[0002]

2. Description of the Related Art Conventionally, as an injection molding nozzle for press-fitting a molten synthetic resin and a pressurized fluid into a mold cavity of a mold, a needle valve for moving back and forth by a force of an external drive mechanism to open and close a resin passage is provided in the nozzle body. It is known that the needle valve is provided with a fluid passage with a check valve at the core thereof (Japanese Patent Laid-Open No. 51-119063).

In this injection molding nozzle, when the needle valve advances, the tip of the needle valve is pressed against the periphery of the nozzle body opening at the tip of the nozzle body connected to the resin passage to close the resin passage. The tip of the needle valve is provided with a needle valve opening connected to the fluid passage.In the closed state of the resin passage, the pressurized fluid is pressed into the mold cavity from the needle valve opening through the nozzle body opening. it can. On the other hand, when the needle valve retracts, the pressure contact between the periphery of the nozzle body opening and the tip of the needle valve is released, and the nozzle body opening is opened to the resin passage, so that the molten synthetic resin is pressed into the mold cavity from the nozzle body opening. it can.

However, in this conventional injection molding nozzle, a check valve is provided in the fluid passage in order to prevent the backflow of the molten synthetic resin into the fluid passage when the molten synthetic resin is pressed into the mold cavity. Therefore, once the pressurized fluid is pressed into the mold cavity, the pressurized fluid cannot be recovered or discharged through the fluid passage. Therefore, the pressurized fluid that has been press-fitted into the mold cavity is discharged by separating the mold from the nozzle body and discharging the pressurized fluid directly from the mold. However, this not only makes it difficult to recover and reuse the pressurized fluid, but it also makes it impossible to control the fluid pressure in the mold cavity, for example, by gradually lowering the fluid pressure in the mold cavity, which causes defects in the molded product. There is an easy problem.

This problem will be described in more detail.

Generally, the pressure of the pressurized fluid that is pressed into the mold cavity is: a. Overcome the molten synthetic resin pressure at the pressure inlet, b. Allowing the molten synthetic resin to be eliminated to flow into the gate and mold cavity when pressed into the sprue and runner to form a hollow therein, c. Passing through a gate section, d. It is required to enable the flow of the molten synthetic resin in the mold cavity, which is eliminated when forming the hollow portion in the mold cavity. The viscosity of the molten synthetic resin, the design of the mold and the molten synthetic resin to the mold cavity are required. Determined by factors such as the filling amount.

The pressurized fluid press-fitted into the core of the molten synthetic resin in the mold cavity is cooled and solidified below the flow temperature after the hollow portion is formed or the molten synthetic resin in the mold cavity is cooled. After that, the resin layer including the hollow portion is pressed to prevent the occurrence of "sink". However, when the pressure of the pressurized fluid is high, residual strain is generated in the resin layer including the hollow portion. Particularly when the hollow portion is selectively formed only at a specific position of the mold cavity, residual strain concentrated at the interface between the hollow portion and the solid portion occurs.

When a high pressure is applied to the resin layer around the hollow portion to cause residual strain in the resin layer, the following quality defects occur due to the characteristics of the resin used. a. Micro-crazing or whitening occurs around the hollow part. Alternatively, crazing occurs after lapse of time due to stress relaxation with time after molding. b. The resin layer around the hollow part swells.

Further, if the pressurizing fluid having an excessive pressure is held in the hollow portion inside the mold cavity, the pressure of the pressurizing fluid in the hollow portion is released up to the atmospheric pressure prior to the step of taking out the molded product. It takes time to lengthen the molding cycle and impairs productivity.

On the other hand, Japanese Patent Application Laid-Open No. 1-30723 proposes an injection molding nozzle capable of collecting or discharging a pressurized fluid press-fitted into a mold cavity through a fluid passage. This injection molding nozzle will be described.

Similar to the conventional injection molding nozzle described above, a needle valve that moves back and forth by a force of an external drive mechanism to open and close the resin passage is provided in the nozzle body, and the needle valve has a core portion at the core thereof. A fluid passage is provided. An actuator bar is connected to the rear end of the needle valve in a direction orthogonal to the needle valve. A fluid passage is formed in the actuator bar, and the fluid passage in the needle valve is connected to this fluid passage.

The fluid passages in the actuator bar include
A check valve on the supply side and a check valve on the discharge side are provided on both sides of the connection portion with the fluid passage in the needle valve. The check valve on the supply side is connected to the pressurized fluid source, while the check valve on the discharge side is also connected to the pressurized fluid source. The check valve on the supply side is opened by the pressure from the pressurized fluid source side and closed by the pressure from the needle valve side.
Further, the check valve on the discharge side is pressed by a spring provided on the pressurized fluid source side, and is opened when the pressure on the needle valve side becomes higher than a certain value by adjusting the pressing force of the spring, and the needle is opened. It allows the flow of the pressurized fluid from the valve side to the pressurized fluid source side.

In the case of the injection molding nozzle, when the pressurized fluid is supplied from the pressurized fluid source when the pressurized fluid is pressed into the mold cavity, the check valve on the supply side is opened by the fluid pressure from the pressurized fluid source side. Thus, the pressurized fluid is allowed to pass, and the pressurized fluid is pressed into the mold cavity. On the other hand, in the check valve on the discharge side, the pressing force of the spring provided on the pressurized fluid source side and the fluid pressure from the pressurized fluid source are applied, while the needle valve side of the check valve on the supply side is Since the pressure of the pressurized fluid that has passed through the check valve is applied and the pressures on the pressurized fluid source side and the needle valve side become approximately equal, they remain closed. Further, when collecting or discharging the pressurized fluid from the mold cavity, by stopping the supply of the pressurized fluid from the pressurized fluid source, it is possible to collect or discharge the pressurized fluid from the mold cavity.

That is, when the supply of the pressurized fluid from the source of the pressurized fluid is stopped, the check valve on the supply side is closed by being pushed by the fluid pressure which tends to flow backward from the mold cavity. On the other hand, in the check valve on the discharge side, the pressure on the needle valve side becomes higher than the pressing force of the spring provided on the pressurized fluid source side due to the fluid pressure that tries to flow backward from the mold cavity, and this difference is equal to or more than a certain pressure. Therefore, it is opened, and the backflow of the pressurized fluid from the mold cavity is allowed.

However, in the case of the above injection molding nozzle, the distance from the tip of the needle valve to the check valve becomes long, and the fluid passage formed between them has to be a complicated and curved path. However, there is a problem that synthetic resin and its scraps easily flow back and become clogged. In order to ensure the operation of the check valve on the discharge side, the pressure difference when the check valve is opened, that is, the difference between the fluid pressure on the needle valve side and the pressing force of the pressurized fluid source side spring Needs to be large and is restricted by this differential pressure, so the degree of freedom in controlling the fluid pressure in the mold cavity is also small.

[0016]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the above-mentioned conventional injection molding nozzle. Synthetic resin and its scraps flow back the pressurized fluid pressed into the mold cavity. Through a fluid passage configured to prevent clogging
It is an object to be able to control the fluid pressure in the mold cavity with a wide degree of freedom while at the same time allowing it to be collected or discharged.

[0017]

The above object is achieved by providing means for arbitrarily opening a check valve provided in a passage for discharging a pressurized fluid press-fitted into a molten resin in a mold cavity. it can.

That is, the present invention, as shown in FIG.
A resin passage 3 communicating with an injection cylinder (not shown) from a nozzle body opening 2 at the tip of the nozzle body 1 is installed inside the nozzle body 1 so as to be movable back and forth in the axial direction, and substantially coincides with the nozzle body opening 2. Operating valve opening 4 at a position to be opened, a fluid passage 7 contained in the operating valve 5 and communicating with the operating valve opening 4 via a check valve 6, and a check valve when discharging pressurized fluid. The injection molding nozzle 7 has a fluid discharge opening / closing means for opening the valve 6.

[0019]

Since the injection molding nozzle 12A of the present invention is provided with the fluid discharge opening / closing means, only one check valve 6 needs to be provided, and the fluid passage can be simply configured without being bent. It is possible to freely press the molten resin, pressurize the pressurized fluid, and discharge / recover the pressurized fluid from the hollow part in the mold cavity at a predetermined timing, making it possible to produce a good molded product. It is possible to efficiently recover and reuse the fluid.

[0020]

EXAMPLES The present invention will be described below with reference to examples.

(First Embodiment) A first embodiment of the present invention will be described below with reference to FIG.

The injection molding nozzle 12A of this embodiment is roughly composed of a nozzle body 1 and an operating valve 5. Nozzle body 1
Has a rear end portion attached to an injection cylinder (not shown) and has a resin passage 3 connecting the nozzle body opening 2 at the front end and the injection cylinder.

The operation valve 5 is arranged inside the nozzle body 1 so as to be movable back and forth. A fluid passage 7 is provided at the center of the actuation valve 5 and is continuous with the actuation valve opening 4 at the tip end via a check valve 6. This operation valve 5 presses its tip end around the nozzle body opening 2 during forward movement to block the nozzle body opening 2 and the resin passage 3, and at the same time, the nozzle body opening 2
Further, the fluid passage 7 is directly connected via the operation valve opening 4 and the check valve 6. Further, when retracted, the nozzle body opening 2 is opened to the resin passage 3 as shown in the drawing.

The check valve 6 provided in the fluid passage 7 is closed so that the molten synthetic resin does not enter the fluid passage 7 at the time of injection of the molten synthetic resin (provided that pressurized fluid is supplied during injection of the molten synthetic resin). When injecting, it is released by adjusting the pressure of the pressurized fluid higher than the pressure of the molten synthetic resin), and when injecting the pressurized fluid, it is released by the action of the pressurized fluid pressure.
Further, a check valve release pin 8 is provided to prevent the check valve 6 from backflow by advancing the check valve release pin 8 when the pressurized fluid in the mold cavity (not shown) is discharged. Ball 9
Is pushed forward to open the check valve 6.

The levers 10 and 11 are provided for the forward and backward movements of the operating valve 5 and the check valve releasing pin 8, respectively.

Next, the operation of the injection molding nozzle 7 of this embodiment will be described. (A) Molten Synthetic Resin Injection Step The nozzle body 1 is pressed against a mold (not shown), the operating valve 5 is retracted, the tip of the operating valve 5 is separated from the inner wall of the tip portion of the nozzle body 1, and the resin passage Open 3. A screw (not shown) of the injection cylinder is advanced to inject the pre-measured molten synthetic resin through the resin passage 3 and into the mold cavity (not shown) through the nozzle body opening 2.

After the injection is completed, the operation valve 5 is advanced to close the resin passage 3. (B) Pressurized fluid press-fitting step An on-off valve (not shown) between the pressurized fluid source (not shown) and the fluid passage 7 is opened to supply the pressurized fluid to the fluid passage 7, and the check valve 6 is opened. It is press-fitted into the mold cavity via the operation valve opening 4 and the nozzle body opening 2.

After a predetermined time, the on-off valve between the pressurized fluid source and the fluid passage 7 is closed, and the supply of pressurized fluid is stopped. The pressurized fluid supplied before that is retained from the check valve 6 of the fluid passage 7 in the hollow portion formed in the synthetic resin in the mold cavity.

The pressurization of the pressurized fluid may be started during the injection of the molten synthetic resin, at the same time as the completion of the injection, or after a fixed time after the completion of the injection. When the pressurized fluid is injected during the injection of the molten synthetic resin, the pressure of the pressurized fluid is adjusted to be higher than the pressure of the molten synthetic resin while the operation valve 5 is in the retracted position and the resin passage 3 is in the open state. Be seen. (C) Step of discharging pressurized fluid After the synthetic resin in the mold cavity is cooled and solidified, the check valve release pin 8 is advanced to move the check valve 6 in the fluid passage 7 forward to prevent the check valve 6 from flowing backward. To open the check valve 6. As a result, the pressurized fluid in the hollow portion formed in the synthetic resin in the mold cavity is discharged from the fluid passage 7 via the nozzle body opening 2 and the operation valve opening 4.

Prior to discharging the pressurized fluid, a portion of the injected pressurized fluid is discharged during the retention of the pressurized fluid pressure to maintain the pressurized fluid pressure in the mold cavity at the lowered set pressure. It is also possible to add the operation of advancing the check valve release pin 8 for a set time and then retracting it.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to FIG.

The injection molding nozzle 12B of this embodiment is also roughly composed of the nozzle body 1 and the operating valve 5. Nozzle body 1
Is an injection cylinder (not shown) as in the first embodiment.
And a resin passage 3 having a similar structure.

The actuating valve 5 is arranged inside the nozzle body 4 so as to be movable back and forth, and opens and closes the resin passage 3 by its back and forth movement, as in the first embodiment. In addition, a fluid passage 7 connected to the operation valve opening 4 via the check valve 6 is formed in the operation valve 5.

The check valve 6 is composed of a needle valve 13 for opening and closing the fluid passage 7 and a check valve body 14 for backflow prevention. The needle valve 13 and the check valve body 14 will be further described.

A needle valve 13 having a fluid passage 7 at its core is provided at the center of the operating valve 5 so as to be movable back and forth.
Further, a backflow prevention valve body 14 is provided at the tip of the needle valve 13.
Are integrally provided with the needle valve 13. A plurality of radial projections are provided at the tip of the check valve body 14, and a passage is formed between the projections. The backflow preventing valve body 14 opens and closes the fluid passage 7 by being pressed against or separated from the valve seat 15 by the forward and backward movement of the needle valve 13.

A spring 16 is provided at the rear portion of the needle valve 13 and pushes the needle valve 13 rearward.
Further, since the forward movement is transmitted to the needle valve 13, the rear end portion of the needle valve 13 is in contact with the drive lever 10.

Further, a drive lever 11 is provided for the back-and-forth movement of the operating valve 5.

Next, the operation of the injection molding nozzle 12 of this embodiment will be described. (A) Molten Synthetic Resin Injection Step The nozzle body 1 is pressed against a mold (not shown), the operating valve 5 is retracted, the tip of the operating valve 5 is separated from the inner wall of the tip portion of the nozzle body 1, and the resin passage 3 Open up. A screw (not shown) of the injection cylinder is advanced to inject the pre-measured molten synthetic resin through the resin passage 3 and into the mold cavity (not shown) through the nozzle body opening 2. At this time, the check valve 14 is pressed against the valve seat 15 by the spring 16 to prevent the molten synthetic resin from entering the fluid passage 7.

After the injection is completed, the operation valve 5 is moved forward to close the resin passage 3. (B) Pressurized Fluid Press-In Step An open / close valve (not shown) between the pressurized fluid source (not shown) and the fluid passage 7 is opened to supply the pressurized fluid to the fluid passage 7. At the same time, the rear end of the needle valve 13 is pushed forward to move the needle valve 13 forward to open the check valve body 14,
Pressurized fluid is injected into the mold cavity through the fluid passage 7, the actuation valve opening 4 and the nozzle body opening 2.

After a predetermined time, the open / close valve between the pressurized fluid source and the fluid passage 7 is closed to stop the supply of the pressurized fluid. At the same time, the pressing of the rear end of the needle valve 13 is released, the needle valve 13 is retracted by the pressing force of the spring 16, and the check valve body 14 is closed. The pressurized fluid that has been press-fitted before that is retained from the check valve body 14 in the hollow portion formed in the synthetic resin in the mold cavity.

The injection of the pressurized fluid may be started either during the injection of the molten synthetic resin, at the same time as the completion of the injection, or after a fixed time after the completion of the injection. When the fluid is injected during the injection of the molten synthetic resin, the fluid pressure is set to the molten synthetic resin pressure with the operation valve 5 in the retracted position and the resin passage 3 kept open while the needle valve 13 is advanced. Adjusted higher than. (C) Step of discharging pressurized fluid After the synthetic resin in the mold cavity is cooled and solidified, the rear end portion of the needle valve 13 is pressed forward again, and the needle valve 13
To open the check valve 14 for backflow prevention. As a result, the pressurized fluid in the hollow portion formed in the synthetic resin in the mold cavity is discharged from the nozzle body opening 2 and the fluid passage 7.

Before the pressurized fluid is discharged, a portion of the pressurized fluid that has been press-fitted is discharged during the maintenance of the pressurized fluid pressure to maintain the pressurized fluid pressure in the mold cavity at the lowered set pressure. It is also possible to add the operation of advancing the needle valve 13 and then retracting it for a set time.

[0043]

As described above, the injection molding nozzle of the present invention has the following effects.

After the hollow portion is formed by the pressurized fluid by injecting the pressurized fluid at the same time as the injection of the molten synthetic resin or after the injection of the molten synthetic resin, the check valve in the fluid passage of the injection molding nozzle device is formed. By opening the check valve for the required time for the pressurized fluid enclosed in the space up to the hollow part formed in the core of the synthetic resin in the mold cavity, and allowing only the required pressurized fluid to flow back It is possible to control the holding pressure of the pressurized fluid in the hollow portion formed in the core of the synthetic resin in the mold cavity to the set pressure. Also,
The check valve can be provided at any position in the fluid passage, and the length of the fluid passage located on the tip side of the check valve can be shortened and the fluid passage can be formed linearly. It is easy to prevent the passage from being closed, it is possible to reliably prevent the molten synthetic resin from flowing back into the fluid passage, and the pressurized fluid can be recovered smoothly and reliably in a short time.

By controlling the pressure of the pressurized fluid held in the hollow portion formed in the core of the synthetic resin in the mold cavity, the excessive residual strain generated in the synthetic resin layer around the hollow portion is alleviated. It is possible to eliminate quality defects such as micro crazing, whitening and crazing, or swelling of only the surface layer of a molded product including a hollow portion.

The molten synthetic resin and the pressurized fluid are press-fitted into the mold cavity to form a hollow portion in the core of the molten synthetic resin in the mold cavity, and then the check valve in the fluid passage is used to form the molten synthetic resin in the mold cavity. The pressurized fluid contained in the space formed in the core portion up to the hollow portion can be gradually caused to flow backward in the same manner as described above to control the pressure of the fluid in the hollow portion. In response to the progress of cooling of the molten synthetic resin in the mold cavity, the pressure of the fluid in the hollow part is gradually reduced to atmospheric pressure, so that the synthetic resin around the hollow part is cooled and solidified under the pressure of the excessive fluid. Further, it is possible to shorten the molding cycle by shortening the time required to lower the pressure of the fluid in the hollow portion to the atmospheric pressure before opening the mold and taking out the molded product.

Furthermore, after the injection of the molten synthetic resin, the screw is retracted, and the compressed volume of the injected molten synthetic resin is caused to flow backward to the cylinder side (suck back).
The pressure of the molten synthetic resin at the injection port of the mold is lowered to enable the operation of injecting the pressurized fluid at a lower pressure.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment according to the present invention.

FIG. 2 is a sectional view showing a second embodiment according to the present invention.

[Explanation of symbols]

 1 Nozzle Body 2 Nozzle Body Opening 3 Resin Passage 4 Actuating Valve Opening 5 Actuating Valve 6 Check Valve 7 Fluid Passage 8 Check Valve Release Pin 9 Backflow Prevention Ball 10, 11 Lever 12A, 12B Main Injection Molding Nozzle 13 Needle Valve 14 Backflow prevention valve body 15 Valve seat 16 Spring

Claims (3)

[Claims] 1. A resin passage communicating with an injection cylinder from a nozzle body opening at the tip of the nozzle body, and is installed inside the nozzle body so as to be movable back and forth in the axial direction, and at a position substantially coincident with the nozzle body opening. An operation valve having an opening; a fluid passage contained in the operation valve and communicating with the operation valve opening via a check valve; and a fluid discharge opening / closing means for opening the check valve when discharging the pressurized fluid. An injection molding nozzle characterized in that 2. A fluid discharge opening / closing means pushes a check valve ball of a check valve, which is installed inside the actuating valve so as to be movable back and forth in the axial direction, forward to open the check valve, and retracts it. 2. A mechanism for enabling the check valve to be closed.
Injection molding nozzle. 3. A check valve, wherein the check valve is installed inside the actuating valve so as to be movable back and forth in the axial direction, and is integrally provided at the tip of a needle valve having a fluid passage in its core. ,
The injection molding nozzle according to claim 1, wherein the fluid discharge opening / closing means is a mechanism that opens the check valve by advancing the needle valve and closes the check valve by retracting the needle valve.