JPH10109319A - Injection mold of hollow molded product and molding thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a molded product having good appearance and high accuracy by providing a fixed mold having a cavity, a movable mold having a parting surface, the movable core capable of advancing to and retreating from the fixed mold and a connection cylinder. SOLUTION: A movable core 9 is slid in a before and behind direction along the piercing hole 13 bored in the almost central part of a movable mold 10 and has a gas injection needle 3 and compressed gas is introduced into a cavity 4. An ejector plate 16 grasps the lower end of the ejector pin 17 extending to the cavity 4. The ejector pin 17 has a core pin part molding a molded product 5 at the upper part of a pin. When high pressure gas is introduced into the molten resin injected into the cavity 4 from a gas injection needle 3 under pressure, the movable core 9 is allowed to retreat and a piston 26 is advanced not only to expand the vol. of the cavity 4 but also not to open a parting surface to press the movable mold 10 to a fixed mold 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection mold for molding a hollow molded article and a method for molding the same.

[0002]

2. Description of the Related Art In general, a method of molding a hollow molded article by injection molding is to inject a molten resin into an injection molding die or while injecting a pressurized gas into the molten resin. There is a method in which a molten resin is pressed against the inner periphery of a cavity to be molded. When this pressurized gas is injected into the molten resin, the movable core fitted into the movable mold must be retracted while the movable mold is pressed against the fixed mold to increase the cavity capacity. As a technique for expanding the cavity volume, for example, there is a technique described in Japanese Patent Application Laid-Open No. Hei 7-016864. The technique described in Japanese Patent Application Laid-Open No. 7-016864 discloses a technique in which a spring is inserted between a movable die and a movable core, and the movable die is retracted while pressing the movable die against the fixed die by the urging force of the spring. This is to increase the cavity capacity.

[0003]

SUMMARY OF THE INVENTION Japanese Patent Application Laid-Open No. 7-01686
According to the technology described in Japanese Patent Publication No. 4 (1994), when the cavity volume is enlarged, the movable mold is pressed against the fixed mold by a spring. Therefore, in the case of a hollow molded article having a relatively large surface area such as a door, it has a wide range. Since a certain mold clamping force is required,
The pressing force is adjusted by adjusting the urging force according to the length, linearity, number of springs, and the like. However, with a spring, it is very difficult to constantly press the movable mold with a pressure opposite to the retraction of the movable core. Therefore, if the movable mold is not pressed firmly against the fixed mold with a constant pressure, the cavity cannot be kept airtight, so that burrs will occur and the appearance of the molded product will not only deteriorate, but also the dimensional accuracy will decrease. Bad moldings are formed.

[0004] In the spring, after the mold is opened, only the movable mold is advanced with respect to the movable core, and an ejector pin or a gas injection nozzle which easily adheres to the molded article is released from the molded article in advance. It is not possible to perform a molding step in which the molded product is released from the movable core by retreating the movable core, and the molded product is taken out. In the case of a molded product with a large surface area such as a door, the number of ejector pins and gas injection nozzles also increases, and the molded product adheres to each core pin, and finally the molded product is released. Otherwise, if the mold is forcibly released, a problem such as peeling of the resin adhered to the core pin portion occurs, and a poor molded product having poor appearance is produced.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, an injection mold for molding a hollow molded product includes a fixed mold having a cavity, and a movable mold for forming the fixed mold and a parting surface. The movable core is slidably disposed through a substantially central hole of the movable type, and is connected to the movable core, which is movable forward and backward with respect to the fixed type. In contrast, a connecting cylinder that is relatively movable, and a movable cylinder are disposed so as to be slidable through the movable core hole in parallel with the moving axis of the movable core, one protrudes from the cavity surface, and the other protrudes from the cavity surface. An ejector pin fixed to a connection plate linked to the movable mold or a core pin portion forming a mold at the tip of the ejector pin, and a gas injection nozzle penetrating the movable core and projecting into the cavity. Provide.

The connecting plate is inserted into a groove formed at right angles to the moving axis of the movable core. The connecting plate is allowed to move a predetermined amount in the moving axis direction of the movable core, and protrudes from the moving core. It has L-shaped parts at both ends for the movable mold,
The tip of the shaped part contacts the movable mold, and with the retreat of the movable mold,
The ejector pin is retracted.

[0007] The cavity of the hollow molded article is molded by the injection molding die at the position where the movable core advances, the molten resin is injected into the cavity, and a pressurized gas is injected into the molten resin. Alternatively, after press-fitting, the movable core is retracted by the mold clamping cylinder of the molding machine while maintaining the state where the movable mold is pressed against the fixed mold by the pressing of the coupling cylinder, thereby increasing the volume of the cavity.
After cooling the molded product, the movable cylinder and the movable core are retracted by the mold clamping cylinder to separate from the fixed mold, and then the connecting cylinder is further advanced, and the molded product is moved for the movable core, the ejector pin and the gas injection. After the mold is released from the nozzle in advance, the connecting cylinder is retracted, and the molded product is released from the cavity and taken out.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, an injection molding machine 100
(Hereinafter referred to as a molding machine) mold plate 101 and mold clamping plate 102
The mold clamping plate 102 is guided by four tie bars 103 and can be moved in the front-rear direction by a mold clamping cylinder 104. An injection device 105 is provided behind the mold platen 101.

The mold is an injection mold for the purpose of gas injection molding. In the injection mold 1, a runner 2 for injecting a molten resin, and a pressurized part at the same place as the runner 2 or at a different place. A gas injection needle 3 for injecting a gas body is provided, and pressurized gas is injected from the gas injection nozzle 3 into the molten resin injected from the runner 2 into the cavity 4 while the molten resin is in a flowing state. The resin is expanded along the surface of the cavity 4 to form the hollow molded article 5.

As shown in FIG. 2, the injection mold 1 includes a fixed mold plate (fixed mold) 8, a fixed attachment plate 12, a movable mold plate (movable mold) 10, a movable core 9, and a movable core attachment. It comprises a plate 14 and an ejector mechanism 11. The fixed mold plate 8 forms the cavity 4 and is fixed to the fixed mounting plate 12. The fixed-side mounting plate 12 is fixed to the mold plate 101.

The movable mold plate 10 has a movable core 9 therein. The movable core 9 is inserted through a through hole 13 formed substantially at the center of the movable mold plate 10, and extends along the through hole 13. It slides in the front-back direction (A direction). The movable core 9 has a gas injection needle 3, and pressurized gas (nitrogen gas) is press-fitted into the cavity 4 from the gas injection needle 3. The movable core 9 is fixed to a movable core mounting plate 14. A groove 15 is formed inside the movable core mounting die plate 14,
, An ejector plate 16 is inserted, and the ejector plate 16 slides in the front-rear direction along the groove 15.
A C-shaped groove 22 is formed in the lower end 21 of the movable mold plate 10.

The ejector mechanism 11 includes an ejector plate (connecting plate) 16, an ejector pin 17, and a stopper (L
), And the ejector plate 16 is
The lower end of the ejector pin 17 extending toward the cavity 4 is sandwiched, and the ejector pin 17 is inserted into a through hole 19 formed in the movable core 9 and slides along the through hole 19 in the front-rear direction. The ejector pin 17 has a projection (core pin portion) 2 for forming a hole in the molded product 5 above the pin.
It has 0. At both ends of the ejector plate 16,
The stopper 18 is fixed. The stopper 18 keeps a constant distance between the movable mold plate 10 and the ejector plate 16 and transmits the retreating operation of the movable mold plate 10 to the ejector plate 16.

The movable core mounting plate 14 includes a driving unit mounting plate 25.
It is fixed to. At the four corners of the drive unit mounting plate 25, a total of four cylinders 24 are provided, one for each cylinder. The drive unit mounting plate 25 is fixed to the mold clamping plate 102 of the molding machine 100, the hydraulic cylinder 24 is fixed in the mold opening direction, and the piston head 26 of the hydraulic cylinder 24 forms a T-shaped flange 27. ing.

In the hydraulic cylinder 24 disposed on the drive unit mounting plate 25, the T-shaped flange portion 27 of the hydraulic cylinder 24 and the C groove 22 formed in the movable mold plate 10 face each other at a predetermined position. If the metal fitting 23 is inserted into the C groove 22 (in the direction B in FIG. 7), the inside of the C-shaped metal fitting 23 and the T-shaped flange 2
7 are engaged, and the drive unit mounting plate 25 and the movable side mold plate 10 are connected.

Next, the operation of the hydraulic cylinder 24 will be described. As shown in FIG. 3, when a high-pressure gas is injected into the molten resin injected into the cavity 4 from the gas injection needle 3, the mold clamping cylinder 104 is used. The movable core 9 is retracted, thereby increasing the volume of the cavity 4, and conversely, by moving the piston 26 forward so that the parting surface is not opened, the movable template 10 is fixed to the fixed template. 8 is pressed.

Next, in FIG. 4, after the injection is completed and the mold opening is completed, in FIG. 5, the piston 26 is further advanced from the state of FIG. When the ejector plate 16 is further advanced,
Abuts against the top surface of the groove 15 of the movable core mounting plate 14 and is retained. When the ejector plate 16 is retained, the protrusion 20 of the ejector pin 17 comes off from the hollow molded product 5, and the movable core 9 is attached to the movable core mounting plate 14.
By further retreating, the tip of the gas injection nozzle 3 comes out of the hollow molded product 5.

This facilitates peeling from the movable core 9 when the hollow molded article 5 is released from the mold. That is, if the hollow molded product 5 has a large surface area, such as a door, the number of ejector pins 17 and gas injection nozzles increases, and if each of them adheres to the hole of the hollow molded product 5, When the mold is released, a large reaction force is generated, and it becomes difficult to take out the hollow molded article 5. Therefore, if only the tip of the pin is removed from the hollow molded product 5 in advance, the release of the product finally becomes easy.

Next, as shown in FIG. 6, the piston 26 is retracted in the opposite direction to that of FIG.
0, the hollow molded article 5 protrudes from the parting surface and the lower end 21
When the stopper 18 is pressed against the movable mold plate 10 and retreats, the tip of the ejector pin 17 sandwiched between the ejector plates 16 retreats from the part surface of the movable core 9, and the ejector 18 The pin 17 comes off, the hollow molded article 5 is released, and the molding of the hollow molded article 5 is completed. Reference numeral 28 is a block for a hot runner, although the internal detailed structure is not shown because it is not directly related to the present application.

Next, a series of operations of the present invention will be described with reference to FIGS. 2 to 6. As shown in FIGS. 4 and 5, the molding machine 100 is brought into a mold-clamped state and the cavity 4 is formed.
Next, the molten resin is injected into the cavity 4, and a pressurized gas is injected into the molten resin while the molten resin is in a flowing state. The volume of the cavity 4 is increased while pressurized gas is injected into the cavity 4. The volume expansion of the cavity 4
Resin injection pressure remaining in the molten resin injected into the cavity 4,
The movable core 9 is retracted by the pressure of the pressurized gas and the operation of the mold clamping cylinder 104 of the molding machine 100. Contrary thereto, the movable side mold plate 1 is moved so that the parting surface is not opened.
0 must be maintained in a state of being pressed against the fixed mold plate 8 by the hydraulic cylinder 24. Hydraulic cylinder 24
Moves forward at a timing opposite to the retreat of the movable core 9, and advances while the movable mold plate 10 is pressed against the fixed mold plate 8. The retraction of the mold clamping cylinder 104 and the synchronization timing of the hydraulic cylinder 24 are determined at the time of test molding of a molded product. Then, the molded article 5 is cooled while the volume of the cavity 4 is enlarged.

Next, when the molded product 5 is completely cooled, as shown in FIG. 4, the mold clamping plate 102 is retracted by the mold clamping cylinder 104, and the fixed mold plate 8 and the movable mold plate 10 are moved. Opens the mold.

Next, as shown in FIG.
When the mold 4 is further advanced, the movable mold plate 10 moves forward, the movable core 9 retreats with respect to the movable mold plate 10, the molded product 5 and the movable core 9 are released, and the protrusions 20 of the ejector pins 17 are formed. Then, the tip of the gas injection needle 3 is released from the molded product 5.

Next, as shown in FIG.
When the movable mold 4 is retracted, the movable mold plate 10 retracts with respect to the movable core 9, the movable core 9 protrudes the molded product 5, and the stopper 18 is urged by the movable mold plate 10, and As a result, the ejector pins 17 are retracted, and the release of the molded product 5 is completed.

[0024]

As described above, since the movable mold is pressed against the fixed mold by the cylinder, a fixed mold clamping force can be obtained in the case of a hollow molded product having a relatively large surface area such as a door, and a parting force can be obtained. A highly accurate molded product having good appearance and no burr on the surface can be obtained.

Further, it is easy to synchronize with the mold clamping cylinder of the molding machine, and it is easy to adjust the cavity volume expansion timing and volume expansion speed, so that the adjustment can be easily performed.

In addition, since the ejector pins and the gas injection nozzle are released from the mold in advance, a molded article having good appearance without peeling or the like at the core pin portions can be obtained.

[Brief description of the drawings]

FIG. 1 is a front view showing a state in which an injection mold is mounted on a molding machine according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the injection mold (in a state where the molten resin is injected after clamping).

FIG. 3 is a cross-sectional view of the injection mold (in a state where the mold is clamped and a pressurized gas is injected into a molten resin to enlarge a cavity).

FIG. 4 is a cross-sectional view of the injection mold (in a state where the mold is opened and the molded product is released from the cavity).

FIG. 5 is also a cross-sectional view of the injection mold (in a state where the hydraulic cylinder has moved forward and the ejector pin has been released).

FIG. 6 is a cross-sectional view of the injection mold (in a state where the hydraulic cylinder is retracted and a molded product is taken out).

FIG. 7 is an explanatory view showing a joining means of the injection mold.

[Explanation of symbols]

 5 Hollow Molded Product 1 Injection Mold 4 Cavity 8 Fixed Mold (Fixed Mold Plate) 10 Movable Mold (Movable Mold Plate) 13 Center Hole (Through Hole) 9 Movable Core 24 Connection Cylinder 19 Movable Core Hole ( 16 Through plate (ejector plate) 17 Ejector pin 20 Core pin (projection) 3 Gas injection needle 15 Groove 18 L-shaped part (stopper) 100 Molding machine 104 Mold clamping cylinder

Claims (3)

[Claims] 1. An injection mold for molding a hollow molded product, comprising: a fixed mold having a cavity, a movable mold forming a parting surface with the fixed mold, and a substantially central hole of the movable mold. A movable core which is not slidably disposed, and which can move forward and backward with respect to the fixed die, connects the movable die and the movable core, and connects the movable core to the movable die so as to be relatively movable; For the movable core, parallel to the moving axis of the movable core, slidably disposed through the movable core hole,
One protrudes from the cavity surface, the other is an ejector pin sandwiched by a connecting plate in contact with the movable mold, a core pin portion forming a mold at the tip of the ejector pin, and a cavity penetrating the movable core. An injection molding die comprising: a gas injection nozzle protruding into the inside. 2. The connecting plate is inserted into a groove formed at right angles to a moving axis of the movable core, and the groove allows a predetermined amount of movement in a moving axis direction of the movable core. At both ends protruding from the core, L
3. The injection molding die according to claim 2, wherein a shape is formed, and the tip of the L-shaped portion comes into contact with the movable die, and the ejector cut pin is retracted as the movable die is retracted. 3. An injection molding die for molding a hollow molded product, comprising: a fixed die having a cavity; a movable die forming a parting surface with the fixed die; and a substantially central hole of the movable die. A movable core that is slidably disposed and is capable of moving forward and backward with respect to the fixed mold, for coupling the movable mold and the movable core, and for moving the movable core relative to the movable mold; In parallel with the cylinder and the axis of movement of the movable core,
A movable core hole is slidably provided, one of which protrudes from the cavity surface, and the other of which is an ejector pin fixed to a connecting plate interlocked with the movable mold and a tip of the ejector pin. Forming a cavity of the molded product at the advanced position of the movable core by a core pin portion forming a mold and a gas injection needle penetrating the movable core and projecting into the cavity, The molten resin is injected into the cavity, and while the pressurized gas is being press-fitted into the molten resin, or after being press-fitted, while maintaining the state where the movable mold is pressed against the fixed mold by pressing the connecting cylinder, the The process of expanding the volume of the cavity by retracting the core by the operation of the mold clamping cylinder of the molding machine, and after cooling the hollow molded product, by the mold clamping cylinder of the molding machine, After the movable die and the movable core are retracted and separated from the fixed die, the coupling cylinder is further advanced while the mold clamping cylinder is kept as it is, and the hollow molded product is moved from the movable core, the ejector pin and the gas injection nozzle. A method of molding a hollow molded article, comprising: a step of releasing the mold in advance; and a step of retracting the connecting cylinder while leaving the mold clamping cylinder as it is, and releasing and removing the hollow molded article from the cavity.