JPH0673875B2 - Hollow body manufacturing method - 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 for manufacturing a hollow body, and more particularly to a method for preventing deformation of molten resin due to injection pressure during manufacturing.

[0002]

2. Description of the Related Art Blow molding or injection molding is generally used to manufacture synthetic resin products. For example,
When manufacturing a hollow product by the blow molding method, the molten resin is extruded and molded as a cylindrical parison by an accumulator head, and both sides of the parison are sandwiched between molds,
It is common to blow air into the inside to form a hollow product, but in this case, there is a relatively large burr on the top and bottom of the product due to the mold, and the product has a nozzle hole for blowing air. As a result, a completely sealed hollow product cannot be obtained, and further, it is difficult to manufacture a uniform thickness. On the other hand, in the case of producing a hollow product by injection molding, a method has been proposed in which a half-molded body obtained by dividing the hollow-molded product into two is injection-molded and the outer circumferences of the abutting portions of both the half-molded bodies are joined with molten resin. (For example, JP-A-61-226060, JP-A-62-87315, JP-A-63-237917).
In this case, there is an advantage that a completely sealed hollow product and a hollow product having a complicated shape can be easily manufactured.

[0003]

However, in the conventional method for manufacturing a hollow body by injection molding, the product halves are butted against each other as they are in the mold, and the molten resin is injected into the outer circumference of the butted portion to be cured. Therefore, especially when manufacturing a thin hollow body, the abutment part of the half-split body is likely to be deformed inward by the injection pressure of the molten resin, and the half-split body is joined while deformed, or the injected resin is There was a risk of leakage.
In view of the above problems, it is an object of the present invention to provide a method for manufacturing a hollow body that can prevent deformation of the abutting portion due to resin injection pressure even if the hollow body is thin.

[0004]

Therefore, in the method of manufacturing a hollow body according to the present invention, two halves obtained by plastic injection molding are abutted against each other in a mold and melted around the abutting portion. When a hollow product is manufactured by injecting and curing resin, fluid pressure is applied to the cavity formed by the two halves in the state where the two halves are abutted and clamped. The gist is that the molten resin is injected into the outer periphery of the abutting portion to be cured. Here, the present invention can be applied to any method as long as it is a method of abutting a half body in a mold and injecting a molten resin around the abutting portion to produce a hollow product. 61-226060, JP-A-62-873.
No. 15, JP-A-63-237917, a method for producing a hollow body, or a method for producing a product half and then a rotary type method in which a mold is rotated to collide the half with each other. Applicable to

[0005]

In the present invention, the halves are abutted and clamped, and in that state, fluid pressure is applied to the cavities of both halves,
Since the molten resin was injected into the outer periphery of the abutting part,
The fluid pressure in the cavity and the injection pressure are balanced at the time of joining the abutting portions, and the abutting portions are not deformed.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the specific examples shown in the drawings. 1 to 3 show a hollow body manufacturing apparatus according to an embodiment of the present invention, which is an example applied to a die slide method for manufacturing a hollow body having one end opened.
In FIG. 1, a mounting frame 11 is provided on a bed 10 of an injection molding machine 1, a die slide type mold 2 is supported on the mounting frame 11, and a molten resin injection mechanism 3 is mounted on the bed 10. Is disposed so as to face the mold 2, and the injection mechanism 3 includes a hopper 30 for storing molten resin, a nozzle 31 for injecting the molten resin, a pressurizing cylinder 32, and a nozzle 3.
It is configured by a drive device 33 that advances and retracts 1.

The mold 2 is constructed by disposing a slide mold 22 between a movable mold 20 and a fixed mold 21.
Is provided with a die slide cylinder 23 that slides the die vertically, and the movable die 20 is provided with a die opening / closing cylinder 24 that opens and closes the die. As shown in FIG. 2, the female mold part 2 is formed on the mold surface of the slide mold 22.
22 and a male mold part 223 are formed, and a female part is formed on the mold parting surface of the movable mold part 20 with the mold parts 222, 223 on the slide mold 22 side to form a divided body-shaped cavity for dividing the product into two parts. A mold part 200 and a male mold part 201 are formed. Further, a sprue 210 which is coaxial with the injection nozzle 31 is provided through the fixed mold 21, and the slide mold 22 is provided with two sprues 220 and 221 connectable to the sprue 210 of the fixed mold 21 in communication with the mold split surface. Have been drilled. Then, the two sprues 220 and 221 of the slide die 22
On the other hand, in order to connect the runner 202 extending in the sliding direction to the mold split surface of the movable mold 20 and to inject the molten resin flowing in the runner 202 into each cavity, the movable mold 20 has a submarine gate. 203 and the side gate 203 ', and the slide mold 22 is now 1
One submarine gate 203 is formed.
Further, the movable die 20 is formed with an air supply passage 204 that communicates with the female die portion 200 and can come into contact with the male die portion 223 of the slide die 22. The air pump 2 is provided in the passage 204.
05 is connected.

Next, the function and effect will be described. When manufacturing a hollow product, first, the slide mold 22 is set to the first mold clamping position, the movable mold 20 is moved forward by the mold opening / closing cylinder 24, and mold matching is performed as shown in FIG. Male and female mold parts 200 and 22 of the slide mold 21
3, 201, 222 forms a half-cavity-shaped cavity formed by dividing the product into two parts, and in that state, the driving device 3
3 is operated, the nozzle 31 is advanced, and the pressure cylinder 3
2 is operated and the molten resin in the hopper 30 is injected. Then, the molten resin is injected into the cavity of the mold part through the sprues 210 and 220, the runner 202 and the submarine gates 203 and 203, and the left and right halves W are manufactured. When the half-divided body W is manufactured, the nozzle 31 is retracted and the mold opening / closing cylinder 24 is operated to move the movable mold 2.
0 is opened, and the molded half-split body W is held in the female mold parts 200 and 222 of the movable mold 20 and the slide mold 22, and the runner is ejected by an ejector (not shown).

When the primary molding is completed, the slide die 22 is slid by the die slide cylinder 23 from the first die clamping position to the second die clamping position, and the movable die 20 is advanced to slide as shown in FIG. When the split resin W in the female mold parts 200 and 222 is abutted against the mold 22 and the molten resin is injected in this state, the molten resin is sprued 20.
0, 221, runner 202 and side gate 203 '
After being injected into the cavity of the mold portion, the outer periphery of the abutting portion C of the divided body W is joined to manufacture a hollow product. At that time, in a state where the half-split bodies W are abutted and clamped,
The molten resin is injected into the outer periphery of the abutting portion C while air is supplied from the air hoop 205 to the inside of the cavity of both halves W through the air supply passage 204 to apply air pressure. The air pressure prevents deformation of the abutting portion C due to the molten resin injection pressure. As a result, even a thin hollow body can be accurately molded into a predetermined shape, and the risk of leakage of molten resin can be reliably eliminated. Further, the molten resin injected into the abutting portion C can be cooled by the supply air, and workability is greatly improved.

FIG. 4 shows another embodiment of the present invention.
This embodiment is applied to the manufacture of a hollow body D having open ends. In this case, an automatic opening / closing valve may be provided in the middle of the air supply passage 204 to adjust the air supply.

[0011]

As described above, according to the method for manufacturing a hollow body according to the present invention, in the state where both parts are abutted and the mold is clamped, the abutting portion is applied while applying the fluid pressure in the cavity of the molded product. Since the molten resin is injected into the outer circumference to cure it, even thin hollow bodies can be prevented from being deformed due to the injection pressure, the risk of leakage of the injected resin can be eliminated, and the resin can be easily cooled. There is an effect that can be done.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an injection molding machine for carrying out a manufacturing method according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a state at the time of primary injection of the injection molding machine.

FIG. 3 is a cross-sectional view showing a state during secondary injection of the injection molding machine.

FIG. 4 is a diagram for explaining another embodiment of the present invention.

[Explanation of symbols]

 200 female mold part 222 female mold part 204 air supply passage 205 air pump C abutting part W half body

Claims (1)

[Claims] 1. 2 obtained by plastic injection molding
In the method for manufacturing a hollow product, two half-split bodies are made to abut each other in a mold, and a molten resin is injected around the abutment portion to be cured to join the two half-split bodies. After clamping the halves in the abutting state, fluid pressure is applied to the cavity formed by the two abutting halves, and molten resin is applied to the outer periphery of the abutting portion while maintaining the pressurized state. A method for producing a hollow body, which comprises injecting and curing.