JPH10235723A - Molding method of hollow molded form - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase molding efficiency by a method wherein first refrigerant is employed as fluid in a first process while a matter to be molded is cooled at the time of molding a fluid pouring hole and a hollow part. SOLUTION: In a gas pouring process, compressed and cooled nitrogen gas is forced into synthetic resin, injected into the part of a base unit 11 in a hollow molded form 10. According to the forcing, a pouring port 14 and a hollow part 15 are formed in the hollow molded form 10. The synthetic resin, forming the part of a hollow part 15, is extruded into parts, corresponding to respective excessive parts 12 in the mold, by the nitrogen gas to form respective excessive parts 12. Next, respective discharging ports 16, communicated with the hollow part 15, are formed on the tip end surfaces of respective excessive parts 12 while compressed and cooled nitrogen gas is poured through the pouring ports 14 of the hollow molded form 10 in a cooling gas pouring process and, thereafter, is discharged out of respective discharging ports 16 through the hollow part 15. The hollow molded form 10 is cooled by the nitrogen gas, passing through the hollow part 15. The cooling is effected in the midst of the gas forcing process whereby cooling efficiency can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a hollow molded article.

[0002]

2. Description of the Related Art Conventionally, a hollow molding method has been used in injection molding of a thermoplastic synthetic resin to improve the cooling efficiency of a thick article.

[0003] The conventional method for molding a hollow molded article is as follows.
In accordance with the timing chart of each step shown in FIG. 5, processing is performed sequentially with each of the following steps [1] to [10] as one cycle.

[1] In a "mold closing" step, a mold of a hollow molded product is prepared so as to be moldable. [2] In the “injection” step, a predetermined amount of the heat-melted synthetic resin is injected into the mold.

[3] In the “holding pressure” step, the injection pressure is held so that the synthetic resin injected into the mold does not flow backward. [4] In the “weighing” step, the synthetic resin to be processed in the next cycle is weighed and prepared for the next cycle.

[5] In the “gas injection delay” step,
From the end of the “injection” step to the start of the “gas injection” step, a delay of a predetermined time is performed. This is because the subsequent “gas injection” step needs to be performed after the synthetic resin in the “injection” step is completely injected into the mold.

[6] In the "gas injection" step, a gas (nitrogen gas, inert gas or the like) is injected into the synthetic resin to make the interior of the synthetic resin hollow. [7] In the “gas pressure holding” step, the gas pressure of the gas pressed into the synthetic resin is held until the synthetic resin itself solidifies to the extent that its shape can be maintained.

[8] In the “gas depressurization” step, the gas pressurized into the synthetic resin is released. [9] In the “cooling” step, the synthetic resin injected into the mold is solidified. The “cooling” step is performed during the “gas injection” step, and is performed only until the synthetic resin is completely solidified.

[10] In the “mold opening” step, the molded synthetic resin (hollow molded article) is removed from the mold. The steps [1] to [4] and the steps [9] and [10] are performed as an injection molding operation. In addition, the above [5]
Steps [8] to [8] are performed as a hollow molding operation.

[0010]

However, in the conventional blow molding method, as shown in FIG. 5, the time required for the "cooling" step required from the "mold closing" step to the "gas depressurizing" step. It takes almost twice the time. Therefore, manufacturing TAT
(Turn Around Time) is prolonged, the molding efficiency is reduced, and the manufacturing cost is increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a method of molding a hollow molded article capable of reducing the manufacturing cost by increasing the molding efficiency. It is in.

[0012]

In order to achieve the above object, according to the first aspect of the present invention, when performing a hollow molding, a fluid is press-fitted into the molded object and the fluid is injected into the molded object. A first step of forming a fluid injection hole and a hollow portion;
The gist of the present invention is to use a first refrigerant as a fluid in the step of (1) and to cool the molded object at the time of molding the fluid injection hole and the hollow portion.

According to a second aspect of the present invention, in the method of molding a hollow molded article according to the first aspect, the surface of the molded article is communicated with the molded article after the first step so as to communicate with the hollow portion. A second step of providing a hole that opens into the hole, and a third step of injecting a second refrigerant into the hollow part from the fluid injection hole and discharging the refrigerant from the hole to cool the molded object. The gist is to have

According to a third aspect of the present invention, in the method for molding a hollow molded product according to the first or second aspect, the same fluid is used for the first refrigerant and the second refrigerant.
The gist is that the steps from the step to the third step are performed continuously.

In the embodiments of the invention described below, the "molded object" described in the claims or the means for solving the problem is constituted by a hollow molded article 10, and similarly, "fluid", The "first refrigerant" and the "second refrigerant" are composed of nitrogen gas, the "fluid injection hole" is composed of the injection hole 14, and the "first step" is composed of the "gas injection" step. Similarly, the "hole" is constituted by the discharge hole 16, the "second step" is constituted by the "product drilling" step, and
The “third step” is constituted by a “cooling gas injection” step.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a hollow molded article 10 molded by the molding method of the present embodiment. FIG. 2 is a cross-sectional view seen from the direction of arrow AA in FIG.

The hollow molded article 10 comprises a base 11 and two surplus parts 12. The base portion 11 is formed in a substantially rectangular parallelepiped having opposing side portions 11a and 11b. A recess 13 is formed substantially at the center of the upper surface of the base 11. Each surplus portion 12 has a substantially rectangular tab 12a.
And the linking portion 12b, each side 1 of the base 11
1b is integrally formed on one side surface.

The injection hole 14 is formed on the side 11b on the side opposite to the side 11b of the base 11 on which the surplus portion 12 is formed.
It is formed almost in the center of. Further, a hollow portion 15 is formed inside the side portion 11b on the side where the injection hole 14 is formed and each side portion 11a. This hollow portion 15 is
It is in communication with 4. In addition, the hollow portion 15 is
Are formed to communicate with the inside of the tab 12a and the linking portion 12b. A discharge hole 16 is formed at the tip end surface of each surplus portion 12 and communicates with the hollow portion 15.

Next, the cooling gas hollow equipment 30 connected to an injection molding machine (not shown) for molding the hollow molded article 10 will be described with reference to FIG. FIG. 3 is a piping diagram of the cooling gas hollow facility 30.

The cooling gas hollow equipment 30 includes a compressor 31, air coolers 32 and 33, an air cooler 34, a pressure accumulator 35,
36, solenoid valves 37 to 45, manual valves 46 to 48, pressure gauge 4
9-51, safety valves 52-55, pressure sensors 56-58,
Check valves 59 and 60, temperature sensors 61 to 63, pressure reducing valve 64 with relief, electromagnetic relief valve 65, filter 66 to
69.

Air is fed from the intake ports Y and Z. The air sent from the intake port Y is supplied to the compressor 31
Drive control. The air taken in from the inlet Z is cooled to about −40 ° C. by the air coolers 32 and 33. Then, the air cooled by the air cooler 32 is sent to the air cooler 34. The air cooled by the air cooler 33 is supplied to the cold storage covers 35 of the pressure accumulators 35 and 36.
a, 36a.

The nitrogen gas is sent from the intake port X and sent to the blow molding machine through the following route. (A) Compressor 31 → (b) Air cooler 34 → (c) Accumulators 35 and 36 → (d) Blow molding machine.

(A) The nitrogen gas sent from the intake port X is sent to the compressor 31. Then, the nitrogen gas is compressed by the compressor 31. At this time, the temperature of the compressed nitrogen gas rises to about 80 ° C. due to the heat of compression.

(B) The compressed nitrogen gas is sent to the air cooler 34. The nitrogen gas is cooled to about 0 ° C. by the air cooled by the air cooler 32 in the air cooler 34.
Is cooled.

(C) The compressed and cooled nitrogen gas is temporarily stored in each of the pressure accumulators 35 and 36. At this time, the temperature of the nitrogen gas is maintained in each of the pressure accumulators 35 and 36 by the air cooled by the cooler 33.

(D) The nitrogen gas stored in each of the pressure accumulators 35 and 36 is sent to a blow molding machine as needed.
The hollow molded product 10 is provided with the cooling gas hollow equipment 30 described above.
Is molded according to a timing chart of each step shown in FIG. Hereinafter, a method of forming the hollow molded article 10 will be described with reference to FIG. In addition, about the same process as the conventional, the name of a process is made the same and description is abbreviate | omitted.

(1) After the “mold closing” step, in the “injection” step, the heat-melted synthetic resin is injected into a portion of the hollow molded article 10 corresponding to the base 11 in the mold (not shown). . At this time, the synthetic resin is not injected into the portion corresponding to the surplus portion 12 in the mold.

(2) Perform the steps of “holding pressure” and “weighing”. (3) After the “gas delay” step, in the “gas injection” step, the compressed and cooled nitrogen gas is injected into the synthetic resin injected into the base 11. The injection hole 14 and the hollow portion 15 are formed in the hollow molded article 10 by the press-fitting of the nitrogen gas. Then, the synthetic resin in the portion that has become the hollow portion 15 is extruded by the nitrogen gas to a portion corresponding to each surplus portion 12 in the mold. Thereby, each surplus portion 12 is formed.

(4) The steps of “holding gas pressure” and “depressurizing gas” are performed. (5) In the “product drilling” step, each discharge hole 16 communicating with the hollow portion 15 is formed at the tip end surface of each surplus portion 12.

(6) In the “cooling gas injection” step, the compressed and cooled nitrogen gas is injected into the injection hole 1 of the hollow molded article 10.
4 and is discharged from each discharge hole 16 through the hollow portion 15. The hollow molded article 10 is cooled by the nitrogen gas passing through the hollow portion 15. In addition, this "cooling gas injection"
The process is performed until the synthetic resin is completely solidified.

(7) The “cooling” step is performed during the “gas injection” step, and ends when the “cooling gas injection” step ends. (8) The “mold opening” step is performed, and the molding of the hollow molded article 10 is completed.

The above (1), (2), (7),
Each step of (8) is performed as an injection molding operation. The operations (3) to (6) are performed as a hollow molding operation. That is, the difference between the molding method of the present embodiment and the conventional molding method is that in the hollow molding operation in the conventional molding method, the nitrogen gas cooled to about 0 ° C. in the “gas injection” step is used. This is a point that a “product drilling” step and a “cooling gas injection” step are added after the “gas depressurization” step.

As described in detail above, according to the present embodiment, the following operations and effects can be obtained. (A) The “cooling” step in the conventional molding method is natural cooling, and no measure is taken to forcibly cool the hollow molded article 10. However, in the “cooling” step in this embodiment, measures are taken to forcibly cool the hollow molded article 10 in the “gas injection” step and the “cooling gas injection” step. Therefore, the cooling efficiency of the hollow molded article 10 can be improved.

That is, in the “gas injection” step, the compressed and cooled nitrogen gas is injected into the synthetic resin injected into the base 11. Therefore, in the "gas injection" step, the hollow molded article 10 is forcibly cooled.

In the “cooling gas injection” step, the compressed and cooled nitrogen gas is injected into the injection hole 1 of the hollow molded article 10.
Injected from 4. Then, the nitrogen gas is supplied to the hollow portion 1.
5 through each discharge hole 16. That is,
Cooled nitrogen gas is sequentially flowed into the hollow portion 15. Therefore, in the “cooling gas injection” step, the hollow molded article 10 is forcibly cooled.

(B) As shown in FIG. 4, the time required for the “cooling” step in the molding method of the present embodiment is the same as the conventional “cooling” shown in FIG. The time required for the process is reduced by about 40%. Therefore, the molding efficiency of the hollow molded article 10 can be increased, and the manufacturing cost of the hollow molded article 10 can be reduced.

(C) When the nitrogen gas is compressed after being cooled, the temperature of the nitrogen gas rises due to the heat of compression, and the cooling effect may be lost. However, in the present embodiment, the nitrogen gas is compressed by the compressor 31 in the cooling gas hollow facility 30 and then cooled by the air cooler 34. Therefore, the nitrogen gas can be reliably cooled.

The cooling temperature range of the nitrogen gas is -10 ° C.
~ 20 ° C is suitable, preferably -10 ° C to 10 ° C,
Particularly desirable is -10 ° C to 0 ° C. If the temperature is higher than this range, the cooling time of the hollow molded article 10 tends to be long, and if it is too low, the material of the hollow molded article 10 may be adversely affected.

The above embodiment may be modified as follows, and the same operation and effect can be obtained in such a case. (1) In the above embodiment, only the molding method of the hollow molded article 10 is embodied, but the molding method of the above embodiment may be applied to all types in which the hollow molding is performed by injection molding.

(2) In the above embodiment, “gas injection”,
Although nitrogen gas was used in each step of “cooling gas injection”, a gas that does not adversely affect the material of the hollow molded article 10, for example, an inert gas such as helium, neon, argon, krypton, xenon, or radon, air, or carbon dioxide It may be changed to gas or the like.

(3) In the above embodiment, the cooling gas hollow equipment 30 is used as a device for compressing and cooling the nitrogen gas. However, any device capable of feeding the compressed and cooled nitrogen gas into the blow molding machine is used. For example, equipment other than the hollow equipment 30 may be used.

While one embodiment has been described above, technical ideas other than the claims that can be grasped from each embodiment will be described below together with their effects. (A) The method for molding a hollow molded article according to any one of claims 1 to 3, wherein the first refrigerant or the second refrigerant is nitrogen gas, helium, neon, argon, krypton, xenon, radon, or the like. A method for molding a hollow molded article using one gas selected from the group consisting of inert gas, air, and carbon dioxide.

In this way, a gas suitable for the material of the molding can be used as the first or second refrigerant. (B) In the method for molding a hollow molded article according to any one of claims 1 to 3 and (a), the first or second refrigerant is cooled after being compressed, and the first or second refrigerant is cooled to the first step. A method for forming a hollow molded product, which comprises feeding the product.

In this way, the first or second refrigerant that has been reliably compressed and cooled can be sent to the first or third step.

[0045]

As described in detail above, according to the first aspect of the present invention, the object can be forcibly cooled. As a result, the manufacturing cost of the hollow molded article can be reduced by increasing the molding efficiency of the molded article.

According to the second aspect of the present invention, it is possible to further increase the molding efficiency of the molded article and reduce the manufacturing cost of the hollow molded article. According to the invention described in claim 3,
The manufacturing process of the hollow molded article can be prevented from being complicated, and the hollow equipment can be simplified.

[Brief description of the drawings]

FIG. 1 is a perspective view of a hollow molded article 10 molded by a molding method according to one embodiment.

FIG. 2 is a sectional view as seen from the direction of arrows AA in FIG. 1;

FIG. 3 is a piping diagram of a cooling gas hollow facility 30.

FIG. 4 is a timing chart of a molding method according to one embodiment.

FIG. 5 is a timing chart of a conventional molding method.

[Explanation of symbols]

10: hollow molded product, 11: base, 12: surplus, 13 ...
Recessed part, 14 ... injection hole, 15 ... hollow part, 16 ... discharge hole, 3
0: Cooling gas hollow equipment.

Claims (3)

[Claims] A first step of press-fitting a fluid into a molded object to form a fluid injection hole and a hollow portion in the molded object when performing the hollow molding; Using a first refrigerant as a fluid,
A method of molding a hollow molded product, wherein the molded object is cooled when the fluid injection hole and the hollow portion are molded. 2. The method of molding a hollow molded article according to claim 1, wherein after the first step, a hole is formed in the surface of the object in communication with the hollow portion in the object after the first step. A hollow molded article comprising: a second step; and a third step of injecting a second refrigerant into the hollow portion from the fluid injection hole and discharging the refrigerant from the hole portion to cool the molded object. Molding method. 3. The method for molding a hollow molded article according to claim 1, wherein the same fluid is used for the first refrigerant and the second refrigerant, and the first to third steps are continuously performed. A method for forming a hollow molded article, characterized in that the method is performed in an integrated manner.