JPH0478510A - Production of hollow resin product - Google Patents

Abstract

PURPOSE:To enhance productivity while preventing adverse effect of molding defect such as sink or deformation due to takeout at an early stage by taking out a hollow resin product while allowing one part of gas to remain in the hollow part of a molded form. CONSTITUTION:A cavity 8 is formed by mold-matching a fixed mold main body 3 and a movable mold main body 6. Molten resin 27 is introduced into the cavity 8 through a sprue push 9 part and high-pressure gas is introduced by a gas introducing mechanism 15. In such a way, gas is introduced into resin at high pressure and the space occupied by this gas in the shape part of a produce is formed at a hollow part 28. In this case, one part of introduced gas is midway discharged. In other words, the gas is returned through a passage 20 for supplying gas and the hollow part 28 is decompressed. When it is decompressed to the prescribed pressure, a gas passage 14 is closed by a gas passage blocking mechanism 16. When this blockade is completed, mold opening is performed and a product is taken out and completely coagulated. A non-productive shape part 13 is cut down and simultaneously the residual gas in the hollow inside 28 is discharged. By such a way, since the product is taken out from the mold at an early stage, productivity can be enhanced.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention reduces the time from injection of molten resin to opening and taking out the mold when molding hollow resin products with an injection mold.
This invention relates to a manufacturing method that improves productivity.

(Prior art) Conventionally, molten resin such as plastic is injected into the cavity of an injection mold, and before the resin is completely cooled and solidified, high-pressure gas is injected into the resin to create a hollow part in a part of the product. Molding methods are known. This method involves drilling a hole in a part of the surface layer when the surface layer of the resin in contact with the mold in the cavity is semi-solidified, and while the resin inside is still unsolidified. High-pressure gas is injected toward the solidified portion to form a gas-filled portion as a hollow portion. For example, by making the thick-walled flange portion at the peripheral end of the product hollow, it is possible to prevent sink marks due to molding shrinkage, prevent deformation due to residual stress, and ensure necessary strength.

(Problems to be Solved by the Invention) However, conventionally, after gas is injected to form a hollow part, it has not been possible to release the molded product until it is completely solidified.

In other words, if the gas pressure filled in the hollow part is released before the product solidifies, molding shrinkage will occur and the appearance will be poor. On the other hand, if the mold is opened early while the gas pressure is maintained, the gas pressure will be reduced. This can cause problems such as deformation due to the influence of gas, so it was necessary to close the mold and allow the product to solidify while maintaining gas pressure. For this reason, the time occupied by the mold in one molding cycle becomes long, and it is desirable to improve production efficiency.

(Means for Solving the Problem) In order to solve the problem, the present invention provides a product shape part and a non-product shape part connected to the product shape part in the mold cavity, and injects molten resin into the product shape part. The first step is to inject gas from the non-product shaped part, the second step is to discharge a part of the injected gas to reduce the pressure to a predetermined pressure, and then seal off the gas passage in the non-product shaped part, and to mold the product. It was decided to manufacture the product through the third step of taking it out, cutting out the non-product shaped part, and exhausting the residual gas in the hollow part.

(Function) By discharging a portion of the high-pressure gas injected into the resin and maintaining the reduced pressure to a predetermined level necessary to prevent sinking of the product, early removal of the product becomes possible.

Therefore, the mold usage cycle is shortened and productivity is increased.

On the other hand, when the product taken out from the mold is solidified, the non-product-shaped portion is cut off to exhaust the residual gas in the hollow portion, thereby eliminating the adverse effects of residual gas.

(Example) An example of the manufacturing method of the present invention will be described based on the attached drawings.

FIG. 1 is an overall view showing an example of a mold apparatus for implementing the present invention, FIG. 2 is an enlarged view of the main parts, and FIG.

FIG. 4 is an enlarged view of main parts showing another embodiment.

As shown in FIG. 1, the injection mold apparatus 1 includes a fixed main body 3 attached to a fixed mounting plate 2 and a movable main body 6 attached to a movable mounting plate 4 via a spacer 5. The movable mold main body 6 is configured to move up and down on the fixed mold main body 3 to open and close the mold, and a cavity 8 is formed in the dividing surface of the two mold bodies 3.6 that are aligned. ing. A spool bushing 9 for injecting molten resin 27 into the cavity 8 is fitted into the fixed body 3.

The movable mounting plate 4 includes an extrusion plate 10 that can move up and down,
An extrusion bottle 11 attached to this extrusion plate 10 is provided, and this extrusion bottle 11 slidably penetrates the movable mold main body 6, with its tip facing the cavity surface.

On the other hand, the cavity 8 is provided with a product-shaped part 12 to be molded as a product and a non-product-shaped part 13 to be molded as a non-product in a connected manner.For example, as shown in FIG. Non-product shaped part 1 formed by protruding from the part
3 is configured to be cut out with a cutting tool C after the molding is completed. Then, gas is injected from this non-product shaped portion 13 by a gas injection mechanism 15 described below, and the gas passage 14 of the resin 27 formed at this time is closed by a gas passage closing mechanism 16. A plurality of such non-product shaped portions 13 may be provided at two or more locations depending on the size of the product.

The gas injection mechanism 15 is incorporated into the movable main body 6,
As shown in FIG. 2, the hydraulic cylinder unit 17 includes a piston 18 that slides within the cylinder, and a bottle 19 that is integrally connected to the piston 18. The downward movement of the piston 18 slides the nozzle hole 21. A hole is made in the surface layer of the resin 27 of the non-product shaped part 13 at the tip of the bottle 19, and then the piston 18 is moved upward to open the nozzle hole 21 and high pressure gas sent from the gas supply path 20 is injected. .

On the other hand, the gas passage blocking mechanism 16 is built into the fixed main body 3, and is configured to heat the pressure member 23, which is moved forward and backward by the compression hydraulic cylinder unit 22, with the heater 24. A thermostat 25 is provided to maintain this heating temperature at a predetermined temperature. And pressure contact member 2
3, the tip faces the gas passage 14 of the non-product shaped part 13, and the pressure contact member 23 is advanced to close the gas passage 14.
At the same time, the surface layer portion is welded by heating with the heater 24.

In the injection mold apparatus 1 configured as described above, molten resin 27 is injected into the cavity 8 in which the fixed mold body 3 and the movable mold body 6 are molded together through the sprue bush 9, and then the gas injection mechanism 15 injects the molten resin 27 under high pressure. Inject gas. At this time, as described above, the tip of the bottle 19 of the gas injection mechanism 15 descends to punch a hole in the semi-solidified surface layer, and then the bottle 19 rises again to open the nozzle hole 21. For this reason, for example, 600
High-pressure gas such as nitrogen gas pressurized to about atmospheric pressure enters the resin 27 through the holes in the surface layer through the gas supply path 20 and the nozzle hole 21, and directs the unsolidified molten resin inside toward the mold wall surface. Penetrate deep into the body while pressing down.

The space occupied by the gas that has entered the resin under high pressure in the product shape is formed as a hollow section 28, but in the case of the present invention, instead of solidifying the gas by maintaining the high pressure, this injection Part of the gas is exhausted on the way.

That is, the gas is refluxed through the gas supply passage 2o to which the gas was supplied, and the pressure of about 600 atmospheres is reduced to about 1.5 to 5 atmospheres. The pressure after this pressure reduction is sufficient to support it from the inside to prevent sinkage due to mold shrinkage during solidification, and the pressure in the hollow part 28 is kept within this range of approximately 1.5 to 5 atm until solidification is completed. It is something to keep.

When the pressure is reduced to a predetermined pressure in this manner, the gas passage 14 is closed by the gas passage closing mechanism 16 in the manner described above.

When the sealing of the gas passage 14 is completed, the mold is opened and the product is taken out and completely solidified. When the solidification is completed, the non-product shaped portion 13 is cut off as shown in FIG. 5, and at the same time, the residual gas in the hollow interior 28 is discharged.

According to this method, productivity can be increased because the material can be removed from the mold at an earlier stage than in the case where the material is completely solidified while being restrained in the mold.

Next, FIG. 3 shows another embodiment of the gas passage blocking mechanism.

The gas passage blocking mechanism 16 of this embodiment has a non-product shaped portion 1.
The pressure member 23 is configured to crush the gas passages 14 of No. 3 along the passage direction, and the pressure contact member 23 is movable horizontally. For this reason, after gas is injected to form the hollow part 28 in the state shown in FIG. The gas passage 14 is closed by heating with the heater 24 as shown in (B).

Next, FIG. 4 shows yet another embodiment of the gas passage blocking mechanism, which is constructed integrally with the gas injection mechanism.

That is, this gas injection/blocking mechanism 30 is constructed by integrating the aforementioned gas injection mechanism 15 and gas passage blocking mechanism 16, and includes a first piston 3 in a cylinder case 31.
2, and inside this first piston 32 is a second piston 3.
3 is provided. Hydraulic lines 34 and 35 for vertical movement of the first piston 32 and hydraulic lines 36 for downward movement of the second piston 33 are provided, and an oil passage 37 is provided in the first piston 32 for upward movement of the second piston 33. and communicates with the hydraulic line 34 side. and hydraulic line 3
6 is provided at the center of the piston rod 38 coupled to the rear surface side of the second piston 33.

Further, a pressure contact member 40 is coupled to the front side of the second piston 33. A heater 4 is placed in the middle of this pressure contact member 40.
1, and appropriate seal members 45 and 46 are disposed at the sliding portion between the cylinder case 31 and the lower end thereof to slide within the nozzle hole 42. The opening of the gas supply path 43 faces this nozzle hole 42 .

A bottle 44 for making a hole in the resin surface layer is built into the tip of the pressing member 40. And this bottle 44 is
For example, a locking portion 49 is attached to the pressure contact member 40 via a spring 48, and is configured such that when the pressure contact member 40 descends to a predetermined position, only the bottle 44 stops at that position and only the pressure contact member 40 descends. It is equipped with

In the gas injection/blocking mechanism 30 thus constructed, first, as shown in FIG. 4(A), the second piston 33 is moved upward and the $1 piston 32 is moved downward, and molten resin is injected into the cavity. At this time, the surface layer of the molten resin 27 filled from the non-product shaped portion 13 to the vicinity of the entrance of the nozzle hole 42 becomes semi-solidified in the same state as if the hole was made by the pin 44 projecting downward.

Next, as shown in Figure (B), when oil is supplied to the hydraulic line 34 and the first piston 32 is moved upward, the previously blocked opening of the gas supply path 43 is opened, and high pressure gas flows into the nozzle. The gas flows through the hole 42 and enters the interior of the resin, and a gas flow path is formed as a hollow portion.

Next, a portion of the gas that has formed the hollow portion is discharged from the gas supply path 43. When the gas pressure is reduced to a predetermined level, the gas passage is closed. That is, as shown in FIG. 3C, hydraulic pressure is applied from the hydraulic line 35 to lower the first piston 32, and hydraulic pressure is also applied from the hydraulic line 36 to lower the second piston 33. Therefore, the nozzle hole 42
The resin that has penetrated into a portion of the hole is crushed by the tip of the pressure contact member 40 to close the hole, and at the same time, the inside is heated and welded.

(Effects of the Invention) As described above, in the method for manufacturing hollow resin products of the present invention, since some gas is taken out while remaining in the hollow part of the molded product, molding defects such as sink marks or deformation due to early removal can occur. It is possible to increase productivity while preventing the negative effects of

In addition, since the non-product shaped portion of the molded body taken out is cut out and all residual gas in the hollow portion is exhausted, there is no subsequent adverse effect.

[Brief explanation of the drawing]

FIG. 1 is an overall view showing an example of a mold apparatus for implementing the present invention, FIG. 2 is an enlarged view of the main parts, and FIG. FIG. 4 is an enlarged view of a main part showing another embodiment, and FIG. 5 is an explanatory view showing removal of a non-product shaped part. In the same figure, 1 is an injection mold device, 8 is a cavity, 12 is a product shape part, 13 is a non-product shape part, 15 is a gas injection mechanism, 16 is a gas passage blocking mechanism, 23 is a pressure contact member, and 28 is a hollow space. 30 is a gas injection/blocking mechanism, and 40 is a pressure contact member. Patent Attorney Representative Patent Attorneys Patent Attorneys Patent Attorneys Honda Motor Co., Ltd. 1) Customers Kuni Ohashi, Yu Koyama (B) Figure 3

Claims (1)

[Claims] A method for manufacturing a hollow resin product in which a molten resin is injected into a mold cavity and a gas is injected into the molten resin to form a hollow part. The first process involves injecting molten resin into the product shape part, then injecting gas from the non-product shape part connected to the product shape part, exhausting a part of the injected gas to reduce the pressure to a predetermined pressure, and then injecting the gas into the non-product shape part. A hollow resin product characterized by comprising a second step of sealing off the gas passage in the hollow portion, and a third step of removing the product from the mold and then cutting off the non-product shaped portion to discharge residual gas in the hollow portion. manufacturing method.