JP2788669B2 - Manufacturing method of hollow resin products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to molding of a hollow resin product in an injection mold.
The present invention relates to a manufacturing method that shortens the time from injection of a molten resin to removal of a mold from the mold to improve productivity.

(Prior art) Conventionally, for example, a molten resin such as plastic is injected into a cavity of an injection mold, and a high-pressure gas is injected into the resin before the resin is completely cooled and solidified to form a hollow in a part of the product. Forming methods for forming are known. According to this method, a hole is formed 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, the hole in the inner layer is formed from the hole. A high-pressure gas is injected toward the solidified portion to form a gas filling portion as a hollow portion. For example, among the products, a thick flange portion or the like at the peripheral end portion is made hollow, thereby preventing sinking due to molding shrinkage, preventing deformation due to residual stress, securing necessary strength, and the like.

(Problems to be solved by the invention) However, conventionally, after forming a hollow portion by injecting a gas,
The mold could not be released until the molded product was completely solidified. That is, if the gas pressure filled in the hollow part is released before the product solidifies, the molding shrinkage is caused and the appearance is deteriorated.On the other hand, when the mold is opened early while maintaining the gas pressure, the gas pressure is reduced. Since a defect such as deformation occurs due to the influence, it is necessary to close the mold and solidify the product while maintaining the gas pressure. For this reason, the occupation time of the mold in one cycle of molding is prolonged, and it is desired to improve the production efficiency.

(Means for Solving the Problems) In order to solve such problems, the present invention provides a product cavity and a non-product cavity connected to the product cavity, and injects a molten resin into the product cavity. A first step of injecting a gas from the non-product shape part, a second step of discharging a part of the injected gas and reducing the pressure to a predetermined pressure, and then closing a gas passage of the non-product shape part; Then, the non-product-shaped portion is cut off, and the residual gas in the hollow portion is discharged, thereby producing the third product.

(Effect) A part of the high-pressure gas injected into the resin is exhausted on the way, and the reduced pressure is maintained to a predetermined pressure necessary for preventing sinking of the product, thereby enabling early removal of the product.

For this reason, the cycle of using the mold is shortened, and the productivity is increased.

On the other hand, when the product taken out of the mold is completely solidified, the non-product-shaped portion is cut off to discharge the residual gas in the hollow portion, thereby removing the adverse effect due to the residual gas.

(Example) An example of the manufacturing method of the present invention will be described with reference to the attached drawings.

1 is an overall view showing one example of a mold apparatus for carrying out the present invention, FIG. 2 is an enlarged view of a main part, and FIGS. 3 and 4 are enlarged views of a main part showing another embodiment. is there.

As shown in FIG. 1, the injection mold apparatus 1 comprises a fixed main body 3 mounted on a fixed mounting plate 2 and a movable mounting plate 4.
And a movable body 6 attached to the fixed body 3 via a spacer 5. The movable body 6 is configured to move up and down on the fixed body 3 to open and close the mold. Cavities 8 are formed in the divided surfaces of the mold bodies 3 and 6. A spool bush 9 for injecting the molten resin 27 into the cavity 8 is fitted into the fixed main body 3.

The movable mounting plate 4 includes an extruding plate 10 that can move up and down,
An extrusion pin 11 attached to the extrusion plate 10 is provided,
The push-out pin 11 slidably penetrates the movable mold body 6 and has a tip portion 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, and is provided, for example, as shown in FIG. Non-product shaped part 13 formed by projecting from the part,
It is configured to cut off with the cutting tool C after the forming is completed. A gas is injected from the non-product shaped portion 13 by a gas injection mechanism 15 described below, and the gas passage 14 of the resin 27 formed at that time is closed by a gas passage closing mechanism 16. Such a non-product shape portion 13 may be provided at two or more places depending on the size of the product.

The gas injection mechanism 15 is incorporated in the movable body 6,
As shown in FIG. 2, a piston 18 is slid in the cylinder of the hydraulic cylinder unit 17, and a pin 19 is integrally connected to the piston 18.
The resin 27 of the non-product shaped part 13 is pierced on the surface layer with the tip of the pin 19 sliding in the nozzle hole 21, then the piston 18 is moved upward to open the nozzle hole 21, and the high-pressure gas sent from the gas supply path 20 is opened. I try to inject.

On the other hand, the gas passage closing mechanism 16 is incorporated in the fixed type main body 3, and heats the pressure contact member 23 which is advanced and retracted by the hydraulic cylinder unit 22 for compression by the heater 24. A thermostat 25 is provided to maintain the heating temperature at a predetermined temperature. The distal end of the pressure contact member 23 faces the gas passage 14 of the non-product shaped portion 13, and the pressure contact member 23
The gas passage 14 is closed by advancing 23 and, at the same time, the surface layer is welded by heating by the heater 24.

In the injection mold apparatus 1 configured as described above, the molten resin 27 is injected through the sprue bush 9 into the cavity 8 in which the fixed mold body 3 and the movable mold body 6 are combined. Inject. On this occasion,
As described above, when the tip of the pin 19 of the gas injection mechanism 15 moves down to make a hole in the semi-solid surface, the pin 19 rises again to open the nozzle hole 21. For this reason, for example, high-pressure gas such as nitrogen gas pressurized to about 600 atm, the gas supply path 20,
Through the nozzle hole 21, the resin enters the inside of the resin 27 from the hole in the surface layer, and penetrates deep into the resin 27 while pressing the unsolidified molten resin toward the mold wall surface.

The space occupied by the gas that has entered the resin at a high pressure in the product shape portion is formed as a hollow portion 28. In the case of the present invention, the gas is not solidified while maintaining the high pressure as it is. Part of the gas is exhausted on the way.

That is, the gas is recirculated from the gas supply passage 20 to which the gas is supplied, and the pressure of about 600 atm is reduced to about 1.5 to 5 atm. The pressure after the pressure reduction is a pressure sufficient to support from the inside to prevent sink due to molding shrinkage during solidification, and the pressure of the hollow portion 28 is increased by about 1.5 until solidification is completed.
The pressure is kept in a range of up to 5 atm.

When the pressure reduction to the predetermined pressure is completed, the gas passage closing mechanism 16 closes the gas passage 14 as described above.

When the gas passage 14 is completely closed, the mold is opened and the product is taken out and completely solidified. When solidification is completed, the non-product shaped part 13 is cut off as shown in FIG.
Discharge 28 residual gases.

According to this method, productivity can be improved because the solid can be taken out of the mold at an earlier stage as compared with a case where the solidification is completely performed while being restrained by the mold.

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

The gas passage closing mechanism 16 of this embodiment includes a non-product shape portion 13.
The gas passage 14 is configured to be crushed along the direction of the passage, so that the press-contact member 23 is movable in the horizontal direction.
For this reason, gas is injected in the state of FIG.
Is formed, when the pressure is reduced to a predetermined pressure, the pressure contact member 23 is advanced by the hydraulic cylinder unit 22 for compression, and at the same time, the distal end is heated by the heater 24, and as shown in FIG.
Block 14

Next, FIG. 4 shows still another embodiment of the gas passage closing mechanism, which is configured integrally with the gas injection mechanism.

That is, the gas injection / sealing mechanism 30 is configured by integrating the gas injection mechanism 15 and the gas passage closing mechanism 16 described above, and includes a first piston 32 in a cylinder case 31, Is provided with a second piston 33. Hydraulic lines 34, 35 for vertically moving the first piston 32 and a hydraulic line 36 for lowering the second piston 33 are provided.
An oil passage 37 is provided to communicate with the hydraulic line 34 side. The hydraulic line 36 is provided at the center of the piston rod 38 connected to the rear side of the second piston 33.

A pressure contact member 40 is connected to the front side of the second piston 33. A heater 41 is provided in the middle of the pressure contact member 40, and seal members 45 and 46 are appropriately disposed in a sliding portion between the pressure contact member 40 and the cylinder case 31.
It slides inside. The opening of the gas supply passage 43 faces the nozzle hole 42.

A pin 44 for making a hole in the resin surface layer is built in the distal end portion of the pressing member 40. The pin 44 is attached to, for example, the press-contact member 40 via a spring 48, and when the press-contact member 40 reaches a predetermined position, only the pin 44 stops at that position and only the press-contact member 40 drops. Locking portion 49 as shown in FIG.

In the gas injection / sealing mechanism 30 configured as described above, first, as shown in FIG. 4A, the molten resin is injected into the cavity with the second piston 33 moved upward and the first piston 32 moved downward. At this time, the nozzle hole 42
The surface layer of the molten resin 27 filled up to the vicinity of the inlet becomes semi-solid in the same state as the hole formed by the pin 44 projecting downward.

Next, when the first piston 32 is moved upward by supplying oil to the hydraulic line 34 as shown in FIG. 2B, the opening of the gas supply passage 43 which has been closed is opened, and the high-pressure gas is It flows from the hole 42 and enters the inside of the resin. Then, the gas flow path is formed as a hollow portion.

Next, a part of the gas forming the hollow portion is discharged from the gas supply path 43. When the pressure is reduced to a predetermined gas pressure, the gas passage is closed. That is, as shown in FIG. 3C, the first piston 32 is lowered by applying hydraulic pressure from the hydraulic line 35, and the second piston 33 is also lowered by applying hydraulic pressure from the hydraulic line 36. For this reason, the resin that has penetrated into a part of the nozzle hole 42 is crushed by the tip of the pressure contact member 40 to close the hole, and is heated at the same time to weld the same.

(Effect of the Invention) As described above, in the method for manufacturing a hollow resin product of the present invention, since a part of the gas is taken out while remaining in the hollow part of the molded product, molding defects such as sink or deformation due to early removal are made. Productivity can be improved while preventing the adverse effects of

Also, cut out the non-product shape part of the molded product taken out,
Since all residual gas in the hollow portion is also discharged, there is no adverse effect thereafter.

[Brief description of the drawings]

1 is an overall view showing an example of a mold apparatus for carrying out the present invention, FIG. 2 is an enlarged view of a main part, FIGS. 3 and 4 are enlarged views of a main part showing another embodiment, FIG. 5 is an explanatory view showing the cutting of the non-product shaped part. In the same figure, 1 is an injection mold device, 8 is a cavity, 12 is a product shape portion, 13 is a non-product shape portion, 15 is a gas injection mechanism, 16 is a gas passage closing mechanism, 23 is a pressure contact member, and 28 is a hollow member. Reference numeral 30 denotes a gas injection / sealing mechanism, and 40 denotes a press-contact member.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Teruo Ichikawa 1-10-1 Shinsayama, Sayama-shi, Saitama Honda Engineering Co., Ltd. (56) References JP-A-3-274120 (JP, A) 2-289327 (JP, A) JP-A-1-157823 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B29C 45/00-45/84 B29L 22:00

Claims (1)

(57) [Claims] 1. A method of manufacturing a hollow resin product wherein a molten resin is injected into a mold cavity and a gas is injected into the molten resin to form a hollow portion. A first step of injecting a molten resin into the shaped part and subsequently injecting a gas from the non-product shaped part connected to the product shaped part, and discharging a part of the injected gas to reduce the pressure to a predetermined pressure, and thereafter, And a third step of removing the product from the mold, cutting off the non-product shape part and discharging the residual gas in the hollow part. Production method.