JPH06226781A - Hollow injection molding and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a sufficient thickness of wall near a gas inlet and to prevent a decrease in rigidity by burying an insert member having a gas introducing inlet at the center of an area corresponding to the inlet of a mold for a hollow injection molding to be molded by introducing inert gas into melt resin injected in a mold cavity. CONSTITUTION:An insert member 12 is formed of synthetic resin substantially in an annular state and has an introducing port 13 having the same diameter as that of a gas inlet 4 of an upper mold 1a. The member 12 is brought at the port 13 into contact with the inner surface of the mold 1a in such a way that the introducing port 13 is aligned with the gas inlet 4. Then, when a hollow injection molding is conducted via the inlet 4, the port 13, resin encloses an outer periphery of the member 12, the thickness of the wall near the port 4 becomes substantially the same as a general part to obtain sufficient rigidity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow injection molded product such as a vehicle assist grip and a method for manufacturing the same.

[0002]

2. Description of the Related Art As is well known, various methods have been conventionally provided for producing a hollow injection molded article, which is produced by injecting a molten resin into a mold and then injecting a gas. For example, there are those described in Japanese Patent Publication No. 57-14968.

The outline thereof will be described with reference to FIGS. 9 and 10. First, a molding die 1 including an upper die 1a and a lower die 1b.
The molten resin 5 is injected into the cavity 2 from the injection nozzle 3 through the injection port 4 formed in the upper mold 1a to such an extent that the cavity 2 is not filled.

After that, as shown in FIG.
An inert pressurizing gas 7 is injected from the gas nozzle 6 through the injection port 4, and the outer periphery of the molten resin 5 is spread to the inner peripheral surface of the cavity 2 by the gas pressure, whereby hollow injection is performed. The molded product is molded.

By the way, as such a hollow injection-molded article, there is, for example, an assist grip 8 attached to a side wall of a vehicle compartment as shown in FIG. 11, which improves rigidity per weight, improves sound quality, saves material, etc. It is often used from the viewpoint of.

[0006]

However, in the above-mentioned conventional method for manufacturing a hollow injection-molded article, when the pressurized gas 7 is injected into the molten resin 5, the pressure of the pressurized gas 7 becomes maximum. The thickness of the molten resin 5 near the injection port 4 is thinly formed. Therefore, after the injection molding of the assist grip 8, the protruding portion 9 of the back surface 8a of the assist grip 8 remaining on the hole edge of the injection port 4 is cut out so as to be flush with the back surface 8a, as shown in FIG. The hole edge portion 10a of the small hole 10 formed in the portion of the inlet 8 becomes thinner than the general portion. Therefore, the small hole 1 of the assist grip 8
The rigidity near 0 is significantly reduced.

[0007]

The present invention has been devised in view of the above-mentioned problems of the prior art. The invention of claim 1 is the method of injecting a molten resin into a cavity of a mold, and thereafter, In a hollow injection-molded article formed by injecting an inert gas into a molten resin through a mold injection port, an insert member having a gas introduction port in the center is provided at a portion corresponding to the injection port of the hollow injection-molded article. It is characterized by being buried.

According to a second aspect of the present invention, a hollow is formed by injecting a predetermined amount of molten resin into the cavity of the mold and then injecting an inert pressurized gas into the molten resin from the injection port of the mold. In the method for producing an injection-molded article, in the cavity near the injection port of the pressurized gas, an insert member having a gas introduction port at the center is preset, and the molten gas is injected into the cavity, and then the pressurized gas is injected. It is characterized by injecting pressurized gas from the inlet and gas inlet

[0009]

According to the present invention having the above-mentioned structure, when the molten resin is injected into the cavity from the injection port and then the inert gas is injected from the pressurized gas injection port and the gas introduction port of the insert member, the molten resin in the cavity is injected. Are extruded to the inner peripheral surface of the cavity by the gas pressure and also enclose the outer peripheral surface of the insert member. Therefore, the insert member remains in the vicinity of the gas injection port after the mold release as it is. Therefore, a sufficient thickness near the gas injection port is secured, and a decrease in rigidity is prevented.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings.

In the first embodiment shown in FIG. 1, a hollow injection molded product applied to the same assist grip 11 as described above is shown, and a molten resin and an inert gas are formed in the cavity in the upper mold 1a. It is premised that the same injection port 4 is used for injection.

More specifically, first, the resin plasticized by a screw for plasticizing and injecting the resin is stored in the injection cylinder. On the other hand, an insert member 12 as shown in FIG. 2 is set in advance in the cavity 2 near the injection port 4 formed in the upper die 1a of the molding die. The insert member 12 is integrally formed of a synthetic resin in a substantially annular shape, has a resin and gas introduction port 13 of the same diameter as the injection port 4 formed in the central axis direction, and an annular groove 14 at the center of the outer peripheral surface. Are formed. Then, the insert member 12 is set while the upper surface 15 is arranged in contact with the inner surface of the upper mold 1a and the introduction port 13 is positioned so as to match the injection port 4.

Thereafter, the molten resin is injected from the injection nozzle into the injection port 4 of the upper mold 1a and the introduction port 13 of the insert member 12.
A predetermined amount is injected into the cavity 2 via. Then, when the inert pressurized gas 7 is injected into the molten resin in the cavity 2 from the same inlet 4 and the inlet 13, the molten resin is pushed out to the inner peripheral surface side of the cavity 2 by the gas pressure. It extends not only to each corner but also to the inside of the annular groove 14 while surrounding the outer peripheral surface of the insert member 12. afterwards,
When the mold is cooled and released, an assist grip 11 as a hollow injection molded product as shown in FIG. 1 is formed.

Since the insert member 12 is integrally provided in the assist grip 11 at a portion near the inlet 4, the wall thickness near the inlet 4 is substantially the same as that of the general portion, which is sufficient. Rigidity can be secured and high strength can be obtained.

Moreover, since the insert member 12 can be provided together during a series of injection moldings, the molding operation is easy.

Further, as shown in FIG. 3, the insert member 12 may have a flange portion 16 formed on the outer peripheral surface thereof to ensure the integrity with the molten resin.

As a further different insert member 12,
As shown in FIG. 4, a cylindrical portion 19 extending upward is provided on the upper portion of a substantially conical body 17 having a locking projection 18 on the inner peripheral surface of the introduction hole 13, and the upper die upper surface is provided with a cylindrical portion 19 on the upper end outer periphery. It is also possible to provide a brim portion 20 that engages with each other so as to obtain a firmly attached state to the upper die. After the molten resin is cooled and solidified, the entire cylindrical portion 19 is cut off as shown in FIG. 5, and the cap 21 that engages with the engaging projection 18 is inserted into the introduction hole 13 of the main body 17. It has become. Therefore, the introduction hole 13 is closed, the rigidity is further improved, and the appearance quality is also improved.

6 and 7 show a second embodiment of the present invention, in which an elbow rest 22 of an office chair is used instead of the assist grip.
It has been applied to. That is, the injection port for the molten resin or the pressurized gas is arranged near the lower surface of the upper portion 22a of the substantially annular elbow pad 22, and the cavity near the injection port is the same as the first embodiment in advance. Insert member 1
2 was set in advance and integrated with the molten resin at the time of pressurized gas injection. Therefore, also in this embodiment, the wall thickness in the vicinity of the injection port is secured, and the rigidity of the elbow pad upper portion 22a can be improved.

The insert member 12 is provided with a locking projection 23 on the inner peripheral surface of the introduction hole 13 as shown in FIG.
You may make it insert the cap 24 of another body.

In each of the above embodiments, the case where the injection port for the molten resin and the injection port for the pressurized gas are the same is shown, but they may be different. In this case, the injection port for the pressurized gas is provided. An insert member is provided. Further, the hollow injection molded product is not limited to the assist grip and the elbow rest.

[0021]

As is apparent from the above description, according to the present invention, since the portion of the molded product corresponding to the injection port can be made to have substantially the same thickness as the general portion by the insert member, the rigidity of the molded product can be improved. The decrease is prevented and sufficient strength is secured.

Further, since the insert member can be embedded in the molded product at the time of injection molding, the integral molding operation is easy.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an assist grip showing a first embodiment of the present invention.

FIG. 2 is a perspective view showing an insert member used in this embodiment.

FIG. 3 is a perspective view showing another example of the insert member.

FIG. 4 is a sectional view showing still another example of the insert member.

FIG. 5 is a cross-sectional view showing a state in which a cap is fitted and inserted into the insert member.

6 is a cross-sectional view taken along the line AA of FIG.

FIG. 7 is a perspective view showing a second embodiment of the present invention.

FIG. 8 is a cross-sectional view taken along the line AA of FIG. 7 showing a state in which the cap is fitted and inserted into the insert member.

FIG. 9 is an explanatory view showing a manufacturing process of a hollow injection molded product.

FIG. 10 is an explanatory view showing a manufacturing process of a hollow injection molded product.

FIG. 11 is a perspective view showing a conventional assist grip that is a molded product.

12 is a cross-sectional view taken along the line BB of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Mold 2 ... Cavity 4 ... Injection port 5 ... Molten resin 7 ... Pressurized gas 8, 11 ... Assist grip (hollow injection molded product) 12 ... Insert member 13 ... Inlet port 22 ... Elbow pad (hollow injection molded product)

Claims (2)

[Claims] 1. A hollow injection-molded article produced by injecting a predetermined amount of molten resin into a cavity of a mold and then injecting an inert gas into the molten resin from an injection port of the mold, wherein the hollow injection is performed. A hollow injection-molded article, wherein an insert member having a gas introduction port in the center is embedded in a portion of the molded article corresponding to the injection port. 2. Production of a hollow injection-molded article which is formed by injecting a predetermined amount of molten resin into a cavity of a mold and then injecting an inert pressurized gas into the molten resin from an injection port of the mold. In the method, in the cavity near the injection port of the pressurized gas, an insert member having a gas introduction port at the center is set in advance, and after the molten resin is injected into the cavity, the pressurized gas injection port and the gas introduction A method for producing a hollow injection-molded article, which comprises injecting a pressure gas from a mouth.