JP3040204B2 - Hollow resin injection molding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding apparatus for preventing a gas for molding a hollow portion from leaking in, for example, hollow injection molding of plastic.

[0002]

2. Description of the Related Art Conventionally, when manufacturing a resin molded product such as plastic by injection molding, a high-pressure gas is injected into the resin until the molten resin injected into the cavity solidifies, and a hollow portion is formed therein. There is known a method for forming a hollow resin molded product as formed.

[0003]

That is, as shown in FIG. 6, for example, a molten resin 54 is injected into a cavity 53 of a closed mold 51, 52, and the surface layer of the resin in contact with the surface of the cavity 53 starts to solidify. At this point, a hole is made by protruding the needle 56 of the gas injection member 55 into a part of the surface layer, and the high-pressure gas sent from the gas supply path 57 toward the inside of the molten resin 54 is to be injected from the hole. However, the high-pressure gas ejected toward the holes leaks from the mating surfaces of the molds 51 and 52, so that the hollow portion cannot be formed in a favorable state due to a decrease in gas pressure. There was a problem of adverse effects.

[0004]

Means for Solving the Problems] To achieve the foregoing object the present invention is seen extraordinary on the tip surface <br/> cavity of a gas injection member mounted in the mold, gas injection unit is on the front end face Provided
Is, this distal end surface of the gas injection member, hollow resin groove communicating with and calibration <br/> Viti Ri Do the recess toward the counter-cavity side while surrounding the gas injection unit is formed injection molded
In the device, the groove was formed wide on the cavity side.
Further, the tip surface of the gas injection member was substantially flush with the side surface of the cavity.

[0005]

When the molten resin enters the groove communicating with the cavity, the molten resin blocks the gas flow while surrounding the gas injection portion, so that gas leakage can be prevented. or,
By forming the cavity side of the groove portion wide, the problem of undercut at the time of mold release does not occur. In addition, the tip of the gas injection member
By making the end face almost the same as the cavity side face, the groove
Excised to protrude the cavity side (convex part) and dent
(Recess)

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the injection molding apparatus according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is an overall view of an injection molding apparatus for plastic molding, and FIGS. 2 and 3 show operation diagrams of a gas injection member. FIG. 2 shows a state in which the needle is projected, and FIG. 3 shows a state in which the needle is retracted.

As shown in FIG. 1, in an injection molding apparatus 1 for molding a hollow resin, a fixed mold body 3 attached to a fixed mold attachment plate 2 and a movable mold body 5 attached to a movable mold attachment plate 4 open. The mold can be closed, and both mold bodies 3, 5 in the mold closed state
A cavity 6 is formed between them. And fixed body 3
Is provided with a sprue 7 for filling the cavity 6 with a molten resin, while the movable mold body 5 is provided with a gas injection member 8 for forming a hollow portion. Not.

Further, an extruding plate 9 is provided on the movable mold mounting plate 4, and an extruding pin 10 whose tip faces the cavity 6 is attached to the extruding plate 9 to extrude a solidified product. It is designed to be able to be released.

As shown in FIG. 2, the gas injection member 8 can slide, for example, a first piston 14 slidable by a first cylinder portion 13 in an upper portion of a casing 12 and a second cylinder portion 15 of the first piston 14. Second piston 16 and the second
A needle 17 extending downward from the piston 16;
The needle 17 is slidable in a through hole 18 at a lower central portion of the casing 12. The opening at the lower surface of the through hole 18 is configured as a gas injection unit 19.

A gas passage 20 communicates with the through hole 18. The communicating portion between the gas passage 20 and the through hole 18 can be freely communicated with the needle 17 described above. That is, the communication is interrupted when the needle 17 moves further downward from the front surface of the communicating portion, and is opened when the needle 17 moves upward. I do. When the second piston 16 moves downward in the second cylinder portion 15, the needle 17 cuts off the communication with the gas passage 20 regardless of the position of the first piston 14. In the state shown in FIG. 2 in which the and the second piston 16 are both moved downward, the tip of the needle 17 is made to protrude into the cavity. The upstream of the gas passage 20 communicates with a gas supply passage 21 that supplies a high-pressure gas.

By the way, the front surface of the cylindrical portion at the tip of the casing 12 faces the cavity 6 as described above, and the front surface is substantially the same as the mating surface of the two mold bodies 3 and 5, that is, the side surface of the cavity 6. In addition to being on the same surface, a groove 23 is provided on the outer periphery thereof. That is, the groove 23 has a circular shape surrounding the central gas injection portion 19 and forms a recess toward the side opposite to the cavity.

The shape of the groove 23 is inclined so that the cavity 6 becomes wider and becomes narrower as seen from the drawing.

The operation and effect of the injection molding apparatus 1 of the present invention having the above configuration are as follows. First, a molten resin is filled from the sprue 7 into the cavity 6 in a state where the mold is closed. At this time, the tip of the needle 17 of the gas injection member 8 may be protruded into the cavity 6 in the state shown in FIG. 2, or only the second piston 16 is retracted from the state shown in FIG. The gas passage 20 may be retracted with the needle 17 closed. However, in the latter case, it is necessary to make a hole in the resin surface layer at the tip of the needle 17 as shown in FIG.

When the surface layer of the filled molten resin is in a semi-solid state, gas injection is started. That is, when the needle 17 is in the advanced state as shown in FIG. 2, the gas passage 20 is opened by retracting the needle 17 as it is,
Is in the middle position, the needle 1
7 is advanced to make a hole, and then retracted to
To release.

For this reason, the high-pressure gas waiting in the gas passage 20 flows into the molten resin through the through hole 18 and the gas injection portion 19. At this time, the inflowing gas tries to escape from the gap between the front surface of the casing 12 and the fixed main body 3 as shown in FIG. 4, but is blocked by the molten resin that has entered the surrounding groove 23 and cannot escape to the outside. . That is, the pressure of the high-pressure gas is not impaired, but effectively enters the resin. The gas that has entered moves inside the thick portion while pressing the unsolidified resin inside against the side surface of the cavity 6, and forms a hollow portion in the circular portion.

Next, after forming a hollow portion in such a state, the molded product 24 solidifies and is released. At this time, the cavity 6
The release is smooth due to the shape of the groove 23 whose side is widened. In addition, the shape of the groove portion 23 has an effect of not only facilitating mold release at the time of mold release, but also an effect of facilitating filling when filling the molten resin.

Further, in the molded product 24, the resin that has entered the groove portion 23 is solidified to form an overhanging piece 25 as shown in FIG. 5, but this overhanging piece 25 is subsequently cut off. Alternatively, a position that does not degrade the appearance quality may be selected and left as it is.

[0018]

As described above, the hollow resin injection molding apparatus according to the present invention can effectively prevent gas from leaking to the atmosphere through a gap, so that the gas pressure is reduced and the gas is lost. A hollow portion having a good shape can be formed without causing a situation. Therefore, the appearance quality of the product is not impaired. In addition, the filling and release of the molten resin can be performed smoothly by expanding the cavity side of the groove. further,
The tip surface of the gas injection member is almost flush with the side surface of the cavity
Therefore, cut out the protruding projecting piece formed in the groove and
The side surface of the tee can be formed in a shape without irregularities.

[Brief description of the drawings]

FIG. 1 is an overall view of an injection molding apparatus.

FIG. 2 is an operation diagram when a needle of a gas injection member protrudes.

FIG. 3 is an operation diagram of the gas injection member when the needle is retracted.

FIG. 4 is an enlarged view of a main part showing a gas injection state.

FIG. 5 is a perspective view of a molded product.

FIG. 6 is a sectional view showing the structure of a conventional gas injection member.

[Explanation of symbols]

 (1) Injection molding device (6) Cavity (8) Gas injection member (12) Casing (17) Needle (19) Gas injection part (23) Groove

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Teruo Ichikawa 1-10-1 Shinsayama, Sayama City, Saitama Prefecture Inside Honda Engineering Co., Ltd. (72) Inventor Riya Saito 1-10-1 Shinzayama, Sayama City, Saitama Prefecture (56) References JP-A-4-41212 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (2)

(57) [Claims] 1. A front end surface of the gas injection member mounted to the mold faces the cavity, the gas injection unit is provided on the distal end surface, the distal end surface of the gas injection member, surrounding the gas injection section In this state, the hollow resin having a concave portion facing the cavity and having a groove communicating with the cavity is formed.
In the outjecting molding device, the groove has a wide cavity side.
The injection molding apparatus of the hollow resin characterized in that formed. The distal end surface of claim 2 wherein said gas injection member to claim 1, characterized in that a side surface substantially the same surface of the cavity
Serial mounting an injection molding apparatus of the hollow resin.