JPH091593A - Blow injection molding machine - Google Patents

Abstract

PURPOSE: To prevent leakage of fluid around an inlet of a fluid nozzle pouring a pressurizing fluid. CONSTITUTION: A fluid nozzle 30 of which one end part faces a cavity 26 is fitted to a mold 20 composed of a fixed mold 21 and a movable mold 22. The fluid nozzle 32 is composed of a hollow main body 31 and an axle 32 inserted concentrically in the main body 31. Besides, an annular groove 37 is formed around an inlet 36 at a tip of the main body 31. After injecting a molten resin 29 into the cavity 26 through a sprue 27, a pressurizing fluid 34 is fed to the cavity 26 through a clearance 35 between the main body constituting the fluid nozzle 30 and its axle 32. At that time, the pressurizing fluid 34 likely to penetrate a slight clearance between a molding surface 20a of the mold 20 and a solidified layer 39 formed along the molding surface 20a is stopped by an annular rib 40 solidified in the annular groove 37.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow injection molding apparatus for injection molding a hollow molded body.

[0002]

2. Description of the Related Art In hollow injection molding, after a suitable amount of molten resin is injected into the cavity in a mold, a pressurized fluid is injected into the molten resin through a fluid nozzle provided in the mold,
The molten resin is expanded by a pressurized fluid to form a hollow portion. FIG. 5 shows a state in which a pressurized fluid is being injected, in which the molten resin 3 has already been injected into the cavity 2 in the mold 1, and the molten resin 3 is injected into the mold 1 by injection. The pressurized fluid 5 is injected from the nozzle 4. The fluid nozzle 4 comprises a hollow main body 6 and a mandrel 7 which is concentrically inserted into the main body 6, and the pressurized fluid 5 passes through a gap 8 between the main body 6 and the mandrel 7 to the nozzle tip side. It is adapted to be supplied into the cavity 2 from the opening (inlet) 9 of the. In this case, the fluid nozzle 4 is arranged so that the end surface of the main body 6 is aligned with the inner surface (molding surface) 1a of the mold 1.
Further, the mandrel 7 is arranged so as to slightly project from the main body 6, and the pressurized fluid 5 diffuses in all directions around the mandrel 7.

[0003]

By the way, the molten resin 3 injected into the cavity 2 is solidified at the same time as it contacts the molding surface 1a of the mold 1 as shown in FIG. At the time of injection, the solidified layer 10 having a predetermined thickness is formed along the molding surface 1a of the mold 1. And
The solidified layer 10 contracts in volume as the thickness thereof increases, and a slight gap is generated between the solidified layer 10 and the molding surface 1a of the mold 1.
As a result, a part of the pressurized fluid 5 supplied from the fluid nozzle 4 into the cavity 2 enters the above-mentioned slight gap around the injection port 9 of the fluid nozzle 4, causing a so-called fluid leak, which may result in The shape accuracy and the appearance quality of the molded product to be obtained are deteriorated.

For example, in Japanese Unexamined Patent Publication No. 5-84787, for the purpose of preventing fluid leakage at the flow end of the molten resin, a flow rate adjusting piece 12 is provided near the gate 11 of the mold 1 as shown in FIGS. Is provided and the recessed portion 13 formed in the flow rate adjusting piece 12 is used to intensively flow the molten resin 3 into a region having a large cavity volume, and then a pressurized fluid is injected into the molten resin 3 through the same flow rate adjusting piece 12. A supply method has been proposed, and by providing a flow rate adjusting piece 12 having the recess 13 appropriately provided at the tip of the fluid nozzle 4, it becomes possible to prevent the fluid leakage around the inlet. . However, in this case, since the relatively large flow rate adjusting piece 12 is exposed in the cavity 2, the trace of the removal remains as a large recess on the surface of the molded body, and the appearance quality of the obtained molded body is significantly deteriorated. It is not a fundamental measure.

The present invention has been made in view of the above-mentioned problems of the prior art, and its object is to provide a fluid around the inlet of a fluid nozzle without significantly deteriorating the appearance quality of the obtained molded product. It is to prevent leakage.

[0006]

In order to solve the above-mentioned problems, the present invention provides a hollow portion by injecting a pressurized fluid into a molten resin injected into a cavity in a mold through a fluid nozzle provided in the mold. In the hollow injection molding apparatus for forming the above-mentioned apparatus, an annular groove filled with the molten resin injected into the cavity is formed around the injection port at the tip of the fluid nozzle.

[0007]

In the hollow injection molding apparatus configured as described above, the molten resin filled in the annular groove at the tip of the fluid nozzle is solidified as it is, and is formed along the molding surface of the mold and the molding surface. The gap between the solidified layer and the solidified layer is sealed against the inlet of the fluid nozzle to prevent the pressurized fluid from entering the gap.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

3 and 4 show the overall structure of the hollow injection molding device according to the present invention. In these figures, 20 is a die, which is composed of a fixed die 21 and a movable die 22. The fixed mold 21 is mounted on a mounting plate 23 that is fixed in position, while the movable mold 22 is mounted on a mounting plate 24 that is driven in the left-right direction in the drawing by driving means (not shown).
When the movable die 22 is fitted to the fixed die 21 by the movement of the mounting plate 24, a cavity 26 is formed at the mating portion of the two. A sprue bush 28 having a sprue 27 is fitted to the fixed mold 21, and a molten resin 29 is passed through the sprue 27 from an injection nozzle (not shown) of a molding machine connected to the rear end of the sprue bush 28 to the cavity 26. (FIG. 4) will be injected.

A fluid nozzle 30 is fitted to the movable die 22 with one end thereof facing the cavity 26. This fluid nozzle 30 has the same basic structure as the conventional one (indicated by reference numeral 4 in FIG. 5). As shown in FIGS. 1 and 2, a hollow body 31 and a concentric body 31 are concentric with each other. And a mandrel 32 inserted in the. This fluid nozzle 3
A pressurized fluid 34 is pumped from the fluid source (not shown) through a hose 33 connected to the rear end of the 0, and the pressurized fluid 34 is supplied to the main body 31 and the mandrel 32.
It is adapted to be supplied into the cavity 26 from an injection port 36 on the tip side of the nozzle through a gap 35 between and (FIG. 1). The fluid nozzle 30 is arranged so that the end surface of the main body 31 is aligned with the molding surface 20a of the mold 20 and the mandrel 32 is slightly protruded from the main body 31, and the pressurizing fluid 35 is the above. It spreads around the mandrel 32 in all directions.

An annular groove 37 is formed at the tip of the main body 31 which constitutes the fluid nozzle 30, as shown in FIG. The annular groove 37 is formed to have a necessary minimum size so that the molten resin 29 injected into the cavity 26 can easily flow in. As an example, the annular groove 37 has a depth and a width of about 1 mm.

In order to perform hollow injection molding using the above-mentioned injection molding apparatus, first, as shown in FIG. 3, the movable die 22 is closed with respect to the fixed die 21 by the operation of the movable side mounting plate 24, and then the sprue 27. Through the cavity 26 molten resin 29
Is injected in an appropriate amount, and after the completion of injection of the molten resin 29 or before the completion of injection, the pressurized fluid 34 is pressure-fed to the fluid nozzle 30 from a fluid source (not shown). Then, the pressurized fluid 34
Is supplied through the gap 35 between the main body 31 and the mandrel 32 forming the fluid nozzle 30 into the cavity 26 from the injection port 36 on the tip side, and the molten resin 29 is cavitated by the pressure as shown in FIG. Expanded into 26, a hollow 38 is formed.

By the way, as shown in FIG. 1, the molten resin 3 injected into the cavity 2 has a molding surface 20 of a mold 20.
At the time when the pressurized fluid 34 is injected as soon as it contacts a, and the pressurized fluid 34 is injected, the solidified layer 39 having a predetermined thickness is formed along the molding surface 20a of the mold 20. The solidified layer 39 undergoes volume contraction as its thickness increases, and a small gap is formed between the solidified layer 39 and the molding surface 20a of the mold 20, and the pressurized fluid 34 injected from the fluid nozzle 30 into this small gap. Tries to get in. However, in this embodiment, since the annular groove 37 is formed at the tip of the fluid nozzle 30 (its main body 31), the molten resin 29 injected into the cavity 26 is also filled in the annular groove 37 and solidified as it is. Then, the annular rib 40 is formed. As a result, the gap between the molding surface 20a of the mold 20 and the solidified layer 39 formed along the molding surface 20a is reduced by the annular rib 40.
The pressurized fluid 34, which is sealed from the inlet 6 and is supplied from the inlet 36, does not enter the gap, or even if it enters, it is in a small area around the inlet 36.

That is, there is almost no fluid leakage around the injection port 36 of the fluid nozzle 30, and deterioration of the shape accuracy and appearance quality of the obtained molded product is prevented. Moreover, since the annular rib 40 is solidified in the small annular groove 37, the annular rib 40 only appears as a slight protrusion on the surface of the molded body.
Its presence is almost negligible compared to the recesses that occur when using (FIGS. 6 and 7). However, if the presence of the annular rib 40 poses a problem in terms of appearance, it may be removed by a cutting means, and the removal can be performed very easily.

In the above embodiment, the fluid nozzle 3
Although 0 is provided on the movable die 22, the present invention does not specify the location where the fluid nozzle 30 is provided.
For example, it may be provided in a fixed type, or may be provided in combination with a sprue bush, a gate or the like. In addition, the fixed mold 21
It goes without saying that the movable mold 22 and the movable die 22 may be arranged in the vertical direction instead of the horizontal arrangement in the above-described embodiment. Furthermore, as an injection molding device, a cavity 26
There is also one in which a sub-cavity is provided so as to communicate with the sub-cavity and a part of the molten resin is caused to flow into the sub-cavity when the pressurized fluid is injected to assist the formation of the hollow portion (for example,
However, the present invention can also be applied to such an injection molding apparatus.

[0016]

As described above in detail, according to the hollow injection molding apparatus of the present invention, it is possible to prevent fluid leakage around the injection port of the fluid nozzle, and to improve the shape accuracy and appearance quality. It is possible to stably obtain a molded article excellent in heat resistance. Moreover, since it is sufficient to simply form an annular groove at the tip of the fluid nozzle, the increase in equipment cost can be almost ignored, and its utility value is great.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a main part structure and a usage mode of a hollow injection molding apparatus according to the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG. 1;

FIG. 3 is a cross-sectional view showing the overall structure of the present hollow injection molding device.

FIG. 4 is a cross-sectional view showing a final stage of molding by the hollow injection molding device.

FIG. 5 is a cross-sectional view showing a main part structure and a usage mode of a conventional hollow injection molding device.

FIG. 6 is a cross-sectional view showing one implementation state of a conventional hollow injection molding method.

7 is a perspective view showing the shape of a flow rate adjusting piece used in the hollow injection molding method shown in FIG.

[Explanation of symbols]

 20 Mold 21 Fixed Type 22 Movable Type 26 Cavity 29 Molten Resin 30 Fluid Nozzle 31 Fluid Nozzle Body 32 Fluid Nozzle Mandrel 34 Pressurized Fluid 36 Fluid Nozzle Inlet 37 Annular Groove 39 Solidified Layer

Claims (1)

[Claims] 1. A hollow injection molding apparatus for forming a hollow portion by injecting a pressurized fluid into a molten resin injected into a cavity in a die through a fluid nozzle provided in the die, wherein the tip of the fluid nozzle is A hollow injection molding device, characterized in that an annular groove filled with the molten resin injected into the cavity is formed around the inlet.