JP3342032B2 - Pressurized fluid injection device for hollow injection molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressurized fluid injection device for hollow injection molding used for hollow injection molding for pressurizing a pressurized fluid into a molten resin in a mold. More particularly, the present invention relates to a pressurized fluid press-fitting device for hollow injection molding used for directly pressurizing a pressurized fluid into a mold space such as a sprue, a runner, and a mold cavity.

[0002]

2. Description of the Related Art Conventionally, in hollow injection molding in which a pressurized fluid is press-fitted into a molten resin injected into a mold, a pressure for hollow injection molding used to press-in a pressurized fluid directly into a mold space. 2. Description of the Related Art As a fluid press-fitting device, those disclosed in JP-B-48-41264 and JP-B-59-19017 are known.

A pressurized fluid press-fitting device for hollow injection molding disclosed in Japanese Patent Publication No. 48-41264 is as shown in FIG. 5, in which a rear end is connected to a pressurized fluid source and the inside is pressurized fluid. A thin cylindrical projection 102 serving as a passage 101 is provided so as to protrude and retreat into the mold 103. When the pressurized fluid press-fitting device for hollow injection molding is used, a molten resin is injected in a state where the projections 102 are projected into the mold 103, a pressurized fluid is press-fitted to form a hollow portion, and cooling and solidification are performed. Thereafter, the pressurized fluid is discharged from the hollow portion, and the protrusion 102
Is withdrawn from the mold 103 to take out the molding die.

[0004] A pressurized fluid press-fitting device for hollow injection molding disclosed in Japanese Patent Publication No. 59-19017 is as shown in FIG. 6, in which molten resin injected into a mold cavity 104 is guided. A valve 10 for opening and closing the pressurized fluid passage 101 by a cylinder device 106 in the middle of the resin passage 105.
7 is provided, and pressurized fluid is injected through the valve 107.

[0005]

However, these pressurized fluid press-fitting devices for hollow injection molding have the advantage that they can be easily provided in the required positions of one mold in the required number, but the following problems are encountered. There is such a problem.

[0006] In the case of the pressurized fluid press-fitting device for hollow injection molding disclosed in Japanese Patent Publication No. 48-41264, when the molten resin is injected, the molten resin flows back into the pressurized fluid passage 101 in the projection 102, and this pressurization is performed. There is a problem that the fluid passage 101 is clogged.

In the pressurized fluid press-fitting device for hollow injection molding disclosed in Japanese Patent Publication No. 59-19017, when the valve 107 is opened when pressurized fluid is press-fitted, molten resin flows from the opened valve 107 into the pressurized fluid passage 101. The pressurized fluid passage 101
There is a problem of clogging. Further, the pressurized fluid during press-fitting does not press-fit into the molten resin, but leaks out of the mold 103 through between the molten resin and the inner surface of the mold 103, so that a hollow portion cannot be formed or the hollow portion cannot be formed. There is also a problem that the required pressure in the section cannot be maintained and mold reproducibility deteriorates.

The present invention has been made in view of the above problems, and has as its object to prevent pressurized resin from flowing back into the pressurized fluid passage and to reliably pressurize the pressurized fluid into the molten resin. And

[0009]

Means taken in the present invention for this purpose will be described with reference to FIG. 1 corresponding to one embodiment.
In the present invention, a pressurized fluid passage 2 having a front end opening into the mold space 1 and a rear end connected to a pressurized fluid source (not shown).
In the vicinity of the opening on the side of the mold space 1, a core body 3 that can move in and out in the axial direction is inserted, leaving a gap around the opening through which the pressurized fluid flows but does not allow the molten resin to enter. Body 3
A pressurized fluid press-fitting device for hollow injection molding, wherein the pressurized fluid is press-fitted into the mold 4 and is advanced by the pressurized pressure of the pressurized fluid so that the tip can protrude into the mold space 1.

[0010]

According to the present invention, the mold space 1 of the pressurized fluid passage 2 is provided.
A gap is formed around the core 3 provided near the side opening to allow the pressurized fluid to flow therethrough but not allow the molten resin to enter, so that the pressurized fluid can be press-fitted through the gap. This is to prevent the molten resin from flowing back into the pressure passage 2.

On the other hand, the tip of the core 3 projects into the mold space 1 when the pressurized fluid is press-fitted. This is for guiding the fluid and for surely guiding the fluid into the molten resin.

The operation of guiding the pressurized fluid at the tip of the core 3 will be further described with reference to FIG.
As shown in the right side of FIG. 2, the pressurized fluid that has flowed out of the mold 4 is guided into the mold 4 along the tip of the core body 3 and further proceeds into the molten resin. The fluid can be pressed into the vicinity of the center in the molten resin. Core body 3 protruding against this
When the pressure fluid does not exist, as shown on the left side of FIG. 2, the pressurized fluid that has flowed out of the pressurized fluid passage 2 proceeds further into the molten resin after being guided toward the inner surface of the mold 4. . Therefore, the pressurized fluid easily enters between the molten resin and the inner surface of the mold 4, and the pressurized fluid leaks easily.

[0013]

FIG. 1 is a longitudinal sectional view showing a first embodiment of the present invention. A mold 4 comprises a stationary mold 4a and a movable mold 4b, and a mold for hollow injection molding is provided on the movable mold 4b side. A pressurized fluid injection device is provided. However, the pressurized fluid press-fitting device for hollow injection molding does not have to be provided on the movable mold 4b side, but may be provided on the fixed mold 4a side.

The pressurized fluid press-fitting device for hollow injection molding will be further described.

A pressurized fluid press-fitting device for hollow injection molding includes a pressurized fluid passage 2 formed in a mold 4 (movable mold 4b in this embodiment) and a core inserted in the pressurized fluid passage 2. The body 3 is a main component.

The pressurized fluid passage 2 has a front end opening into the mold space 1 and a rear end connected to a pressurized fluid source (not shown). Pressurized fluid passage 2 in this embodiment
Has an opening in a mold cavity which is a mold space 1 formed between the fixed mold 4a and the movable mold 4b. However, the present invention is not limited to this, and may be a space inside the mold 4 such as a sprue or a runner.

At the tip of the pressurized fluid passage 2, a core 3 is inserted around the periphery so as to be able to advance and retreat in the axial direction, leaving a gap with a width that allows the pressurized fluid to flow but does not allow the molten resin to enter. ing.

The axial length and width of the gap around the core 3 are determined according to the viscosity of the molten resin, the pressure of the molten resin in the mold 4, and the like. ~ 50m
m, preferably 3-20 mm, width 0.02-0.2
mm, preferably 0.05 to 0.15 mm.

Since the state of the gap is set by the difference between the diameter of the pressurized fluid passage 2 and the outer diameter of the core 3, it is possible to repeatedly machine with a normal precision machine tool with good reproducibility. .

The gap may be left over the entire circumference of the core body 3, but the peripheral wall surface of the pressurized fluid passage 2 and / or the core body 3 may be formed so as to have the width and the axial length of the gap. The outer peripheral surface is provided with about 1 to 4 grooves, and is discontinuous in the core 3 circumferential direction.
Can be formed in an arc shape when viewed from the inner surface side. This groove is generally formed parallel to the central axis of the core 3, but can also be formed diagonally.

The core body 3 may have the same diameter over the entire length, but as shown in the figure, it is preferable that the diameter of the front end part is large and the diameter of the rear part is slightly smaller and is stepped. preferable. With this configuration, it is possible to prevent an increase in the press-fitting resistance of the pressurized fluid due to the narrow gap portion being unnecessarily long. When this stepped core 3 is used,
The axial length of the large diameter portion and the amount of forward movement of the core 3 are determined so that the core 3 does not protrude into the mold space 1 beyond the large diameter portion of the core 3 when the core 3 described later advances.

The pressurized fluid passage 2 has a smaller diameter near the mold space 1 and a larger diameter behind the mold space 1. A pressure receiving portion 5 having a large area is provided integrally with the core body 3 and housed therein. The pressure receiving portion 5 is provided for receiving the pressure of the pressurized fluid supplied from the rear thereof, thereby facilitating the advance of the core body 3 by the press-in pressure of the pressurized fluid, and is not essential. Preferably, it is provided.

The cross-sectional area of the pressure receiving section 5 is preferably determined according to the properties of the pressurized fluid to be used, particularly the viscosity. As the pressurized fluid, a gas or liquid that does not react with the resin used at the temperature and pressure at the time of injection is used. Specifically, for example, an inert gas such as nitrogen or a gas such as air, high-temperature high-pressure water or liquid paraffin And the like. Generally, the cross-sectional area of the pressure receiving portion 5 is preferably at least twice the minimum cross-sectional area of the core 3. In particular, when a gas such as nitrogen is used as the pressurized fluid, it is preferably at least 10 times the minimum sectional area of the core 2.

When the pressurized fluid is press-fitted into the mold 4, the core 3 is pushed forward by the press-fitting pressure of the pressurized fluid, and its forward end projects into the mold space 1.

The amount of protrusion of the core body 3 into the mold space 1 when the core body 3 moves forward is determined by the distance between the mold space 1 in which the core body 2 protrudes in the direction in which the core body 3 protrudes (hereinafter referred to as “applicable mold space distance”). It is preferable to set the distance between 0.01 mm or more and 1/2 or less of the mold space. Generally, it is preferred to be between 0.05 and 5 mm.

In the figure, reference numeral 6 denotes an O-ring for sealing.

The hollow injection molding by the mold 4 having the above-described pressurized fluid press-fitting device for hollow injection molding can be performed in the same manner as in the prior art. That is, the molten resin is injected, and at the same time or after the injection of a predetermined amount of the molten resin, a pressurized fluid is press-fitted to form a hollow portion, and the resin in the mold 4 is cooled and solidified, and the resin in the hollow portion is cooled. After the pressurized fluid is discharged from the hollow portion, the mold 4 is opened and the hollow product is taken out.

The pressurized fluid can be discharged from the hollow portion by flowing the pressurized fluid back through the pressurized fluid passage 2. The pressurized fluid may be discharged from the hollow portion by cutting off the connection between the pressurized fluid passage 2 and the pressurized fluid source and opening the pressurized fluid passage 2 to the atmosphere. If the connection 2 is switched from a pressurized fluid source to a collection container (not shown), the pressurized fluid can be collected and reused.

In discharging the pressurized fluid in the hollow portion, whether the pressurized fluid in the hollow portion is discharged to the atmosphere or in a collecting container, the pressurized fluid in the pressurized fluid passage 2 is pressed by the pressure of the pressurized fluid flowing backward. Then, the core body 3 retreats. The core 3 is
The tip surface may be retracted until it reaches a position substantially coincident with the inner surface of the mold 4 or a position slightly retracted from the inner surface of the mold 4, but the tip portion also projects into the mold space 1 at the time of retreat. Is preferred. If the leading end of the core body 3 projects into the mold space 1 even during retreat, the above-described pressurized fluid guiding action can be obtained more reliably.

FIG. 3 shows a second embodiment of the present invention, which is substantially the same as that of the first embodiment described above, except that the pressurized fluid passage 2 is provided around the opening of the mold space 1 side. It differs from that of FIG. 1 in that the annular convex portion 7 is formed and that the tip of the core body 3 is gradually narrowed in the tip direction.

The annular convex portion 7 prevents the pressurized fluid flowing out of the pressurized fluid passage 2 from flowing along the inner surface of the mold 4 without following the core 3 projecting into the mold space 1. It is to prevent. Therefore, the provision of the annular projection 7 can more reliably prevent the pressurized fluid from leaking.

If the tip of the core 3 is gradually narrowed in the tip direction, the molten resin in the advancing direction is easily pushed away when the core 3 advances, and the advancing operation of the core 3 is facilitated. Become. Examples of the shape of the tip of the core body 3 include:
Conical, hemispherical, and polygonal pyramids can be mentioned.

FIG. 4 shows a third embodiment of the present invention, in which the pressurized fluid passage 2 is constituted by a cylindrical body 8 inserted into a mold 4, and the distal end of the cylindrical body. The point that the portion protrudes into the mold space 1 is different from that of FIG.

As described above, when the pressurized fluid passage 2 is constituted by the cylindrical body 8 and its tip is projected into the mold space 1, the annular convex portion 7 described in FIG. 8 has the advantage that it can be easily configured. Even when this cylindrical body 8 is used, the distal end of the cylindrical body 8 does not protrude into the mold space 1 and the distal end surface of the cylindrical body 8 coincides with the inner surface of the mold 4. It can also be in position.

[0035]

The present invention is as described above, and has the following effects.

(1) Since the opening of the pressurized fluid passage 2 on the mold space 1 side is formed by a gap through which the pressurized fluid can flow but the molten resin cannot enter, the pressurized fluid passage due to the backflow of the molten resin. Clogging can be prevented.

(2) The pressurized fluid is guided into the mold 4 by the tip of the core 3 projecting into the mold space 1 at the time of press-fitting. 4 can be prevented from leaking between the inner surface and the pressurized fluid can be reliably injected into the deep portion of the molten resin.

(3) Since the leakage of the pressurized fluid can be prevented as described above, the necessary hollow portion can be reliably formed, and
It is possible to reliably maintain the pressure of the pressurized pressurized fluid and obtain a hollow injection mold having excellent mold reproducibility.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of the present invention.

FIG. 2 is an explanatory view of an operation of a tip end of a core body protruding into a mold space.

FIG. 3 is a longitudinal sectional view showing a second embodiment of the present invention.

FIG. 4 is a longitudinal sectional view showing a third embodiment of the present invention.

FIG. 5 is an explanatory diagram of a conventional technique.

FIG. 6 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

 Reference Signs List 1 mold space 2 pressurized fluid passage 3 core body 4 mold 4a fixed mold 4b movable mold 5 pressure receiving part 6 O-ring 7 annular convex part 8 cylindrical body

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-87224 (JP, A) JP-A-3-224719 (JP, A) JP-A-5-177668 (JP, A) JP-A-5-177668 177667 (JP, A) Japanese Utility Model Application Hei 4-54815 (JP, U) Japanese Utility Model Application Hei 4-47517 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/00-45 / 84

Claims (5)

(57) [Claims] 1. A pressurized fluid is allowed to flow through a mold space near a mold space side opening in a pressurized fluid passage connected to a pressurized fluid source. A core body that can move forward and backward in the axial direction is inserted, leaving a gap that does not allow penetration, and this core body, when pressurized fluid is pressed into the mold,
A pressurized fluid press-fitting device for hollow injection molding, wherein the pressurized fluid can be advanced by a pressurized pressure of the pressurized fluid and a tip thereof can protrude into a mold space. 2. The pressurized fluid passage has a small diameter in the vicinity of an opening on the mold space side and a large diameter in a rear portion thereof. 2. The pressurized fluid press-fitting device for hollow injection molding according to claim 1, wherein a pressure-receiving portion having a cross-sectional area of at least twice is provided integrally with the core. 3. The pressure for hollow injection molding according to claim 1, wherein the tip of the core projecting into the mold space at the time of press-in of the pressurized fluid is gradually narrowed in the tip direction. Fluid injection device. 4. A pressurized fluid passage at least in the vicinity of a mold space side opening is formed of a tubular body inserted into a mold, and a tip of the tubular body projects into the mold space. The pressurized fluid press-fitting device for hollow injection molding according to any one of claims 1 to 3, wherein: 5. The pressurized fluid press-fitting device for hollow injection molding according to claim 1, wherein the tip of the core body projects into the mold space even when the core body is retracted.