JPH11226987A - Pressurized fluid press-in / out device for hollow injection molding - Google Patents

Abstract

(57) [Summary] (Modifications) [Problem] A pressurized fluid can be discharged from a hollow portion in a short time, and a problem of leakage of the pressurized fluid between a molten resin and an inner surface of a mold can be solved. Provided is a pressurized fluid press-in / out device for hollow injection molding in which a molded body after cooling is easily taken out of a mold. SOLUTION: The tip is a cavity 1a of an injection molding die 1.
A shaft core 3 is inserted into a sleeve 2 fixedly opened in the axial direction so as to be able to advance and retreat in the axial direction, and a pressurized fluid formed by an inner wall 2 b of the sleeve 2 and an outer wall 3 b of the shaft core 3. The molten resin P injected into the cavity 1a from the passage 4
A pressurized fluid press-fitting for hollow injection molding, in which a pressurized fluid is pressurized and the molten resin P is pressed against the surface of the cavity 1a to form a compact having a hollow portion, and after the compact is cooled, the pressurized fluid in the hollow portion is discharged. Discharge device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pressurized fluid press-in / out device for hollow injection molding. More specifically, a pressurized fluid is injected into the molten resin injected into the cavity of the injection mold, and the molten resin is pressed against the cavity surface to form a molded body having a hollow portion. The present invention relates to a pressurized fluid press-in / discharge device used in a hollow injection molding method for discharging a pressurized fluid in a section, then opening a mold and taking out a molded body.

[0002]

2. Description of the Related Art Heretofore, as a method of molding an injection molded article having a hollow portion, a sufficient amount of molten resin to fill a cavity of an injection mold has been injected into a cavity or while being injected. A pressurized fluid is pressed into the molten resin inside, and the molten resin is pressed against the cavity surface to form a molded body having a hollow portion. After the molded body is cooled, the pressurized fluid in the hollow portion is discharged, and then the mold is opened. There is known a method of taking out a molded body by using the method. Furthermore, as a method of molding an injection-molded article having a large hollow portion, following the step of injecting a molten resin into the cavity and then press-fitting a pressurized fluid, the mold or a part thereof is retracted to increase the cavity volume. There is also known a method for causing such a situation.

As a pressurized fluid press-in / discharge device used in these molding methods, for example, Japanese Unexamined Patent Publication No.
177667 and JP-A-5-177668 disclose a gap between a cylindrical sleeve having an inner diameter of a tip portion smaller than a rear portion thereof and a shaft inserted in the sleeve as a pressurized fluid passage, In addition, the mold part in contact with the outer wall of the tip of the sleeve is cut out to form an annular groove, and while preventing leakage of the pressurized fluid between the molten resin and the mold inner surface,
By the forward and backward movement of the shaft core in the axial direction, the pressurized fluid passes between the inner wall of the sleeve and the outer wall of the shaft, but is variable between a narrow state and an expanded state in which the molten resin does not enter. The axle is advanced to make the pressurized fluid passage narrow, and the tip of the protruded portion is protruded into the mold cavity. On the other hand, there is disclosed a method of discharging a pressurized fluid in a hollow portion by retracting a shaft core to a rear portion of a sleeve so as to expand a pressurized fluid passage when discharging a pressurized fluid.

However, this pressurized fluid press-in / discharge device cannot discharge the pressurized fluid from the hollow portion in a short time, and further pressurizes the pressurized fluid to be injected into the molten resin injected into the mold cavity. A part of the fluid still leaks between the molten resin and the inner surface of the mold, resulting in poor appearance of the obtained molded body, or lack of pressurized fluid pressure in the hollow part to obtain a molded body as designed. There was a problem that it could not be done.

On the other hand, in order to solve these problems, Japanese Unexamined Patent Publication No. Hei 7-290508 discloses a cylindrical sleeve having a tip portion having an inner diameter smaller than that of a central portion, and a sleeve inserted into the sleeve. A gap between the outer diameter of the center portion of the central portion on the tip end side and a shaft core having a small diameter is used as a pressurized fluid passage, and the tip portion of the sleeve is provided so as to protrude from the mold cavity surface,
An annular groove is provided in the outer wall at the tip to prevent leakage of the pressurized fluid between the molten resin and the mold inner surface, and the sleeve inner wall and the shaft outer wall are formed by advancing and retracting the shaft in the axial direction. Between the narrowed state and the expanded state where the pressurized fluid passes but does not allow the molten resin to penetrate.When pressurized fluid is press-fitted, the shaft tip is retracted to match the sleeve tip and pressurized. A method is disclosed in which the pressurized fluid is press-fitted while the fluid passage is narrowed, and when the pressurized fluid is discharged, the shaft is advanced to expand the pressurized fluid passage and discharge the pressurized fluid in the hollow portion. .

However, this pressurized fluid press-in / discharge device can discharge the pressurized fluid from the hollow portion in a short time,
In addition, although the pressurized fluid can be prevented from leaking, there is a new problem that when the molded body after cooling is removed from the mold, the annular groove becomes an obstacle and the molded body cannot be easily removed.

[0007]

DISCLOSURE OF THE INVENTION In view of the above-mentioned prior art, the present invention can discharge a pressurized fluid from a hollow portion in a short time, and can apply a pressurized fluid between a molten resin and a mold inner surface. An object of the present invention is to provide a pressurized fluid press-in / out device for hollow injection molding, which has no problem of leakage of a pressurized fluid and easily removes a compact after cooling from a mold.

[0008]

According to the present invention, an axial center is inserted in a sleeve fixedly opened with its tip end opened in a cavity of an injection mold so as to be able to advance and retreat in the axial direction. A pressurized fluid is injected into the molten resin injected into the cavity from the pressurized fluid passage formed by the inner wall and the outer wall of the shaft, and the molten resin is pressed against the cavity surface to form a molded body having a hollow portion. A pressurized fluid press-in / discharge device for hollow injection molding for discharging a pressurized fluid in a hollow portion after cooling a molded body, wherein the sleeve has a tip surface provided substantially flush with the cavity surface; The inner diameter of the portion is smaller than the inner diameter of the intermediate portion, the intermediate portion forms a space for the pressurized fluid passage including the pressurized fluid port, and the distal end surface has an angle of -2 to +2 degrees with respect to the axial direction of the sleeve. An annular groove with draft side walls in the range of On the other hand, the shaft core has an outer diameter at the distal end portion and the inner wall at the distal end portion of the sleeve, which can form a narrow gap through which pressurized fluid can pass but molten resin cannot enter. The outer diameter of the middle portion is smaller than the outer diameter of the front end portion, and the rear end is connected to the shaft drive mechanism, and by the operation of the shaft drive mechanism, the front end of the shaft becomes
Between the inside of the distal end of the sleeve and the inside of the cavity, a retracted state inserted into the distal end of the sleeve when pressurized fluid is inserted, and an advanced state protruded into the cavity when the pressurized fluid is discharged can be advanced and retracted. The gist of the invention is a pressurized fluid press-in / out device for hollow injection molding.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings, but the present invention is not limited to the examples described below unless departing from the gist thereof. 1 and 2
1 is a schematic cross-sectional view showing an embodiment of a pressurized fluid press-in / discharge device for hollow injection molding of the present invention, and FIG. 1 shows a state when pressurized fluid is press-fitted into a molten resin injected into a mold cavity. FIG. 2 shows a state in which the pressurized fluid in the hollow portion of the molded body after the molten resin is cooled and solidified is discharged.

In the pressurized fluid press-in / out device for hollow injection molding according to the present invention, the front end is opened in the cavity 1a of the injection molding die 1 and fitted into a space formed in the die 1 to fix the cavity. A cylindrical shaft core 3 is inserted into the provided cylindrical sleeve 2 so as to be able to advance and retreat in the axial direction, and an inner wall 2b of a distal end portion 2a of the sleeve 2 and an outer wall of the distal end portion 3a of the shaft core 3. 3b, pressurized fluid is injected into the molten resin P injected into the cavity 1a, and the molten resin P is pressed against the surface of the cavity 1a to form a molded body having a hollow portion Ma. M has a function of discharging the pressurized fluid in the hollow portion Ma after cooling the molded body M.

In the present invention, the sleeve 2 has a tip surface 2c substantially flush with the cavity 1a surface, the inner diameter of the tip 2a is smaller than the inner diameter of the intermediate portion 2f, and the tip 2 has a smaller inner diameter. The portion 2a has an inner wall 2b and a distal end outer wall 3b of the shaft core 3 to form a narrow gap through which pressurized fluid can pass but molten resin cannot enter.
The intermediate portion 2f having a larger inner diameter enables the formation of a wider gap between the inner wall and the intermediate portion outer wall of the shaft core 3 so that the pressurized fluid can be quickly discharged.

The sleeve 2 has an intermediate portion 2f.
Form a pressurized fluid passage space 6 including a pressurized fluid port 5 communicating with a pressurized fluid supply source (not shown). The pressurized fluid supplied from is introduced into the pressurized fluid press-in / discharge device of the present invention,
Further, it has a function for discharging the pressurized fluid in the hollow portion Ma of the molded body M through the pressurized fluid press-in / discharge device of the present invention. The rear end 2g of the sleeve 2 constitutes a cylinder portion 7a of a shaft center movable mechanism 7, which will be described later.

Furthermore, in the present invention, the sleeve 2
An annular groove 2d is formed in the tip end surface 2c of the annular groove 2d, thereby preventing the pressurized pressurized fluid from leaking between the molten resin and the inner surface of the mold, and the side wall 2 of the annular groove 2d.
The draft of e was set in the range of -2 to +2 degrees, preferably -1 to +1 degrees with respect to the axial direction of the sleeve, to prevent leakage of the pressurized fluid between the molten resin and the mold inner surface. Above, the molded article after cooling is easily taken out of the mold. That is, when the molten resin intrudes into the annular groove 2d, even if the pressurized pressurized fluid flows between the molten resin and the inner surface of the mold, the molten resin entering the annular groove 2d becomes a barrier. Then, the flow of the pressurized fluid is prevented from flowing forward, and by setting the draft of the side wall 2e within the above range, there is no resistance in the removal direction in removing the molded body from the mold after cooling. Is what you do.

Here, the planar shape of the annular groove 2d is generally circular, but may be polygonal or the like. It may be provided. The width and depth are not particularly limited, and are appropriately determined by the viscosity of the molten resin P in the cavity 1a, the resin pressure, the pressure of the pressurized fluid to be injected, and the like.
Generally, the width is about 0.5 to 10 mm, particularly 1 to 10 mm.
It is preferably about 3 mm, and the depth is 0.5 to 10 mm.
It is preferably about mm, especially about 1 to 5 mm.
And the ratio of the width at the bottom to the depth is 0.05 to
It is preferably about 5, particularly about 0.1 to 1.
The draft of the side wall 2e is taken as an angle connecting the start end and the end of the side wall 2e, and the same applies when a step or the like is provided therebetween.

On the other hand, according to the present invention, the outer diameter of the tip 3a of the shaft core 3 is equal to the inner wall 2b of the tip of the sleeve 2.
Thus, a narrow gap through which the pressurized fluid can pass but the molten resin cannot enter can be formed, and the outer diameter of at least the tip 3a side of the intermediate portion 3c is made smaller than the outer diameter of the tip 3a. The tip 3a having a larger diameter allows the formation of a narrow gap between the outer wall 3b and the inner wall 2b at the tip of the sleeve 2 through which pressurized fluid can pass but molten resin cannot enter.
Also, an intermediate portion 3c having a smaller outer diameter on the tip portion 3a side.
Enables a wider gap to be formed between the outer wall and the inner wall of the intermediate portion of the sleeve 2 so that the pressurized fluid can be quickly discharged.

Here, the gap and the axial length of the narrow gap are appropriately determined by the viscosity of the molten resin P in the cavity 1a, the resin pressure, the pressure of the pressurized fluid to be injected, and the like. The gap is preferably about 0.02 to 0.2 mm, particularly about 0.03 to 0.1 mm, and the axial length is about 1 to 20 mm, particularly 3 to 10 mm.
It is preferred to be on the order of magnitude.

The outer diameter of the intermediate portion 3c excluding the tip portion 3a may be the same as the outer diameter of the tip portion 3a, but is shown in FIG. It is preferable that the outer diameter is approximately the same as the outer diameter of the distal end portion 3a. or,
The tip shape of the tip portion 3a is not particularly limited, and may be a flat shape. However, in view of the ease of projection into the cavity 1a in the forward state at the time of discharging the pressurized fluid, as shown in the figure, It is more preferable that the shape is a conical shape, a truncated cone shape, a pyramid shape, a truncated pyramid shape or the like. The rear end 3d of the shaft core 3 constitutes a piston portion 7b of a shaft center movable mechanism 7 described later, and is connected to a shaft center drive mechanism 8 described later.

The pressurized fluid press-in / out device for injection molding according to the present invention operates by the operation of the shaft driving mechanism 8.
Between the tip 2a of the sleeve 2 and the cavity 1a of the mold 1 when the pressurized fluid is press-fitted, the tip 3a is inserted into the tip 2a of the sleeve 2 so as to be in a retracted state. At the time of discharge, it can be moved forward and backward to be in a forward state protruded into the cavity 1a.

Here, the position of the tip of the tip 3a of the shaft core 3 in the retracted state at the time of pressurized fluid press-fitting is determined by the position of the cavity
It may be flush with the front end surface 2c of the sleeve 2 without projecting into the inside of the sleeve 2. However, in order to ensure the press-fitting of the pressurized fluid into the molten resin P, it is necessary to project it slightly. Preferably it is. Further, the shaft core 3 in the forward state at the time of discharging the pressurized fluid
Of the tip 3a is projected into the cavity 1a, and the intermediate portion 3c on the tip 3a side is
In the distal end portion 2a.

In the present invention, when the shaft core 3 is advanced and retracted in the axial direction, the rear end 2g of the sleeve 2 constitutes a cylinder portion 7a so that the pressurized fluid passage space 6 is sealed from the outside. And the rear end 3d of the shaft core 3 is connected to the shaft center moving mechanism 7 constituting the piston portion 7b sliding in the cylinder portion 7a and the piston portion 7b of the shaft center moving mechanism 7. A piston 8b is provided for moving the piston portion 7b forward and backward, and a shaft drive mechanism 8 including the cylinder 8a. In the figure, 7c is
This is an O-ring provided on the outer periphery of the piston portion 7b.

At the time of pressurized fluid injection, the piston 8b of the shaft drive mechanism 8 is retracted, and the shaft core 3 is retracted through the piston portion 7b of the shaft movable mechanism 7, so that the tip 3
a is inserted into the distal end portion 2a of the sleeve 2, and a narrow gap between the distal end inner wall 2b of the sleeve 2 and the distal end outer wall 3b of the shaft core 3 through which pressurized fluid passes but molten resin cannot enter. On the other hand, at the time of discharging the pressurized fluid, the piston 8b of the shaft drive mechanism 8 is advanced, the shaft 3 is advanced through the piston portion 7b of the shaft movable mechanism 7, and the tip 3a is moved into the cavity 1a. In this state, the inner wall 2b of the distal end portion of the sleeve 2 and the outer wall of the intermediate portion of the shaft core 3 form a wider gap through which the pressurized fluid can be quickly discharged.

The pressurized fluid press-in / out device for hollow injection molding of the present invention described in detail above is disclosed, for example, in Japanese Patent Application Laid-Open No. 6-339950.
It is incorporated in a conventionally known hollow injection molding apparatus described in Japanese Patent Application Laid-Open No. H10-163, etc., and is suitably used particularly for molding a large-sized hollow injection molded article.

[0023]

According to the present invention, the pressurized fluid can be discharged from the hollow portion in a short time, and there is no problem of leakage of the pressurized fluid between the molten resin and the inner surface of the mold. Further, it is possible to provide a pressurized fluid press-in / discharge device for hollow injection molding, in which a molded body after cooling can be easily taken out of a mold.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an embodiment showing a state in which a pressurized fluid is injected into a molten resin injected into a mold cavity in a pressurized fluid injection device for hollow injection molding of the present invention. .

FIG. 2 shows an example of a state in which a pressurized fluid in a hollow portion of a molded body after a molten resin is cooled and solidified is discharged in a pressurized fluid press-in / discharge device for hollow injection molding of the present invention. 1 is a schematic sectional view.

[Explanation of symbols]

 Reference Signs List 1; mold 1a; cavity 2; sleeve 2a; tip 2b; tip inner wall 2c; tip 2d; annular groove 2e; annular groove side wall 2f; middle 2g; Front end outer wall 3c; front end side of middle part 3d; rear end 4; pressurized fluid passage 5; pressurized fluid port 6; space for pressurized fluid passage 7; O-ring 8; shaft drive mechanism 8a; cylinder 8b; piston P; molten resin M; molded body Ma;

Claims (1)

[Claims] An axial core is inserted in a sleeve fixedly opened with its tip end into a cavity of an injection molding die so as to be able to advance and retreat in the axial direction, and an inner wall of the sleeve and an outer wall of the axial core are provided. From the pressurized fluid passage formed by, pressurized fluid is injected into the molten resin injected into the cavity, and the molten resin is pressed against the cavity surface to form a molded body having a hollow portion. A pressurized fluid press-fitting / discharging device for hollow injection molding for discharging pressurized fluid in a portion, wherein the sleeve has a tip surface substantially flush with the cavity surface, and an inner diameter of the tip portion is an inner diameter of an intermediate portion. It is made smaller, the middle part forms a space for pressurized fluid passage including a pressurized fluid port,
In addition, the tip surface is -2 to +2 in the axial direction of the sleeve.
An annular groove having a side wall with a draft angle in the range of degrees is drilled.On the other hand, the shaft core has an outer diameter at the distal end thereof and an inner wall at the distal end of the sleeve, and pressurized fluid passes therethrough, but molten resin does not It is possible to form a narrow gap that can not enter, the outer diameter of the middle part on the tip side is smaller than the outer diameter of the tip part, the rear end is connected to the shaft drive mechanism, and the shaft drive mechanism With this operation, the distal end of the shaft core is inserted into the distal end of the sleeve between the distal end of the sleeve and the inside of the cavity when the pressurized fluid is press-fitted, and protrudes into the cavity when the pressurized fluid is discharged. A pressurized fluid press-in / discharge device for hollow injection molding, wherein said pressurized fluid press-in / discharge device is configured to be capable of moving forward and backward to a predetermined forward state.