JP2002234055A - Gas nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cheaply provide a gas nozzle simple in structure which can charge and discharge compressed gas safely. SOLUTION: The main body 35 of a needle 33 is inserted forward/backward moveably into a sleeve 15. When the compressed gas is charged into a molten resin in the cavity 7 of a mold 5 through a compressed gas passage 43 formed between the main body 35 and the sleeve 15, by making the compressed gas introduced from a compressed gas introduction pipe 31 into an adapter 21 act on the large-diameter head part 37 of the needle 33, the needle 33 is advanced toward the cavity 7. When the charge of the compressed gas is stopped, the needle 33 is retracted by the pressure of the compressed gas in the cavity 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a gas nozzle used for gas injection molding of a hollow resin molded article having a hollow portion therein.

[0002]

2. Description of the Related Art When a hollow resin molded product is subjected to gas injection molding, after a molten resin is injected into a cavity of a mold, a pressurized gas is injected into the molten resin from a gas nozzle.

In general, the basic structure of such a gas nozzle for forming a hollow portion is such that a needle is fitted in a hollow sleeve attached to a mold, as disclosed in, for example, Japanese Patent Application Laid-Open No. 8-207082. A pressurized gas passage having an annular cross section is formed between the needle and the sleeve by being inserted, and the pressurized gas is pressed into the molten resin in the cavity of the mold via the pressurized gas passage. ing.

As an improved type of the gas nozzle having the basic configuration as described above, as disclosed in Japanese Patent Application Laid-Open No. 5-177667, a needle is inserted into a sleeve so as to be able to advance and retreat, and when pressurized gas is press-fitted, the needle is inserted. While moving forward, narrowing the cavity-side opening of the pressurized gas passage to prevent molten resin from entering the sleeve,
There is also known a gas nozzle in which the needle is retracted to open the cavity-side opening of the pressurized gas passage so that the press-in gas is quickly discharged from the hollow portion of the hollow resin molded product.

[0005]

By the way, in the process of repeatedly performing gas injection molding of a hollow resin molded product, volatile components in the molten resin enter the pressurized gas passage between the needle and the sleeve and become sticky. A tar-like semi-solidified state may occur, and if the tar-like semi-solidified material is clogged in the pressurized gas passage, it will hinder the press-in and discharge of the pressurized gas.

As a countermeasure against this problem, if the needle is inserted into the sleeve so as to be able to advance and retreat as in the above-mentioned publication, the volatile component entering the sleeve is moved by the advance and retreat operation of the needle, and the tar is removed. It is possible not to give a margin for a semi-solid state. However, in this publication, the needle is connected to the piston rod of the hydraulic cylinder and the needle is advanced and retracted by the expansion and contraction operation of the hydraulic cylinder. Cost increases.

The present invention has been made in view of the above points, and an object of the present invention is to provide a gas nozzle capable of stably injecting and discharging pressurized gas with a simple structure at a low cost. .

[0008]

In order to achieve the above object, the present invention is characterized in that the needle is automatically advanced and retracted by the gas pressure at the time of pressurized gas injection and discharge.

Specifically, according to the present invention, a needle is inserted into a hollow sleeve attached to a mold to form a pressurized gas passage having an annular cross section between the needle and the sleeve. The following solution was taken for a gas nozzle for injecting a pressurized gas into the molten resin in the cavity of the mold through the pressurized gas passage.

That is, according to the first aspect of the present invention, the sleeve is connected to an adapter to which a pressurized gas introduction pipe is connected, and the needle is provided integrally with a needle body and a base end of the needle body. The needle body is inserted into the sleeve so as to be able to advance and retreat in the axial direction, and the large-diameter head is attached to the adapter. The needle is advanced toward the cavity by the pressurized gas introduced into the adapter from the pressurized gas introduction pipe acting on the large-diameter head when pressurized gas is press-fitted. On the other hand, when the pressurized gas injection is stopped, the needle is retracted by the pressure of the pressurized gas in the cavity.

With the above arrangement, in the first aspect of the present invention, the pressurized gas is press-fitted from the pressurized gas introduction pipe into the molten resin in the cavity of the mold via the adapter and the pressurized gas passage, and the molten gas is injected. A hollow portion is formed in the resin, and the molten resin is cooled and solidified to form a hollow resin molded product having a predetermined hollow portion inside. At the time of pressurized gas injection, the pressurized gas introduced into the adapter from the pressurized gas introduction pipe acts on the large diameter head of the needle, and the needle is pushed out by the gas pressure at that time, and the inside of the sleeve is moved to the cavity side. Move forward towards.

When a hollow resin molded product having a predetermined hollow portion is formed and pressurized gas injection is stopped, the gas pressure on the large-diameter head of the needle disappears, and the inside of the adapter becomes atmospheric pressure. The pressurized gas in the cavity (hollow resin molded product) is discharged to the atmosphere through the pressurized gas passage, the adapter, and the pressurized gas introduction pipe in the opposite manner.
When the pressurized gas injection is stopped, the pressurized gas in the cavity (hollow resin molded product) acts on the entire needle, and the needle is pushed back by the gas pressure at that time, and retreats in the sleeve toward the adapter.

As described above, since the needle is automatically advanced and retracted by the gas pressure at the time of pressurized gas injection and at the time of pressurized gas injection stop, no separate needle driving means is required, the structure of the gas nozzle is simple, and its manufacture is simple. Costs are lower.

Moreover, in the process of repeatedly performing gas injection molding of the hollow resin molded product, even if volatile components in the molten resin enter the pressurized gas passage between the needle and the sleeve, the volatile resin enters the sleeve. Volatile components are moved by the reciprocating movement of the needle, and there is no allowance for a tar-like semi-solidified state. Discharge is performed stably without hindrance.

[0015]

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

FIG. 4 shows a molding apparatus M for performing gas injection molding of a hollow resin molded product. The molding apparatus M includes a mold 5 including a fixed mold 1 and a movable mold 3, and a cavity 7 is formed between the fixed mold 1 and the movable mold 3 in a state where the mold is closed. ing.

An injection nozzle 9 of an injection molding machine is connected to the back surface of the movable mold 3, and a needle valve 11 is arranged inside the injection nozzle 9 so as to be able to advance and retreat. The injection nozzle 9 is communicated with one end (the right end in FIG. 4) of the cavity 7 through the resin supply path 13, and the molten resin R is injected into the cavity 7 from the injection nozzle 9.
It is designed to inject through. The resin supply path 1
Reference numeral 3 denotes a sprue 13a on the injection nozzle 9 side, a gate 13b on the cavity 7 side, and a runner 13c communicating with the sprue 13a and the gate 13b.
a is opened and closed by the reciprocating operation of the needle valve 11 of the injection nozzle 9.

On the other hand, a gas nozzle N according to an embodiment of the present invention is inserted into the fixed die 1 so as to correspond to the other end (the left end in FIG. 4) of the cavity 7. In other words, the injection nozzle 9 and the gas nozzle N are disposed at a large distance from each other so as to be located at 180 ° opposite sides to the cavity 7 of the mold 5, and the molten resin R injected into the cavity 7 Then, pressurized gas is injected from the filling end side where the gas nozzle N solidifies a little earlier in the cavity 7. This allows the pressurized gas to be spread evenly throughout the molten resin R to form the hollow portion r1, and a hollow resin molded product having a uniform thickness at every corner can be obtained.

As shown in FIG. 1, the gas nozzle N has a hollow cylindrical sleeve 15,
Almost half of the distal end side is inserted into and attached to the through hole 1a of the fixed die 1, and a flange portion 19 formed integrally with the sleeve main body 17 and protruding greatly in the radial direction beyond its outer diameter. The sleeve body 17 and the flange portion 19 are formed with a through hole 15a penetrating in the axial direction.
At the base end of 7, a male screw portion 17a is formed.

The base end of the sleeve body 17 is connected to a cylindrical adapter 21. The adapter 21 includes a first cylindrical body 23 having a bottom and a second cylindrical body 25 having no bottom.
Are connected by a first connection member 27. Specifically, one male screw portion 27a formed on the first connection member 27 is screwed into a female screw portion 23a formed on the inner periphery of the open end of the first cylinder 23, and the first connection member 27 is screwed. The other male screw portion 27b formed on the second
Female screw portion 25 formed on the inner periphery of one open end of cylindrical body 25
By screwing the adapter 21 into the adapter 21a, the adapter 21 is configured by integrating these three members. A female thread 23c is formed on the bottom surface 23b of the first cylinder 23, and the male thread 17a of the sleeve main body 17 is connected to the first cylinder 23.
Screwed into the female screw portion 23c of the
9 is brought into contact with the bottom surface 23 b of the first cylindrical body 23, whereby the sleeve 15 is connected to the adapter 21.

The first connecting member 27 is formed with a through hole 27c penetrating in the axial direction, and a female screw portion 27d is formed at one end of the through hole 27c.
The second connection member 29 is connected to the first connection member 27 by screwing the male screw portion 29a of the second connection member 29 into 7d. The second connecting member 29 is also formed with a through hole 29b penetrating in the axial direction, and a pressurized gas introducing pipe 31 is connected to the through hole 29b. The pipe 31 is connected to a pressurized gas supply source (not shown).

In the through hole 15a of the sleeve 15,
An elongated needle 33 having a circular cross section is movably fitted. Specifically, the needle 33 is formed integrally with the needle body 35 inserted into the through hole 15 a so that the tip end projects into the cavity 7 of the mold 5, and at the base end of the needle body 35. A large-diameter head 37 that protrudes more in the radial direction than the outer diameter of the needle main body 35 is formed.
The connection member 27 is arranged in a space 39 between the connection member 27 and the recess 27 e. An O-ring 41 is interposed around the outer periphery of the space 39, and the O-ring 41 secures a seal around the large-diameter head 37. Thereby, the needle body 35
Is inserted in the sleeve body 17 of the sleeve 15 so as to be able to advance and retreat in the axial direction, and the large-diameter head 37 is accommodated in the space 39 in the adapter 21 so as to be able to advance and retreat. The reason why the tip portion of the needle body 35 is projected into the cavity 7 is that pressurized gas press-fitted along the needle body 35 is supplied to the cavity 7 at the tip portion.
This is for guiding the pressurized gas into the molten resin R in a stable manner.

The needle body 35 and the sleeve body 17
A pressurized gas passage 43 having an annular cross section is formed between the two. The pressurized gas passage 43 has a narrow distal end portion as shown in FIG. 3 (a), and the other portion except the distal end portion extends toward the base end side as shown in FIG. 3 (b). Notch 35 cut out in the axial direction of
a. This wide pressurized gas passage 39
The presence of the portion makes it difficult for the volatile component in the molten resin R that has entered the sleeve main body 17 to become a tar-like semi-solidified state.

As shown in FIG. 3C, a groove 37 extending radially from the base end of the needle body 35 in a cross shape is formed on the surface of the large diameter head 37 of the needle 33 on the needle body 35 side.
a is formed, and a similar cross-shaped groove 37b is formed on the opposite surface, as shown in FIG. 3D. Thereby, the cavity 7 of the mold 5 is formed by the pressurized gas passage 43 in the sleeve 15, the space 39 in the adapter 21, the through hole 27c of the first connecting member 27, the through hole 29b of the second connecting member 29, and the pressurized gas. It is connected to a pressurized gas supply source (not shown) through the introduction pipe 31, and the pressurized gas introduction pipe 31, the through hole 29 b of the second connection member 29, the through hole 27 c of the first connection member 27, and the inside of the adapter 21. Space 39
The pressurized gas is injected into the molten resin R in the cavity 7 of the mold 5 via the pressurized gas passage 43 in the sleeve 15.

The pressurized gas introduced into the adapter 21 from the pressurized gas introduction pipe 31 acts on the large-diameter head 37 when the pressurized gas is press-fitted. It is configured to move forward while moving backward when the pressurized gas injection is stopped by the pressure of the pressurized gas in the cavity 7. 1 and 2 show the advanced state of the needle 33. In this advanced state, the large-diameter head 37 is in contact with the flange portion 19 of the sleeve 15, but is pressurized by the groove 37a of the large-diameter head 37. Gas passage 43
And the space 39 in the adapter 21 communicate with each other, whereby the pressurized gas introduction pipe 31 and the cavity 7 are opened to allow the pressurized gas to be injected into the molten resin R in the cavity 7. On the other hand, the solid line in FIG. 2 shows a state in which the needle 33 is retracted. In this retracted state, the large-diameter head 37 is in contact with the bottom surface of the concave portion 27e of the first connection member 27. 1 Through-hole 27 of connection member 27
The space c communicates with the space 39, thereby opening the pressurized gas introduction pipe 31 and the cavity 7, thereby enabling the pressurized gas to be discharged from the cavity 7 (hollow resin molded product).

Therefore, in this embodiment, the mold 5
After the molten resin R is injected into the cavity 7, the pressurized gas is injected into the molten resin R from the pressurized gas introduction pipe 31 via the adapter 21 and the pressurized gas passage 43, and the pressurized gas introduction pipe 31 The pressurized gas introduced into the adapter 21 from the valve acts on the large-diameter head 37 of the needle 33 to push out the needle 33 with the gas pressure at that time, and the sleeve 15
The inside is advanced toward the cavity 7 side.

When a hollow portion r1 is formed in the molten resin R in the cavity 7 and a hollow resin molded product is formed, press-in of the pressurized gas is stopped, and the large-diameter head 37 of the needle 33 is stopped.
The gas pressure in the adapter 21 is reduced to the atmospheric pressure, and the pressurized gas in the cavity 7 (hollow resin molded product) is supplied to the pressurized gas passage 43, the adapter 21, and the pressurized gas in the opposite manner to the above. The gas is discharged into the atmosphere via the gas introduction pipe 31. When the pressurized gas injection is stopped, the cavity 7
The pressurized gas in the (hollow resin molded product) acts on the entire needle 33 and pushes the needle 33 back at the gas pressure at that time, and retreats the inside of the sleeve 15 toward the adapter 21 side.

As described above, the needle 33 is automatically advanced and retracted by the gas pressure at the time of pressurized gas injection and at the time of stoppage of the pressurized gas injection. The structure of N can be simplified and the manufacturing cost can be reduced.

In addition, in the process of repeatedly performing gas injection molding of the hollow resin molded product, even if the volatile component in the molten resin R enters the pressurized gas passage 43 between the needle 33 and the sleeve 15, this sleeve is There is no room for the volatile components that have penetrated into 15 to be moved by the advancing and retreating operation of the needle 33 to become a tar-like semi-solidified state. Pressurized gas injection and discharge can be performed stably without hindrance.

In this embodiment, the grooves 37a and 37b are formed in the large diameter head 37 of the needle 33. However, the grooves 37a and 37b may be formed in the flange 19 of the sleeve 15 and the end face of the first connection member 27 on the side of the recess 27e. Often, the groove shape is not limited to the cross.

[0031]

As described above, according to the present invention, when pressurized gas is injected, the pressurized gas introduced into the adapter from the pressurized gas introduction pipe acts on the large-diameter head of the needle. While the needle is advanced, when the pressurized gas injection is stopped, the needle is retracted by the pressure of the pressurized gas in the cavity. can do. In addition, since the volatile components in the molten resin that have entered the pressurized gas passage are not solidified by the advancing and retreating operation of the needle, the pressurized gas can be stably injected and discharged without any trouble.

[Brief description of the drawings]

FIG. 1 is a sectional view of an entire gas nozzle according to an embodiment of the present invention.

FIG. 2 is an enlarged view corresponding to a portion A of FIG. 1 showing a state in which a large-diameter head of a needle is retracted when pressurized gas injection is stopped.

3A and 3B are cross-sectional views of respective parts in FIG. 1, wherein FIG. 3A is a cross-sectional view taken along line BB, FIG. 3B is a cross-sectional view taken along line CC,
(C) is a sectional view taken along line DD, and (d) is a sectional view taken along line EE.

FIG. 4 is a sectional view showing a pressurized gas press-fit state in a molding apparatus to which the gas nozzle according to the embodiment of the present invention is applied.

[Explanation of symbols]

 5 Mold 7 Cavity 15 Sleeve 21 Adapter 33 Needle 35 Needle Body 37 Large Diameter Head 43 Pressurized Gas Passage R Molten Resin N Gas Nozzle

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F202 AG07 AM32 CA11 CB01 CS00 CS10 4F206 AG07 AM32 JA05 JN27 JQ90

Claims (1)

[Claims] A needle is inserted into a hollow sleeve attached to a mold to form a pressurized gas passage having an annular cross section between the needle and the sleeve. A gas nozzle for pressurizing a pressurized gas into a molten resin in a cavity of the mold, wherein the sleeve is connected to an adapter to which a pressurized gas introduction pipe is connected, and the needle is a needle body and the needle A large-diameter head that is provided integrally with the base end of the main body and protrudes larger in the radial direction than the diameter of the needle main body, and the needle main body is inserted into the sleeve so as to be able to advance and retreat in the axial direction, The large-diameter head is accommodated in the adapter so as to be able to advance and retreat, and at the time of pressurized gas injection, the pressurized gas introduced into the adapter from the pressurized gas introduction pipe acts on the large-diameter head. A gas nozzle characterized in that the needle is advanced toward the cavity, and the needle is retracted by the pressure of the pressurized gas in the cavity when pressurized gas injection is stopped.