JPH1190954A - Gas-assisted molding gas injection needle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate influence of clamping torque of an end screw to a size of a gas injection port. SOLUTION: A needle body 12 of a gas injection needle has female threads 12a at an end side of a hollow part 12b to which gas is supplied. And, an end screw 13 is engaged with the threads 12a. A cutout 15a for a gas passage is formed at a shaft 15 of the screw 13 to become a gap for passing gas. A groove 12c for the passage is formed at an upper end face of the body 12. Supplied gas is passed through the gap of the cutout 15a for the passage, and injected from the groove 12c, that is, gas injection port into resin immediately after filling in a mold. Shrink is prevented by this gas-assisted molding. Size change of the groove 12c for the passage due to clamping torque of the screw 13 scarcely occurs different from a conventional structure in which the groove for the passage is disposed at the screw side. And, difficulty in working technique of forming the groove for the passage at the screw does not occur as well.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas injection needle for gas assist molding, which is provided in a mold as a gas injection part when performing gas assist molding of a synthetic resin.

[0002]

2. Description of the Related Art In a gas-assist molding, when a casing having bosses, ribs, or the like, such as a cabinet of a CRT display device, is injection-molded, the resin is injected into the resin from a gas injection port of a gas injection needle immediately after the resin is filled. It is used to prevent sink marks by injecting gas and injecting gas into the roots of the bosses and ribs to expand the roots, thereby preventing sinks from occurring in the bosses and ribs. Molding method. It is mainly used when the measure for preventing sink mark by holding pressure is not effective.

FIGS. 10 to 15 show a conventional gas injection needle 1 used for the gas assist molding. 10 is a front view of the conventional gas injection needle 1, FIG. 11 is a cross-sectional view taken along the line DD in FIG. 10, FIG. 12 is a cross-sectional view taken along the line EE in FIG. 11, and FIG. FIG. 14 is a plan view of the needle main body 2, and FIG. 15 is a cross-sectional view of the tip screw 3 (a cross-sectional view taken along line FF in FIG. 13).
As shown in these figures, a gas injection needle 1 has a hollow cylindrical needle body 2 having a female screw 2a formed on the inner surface of a hollow portion 2b on the tip side, and a head screwed into the female screw 2a of the needle body 2. And a tip screw 3 with The tip screw 3 forms a gas passage cutout 5 a extending in the axial direction on the outer surface of the screw shaft portion 5, and connects to the gas passage cutout 5 a on the lower surface side of the head 6 of the tip screw 3. A radial gas passage groove 6a is formed.

As described above, the conventional gas injection needle 1
Is a gas inlet groove 6a on the tip screw 3 side as a gas inlet.
Had formed.

[0005]

In the conventional gas injection needle 1 described above, the gas sent into the hollow portion 2b of the needle body 2 is supplied to the gas passage cutout 5a provided on the outer surface of the tip screw 3. After passing through the formed gap, the tip screw 3
Is injected into the resin in the molding die through the gas passage groove 6a formed on the back surface of the head 6 of FIG. In the conventional gas injection needle 1 described above, the presence of the gas passage groove 6a lowers the strength of the tip screw 3, and the tightening torque of the tip screw 3 deforms the tip screw 3 as a whole, making it unusable. Gas passage groove 6 which is a gas inlet
There is a problem that the dimension of a changes.

Further, in forming the gas passage groove 6a on the lower surface of the head 6 of the tip screw 3, the tip screw 3 has an outer diameter of the head (= the outer diameter of the gas injection needle 1) of 6 to 9 mm. Since the thickness is as small as 0.5 to 2.0 mm and the like, the lower surface of the head of the tip screw 3 is difficult to machine, the depth of the tip screw 3 is 0.03 to 0.05 mm. There is also a problem that processing for forming the gas passage groove 6a is not technically easy. Further, even if the gas injection direction is directed to a specific direction, the gas injection direction is determined by the final rotation position when the tip screw 3 is tightened. The direction cannot be controlled to the desired direction.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional disadvantages, and the dimensions of the gas inlet are not affected by the tightening torque of the screw, and the tip screw is deformed by the tightening strength of the screw. Another object of the present invention is to provide a gas injection needle for gas assist molding in which a gas passage groove serving as a gas injection port can be easily processed without becoming unusable.

[0008]

According to the present invention, there is provided a hollow cylindrical needle body having a female thread formed on the inner surface of a hollow portion on the distal end side, and a head screwed into the female thread portion of the needle body. In the gas injection needle for gas assist molding provided with a tip screw, a notch for a gas passage extending in an axial direction is formed on an outer surface of a screw shaft portion of the tip screw, and a tip face of the needle main body is formed on the tip face. ,
A gas passage groove capable of communicating with a gap formed by the gas passage cutout of the tip screw is formed.

[0009]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described with reference to the embodiment shown in FIGS. FIG. 1 is a front view of a gas injection needle 11 according to one embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1, and FIG.
FIG. 4 is a cross-sectional view of FIG. 2 with the tip screw 13 removed, FIG. 5 is a plan view of the needle body 12, and FIG. 6 is a cross-sectional view of the tip screw 13 (a cross-sectional view taken along line CC in FIG. 4). .
As shown in these figures, this gas injection needle 11
The needle body 12 comprises a hollow cylindrical needle body 12 having a female screw 12a formed on the inner surface on the distal end side of the hollow portion 12b, and a head screw 13 with a head screwed into the female screw 12a of the needle body 12. And this tip screw 13
A gas passage cutout 15a extending in the axial direction is formed on the outer surface of the screw shaft portion 15. In the illustrated example, the gas passage cutout 15 a is formed at one position of the screw shaft portion 15. On the other hand, on the upper end surface of the needle main body 12, a radial gas passage groove 12c is formed which can communicate with a gap formed by the gas passage cutout 15a of the tip screw 13. In the illustrated example, the gas passage grooves 12c are formed in four cross-shaped directions.

In the gas injection needle 11 described above, the gas sent into the hollow portion 12 b of the needle body 12 passes through a gap formed in a gas passage cutout 15 a provided on the outer surface of the tip screw 13, Next, the needle body 1
The gas is injected into the resin in the molding die through the gas passage groove 12c formed on the upper end surface of the mold 2, that is, the gas injection port.
The injected gas enters the roots of the bosses and ribs (parts to be formed) and expands the roots, thereby preventing sinks from being generated in the bosses and ribs.

Since the gas passage groove 12c on the needle body 12 is located on all sides, the gas passage notch 15a of the tip screw 13 can be used regardless of the final rotation position when the tip screw 13 is tightened. It is possible to ensure communication with the formed gap.

In the gas injection needle 11 described above,
Since the tip screw 13 does not have a gas passage groove, it is possible to avoid the difficulty in processing technology of forming a gas passage groove on the lower surface of the head 16 of the small-sized tip screw 13. There is no particular difficulty in forming the gas passage groove 12c on the upper end surface of the needle body 12. In addition, the process of forming the gas passage cutout 15a in the distal end screw 13 is not particularly difficult because it only makes a part of the screw shaft portion 15 having a circular cross section flat.

Further, since there is no gas passage groove in the tip screw 13, there is no problem that the dimension of the gas passage groove serving as the gas inlet changes. Further, there is no reduction in the strength of the tip screw 13 and no damage such as the tip screw 13 being entirely deformed by the tightening torque of the tip screw 13 occurs.

In the above embodiment, the gas passage cutout 15
a is formed at one position of the screw shaft portion 15 of the tip screw 13, but as shown in FIG. 7, gas passage cutouts 15 a are formed at two positions 180 ° opposite to each other with respect to the screw shaft portion 15 of the tip screw 13. You may. As a result, the gas passage notch 15
Communication between the gap formed by a and the gas passage groove 12c on the needle body 12 side can be further ensured.

FIG. 8 shows another embodiment of the gas passage groove of the needle body 12. In this embodiment, the gas passage grooves 12′c are formed only in two directions of 180 °.
The width of the gas passage groove 12'c is formed so that the two gas passage grooves 12'c can always communicate with the gap formed by the gas passage notch 15a. In this case, since the gas injection direction is determined by the gas passage groove 12'c on the needle body 12, the needle body 12 is installed so as to be oriented in a desired gas passage groove 12'c. The gas injection direction can be set to two desired directions.

FIG. 9 shows still another embodiment of the gas passage groove of the needle body 12. In this embodiment, the gas passage groove 12 "c is formed only in one direction, and one gas passage groove 12" c can always communicate with the gap formed by the gas passage notch 15a. The width of the gas passage groove 12'c is further increased. In this case, the gas injection direction can be set to a desired one direction.

In the present invention, the gas passage groove formed on the upper end surface of the needle main body is not limited to the case of each of the above-described embodiments. In short, the gas passage groove is always formed regardless of the rotational position of the tip screw 13. Any position and width may be used so long as they can communicate with the gap formed by the gas passage cutout on the tip screw 13 side.

[0018]

According to the present invention, since the gas passage groove is not provided on the tip screw side but formed on the needle body side, the size of the gas passage groove, that is, the size of the gas injection port is changed. Does not occur. Further, there is no reduction in the strength of the tip screw, and there is no damage that the tip screw is entirely deformed by the tightening torque of the tip screw.

Since the gas passage groove is not provided on the tip screw side, it is possible to avoid the difficulty in forming the gas passage groove in the small tip screw in terms of processing technology.

Since the gas passage groove is located on the needle body side, the gas injection direction is determined by the needle body regardless of the final rotational position when the tip screw is tightened.
Therefore, it is possible to control the gas injection direction, that is, to direct the gas injection direction to a desired direction.

[Brief description of the drawings]

FIG. 1 is a front view of the vicinity of a distal end portion of a gas injection needle for gas assist molding according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA in FIG.

FIG. 3 is a sectional view taken along line BB in FIG. 2;

FIG. 4 is a view showing a state where a tip screw is removed in FIG. 2;

FIG. 5 is a plan view of the needle main body in FIG.

FIG. 6 is a sectional view of the tip screw taken along the line CC in FIG. 4;

7 shows another embodiment of the needle body according to the present invention, and corresponds to a sectional view taken along the line BB of FIG. 2 (corresponding to FIG. 3).

FIG. 8 is a view showing still another embodiment of the needle body according to the present invention, and is a view corresponding to a sectional view taken along line BB of FIG. 2 (corresponding to FIG. 3).

9 shows still another embodiment of the needle body according to the present invention, and is a view corresponding to the cross-sectional view taken along the line BB of FIG. 2 (corresponding to FIG. 3).

FIG. 10 is a front view showing the vicinity of the tip of a conventional gas injection needle for gas assist molding.

11 is a sectional view taken along line DD in FIG.

FIG. 12 is a sectional view taken along line EE in FIG. 11;

FIG. 13 is a view showing a state where a tip screw is removed in FIG. 11;

FIG. 14 is a plan view of the needle main body in FIG.

FIG. 15 is a sectional view of the tip screw taken along line FF in FIG. 13;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Gas injection needle 12 Needle main body 12a Female screw 12b Hollow part 12c Gas passage groove 13 Tip screw 15 Screw shaft part 15a Notch for gas passage 16 Head of tip screw

Claims (1)

[Claims] 1. A gas for gas assist molding, comprising: a hollow cylindrical needle body having a female screw formed on the inner surface of a hollow portion on the distal end side; and a head screw having a head screwed into the female screw portion of the needle body. In the injection needle, a gas passage notch extending in the axial direction is formed on an outer surface of a screw shaft portion of the tip screw, and a gas passage notch of the tip screw is formed on a tip surface of the needle body. A gas injection needle for gas assist molding, wherein a gas passage groove capable of communicating with a gap is formed.