JP3235170B2 - Injection nozzle for gas 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 an injection nozzle designed to perform good gas injection and recovery to enable smooth and economical gas injection molding.

[0002]

2. Description of the Related Art A gas injection molding technique has been already known in Japanese Patent Publication No. 48-41264 and the like. It is widely used to obtain products with good accuracy. This technology has come to the spotlight
This is also due to the recent increase in demand for large electrical equipment and the like, and is a relatively new technology. Accordingly, there are few specific examples of nozzles used for this gas injection molding, and for example, there is the extent that JP-B-55-9865 can be mentioned.

[0003] The gas used in the present method is generally nitrogen, but when used, the pressure is several hundred atm. This nitrogen gas is used to avoid the burning of high-temperature resin, but as described above, even if the volume is small due to high pressure, the amount becomes considerably large, and if it is discarded for each process, It was uneconomic. Therefore, it is necessary to recover and reuse the resin. However, there has been no nozzle structure that satisfies the demand and can perform steps such as smooth resin injection, gas injection, and recovery.

[0004]

That is, the steps of gas injection molding include injection of resin, injection of high-pressure gas into the resin in the mold, maintenance of the gas pressure in the mold, and release of gas. Includes the cycle of recovery, but the problem of intrusion of the high-pressure resin into the gas inlet and outlet at the time of injection and the entrained resin powder at the time of discharging gas, and the nozzle of the high-pressure gas remaining at the time of gas injection There are problems such as intrusion into the resin (so-called silver streaks occur at the next shot). However, measures against these problems have not been sufficiently taken by the above-mentioned known technology.

[0005] In particular, the space between the injection nozzle and the injection mold is narrow, and it is difficult to incorporate a structure for solving the above problems between the nozzle and the injection mold. Therefore, when the passage for blowing and discharging the gas is common as in the prior art, there is a problem that the resin accompanying the gas reciprocates together in the passage, and the passage is often closed. On the other hand, in order to provide a gas passage in the injection passage, it is necessary to form a bridge-girder-shaped resin passage and to make a structure in which the gas passage is perforated in the bridge girder, but of course, the work is difficult, and There was a problem that the production cost increased.

[0006]

SUMMARY OF THE INVENTION The present invention provides an injection nozzle having a structure for solving the above-mentioned problems. That is, in the present invention, a gas inlet and a gas discharge port are provided in a jacket directly connected to and fixed to the tip of the injection unit, and the inner wall and the outer periphery of the nozzle are slidable in the jacket, and the thrust is provided. Receiving the injection nozzle is provided, and the tip of the nozzle is provided so as to be in close contact with the gate of the injection molding die at a predetermined position of the injection unit so that both resin passages communicate with each other. And the resin passage is
When the upstream side is closed from the resin in the injection unit by the sliding surface of the outer jacket inner wall, the gas discharge port is opened, while the injection unit advances to the forward limit,
When the resin in the unit is injected, the upstream resin passage is open, the above-mentioned gas discharge port is closed, and when the gas is blown, the gas communicating with the high-pressure gas source via the check valve is returned. An object of the present invention is to provide an injection nozzle for gas injection molding, having a structure in which an injection port is opened.

[0007]

Next, the present invention will be described with reference to FIG. 1 showing an embodiment. FIG. 1 is a cross-sectional view of a main part of a gas blow injection molding machine having an injection nozzle according to the present invention, in a state where an injection unit 1 advances to a predetermined distance less than a forward limit and stops.

An outer jacket 2 is directly connected to the front end portion 101 of the injection unit 1 downstream thereof. The injection nozzle 3 is built in the outer jacket 2, and a tip portion 301 of the injection nozzle 3 is
By the force of the leaf spring 5 interposed between the tip 201 of the nozzle 3 and the stopper 4 fixed to the tip 301 of the nozzle 3,
The resin passage 8 in the nozzle 3 is in close contact with the gate 7 of the injection mold 6, while the resin passage 8 in the nozzle 3 passes through the resin passage 801 in the front part and the resin passage 701 in the gate 7, and the cavity 601 in the mold 6 for injection molding. Leads to. In this state, the front resin passage 801 communicates with the rear resin passage 802 via the check valve 9, but immediately before the check valve 9, the resin passage 80.
1 is branched, and is connected to a small hole 803 opening to a sliding portion of the side wall of the nozzle 3.

In the above-described state, the small hole 803 is closed on the sliding surface with the outer jacket 2 with respect to the groove-shaped gas inlet 10 provided on the inner circumference of the outer jacket 2. The groove-shaped gas discharge port 11 provided on the outer periphery of the nozzle is in an open state. The rear resin passage 802 communicates with a small hole 804 that opens at a sliding portion of the side wall of the nozzle 3 at the rear portion. is there. Therefore, the resin material 1 in the resin injection unit 1
The outflow of the resin due to the pressure of 02 is prevented. Therefore, even if the gas is released in this state, no resin is entrained.

Next, when injecting the resin, the injection unit 1 moves forward to its forward limit, and the resin passages 801, 80
Numeral 2 communicates with the resin chamber 102 of the injection unit and the gas inlet 10. On the other hand, the gas outlet 11 is closed, so that the high-pressure resin can be prevented from entering the gas outlet 11 during injection. The gas inlet 10 has a check valve 12 to prevent the resin from entering. When the high-pressure gas is blown at this position after the injection of the resin or after the pressure of the resin has dropped, the intrusion of the high-pressure gas into the resin chamber 102 can be prevented by the check valve 9. Next, after the blowing of the gas is completed and is maintained for a predetermined time, the injection unit is retracted to a predetermined position of the injection unit, and the gas is discharged and collected.

In the above example, the gas inlet 10
Must be open, not necessarily at the time of gas injection, but can be opened or closed at any other time as long as the check valve 12 is present. However, when gas is blown and discharged at the same position as the outer jacket, as shown in FIG.
3 needs to be attached to the rear of the gas outlet 11, and a gas pressure equivalent to the injection or blowing pressure needs to be applied to the rear.

However, since the injection pressure is generally very high and it is sometimes difficult to carry out the injection, in such a case, the position of the gas discharge port can be used, and the cutoff with the resin can be carried out on the sliding surface. . Therefore, in some cases, a check valve is not required, and the check valve can be implemented by installing a blow-off and gas release on-off valve at a remote pipe position. The gas inlet can also be used as the outlet 11. In that case, the inlet pipe and the discharge pipe may be branched behind.

Further, the check valve 9 is omitted, and the rear resin passage 8 is removed.
The sliding portion between the opening of the small hole 804 and the inner wall of the jacket 2 can be used instead. In this case, the opening / closing valve of the resin passage functions as the check valve 9.
The apparatus is effective when a part of the injection resin in the mold cavity is allowed to flow back into the injection unit again, since the gas can be blown after the injection is completed. In the above embodiment, a spring is used to obtain the forward force of the nozzle. However, the spring may be applied by resin pressure in the injection unit.

In FIG. 1, the gas discharge port 11 and the resin passage 8 are shut off at the sliding surface between the injection nozzle 3 and the jacket 2 where the small hole 803 is in contact. In order to complete the above, it is preferable that the outer surface of the injection nozzle 3 and the inner surface of the jacket 2 have a structure as shown in FIG. That is, the jacket 2 is located near the gas inlet 10 and the gas outlet 11.
A step 202 having a concave shape is provided on the inner circumference of the nozzle, and a step 302 having a convex shape is provided on the outer circumference of the injection nozzle 3.

Then, except when the resin is injected, the gas discharge port 11 communicates with the resin passage 8, while when injecting the resin, the injection unit 1 advances and the steps 202 and 302 are caused by the advance force. Are engaged, and this engaging surface serves as a forward limit of the injection unit 1, and a strong forward force is applied to the engaging surface. Therefore, it is possible to completely block outflow of resin at the time of injection. You can. At this time, the gas inlet 10
And the resin passage 8 communicate with each other.

[0016]

According to the present invention, high-pressure resin at the time of injection in gas injection molding is prevented from entering the gas inlet and the gas outlet, and at the time of gas injection, gas enters the injection unit. In addition to the above, there is an effect that the processing for the trouble due to the entrained resin in the released gas can be performed by the simple operation of the injection molding, that is, the forward and backward movement of the injection cylinder, and the complicated operation such as the opening and closing of the valve due to the external force. In addition, the effect of avoiding the complicated apparatus can be obtained. In particular, it was generally difficult to handle a large discharge pressure at the gas discharge port with a simple mechanism called a check valve, but this was achieved by a simple operation of moving the injection unit forward and backward. The effect obtained can be said to be great.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a gas injection molding apparatus having an injection nozzle of the present invention in a state where an injection unit advances to a predetermined position and stops.

FIG. 2 is a sectional view of a main part of a gas injection molding apparatus having an injection nozzle of the present invention in which a step is provided in a jacket and an injection nozzle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection unit 2 Outer jacket 3 Injection nozzle 4 Stopper 5 Leaf spring 6 Injection mold 7 Gate 8 Resin passage 9 Check valve 10 Gas inlet 11 Gas outlet 12 Check valve 13 Check valve 101 Front end of injection unit Reference Signs List 102 Resin chamber in injection unit 201 Tip of jacket 202 Step of jacket 301 Tip of injection nozzle 302 Step of injection nozzle 601 Cavity of injection mold 701 Resin passage in gate, 801 Resin passage in front of injection nozzle 802 Resin passageway behind injection nozzle 803 Gas flow small hole opening in injection nozzle on side wall 804 Resin flow small hole opening in injection nozzle rear side wall

Claims (7)

(57) [Claims] 1. An outer jacket directly connected and fixed to a tip end of an injection unit is provided with a gas inlet and a gas outlet, and the inner wall and the outer periphery of a nozzle are slidable in the outer jacket, and a thrust force is provided. Receiving the injection nozzle is provided, and the tip of the nozzle is provided so as to be in close contact with the gate of the injection molding die at a predetermined position of the injection unit so that both resin passages communicate with each other. And, when the resin passage is closed from the resin in the injection unit by the sliding surface of the outer jacket inner wall upstream thereof, the gas discharge port is opened, while the injection unit advances to the forward limit, and When the resin in the unit is injected, the upstream resin passage is open, the gas discharge port is closed, and the gas blow port is opened when gas is blown. Gas injection Injection nozzle for shapes. 2. The injection nozzle according to claim 1, wherein the thrust exerted on the injection nozzle is given by a pressure between a front portion of the nozzle and a front end portion of the outer wall or a resin in the injection unit. 3. The injection nozzle according to claim 1, wherein opening and closing of the gas discharge port are performed by sliding of the jacket and the nozzle. 4. The injection nozzle according to claim 1, further comprising a check valve at the gas inlet. 5. The injection nozzle according to claim 1, wherein the gas discharge port has a check valve when the gas is blown and discharged at the same position of the injection unit. 6. The injection nozzle according to claim 1, further comprising a check valve in a resin passage upstream of the gas inlet and the outlet. 7. The injection nozzle according to claim 1, wherein the inner surface of the jacket near the gas inlet and the outlet and the outer surface of the injection nozzle are provided with steps which can be engaged and disengaged from each other.