JPH08238651A - Injection mold - Google Patents

Abstract

PURPOSE: To provide an injection mold equipped with a gas venting pin sustaining gas venting effect. CONSTITUTION: A gas venting pin 20 is constituted of the fine diameter part 21 becoming a gas escape part positioned on the leading end side thereof and a large diameter part 22 positioned behind the fine diameter part 21. A sliding hole 23 in which a molten resin flows is formed to the central part of the fine diameter part 21 and has an undercut shape wherein the inner diameter on the leading end surface side thereof is smaller than that on the bottom surface side thereof. Therefore, when a molded product is ejected from a cavity part after the molten resin flows in the sliding hole 23 to be solidified, the gas venting hole 20 is moved in the same direction along with the movement of the molded product and the substance contained in gas bonded to the fine diameter part 21 is removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding die having a degassing structure.

[0002]

2. Description of the Related Art In recent years, resin molded products (hereinafter referred to as molded products) have been used everywhere in electric appliances such as refrigerators, televisions, vacuum cleaners, video equipment, AV equipments such as personal computers. Among these molded products, small and precise molded products that are used in large quantities are mainly injection-molded because continuous molding is relatively easy.

In order to obtain a molded product by injection molding, a mold having a resin material having a desired function and a space portion (hereinafter referred to as a cavity portion) for forming the resin material into a desired shape. And melting the resin material,
An injection molding machine is required that sends molten resin under high pressure to the cavity formed in the mold.

Since the resin material melted in the cylinder of the injection molding machine is fed into the cavity of the mold, the fixed side and the moving side of the mold are tightly clamped by the mold clamping mechanism of the injection molding machine. ing. Therefore, air is trapped in the cavities that form the shapes of the sprue and runners and the product, which are the channels of the molten resin formed in the mold. Gas is generated from the resin material melted in the injection molding machine.

In this state, the molten resin is fed into the mold within a few seconds by applying a predetermined pressure. Then, the air accumulated in the mold and the gas generated from the molten resin move with the flow of the resin. At this time, a lot of air and gas are discharged to the outside of the mold from the gas escape part of the runner end part and the gas escape part of the molded product ejecting pin that are formed for gas release due to the pressure of the flowing resin. However, the air and gas remaining in the cavity are compressed by the pressure of the resin that flows into the cavity and generate high heat, which causes burnt parts in the molded product and the molten resin to spread in every corner of the cavity. It was blocked from flowing into and a flesh was formed.

In order to deal with this problem, as shown in FIG. 7, a plurality of molded product ejecting pins 3, 3 ,. ． ． Besides, the gas escape pin 4 or the gas escape portion 5 is formed in the cavity portion where air and gas are concentrated. However, in order to prevent burrs from being generated in the molded product, such as PPS resin, which has good resin flowability, the gap for releasing gas is set to 7/1000 m.
Since it had to be formed below m, the substance contained in the gas generated from the molten resin adhered to the gap for allowing the gas to escape in a short time, causing clogging at the gas escape part. The degassing effect did not last. Therefore, it has been necessary to frequently disassemble the mold to remove the deposits on the gas escape portion. In addition, a material for improving the degassing efficiency is commercially available, but since this material has a gap for degassing, the same degassing effect does not last long for clogging. There was a flaw.

However, when the mold was disassembled, the gas escape portion formed on the pin for ejecting the molded product had less deposit than the gas escape portions of the other portions. This is because when the molded product ejecting pin moves up and down in the mold to eject the molded product every cycle, the molded product ejecting pin slides on the block where the molded product ejecting pin is arranged. This was because the substance adhering to the gas escape portion of the work pin was scraped off. For this reason, a pin for ejecting a molded product has been provided in a portion of the cavity where air and gas are concentrated.

On the other hand, even in the case of a resin material which can take a relatively large gap in the gas escape portion, air and gas are sufficiently discharged from the inside of the mold quickly when performing molding that requires high speed filling. Otherwise, gas burns and lack of meat will occur. For this reason, there is a structure in which a vacuum generator is connected to the injection molding die to apply a negative pressure to the cavity to expel air and gas promptly.

[0009]

However, depending on the shape of the product or the like, it is difficult to dispose the pin for ejecting the molded product in the portion of the cavity where air and gas are concentrated.

As a measure against clogging of the degassing pin, the degassing pin was slid by using a driving source such as a molded product ejecting mechanism or a cylinder of an injection molding machine. Degassing pin that slides by using a drive source on the part where air and gas are concentrated due to the mold structure restrictions such as the position of the pipes and the hole position where blocks and bolts are installed to receive resin pressure Was difficult to provide.

Further, there is a problem that a large amount of loss is generated between the cavity portion and the vacuum generator and a sufficient negative pressure cannot be applied to the cavity portion.

The present invention has been made in view of the above-mentioned problems, and provides an injection molding die having a degassing structure for maintaining a degassing effect and an injection molding die capable of high-speed degassing. The purpose is to do.

[0013]

An injection molding die according to the present invention is an injection molding die having a degassing structure which is attached to an injection molding machine to continuously obtain molded articles. A gas vent pin is slidably provided in the cavity formed by.

On the other hand, a vacuum generating mechanism for sucking the air generated in the cavity portion forming the molded product or the gas generated from the molten resin to the outside of the cavity portion is provided in the mold.

[0015]

In the injection-molding die having the above structure, the degassing pin arranged in the cavity slides, so that the degassing effect is maintained.

On the other hand, the gas generated from the air in the cavity and the molten resin is quickly discharged from the cavity by the vacuum generating mechanism provided in the mold.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 relate to a first embodiment of the present invention, FIG. 1 is a view for explaining the inside of a mold during a molding process, FIG. 2 is an explanatory view showing the structure of a gas vent pin, and FIG. 3 is a gas vent pin. FIG. 4 is an explanatory view showing a schematic configuration of a block in which is arranged, and FIG. 4 is an explanatory view showing the action of the gas vent pin.

As shown in FIG. 1, in the injection molding die 10 of this embodiment, a degassing pin is provided in a block 12 where air generated in the die and gas generated from molten resin are most concentrated during the molding process. The hole 13 is formed, and the gas release pin mounting hole 13 is formed.
A gas vent pin 20 is provided in the. Reference numeral 11 denotes a molded product ejecting pin (hereinafter referred to as an ejecting pin) for ejecting the molded product 1 and the runner 2 from the mold 10, and air or air is discharged from a gap between the tip portion of the protruding pin 11 and the mold. Gas is discharged to the outside.

As shown in FIG. 2A, the gas vent pin 20
Is composed of a small diameter portion 21 which is a gas escape portion on the tip side and a large diameter portion 22 which is located on the rear side of the small diameter portion 21. A sliding hole 23 into which molten resin flows is formed at the center of the small diameter portion 21. As shown in FIG. 2B, the sliding hole 23 has an undercut shape in which the inner diameter on the tip side is smaller than the inner diameter on the bottom side. Therefore, when the molten resin flows into the sliding hole 23 and solidifies, and the molded product is projected from the cavity, the degassing pin 20 moves in the same direction as the molded product moves.

In addition, in order to guide the air or gas in the cavity, which has passed through the gap between the gas vent pin disposing hole 13 of the block 12 and the small diameter portion 21, to the outside of the mold on the outer periphery of the large diameter portion 22. A plurality of exhaust grooves 24 are formed. The depth d of these exhaust grooves 24 is set so that the degassing pin disposing hole 13 and the small diameter portion 21 do not adversely affect degassing even if a substance contained in the gas generated from the molten resin adheres. It is formed larger than the gap.

Further, an inclined surface portion 25 is formed between the small diameter portion 21 and the large diameter portion 22.

As shown in FIG. 3, the block 12 has a cavity portion 14 for forming a product shape and the degassing pin 2.
0 is provided, and a vent pin disposing hole 13 communicating with the cavity portion 14 is provided. The gas vent pin mounting hole 13 has a large diameter hole 15 in which the large diameter portion 22 of the gas vent pin 20 is arranged and a small diameter hole 1 in which the small diameter portion 21 is arranged.
6 and 6. Between the large-diameter hole 15 and the small-diameter hole 16, an inclined surface 17 with which the inclined surface portion 25 of the gas vent pin 20 abuts is formed.

The length L1 of the small diameter portion 21 of the gas vent pin 20 and the length L2 of the small diameter hole 16 of the gas vent pin mounting hole 13
The relation of L1 <L2 is established between and. Also,
The inner diameter of the small diameter hole 16 is the small diameter portion 21 of the gas vent pin 20.
The diameter is almost the same as the outer diameter of No. 1, and since a minute gap is provided between the small diameter hole 16 and the small diameter portion 21, it melts from the gap between the gas vent pin disposing hole 13 and the small diameter portion 21. The resin does not flow out to form burrs, and only the air and gas in the cavity pass through. Further, the inner diameter of the large diameter hole 15 is slightly larger than the outer diameter of the large diameter portion 22 of the gas vent pin 20, and the gas vent pin 20 moves smoothly inside the gas vent pin installation hole 13.

Reference numeral 18 is a through hole for the protruding pin through which the protruding pin 11 is inserted, and reference numeral 19 is in the cavity between the gas vent pin disposing hole 13 and the small diameter portion 21 and the exhaust groove 24. It is an exhaust hole for introducing air and gas to the outside of the mold. .

The operation of the injection molding die configured as described above will be described with reference to FIG. As shown in FIG. 4 (a), when the molten resin 1a flows into the cavity, the air in the cavity and the gas generated from the resin are discharged through the gap between the ejection pin 11 and the mold, while the remaining Air and gas are concentrated by the resin pressure in the vicinity where the degassing pin 20 is arranged.

Then, as shown in FIG. 4B, the molten resin 1a is further filled in the cavity. Then, air or gas in the cavity portion is discharged to the side of the gas vent pin installation hole through the gap between the small diameter hole 16 of the gas vent pin installation hole 13 and the small diameter portion 21 of the gas vent pin 20.
At this time, the substance contained in the melted gas tries to pass through the gap together with the gas, but a part of the substance contained in the gas adheres to the outer peripheral surface of the small diameter portion 21. . Then, at the same time as the air or gas in the cavity is completely discharged, the molten resin 1a is filled in the sliding hole 23 provided in the cavity and at the tip of the degassing pin 20. Air and gas discharged to the side of the vent pin are discharged to the outside of the mold through the exhaust groove 24 and the exhaust hole 19.

After a few seconds, the molten resin 1a filled in the cavity is solidified to form the molded article 1. Then, in order to eject this molded product from the mold, the moving side of the mold is retracted to operate the ejector pin 11. Then, FIG. 4 (c)
As shown in (4), the protrusion pin 11 starts to move, so that the molded product 1 starts to move away from the inner surface of the cavity portion 14. At this time, the degassing pin 20 moves in the same direction so as to be pulled by the resin filled in the sliding hole 23 in accordance with the movement of the molded product 1. At this time, the outer peripheral surface of the small diameter portion 21 of the gas vent pin 20 slides on the inner peripheral surface of the small diameter hole 16 of the gas vent pin mounting hole 13. As a result, the substance contained in the gas attached to the outer peripheral surface of the small diameter portion 21 is removed so as to be scraped off. The removed substance falls into the exhaust groove 24.

As shown in FIG. 4 (d), the protrusion pin 11 further moves. Then, the inclined surface portion 25 of the gas vent pin 20 and the inclined surface 17 of the mold come into contact with each other, and the gas vent pin 20
The molded product 1 is pulled out from the sliding hole 23 formed in the front end surface of the molded product 1 and the molded product 1 is projected to the outside of the cavity portion 14, and the protruding pin 11 is arranged at the original position.

When the molten resin is filled in the cavity again, the gas releasing pin 20 is pressed by the resin pressure.
Returns to the predetermined position shown in FIG. 4 (a), and the molding is repeated continuously.

As described above, the undercut-shaped sliding hole is formed at the tip of the gas vent pin, and the sliding hole is filled with the molten resin, so that the gas vent pin corresponds to the ejection operation of the molded product. By sliding the outer peripheral surface of the small diameter part of the gas vent pin to the inner peripheral surface of the small diameter hole of the gas vent pin installation hole, the gas adhering to the small diameter part of the gas vent pin The substances contained in are removed. As a result, the clogging of the gap between the gas vent pin and the hole for disposing the gas vent pin is eliminated every cycle, and the gas vent effect is greatly maintained.

Further, since the gas vent pin can be slid without using a drive source, the gas vent pin can be arranged at a desired position, so that the degree of freedom in designing the die is expanded.

Further, in order to prevent the resin filled in the sliding holes from protruding from the outer peripheral surface of the molded product, an undercut sliding hole is formed at the tip of the gas vent pin as shown in FIG. Alternatively, the same effect can be obtained by providing the sliding protrusion 26 having an undercut.

FIG. 6 shows a vacuum generating mechanism according to the second embodiment of the present invention. As shown in the figure, the vacuum generating mechanism of the present embodiment has a gas escape groove 61 in which a gap formed at a position where air and gas are accumulated in the cavity portion 14 is formed to be, for example, 2/100 mm. A suction secondary side groove 62 formed deeper than the communicating gas escape groove 61;
The suction primary side groove 63 communicates with the suction secondary side groove 62 and compressed air flows in a predetermined direction.

The suction primary side groove 63 is formed separately on the compressed air supply side 64 and the gas exhaust side 65. The air sent from the compressed air supply side 64 passes through the nozzle portion 66 formed by sharply narrowing the groove width, and is exhausted from the exhaust side 65 that gradually widens the groove width. Therefore, when the compressed air supplied from the suction primary side groove 63 passes through the nozzle portion 66, it expands and the thermal energy of the compressed air is converted into velocity energy.
At this time, the pressure in this vicinity decreases. As a result, the air or gas accumulated in the cavity 14 flows into the suction primary side groove 63 via the gas escape groove 61 and the suction secondary side groove 62 and is discharged from the exhaust side. It should be noted that the suction primary side groove 63 and the suction secondary side groove 62 are arranged in the nozzle portion 6.
The exhaust groove 63 communicates with a portion of the exhaust side 65 where the exhaust groove 63 gradually expands.

As described above, by generating the negative pressure portion at a desired position in the mold by the groove formed in the mold,
Air or gas in the cavity can be forcibly and efficiently sucked and discharged to the outside of the mold. Further, the gas escape groove can be set at any position according to the shape of the molded product.

[0036]

As described above, according to the present invention, there is an effect that it is possible to provide an injection-molding die provided with a gas venting pin that maintains the gas venting effect. Also,
There is an effect that it is possible to provide an injection molding die capable of high-speed air bleeding.

[Brief description of drawings]

1 to 4 relate to a first embodiment of the present invention,
FIG. 1 is a view for explaining the inside of a mold for injection molding during a molding process.

2A and 2B are explanatory views showing the structure of a gas vent pin, and FIG. 2A is a front view and a top view of the gas vent pin, and FIG. 2B is a sectional view taken along the line AA of FIG. Diagram explaining the shape

FIG. 3 is an explanatory diagram showing a schematic configuration of a block in which a gas vent pin is provided.

FIG. 4 is an explanatory view showing the action of the gas vent pin, and (a) a view for explaining the molten resin flowing into the cavity portion, and (b) a state in which air and gas in the cavity are discharged from the gas vent pin. The figure explaining (c) The figure explaining a mode that a degassing pin moves with a molded product. (D) The figure explaining a mode that a molded product is released from a sliding hole and is projected from a cavity part.

FIG. 5 is a view showing another structure of the tip of the gas vent pin.

FIG. 6 is an explanatory view showing a vacuum generating mechanism provided in a mold.

FIG. 7 is an explanatory view showing a degassing structure of a conventional injection molding die.

[Explanation of symbols]

 20 ... Gas vent pin 23 ... Sliding hole

Claims (2)

[Claims] 1. An injection-molding die having a degassing structure, which is attached to an injection molding machine to continuously obtain molded articles, wherein a degassing pin is slidably provided in a cavity portion forming the molded article. A mold for injection molding. 2. An injection molding die having a degassing structure, which is attached to an injection molding machine to continuously obtain molded products, wherein air generated in a cavity portion forming the molded product or gas generated from molten resin is discharged. A mold for injection molding, characterized in that a vacuum generating mechanism for sucking to the outside of the cavity is provided in the mold.