JPH0262216A - Plastics molding die - Google Patents

Abstract

PURPOSE:To exhaust the air in cavities and generated gas in the open air by a method wherein a vacuum chamber in a mold is vacuumized under the condition that a movable retainer plate approaches a retainer plate and grooves, each of which surrounds each cavity, are provided on the mating surfaces of the retainer plate and of the movable retainer plate and the connection between the vacuum chamber and the grooves is opened by means of a valve just before the finish of the closing of the mold. CONSTITUTION:Cavities 3, each of which is surrounded by an individual groove 10, are provided on the mating surface 2a of a movable retainer plate 2. Further, a groove 11, which surrounds the whole cavities surrounded by the grooves 10, is provided. On the mating surface 1a of a retainer plate 1, connecting grooves 12 are made and an elastomer seal ring 13 is fitted so as to surround the groove 11. In the retainer plate, a vacuum chamber 14, in which a piston 16 pushed with a spring 15 is housed, is provided. An exhaust port 18 is pored on a fixed head die plate 17. A piston 16 is pushed by the tip of a push pin 19, which is fixed to the movable retainer plate 2, when the movable retainer plate 2 gets near to the retainer plate 1. A valve 20, which communicates the groove 11 with the vacuum chamber 14, is produced by notching a part of the push pin 19. Simultaneously with the abutment of the seal ring 13 against the mating surface 2a, the valve 20 communicates the groove 11 with the vacuum chamber 14.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a mold for injection molding of plastics.

2. Description of the Related Art Conventionally, this type of mold has generally had a structure as shown in FIG. In Fig. 5, a cavity 3 is formed between the stationary mold plate 1 and the movable mold plate 2, and molten plastic is injected from sp. It is about to be manufactured. In this case, the cavity 3 is actually formed between the stationary side template 1 and the core 6, but for the sake of simplicity, the core 5 is integral with the movable side template 2 without any special distinction. Give an explanation.

An ejector pin 6 is arranged to penetrate through the movable mold plate 2 and push out the molded product from the movable mold plate 2. It's meant to be moved.

Since the other parts have a very general configuration, their explanation will be omitted.

Problem to be Solved by the Invention However, in such a conventional configuration, when molten plastic is injected into the cavity 3, gas generated from the air and plastic in the cavity 3 (hereinafter referred to as The gas (abbreviated as "gas") is discharged into the atmosphere through the minute gap between the fixed side mold plate 1 and the movable side mold plate 2 and the minute gap between the ejector pin 6 and the movable side mold plate 2. Ru.

At this time, the gap between each part is approximately 0.01 to prevent the occurrence of paris! Since it is set to about n, it is difficult for air etc. to escape. As a result, the cavity 3 is not sufficiently filled with plastic, resulting in a so-called short shot.

Further, the air in the cavity 3 is adiabatically compressed by the injection pressure of the plastic and becomes high temperature, which causes burning of the plastic and corrosion of the surface of the mold.

Furthermore, the gas passing between the ejector pin 6 and the movable mold plate 2 cools and turns into a tar-like substance (hereinafter abbreviated as tar) that fills the gap, so it is necessary to disassemble and clean the mold. There was also a problem.

In order to solve these problems, it is known to create a negative pressure inside the cooling water pipe (not shown) in the mold, but this method is limited by the structure of the mold. In addition, there was a problem in that a dedicated and relatively expensive device was required.

In addition, it is recommended to use a vacuum pump to solve this kind of problem. , p. 97), but the specific method is not shown.

Means for Solving the Problem In order to solve this problem, the plastic molding mold of the present invention utilizes the movement of the movable side mold plate toward the fixed side mold plate during the mold closing operation to close the inside of the mold. The vacuum chamber provided at The feature is that the space between the two is opened by a valve.

Effect: With this configuration, when an open mold closes, that is, when the movable mold plate approaches the fixed mold plate, the vacuum chamber first becomes vacuum, and then the seal ring connects the fixed mold plate and the movable mold plate. The inner part of the mating surface of the groove is sealed, and finally the gap between the vacuum chamber and the groove is opened, and a vacuum is created between the groove and the cavity that the groove surrounds.

When plastic is injected into the cavity after the mold is fully closed, the gas generated from the plastic will also be sucked into the vacuum of the groove through the gap between the mating surfaces.

EXAMPLE Hereinafter, an example of the present invention will be described based on the drawings. The same numbers are used for parts corresponding to those in the conventional example, and descriptions of overlapping parts are omitted.

FIG. 1 is a sectional view of a plastic molding die according to an embodiment of the present invention, in which a cavity 3 is formed between a stationary mold plate 1 and a movable mold plate 2. As shown in FIG.

There are actually a plurality of cavities 3, and each cavity 3 is provided on the mating surface 2a of the movable mold plate 2 so that an individual groove 10 surrounds each cavity 3.

A groove 11 is provided on the mating surface 2a to entirely surround the cavity 3 and the individual grooves 1Q.

A communication groove 12 is carved in the mating surface 1a of the movable template 1, and an elastomer seal ring 13, which is a round belt of urethane rubber, is fitted surrounding the groove 11. The seal ring 13 is made to protrude about 0.2 to 0.6 nm beyond the mating surface 1a when the mold is open. The fixed side mold plate has a cylindrical vacuum chamber 14, and the spring 1
A piston 16 pushed by 5 is housed. An exhaust hole 18 is opened in the fixed side mounting plate 1.

A push pin 19 is fixed to the movable mold plate 2, passes through a hole in the fixed mold plate 1, and its tip pushes the piston 16. A portion of the push pin 19 is cut out to form the groove 1.
A valve 20 opens communication between the vacuum chamber 14 and the vacuum chamber 14. 2.1 is an O-ring moistened with silicone grease to maintain airtightness.

FIG. 2 shows a plan view of the mating surfaces of the movable template 2. Some of the items attached to the stationary template are shown overlapped by broken lines. FIG. 1 is a sectional view taken along line A-B-C-D in FIG. 2 f.

FIG. 3 shows a sectional view of the mold after molding is completed and the mold is opened. 22 is a hole into which the push pin 19 is inserted, and 23 is a finished product.

In all of the above, general configuration parts not directly related to the present invention are omitted from illustration.

Next, the operation of the mold according to the present invention will be explained.

First, after the sprue 4 and the product 23 are pushed out in the usual manner from the state shown in FIG. 3, the movable mold plate 2 is moved toward the stationary mold plate 1 by a conventional crank mechanism or the like. Then, the push pin 19 pushes the piston 16, and when the distance between the mating surfaces 1a and 2a narrows to about 0.5 to 0.2 m, the seal ring 13 comes into contact with the mating surface 2a. Almost at the same time, the valve 20 opens the groove 11 and the vacuum chamber 14, and the molds are assembled to the state shown in FIG. 1. When the valve 2o opens, the seal ring 13
The air inside the vacuum chamber 14 is sucked into the vacuum created by the piston 16 being pushed up, or flows out, so that the inside of the cavity 3 also becomes vacuum in FIG.

Next, when plastic is injected from sprue 4, the gas generated from the plastic also enters the cavity 3° mating surface 1.
It passes through the groove 11 and the minute gap mainly caused by the surface roughness between a and 2a, and is sucked into the vacuum chamber 14. Also, a small amount of air flows into the cavity 3 through the gap between the ejector pin 6 and the movable mold plate 2, but this gap does not need to function as a gas vent in the present invention. It can be narrowed down to about 0.005fl. Therefore, air leakage through this gap is virtually negligible.

Thereafter, the plastic filling the cavity 3 is cooled and solidified to form a molded product, and the movable mold plate 2 is moved back toward the position shown in FIG. 3 again. At this time, the piston is spring 1
6, and when the push pin 19 is removed from the hole 22, the air and gas sucked into the vacuum chamber 14 are discharged from the hole 22, and it stops when it reaches the position shown in Fig. 3. .

Since the exhaust hole 18 is open on the rear side of the piston 16, the movement of the piston 16 is not hindered by back pressure. In order to eliminate a gap between the piston 16 and the cylindrical inner wall of the vacuum chamber 14, a piston ring commonly used in gasoline engines may be used. A plurality of pistons 16 can be provided, avoiding the core 5, etc., and the total area is 5 to 10% of the area surrounded by the seal ring 13, and the stroke is 20 to 10%.
5 Q It is easy to make it an IIM. therefore,
Depending on the volume of the cavity 3, the inside of the seal ring 13 can be vacuumed to a fraction of an atmosphere when the mold is completely closed.

The valve 20 provided on the push pin 19 is constructed by providing a circumferential groove 20a in the push pin 19 so that the air in the groove 11 can quickly flow out into the vacuum chamber 14, as shown in FIG. It is better to make it . In either case, by providing the valve 20 on the push pin 19, the valve opening timing can be synchronized with the mold closing stroke with high precision. Therefore, the valve is more accurate and cheaper than when a limit switch or sequence timer is used to operate a solenoid valve.

The piston 16 can be obtained at a very low cost by reusing one that is sold as a repair part for engines such as commercially available motorcycles.

Although the above explanation was about the most standard type of mold commonly known as the two-plate type, it goes without saying that it can be similarly applied to other types of molds such as the three-plate type.

Further, the number of cavities may be plural or only one. Matching surface 1 between cavity 〒3 and groove 11
If a and 2a are roughened to an extent that no cracks are generated by electrical discharge machining, that is, to a roughness of approximately 0.01 f1 or less, air and gas in the cavity 3 can escape easily.

If the mold closes quickly, seal ring 13
is not necessarily necessary. The same applies to the O-ring 21. On the other hand, if the mold closes slowly, the piston 1
If an O-ring moistened with silicone grease is used in place of the piston ring 6, the vacuum chamber 14 will be completely sealed.

Effects of the Invention As explained above, according to the present invention, the following effects can be obtained.

(a) The vacuum inside the cavity prevents short shots, burns, and corrosion.

(b) Since gas does not flow around the ejector pin, resin does not accumulate around the ejector pin, thus saving the effort of cleaning the mold for several minutes.

(C) Valve operation timing is accurate.

(d) The entire structure can be constructed relatively simply and easily without using any special technology.

(e) Since the equipment does not protrude outside the mold, and there are no external devices or piping connected to the mold, there is no information regarding the molding machine that uses this mold or the installation location of the molding machine. There are no restrictions.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the main parts of a plastic molding die according to an embodiment of the present invention, Fig. 2 is a plan view of the mating surfaces thereof, Fig. 3 is a sectional view showing the mold in an open state, and Fig. 4. is a partial cross-sectional view of the mold in a closed state, and FIG. 5 is a cross-sectional view showing an example of a conventional mold. 1... fixed side template, 1a... mating surface, 2... movable side template, 2a... mating surface, 3...・Cavity, 11... Groove, 13... Seal link, 14... Vacuum chamber, 16... Piston, 19... Push pin , 20... Valve. Name of agent: Patent attorney Shigetaka Awano and 1 other person 1st
Figure/-m-plane fixed number 11L. k, Mu upper surface z ′-1 movable a, 11 [view 1 “”l-tM, 3
- No. 11 - - La - - f, 3 - Seaf ring 14 - Shinsen 1 16 - H 0 s F n tq" - Upper press Renine 20 - Square diagram? Figure with diagram Figure B

Claims (4)

[Claims] (1) A fixed side template, a movable side template, a cavity formed between the fixed side template and the movable side template, and when the movable side template approaches the fixed side template. a vacuum chamber that is evacuated immediately before the vacuum is applied; A plastic molding die comprising a valve that opens communication between the chamber and the groove. (2) The vacuum chamber has a piston, one vacuum chamber and one push pin are provided on either the fixed side mold plate and the movable side mold plate, and the movable side mold plate approaches the fixed side mold plate. 2. The plastic molding die according to claim 1, wherein the vacuum chamber is evacuated by moving the piston while being pushed by the push pin. (3) The plastic molding die according to claim 1 or 2, wherein at least one of the mating surfaces is provided with an elastomer seal ring that protrudes from the mating surface and surrounds the groove. (4) The plastic mold according to any one of claims 1 to 3, wherein the valve is formed by cutting out a part of the push pin.