JPS6046222A - Mold device for vacuum exhaustion - Google Patents

Abstract

PURPOSE:To prevent resin from whitening and blackening when a nozzle touches the sprue in injection molding or in injection compression molding by a method wherein a mold the movable side is engaged with the fixed one so that vacuum seal can be obtained under the state where the parting line is separated at a specified distance from the contact line. CONSTITUTION:In injection molding or injection compression molding, the nozzle is brought in contact with the sprue. In the mold, the movable side is contrived to be engaged with the fixed one so that vacuum sealing can be obtained when the parting line is separated by 3-20mm.. The structure is improved in conductance in vacuum exhaustion and made convenient for exhaustion. The exhaustion is conducted by a high-efficient vacuum device at a stroke and completely so that the whitening or efflorescence of resin due to the adiabatic compression of the residual air can be prevented in a future injection. In the figure the upper part of the center line shows the exhausted state while the lower part shows the injecting state. O-ring 24 is fixed on the external periphery 26 to complete the preliminary sealing. After a specified vacuum degree is attained, in such a state, the retainer plates on both sides are clamped to inject resin while exhaustion is continued.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a vacuum evacuation mold device for evacuating the cavity of a mold in resin molding such as injection molding or injection compression molding.

(Conventional structure and its problems) When resin is injected in resin processing such as injection molding, injection compression molding, or transfer molding, the space inside the cavity is gradually narrowed by the resin, so If there is no escape port, the air will be adiabatically compressed and the resin will turn white, and in severe cases it will turn black.

For this purpose, as shown in FIG. 1, a method is used in which a gap called an air vent 5 is created in the running line, and as the resin flows through the gap, the air inside is pushed out. In other words, between the cavity 4 and the air passageway (air escape port) 3 leading to the outside air, there is a thin space that allows air to pass through, but not enough resin! ! 5 (for example d=50μm to 100μm
m) is often provided on the part line of templates 1 and 2. The land e of the air vent 50 is designed to be small within a range that does not cause any problem in terms of strength9, so that air can easily escape.

This method is effective when the flow end of the resin and its escape area coincide, but as shown in Figure 2, when the center is thin and the outer periphery is thick, the resin is filled from the periphery first.
This is very effective when the interior is filled at the end.

The resin flowing in from the dart 8 flows into the outer periphery where the flow resistance is low because the periphery is thick, and when the resin reaches the thin part in the center, it grows and does not move forward, causing air pocket shift. There is no problem when this air passes through the merging part and is released to the outside, but if high resin pressure is applied while it remains in the center, it will be adiabatically compressed there.

Figure 3 shows a product with an internal hole, pin 14 in the mold.
, the resin flowing in from the gate 13 is divided there and merges on the opposite side. An air pocket 15 is generated in the light removing resin 12. In this case, the clearance between the pin 14 and the template 11 should be made a little larger.
Although air is allowed to escape along the pins 14, increasing the efficiency of the escape has the disadvantage that the dimensional accuracy of positioning by the pins deteriorates. This will be a fatal defect if the corresponding template 10 is infiltrated with a gun.

(Object of the Invention) An object of the present invention is to provide a mold device having a vacuum seal structure suitable for forcibly and efficiently evacuating the inside of the mold prior to injecting resin into the cavity. It is.

(Structure of the Invention) In the vacuum evacuation mold device of the present invention, if the nozzle is kept in contact with the stripe during injection molding or injection compression molding, the vacuum evacuation mold device of the present invention The movable side and fixed side of the mold are fitted together to obtain a seal, and the structure is designed to improve the conductance of vacuum evacuation and facilitate evacuation.
By evacuating the resin all at once and completely using a high-efficiency vacuum device, whitening or blackening of the resin due to adiabatic compression of residual air is prevented during subsequent injections.

(Description of Embodiment) An embodiment of the present invention will be described based on FIGS. 4 to 6.

FIG. 4 shows the first embodiment, in which the nozzle 21 of the injection device comes into contact with the stationary side of the mold to seal the inlet of the strip 30. The area above the center line in FIG. 4 shows a state in which a vacuum seal is made and exhaust is being performed, and the area below shows a state in which injection is in progress. A vacuum seal between the foot template 22 and the movable template 27 is formed by the degree of clearance between the inner circumferential surface 25 of the fixed template 22 and the outer circumferential surface 26 of the movable template 27. An O-ring 24 is provided on the outer circumferential surface 26 of the movable template to complete the auxiliary sole. Exhaust is performed through the flow path of the exhaust hole 23. The piping should be made as large as possible to provide sufficient conductance for highly efficient exhaust.

In this state, the mold plate 23 on the movable side is slightly protruding from the template plate 22 on the fixed side, so the cavity portion C is wide, and the air in the cavity portion is not in contact with the groove line portion, so good conductance can be achieved. Exhaust is also performed. Also, fit an O-ring 2B around the outer circumference of the tip of the ejector pin to ensure complete sealing of the cavity.

In this state, after reaching a predetermined degree of vacuum, the mold plates on both sides are clamped while the evacuation continues, and the resin is injected. At this time, exhaust air is passed through the exhaust hole 23 and the near vent 29.

In Fig. 5, instead of directly machining the template into convex and concave shapes, a concave portion 33 is provided in the template 27 on one side, in the example of this figure, the movable side.
A protruding ring 32 wrapped around an O-ring 31 is provided on the other side to play the same role as in the case of Figure 4.

The processing problems of the first and second embodiments are on both sides, 25 and 2.
If the degree of clearance of 6 is too small, it will cause galling, and if the seal depends only on the 0 ring, there will be a phenomenon that the sealing performance will be deteriorated. It also causes the O-ring to peel off.

In the third embodiment shown in FIG. 6, a seal member 40, for example, a ring-shaped rubber member such as silicone thread or trill thread, is mounted on the movable template 27, and the other seal member 41 is made of metal such as stainless steel. Then, use the spring 42 to attach the sealing member 4.
Sealing is performed by pressing down to zero. In this case, the clearance between the fixed template 22 and the movable template 27 is loose or tapered. As a result, no galling can be seen on both templates. The arrangement of the metal and rubber of the sealing member may be interchangeable, but in that case, the sealing member 41 is a metal member with rubber pasted on top.

By applying a vacuum to the cedar, particles will come out of the injected resin and reduce the degree of vacuum.

The intended purpose can be achieved by performing vacuum evacuation using pin clearances and air vents so that evacuation is performed even after the mold is closed. In addition, if the injection rate is small or the product is thick and the injection time is long, a vacuum switch (air cylinder, hydraulic cylinder, electric) that opens and closes according to an external signal is installed in contact with the cavity.
Effectiveness can be increased by addressing leaks. In this case, it is read from the injection 2 creu position that the resin has been injected and filled nearby, and the vacuum switch is closed to stop evacuation and finish the resin filling.

(Effects of the Invention) According to the present invention, in injection molding or injection compression molding, if the nozzle is kept in contact with the sprue, the mold can be sealed so that a vacuum seal can be obtained when the ting line is slightly separated. The movable side and fixed side of the vacuum pump are designed to fit together to improve the conductance of vacuum evacuation, so a high-vacuum cavity can be instantly obtained using a high-efficiency evacuation device. It is possible to prevent whitening and blackening of the resin due to the adiabatic compression of air remaining during injection, and has the effect of reducing the number of products with poor appearance.

[Brief explanation of drawings]

Figure 1 is a sectional view of a mold with a conventional air vent, Figure 2 is a cross-sectional view of a mold with a conventional air vent.
The figure is an explanatory diagram showing a residual air pocket with a thin wall at the center and a thick wall at the periphery, and Figure 3 is a cross-sectional view of a product with holes inside.
FIG. 4 is a sectional view of a mold according to an embodiment of the present invention, FIG. 5 is a sectional view of a mold with a modified sealing method, and FIG. 6 is a sectional view of yet another mold. 1... fixed side template, 2... movable side template, 3... air escape port, 4... cavity containing filling resin,
5... Air vent, 7... Air pocket, 8... Dirt, 1 sail 11... Template, 12... Filling resin, 13
...Kate, 14...Bin, 15...Air pocket, 21...Nozzle, 22...Fixed side template, 23...
... Exhaust hole, 24... O-ring, 25... Inner circumferential surface of fixed side template, 26... Outer circumferential surface of movable side template, 27...
・Movable side template, 29...Air vent, 30...Sugeru, 31...0 link, 32...Protruding ring, 33
...Movable side recess, 40, 41...Seal member, 4
2...Spring assembly. Patent applicant Matsushita Electric Industrial Co., Ltd., agent Hoshino
Tsukasa Tsune: 1. Figure 1 1 Figure 2 (0) (b) Figure 3 (0) (b) 0 Figure 4 3 Figure 5 1

Claims (1)

[Claims] In injection molding or injection compression molding, if the nozzle is in contact with the null, the movable side and fixed side of the mold should be placed so that a vacuum seal can be obtained with 3 or 2 (1+11) distances between the shooting lines. A vacuum evacuation mold device characterized by being fitted together.