JPS5846387B2 - Gas venting device for mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mold gas venting device for extracting a large amount of gas from a mold cavity during molding in a molding machine such as a die casting machine or an injection molding machine. It is.

Traditionally, die casting has been widely used as a molding method for manufacturing precision products in large quantities.
The temperature was not suitable for products for which integrity is important.

This is because the cavity is filled with molten metal at high speed and high pressure, so the gas in the cavity may not be sufficiently vented and may mix with the molten metal and remain in the product.

As a countermeasure, conventional methods have been considered, such as a non-porous die casting method in which the inside of the cavity is replaced with an active gas, which is combined with the molten metal and fixed, and a method of reducing pressure.
These require complicated molds and equipment, and are not common.

The inventor of this invention investigated the relationship between the area of the air vent and the specific gravity value of the cast product using a die-cast model, and found that as the area of the air vent increases, the specific gravity value of the cast product also increases. .

However, the number of air vents is limited by the size of the product, and the thickness of the air vent must be approximately 0.1 rrrm or more to prevent molten metal from passing through.
.

This invention makes it possible to extract a large amount of gas, eliminate gas entrainment, and obtain sound die-cast products without being restricted by such products or mold structures.

That is, in this invention, the gas discharge path leading from the mold cavity to the outside of the mold is opened (・down・・injection) by the action of a valve. When the discharge through the discharge path is almost completed, the inertial force of the mass of the injected melt that has advanced from inside the cavity is applied directly to the valve, thereby moving the valve reliably and quickly. The gas exhaust path is directly shut off by the valve to prevent the molten material to be injected from flowing out from the gas exhaust path, so that gas inside the mold can be reliably and easily vented during injection. This is how it was done.

Next, the present invention will be explained with reference to embodiments shown in the drawings.

In the embodiment shown in Figures 1 and 2, 1 is a fixed plate, 2
is a movable plate, 3 is a fixed mold, 4 is a movable mold, 5 is an extrusion plate,
6 is an extrusion pin, T is a cavity of the molds 3 and 4, and 8 is a casting hole for molten metal which is the molten material to be injected.

In the movable mold 4, a thin L gas venting path 9 having a sufficient area is provided in the part facing the fixed mold 3 around the cavity 7, and connected to the upper end of the gas venting path 9. A gas vent groove 10 extending upward was provided on the 3-40 dividing surface of the two molds or on the 40-dividing surface of the movable mold.

A valve 1 is inserted into the gas vent groove 10 led from the cavities 7 of the molds 3 and 4 and is moved directly in the direction of action of the molten metal by the action of the molten metal advancing from the cavity 7.
4 was established.

The valve 14 is moved directly by the action of molten metal from the same direction as the moving direction of the valve 14, so that the same valve 14 directly blocks off a first gas discharge path consisting of a bypass 15, etc., which will be described later. Only one item was provided.

That is, two molds 3,
Valve chamber 11 that can be split in half on the 40-way split surface. Valve seat 12,
The gas discharge holes 13 are arranged in series facing upward, and the valve chamber 11
A valve 14 that can be slid in the vertical direction is built inside.

The valve 14 was shaped like a disk, and the outer peripheral surface of the upper end was tapered.

That is, as the valve 14, a valve having a shape called a disk type or seat type having a valve head is used.

A spool 22 that slidably supports this valve 14 and itself slides in the axial direction is provided, and the spool 22
A tapered valve seat 12 is seated with a tapered surface provided on the outer periphery of the back surface of the valve head of the valve 14 pressed against the valve-side end of the valve seat 12.
has been established.

Further, a gas exhaust port 20 is provided as a second gas exhaust path that communicates the gas exhaust hole 13 inside the spool 22 with the outside of the fixed mold 3.

Details of this device are shown in FIG.

18 is a cylinder attached to the fixed mold 3, 18a is a piston, and 19 is a piston rod.
A spool 22 is fixed to the lower end of the spool 22, and the spool 22 is inserted into a vertical half hole 23 formed in the fixed mold 3 and a vertical half hole formed in the movable mold 4 that matches this half hole. It was designed to be able to slide.

A chamber 24 is provided in the upper part of the spool 22, and a downwardly opened gas discharge hole 13 and a valve seat 12 are provided in the lower part of the spool 22.

A vertical rod 25 is provided at the center of the upper end of the valve 14 to open the chamber 2.
A nut 26 was attached to the tip of the rod 25 that penetrated into the inside of the rod 4.

Of course, the rod 25 is provided slidably relative to the spool 22.

A compression spring 1 is connected around the rod 25 between the upper end surface of the valve 14 and the bottom surface of the gas discharge hole 13 of the spool 22.
7 was established.

Between the middle of the gas vent groove 10 immediately in front of the valve chamber 11 and the side surface of the valve chamber 11 immediately in front of the valve seat 12, which is the side surface of the movement path of the valve 14, there is a first groove around the valve chamber 14. A bypass 15, which is a passage for gas discharge, is provided, and the operation of the valve 14 directly controls communication and interruption of the gas discharge passage between the bypass 15 and the outside of the mold.

The intersecting angle θ between the gas vent groove 10 and the inlet of the bypass 15 was set to be an acute angle or a right angle.

The opening 16 of the gas vent groove 100 facing the valve chamber 12 is narrowed into a nozzle shape.

That is, in this embodiment, a gas vent groove 10 led from the cavity 7, a valve 14 that slides in the axial direction at the end of the gas vent groove 10, and a valve are provided on the separation surface of the molds 3 and 4. 1
A spool 22 that supports the gas valve 4 in a freely slidable manner and can itself slide in the axial direction, and a first gas exhaust passage that detours from the middle of the gas vent groove 10 to the side surface of the valve 14 portion. A bypass 15 is provided, and a gas exhaust port 20 is provided as a second gas exhaust path that communicates the inside of the spool 22 with the outside of the mold 3. has been established.

Additionally, a compression spring 17 is provided between the spool 22 and the valve 14.
was arranged.

The position of the compression spring 17 is as shown in FIG.
As shown in FIGS. 6 to 8, the upper surface of the valve 140 head 26a corresponding to the nut 26 in the chamber 24 and the ceiling surface of the spool 22 Good between L.

However, it is not necessary to provide the compression spring 1γ, and the downward pressing force may be set to O after the valve 14 is allowed to fall naturally or is lowered by another cylinder, etc. (
・.

Next, the operation sequence of the embodiment of the present invention will be explained.

mass, raise the piston rod 19, and compress the compression spring 17.
The force is weakened and the mold is clamped with the valve 14 slightly floating above the lower end of the valve chamber 11. Then, the piston rod 1 is closed.
9 is lowered to ensure that the valve 14 is in close contact with the lower end of the valve chamber 11.

In this state, the bypass 15 leads to the upper part of the valve chamber 11.

In this state, if molten metal is poured into the cavity T from the pouring hole 8, the gas in the cavity 7 will flow through the gas vent path 9, the gas vent groove 10, the bypass 15, and the valve. The gas passes through the gas exhaust hole 13 in the upper part of the chamber 11 and is discharged from the gas exhaust port 20 .

During this time, the valve 14 remains pressed against the lower part of the valve chamber 11, as shown in FIG. 3a, and a large amount of gas escapes through the bypass 15, as shown by the arrow.

Of course, at this time, the gas also acts on the lower surface of the valve 14 through the opening 16, but since the mass of the gas is extremely small L, the valve 14 does not rise L.

When the filling of the molten metal into the cavity 7 is almost completed,
The large mass of the molten metal 21 rises inside the gas vent groove 10 and collides with the lower surface of the valve 14, and as a result, the valve 14 is pushed up against the compression spring 17.

Then, the molten metal 21 pushes up the valve 14 and a part of it begins to enter the bypass 15.

The state at this time is shown in Figure 3.

Eventually, the valve 14 is closed by pushing up the molten metal 21, and the molten metal 21 is dammed up.

At this time, the L. ivy gas that has passed through the bypass 15 is
The L. is completely removed and only a small amount remains near the valve seat 12, but this does not have any adverse effect on the cast product.

The state at this time is shown in FIG. 3C.

When the casting operation is completed, the cylinder 18 is operated to raise the piston rod 19 to lift the sleeve 22 and valve 14 to some extent, and then the mold is opened.

The state at this time is shown in FIG. 3d.

Continuation L. By operating the extrusion pin 6, the cast product is taken out, and at the same time, the solidified metal 21a in the gas vent groove 10, the lower part of the valve chamber 11, and the bypass 15 is taken out.

If this device is used, the valve 14 can be used permanently.

Note that a dish-shaped recess 14a may be provided on the bottom surface of the valve 14, as shown in FIGS. In that case, the sleeve 22 and valve 14 must be raised to a level greater than the thickness of the recess 14a before the mold is opened.

This invention utilizes the difference in specific gravity between gas and molten metal, for example, the difference in specific gravity between air and molten aluminum, which is about 1=2000, and the difference in inertia based on this difference in specific gravity. It is.

Then, one valve 14 that slides in the same direction as the axis of the gas vent groove 10 is provided in the gas vent groove 10 portion led from the cavity 7 of the molds 3 and 4. Mold 4 with a reverse bypass 15 on the side of the valve 14 part
The injection was carried out with the gas discharge passage leading from the cavity 7 to the outside of the molds 3 and 4 open by the action of the valve 140. First, the small mass L that had advanced from the cavity 7 - When gas acts on the end face of the valve 14 on the gas vent groove 10 side, the valve 14 is not pushed by the gas having a small mass and is at the end face on the gas vent groove 10 side, and the bypass 15
The gas is discharged through a reverse gas discharge path consisting of 14 parts and valves, etc., and along the way, the small mass L gas is followed by L gas.
The large mass (molten metal to be injected) that has advanced from the cavity 7 directly acts on the end face of the valve 14 on the side of the gas venting mechanism 10 from the same direction as the moving direction of the valve 14. The valve 14 is moved to directly block the gas discharge path so that molten metal is not discharged from the valve 14 to the outside.
In this way, injection can be performed while degassing the molds 3 and 4 at a temperature of .degree.

In addition, in order to prevent the molten metal 21 rising in the gas vent groove 10 from directly jumping into the bypass 15, the molten metal 21 is placed between the valve 14 and the valve seat 12 before the valve 14 is closed. The angle between the gas vent groove 10 immediately below the nozzle portion 16 and the inlet portion of the bypass 150 was set to be an acute angle or a right angle so that the gas vent groove 10 did not pass through the gap.

Of course, it is more effective to make this angle acute.

In this embodiment, the mold degassing device of the present invention was provided on the dividing surface of the fixed mold 3 and the movable mold 40.
This may be provided on the separation surface or contact surface of other molds, such as between the movable mold 4 and the core mold, or between two core molds.

In addition, in these embodiments, from the gas exhaust port 20,
It is even more effective if the gas is actively sucked in by operating the device shown below or a vacuum device.

When the suction of gas from the gas discharge port 20 is performed in synchronization with the injection operation, it is performed as shown in FIG. 5, for example.

In Fig. 5, 1 is a fixed plate, 2 is a movable plate, 3 is a fixed mold, 4 is a movable mold, 5 is an extrusion plate, 6 is an extrusion pin, 7 is a cavity, and 8 is a casting hole. , 27 is a machine base, 28 is an injection cylinder, 29 is a piston rod, 30 is an injection plunger, 31 is a plunger tip, and 32 is a cast sleeve.

At the top of the fixed mold 3 and movable mold 40 dividing plane (East No. 1 and 2)
The mold degassing device 33 of the present invention shown in the figures and FIG. 4 was installed.

A suction cylinder 34 is installed above the injection cylinder 28 in parallel with the injection cylinder 28, and the tip of the L-shaped piston rod 36, which is integrated with the piston 35 of the suction cylinder 34, is attached to the piston rod 29 of the injection cylinder 28. The two piston rods 29 and 36 are integrally connected by a lever 37 so that the two piston rods 29 and 36 move simultaneously.

Then, the gas exhaust port 20 of the mold gas venting device 33 is
It was connected to the head end side of the suction cylinder 34 by a pipe 38.

In conjunction with the forward movement of the injection cylinder 28, the gas inside the cavity 7 can be discharged to the outside of the molds 3 and 4 via the mold gas venting device 33.

39 is a check valve. However, the inner diameter of the suction cylinder 34 is made larger than the inner diameter d of the casting sleeve 32, so that the inside of the cavity 7 becomes a negative pressure during casting, so that degassing can be performed satisfactorily.

Note that the reduction in the output of the injection cylinder 28 due to the suction cylinder 34 is extremely small and is hardly affected.

In addition, in the above embodiment, the valve 14 was moved up and down in the vertical direction and was used in a die-casting machine. It may be moved at a temperature of 10°C, or may be used for an injection molding machine.

Other embodiments of the invention are shown in FIGS. 6-8.

What is shown in FIGS. 6 to 8 is a version of what is shown in FIG. 4 based on the manufacturing drawings, and therefore is almost the same as what is shown in FIG.

6 to 8, parts that are the same as those shown in FIG. 4 are designated by the same reference numerals as used in FIG. 4.

What is shown in FIGS. 6 to 8 is somewhat different from that shown in FIG. The upper surface of the head 26a of the valve 14 is attached between the top surface of the toss boule 22 and the ceiling surface of the valve 14, and the lower surface of the valve 14 is provided with a dish-shaped recess 14a.

The cylinder 18 was attached to the fixed mold 3 by a bracket 40, and the spool 22 was slidably held by a guide 41 attached to a part of the bracket 40.

Furthermore, sensors 42 and 43 such as limit switches and non-contact switches are provided on the side of the bracket 40, and a bar 44 that operates sensors 42 and 43 is attached to a part of the spool 22. Check the lower limit and upper limit of the spool 22.

The bar 45 is connected to the spool 22 from the head 26a of the valve 14.
By extending the bar 45 to the outside of the spool 22 through the notch 22a, attaching a sensor 46 such as a limit switch or a non-contact switch to a part of the spool 22, and confirming that the bar 45 is separated from the sensor 46. Before pouring molten metal, make sure that the valve 14 is securely separated from the valve seat 12 and opened.

After confirming that the valve 14 is definitely open, the molten metal can be poured.Also, as mentioned above, before or during casting, a vacuum is drawn from the gas outlet. There is a low-pressure die-casting method in which the casting operation is performed by actively sucking the gas in the cavity 7 when the device is activated, or the casting operation is performed after filling the cavity T with reactive gas such as oxygen before casting. Die casting can also be carried out using a non-porous die casting method.

As described above, since the present invention has the configuration as described in the claims, there is no need to use a vacuum pump or a decompression tank as in the conventional depressurization method, and the structure is extremely simple. .

In this invention, the inertial force of the molten metal, which is the molten material to be injected, is absorbed by opening the gas exhaust path outside the mold.
・The valve acts directly on the valve and directly blocks the gas exhaust path, so the valve can be quickly tightened with a large force.

That is, in this invention, the molten metal that has advanced at high speed to the nozzle part under the valve through the gas vent groove collides with the bottom of the valve, so that it directly lines the valve. The kinetic energy of the molten metal due to the impact force, that is, the dynamic pressure of the molten metal, is used to directly line the valve.

In this case, the force required to close the valve is proportional to the square of the speed at which the molten metal collides with the bottom of the valve, resulting in a very large force.

Since the molten metal can be applied to the entire bottom surface of the valve, the force to close the valve is large, and the valve can be closed directly.
Since the gas exhaust passage is directly closed by the valve, the valve itself has a simple structure and is relatively light in weight, and the valve can be quickly closed to quickly, reliably, and easily close the gas exhaust passage.

In addition, according to the present invention, the time required to close the valve at the bottom is extremely short, about 5 to 77 seconds.

In addition, in this invention, due to the action of the inertial force of the molten metal,
Since the valve that is discharging gas is directly and instantly closed, there is no need to create resistance by narrowing the entrance or middle of the gas discharge passage, also known as a bypass, which leads from the gas vent groove to the side of the valve travel path. There is no need to make this passage longer than necessary, and the passage can be simplified and made relatively wide, so the degassing capacity is large and degassing can be performed reliably.

In the first place, during injection, gas should be sufficiently vented from the mold cavity to prevent the formation of cavities in the injection product, and to achieve a satisfactory L.
In order to continue the injection operation, sufficient gas can escape from the valve part, but it is necessary to prevent the molten metal from flowing outside. It is necessary to keep the valve open until you approach the valve seat, which is the opening part of the valve, and then close the valve quickly, that is, in a very short time, when the gas has fully escaped. In the present invention, as described above, this operation can be performed reliably and easily, and can be performed repeatedly for each injection.

Furthermore, since the present invention (the east valve itself is made of one piece and is simple), the structure of the entire degassing device is relatively simple, and maintenance and inspection are easy.

Furthermore, it is important to note that the present invention includes a disk-type valve having a valve head that slides in the axial direction along the separating surface of the mold at the end of the gas vent groove, and Since a valve seat on which the valve head is seated is provided at the end of the spool, when the valve is pushed and tightened by the inertia of the molten metal, the outer circumferential surface of the back side of the valve head is completely attached to the valve seat having an inclined surface. It is strongly pressed so that it comes into close contact with the body, ensuring a secure seal.

Further, the gap between the valve seat of the spool and the valve head will not be clogged with molten metal, and the valve will not malfunction, so it is of course easy to open the valve again.

In addition, even if the valve head and valve seat change their diameter due to thermal expansion due to the high temperature of the molten metal, the slanted valve seat seals the valve head and valve seat, so there will be no adverse effects, and the valve will always be securely operated. It is tightened.

Therefore, the operation of this device is stable and reliable, so even if it is used repeatedly for each injection, no trouble will occur, and it can be used continuously for a semi-permanent period.

Of course, unlike spool-type valves, disc-type valves have less sliding surface area, so they have less operating resistance and are more practical.

Furthermore, the structure is relatively simple, easy to operate, and inexpensive.

In addition, in this invention, even if there is debris around the valve head, this will be combined with the solidified molten metal that entered the passageway and nozzle when the valve was lifted together with the spool. All of these are taken out of the mold together with the injection product and removed naturally.

When the mold is opened, the spool can be lifted up along with the valve, allowing the valve to be opened (and the valve head, valve seat, valve chamber, etc. to be easily cleaned with compressed air). , the degassing device can be operated more satisfactorily each time.

In addition to this, there are the following effects.

(1) The valve is pushed directly by the molten material to be injected in the direction of movement of the molten material to be injected, which is moving straight through the gas vent groove, and the gas discharge path is blocked, so that the operation of the valve is prevented. It is quick and reliable, and gas venting and prevention of discharge of the molten material to be injected from the valve part can be performed reliably and easily.

(2) Since gas can be sufficiently vented during injection, residual gas in the injection product is significantly reduced, and the hot water performance, pressure resistance, and airtightness of the injection product are significantly improved.

(3) Since the occurrence of debris at the air vent area around the cavity periphery is reduced, there is no need to remove the debris, and there is no risk of damaging the mold.

The result is easier automation and longer mold life.

(4) Since gas degassing is sufficient, good quality injection products can be obtained with low injection pressure.

Of course, this also facilitates automation and extends the life of the mold.

In other words, if you inject with gas in the cavity as in conventional general injection, the gas that cannot escape from the cavity will be compressed and filled into the cavity with molten metal, which is the molten material to be injected. Therefore, a very large force is required to fill every corner of the cavity with molten metal.

On the other hand, if this invention is used, the injection is performed after the gas in the cavity is sufficiently released, so that the injection pressure can be kept relatively low to ensure that the molten metal is fully filled to every corner of the cavity. It is possible to obtain an L. injection product.

In addition, since the injection pressure is low, there is no occurrence of paris.

Therefore, the molten metal spreads to every corner, making the L.
Good injection products can be obtained.

In addition, according to the experimental results, L・
The molten metal pressure inside the cavity is approximately 700 to 1000 ky.
/crA is required, about 1.5 to 2.5 as high injection speed
Although it depends on the shape and dimensions of the injection product, what used to require 1 sec can be reduced to about 200 to 50 sec by using this invention.
Molten metal pressure in the cavity of 0 ky/cat and approximately 1 m/
A high injection speed of sec was sufficient.

In addition, once the injected product is free of paris, no paris remains in the mold, unlike conventional methods, and there is no need to clean the mold to remove the remaining paris, so automatic continuous operation is possible. becomes easier.

In addition, since injection can be performed at relatively low speed and low pressure, there is less shock at the end of injection, less seizure of the mold, and no damage to parts of the mold.

In particular, the protruding parts of the mold, such as the core part of the mold and long thin cast-out pins, will not break or bend (this will extend the life of the mold and ensure that high-quality products can be obtained continuously). You can also do it.

(5) Since gas degassing is sufficiently performed, the range of injection conditions is expanded, the test shot time is shortened, and the quality of the injection product is stabilized.

Traditionally, we have searched for good conditions for injection pressure, injection speed, and high-speed injection start position, and set the temperature at a location with good degassing.However, it took time to find these conditions, and The conditions also gradually changed during injection, however,
By using this invention, degassing can be carried out sufficiently, so the range of options for selecting injection conditions can be considerably expanded.

(6) Conventionally, it has been considered to use a vacuum device to extract the air inside the cavity through a thin groove between the molds, but in this case, the amount of air removed from the cavity is small.
・With this invention, outside air enters from the mating surfaces of the fixed mold and the movable mold, and the cavity does not become a vacuum.
Since a large amount of air is removed, the precision of the mating surfaces of the molds is not a big problem, and the air in the cavity can be removed sufficiently.

Therefore, if used in combination with the decompression method, the effect will further increase.

(7) If used in conjunction with the non-porous die casting method, in which the cavity is filled with an atmosphere of active gas such as oxygen, the effect will be even greater.

In this case, from the open valve part of the gas venting device of this invention,
After entering the active gas into the cavity, it is injected.

Active gas can also be introduced into the cavity during injection.

(8) If L is used for magnesium die-casting, the effect will be worse. In other words, for aluminum die-casting,
I could try to inject slowly and let the gas in the cavity out through the vent, but since the solidification rate of magnesium alloy is so fast, low-speed injection was not possible, and I had to start high-speed injection immediately after starting injection. I needed to move.

Originally, during injection, it is necessary to release a large amount of gas from the cavity and injection sleeve, which have a volume approximately twice that of the cavity, to the outside of the mold, but in the case of magnesium die casting, compared to aluminum die casting, , Since high-speed injection was required, a large amount of gas was forced into the injection product.

However, if the present invention is used, degassing is sufficiently performed, so even when die-casting magnesium, it is possible to reliably and easily obtain a high-quality injection product without air bubbles.

(9) Can also be used for hot chamber complete die casting.

αO) 1 Conventionally, cooling water or a water-soluble mold release agent was sprayed onto the mold after the mold was opened, but when the mold was clamped, if water droplets remained on the mold and the temperature reached ℃, there was a place for water vapor to escape. If the product is injected as is, the surface of the injected product will become black, the hot water flow will be poor, and it will not be possible to obtain a high-quality injected product.

Therefore, it was necessary to clamp the mold after the water droplets on the surface of the mold had sufficiently dried and disappeared.

However, if this invention is used, hot air can be sent into the mold through the valve that opens in the gas venting device when the mold is clamped, and the water vapor inside the mold can be released to the outside through the injection sleeve.

This feeding of hot air can also be performed after mold clamping or during hot water supply.

Therefore, if hot air is sent into the cavity through the gas venting device during mold clamping, the mold can be clamped quickly after spraying, and the cycle can be shortened.

αυ can of course be used as a permanent valve device.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view showing one embodiment of the present invention, Fig. 2 is a sectional view taken along the line ■-■ in Fig. 1, and Fig. 3 a - d are the first and second
An explanatory diagram of the operation of the sliding valve shown in the figure, Figure 4 is 1 in Figure 2.
5 is a vertical cross-sectional view showing another embodiment of the present invention, FIG. 6 is a vertical cross-sectional view showing still another embodiment of the present invention, and FIG. 7 is a cross-sectional view of FIG. 8 is a sectional view taken along the line ■--■ in FIG. 7. 1...Fixed plate, 2...Movable plate, 3...
...Fixed mold, 4...Movable mold, γ...
...Cavity, 9...Gas venting path, 10.
...Gas vent groove, 11...Valve chamber, 12.
... Co-production, 13 ... Gas discharge hole, 14 ...
... Valve, 15 ... Bypass (first gas discharge path), 17 ... Compression spring, 18 ...
Cylinder, 20... Gas exhaust port (second gas exhaust path), 21... Molten metal, 22...
Spool, 28...Injection cylinder, 29°36
...Piston rod, 30...61. Injection plunger, 31...Plunger tip, 32.
...Cast sleeve, 34...Suction cylinder.

Claims (1)

[Claims] 1. A disc-type valve that has a valve head on the separation surface of the mold that slides in the axial direction along the separation surface of the mold at the end of the gas vent groove led from the cavity, and this valve can be slid freely. a spool supported on and capable of sliding itself axially;
and providing a first gas exhaust path leading from the middle of the gas vent groove to a side surface of the valve head, and providing a second gas exhaust path communicating the inside of the spool with the outside of the mold. At the same time, a valve seat on which the valve head is seated is provided at the end of the spool on the valve side, and the first gas discharge path is opened.
- A gas venting device for a mold, wherein the valve is directly moved by the inertial force of the molten material to be injected advancing from the cavity to directly shut off the first gas exhaust path.