JPS6224497Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a mold, particularly a mold for plastic injection molding.

Conventionally, injection molds have been designed to eject a molded product from a cavity formed in a pair of molds that move toward and away from each other using an ejecting pin, and when ejecting, a molded product is ejected from the outer periphery of the ejecting pin. The molded product is taken out from the cavity by blowing out compressed air.

By the way, the ejection mechanism of the above-mentioned injection mold is such that when compressed air is press-fitted into the mold 1 as shown in FIG. It flows into the blow-off holes 2... and pushes out the protruding pin 3 formed in the shape of a morning glory against the spring 4, and as a result, a gap is created between the mold 1 and the outer periphery of the protruding pin 3. , in which compressed air is blown out from this gap to take out the molded product from inside the cavity, or when compressed air is press-fitted into the mold 1 as shown in Fig. 2 A and B, it is approximately circular. The compressed air flows into the hole 6 formed in the protruding pin 5 formed in a columnar shape and pushes out the protruding pin 5 against the spring 7. As a result, compressed air is blown out to the outer periphery of the tip of the protruding pin 5. Some are known that allow molded products to be taken out from inside the cavity.
All of these are designed to ensure a space for compressed air to pass through after the protruding pins 3 and 5 are pushed out, and to eject the compressed air.

However, the above-mentioned protrusion mechanism is not used unless it is for molding a completely flat product or a deep box-shaped product with vertical walls all around, and it is difficult to mold such a product. In this case, since a plurality of the above-mentioned protrusion mechanisms are arranged, the timing of the protrusion pins 3..., 5... and the balance of compressed air may not be maintained when taking out the molded product from the cavity. In such a case, the molded product would tilt, making it difficult to take out the molded product from the cavity, which would lead to damage to the product.

In addition, those with a protrusion mechanism as shown in FIG. Resin powder accumulates on the top, and as a result, the morning glory-shaped protruding pin 3 does not return to its original state completely, and as a result, not only is the mark of the protruding pin 3 clearly left on the molded product, but also damage to the protruding pin 3 is caused. There was a drawback.

Furthermore, with the ejecting mechanism shown in Figure 2 A and B, the fluidity of the resin injected into the cavity is high, so the resin will enter there even with a small clearance, so the diameter of the ejecting pin 5 should be Although it is preferable to make the diameter of the protruding pin 5 as small as possible, it is difficult to make the diameter of the protruding pin 5 with the hole 6 formed inside it as small as possible, and if the diameter is made small, the mold 1 and Since the clearance between the protruding pin 5 and the outer circumferential surface is also reduced, frictional resistance increases and the operation of the protruding pin becomes poor.

This idea was made in view of the above circumstances, and its purpose is to be able to blow out compressed air without pushing out the protruding pin when taking out the molded product from the cavity, and to allow the compressed air to flow from multiple locations. An object of the present invention is to provide an injection mold that can obtain a uniform ejection force (blowout force) even when it is blown out.

Hereinafter, one embodiment of this invention will be described in detail based on the drawings. In the figure, 10 is a pair of mold bases, and these mold bases 10, 10 have spacers 11,
The mold bodies 12, 12 are disposed via the mold body 11, and the mold body 1 is moved by a drive device (not shown).
2 and 12 are mold bases 10 and 10 and spacer 1
1 and 11 so that they approach and separate from each other. This pair of mold bodies 12, 12
Cavities 13, 13 into which the molding material is injected are formed on the mutually opposing surfaces of the two.
Further, a valve bushing 14 formed in the shape of a cylinder with a bottom is provided in the mold body 12 and is connected to the cavity 13.
and the mold base 10. A piston 15 is disposed on the bottom side of the valve bushing 14 so as to be pressed toward the cavity 13 via a coil spring 16. This piston 15 has a needle presser plate 17 attached to the bolt 1.
8, and a needle (valve body) 19 is provided so as to protrude toward the cavity 13 side by this needle presser plate 17, and compressed air flows into the valve bushing 14 and the needle presser plate 17 is attached. 17 in the direction of arrow X, the piston 15 is moved in the same direction against the coil spring 16, and the needle 19 is moved in the same direction.
are also moved in the same direction. Further, a cap 21 in which a through hole 20 is formed is disposed in contact with the needle holding plate 17,
This cap 21 is attached to a valve case 23 via bolts 22. This valve case 23 is disposed within the valve bushing 14 so as to be flush with the cavity 13.
A hole 24 into which the needle 19 is inserted is formed in the valve case 23. That is, the hole 24 has a large diameter on the bottom side of the valve bushing 14, and a small diameter and tapered shape on the cavity 13 side to form a compressed air outlet 24a. The hole 24 is formed with an opening.
The tip of the needle 19 is brought into close contact with the tapered portion of the needle 19. And this hole 2
A resin contamination prevention plate 26 is disposed in the large diameter portion of the cap 4 so as to come into contact with the cap 21 via a coil spring 25, and compressed air is supplied into the through hole 20 formed in the cap 21. Then, the resin contamination prevention plate 26 moves toward the cavity 13 against the coil spring 25 to open the through hole 20. Further, compressed air is contained within the peripheral wall of the valve bushing 14 between the valve case 23 and the piston 15.
7 (that is, the space in which the cap 21 and the needle presser plate 17 are located) is provided with a communication hole 28 for feeding compressed air. This communication hole 28 communicates with a compressed air supply hole 29 formed in the mold base 10. Further, a communication hole 30 is formed in the valve bushing 14 and the mold base 10, through which compressed air flows to return the piston 15 to its original state.

Next, the operation of the injection mold configured as described above will be explained. First, the mold base 10,
10 and the mold bodies 12, 12 are brought close to each other by a drive device (not shown). Next, high pressure air is forced in through the communication hole 30 to press the piston 15 toward the cavity. Then, the needle 1
The tip of the hole 24 is brought into contact with the tapered portion of the hole 24 and pressed, thereby reliably closing the outlet for compressed air into the cavity. Thereafter, a molding material is injected into the cavities 13, 13 of the mold bodies 12, 12 and fixed. Thereafter, the mold bodies 12, 12 and the mold bases 10, 10 are separated by the driving device, and the molded product is taken out from the cavities 13, 13. In this way, the cavities 13, 13
The case where the molded product is taken out from inside will be explained below. The mold bases 10, 10 and the mold body 1
When 2 and 12 are separated from each other by the drive device, compressed air is sent into the air 27 through the supply hole 29 and the circulation hole 28. At this time, the communication hole 3
It goes without saying that the compressed air sent through 0 must be extracted in advance through the communication hole 30.
In this way, when compressed air is sent into the air 27, the needle presser plate 17 is moved in the direction of arrow X against the coil spring 16 and separated from the cap 21. At this time,
The needle 19 is moved in the same direction as the needle presser plate 17 is moved, whereby a hole 24 formed in the valve case 23 is opened and communicated with the cavity 13. Thereafter, the compressed air passes through the through hole 20 formed in the cap 21 and moves the resin contamination prevention plate 26 toward the cavity 13 side against the coil spring 25.
It flows into the hole 24 of the valve case 23 through a ventilation hole provided at a position not facing the through hole 20 . When the compressed air flows into the hole 24 in this way, the needle 19 is moved in the direction of the arrow X and the hole 24 is communicated with the cavity 13, so that the compressed air flows from the hole 24 into the cavity 13. Blow out the cavity 13
Extrude the molded product from inside. That is, since high pressure is created between the cavity 13 and the molded product, the molded product can be easily removed from the cavity 13. After the molded product is taken out from the mold bodies 12, 12 in this way, the communication hole 30 formed in the valve bushing 14 and the mold base 10
Compressed air is sent into the piston 15.
is returned to its original state together with the coil spring 16. Then, the tip of the needle 19 comes into contact with the tapered part of the hole 24 formed in the valve case 23 to reliably close the compressed air outlet, and the needle presser plate 17 and the cap 21 come into contact with each other. , each of the holes 24, 20 is closed.

As explained in detail above, this invention forms a first passage in the mold through which compressed air flows for removing the molded product from the cavity, and the mold A piston is slidably disposed to be moved in a direction away from the front cavity by compressed air pressurized through the first passage, and together with the piston, the piston is moved in a direction away from the cavity. The piston is provided with a valve that moves to open the compressed air outlet of the first passage, and the compressed air is moved by the valve to push the piston toward the cavity to close the compressed air outlet. Since the mold is provided with a second passage through which the compressed air flows, when the compressed air is blown out, the piston moves in the direction away from the cavity (the direction in which it is pushed in) and blows out the compressed air. Unlike conventional morning glory-shaped protruding pins, the resin powder does not get stuck and leave marks on the molded product, and compressed air can be blown out uniformly from multiple locations. Since the piston is provided with a valve that moves in a direction away from the cavity to open the compressed air outlet of the hole, the diameter of the outlet can be made extremely small, and even if the clearance is small, the valve can It works well and improves accuracy.Furthermore, since the valve is moved in the axial direction by compressed air and comes into contact with the valve seat of the compressed air outlet, It is possible to absorb misalignment in the axial direction between the valve and the valve seat, and therefore the valve can be maintained in a closed state reliably and easily.

In addition, in this invention, when closing the compressed air outlet with a valve, the piston to which the valve is attached is pressed by the compressed air, so the cylinder part into which the piston is inserted is made smaller. As a result, the dimensional accuracy of the molded product can be improved. That is, if the piston is simply pressed and moved, a coil spring may be used.

However, when using a coil spring,
There are the following problems.

The injection pressure in the injection molding method is very high (usually about 500 kg/cm ² ), and this injection pressure exerts a large pressing force on the piston via the valve. In order to prevent the valve and piston from moving against this large pressing force during injection and to prevent leakage of molten resin, the coil spring must have a very high spring constant. However, on the other hand, the coil spring must be compressively deformed by a predetermined amount to allow movement of the valve and piston when the molded product is released from the mold. In order to satisfy both of these requirements, it is necessary to use a coil spring with a large wire diameter and a large diameter, which greatly limits the degree of freedom in mold design. Furthermore, if a coil spring with a large diameter is used, the diameter of the cylinder section (in which the piston is accommodated) that houses the coil spring must be increased. When the diameter of the cylinder portion is increased, a difference occurs in the heat capacity of each part of the mold, and this difference in heat capacity causes a delay in the cooling rate of each part of the molten resin when the molten resin is cooled and solidified. For this reason, when a coil spring is used, a problem may arise in which deformation such as warping occurs in the molded product. In particular, in the case of small molds, the ratio of the cylinder part to the mold increases, resulting in a large amount of deformation of the molded product, and the dimensional accuracy may exceed the allowable value, forcing the product to be lost. There is.
This is a major practical problem since injection molding is used for mass production.

In contrast, in this invention, the pressing force for differentially closing the valve is obtained by compressed air. With compressed air, by increasing or decreasing its pressure, a constant pressing force can always be obtained regardless of the diameter of the cylinder portion. Therefore, the degree of freedom in mold design can be greatly improved. Moreover,
Since the diameter of the cylinder part can be made smaller to obtain the pressing force to counter the injection pressure, the difference in heat capacity in each part of the mold can be made extremely small, thus preventing deformation such as warping in the molded product. can be prevented from occurring.

Furthermore, when coil springs are used, problems such as cracking of the molded product may occur during demolding.
According to this invention, such problems can be reliably prevented. That is, the coil spring presses the piston with a large force to counter the injection pressure. Therefore, it is necessary to apply a pressure higher than the pressing force of the coil spring to the compressed air for releasing the molded product. However, when the pressure of compressed air to release the molded product is increased,
When the compressed air moves the piston toward the coil spring and opens the valve, the compressed air flows into an extremely narrow area of the molded product, even though most of the molded product is attached to the mold. (A range corresponding to the compressed air outlet) is pressed instantaneously with a large amount of force, so cracks may occur starting from the pressed area.

In this regard, in this invention, since the opening and closing operations of the valve and piston are both performed using compressed air, the piston and piston are The pressure of compressed air used to open the valve can be lowered. Therefore, the molded product can be pressed with an appropriate force, and cracking can be prevented.

[Brief explanation of the drawing]

Fig. 1 A, B, and C are schematic diagrams showing a conventional ejecting device, Fig. 2 A, B are schematic diagrams showing another conventional ejecting device, and Fig. 3 is a schematic cross-section showing an embodiment of this invention. It is a diagram. 12... Mold body, 13... Cavity, 14
... Valve bushing, 15 ... Piston, 1
6, 25...Coil spring, 17...Needle holding plate, 19...Needle (valve body), 20...Through hole, 21...Cap, 23...Valve case,
24...hole, 24a...compressed air outlet, 26...
... Resin contamination prevention plate, 27... Empty, 28... Communication hole, 29... Supply hole, 30... Communication hole.

Claims (1)

[Scope of utility model registration request] In a mold for injection molding, a cavity for forming a molded article is formed in a pair of molds that move toward each other and move away from each other, and the molded article is removed from the cavity when the pair of molds is separated from each other. , a first tube through which compressed air flows in the mold for removing the molded product from the cavity;
A passageway is formed by opening into the cavity, and a piston is slidably moved in a direction away from the cavity by compressed air that is pressurized into the mold through the first passageway. a direction in which the compressed air outlet is disposed in the opening of the first passageway into the cavity and is fitted into the compressed air outlet formed in the opening of the first passage to close the compressed air outlet, and moves away from the cavity together with the piston; The piston is provided with a valve body that moves to open the compressed air outlet of the first passage, and the piston is pushed and moved toward the cavity by the valve body to close the compressed air outlet. A mold for injection molding, characterized in that the mold is provided with a second passage through which compressed air flows.