JPH10138302A - Injection mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection mold excellent in resin filling properties and capable of easily performing separation work of a gate molded article by the bending of the gate molding article. SOLUTION: The height dimension of a gate injection port 2a is made largish at a time of the injection of a resin, for example, set to a larger value (h) in consideration of the filling of a molding space with a resin by the operation of a gate block 6 and, after the injection of the resin is completed, the height dimension of the gate injection port 2a is altered to a smaller value h' to locally reduce the thickness of the product bonding part of a gate molded article and, by this constitution, the gate molded article can be easily cut and separated from a product by the bending of the gate molded article.

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, and more particularly, to a gate for injecting a molten resin into a molding space in the die, such as a side gate or a fan gate, which requires gate finishing. The present invention relates to a suitable injection molding die.

[0002]

2. Description of the Related Art In an injection molding technique, a mold is filled with a molten resin through a runner and a gate. After the injection is completed, an unnecessary molded product (hereinafter, referred to as a runner and a gate) is taken out of the molded product taken out of the mold. Are collectively referred to as a “gate molded product”), and the operation of removing the gate molded product in a later step (post-gate finishing) is performed.

The post-gate finishing can be omitted by using a pin gate, a tunnel gate, or the like which can automatically cut a gate molded product at the same time as opening a mold as a gate. However, when a side gate or a fan gate, which is known as a gate most commonly used as a gate excellent in filling a resin into a mold, is used, post-gate finishing is indispensable.

Therefore, there is a need for a means for efficiently performing post-gate finishing. As one of the means, there is a method in which a cutting tool such as a nipper is attached to a device for extruding a molded product from a mold, and the gate molded product is automatically cut in a process of removing the molded product from the mold.

[0005]

However, the efficiency of the post-gate finishing greatly depends on the thickness of the gate. When the gate is made thicker with priority given to resin filling, it takes more time to cut, and conversely, the cutting becomes easier. Therefore, when the gate thickness is reduced, the filling property of the resin is deteriorated.

[0006] Further, a method of completely cutting a gate molded product from a product by operating a gate opening / closing member called a gate block in a direction to close the gate after filling the resin into the mold has been implemented in part. However, in this case, a strict positional accuracy between the gate block and the mold is required. If there is a slight deviation in the positional accuracy, for example, a slight overstroke of the gate block at the time of cutting may cause the end of the gate block and the metal die to move. Each time the mold is cut, it collides, causing tears and wear on both sides. For this reason, frequent replacement work of the mold and the gate block is required, and very complicated maintenance and management are required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is intended to provide an injection mold having excellent resin filling properties and capable of easily separating a gate molded product by bending the gate molded product. It is intended to be provided.

[0008]

In order to achieve the above-mentioned object, an injection mold of the present invention comprises a gate communicating with a molding space in the mold and a height of an injection opening opened in the molding space of the gate. A gate block that is movably provided to change the dimensions, and a gate block that operates the gate block such that the height of the gate injection port becomes smaller than that at the time of resin injection after the resin injection into the molding space is completed. Operating means.

In other words, according to the present invention, the height of the gate injection port is increased when the resin is injected by the operation of the gate block. For example, the height is set to a large value in consideration of the filling property of the resin into the molding space. After the injection is completed, the height of the gate injection port is changed to a smaller value to locally reduce the thickness of the product connection part of the gate molded product, so that the gate molded product can be easily cut and bent from the product. Can be separated.

[0010]

Embodiments of the present invention will be described below.

FIG. 1 is a sectional view showing the structure of an injection mold according to a first embodiment.

In FIG. 1, 3 is a core, 5 is a cavity, and 1 is a molding space formed by the core 3 and the cavity 5. The core 3 is provided with a sculpture for the gate 2 leading to the molding space 1, and the cavity 5 is provided with a runner 4 leading to the gate 2. Reference numeral 6 denotes a gate block for varying the height of the gate injection port 2a opened in the molding space 1. The gate block 6 is a slide piece 7.
Up and down by the hydraulic cylinder 8.

The hydraulic cylinder 8 moves the slide piece 7 in the horizontal direction under the control of a controller (not shown). That is, the controller arranges the slide piece 7 at the retracted position shown in FIG. 1A from the start of the injection molding until the set time elapses, and moves the hydraulic cylinder 8 forward by a certain distance after the set time elapses. Control.

As shown in FIG. 1 and FIG.
And the gate block 6 are in contact with each other on an inclined surface, and the gate block 6 moves up and down with the horizontal movement of the slide piece 7. That is, as shown in FIG. 1A, when the slide piece 7 is at the retreat position, the gate block 6 is at a predetermined low position, and as shown in FIG. 1B, the slide piece 7 is at the forward position. At one time, the gate block 6 is at a predetermined high position.

The upper end face 6a of the gate block 6 is formed in a tapered shape, and the height of the gate outlet 2a opened in the molding space 1 is determined by the height of the apex of the taper.

Here, as shown in FIG. 1 (a), when the gate block 6 is at a predetermined low position,
The height h of a is substantially equal to the height of the gate 2 provided on the core 3. FIG.
As shown in (b), the height dimension h 'of the gate injection port 2a when the gate block 6 is at a predetermined height position is a value that can be easily cut and separated by bending the gate molded product from the product. Is set to

Next, the operation when performing injection molding using this injection mold will be described. When the resin is injected into the molding space 1, the gate block 6 is at the low position shown in FIG. 1A, and the gate injection port 2a is in a fully opened state. Therefore, the resin introduced through the runner 4 flows into the molding space 1 via the gate 2 smoothly.

After a lapse of a set time from the start of injection molding (after resin injection into the molding space 1 is completed), the hydraulic cylinder 8 is operated by the controller to move the slide piece 7 forward. It rises to the high position shown in FIG. As a result, the tip of the gate block 6 bites into the gate 2, and the resin thickness of the gate outlet 2a is reduced to h '.

After the resin in the mold is cooled and solidified, the mold is opened and the gate block 6 is lowered to a low position. Thereafter, a product 10 integrated with the gate molding 9 as shown in FIG. 3 is taken out of the mold by an automatic take-out machine or the like.

In this molded product with a gate, the product 10
As shown in FIG. 4, since the thickness of the joint portion between the mold and the gate molding 9 is thin, the gate molding is performed while the product 10 taken out of the mold using an automatic take-out machine is fixed to a chuck or the like. By folding the object 9, the product 1
The gate molding 9 can be easily cut and separated from zero.

Next, an injection mold according to a second embodiment will be described.

FIG. 5 is a sectional view showing the structure of the injection mold of the second embodiment.

In the figure, 13 is a core, 15 is a cavity, and 11 is a molding space formed by the core 13 and the cavity 15. The core 13 is provided with an engraving for the gate 12 leading to the molding space 11, and the cavity 15 is provided with a runner 14 leading to the gate 12. 1
Reference numeral 6 denotes a gate block for varying the height of a gate injection port 12a opened in the molding space 11. Reference numeral 17 denotes an eject pin for extruding a molded product from the core 13.

Eject pin 17 and gate block 1
The lower part 6 is supported by an eject holding plate 18 and an eject plate 19 which move up and down under the control of a controller (not shown). Here, the gate block 16 is fixed to the eject holding plate 18 and the eject plate 19 so as to always move up and down integrally therewith.

On the other hand, the eject pin 17 is provided with a flange portion 17a, which can move up and down within the range of the height H within the flange engagement hole 19a of the eject plate 19. I have. However, at the time of injection molding, the lower end of the eject pin 17 abuts on and is supported by the upper surface of the mounting plate 20 attached to the core 13, so that the pressure of the injection molding causes the flange portion 17 of the eject pin 17 to be pressed.
a does not sink to the lower end of the flange plate 19a of the eject plate 19.

The controller sets the heights of the eject pressing plate 18 and the eject plate 19 at the positions shown in FIG. 5A from the start of the injection molding until the set time has elapsed. At this time, the gate block 16 is at a predetermined low position, and the height dimension h of the gate emission port 12a is substantially equal to the height dimension of the gate 12 provided on the core 13.

On the other hand, at this time, the lower end of the flange portion 17a of the eject pin 17 and the upper end of the eject pressing plate 18 are separated from each other by a distance H.

After the set time has elapsed from the start of the injection molding, the controller raises the eject holding plate 18 and the eject plate 19 by the height H as shown in FIG. As a result, the height of the gate block 16 also rises by the height H, the tip of the gate block 16 bites into the gate 12, and the resin thickness of the gate outlet 12a is reduced to h '. On the other hand, even if the eject holding plate 18 and the eject plate 19 rise by the height H, the eject pin 17 moves only to the lower end in the flange engaging hole 19a, and the eject pin 17 To rise.

After the resin in the mold is cooled and solidified, the mold is opened and the eject press plate 18 and the eject plate 19 are further raised by a certain distance. As a result, the eject pin 17 rises with respect to the core 13, and the molded product is pushed up from the core 13.

Table 1 shows the test results of the gate thickness, the number of bendings required for cutting, and the remaining gate amount. As a test piece for test evaluation, as shown in FIG.
× 150 (mm) and a thickness of 4 mm were used. The remaining gate is the maximum protrusion after the gate from the cut surface on the product side.

[0031]

[Table 1] From this test result, it was confirmed that the larger the gate thickness, the greater the number of times of bending and the larger the remaining gate amount. In particular, if the gate thickness is 0.5 mm or less, once to two times
The gate molding can be cut by folding twice and the remaining gate
It was confirmed that good results were obtained when the thickness was 0.5 mm or less.

FIG. 6 shows the results of measuring the distortion of the gate cut surface of each of the sample obtained by cutting the gate molded product with the nippers and the sample obtained by cutting the gate molded product according to the present invention.
The sample used here is an acrylic light guide plate of a lighting device. Light was irradiated to the gate cut surface of the sample from below, and the luminance of each surface of the gate cut surface was measured. The higher the distortion, the more light is refracted, so that high brightness is measured. From this test result, it was confirmed that the distortion appearing on the surface cut by bending the back of the gate according to the present embodiment was equal to or less than the distortion appearing on the surface cut by the nippers after molding.

[0033]

As described above, according to the injection molding die of the present invention, the filling property of the resin into the molding space is improved by setting the height of the gate injection port to a relatively large value during the resin injection. After the resin injection is completed, the height of the gate injection port is changed to a smaller value to locally reduce the thickness of the product connection part of the gate molded product, thereby bending the separation operation of the gate molded product Thus, a molded product that can be easily obtained is obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an injection mold according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a slide block and a gate block in FIG. 1;

FIG. 3 is a perspective view showing a molded product with a gate that is injection-molded using the injection mold of FIG. 1;

FIG. 4 is a diagram for explaining a method of cutting and separating a gate molded product.

FIG. 5 is a cross-sectional view showing a configuration of an injection mold according to a second embodiment of the present invention.

FIG. 6 is a view showing the results of measuring the strain of the gate cut surface of each of a sample obtained by cutting a gate molded product with a nipper and a sample cut by the present invention.

[Explanation of symbols]

 1 ... molding space 2 ... gate 2a ... gate injection port 3 ... core 4 ... runner 5 ... cavity 6 ... gate block 7 ... slide piece 8 ... hydraulic cylinder 9 gate molding 10 product 11 molding space 12 gate 12a gate outlet 13 core 14 runner 15 cavity 16 gate block 17 eject pin 18 Eject plate 19 Eject plate

Claims (1)

[Claims] 1. A gate communicating with a molding space in a mold, a gate block movably provided so as to vary a height dimension of an injection opening of the gate in the molding space, and a gate for the molding space. An injection molding die comprising: gate block operating means for operating the gate block such that the height of the injection port of the gate becomes smaller than that at the time of resin injection after the resin injection is completed.