JPH04334423A - Valve gate device for injection molding die - Google Patents

Abstract

PURPOSE:To eliminate the generation of flash in a gate trace of a molded product. CONSTITUTION:A gate 23 is formed in the tapered shape getting thinner toward a cavity 13. The end of a valve 26 is protruded from the gate 23 into the cavity 13 when the gate 23 is blocked. The length (c) in the axial direction of a contact section of the peripheral face of the gate 23 with the valve 26 is made as close as possible to zero (0). As the gate 23 is of tapered shape, resin in the peripheral sections in said gate 23 is returned as shown by the arrow mark when the gate 23 is getting closer. As the length (c) in the axial direction of the contact section is very small, the resin is almost not pushed out to the side of the cavity 13 from between the peripheral surface of the gate 23 and the valve 26. The generation of flash can be prevented by said arrangement. Nevertheless, the gate 23 can be closed securely by making the valve 26 protruded into the cavity 13.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve gate device for an injection mold.

0002

2. Description of the Related Art As a conventional valve gate device for an injection mold of this type, one shown in FIG. 6, for example, is known. This is a bush 4 assembled to a stationary mold member 3 that forms a cavity 2 together with a movable mold member 1.
A valve 5 is provided within the interior so as to be movable in the vertical direction in the drawing as shown by the arrow, and a substantially cylindrical closing portion 6 at the tip end (lower end in the drawing) of the valve 5 closes the gate 7 in the same substantially cylindrical shape.
This is to close the area as appropriate. That is, during the injection process in which molten resin is injected into the cavity 2, the valve 5 is raised to remove the closed portion 6 from the gate 7 to open the gate 7, and after the injection process, the valve 5 is lowered. The closing portion 6 is fitted into the gate 7 to close the gate 7. In this conventional valve gate device, the tip of the closing part 6 of the gate 7 is positioned flush with the tip of the gate 7, that is, the cavity surface, or slightly recessed from the cavity surface. In order to ensure the closure of the gate 7, a straight fitting length a is provided in the axial direction with the closure portion 6 of the substantially cylindrical valve 5, which is the same as the substantially cylindrical gate 7.
is set to a sufficient length, for example, 0.1 to 1 mm.

0003

[Problem to be Solved by the Invention] In the case where the gate 7 is closed by fitting the closing portion 6 of the valve 5 into the substantially cylindrical gate 7 with a sufficient straight fitting length a, the injection When the gate 7 is closed after the process, the resin that has solidified in the gate 7 part will leak into the cavity 2.
However, due to the resin between the closing part 6 and the circumferential surface of the gate 7, burrs 9 tend to occur at the gate marks on the molded product 8, as shown in FIG. 7, and the appearance of the molded product 8 becomes The problem was that it got worse. The present invention solves the above problems and provides a valve gate device for an injection mold that can prevent burrs from forming on the gate marks of a molded product without impairing the reliability of gate closure. purpose.

0004

[Means for Solving the Problems] In order to achieve the above object, the valve gate device for an injection molding mold of the present invention includes a valve gate device for an injection molding mold, in which a gate opening into a cavity formed in an injection molding mold is connected to an axis of the gate. In a valve gate device for an injection mold that is opened and closed by a valve that is movable in a direction and that contacts the circumferential surface of the gate over the entire circumference, the valve includes:
The gate is movable to a position where its cavity side end protrudes into the cavity beyond the gate, and the distance between the peripheral surface of the gate and the central axis gradually becomes smaller as it approaches the cavity. The contact portion between the circumferential surface of the gate and the valve is substantially linear.

[0005]

[Operation] According to the above structure, when the valve is moved away from the cavity during the injection process, the gate is opened and the molten resin is injected into the cavity through this gate. When the valve is moved toward , the cavity side end of the valve protrudes beyond the gate into the cavity, and the valve comes into almost linear contact with the circumferential surface of the gate, ensuring that the gate is closed. However, when the valve moves toward the cavity, the distance between the peripheral surface of the gate and the central axis gradually decreases as it approaches the cavity, so the resin at the periphery inside the gate is The resin is guided by the circumferential surface of the gate and returned in the direction away from the cavity, and since the contact area between the circumferential surface of the gate and the valve is almost linear, the resin flows from between the circumferential surface of the gate and the valve toward the cavity side. This prevents burrs from forming on the gate marks of the molded product.

[0006]

Embodiments Hereinafter, embodiments of the present invention will be explained in detail with reference to the accompanying drawings. 1 to 3 show a first embodiment of the present invention, and in these figures, 10 is an injection mold, and this injection mold 10 has a fixed side mold member that can be opened and closed. 11 and a movable mold member 12, and a cavity 1 is formed between these mold members 11 and 12 during mold clamping.
3 is formed. The stationary mold member 11 has a receiving plate 1
4 and a spacer block 15 to be attached to a fixed side attachment plate 16 for attachment to the injection molding machine main body. Although not shown, the movable mold member 12 is attached to a movable mounting plate for attachment to the injection molding machine main body. Further, the fixed side mounting plate 16 is provided with a nozzle receiver 17 to which a nozzle of the injection molding machine main body is attached, and this nozzle receiver 17 is connected to the receiver plate 14 and the spacer block 15.
and the fixed side mounting plate 16 (
runners 19 in manifold 18 with (not shown)
is connected to.

A bush 21 is assembled within the stationary mold member 11 and the receiving plate 14, and a sprue 22 formed within the bush 21 communicates with the runner 19 within the manifold 18. . At the same time, the sprue 22 communicates with a gate 23 formed in the stationary mold member 11 and opening into the cavity 13 whose axial direction is the vertical direction in the figure. The gate 23 has a tapered shape in which the diameter continuously decreases toward the bottom in the figure, that is, as it approaches the cavity 13. Here, gate 2 with respect to the axial direction of gate 23
The inclination angle α of the circumferential surface of No. 3 is about 1 to 30°, and 15°
Preferably. Furthermore, the bush 21 and the manifold 18 are provided with a valve 26 that opens and closes the gate 23.
is supported so as to be movable in the vertical direction in the drawing. This valve 26 is driven by a drive device 27 which is a hydraulic or pneumatic (fluid pressure) cylinder device or the like built into the fixed side mounting plate 16. A cylindrical closing portion 28 whose axial direction is in the vertical direction is formed at the lower part of the valve 26 . The diameter of this closing portion 28 is approximately equal to the diameter of the tip 23a of the gate 23, which has the smallest diameter. In addition, when the valve 26 is raised, the lower end of the closing portion 28, that is, the tip on the cavity 13 side, is located above the tip 23a of the gate 23, and when the valve 26 is lowered, the tip on the cavity 13 side exceeds the gate 23. It protrudes slightly into the cavity 13. Note that the protrusion amount b of the distal end of the closing portion 28 into the cavity 13 is, for example, 0.02 to 0.2 mm. With this configuration, the gate 23 is opened when the valve 26 is raised, and when the valve 26 is lowered, the closing portion 28 contacts the tip 23a of the circumferential surface of the gate 23 over the entire circumference, thereby closing the gate 23. It has become so. At this time, the axial length (fitting length) c of the contact portion between the circumferential surface of the gate 23 and the closing portion 28 is, for example, 0 to 0.0.
It is 5 mm, extremely short, and almost linear.

Next, the operation of the above structure will be explained. During the injection process after mold clamping, as shown in FIG.
It rises in the direction away from 3. When the valve 26 rises, the tip of the closing portion 28 moves upward away from the tip 23a of the tapered gate 23, thereby opening the gate 23. The molten resin injected from the nozzle of the injection molding machine body passes through the nozzle receiver 17, the runner 19 of the manifold 18, the sprue 22 of the bush 21, and the gate 23, and enters the cavity formed between the mold members 11 and 12. It is injected into 13. Then, after the injection process, the valve 26 is lowered toward the cavity 13 by driving the driving device 27, as shown in FIG. The valve 26 descends until the tip of the closing portion 28 slightly protrudes into the cavity 13 beyond the tip 23a of the gate 23, and the closing portion 28 extends all around the tip 23a of the tapered circumferential surface of the gate 23. There is almost linear contact across the area. This closes the gate 23. By the way, when the valve 26 descends toward the cavity 13 in this way, since the gate 23 has a tapered shape that becomes thinner toward the cavity 13, as shown by the thin arrow in FIG. The resin on the periphery of the gate 23
is guided by the circumferential surface of and returned in a direction away from the cavity 13. At the same time, since the fitting length c between the circumferential surface of the gate 23 and the closing portion 28 of the valve 26 is close to 0, resin is pushed out from between the circumferential surface of the gate 23 and the closing portion 26 toward the cavity 13 side. There are almost no Therefore, it is possible to prevent burrs from forming on the gate marks of the molded product.

As described above, in the above embodiment, the gate 23 is tapered and the fitting length c between the circumferential surface of the gate 23 and the closing portion 28 of the valve 26 is made very small. It is possible to prevent burrs from forming on the gate marks of the product. Even though the fitting length c between the circumferential surface of the gate 23 and the closing part 28 of the valve 26 is made very small, by making the tip of the closing part 28 slightly protrude into the cavity 13, the gate 23 can be closed. Can be closed securely. In other words, by slightly protruding the tip of the closing portion 28 into the cavity 13, it is possible to make the fitting length c between the circumferential surface of the gate 23 and the closing portion 28 close to zero.

FIG. 4 shows a second embodiment of the present invention,
The same parts as in the first embodiment are given the same reference numerals, and detailed explanation thereof will be omitted. In the second embodiment, the gate 23
The circumferential surface has an R-shaped cross section. More specifically, the circumferential surface of the gate 23 has a cross-sectional shape taken along a plane including its central axis and has an arc shape with the center O on the cavity surface. Therefore, the inclination angle of the circumferential surface of the gate 23 with respect to the axial direction of the gate 23 becomes smaller continuously as it approaches the cavity 13, and the tip 2 of the gate 23 becomes smaller as it approaches the cavity 13.
It becomes 0° at 3a. The other structure is the same as that of the first embodiment, but the peripheral surface of the gate 23 is connected to the cavity 1.
The second curved surface becomes narrower as it approaches 3.
The structure of this embodiment also provides the same effects as those of the first embodiment.

FIG. 5 shows a third embodiment of the present invention,
The same parts as those in the first and second embodiments are designated by the same reference numerals, and detailed explanation thereof will be omitted. The third embodiment is based on the first
In this embodiment, only the tip of the gate 23 on the cavity 13 side is formed into a small rounded curved surface 31 similar to the second embodiment.

Note that the present invention is not limited to the above-mentioned embodiments, and various modifications are possible. For example, the shape of the gate is not limited to the shape as in each of the above embodiments, but may be any shape in which the distance between the peripheral surface of the gate and the central axis gradually decreases as it approaches the cavity. .

[0013]

[Effects of the Invention] The present invention provides a gate opening into a cavity formed in an injection mold by a valve that is movable in the axial direction of the gate and that contacts the circumferential surface of the gate over the entire circumference. In a valve gate device for an injection mold that opens and closes, the valve is movable to a position where its cavity side end protrudes into the cavity beyond the gate, and the gate is arranged so that the peripheral surface and the center of the gate The distance between the shaft and the shaft gradually decreases as it approaches the cavity, and the contact area between the circumferential surface of the gate and the valve is approximately linear, so that when the gate is closed, The resin around the gate is returned in the direction away from the cavity, and almost no resin is pushed out from between the gate circumference and the valve toward the cavity, causing burrs to form at the gate mark on the molded product. In addition, the reliability of closing the gate is not impaired.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing the first embodiment of the present invention when the gate is closed.

FIG. 3 is an enlarged sectional view showing the first embodiment of the present invention when the gate is open.

FIG. 4 is a sectional view of a gate portion showing a second embodiment of the present invention.

FIG. 5 is a sectional view of a gate portion showing a third embodiment of the present invention.

FIG. 6 is a sectional view of a gate portion showing a conventional example.

FIG. 7 is a perspective view of a molded product showing a conventional example.

[Explanation of symbols]

10 Injection mold 13 Cavity 23 Gate 26 Valve

Claims (3)

[Claims] Claim 1: Injection molding in which a gate opening into a cavity formed in an injection mold is opened and closed by a valve that is movable in the axial direction of the gate and that contacts the circumferential surface of the gate over its entire circumference. In the valve gate device for a metal mold, the valve is movable to a position where its cavity side end protrudes into the cavity beyond the gate, and the gate is arranged between the peripheral surface of the gate and the center axis. A valve gate device for an injection mold, characterized in that the distance between the gate and the valve gradually decreases as the distance approaches the cavity, and the contact area between the circumferential surface of the gate and the valve is substantially linear. . 2. The valve gate device for an injection mold according to claim 1, wherein the inclination angle of the circumferential surface of the gate with respect to the axial direction of the gate is 1 to 30 degrees. 3. The valve gate device for an injection mold according to claim 1, wherein the circumferential surface of the gate is a curved surface whose width gradually decreases as it approaches the cavity.