JPH04334421A - 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 space 29 is formed between the peripheral face of a gate 23 and a valve 26 in the state of making the valve 26 pass through the gate 23. A blocking section 31 is formed at the end of the valve 26. At the time of injection process, the valve 26 is pressed toward a cavity 13 and the blocking section 31 is separated from the gate 23 to open the gate 23. After the injection process, the valve 26 is drawn from the side of the cavity 13 and the gate 23 is blocked from the side of the cavity 13 by the blocking section 31. Gate cutting, therefore, is carried out securely by blocking the gate 23 from the side of 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. 9, 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 predetermined length, for example, 0.1 to 1 mm.

0003

[Problem to be Solved by the Invention] The valve 5 is moved toward the cavity 2, and the closing portion 6 of the valve 5 is moved toward the gate 7.
In the case where the gate 7 is closed by fitting the gate 7 with a predetermined straight fitting length a, when closing the gate 7 after the injection process, the resin that has hardened in the gate 7 will be pushed out toward the cavity 2. , gate cutting becomes insufficient, and the resin between the closing part 6 and the circumferential surface of the gate 7 tends to cause burrs 9 at the gate marks on the molded product 8, as shown in FIG. There was a problem that it looked bad. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a valve gate device for an injection mold that can prevent burrs from forming on the gate marks of a molded product.

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 movable in a direction, a gap is formed between the circumferential surface of the gate and the valve in a state where the valve is penetrated from the gate, and a gap is formed between the peripheral surface of the gate and the valve. A closing part is provided at the end to close the gate from the cavity side.

[0005]

[Operation] According to the above structure, when the valve is moved toward the cavity during the injection process, the closed part of the valve is separated from the gate, the gate is opened, and a gap is formed between the circumferential surface of the gate and the valve. The molten resin is injected into the cavity through the gap, and when the valve is moved in the opposite direction after the injection process, the closing part at the end of the valve closes the gate from the cavity side, ensuring gate cutting. This prevents burrs from forming on the gate marks on the molded product.

[0006]

Embodiments Hereinafter, embodiments of the present invention will be explained in detail with reference to the accompanying drawings. 1 to 5 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 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 cylindrical gate 23 that is formed in the stationary mold member 11 and opens into the cavity 13, with the vertical direction in the drawing being the axial direction. Further, a valve 26 for opening and closing the gate 23 is supported by the bush 21 and the manifold 18 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 through-rod portion 28 is formed at the bottom of the valve 26, and this through-rod portion 28
can pass through the gate 23. Penetrating rod part 2
A plurality of circulation grooves 29 are formed on the outer peripheral surface of the gate 8 and extend in the axial direction, that is, in the vertical direction. A gap is formed between the gate 23 and the peripheral surface of the gate 23 through which the molten resin passes. On the other hand, the outer circumferential surface of the penetrating rod portion 28 excluding the portion of the flow groove 29 serves as a guide surface 30 that slides on the circumferential surface of the gate 23 . Further, a cylindrical closing portion 31 is formed at the tip of the through-rod portion 28 that protrudes from the gate 23 into the cavity 13 . This blockage part 3
1 has the same diameter as the gate 23, and is fitted into the gate 23 to close it from the cavity 13 side.

Next, the operation of the above structure will be explained. During the injection process after mold clamping, as shown in FIG.
Descend toward 3. When the valve 26 is lowered, its closing portion 31 is pushed out into the cavity 13 and away from the 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 and the runner 19 of the manifold 18, and then, as shown by the thin arrow in FIG. The liquid is injected through the flow groove 29 of the part 28 into the cavity 13 formed between the mold members 11 and 12. Then, after the injection process, the valve 26 is raised by driving the driving device 27, as shown in FIG. When the valve 26 rises, its closing portion 31 fits into the gate 23 and closes the gate 23 from the cavity 13 side.

In this way, instead of pushing the valve toward the cavity to close the gate, by pulling the valve 26 from the cavity 13 to close the gate 23, the gate is reliably cut and the molded product 36 is closed. This prevents burrs from forming on the gate marks.

By the way, in the embodiment described above, since the closing portion 31 of the valve 26 protrudes into the cavity 13 from the gate 23, a hole 37 is formed at the gate mark of the molded product 36, as shown in FIG. Therefore, in the case of a particularly thin molded product 36, in order to increase the strength of the hole 37, a built-up portion 38 is formed on the back side of the hole 37 in the molded product 36, as in the second embodiment shown in FIG. However, this built-up portion 38 is not essential.

FIGS. 7 and 8 show a third embodiment of the present invention, in which the same parts as in the first embodiment are designated by the same reference numerals and detailed explanation thereof will be omitted. In this third embodiment, by making the diameter of the cylindrical through-rod portion 41 smaller than the diameter of the cylindrical gate 23, the through-rod portion 41 and the gate 23 are
A gap 42 is formed over the entire circumference between the circumferential surface and the circumferential surface.

Note that the present invention is not limited to the above-mentioned embodiments, and various modifications are possible. For example, in the first embodiment, the through-rod portion of the valve is made into a columnar shape, and a plurality of flow grooves are formed on the outer peripheral surface thereof, and in the third embodiment, the diameter of the cylindrical gate is By reducing the diameter of the cylindrical penetrating rod, a gap is formed between the penetrating rod and the circumferential surface of the gate, but the shape of the penetrating rod can be freely selected, such as a square prism or a triangular prism. If the cross-sectional shape of the penetrating rod portion and the cross-sectional shape of the gate are made irregular in some way, a gap can be formed between the penetrating rod portion and the circumferential surface of the gate.

[0013]

Effects of the Invention The present invention provides a valve gate device for an injection mold, in which a gate opening into a cavity formed in the injection mold is opened and closed by a valve movable in the axial direction of the gate. A gap is formed between the circumferential surface of the gate and the valve in a state where the valve penetrates through the gate, and a closing part is provided at the end of the valve to close the gate from the cavity side. When the gate is blocked, the gate is reliably turned off.
This prevents burrs from forming on the gate marks on the molded product.

[Brief explanation of drawings]

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 through-rod portion of a valve showing a first embodiment of the present invention.

FIG. 5 is a sectional view of a gate trace portion of a molded product showing a first embodiment of the present invention.

FIG. 6 is a sectional view of a gate trace portion of a molded product showing a second embodiment of the present invention.

FIG. 7 is an enlarged sectional view of a gate portion showing a third embodiment of the present invention.

FIG. 8 is a sectional view of a through-rod portion of a valve showing a third embodiment of the present invention.

FIG. 9 is a sectional view of a gate portion showing a conventional example.

FIG. 10 is a perspective view of a molded product showing a conventional example.

[Explanation of symbols]

10 Injection mold 13 Cavity 23 Gate 26 Valve 29 Distribution groove (gap) 31 Blocked part 42 Gap

Claims (1)

[Claims] 1. A valve gate device for an injection mold in which a gate opening into a cavity formed in an injection mold is opened and closed by a valve movable in the axial direction of the gate, wherein the valve is connected to the gate. An injection mold characterized in that a gap is formed between the circumferential surface of the gate and the valve in a more penetrating state, and a closing part is provided at the end of the valve to close the gate from the cavity side. valve gate device.