JP3035892B2 - Injection mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, in injection molding, after a molten resin is injected into a cavity formed in a mold, a backflow of the molten resin from the cavity is prevented, and a shrinkage due to cooling of the molten resin in the cavity is prevented. The pressure for refilling the resin into the cavity is maintained, for example, by applying a forward pressure to the screw of the main body of the injection molding machine. Since this screw rotates and retracts when the injected resin is measured, in the conventional injection molding, a measuring step for the next injection is started after the pressure-holding step is completed.

[0003]

In the case where the pressure is maintained by applying pressure to the screw of the main body of the injection molding machine, the resin cannot be measured for the next injection during the pressure maintenance. There is a problem that the time of one molding cycle becomes longer. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide an injection mold capable of starting weighing from the start of holding pressure and shortening the time of one molding cycle.

[0004]

In order to achieve the above object, an injection mold of the present invention is provided with a valve for opening and closing a gate opening to a cavity in a gate passage communicating with a nozzle of an injection molding machine body. In an injection mold provided so as to be movable in an axial direction of a gate, a pressure holding member for opening and closing an upstream passage from the nozzle to a gate passage is provided around the valve independently of the valve and the same as the valve. It is provided so as to be movable in the direction.

[0005]

According to the above construction, after the gate is opened and the molten resin is injected from the nozzle of the injection molding machine body into the cavity through the gate passage and the gate, the pressure-holding member is connected to the gate with the gate opened. To the upstream side from the nozzle to the gate passage, close the upstream passage from the nozzle, and apply pressure to the molten resin in the gate passage to hold the pressure. Since there is no need to do this, weighing can be started on the injection molding machine main body side from the start of holding pressure.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the accompanying drawings. FIGS. 1 to 4 show a first embodiment of the present invention. In these figures, reference numeral 10 denotes an injection mold, and the injection mold 10 is a fixed-side mold member that can be freely opened and closed. The mold includes a movable side mold member 12 and a cavity 13 is formed between the mold members 11 and 12 at the time of mold clamping. The fixed-side mold member 11 is mounted on a fixed-side mounting plate 15 for mounting to an injection molding machine main body via a receiving plate 14 and a spacer block (not shown). Although not shown, the movable mold member 12 is attached to a movable attachment plate for attachment to an injection molding machine main body. Further, the fixed side mounting plate 15 is provided with a nozzle receiver 16 to which a nozzle of the injection molding machine body is mounted.
Is connected to a hot runner 18 in a manifold 17 having a heater (not shown) provided between the receiving plate 14 and the fixed-side mounting plate 15.

Further, a bush 21 is assembled in the fixed-side mold member 11 and the receiving plate 14, and a through hole 22 is formed in the bush 21 so as to extend in the vertical direction in the figure. The through-hole 22 communicates directly with a gate 23 that opens into the cavity 13 and has an axial direction in the vertical direction. A cylindrical valve guide 24 also serving as a pressure-holding member is slidably fitted in the upper part of the through-hole 22 in the up-down direction.
A pin-shaped valve 25 that opens and closes is fitted and supported slidably in the up-down direction, and a gap between the valve 25 and the peripheral surface of the through hole 22 forms a gate passage 26. A manifold passage, which is an upstream passage, is provided in the bush 21.
27 is formed, and one end of the manifold passage 27 is opened at the upper part of the peripheral surface of the gate passage 26. And
The valve guide 24 is movable between a position where the opening 27a of the manifold passage 27 to the gate passage 26 is fully opened and a position where it is fully closed. On the other hand, the other end of the manifold passage 27 communicates with the hot runner 18 of the manifold 17 which communicates with the nozzle of the injection molding machine main body. Further, a fluid pressure (hydraulic or pneumatic) cylinder device 23 is provided on the back side of the fixed-side mounting plate 15 as a driving device for moving a valve 25 passing through the manifold 17 in the vertical direction. Separately, a hydraulic cylinder device 29 is provided as a driving device for moving the valve guide 24 passing through the manifold 17 in the vertical direction.

Next, the operation of the above configuration will be described. Before the injection step, as shown in FIG. 1, the valve 25 is at the lowered position, and the lower end of the valve 25 is fitted to the gate 23 to close the gate 23. On the other hand, the valve guide 24 is in the raised position, and the opening 27a of the manifold passage 27 is
Is fully open. Then, at the time of the injection step, as shown in FIG. 2, first, the valve 25 is raised by driving the cylinder device 28, the valve 25 is separated from the gate 23, and the gate 23 is opened. On the other hand, the valve guide 24 remains at the raised position, and the opening 27a of the manifold passage 27 is fully opened. Then, the molten resin injected from the nozzle of the injection molding machine main body by pressing the screw of the injection molding machine main body passes through the hot runner 18 of the manifold 17, and further, as shown by the arrow, to the manifold passage 27, the gate passage 26 thereof. Opening 27a, gate passage 26 in bush 21 and gate
Injected into cavity 13 through 23. When the injection process is completed, a pressure-holding process is performed. In the pressure-holding process, as shown in FIG. 3, first, the valve guide 24 is pushed toward the gate 23 with an appropriate pressure by the driving of the cylinder device 29, and descends. The valve guide 24 closes the opening 27a of the manifold passage 27 at least halfway. In this way, the pressure is applied to the molten resin in the gate passage 26 by the valve guide 24 pushed toward the gate 23, as indicated by the arrow, and the pressure is maintained. At this time, since the opening 27a of the manifold passage 27 is at least partially closed, the pressure applied in the gate passage 26 has almost no effect on the injection molding machine main body side and is applied to the gate 23 side. On the other hand, from the start of the pressure-holding step, measurement of the resin for the next injection by the screw starts on the side of the injection molding machine main body.
When the pressure-holding step is completed, as shown in FIG.
Block 23.

As described above, in the above-described embodiment, the valve guide 24 is pushed toward the gate 23, and the manifold passage is pushed.
By closing the opening 27a of 27 and applying pressure to the molten resin in the gate passage 26 to maintain the pressure, it is not necessary to apply pressure to the screw on the side of the injection molding machine main body to maintain the pressure. On the other hand, the pressure-holding step can be omitted on the side of the injection molding machine main body, and the measurement by the screw on the side of the injection molding machine main body can be started from the start of the pressure holding, so that the time of one molding cycle can be shortened.

FIGS. 5 and 6 show a second embodiment of the present invention. In the second embodiment, a valve 25 is guided into a cylindrical through hole 22 of a bush 21 and a pressure-holding member is provided. The valve guide 31 having a cylindrical shape, which also serves as a movable member, is fitted not only to be movable in the axial direction but also to be rotatable. It is intended to rotate. The lower end surface of the valve guide 31 which moves up and down is always located below the opening 27a of the manifold passage 27 to the gate passage 26. At the same time, a spiral groove 32 is formed on the outer peripheral surface of the valve guide 31, and the lower end of the spiral groove 32 passes through the lower end surface of the valve guide 31 and opens to the gate passage 26 leading to the gate. . With such a configuration, when the spiral groove 32 overlaps the opening 27a of the manifold passage 27, this opening
27a is fully open and communicates with the gate passage 26, and the valve guide 31
When the portion without the spiral groove 32 on the outer peripheral surface of the opening overlaps the opening 27a of the manifold passage 27, the opening 27a
Is completely shut off from the gate passage 26.

In the second embodiment, during the injection step, as shown in FIG.
32 overlaps the opening 27a of the manifold passage 27, and the molten resin flows out to the gate passage 26 through the manifold passage 27, the fully opened opening 27a, and the spiral groove 32 as indicated by the arrow. On the other hand, during the pressure-holding step, as shown by the arrow, the valve guide 31 is pushed toward the gate (downward in the figure) in the axial direction, and the valve guide 31 rotates to form a portion of the outer peripheral surface where there is no spiral groove 32. Overlaps the opening 27a of the manifold passage 27, and the opening 27a is fully closed.

By the way, simply pushing the valve guide in the axial direction toward the gate during the pressure holding step does not always make the amount of movement of the valve guide sufficiently large due to the pressure from the molten resin in the gate passage. As a result, the opening of the manifold passage to the gate passage cannot always be completely closed. However, in the second embodiment, the lower end surface of the valve guide 31 is always located below the opening 27a of the manifold passage 27, and this opening 27a is communicated with the gate passage 26 by the spiral groove 32 of the valve guide 31. At the same time, not only by moving the valve guide 31 in the axial direction but also by rotating it, the opening 27a of the manifold passage 27 can be completely closed during the pressure holding step.

The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, in both the above embodiments, the valve guide for guiding the valve is also used as the pressure holding member, but the pressure holding member may be provided around the valve separately from the valve guide.

[0014]

According to the present invention, there is provided an injection molding die provided with a valve for opening and closing a gate opening to a cavity in a gate passage communicating with a nozzle of an injection molding machine main body so as to be movable in an axial direction of the gate. Around the valve, a pressure holding member that opens and closes an upstream passage from the nozzle to the gate passage is provided independently of the valve and movably in the same direction as the valve, so that the screw on the injection molding machine main body side is provided. This eliminates the need to apply pressure to maintain the pressure, and the metering by the screw on the main body of the injection molding machine can be started from the start of the pressure holding, so that the time of one molding cycle can be shortened.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention before an injection step.

FIG. 2 is a sectional view showing an injection step according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a first embodiment of the present invention during a pressure holding step.

FIG. 4 is a sectional view showing a state after a pressure holding step according to the first embodiment of the present invention.

FIG. 5 is a sectional view showing an injection step according to a second embodiment of the present invention.

FIG. 6 is a cross-sectional view illustrating a pressure holding step according to a second embodiment of the present invention.

[Explanation of symbols]

 10 Mold for injection molding 13 Cavity 23 Gate 24 Valve guide (pressure-holding member) 25 Valve 26 Gate passage 27 Manifold passage (upstream side passage) 31 Valve guide (pressure-holding member)

Claims (1)

(57) [Claims] In an injection mold, a valve for opening and closing a gate opening to a cavity is provided in a gate passage communicating with a nozzle of an injection molding machine main body so as to be movable in an axial direction of the gate. And a pressure holding member that opens and closes an upstream passage from the nozzle to the gate passage is provided independently of the valve and movably in the same direction as the valve.