JPH06238717A - Injection mold - Google Patents

Abstract

PURPOSE:To provide an injection mold capable of automatically cutting a gate and also decreasing lowering of pressure drop of resin in the beginning of injection. CONSTITUTION:A cutter 19 for cutting a gate is provided in a retainer plate 8 at the movable side. The cutter 19 is provided so as to be pushed in the direction of a parting face by a coil spring 21. On one side, an attenuation device 23 is provided in a retainer plate 2 at the stationary side. A shaft 24 for separating the cutter 19 from the parting face is freely movably provided in the attenuation device 23. Pressure drop of resin pressure is decreased because the cutter 19 is pushed by the shaft 24 in a time for clamping a mold and transferred in the direction wherein a gate part 14 is opened. Further, while molten resin is fluidized through the gate part 14, the cutter 19 is pushed down by resin. Then fluidization is stopped, the cutter 19 is transferred in the direction of the gate part 14 and the gate is cut.

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 provided with a cutter for cutting a gate of a molded product to be injection molded.

[0002]

2. Description of the Related Art Conventionally, as a mold structure for cutting a gate of a molded article, as disclosed in Japanese Patent Laid-Open No. 64-22522, a rotary piece provided with a gate portion is provided to interlock with mold opening. There is known an injection molding die for rotating a rotating piece to cut a gate. Further, JP-A-2-57314 discloses an injection molding die in which a gate portion is formed by a female cutter and a male cutter, and the male cutter is moved in the female cutter direction to punch the gate. Further, in Japanese Patent Laid-Open No. 1-210322, a movable pin that retracts from the gate portion by the pressure of the injected resin is provided, and after the resin is filled in the cavity portion, the movable pin advances to disconnect the gate portion. An injection molding die having a reduced area is disclosed.

[0003]

However, JP-A-64-64
The injection mold of JP 22522 has a problem that the gate position is restricted because the gate method is restricted to the jump gate. In addition, the number of gates is limited to one, so in the case of a molded product that requires a high filling pressure in the cavity (for example, a large body or a thin product),
In terms of appearance, there was a problem that defects such as sink marks and short shots were likely to occur. Further, the injection mold of JP-A-2-57314 has a problem that a cylinder for pushing out the male cutter and a hydraulic device for operating the cylinder are required. Furthermore, JP-A 1-2103
According to Japanese Patent Laid-Open No. 22-22, since the movable pin is retracted by the resin pressure when the resin at the time of injection passes through the gate portion, resistance is generated between the movable pin and the movable pin, and the pressure loss at the initial stage of injection is large, so that the resin is filled. There is a problem that molding defects such as defects are likely to occur.

The present invention has been made in view of the above-mentioned problems of the prior art, is not restricted by the gate position and the number of points, can perform a gate cut with a simple structure, and has a small pressure loss in the initial stage of injection. An object is to provide a mold for injection molding.

[0005]

In order to achieve the above-mentioned object, an injection molding die of the present invention is provided at a gate portion of either a fixed side or a movable side of a die plate, and is attached to a parting surface. A shaft that is provided on the cutter plate that can move back and forth and is biased toward the parting surface and the mold plate on the opposite side of the mold plate on which the cutter is placed, and that moves the cutter in the direction away from the parting surface. And a damping device that is movably provided.

[0006]

According to the above construction, the shaft provided in the damping device is made to protrude from the parting surface when the mold is closed, and the cutter moving support attached to the cutter is pressed to remove the cutter protruding from the gate. Store in the template and move in the direction to open the gate. After that, when injecting the molten resin from the injection molding machine, the cutter projects to the gate portion by the urging force, but when the molten resin flows through the spool portion and the runner portion and passes through the gate portion, the cutter It is pressed by pressure, moves again in the direction to open the flow path of the gate part, and is housed in the template.

Then, when the molten resin is filled in the cavity and the flow of the molten resin ends and the resin pressure drops, the cutter protrudes into the gate by the urging force and bites into the molten resin forming the gate, and the cavity and the runner. Or the notch is formed in the gate to a thin thickness that allows for hand folding. After that, when the resin is cooled and solidified and the mold is opened, the ejector plate of the molding machine pushes the ejector plate, and the cavity (molded product), gate, and runner are separated by the ejector pin or the gate can be folded by hand. Is ejected at. Then, after the molded product is taken out, continuous molding can be performed by repeatedly closing the mold.

[0008]

[Embodiment 1] FIG. 1 is a half cross-sectional view showing Embodiment 1 of the present invention, FIG. 2 is a plan view showing a parting surface of a movable side template of a portion A in FIG. 1, and FIG. 7 is an enlarged cross-sectional view of the A part viewed from the runner side, FIGS. 4 and 5 are cross-sectional views showing the damping device, and FIG. 6 is an enlarged cross-sectional view showing the A part of FIG. 1 when the molten resin is filled. FIG. 2 is an enlarged cross-sectional view showing a portion A of FIG. 1 after completion of filling molten resin.

A spool bush 3 is embedded in a stationary mold plate 2 of an injection molding die 1 and is fixed by a bolt 4. On the surface of the fixed-side mold plate 2, a fixed-side mounting plate 5 having a fitting hole with the outer circumference of the head of the spool bush 3 is fixed by bolts 6, and the fixed-side mounting plate 5 has a surface. A locate ring 7 is provided so as to surround the fitting hole. The movable block 8 has a spacer block 9
The movable side mounting plate 10 is fixed by bolts 11 with the intervening.

A parting line P. where the fixed side mold plate 2 and the movable side mold plate 8 contact each other. In L, a cavity portion 12 for molding a molded product, a runner portion 13 for guiding the molten resin injected into the spool bush 3 to the cavity portion 12, and a gate portion 14 are formed. The movable side mold plate 8 has an ejector pin 1 whose tip can freely project into the runner portion 13.
5 and the ejector pin 16 which can freely project into the cavity portion 12 are provided so as to slidably penetrate therethrough. The base end portion of the ejector pin 16 is sandwiched between a projecting plate upper part 17 and a projecting plate lower part 18 which are movably arranged between the movable side mold plate 8 and the movable side mounting plate 10.

A cutter 19 that is movable at right angles to the resin flow direction of the gate portion 14 is provided in the movable side mold plate 8, and a blade portion 19a formed at the tip of the cutter 19 can move in and out of the gate portion 14. And is arranged so that it can be applied to the parting surface of the fixed-side template 2. This cutter 19
Is formed of a steel material or the like having the same material as the mold or a hardness higher than that. Further, the blade portion 19a is formed on an inclined surface with a thicker wall thickness on the runner portion 13 side and the movable side mold plate 8 side, and receives the pressure of the resin flowing through the gate portion 14 on the inclined surface to allow the cutter 19 to move. It can be pushed back into the movable side mold plate 8.

At the rear end of the cutter 19, the cutter mounting shaft 2 inserted into the movable side mold plate 8 from the movable side mounting plate 10 side.
The tip of 0 is fixed. The head of the cutter mounting shaft 20 is formed to have a diameter larger than that of the shaft, and the head and the movable side mold plate 8 are locked to restrict the amount of the cutter 19 protruding in the parting surface direction. The cutter 19 is held so as not to fall off from the side. Cutter 19
A coil spring 21 for projecting the cutter 19 to the gate portion 14 is arranged between the rear end and the movable side mold plate 8 in a direction perpendicular to the parting surface. Coil spring 2
The elastic force of No. 1 is set so that the cutter 19 can be retracted from the gate portion 14 by the resin pressure at the time of injection, and the cutter 19 can be ejected to the gate portion 14 when the flow of the resin is finished. Further, as shown in FIG. 3, a cutter moving column 22 that is in contact with the tip of the shaft 24 of the damping device 23 is integrally attached to the side surface of the cutter 19.

The damping device 23 is arranged in the fixed-side mold plate 2, and a shaft 24 is connected and arranged so as to project from the parting surface of the fixed-side mold plate 2 by the moving amount of the cutter 19 when the mold is opened. The shaft 24 is a coil spring 24 when the mold is clamped.
After pushing down the cutter 19 against the resilience of the blade, it is gradually pushed back. This damping device 23
As shown in FIG. 4 and FIG.
6 and the damping oil sump 27 are arranged, and the outer peripheral surface of the piston 26 and the inner peripheral surface of the damping oil sump 27 are fitted in a watertight slidable manner. Further, a rotatable flow rate control valve 28 is provided on the inner diameter portion of the damping oil sump portion 27 so as to be in contact with the inner peripheral surface of the damping oil sump portion 27. The inner peripheral surface of the damping oil sump 27 and the flow rate adjusting valve 28 respectively pass through the flow rate adjusting holes 3 through which the damping oil 29 passes.
It is provided at a position where 0 and 31 match, and by rotating the flow rate adjusting valve 28 and changing the positional relationship of the flow rate adjusting holes 30 and 31, the area through which the damping oil 29 passes can be freely set and changed. The moving speed can be changed freely.

Further, in the case 25, a piston 26
A spring 32, which pulls the piston 26 toward the parting surface of the stationary mold plate 2, is provided between the case 24 and the bottom surface of the case 25 around the shaft 24 connected to the piston 26. When a force is applied to the shaft 24 and the piston 26 is pushed in, the damping oil 29, as shown in FIG.
While moving through 1 to the damping oil sump 27,
The force applied to the shaft 24 is removed, and as shown in FIG. 5, when the piston 26 returns to its original position by the contracting force of the spring 32, the piston 26 moves from the damping oil sump 27.

Next, the operation of the injection molding die of this embodiment will be described. Before the injection molding is started, that is, when the fixed mold plate 2 and the movable mold plate 8 are opened, the shaft 24 of the damping device 23 moves from the parting surface of the fixed mold plate 2 to the cutter 1.
The depression amount of 9 is in a protruding state. When the mold is clamped immediately before the start of injection molding, the tip of the shaft 24 is attached to the cutter moving post 22 attached to the cutter 19.
And the cutter moving column 22 is pushed down. As a result, the cutter 19 is moved in the direction away from the parting surface against the elastic force of the coil spring 21, and the blade portion 1
9 a is accommodated in the movable side mold plate 8 from the gate portion 14.

Here, the moving speed of the piston 26 in the damping device 23, that is, the pressure inside the damping device 23 related to the moving speed of the cutter 19 is adjusted by the elastic force of the spring 32 and the flow resistance of the damping oil 29. When the mold is closed, the blade portion 19a of the cutter 19 can be completely housed in the movable side mold plate 8 against the elastic force of the coil spring 21, and thereafter, the elastic force of the coil spring 21 causes the cutter 1 to move.
9 is set so that it can gradually enter the gate portion 14 at a desired speed. Gate part 1 of this cutter 19
The invasion speed into the cutter 4 is within the time from the mold clamping until the molten resin is injected into the cavity 12
It is set so that the blade portion 19a of the above does not come into contact with the parting surface of the fixed-side template 2.

After the mold is closed, the blade portion 19a of the cutter 19 is
Within a time that does not enter the gate section 14 much,
That is, the molten resin is injected from the injection molding machine (not shown) into the spool bush 3 within a time period during which the blade portion 19a does not contact the parting surface of the fixed-side mold plate 2, and passes through the runner portion 13 and the gate portion 14 into the cavity portion 12. Fill. At this time, the molten resin passing through the gate portion 14 collides with the inclined surface forming the blade portion 19a of the cutter 19 which is entering the gate portion 14, and the pressure of the molten resin causes the cutter 19 to move again to the movable side mold. It is pushed back into the plate 8 and brought into the state shown in FIGS.

When the resin has finished flowing, the cutter 19
Is released from the pressure of the resin and again projects to the gate portion 14. At this time, since the ejection speed is limited by the damping device 23, the gate of the molded product is connected until the pressure holding step is completed. Then, as shown in FIG. 5, when the cutter 19 is completely projected and comes into contact with the parting surface of the fixed-side template 2, the gate of the molded product is cut by the cutter 19, and the separation of the molded product and the runner is completed. . After that, the mold is opened, and the ejector pins (15, 16) are ejected in order to eject the upper and lower parts (17, 18) of the ejector plate by an ejector rod (not shown) of the injection molding machine and release the molded product and the runner. After this protrusion is completed, the molded product is free-falled or taken out by a robot, and then the mold is clamped again.

In the above structure, the blade portion 19 of the cutter 19 may be adjusted depending on the adjustment of the damping device 23 and the coil spring 21.
It becomes possible to perform injection molding in a state in which a does not enter the gate portion 14. Further, this is to further increase the amount by which the shaft 24 of the damping device 23 is projected from the parting surface, that is, the length of the shaft 23, and to further deepen the depth at which the cutter 19 is pushed into the movable side mold plate 8. It is also possible by.

According to this embodiment, before injecting the molten resin,
The blade portion 19 of the cutter 19 entering the gate portion 14
Since the a is forcibly pushed down by the shaft 24 of the damping device 23 to open the gate portion 14, it is possible to reduce the pressure loss of the molten resin pressure at the initial stage of injection. Further, after the molten resin is filled in the cavity portion 12 and when the molten resin has finished flowing, the cutter 19 can automatically enter the gate portion 14 to perform gate cutting.

[0021]

[Embodiment 2] FIGS. 8 and 9 are sectional views showing the essential parts of Embodiment 2 of the present invention. FIG. 8 shows the mold clamping and FIG. 9 shows the mold opening. In this embodiment, the length of the cutter mounting shaft 20 is adjusted, and the amount of protrusion of the blade portion 19a of the cutter 19 into the gate portion 14 is adjusted. Other configurations are the same as those of the first embodiment. Has been done. That is, the maximum amount of protrusion of the cutter 19 is set so that the blade tip of the blade portion 19a does not reach the parting surface of the stationary mold plate 2 during mold clamping.
A gap 35 is formed between the cutting edge and the parting surface.

In this embodiment, injection molding is carried out in the same manner as in Embodiment 1, but the cutter 19 creates the gap 35 at the time when the resin flow is stopped and the resin pressure is released. The movement stops in this state (see FIG. 8). And
After the molten resin is cooled and solidified in this state, the cavity forming the molded product and the runner are separated by the gap 35 (see FIG. 9).

According to the present embodiment, the gate portion of the molded product can be made thin enough to be folded by hand without reducing the flow path of the gate portion 14 during the resin flow. If the molded product cannot be dropped, such as a plastic lens, or if handling of the robot is difficult, the nipper, etc. can be removed from the mold during the inspection process without damaging the molded product. The gate can be easily cut by hand without using it.

[0024]

Third Embodiment FIG. 10 is a half sectional view showing a third embodiment of the present invention, and FIG. 11 is a sectional view showing a main part. In this embodiment, the cutter 19, the cutter mounting shaft 20, the coil spring 21 and the like are arranged in the fixed-side mold plate 2 in the same configuration as in the first embodiment, and the damping device 23 is arranged in the movable-side mold plate 8. It is provided in the same configuration as 1. Other configurations are similar to those of the first embodiment.

In this embodiment, as in the first embodiment,
When the mold is clamped, the cutter 19 is pushed by the shaft 24 of the damping device 23 via the cutter moving column 22 (see FIG. 3), and the blade portion 19a of the cutter 19 is housed in the stationary mold plate 2.
When the molten resin has finished flowing, the cutter 19
Is released from the resin pressure and is again projected to the gate portion 14, and its blade portion 19a abuts the parting surface of the movable side mold plate 8 to cut the gate, and is cooled in a state in which the cavity and runner are separated. .

According to the present invention, since the cutter 19 is provided on the fixed-side mold plate 2, even if the mold has a complicated structure in which the movable-side mold plate 8 is provided with a slide insert, etc., the cutter 1 is provided on the gate portion 14.
9 can be provided, and continuous molding can be performed while automatically cutting the gate in the mold.

[0027]

As described above, according to the injection molding die of the present invention, the type of gate and the number of gates are regulated with a simple structure without the need for equipment such as hydraulic pressure, pneumatic pressure, and electric equipment. A gate-cutting cutter can be placed without any need for reliable gate-cutting. In addition, by providing a damping device, it is possible to fill the cavity with molten resin without causing unnecessary pressure loss at the beginning of injection, so injection molding with good shape accuracy can be performed continuously while reliably performing gate cutting. It becomes possible.

[Brief description of drawings]

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

FIG. 2 is a plan view showing a parting surface of a movable side mold plate of a portion A in FIG.

FIG. 3 is an enlarged cross-sectional view of part A in FIG. 1 viewed from the runner side.

FIG. 4 is a cross-sectional view showing a damping device used in Examples 1 to 3.

FIG. 5 is a cross-sectional view showing a damping device used in Examples 1 to 3.

FIG. 6 is an enlarged cross-sectional view showing a portion A of FIG. 1 at the time of filling with molten resin.

FIG. 7 is an enlarged cross-sectional view showing a portion A of FIG. 1 at the time of completion of filling with molten resin.

FIG. 8 is an enlarged cross-sectional view showing a main part of a second embodiment of the present invention,
It shows the end of filling of the molten resin.

FIG. 9 is an enlarged cross-sectional view showing a main part of a second embodiment of the present invention,
It shows the time of mold release.

FIG. 10 is a half sectional view showing a third embodiment of the present invention.

FIG. 11 is an enlarged sectional view showing a main part of a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold for injection molding 2 Fixed-side mold plate 8 Movable-side mold plate 12 Cavity part 13 Runner part 14 Gate part 19 Cutter 20 Cutter mounting shaft 21 Coil spring 23 Damping device 24 Shaft

Claims (1)

[Claims] 1. A cutter, which is provided on the gate portion of either the fixed side or the movable side, is movable forward and backward with respect to the parting surface and is biased toward the parting surface, and the cutter are arranged. An injection molding die, comprising: a damping device, which is provided on a mold plate opposite to the mold plate and is movably provided with a shaft for moving the cutter in a direction away from the parting surface.