JPH0315512A - Mold for injection mold - Google Patents

Abstract

PURPOSE:To improve qualities such as an external appearance, physical properties, dimensional accuracy, etc., of a molded form by providing a pressure detection pin to be telescopically movable, and a gate regulating pin telescopically movable in a direction for opening and closing a resin passage at the end, and moving the regulating pin to a position for opening and closing the passage by the forward or reverse force of the detection pin. CONSTITUTION:After resin is completely poured in a cavity 2, resin pressure in the cavity 2 is increased at the stages of compressing and pressure holding, a pressure detection pin 3 is retracted until a bottom end is brought into contact with a stroke regulating screw 36 against the repelling force of an elastic unit 35, a second tapered block 5 is moved down against the repelling force of an elastic material 51 upon movement of a first tapered block 33, a third tapered block 41 is moved rightward against the repelling force of an elastic material 42, and a gate regulating pin 4 is moved in a direction for blocking the passage in conjunction therewith, thereby reducing a gate 15.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a mold for injection molding.

(Prior art) Injection molding involves two stages: an injection stage in which molten resin is injected from an injection molding machine, flows into the mold cavity through a sprue, runner, and gate, and fills the mold cavity; There is a compression stage in which the pressure inside the resin passages and cavities such as Subluu rapidly rises, the molten resin in the resin passages and cavities is cooled and volumetric contraction occurs, and finally the gate is sealed. It can be divided into a pressure holding stage in which the injection pressure is kept lower than the peak pressure so that the molten resin in the cavity does not backflow in one direction toward the runner.

By the way, the larger the gate size at the injection stage, the easier it is to fill the cavity with molten resin, which will have a positive effect on the quality of the molded product. Therefore, it is clear that a smaller value is better in terms of shortening the gate sealing time and controlling the peak pressure.

Conventionally, in order to satisfy these contradictory conditions, the number, dimensions, position, etc. of gates were set by taking into consideration the number of cavities, the length of the runner, the flow resistance in the resin passage and the cavity, and other factors. However, with a single mold, the dimensions of the gate were fixed, so there was a limit.

Recently, various efforts have been made to solve this problem. For example, Japanese Patent Application Laid-Open No. 62-3913 discloses a device in which a nested Taber pin that is reciprocated by a hydraulic cylinder is provided in the gate section. It has a structure that allows the area to be freely changed and allows for both high-speed molding and precision shaping with a single mold. In addition, Japanese Patent Application Laid-open No. 61-63428 discloses that the above conventional technology is taken one step further by fixing the gate part of the runner in a fixed mold based on the detection signal of a resin pressure sensor that detects the resin pressure in the cavity. It is shown with a hydraulically driven torpedo that opens and closes from the side. By doing this, the opening amount can be adjusted according to the resin pressure inside the cavity, and the aim is to always maintain the resin pressure at an appropriate value and prevent the flow of molten resin from being poor and the occurrence of cracks. .

(Problem to be Solved by the Invention) However, in the above-mentioned conventional technology, in the former case, it is difficult to determine when the Taber bin is activated, and in the latter case, a time lag is unavoidable from the detection of resin pressure to the actuation. However, there was a problem in that a control device and drive device were indispensable.

SUMMARY OF THE INVENTION An object of the present invention is to provide an injection molding die that can change the dimensions of a gate portion simply by utilizing cavity internal pressure without using a special control device or drive device.

(Means for Solving the Problems) The gist of the present invention is an injection mold consisting of a fixed mold and a movable mold that can be opened and closed to form a cavity when closed, and that is configured to form a cavity or a movable mold by resin pressure. It has a pressure detection pin that can move forward and backward with respect to the resin passage, and a gate adjustment pin whose tip can move in and out in the direction of opening and closing the resin passage at or near the gate. The present invention relates to a mold for injection molding characterized by having a movement mechanism movable in directions for opening and closing a resin passage by forward and backward forces.

The interlocking mechanism in the first aspect of the present invention is such that the pressure detection pin is always biased against the resin passage, a first taper block is fixed in the middle of the pin, and the outer surface of the first taper block is fixed. A second taper block that is constantly pressed and biased is arranged, and a third taper block that is constantly pressed and biased is fixed to the outer surface of the second taper block at the rear end of the gate adjustment bin. A mechanism that interlocks by mutual sliding action (2 of the present invention) is preferable.

Further, in the above-mentioned interlocking mechanism, a spring such as a disc spring or a coil spring, or an elastic body such as rubber is suitably used to press the adjacent blocks.

The injection molding mold of the present invention can be used not only for injection molding but also for transfer molding.

It is preferable that the gate dimension H at the injection stage is approximately the standard wall pressure of the large-sized product.

The stroke adjustment screw may be loosened to set the gate dimension H' to 0 during the compression and pressure holding stages, thereby completely blocking the inflow of molten resin and maintaining the cavity internal pressure above a certain value.

(Function) The present invention includes a pressure detection bottle that can move forward and backward with respect to the resin passage using resin pressure, and a gate adjustment pin whose tip can move in and out in the direction of opening and closing the resin passage at or near the gate. However, since the gate adjustment pin can be moved in the direction of opening and closing the resin passage by the forward and backward force of the pressure detection pin, it is possible to mechanically change the gate dimensions as the resin pressure in the resin passage and cavity changes. I can do it.

That is, during the injection stage when the resin pressure is relatively low, the pressure detection bin does not operate and therefore the gate adjustment pin does not operate.
At this stage, if the gate dimensions are set in advance to be the maximum, the pressure detection pin will operate and move back during the compression stage and pressure holding stage when the resin pressure is high, and the gate adjustment pin will be activated via the interlocking mechanism. It operates in the closing direction, and the size of the gate 1 becomes smaller.

(Example) Next, embodiments of the present invention will be described based on the drawings.

In FIG. 1, 1 is a mold consisting of a fixed mold 11 and a movable mold 12 which can be opened and closed, 13 is a sprue, 14 is a runner, 15 is a rectangular gate, and 2 is a cavity.

In the cavity 2, a pressure detection pin 3 is provided on the side of the movable mold 12, and in the middle part of the pressure detection pin 3 there is a substantially conical cam 31 whose diameter increases toward the tip, and a retaining ring for fixing the cam 31. A first taper block 33 consisting of 32 is fixed, and the tsuba 34 is injected into the cavity 2 through the plate 7 and 15. During the injection stage until the cavity 2 is completely filled, The resin pressure inside the gate 2 is mainly due to the flow pressure of the resin and is still small, and is not sufficient to resist the repulsive force of the elastic bodies 35, 42, and 51. Therefore, the cross-sectional area of the gate 15 is large, and the molten resin is easily It flows into the cavity 2 in a short time.

In the compression and pressure holding stage after the injection of resin into the cavity 2 is completed, as shown in FIG. Against this, the bottom end retreats until it touches the stroke adjustment screw 36, and as the first taper block 33 moves, the second taper block 5 resists the repulsive force of the elastic body 51 and moves back as shown in the drawing. Move downward and third taper block 4
1 is moved to the right in the drawing against the repulsive force of the elastic body 42, and in cooperation with this, the gate adjustment pin 4 moves in the direction of closing the resin passage, thereby reducing the size of the gate 15.

FIG. 3 shows another embodiment of the present invention, which is biased toward the fixed mold by an elastic body 35 made of a spring. 3
6 is a stroke adjustment screw for the pressure detection pin 3.

Reference numeral 4 denotes a gate adjustment bottle whose tip forms one side of the game H5, and a third taper block 4l consisting of a bottom flange is fixed to the rear end, and an elastic body 42 made of a coil spring extends rearwardly. It is energizing.

Reference numeral 5 denotes a substantially oblique bottomed cylinder which is slidable and in contact with both the slope of the first taper block 33 of the pressure detection pin 3 and the oblique bottom surface of the third taper block 4l of the gate adjustment pin 4. The second taper block is biased toward the first taper block 33 by an elastic body 51 made of a coil spring inserted into a blind hole.

6 is a slug well, 7 is a sprue lock pin, and 8 is an ejector pin.

Next, the operation of this embodiment will be explained.

The molten resin is injected from the nozzle (not shown) of the injection molding machine, and the tips of the sprue 13, runner 14, gauge 8, and pressure detection pin face not the cavity 2 but the slug well 6, which is the resin passage. Except for this, it is the same as the previous embodiment, and its operation is also the same. Incidentally, in each member of the mold, the same reference numerals are given to the parts corresponding to those in the above embodiment.

Experimental Example Next, when using the mold shown in Figure 3 to injection mold an acrylic butadiene-styrene copolymer resin as a raw material, there was a Figure 4 shows the results of an experiment to see how the behavior of resin pressure differs compared to a conventional mold with a constant gate size.

In the same figure, (a), (b) and (C) are the third
It shows a profile diagram of the resin pressure at the runner R point, cavity 01 point, and cavity 02 point shown in the figure, and also shows the measured values at the same positions in the case of a conventional mold.

Further, in FIGS. 3(a), ω, and (c), the solid line indicates the case of the present invention, and the broken line indicates the case of the conventional mold.

In addition, in the experimental example, the gate dimension (unit: mm) was set to hl = 3.5 at the injection stage, but after the compression stage, hl = 3.5.
2. -1.5, whereas in the comparative example it remained constant at 1.5, and the runner dimensions were set to H=8 in both the experimental and comparative examples.

Further, in FIGS. 11A, 10B, and 1C, T1 indicates an injection stage, Tc indicates a compression stage, and Tl+ indicates a pressure holding stage.

Further, as can be seen from the same figure (C), the peak pressure (P czmax) at point C2 in the cavity was set to 30 MPa in both the case of the present invention and the case of the conventional mold.

By the way, looking at FIG. 4(a), the time required for the injection stage is 3.2 seconds in the case of the conventional mold, but only 2.5 seconds in the case of the present invention, which is a reduction of about 0.7 seconds. done. This shortens the time required for one shot and, by extension, the time required for appearance.

Also, based on (C) and (C) of the same figure, looking at the pressure distribution situation in the entire cavity from the pressure difference between points C1 and C2,
In the case of the present invention, Pc+max - Pczmax = 341
1 1 - mold, 2 - cavity, 3 - pressure detection pin, 4 - gate adjustment pin, 5 - second taper block, 11 - fixed type, 12 - movable type, 33 - first taper block , 41-3rd taper block.

Claims (1)

[Claims] 1. An injection mold consisting of a fixed mold and a movable mold that can be opened and closed to form a cavity when closed, which can move forward and backward with respect to the cavity or resin passage by resin pressure. and a gate adjustment pin whose tip can move in and out in the direction of opening and closing the resin passage at or near the gate, and the gate adjustment pin opens and closes the resin passage by the forward and backward force of the pressure detection pin. An injection mold characterized by having a movement mechanism movable in a direction. 2. A first taper block fixed to the middle of the pressure detection pin, a second taper block constantly pressed against the outer surface of the first taper block, and fixed to the rear end of the gate adjustment pin, 2. The injection mold according to claim 1, characterized in that the second taper block is combined with a third taper block which is constantly pressed against the outer surface of the second taper block.