JPH0752205A - Injection mold - Google Patents

Abstract

PURPOSE:To obtain an injection mold which can cut off and separate completely a molded product from resin of a runner part and obtain the molded product whose stress being left behind within the molded product is mitigated drastically at a side gate position on the inside of a mold. CONSTITUTION:A resin rich area 25 forming a recessed form toward the inside of a mold further from a side gate 23 is formed on either one of a front mold 20 or a rear cavity 21 of a mold wherein a cavity 22 and the side gate 23 which is provided on a side part of the cavity and is for introduction of resin within the cavity are formed between the front mold 20 and rear cavity 21 provided contactably and separatably freely to the front mold 20. Along with that, a pin 27 made movably freely up to the inside of the resin rich area 25 from the side gate 23 is provided on either of the other ones.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection mold used for molding various resin materials, and in particular, an injection mold capable of reliably cutting and separating a molded product at a side gate position in the mold. It is related to the mold.

[0002]

2. Description of the Related Art Conventionally, when a thermoplastic resin or a thermosetting resin is injection-molded, for example, an injection-molding apparatus incorporating an injection-molding die as shown in FIG. 5 is used.
In FIG. 5, this injection molding die (hereinafter abbreviated as a die) is composed of a fixed-side die 1 and a movable-side die 2 which is provided in the fixed-side die 1 so as to come into contact with and separate from the fixed-side die 1. In between, a cavity 3 that defines a product shape, a side gate 4 that is provided on a side portion of the cavity 3 for introducing a resin into the cavity 3, and a resin flow path toward the side gate 4. The runner 5 and the sprue 6 are formed.

In the molding of resin using the above-mentioned conventional mold, first, the resin melted by heating in the heating cylinder 7 of the injection molding machine is injected from the injection nozzle 9 with the screw 8 into the sprue 6, runner 5 and the like in the mold. After filling the cavity 3 through the side gate 4 and performing a pressure-holding step, the resin in the cavity 3 is cooled and solidified, and then the movable side mold 2 is separated from the fixed side mold 1, Ejector pin 1
At 0, the molded product in the cavity 3 and the resin in the sprue 6 and the runner 5 are projected and separated from the movable side mold 2. In this way, since the molded product separated from the movable mold 2 is integrally molded with the resin of the sprue part and the runner part, the molded product is manually molded by using a hot nipper or the like. The molded product is separated by cutting between the sprue and the resin.

[0004]

In such a conventional mold, after the molded body is separated, the molded product must be manually cut and separated from the resin such as sprue. There is a drawback that it takes a lot of time to obtain and the molding efficiency is poor. Therefore, as shown in FIG. 6, at a position facing the side gate 12 of the movable mold 11,
By providing the pressure pin 16 so as to be retractable toward the fixed-side mold 17 side, the resin of the side gate 12 between the cavity 13 and the runner 14 in the mold can be cut by the pressure pin 16. Die molds have been proposed.

However, in the case of the above-mentioned mold, as shown in FIG.
As shown in FIG. 2, when the pressure pin 16 is projected into the side gate 12 to cut the resin after the cavity 13 is filled with the resin, a part of the resin in the side gate 12 is located on the cavity 13 side. The resin that is pushed into the runner 14 side but cannot move from inside the side gate 12 is compressed while being sandwiched between the upper surface of the pressure pin 16 and the fixed-side die 17. Therefore, when the molded body is ejected after cooling and solidification, as shown in FIG.
The resin 15 compressed by 6 remains in a state where the molded product 18 and the resin 19 of the runner portion are connected, and eventually the molded product 18 and the resin 19 of the runner portion cannot be completely separated. There was a problem. Further, at this time, there is also a problem that a large internal stress remains in the obtained molded product 18 because an excessive pressure is applied to the resin near the side gate of the molded product 18.

The present invention has been made to solve the above problems, and in a mold having a side gate, a molded product is obtained by automatically cutting the resin at the side gate position by a pin in the mold. It is an object of the present invention to provide a mold capable of separating the resin from the resin such as the runner portion.

[0007]

A mold of the present invention includes a cavity and a cavity between the fixed-side die and a movable-side die provided so as to come in contact with and separate from the fixed-side die. One of the above-mentioned fixed-side mold and movable-side mold of a mold provided with a side gate for introducing a resin into the cavity is further provided with the side gate. It is characterized in that a resin reservoir having a concave shape is formed inward, and a pin that is movable back and forth from the side gate to the inside of the resin reservoir and cuts the resin at the side gate position is provided on either side. It is a thing.

Here, it is preferable that the inner wall surface of the resin reservoir has an inclined surface shape in which the bottom gradually becomes shallower toward the resin inflow side to the side gate.

[0009]

According to the mold of the present invention having the above structure,
When the pin is projected into the resin reservoir provided in the side gate, the resin in the side gate is extruded in three directions: the molded product side, the runner side, and the resin reservoir. For this reason,
Excessive pressure does not act near the side gate of the molded product, and the resin can be reliably cut at the side gate position.

In addition, if the inner wall surface of the resin reservoir is formed in the shape of an inclined surface which gradually becomes shallower toward the resin inflow side to the side gate, the flow of the resin extruded from the inside of the side gate when the pin is projected. It can be further smoothed, and as a result, it becomes possible to further prevent local stress from remaining in the molded product.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view of the essential parts showing an embodiment of the mold of the present invention. In FIG. 1, reference numeral 20 in the figure denotes a fixed-side mold attached to a fixed platen (not shown) of the injection molding machine. A movable side mold 21 attached to a movable platen (not shown) of the injection molding machine is provided on the facing surface side of the fixed side mold 20 so as to be able to come into contact with and separate from the fixed side mold 20. ing. A cavity 22 that defines a product shape is provided between the facing surfaces of the fixed-side mold 20 and the movable-side mold 21, and a resin is introduced into the cavity 22 that is formed on the side of the cavity 22. And a runner 24 communicating with the inside of the injection nozzle of the injection molding machine and serving as a resin flow path to the side gate 23.

A resin pool 25 is formed on the fixed-side mold 20 side of the side gate 23, and the fixed-side mold 23 is further shaved off from the side gate 23. Here, the runner 2 of the resin pool 25
An inclined surface 26 is formed on the inner wall surface on the fourth side so that the bottom surface gradually shallows toward the runner 24 side.

On the other hand, the side gate 23 of the movable mold 21
A pressure pin (pin) 27 for cutting the resin at the position of the side gate 23 is provided at a position facing to the side gate 23 so as to be movable back and forth from the side gate 23 to the inside of the resin reservoir 25. The base end portion of the pressure pin 27 is fixed to a pressure plate (not shown), and the pressure plate is attached to the rod tip of a pressure cylinder for driving the pressure pin 27 forward. ing. When it is desired to apply vibration when advancing the pressure pin 27, a proportional pressure reducing valve for supplying pressure oil in a pulsed manner into the pressure cylinder is connected to the pressure cylinder. Further, a spring (not shown) for urging the pressure pin 27 toward the backward side is arranged at the base end portion of the pressure pin 27.

Next, the operation of the mold having the above construction will be described. First, the movable mold 21 is pressed against the fixed mold 20 by the mold clamping device of the injection molding machine to clamp the mold. Then, the resin melted in the heating cylinder,
It is injected into the mold by advancing the screw, and is filled into the cavity 22 from the side gate 23 via the sprue and runner 24. Then, by further advancing the screw and pushing the resin into the cavity 22,
The resin pressure in the cavity 22 is increased.

Next, the pressure pin 27 is projected into the side gate 23. Alternatively, pressurized with a pressure pin 27 is vibrated, to protrude into the side gate 23, as shown in FIG. 4, after the vibration delay time Td elapses, the end from the initial pressurizing force P ₁ to the pressure cylinder by a proportional pressure reducing valve A pulse-like urging force having an oscillating cycle time Tb is applied for a oscillating time Ta up to an oscillating force P _{2 with a} pressure reducing force ΔP. Then, the pressure pin 27 is oscillated by repeating the minute forward movement when the urging force acts and the minute retreat due to the urging force of the spring at the time of decompression, through the pressure plate, while vibrating. It gradually protrudes inside. As the pressure pin 27 is projected, the resin in the portion of the side gate 23 located above the pressure pin 27 is stored in the cavity 22, the runner 24, and the resin pool 25.
Is extruded in. Then, as shown in FIG. 2, when the pressurizing pin 27 is further advanced and the tip portion thereof passes through the side gate 23 and projects into the resin pool 25, the molded product resin in the cavity 22 is The resin in the resin reservoir 25 and the runner 24 is completely cut and separated.

Then, after the cooling time has passed, the movable mold 21 is separated from the fixed mold 20 (mold opening), and the molded product and the resin of the sprue runner portion are respectively ejected by ejector pins. As shown in FIG. 3, the molded product 30 and the resin 31 of the sprue runner portion are completely separated from each other and taken out from the mold.

According to such a mold, by pressing the pressure pin 27 into the resin reservoir 25 during molding,
Since the resin in the side gate 23 can be extruded in three directions in the cavity 22 side, the runner 24 side, and the resin reservoir 25, excessive pressure does not act in the vicinity of the side gate 23 of the molded product. Therefore, it is possible to obtain a molded product in which the stress remaining inside is relieved significantly.

Moreover, the pressure pin 27 is attached to the side gate 23.
Since the resin in the cavity 23 and the resin on the runner 24 side are cut at the time of passing through, the molded product can be reliably cut and separated from the resin on the runner 24 portion at the position of the side gate 23 in the mold. it can. Therefore, unlike the conventional one, it is not necessary to carry out a secondary processing step such as separating a molded product after molding, so that the molding cost can be reduced.

In addition, on the inner wall surface of the resin reservoir 25,
Since the inclined surface 26 having a gradually shallower bottom is formed toward the runner 24 side, the resin extruding flow in the direction of the runner 24 at the time of the protrusion of the pressure pin 27 can be further smoothed, and thus the molding can be performed. It becomes possible to further prevent the local stress from remaining in the product. In addition, in the above-mentioned embodiment, the example in which the pressure pin 27 is used as the pin for cutting the resin at the position of the side gate 23 has been described, but the present invention is not limited to this, and instead of the pressure pin 27, the runner Other pins such as an ejector pin for sticking out the resin of the portion may be used.

[0020]

As described in detail above, the mold according to the present invention has a cavity between the fixed side mold and the movable side mold provided so as to come in contact with and separate from the fixed side mold. A side gate is provided on a side portion of the cavity for introducing a resin into the cavity, and one of the fixed-side mold and the movable-side mold is further provided with a side gate inside the mold. Since a concave resin puddle is formed toward the side and a pin that can be moved back and forth from the side gate to the inside of the puddle is provided on either side, excessive pressure acts near the side gate of the molded product. As a result, it is possible to obtain a molded product in which the residual stress inside is largely relieved, and it is possible to reliably cut and separate the molded product from the resin of the runner at the side gate position in the mold. Because, as in the conventional ones, but require secondary processing steps such as separating the molded article after molding,
Therefore, the molding cost can be reduced.

Further, in particular, by forming the inner wall surface of the resin reservoir in the shape of an inclined surface which gradually becomes shallower toward the resin inflow side to the side gate, the resin extruded from the inside of the side gate when the pin is projected. Since the flow can be further smoothed, it becomes possible to further prevent local stress from remaining in the molded product.

[Brief description of drawings]

FIG. 1 is a side sectional view of an essential part showing an embodiment of an injection molding die of the present invention.

FIG. 2 is a side sectional view showing a state in which a pressure pin of the mold of FIG. 1 is projected.

FIG. 3 is a schematic view showing the shape of a molded product or the like obtained by the mold of FIG.

FIG. 4 is a diagram showing program control for operating a pressure pin in injection molding using the mold of FIG.

FIG. 5 is a schematic configuration diagram showing a molding apparatus in which a conventional mold is incorporated.

FIG. 6 is a side sectional view of an essential part showing another conventional mold.

FIG. 7 is a side sectional view showing a state in which a pressing pin of the mold of FIG. 6 is projected.

8 is a schematic view showing the shape of a molded product or the like obtained by the mold of FIG.

[Explanation of symbols]

 20 Fixed Side Mold 21 Movable Side Mold 22 Cavity 23 Side Gate 24 Runner 25 Resin Reservoir 26 Sloping Surface 27 Pressure Pin (Pin) 30 Molded Product

Claims (2)

[Claims] 1. A cavity is provided between a fixed side mold and a movable side mold which is provided so as to be capable of coming into contact with and separated from the fixed side mold, and a resin provided in the side part of the cavity. In a mold for injection molding in which a side gate for introducing is formed, in one of the fixed side mold and the movable side mold, a concave shape is further formed from the side gate toward the inside of the mold. A mold for injection molding, characterized in that a resin reservoir is formed and a pin that is movable back and forth from the side gate into the resin reservoir and cuts the resin at the side gate position is provided on the other side. . 2. The injection molding according to claim 1, wherein an inner wall surface of the resin reservoir has an inclined surface shape that gradually becomes shallower toward a resin inflow side to the side gate. Mold.