JP2000167882A - Valve gate type mold apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an accuracy and characteristics of a product to be molded by making a flow of a resin from a gate to a product cavity more uniform. SOLUTION: A valve pin 32 for opening and closing a gate 14 is always engaged with a valve pin support hole formed at a front end of a valve casing 26 at the gate 14 side. A plurality of grooves 31 are formed at a periphery of a valve pin support hole to feed a resin. A recess 30 is formed at a part of the end of the casing 26 further to the gate 14 side from the hole 29. The recess 30 is opened toward the gate 14 to surround the overall periphery of the pin 32. A deviation of a flow of the resin of the groove 31 is alleviated by the recess 30 and the flow of the resin from the gate 14 to the cavity 3 is made more uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve gate type mold apparatus used for injection molding of a thermoplastic resin.

[0002]

SUMMARY OF THE INVENTION For example, JP-A-10-1
As described in, for example, Japanese Patent No. 5995, in a hot runner mold apparatus for heating a resin in a material passage to a gate to a product cavity and keeping the resin in a molten state at all times, a valve that mechanically opens and closes a gate with a valve pin Gate type mold devices are known. The hot runner mold device aims at increasing the molding efficiency, and the reason why the gate is closed is to prevent the resin from leaking from the gate when the mold is opened.

[0003] In a valve gate type mold apparatus, a valve pin is generally housed in a cylindrical valve casing having a resin passage therein. However, misalignment between the gate and the valve pin causes malfunction or malfunction. Since the molding failure due to the uneven flow of the resin is caused, in the valve gate type mold device described in the above-mentioned publication, the valve pin is always slidably inserted into the valve pin support hole (through hole) formed at the gate end of the valve casing. The fitting and the resin as a molding material pass through a concave groove (flow groove) formed around the valve pin support hole. These concave grooves extend in parallel with the sliding direction of the valve pin, which coincides with the axial direction of the resin passage, reach the front end surface of the valve casing on the gate side, and are formed three at a distance of 120 ° from each other.

However, since the resin is passed through the three grooves separated from each other, a directed flow is created by these grooves, and the flow of the resin in the product cavity also decreases. It is close to a triangular shape biased to a certain part. For this reason, in particular, when the fluidity of the resin in the product cavity is poor, for example, when the resin contains glass fiber, molding failure may occur. Further, there is a possibility that a variation in density (dense / dense) in a weld line or a circumferential direction may occur due to the orientation of the resin caused by the flow. And, for example, in the case of rotating parts,
If there is a variation in the density in the circumferential direction, surface runout occurs during rotation. In the case of a petri dish used for optical observation, uneven orientation of the resin adversely affects the optical characteristics.

The present invention is intended to solve such a problem. A valve pin is slidably fitted in a valve pin support hole formed at a gate-side tip of a valve casing, and a molding material is formed in the valve pin support hole. In a valve gate type mold device which is made to pass through a concave groove formed in the peripheral portion of
It is an object of the present invention to make the flow of molding material from a gate to a product cavity more uniform, and to improve the accuracy and characteristics of a molded product.

[0006]

According to a first aspect of the present invention, there is provided a valve gate type mold apparatus comprising a plurality of molds which are opened and closed with each other and form a product cavity when the mold is closed. And a valve device provided in a mold having a gate opening to a product cavity among these molds, and the valve device is incorporated into an assembling hole formed in a main body of the mold, and a material is provided. A valve casing having a passage formed therein, a heater provided in the valve casing, and a valve pin provided in the valve casing to open and close the gate; A valve pin support hole in which the valve pin is slidably fitted is formed, and the material of the valve casing is formed around the valve pin support hole. In addition to forming a concave groove for communicating the passage with the gate, a concave portion that opens toward the gate and surrounds the valve pin over the entire periphery at the tip end of the valve casing further on the gate side than the valve pin support hole. It is formed.

At the time of molding, a plurality of molds are closed, a product cavity is formed between these molds, a valve pin is moved to open a gate, and a molding material is filled in the product cavity. At this time, the molding material flows into the product cavity through a material passage in the valve casing, a concave groove, a concave portion, and a gate in the periphery of the valve pin support hole in which the valve pin is fitted. The presence of the concave portion alleviates the uneven flow of the molding material due to the concave groove, and makes the flow of the molding material from the gate to the product cavity more uniform. After filling the molding material into the product cavity, the valve pin is moved to close the gate. Further, after the molding material in the product cavity is cooled and solidified, the mold is opened and the solidified molding material in the product cavity, that is, the molded product is taken out. During this time, the molding material in the material passage is always kept in a molten state by the heating of the heater.

According to a second aspect of the present invention, in the valve gate type mold apparatus of the first aspect of the present invention, the concave portion is formed into a smooth curved surface gradually expanding toward the gate.

Since the molding material is guided on the curved surface, the flow of the molding material from the concave groove to the gate and further to the product cavity through the concave portion becomes smoother.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a valve gate type mold apparatus according to the present invention will be described below with reference to the drawings. FIG. 4 shows the final shape of the product A to be molded.
This product A is a rotating machine part.

In FIG. 1, reference numeral 1 denotes a fixed mold, and 2 denotes a movable mold. The fixed mold 1 and the movable mold 2, which are molds, move in the vertical direction (the mold opening and closing direction) to open and close, and close. Sometimes product cavities 3 of product shape are formed between each other. The fixed mold 1 includes a fixed mold plate 6, a fixed receiving plate 7 fixed to the upper surface of the fixed mold plate 6, that is, a surface opposite to the movable mold 2, and a back side of the fixed receiving plate 7. A fixed-side mounting plate (not shown) fixed via a spacer block is provided. A manifold 8 is provided between the fixed-side mounting plate and the fixed-side receiving plate 7. The manifold 8 has a runner 9 as a material passage formed therein, and the thermoplastic resin as a molding material in the runner 9 is always in a molten state by heating a heater (not shown) provided in the manifold 8. Is to be kept.

A gate bush 12 which forms the main body of the fixed mold 1 together with the fixed mold plate 6 and the fixed receiving plate 7 is detachably mountable in a gate bush mounting hole 11 formed through the fixed mold plate 6. Is fitted. The gate bush 12 has a tapered portion 13 on the lower side in the drawing, that is, the product cavity 3 side tapered toward the product cavity 3 side. Is formed. And
Inner surface of gate bush mounting hole 11 and gate bush 12
A cooling water passage 15 is formed between
An O-ring 16 for preventing water leakage is mounted with the cooling water passage 15 interposed therebetween.

The fixed mold 1 has a valve device 21 for opening and closing the gate 14 incorporated therein. Next, the configuration of the valve device 21 will be described. The fixed side receiving plate 7 is formed with a mounting hole 22 penetrating in the mold opening and closing direction, and the inside of the gate bush 12 is a mounting hole 23 communicating with the mounting hole 22. A substantially cylindrical valve casing 26 is installed in the installation holes 22 and 23. One end of the valve casing 26 forms a flange 27 and is fixed to the manifold 8 and the fixed-side receiving plate 7.

The interior of the valve casing 26 is a material passage 28 for communicating the runner 9 in the manifold 8 with the gate 14. As shown in FIGS. 2 and 3, a valve pin support hole 29 having a smaller diameter than other portions of the material passage 28 is formed at the lower end of the material passage 28 in the drawing, that is, at the tip end on the gate 14 side. At the same time, a recess 30 opening toward the gate 14 is formed in a portion closer to the gate 14 than the valve pin support hole 29.
The concave portion 30 is substantially cylindrical and coaxially opposes the gate 14, but is formed into a smooth curved surface gradually expanding toward the gate 14. That is, the length L of the valve pin support hole 29 in the mold opening and closing direction is shortened by forming the concave portion 30. Further, the inner surface of the peripheral portion of the valve pin support hole 29 is 120 ° apart from each other.
Three concave grooves 31 spaced apart from each other are formed to penetrate in the mold opening and closing direction. These grooves 31
The material passage 28 in 26 is communicated with the gate 14 through the recess 30. In a cross section orthogonal to the mold opening and closing direction, the total area of the three concave grooves 31 is larger than the area of the gate 14. Although the number of the grooves 31 is not limited to three, it is preferable that the grooves 31 be provided at equal intervals in order to make the flow of the thermoplastic resin as a molding material as uniform as possible.

As shown in FIG. 1, a valve pin 32 as a valve body which moves in the mold opening / closing direction by driving a hydraulic cylinder (not shown) provided on a fixed-side mounting plate is provided in a valve casing 26. Is built-in. The valve pin 32 is always slidably fitted in the valve pin support hole 29, and is fitted to the gate 14 so as to be freely inserted and removed to close the gate 14. The length L of the valve pin support hole 29 in the mold opening and closing direction is ensured to such an extent that the reliability of the support of the valve pin 32 is not impaired. A recess 30 in the valve casing 26 closer to the gate 14 than the valve pin support hole 29 surrounds the valve pin 32 all around. In addition, valve pins
32 is supported by a guide bush 33 fixed in the valve casing 26 at an end of the valve casing 26 on the manifold 8 side. That is, the valve pin 32 slidably passes through the guide bush 33.

A band heater 36 for heating the material passage 28 and a substantially cylindrical heater cover for covering the heater 36 from the outside are provided on the outer peripheral surface of the valve casing 26.
37 are fitted. Reference numeral 38 denotes a temperature sensor provided along the heater 36.

A step portion 41 is formed on the outer peripheral side of the end of the valve casing 26 on the gate 14 side, and a short cylindrical heat insulating ring 42 is fitted and fixed to the step portion 41. This fixation is due to shrink fitting. On the inner peripheral surface of the heat insulating ring 42, a concave groove 43 forming an air heat insulating layer is formed. The outer peripheral surface of the heat insulating ring 42 is fitted to a cylindrical fitting surface 44 of the same diameter formed in the mounting hole 23 of the gate bush 12. As a result, the valve casing 26 is supported by the gate bush 12 forming the main body of the fixed mold 1 at the tip of the gate 14 on the gate 14 side. In addition, except for the fitting surface 44 between the heat insulating ring 42 and the gate bush 12, for heat insulation, the mounting holes 22, 2 are provided.
3 inner surface and valve casing 26 or heater cover 3
A gap 45 is formed between the outer surface 7 and the outer surface. The heat insulating ring 42 is provided between the portion of the gap 45 on the gate 14 side and the heater 36.
The side part is shut off.

The heat insulating ring 42 in the gap 45
A heat-insulating sealing cap 51 formed of a tapered cylinder as a heat-insulating sealing member is fitted to a portion closer to the gate 14 than the gate. The material of the heat-insulating sealing cap 51 is made of, for example, a hard polyimide resin having excellent heat resistance and abrasion resistance that is not melted by heat of a molding material such as a thermoplastic resin molded by the present mold apparatus. . Insulation sealing cap 51
By preventing the resin of the molding material from entering the gap 45 while ensuring a certain degree of heat insulation between the valve casing 26 and the gate bush 12, for example, when changing colors, the gap can be reduced with a small number of shots. This is to ensure that the resin of the color before it has accumulated in the 45 can be discharged quickly and without residue.

Reference numeral 56 denotes a movable mold plate of the movable mold 2.

Next, the operation of the above configuration will be described. In molding, first, the fixed mold 1 and the movable mold 2 are closed, a product cavity 3 is formed between the fixed mold 1 and the movable mold 2, and then the valve pin 32 is moved in a direction away from the movable mold 2. Gate 14 is opened. Note that, even when the gate 14 is opened, the valve pin 32 remains fitted in the valve pin support hole 29 of the valve casing 26. Then, a molten thermoplastic resin as a molding material is injected into the fixed mold 1 from the injection molding machine. The resin flows from the gate 14 into the product cavity 3 through the runner 9 of the manifold 8, the material passage 28 in the valve casing 26, the concave groove 31 and the concave portion 30 around the valve pin support hole 29, and the like. . Thus, the product cavity 3
After the resin is filled, the valve pin 32 moves toward the movable mold 2 through the holding pressure, and is fitted to the gate 14 to fit this gate.
Close 14. The resin in the product cavity 3 is
The cooling water is positively cooled by passing the cooling water. After the resin in the product cavity 3, that is, the product A is cooled and solidified, the fixed mold 1 and the movable mold 2 are opened, and the molded product A is taken out. Thereafter, the mold is closed again, the above steps are repeated, and the molding is repeated. During this time, the resin in the material passage 28 of the valve casing 26 is always kept in a molten state by the heating of the heater 36.

According to the configuration of the above-described embodiment, the valve casing 26 is opened toward the gate 14 at the end of the valve casing 26 further than the valve pin support hole 29 and surrounds the valve pin 32 over the entire circumference. Since the concave portion 30 is formed and the valve pin support hole 29 having the concave groove 31 is shortened as much as possible, when the resin flows from the material passage 28 in the valve casing 26 to the gate 14, the resin flows into the plurality of concave grooves 31 and flows. Nevertheless, the unevenness of the resin flow due to the plurality of concave grooves 31 is alleviated in the subsequent concave portion 30, and the resin flow from the gate 14 to the product cavity 3 becomes more uniform. Further, since the concave portion 30 is formed into a smooth curved surface gradually spreading toward the gate 14 side, the resin is guided on this curved surface, so that the resin reaches the gate 14 and the product cavity 3 from the concave groove 31 through the concave portion 30. The resin flow becomes smoother. As described above, the flow of the resin from the gate 14 to the product cavity 3 becomes more uniform, and the orientation of the resin becomes more uniform, so that molding defects can be prevented, and the precision and accuracy of the product A to be molded can be improved. The characteristics are improved. For example, even when the resin contains a glass filler and has poor fluidity, it is possible to prevent molding defects such as the occurrence of weld lines. Further, for example, when the product A is a rotating part as in the present embodiment, the surface runout during rotation can be prevented by making the density more uniform in the circumferential direction. The same level of accuracy as cutting and processing a metal material can be ensured only by injection molding.

It should be noted that the present invention is not limited to the above embodiment, and various modifications can be made. For example,
In the above-described embodiment, the gate bush 12 is provided separately from the fixed-side template 6 and the gate 14 is provided on the gate bush 12, but the gate is formed directly on the fixed-side template without providing the gate bush. You may.

[0023]

According to the first aspect of the present invention, the valve pin is slidably fitted into the valve pin support hole formed at the gate-side tip of the valve casing, and the molding material is formed around the valve pin support hole. In a valve gate type mold device through which a concave groove is passed, a concave portion which opens toward the gate and surrounds the valve pin over the entire periphery is provided at a tip portion of the valve casing closer to the gate than the valve pin support hole. Since it is formed, the flow of the molding material from the gate to the product cavity can be made more uniform, and the accuracy and characteristics of the molded product can be improved.

According to the valve gate type mold apparatus of the second aspect of the present invention, in addition to the effect of the first aspect of the present invention, the concave portion is formed in a smooth curved surface gradually expanding toward the gate side. The flow of the molding material from the mold to the product cavity can be made smoother.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a valve gate type mold apparatus of the present invention.

FIG. 2 is an enlarged sectional view of a gate-side tip portion of the valve casing.

FIG. 3 is a sectional view taken along the line III-III of FIG. 2;

FIG. 4 is a perspective view of the product to be molded.

[Explanation of symbols]

 Reference Signs List 1 fixed mold (mold) 2 movable mold (mold) 3 product cavity 6 fixed mold plate (main body) 7 fixed-side receiving plate (main body) 12 gate bush (main body) 14 gate 21 valve device 22 mounting hole 23 Assembly hole 26 Valve casing 28 Material passage 29 Valve pin support hole 30 Recess 31 Groove 32 Valve pin 36 Band heater (heater)

Claims (2)

[Claims] A plurality of molds which are opened and closed with each other to form a product cavity therebetween when the mold is closed, and a valve device provided in a mold having a gate which opens to the product cavity among these molds. The valve device is installed in a mounting hole formed in a main body of the mold body and has a material passage formed therein, a heater provided in the valve casing, and a valve housing. A valve pin for opening and closing the gate, a valve pin support hole in which the valve pin is slidably fitted is formed at a tip end of the valve casing on the gate side, and the valve is provided around the valve pin support hole. A groove for communicating the material passage of the casing with the gate is formed, and the distal end of the valve casing forms the groove. A valve gate type mold device, wherein a concave portion which opens toward the gate and surrounds the valve pin over the entire periphery is formed in a portion closer to the gate than the valve pin support hole. 2. The valve gate type mold apparatus according to claim 1, wherein the concave portion is formed in a smooth curved surface gradually expanding toward the gate side.