JP3196464B2 - 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 pin-shaped valve for opening and closing a gate.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional example of this type of injection mold.
And FIG. In the figure, reference numeral 1 denotes a fixed mold plate, 2 denotes a movable mold plate, 3 denotes a cavity formed between the fixed mold plate 1 and the movable mold plate 2, 4 denotes a cavity fitted to the fixed mold plate 1 and a cavity 3
, A gate bush provided with a gate 4a formed so as to face, a valve casing 6, and a valve 7 for opening and closing the gate 4a. The valve 7 is guided at its upper part by a guide bush 8 fixed to the valve casing 6 and at the lower part by a valve holder 10 fixed to the lower part of the valve casing 7 via a cap 9, thereby forming the gate 4 a. It moves up and down while being held coaxially with respect to. A band heater 1 is provided on the outer periphery of the valve casing 7.
The outer periphery of the band heater 11 is covered with a heater cover 12.

[0003] As shown in FIG. 3, the valve holder 10 has an outer ring portion 1 fitted to the inner peripheral surface of the valve casing 6.
0a and an inner ring portion 10b for slidably guiding the valve 7
And a plurality of blade portions 10c connecting the outer ring portion 10a and the inner ring portion 10b. A communication passage 13 is formed between the blade portions 10c to connect the resin passage 6a in the valve casing 6 to the gate 4a. I do.

Then, in the injection mold, the movable mold plate 2 is raised to be in a mold-clamped state as shown by a solid line in FIG.
The valve 7 is raised to open the gate 4a, and the molten resin is injected into the cavity 3 through the resin passage 6a in the valve casing 6 and the communication passage 13 of the valve holder 10 from the nozzle of the injection molding machine body (not shown). Let it. After the filling is completed, the valve 7 is lowered to close the gate 4a as shown by the solid line in the figure. After the resin in the cavity 3 is cooled and solidified, the movable mold plate 2 is lowered to open the mold, and the molded product is taken out.

[0005]

The above-mentioned conventional injection mold has the following problems. That is, there is a certain limit in securing the predetermined strength even if the thickness of the blade portion 10c and the inner ring portion 10b of the valve holder 10 is set to be thin. As described above, since the thickness of the blade portion 10c and the inner ring portion 10b of the valve holder 10 cannot be reduced to a certain degree or more, when the molten resin passes through the communication passage 13 formed between the blade portions 10c of the valve holder 10, Inevitably, flow path resistance is generated and smooth flow of the molten resin is hindered. Since the smooth flow of the molten resin is hindered as described above, the molten resin tends to stay in the resin passage 6a in the valve casing 6 on the upstream side of the valve holder 10 as shown by S in the figure. Here, the heat supplied from the band heater 11 and the heat of the molten resin itself cause the valve casing 6 and the valve
And the like are heated, but since the valve 7 has no radiating portion, the temperature always becomes high during operation. Then, there is a problem in that the resin staying at the substantially central portion of the resin passage 6a may be carbonized due to the thermal influence of the valve 7, which becomes high heat.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to prevent a molten resin from remaining in a resin passage in a valve casing and being affected by heat to cause deterioration such as carbonization. The purpose is to provide.

[0007]

In order to achieve the above object, according to the present invention, a cavity is formed between a pair of mold plates,
A cylindrical valve casing having a resin passage communicating with the cavity through a gate facing the cavity is provided in one mold plate, and a pin-shaped valve is movable in an axial direction in the resin passage of the valve casing. Placed in
In the injection mold for opening and closing the gate by the tip of the valve, the tip of the valve is guided by a valve holder provided at the tip of the valve casing and moves in the axial direction. On the inner peripheral surface forming the resin passage, a tapered narrow portion whose minimum diameter is approximately at the center in the length direction and whose diameter gradually increases from there toward the upper and lower ends is pre-determined at the location where the molten resin stays.
And the inner peripheral surface of the narrow portion is a smooth surface.
Finished configuration.

[0008]

According to the present invention, the inner peripheral surface forming the resin passage of the valve casing where the molten resin tends to stay is made a narrow portion, and the portion where the molten resin stays is removed in advance.
The stagnation of the molten resin in the resin passage of the valve casing can be avoided. Further, since the narrow portion is formed in a tapered shape, the flow of the molten resin is not disturbed, and the molten resin can be smoothly supplied to the valve holder on the downstream side.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. In these figures, reference numeral 20 denotes a fixed mold plate, and a movable mold plate 21 is provided so as to be openable and closable in opposition to the fixed mold plate 20. Then, a cavity 22 having a shape of a molded product is formed between the fixed mold plate 20 and the movable mold plate 21. The fixed mold plate 20 is fixed to a fixed mounting plate (not shown) via a first receiving plate 23a and a second receiving plate 23b, and the movable mold 21 is also fixed to a movable mounting plate (not shown).

A gate bush 24 is fixed in the fitting hole 20a of the fixed mold plate 20 in a state of being embedded. The gate bush 24 has a lower end exposed to the cavity 22, and an opening exposed to the cavity 22 corresponds to the gate 2.
4a.

A valve casing 26 is arranged inside the fixed mold plate 20 and the receiving plate 23 so that the tip side faces downward. A resin passage 27 extending in the vertical direction is formed inside the valve casing 26.
Is connected to the cavity 22 through the gate 24a of the gate bush 24, and the resin passage 2
The upper portion of 7 is communicated with a resin passage 30a in the manifold 30 through a communication passage 27a obliquely penetrating the upper portion of the valve casing 26, from which the molten resin is supplied.

A band heater 32 is provided on the outer periphery of the valve casing 26, and the outer periphery of the band heater 32 is covered by a heater cover 33. A vertical groove 34 is provided on the outer periphery of the valve casing 26, and a temperature sensor 35 is mounted in the vertical groove 34. A lead wire 35a extending from the temperature sensor 35 extends to a predetermined external location through a hole 36 formed in the second receiving plate 23b. Reference numeral 37 denotes an outer cylinder disposed outside the band cover 33.

In the resin passage 27 of the valve casing 26, a pin-shaped valve 38 extending through the manifold 30 along the center axis thereof is disposed so as to be movable in the vertical direction, and is driven up and down by a moving plate (not shown). You. The valve 38 includes a valve body 38a, a cylindrical gate closing portion 38b formed at the distal end of the valve body 38a and having an outer diameter slightly smaller than the opening diameter of the gate 24a, and a valve body 38a and a gate. And a conical portion 38c formed between the closing portion 38b. In the valve 38, the upper part of the valve body 38a is guided by the guide bush 39 fixed to the valve casing 26, and the lower part (tip) of the valve body 38a is fixed to the lower part of the valve casing 26. Is held coaxially with the gate 24a.

The valve holder 40 is inserted into a fitting hole formed in a lower portion of the valve casing 26, and the cap 4 screwed into the fitting hole of the valve casing 26 from below.
1 is fixed. The valve holder 40 is
As described above, the outer ring 40a, the inner ring 40b for slidably guiding the valve 38, the outer ring 40a and the inner ring 4
0b and a plurality of blades 40c connecting the
A communication passage 43 that connects the resin passage 27 in the valve casing 26 to the gate 24a is formed between the blade portions 40c.

The resin passage 27 of the valve casing 26
The tapered narrow portion 45 is formed in an inner peripheral portion of the valve casing 26. The tapered narrow portion 45 has a minimum diameter substantially at the center in the length direction of the valve casing 26, and gradually increases in diameter from both ends toward upper and lower ends. The narrow portion 45 is formed separately from the valve casing 26 and has tapered portions at upper and lower ends obtained by cutting the inner peripheral portion of the cylindrical body so as to gradually become deeper from the center toward the upper and lower ends. The member 46 is formed by assembling the member 46 with fixing means such as press fitting or welding inside the valve casing 26. Also, the narrow portion 45
Is smoothed so that the flow resistance of the molten resin flowing in the resin passage 27 does not become large.

Next, the operation of the injection mold having the above configuration will be described. In order to obtain a resin molded product having a predetermined shape using the mold, first, the movable mold plate 21 is raised to a mold clamped state as shown by a solid line in the figure. Then, the valve 30 is raised to open the gate 24a, and molten resin is supplied from a nozzle of the injection molding machine main body (not shown) to the resin passage 30a in the manifold 30 and the resin passages 27a and 27 in the valve casing 26.
7 and communication passage 43 of valve holder 40 and gate 24
Inject into the cavity 22 through a. After the filling is completed, the valve 38 is lowered to close the gate 24a as shown by a two-dot chain line in the figure. And the cavity 22
After the resin inside is cooled and solidified, the movable mold plate 21 is lowered to open the mold, and the molded product is taken out from the cavity 22.

Here, the narrow portion 45 is formed in advance on the inner peripheral surface of the valve casing 26 where the resin passage 27 is formed, where the molten resin tends to stay, and the place where the molten resin stays is removed in advance. Thus, it is possible to prevent the molten resin from staying substantially at the center of the resin passage 27 of the valve casing 26. Therefore, it is of course possible to prevent the molten resin from accumulating in the substantially central portion of the resin passage 27 and undergoing heat deterioration of the valve 38 to cause deterioration such as carbonization.

Since the narrow portion 45 is tapered on both the upper and lower sides, the flow of the molten resin flowing through the resin passage 27 is not disturbed, and the molten resin flows smoothly to the valve holder 40 on the downstream side. Can be supplied, and it is possible to avoid occurrence of defective filling in the molded article and non-uniform density.

The present invention is not limited to the above-described embodiment, but can be modified as appropriate upon implementation. For example, in the above-described embodiment, the narrow portion 45 is formed by fixing a member 46 separate from the valve casing 26 to the inner peripheral surface of the valve casing 26, but is not limited thereto.
The narrow portion 45 may be formed integrally with the valve casing 26 by processing the inner peripheral surface of the valve casing 26.

Further, the narrow portion 45 does not necessarily need to be formed at the center of the resin passage 27 in the valve casing 26, but may be formed so as to be shifted in any one of the up and down directions according to the situation where the molten resin stays. In this case, it goes without saying that the shapes of the upper and lower tapered portions of the narrow portion 45 need not necessarily be provided symmetrically.

[0021]

According to the present invention, a narrow portion is formed in advance on the inner peripheral surface of the valve casing forming the resin passage where the molten resin tends to stay, and the portion where the molten resin stays is removed in advance. Therefore, it is possible to prevent the molten resin from staying at the substantially central portion of the resin passage of the valve casing, and it is also possible to avoid the molten resin from staying at the substantially central portion of the resin passage and deteriorate such as carbonization. Further, since the narrow portion is formed in a tapered shape on both the upper and lower sides, the molten resin can be smoothly supplied to the downstream valve holder side without disturbing the flow of the molten resin flowing through the resin passage, and the molded product can be formed. It is possible to avoid poor filling and uneven density.

[Brief description of the drawings]

FIG. 1 is an enlarged view showing a main part of an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating an example of a conventional injection mold.

FIG. 3 is a front view showing a valve holder used in a conventional injection mold.

[Explanation of symbols]

 Reference Signs List 20 fixed mold plate 21 movable mold plate 22 cavity 24a gate 26 valve casing 27 resin passage 38 valve 40 valve holder 45 narrow portion 46 member having tapered portions on both upper and lower ends

Claims (1)

(57) [Claims] 1. A cavity is formed between a pair of mold plates,
A cylindrical valve casing having a resin passage communicating with the cavity through a gate facing the cavity is provided in one mold plate, and a pin-shaped valve is movable in the axial direction in the resin passage of the valve casing. Placed in
In an injection molding die in which the distal end of the valve is guided by a valve holder provided at the distal end of the valve casing and moves in the axial direction, the gate is opened and closed by the distal end of the valve. On the inner peripheral surface forming the resin passage,
The tapered narrow part where the diameter is gradually increased toward the upper and lower ends from the minimum diameter at the approximate center in the length direction is the molten resin
It is previously formed where the residence are, and the inner peripheral surface of the narrow portion is injection mold, characterized in that it is finished to a smooth surface.