JP2000271977A - Injection mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection mold preventing such a phenomenon that the resin remaining in a sprue exerts adverse effect on a molded product at a time of next injection and obstructs the injection of the resin into the sprue to lower production efficiency by eliminating the molten resin at a time of mold opening. SOLUTION: In an injection mold wherein a cavity 4 corresponding to the shape of a molded product is formed between a fixed side mold 2 and a movable side mold 3 and a sprue 5 is formed to the fixed side mold 2 and an ejector pin 61 ejecting the resin solidified within the sprue 5 from the fixed side mold 2 is provided so as to be able to advance and retreat, the ejector pin 61 consists of an outer pipe 611 and a telescopic piece 612 slidable along the inner surface of the outer pipe 611.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for injection molding (hereinafter sometimes simply referred to as "mold").

[0002]

2. Description of the Related Art Conventionally, a mold for injection molding is provided with an ejector pin on a movable mold so as to inject a resin into a cavity, solidify the resin, and release the resin from the mold. ing. The ejector pins project resin solidified in the cavity, that is, a molded product, and simultaneously eject resin solidified in the sprue and the runner.

[0003] On the other hand, the diameter T of the sprue varies depending on the shape of the molded article to be molded, but may be larger than the thickness of the molded article. For example, when the molded article (a) shown in FIG. 5 is molded, when the height H of the molded article is increased, the maximum diameter T of the resin (b) solidified by the sprue is larger than the thickness t of the molded article (a). May be larger. In such a case, the resin injected from an injection molding machine (not shown) passes through a sprue, a runner, and a gate, is injected into a cavity, and is formed into a molded product (a).
The resin solidified by sprue (b)
It becomes difficult to cool near the intersection (e) between the resin (c) and the resin solidified by the runner (c).
Although the resin that forms is solidified, the resin (e) that forms the vicinity of the intersection of the resin solidified by the sprue (b) and the resin solidified by the runner (c) is in a molten state Yes, it is torn off when the mold is opened, and the resin remains in the sprue (see FIG. 6).

[0004] The resin remaining in the sprue flows into the cavity and exerts an adverse effect on the molded product, or the resin may enter the sprue if the mold does not have a cold slug well at the next injection. It may hinder the injection.

Therefore, the above problem is solved by extending the cooling time during the injection step so that the resin (e) is sufficiently solidified. However, the time required for one step becomes longer. There were problems such as a decrease in manufacturing efficiency.

Therefore, as shown in FIG. 7, a notch (nu) is provided near the intersection of the sprue (h) and the runner (ri) in the fixed mold (g), and the notch is formed when the mold is opened. It is also conceivable that the (nu) portion is reinforced by a rib structure to prevent breakage at this portion.

[0007]

However, even with the above-mentioned method, since a molten resin component exists, a sprue (h) is removed from the fixed mold (g) at the time of opening the mold without leaving the sprue. It was not enough to release.

The present invention solves the above-mentioned problems, and eliminates the resin in a molten state when the mold is opened, so that the resin remaining in the sprue may adversely affect a molded product during the next injection. It is an object of the present invention to provide an injection molding die that does not hinder the injection of a resin into a sprue and does not lower the production efficiency.

[0009]

According to the injection mold of the present invention, a cavity corresponding to the shape of a molded article to be molded is formed between a fixed mold and a movable mold. A sprue is formed on the side mold side, and an ejector pin for projecting the resin solidified in the sprue from the movable mold side is an injection mold provided so as to be able to advance and retreat, and the ejector pin is provided. , An outer tube and a pin nest that can slide on the inner surface of the outer tube.

(Effect) In the injection mold of the present invention, an ejector pin for projecting the resin solidified in the sprue is provided from the movable mold side so as to be able to advance and retreat, and the ejector pin is connected to the outer tube. Since the inner tube has a pin nest that can slide on the inner surface of the outer tube, the pin nest is inserted into the sprue after the end of the injection step in the injection molding, thereby reducing the maximum distance from the mold to the sprue in the cooling step. At the same time, the resin is also cooled by the pin nesting, so that the resin melted in the sprue and the runner at the time of opening the mold can be eliminated, and the resin is not torn off near the intersection of the sprue and the runner. . Further, when the pin insert is inserted into the sprue, the molten resin is pressed to prevent sinking of a molded product or the like.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of the injection mold of the present invention, and shows a state before resin is injected. In FIG. 1, 1 is an injection mold, 2 is a fixed mold, 3 is a movable mold, 4 is a cavity, 5 is a sprue, and 61 and 62 are ejector pins.

In the injection mold 1 of the present invention, a cavity 4 corresponding to the shape of a molded product to be molded is formed between a fixed mold 2 and a movable mold 3. The fixed mold 2 includes a fixed mold plate 21 and a fixed mounting plate 22, and the fixed mounting plate 22 is connected to a nozzle of an injection molding machine (not shown). The fixed-side mold 2 is formed with a sprue 5 whose diameter gradually increases from the fixed-side mounting plate 22 toward the fixed-side mold plate 21.

On the other hand, the movable mold 3 includes a movable mold plate 31,
It comprises a movable side mounting plate 32 and a spacer block 33. The movable mold plate 31 is provided with a core 311 and forms a part of the cavity 4. An ejector pin 61 for ejecting resin solidified in the sprue 5 and a molded product are ejected into a space (ejector box) 6 surrounded by the movable mold plate 31, the movable mounting plate 32, and the spacer block 33. An ejector pin 62 is provided so as to be able to advance and retreat.

The ejector pin 61 has an outer tube 611.
And a pin insert 612 slidable on the inner surface of the outer tube. The first ejector plates 63a and 63b and the second ejector
Ejector plates 64a and 64b are provided,
The pin insert 612 of the ejector pin 61 is attached to the first ejector plates 63a and 63b.
The outer tube 611 and the ejector pin 62 for projecting the molded product are screwed to the second ejector plates 64a and 64b, respectively.

FIG. 2 is an enlarged sectional view showing a main part of FIG. The pin insert 612 of the ejector pin 61 has a tapered tip portion so that it can be easily inserted into the sprue 5.
11 is made to coincide with the tip. That is, if the tapered portion enters the outer tube 611, the resin may be filled between the tapered portion and the outer tube 611 when the resin is injected.

When resin is injected into the mold 1 from a nozzle of an injection molding machine (not shown), the resin is sprue 5 and runner 5
1. The cavity 4 is filled through the gate 52.

FIG. 3 is a sectional view showing a state in which a resin is injected into the injection mold shown in FIG. 1 during a cooling step, and FIG. 4 is an enlarged view of a main part thereof. As shown in FIGS. 3 and 4, after the injection of the resin 7 is completed, the upper end of the first ejector plate 63b shown in FIG. 1 is advanced by a distance L until it contacts the lower end of the second ejector plate 64b. The pin insert 612 is projected into the sprue 5. At this time, the maximum value X of the diameter of the sprue 5 is
Is preferably smaller than the case where T is not projected into the sprue 5 (T in FIG. 5), and is close to the width of the runner 51 (Y in FIG. 4) and the thickness of the molded product (t in FIG. 5). At this time, the molten resin also passes through the runner 51 and the gate 52, and also pressurizes the resin filled in the cavity 4, so that sinks and the like generated in the molded product can be reduced.

Next, the mold is opened, the resin filled in the sprue 5, the runner 51, the gate 52, and the molded product are released from the fixed mold 2, and are brought into close contact with the movable mold 3. At this time, since the pin insert protrudes into the sprue 5 and the resin is solidified, it becomes a resistance when the mold is released from the fixed mold 2 and can be smoothly removed. When the second ejector plates 64a and 64b are advanced, the molded product is released from the movable mold 3 together with the resin filled in the sprue 5, the runner 51 and the gate 52.

[0019]

Since the injection mold of the present invention has the above-described structure, the resin remaining in the sprue is removed by removing the resin in the molten state when the mold is opened. In this case, there is no adverse effect on the molded product, no hindrance to the injection of the resin into the sprue, and no reduction in the production efficiency.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of an injection mold according to the present invention, showing a state before resin is injected.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a cross-sectional view showing a state during a cooling step of injecting a resin in the injection mold shown in FIG. 1; FIG. 3 is a cross-sectional view showing an example of the injection mold of the present invention; This shows the state before injection.

FIG. 4 is an enlarged view of a main part of FIG. 3;

FIG. 5 is a cross-sectional view illustrating an example of a molded product (including a sprue, a runner, and a gate) molded using a conventional injection molding die.

FIG. 6 is an enlarged view of a main part of FIG. 6;

FIG. 7 shows another example of a conventional injection mold, and FIG.
Is a sectional view thereof, and (b) is a sectional view taken along the line AA.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 injection molding die 2 fixed die 3 movable die 4 cavity 5 sprue 6 ejector box 61, 62 ejector pin 611 outer tube 612 pin insert 7 resin

Claims (1)

[Claims] 1. A cavity corresponding to the shape of a molded product to be molded is formed between a fixed mold and a movable mold, a sprue is formed on the fixed mold side, and a movable mold is provided. An ejector pin that projects resin solidified in the sprue from the side is an injection molding die provided so as to be able to advance and retreat, and the ejector pin is an outer tube and a pin that can slide on the inner surface of the outer tube. A mold for injection molding, comprising a nest.